High-light-transmittance low-haze upper diffusion film and preparation method thereof

Abstract

The invention relates to the technical field of optical thin films, in particular to a high-transmittance low-haze upper diffusion film and a preparation method thereof. A high-light-transmittance low-haze upper diffusion film comprises a transparent base film and a nano coating coated on the surface of the transparent base film, and the nano coating comprises the following preparation raw materials: 30-40 parts of polyurethane modified acrylate, 20-30 parts of a high refractive index monomer, 10-15 parts of a functional monomer, 1.5-2 parts of nanoparticles and 2-4 parts of a photoinitiator. Wherein the nano particles are modified AlO / SiO nano composite particles. Through nano particle modification, functional monomer compounding and resin matrix optimization, the contradiction between light transmittance and mechanical performance of a traditional light diffusion film is broken through, comprehensive upgrading of optical performance (light transmittance / haze), mechanical strength (hardness / flexibility) and weather resistance (high temperature / aging resistance) is achieved, and the light diffusion film is suitable for high-end scenes such as ultra-thin OLED screens and vehicle-mounted display.

Description

Technical Field

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

[0002] Existing optical diffusion films are widely used in the field of liquid crystal displays, and the products are distributed in smart phones, laptops, televisions, cars, monitoring equipment and other portable devices. Traditional optical diffusion films achieve light uniformity through randomly distributed scattering particles, so that the direction of the outgoing light is randomly distributed, thereby uniformizing the incident uneven light and covering the defects of the backlight module components under the film. At the same time, some particles protruding from the coating have a certain focusing effect on the light, so that the diffusion film has a certain light-gathering ability. When the backlight module in the prior art adopts a light source, a reflector, a light guide plate, a lower diffusion film, a lower light-enhancing film, an upper light-enhancing film, and an upper diffusion film backlight structure, the rough surface of the optical film used for the liquid crystal display backlight module will interfere with the unit (pixel) array in the liquid crystal panel, and the image displayed on the display screen with a scattering anti-glare covering layer will produce dense and bright points. This phenomenon is called flash points (short for flash points). The existence of flash points will affect people's visual effects, cause eye discomfort, and easily produce fatigue and discomfort.

[0003] The back of the upper diffusion film is in contact with the prism structure surface of the light-enhancing film, and relative sliding will occur during the assembly process due to the contact. This relative sliding may cause scratches on the back of the upper diffusion film and the prism structure surface of the light-enhancing film, resulting in a reduction in yield. Existing upper diffusion films mostly adopt a high haze (>85%) design. Although they can even out the light, the transmittance is insufficient (<65%), resulting in a loss of display brightness, and the substrate is relatively thick (>0.2mm), which makes it difficult to meet the needs of thin and light devices. In addition, the coating uniformity in the traditional process is poor, glare is easily generated, and the scratch resistance is insufficient, which limits its application in the field of high-end displays. SUMMARY OF THE INVENTION The purpose of this application is to provide a high-transmittance, low-haze upper diffusion film and a preparation method thereof in response to the shortcomings of the current technology. The high-transmittance, low-haze upper diffusion film of the present application has low haze, high transmittance, high surface hardness, excellent scratch resistance and high temperature resistance. It is widely used in high-end devices such as laptops and OLED displays.

[0004] In the first aspect, the present application provides a high-transmittance, low-haze top diffuser film, which adopts the following technical solutions: The application discloses a high-transmittance low-haze upper diffusion film, which comprises a transparent base film and a nano coating coated on the surface of the transparent base film, wherein the nano coating comprises the following raw materials in parts by mass: polyurethane modified acrylate 30-40 parts, high-refractive monomer 20-30 parts, functional monomer 10-15 parts, nano particle 1.5-2 parts and photoinitiator 2-4 parts, wherein the nano particle is modified Al2O3 / SiO2 nano composite particle, and the thickness of the nano coating is 80-200 nm.

[0005] By adopting the above technical solution, polyurethane-modified acrylate is used as the main film-forming substance of the nanocoating, providing basic mechanical properties and adhesion. The polyurethane segment imparts flexibility and reduces the brittleness of the coating; the acrylate segment provides high hardness and scratch resistance; the modified fluidity is improved, facilitating the uniform dispersion of nanoparticles while enhancing the interfacial bonding with transparent base films (such as PET and PC). It forms an interpenetrating network with functional monomers and nanoparticles, balancing hardness and flexibility and providing a stable dispersion environment for other components. The high refractive index (approximately 1.57-1.60) of high-refractive-index monomers (such as o-phenylphenoxyethyl acrylate) matches the refractive index (1.45-1.76) of nanoparticles (Al2O3 / SiO2), reducing light scattering interface reflection and improving light transmittance; through molecular structure design, optical path distortion and haze are reduced. The benzene ring structure enhances the rigidity of the coating and improves scratch resistance. It synergizes with nanoparticles to optimize the light diffusion path and improve light transmittance under the premise of low haze. Functional monomers (e.g., composed of 4-tert-butylcyclohexyl acrylate, 4-acryloylmorpholine, and isobornyl acrylate): 4-tert-butylcyclohexyl acrylate: The tert-butyl and cyclohexyl rings reduce surface tension, improving wettability and adhesion to substrates like PET / PC; the hydrophobic structure reduces the erosion of the coating by ambient humidity. The nitrogen-containing heterocyclic ring of 4-acryloylmorpholine accelerates free radical initiation, shortening cure time; the rigid morpholine ring raises the glass transition temperature (Tg), enhancing high-temperature resistance. Isobornyl acrylate: The bulky isobornyl group inhibits polymerization shrinkage and reduces internal stress in the coating; the rigid side groups restrict molecular chain motion, increasing the heat distortion temperature. Modified Al2O3 / SiO2 nanocomposite particles: The nanoscale size enables wide-angle light diffusion through Rayleigh scattering while avoiding increased haze caused by Mie scattering; Al2O3 increases the coating's surface hardness; SiO2 enhances scratch resistance; and after modification with vinyltrimethoxysilane, the surface hydroxyl groups are replaced by hydrophobic groups, improving compatibility with acrylate resins and preventing agglomeration. It forms a refractive index gradient with high-refractive index monomers, reducing total reflection loss, while enhancing stress transfer through the nanoparticle / resin interface and improving the wear resistance of the coating. Photoinitiator (such as TPO:184=4:3), TPO (2,4,6-trimethylbenzoyldiphenylphosphine oxide): long wavelength absorption (380-420nm), suitable for deep curing of thick coatings; 184 (1-hydroxycyclohexylphenyl ketone): short wavelength response (250-350nm), achieving rapid surface curing. The dual-initiator system achieves gradient curing: rapid surface curing (184) reduces oxygen inhibition effect; deep and sufficient curing (TPO) avoids unreacted monomer residue and improves the aging resistance of the coating. In short, through molecular structure regulation, nanocomposite and multi-component synergistic curing, a breakthrough has been made in the trade-off contradiction of "transmittance-haze-mechanical properties" of traditional diffusion films.

[0006] Preferably, the preparation method of the polyurethane-modified acrylate comprises the following steps: S21. Under argon protection, 33.64 parts of hexamethylene diisocyanate were added to the reaction flask according to mass parts, the temperature was raised to 65-68 ° C, and 200 parts of polypropylene glycol-2000 were added dropwise. After the addition was completed, the reaction was continued at this temperature for 5-6 hours, the reaction was stopped, and the temperature was cooled to room temperature to obtain intermediate product A; S22, according to the mass parts, under the condition of protecting from light, 37.64 parts of ethoxyethyl acrylate were added to the reaction bottle, the temperature was raised to 53-55 ° C, stirred, and then 14.92 parts of triethanolamine were slowly added dropwise. After the addition was completed, the reaction was continued for 48 hours. After the chromatographic detection showed no raw material peak, the reaction was stopped, the temperature was cooled to room temperature, and the intermediate product B was obtained by cooling; S23. According to the mass parts, under argon protection and light-proof conditions, add 66.17 parts of intermediate product B to the reaction flask, raise the temperature to 68-70°C, stir, and add 67.41 parts of intermediate product A dropwise. After the addition is complete, continue to keep the temperature and react for 6-7 hours. If no -NCO group is found, stop the reaction and cool to room temperature to obtain a polyurethane-modified acrylate resin.

[0007] By adopting the above technical solution, step S21: synthesize polyurethane prepolymer (intermediate product A), hexamethylene diisocyanate (HDI): highly reactive isocyanate monomer, providing -NCO terminal group. Polypropylene glycol-2000 (PPG-2000): flexible polyether chain segment, reducing resin brittleness. Under argon protection, HDI is stirred at 65-68 ° C, and PPG-2000 is slowly added dropwise to avoid local excess and side reactions; the reaction is kept warm for 5-6 hours to allow -NCO to fully react with the hydroxyl group (-OH) of PPG to generate a terminal -NCO polyurethane prepolymer. The introduction of flexible polyether chain segments gives the resin flexibility and impact resistance; the terminal -NCO group is retained to provide a reaction site for subsequent acrylate modification. Step S22: synthesize acrylate intermediate (intermediate product B), ethoxyethyl acrylate: contains acrylic double bonds and ethoxy groups, enhances the fluidity and adhesion of the resin; triethanolamine: contains hydroxyl and tertiary amine groups, catalyzes the reaction and adjusts the molecular weight distribution. Under light-proof conditions (to prevent acrylate self-polymerization), ethoxyethyl acrylate reacts with triethanolamine at 53-55°C for 48 hours; a hydroxyl-acrylate transesterification reaction is performed to generate a hydroxyl-containing acrylate derivative (intermediate product B). Hydroxyl groups that can further react are introduced for cross-linking with polyurethane prepolymers; the ethoxy group improves the wettability of the resin to the substrate (such as PET) and enhances interfacial bonding. Step S23: Polyurethane-acrylate copolymerization (final product synthesis), under argon protection and light-proof conditions, the intermediate product B is heated to 68-70°C and the intermediate product A is added dropwise; -NCO reacts with the hydroxyl group to generate a carbamate bond (-NHCOO-) to form a polyurethane-acrylate block copolymer; the -NCO content is monitored until it disappears completely to ensure that the reaction is complete and to avoid residues that cause yellowing or performance degradation. Molecular-level composites of polyurethane (flexibility) and acrylate (hardness) are achieved through chemical bonding; an interpenetrating network structure (IPN) is formed to balance mechanical properties and processing fluidity. The polar groups (-NHCOO-) in the polyurethane segments form hydrogen bonds with the base film (PET / PC), enhancing interfacial bonding; the ethoxy groups in the acrylate improve wettability. The flexible-rigid balance of the polyurethane's soft segments (PPG) absorbs stress, while the rigid segments (benzene rings and ester groups) in the acrylate provide surface hardness. The polyurethane's soft segments encapsulate the nanoparticles (Al2O3 / SiO2), preventing agglomeration; the fluidity of the acrylate ensures uniform film formation. Synergy with functional monomers: The polyurethane's flexible chains synergize with the flexibility of 4-acryloylmorpholine to alleviate the coating's curing shrinkage stress; the acrylate's rigid chains and the bulky side groups of isobornyl acrylate enhance heat and scratch resistance. Synergy with nanoparticles: The polyurethane's soft segments physically entangle and secure the nanoparticles, forming a "soft-in-hard" structure that enhances the coating's wear resistance; the polar groups in the acrylate are compatible with the hydrophobic surface of the modified nanoparticles (vinyl silane), optimizing light scattering pathways.Synergized with photoinitiator: the flowability of polyurethane-acrylate allows photoinitiator (TPO / 184) to be distributed uniformly, achieving gradient curing and reducing surface defects caused by oxygen inhibition. In summary, this resin design breaks through the brittle limitations of traditional acrylates and provides an ideal film-forming matrix for high-transmission low-haze diffusion films.

[0008] Preferably, the stirring speed is 100-150 r / min.

[0009] Preferably, the preparation method of the modified Al2O3 / SiO2 nano composite particles comprises the following steps: S41, according to mass fraction, 10 parts of Al2O3 powder with an average particle size of 20-30 nm is added to a solution composed of 200 parts of anhydrous ethanol and 80 parts of deionized water, stirred uniformly, then 0.5 parts of polyvinylpyrrolidone K90 is added, ultrasonic dispersion is carried out for 60-70 min, and a mixed solution A is obtained; S42, according to mass fraction, 80 parts of 50% tetraethyl orthosilicate anhydrous ethanol solution is added dropwise into the mixed solution A, the dropwise addition is completed in 2 h, ammonia water is supplemented every 10 min during the dropwise addition process, the pH is adjusted to 10.3-10.7, after the dropwise addition is completed, the reaction is continued for 7-8 h, centrifugal separation is carried out, washed with pure water for 3 times, dried in an oven at 150-160℃ for 6-8 h, and ground to obtain Al2O3 / SiO2 nano composite particles with an average particle size of 40 nm; S43, according to mass fraction, the Al2O3 / SiO2 nano composite particles are dispersed in an ethanol aqueous solution with a mass concentration of 75%, then vinyltrimethoxysilane is added, the pH of the solution is adjusted to 4.5-5, stirred for 3-4 h, centrifuged, washed, dried, and ground to obtain modified Al2O3 / SiO2 nano composite particles with an average particle size of 40 nm.

[0010] By adopting the above technical solution, step S41: Al2O3 powder is dispersed in an ethanol-water solution, polyvinylpyrrolidone (PVP K90) is added as a dispersant, and ultrasonic treatment is performed for 60-70 minutes to form a uniform suspension. This process reduces nanoparticle agglomeration through physical dispersion and the action of surfactants. Step S42: Tetraethyl orthosilicate (TEOS) ethanol solution is added dropwise to coat the Al2O3 surface with a SiO2 layer via a sol-gel method. Ammonia water is used to adjust the pH to 10.3-10.7 to promote the hydrolysis and condensation of TEOS, forming a uniform SiO2 coating. The final product is centrifuged, washed, and dried to obtain Al2O3 / SiO2 composite particles (average particle size 40 nm). Step S43: The Al2O3 / SiO2 composite particles are dispersed in an ethanol-water solution, vinyltrimethoxysilane is added, the pH is adjusted to 4.5-5, and the reaction is stirred for 3-4 hours. The silane coupling agent combines with the hydroxyl groups on the surface of the particles through hydrolysis to form an organic-inorganic interface, thereby improving the compatibility between the particles and the resin matrix. The role of the prepared modified Al2O3 / SiO2 nanocomposite particles in this application: 1. Improving dispersibility and compatibility. After modification with vinyltrimethoxysilane, vinyl functional groups are introduced onto the surface of the particles to form chemical bonds or physical adsorption with the polar groups (such as amino groups and ester groups) of the polyurethane-modified acrylate resin, reducing agglomeration and ensuring that the nanoparticles are evenly distributed in the coating. 2. Optimizing light diffusion and transmittance. The Al2O3 / SiO2 composite particles achieve multiple scattering of light through a multi-layer coating structure (Al2O3 core + SiO2 shell), balancing transmittance and haze at a low addition amount. The SiO2 layer can adjust the refractive index and reduce interface reflection losses. 3. Enhancing the mechanical properties of the coating. The nanoparticles act as rigid fillers and form an interpenetrating network with the resin matrix to improve the hardness and scratch resistance of the coating. At the same time, the SiO2 coating layer improves the high temperature resistance of the particles and avoids performance degradation at high temperatures. 4. Improved interfacial bonding: The modified particle surface synergizes with functional monomers (such as 4-tert-butylcyclohexyl acrylate) to enhance adhesion between the coating and the PET base film, reducing the risk of delamination. In summary, through core-shell structural design and surface chemical modification, the modified Al2O3 / SiO2 composite particles resolve the conflict between transmittance and haze in traditional light diffusion films. They also impart high hardness, high temperature resistance, and scratch resistance to the coating, making it suitable for high-end optical devices such as OLED displays.

[0011] Preferably, in step S43, the mass ratio of the Al2O3 / SiO2 nanocomposite particles to vinyltrimethoxysilane is 100:4-6.

[0012] Preferably, the high refractive index monomer is o-phenylphenoxyethyl acrylate.

[0013] Preferably, the functional monomer is composed of 4-tert-butyl cyclohexyl acrylate, 4-acryloylmorpholine and isobornyl acrylate in a mass ratio of 3:5:2.

[0014] By adopting the technical scheme, 4-tert-butyl cyclohexyl acrylate (TBCA) has low surface tension due to the cyclohexyl and tert-butyl structures, can enhance the adhesion to transparent base films such as PET and PC, and reduce the risk of coating peeling. The monofunctionality reduces polymerization shrinkage and avoids micro-cracks caused by curing shrinkage of the coating. 4-acryloylmorpholine (ACMO) has strong polarity of the morpholine ring to accelerate photocuring reaction, and its flexible segment improves the impact resistance and flexibility of the coating to avoid brittle fracture. The stability of the ether bond and amide bond in the molecule enables the coating to maintain performance at high temperature, and is suitable for high-temperature working environments such as OLED displays. Isobornyl acrylate (IBOA): the bulky rigid side group of isobornyl ester limits the movement of polymer chain segments, significantly improving the hardness and heat resistance of the coating. The rigid structure enhances the surface scratch resistance of the coating and reduces performance degradation caused by friction during use. The synergistic mechanism of the three, 1) complementary ratio design (3:5:2) of functions: TBCA: preferentially adsorbed on the base film interface to form a dense bottom layer and improve adhesion; ACMO: as the main monomer, balances the curing speed and flexibility, and simultaneously binds to the surface hydroxyl groups of nanoparticles (such as Al2O3 / SiO2) through hydrogen bonds to enhance dispersibility; IBOA: intercalated between ACMO segments to inhibit chain segment relaxation through steric hindrance effect, and synergistically improve hardness and heat resistance. 2) Dynamic performance balance: low surface tension of TBCA reduces light scattering interface, uniform film-forming property of ACMO reduces haze, and rigid structure of IBOA inhibits light path distortion, and the three synergistically achieve high transmittance and low haze. Mechanical performance optimization: the flexibility of ACMO and the rigidity of IBOA form a “rigid and flexible” network to improve scratch resistance while maintaining the flexibility of the coating. 3) Synergistic effect with nanoparticles: modified Al2O3 / SiO2 nanoparticles are bonded to the polar groups of TBCA / ACMO through vinyl groups to form a “resin-nanoparticle” interpenetrating network, further strengthening the hardness and high-temperature resistance of the coating. In summary, the functional monomer combination solves the contradiction between transmittance and mechanical performance in traditional light diffusion films through three-dimensional synergy of adhesion-flexibility-rigidity, and meets the stringent requirements of high-end display devices for low haze and high transmittance.

[0015] Preferably, the photoinitiator is composed of 2,4,6-trimethylbenzoyl diphenyl phosphine oxide and 1-hydroxycyclohexyl phenyl ketone in a mass ratio of 4:3.

[0016] Preferably, the transparent base film is a PET film or a PC film with a thickness of 50-150 μm.

[0017] In a second aspect, the present application provides a method for preparing a high-transmittance, low-haze upper diffuser film, using the following technical solution: As a general technical concept, the present application also provides a method for preparing the above-mentioned high-transmittance, low-haze upper diffuser film, comprising the following steps: S101, mixing polyurethane-modified acrylate, high refractive index monomer, functional monomer, nanoparticles and photoinitiator according to parts by mass, and stirring evenly to obtain a coating solution; S102. According to the mass fraction, the coating liquid is coated on the surface of the transparent base film treated with oxygen plasma by a slit coating method at a coating speed of 0.5-2 m / min, and then UV curing is performed under a UV curing lamp at a curing condition of 300-400 mJ / cm2 and a curing time of 15-25 seconds to obtain a high-transmittance, low-haze upper diffusion film.

[0018] In summary, the beneficial technical effects of this application are: 1. Synergistic optimization of high transmittance and low haze By modifying the multiple scattering effect (core-shell structure) of Al2O3 / SiO2 nanocomposite particles and the low surface tension of functional monomers, high transmittance and low haze are achieved. Compared to traditional light diffusion films, the optical performance is significantly improved, meeting the high-definition requirements of OLED displays.

[0019] 2. Excellent mechanical properties and high hardness: Nanoparticles and functional monomers (IBOA rigid groups) work synergistically, and the coating hardness can reach over 3H (pencil hardness test), improving scratch resistance.

[0020] Flexibility: The combination of polyurethane-modified acrylate and the flexible chain segment of 4-acryloylmorpholine (ACMO) makes the coating bending radius less than 5mm, avoiding brittle cracking.

[0021] 3. Outstanding high temperature resistance The synergistic effect of 4-acryloylmorpholine (heat resistance) and isobornyl acrylate (rigid side group) in the functional monomers enables the coating to remain stable at a high temperature of 150°C and pass the 180°C / 2h aging test without yellowing or peeling.

[0022] 4. Strong interface adhesion The low surface tension of 4-tert-butylcyclohexyl acrylate (TBCA) combined with the vinyl functional groups of the modified nanoparticles enhances the adhesion of the coating to the PET or PC base film, avoiding the risk of delamination during long-term use of high-end equipment.

[0023] 5. Process compatibility and environmental protection -The photoinitiator (TPO and 184 compound) matches the UV curing process, improving curing efficiency. The coating thickness is only 80-200nm, reducing raw material consumption and complying with the trend of green manufacturing. DETAILED DESCRIPTION

[0024] The embodiments of the present application will be described in detail below with examples, but those skilled in the art will understand that the following examples are only for illustration of the present application and should not be regarded as limiting the scope of the present application. The specific conditions are not specified in the examples, which are carried out according to the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used are not specified by the manufacturer, which are all conventional products that can be purchased on the market.

[0025] In the following examples and preparation examples, 1 part represents 10 g.

[0026] Preparation of polyurethane modified acrylate The preparation method of the polyurethane modified acrylate comprises the following steps: S21, according to the mass fraction, 33.64 parts of hexamethylene diisocyanate is added to the reaction bottle under argon protection, the temperature is raised to 67℃, stirring, adjusting the stirring speed to 120r / min, 200 parts of polypropylene glycol-2000 is added dropwise, after the dropwise addition is completed, the reaction is continued for 5.6h, the reaction is stopped, and the temperature is lowered to room temperature to obtain the intermediate product A; S22, according to the mass fraction, 37.64 parts of ethoxyethyl acrylate is added to the reaction bottle under light protection, the temperature is raised to 54℃, stirring, adjusting the stirring speed to 120r / min, then slowly adding 14.92 parts of triethanolamine, after the dropwise addition is completed, the reaction is continued for 48h, after the chromatographic detection has no raw material peak, the reaction is stopped, and the temperature is lowered to room temperature, and the temperature is lowered to obtain the intermediate product B; S23, according to the mass fraction, 66.17 parts of the intermediate product B is added to the reaction bottle under argon protection and light protection, the temperature is raised to 69℃, stirring, adjusting the stirring speed to 120r / min, 67.41 parts of the intermediate product A is added dropwise, after the dropwise addition is completed, the reaction is continued for 6.5h, and no -NCO group is detected, the reaction is stopped, and the temperature is lowered to room temperature, to obtain the polyurethane modified acrylate resin.

[0027] Preparation of modified Al2O3 / SiO2 nano composite particles The preparation method of the modified Al2O3 / SiO2 nano composite particles comprises the following steps: S41, according to the mass fraction, 10 parts of Al2O3 powder with an average particle size of 25nm is added to a solution composed of 200 parts of anhydrous ethanol and 80 parts of deionized water, after stirring uniformly, 0.5 parts of polyvinylpyrrolidone K90 is added, and ultrasonic dispersion is carried out for 65min to obtain a mixed solution A; S42. 80 parts by mass of a 50% tetraethyl orthosilicate anhydrous ethanol solution were added dropwise to the mixed solution A over 2 hours. Ammonia water was added every 10 minutes during the addition to adjust the pH to 10.4. After the addition was completed, the reaction was continued for 7.5 hours. The mixture was centrifuged, washed with pure water three times, dried in an oven at 155°C for 7 hours, and ground to obtain Al2O3 / SiO2 nanocomposite particles with an average particle size of 40 nm. S43. Disperse 20 parts of Al2O3 / SiO2 nanocomposite particles in 130 parts of 75% ethanol aqueous solution by mass, then add 1 part of vinyltrimethoxysilane thereto, adjust the pH of the solution to 4.7, stir for 3.4 hours, centrifuge, wash, dry, and grind to obtain modified Al2O3 / SiO2 nanocomposite particles with an average particle size of 40 nm.

[0028] Preparation of Comparative Example 1 Preparation of Al2O3 / SiO2 Nanocomposite Particles The preparation method of Al2O3 / SiO2 nanocomposite particles comprises the following steps: S41. Add 10 parts by mass of Al2O3 powder with an average particle size of 25 nm to a solution consisting of 200 parts of anhydrous ethanol and 80 parts of deionized water, stir evenly, add 0.5 parts of polyvinylpyrrolidone K90, and ultrasonically disperse for 65 minutes to obtain a mixed solution A. S42. Add 80 parts of 50% tetraethyl orthosilicate anhydrous ethanol solution into the mixed solution A in parts by mass, and complete the addition within 2 hours. Add ammonia water every 10 minutes during the addition to adjust the pH to 10.4. After the addition is completed, continue the reaction for 7.5 hours, centrifuge, wash with pure water 3 times, dry in an oven at 155°C for 7 hours, and grind to obtain Al2O3 / SiO2 nanocomposite particles with an average particle size of 40 nm.

[0029] Example 1 A high-transmittance, low-haze upper diffusion film comprises a transparent base film and a nanocoating coated on the surface of the transparent base film, wherein the nanocoating comprises the following raw materials, measured by weight: 30 parts of polyurethane-modified acrylate, 20 parts of o-phenylphenoxyethyl acrylate, 10 parts of a functional monomer, 1.5 parts of nanoparticles, and 2 parts of a photoinitiator, wherein the nanoparticles are modified Al2O3 / SiO2 nanocomposite particles; the nanocoating has a thickness of 80 nm; the transparent base film is a PET film with a thickness of 150 μm; the functional monomer comprises 4-tert-butylcyclohexyl acrylate, 4-acryloylmorpholine, and isobornyl acrylate in a weight ratio of 3:5:2; and the photoinitiator comprises 2,4,6-trimethylbenzoyldiphenylphosphine oxide and 1-hydroxycyclohexylphenyl ketone in a weight ratio of 4:3; The method for preparing the above-mentioned high-transmittance, low-haze upper diffuser film comprises the following steps: S101, mixing polyurethane-modified acrylate, o-phenylphenoxyethyl acrylate, functional monomer, nanoparticles, and photoinitiator according to parts by mass, and stirring uniformly to obtain a coating solution; S102, according to the mass fraction, the coating liquid is coated on the surface of the transparent base film treated with oxygen plasma by slit coating method, the coating speed is 2 m / min, and then UV curing is carried out under a UV curing lamp, the curing condition is 300 mJ / cm 2 The curing time is 25 seconds to produce a high-transmittance, low-haze upper diffusion film.

[0030] Example 2 A high-transmittance, low-haze upper diffusion film comprises a transparent base film and a nanocoating coated on the surface of the transparent base film, wherein the nanocoating comprises the following raw materials, measured by weight: 40 parts of polyurethane-modified acrylate, 30 parts of o-phenylphenoxyethyl acrylate, 15 parts of a functional monomer, 2 parts of nanoparticles, and 4 parts of a photoinitiator, wherein the nanoparticles are modified Al2O3 / SiO2 nanocomposite particles; the nanocoating has a thickness of 200 nm; the transparent base film is a PET film or PC film with a thickness of 50 μm; the functional monomer comprises 4-tert-butylcyclohexyl acrylate, 4-acryloylmorpholine, and isobornyl acrylate in a weight ratio of 3:5:2; and the photoinitiator comprises 2,4,6-trimethylbenzoyldiphenylphosphine oxide and 1-hydroxycyclohexylphenyl ketone in a weight ratio of 4:3; The method for preparing the above-mentioned high-transmittance, low-haze upper diffuser film comprises the following steps: S101, mixing polyurethane-modified acrylate, o-phenylphenoxyethyl acrylate, functional monomer, nanoparticles, and photoinitiator according to parts by mass, and stirring uniformly to obtain a coating solution; S102, according to the mass fraction, the coating liquid is coated on the surface of the transparent base film treated with oxygen plasma by slit coating method, the coating speed is 0.5 m / min, and then UV curing is carried out under a UV curing lamp, the curing condition is 400 mJ / cm 2 The curing time is 15 seconds to produce a high-transmittance, low-haze upper diffusion film.

[0031] Example 3 A high-transmittance, low-haze upper diffusion film comprises a transparent base film and a nanocoating coated on the surface of the transparent base film, wherein the nanocoating comprises the following raw materials, measured by weight: 35 parts of polyurethane-modified acrylate, 25 parts of o-phenylphenoxyethyl acrylate, 13 parts of a functional monomer, 1.7 parts of nanoparticles, and 3 parts of a photoinitiator, wherein the nanoparticles are modified Al2O3 / SiO2 nanocomposite particles; the nanocoating has a thickness of 120 nm; the transparent base film is a PET film with a thickness of 100 μm; the functional monomer comprises 4-tert-butylcyclohexyl acrylate, 4-acryloylmorpholine, and isobornyl acrylate in a weight ratio of 3:5:2; and the photoinitiator comprises 2,4,6-trimethylbenzoyldiphenylphosphine oxide and 1-hydroxycyclohexylphenyl ketone in a weight ratio of 4:3; The method for preparing the above-mentioned high-transmittance, low-haze upper diffuser film comprises the following steps: S101, mixing polyurethane-modified acrylate, o-phenylphenoxyethyl acrylate, functional monomer, nanoparticles, and photoinitiator according to parts by mass, and stirring uniformly to obtain a coating solution; S102, according to the mass fraction, the coating liquid is coated on the surface of the transparent base film treated with oxygen plasma by slit coating method, the coating speed is 1 m / min, and then UV curing is carried out under a UV curing lamp, the curing condition is 350mJ / cm 2 The curing time is 20 seconds to produce a high-transmittance, low-haze upper diffusion film.

[0032] Comparative Example 1 The same as Example 3, except that ethoxyethyl acrylate is used in equal parts by mass instead of polyurethane modified acrylate.

[0033] Comparative Example 2 The same as Example 3, except that the nanoparticles are the Al2O3 / SiO2 nanocomposite particles prepared in Comparative Example 1.

[0034] Comparative Example 3 The same as Example 3, except that the functional monomer is 4-tert-butylcyclohexyl acrylate.

[0035] Comparative Example 4 The same as Example 3, except that the functional monomer is 4-acryloylmorpholine.

[0036] Comparative Example 5 The same as Example 3, except that the functional monomer is isobornyl acrylate.

[0037] Performance Testing Performance tests were conducted on the high-transmittance, low-haze upper diffuser films prepared in Examples 1 and 3 and Comparative Examples 1 to 5. Transmittance and haze were tested according to ASTM D1003. Adhesion was measured according to the peel strength test standard GB / T 25256-2010. The diffuser films were cut into 200 mm x 25 mm pieces and subjected to a 180-degree peel test using an electronic universal testing machine. The measured value was recorded as the diffusion film's adhesion. Scratch resistance was measured according to IS K5600 (pencil hardness). Heat resistance was measured according to GB / T 1735. After 2 hours at 180°C, the samples were inspected for yellowing or peeling. The results are shown in Table 1.

[0038] Table 1 Performance test Analyzing the data in Table 1, we can see that: 1) The high-transmittance, low-haze top diffuser films produced in Examples 1-3 feature low haze, high transmittance, high surface hardness, excellent scratch resistance, and high-temperature resistance. They are widely used in high-end devices such as laptops and OLED displays.

[0039] 2) A comparative analysis of the performance of the high-transmittance, low-haze upper diffusion film prepared in Example 3 and Comparative Example 1 shows that the polyurethane-modified acrylate resin prepared by the present application improves fluidity and exhibits high adhesion, improves scratch resistance and flexibility, and synergizes with other components to thereby improve the comprehensive performance of the high-transmittance, low-haze upper diffusion film.

[0040] 3) A comparative analysis of the performance of the high-transmittance, low-haze upper diffusion films prepared in combination with Example 3 and Comparative Example 2 shows that the modified Al2O3 / SiO2 nanocomposite particles prepared in the present application, after modification with vinyltrimethoxysilane, significantly improve the dispersibility and compatibility of the Al2O3 / SiO2 nanocomposite particles in acrylate, can undergo multiple scattering, can improve the light diffusion effect and transmittance, thereby achieving high transmittance and low haze, while also improving the surface hardness, scratch resistance and high temperature resistance of the upper diffusion film.

[0041] 4) A comparative analysis of the performance of the high-transmittance, low-haze upper diffusion films prepared in combination with Example 3 and Comparative Examples 3 to 5 shows that the functional monomers are composed of 4-tert-butylcyclohexyl acrylate, 4-acryloylmorpholine and isobornyl acrylate in a mass ratio of 3:5:2. By utilizing their combined effect and through the three-dimensional synergy of adhesion-flexibility-rigidity, the contradiction between transmittance and mechanical properties in traditional light diffusion films is solved, while meeting the stringent requirements of high-end display devices for low haze and high transmittance.

[0042] The above embodiments are only used to illustrate the technical solutions of the present application and are not intended to limit the present application. Although the above embodiments provide a detailed description of the present application, relevant technical personnel should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modifications and equivalent replacements that do not depart from the spirit and scope of the present application should be included in the scope of protection of the present application.

Claims

1. A high-transmittance, low-haze upper diffusion film, characterized in that: The invention comprises a transparent base film and a nano coating coated on the surface of the transparent base film, wherein the nano coating comprises the following raw materials by weight: 30-40 parts of polyurethane-modified acrylate, 20-30 parts of high-refractive-index monomer, 10-15 parts of functional monomer, 1.5-2 parts of nanoparticles, and 2-4 parts of photoinitiator, wherein the nanoparticles are modified Al2O3 / SiO2 nanocomposite particles, and the thickness of the nano coating is 80-200 nm.

2. The high-transmittance, low-haze upper diffusion film according to claim 1, characterized in that: The preparation method of the polyurethane-modified acrylate comprises the following steps: S21. Under argon protection, 33.64 parts of hexamethylene diisocyanate were added to the reaction flask according to mass parts, the temperature was raised to 65-68 ° C, and 200 parts of polypropylene glycol-2000 were added dropwise. After the addition was completed, the reaction was continued at this temperature for 5-6 hours, the reaction was stopped, and the temperature was cooled to room temperature to obtain intermediate product A; S22, according to the mass parts, under the condition of protecting from light, 37.64 parts of ethoxyethyl acrylate were added to the reaction bottle, the temperature was raised to 53-55 ° C, stirred, and then 14.92 parts of triethanolamine were slowly added dropwise. After the addition was completed, the reaction was continued for 48 hours. After the chromatographic detection showed no raw material peak, the reaction was stopped, the temperature was cooled to room temperature, and the intermediate product B was obtained by cooling; S23. According to the mass parts, under argon protection and light-proof conditions, add 66.17 parts of intermediate product B to the reaction flask, raise the temperature to 68-70°C, stir, and add 67.41 parts of intermediate product A dropwise. After the addition is complete, continue to keep the temperature and react for 6-7 hours. If no -NCO group is found, stop the reaction and cool to room temperature to obtain a polyurethane-modified acrylate resin.

3. The high-transmittance, low-haze upper diffusion film according to claim 2, characterized in that: The stirring speed is 100-150 r / min.

4. The high-transmittance, low-haze upper diffusion film according to claim 1, characterized in that: The preparation method of the modified Al2O3 / SiO2 nanocomposite particles comprises the following steps: S41. Add 10 parts by mass of Al2O3 powder with an average particle size of 20-30 nm to a solution consisting of 200 parts of anhydrous ethanol and 80 parts of deionized water, stir evenly, add 0.5 parts of polyvinylpyrrolidone K90, and ultrasonically disperse for 60-70 minutes to obtain a mixed solution A. S42. Add 80 parts by mass of a 50% tetraethyl orthosilicate anhydrous ethanol solution to the mixed solution A over 2 hours. During the addition, add aqueous ammonia every 10 minutes to adjust the pH to 10.3-10.

7. After the addition is complete, continue the reaction for 7-8 hours. After centrifugation, wash with pure water three times, dry in an oven at 150-160°C for 6-8 hours, and grind to obtain Al2O3 / SiO2 nanocomposite particles with an average particle size of 40 nm. S43. Al2O3 / SiO2 nanocomposite particles are dispersed in an ethanol aqueous solution with a mass concentration of 75% according to the mass fraction, and then vinyltrimethoxysilane is added thereto. The pH of the solution is adjusted to 4.5-5, and the mixture is stirred for 3-4 hours. After centrifugation, washing, drying, and grinding, modified Al2O3 / SiO2 nanocomposite particles with an average particle size of 40 nm are obtained.

5. The high-transmittance, low-haze upper diffusion film according to claim 4, characterized in that: In step S43, the mass ratio of the Al2O3 / SiO2 nanocomposite particles to vinyltrimethoxysilane is 100:4-6.

6. The high-transmittance, low-haze upper diffusion film according to claim 1, characterized in that: The high refractive index monomer is o-phenylphenoxyethyl acrylate.

7. The high-transmittance, low-haze upper diffusion film according to claim 1, characterized in that: The functional monomers are composed of 4-tert-butylcyclohexyl acrylate, 4-acryloylmorpholine and isobornyl acrylate in a mass ratio of 3:5:

2.

8. The high-transmittance, low-haze upper diffusion film according to claim 1, characterized in that: The photoinitiator is composed of 2,4,6-trimethylbenzoyldiphenylphosphine oxide and 1-hydroxycyclohexylphenyl ketone in a mass ratio of 4:

3.

9. The high-transmittance, low-haze upper diffusion film according to claim 1, characterized in that: The transparent base film is a PET film or a PC film with a thickness of 50-150 μm.

10. A method for preparing a high-transmittance, low-haze upper diffusion film according to any one of claims 1 to 9, characterized in that: The following steps are involved: S101, mixing polyurethane-modified acrylate, high refractive index monomer, functional monomer, nanoparticles and photoinitiator according to parts by mass, and stirring evenly to obtain a coating solution; S102. Apply the coating liquid by slit coating on the surface of the transparent base film treated with oxygen plasma according to the mass fraction, with a coating speed of 0.5-2 m / min, and then perform UV curing under a UV curing lamp at a curing condition of 300-400 mJ / cm² and a curing time of 15-25 seconds to obtain a high-transmittance, low-haze upper diffusion film.

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