Semi-cured hardened film as well as preparation method and application thereof

Abstract

The invention relates to the technical field of automotive interior materials, in particular to a semi-cured material as well as a preparation method and application thereof. According to the invention, a composition containing specific three-functional-group and six-functional-group UV resin with high viscosity and high molecular weight is adopted, and a two-step process of performing excimer ultraviolet light surface exposure and then performing low-energy UV overall pre-curing is performed to prepare the stretchable'solidification state 'semi-cured hardened film. After the film is subjected to high-pressure forming, uniform volume shrinkage is generated in the coating through UV full curing, so that a matte structure prefabricated on the surface is uniformly stretched and fixed. According to the invention, a uniform, fine and crack-free matte effect of a complex three-dimensional part on the whole surface, especially at a high-stress bending angle, is realized, the problems of gloss mutation and cracking at the position in the traditional technology are solved, and the matte paint is particularly suitable for high-end automotive upholstery.

Description

Technical Field

[0001] This invention relates to the field of automotive interior materials technology, specifically to a semi-cured hardening film, its preparation method, and its application. Background Technology

[0002] As automotive interior design increasingly emphasizes texture and aesthetics, consumers are demanding higher standards for the surface finish of interior components, particularly in terms of matte, smooth, and uniform texture. In-mold labeling (IMC) technology is widely used in automotive interior manufacturing due to its ability to integrate decoration with the substrate. However, this process requires the film material to maintain a consistent surface texture across complex curves and corners after high-pressure molding, posing a significant challenge to the tensile properties and optical uniformity of the hardened film coating. Therefore, developing a hardened film material that maintains a consistent matte finish and is crack-free across the entire surface (including high-stress corner areas) after high-pressure molding has become an urgent task for improving the quality of automotive interiors and meeting the market's high-end demands.

[0003] Currently, the industry primarily employs two technical approaches to achieve a matte finish and adapt to molding processes. One approach involves adding matte powder (such as silica) to the coating, which physically scatters light to achieve a matte effect. This method is simple and a common way to achieve a matte finish. The other approach uses excimer ultraviolet (UV) curing technology. This involves irradiating the coating surface with short-wavelength, high-energy light, inducing selective curing and shrinkage of the surface thin layer, thereby forming a microscopic wrinkled structure to achieve a matte finish. This method avoids the addition of physical fillers and theoretically can achieve a finer surface texture.

[0004] However, all of the aforementioned existing technologies have significant limitations. For traditional methods involving the addition of matte powder, during high-pressure molding (with a stretch ratio typically 1.5-3 times), the coating is subjected to tensile stress. The internal matte powder particles easily lead to stress concentration, causing microcracks in high-strength areas such as corners (R-angles). Simultaneously, the distribution of matte powder changes due to stretching, resulting in significant differences in gloss between flat surfaces and corners, leading to uneven surface texture and failing to meet the stringent visual consistency requirements of high-end automotive interiors. While conventional excimer curing technology can create a matte surface, its resin system is usually based on general decorative film designs and does not fully consider the balance between coating cohesive strength and tensile ductility necessary for high-pressure molding. If directly applied to films requiring high-pressure molding, the coating often suffers from brittle cracking or excessive deformation during subsequent molding due to mismatched crosslinking density or resin molecular structure, leading to damage to the matte structure and failing to guarantee the uniformity and integrity of the matte finish across the entire surface after molding.

[0005] Therefore, under the premise of taking into account efficient production, environmental protection requirements, and high-quality appearance of the final product, developing a curing film preparation scheme that can coordinate the design of multiple links from the formulation resin molecular structure, viscosity, and functionality to excimer pretreatment and pre-curing energy control, so as to ensure that the coating is in a suitable semi-cured "solidified state" before high-pressure molding, has excellent tensile properties during molding, and can stably present a uniform matte effect on the entire surface through full curing after molding, has become a key issue that urgently needs to be addressed in this technical field. Summary of the Invention

[0006] To address the shortcomings of existing matte-cured films that are prone to uneven gloss, cracking, and surface texture degradation in curved areas after high-pressure molding, this invention proposes a semi-curing method, its preparation, and its applications. This invention provides an innovative solution for achieving high-pressure molding adaptability and uniform matte finish across the entire surface of the film material through a synergistic process combining excimer ultraviolet surface exposure under an inert atmosphere with specific low-energy UV overall pre-curing.

[0007] The first objective of this invention is achieved through the following technical solution:

[0008] A method for preparing a semi-cured hardening film, characterized by comprising the following steps:

[0009] (1) Apply a UV-curable composition to a substrate;

[0010] (2) The coating is surface exposed using excimer ultraviolet light under an inert atmosphere;

[0011] (3) The energy used is 20-80 mJ / cm 2 The coating is pre-cured entirely by UV light.

[0012] Preferably, in step (2), the wavelength of the excimer ultraviolet light is 165-180 nm, and the exposure power is 10-50 mW / cm². 2 The exposure time is 0.2-5s; the inert atmosphere is a nitrogen atmosphere or an argon atmosphere.

[0013] Preferably, the oxygen concentration in the inert atmosphere is less than 30 ppm.

[0014] Preferably, the UV curing composition comprises a trifunctional UV resin, a hexafunctional UV resin, and a 2-3 functional acrylate monomer.

[0015] More preferably, based on 100 parts by weight of total resin and monomer, the trifunctional UV resin comprises 60-75 parts, the hexafunctional UV resin comprises 15-30 parts, and the 2-3 functional acrylate monomer comprises 5-20 parts.

[0016] More preferably, the trifunctional UV resin has a viscosity of 30,000-100,000 cps at 25°C and a molecular weight greater than 1,500.

[0017] More preferably, the hexafunctional UV resin has a viscosity greater than 50,000 cps and a molecular weight greater than 1,000 at 25°C.

[0018] Preferably, the trifunctional UV resin is selected from at least one of aliphatic polyurethane acrylate, polycarbonate acrylate, and polycaprolactone acrylate.

[0019] Preferably, the hexafunctional UV resin is selected from hexafunctional polyurethane acrylate resins.

[0020] Preferably, the 2-3 functional acrylate monomer is selected from at least one of tricyclodecanediethanol diacrylate, 9,9-bis[4-(2-acryloyloxyethoxy)phenyl]fluorene, urethane dimethacrylate, trimethylolpropane triacrylate, and triallyl isocyanurate.

[0021] Preferably, the UV curing composition further comprises a photoinitiator.

[0022] More preferably, the photoinitiator is one or more of 2-hydroxy-2-methyl-1-phenylpropanone, 1-hydroxycyclohexylphenyl ketone, 2-methyl-2-(4-morpholino)-1-[4-(methylthio)phenyl]-1-propanone, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, ethyl 2,4,6-trimethylbenzoylphenylphosphonate, and 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone.

[0023] More preferably, the amount of photoinitiator added is 0.03-0.06 parts by weight of acrylic resin.

[0024] Preferably, the UV curing composition further comprises a silicone-based leveling agent.

[0025] More preferably, the organosilicon leveling agent is polyether-modified polydimethylsiloxane or polyester-modified polydimethylsiloxane.

[0026] Preferably, the UV curing composition contains an organic solvent, which is one or more selected from dimethyl carbonate, ethyl acetate, isopropanol, and butanediol.

[0027] More preferably, the organic solvent is a mixture of dimethyl carbonate, ethyl acetate, and isopropanol in a mass ratio of (2~7):3:(2~5).

[0028] Preferably, the coating step employs a microgravure coating process.

[0029] More preferably, the coating roller in the micro-groove coating process is 180-220 mesh.

[0030] More preferably, the viscosity of the coating liquid in the microgravure coating process is 20-60 cps.

[0031] More preferably, the coating speed of the microgravure coating process is 5-15 m / min.

[0032] Preferably, after the coating step and before the surface exposure step, a drying step is also included.

[0033] More preferably, the maximum temperature of the drying step is not higher than 120°C.

[0034] This scheme employs a synergistic process of first excimer ultraviolet (UV) surface exposure under an inert atmosphere, followed by low-energy UV pre-curing. Through a specific high-viscosity, high-molecular-weight multifunctional resin formulation system, a semi-cured hardened film suitable for delivery before high-pressure molding is achieved. The technical principle of this scheme is as follows: First, excimer ultraviolet light (possessing high energy and shallow penetration) can directly act on the outermost layer of the coating in an oxygen-free environment, initiating free radical polymerization of acrylate double bonds to form an extremely thin but dense cross-linked network. This micro-cured layer will wrinkle due to inner layer shrinkage during subsequent full curing, forming the structural basis for the final matte effect. Second, the subsequent low-energy UV pre-curing is crucial, with an energy range of 20-80 mJ / cm². 2 This is far lower than the energy required for conventional complete curing (typically 200-700 mJ / cm). 2 By selecting high-viscosity, high-molecular-weight resins with long molecular chains and limited mobility, the photocuring activity is partially suppressed. Under this low-energy irradiation, the coating matrix does not fully cross-link but undergoes partial polymerization, transforming the entire coating from a liquid state into a "solidified state" at room temperature. This provides a certain degree of cohesive strength and initial morphological stability, facilitating winding, transportation, and storage. However, the cross-linking density is strictly controlled at a low level, retaining a large number of unreacted double bonds and sufficient molecular chain mobility within the coating. This preserves excellent tensile strength for subsequent high-pressure molding processes, preventing brittle cracking caused by over-curing. This two-step pre-curing process—surface micro-curing followed by overall shallow curing—works synergistically with a specially designed resin system to precisely achieve a "solid surface, soft interior" semi-cured state before delivery. This lays the core technological foundation for achieving a uniform matte finish across the entire surface of the final product after high-pressure molding.

[0035] The second objective of this invention is achieved through the following technical solution:

[0036] A semi-cured hardening film prepared by any of the methods described above.

[0037] The third objective of this invention is achieved through the following technical solution:

[0038] A method for preparing a matte curing film includes the following steps:

[0039] (1) The semi-cured hardened film as described above is subjected to high pressure molding;

[0040] (2) UV curing is performed on the molded film material.

[0041] Preferably, the energy of the UV curing process is 800-1000 mJ / cm². 2 .

[0042] This solution provides a downstream method for converting a semi-cured film into a final matte product. The technical principle is as follows: First, utilizing the low cross-linking density and abundant unreacted double bonds within the semi-cured coating's "solidified" state, the molecular chains can fully extend to accommodate deformation during high-pressure molding, ensuring no cracking even at high draw ratios (R-angles). Subsequently, high-energy UV full curing excites complete polymerization within the coating, resulting in significant volume shrinkage. The already cured, dense surface layer shrinks less, and the difference in shrinkage between the inside and outside causes uniform tensile stress on the surface, thereby generating a uniform micro-wrinkled structure across the entire product surface (including planes and R-angles). This structure effectively scatters light, creating a consistent matte effect. This effect is "self-generated" by the material's own stress after molding, fundamentally avoiding uneven gloss and cracking problems caused by the addition of foreign substances or improper curing before molding.

[0043] The fourth objective of this invention is achieved through the following technical solution:

[0044] An automotive interior component comprising a matte hardened film prepared by the above method.

[0045] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0046] 1. This invention employs a two-step synergistic process: first, excimer ultraviolet surface exposure, followed by low-energy UV overall pre-curing. This method utilizes excimer light to form an extremely thin cured layer on the outermost surface of the coating to pre-fabricate a matte structure. Subsequently, precisely controlled low-energy exposure allows the coating's interior to reach a semi-solidified, incompletely cross-linked state. This process path fundamentally and synergistically resolves the technical contradiction between pre-fabricating a matte effect and preserving the tensile strength of high-pressure molding.

[0047] 2. The UV-curable composition formulation of the present invention is specifically designed by selecting resin systems with specific functionality, ultra-high viscosity, and high molecular weight, and combining them with the two-step process. This formulation system itself inhibits excessive reaction of the resin in the pre-curing stage, ensuring that it can form a stable semi-solid coating state suitable for subsequent stretching processing under low-energy exposure, thus guaranteeing the successful implementation of the method from the material basis.

[0048] 3. This invention achieves a balanced regulation of the curing depth and internal cross-linking degree of the coating surface through precise and coordinated control of the excimer exposure environment, energy, and overall pre-curing energy. This control ensures the uniformity and stability of the semi-cured film performance, providing a reliable and forgiving process window for large-scale production.

[0049] 4. The semi-cured hardened film product obtained by the method of this invention exhibits a stable semi-solid state at room temperature, solving the problems of adhesion and deformation of incompletely cured coatings during storage and transportation. As a reliable standardized intermediate material, this product can be directly delivered to customers for high-pressure molding, greatly simplifying the production process of complex three-dimensional interior parts.

[0050] 5. The final matte hardened film product achieves a uniform, smooth, and crack-free matte finish across the entire three-dimensional surface, especially at high-stress corners. This is thanks to the uniform volumetric shrinkage force generated within the semi-cured film during final full curing, which further stretches and shapes the already formed matte layer, thus completely overcoming the uneven matte finish and cracking defects that occur in the corner areas after high-pressure molding using traditional methods. Attached Figure Description

[0051] Figure 1 Photographs showing the surface state of the semi-cured film prepared in Example 1 after high-pressure molding;

[0052] Figure 2 Photographs showing the surface state of the semi-cured film prepared in Example 2 after high-pressure molding;

[0053] Figure 3 Photographs showing the surface state of the semi-cured hardened film prepared in Example 3 after high-pressure molding;

[0054] Figure 4 Photographs showing the surface state of the semi-cured film prepared for Comparative Example 1 after high-pressure molding.

[0055] Figure 5 Photographs showing the surface state of the semi-cured film prepared in Comparative Example 2 after high-pressure molding.

[0056] Figure 6 Photographs of the surface state of the matte hardened film prepared for Comparative Example 3 after a sunscreen resistance test.

[0057] Figure 7 Photographs showing the surface state of the semi-cured film prepared for Comparative Example 4. Detailed Implementation

[0058] The following will provide a clear and complete description of the concept, specific structure, and technical effects of the present invention in conjunction with embodiments, so as to fully understand the purpose, solution, and effects of the present invention. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of the present invention can be combined with each other.

[0059] The present invention will be further illustrated by specific embodiments below, but the scope of protection of the present invention is not limited thereto.

[0060] Example 1

[0061] The method for preparing the matte curing film in Example 1 includes the following steps:

[0062] (1) Preparation of coating solution: Weigh out 70 parts by weight of trifunctional UV resin (manufacturer: Allnex, brand: EBCURE 4900, viscosity 50000 cps / 25℃, molecular weight 18000), 20 parts by weight of hexafunctional UV resin (manufacturer: miwon, brand: PU610, viscosity 100000 cps / 25℃, molecular weight 1800), 10 parts by weight of difunctional acrylate monomer (manufacturer: Changxing Chemical, brand: EM2204), 5 parts by weight of photoinitiator (2-hydroxy-2-methyl-1-phenylpropanone), 0.05 parts by weight of surface additive (manufacturer: BYK-333, Germany), and 157.5 parts by weight of organic solvent (dimethyl carbonate, ethyl acetate, isopropanol, mass ratio 2:3:2). Mix the above materials and stir evenly to obtain a UV resin coating solution with a solid content of 40%.

[0063] (2) Coating and drying: The micro-gravure coating process is used to evenly coat the coating liquid onto the surface of the PC substrate, followed by drying. The maximum temperature of the oven is 100℃.

[0064] (3) Excimer ultraviolet surface exposure: In a nitrogen atmosphere with an oxygen concentration of less than 20 ppm, the coating surface is exposed using excimer ultraviolet light with a wavelength of 172 nm and an exposure power of 10 mW / cm. 2 The exposure time is 2 seconds.

[0065] (4) UV overall pre-curing: The coating is irradiated with a UV light source at an energy of 50 mJ / cm². 2 A semi-cured hardened film is obtained.

[0066] (5) High pressure molding: The obtained semi-cured hardened film is subjected to high pressure molding with a stretching ratio of 1.5 times.

[0067] (6) UV curing: The molded film is irradiated with UV light at an energy of 900 mJ / cm². 2 A matte hardened film is obtained.

[0068] Example 2

[0069] The matte curing film preparation method of Example 2 is the same as that of Example 1, with steps (2) to (6) being the same.

[0070] The difference lies in step (1), which is:

[0071] Preparation of the coating solution: Weigh out 70 parts by weight of a trifunctional UV resin (manufacturer: miwon, brand: PU340, viscosity 70000cps / 25℃, molecular weight 2400), 20 parts by weight of a hexafunctional UV resin (manufacturer: Allnex, brand: EBECRYL1290, viscosity 60000cps / 25℃, molecular weight 2000), 10 parts by weight of a difunctional acrylate monomer (manufacturer: Changxing Chemical, brand: EM2204), 5 parts by weight of a photoinitiator (2-hydroxy-2-methyl-1-phenylpropanone), 0.05 parts by weight of a surface additive (manufacturer: BYK-333, Germany), and 315 parts by weight of an organic solvent (dimethyl carbonate, ethyl acetate, isopropanol, mass ratio 2:3:2). Mix the above materials thoroughly to obtain a UV resin coating solution with a solid content of 25%.

[0072] Example 3

[0073] The matte curing film preparation method of Example 3 is the same as that of Example 1, with steps (2) to (6) being the same.

[0074] The difference lies in step (1), which is:

[0075] Preparation of the coating solution: Weigh out 70 parts by weight of trifunctional UV resin (manufacturer: Allnex, brand: EBECRYL264, viscosity 45000cps / 25℃, molecular weight 2000), 20 parts by weight of hexafunctional UV resin (manufacturer: Meiyuan, brand: PU610, viscosity 100000cps / 25℃, molecular weight 1800), 10 parts by weight of difunctional acrylate monomer (manufacturer: Changxing Chemical, brand: EM2204), 10 parts by weight of photoinitiator (2-hydroxy-2-methyl-1-phenylpropanone), 0.05 parts by weight of surface additive (manufacturer: BYK-333, Germany), and 245 parts by weight of organic solvent (dimethyl carbonate, ethyl acetate, isopropanol, mass ratio 2:3:2). Mix the above materials and stir evenly to obtain a 30.1% UV resin coating solution.

[0076] Comparative Example 1

[0077] The preparation method of the matte curing film of Comparative Example 1 is the same as that of Example 1, steps (2) to (6).

[0078] The difference lies in step (1), which is as follows: Weigh out 70 parts by weight of trifunctional UV resin (manufacturer: Allnex, brand name: EBECRYL 4101, viscosity 7000cps / 25℃, molecular weight 1100), 20 parts by weight of hexafunctional UV resin (manufacturer: miwon, brand name: PU610, viscosity 100000 cps / 25℃, molecular weight 1800), 10 parts by weight of difunctional acrylate monomer (manufacturer: Changxing Chemical, brand name: EM2204), 5 parts by weight of photoinitiator (2-hydroxy-2-methyl-1-phenylpropanone), 0.05 parts by weight of surface additive (manufacturer: BYK-333, Germany), and 157.5 parts by weight of organic solvent (dimethyl carbonate, ethyl acetate, isopropanol, mass ratio 2:3:2). Mix the above materials and stir evenly to obtain a UV resin coating liquid with a solid content of 40%.

[0079] Comparative Example 2

[0080] The preparation method of the matte curing film of Comparative Example 2 is the same as that of Example 2, steps (2) to (6).

[0081] The difference lies in step (1), which is as follows: Weigh out 70 parts by weight of trifunctional UV resin (manufacturer: miwon, brand: PU340, viscosity 70000cps / 25℃, molecular weight 2400), 20 parts by weight of hexafunctional UV resin (manufacturer: Allnex, brand: EBECRYL220, viscosity 25000cps / 25℃, molecular weight 1000), 10 parts by weight of difunctional acrylate monomer (manufacturer: Changxing Chemical, brand: EM2204), 5 parts by weight of photoinitiator (2-hydroxy-2-methyl-1-phenylpropanone), 0.05 parts by weight of surface additive (manufacturer: BYK, brand: BYK-333), and 315 parts by weight of organic solvent (dimethyl carbonate, ethyl acetate, isopropanol, mass ratio 2:3:2). Mix the above materials and stir evenly to obtain a UV resin coating liquid with a solid content of 25%.

[0082] Comparative Example 3

[0083] The preparation method of the matte curing film of Comparative Example 3 is the same as that of Example 1, with steps (2) to (6) being the same.

[0084] The difference lies in step (1), which is as follows: Weigh out 70 parts by weight of trifunctional UV resin (Allnex, brand name: EBCURE 4900, viscosity 50000 cps / 25℃, molecular weight 18000), 5 parts by weight of hexafunctional UV resin (manufacturer: miwon, brand name: PU610, viscosity 100000 cps / 25℃, molecular weight 1800), 25 parts by weight of difunctional acrylate monomer (manufacturer: Changxing Chemical, brand name: EM2204), 5 parts by weight of photoinitiator (2-hydroxy-2-methyl-1-phenylpropanone), 0.05 parts by weight of surface additive (manufacturer: BYK-333, Germany), and 157.5 parts by weight of organic solvent (dimethyl carbonate, ethyl acetate, isopropanol, mass ratio 2:3:2). Mix the above materials and stir evenly to obtain a UV resin coating liquid with a solid content of 40%.

[0085] Comparative Example 4

[0086] The preparation method of the matte curing film of Comparative Example 4 is the same as that of Example 1, with steps (2) to (6) being the same.

[0087] The difference lies in step (1), which is as follows: Weigh 40 parts of trifunctional UV resin (Allnex, brand name: EBCURE 4900, viscosity 50000 cps / 25℃, molecular weight 18000) by mass, 50 parts of hexafunctional UV resin (manufacturer: miwon, brand name: PU610, viscosity 100000 cps / 25℃, molecular weight 1800), 10 parts of difunctional acrylate monomer (manufacturer: Changxing Chemical, brand name: EM2204), 0.03 parts of photoinitiator (2-hydroxy-2-methyl-1-phenylpropanone), 0.05 parts of surface additive (manufacturer: BYK, brand name: BYK-333), and 113 parts of organic solvent (dimethyl carbonate, ethyl acetate, isopropanol, mass ratio 2:3:2). The above materials are mixed and stirred evenly to obtain a UV resin coating liquid with a solid content of 30%.

[0088] The final matte cured films obtained in Examples 1-3 and Comparative Examples 1-4 were tested under the following standard conditions:

[0089] Appearance and condition observation: Observe and record the surface condition of the coating under standard laboratory conditions (25±2℃, 50±5%RH).

[0090] Gloss test: According to standard ASTM D523, a gloss meter was used to measure the gloss of the flat area of ​​the hardened film and the R-corner area after high pressure forming at 85°. Five points were measured for each part and the average value was taken.

[0091] Adhesion test: The adhesion grade of the coating is evaluated by performing a cross-cut adhesive tape tear test according to the standard ASTM D3359 Method B.

[0092] Molding performance observation: During and after high-pressure molding, observe whether the coating has defects such as cracks, flow or loss of gloss.

[0093] Sunscreen resistance test: Take a sample, cover its surface with a layer of gauze, and evenly apply sunscreen (brand: La Roche-Posay Anthelios, SPF 50+). Then place it in an 80℃ oven for 24 hours. After cooling, wipe the surface clean and observe whether the coating shows defects such as corrosion, white spots, or discoloration.

[0094] The above test methods are a unified standard and are applicable to the performance comparison and evaluation of all embodiments and comparative samples. The results are summarized in the table below.

[0095] Table 1 Performance test results of the examples and comparative examples

[0096]

[0097] The semi-cured film obtained in Example 1 was subjected to high-pressure molding and UV full-curing treatment to obtain... Figure 1 The obtained matte hardened film showed a clean surface without cracks. The semi-cured hardened film obtained in Example 2 was subjected to high-pressure molding and UV full-curing treatment to obtain… Figure 2 The obtained matte hardened film showed a clean surface without cracks. The semi-cured hardened film obtained in Example 3 was subjected to high-pressure molding and UV full-curing treatment to obtain… Figure 3 The obtained matte hardened film showed a clean surface without cracks. The semi-cured hardened film obtained in Comparative Example 1 was subjected to high-pressure molding and UV full-curing treatment to obtain… Figure 4 The obtained film material showed cracks on its surface. The semi-cured film obtained in Comparative Example 2 was subjected to high-pressure molding and UV full-curing treatment to obtain... Figure 5 The results showed cracks appearing on the surface of the obtained film. A sunscreen resistance test was conducted on the matte cured film finally prepared in Comparative Example 3, and the results were... Figure 6 The test area showed obvious white corrosion spots. Direct observation of the semi-cured film obtained after coating, drying, and pre-curing in Comparative Example 4 revealed... Figure 7 This indicates that it exhibits a fluid dynamic and has not formed a uniformly solidified film.

[0098] The test results show that the semi-cured film prepared by the method of this invention exhibits a uniform and stable solidified state upon delivery, facilitating subsequent processing and transportation. After high-pressure molding and full curing, the resulting product demonstrates excellent comprehensive performance across the entire three-dimensional surface, with minimal gloss difference between flat and curved areas, achieving a uniform and delicate matte finish without any cracks, and achieving the highest level of adhesion. Chemical resistance tests indicate that its surface effectively resists the erosion of everyday chemicals such as sunscreen, meeting the long-term use requirements of automotive interior parts.

[0099] The resins used in Examples 1 to 3 of this invention are all within a specific viscosity and molecular weight range. Combined with the disclosed two-step curing process, qualified products with smooth surfaces, uniform matte finish after molding, and no cracks were successfully prepared, proving the effectiveness and repeatability of the technical solution of this invention.

[0100] Comparative Example 1, using a low-viscosity, low-molecular-weight, 3-functional resin, resulted in cracking after molding, demonstrating that high-viscosity, high-molecular-weight resins are crucial for providing the necessary molecular chain entanglement and cohesive strength. Comparative Example 2, using a low-molecular-weight, 6-functional resin, also resulted in molding cracking, further confirming the key role of high-molecular-weight resins in constructing a robust network that resists molding stress.

[0101] Comparative Example 3 reduced the amount of hexafunctional resin and significantly increased the total monomer ratio, resulting in a significant decrease in the chemical resistance of the finished product and the appearance of white corrosion spots, indicating that an inappropriate component ratio can damage the integrity of the cross-linking network. In Comparative Example 4, the proportion of hexafunctional resin was too high. Under the low-energy pre-curing conditions, the system reaction was too violent and uneven, resulting in the coating failing to form a uniform solidified state and instead exhibiting a flowing state, indicating that excessively high cross-linking activity can disrupt the formation window of the semi-cured state.

[0102] In summary, the advantage of this invention lies in the synergistic innovation of its process and formulation. The two-step curing process pre-forms a matte structure on the surface while preserving sufficient internal flexibility. The matched high-viscosity, high-molecular-weight resin system ensures controllability of the reaction during low-energy pre-curing, allowing the coating to precisely remain in a semi-cured stage that possesses both sufficient strength and good molding potential. This "solid surface, soft interior" intermediate state is a prerequisite for achieving uniform matte finish, crack resistance, and high durability on complex three-dimensional surfaces in the final product. Test data demonstrate that this method successfully solves the common problems of uneven gloss and cracking in matte hardened films after high-pressure molding, providing a stable and reliable solution.

[0103] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. A method for preparing a semi-cured hardening film, characterized in that, Includes the following steps: (1) Apply a UV-curable composition to a substrate; (2) The coating is surface exposed using excimer ultraviolet light under an inert atmosphere; (3) The energy used is 20-80 mJ / cm 2 The coating is pre-cured entirely by UV light.

2. The method according to claim 1, characterized in that, The UV curing composition comprises a trifunctional UV resin, a hexafunctional UV resin, and a 2-3 functional acrylate monomer; based on a total mass of 100 parts of resin and monomer, the trifunctional UV resin comprises 60-75 parts, the hexafunctional UV resin comprises 15-20 parts, and the 2-3 functional acrylate monomer comprises 10-20 parts.

3. The method according to claim 1, characterized in that, The trifunctional UV resin has a viscosity of 30,000-100,000 cps at 25°C and a molecular weight greater than 1,500; the hexafunctional UV resin has a viscosity greater than 50,000 cps at 25°C and a molecular weight greater than 1,000.

4. The method according to claim 1, characterized in that, In step (b), the wavelength of the excimer ultraviolet light is 165-180 nm, and the exposure power is 10-50 mW / cm². 2 The exposure time is 0.2-5 seconds.

5. The method according to claim 1, characterized in that: The process includes a drying step after the coating step and before the surface exposure step, wherein the maximum temperature of the drying step is not higher than 120°C.

6. A semi-cured hardening film, characterized in that, It is prepared by the method according to any one of claims 1 to 5.

7. A method for preparing a matte curing film, characterized in that, Includes the following steps: (1) The semi-cured hardened film of claim 6 is subjected to high-pressure molding; (2) UV curing is performed on the molded film material.

8. The method according to claim 7, characterized in that, The energy of the UV curing process is 800-1000 mJ / cm². 2 .

9. A matte curing film, characterized in that, It is prepared by the method described in claim 7 or 8.

10. An automotive interior component, characterized in that, It includes the matte curing film as described in claim 9.

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