A celluloid composite film for off-mold decoration process and a manufacturing method thereof

Abstract

This invention discloses a celluloid composite film for out-of-mold decoration processes and its manufacturing method. The composite film comprises, from bottom to top, an injection molding substrate, a polyurethane adhesive layer, a celluloid decorative film layer, a high-transparency polyurethane adhesive layer, and a protective film layer. The injection molding substrate is a PC or ABS injection molded part; the protective film layer is a PMMA or PC film; the polyurethane adhesive layer is used to firmly bond the celluloid decorative film layer to the injection molding substrate, and the high-transparency polyurethane adhesive layer is used to firmly bond the protective film layer and the celluloid decorative film layer together. The aforementioned celluloid composite film for out-of-mold decoration processes, through its composite structure design of the injection molding substrate, polyurethane adhesive layer, celluloid decorative film layer, high-transparency polyurethane adhesive layer, and protective film layer, avoids the defects of poor weather resistance, easy yellowing, poor solvent resistance, and low surface gloss inherent in using celluloid film alone. The double-layer polyurethane adhesive layer enables tight bonding between the film layers, ensuring the overall structural stability of the composite film.

Description

Technical Field

[0001] This invention belongs to the field of external decoration technology, and particularly relates to a celluloid composite film for external decoration process and its manufacturing method. Background Technology

[0002] Compared to in-mold decoration (IMD), external mold decoration (OMD) eliminates the need for slitting fixtures, stamping fixtures, and injection fixtures, effectively reducing mold development costs and significantly shortening product prototyping cycles, demonstrating significant overall advantages. Currently, external mold decoration (OMD) is still in its early stages of application, with broad prospects for industry development.

[0003] Currently, the variety of decorative films used in OMD (Off-Mold Decoration) processes is relatively limited. Commonly used films are mainly printed and embossed films made of materials such as PVC, PC, PET, and ABS. Among them, celluloid (nitrocellulose) films can create various mother-of-pearl decorative effects, which are visually appealing to consumers, and the purchase cost of these films is low. However, celluloid films have significant performance defects, specifically poor weather resistance, a tendency to yellow during use, poor solvent resistance, and low surface gloss, making them unsuitable for direct use alone in OMD processes. Summary of the Invention

[0004] The purpose of this invention is to provide a celluloid composite film for out-of-mold decoration processes and a manufacturing method thereof, so as to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: In one aspect, a celluloid composite film for out-of-mold decoration process is provided, comprising, from bottom to top, an injection molding substrate, a polyurethane adhesive layer, a celluloid decorative film layer, a high-transparency polyurethane adhesive layer, and a protective film layer. The injection molding substrate is a PC or ABS injection molded part; The protective film layer is a PMMA film or a PC film; The polyurethane adhesive layer is used to firmly bond the celluloid decorative film layer to the injection-molded substrate, and the high-transparency polyurethane adhesive layer is used to firmly composite the protective film layer and the celluloid decorative film layer into one unit.

[0006] Furthermore, the thickness of the celluloid decorative film layer is 0.1mm to 0.3mm.

[0007] Furthermore, the cured polyurethane adhesive layer has a thickness of 20μm to 80μm; the cured high-transparency polyurethane adhesive layer has a thickness of 20μm to 80μm.

[0008] Furthermore, in the protective film layer, the PMMA film thickness is 50μm to 200μm, and the PC film thickness is 120μm to 300μm.

[0009] Furthermore, the composite film is compatible with DOD differential pressure coating equipment and can be formed and prepared under vacuum differential pressure coating process conditions, making it suitable for use in external mold decoration processes.

[0010] Furthermore, the finished composite film can pass conventional boiling water tests and pull-out tests, and possesses properties such as solvent resistance, weather resistance, non-yellowing, and high gloss, making it suitable for outdoor product decoration.

[0011] Secondly, a method for manufacturing a celluloid composite film for out-of-mold decoration processes is provided, comprising the following steps: S1. Select celluloid film with a thickness of 0.1mm to 0.3mm, and select PC or ABS injection molding substrate for later use; S2. Coat polyurethane adhesive evenly on one side of the celluloid film, controlling the coating thickness to be 20μm~80μm, and bake in a constant temperature environment of 40℃~70℃ for 20min~120min. S3. Using an external mold decoration vacuum differential pressure coating process, adhesive celluloid film is bonded to the surface of PC / ABS injection molding substrate to form a semi-finished product with a celluloid decorative layer; S4. Select PMMA film or PC film as protective film, coat one side of the protective film with high transparency polyurethane adhesive, control the coating thickness to 20μm~80μm, and bake in a constant temperature environment of 40℃~60℃ for 20min~120min. S5. Vacuum pressure differential lamination process is used again to attach the coated protective film to the surface of the semi-finished celluloid film to obtain celluloid composite film for external decoration. S6. During processing and use, the composite film is loaded onto the DOD differential pressure coating and decoration equipment to complete the external decoration forming process.

[0012] Furthermore, in step S1, a celluloid film with a thickness of 100 μm is selected; In step S2, the polyurethane adhesive coating thickness is controlled to be 20μm~25μm, and it is baked in a constant temperature environment of 50℃ for 30 minutes. In step S4, a PMMA film with a thickness of 100 μm is selected, and a high-transparency polyurethane adhesive is applied with a thickness of 25 μm to 30 μm. The film is then baked at a constant temperature of 50°C for 40 minutes.

[0013] Furthermore, in step S1, a celluloid film with a thickness of 120 μm is selected; In step S2, the polyurethane adhesive coating thickness is controlled to be 20μm~25μm, and it is baked in a constant temperature environment of 50℃ for 30 minutes. In step S4, a PC film with a thickness of 175 μm is selected, and a high-transparency polyurethane adhesive is applied with a thickness of 25 μm to 30 μm. The film is then baked at a constant temperature of 50°C for 40 minutes.

[0014] To elaborate further, the two layers of polyurethane adhesive, combined with two vacuum pressure differential coating processes, create a protective film that isolates the solvent from ultraviolet rays.

[0015] The beneficial effects of the present invention are as follows: Compared with the prior art, the celluloid composite film and manufacturing method for the out-of-mold decoration process have the following advantages: 1) Through the composite structure design of injection-molded substrate, polyurethane adhesive layer, celluloid decorative film layer, high-transparency polyurethane adhesive layer, and protective film layer, while retaining the unique mother-of-pearl decorative visual effect of celluloid film, the outer PMMA film or PC film forms a protective barrier to block ultraviolet rays and chemical solvents. This solves the defects of poor weather resistance, easy yellowing, poor solvent resistance, and low surface gloss of celluloid film when used alone from the overall structure. The double-layer polyurethane adhesive layer can achieve tight bonding between the film layers, effectively preventing delamination and peeling during use, and ensuring the overall structural stability of the composite film. 2) By setting the thickness of the celluloid decorative film layer between 0.1mm and 0.3mm, the delicate and rich mother-of-pearl texture can be fully presented, avoiding the defects of the decorative texture and poor visual effect caused by the film thickness being too thin. At the same time, it avoids the defects of uneven stretching and surface wrinkling when the film is too thick during vacuum pressure differential lamination, and takes into account both the excellent appearance decoration effect and the molding and processing compatibility of OMD external decoration process. 3) The thickness of the cured polyurethane adhesive layer and the high-transparency polyurethane adhesive layer is limited to 20μm to 80μm. The lower limit of the adhesive layer thickness ensures that the adhesive layer fully wets the interfaces of each film layer, improves the interlayer bonding strength, and ensures that the product passes the pull-out force test smoothly; the upper limit of the adhesive layer thickness can avoid problems such as glue overflow, internal bubbles, and increased surface haze caused by excessive glue coating, ensuring the overall high light transmittance of the composite film, fully displaying the mother-of-pearl texture of the celluloid film, and improving the reliability of the boiling water test. Attached Figure Description

[0016] Figure 1 A schematic diagram of the stacked structure of a celluloid composite film for out-of-mold decoration process provided in an embodiment of the present invention; Figure 2 A flowchart illustrating the steps of a method for manufacturing a celluloid composite film for out-of-mold decoration process according to an embodiment of the present invention; Figure 3 This is a flowchart of the steps provided in Embodiment 1 of the present invention; Figure 4 The flowchart is provided for Embodiment 2 of the present invention. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] Please see Figure 1 As shown, the present invention provides a celluloid composite film for out-of-mold decoration, comprising, from bottom to top, an injection molding substrate, a polyurethane adhesive layer, a celluloid decorative film layer, a high-transparency polyurethane adhesive layer, and a protective film layer; the injection molding substrate is a PC or ABS injection molded part; the protective film layer is a PMMA film or a PC film; the polyurethane adhesive layer is used to firmly bond the celluloid decorative film layer to the injection molding substrate, and the high-transparency polyurethane adhesive layer is used to firmly composite the protective film layer and the celluloid decorative film layer into one piece.

[0019] As can be seen, the composite structure design of injection-molded substrate, polyurethane adhesive layer, celluloid decorative film layer, high-transparency polyurethane adhesive layer, and protective film layer not only retains the unique mother-of-pearl decorative visual effect of celluloid film, but also relies on the outer PMMA film or PC film to form a protective barrier, blocking ultraviolet rays and chemical solvents. This solves the defects of poor weather resistance, easy yellowing, poor solvent resistance, and low surface gloss of celluloid film used alone from the overall structure. The double-layer polyurethane adhesive layer can achieve tight bonding between the film layers, effectively preventing delamination and peeling during use, and ensuring the overall structural stability of the composite film.

[0020] In one implementation method, the thickness of the celluloid decorative film layer is 0.1mm to 0.3mm.

[0021] It is evident that by setting the thickness of the celluloid decorative film layer between 0.1mm and 0.3mm, the delicate and rich mother-of-pearl texture can be fully presented, avoiding the defects of incomplete decorative texture and poor visual effect caused by excessively thin film thickness. At the same time, it avoids the defects of uneven stretching and surface wrinkling during vacuum differential lamination when the film is too thick, thus balancing excellent appearance decoration effect with the molding and processing compatibility of OMD external decoration process.

[0022] As one implementation method, the thickness of the polyurethane adhesive layer after curing is 20μm to 80μm; the thickness of the high-transparency polyurethane adhesive layer after curing is 20μm to 80μm.

[0023] As can be seen, the cured thickness of both the polyurethane adhesive layer and the high-transparency polyurethane adhesive layer is limited to 20μm to 80μm. The lower limit of the adhesive layer thickness ensures that the adhesive layer fully wets the interfaces of each film layer, improves the interlayer bonding strength, and ensures that the product passes the pull-out force test smoothly. The upper limit of the adhesive layer thickness can avoid problems such as glue overflow, internal bubbles, and increased surface haze caused by excessive glue coating, ensuring the overall high light transmittance of the composite film, fully displaying the mother-of-pearl texture of the celluloid film, and improving the reliability of the boiling water test.

[0024] In one implementation, the PMMA film thickness is 50μm to 200μm and the PC film thickness is 120μm to 300μm in the protective film layer.

[0025] It is evident that by limiting the thickness of the PMMA film in the protective layer to 50μm–200μm and the PC film thickness to 120μm–300μm, the PMMA and PC films within this thickness range can provide sufficient surface gloss, surface hardness, and UV protection. Thin protective films are suitable for lightweight and small decorative parts, while thick protective films meet the high weather resistance requirements of outdoor products. At the same time, it avoids the production defects of insufficient protection due to excessively thin protective films and bending and cracking due to excessively thick films, thus adapting to the processing needs of multiple product categories.

[0026] As one implementation method, the composite film is adapted to the DOD differential pressure coating decoration equipment and can be formed and prepared under vacuum differential pressure coating process conditions, and is suitable for use in external decoration processes.

[0027] It is evident that by adapting the composite film to the DOD differential pressure coating equipment, molding can be completed under vacuum differential pressure coating conditions, making it suitable for use in external decoration processes. The composite film of this application can be directly matched with existing mature mass production equipment, eliminating the need for large-scale production line modifications and effectively reducing enterprise equipment upgrade investment. The vacuum differential pressure coating process achieves bubble-free and wrinkle-free complete bonding, enabling stable large-scale industrial production and broadening the application scope of celluloid film in the OMD external decoration field.

[0028] As one implementation method, the finished composite film can pass the conventional boiling water test and pull-out test, and has the characteristics of solvent resistance, weather resistance, non-yellowing, and high gloss, making it suitable for outdoor product decoration.

[0029] As can be seen, through conventional boiling water tests and pull-out tests, it possesses solvent resistance, weather resistance, resistance to yellowing, and high gloss properties, making it suitable for outdoor product decoration. Compared to the limitations of traditional celluloid films, which are only suitable for short-term indoor use, the composite film of this invention can withstand humid heat, chemical solvents, and ultraviolet radiation. It is not prone to loss of gloss, yellowing, or delamination with long-term use, significantly expanding the product's application scenarios, meeting the reliability requirements for long-term use of outdoor decorative components, and enhancing the product's market competitiveness.

[0030] Please see Figure 2 As shown, based on the above-mentioned celluloid composite film for out-of-mold decoration process, a method for manufacturing a celluloid composite film for out-of-mold decoration process is provided, which is used to prepare the above-mentioned celluloid composite film for out-of-mold decoration process, including the following steps: S1. Select celluloid film with a thickness of 0.1mm to 0.3mm, and select PC or ABS injection molding substrate for later use; S2. Coat polyurethane adhesive evenly on one side of the celluloid film, controlling the coating thickness to be 20μm~80μm, and bake in a constant temperature environment of 40℃~70℃ for 20min~120min. S3. Using an external mold decoration vacuum differential pressure coating process, adhesive celluloid film is bonded to the surface of PC / ABS injection molding substrate to form a semi-finished product with a celluloid decorative layer; S4. Select PMMA film or PC film as protective film, coat one side of the protective film with high transparency polyurethane adhesive, control the coating thickness to 20μm~80μm, and bake in a constant temperature environment of 40℃~60℃ for 20min~120min. S5. Vacuum pressure differential lamination process is used again to attach the coated protective film to the surface of the semi-finished celluloid film to obtain celluloid composite film for external decoration. S6. During processing and use, the composite film is loaded onto the DOD differential pressure coating and decoration equipment to complete the external decoration forming process.

[0031] As can be seen, by defining the entire process of composite film preparation, including material selection, adhesive coating and baking, and two vacuum differential pressure coating molding processes, the whole process steps are clear and logically complete. Those skilled in the art can directly achieve mass production processing according to this process. The segmented coating process of first bonding the celluloid decorative layer and then bonding the protective film layer can control the degree of curing of the adhesive layer step by step, avoiding defects such as bubbles and distortion of decorative texture caused by single bonding. The process has a high degree of standardization and strong applicability.

[0032] In one implementation, in step S1, a celluloid film with a thickness of 100 μm is selected; In step S2, the polyurethane adhesive coating thickness is controlled to be 20μm~25μm, and it is baked in a constant temperature environment of 50℃ for 30 minutes. In step S4, a PMMA film with a thickness of 100 μm is selected, and a high-transparency polyurethane adhesive is applied with a thickness of 25 μm to 30 μm. The film is then baked at a constant temperature of 50°C for 40 minutes.

[0033] Specifically, this application provides two embodiments: Please see Figure 3 As shown, Example 1 includes the following steps: Step 1: Select a celluloid film with a thickness of 100μm; Step 2: Coat the celluloid film with polyurethane adhesive and bake it at a constant temperature of 50°C for 30 minutes. The coating thickness should be controlled at 20μm to 25μm. Step 3: The celluloid film is laminated onto the ABS / PC using a vacuum differential pressure lamination process; Step 4: Select a PMMA film with a thickness of 100 μm; Step 5: Apply high-transparency polyurethane adhesive to PMMA and bake at a constant temperature of 50°C for 40 minutes to achieve a coating thickness of 25μm to 30μm. Step 6: Apply PMMA to the ABS / PC injection molded part that has been coated with celluloid film using a vacuum differential pressure coating process.

[0034] As can be seen, the first preferred preparation process parameters are provided, matching the production scheme of 100μm celluloid film and 100μm PMMA protective film, and limiting the corresponding coating thickness and baking conditions. This set of parameters forms a standardized and lightweight production process with high consistency in the production process, excellent light transmittance of the finished product, and clear and complete mother-of-pearl texture. It is suitable for mass production of small 3C appearance parts and can steadily improve the production yield.

[0035] In one implementation, in step S1, a celluloid film with a thickness of 120 μm is selected; In step S2, the polyurethane adhesive coating thickness is controlled to be 20μm~25μm, and it is baked in a constant temperature environment of 50℃ for 30 minutes. In step S4, a PC film with a thickness of 175 μm is selected, and a high-transparency polyurethane adhesive is applied with a thickness of 25 μm to 30 μm. The film is then baked at a constant temperature of 50°C for 40 minutes.

[0036] For details, please refer to Figure 4 As shown, Embodiment 2 includes the following steps: Step 1: Select a celluloid film with a thickness of 120μm; Step 2: Coat the celluloid film with polyurethane adhesive and bake it at a constant temperature of 50°C for 30 minutes. The coating thickness should be controlled at 20μm to 25μm. Step 3: The celluloid film is laminated onto the ABS / PC using a vacuum differential pressure lamination process; Step 4: Select a PC film with a thickness of 175μm; Step 5: Apply high-transparency polyurethane adhesive to the PC and bake at a constant temperature of 50°C for 40 minutes to achieve a coating thickness of 25μm to 30μm. Step 6: The PC is bonded to the ABS / PC injection molded part that has been coated with celluloid film using a vacuum differential pressure coating process.

[0037] As can be seen, a second set of differentiated manufacturing process parameters is provided, matching the production schemes for 120μm celluloid film and 175μm PC protective film, limiting the corresponding coating thickness and baking conditions. The PC protective film has stronger scratch and abrasion resistance, making this process suitable for household appliances and thick outdoor decorative products. The two sets of differentiated process parameters can be flexibly selected according to product thickness, abrasion resistance, and weather resistance requirements, improving the versatility of the entire manufacturing process.

[0038] As one implementation method, two layers of polyurethane adhesive are combined with two vacuum pressure differential coatings to create a protective film that isolates the solvent from ultraviolet rays.

[0039] As can be seen, the double-layer polyurethane adhesive forms a sealed protective structure, which, together with the outer PMMA or PC protective film, blocks ultraviolet rays and corrosive solvents. This process prevents the yellowing, corrosion, and loss of gloss of the celluloid film, ensuring long-term stable appearance and further improving the product's service life and appearance stability under outdoor conditions.

[0040] It should be noted that in this way, celluloid can be transferred to ABS / PC injection molded parts through DOD differential pressure coating equipment under vacuum differential pressure coating process conditions and applied to OMD (Out Mold Decoration) decoration process. The surface effect is bright and wear-resistant and chemical-resistant. Its performance can pass the conventional boiling water and pull-out force tests, and it can be used outdoors by utilizing the weather resistance protection of PMMA. Celluloid, with nitrocellulose as its base material, is a thermoplastic film / sheet made by nitrifying cotton linters / wood pulp cellulose with nitric acid and sulfuric acid, adding camphor as a plasticizer, and combining it with solvents, colorants, and pearlescent fillers through kneading, calendering, and drying. It is one of the earliest industrially mass-produced synthetic plastics. The celluloid decorative film used in this application has a thickness ranging from 0.1 mm to 0.3 mm. PMMA, short for polymethyl methacrylate, is commonly known in the industry as acrylic or plexiglass. It is an amorphous thermoplastic transparent polymer material polymerized from methyl methacrylate monomers. In this application, an ultra-thin PMMA film is produced by extrusion molding as the outermost protective film layer of the composite film, with a thickness range of 50μm to 200μm. In the composite film laminate structure of this application, the PMMA film serves as the outermost protective layer, forming a complete sealing barrier in conjunction with a highly transparent polyurethane adhesive layer. This barrier blocks ultraviolet rays, moisture, and chemical solvents, interrupting the denitrification and aging path of celluloid (nitrocellulose), thus addressing the root causes of celluloid's yellowing and corrosion failure. It also provides a high-gloss surface, enhancing the finished product's gloss and compensating for celluloid's inherent low-gloss defect. Furthermore, it isolates external dust, cleaning agents, and rainwater from direct contact with the celluloid decorative layer, significantly improving the product's wear resistance, chemical resistance, and outdoor weather resistance. The high light transmittance ensures the complete presentation of the inner celluloid mother-of-pearl texture without diminishing the decorative visual effect. PC stands for polycarbonate, which is an amorphous thermoplastic transparent polymer material polymerized from bisphenol A type carbonate. This application includes two types of PC materials: one is PC injection molding substrate as the bottom support, and the other is PC film as the surface protective film; wherein the thickness range of the protective PC film is 120μm to 300μm. The functions of the PC film layer are as follows: As the outermost physical barrier of the composite film, it resists friction, scratches, moisture, and daily chemicals, protecting the inner celluloid decorative film from corrosion and damage; it provides a high-gloss surface, enhancing the appearance and texture of the finished product and solving the problem of insufficient gloss of pure celluloid film; relying on its excellent tensile toughness, it is compatible with the vacuum differential pressure lamination process of DOD differential pressure lamination equipment, ensuring that complex curved surfaces are laminated without cracks or wrinkles; and in conjunction with a high-transparency polyurethane adhesive layer, it seals and encapsulates the celluloid film, reducing direct contact with external media and delaying the aging and failure of the celluloid.

[0041] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A celluloid composite film for out-of-mold decoration process, characterized in that, The celluloid composite film used in the external decoration process includes, from bottom to top, an injection molding substrate, a polyurethane adhesive layer, a celluloid decorative film layer, a high-transparency polyurethane adhesive layer, and a protective film layer. The injection molding substrate is a PC or ABS injection molded part; The protective film layer is a PMMA film or a PC film; The polyurethane adhesive layer is used to firmly bond the celluloid decorative film layer to the injection-molded substrate, and the high-transparency polyurethane adhesive layer is used to firmly composite the protective film layer and the celluloid decorative film layer into one unit.

2. The celluloid composite film for external molding decoration process according to claim 1, characterized in that, The thickness of the celluloid decorative film layer is 0.1mm to 0.3mm.

3. The celluloid composite film and manufacturing method for external molding decoration process according to claim 1, characterized in that, The cured polyurethane adhesive layer has a thickness of 20μm to 80μm; the cured high-transparency polyurethane adhesive layer has a thickness of 20μm to 80μm.

4. The celluloid composite film and manufacturing method for external molding decoration process according to claim 1, characterized in that, In the protective film layer, the PMMA film thickness is 50μm to 200μm, and the PC film thickness is 120μm to 300μm.

5. The celluloid composite film and manufacturing method for external molding decoration process according to claim 1, characterized in that, The composite film is compatible with DOD differential pressure coating equipment and can be formed and prepared under vacuum differential pressure coating process conditions, making it suitable for use in external mold decoration processes.

6. The celluloid composite film and manufacturing method for external molding decoration process according to claim 1, characterized in that, The finished composite film can pass conventional boiling water tests and pull-out tests, and has the characteristics of solvent resistance, weather resistance, non-yellowing, and high gloss, making it suitable for outdoor product decoration.

7. A method for manufacturing a celluloid composite film for external molding decoration, characterized in that, The method for preparing the celluloid composite film for out-of-mold decoration process according to any one of claims 1 to 6 includes the following steps: S1. Select celluloid film with a thickness of 0.1mm to 0.3mm, and select PC or ABS injection molding substrate for later use; S2. Coat polyurethane adhesive evenly on one side of the celluloid film, controlling the coating thickness to be 20μm~80μm, and bake in a constant temperature environment of 40℃~70℃ for 20min~120min. S3. Using an external mold decoration vacuum differential pressure coating process, adhesive celluloid film is bonded to the surface of PC / ABS injection molding substrate to form a semi-finished product with a celluloid decorative layer; S4. Select PMMA film or PC film as protective film, coat one side of the protective film with high transparency polyurethane adhesive, control the coating thickness to 20μm~80μm, and bake in a constant temperature environment of 40℃~60℃ for 20min~120min. S5. Vacuum pressure differential lamination process is used again to attach the coated protective film to the surface of the semi-finished celluloid film to obtain celluloid composite film for external decoration. S6. During processing and use, the composite film is loaded onto the DOD differential pressure coating and decoration equipment to complete the external decoration forming process.

8. The method for manufacturing a celluloid composite film for external molding decoration according to claim 7, characterized in that, In step S1, a celluloid film with a thickness of 100 μm is selected; In step S2, the polyurethane adhesive coating thickness is controlled to be 20μm~25μm, and it is baked in a constant temperature environment of 50℃ for 30 minutes. In step S4, a PMMA film with a thickness of 100 μm is selected, and a high-transparency polyurethane adhesive is applied with a thickness of 25 μm to 30 μm. The film is then baked at a constant temperature of 50°C for 40 minutes.

9. The method for manufacturing a celluloid composite film for external molding decoration according to claim 7, characterized in that, In step S1, a celluloid film with a thickness of 120 μm is selected; In step S2, the polyurethane adhesive coating thickness is controlled to be 20μm~25μm, and it is baked in a constant temperature environment of 50℃ for 30 minutes. In step S4, a PC film with a thickness of 175 μm is selected, and a high-transparency polyurethane adhesive is applied with a thickness of 25 μm to 30 μm. The film is then baked at a constant temperature of 50°C for 40 minutes.

10. The method for manufacturing a celluloid composite film for external molding decoration according to claim 7, characterized in that, Two layers of polyurethane adhesive are combined with two vacuum pressure differential coatings to create a protective film that isolates the solvent and ultraviolet rays.

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