High-haze high-temperature-resistant lower diffusion film and preparation method thereof

Abstract

The invention relates to the technical field of optical thin films, in particular to a high-haze high-temperature-resistant lower diffusion film and a preparation method thereof. The invention relates to a high-haze high-temperature-resistant lower diffusion film, which comprises a transparent base film and a diffusion layer coated on the surface of the transparent base film through a micro gravure roller, comprising the following preparation raw materials: 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 double innovation of material chemical modification (such as SiO surface treatment and resin molecule design) and process formula optimization (such as the ratio of a photo-initiation system to a diluent), the technical bottlenecks of a traditional diffusion film, including the problems of easy aging, insufficient scratch resistance, poor light uniformity and the like in a high-temperature and high-humidity environment, are solved.

Description

Technical Field

[0001] The present application relates to the technical field of optical films, and in particular to a high-haze, high-temperature-resistant diffusion film and a preparation method thereof. Background Art

[0002] Liquid Crystal Display (LCD) is the most common display technology at present. However, LCD is a non-luminous display device and needs the help of a backlight unit (BLU) to provide a bright and uniform light source to achieve the display effect. The traditional backlight unit is mainly composed of four films: a lower diffusion film, a lower brightness enhancement film, an upper brightness enhancement film, and an upper diffusion film. Among them, the light-emitting surface of the diffusion film (DIF, Diffuser Film) has a diffusion layer structure, and its optical function is mainly to diverge the incident light, atomize it, and improve the uniformity of the LCD screen.

[0003] The diffusion film used for LCD display screens in the prior art has a haze of more than 90% on the front light diffusion layer and less than 15% on the back light diffusion layer. The structure of the light diffusion layer is in the form of solvent-based thermosetting resin plus light-scattering particles. The light-scattering particles are more complicated to produce and may cause particle drop and other undesirable phenomena. In addition, the diffusion film has poor friction resistance and temperature resistance, and poor bonding with the substrate. The purpose of this application is to provide a high-haze high-temperature resistant diffusion film and a preparation method thereof in view of the shortcomings of the current technology. The high-haze high-temperature resistant diffusion film of the present application has high scratch resistance, high temperature resistance and strong bonding with the transparent base film. At the same time, the surface has a rough structure, which is used to eliminate local bright spots in the backlight module and protect the light guide plate from damage by the upper prism film. It is widely used in large-size LCD devices (such as car displays).

[0004] In the first aspect, the present application provides a high-haze, high-temperature-resistant diffusion membrane, which adopts the following technical solution: 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 micro-gravure roller, wherein the diffusion layer comprises the following preparation raw materials by mass: 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, wherein the scratch resistant agent is modified silica, and the thickness of the diffusion layer is 30-50 μm.

[0005] By adopting the above technical solutions, the benzene ring groups in the acrylic resin oligomer endow the material with a rigid structure, enhancing the wear resistance and scratch resistance of the diffusion layer. The organosiloxane chain segments enhance the temperature resistance of the material (the silicon-oxygen bond has high thermal stability); form chemical bonds with the PET base film through silane coupling to improve the interfacial bonding force. As the film-forming matrix, it provides 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 oligomer to enhance the rigidity of the cross-linked network; form a three-dimensional network structure through UV-initiated polymerization to enhance the mechanical strength. Modified silica, surface modification: After pretreatment with vinyltrimethoxysilane, its compatibility with the acrylic resin is improved; the surface vinyl groups participate in the curing reaction to form chemical bond binding. Increase the surface roughness (micrometer level) to enhance the light scattering efficiency (high haze); as a hard filler, significantly enhance the scratch resistance. Triphenyl phosphate is used as a heat stabilizer: inhibits the high-temperature decomposition of the PET base film by absorbing free radicals. Photoinitiator system (such as TPO:1173 = 3:2), TPO (long-wavelength absorption) ensures sufficient curing inside the coating; 1173 (broad-spectrum absorption) avoids surface oxygen inhibition of polymerization; the dual initiation mechanism ensures uniform curing of a 30-50 μm thick coating. Diluent (such as butyl acetate:isohexanone = 4:3), the strong dissolving power of butyl acetate ensures sufficient dispersion of the resin, and isohexanone adjusts the evaporation rate; optimizes the leveling property to avoid stripe defects during microgravure roll coating. Synergistic effects among components, 1. Scratch resistance-temperature resistance synergy: benzene ring (oligomer / monomer) + modified silica → form a dual wear-resistant mechanism through enhanced rigidity and hard filling; organosiloxane (oligomer) + triphenyl phosphate → chemical bond temperature resistance and heat stabilizer synergistically inhibit thermal degradation. 2. Optical property synergy, modified silica surface roughness + acrylic resin refractive index regulation → achieve high haze (>90%) and light uniformity (no bright spots); control of the diluent evaporation gradient → form a gradient curing structure to reduce the anisotropy of light scattering. 3. Interface bonding strengthening, organosiloxane (oligomer) reacts with the hydroxyl groups of the PET base film → chemical bond binding; surface silane coupling of modified silica → no defects at the filler-resin interface, avoiding stress concentration. In summary, through chemical structure design (benzene ring / siloxane) and component function compounding (rigid filler + heat stabilizer + gradient curing system), this formulation achieves high scratch resistance, high temperature resistance, strong bonding force with the transparent base film, and at the same time has a rough surface structure to eliminate local bright spots in the backlight module and protect the light guide plate from damage by the upper prism film. It is widely used in large-size LCD devices (such as in-vehicle displays).

[0006] Preferably, the preparation method of the acrylic resin oligomer is as follows: By mass, 100 parts 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 of vinyltrimethoxysilane, 21 parts of methylphenyldivinylsilane, and 0.25 - 0.35 parts of a catalyst are added. The temperature is continuously raised to 90 - 95 °C under stirring conditions and stirred for 2 - 3 h. Then, the temperature is lowered to 50 - 55 °C under stirring conditions, and 5 parts of hydrochloric acid with a mass concentration of 37% are added, and a hydrolysis-condensation reaction is carried out for 3.5 - 4.5 h under stirring conditions to obtain the acrylic resin oligomer.

[0007] By adopting the above technical solution, isopropyl methacrylate serves as the main chain monomer, providing acrylate groups, endowing the oligomer with flexibility and optical transparency; the isopropyl ester group reduces the reaction activity, facilitating the control of the polymerization process. Vinyltrimethoxysilane introduces hydrolyzable methoxy groups (-OCH3) and vinyl groups (-CH=CH2): The methoxy groups form Si-OH through hydrolysis and participate in the condensation reaction to construct the Si-O-Si network; the vinyl groups copolymerize with acrylic monomers during UV curing, enhancing the interfacial crosslinking. Methylphenyldivinylsilane, with two vinyl groups, increases the crosslinking density and improves the thermal stability; the methyl group adjusts the molecular chain spacing, avoiding brittleness caused by excessive crosslinking. The catalyst (such as tetraisopropyl titanate) controls the polymerization rate. In the first stage (60 - 65 °C), the preliminary copolymerization of isopropyl methacrylate and silane monomers is achieved under mild conditions; this avoids premature reaction of vinyl groups leading to gelation. In the second stage (90 - 95 °C, 2 - 3 h), the temperature is raised to accelerate free radical polymerization, forming the acrylic main chain; the methoxy groups on the side chains of silane monomers remain inert temporarily, avoiding hydrolysis interfering with the polymerization. In the third stage (50 - 55 °C + hydrochloric acid hydrolysis condensation), hydrochloric acid catalyzes the hydrolysis of methoxy groups, and the condensation reaction constructs a three-dimensional network, forming an organic-inorganic hybrid structure with both the flexibility of the resin and the heat resistance of siloxane. In short, for the prepared acrylic resin oligomer, on the one hand, the chemical structural formula of this substance contains benzene ring groups, which can improve the scratch resistance of the diffusion layer; on the other hand, the organosiloxane contained in the chemical structural formula of this substance can improve the temperature resistance of the diffusion layer and the binding force with the transparent base film.

[0008] Preferably, the rotation speed of the stirring is 40 - 50 r / min.

[0009] Preferably, the catalyst is tetraisopropyl titanate.

[0010] Preferably, the preparation method of the modified silica includes the following steps: S51. According to parts by mass, disperse silica with an average particle size of 0.2 - 0.4 μm in an ethanol aqueous solution with a mass concentration of 75%, then add vinyltrimethoxysilane thereto, adjust the pH of the solution to 4.5 - 5, stir for 3 - 4 h, and after centrifugation, washing, and drying, obtain pretreated silica; S52. According to parts by mass, 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 °C and reflux for 2 - 3 h. After the reaction is completed, centrifuge, wash, and dry the reaction product to obtain modified silica.

[0011] By adopting the above technical solution, in S51, for the pretreated silica (silane coupling modification), ethanol aqueous solution (75%): As a dispersion medium, the polarity of ethanol is moderate, which can fully wet the surface of SiO2, and at the same time, water molecules participate in the silane hydrolysis reaction. Acid hydrolysis of vinyltrimethoxysilane (VTMS) (pH = 4.5 - 5): The generated silanol (Si - OH) undergoes dehydration condensation with the hydroxyl groups (-OH) on the SiO2 surface to form covalent bonds: Vinyl groups (-CH = CH2) are introduced on the surface, providing reaction sites for subsequent radical grafting; improving the interfacial compatibility between SiO2 and organic resins and reducing the tendency of agglomeration. In S52, chemical grafting modification (acrylamide polymerization), initiator (such as benzoyl peroxide, BPO): Decompose to generate free radicals at 70 - 75 °C, and the free radicals attack the vinyl double bond to initiate the chain polymerization of acrylamide. Polyacrylamide branches: Contain a large number of amide groups (-CONH2), which form hydrogen bonds with the ester groups (-COOR) in the acrylic resin; the flexible chain segments buffer stress to avoid brittle cracks caused by direct contact of hard SiO2. For the prepared modified silica, the vinyl group of the pretreated SiO2 copolymerizes with the acrylic resin monomer (2 - phenoxyethyl acrylate) during UV curing to form a covalent bond connection; the grafted polyacrylamide chains are wound around the resin main chain through hydrogen bonds to achieve physical - chemical dual anchoring. The steric hindrance effect of the grafted chains enables SiO2 to be uniformly dispersed in the resin; preventing haze unevenness caused by filler sedimentation during the coating process. The surface roughness (Ra = 0.8 - 1.2 μm) is synergistically regulated by the SiO2 particle size and the topological structure of the grafted chains to achieve efficient light scattering (haze > 90%); refractive index matching reduces interfacial Fresnel reflection and improves the 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 °C) is higher than the application temperature (vehicle environment ≤ 150 °C). In short, through the gradient modification strategy of silane coupling pretreatment + acrylamide grafting, the "rigid - flexible combination" interface design of the SiO2 filler is realized, making it the core functional unit for the high scratch resistance, high haze, and high temperature resistance of the diffusion film.

[0012] Preferably, in step S51, the mass ratio of the silica to vinyltrimethoxysilane is 100:2 - 3; in step S52, the mass ratio of the pretreated silica, acrylamide, and benzoyl peroxide is 10:(2 - 3):(0.2 - 0.3).

[0013] Preferably, the acrylic resin monomer is 2 - phenoxyethyl acrylate.

[0014] 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; By adopting the above technical solutions, 1. 2,4,6-Trimethylbenzoyl diphenylphosphine oxide (TPO): The maximum absorption wavelength of TPO (λmax≈380nm) matches the 365nm / 405nm spectral lines of medium-pressure mercury lamps, which is particularly suitable for deep curing (30 - 50μm thick coatings); it generates phosphorus-centered radicals (PO·) and benzoyl radicals (PhCO·) through Norrish type I cleavage to initiate the chain polymerization of acrylic monomers; the PO· radicals have better tolerance to oxygen inhibition than traditional thioxanthone initiators, reducing the surface tackiness phenomenon. 2-Hydroxy-2-methyl-1-phenylpropan-1-one (1173) has strong absorption in the range of 250 - 350nm, which can effectively utilize the short-wavelength energy of UV light sources; the α-hydroxy radicals (·OH) generated by its decomposition rapidly initiate the polymerization of surface monomers, making up for the insufficient absorption of TPO in the short-wavelength region; the decomposition products of 1173 (acetophenone derivatives) can migrate to the coating surface to reduce the interfacial energy and improve the leveling property. The synergistic mechanism of TPO and 1173: 1. Spectral complementarity and energy matching, absorption band coverage: The two form continuous absorption in the full wavelength range of 254 - 405nm, improving the utilization rate of UV energy. Light intensity gradient matching: The short wavelength (254nm) is rapidly absorbed by 1173 on the coating surface, and the long wavelength (365nm) penetrates to the deep layer and is utilized by TPO to achieve gradient curing. 2. Synergy in radical generation kinetics, complementary initiation rates: The initiation rate of TPO is slow but persistent, suitable for step-by-step curing of thick layers; the initiation rate of 1173 is fast but the half-life is short, quickly establishing the initial cross-linking network; the compounding of the two shortens the gel time to 15 - 20 seconds while maintaining the sufficiency of deep curing. 3. Compatibility with the resin system, solubility matching: The solubility of TPO (lipophilic) and 1173 (medium polarity) is balanced in the mixed solvent of butyl acetate / isocetone, avoiding uneven curing caused by the precipitation of initiators. Thermal stability synergy: The decomposition temperature of TPO is higher than that of 1173, remaining stable during the coating pre-baking stage and reducing thermal-initiated side reactions. In summary, TPO and 1173 are compounded at a mass ratio of 3:2, and through the following synergistic mechanisms, high-efficiency curing of thick layers and balanced improvement of performance are achieved: 1) Full-band light energy utilization: covering the main emission spectral lines of UV-LED / mercury lamps, reducing energy consumption; 2) Gradient curing network: surface densification and deep cross-linking are completed synchronously, avoiding warping caused by shrinkage stress; 3) Dynamic inhibition of oxygen inhibition: TPO consumes the bulk oxygen, and 1173 quickly seals the surface, improving the comprehensive curing efficiency; 4) Thermal-photostability balance: 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 high-demand scenarios such as in-vehicle displays.

[0015] Preferably, the diluent is composed of butyl acetate and isocetone in a mass fraction ratio of 4:3.

[0016] Preferably, the transparent base film is a PET film with a thickness of 80 - 250 μm.

[0017] In a second aspect, the present application provides a method for preparing a high haze and high temperature resistant diffusion film, adopting the following technical solution: As a general technical concept, the present application also provides the method for preparing the above-mentioned high haze and high temperature resistant diffusion film, including the following steps: S101. According to parts by mass, mix an acrylic resin oligomer, an acrylic resin monomer, triphenyl phosphate, a scratch resistance agent, a photoinitiator, and a diluent, and stir evenly to obtain a coating solution; S102. According to parts by mass, coat the coating solution on the surface of a transparent base film treated with oxygen plasma through a gravure roll, and then perform UV curing under an ultraviolet light curing lamp. The curing condition is 500 - 600 mJ / cm 2 to obtain a high haze and high temperature resistant diffusion film.

[0018] In summary, the beneficial technical effects of the present application are as follows: 1. High temperature resistance and stability Synergistic effect of triphenyl phosphate: By adding triphenyl phosphate, the decomposition reaction of the substrate in a high temperature environment is effectively inhibited, the material aging is delayed, and the service life of the diffusion film is significantly extended.

[0019] Reinforcement of organosiloxane groups: The organosiloxane structure contained in the acrylic resin oligomer not only improves the high temperature resistance of the diffusion layer itself (possibly tolerating harsh environments such as in-vehicle), but also enhances the chemical bonding between the PET base film, avoiding interlayer peeling caused by differences in thermal expansion at high temperatures.

[0020] 2. Excellent scratch resistance Enhanced surface hardness by modified silica: Silica particles pretreated with vinyltrimethoxysilane improve the interfacial bonding force and dispersibility with the acrylic resin through chemical modification, thereby forming a uniform micro-nano rough structure on the coating surface, significantly improving the surface hardness and scratch resistance.

[0021] Support of benzene ring rigid structure: The benzene ring groups in the acrylic resin oligomer and monomer (such as 2-phenoxyethyl acrylate) endow the diffusion layer with higher rigidity, further reducing surface damage caused by external forces.

[0022] 3. High haze and light uniformity Dual-scale scattering structure: The uniform dispersion of modified silica particles forms micron-scale scattering centers; a controllable rough structure (layer thickness of 30 - 50 μm) is formed on the surface through a coating process to achieve multiple scattering of light. The synergistic effect of the two significantly increases the haze value, eliminates local bright spots in the backlight module, and improves light uniformity.

[0023] Diluent Optimizes Coating Effect: The mixed solvent system of butyl acetate / isohexanone (4:3) balances the evaporation rate and leveling property, ensuring the uniformity and controllability of the surface roughness of the coating.

[0024] 4. Synergy of Material Systems Efficient Matching of Photoinitiators: 2,4,6-Trimethylbenzoyl diphenylphosphine oxide (TPO) and 2-Hydroxy-2-methyl-1-phenyl-1-propanone (1173) are compounded in a ratio of 3:2, taking into account deep curing (TPO absorbs long-wavelength UV) and surface curing (1173 absorbs short-wavelength UV), ensuring the complete crosslinking of thick coatings (30 - 50 μm) and avoiding the decline in mechanical properties caused by insufficient curing.

[0025] Synergistic Effect of Oligomer-Monomer: Acrylic resin oligomer provides a crosslinking framework, and high-functional monomers (such as 2-Phenoxyethyl acrylate) optimize the curing shrinkage rate, balancing hardness and adhesion.

[0026] 5. Application Adaptation Advantages Adaptability to In-vehicle Environment: The high-temperature resistance characteristic (can withstand long-term use above 120 °C) and scratch resistance perfectly meet the stringent requirements of in-vehicle displays for reliability.

[0027] Light Guide Plate Protection Function: The surface rough structure can not only scatter light but also serve as a physical buffer layer to prevent the prism film from directly contacting the light guide plate and causing scratches, reducing the assembly damage rate of the backlight module. Specific Embodiment Modes

[0028] The implementation schemes of the present application will be described in detail below in combination with embodiments. However, those skilled in the art will understand that the following embodiments are only used to illustrate the present application and should not be regarded as limiting the scope of the present application. For those not specified in the embodiments, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. Those reagents or instruments not specified by the manufacturer can be obtained as conventional products through commercial purchase.

[0029] In the following examples and preparation examples, 1 part represents 100 g.

[0030] Preparation Example 1 Preparation of Acrylic Resin Oligomer The preparation method of the acrylic resin oligomer is as follows: By mass parts, 100 parts of isopropyl methacrylate are added to a reactor, stirring is started, the rotation speed is adjusted to 45 r / min, and the temperature is raised to 63 °C under stirring conditions. Then, 26.5 parts of vinyltrimethoxysilane, 21 parts of methylphenyldivinylsilane, and 0.32 part of tetra-isopropyl titanate are added. The temperature is continuously raised to 92 °C under stirring conditions, and stirring reaction is carried out for 2.3 h. Then, the temperature is lowered to 53 °C under stirring conditions, and 5 parts of hydrochloric acid with a mass concentration of 37% are added, and hydrolysis-condensation reaction is carried out for 4 h under stirring conditions to obtain the acrylic resin oligomer.

[0031] Preparation Example 2 Preparation of Modified Silicon Dioxide The preparation method of modified silicon dioxide includes the following steps: S51. By mass parts, 100 parts of silicon dioxide with an average particle size of 0.3 μm are dispersed in 200 parts of an ethanol aqueous solution with a mass concentration of 75%. Then, 2.5 parts of vinyltrimethoxysilane are added thereto, the pH of the solution is adjusted to 4.7, and stirring is carried out for 3.4 h. After centrifugation, washing, and drying, pretreated silicon dioxide is obtained; S52. By mass parts, 100 parts of pretreated silicon dioxide are dispersed in 200 parts of an ethanol aqueous solution with a mass concentration of 75%. 25 parts of acrylamide are added and stirred evenly. Then, 2.6 parts of dibenzoyl peroxide are added, and the mixture is heated to 73 °C for reflux reaction for 2.5 h. After the reaction is completed, the reaction product is centrifuged, washed, and dried to obtain modified silicon dioxide.

[0032] Example 1 A high haze and 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 gravure roll. Among them, the diffusion layer, by mass parts, includes the following preparation raw materials: 60 parts of acrylic resin oligomer, 20 parts of 2-phenoxyethyl acrylate, 2 parts of triphenyl phosphate, 6 parts of modified silicon dioxide, 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 mass ratio of 3:2; the diluent is composed of butyl acetate and isohexanone in a mass ratio of 4:3. The transparent base film is a PET film with a thickness of 250 μm; The preparation method of the above high haze and high temperature resistant diffusion film includes the following steps: S101. By mass parts, the acrylic resin oligomer, 2-phenoxyethyl acrylate, triphenyl phosphate, modified silicon dioxide, photoinitiator, and diluent are mixed and stirred evenly to obtain a coating solution; S102. According to the parts by mass, coat the coating solution on the surface of the transparent base film treated with oxygen plasma through a gravure roll, and then carry out UV curing under an ultraviolet curing lamp. The curing conditions are 500 mJ / cm 2 , to obtain a high haze and high temperature resistant diffusion film.

[0033] Example 2 A high haze and high temperature resistant diffusion film, comprising a transparent base film and a diffusion layer coated on the surface of the transparent base film through a gravure roll. Among them, the diffusion layer, by parts by mass, comprises the following preparation raw materials: 70 parts of an acrylic resin oligomer, 30 parts of 2-phenoxyethyl acrylate, 3 parts of triphenyl phosphate, 8 parts of modified silica, 5 parts of a photoinitiator, and 9 parts of a 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 mass ratio of 3:2; the diluent is composed of butyl acetate and isohexanone in a mass ratio of 4:3. The transparent base film is a PET film with a thickness of 80 μm; The preparation method of the above-mentioned high haze and high temperature resistant diffusion film comprises the following steps: S101. According to the parts by mass, mix the acrylic resin oligomer, 2-phenoxyethyl acrylate, triphenyl phosphate, modified silica, photoinitiator and diluent, and stir evenly to obtain a coating solution; S102. According to the parts by mass, coat the coating solution on the surface of the transparent base film treated with oxygen plasma through a gravure roll, and then carry out UV curing under an ultraviolet curing lamp. The curing conditions are 600 mJ / cm 2 , to obtain a high haze and high temperature resistant diffusion film.

[0034] Example 3 A high haze and high temperature resistant diffusion film, comprising a transparent base film and a diffusion layer coated on the surface of the transparent base film through a gravure roll. Among them, the diffusion layer, by parts by mass, comprises the following preparation raw materials: 65 parts of an acrylic resin oligomer, 25 parts of 2-phenoxyethyl acrylate, 2.5 parts of triphenyl phosphate, 7 parts of modified silica, 4 parts of a photoinitiator, and 7.5 parts of a 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 mass ratio of 3:2; the diluent is composed of butyl acetate and isohexanone in a mass ratio of 4:3. The transparent base film is a PET film with a thickness of 150 μm; The preparation method of the above-mentioned high haze and high temperature resistant diffusion film comprises the following steps: S101. Mix the acrylic resin oligomer, 2-phenoxyethyl acrylate, triphenyl phosphate, modified silica, photoinitiator and diluent according to the parts by mass, and stir evenly to obtain a coating solution; S102. Coat the coating solution on the surface of the oxygen plasma-treated transparent base film by a gravure roll, and then perform UV curing under a UV curing lamp. The curing condition is 550 mJ / cm 2 , to obtain a high haze and high temperature resistant diffusion film.

[0035] Comparative Example 1 Same as Example 3, except that polyethylene glycol o-phenylphenyl ether acrylate with an equal number of parts by mass is used instead of the acrylic resin oligomer.

[0036] Comparative Example 2 Same as Example 3, except that unmodified silica with an equal number of parts by mass is used instead of the modified silica.

[0037] Comparative Example 3 Same as Example 3, except that the photoinitiator is 2,4,6-trimethylbenzoyl diphenylphosphine oxide.

[0038] Comparative Example 4 Same as Example 3, except that the photoinitiator is 2-hydroxy-2-methyl-1-phenyl-1-propanone.

[0039] Performance Test Perform performance tests on the high haze and high temperature resistant diffusion films prepared in Example 1, Example 3 and Comparative Examples 1-4. Among them, the haze: Refer to ASTM D1003 and test with an NDH2000 haze meter; Adhesion: Refer to the peel strength test standard GB / T 25256-2010, cut the diffusion film into 200 mm * 25 mm, and perform a 180-degree peel test with an electronic universal testing machine to obtain the test value recorded as the adhesion of the diffusion film; Abrasion resistance: The diffusion film is placed statically on the light-emitting surface of the light guide plate, and then a 500-gram weight is placed on the diffusion film, and it is moved back and forth 10 times within a distance of 10 cm. Calculate the mass difference before and after the test as the evaluation of abrasion resistance. The larger the difference, the less wear-resistant; Surface roughness: Refer to ISO 4287 profilometer for testing; Heat resistance: Refer to GB / T 16422.2 for high temperature aging, and test the yellowing rate after 500 h at 120 °C; The results are shown in Table 1.

[0040] Table 1 Performance Test Analyzing the data in Table 1, it can be seen that: 1) The high haze and high temperature resistant diffusion films prepared in Examples 1 - 3 have high scratch resistance, high temperature resistance, and strong bonding force with the transparent base film. At the same time, they have a rough surface structure, which is used to eliminate local bright spots in the backlight module and protect the light guide plate from damage by the upper prism film. They are widely used in large - size LCD devices (such as in - vehicle displays).

[0041] 2) Combining the performance comparative analysis of the high haze and high temperature resistant diffusion films prepared in Example 3 and Comparative Example 1 shows that using the acrylic resin oligomer prepared in this application, on the one hand, the chemical structural formula of this substance contains a benzene ring group, which can improve the scratch resistance of the diffusion layer; on the other hand, the organosiloxane contained in the chemical structural formula of this substance can improve the temperature resistance of the diffusion layer and the bonding force with the transparent base film, thereby improving the comprehensive performance of the high haze and high temperature resistant diffusion film.

[0042] 3) Combining the performance comparative analysis of the high haze and high temperature resistant diffusion films prepared in Example 3 and Comparative Example 2 shows that using the modified silica prepared in this application, through the gradient modification strategy of silane coupling pretreatment + acrylamide grafting, the interface design of "rigidity and flexibility combined" of the SiO2 filler is realized, which can significantly improve the high scratch resistance, high haze and high temperature resistance of the diffusion film.

[0043] 4) Combining the performance comparative analysis of the high haze and high temperature resistant diffusion films prepared in Example 3 and Comparative Examples 3 - 4 shows that 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. Utilizing their synergistic effect can significantly improve the comprehensive performance of the high haze and high temperature resistant diffusion film.

[0044] The above - mentioned examples are only used to explain the technical solutions of this application rather than to limit them. Although the above - mentioned examples have specifically described this application, those skilled in the art should understand that the specific implementation manners of the present invention can still be modified or equivalently replaced. Any modification and equivalent replacement without departing from the spirit and scope of this application shall be covered by the protection scope of this application.

Claims

1. A high haze and high temperature resistant diffusion film, characterized in that, It includes a transparent base film and a diffusion layer coated on the surface of the transparent base film by a gravure roll. Among them, the diffusion layer, by mass fraction, includes the following preparation 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, and the thickness of the diffusion layer is 30-50μm.

2. The high haze and high temperature resistant diffusion film according to claim 1, wherein The preparation method of the acrylic resin oligomer is as follows: By mass fraction, add 100 parts of isopropyl methacrylate to a reactor, start stirring, heat up to 60-65°C under stirring conditions, then add 26.5 parts of vinyltrimethoxysilane, 21 parts of methylphenyldivinylsilane, and 0.25-0.35 parts of catalyst, continue to heat up to 90-95°C under stirring conditions, and stir and react for 2-3h. Then cool down to 50-55°C under stirring conditions, add 5 parts of hydrochloric acid with a mass concentration of 37%, and carry out hydrolysis-condensation reaction for 3.5-4.5h under stirring conditions to obtain the acrylic resin oligomer.

3. The high haze and high temperature resistant diffusion film according to claim 2, wherein The rotation speed of the stirring is 40-50 r / min.

4. The high haze and high temperature resistant diffusion film according to claim 2, wherein The catalyst is tetra-isopropyl titanate.

5. The high haze and high temperature resistant diffusion film according to claim 1, wherein The preparation method of the modified silica includes the following steps: S51. By mass fraction, disperse silica with an average particle size of 0.2-0.4μm in an ethanol aqueous solution with a mass concentration of 75%, then add vinyltrimethoxysilane to it, adjust the pH of the solution to 4.5-5, stir for 3-4h, and obtain pretreated silica through centrifugation, washing, and drying. S52. By 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°C and reflux for 2-3h. After the reaction is completed, centrifuge, wash, and dry the reaction product to obtain modified silica.

6. The high haze and high temperature resistant diffusion film according to claim 5, wherein In step S51, the mass fraction ratio of the silica to the vinyltrimethoxysilane is 100:2-3; in step S52, the mass fraction ratio of the pretreated silica, acrylamide, and benzoyl peroxide is 10:(2-3):(0.2-0.3).

7. The high haze and high temperature resistant diffusion film according to claim 1, wherein The acrylic resin monomer is 2-phenoxyethyl acrylate.

8. The high haze and high temperature resistant diffusion film according to claim 1, characterized in that, The photoinitiator is composed of 2,4,6-trimethylbenzoyl diphenylphosphine oxide and 2-hydroxy-2-methyl-1-phenyl-1-propanone in a mass fraction ratio of 3:2; the diluent is composed of butyl acetate and isohexanone in a mass fraction ratio of 4:

3.

9. The high haze and high temperature resistant diffusion film according to claim 1, wherein The transparent base film is a PET film with a thickness of 80-250μm.

10. A method for preparing a high haze and high temperature resistant diffusion film according to any one of claims 1-9, characterized in that, It includes the following steps: S101. By mass fraction, mix the acrylic resin oligomer, acrylic resin monomer, triphenyl phosphate, scratch-resistant agent, photoinitiator, and diluent, and stir evenly to obtain a coating solution. S102. According to the mass parts, coat the coating liquid on the surface of the transparent base film treated with oxygen plasma by a gravure roll, and then perform UV curing under an ultraviolet curing lamp. The curing conditions are 500 - 600 mJ / cm 2 , to obtain a high haze and high temperature resistant diffusion film.

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