Scratch-resistant film as well as preparation method and application thereof

Abstract

The invention discloses a scratch-resistant film as well as a preparation method and application thereof, and belongs to the technical field of automobile protection materials. The film adopts a multi-layer composite structure and comprises a scratch-resistant coating, a first base material layer, an adhesive layer and a second base material layer from top to bottom. Wherein the scratch-resistant coating is formed by coating the surface of the first base material layer with a coating composition consisting of polyurethane acrylate, nano silicon dioxide, a photoinitiator and the balance of a solvent in specific parts by weight through a gravure coating process and then curing through ultraviolet irradiation with specific parameters. The first base material layer is preferably a thermoplastic polyurethane film, the second base material layer is preferably a polyethylene glycol terephthalate film, and the adhesive layer is an acrylic acid pressure-sensitive adhesive layer. The surface of the film has high hardness and good flexibility, not only has excellent scratch resistance, but also can realize scratch self-repairing under thermal stimulation, and shows excellent weather resistance and yellowing resistance at the same time. The scratch-resistant film is particularly suitable for manufacturing automobile paint surface protective films and automobile windshield solar films.

Description

Technical Field

[0001] This invention relates to the field of automotive protective materials technology, specifically to a scratch-resistant film, its preparation method, and its applications. More specifically, it relates to a multilayer composite film with excellent scratch resistance, self-healing properties, and weather resistance, its preparation method, and its applications in the field of automotive protection (such as car covers and solar films). Background Technology

[0002] With the continuous development of the automotive industry and the increasing awareness of consumers regarding car exterior maintenance, the application of automotive paint protection film and automotive window film has become very common. These film products are applied to the car body paint or window glass to protect the original paint from damage caused by various factors such as stone impacts, minor scratches from tree branches, acid rain erosion, and ultraviolet aging during daily use. They also improve heat insulation performance, enhance privacy, and provide explosion-proof safety.

[0003] However, those skilled in the art are aware that existing automotive protective films have revealed a series of unresolved technical problems during long-term practical use. The most prominent contradiction lies in the imbalance between the film's surface scratch resistance and other key performance characteristics. Many products, in pursuit of high hardness and scratch resistance, often use highly cross-linked, brittle coating materials. This results in insufficient flexibility when the film is applied to car bodies with complex curves, easily leading to loose adhesion, edge lifting, and the risk of brittle cracking under significant external impact. Conversely, if too much emphasis is placed on flexibility, surface hardness must be sacrificed, making the film surface easily scratched by daily car washes and windblown sand, severely affecting aesthetics and long-lasting protective effects.

[0004] Furthermore, while some existing products claim to possess a certain degree of self-healing capability, their repair effectiveness often relies on high trigger temperatures, and their repair efficiency significantly decreases after repeated scratches. Simultaneously, prolonged exposure to harsh outdoor environments, particularly strong ultraviolet radiation, causes many thin-film materials to exhibit irreversible yellowing, increased haze, and physical property degradation—in other words, insufficient weather resistance—failing to maintain their initial optical performance and protective function throughout their expected lifespan. Therefore, the market urgently needs a novel thin-film structure that comprehensively balances scratch resistance, flexibility, long-term weather resistance, and reliable self-healing performance to overcome the aforementioned shortcomings of existing technologies. Summary of the Invention

[0005] The purpose of this invention is to provide a scratch-resistant film, its preparation method and application. To achieve the above purpose, this invention provides the following technical solution: a scratch-resistant film, comprising, from top to bottom, a scratch-resistant coating (1), a first substrate layer (2), an adhesive layer (3), and a second substrate layer (4); the scratch-resistant coating (1) is formed by ultraviolet light curing of a coating composition comprising polyurethane acrylate, nano-silica, photoinitiator and solvent.

[0006] Furthermore, by weight, the coating composition comprises the following components: 50-70 parts polyurethane acrylate; 5-20 parts nano silica; 1-5 parts photoinitiator; and the balance solvent.

[0007] Furthermore, the solvent is at least one selected from ethyl acetate, acetone, and butanone.

[0008] Furthermore, the first substrate layer (2) is a thermoplastic polyurethane film; and / or, the second substrate layer (4) is a polyethylene terephthalate film.

[0009] Furthermore, the adhesive layer (3) is an acrylic pressure-sensitive adhesive layer.

[0010] A method for preparing a scratch-resistant film includes the following steps: coating the coating composition onto one surface of the first substrate layer (2) by gravure coating.

[0011] The coating composition is cured by ultraviolet light to form the anti-scratch coating (1).

[0012] The adhesive layer (3) is disposed on the other surface of the first substrate layer (2).

[0013] The second substrate layer (4) is laminated onto the adhesive layer (3).

[0014] Furthermore, the wavelength of the ultraviolet light irradiation curing is 320-390nm, and the irradiation energy is 400-800mJ / cm2.

[0015] An application of a scratch-resistant film for protecting the surface of automotive paint from scratches.

[0016] An application of a scratch-resistant film to block ultraviolet rays from automotive windshields.

[0017] An article having the aforementioned anti-scratch film attached to its surface; the article being a car body or car glass. Beneficial effects

[0018] The anti-scratch film and its preparation method provided by this invention, through ingenious multi-layer structure design and unique coating composition, produce the following series of positive and interrelated technical effects: 1. This invention significantly improves the microscopic hardness and wear resistance of the film surface by constructing an ultraviolet-cured anti-scratch coating composed of a specific ratio of polyurethane acrylate and nano-silica in the outermost layer. The nano-silica particles are uniformly dispersed in the cross-linked network of the polymer, forming a robust organic-inorganic composite structure that can effectively resist mechanical scratches caused by car wash brushes, gravel, etc., keeping the film surface smooth and new for a long time.

[0019] 2. This invention uses aliphatic polyurethane acrylate with moderate functionality as the main film-forming material for the coating. While achieving a high crosslinking density, the molecular chain segments retain a certain degree of mobility. This allows the polymer chains to creep and fill the gaps left by the scratches when minor scratches appear on the film surface, under the stimulation of ambient temperature or sunlight, thus achieving effective self-repair and restoring the surface smoothness and optical uniformity.

[0020] 3. The multilayer structure described in this invention, particularly the combination of thermoplastic polyurethane as the first substrate layer and polyethylene terephthalate as the second substrate layer, creates a reasonable gradient in material mechanical properties, from a hard surface to a flexible interior. This design allows energy to be absorbed and dissipated layer by layer when the film is subjected to impact, avoiding coating cracking or overall damage caused by stress concentration, and ensuring that the film has excellent adhesion and deformation adaptability on various complex vehicle body surfaces.

[0021] 4. The aliphatic polyurethane acrylate matrix used in the anti-scratch coating of this invention possesses excellent anti-UV aging properties. Combined with the surface-modified nano-silica, which scatters and absorbs UV light, the two work synergistically to greatly enhance the weather resistance of the entire film system. Under long-term outdoor exposure, this film effectively inhibits yellowing, maintains high light transmittance and low haze, and significantly reduces the rate of degradation of its physical and mechanical properties, thus extending its service life.

[0022] 5. The preparation method employed in this invention, particularly through precise control of coating thickness and uniformity via gravure coating and curing with ultraviolet light of a specific wavelength and energy range, ensures the formation of a dense and defect-free anti-scratch coating. This process is mature and stable, suitable for large-scale continuous production, and yields thin film products with consistent performance and reliable quality. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the layered structure of a scratch-resistant film.

[0024] Reference numerals: 1. Anti-scratch coating; 2. First substrate layer; 3. Adhesive layer; 4. Second substrate layer. Detailed Implementation

[0025] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0026] All experiments were conducted in a standard laboratory environment with standard atmospheric pressure, room temperature of 25±2℃, and relative humidity of 50%±10%, unless otherwise stated. Example 1

[0027] This embodiment provides a scratch-resistant film and its preparation method. A schematic diagram of the layered structure of the scratch-resistant film is shown below. Figure 1 .

[0028] First, prepare the anti-scratch coating solution: Add 67 parts by weight of aliphatic polyurethane acrylate (functionality 4), 13 parts by weight of nano-silica (average particle size 30nm) modified with silane coupling agent KH-570, 3.5 parts by weight of photoinitiator 184, and 16.5 parts by weight of ethyl acetate solvent to a stirred tank. Stir continuously at 1200 rpm using a high-speed disperser for 2.5 hours until the nanoparticles are completely dispersed and the system becomes homogeneous and transparent, thus obtaining the anti-scratch coating solution.

[0029] A thermoplastic polyurethane film with a thickness of 75 μm was selected as the first substrate layer 2. Using a precision gravure coating machine, the above coating liquid was uniformly coated on one surface of the first substrate layer 2, and the wet film thickness was controlled at 45 μm. Subsequently, the coated film was passed through a drying tunnel with a length of 8 meters. The temperature zones of the drying tunnel were set to 60°C, 75°C, and 85°C, with a total residence time of 90 seconds to allow the solvent to evaporate fully.

[0030] The dried film was immediately introduced into a UV curing apparatus and cured under a nitrogen protective atmosphere using a 365nm UV-LED light source, with the irradiation energy controlled at 650mJ / cm². 2 The curing time is 35 seconds, forming a scratch-resistant coating with a thickness of approximately 12 μm.

[0031] On the other surface of the first substrate layer 2, a 28 μm thick layer of acrylic pressure-sensitive adhesive is uniformly coated using a doctor blade coater to form an adhesive layer 3. Subsequently, a 50 μm thick polyethylene terephthalate film is used as the second substrate layer 4, and laminated with the adhesive layer 3 using a hot press roller under a pressure of 0.4 MPa and a temperature of 65°C. Finally, the laminated film roll is placed in a 45°C curing chamber and left to stand for 48 hours to obtain the scratch-resistant film of this embodiment. Example 2

[0032] The main difference between this embodiment and Embodiment 1 lies in the anti-scratch coating formulation and the selection of the substrate.

[0033] The anti-scratch coating liquid is composed of: 52 parts by weight of aliphatic polyurethane acrylate (functionality 2), 18 parts by weight of nano-silica (average particle size 15nm) modified with silane coupling agent KH-550, 4 parts by weight of photoinitiator TPO, and 26 parts by weight of a mixed solvent of acetone and butanone (volume ratio 1:1).

[0034] The first substrate layer 2 is a 125μm thick polyvinyl chloride film. The UV curing conditions after coating are adjusted to: wavelength 385nm, irradiation energy 480mJ / cm². 2 The curing time is 42 seconds.

[0035] The adhesive layer 3 is a 18μm thick silicone pressure-sensitive adhesive. The second substrate layer 4 is a 100μm thick polyethylene terephthalate film. The curing conditions are 35℃ for 60 hours. Example 3

[0036] This embodiment focuses on verifying the structure of a thinner substrate layer.

[0037] The anti-scratch coating liquid consists of: 70 parts by weight of aliphatic polyurethane acrylate (functionality 6), 8 parts by weight of modified nano silica (average particle size 45nm), 2 parts by weight of photoinitiator 1173, and 20 parts by weight of ethyl acetate solvent.

[0038] The first substrate layer 2 is a 38μm thick thermoplastic polyurethane film. After coating, it is cured by ultraviolet light with a wavelength of 355nm and an irradiation energy of 820mJ / cm². 2 Curing time: 28 seconds.

[0039] The adhesive layer 3 is a 35μm thick acrylic pressure-sensitive adhesive. The second substrate layer 4 is a 25μm thick polyethylene terephthalate film. The curing conditions are 55℃ for 30 hours. Comparative Example 1

[0040] This comparative example is essentially the same as Example 1, except that no nano-silica is added to the anti-scratch coating liquid. Accordingly, 13 parts by weight of nano-silica are replaced with an equal amount of polyurethane acrylate, increasing its amount to 80 parts by weight, while other components and preparation processes remain unchanged. Comparative Example 2

[0041] This comparative example is basically the same as Example 1, except that an equal amount of epoxy acrylate with a functionality of 6 is used to replace aliphatic polyurethane acrylate, while other components and preparation processes remain unchanged. Comparative Example 3

[0042] This comparative example is basically the same as Example 1, except that the gravure coating process was not used, but the ordinary doctor blade coating method was used instead, and the coating thickness uniformity was not strictly controlled. Other components and process conditions remained unchanged. Performance Testing and Results Analysis

[0043] The thin film samples prepared in the above embodiments and comparative examples were tested according to standard methods, and the results are recorded in the table below:

[0044] *The steel wool scratch test uses 0000 grade steel wool. After scratching 10 times under a 500g load, the surface condition is observed.

[0045] The test results show that the scratch-resistant films prepared in Examples 1 to 3 of this invention have achieved good overall performance in terms of hardness, scratch resistance, flexibility, self-healing ability, and weather resistance. Example 1, in particular, demonstrates balanced and outstanding performance across all test items.

[0046] Comparative Example 1, due to the absence of nano-silica, showed a sharp decline in surface hardness and scratch resistance, and completely lacked self-healing ability, demonstrating that the addition of nanoparticles is crucial for improving mechanical properties and forming a repairable network.

[0047] In Comparative Example 2, although the hardness was further improved by replacing polyurethane acrylate with epoxy acrylate, the brittleness of the coating increased significantly, and it cracked during bending and impact tests. At the same time, it completely lost its self-healing function and had poor yellowing resistance. This proves that polyurethane acrylate with a specific structure is the key to achieving toughness, self-healing and weather resistance.

[0048] Comparative Example 3 showed poor coating uniformity and a certain degree of decline in various properties due to insufficient precision in the preparation process, demonstrating that a specific gravure coating process plays an important role in ensuring the consistency of product performance.

[0049] The above embodiments are merely typical implementations of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A scratch resistant film characterized by, The scratch-resistant film comprises, from top to bottom, a scratch-resistant coating (1), a first substrate layer (2), an adhesive layer (3) and a second substrate layer (4); the scratch-resistant coating (1) is formed by ultraviolet curing of a coating composition comprising polyurethane acrylate, nano-silica, photoinitiator and solvent.

2. The scratch resistant film according to claim 1, wherein, The coating composition consists of the following components by weight parts: 50-70 parts of polyurethane acrylate; 5-20 parts of nano-silica; 1-5 parts of photoinitiator; and the balance of solvent.

3. The scratch resistant film according to claim 2, wherein, The solvent is at least one of ethyl acetate, acetone and butanone.

4. The scratch resistant film of claim 1, wherein The first substrate layer (2) is a thermoplastic polyurethane film; and / or the second substrate layer (4) is a polyethylene terephthalate film.

5. The scratch resistant film of claim 1, wherein The adhesive layer (3) is an acrylic pressure-sensitive adhesive layer.

6. A method of making a scratch resistant film as claimed in any one of claims 1 to 5, characterised in that, The method comprises the following steps: coating the coating composition on one surface of the first substrate layer (2) by gravure coating; ultraviolet irradiation curing of the coating composition to form the scratch-resistant coating (1); providing the adhesive layer (3) on the other surface of the first substrate layer (2); laminating the second substrate layer (4) on the adhesive layer (3).

7. The method of claim 6, wherein the anti-scratch film is prepared by the steps of: The wavelength of the ultraviolet light irradiation curing is 320-390 nm, and the irradiation energy is 400-800 mJ / cm 2 .

8. Use of the scratch-resistant film according to any one of claims 1 to 5 for protecting the surface of automobile paint from scratches.

9. Use of the scratch-resistant film according to any one of claims 1 to 5 for blocking ultraviolet rays of automobile windshields.

10. An article of manufacture characterized by, The article is an automobile body or automobile glass. The scratch-resistant film comprises, from top to bottom, a scratch-resistant coating (1), a first substrate layer (2), an adhesive layer (3) and a second substrate layer (4); the scratch-resistant coating (1) is formed by ultraviolet curing of a coating composition comprising polyurethane acrylate, nano-silica, photoinitiator and solvent. The coating composition consists of the following components by weight parts: 50-70 parts of polyurethane acrylate; 5-20 parts of nano-silica; 1-5 parts of photoinitiator; and the balance of solvent. The solvent is at least one of ethyl acetate, acetone and butanone. The first substrate layer (2) is a thermoplastic polyurethane film; and / or the second substrate layer (4) is a polyethylene terephthalate film. The adhesive layer (3) is an acrylic pressure-sensitive adhesive layer. The method comprises the following steps: coating the coating composition on one surface of the first substrate layer (2) by gravure coating; ultraviolet irradiation curing of the coating composition to form the scratch-resistant coating (1); providing the adhesive layer (3) on the other surface of the first substrate layer (2); laminating the second substrate layer (4) on the adhesive layer (3).

8. Use of the scratch-resistant film according to any one of claims 1 to 5 for protecting the surface of automobile paint from scratches.

9. Use of the scratch-resistant film according to any one of claims 1 to 5 for blocking ultraviolet rays of automobile windshields. The article is an automobile body or automobile glass. The scratch-resistant film comprises, from top to bottom, a scratch-resistant coating (1), a first substrate layer (2), an adhesive layer (3) and a second substrate layer (4); the scratch-resistant coating (1) is formed by ultraviolet curing of a coating composition comprising polyurethane acrylate, nano-silica, photoinitiator and solvent. The coating composition consists of the following components by weight parts: 50-70 parts of polyurethane acrylate; 5-20 parts of nano-silica; 1-5 parts of photoinitiator; and the balance of solvent. The solvent is at least one of ethyl acetate, acetone and butanone. The first substrate layer (2) is a thermoplastic polyurethane film; and / or the second substrate layer (4) is a polyethylene terephthalate film. The adhesive layer (3) is an acrylic pressure-sensitive adhesive layer. The method comprises the following steps: coating the coating composition on one surface of the first substrate layer (2) by gravure coating; ultraviolet irradiation curing of the coating composition to form the scratch-resistant coating (1); providing the adhesive layer (3

Images