A UV coating and its preparation method and application

Abstract

The application provides a UV coating and a preparation method and application thereof.The UV coating of the application is prepared from raw materials including ultraviolet light curing resin, active monomer, thermoplastic acrylic resin, photoinitiator, adhesion promoter, base material wetting agent, ethyl acetate, butyl acetate, fumed silica, polyamide wax anti-settling slurry, pigment and flatting powder.The UV coating of the application reduces the influence of pigment light absorption on UV curing by increasing UV light intensity, and realizes appropriate color addition of the coating.The application increases the color addition ratio by increasing light intensity, and the color addition and hiding property are superior to those of the prior art.The application also provides a preparation method and application of the UV coating.

Description

Technical Field

[0001] This invention belongs to the field of coating technology, specifically relating to a UV coating, its preparation method, and its application. Background Technology

[0002] In the 3C industry, the trend in mobile phones and laptops is towards thinner and lighter designs. Aluminum-magnesium alloys, with their low density, high strength, and good rigidity, perfectly meet these requirements, making them the preferred material for high-end mobile phones and laptops. However, magnesium's high chemical reactivity and poor corrosion resistance limit the use of aluminum-magnesium alloys. To improve their corrosion resistance, anti-corrosion treatments are typically applied to the surface of aluminum-magnesium alloys. Micro-arc oxidation is a simple, efficient, and environmentally friendly surface treatment process.

[0003] Micro-arc oxidation technology is a method that utilizes a combination of electrolyte and appropriate electrical parameters to grow a ceramic film layer mainly composed of the base metal oxide on the surface of aluminum, magnesium, titanium, and their alloys through the instantaneous high temperature and pressure generated by arc discharge. This significantly improves the corrosion resistance, wear resistance, and insulation of magnesium alloys. Simultaneously, the porous structure of the metal oxide layer facilitates surface anchoring of the coating and enhances its adhesion to the metal. Generally, after surface treatment, aluminum-magnesium alloys have a smooth surface, making coating adhesion difficult. Surface coating often employs a three-coat process: PU primer + PU color paint + UV topcoat, which is complex, inefficient, and energy-intensive. However, after micro-arc oxidation treatment, the porous surface of aluminum-magnesium alloys allows for a single-coat UV coating to adhere to the metal surface, greatly improving production efficiency, reducing energy consumption, and saving costs.

[0004] CN110452599A discloses a method for preparing a baking-cured coating. This method requires baking for over 30 minutes, resulting in high energy consumption, low efficiency, and generally poor wear resistance, making it unsuitable for applications requiring high wear resistance, such as mobile phones and laptops. CN116515351A employs a dual-curing system of UV + baking paint, using the baking paint portion to provide adhesion and the UV curing portion to provide performance. This coating requires both UV curing and baking at 150℃, also resulting in high energy consumption and low efficiency. Currently, aluminum-magnesium alloy micro-arc oxidation treatment results in limited color options, hindering the multi-color options available for mobile phones and laptops. There is a need to develop a coating that facilitates color addition and maintains good adhesion on micro-arc oxidation substrates to meet diverse and differentiated customer needs. Summary of the Invention

[0005] This invention aims to at least solve one of the aforementioned technical problems existing in the prior art. To this end, this invention provides a UV coating that, by increasing UV light intensity, reduces the impact of pigment light absorption on UV curing, thus achieving appropriate color addition to the coating. This invention, by increasing light intensity, improves the color addition ratio, resulting in superior color addition properties and hiding power compared to existing technologies.

[0006] The present invention also provides a method for preparing a UV coating.

[0007] The present invention also provides a surface treatment layer.

[0008] The present invention also provides a method for preparing a surface treatment layer.

[0009] This invention also provides the application of surface treatment layers in 3C products.

[0010] The first aspect of the present invention provides a UV coating, the raw materials of which include ultraviolet curable resin, active monomer, thermoplastic acrylic resin, photoinitiator, adhesion promoter, substrate wetting agent, ethyl acetate, butyl acetate, fumed silica, polyamide wax antisettling paste, pigment and matting powder.

[0011] One of the technical solutions of the present invention concerning UV coatings has at least the following beneficial effects:

[0012] Existing conventional paint baking methods allow for the addition of color because it doesn't affect the paint's curing. However, for UV-cured paints, pigments absorb light, which affects the curing process, leading to difficulties in curing existing UV paints after color addition. This invention's UV paint, by increasing UV light intensity, reduces the impact of pigment light absorption on UV curing, achieving appropriate color addition. This invention, by increasing light intensity, improves the color addition ratio, resulting in superior colorability and opacity compared to existing technologies.

[0013] This invention provides a color-adding one-coat UV coating that can ensure good adhesion on micro-arc oxidation treated substrates, protect metal surfaces, and provide different color effects to meet the diverse and differentiated needs of customers.

[0014] The UV coating of this invention requires only baking at 50-60℃ for 3-5 minutes, followed by UV curing, to obtain a UV protective layer with high hardness, high wear resistance, and good chemical resistance. It exhibits good adhesion to micro-arc oxidation substrates, maintaining an adhesion ≥4B after boiling at 85℃ for 1 hour; it possesses high hardness (≥6H for 1000g pencil hardness); high wear resistance (≥300 cycles for 150g RCA paper tape abrasion); and good chemical resistance (≥4B adhesion after 48 hours of salt spray); and it can be tinted to produce different color effects, such as black, white, silver, and gold. The UV coating of this invention features simple processing, high efficiency, energy saving, and environmental friendliness.

[0015] According to some embodiments of the present invention, the raw materials for preparation, by weight, include:

[0016] UV-curable resin: 30-40 parts

[0017] Active monomer: 5-10 parts

[0018] Thermoplastic acrylic resin: 5-10 parts

[0019] Photoinitiator: 1-4 parts

[0020] Adhesion promoter: 1-4 parts

[0021] Substrate wetting agent: 0.2-0.5 parts,

[0022] Ethyl acetate: 10-20 parts

[0023] Butyl acetate: 10-20 parts

[0024] Fumed silica: 1-5 parts

[0025] Polyamide wax antisettling slurry: 1-5 parts,

[0026] Pigment: 5-10 parts

[0027] Matte powder: 0-5 parts.

[0028] For UV curing, a combination of low-functionality and high-functionality resins is used. The low-functionality resin is a 2-3 functional group epoxy-modified acrylic resin with good adhesion to metals, ensuring adhesion of the coating to the micro-arc oxidation substrate while adjusting the film's flexibility. The micro-arc oxidation substrate has high hardness, requiring a film hardness of 6H or higher. The coating cannot be too hard, otherwise, it is prone to cross-cutting defects. Therefore, a flexible resin is added to adjust the flexibility and improve the coating's resilience. The high-functionality resin is a 6-12 functional group polyurethane acrylic resin, which has good reactivity and high cross-linking density, improving the film's chemical resistance and abrasion resistance, while ensuring deep curing and improving film adhesion.

[0029] According to some embodiments of the present invention, the active monomer includes dipentaerythritol hexaacrylate resin, which has high functionality and good reactivity, and can enhance the reactivity of color-added UV coatings, ensure deep curing of the coating, and thus ensure the adhesion of the paint film.

[0030] According to some embodiments of the present invention, the Tg value of the thermoplastic acrylic resin is between 80 and 120°C.

[0031] According to some embodiments of the present invention, the molecular weight of the thermoplastic acrylic resin is 100,000 to 200,000.

[0032] Choose a high-molecular-weight thermoplastic acrylic resin with a Tg value between 80-120℃ and a molecular weight between 100,000 and 200,000. During paint film curing, this reduces volume shrinkage, lowers shrinkage stress, and improves adhesion. Simultaneously, the good solvent release and thixotropic properties of thermoplastic acrylic resins can improve paint film defects such as edge accumulation and sagging during application.

[0033] Photoinitiators absorb UV energy, generate free radicals, and thus initiate the polymerization, cross-linking, and curing of monomer compounds.

[0034] According to some embodiments of the present invention, the adhesion promoter comprises trifunctional phosphate methacrylate. This can improve the adhesion of the coating when boiled in water. It is necessary to select an adhesion promoter with high functionality and good reactivity to ensure that the adhesion promoter can participate in the reaction in UV dyeing, thereby improving adhesion. Otherwise, a slow reaction rate or incomplete reaction may lead to blistering when boiled in water.

[0035] The surface of micro-arc oxidation substrates has a microporous structure. After coating is applied, tiny microbubbles easily remain on the substrate surface. During boiling water tests, the air inside these microbubbles expands and contracts with temperature changes, causing the paint film to blister. Adding a substrate wetting agent improves the wettability of the coating to the substrate. When the coating is applied to the substrate surface, it ensures good wetting of the microporous structure, guaranteeing the filling of the micropores and expelling air from them. This solves the blistering problem during boiling water tests and also anchors the coating to the substrate, improving the adhesion of the coating on the micro-arc oxidation substrate.

[0036] The surface of fumed silica contains a large number of hydroxyl groups, which allow silica particles to be linked together through hydrogen bonding to form a three-dimensional network structure. This can prevent the agglomeration and sedimentation of pigments and silver beads in the coating, thereby improving the storage stability of the coating.

[0037] Polyamide wax is a thixotropic additive that forms a network structure in coatings, exhibiting excellent thixotropic properties, anti-sagging properties, and anti-settling properties. It effectively prevents the agglomeration and sedimentation of color pastes and silver powder in coatings, ensuring the uniformity and storage stability of the coating, and improving the workability of the coating.

[0038] Pigments can be selected from color pastes, aluminum silver pastes, pearlescent powders, and other pigments to meet different customer requirements for appearance effects.

[0039] According to some embodiments of the present invention, the matting agent comprises silicon dioxide.

[0040] A second aspect of the present invention provides a method for preparing the UV coating of the first aspect of the present invention, comprising the following steps:

[0041] S1: The thermoplastic acrylic resin and butyl acetate are added to a dispersion vessel for dispersion to obtain dissolved thermoplastic acrylic resin;

[0042] S2: Dissolve the photoinitiator in ethyl acetate, add the dissolved thermoplastic acrylic resin, UV-curable resin, active monomer, substrate wetting agent, and adhesion promoter, and while dispersing, add the polyamide wax anti-settling slurry and fumed silica to obtain a dispersion, and grind the dispersion.

[0043] S3: Add the pigment and matting powder to the dispersion, and obtain the UV coating after dispersion.

[0044] One technical solution of the present invention relating to the preparation method of UV coating has at least the following beneficial effects:

[0045] The preparation method of the present invention does not require expensive equipment and complex process control, the reaction conditions are not harsh, the raw materials are readily available, the production cost is low, and it is easy to industrialize.

[0046] In step S1:

[0047] Add thermoplastic acrylic resin and butyl acetate to a dispersion vessel and disperse at a speed of 800-1000 rpm until the resin is completely dissolved.

[0048] In step S2:

[0049] Dissolve the photoinitiator in ethyl acetate, then add the dissolved thermoplastic acrylic resin, UV-curable resin, reactive monomer, substrate wetting agent, and adhesion promoter. Disperse at 800-1000 rpm for 10 minutes. While dispersing, add polyamide wax anti-settling slurry and fumed silica, and disperse at 1000-1200 rpm for 30 minutes to prepare a dispersion. Transfer the dispersion to a grinder and grind to a fineness ≤5μm. Transfer the ground liquid to a dispersion vessel.

[0050] In step S3:

[0051] Pigment (silver paste is added after soaking in solvent for 30 minutes) can be added to the well-ground grinding slurry, and silica matting powder is added while dispersing. Then, the mixture is dispersed at a high speed of 1000-1200 rpm for 30 minutes to obtain a micro-arc oxidation substrate one-coat color-added UV coating.

[0052] A third aspect of the present invention provides a surface treatment layer, including a micro-arc oxidation treatment layer, wherein the surface of the micro-arc oxidation treatment layer is coated with a UV coating of the first aspect of the present invention.

[0053] One of the technical solutions of the present invention concerning the surface treatment layer has at least the following beneficial effects:

[0054] The surface treatment layer provided by the present invention, comprising a micro-arc oxidation treatment layer and a coated UV coating, has the following beneficial effects:

[0055] Micro-arc oxidation can form a dense ceramic layer on the metal surface, providing better adhesion for UV coatings. After applying UV coatings, the adhesion of the coating can be further enhanced, ensuring that the coating is not easily peeled off or worn under external forces or harsh environments.

[0056] The micro-arc oxidation treatment layer has good corrosion resistance, while the UV coating itself has good chemical resistance (such as salt spray resistance, damp heat resistance, etc.). The combination of the two makes the surface treatment layer have stronger oxidation and corrosion resistance, effectively improving the durability of the metal substrate, and is especially suitable for metal items exposed to corrosive environments.

[0057] The micro-arc oxidation layer itself has high hardness and wear resistance, while the UV coating can also provide high hardness and wear resistance after curing. In particular, when the coating hardness reaches 6H, it can effectively resist scratches and wear, and increase the service life of the product.

[0058] After applying UV coating, the color effect can be adjusted (such as black, white, silver, gold, etc.), so that the metal surface not only has functional protection, but also meets consumers' diverse needs for appearance, providing personalized and differentiated aesthetic effects.

[0059] Compared to traditional hot-baking coatings, UV coatings offer a more energy-efficient and environmentally friendly curing process, reducing energy consumption and the emission of harmful substances. Furthermore, UV coatings have a lower content of volatile organic compounds (VOCs), which helps reduce environmental pollution and meets modern green environmental protection requirements.

[0060] By using low-temperature (50-60℃) baking followed by UV curing, the production cycle can be significantly shortened, energy consumption reduced, and the processing becomes more efficient and simpler. The simplicity of this process also helps improve production efficiency and reduce manufacturing costs.

[0061] After micro-arc oxidation treatment, the substrate surface is rough and has strong hydrophilicity, which can effectively react with UV coatings through physical and chemical processes, improving the adhesion and uniformity of the coating. This makes the surface treatment layer suitable for different types of metal substrates and meets a variety of application requirements.

[0062] Therefore, the surface treatment layer of the present invention, by combining the characteristics of micro-arc oxidation and UV coating, not only enhances the protective performance of the metal surface, but also improves its decorative properties, meeting the functional and aesthetic needs of different customers, while also having the advantages of simple process, environmental protection and energy saving.

[0063] According to some embodiments of the present invention, the thickness of the coating formed by the UV coating is 15-20 micrometers.

[0064] A fourth aspect of the present invention provides a method for preparing a surface treatment layer according to the third aspect of the present invention, comprising the following steps:

[0065] After coating the surface of the micro-arc oxidation treatment layer with the UV coating of the first aspect of the present invention, it is baked at 50-60°C for 3-5 minutes and then transferred to a UV oven for curing.

[0066] One technical solution of the present invention relating to a method for preparing a surface treatment layer has at least the following beneficial effects:

[0067] Baking at 50-60℃ for 3-5 minutes is considered low-temperature baking. Compared with the high energy consumption and low efficiency of existing high-temperature baking processes for coatings, the curing process of the UV coating of this invention has the characteristics of energy saving, environmental protection and high efficiency.

[0068] According to some embodiments of the present invention, the UV energy of the curing treatment is 1000-2000 mJ / cm. 2 .

[0069] According to some embodiments of the present invention, the UV light intensity of the curing treatment is >150mW / cm². 2 .

[0070] Firstly, in additive UV coatings, the added color is pigment. Pigments absorb and block light, affecting UV penetration. When the UV light intensity is insufficient, its penetration is also insufficient, preventing it from reaching the bottom of the coating and thus failing to stimulate the coating's reaction, thereby affecting the coating's adhesion and other properties. While energy can be increased by extending the time and increasing light intensity, the effect of increased energy is not equivalent to the effect of increased light intensity.

[0071] According to some embodiments of the present invention, if the coating viscosity is high, it needs to be diluted with a thinner before being applied by air spraying.

[0072] The fifth aspect of the present invention provides the application of the surface treatment layer of the third aspect of the present invention in 3C products.

[0073] The present invention relates to a technical solution for the application of surface treatment layers in 3C products, which has at least the following beneficial effects:

[0074] 3C products are often subjected to frequent friction and impacts, such as the outer casings of mobile phones, laptops, and headphones. The ceramic layer formed by micro-arc oxidation and the high hardness of the UV coating work together to give the surface very high wear resistance, effectively resisting scratches and wear in daily use and extending the product's lifespan.

[0075] Micro-arc oxidation treatment can form a dense oxide layer on the metal surface, effectively preventing oxidation and corrosion. Combined with the anti-corrosion function of UV coatings, it enhances the corrosion resistance of 3C products in humid, high-temperature, or salt spray environments, ensuring the long-term stability of the products.

[0076] The casings of 3C products typically require multiple layers of protective coatings (such as paint, electroplating, etc.), making adhesion crucial. Micro-arc oxidation treatment can form a uniform base on the metal surface, enhancing the adhesion between the coating and the metal substrate and preventing problems caused by coating peeling or detachment during use. After UV curing, the adhesion of UV coatings is further enhanced, making them particularly suitable for application on plastic and metal surfaces, ensuring that the coating will not peel, fade, or blister during long-term use.

[0077] 3C products have high requirements for appearance, and consumers pursue more refined and personalized aesthetics. UV coatings can be adjusted to different color effects (such as black, silver, gold, etc.), providing a wide range of color choices for 3C products and meeting the market's demand for differentiated products. The micro-arc oxidation layer itself has a good texture, and its combination with UV coatings can enhance the gloss and visual effect of the product surface, making the product not only highly functional but also more attractive in appearance.

[0078] 3C products are easily scratched or bumped by sharp objects during daily use, especially mobile phone screens and laptop casings. The high hardness of UV coatings (e.g., pencil hardness ≥6H) effectively improves the coating's scratch resistance, preventing scratches from affecting the product's appearance and function. UV coatings themselves have strong UV resistance, effectively preventing aging, fading, and surface damage under sunlight. This is especially important for 3C products frequently exposed to sunlight (such as smartwatches, headphones, and phone cases), as it can slow down the aging process and maintain their color and appearance for a longer period.

[0079] The process of using low-temperature (50-60℃) baking followed by UV curing can significantly shorten the production cycle. Compared with traditional high-temperature baking or electroplating processes, it saves a lot of energy consumption and improves production efficiency. This is especially important for the mass production of 3C products, helping to reduce manufacturing costs and enhance market competitiveness.

[0080] 3C products face increasingly stringent environmental requirements, and low VOC (volatile organic compound) emissions meet modern environmental standards. 3C products employing this coating process not only comply with environmental requirements and reduce harmful gas emissions, but also enhance corporate social responsibility. Reducing energy consumption and improving production efficiency through energy-saving processes not only helps lower production costs but also aligns with the concept of sustainable development.

[0081] 3C products are frequently exposed to various chemicals in daily life (such as detergents, hand oil, fingerprints, sweat, etc.). UV coatings have good chemical resistance, effectively preventing these substances from corroding and damaging the product surface, keeping the surface clean and glossy. For 3C products with high waterproof requirements, such as smartphones, smartwatches, and sports headphones, the combination of micro-arc oxidation layer and UV coating can effectively prevent moisture penetration, protect internal circuits from moisture damage, and enhance the product's waterproof performance.

[0082] Therefore, the application of the surface treatment layer (micro-arc oxidation + UV coating) of this invention in 3C products can significantly improve the product's durability, appearance quality, corrosion resistance, scratch resistance, and chemical resistance. At the same time, this process is environmentally friendly, energy-saving, and simple, making it very suitable for the efficient production and market demands of modern 3C products. It not only enhances the overall performance and aesthetics of the product but also meets consumers' needs for high quality, cost-effectiveness, and personalization. Detailed Implementation

[0083] The following are specific embodiments of the present invention, and the technical solutions of the present invention will be further described in conjunction with the embodiments, but the present invention is not limited to these embodiments.

[0084] In a first aspect, some embodiments of the present invention provide a UV coating, the raw materials of which include ultraviolet curable resin, active monomer, thermoplastic acrylic resin, photoinitiator, adhesion promoter, substrate wetting agent, ethyl acetate, butyl acetate, fumed silica, polyamide wax antisettling paste, pigment and matting powder.

[0085] Existing conventional paint baking methods allow for the addition of color because it doesn't affect the paint's curing. However, for UV-cured paints, pigments absorb light, which affects the curing process, leading to difficulties in curing existing UV paints after color addition. This invention's UV paint, by increasing UV light intensity, reduces the impact of pigment light absorption on UV curing, achieving appropriate color addition. This invention, by increasing light intensity, improves the color addition ratio, resulting in superior colorability and opacity compared to existing technologies.

[0086] This invention provides a color-adding one-coat UV coating that can ensure good adhesion on micro-arc oxidation treated substrates, protect metal surfaces, and provide different color effects to meet the diverse and differentiated needs of customers.

[0087] The UV coating of this invention requires only baking at 50-60℃ for 3-5 minutes, followed by UV curing, to obtain a UV protective layer with high hardness, high wear resistance, and good chemical resistance. It exhibits good adhesion to micro-arc oxidation substrates, maintaining an adhesion ≥4B after boiling at 85℃ for 1 hour; it possesses high hardness (≥6H for 1000g pencil hardness); high wear resistance (≥300 cycles for 150g RCA paper tape abrasion); and good chemical resistance (≥4B adhesion after 48 hours of salt spray); and it can be tinted to produce different color effects, such as black, white, silver, and gold. The UV coating of this invention features simple processing, high efficiency, energy saving, and environmental friendliness.

[0088] In conjunction with the first aspect, in some embodiments of the present invention, the raw materials, by weight, include:

[0089] UV-curable resin: 30-40 parts

[0090] Active monomer: 5-10 parts

[0091] Thermoplastic acrylic resin: 5-10 parts

[0092] Photoinitiator: 1-4 parts

[0093] Adhesion promoter: 1-4 parts

[0094] Substrate wetting agent: 0.2-0.5 parts,

[0095] Ethyl acetate: 10-20 parts

[0096] Butyl acetate: 10-20 parts

[0097] Fumed silica: 1-5 parts

[0098] Polyamide wax antisettling slurry: 1-5 parts,

[0099] Pigment: 5-10 parts

[0100] Matte powder: 0-5 parts.

[0101] For UV curing, a combination of low-functionality and high-functionality resins is used. The low-functionality resin is a 2-3 functional group epoxy-modified acrylic resin with good adhesion to metals, ensuring adhesion of the coating to the micro-arc oxidation substrate while adjusting the film's flexibility. The micro-arc oxidation substrate has high hardness, requiring a film hardness of 6H or higher. The coating cannot be too hard, otherwise, it is prone to cross-cutting defects. Therefore, a flexible resin is added to adjust the flexibility and improve the coating's resilience. The high-functionality resin is a 6-12 functional group polyurethane acrylic resin, which has good reactivity and high cross-linking density, improving the film's chemical resistance and abrasion resistance, while ensuring deep curing and improving film adhesion.

[0102] In conjunction with the first aspect, in some embodiments of the present invention, the active monomer includes dipentaerythritol hexaacrylate resin, which has high functionality and good reactivity, and can enhance the reactivity of color-added UV coatings, ensuring deep curing of the coating and thus ensuring the adhesion of the paint film.

[0103] In conjunction with the first aspect, in some embodiments of the present invention, the Tg value of the thermoplastic acrylic resin is between 80 and 120°C.

[0104] In conjunction with the first aspect, in some embodiments of the present invention, the molecular weight of the thermoplastic acrylic resin is 100,000 to 200,000.

[0105] Choose a high-molecular-weight thermoplastic acrylic resin with a Tg value between 80-120℃ and a molecular weight between 100,000 and 200,000. During paint film curing, this reduces volume shrinkage, lowers shrinkage stress, and improves adhesion. Simultaneously, the good solvent release and thixotropic properties of thermoplastic acrylic resins can improve paint film defects such as edge accumulation and sagging during application.

[0106] Photoinitiators absorb UV energy, generate free radicals, and thus initiate the polymerization, cross-linking, and curing of monomer compounds.

[0107] In conjunction with the first aspect, in some embodiments of the present invention, the adhesion promoter includes trifunctional phosphate methacrylate. This can improve the adhesion of the coating when boiled in water. It is necessary to select an adhesion promoter with high functionality and good reactivity to ensure that the adhesion promoter can participate in the reaction in the UV dyeing process, thereby improving adhesion. Otherwise, a slow reaction rate or incomplete reaction may lead to blistering when boiled in water.

[0108] The surface of micro-arc oxidation substrates has a microporous structure. After coating is applied, tiny microbubbles easily remain on the substrate surface. During boiling water tests, the air inside these microbubbles expands and contracts with temperature changes, causing the paint film to blister. Adding a substrate wetting agent improves the wettability of the coating to the substrate. When the coating is applied to the substrate surface, it ensures good wetting of the microporous structure, guaranteeing the filling of the micropores and expelling air from them. This solves the blistering problem during boiling water tests and also anchors the coating to the substrate, improving the adhesion of the coating on the micro-arc oxidation substrate.

[0109] The surface of fumed silica contains a large number of hydroxyl groups, which allow silica particles to be linked together through hydrogen bonding to form a three-dimensional network structure. This can prevent the agglomeration and sedimentation of pigments and silver beads in the coating, thereby improving the storage stability of the coating.

[0110] Polyamide wax is a thixotropic additive that forms a network structure in coatings, exhibiting excellent thixotropic properties, anti-sagging properties, and anti-settling properties. It effectively prevents the agglomeration and sedimentation of color pastes and silver powder in coatings, ensuring the uniformity and storage stability of the coating, and improving the workability of the coating.

[0111] Pigments can be selected from color pastes, aluminum silver pastes, pearlescent powders, and other pigments to meet different customer requirements for appearance effects.

[0112] In conjunction with the first aspect, in some embodiments of the present invention, the matting agent comprises silicon dioxide.

[0113] In a second aspect, some embodiments of the present invention provide a method for preparing the UV coating of the first aspect of the present invention, comprising the following steps:

[0114] S1: Thermoplastic acrylic resin and butyl acetate are added to a dispersion vessel and dispersed to obtain dissolved thermoplastic acrylic resin;

[0115] S2: Dissolve the photoinitiator in ethyl acetate, add dissolved thermoplastic acrylic resin, UV-curable resin, active monomer, substrate wetting agent, and adhesion promoter, and while dispersing, add polyamide wax anti-settling slurry and fumed silica to obtain a dispersion, and grind the dispersion.

[0116] S3: Add pigment and matting agent to the dispersion, and obtain UV coating after dispersion.

[0117] It is easy to understand that the preparation method of the present invention does not require expensive equipment and complex process control, the reaction conditions are not harsh, the raw materials are readily available, the production cost is low, and it is easy to industrialize.

[0118] In step S1:

[0119] Add thermoplastic acrylic resin and butyl acetate to a dispersion vessel and disperse at a speed of 800-1000 rpm until the resin is completely dissolved.

[0120] In step S2:

[0121] Dissolve the photoinitiator in ethyl acetate, then add the dissolved acrylic resin, UV-curable resin, reactive monomer, substrate wetting agent, and adhesion promoter. Disperse at 800-1000 rpm for 10 minutes. While dispersing, add polyamide wax anti-settling slurry and fumed silica, and disperse at 1000-1200 rpm for 30 minutes to prepare a dispersion. Transfer the dispersion to a grinder and grind to a fineness ≤5μm. Transfer the ground liquid to a dispersion vessel.

[0122] In step S3:

[0123] Pigment (silver paste is added after soaking in solvent for 30 minutes) can be added to the well-ground grinding slurry, and silica matting powder is added while dispersing. Then, the mixture is dispersed at a high speed of 1000-1200 rpm for 30 minutes to obtain a micro-arc oxidation substrate one-coat color-added UV coating.

[0124] In a third aspect, some embodiments of the present invention provide a surface treatment layer, including a micro-arc oxidation treatment layer, the surface of which is coated with the UV coating of the first aspect of the present invention.

[0125] It is understood that the surface treatment layer provided by the present invention, including the micro-arc oxidation treatment layer and the coated UV coating, has the following beneficial effects:

[0126] Micro-arc oxidation treatment can form dense ceramic micropores on the metal surface. This microporous structure allows the coating to anchor itself to the metal oxide layer, increasing adhesion. This provides better adhesion for UV coatings. Applying UV coatings further enhances the coating's bonding strength, ensuring it is less prone to peeling or wear under external forces or harsh environments.

[0127] The micro-arc oxidation treatment layer has good corrosion resistance, while the UV coating itself has good chemical resistance (such as salt spray resistance, damp heat resistance, etc.). The combination of the two makes the surface treatment layer have stronger oxidation and corrosion resistance, effectively improving the durability of the metal substrate, and is especially suitable for metal items exposed to corrosive environments.

[0128] The micro-arc oxidation layer itself has high hardness and wear resistance, while the UV coating can also provide high hardness and wear resistance after curing. In particular, when the coating hardness reaches 6H, it can effectively resist scratches and wear, and increase the service life of the product.

[0129] After applying UV coating, the color effect can be adjusted (such as black, white, silver, gold, etc.), so that the metal surface not only has functional protection, but also meets consumers' diverse needs for appearance, providing personalized and differentiated aesthetic effects.

[0130] Compared to traditional hot-baking coatings, UV coatings offer a more energy-efficient and environmentally friendly curing process, reducing energy consumption and the emission of harmful substances. Furthermore, UV coatings have a lower content of volatile organic compounds (VOCs), which helps reduce environmental pollution and meets modern green environmental protection requirements.

[0131] By using low-temperature (50-60℃) baking followed by UV curing, the production cycle can be significantly shortened, energy consumption reduced, and the processing becomes more efficient and simpler. The simplicity of this process also helps improve production efficiency and reduce manufacturing costs.

[0132] After micro-arc oxidation treatment, the substrate surface is rough and has strong hydrophilicity, which can effectively react with UV coatings through physical and chemical processes, improving the adhesion and uniformity of the coating. This makes the surface treatment layer suitable for different types of metal substrates and meets a variety of application requirements.

[0133] Therefore, the surface treatment layer of the present invention, by combining the characteristics of micro-arc oxidation and UV coating, not only enhances the protective performance of the metal surface, but also improves its decorative properties, meeting the functional and aesthetic needs of different customers, while also having the advantages of simple process, environmental protection and energy saving.

[0134] In conjunction with the third aspect, in some embodiments of the present invention, the thickness of the coating formed by the UV coating is 15-20 micrometers.

[0135] In a fourth aspect, some embodiments of the present invention provide a method for preparing a surface treatment layer according to the third aspect of the present invention, comprising the following steps:

[0136] After coating the surface of the micro-arc oxidation treatment layer with the UV coating of the first aspect of the present invention, bake it at 50-60°C for 3-5 minutes, and then transfer it to a UV oven for curing.

[0137] It should be noted that baking at 50-60℃ for 3-5 minutes is considered low-temperature baking, intended to allow the organic solvents (ethyl acetate and butyl acetate) to evaporate. These solvents do not participate in the reaction; their purpose is to facilitate application. Compared to existing high-temperature baking processes for coatings, which are energy-intensive and inefficient, the curing process of the UV coating of this invention is energy-saving, environmentally friendly, and highly efficient.

[0138] In conjunction with the fourth aspect, in some embodiments of the present invention, the UV energy for the curing treatment is 1000-2000 mJ / cm². 2 .

[0139] In conjunction with the fourth aspect, in some embodiments of the present invention, the UV light intensity of the curing treatment is >150mW / cm². 2 .

[0140] Firstly, in additive UV coatings, the added color is pigment. Pigments absorb and block light, affecting UV penetration. When the UV light intensity is insufficient, its penetration is also insufficient, preventing it from reaching the bottom of the coating and thus failing to stimulate the coating's reaction, thereby affecting the coating's adhesion and other properties. While energy can be increased by extending the time and increasing light intensity, the effect of increased energy is not equivalent to the effect of increased light intensity.

[0141] In conjunction with the fourth aspect, in some embodiments of the present invention, if the coating viscosity is high, it needs to be diluted with a thinner before being applied by air spraying.

[0142] In a fifth aspect, some embodiments of the present invention provide the application of the surface treatment layer of the third aspect of the present invention in 3C products.

[0143] It's understandable that 3C products typically experience frequent friction and impacts, such as the outer casings of mobile phones, laptops, and headphones. The ceramic layer formed by micro-arc oxidation and the high hardness of the UV coating work together to give the surface extremely high wear resistance, effectively resisting scratches and abrasions during daily use and extending the product's lifespan.

[0144] Micro-arc oxidation treatment can form a dense oxide layer on the metal surface, effectively preventing oxidation and corrosion. Combined with the anti-corrosion function of UV coatings, it enhances the corrosion resistance of 3C products in humid, high-temperature, or salt spray environments, ensuring the long-term stability of the products.

[0145] The casings of 3C products typically require multiple layers of protective coatings (such as paint, electroplating, etc.), making adhesion crucial. Micro-arc oxidation treatment can form a uniform base on the metal surface, enhancing the adhesion between the coating and the metal substrate and preventing problems caused by coating peeling or detachment during use. After UV curing, the adhesion of UV coatings is further enhanced, making them particularly suitable for application on plastic and metal surfaces, ensuring that the coating will not peel, fade, or blister during long-term use.

[0146] 3C products have high requirements for appearance, and consumers pursue more refined and personalized aesthetics. UV coatings can be adjusted to different color effects (such as black, silver, gold, etc.), providing a wide range of color choices for 3C products and meeting the market's demand for differentiated products. The micro-arc oxidation layer itself has a good texture, and its combination with UV coatings can enhance the gloss and visual effect of the product surface, making the product not only highly functional but also more attractive in appearance.

[0147] 3C products are easily scratched or bumped by sharp objects during daily use, especially mobile phone screens and laptop casings. The high hardness of UV coatings (e.g., pencil hardness ≥6H) effectively improves the coating's scratch resistance, preventing scratches from affecting the product's appearance and function. UV coatings themselves have strong UV resistance, effectively preventing aging, fading, and surface damage under sunlight. This is especially important for 3C products frequently exposed to sunlight (such as smartwatches, headphones, and phone cases), as it can slow down the aging process and maintain their color and appearance for a longer period.

[0148] The process of using low-temperature (50-60℃) baking followed by UV curing can significantly shorten the production cycle. Compared with traditional high-temperature baking or electroplating processes, it saves a lot of energy consumption and improves production efficiency. This is especially important for the mass production of 3C products, helping to reduce manufacturing costs and enhance market competitiveness.

[0149] With increasingly stringent environmental requirements for 3C products, UV coatings eliminate the need for solvents during curing and exhibit low VOC (volatile organic compound) emissions, meeting modern environmental standards. 3C products employing this coating process not only comply with environmental requirements and reduce harmful gas emissions but also enhance corporate social responsibility. Furthermore, reducing energy consumption and improving production efficiency through energy-saving processes not only helps lower production costs but also aligns with the principles of sustainable development.

[0150] 3C products are frequently exposed to various chemicals in daily life (such as detergents, hand oil, fingerprints, sweat, etc.). UV coatings have good chemical resistance, effectively preventing these substances from corroding and damaging the product surface, keeping the surface clean and glossy. For 3C products with high waterproof requirements, such as smartphones, smartwatches, and sports headphones, the combination of micro-arc oxidation layer and UV coating can effectively prevent moisture penetration, protect internal circuits from moisture damage, and enhance the product's waterproof performance.

[0151] Therefore, the application of the surface treatment layer (micro-arc oxidation + UV coating) of this invention in 3C products can significantly improve the product's durability, appearance quality, corrosion resistance, scratch resistance, and chemical resistance. At the same time, this process is environmentally friendly, energy-saving, and simple, making it very suitable for the efficient production and market demands of modern 3C products. It not only enhances the overall performance and aesthetics of the product but also meets consumers' needs for high quality, cost-effectiveness, and personalization.

[0152] The following will describe the concept and technical effects of the present invention clearly and completely with reference to embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.

[0153] In the description of this invention, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0154] Unless otherwise specified, "room temperature" in this invention means 25℃±5℃.

[0155] Unless otherwise specified, "about" in this invention means that the allowable error is within ±2%.

[0156] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0157] The types and manufacturers of raw materials used in the embodiments and comparative examples of the present invention are shown in Table 1.

[0158] Table 1

[0159] raw material Manufacturer model Photoinitiator 1 IGM Omnirad 1173 Photoinitiator 2 IGM Omnirad 819 Ethyl acetate / / Butyl acetate / / thermoplastic acrylic resin Boril MB-18-A UV-curable resin 1 Changxing Chemical 61967 UV-curable resin 2 Bahe New Materials BW 8288-2 Dipentaerythritol hexaacrylate Changxing Chemical EM266 Adhesion promoter Runao Chemical R9107 Substrate wetting agent 3M FC-4430 Polyamide wax Desparon 6900-HV Fumed silica Degussa A380 Silver paste / color paste Aika HP Z 1255IL Butyl acetate / / Silica matte powder Dong Cao K500

[0160] Example 1

[0161] Two UV coatings, A and B, were prepared. The raw materials are shown in Table 2, and the preparation methods are as follows:

[0162] S1: Thermoplastic acrylic resin and butyl acetate are added to a dispersion vessel and dispersed to obtain dissolved thermoplastic acrylic resin;

[0163] S2: Dissolve the photoinitiator in ethyl acetate, add dissolved thermoplastic acrylic resin, UV-curable resin, active monomer, substrate wetting agent, and adhesion promoter, and while dispersing, add polyamide wax anti-settling slurry and fumed silica to obtain a dispersion, and grind the dispersion.

[0164] S3: Add pigment and matting agent to the dispersion, and obtain UV coating after dispersion.

[0165] In step S1:

[0166] Add thermoplastic acrylic resin and butyl acetate to a dispersion vessel and disperse at a speed of 800-1000 rpm until the resin is completely dissolved.

[0167] In step S2:

[0168] Dissolve the photoinitiator in ethyl acetate, then add the dissolved acrylic resin, UV-curable resin, reactive monomer, substrate wetting agent, and adhesion promoter. Disperse at 800-1000 rpm for 10 minutes. While dispersing, add polyamide wax anti-settling slurry and fumed silica, and disperse at 1000-1200 rpm for 30 minutes to prepare a dispersion. Transfer the dispersion to a grinder and grind to a fineness ≤5μm. Transfer the ground liquid to a dispersion vessel.

[0169] In step S3:

[0170] Pigment (silver paste is added after soaking in solvent for 30 minutes) can be added to the well-ground grinding slurry, and silica matting powder is added while dispersing. Then, the mixture is dispersed at a high speed of 1000-1200 rpm for 30 minutes to obtain a micro-arc oxidation substrate one-coat color-added UV coating.

[0171] The use of photoinitiator 1173 and photoinitiator 819 in combination is to fully absorb ultraviolet light, improve initiation efficiency, and thus improve the curing effect of the coating's underlying layer.

[0172] The purpose of using a blend of UV-curable resin 1 and UV-curable resin 2 is to improve the overall reaction rate of the coating and enhance the curing effect of the underlying layer.

[0173] Comparative Example 1

[0174] Five UV contrast coatings, C to G, were prepared using raw materials as shown in Table 2. The preparation methods were the same as those used for the coatings in Example 1.

[0175] Table 2

[0176]

[0177]

[0178] Example 2

[0179] UV coatings A and B were prepared into coating A and coating B, and the process parameters are shown in Table 3.

[0180] Comparative Example 2

[0181] The UV contrast coatings C to G were prepared into coatings C to G, and the process parameters are shown in Table 3.

[0182] Table 3

[0183] Coating A Coating B Coating C Coating D Coating E Coating F Coating G dilution ratio 100:100 100:100 100:100 100:100 100:100 100:100 100:100 Baking temperature 60℃ 60℃ 60℃ 60℃ 60℃ 60℃ 60℃ Baking time 5 minutes 5 minutes 5 minutes 5 minutes 5 minutes 5 minutes 5 minutes UV curing light intensity 200 200 200 200 100 200 200 UV curing energy 1500 1500 1500 1500 1500 1500 1500

[0184] The thickness of coatings A to G is 16 micrometers.

[0185] Performance testing

[0186] The properties of coatings A through G were tested, including:

[0187] 1. Conventional adhesion: The adhesion test is conducted according to the method specified in GB / T 9826. 100 / 100 means that 10*10 grids were drawn on the coating, and no coating peeled off in any of the 100 grids after the test.

[0188] 2. Water resistance: Place in a constant temperature water bath at 85℃ for 1 hour, remove and wipe clean with a cloth, observe whether the paint film has discoloration, bubbling or other phenomena, and test the adhesion.

[0189] 3. RCA Abrasion Resistance: RCA paper bag abrasion tester (Norman Tool RCAAbrader), 175g load, record the number of times the paint film breaks. Samples and abrasive media should be placed in an environment of 23±2℃ and 50±10% relative humidity for 24 hours before testing.

[0190] 4. Hardness: Pencil hardness tester. Mitsubishi pencil, H, 750g (Japan).

[0191] 5. Stain resistance: Using a ZEBRA oil-based pen (model: MO-120-MC, fine tip test), with the pen at approximately a 90° angle to the coating surface, apply a force of approximately 1-2N to draw 5 lines of 5-10mm on the coating surface at a uniform speed. After standing at room temperature for 10 minutes, wipe the surface with alcohol (concentration ≥99.5%). There are no traces left after wiping.

[0192] 6. Chemical resistance test: Apply petroleum jelly to the surface of the paint film, and then place it in a constant temperature and humidity chamber (temperature 85℃, humidity 85%) for 96 hours. After taking it out, wipe it clean with a cloth and observe whether there are any discoloration, bubbling, or paint peeling phenomena in the paint film.

[0193] 7. Salt spray: Neutral salt spray, place for 96 hours, remove and wipe clean with a cloth, and observe whether the paint film has discoloration, bubbling, or peeling.

[0194] The test results are shown in Table 4.

[0195] Table 4

[0196]

[0197]

[0198] A comparison of coating A and coating C shows that adding a substrate wetting agent can ensure that the coating fully wets the microporous structure of the micro-arc oxidation substrate, ensuring that the coating fills the microporous structure, forming an anchoring effect, improving the adhesion of the coating on the micro-arc oxidation substrate, and improving the adhesion in boiling water.

[0199] A comparison of coating A and coating D shows that acid phosphate ester adhesion promoters form a stable bridge between the coating and the substrate through chemical bonding, improving the coating's adhesion and water resistance.

[0200] A comparison of coating B and coating E shows that the higher the UV curing light intensity, the higher the UV penetration ability, which can improve the deep curing effect of the color-added UV coating, thereby improving the adhesion and water resistance of the coating.

[0201] A comparison of coatings B and F shows that the combined use of photoinitiators can improve the utilization rate of UV energy, enhance the curing effect of the coating, and thus improve the coating's wear resistance, water resistance, and other properties.

[0202] Comparing coating B and coating G, it can be seen that UV-curing resin 1 is a high-functionality resin (6-12 functional groups), while UV-curing resin 2 is a low-functionality resin (2-3 functional groups). Introducing high-functionality UV resin into the formulation can improve the overall reaction rate of the coating, improve the deep curing effect of the color-added UV coating, and thus improve the wear resistance and water resistance of the paint film.

[0203] It should also be noted that existing one-coat color-adding UV coatings are mainly suitable for plastic substrates. Plastic substrates are easily swollen by solvents and easily attracted by active monomers, forming an anchoring effect, thus adhesion is easily solved. However, metal surfaces have high hardness and are not easily attracted, making coating adhesion more difficult. Currently, the color after micro-arc oxidation of substrates is generally grayish-white. If it is necessary to produce colors that are significantly different from white, such as black, blue, or red, the substrate is prone to showing through, which is not conducive to color control. This invention controls the UV light intensity at 150mW / cm². 2 In summary, even with the color addition ratio of UV coatings increased to 5-10%, the deep curing effect of the coating can still be guaranteed, as well as the coverage and vibrancy of the coating appearance. It also facilitates color control during the production process.

[0204] The present invention has been described in detail above with reference to the embodiments. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A surface treatment layer, characterized by, The micro-arc oxidation treatment layer is coated with a UV coating on the surface; The raw materials for preparing the UV coating include ultraviolet curing resin, active monomer, thermoplastic acrylic resin, photoinitiator, adhesion promoter, substrate wetting agent, ethyl acetate, butyl acetate, fumed silica, polyamide wax anti-settling slurry, pigment and flatting powder; The ultraviolet curing resin is composed of 2-3 functional group epoxy modified acrylic resin and 6-12 functional group polyurethane acrylic resin; The photoinitiator is a compound of photoinitiator 1173 and photoinitiator 819; The surface treatment layer is prepared by the following steps: After the UV coating is coated on the surface of the micro-arc oxidation treatment layer, it is baked at 50-60℃ for 3-5min and then cured in a UV oven; the UV energy for the curing treatment is 1000-2000mJ / cm²; the UV light intensity for the curing treatment is >150mW / cm².

2. The surface treatment layer according to claim 1, characterized in that, The raw materials for preparing the UV coating include, by weight: Ultraviolet curing resin: 30-40 parts, Active monomer: 5-10 parts, Thermoplastic acrylic resin: 5-10 parts, Photoinitiator: 1-4 parts, Adhesion promoter: 1-4 parts, Substrate wetting agent: 0.2-0.5 parts, Ethyl acetate: 10-20 parts, Butyl acetate: 10-20 parts, Fumed silica: 1-5 parts, Polyamide wax anti-settling slurry: 1-5 parts, Pigment: 5-10 parts, Flatting powder: 0-5 parts.

3. The surface treatment layer according to claim 1 or 2, characterized in that, The active monomer includes di-pentaerythritol hexaacrylate resin.

4. The surface treatment layer according to claim 1 or 2, characterized by The Tg value of the thermoplastic acrylic resin is 80-120℃; and / or, the molecular weight of the thermoplastic acrylic resin is 100-200 thousand.

5. The surface treatment layer according to claim 1 or 2, characterized by The adhesion promoter includes trifunctional methacrylic acid phosphate ester.

6. The surface treatment layer according to claim 1 or 2, characterized by The flatting powder includes silicon dioxide.

7. The surface treatment layer according to claim 1 or 2, characterized by The preparation method of the UV coating includes the following steps: S1: the thermoplastic acrylic resin and butyl acetate are added into a dispersion kettle for dispersion to obtain dissolved thermoplastic acrylic resin; S2: the photoinitiator is dissolved in ethyl acetate, and the dissolved thermoplastic acrylic resin, ultraviolet curing resin, active monomer, substrate wetting agent and adhesion promoter are added, while the polyamide wax anti-settling slurry and fumed silica are added for dispersion, to obtain a dispersion liquid which is grinded; S3: the pigment and flatting powder are added into the dispersion liquid, and the UV coating is obtained after dispersion.

8. Application of the surface treatment layer of any one of claims 1-7 in 3C products.

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