High haze high temperature resistant diffusion film and preparation method thereof

Abstract

The application relates to the technical field of optical films, in particular to a high-haze high-temperature-resistant diffusion film and a preparation method thereof. The high-haze high-temperature-resistant diffusion film comprises a transparent base film and a diffusion layer coated on the surface of the transparent base film by a microgravure roll, wherein the diffusion layer comprises the following preparation raw materials in parts by mass: 60-70 parts of an acrylic resin oligomer, 20-30 parts of an acrylic resin monomer, 2-3 parts of triphenyl phosphate, 6-8 parts of a scratch-resistant agent, 3-5 parts of a photoinitiator and 6-9 parts of a diluent, wherein the scratch-resistant agent is modified silicon dioxide. Through the dual innovation of material chemical modification (such as SiO2 surface treatment and resin molecular design) and process formula optimization (such as photoinitiating system and diluent ratio), the technical bottleneck of the traditional diffusion film is solved, and problems such as easy aging under a high-temperature and high-humidity environment, insufficient scratch resistance and poor light uniformity are solved.

Description

Technical Field

[0001] This application relates to the field of optical thin film technology, and in particular to a high-haze, high-temperature resistant diffusion film and its preparation method. Background Technology

[0002] Liquid crystal displays (LCDs) are currently the most common display technology. However, LCDs are non-emissive display devices and require a backlight unit (BLU) to provide a bright and uniform light source to achieve the desired display effect. Traditional backlight modules are mainly composed of four films: a lower diffuser film, a lower brightness enhancement film, an upper brightness enhancement film, and an upper diffuser film. The diffuser film (DIF) has a diffuser layer structure on its light-emitting surface; its main function is to disperse incident light, acting as a diffuser to improve the uniformity of the LCD screen.

[0003] Existing diffusion films for LCD displays have a haze of over 90% on the front side and less than 15% on the back side. Furthermore, the structure of the diffusion layer consists of solvent-based thermosetting resin and light-diffusing particles. The production process for these particles is complex and prone to defects such as particle shedding. Additionally, the diffusion film exhibits poor abrasion resistance, temperature resistance, and adhesion to the substrate. Summary of the Invention

[0004] The purpose of this application is to address the shortcomings of current technologies by providing a high-haze, high-temperature resistant diffusion film and its preparation method. The high-haze, high-temperature resistant diffusion film of this application possesses high scratch resistance, high-temperature resistance, and strong adhesion to a transparent base film. Simultaneously, it has a rough surface structure to eliminate localized bright spots in backlight modules and protect the light guide plate from damage by the upper prism film. It is widely used in large-size LCD devices (such as automotive displays).

[0005] In a first aspect, this application provides a high-haze, high-temperature-resistant diffusion film, employing the following technical solution:

[0006] A high-haze, high-temperature resistant diffusion film includes a transparent base film and a diffusion layer coated on the surface of the transparent base film by a micro-gravure roller. The diffusion layer, by mass parts, includes the following raw materials: 60-70 parts of acrylic resin oligomer, 20-30 parts of acrylic resin monomer, 2-3 parts of triphenyl phosphate, 6-8 parts of scratch-resistant agent, 3-5 parts of photoinitiator, and 6-9 parts of diluent. The scratch-resistant agent is modified silica. The thickness of the diffusion layer is 30-50 μm.

[0007] By employing the above technical solutions, the benzene ring groups in the acrylic resin oligomers: impart a rigid structure to the material, improving the wear resistance and scratch resistance of the diffusion layer. Organosiloxane segments: enhance the material's temperature resistance (siloxane bonds have high thermal stability); form chemical bonds with the PET base film through silane coupling, improving interfacial adhesion. As the film-forming host, they provide structural support and optical transparency. Acrylic resin monomers (such as 2-phenoxyethyl acrylate) adjust the system viscosity, promote the dispersion of other components; form π-π stacking with the benzene rings in the oligomers, enhancing the rigidity of the crosslinking network; form a three-dimensional network structure through UV-initiated polymerization, improving mechanical strength. Modified silica, surface modification: pretreatment with vinyltrimethoxysilane improves compatibility with acrylic resin; surface vinyl groups participate in the curing reaction, forming chemical bonds. Increased surface roughness (micron-level), improving light scattering efficiency (high haze); as a hard filler, significantly improving scratch resistance. Triphenyl phosphate, as a heat stabilizer: inhibits the high-temperature decomposition of the PET base film by absorbing free radicals. The photoinitiator system (e.g., TPO:1173 = 3:2) ensures full curing of the coating interior through TPO (long-wavelength absorption) and avoids surface oxygen inhibition of polymerization through 1173 (broad-spectrum absorption). This dual initiation mechanism guarantees uniform curing of the 30-50μm thick coating. The diluent (e.g., butyl acetate:isohexanone = 4:3) ensures full resin dispersion through butyl acetate's strong dissolving power and regulates the evaporation rate with isohexanone, optimizing leveling properties and preventing streaking defects during microgravure roller coating. Synergistic effects between components include: 1. Scratch and temperature resistance synergy: Benzene rings (oligomers / monomers) + modified silica → forming a dual wear-resistant mechanism through rigidity reinforcement and hard filling; Organosiloxanes (oligomers) + triphenyl phosphate → chemical bond temperature resistance and thermal stabilizer synergistically inhibit thermal degradation. 2. Synergistic optical performance: Modified silica surface roughness + acrylic resin refractive index control → achieves high haze (>90%) and light uniformity (no bright spots); diluent evaporation gradient control → forms a gradient curing structure, reducing light scattering anisotropy. 3. Enhanced interfacial bonding: Organosiloxane (oligomer) reacts with the hydroxyl groups of the PET base film → chemical bonding; silane coupling on the modified silica surface → filler-resin interface is defect-free, avoiding stress concentration. In summary, this formulation, through chemical structure design (benzene ring / siloxane) and component functional compounding (rigid filler + heat stabilizer + gradient curing system), achieves high scratch resistance, high temperature resistance, and strong adhesion to transparent base films. Simultaneously, the surface roughness eliminates local bright spots in the backlight module and protects the light guide plate from damage by the upper prism film. It is widely used in large-size LCD devices (such as automotive displays).

[0008] Preferably, the preparation method of the acrylic resin oligomer is as follows: 100 parts by mass of isopropyl methacrylate are added to a reactor, stirring is started, and the temperature is raised to 60-65°C under stirring conditions. Then, 26.5 parts by mass of vinyltrimethoxysilane, 21 parts by mass of methylphenyldivinylsilane, and 0.25-0.35 parts by mass of catalyst are added. The temperature is raised to 90-95°C under stirring conditions, and the reaction is stirred for 2-3 hours. Then, the temperature is lowered to 50-55°C under stirring conditions, and 5 parts by mass of 37% hydrochloric acid are added. The hydrolysis-condensation reaction is carried out under stirring conditions for 3.5-4.5 hours to obtain the acrylic resin oligomer.

[0009] By employing the above technical solution, isopropyl methacrylate, as the main chain monomer, provides acrylate groups, imparting flexibility and optical transparency to the oligomer; the isopropyl ester groups reduce reactivity, facilitating control of the polymerization process. Vinyltrimethoxysilane introduces hydrolyzable methoxy (-OCH3) and vinyl (-CH=CH2): the methoxy group hydrolyzes to form Si-OH, participating in the condensation reaction to construct a Si-O-Si network; the vinyl group copolymerizes with the acrylic monomer during UV curing, enhancing interfacial crosslinking. Methylphenyldivinylsilane, with its divinyl group increasing crosslinking density and improving thermal stability, and the methyl group regulating the molecular chain spacing, prevents excessive crosslinking leading to brittleness. A catalyst (such as tetraisopropyl titanate) controls the polymerization rate. In the first stage (60-65℃), mild conditions achieve the initial copolymerization of isopropyl methacrylate and the silane monomer, preventing premature reaction of the vinyl group that could lead to gelation. In the second stage (90-95℃, 2-3h), the increased temperature accelerates free radical polymerization, forming the acrylic main chain; the methoxy groups on the silane monomer side chains remain temporarily inert, preventing hydrolysis from interfering with polymerization. The third stage (50-55℃ + hydrochloric acid hydrolysis and condensation) involves hydrochloric acid-catalyzed hydrolysis of methoxy groups, followed by condensation to construct a three-dimensional network, forming an organic-inorganic hybrid structure that combines the flexibility of resin with the heat resistance of siloxanes. In summary, the prepared acrylic resin oligomer, on the one hand, possesses benzene ring groups in its chemical structure, which enhances the scratch resistance of the diffusion layer; on the other hand, the organosiloxanes in its chemical structure enhance the temperature resistance of the diffusion layer and its adhesion to the transparent base film.

[0010] Preferably, the stirring speed is 40-50 r / min.

[0011] Preferably, the catalyst is tetraisopropyl titanate.

[0012] Preferably, the method for preparing the modified silica includes the following steps:

[0013] S51. According to the mass fraction, disperse silica with an average particle size of 0.2-0.4 μm in an aqueous ethanol solution with a mass concentration of 75%, then add vinyltrimethoxysilane to adjust the pH of the solution to 4.5-5, stir for 3-4 hours, and then centrifuge, wash and dry to obtain pretreated silica.

[0014] S52. According to the mass fraction, disperse the pretreated silica in an ethanol aqueous solution with a mass concentration of 75%, add acrylamide, stir evenly, then add benzoyl peroxide, heat to 70-75℃ and reflux for 2-3 hours. After the reaction is completed, centrifuge, wash and dry the reaction product to obtain modified silica.

[0015] By adopting the above technical solutions, S51. Pretreatment of silica (silane coupling modification), ethanol aqueous solution (75%): As a dispersion medium, ethanol has moderate polarity and can fully wet the SiO2 surface, while water molecules participate in the silane hydrolysis reaction. Acidic hydrolysis of vinyltrimethoxysilane (VTMS) (pH=4.5-5): The generated silanol (Si-OH) dehydrates and condenses with the hydroxyl groups (-OH) on the SiO2 surface to form covalent bonds: Vinyl groups (-CH=CH2) are introduced to the surface, providing reaction sites for subsequent free radical grafting; improving the interfacial compatibility between SiO2 and organic resins and reducing the tendency to agglomerate. S52. Chemical grafting modification (acrylamide polymerization), initiator (such as benzoyl peroxide, BPO): Decomposition at 70-75℃ generates free radicals, which attack the vinyl double bonds and initiate the chain polymerization of acrylamide. Polyacrylamide side chains contain a large number of amide groups (-CONH2), which form hydrogen bonds with the ester groups (-COOR) in acrylic resin. The flexible chain segments buffer stress, preventing brittle cracking caused by direct contact with hard SiO2. The prepared modified silica, with pretreated SiO2 vinyl groups copolymerized with acrylic resin monomers (2-phenoxyethyl acrylate) during UV curing, forms covalent bonds. The grafted polyacrylamide chains entwine with the resin backbone through hydrogen bonds, achieving a dual physical-chemical anchoring. The steric hindrance effect of the grafted chains ensures uniform dispersion of SiO2 in the resin, preventing uneven haze caused by filler sedimentation during coating. Surface roughness (Ra = 0.8-1.2 μm) is synergistically controlled by SiO2 particle size and grafted chain topology, achieving efficient light scattering (haze > 90%). Refractive index matching reduces interfacial Fresnel reflection, improving light transmission uniformity. The Si-O-Si network (pretreatment layer) forms a thermally stable interpenetrating network with the siloxane segments in the resin; the decomposition temperature of polyacrylamide (>200℃) is higher than the application temperature (vehicle environment ≤150℃). In summary, through a gradient modification strategy of silane coupling pretreatment + acrylamide grafting, a "rigid-flexible" interface design of SiO2 filler was achieved, making it the core functional unit of the diffusion film with high scratch resistance, high haze, and high temperature resistance.

[0016] Preferably, in step S51, the mass ratio of silicon dioxide to vinyltrimethoxysilane is 100:2-3; in step S52, the mass ratio of pretreated silicon dioxide, acrylamide, and benzoyl peroxide is 10:(2-3):(0.2-0.3).

[0017] Preferably, the acrylic resin monomer is 2-phenoxyethyl acrylate.

[0018] Preferably, the photoinitiator is composed of 2,4,6-trimethylbenzoyl diphenylphosphine oxide and 2-hydroxy-2-methyl-1-phenyl-1-propanone in a mass ratio of 3:2;

[0019] By adopting the above technical solution, 1,2,4,6-trimethylbenzoyldiphenylphosphine oxide (TPO): TPO's maximum absorption wavelength (λmax≈380nm) matches the 365nm / 405nm spectrum of medium-pressure mercury lamps, making it particularly suitable for deep curing (30-50μm thick coatings); through Norrish I-type cleavage, phosphorus-centered free radicals (PO·) and benzoyl free radicals (PhCO·) are generated, initiating the chain polymerization of acrylic monomers; PO· free radicals have better tolerance to oxygen inhibition than traditional thioxanthone initiators, reducing surface stickiness. 2-Hydroxy-2-methyl-1-phenyl-1-propanone (1173) has strong absorption in the 250-350nm range, which can effectively utilize the short-wavelength energy of UV light sources; the α-hydroxy free radicals (·OH) generated by decomposition rapidly initiate surface monomer polymerization, compensating for the insufficient absorption of TPO in the short-wavelength region; the decomposition products of 1173 (acetophenone derivatives) can migrate to the coating surface, reducing interfacial energy and improving leveling properties. Synergistic Mechanism of TPO and 1173: 1. Spectral Complementarity and Energy Matching, Absorption Band Coverage: Both form continuous absorption across the entire 254-405nm wavelength range, improving UV energy utilization. Light Intensity Gradient Matching: Short wavelengths (254nm) are rapidly absorbed by 1173 on the coating surface, while long wavelengths (365nm) penetrate to deeper layers and are utilized by TPO, achieving gradient curing. 2. Synergistic Free Radical Generation Kinetics and Complementary Initiation Rates: TPO has a slower but more persistent initiation rate, suitable for thick-layer gradual curing; 1173 has a faster initiation rate but a shorter half-life, quickly establishing an initial cross-linking network; the combination of the two shortens the gel time to 15-20 seconds while maintaining sufficient deep curing. 3. Compatibility with Resin Systems and Solubility Matching: TPO (lipophilic) and 1173 (moderately polar) have balanced solubility in a butyl acetate / isohexanone mixed solvent, avoiding initiator precipitation that leads to uneven curing. Synergistic Thermal Stability: TPO decomposes at a temperature higher than 1173°C, remaining stable during the coating pre-baking stage and reducing thermally initiated side reactions. In summary, the 3:2 mass ratio of TPO and 1173 achieves efficient thick-layer curing and balanced performance enhancement through the following synergistic mechanisms: 1) Full-band light energy utilization: Covering the main emission lines of UV-LEDs / mercury lamps, reducing energy consumption; 2) Gradient curing network: Surface densification and deep cross-linking are completed simultaneously, avoiding warping caused by shrinkage stress; 3) Dynamic inhibition of oxygen polymerization: TPO consumes bulk oxygen, and 1173 rapidly seals the surface, improving overall curing efficiency; 4) Balanced thermal-optical stability: The initiator does not decompose prematurely during high-temperature coating, ensuring process stability. This design enables the diffusion film to withstand cyclic shocks from -40°C to 150°C and maintain stable optical performance in demanding applications such as automotive displays.

[0020] Preferably, the diluent is composed of butyl acetate and isohexone in a mass ratio of 4:3.

[0021] Preferably, the transparent base film is a PET film with a thickness of 80-250 μm.

[0022] Secondly, this application provides a method for preparing a high-haze, high-temperature resistant diffusion film, employing the following technical solution:

[0023] As a general technical concept, this application also provides a method for preparing the above-mentioned high-haze, high-temperature resistant diffusion film, including the following steps:

[0024] S101. According to the mass fractions, mix the acrylic resin oligomer, acrylic resin monomer, triphenyl phosphate, scratch-resistant agent, photoinitiator and diluent, stir evenly to obtain the coating liquid.

[0025] S102. According to the mass fraction, the coating liquid is applied to the surface of the transparent base film treated with oxygen plasma using a micro-gravure roller, and then UV cured under a UV curing lamp at a curing condition of 500-600 mJ / cm². 2 A high-haze diffusion film resistant to high temperatures was prepared.

[0026] In summary, the beneficial technical effects of this application are as follows:

[0027] 1. High temperature resistance and stability

[0028] Synergistic effect of triphenyl phosphate: By adding triphenyl phosphate, the decomposition reaction of the substrate under high temperature environment is effectively inhibited, the aging of the material is delayed, and the service life of the diffusion film is significantly extended.

[0029] Organosiloxane group reinforcement: The organosiloxane structure contained in acrylic resin oligomers not only improves the high temperature resistance of the diffusion layer itself (potentially able to withstand harsh environments such as automotive), but also enhances the chemical bond between it and the PET base film, avoiding interlayer delamination caused by thermal expansion differences at high temperatures.

[0030] 2. Excellent scratch resistance

[0031] Modified silica enhances surface hardness: Silica particles pretreated with vinyltrimethoxysilane are chemically modified to improve interfacial bonding and dispersibility with acrylic resin, thereby forming a uniform micro-nano-level rough structure on the coating surface, significantly improving surface hardness and scratch resistance.

[0032] Rigid benzene ring structure support: The benzene ring groups in acrylic resin oligomers and monomers (such as 2-phenoxyethyl acrylate) give the diffusion layer higher rigidity, further reducing surface damage caused by external forces.

[0033] 3. High haze and light uniformity

[0034] Dual-scale scattering structure: Uniform dispersion of modified silica particles forms micron-level scattering centers; a controllable rough structure (30-50μm layer thickness) is formed on the surface through a coating process, enabling multiple scattering of light. The synergistic effect of these two elements significantly improves haze, eliminates local bright spots in the backlight module, and enhances light uniformity.

[0035] Diluent optimizes coating effect: The butyl acetate / isohexanone (4:3) mixed solvent system balances evaporation rate and leveling properties, ensuring uniformity and controllability of coating surface roughness.

[0036] 4. Synergy of material systems

[0037] Highly efficient photoinitiator matching: 2,4,6-trimethylbenzoyl diphenylphosphine oxide (TPO) and 2-hydroxy-2-methyl-1-phenyl-1-propanone (1173) are compounded in a 3:2 ratio, which takes into account both deep curing (TPO absorbs long-wavelength UV) and surface curing (1173 absorbs short-wavelength UV), ensuring complete cross-linking of thick coatings (30-50μm) and avoiding mechanical property degradation due to insufficient curing.

[0038] Oligomer-monomer synergistic effect: Acrylic resin oligomers provide a crosslinking backbone, while high-functionality monomers (such as 2-phenoxyethyl acrylate) optimize curing shrinkage and balance hardness and adhesion.

[0039] 5. Application Adaptation Advantages

[0040] Vehicle environment adaptability: High temperature resistance (can withstand long-term use above 120℃) and scratch resistance perfectly meet the stringent reliability requirements of vehicle displays.

[0041] Light guide plate protection function: The rough surface structure can both scatter light and act as a physical buffer layer to prevent the prism film from directly contacting the light guide plate and causing scratches, thereby reducing the damage rate of the backlight module assembly. Detailed Implementation

[0042] The embodiments of this application will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of this application. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0043] In the following examples and preparation examples, 1 part represents 100g.

[0044] Preparation Example 1: Preparation of acrylic resin oligomers

[0045] The preparation method of acrylic resin oligomers is as follows: 100 parts by mass of isopropyl methacrylate are added to a reactor, stirring is started and the speed is adjusted to 45 r / min. The temperature is raised to 63℃ under stirring conditions, and then 26.5 parts by mass of vinyltrimethoxysilane, 21 parts by mass of methylphenyldivinylsilane and 0.32 parts by mass of tetraisopropyl titanate are added. The temperature is raised to 92℃ under stirring conditions and stirred for 2.3 h. Then the temperature is lowered to 53℃ under stirring conditions, and then 5 parts by mass of 37% hydrochloric acid are added. The hydrolysis-condensation reaction is carried out under stirring conditions for 4 h to obtain acrylic resin oligomers.

[0046] Preparation Example 2: Preparation of Modified Silica

[0047] The method for preparing modified silica includes the following steps:

[0048] S51. According to the mass fraction, 100 parts of silica with an average particle size of 0.3 μm are dispersed in 200 parts of 75% ethanol aqueous solution, and then 2.5 parts of vinyltrimethoxysilane are added to adjust the pH of the solution to 4.7. The solution is stirred for 3.4 h, centrifuged, washed and dried to obtain pretreated silica.

[0049] S52. According to the mass fraction, 100 parts of pretreated silica are dispersed in 200 parts of 75% ethanol aqueous solution, 25 parts of acrylamide are added, and the mixture is stirred evenly. Then, 2.6 parts of benzoyl peroxide are added, and the mixture is heated to 73°C and refluxed for 2.5 hours. After the reaction is completed, the reaction product is centrifuged, washed, and dried to obtain modified silica.

[0050] Example 1

[0051] A high-haze, high-temperature resistant diffusion film comprises a transparent base film and a diffusion layer coated on the surface of the transparent base film by a microgravure roller. The diffusion layer, by weight parts, comprises the following raw materials: 60 parts of acrylic resin oligomer, 20 parts of 2-phenoxyethyl acrylate, 2 parts of triphenyl phosphate, 6 parts of modified silica, 3 parts of photoinitiator, and 6 parts of diluent. The thickness of the diffusion layer is 30 μm. The photoinitiator is composed of 2,4,6-trimethylbenzoyl diphenylphosphine oxide and 2-hydroxy-2-methyl-1-phenyl-1-propanone in a weight ratio of 3:2. The diluent is composed of butyl acetate and isohexanone in a weight ratio of 4:3. The transparent base film is a PET film with a thickness of 250 μm.

[0052] The above-mentioned method for preparing a high-haze, high-temperature resistant diffusion film includes the following steps:

[0053] S101. According to the mass fractions, mix the acrylic resin oligomer, 2-phenoxyethyl acrylate, triphenyl phosphate, modified silica, photoinitiator and diluent, stir evenly to obtain the coating liquid.

[0054] S102. According to the mass fraction, the coating liquid is applied to the surface of the transparent base film treated with oxygen plasma using a micro-gravure roller, and then UV cured under a UV curing lamp at a curing condition of 500 mJ / cm². 2 A high-haze diffusion film resistant to high temperatures was prepared.

[0055] Example 2

[0056] A high-haze, high-temperature resistant diffusion film comprises a transparent base film and a diffusion layer coated on the surface of the transparent base film by a microgravure roller. The diffusion layer, by weight, comprises the following raw materials: 70 parts acrylic resin oligomer, 30 parts 2-phenoxyethyl acrylate, 3 parts triphenyl phosphate, 8 parts modified silica, 5 parts photoinitiator, and 9 parts diluent. The thickness of the diffusion layer is 50 μm. The photoinitiator is composed of 2,4,6-trimethylbenzoyl diphenylphosphine oxide and 2-hydroxy-2-methyl-1-phenyl-1-propanone in a weight ratio of 3:2. The diluent is composed of butyl acetate and isohexanone in a weight ratio of 4:3. The transparent base film is a PET film with a thickness of 80 μm.

[0057] The above-mentioned method for preparing a high-haze, high-temperature resistant diffusion film includes the following steps:

[0058] S101. According to the mass fractions, mix the acrylic resin oligomer, 2-phenoxyethyl acrylate, triphenyl phosphate, modified silica, photoinitiator and diluent, stir evenly to obtain the coating liquid.

[0059] S102. According to the mass fraction, the coating liquid is applied to the surface of the transparent base film treated with oxygen plasma using a micro-gravure roller, and then UV cured under a UV curing lamp at a curing condition of 600 mJ / cm². 2 A high-haze diffusion film resistant to high temperatures was prepared.

[0060] Example 3

[0061] A high-haze, high-temperature resistant diffusion film comprises a transparent base film and a diffusion layer coated on the surface of the transparent base film by a microgravure roller. The diffusion layer, by weight, comprises the following raw materials: 65 parts of acrylic resin oligomer, 25 parts of 2-phenoxyethyl acrylate, 2.5 parts of triphenyl phosphate, 7 parts of modified silica, 4 parts of photoinitiator, and 7.5 parts of diluent. The thickness of the diffusion layer is 40 μm. The photoinitiator is composed of 2,4,6-trimethylbenzoyl diphenylphosphine oxide and 2-hydroxy-2-methyl-1-phenyl-1-propanone in a weight ratio of 3:2. The diluent is composed of butyl acetate and isohexanone in a weight ratio of 4:3. The transparent base film is a PET film with a thickness of 150 μm.

[0062] The above-mentioned method for preparing a high-haze, high-temperature resistant diffusion film includes the following steps:

[0063] S101. According to the mass fractions, mix the acrylic resin oligomer, 2-phenoxyethyl acrylate, triphenyl phosphate, modified silica, photoinitiator and diluent, stir evenly to obtain the coating liquid.

[0064] S102. According to the mass fraction, the coating liquid is applied to the surface of the transparent base film treated with oxygen plasma using a micro-gravure roller, and then UV cured under a UV curing lamp at a curing condition of 550 mJ / cm². 2 A high-haze diffusion film resistant to high temperatures was prepared.

[0065] Comparative Example 1

[0066] Similar to Example 3, except that an equal mass fraction of polyethylene glycol o-phenylphenyl ether acrylate is used instead of acrylic resin oligomer.

[0067] Comparative Example 2

[0068] Similar to Example 3, except that an equal mass fraction of unmodified silica was used instead of modified silica.

[0069] Comparative Example 3

[0070] Same as in Example 3, except that the photoinitiator is 2,4,6-trimethylbenzoyldiphenylphosphine oxide.

[0071] Comparative Example 4

[0072] Same as in Example 3, except that the photoinitiator is 2-hydroxy-2-methyl-1-phenyl-1-propanone.

[0073] Performance testing

[0074] The high-haze, high-temperature resistant diffusion films prepared in Examples 1 and 3, and Comparative Examples 1-4 were subjected to performance tests. For example, haze was measured using an NDH2000 haze meter according to ASTM D1003; adhesion was tested according to the peel strength test standard GB / T25256-2010, where the diffusion film was cut into 200mm*25mm pieces and peeled at 180 degrees using an electronic universal testing machine, and the test value was recorded as the adhesion strength of the diffusion film; abrasion resistance was assessed by placing the diffusion film statically on the light-emitting surface of the light guide plate, placing a 500g weight on top of the diffusion film, and moving it back and forth 10 times within a 10cm distance, calculating the mass difference before and after the test, which was used as an evaluation of abrasion resistance; the larger the difference, the less wear-resistant the film; surface roughness was tested according to the profilometer test of ISO 4287; and temperature resistance was assessed according to GB / T 16422.2 high-temperature aging, where the yellowing rate was tested after 500 hours at 120℃. The results are shown in Table 1.

[0075] Table 1 Performance Tests

[0076]

[0077] Analyzing the data in Table 1, we can see that:

[0078] 1) The high-haze, high-temperature resistant diffusion films prepared in Examples 1-3 have high scratch resistance, high-temperature resistance, and strong adhesion to the transparent base film. They also have a rough surface structure, which helps eliminate localized bright spots in the backlight module and protects the light guide plate from damage by the upper prism film. They are widely used in large-size LCD devices (such as automotive displays).

[0079] 2) The performance comparison analysis of the high haze high temperature resistant diffusion film prepared in Example 3 and Comparative Example 1 shows that the acrylic resin oligomer prepared in this application has the following advantages: on the one hand, the presence of benzene ring groups in the chemical structure of the substance can improve the scratch resistance of the diffusion layer; on the other hand, the presence of organosiloxanes in the chemical structure of the substance can improve the temperature resistance of the diffusion layer and the bonding force with the transparent base film, thereby improving the overall performance of the high haze high temperature resistant diffusion film.

[0080] 3) The performance comparison analysis of the high haze and high temperature resistant diffusion films prepared in Example 3 and Comparative Example 2 shows that the modified silica prepared in this application, through the gradient modification strategy of silane coupling pretreatment + acrylamide grafting, achieves the interface design of "rigid and flexible" SiO2 filler, which can significantly improve the high scratch resistance, high haze and high temperature resistance of the diffusion film.

[0081] 4) The performance comparison analysis of the high haze high temperature resistant diffusion films prepared in Example 3 and Comparative Examples 3-4 shows that the photoinitiator is composed of 2,4,6-trimethylbenzoyldiphenylphosphine oxide and 2-hydroxy-2-methyl-1-phenyl-1-propanone in a mass ratio of 3:2. By utilizing their synergistic effect, the overall performance of the high haze high temperature resistant diffusion film can be significantly improved.

[0082] The above embodiments are only used to explain the technical solutions of this application and are not intended to limit it. Although the above embodiments have provided specific descriptions of this application, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of this invention. Any modifications and equivalent substitutions that do not depart from the spirit and scope of this application should be covered within the protection scope of this application.

Claims

1. A high-haze, high-temperature resistant diffusion film, characterized in that, The invention comprises a transparent base film and a diffusion layer coated on the surface of the transparent base film by a microgravure roller. The diffusion layer, by mass parts, comprises the following raw materials: 60-70 parts of acrylic resin oligomer, 20-30 parts of 2-phenoxyethyl acrylate, 2-3 parts of triphenyl phosphate, 6-8 parts of scratch-resistant agent, 3-5 parts of photoinitiator, and 6-9 parts of diluent. The scratch-resistant agent is modified silica. The thickness of the diffusion layer is 30-50 μm. The method for preparing the acrylic resin oligomer is as follows: 100 parts by mass of isopropyl methacrylate are added to a reactor, and stirring is started. The temperature is raised to 60-65°C under stirring at 40-50 r / min. Then, 26.5 parts by mass of vinyltrimethoxysilane, 21 parts by mass of methylphenyldivinylsilane, and 0.25-0.35 parts by mass of tetraisopropyl titanate are added. The temperature is raised to 90-95°C under stirring and the reaction is carried out for 2-3 hours. Then, the temperature is lowered to 50-55°C under stirring. Then, 5 parts by mass of 37% hydrochloric acid are added. The hydrolysis-condensation reaction is carried out under stirring for 3.5-4.5 hours to obtain the acrylic resin oligomer. The method for preparing the modified silica includes the following steps: S51. According to the mass fraction, silica with an average particle size of 0.2-0.4 μm is dispersed in an aqueous ethanol solution with a mass concentration of 75%, and then vinyltrimethoxysilane is added to adjust the pH of the solution to 4.5-5. The solution is stirred for 3-4 hours, and then centrifuged, washed and dried to obtain pretreated silica. The mass fraction ratio of silica to vinyltrimethoxysilane is 100:2-3. S52. According to the mass fraction, the pretreated silica is dispersed in a 75% ethanol aqueous solution, acrylamide is added, and the mixture is stirred evenly. Then, benzoyl peroxide is added, and the mixture is heated to 70-75℃ and refluxed for 2-3 hours. After the reaction is completed, the reaction product is centrifuged, washed, and dried to obtain modified silica. The mass fraction ratio of the pretreated silica, acrylamide, and benzoyl peroxide is 10:(2-3):(0.2-0.3). The photoinitiator is composed of 2,4,6-trimethylbenzoyl diphenylphosphine oxide and 2-hydroxy-2-methyl-1-phenyl-1-propanone in a mass ratio of 3:

2. The diluent is composed of butyl acetate and isohexone in a mass ratio of 4:

3. The transparent base film is a PET film with a thickness of 80-250μm.

2. A method for preparing a high-haze, high-temperature resistant diffusion film as described in claim 1, characterized in that, Includes the following steps: S101. According to the mass fractions, mix the acrylic resin oligomer, acrylic resin monomer, triphenyl phosphate, scratch-resistant agent, photoinitiator and diluent, stir evenly to obtain the coating liquid. S102. According to the mass fraction, the coating liquid is applied to the surface of the transparent base film treated with oxygen plasma using a micro-gravure roller, and then UV cured under a UV curing lamp at a curing condition of 500-600 mJ / cm². 2 A high-haze diffusion film resistant to high temperatures was prepared.

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