A mirror-leveling UV coating and its preparation method and application

Abstract

The present invention discloses a mirror-leveling UV coating, a preparation method, and applications thereof. The mirror-leveling UV coating can be used in the preparation process of electronic product housings and comprises: 30-45 parts of a hydroxyl-containing aliphatic polyurethane acrylate, 8-15 parts of a polycarbonate polyurethane acrylate, 3-5 parts of a high-functionality polyurethane acrylate, 3-5 parts of an electroplated silver resin, 2-5 parts of a photoinitiator, 1-2 parts of a leveling agent, and 35-45 parts of a diluent. The mirror-leveling UV coating of the present invention suppresses the generation of a surface tension gradient between the edge and the middle of the workpiece during the flash-drying process, effectively improving the edge buildup phenomenon. Furthermore, it achieves excellent leveling, moisture and heat resistance, toughness, and other properties. The preparation process is simple, the requirements for production equipment are low, and it is suitable for large-scale industrial production. A perfect mirror-leveling coating without edge buildup can be directly obtained on the surface of the electronic device housing. Compared with existing processes, the process complexity and production cost are significantly reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of coatings, and in particular to a mirror-leveling UV coating, a preparation method thereof, and applications thereof. Background Art

[0002] To prevent paint buildup on the edges of workpieces like mobile phone midframes and achieve flawless coatings, our company has proposed in its invention patent CN116478585B a new, easily strippable coating and a process based on this coating that involves vacuum coating the PC mobile phone midframe material, followed by CNC edge coating, touch-up, and paint stripping. This coating and process have been successfully applied to a certain brand of mobile phone terminals. However, in actual production, these coatings and processes still present the following technical issues: a high defective rate of vacuum-plated topcoat scratches after paint stripping, and high process costs, hindering product promotion.

[0003] Therefore, there is an urgent need to develop new products and methods to obtain coatings that meet performance requirements, reduce production costs, and improve economic benefits. Summary of the Invention

[0004] The present invention provides a mirror-leveling UV coating, a preparation method and an application thereof, which are used to solve the technical problems mentioned in the background art, such as low yield rate, complex use process and high cost of coatings formed by existing UV curing coatings.

[0005] In order to solve the above technical problems, the technical solution proposed by the present invention is:

[0006] A mirror-leveling UV coating comprises the following components in parts by weight:

[0007] 30~45 parts of hydroxyl-containing aliphatic polyurethane acrylate, 8~15 parts of polycarbonate polyurethane acrylate, 3~5 parts of high-functionality polyurethane acrylate, 3~5 parts of electroplating silver resin, 2~5 parts of photoinitiator, 1~2 parts of leveling agent and 35~45 parts of diluent.

[0008] The design concept of the above technical solution lies in the fact that the present invention studies the phenomenon of paint accumulation on the edges of workpieces (such as the right-angled edges of mobile phone midframes). This phenomenon is caused by a surface tension gradient, and the vapor pressure of the solvent is related to the liquid surface state. The vapor pressure of a convex surface is higher than that of a flat surface, and the smaller the radius of curvature of the convex surface, the greater the vapor pressure. At the right-angled edge of the midframe, the coating film has a relatively large specific surface area and a convex surface state with a small radius of curvature. Therefore, the solvent in this area often evaporates faster. If the surface tension of the solvent is lower than that of the system resin and pigment, then after the solvent in the paint film evaporates, the surface tension at the edge increases more than that in the interior, resulting in a gradient of gradually decreasing surface tension from the edge to the interior. The low surface tension portion in the middle flows to the high surface tension portion at the edge, causing the edge to thicken. On the one hand, the present invention suppresses the generation of surface tension gradients between the edge and the middle of the workpiece during the flash-drying process of the paint film by optimizing the combination of resins and additives, and uses a small amount of high-molecular-weight electroplated silver resin as a modifier to accelerate the flash-drying of the solvent in the wet film state of the coating, thereby effectively improving the edge buildup phenomenon. In addition, high-functionality polyurethane acrylate is used to increase the UV reaction speed and play an auxiliary curing role. Compared with the curing method of adding high-functional monomers to conventional coatings, the shrinkage is lower, the fluidity is worse, and it is less likely to cause edge buildup. On the other hand, the performance of the coating in all aspects is improved through resin combination - hydroxyl-containing aliphatic polyurethane acrylate is used as the main component of the resin system, and its advantages of excellent leveling and fullness, good plating properties and medium reaction speed are used to replace the high molecular weight difunctional plating resin in the existing traditional NCVM primer, solving the problems of poor leveling and slow reaction speed of the existing NCVM primer, and giving the coating a mirror leveling effect; at the same time, polycarbonate polyurethane acrylate is added as a supplement to the plating performance without affecting the leveling effect of the coating, and can also provide good moisture and heat resistance and toughness for the coating and the coating, and adjust the overall chemical resistance of the coating; and then combined with a specific amount of high-functionality polyurethane acrylate, without affecting the plating properties and hardness of the coating, it greatly improves the curing reaction rate of the coating.

[0009] As a further preferred embodiment of the above technical solution, the hydroxyl-containing aliphatic urethane acrylate has a functionality of 2 to 4, a hydroxyl value of 80 to 110 mgKOH / g, and a viscosity of 10,000 to 35,000 mPa·s / 25°C. Hydroxyl-containing aliphatic urethane acrylates with these parameters exhibit high solids, low viscosity, and excellent leveling properties, making them particularly suitable for the coating system of the present invention.

[0010] As a further preferred embodiment of the above technical solution, the high-functionality polyurethane acrylate has a functionality of 6 or 9 and a viscosity of 1000 Pa·s / 25°C. Polyurethane acrylates with these parameters can increase UV reaction speed, better assist in curing, and exhibit lower shrinkage, poorer fluidity, and less risk of edge buildup compared to conventional coating curing methods that incorporate high-functionality monomers.

[0011] As a further preferred embodiment of the above technical solution, the functionality of the polycarbonate polyurethane acrylate is 2. Polycarbonate polyurethane acrylate with a functionality of 2 has better plating properties when used as a primer resin, while too high a functionality will result in a hard paint film.

[0012] As a further preferred embodiment of the above technical solution, the TG point of the electroplating silver resin is 85-105°C. Electroplating silver resin is generally composed of cellulose and has a generally high TG point. When used in the UV system of the present invention, its high molecular weight can be utilized to achieve rapid surface drying of the coating and reduce edge buildup.

[0013] As a further preferred embodiment of the above technical solution, the leveling agent is a polydimethylsiloxane / polyether-modified polyacrylate. This leveling agent has both leveling and wetting functions, and can also adjust long- and short-wave leveling. Compared to commonly used leveling agents, the auxiliary ingredients are polyacrylate modified with silicone and polyether macromonomers. The polyether modification increases surface tension, while the silicone modification slightly reduces surface tension. The combination of the two does not affect the surface tension of the coating. Therefore, the coating film is less likely to form a surface tension gradient during solvent evaporation, effectively suppressing edge accumulation.

[0014] As a further preferred embodiment of the above technical solution, the photoinitiator includes at least one of 1-hydroxycyclohexyl phenyl ketone and benzophenone.

[0015] As a further preferred embodiment of the above technical solution, the diluent comprises the following components by weight: 10-15 parts ethyl acetate, 5-8 parts butyl acetate, 5-8 parts propylene glycol methyl ether acetate, and 3-5 parts diacetone alcohol. This diluent composition ensures that the surface tension of the diluent is greater than that of the other components, significantly reducing the surface tension gradient during solvent evaporation, thereby improving edge buildup. Furthermore, the diluent requires an evaporation gradient; either too fast or too slow can lead to paint film defects. The above diluent combination ensures that evaporation is neither too fast nor too slow.

[0016] Based on the same technical concept, the present invention also provides a method for preparing the above-mentioned mirror-leveling UV coating, comprising the following steps:

[0017] S1, mixing the photoinitiator with the first part of the diluent to obtain system A;

[0018] S2, mixing the hydroxyl-containing aliphatic polyurethane acrylate, polycarbonate polyurethane acrylate, high-functionality polyurethane acrylate and electroplating silver resin with the second part of the diluent to obtain system B;

[0019] S3. Add the system A to the system B, mix well, then add the leveling agent and the remaining diluent, and mix well to obtain the mirror leveling UV coating.

[0020] As a further preferred embodiment of the above technical solution, in S1, the mass ratio of the photoinitiator to the first part of the diluent is 1:3; in S2, the mass of the second part of the diluent accounts for 1 / 4 to 1 / 3 of the total mass of the diluent.

[0021] As a further preferred embodiment of the above technical solution, in S1, the photoinitiator is added to the diluent, soaked for 20 minutes, and then stirred and mixed for 10 to 15 minutes to obtain a mixed system A.

[0022] As a further preferred embodiment of the above technical solution, in S2, the hydroxyl-containing aliphatic polyurethane acrylate, polycarbonate polyurethane acrylate, high-functionality polyurethane acrylate and electroplating silver resin A are preheated and then mixed with the diluent, the preheating temperature is 60~70℃, and the preheating time is 3~4h; the mixing temperature is 40~50℃, the mixing stirring speed is 950~1050r / min, and the mixing time is 25~30min.

[0023] As a further preferred embodiment of the above technical solution, in S3, the mixing stirring speed of system A and system B is 500~600r / min, and the mixing time is 25~30min; after adding the leveling agent and diluent, the mixing speed is 500~600r / min, and the mixing time is 15~20min.

[0024] Based on the same technical concept, the present invention also provides an application of the mirror-leveling UV coating described in the above technical solution, wherein the mirror-leveling UV coating is used to form a coating on the surface of an electronic product housing.

[0025] As a further preferred embodiment of the above technical solution, the mirror-leveling UV coating is applied to the surface of the electronic product housing by vertical spraying. During the coating, the electronic product housing is placed vertically to the ground.

[0026] The present invention has the following beneficial effects:

[0027] (1) The mirror-leveling UV coating of the present invention suppresses the generation of a surface tension gradient between the edge and the middle of the workpiece during the flash-drying process of the paint film by optimizing the combination of resin, diluent, and additives, thereby effectively improving the edge accumulation phenomenon. On the other hand, it obtains other properties such as good leveling, moisture and heat resistance, and toughness, thereby obtaining a UV coating with a mirror-leveling effect, good tolerance, and toughness, which is not prone to edge accumulation at the edge of the workpiece.

[0028] (2) The preparation process of the mirror-leveling UV coating of the present invention is simple, has low requirements on production equipment, and is suitable for large-scale industrial production;

[0029] (3) The mirror-leveling UV coating of the present invention can be directly used for coating the housing of electronic equipment. By combining the coating with the vertical spray coating process, a perfect mirror-surface coating without edge accumulation can be directly obtained on the surface of the electronic equipment housing. Compared with the existing process, the complexity of the process and the production cost of this application are greatly reduced. DETAILED DESCRIPTION

[0030] The present invention will be described in detail below with reference to the embodiments thereof, but the present invention can be implemented in many different ways as defined and covered by the claims.

[0031] In some preferred embodiments of the present invention, the hydroxyl-containing aliphatic urethane acrylate has a functionality of 2-4 and a hydroxyl value of 80-110 mgKOH / g. It exhibits fast curing, excellent leveling and fullness, and excellent water boiling and weather resistance. When added in an amount of 30-45 parts by weight as the main resin in the system, it can achieve a mirror-like leveling effect in the paint film. The hydroxyl-containing aliphatic urethane acrylate is selected from one or more of Bahe New Materials' BW8214 and Wuxing New Materials' W2815 (BW8214 is selected in all examples).

[0032] In some preferred embodiments of the present invention, a high-functionality polyurethane acrylate resin with a viscosity of 1000-2000 mPa.s (25°C) and a functionality of 6 or 9 is added in an amount of 3-5 parts. This resin has a minimal effect on the surface hardness of the cured paint film and does not affect the plating properties of the primer, but significantly improves the primer's curing reaction rate. The high-functionality polyurethane acrylate resin is selected from one or more of Changxing Chemical's 6145-100 and Sartomer's CN9010NS (CN9010NS was selected in each example).

[0033] In some preferred embodiments of the present invention, polycarbonate polyurethane acrylate exhibits resistance to moisture, heat, and water boiling. Its functionality is difunctional, resulting in excellent flexibility, which can complement the main resin in improving the coating system's coating performance. When added in an amount of 8 to 15 parts by weight, it effectively adjusts the coating's toughness without affecting the coating's mirror leveling effect, while also improving the coating's environmental performance. The polycarbonate polyurethane acrylate is selected from one or more of Shanghai Difeng DF6372, Allnex 1114, Dongguan Fengjin FJ228, and Sartomer CN9001NS (CN9001NS was selected in each example).

[0034] In some preferred embodiments of the present invention, the electroplating silver resin has a high molecular weight and is primarily composed of cellulose resin. Its properties include accelerating solvent release from the paint film and good compatibility with UV systems. Its high molecular weight and poor fluidity effectively suppress edge buildup. The electroplating silver resin is selected from Shenzhen Xiyu A-308W.

[0035] In some embodiments of the present invention, the leveling agent is a polyether-silicone dual-modified polyacrylate, which combines leveling and wetting properties, can adjust long- and short-wave leveling, and does not affect the coating's surface tension. Therefore, the coating does not form a surface tension gradient during solvent evaporation, effectively suppressing edge buildup. The leveling agent was purchased from BYK, Germany, and is model number BYK-3558.

[0036] Example 1:

[0037] The mirror-leveling UV coating of this embodiment includes the components in parts by weight shown in Table 1.

[0038] The mirror-leveling UV coating of this embodiment is prepared by the following method:

[0039] S1. Add the photoinitiator to the first portion of the diluent (mass ratio of 1:3) and soak for 20 minutes, then stir and mix for 15 minutes to obtain System A.

[0040] S2. Preheat the hydroxyl-containing aliphatic polyurethane acrylate, polycarbonate polyurethane acrylate, high-functionality polyurethane acrylate, and electroplating silver resin to 70°C and maintain for 3–4 hours. Then, stir and mix with the second portion of diluent (1 / 3 of the total diluent mass) at 50°C and 1000 rpm for 30 minutes to obtain System B.

[0041] S3. Add system A to system B and mix at 600 r / min for 30 min;

[0042] S4. Add the leveling agent and the remaining diluent to the system obtained in step S3, and mix at 600 r / min for 20 min to obtain the mirror-leveling UV coating of this embodiment.

[0043] The mirror-leveling UV coating of this embodiment can be used to form a coating on the surface of an electronic product housing. The specific application method includes the following steps:

[0044] D1. Primer (SP100-00053 produced by Matsui Chemical) was sprayed on the surface of the electronic product. The coating method was vertical spraying (the material was perpendicular to the ground). The coating film thickness was 10 μm and leveled at 55°C for 6 minutes.

[0045] D2. Spray the mirror-leveling UV coating of this embodiment on the surface of the Primer after leveling. The coating method is vertical spraying (the material is perpendicular to the ground). The coating film thickness is 35μm. The Primer is leveled at 60℃ for 8 minutes. Then, the Primer is leveled at 800mJ / cm 2 Curing and drying under energy-efficient UV light;

[0046] D3. A vacuum coating process is performed on the dried vacuum coating primer. The coating material is indium, and the coating thickness is approximately 30 nm.

[0047] D4. Spray vacuum coating primer (SP120-20013-1 produced by Songjing Chemical Co., Ltd.) onto the coated surface of the vacuum coating primer. The coating method is flat spraying (the material is parallel to the ground). The coating film thickness is 7 μm and leveling is carried out at 65°C for 8 minutes. Then, the coating is sprayed at 500 mJ / cm 2 Curing and drying under energy-efficient UV light;

[0048] D5. Spray vacuum coating topcoat (SP130-30070 produced by Songjing Chemical Co., Ltd. was used in all examples) on the cured and dried vacuum coating midcoat. The coating method was flat spraying (the material was parallel to the ground). The coating film thickness was 25 μm. The coating was first leveled at 70°C for 8 minutes and then at 1200 mJ / cm 2 Curing under high energy UV light.

[0049] Example 2:

[0050] The mirror-leveling UV coating of this embodiment includes the components in parts by weight shown in Table 1.

[0051] The preparation method of the mirror-leveling UV coating of this embodiment is the same as that of Example 1.

[0052] The mirror-leveling UV coating of this embodiment can be used to form a coating on the surface of an electronic product housing, and the specific application method is the same as that of Example 1.

[0053] Example 3:

[0054] The mirror-leveling UV coating of this embodiment includes the components in parts by weight shown in Table 1.

[0055] The preparation method of the mirror-leveling UV coating of this embodiment is the same as that of Example 1.

[0056] The mirror-leveling UV coating of this embodiment can be used to form a coating on the surface of an electronic product housing, and the specific application method is the same as that of Example 1.

[0057] Example 4:

[0058] The mirror-leveling UV coating of this embodiment includes the components in parts by weight shown in Table 1.

[0059] The preparation method of the mirror-leveling UV coating of this embodiment is the same as that of Example 1.

[0060] The mirror-leveling UV coating of this embodiment can be used to form a coating on the surface of an electronic product housing, and the specific application method is the same as that of Example 1.

[0061] Example 5:

[0062] The mirror-leveling UV coating of this embodiment includes the components in parts by weight shown in Table 1.

[0063] The preparation method of the mirror-leveling UV coating of this embodiment is the same as that of Example 1.

[0064] The mirror-leveling UV coating of this embodiment can be used to form a coating on the surface of an electronic product housing, and the specific application method is the same as that of Example 1.

[0065] Example 6:

[0066] The mirror-leveling UV coating of this embodiment includes the components in parts by weight shown in Table 1.

[0067] The preparation method of the mirror-leveling UV coating of this embodiment is the same as that of Example 1.

[0068] The mirror-leveling UV coating of this embodiment can be used to form a coating on the surface of an electronic product housing, and the specific application method is the same as that of Example 1.

[0069] Table 1. Component ratios of the mirror-leveling UV coatings of Examples 1 to 6 (parts by mass)

[0070]

[0071] Comparative Example 1:

[0072] The coating of this comparative example differs from that of Example 6 only in that 10 parts by weight of a conventional 2-functionality coatable polyurethane acrylic resin (trade name: Japan Synthetic UV-3000B) is used to replace 10 parts by weight of the hydroxyl-containing aliphatic polyurethane acrylate of Example 6; the remaining component proportions, preparation methods, and application methods are the same as those of Example 6.

[0073] Comparative Example 2:

[0074] The coating of this comparative example differs from that of Example 6 only in that 5 parts by mass of the high-functionality polyurethane acrylate in Example 6 are replaced by 5 parts by mass of a high-functionality monomer (trade name: Sadomar SR399) in this comparative example, and the remaining component proportions, preparation methods, and application methods are the same as those in Example 6.

[0075] Comparative Example 3:

[0076] The coating of this comparative example differs from that of Example 6 only in that 2 parts by weight of a polyacrylate solution (trademark BYK358N) is used to replace 2 parts by weight of a polyether and silicone dual-modified polyacrylate additive in Example 6. The remaining component proportions, preparation methods, and application methods are the same as those of Example 6.

[0077] The coatings of each embodiment and comparative example were tested for their appearance leveling and edge buildup effects, high temperature and high humidity resistance, and cylindrical bending performance when applied to the middle frame of a smartphone. The test methods are as follows, and the specific results are shown in Table 2.

[0078] The leveling and edge accumulation effects are judged and compared visually.

[0079] High temperature and high humidity resistance test method: The product is placed in a 65°C, 95% RH environment for 168 hours. It is qualified if there is no obvious discoloration or blistering and the adhesion reaches 4B or above.

[0080] Cylindrical bending test method: Cut the workpiece to be tested into a flat sample and test the cracking size of the paint film. The diameters of the cylindrical shafts are 40mm and 50mm respectively.

[0081] Table 2. Performance test results of the paint films formed in various embodiments and comparative examples

[0082]

[0083] The results in Table 3 illustrate that the paint films obtained in Examples 1-6 achieved a balanced appearance with respect to leveling and edge buildup, thanks to the adjustment of the high-solids, low-viscosity system, the optimization of the surface tension gradient, and the combination of the vertical spraying process. Through the optimization of multiple factors, the desired results were achieved. The relatively poor cylindrical bending in Example 6 was due to the excessive amount of high-functional resin, which resulted in a relatively hard paint film.

[0084] Comparing Comparative Example 1 with Example 6, a conventional 2-functionality coatable polyurethane acrylic resin (trade name: Japan Synthetic UV-3000B) was used to partially replace the hydroxyl-containing aliphatic polyurethane acrylate in Example 6. The introduction of high molecular weight polyurethane affected the surface leveling effect of the primer, resulting in the appearance of fine orange stripes, demonstrating that conventional vacuum plating primer systems cannot meet the requirements of high leveling.

[0085] Compared with Example 6, Comparative Example 2 uses a high-functionality monomer (trade name Sadomar SR399) instead of the high-functionality polyurethane acrylate in Example 6, which increases the fluidity of the vacuum plating primer and accelerates the flow of the paint film during baking, resulting in edge accumulation.

[0086] Compared with Example 6, Comparative Example 3 uses a conventional polyacrylate solution (trademark number BYK358N) to replace the polyether and silicone dual-modified polyacrylate additives in Example 6. This has no effect on the short-wave leveling of the paint film, and there are small waves overall. In addition, the compatibility with the system is poor, and whitening is poor after high temperature and high humidity testing.

[0087] The above are only preferred embodiments of the present invention, and the scope of protection of the present invention is not limited to the above embodiments. For those skilled in the art, improvements and modifications obtained without departing from the technical concept of the present invention should also be considered as the scope of protection of the present invention.

[0088] Although embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A mirror leveling UV coating, characterized in that: It is composed of the following components in parts by mass: 30-45 parts of hydroxyl-containing aliphatic polyurethane acrylate, 8-15 parts of polycarbonate polyurethane acrylate, 3-5 parts of high-functionality polyurethane acrylate, 3-5 parts of electroplating silver resin, 2-5 parts of photoinitiator, 1-2 parts of leveling agent and 35-45 parts of diluent; The hydroxyl-containing aliphatic polyurethane acrylate has a functionality of 2 to 4, a hydroxyl value of 80 to 110 mgKOH / g, and a viscosity of 10,000 to 35,000 mPa·s / 25°C; the high-functionality polyurethane acrylate has a functionality of 6 or 9 and a viscosity of 1,000 Pa·s / 25°C; The leveling agent is polydimethylsiloxane / polyether modified polyacrylate.

2. The mirror-leveling UV coating according to claim 1, characterized in that: The functionality of the polycarbonate polyurethane acrylate is 2.

3. The mirror-leveling UV coating according to claim 1, characterized in that: The TG point of the electroplated silver resin is 85-105°C.

4. The mirror-leveling UV coating according to any one of claims 1 to 3, characterized in that: The photoinitiator includes at least one of 1-hydroxycyclohexyl phenyl ketone and benzophenone; the diluent is composed of the following components in parts by mass: 10 to 15 parts of ethyl acetate, 5 to 8 parts of butyl acetate, 5 to 8 parts of propylene glycol methyl ether acetate and 3 to 5 parts of diacetone alcohol.

5. A method for preparing the mirror-leveling UV coating according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1, mixing the photoinitiator with the first part of the diluent to obtain system A; S2, mixing the hydroxyl-containing aliphatic polyurethane acrylate, polycarbonate polyurethane acrylate, high-functionality polyurethane acrylate and electroplating silver resin with the second part of the diluent to obtain system B; S3. Add the system A to the system B, mix well, then add the leveling agent and the remaining diluent, and mix well to obtain the mirror leveling UV coating.

6. The method for preparing the mirror-leveling UV coating according to claim 5, characterized in that: In S1, the mass ratio of the photoinitiator to the first part of the diluent is 1:3; in S2, the mass of the second part of the diluent accounts for 1 / 4 to 1 / 3 of the total mass of the diluent.

7. The method for preparing the mirror-leveling UV coating according to claim 5, wherein: In S2, the hydroxyl-containing aliphatic polyurethane acrylate, polycarbonate polyurethane acrylate, high-functionality polyurethane acrylate and electroplating silver resin A are preheated and then mixed with the diluent, the preheating temperature is 60-70°C, and the preheating time is 3-4 hours; the mixing temperature is 40-50°C, the mixing stirring speed is 950-1050 r / min, and the mixing time is 25-30 minutes.

8. Use of the mirror-leveling UV coating according to any one of claims 1 to 4 or the mirror-leveling UV coating prepared by the preparation method according to any one of claims 5 to 7, characterized in that: The mirror-leveling UV coating is used to form a coating on the surface of the electronic product housing; The mirror-leveling UV coating is applied to the surface of the electronic product housing by vertical spraying. During the coating, the electronic product housing is placed vertically to the ground.

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