A uv-enhanced pre-coat film and a method of making the same

Abstract

This application discloses a UV-enhanced pre-coated film and its preparation method, belonging to the field of polymer materials and functional coating technology. The UV-enhanced pre-coated film includes a polyester base film and a UV-enhanced primer coated on the polyester base film. The UV-enhanced primer is formed by curing a UV-enhanced primer liquid. By mass percentage, the UV-enhanced primer liquid comprises the following components: 15%–25% aqueous film-forming resin; 0.08%–0.12% substrate wetting agent; 2%–4% crosslinking agent; 0.1%–0.5% crosslinking accelerator; 0.05%–0.2% defoamer; and solvent balance to 100%.

Description

Technical Field

[0001] This application relates to the field of polymer materials and functional coatings, and more specifically, to a UV-enhanced pre-coated film and its preparation method. Background Technology

[0002] With the development of photocurable materials technology, UV curing technology has been widely used in printing, packaging, advertising, and other fields due to its advantages such as fast curing speed, high production efficiency, low energy consumption, environmental friendliness, and wide applicability to substrates. Existing UV-cured products mainly include UV coatings, UV inks, and UV adhesives, which play an important role in various functional surface treatments and the carrying of graphic information. Against this backdrop, applying UV coatings to polymer film surfaces, especially to biaxially oriented polyethylene terephthalate (BOPET) films, has become one of the important technological directions for enhancing the added value of films.

[0003] BOPET polyester film, due to its excellent mechanical properties, good heat resistance, high transparency and gloss, as well as low water vapor and oxygen permeability and excellent chemical corrosion resistance, has been widely used in vacuum packaging, thermoforming packaging, and functional composite materials. However, in practical applications, simply relying on corona treatment to activate the surface of BOPET film, while increasing its surface tension to some extent, still easily leads to insufficient adhesion and easy coating peeling when directly coating with UV coatings, making it difficult to meet the requirements of subsequent processing and use. Therefore, it is usually necessary to introduce a primer coating on the surface of BOPET film to enhance the bonding strength between the UV coating and the substrate.

[0004] As the packaging industry moves towards lightweighting and lower costs, while simultaneously demanding higher product performance, achieving further reductions in coating thickness and effective control of material costs while ensuring adhesion has become a crucial trend in current technological development. Therefore, developing primer systems with excellent adhesion properties suitable for online coating processes has become a key focus in the industry.

[0005] In existing technologies, there are solutions for forming a base coating on the surface of a polyester film through online coating. For example, Chinese patent CN116874859A discloses an online coated polyester film for high-adhesion UV inkjet printing, which improves the adhesion of UV inkjet printing through a compound system of water-based polyurethane resin emulsion or dispersion, anti-adhesion agent, substrate wetting agent, and crosslinking agent. However, this type of technology mainly relies on hydrogen bonding or van der Waals forces between the base coating and the UV coating to achieve bonding, lacking sufficient chemical bonding, resulting in limited interfacial bonding strength, and still has shortcomings in applications requiring high adhesion and durability.

[0006] In summary, how to construct a UV-enhanced pre-coated film and its preparation method that can achieve effective chemical bonding between the base coating and the UV coating while ensuring the processing adaptability of BOPET film has become an urgent technical problem to be solved. Summary of the Invention

[0007] To overcome a series of defects in the existing technology, the purpose of this application is to provide a UV-enhanced pre-coated film, comprising a polyester base film and a UV-enhanced primer coating applied to the polyester base film, wherein the UV-enhanced primer coating is formed by curing a UV-enhanced primer liquid; the UV-enhanced primer liquid comprises the following components by weight percentage: Waterborne film-forming resin 15%–25%; Substrate wetting agent: 0.08%–0.12%; Crosslinking agent 2%–4%; Crosslinking accelerator 0.1%–0.5%; Defoamer 0.05%–0.2%; Solvent balance to 100%.

[0008] Furthermore, the aqueous film-forming resin comprises aqueous polyurethane and aqueous UV oligomer, with a mass ratio of 7.5:2.5 to 9.5:0.5; wherein the aqueous polyurethane has a minimum film-forming temperature of 30℃ to 80℃, a hydroxyl value of 20 to 60 mg KOH / g, a solid content of 30% to 40%, and a particle size of 50 to 150 nm; the aqueous UV oligomer is one of aqueous polyurethane acrylate and aqueous acrylate, or a mixture of the two in a mass ratio of 1:1 to 3:1, with a solid content of 35% to 45%.

[0009] Furthermore, the substrate wetting agent is selected from one of acetylenic diol wetting agents and anionic wetting agents, or a mixture of the two in a mass ratio of 1:1 to 2:1; wherein, the acetylenic diol wetting agent is 2,4,7,9-tetramethyl-5-decyn-4,7-diol or its ethoxylated derivative; and the anionic wetting agent is an alkyl sulfonate or an alkyl sulfate.

[0010] Furthermore, the crosslinking agent is a compound system of a blocked aqueous isocyanate crosslinking agent and a aziridine crosslinking agent, with a mass ratio of (5-9):(1-5).

[0011] Furthermore, the crosslinking accelerator is a aziridinium-based crosslinking accelerator, selected from one or more of tris(1-aziridinyl)phosphine oxide, tris(2-methyl-1-aziridinyl)phosphine oxide, and hexamethylene-1,6-bis(1-aziridinylformamide).

[0012] Furthermore, the solvent is a mixed solvent composed of deionized water and an alcohol solvent, wherein the alcohol solvent includes one or more of ethanol, isopropanol, and n-propanol; the mass ratio of the deionized water to the alcohol solvent is 1:(0-1).

[0013] Furthermore, the preparation method of the UV-enhanced primer is as follows: Mix deionized water with alcohol solvent and add it to a mixing tank equipped with a mechanical stirrer. Stir at 200-500 rpm under conditions of 20-30°C. Under stirring conditions, waterborne polyurethane, waterborne UV oligomer, substrate wetting agent and defoamer are added sequentially. The stirring time for the waterborne polyurethane is 5 to 15 minutes, the stirring time for the waterborne UV oligomer is 10 to 20 minutes, the stirring time for the substrate wetting agent is 5 to 10 minutes, and the stirring time for the defoamer is 3 to 5 minutes, so that each component is fully and evenly dispersed. After the crosslinking agent and crosslinking accelerator are premixed evenly, they are slowly added to the mixing tank and stirred for 10 to 20 minutes to obtain the main agent system; The main agent system is filtered through a 200-mesh filter and allowed to stand for 20–60 minutes to obtain a UV-enhanced primer.

[0014] The purpose of this application is also to provide a method for preparing a UV-enhanced pre-coated film, which includes the following steps: Step 1: Melt and extrude polyester chips at 285-292℃, and cast them on a casting roller at 25-35℃ to cool and form a polyester base film. Step 2: Perform corona treatment on the polyester film, with a corona power of 0.5–1.5 W·min / m. 2 The electrode spacing is 1.5–2.5 mm, and the processing speed is 80–300 m / min; Step 3: After preheating the corona-treated polyester film at 75-90℃ for 8-12 seconds, perform longitudinal stretching with a longitudinal stretching ratio of 3.8-4.2 times, a stretching temperature of 90-105℃, and a stretching speed of 100-300 m / min. Step 4: Apply a UV-reinforcing primer to the longitudinally stretched polyester base film using a micro-grooving roller coating or anilox roller coating method. The wet coating amount is 1.2–2.8 g / m². 2 The coating speed is 100–280 m / min; Step 5: Preheat the coated polyester film at 80-110℃ for 10-25 seconds; Step 6: Perform transverse stretching on the preheated polyester film, with a stretching ratio of 3.8 to 4.2 times and a stretching temperature of 100 to 125°C; Step 7: The transversely stretched polyester film is heat-set using a segmented temperature control method, including: preheating section temperature 195-210℃, time 5-12 s; main setting section temperature 215-235℃, time 8-20 s; slow cooling section temperature 185-205℃, time 5-15 s; relaxation section temperature 150-175℃, time 3-8 s; total setting time is 20-45 s. Step 8: After cooling to 55-75°C, the film is wound up under a winding tension of 100-160 N / m to obtain a UV-enhanced pre-coated film.

[0015] Furthermore, the polyester chips have an intrinsic viscosity of 0.64–0.72 dL / g, a water content ≤50 ppm, a diethylene glycol content ≤1.5%, and a terminal carboxyl group content ≤25 eq / 10. 6 g.

[0016] Compared with the prior art, this application has the following beneficial effects: This application constructs a composite film-forming system of waterborne polyurethane and waterborne UV oligomers, and combines the synergistic crosslinking effect of aziridine and epoxy silane crosslinking agents to enable the base coating to possess excellent interfacial compatibility and chemical reactivity. This not only significantly enhances the adhesion between the base coating and the polyester base film and the UV coating, but also effectively improves the cohesive strength and water resistance of the coating by forming a dense three-dimensional network structure, thereby avoiding the problem of UV coating peeling off and improving the overall stability and mechanical properties of the pre-coated film. Detailed Implementation

[0017] The technical solution of this application will be clearly and completely described below with reference to the embodiments of this application, but these embodiments should not be construed as limiting the scope of protection of this application.

[0018] Example 1 The UV-enhancing primer was prepared according to the following mass percentages: waterborne polyurethane (35% solids content, minimum film-forming temperature 50℃, hydroxyl value 40mg KOH / g, particle size 100nm): 20%; waterborne polyurethane acrylate (40% solids content): 5%; 2,4,7,9-tetramethyl-5-decyn-4,7-diol ethoxylated derivative: 0.1%; blocked waterborne isocyanate crosslinking agent: 2.1%; aziridine crosslinking agent: 0.9%; tris(1-aziridine)phosphine oxide: 0.3%; silicone defoamer: 0.1%; deionized water: 50%; ethanol: 21.5%.

[0019] The preparation steps for the UV-enhanced primer are as follows: After mixing deionized water and ethanol, add the mixture to a mixing tank equipped with a mechanical stirrer and stir at 300 rpm at 25°C. Under stirring conditions, add waterborne polyurethane and stir for 10 minutes, waterborne polyurethane acrylate and stir for 15 minutes, substrate wetting agent and stir for 8 minutes, and defoamer and stir for 4 minutes in sequence to ensure that each component is fully and evenly dispersed. After pre-mixing the closed-type waterborne isocyanate crosslinking agent and the aziridine crosslinking agent evenly, slowly add them to the mixing tank and continue stirring for 15 minutes; After adding tri(1-aziridinyl)phosphine oxide and stirring for 10 minutes, the main agent system was obtained; The main agent system was filtered through a 200-mesh filter and allowed to stand for 30 minutes to obtain a UV-enhanced primer.

[0020] The obtained UV-enhanced primer liquid has a solid content of 5%, a viscosity of 40 mPa·s at 25℃, a pH value of 8.0, and a surface tension of 31 mN / m.

[0021] The preparation steps for the UV-enhanced pre-coated film are as follows: The intrinsic viscosity was 0.68 dL / g, the water content was 30 ppm, the diethylene glycol content was 1.2%, and the terminal carboxyl group content was 20 eq / 10. 6 g of polyester chips were melt-extruded at 288°C and cast onto a casting roller at 30°C to cool and form a polyester-based film. The polyester-based film was subjected to corona treatment with a corona power of 1.0 W·min / m. 2， The electrode spacing is 2.0 mm, and the processing speed is 200 m / min; The corona-treated polyester film was preheated at 85℃ for 10 seconds and then longitudinally stretched. The longitudinal stretching ratio was 4.0 times, the stretching temperature was 98℃, and the stretching speed was 200 m / min. A UV-reinforcing primer was applied online to the surface of the longitudinally stretched polyester film using a micro-grooving roller coating method, with a wet coating amount of 2.0 g / m². 2， The coating speed is 200 m / min; The coated polyester film was preheated at 95°C for 18 seconds. The preheated polyester film was subjected to transverse stretching at a ratio of 4.0 and a stretching temperature of 115℃. The transversely stretched polyester film was subjected to heat setting using a segmented temperature control method: preheating section temperature 200℃, time 8s; main setting section temperature 225℃, time 15s; slow cooling section temperature 195℃, time 10s; relaxation section temperature 160℃, time 5s; total setting time 38s. After cooling to 65°C, the film is wound up at a tension of 130 N / m to obtain a UV-enhanced pre-coated film.

[0022] The dry film thickness of the UV-enhanced primer layer in the obtained UV-enhanced pre-coated film is 0.75 μm.

[0023] Example 2 Prepare the UV-enhancing primer according to the following mass percentages: Waterborne polyurethane (solid content 38%, minimum film-forming temperature 60℃, hydroxyl value 35mg KOH / g, particle size 80nm): 22%; Waterborne acrylate (solid content 42%): 3%; Alkyl sulfonate: 0.08%; Blocked waterborne isocyanate crosslinking agent: 2.7%; Aziridine crosslinking agent: 0.3%; Hexamethylene-1,6-bis(1-aziridinecarboxamide): 0.2%; Mineral oil defoamer: 0.08%; Deionized water: 55%; Isopropanol: 16.64%.

[0024] The preparation method of the UV-enhanced primer is the same as in Example 1.

[0025] The obtained UV-enhanced primer liquid has a solid content of 6%, a viscosity of 35 mPa·s at 25℃, a pH value of 7.5, and a surface tension of 30 mN / m.

[0026] The following parameters are used in the preparation of the UV-enhanced pre-coated film: The intrinsic viscosity of the polyester chips is 0.66 dL / g, the melt extrusion temperature is 290℃, and the casting roll temperature is 28℃. Corona power 1.2 W·min / m 2 Electrode spacing 1.8mm, processing speed 250m / min; Longitudinal stretching preheating temperature 80℃, time 9s, stretching ratio 3.9 times, stretching temperature 95℃, stretching speed 150m / min; Wet coating amount: 1.8 g / m² 2 Coating speed 180m / min; Preheating temperature after coating: 90℃, time: 15s; Transverse elongation ratio 3.9 times, elongation temperature 110℃; Heat setting: Preheating section 205℃ / 10s, main setting section 230℃ / 18s, slow cooling section 200℃ / 12s, relaxation section 165℃ / 6s; Cooling temperature 60℃, winding tension 120N / m.

[0027] The dry film thickness of the UV-enhanced primer layer in the obtained UV-enhanced pre-coated film is 0.68 μm.

[0028] Example 3 The UV-enhancing primer was prepared according to the following mass percentages: waterborne polyurethane (32% solids content, minimum film-forming temperature 45℃, hydroxyl value 50mg KOH / g, particle size 120nm): 18%; waterborne polyurethane acrylate (38% solids content): 6%; waterborne acrylate (40% solids content): 1%; 2,4,7,9-tetramethyl-5-decyn-4,7-diol: 0.06%; alkyl sulfate: 0.06%; blocked waterborne isocyanate crosslinking agent: 3.2%; aziridine crosslinking agent: 0.8%; tris(2-methyl-1-aziridine)phosphine oxide; polyether defoamer: 0.12%; deionized water: 48%; n-propanol: 22.36%.

[0029] The preparation method of the UV-enhanced primer is the same as in Example 1.

[0030] The obtained UV-enhanced primer liquid has a solid content of 7%, a viscosity of 50 mPa·s at 25℃, a pH value of 8.5, and a surface tension of 29 mN / m.

[0031] The following parameters are used in the preparation of the UV-enhanced pre-coated film: The intrinsic viscosity of the polyester chips is 0.70 dL / g, the melt extrusion temperature is 286℃, and the casting roll temperature is 32℃. Corona power 0.8 W·min / m 2 Electrode spacing 2.2mm, processing speed 150m / min; Longitudinal stretching preheating temperature 88℃, time 11s, stretching ratio 4.1 times, stretching temperature 102℃, stretching speed 250m / min; The anilox roller coating method is used, with a wet coating amount of 2.5 g / m². 2 Coating speed 220m / min; Preheating temperature after coating: 105℃, time: 20s; Transverse stretch ratio 4.1 times, stretching temperature 120℃; Heat setting: Preheating section 210℃ / 12s, main setting section 235℃ / 20s, slow cooling section 205℃ / 15s, relaxation section 175℃ / 8s; Cooling temperature 70℃, winding tension 150N / m.

[0032] The dry film thickness of the UV-enhanced primer layer in the obtained UV-enhanced pre-coated film is 0.92 μm.

[0033] Example 4 The UV-enhancing primer was prepared according to the following mass percentages: waterborne polyurethane (40% solids content, minimum film-forming temperature 70℃, hydroxyl value 25mg KOH / g, particle size 60nm): 15%; waterborne polyurethane acrylate (45% solids content): 10%; 2,4,7,9-tetramethyl-5-decyn-4,7-diol ethoxylated derivative: 0.08%; alkyl sulfonate: 0.04%; blocked waterborne isocyanate crosslinking agent: 1.6%; aziridine crosslinking agent: 0.4%; tris(1-aziridine)phosphine oxide: 0.1%; organosilicon defoamer: 0.05%; deionized water: 60%; ethanol: 12.73%.

[0034] The preparation method of the UV-enhanced primer is the same as in Example 1.

[0035] The obtained UV-enhanced primer liquid has a solid content of 4.5%, a viscosity of 25 mPa·s at 25℃, a pH value of 7.2, and a surface tension of 32 mN / m.

[0036] The following parameters are used in the preparation of the UV-enhanced pre-coated film: The intrinsic viscosity of the polyester chips is 0.64 dL / g, the melt extrusion temperature is 285℃, and the casting roll temperature is 25℃. Corona power 0.5 W·min / m 2 Electrode spacing 1.5mm, processing speed 80m / min; Longitudinal stretching preheating temperature 75℃, time 8s, stretching ratio 3.8 times, stretching temperature 90℃, stretching speed 100m / min; Wet coating amount: 1.2 g / m² 2 Coating speed 100m / min; Preheating temperature after coating: 80℃, time: 10s; Transverse stretch ratio 3.8 times, stretching temperature 100℃; Heat setting: Preheating section 195℃ / 5s, main setting section 215℃ / 8s, slow cooling section 185℃ / 5s, relaxation section 150℃ / 3s; Cooling temperature 55℃, winding tension 100N / m.

[0037] The dry film thickness of the UV-enhanced primer layer in the obtained UV-enhanced pre-coated film is 0.50 μm.

[0038] Example 5 The UV-enhancing primer was prepared according to the following mass percentages: waterborne polyurethane (30% solids content, minimum film-forming temperature 80℃, hydroxyl value 60mg KOH / g, particle size 150nm): 23.75%; waterborne acrylate (35% solids content): 1.25%; alkyl sulfonate: 0.12%; blocked waterborne isocyanate crosslinking agent: 3.6%; aziridine crosslinking agent: 0.4%; hexamethylene-1,6-bis(1-aziridinecarboxamide): 0.5%; polyether defoamer: 0.2%; deionized water: 40%; isopropanol: 30.06%.

[0039] The preparation method of the UV-enhanced primer is the same as in Example 1.

[0040] The obtained UV-enhanced primer liquid has a solid content of 7.5%, a viscosity of 58 mPa·s at 25℃, a pH value of 9.0, and a surface tension of 28 mN / m.

[0041] The following parameters are used in the preparation of the UV-enhanced pre-coated film: The intrinsic viscosity of the polyester chips is 0.72 dL / g, the melt extrusion temperature is 292℃, and the casting roll temperature is 35℃. Corona power 1.5 W·min / m 2 Electrode spacing 2.5mm, processing speed 300m / min; Longitudinal stretching preheating temperature 90℃, time 12s, stretching ratio 4.2 times, stretching temperature 105℃, stretching speed 300m / min; Wet coating amount: 2.8 g / m² 2 Coating speed 280m / min; Preheating temperature after coating: 110℃, time: 25s; Transverse stretch ratio 4.2 times, stretching temperature 125℃; Heat setting: Preheating section 210℃ / 12s, main setting section 235℃ / 20s, slow cooling section 205℃ / 15s, relaxation section 175℃ / 8s; Cooling temperature 75℃, winding tension 160N / m.

[0042] The dry film thickness of the UV-enhanced primer layer in the obtained UV-enhanced pre-coated film is 1.0 μm.

[0043] Comparative Example 1 The difference from Example 1 is that UV curing is not performed, but all other conditions are the same.

[0044] Comparative Example 2 The difference from Example 1 is that no crosslinking agent and crosslinking accelerator are used, the proportions of the remaining components are adjusted accordingly, and other conditions are the same.

[0045] Comparative Example 3 The difference from Example 1 is that only 25% of the waterborne film-forming resin is used, and no waterborne UV oligomer is used, while other conditions are the same.

[0046] The following performance tests were performed on the UV-enhanced pre-coated films prepared in the above embodiments and comparative examples: 1. Surface roughness (Ra): Tested using a white light interferometer, with a test area of ​​1mm × 1mm.

[0047] 2. Adhesion: A UV coating was applied to the prepared UV-enhanced pre-coated film using conventional methods, with a coating thickness of 60 μm. The film was then fully cured using a UV-LED lamp to obtain a sample with a UV coating. The adhesion at room temperature and the adhesion after boiling in water at 100℃ for 2 hours were tested in accordance with GB / T 9286-2021 "Cross-cut test for paint and varnish film".

[0048] 3. Weather resistance: The samples were subjected to a 1000-hour aging test in a xenon lamp aging test chamber (irradiance 550W / m²). 2， (Blackboard temperature 65℃, relative humidity 50%), test the color difference ΔE and peel strength retention rate before and after aging.

[0049] The test results are as follows: Example 1 has a surface roughness Ra of 12.5 nm, an adhesion of 5B at room temperature, an adhesion of 5B after boiling in water at 100°C for 2 hours, a color difference ΔE of 1.2 after weathering for 1000 hours, and a peel strength retention rate of 92%.

[0050] Example 2 has a surface roughness Ra of 11.8 nm, an adhesion of 5B at room temperature, an adhesion of 5B after boiling in water at 100°C for 2 hours, a color difference ΔE of 1.0 after weathering for 1000 hours, and a peel strength retention rate of 94%.

[0051] Example 3 has a surface roughness Ra of 13.2 nm, an adhesion of 5B at room temperature, an adhesion of 5B after boiling in water at 100°C for 2 hours, a color difference ΔE of 0.9 after weathering for 1000 hours, and a peel strength retention rate of 95%.

[0052] Example 4 has a surface roughness Ra of 14.0 nm, an adhesion of 5B at room temperature, an adhesion of 5B after boiling in water at 100°C for 2 hours, a color difference ΔE of 1.5 after weathering for 1000 hours, and a peel strength retention rate of 88%.

[0053] Example 5 has a surface roughness Ra of 10.5 nm, an adhesion of 5B at room temperature, an adhesion of 5B after boiling in water at 100°C for 2 hours, a color difference ΔE of 0.8 after weathering for 1000 hours, and a peel strength retention rate of 96%.

[0054] Comparative Example 1 has a surface roughness Ra of 15.8 nm, an adhesion of 4B at room temperature, an adhesion of 1B after boiling in water at 100℃ for 2 hours, a color difference ΔE of 3.8 after weathering for 1000 hours, and a peel strength retention rate of 65%.

[0055] Comparative Example 2 has a surface roughness Ra of 16.5 nm, an adhesion of 3B at room temperature, an adhesion of 0B after boiling in water at 100℃ for 2 hours, a color difference ΔE of 4.2 after weathering for 1000 hours, and a peel strength retention rate of 62%.

[0056] Comparative Example 3 has a surface roughness Ra of 14.2 nm, an adhesion of 5B at room temperature, an adhesion of 3B after boiling in water at 100℃ for 2 hours, a color difference ΔE of 2.5 after weathering for 1000 hours, and a peel strength retention rate of 75%.

[0057] As can be seen from the above test results, the UV-enhanced pre-coated film prepared in the embodiments of the present invention has excellent surface smoothness, adhesion, and weather resistance. Specifically: Examples 1-5 all achieved a 5B adhesion rating at room temperature, and the adhesion remained at 5B after boiling in water at 100°C for 2 hours, indicating that the coating and the substrate have extremely strong interfacial bonding and excellent resistance to damp heat. In contrast, Comparative Example 1 showed an adhesion rating of 4B at room temperature and only 1B after boiling, Comparative Example 2 showed an adhesion rating of only 3B at room temperature and only 0B after boiling, and Comparative Example 3 showed an adhesion rating of only 3B after boiling, all of which were significantly inferior to the examples.

[0058] After 1000 hours of weathering test, the color difference ΔE of Examples 1-5 was less than 1.5, and the peel strength retention rate was over 88%; while the color difference ΔE of the comparative examples exceeded 2.5, and the peel strength retention rate was only 62%-75%.

[0059] The above results show that the UV-enhanced pre-coated film prepared by the present invention using waterborne film-forming resin (a mixture of waterborne polyurethane and waterborne UV oligomer), a compound crosslinking system, and reasonable process parameters has excellent comprehensive performance and meets the application requirements of high-quality pre-coated films.

[0060] The above embodiments are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A UV-enhancing pre-coat film comprising a polyester base film and a UV-enhancing base coat layer applied to the polyester base film, wherein, The UV-enhanced primer coating is formed by curing a UV-enhanced primer liquid, characterized in that, by mass percentage, the UV-enhanced primer liquid comprises the following components: Waterborne film-forming resin 15%–25%; Substrate wetting agent: 0.08%–0.12%; Crosslinking agent 2%–4%; Crosslinking accelerator 0.1%–0.5%; Defoamer 0.05%–0.2%; Solvent balance to 100%.

2. The UV-enhancing pre-coat film according to claim 1, characterized in that The aqueous film-forming resin comprises aqueous polyurethane and aqueous UV oligomer, with a mass ratio of 7.5:2.5 to 9.5:0.

5. The aqueous polyurethane has a minimum film-forming temperature of 30°C to 80°C, a hydroxyl value of 20 to 60 mg KOH / g, a solid content of 30% to 40%, and a particle size of 50 to 150 nm. The aqueous UV oligomer is one of aqueous polyurethane acrylate and aqueous acrylate, or a mixture of the two in a mass ratio of 1:1 to 3:1, with a solid content of 35% to 45%.

3. The UV-enhancing pre-coat film according to claim 2, wherein The substrate wetting agent is selected from one of the following: acetylenic diol wetting agents and anionic wetting agents, or a mixture of the two in a mass ratio of 1:1 to 2:1; wherein the acetylenic diol wetting agent is 2,4,7,9-tetramethyl-5-decyn-4,7-diol or its ethoxylated derivative; and the anionic wetting agent is an alkyl sulfonate or an alkyl sulfate.

4. The UV-enhancing pre-coated film according to claim 2, characterized in that The crosslinking agent is a compound system of a blocked aqueous isocyanate crosslinking agent and a aziridine crosslinking agent, with a mass ratio of (5-9):(1-5).

5. The UV-enhancing pre-coated film according to claim 2, wherein The crosslinking accelerator is a aziridinium-based crosslinking accelerator, selected from one or more of tris(1-aziridinyl)phosphine oxide, tris(2-methyl-1-aziridinyl)phosphine oxide, and hexamethylene-1,6-bis(1-aziridinylformamide).

6. The UV-enhancing pre-coated film according to claim 2, wherein The solvent is a mixed solvent composed of deionized water and an alcohol solvent, wherein the alcohol solvent includes one or more of ethanol, isopropanol, and n-propanol; the mass ratio of the deionized water to the alcohol solvent is 1:(0-1).

7. The UV-enhancing pre-coat film according to claim 6, wherein The preparation method for UV-enhanced primer is as follows: Mix deionized water with alcohol solvent and add it to a mixing tank equipped with a mechanical stirrer. Stir at 200-500 rpm under conditions of 20-30°C. Under stirring conditions, waterborne polyurethane, waterborne UV oligomer, substrate wetting agent and defoamer are added sequentially, wherein the stirring time of the waterborne polyurethane is 5 to 15 minutes, the stirring time of the waterborne UV oligomer is 10 to 20 minutes, the stirring time of the substrate wetting agent is 5 to 10 minutes, and the stirring time of the defoamer is 3 to 5 minutes, so that each component is fully and evenly dispersed. After the crosslinking agent and crosslinking accelerator are premixed evenly, they are slowly added to the mixing tank and stirred for 10 to 20 minutes to obtain the main agent system; The main agent system is filtered through a 200-mesh filter and allowed to stand for 20–60 minutes to obtain a UV-enhanced primer.

8. A method for producing a UV-enhancing pre-coated film, for producing a UV-enhancing pre-coated film according to claim 7, characterized in that Includes the following steps: Step 1: Melt and extrude polyester chips at 285-292℃, and cast them on a casting roller at 25-35℃ to cool and form a polyester base film. Step 2: Corona treatment of the polyester-based film at a corona power of 0.5 to 1.5 W-min / m 2 at an electrode distance of 1.5 to 2.5 mm and a treatment speed of 80 to 300 m / min. Step 3: After preheating the corona-treated polyester film at 75-90℃ for 8-12 seconds, perform longitudinal stretching with a longitudinal stretching ratio of 3.8-4.2 times, a stretching temperature of 90-105℃, and a stretching speed of 100-300 m / min. Step 4: The UV enhancing primer solution is coated on the surface of the longitudinally stretched polyester base film by micro-concave roller coating or anilox roller coating at a wet coating amount of 1.2-2.8 g / m 2 at a coating speed of 100-280 m / min. Step 5: Preheat the coated polyester film at 80-110℃ for 10-25 seconds; Step 6: Perform transverse stretching on the preheated polyester film, with a stretching ratio of 3.8 to 4.2 times and a stretching temperature of 100 to 125°C; Step 7: The transversely stretched polyester film is heat-set using a segmented temperature control method, including: preheating section temperature 195-210℃, time 5-12 s; main setting section temperature 215-235℃, time 8-20 s; slow cooling section temperature 185-205℃, time 5-15 s; relaxation section temperature 150-175℃, time 3-8 s; total setting time is 20-45 s. Step 8: After cooling to 55-75°C, the film is wound up under a winding tension of 100-160 N / m to obtain a UV-enhanced pre-coated film.

9. The method for preparing the UV-enhanced pre-coated film according to claim 8, characterized in that, The intrinsic viscosity of the polyester chips is 0.64-0.72 dL / g, the water content is ≤50 ppm, the diethylene glycol content is ≤1.5%, the terminal carboxyl group content is ≤25 eq / 10 6 g.