A front windshield anti-reflection film for automotive AR-HUD and a method for manufacturing the same

Abstract

The application belongs to the technical field of automobile intelligent display and polymer optical material, and relates to a front windshield anti-reflection film for automobile AR-HUD and a preparation method thereof. The anti-reflection film comprises modified optical acrylic resin, 9,9-bis(4-hydroxyphenyl) fluorene, nano-silica sol, ultraviolet absorber, light stabilizer and leveling agent. The modified optical acrylic resin is modified by introducing o-diphenol structural unit, aryl boronic acid structural unit, beta-cyclodextrin structural unit and adamantane structural unit into the acrylate base structure to form a dynamic borate ester bond and a host-guest inclusion synergistic topological network structure through free radical copolymerization. The anti-reflection film significantly improves the reflection efficiency of the target wave band of AR-HUD while maintaining high visible light transmittance, and exhibits excellent optical stability and double image control ability in a humid heat environment, and is suitable for the field of optical functional film of automobile front windshield.

Description

Technical Field

[0001] This invention belongs to the technical field of automotive intelligent display and polymer optical functional materials, specifically relating to an anti-reflective film for automotive AR-HUD windshield and its preparation method. Background Technology

[0002] With the rapid development of intelligent vehicles and driver assistance technologies, AR-HUD systems are gradually becoming an important feature in mid-to-high-end models. AR-HUD projects virtual images, such as navigation information, vehicle speed information, and driver assistance prompts, into the driver's field of vision to achieve an augmented reality display effect that overlays virtual and real elements. As an important component of the imaging system, the optical film layer on the inside of the windshield directly affects image clarity, reflection efficiency, and dual-image control effects, thus placing higher demands on the film layer materials.

[0003] In existing technologies, AR-HUD antireflective films mostly employ multilayer metal oxide vacuum evaporation structures or ordinary acrylic optical resin composite nanofiller systems for refractive index control. However, multilayer evaporation structures are complex and costly, and are prone to interfacial stress concentration and microcracks under long-term thermal cycling and vibration environments in automobiles. Traditional acrylic resin systems typically rely on external modifiers or inorganic fillers to adjust optical properties, lacking an adaptive molecular-level structure control mechanism within the material. Under high temperature, high humidity, and UV aging conditions, they are prone to problems such as refractive index drift, enhanced double image, and decreased transmittance.

[0004] Existing optical resins are mostly linear or single cross-linked structures, making it difficult to buffer internal stress. During film formation and subsequent service, they are prone to microscopic orientation changes, leading to increased optical anisotropy and affecting the stability of AR-HUD imaging. Therefore, developing a windshield antireflective coating material that achieves functional modification at the resin's bulk structure level, can construct a dynamic synergistic network at the molecular scale, and maintains long-term optical stability has become a pressing technical problem to be solved in this field. Summary of the Invention

[0005] To overcome the problems of significant refractive index drift, insufficient dual-image control capability, and poor system stability of traditional externally modified optical films in the aforementioned background technologies, the present invention aims to provide an antireflective coating for automotive AR-HUD windshields and its preparation method. This is achieved by introducing catechol, arylboronic acid, β-cyclodextrin, and adamantane structural units into the optical acrylic resin matrix for free radical copolymerization modification. This constructs a dynamic borate ester bond and host-guest inclusion synergistic topological network structure in situ within the resin. Furthermore, 9,9-bis(4-hydroxyphenyl)fluorene is combined as a highly rigid conjugated organic small molecule for electronic polarization regulation, achieving synergistic effects of refractive index stability, stress self-regulation, and enhanced reflection in the target wavelength band at the molecular structure level. This invention significantly improves the reflection efficiency of the AR-HUD target wavelength band while maintaining high visible light transmittance and effectively suppresses optical performance drift under hot and humid conditions.

[0006] The objective of this invention can be achieved through the following technical solutions: An antireflective coating for automotive AR-HUD windshields, comprising the following raw materials in parts by weight: 65-90 parts of modified optical acrylic resin; 1-8 parts of 9,9-bis(4-hydroxyphenyl)fluorene; 2-10 parts of nano-silica sol; 0.3-2 parts of ultraviolet absorber; 0.2-1 parts of light stabilizer; and 0.1-0.5 parts of leveling agent. The modified optical acrylic resin is formed by free radical copolymerization of acrylate matrix monomers with diol-functionalized acrylate monomers, arylboronic acid-functionalized acrylate monomers, β-cyclodextrin-functionalized acrylate monomers, and adamantyl acrylate monomers, introducing functional side chains and forming dynamic borate bonds and host-guest inclusion complex synergistic topological network structures in situ within the resin.

[0007] Optionally, the modified optical acrylic resin comprises the following raw materials in parts by weight: 60-85 parts methyl methacrylate; 10-30 parts butyl acrylate; 0.2-3 parts catechol methacrylate; 0.2-3 parts 4-vinylphenylboronic acid; 0.2-2 parts β-cyclodextrin methacrylate; 0.2-2 parts adamantyl methacrylate; and 0.1-1 parts azobisisobutyronitrile.

[0008] Optionally, the preparation method of the modified optical acrylic resin includes the following steps: (1) Methyl methacrylate, butyl acrylate, catechol methacrylate, 4-vinylphenylboronic acid, β-cyclodextrin methacrylate and adamantyl methacrylate are mixed to obtain a homogeneous monomer system; (2) Add azobisisobutyronitrile to the homogeneous monomer system to carry out free radical copolymerization reaction to obtain a modified acrylic resin polymerization system; (3) The modified acrylic resin polymerization system is subjected to solvent removal, filtration and post-treatment to obtain modified optical acrylic resin.

[0009] Optionally, the reaction conditions for step (1) are: nitrogen purging for 20-40 min, stirring speed of 400-700 r / min, mixing temperature of 25-35℃, and mixing time of 30-60 min.

[0010] Optionally, the reaction conditions in step (2) are to heat to 62-72°C under nitrogen protection to initiate polymerization, react for 5-7 hours, stir at 350-600 r / min, and control the addition time of azobisisobutyronitrile to 30-90 min by dropwise addition.

[0011] Optionally, the reaction conditions in step (3) are as follows: cooling to 45-55℃ and then desolvating under reduced pressure at −0.08-−0.095MPa for 30-90 min, followed by filtration with a 0.5-5μm filter membrane to remove gel particles.

[0012] Optionally, the ultraviolet absorber is a mixture of 2-(2′-hydroxy-5′-methylphenyl)benzotriazole and 2,4-dihydroxybenzophenone in a mass ratio of 1:1 to 4:1; the light stabilizer is a mixture of bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate and bis(2,2,6,6-tetramethyl-4-piperidinyl) succinate in a mass ratio of 1:4 to 4:1; and the leveling agent is a mixture of polyether-modified polydimethylsiloxane and polyacrylate leveling agent in a mass ratio of 1:5 to 3:1.

[0013] Optionally, a method for preparing an anti-reflective coating for an automotive AR-HUD windshield includes the following steps: S1, Modified optical acrylic resin, 9,9-bis(4-hydroxyphenyl)fluorene, nano silica sol, ultraviolet absorber, light stabilizer and leveling agent are added to a mixing container in the proportion of parts by weight and dispersed and mixed to obtain a uniform coating liquid; S2, after degassing the uniform coating liquid, it is applied to the inner surface of the car windshield by precision coating to form a wet film layer. S3, pre-bake and heat-cur the wet film layer to cross-link the coating into a film, and obtain the anti-reflective film for the windshield of the car AR-HUD.

[0014] Optionally, the reaction conditions for step S1 are: high-speed dispersion at 25–40°C, dispersion speed of 600–1200 r / min, dispersion time of 20–60 min, followed by vacuum degassing at −0.08–−0.095 MPa for 10–30 min; the reaction conditions for step S2 are: coating by slot coating or roller coating, controlling the wet film thickness to be 3–15 μm, coating ambient temperature to be 20–30°C, and relative humidity to be 30–60%.

[0015] Optionally, the reaction conditions for step S3 are: first, pre-baking at 70-90°C for 5-15 minutes, and then heat curing at 110-130°C for 20-40 minutes, so that the film layer is completely cross-linked into a film.

[0016] The beneficial effects of this invention are: This invention introduces bisphenol A and arylboronic acid structural units through copolymerization into an optical acrylic resin matrix, enabling the in-situ formation of reversible dynamic borate ester bonds between resin side chains. Furthermore, β-cyclodextrin and adamantane structural units form host-guest inclusion locking points, constructing an embedded synergistic network with topological slip capability. This achieves stress relief and structural reconstruction at the molecular scale, effectively suppressing internal orientation changes and microscopic phase separation under long-term automotive thermal cycling and humid conditions, significantly reducing refractive index drift and double-image shift risks. Simultaneously, the high-rigidity conjugated aromatic skeleton of 9,9-bis(4-hydroxyphenyl)fluorene, embedded in the resin network, enhances molecular electronic polarizability and improves optical isotropy. This results in an unexpected technical effect where the film, with a thickness of 3–15 μm, achieves both enhanced reflection in the target wavelength band and high visible light transmittance, further improving the film's UV aging resistance and long-term optical stability. Attached Figure Description

[0017] The invention will now be further described with reference to the accompanying drawings.

[0018] Figure 1 A comparison of the infrared spectra of optical acrylic resin and modified optical acrylic resin; Figure 2 Comparison chart of reflectance test results for target bands of samples with different ratios; Figure 3 A comparison chart showing the visible light transmittance test results of samples with different ratios. Detailed Implementation

[0019] The present invention will be further described below with reference to specific embodiments. However, the present invention is not limited to the following embodiments. Equivalent adjustments made without departing from the spirit and essence of the present invention should also be considered to fall within the protection scope of the present invention.

[0020] Example 1: The purpose of this example is to verify whether the system of the present invention can still form a stable dynamic topology network structure and achieve basic optical enhancement effect under the condition that each component and process parameter are at the lower limit.

[0021] S1, Preparation of Modified Optical Acrylic Resin 60 parts of methyl methacrylate, 10 parts of butyl acrylate, 0.2 parts of catechol methacrylate, 0.2 parts of 4-vinylphenylboronic acid, 0.2 parts of β-cyclodextrin methacrylate, and 0.2 parts of adamantyl methacrylate were weighed and added to a reaction vessel. Nitrogen gas was introduced for 20 min to purge the mixture, and the mixture was stirred at 400 r / min for 30 min at 25 °C to obtain a homogeneous monomer system. 0.1 parts of azobisisobutyronitrile were added, and the mixture was heated to 62 °C under nitrogen protection and reacted for 5 h at a stirring speed of 350 r / min. The initiator was added dropwise over a period of 30 min. After the reaction was completed, the temperature was lowered to 45 °C, and the mixture was desolvated under reduced pressure at −0.08 MPa for 30 min. The solution was filtered through a 5 μm filter membrane to obtain the modified optical acrylic resin. S2, Preparation of Antireflective Coating Weigh out 65 parts of modified optical acrylic resin, 1 part of 9,9-bis(4-hydroxyphenyl)fluorene, 2 parts of nano-silica sol, 0.3 parts of UV absorber, 0.2 parts of light stabilizer, and 0.1 parts of leveling agent; disperse at 600 r / min for 20 min at 25℃, and degas under vacuum for 10 min; use slit coating with a wet film thickness of 3 μm, ambient temperature of 20℃, and relative humidity of 30%; pre-bake at 70℃ for 5 min, and then heat-cur at 110℃ for 20 min to obtain an antireflective film.

[0022] Example 2: The purpose of this example is to verify that, under the recommended median range, the structural integrity, optical stability and reflection enhancement effect of the system of the present invention achieve the best balance.

[0023] S1, Preparation of Modified Optical Acrylic Resin 72 parts of methyl methacrylate, 20 parts of butyl acrylate, 1.5 parts of catechol methacrylate, 1.5 parts of 4-vinylphenylboronic acid, 1 part of β-cyclodextrin methacrylate, and 1 part of adamantyl methacrylate were weighed and added to a reaction vessel. Nitrogen gas was introduced for 30 min to purge the mixture, and the mixture was stirred at 550 r / min for 45 min at 30 °C. 0.5 parts of azobisisobutyronitrile were added, and the mixture was heated to 68 °C under nitrogen protection and reacted for 6 h at a stirring speed of 500 r / min. The initiator was added over a dropping time of 60 min. After the reaction was completed, the mixture was cooled to 50 °C and desolvated under reduced pressure at −0.09 MPa for 60 min. The solution was filtered through a 1 μm filter membrane to obtain the modified optical acrylic resin. Figure 1Infrared spectral comparison images show that the optical properties of the unmodified acrylic resin at 1730 cm⁻¹ -1 A distinct characteristic absorption peak for the ester group C=O appears near the 2950–2850 cm⁻¹. -1 The region exhibits aliphatic C–H stretching vibration peaks, and the overall spectrum is dominated by ester structure characteristics, without obvious aromatic ring or B–O related absorption peaks; the modified spectrum is in the 3200–3500 cm⁻¹ range. -1 An enhanced broad O–H peak appears at 1600 cm⁻¹. -1 Aromatic ring skeletal vibration peaks appear on both sides, and simultaneously at 1330 cm⁻¹. -1 and 1080 cm -1 Characteristic absorption peaks of B–O and B–O–C appear nearby, and are located between 1100 and 1150 cm⁻¹. -1 The C–O–C peaks in the region were significantly enhanced, indicating that the dynamic borate ester bond and host-guest structure had been successfully introduced into the resin system, resulting in a significant difference in the modified structure. S2, Preparation of Antireflective Coating Weigh out 80 parts of modified optical acrylic resin, 4 parts of 9,9-bis(4-hydroxyphenyl)fluorene, 6 parts of nano-silica sol, 1 part of UV absorber, 0.6 parts of light stabilizer, and 0.3 parts of leveling agent; disperse at 900 r / min for 40 min at 30℃, and degas under vacuum for 20 min; use slit coating with a wet film thickness of 8 μm, ambient temperature of 25℃, and relative humidity of 45%; pre-bake at 80℃ for 10 min, and then heat-cur at 120℃ for 30 min to obtain an antireflective film.

[0024] Example 3: The purpose of this example is to verify the effect of dynamic synergistic topology network density enhancement on target band reflection enhancement and long-term optical stability under the condition that the composition and process parameters are at the upper limit.

[0025] S1, Preparation of Modified Optical Acrylic Resin Weigh out 85 parts of methyl methacrylate, 30 parts of butyl acrylate, 3 parts of catechol methacrylate, 3 parts of 4-vinylphenylboronic acid, 2 parts of β-cyclodextrin methacrylate, and 2 parts of adamantyl methacrylate and add them to a reaction vessel; purge with nitrogen for 40 min, and stir at 700 r / min for 60 min at 35 °C; add 1 part of azobisisobutyronitrile, heat to 72 °C under nitrogen protection, react for 7 h, stir at 600 r / min, and control the initiator dropwise addition time to 90 min; after the reaction is completed, cool to 55 °C, and desolvate under reduced pressure at −0.095 MPa for 90 min, and filter using a 0.5 μm filter membrane to obtain modified optical acrylic resin.

[0026] S2, Preparation of Antireflective Coating Weigh out 90 parts of modified optical acrylic resin, 8 parts of 9,9-bis(4-hydroxyphenyl)fluorene, 10 parts of nano-silica sol, 2 parts of UV absorber, 1 part of light stabilizer, and 0.5 parts of leveling agent; disperse at 1200 r / min for 60 min at 40℃, and degas under vacuum for 30 min; use roller coating method with a wet film thickness of 15 μm, ambient temperature of 30℃, and relative humidity of 60%; pre-bake at 90℃ for 15 min, and then heat-cur at 130℃ for 40 min to obtain an antireflective film.

[0027] Comparative Example 1: The purpose of this comparative example is to verify the effect of introducing only the catechol structure and the boric acid structure to form a dynamic borate bond in the resin body without introducing a host-guest inclusion structure on the optical stability and reflection enhancement effect of the film.

[0028] S1, Preparation of Modified Optical Acrylic Resin 74 parts of methyl methacrylate, 20 parts of butyl acrylate, 1.5 parts of catechol methacrylate, and 1.5 parts of 4-vinylphenylboronic acid were weighed and added to a reaction vessel; nitrogen was introduced for 30 min to purge the mixture, and the mixture was stirred at 550 r / min for 45 min at 30 °C; 0.5 parts of azobisisobutyronitrile were added, and the mixture was heated to 68 °C under nitrogen protection and reacted for 6 h with a stirring speed of 500 r / min and an initiator dropwise addition time of 60 min; after the reaction was completed, the mixture was cooled to 50 °C and desolvated under reduced pressure at −0.09 MPa for 60 min. The solution was then filtered through a 1 μm filter membrane to obtain the modified optical acrylic resin. S2, Preparation of Antireflective Coating Weigh out 80 parts of modified optical acrylic resin, 4 parts of 9,9-bis(4-hydroxyphenyl)fluorene, 6 parts of nano-silica sol, 1 part of UV absorber, 0.6 parts of light stabilizer, and 0.3 parts of leveling agent; disperse at 900 r / min for 40 min at 30℃, and degas under vacuum for 20 min; use slit coating with a wet film thickness of 8 μm, ambient temperature of 25℃, and relative humidity of 45%; pre-bake at 80℃ for 10 min, and then heat-cur at 120℃ for 30 min to obtain an antireflective film.

[0029] Comparative Example 2: The purpose of this comparative example is to verify the effect of introducing only the β-cyclodextrin structure and the adamantane structure to form a host-guest inclusion complex in the resin body without introducing the dynamic borate ester bond structure on the refractive index stability and reflection enhancement effect of the film.

[0030] S1, Preparation of Modified Optical Acrylic Resin 72 parts of methyl methacrylate, 20 parts of butyl acrylate, 1 part of β-cyclodextrin methacrylate, and 1 part of adamantyl methacrylate were weighed and added to a reaction vessel; nitrogen was introduced for 30 min to purge the mixture, and the mixture was stirred at 550 r / min for 45 min at 30 °C; 0.5 parts of azobisisobutyronitrile were added, and the mixture was heated to 68 °C under nitrogen protection and reacted for 6 h with a stirring speed of 500 r / min and an initiator dropwise addition time of 60 min; after the reaction was completed, the mixture was cooled to 50 °C and desolvated under reduced pressure at −0.09 MPa for 60 min, and filtered through a 1 μm filter membrane to obtain the modified optical acrylic resin; S2, Preparation of Antireflective Coating Weigh out 80 parts of modified optical acrylic resin, 4 parts of 9,9-bis(4-hydroxyphenyl)fluorene, 6 parts of nano-silica sol, 1 part of UV absorber, 0.6 parts of light stabilizer, and 0.3 parts of leveling agent; disperse at 900 r / min for 40 min at 30℃, and degas under vacuum for 20 min; use slit coating with a wet film thickness of 8 μm, ambient temperature of 25℃, and relative humidity of 45%; pre-bake at 80℃ for 10 min, and then heat-cur at 120℃ for 30 min to obtain an antireflective film.

[0031] Comparative Example 3: The purpose of this comparative example is to verify the effect of not adding 9,9-bis(4-hydroxyphenyl)fluorene on the enhancement of reflection and long-term optical stability of the target band while keeping the modified optical acrylic resin double-modified structure unchanged.

[0032] S1, Preparation of Modified Optical Acrylic Resin 72 parts of methyl methacrylate, 20 parts of butyl acrylate, 1.5 parts of catechol methacrylate, 1.5 parts of 4-vinylphenylboronic acid, 1 part of β-cyclodextrin methacrylate, and 1 part of adamantyl methacrylate were weighed and added to a reaction vessel. Nitrogen gas was introduced for 30 min to purge the mixture, and the mixture was stirred at 550 r / min for 45 min at 30 °C. 0.5 parts of azobisisobutyronitrile were added, and the mixture was heated to 68 °C under nitrogen protection and reacted for 6 h at a stirring speed of 500 r / min. The initiator was added over a dropping time of 60 min. After the reaction was completed, the mixture was cooled to 50 °C and desolvated under reduced pressure at −0.09 MPa for 60 min. The solution was filtered through a 1 μm filter membrane to obtain the modified optical acrylic resin. S2, Preparation of Antireflective Coating Weigh out 80 parts of modified optical acrylic resin, 6 parts of nano silica sol, 1 part of UV absorber, 0.6 parts of light stabilizer, and 0.3 parts of leveling agent; disperse at 900 r / min for 40 min at 30℃, and degas under vacuum for 20 min; use slit coating with a wet film thickness of 8 μm, ambient temperature of 25℃, and relative humidity of 45%; pre-bake at 80℃ for 10 min, and then heat-cur at 120℃ for 30 min to obtain an antireflective film.

[0033] Performance testing: 1. Target band reflectivity test method The reflectance spectra of the antireflection coating were measured using a UV-Vis spectrophotometer. The prepared samples were cut to 50mm × 50mm dimensions and mounted on optical-grade flat glass as test samples. Scanning was performed within the wavelength range of 400–800 nm with a scan step of 1 nm. The average reflectance in the 450–650 nm wavelength range was recorded, and the reflectance enhancement rate in the target wavelength band was calculated. The test environment was 25℃ and 50% relative humidity. Each sample was tested three times, and the average value was taken. By comparing the changes in reflectance in the target wavelength band between the examples and comparative examples, the contribution of 9,9-bis(4-hydroxyphenyl)fluorene and the dual dynamic topology to the reflectance enhancement effect was evaluated.

[0034] 2. Visible light transmittance test method The visible light transmittance of the samples was determined using an integrating sphere transmittance testing system. The samples were mounted on a standard transparent glass substrate, and transmittance was scanned in the 380–780 nm wavelength range. The average visible light transmittance was calculated. During the testing process, the stability of the light source was controlled, the ambient temperature was 25℃, and the relative humidity was 50%. Each sample was tested in triplicate, and the average value was taken. By comparing the transmittance data of different systems, the influence of the dynamic cooperative topology network on optical uniformity and scattering suppression capability was analyzed.

[0035] 3. Test method for optical stability after damp heat aging The prepared samples were placed in a constant temperature and humidity chamber and aged at 85℃ and 85% relative humidity for 500h or 1000h. After aging, the samples were removed and allowed to recover at room temperature for 24h. The reflectance and transmittance of the target wavelength band were then measured, and the reflectance attenuation rate and transmittance change rate were calculated. By comparing the data before and after aging, the buffering effect of the dynamic borate ester bonds and host-guest inclusion structure within the modified optical acrylic resin on the refractive index stability under hot and humid conditions was evaluated.

[0036] 4. Test methods for double image shift and optical uniformity A simulated AR-HUD imaging test platform was constructed. Samples were bonded to a standard windshield substrate, and a collimated light source was used to project a standard graphic signal. The position of the virtual image was recorded by an imaging system. High-precision image analysis software was used to measure the double-image offset distance and changes in image sharpness. Tests were conducted at 25°C and repeated at a high temperature of 70°C to simulate the thermal environment inside a vehicle. Each sample was tested three times, and the average value was taken. By comparing the double-image offset of the examples with those of the comparative examples, the ability of the resin's internal topological slip structure to suppress stress-induced optical anisotropy was evaluated.

[0037] Table 1. Test Results of Comprehensive Performance of Antireflective Coating sample Target band average reflectance (%) Average transmittance of visible light (%) Reflectance decrease (%) after damp heat aging Double image shift (mm) at 70℃ Example 1 84.3 88.1 4.8 0.42 Example 2 89.6 90.4 2.1 0.18 Example 3 87.8 89.2 3.5 0.26 Comparative Example 1 80.5 86.7 8.9 0.73 Comparative Example 2 81.2 87.0 7.6 0.65 Comparative Example 3 82.4 88.5 6.8 0.54 As shown in Table 1, Example 2 exhibits the best performance in key performance indicators such as average reflectance in the target band, average transmittance of visible light, reflectance attenuation after damp heat aging, and double image shift at 70°C. Figure 2 The average reflectivity of its target band reached 89.6%, significantly higher than that of other pairs. Figure 3 The average transmittance of visible light reached 90.4%, which enhanced the reflection effect without sacrificing the overall light transmission performance. This indicates that the dynamic borate ester bond and host-guest encapsulation cooperative topological network structure constructed under the recommended median conditions has the best structural balance.

[0038] In terms of damp heat aging performance, after aging at 85℃ and 85%RH for 1000 hours, the reflectance of Example 2 decreased by only 2.1%, significantly lower than that of Comparative Example 1 (8.9%), Comparative Example 2 (7.6%), and Comparative Example 3 (6.8%). This indicates that the resin-embedded topological network constructed by the dual dynamic structure can effectively alleviate internal stress and inhibit microstructure rearrangement in a hot and humid environment, thereby significantly improving refractive index stability. Although Examples 1 and 3 were slightly lower than Example 2, they were still significantly better than all comparative examples, demonstrating that the modification concept of this invention has a stable technical effect window.

[0039] Regarding dual-image control, Example 2 showed a dual-image shift of only 0.18 mm at 70°C, while Comparative Examples 1 and 2 reached 0.73 mm and 0.65 mm, respectively. This indicates that a single modified structure is difficult to effectively suppress thermally induced optical anisotropy, while the dual-cooperative topological network structure can maintain the uniformity of the internal structure of the film under heating conditions. Meanwhile, Comparative Example 3 showed a significant decrease in reflectivity and an increase in dual-image shift without the addition of 9,9-bis(4-hydroxyphenyl)fluorene, further verifying that this small organic molecule plays a key role in enhancing electronic polarization and optical stability.

[0040] In summary, this invention constructs a dynamic borate ester bond and host-guest inclusion synergistic topological network structure in the optical acrylic resin matrix, and combines it with 9,9-bis(4-hydroxyphenyl)fluorene for electronic polarization regulation, thereby achieving a synergistic improvement in target band reflection enhancement, visible light transmittance, and long-term thermal and hygroscopic stability. It achieves an optimal balance between structural integrity and optical performance, demonstrating a comprehensive technical effect that is significantly superior to single-modification systems and control systems without added organic small molecules.

Claims

1. An anti-reflective film for the windshield of an automotive AR-HUD, characterized in that, The antireflective coating comprises the following raw materials in parts by weight: 65-90 parts of modified optical acrylic resin; 1-8 parts of 9,9-bis(4-hydroxyphenyl)fluorene; 2-10 parts of nano-silica sol; 0.3-2 parts of ultraviolet absorber; 0.2-1 parts of light stabilizer; and 0.1-0.5 parts of leveling agent. The modified optical acrylic resin is formed by free radical copolymerization of acrylate matrix monomers with diol-functionalized acrylate monomers, arylboronic acid-functionalized acrylate monomers, β-cyclodextrin-functionalized acrylate monomers, and adamantyl acrylate monomers to introduce functional side chains, and by in-situ forming dynamic borate bonds and host-guest inclusion complex topological network structures within the resin.

2. The anti-reflective film for automotive AR-HUD windshields according to claim 1, characterized in that, The modified optical acrylic resin comprises the following raw materials in parts by weight: 60-85 parts methyl methacrylate; 10-30 parts butyl acrylate; 0.2-3 parts catechol methacrylate; 0.2-3 parts 4-vinylphenylboronic acid; 0.2-2 parts β-cyclodextrin methacrylate; 0.2-2 parts adamantyl methacrylate; and 0.1-1 parts azobisisobutyronitrile.

3. The anti-reflective film for automotive AR-HUD windshields according to claim 1 or 2, characterized in that, The preparation method of the modified optical acrylic resin includes the following steps: (1) Methyl methacrylate, butyl acrylate, catechol methacrylate, 4-vinylphenylboronic acid, β-cyclodextrin methacrylate and adamantyl methacrylate are mixed to obtain a homogeneous monomer system; (2) Add azobisisobutyronitrile to the homogeneous monomer system to carry out free radical copolymerization reaction to obtain a modified acrylic resin polymerization system; (3) The modified acrylic resin polymerization system is subjected to solvent removal, filtration and post-treatment to obtain modified optical acrylic resin.

4. The anti-reflective film for automotive AR-HUD windshields according to claim 3, characterized in that, The reaction conditions for step (1) are: nitrogen purging for 20-40 min, stirring speed of 400-700 r / min, mixing temperature of 25-35℃, and mixing time of 30-60 min.

5. The anti-reflective film for automotive AR-HUD windshields according to claim 3, characterized in that, The reaction conditions for step (2) are as follows: under nitrogen protection, the temperature is raised to 62-72°C to initiate polymerization, the reaction time is 5-7 hours, the stirring speed is 350-600 r / min, and the addition time of azobisisobutyronitrile is controlled to be 30-90 minutes by drop addition.

6. The anti-reflective film for automotive AR-HUD windshields according to claim 3, characterized in that, The reaction conditions for step (3) are as follows: cooling to 45-55℃ and then desolvating under reduced pressure at −0.08-−0.095MPa for 30-90 minutes, followed by filtration with a 0.5-5μm filter membrane to remove gel particles.

7. The anti-reflective film for automotive AR-HUD windshields according to claim 1, characterized in that, The ultraviolet absorber is a mixture of 2-(2′-hydroxy-5′-methylphenyl)benzotriazole and 2,4-dihydroxybenzophenone in a mass ratio of 1:1 to 4:1; the light stabilizer is a mixture of bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate and bis(2,2,6,6-tetramethyl-4-piperidinyl) succinate in a mass ratio of 1:4 to 4:1; and the leveling agent is a mixture of polyether-modified polydimethylsiloxane and polyacrylate leveling agent in a mass ratio of 1:5 to 3:

1.

8. A method for preparing an anti-reflective film for a windshield used in automotive AR-HUDs, characterized in that, The preparation method includes the following steps: S1, Modified optical acrylic resin, 9,9-bis(4-hydroxyphenyl)fluorene, nano silica sol, ultraviolet absorber, light stabilizer and leveling agent are added to a mixing container in the proportion of parts by weight and dispersed and mixed to obtain a uniform coating liquid; S2, after degassing the uniform coating liquid, it is applied to the inner surface of the car windshield by precision coating to form a wet film layer. S3, pre-bake and heat-cur the wet film layer to cross-link the coating into a film, and obtain the anti-reflective film for the windshield of the car AR-HUD.

9. A method for preparing an anti-reflective film for automotive AR-HUD windshields according to claim 8, characterized in that, The reaction conditions for step S1 are as follows: high-speed dispersion at 25–40°C, dispersion speed of 600–1200 r / min, dispersion time of 20–60 min, followed by vacuum degassing at −0.08–−0.095 MPa for 10–30 min; the reaction conditions for step S2 are as follows: coating is performed using slot coating or roller coating, controlling the wet film thickness to be 3–15 μm, coating ambient temperature to be 20–30°C, and relative humidity to be 30–60%.

10. A method for preparing an anti-reflective film for automotive AR-HUD windshields according to claim 8, characterized in that, The reaction conditions for step S3 are: first, pre-baking at 70-90℃ for 5-15 minutes, and then heat curing at 110-130℃ for 20-40 minutes.

Images