A process for manufacturing a mobile phone back cover

Abstract

The application discloses a process method for manufacturing a mobile phone back cover, and belongs to the technical field of 3C composite material back cover manufacturing. The method comprises the following steps: using 0.5mm PMMA+PC plate as a mother body, and performing nano-texture transfer printing, NCVM coating and cover bottom ink printing on the PC side of the mother body in sequence; using 2.0mm PMMA+PC plate as a child body, performing UV structural adhesive coating and hardening treatment on the PMMA surface of the child body, and attaching a high-temperature-resistant protective film to the camera area, the protective film is reserved during the subsequent CNC and grinding processes; aligning and attaching the PC surface of the child body to the PMMA surface of the mother body through UV structural adhesive, and performing vacuum pressing and synchronous UV curing to form an integrated blank; and then performing CNC fine milling of the transition arc of the attached interface, plane grinding to remove tool marks, and full-area excimer spraying in sequence, and finally tearing the film and curing to obtain the mobile phone back cover, wherein the main body is excimer skin-friendly matte, and the camera area is high-gloss wear-resistant. The application has the advantages of low material loss, high efficiency, high yield, excellent surface texture, and the like, and can realize differentiated effects, and is suitable for large-scale production.

Description

Technical Field

[0001] This disclosure relates to the field of 3C composite material back cover manufacturing technology, and more specifically, to a process method for manufacturing mobile phone back covers, which is particularly suitable for mass production to achieve a differentiated effect between the skin-friendly matte finish of the back cover body and the high-gloss, wear-resistant finish of the camera area. Background Technology

[0002] Currently, traditional mobile phone back covers generally use a single piece of thickened PMMA (polymethyl methacrylate) and PC (polycarbonate) composite co-extruded sheet, formed in one step by large-area CNC hollowing and precision milling. This existing process has the following significant drawbacks:

[0003] (1) The cutting amount of the whole plate is large, the raw material loss is extremely high, and the loss rate is usually over 60%; the CNC machining time is long, and the machining time for a single piece is 15 to 20 minutes; the tool wear is serious, and the manufacturing cost remains high.

[0004] (2) Performing overall CNC machining first, followed by texturing, coating, and ink application, can easily cause texture damage, coating scratches, and ink loss at the edges, resulting in a low appearance yield.

[0005] (3) CNC machining is prone to leaving tool marks and tool lines. Simple machining cannot achieve an extremely smooth appearance, and the surface texture and anti-fouling performance are insufficient.

[0006] (4) The stress concentration during the whole-board processing makes the finished product prone to warping and delamination, and it is difficult to achieve both surface hardness and wear resistance and weather resistance.

[0007] (5) Traditional processes are difficult to achieve different surface effects in different areas of the same back cover, and cannot simultaneously meet the user's dual needs for a skin-friendly feel on the main body and a high-gloss, wear-resistant finish on the camera area.

[0008] (6) The yield of traditional processes is generally only about 75%, and the combined costs of consumables, labor time, and defective products result in high overall production costs.

[0009] To address the shortcomings of existing technologies, this invention provides a novel manufacturing process that replaces whole-board CNC with split-part bonding. It optimizes material layering, pre-processing, vacuum curing, precision CNC transition, planar grinding, and partitioned surface treatment in all aspects, thus solving the drawbacks of traditional processes. Summary of the Invention

[0010] Overcoming the problems of existing whole-plate CNC molding, such as high material consumption, long processing time, low yield, easy damage to appearance, easy delamination of structure, difficulty in eliminating surface tool marks, poor texture, and inability to achieve differentiated surface effects, this paper provides a manufacturing process for mobile phone back covers that involves separate prefabrication, functional layering, vacuum pressing and UV curing, local CNC precision finishing, grinding to remove tool marks, and zoned surface treatment. This process reduces costs, improves efficiency, improves quality, achieves high yield, and upgrades the appearance and texture. It can also simultaneously present the skin-friendly effect of the main body excimer and the high-gloss and wear-resistant effect of the camera area.

[0011] A manufacturing process for a mobile phone back cover includes the following steps:

[0012] 1. Prefabrication of the matrix: PMMA+PC double-layer co-extruded composite board is selected as the matrix. Nano-texture transfer, NCVM vacuum coating and cover ink printing are performed sequentially on the PC side of the matrix.

[0013] 2. Subbody Prefabrication and Zoned Protection: PMMA+PC double-layer co-extruded composite sheet is selected as the subbody. The PMMA surface of the subbody is subjected to UV coating hardening treatment, and a high-temperature resistant protective film is attached to the camera area of ​​the subbody. The protective film is retained in the subsequent CNC precision machining and surface grinding process.

[0014] 3. Simultaneous curing of UV adhesive bonding and vacuum pressing: UV structural adhesive is used to align and bond the PC interface of the sub-body with the PMMA interface of the parent body. The bonding is then carried out simultaneously by vacuum negative pressure pressing and UV light irradiation to form an integral blank.

[0015] 4. CNC precision machining: The bonding interface of the integral blank is precision milled by CNC with transition arc, during which the protective film is retained.

[0016] 5. Surface grinding to remove tool marks: Perform full-area surface precision grinding on the CNC machined blank to remove CNC tool marks, while retaining the protective film.

[0017] 6. Zoned excimer spraying: The semi-finished product after grinding is coated with an excimer laser over the entire area. Then, the high-temperature protective film in the camera area is removed, and the product is dried and cured to obtain the finished product.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) The present invention adopts a separate prefabricated functional layer of mother body and daughter body to replace the traditional whole plate thick material full CNC hollowing molding; the raw material loss is reduced by 45% to 60% compared with the traditional method, the CNC processing time is shortened by more than 50%, the tool consumables loss is reduced by 40% to 55%, and the single-piece comprehensive production cost is reduced by 18% to 25%.

[0020] (2) The mother body completes texture transfer, NCVM coating and base ink in advance, and the daughter body is UV hardened in advance. All appearance and functional processes are carried out in advance to avoid scratches and damage to texture and film layers in later processing. The product yield rate is increased from the traditional 75% to more than 92%.

[0021] (3) Vacuum negative pressure pressing + synchronous UV curing is adopted, the bonding strength of the bonding interface is high (peel strength ≥15N / 25mm), there are no bubbles, no gaps, no misalignment, and no delamination or cracking during high and low temperature cycles (-40℃~85℃, 72h), and the overall structural stability is greatly improved.

[0022] (4) A new planar grinding process is added to completely eliminate CNC tool marks, with a surface roughness Ra≤0.2μm and extremely smooth surface; the end section is coated with excimer laser to greatly improve the back cover's anti-fouling, anti-fingerprint, and wear-resistant properties, while retaining the high-gloss transparency of the camera area to achieve a differentiated surface texture.

[0023] (5) The surface of the sub-body undergoes multiple hardening treatments, and the surface hardness of the main body can reach 2H or above, while the hardness of the camera area is 2H to 5H, resulting in excellent overall wear resistance and scratch resistance.

[0024] (6) The protective film is retained throughout the CNC and grinding process, which effectively prevents cutting chips and grinding slurry from contaminating or scratching the camera area, ensuring the stable realization of the high-gloss effect.

[0025] (7) The entire process has a clear division of labor and complete parameter boundaries, which can be standardized for mass production. It is suitable for large-scale production of mobile phone composite board back covers and can meet the current market demand for diversified and high-quality mobile phone back covers. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the overall appearance of the mobile phone back cover according to an embodiment of the present invention, showing the differentiated surface treatment effects of different areas of the back cover: the red area is the main body of the back cover, presenting an excimer-like skin-friendly matte effect; the yellow area is the camera decoration area, retaining a high-gloss and wear-resistant effect.

[0027] Figure 2 This is an exploded view of the mobile phone back cover structure according to an embodiment of the present invention.

[0028] Figure 3 This is a flowchart of the present invention.

[0029] The correspondence between the reference numerals and the names of the components in the attached drawings is as follows:

[0030] 1-Excimer layer; 2-Coated hardening layer; 3-Substitute PMMA layer; 4-Substitute PC layer; 5-UV adhesive bonding layer; 6-Main PMMA layer; 7-Main PC layer; 8-UV texture layer; 9-NCVM coating layer; 10-Cover ink layer. Detailed Implementation

[0031] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. It is understood that the specific embodiments described herein are only for explaining this application and not for limiting it. Furthermore, it should be noted that, for ease of description, only the parts related to this application are shown in the accompanying drawings, not all structures. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0032] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0033] Example: First, prefabrication of the substrate; a PMMA+PC double-layer co-extruded composite board with a thickness of 0.5mm±0.02mm is selected as the substrate, wherein the PMMA layer is 0.05mm thick and the PC layer is 0.45mm thick. The overall board size is 370mm×470mm, and the light transmittance of the PC raw material is ≥90%. Before all composite boards are processed online, they are placed in a Class 10,000 cleanroom under constant temperature and humidity (temperature 22~28℃, humidity 50%~65%) for more than 24 hours to release internal stress and prevent warping during subsequent processing.

[0034] Perform the following processes sequentially on the mother PC interface:

[0035] (1) Nanotexture transfer: The texture type is nano-optical brushed texture, the texture depth is 0.05mm, and the transfer line speed is 8m / min. The mercury lamp curing energy is 750mj / cm²; the texture did not fall off after the plant-based tape peel test.

[0036] Precautions: The mercury lamp energy must be strictly controlled. Too high an energy level (>1000 mj / cm²) will cause thermal deformation of the PMMA layer, while too low an energy level (450 mj / cm²) will result in poor texture adhesion and texture peeling. If the mercury lamp curing energy exceeds the set range, texture peeling or board warping may occur. The machine should be stopped immediately and the energy control system adjusted.

[0037] (2) NCVM vacuum coating: The coating material is a non-metallic conductive optical film with a thickness of 350 nm, a coating vacuum degree of 1.5 × 10⁻² Pa, and a coating rate of 0.8 nm / s. The adhesion of the film layer is >4B grade according to the cross-cut adhesion test.

[0038] Precautions: The PC surface must be plasma cleaned before coating to remove oil and dirt. If the vacuum level is insufficient (>3×10⁻²Pa), the film adhesion will decrease, and the cross-cut adhesion test may drop in grade (<4B). In this case, the vacuum must be re-exposed and the evacuation time extended.

[0039] (3) Printing of the base ink: Black opaque screen printing ink is used, the dry film thickness is 8μm, the baking temperature is 80℃, and the constant temperature baking time is 35min. The light transmittance of the finished product is ≤5%, the pencil hardness is 2H, and it can withstand 50 alcohol wipes without fading.

[0040] Precautions: The screen printing stencil must be accurately aligned to avoid ink seeping into the texture pits. Excessive baking temperature (>95℃) will cause the ink to become brittle and reduce its resistance to alcohol wiping (<30 times). In this case, reprinting and recalibrating the oven temperature are necessary.

[0041] Second, carry out sub-unit prefabrication and zoned protection.

[0042] A PMMA+PC double-layer co-extruded composite sheet with a thickness of 2.0mm±0.03mm was selected as the substrate, wherein the PMMA layer is 0.06mm thick and the PC layer is 1.94mm thick. The sheet has a bending strength ≥85MPa and a warpage ≤0.5mm / m².

[0043] (1) UV coating hardening treatment: UV liquid coating hardening treatment is performed on the surface of the PMMA substrate. A special wear-resistant UV hardening coating for PMMA is used, with a viscosity of 28 cps at 25℃; the dry film thickness is 10 μm, and the UV curing energy is 1100 mJ / cm². After curing, the pencil hardness is 5H, and there are no scratches after 300 cycles of rubbing with 500g steel wool. The surface roughness Ra≤0.4μm.

[0044] Precautions: Electrostatic dust removal is required on the PMMA surface before coating to ensure no particles are present. Film thicknesses below 8μm may result in insufficient hardness (<2H); thicknesses above 20μm may cause orange peel or cracking, necessitating adjustment of the coating head flow rate.

[0045] (2) Applying a high-temperature resistant protective film: Apply a high-precision, high-temperature resistant protective film to the camera area of ​​the sub-body (according to the CAD outline of the specific model), ensuring that the edge of the protective film is completely aligned with the outline of the camera area, without bubbles or curling. The protective film has a temperature resistance of ≥80℃ and moderate adhesion, ensuring that there is no residue peeling after subsequent excimer laser spraying.

[0046] This protective film must be retained throughout the subsequent CNC finishing and surface grinding processes, and is only removed after the excimer spraying is completed.

[0047] Precautions: After applying the film, use a rubber roller to press it down and remove air bubbles. If the edges of the protective film peel up, the subsequent excimer laser coating will seep into the camera area, causing that area to lose its highlight effect (become matte), making it irreparable and unusable. Therefore, each film must be inspected for application quality under a strong light table.

[0048] Third, UV adhesive bonding and vacuum pressing are cured simultaneously.

[0049] A dedicated UV-curing structural adhesive for PMMA / PC is used, with a viscosity of 1000 cps (25℃). It is uniformly coated onto the PMMA interface of the substrate using a precision screen, with the coating thickness controlled to 0.04 mm.

[0050] Align and bond the PC interface of the daughter body with the PMMA interface of the mother body, with an alignment accuracy of ±0.05mm. Avoid slippage during bonding.

[0051] The bonded workpieces are then fed into a vacuum press for negative pressure vacuuming and mechanical pressing, while simultaneously undergoing UV curing to form a single, integral blank. The process parameters are as follows:

[0052] Negative pressure vacuum degree: 0.09MPa; mechanical pressing pressure: 0.5MPa; constant temperature environment for pressing: 50℃; UV light intensity: 1000mW / cm²; curing time: 40s.

[0053] Finished product specifications: peel strength ≥15N / 25mm, no air bubbles, gaps, or misalignments inside the bond; withstands high and low temperatures of -40℃ to 85℃ for 72 hours without delamination or cracking.

[0054] Precautions: The vacuum level must reach the set value within 5 seconds to prevent air bubbles from remaining. If the vacuum level is insufficient (>-0.08MPa), tiny air bubbles will remain at the bonding interface. These bubbles will expand during high and low temperature cycling, leading to delamination. If the UV light intensity is uneven, the adhesive layer will not cure completely, resulting in fluctuating peel strength. The UV lamp energy needs to be checked periodically with a radiometer.

[0055] Fourth, CNC precision machining.

[0056] For the integral blank after bonding and curing, only the interface between the sub-body and the parent body is subjected to CNC precision milling of the transition arc. Process parameters: bonding transition arc R angle: R0.5mm; CNC spindle speed: 21000r / min; feed rate: 800mm / min; single cutting depth: 0.12mm; surface roughness Ra≤0.8μm after machining; external contour dimensional tolerance: ±0.03mm.

[0057] During this process, a high-temperature resistant protective film must be retained in the camera area to prevent cutting dust or cutting fluid from contaminating the camera area, while also protecting the hardened layer from accidental scratches.

[0058] Precautions: Use a special fixture to hold the PMMA surface of the substrate in place to avoid damaging the protective film. If the protective film is not retained or is damaged prematurely, CNC machining debris may become embedded in the camera area, which is difficult to remove later. The hardening layer may also be scratched, resulting in pitting or scratches on the highlight effect. Such defects are irreparable.

[0059] Fifth, surface grinding to remove tool marks.

[0060] The CNC-machined blank is subjected to full-area precision grinding to thoroughly remove CNC tool marks, tool lines, and burrs at the interface and transition arcs, ensuring surface flatness and smoothness. Process parameters: Grinding method: single-sided floating grinding; grinding pad material: polyurethane polishing pad; grinding pressure: 0.4MPa; grinding speed: 65r / min; grinding fluid: water-based diamond grinding fluid (particle size 3μm); surface roughness Ra ≤ 0.2μm after grinding, no tool marks, no burrs, no chipping, flatness ≤ 0.05mm.

[0061] During this process, a high-temperature resistant protective film must be maintained in the camera area to prevent the abrasive slurry from entering the camera area and causing scratches or contamination.

[0062] Precautions: After polishing, rinse with deionized water and blot dry the edges with a lint-free cloth. If polishing slurry seeps into the edges of the protective film, it will be difficult to remove after drying, reducing the light transmittance of the camera area (<85%) and affecting the photo quality. In this case, the film must be scrapped or downgraded.

[0063] Sixth, zoned excimer laser coating

[0064] The semi-finished product after grinding is subjected to full-area excimer spraying for surface passivation, stain resistance, and texture enhancement. Before spraying, check that the protective film is intact and free of peeling edges, and clean the workpiece surface with an electrostatic dust removal gun.

[0065] In a Class 10,000 cleanroom, an automated spraying line is used to spray UV excimer matte coating with a film thickness of 24μm. After leveling for 3 minutes, the coating enters the UV excimer curing oven and is then baked at 70℃ for 25 minutes after curing.

[0066] After spraying, allow the workpiece to cool to room temperature, then peel off the high-temperature protective film around the camera area. Pull the film off slowly at a 45° angle to avoid leaving adhesive residue. After drying and curing, you will obtain the finished phone back cover.

[0067] This process achieves a perfect combination of the skin-friendly matte finish of the excimer laser coating on the back cover and the high-gloss, wear-resistant finish on the camera area. After curing, the surface of the main body has a pencil hardness of ≥2H, a fingerprint resistance level of 5, and is resistant to 500 sweat wiping cycles without any abnormalities; the camera area retains the high-gloss effect of the coating hardened layer, with a pencil hardness of 2H and a light transmittance of ≥92%.

[0068] Precautions: Excimer laser curing requires LED curing. Excessive LED energy (greater than 50%) will suppress the matte finish. Insufficient LED energy (less than 30%) will increase the matte finish and make the surface feel rougher. If residual adhesive is found on the protective film, gently wipe it with a lint-free cloth dampened with isopropyl alcohol (do not touch the excimer coating). Excessive force when peeling off the film may also lift the hardened layer at the edge of the camera area, causing edge chipping. Operators must be trained to control the force applied.

[0069] VII. Working Environment and Quality Control

[0070] The entire production process takes place in a Class 10,000 cleanroom, with an ambient temperature of 22–28°C and humidity of 50%–65%. All composite panels are kept at a constant temperature and humidity for at least 24 hours before being put into production.

[0071] The process inspection nodes are set as follows:

[0072] After applying the base ink: transmittance ≤5%, cross-cut test.

[0073] After the film is applied to the substrate: 100% strong light inspection for bubbles and curling edges.

[0074] After bonding and curing: Ultrasonic testing for voids.

[0075] After CNC machining: Measure the profile tolerance using a coordinate measuring machine.

[0076] After grinding: Ra is measured with a roughness tester, and flatness is measured with a flatness tester.

[0077] Final product: appearance, hardness, wear resistance, fingerprint resistance, and light transmittance of the camera area ≥90%.

[0078] The overall yield is expected to reach over 92%.

[0079] The embodiments described above are merely preferred embodiments of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications, improvements, and substitutions without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A process for manufacturing a mobile phone back cover, characterized in that, Includes the following steps: Step 1: Prefabrication of the matrix: PMMA+PC double-layer co-extruded composite board is selected as the matrix. Nano-texture transfer, NCVM vacuum coating and cover ink printing are performed sequentially on the PC side of the matrix. Step 2, Subbody Prefabrication and Zoned Protection: PMMA+PC double-layer co-extruded composite sheet is selected as the subbody. The PMMA surface of the subbody is subjected to UV coating hardening treatment, and a high-temperature resistant protective film is attached to the camera area of ​​the subbody. The protective film is retained in the subsequent CNC precision machining and surface grinding process. Step 3: Simultaneous curing of UV adhesive bonding and vacuum pressing: The PC interface of the sub-body and the PMMA interface of the mother body are aligned and bonded using UV structural adhesive, and then simultaneously cured by vacuum negative pressure pressing and UV light irradiation to form an integral blank. Step 4, CNC precision machining: The bonding interface of the integral blank is precision milled with CNC to create a transition arc, while retaining the protective film during the process; Step 5: Surface grinding to remove tool marks: Perform full-area surface precision grinding on the CNC machined blank to remove CNC tool marks, while retaining the protective film during the process; Step 6, Zoned Excimer Spraying: Perform full-area excimer spraying on the ground semi-finished product, then remove the high-temperature resistant protective film in the camera area, dry and cure to obtain the finished product.

2. The manufacturing process for a mobile phone back cover according to claim 1, characterized in that, The thickness of the parent body is 0.5mm ± 0.02mm, the thickness of its PMMA layer is 0.05mm, and the thickness of its PC layer is 0.45mm; the thickness of the daughter body is 2.0mm ± 0.03mm, the thickness of its PMMA layer is 0.06mm, and the thickness of its PC layer is 1.94mm.

3. The manufacturing process for a mobile phone back cover according to claim 1, characterized in that, In step one: The texture depth of nanotexture transfer is 0.03–0.08 mm; the transfer linear speed is 6–10 m / min; and the mercury lamp curing energy is 650–850 mJ / cm². The NCVM coating thickness is 200–500 nm, the vacuum degree is 8 × 10⁻³–2 × 10⁻² Pa, and the coating rate is 0.5–1.0 nm / s; The base ink is a black opaque screen printing ink with a dry film thickness of 5–10 μm. The baking temperature is 70–85℃ and the baking time is 30–45 min.

4. The manufacturing process for a mobile phone back cover according to claim 1, characterized in that, In step two: The UV hardening coating used in the UV coating hardening treatment has a viscosity of 20-35 cps at 25℃, a dry film thickness of 8-15 μm, a UV curing energy of 900-1300 mJ / cm², and a pencil hardness of 2H-5H after curing. The protective film has a temperature resistance of ≥100℃, moderate adhesion, and can be peeled off without residue after spraying with UV hardening coating.

5. The manufacturing process for a mobile phone back cover according to claim 1, characterized in that, In step three: The viscosity of the UV structural adhesive is 800–1200 cps, and the coating thickness is 0.03–0.10 mm. The vacuum degree of vacuum pressing is -0.085 to -0.095 MPa, the mechanical pressing pressure is 0.4 to 0.6 MPa, and the pressing environment temperature is 40 to 60℃. The UV light intensity is 800–1200 mW / cm², and the curing time is 30–60 s.

6. The manufacturing process for a mobile phone back cover according to claim 1, characterized in that, In step four: The radius of the transition arc is R0.3~R0.8mm, the CNC spindle speed is 18000~24000r / min, the feed rate is 600~1000mm / min, the depth of cut in a single pass is 0.1~0.15mm, and the surface roughness after machining is Ra≤0.8μm.

7. The manufacturing process for a mobile phone back cover according to claim 1, characterized in that, In step five: The grinding method is single-sided floating grinding, the grinding pad material is polyurethane polishing pad, the grinding pressure is 0.3~0.5MPa, the grinding speed is 50~80r / min, and the surface roughness Ra≤0.2μm and flatness≤0.05mm after grinding.

8. The manufacturing process for a mobile phone back cover according to claim 1, characterized in that, In step six: The excimer coating is a UV excimer matte coating with a sprayed film thickness of 20–26 μm, a baking temperature of 60–75 °C, and a baking time of 20–35 min. After curing, the surface of the main body has a pencil hardness of ≥2H and a fingerprint resistance level of 5; the camera area retains the high-gloss effect of the coating hardened layer, with a pencil hardness of 2H~5H and a light transmittance of ≥90%.

9. The manufacturing process for a mobile phone back cover according to claim 1, characterized in that, The manufacturing process for the mobile phone back cover is carried out entirely in a Class 10,000 cleanroom, with an ambient temperature of 22–28°C and a humidity of 50%–65%. All composite boards are kept at constant temperature and humidity for more than 24 hours before being put into production.

10. A mobile phone back cover, characterized in that, The back cover is manufactured using the process described in any one of claims 1 to 9, comprising a matrix, a daughter body, and a UV-curable adhesive layer between them, wherein: The PMMA surface of the subbody is coated with a hardening layer, and the hardening layer outside the camera area is also coated with an excimer matte coating. The PC side of the substrate is sequentially provided with a UV texture layer, an NCVM coating layer, and a cover ink layer.

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