An ultra-high performance diffusion membrane and a method of making the same

Abstract

The application relates to the technical field of diffusion films, in particular to an ultrahigh-performance diffusion film and a preparation method thereof; the ultrahigh-performance diffusion film comprises a transparent base film and a functional coating layer arranged on at least one side of the transparent base film; the functional coating layer comprises a cured resin and bidirectional heterogeneous light scatterers generated in situ and dispersed in the cured resin; the bidirectional heterogeneous light scatterers comprise first scattering particles with a refractive index n1 and second scattering particles with a refractive index n2; through the design of the bidirectional heterogeneous light scatterers, the nanoscale first scattering particles mainly perform Rayleigh scattering on short-wavelength light, and the submicron second scattering particles are responsible for Mie scattering, so that the full-spectrum light is synergistically and accurately controlled, the scatterer part is orderly arranged in combination with external field-induced ordering, so that the ultrahigh haze is obtained, the ultrahigh light transmittance (>92%) is maintained, and the horizontal viewing angle uniformity (luminance half-peak width) is greatly improved to more than + / - 80 degrees.

Description

Technical Field

[0001] This invention relates to the field of diffusion membrane technology, and specifically to an ultra-high performance diffusion membrane and its preparation method. Background Technology

[0002] The diffuser film is a key optical component in the backlight module of a liquid crystal display. Its main function is to uniformly diffuse the light emitted from a point light source or a line light source to form a surface light source with uniform brightness, while minimizing light loss and maintaining high optical transmittance. As display technology develops towards higher brightness, higher contrast, wider viewing angles, and ultra-thinness, higher requirements are placed on the overall performance of the diffuser film.

[0003] Currently, the mainstream diffusion film technology usually involves coating a layer of resin containing light-scattering particles (such as silica, organic microspheres, etc.) onto a transparent base film (such as PET film). The scattering and homogenization of light are achieved through the difference in refractive index between the scattering particles and the resin matrix.

[0004] However, existing technologies generally suffer from the following problems: In order to improve haze (light uniformity), existing technologies usually require increasing the amount or particle size of scattering particles, but this often leads to a significant decrease in total light transmittance and overall light efficiency; and traditional randomly distributed scattering particles are difficult to precisely control the light, resulting in poor brightness uniformity of the diffusion film at different viewing angles, affecting display quality; when the content of scattering particles is high, the particles are very easy to agglomerate and settle in the resin, resulting in uneven coating and unstable optical performance; In view of this, we propose an ultra-high performance diffusion film and its preparation method. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings mentioned in the background section and provide an ultra-high performance diffusion film and its preparation method.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: An ultra-high performance diffusion film includes a transparent base film and a functional coating disposed on at least one side of the transparent base film. This structure is a classic and necessary component of diffusion films. The transparent base film provides mechanical support and basic light transmittance, while the functional coating carries the core optical control function. This layered structure is beneficial for industrial production (such as roll-to-roll coating) and facilitates the design of single-sided or double-sided coatings according to application requirements. The functional coating includes a cured resin and a bidirectional heterogeneous light scatterer generated in situ and dispersed within the cured resin. The "in situ generation" technology is the core of this invention to overcome the problem of particle agglomeration under high doping. The precursor is uniformly dissolved in the liquid resin and reacts to generate scattering particles during curing, which fundamentally avoids particle agglomeration and sedimentation caused by physical blending methods, ensuring that even at high content, the particles can achieve uniform dispersion at the nanoscale. The "bidirectional heterogeneous" design means that two scatterers with different characteristics are used at the same time, providing a material basis for precisely controlling light of different wavelengths and angles. The bidirectional heterogeneous light scatterer comprises a first scattering particle with a refractive index of n1 and a second scattering particle with a refractive index of n2, where |n1-n2|≥0.05. The number-average particle size of the first scattering particle is 20nm-50nm, and the number-average particle size of the second scattering particle is 200nm-500nm. Setting the refractive index difference (≥0.05) ensures sufficient optical contrast between the particles and the resin matrix, which is a prerequisite for effective light scattering. More importantly, the design of the bimodal particle size distribution has a synergistic effect: the nanoscale (20-50nm) first scattering particles mainly produce Rayleigh scattering of short-wavelength blue-violet light, and its scattering intensity is inversely proportional to the fourth power of the wavelength, which can efficiently homogenize short-wavelength light without causing excessive light loss; the submicron-scale (200-500nm) second scattering particles produce Mie scattering of the main bands of visible light, which can efficiently diffuse light over a wide angle and improve haze. The combination of the two achieves "band-specific management" of the full spectrum of light, thereby achieving high haze while minimizing transmittance loss. Furthermore, the mass ratio of the first scattering particle to the second scattering particle is 1:5 to 5:1. The bidirectional heterogeneous light scatterer in the functional coating accounts for 30%-80% of the cured resin by mass. Defining the ratio range of the two types of particles is crucial. Experiments of this invention show that within this ratio range, the two scattering modes can achieve the best balance and obtain the optimal comprehensive optical performance (transmittance, haze, viewing angle). If the ratio is unbalanced, for example, too many small particles may lead to a decrease in transmittance; too many large particles may increase haze but worsen the uniformity of the viewing angle. Setting the total content to 30%-80% ensures sufficient scattering centers to obtain high haze (>96%), while avoiding excessive light absorption and backscattering through in-situ generation technology and particle size optimization, thereby achieving ultra-high transmittance (>92%). This high content range is difficult to achieve stably by traditional physical blending methods.

[0007] Preferably, the cured resin is formed by mixing and curing a prepolymer, which serves as a solid solvent, with an active monomer. The prepolymer is selected from at least one of modified acrylate resin, polyurethane acrylate resin, and epoxy acrylate resin. The active monomer is selected from at least one of isobornyl acrylate (IBOA), tripropylene glycol diacrylate (TPGDA), and 1,6-hexanediol diacrylate (HDDA). The mass ratio of the prepolymer to the active monomer is 100:10 to 100:50. It should be noted that by selecting specific types and proportions of prepolymers and active monomers to form a "solid solvent" system, these resin materials not only have high light transmittance, good curing performance and adhesion, but more importantly, they have excellent solubility for the selected precursors (such as metal alkoxides and MMA monomers). This ensures that all precursors can be completely dissolved during the coating solution preparation stage to form a truly homogeneous and stable solution, rather than a suspension. This is a prerequisite for achieving in-situ uniform particle generation and excellent coating appearance. The active monomers also play a role in regulating the system viscosity, reaction rate and final coating hardness.

[0008] Preferably, the first scattering particle is at least one of nano-titanium dioxide, nano-zirconia, and nano-zinc oxide, and the second scattering particle is at least one of cross-linked polymethyl methacrylate (PMMA) microspheres, cross-linked polystyrene (PS) microspheres, and silica microspheres; It should be noted that these materials are commonly used and stable substances in the fields of optics and chemistry. Inorganic particles such as nano-titanium dioxide have high refractive index (~2.5) and high hardness, which can effectively provide Rayleigh scattering and enhance the wear resistance of the coating. The refractive index (~1.49-1.59) of cross-linked PMMA or PS organic microspheres is controllable with the resin matrix, and the particle size can be easily controlled by the degree of polymerization. They also have good flexibility, which is beneficial to maintaining the mechanical properties of the coating. The interfacial compatibility of the two in the resin can be naturally optimized through the in-situ generation process, reducing the internal stress caused by the difference in thermal expansion coefficients, thereby improving the stability of the coating under thermal cycling or high humidity environments.

[0009] Preferably, the bidirectional heterogeneous light scatterer is partially ordered or gradient distributed within the functional coating. This distribution pattern is formed by applying an external field before the coating liquid cures, such that the brightness half-width angle of the diffusion film in the horizontal direction is greater than or equal to ±80°.

[0010] It should be noted that this is the key innovation of the present invention in achieving ultra-wide viewing angle uniformity. Traditional randomly distributed scatterers result in equal probability of light scattering in all directions, with limited viewing angle uniformity. By inducing external fields (such as tilted light fields or temperature gradient fields), precursor molecules or initially formed nanoclusters can be guided to migrate or align in a directional manner, so that the final scatterer exhibits a spatially non-completely random, partially ordered, or concentration gradient distribution. This special structure can guide the light path more intelligently, making the energy distribution of the emitted light more uniform in the horizontal direction, thereby significantly increasing the brightness half-peak viewing angle from the conventional ±65° to ±80° or even wider, significantly improving the visual effect of viewing the display from the side.

[0011] Preferably, the transparent base film is a polyethylene terephthalate (PET) film, a polycarbonate (PC) film, or a cyclic olefin polymer (COP) film, with a thickness of 25 μm-250 μm; the thickness of the functional coating is 3 μm-30 μm.

[0012] It should be noted that PET, PC, and COP are the most commonly used and reliable substrates in the field of optical films, with advantages such as high light transmittance, heat resistance, and dimensional stability. Given the range of base film thickness (25-250μm) and functional coating thickness (3-30μm), flexibility is provided for product design. Thinner films (such as total thickness <100μm) are suitable for ultra-thin display devices; thicker coatings can accommodate more scatterers and are suitable for applications requiring extremely high haze. These ranges are determined based on a comprehensive consideration of ensuring mechanical strength, optical performance, and coating process stability.

[0013] A method for preparing an ultra-high performance diffusion film includes the following steps: S1. Preparation of coating solution: Mix the prepolymer, active monomer, first scatterer precursor, second scatterer precursor and photoinitiator as solid solvent, and stir at 40℃-60℃ for 2-4 hours to form a uniform and transparent coating solution. Gentle heating (40-60℃) and thorough stirring help the precursor to dissolve completely and promote the uniform mixing of each component at the molecular level to form a uniform and clear coating solution. This is the primary guarantee for obtaining a defect-free, high-performance coating. The long-term storage stability of the coating solution is also excellent. Wherein, the first scatterer precursor is a metal alkoxide that can be hydrolyzed to generate the first scattering particle, and the second scatterer precursor is a polymer monomer or prepolymer that can be polymerized to generate the second scattering particle. S2. Coating and Field Induction: The coating solution is coated onto the surface of a transparent base film to form a wet film. Subsequently, an external field treatment is applied to the wet film. The external field has a wavelength of 300nm-400nm and an intensity of 5mW / cm. 2 -50mW / cm 2The ultraviolet light field, or the thermal field with a temperature of 40℃-70℃, is used for processing for 10 seconds to 300 seconds; It should be noted that this step is the core of this method. "Coating" forms the initial film layer, while "field induction" is a key pretreatment step before curing begins. Using ultraviolet light of a specific wavelength and intensity or a thermal field of a specific temperature, the energy is sufficient to trigger the initial reaction or molecular orientation of the precursor, but not enough to trigger the complete curing of the resin system. This time window (10-300 seconds) allows the scattering precursor to align in an orderly manner under the drive of the external field (such as the direction of the light field or the direction of the temperature gradient), thereby "locking in" the prototype of the ordered structure and laying the foundation for the final formation of a partially ordered scattering distribution. S3. In-situ curing and molding: The wet film after step S2 is cured. During the curing process, the first scattering precursor and the second scattering precursor react in situ to generate the first scattering particle and the second scattering particle, respectively, thereby forming the functional coating and obtaining the ultra-high performance diffusion film. It should be noted that the final curing is carried out in the system that has already undergone field induction, so that the generation reaction of scattered particles takes place in the preset "template". In this way, the particles generated in situ can inherit and fix the ordered or gradient structure formed by induction. The whole process is completed in one step, which tightly combines the generation, dispersion and arrangement of particles with the curing of resin. The process is smooth and efficient, and avoids post-processing steps.

[0014] Preferably, in step S1, based on a total mass of 100 parts of the prepolymer and active monomer, the amount of the first scatterer precursor added is 5-30 parts, the amount of the second scatterer precursor added is 10-50 parts, and the amount of the photoinitiator added is 0.5-5 parts.

[0015] Preferably, in step S2, a microgravure coating method is used. The coating thickness of the wet film is controlled by the cell depth and coating speed of the microgravure roller. The cell depth is 5μm-35μm, and the coating speed is 5m / min-30m / min. Microgravure coating is a high-precision and high-efficiency coating method, which is particularly suitable for coating a thin and uniform liquid layer on flexible films. By precisely controlling the cell depth (5-35μm) and coating speed (5-30m / min), the thickness of the wet film can be stably and repeatably controlled, thereby ensuring the consistency of the optical performance of the final product. This is crucial for yield control in large-scale production.

[0016] Preferably, in step S3, the curing treatment is ultraviolet curing, and the curing energy is 300 mJ / cm². 2 -1500mJ / cm 2Alternatively, it can be thermosetting, with a curing temperature of 80℃-120℃ and a curing time of 1 minute-10 minutes. The specific range of UV curing energy or thermosetting temperature and time is given to ensure that the resin can be completely cured to form a tough coating, while ensuring that the reaction of the scattering precursor is fully completed. Insufficient curing will cause the coating to become sticky and its performance to decline; excessive curing may cause the base film to deform or the coating to become brittle.

[0017] Preferably, in step S2, the external field treatment is an ultraviolet light field, the irradiation direction of which is tilted at an angle of 15°-75° to the normal direction of the transparent base film; or the external field treatment is a thermal field, and the environment in which the wet film is located has a temperature gradient along the film surface direction, the temperature gradient being 1℃ / cm-5℃ / cm.

[0018] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention utilizes a "bidirectional heterogeneous light scatterer" design. The nanoscale first scattering particles primarily perform Rayleigh scattering for short-wavelength light, while the submicron-scale second scattering particles are responsible for Mie scattering. This achieves coordinated and precise control of the entire spectrum of light. Combined with "external field-induced ordering," the scatterers are partially arranged in an orderly manner, thereby achieving extremely high haze (>96%) while maintaining ultra-high transmittance (>92%), and significantly improving the horizontal viewing angle uniformity (brightness half-width) to over ±80°. 2. This invention uses the "solid solvent method", in which the precursor is completely dissolved in the resin system before curing, which fundamentally avoids the problems of agglomeration and sedimentation of scattered particles in the traditional physical blending method. Even at high content (up to 80%), the uniformity and stability of the coating liquid can be guaranteed, resulting in excellent coating quality.

[0019] 3. The preparation method of the present invention only requires one coating. By combining the continuous process of "coating-field induction-in-situ curing", the construction of complex optical structures can be realized, avoiding complex processes such as multi-layer coating and nanoimprinting. The production efficiency and yield are high, and the cost is controllable. Detailed Implementation

[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] The present invention will describe the above technical solution in detail through the following embodiments: Example 1

[0022] 1. Raw material preparation: Transparent base film: 125μm thick PET film (commercially available optical grade).

[0023] Prepolymer: Polyurethane acrylate (PUA), 100g.

[0024] Active monomer: IBOA (isobornyl acrylate), 20g.

[0025] First scatterer precursor: Tetraisopropyl titanate (TTIP), 15g.

[0026] Second scatterer precursor: Methyl methacrylate (MMA) monomer, 30g.

[0027] Photoinitiator: 2-hydroxy-2-methyl-1-phenyl-1-propanone (1173), 3g.

[0028] 2. Preparation process: S1. Preparation of coating solution: Add polyurethane acrylate, isobornyl acrylate, tetraisopropyl titanate, methyl methacrylate and 2-hydroxy-2-methyl-1-phenyl-1-propanone to a reaction vessel and stir magnetically for 3 hours in a water bath at 50°C to obtain a uniform and transparent coating solution.

[0029] S2. Coating and Field Induction: A microgravure coating machine (cell depth 15μm, coating speed 15m / min) was used to uniformly coat the coating solution onto the PET base film. Immediately afterwards, a beam of light was applied at a 45° angle to the film normal, with a wavelength of 365nm and an intensity of 20mW / cm. 2 The wet film was irradiated with an ultraviolet LED light source for 60 seconds to induce a field.

[0030] S3. In-situ curing: The field-induced wet film is placed in a UV curing chamber and cured under nitrogen protection at 1000 mJ / cm². 2 The energy is used for full irradiation curing. During the curing process, tetraisopropyl titanate hydrolyzes and condenses to generate nano-titanium dioxide (first scattering particles, with a particle size of about 30 nm), and methyl methacrylate undergoes free radical polymerization to generate cross-linked polymethyl methacrylate microspheres (second scattering particles, with a particle size of about 300 nm), thereby forming a functional coating with a thickness of about 10 μm on the PET film, which is the ultra-high performance diffusion film.

[0031] Example 2

[0032] The only difference between this embodiment and embodiment 1 is that the field induction conditions in step S2 are different. The tilted ultraviolet light field induction is replaced with the horizontal temperature gradient field induction. Specifically, after coating, the wet film is placed on a hot plate with a horizontal temperature gradient (3℃ / cm) and treated at 60℃ for 120 seconds, and then ultraviolet curing is performed in step S3. All other conditions are the same.

[0033] Example 3

[0034] The only difference between this embodiment and Embodiment 1 is that the proportion of the bidirectional heterogeneous light scatterer is changed in this embodiment, the amount of the first scatterer precursor TTIP is increased to 25g, and the amount of the second scatterer precursor MMA is reduced to 20g, while all other conditions remain the same.

[0035] Example 4

[0036] The only difference between this embodiment and Embodiment 1 is that the total thickness of the functional coating is different in this embodiment. By adjusting the depth of the microgravure roller to 25μm and adjusting the coating parameters accordingly, the final thickness of the functional coating is approximately 18μm. All other conditions are the same.

[0037] Comparative Example 1 This comparative example simulates traditional techniques. In this comparative example, 15g of commercially available nano-titanium dioxide powder (particle size 30nm) and 30g of commercially available cross-linked PMMA microspheres (particle size 300nm) were directly added to a mixed resin composed of 100g PUA and 20g IBOA. 3g of 1173 was added, and the mixture was first mechanically stirred at high speed for 1 hour, and then ultrasonically dispersed for 1 hour to obtain a milky white suspension coating liquid. This liquid was then directly coated on a PET base film (under the same conditions as in Example 1) and immediately cured under ultraviolet light (under the same conditions as in Example 1). The field induction step was omitted, and all other conditions were the same as in Example 1.

[0038] Comparative Example 2 This comparative example is used to verify the necessity of "external field induction". It uses the same raw materials and proportions as Example 1, but the ultraviolet light field induction treatment is omitted in step S2. After coating, it is directly cured in step S3. All other conditions are the same as in Example 1.

[0039] Comparative Example 3 This comparative example is used to verify the necessity of the "two-way heterogeneous" design. Only the second scatterer precursor is used, TTIP is not added to the raw materials, and the amount of MMA is increased to 45g so that the total scatterer precursor content is equivalent to that of Example 1. The preparation steps are the same as those of Example 1 (including field induction).

[0040] Comparative Example 4 This comparative example is used to verify the advantages of high doping levels. The amount of TTIP was reduced to 5g and the amount of MMA was reduced to 10g (the total scatterer precursor content was significantly reduced). The preparation steps were the same as in Example 1 (including field induction).

[0041] According to Examples 1-4 and Comparative Examples 1-4 above, diffusion film samples were prepared and their performance was tested. 1. Test items: Total light transmittance and haze Test standard: GB / T 2410-2008 "Determination of light transmittance and haze of transparent plastics".

[0042] Test procedure: Using a standard haze meter (such as the Murakami Color Technology Research Institute HM-150 model in Japan), cut the sample to the specified size (such as 50mm×50mm) and attach it tightly to the test window. The instrument will measure the light flux (T1) and scattered light flux (T2) transmitted through the sample, and automatically calculate and output the total light transmittance (Tt) and haze (H).

[0043] Significance of the test: Light transmittance reflects light efficiency, while haze reflects light uniformity; both must be evaluated simultaneously.

[0044] 2. Test item: Horizontal viewing angle uniformity (half-peak width at half-peak viewing angle) Testing standards: Refer to industry-standard methods.

[0045] Test process: Set up the test platform: Place the sample in close contact with the light-emitting surface of a standard uniform surface light source (LED backlight module).

[0046] Use a luminance meter (such as Konica Minolta CS-2000) to measure and record the luminance L0 at the center point at a fixed distance (0°) in the sample normal direction.

[0047] Keeping the distance between the luminance meter and the sample constant, rotate the sample or the luminance meter horizontally and measure the luminance L(θ) at different horizontal viewing angles (θ).

[0048] Plot the curve of brightness L(θ) as a function of viewing angle θ, and find the two viewing angles θ1 and θ2 on the left and right when the brightness value drops to half of L0.

[0049] The half-peak width of brightness is expressed as ±|θ|, where |θ| is the average of the absolute values ​​of θ1 and θ2.

[0050] Test significance: Directly quantifies the brightness uniformity of display devices at different horizontal viewing angles; the larger the value, the better the viewing angle performance.

[0051] 3. Test Items: High Temperature and High Humidity Reliability Test Testing standards: Refer to environmental testing standards such as IEC 60068-2-78.

[0052] Test process: The initial haze value of the sample is denoted as H0.

[0053] The sample was placed in a constant temperature and humidity test chamber, with the conditions set as 85°C and 85% relative humidity.

[0054] After 500 hours of continuous testing, the sample was removed and allowed to recover for 24 hours under standard temperature and humidity conditions (23±2°C, 50±10% RH).

[0055] The haze value of the sample was measured again and recorded as H1.

[0056] Calculate the haze retention rate: Retention rate (%) = (H1 / H0) × 100%.

[0057] Significance of the test: To evaluate the performance stability of the diffusion membrane under harsh environments; a higher retention rate indicates a more reliable product.

[0058] The specific data are shown in Tables 1 and 2 below: Table 1 Table 2 As can be seen from the data in Tables 1 and 2 above, Comparative Example 1, which uses a conventional process of directly mixing and dispersing ready-made nano-titanium dioxide and PMMA microspheres, has significantly outperformed the conventional method in all aspects of testing: the transmittance (90.5%) and haze (94.0%) are the lowest, and the viewing angle (±65°) is narrow. In particular, the haze retention rate (85.3%) drops sharply after high temperature and high humidity testing. This directly exposes the inherent defects of the traditional method under high doping levels: particle aggregation and weak interfacial bonding. Aggregation leads to reduced light scattering efficiency and increased loss (affecting transmittance and haze), while poor interfacial bonding leads to rapid performance degradation in humid and hot environments.

[0059] In contrast, Example 1, which employs the "solid solvent method" and "in-situ generation" technology, achieved a leap in all performance indicators, especially in stability (98.5% retention rate), which is close to perfect. This directly proves the first core advantage of the present invention: through precursor molecular-level dissolution and in-situ reaction, particle agglomeration is fundamentally eliminated, and a strong chemical / physical bond is formed between the scatterer and the resin matrix. Thus, while achieving high haze (96.5%) and high transmittance (92.8%), unprecedented environmental stability is obtained.

[0060] Comparative Example 2 used the exact same raw materials and in-situ generation technology as Example 1, only omitting the tilted ultraviolet light field induction step. Although its results were better than those of Comparative Example 1, which was physically blended (proving that in-situ generation itself is beneficial), its horizontal viewing angle (±68°) was comparable to that of conventional products, and it failed to achieve a breakthrough.

[0061] In Example 1, after being induced by a 45° ultraviolet light field, the viewing angle was significantly widened to ±85°. This significant difference (the viewing angle increased by about 25%) irrefutably proves that "external field induction" is the decisive step in achieving ultra-wide viewing angle uniformity. It is not an optional optimization, but the key to guiding the scatterer to form a special microstructure of "partially ordered or gradient distribution" and thus intelligently controlling the optical path.

[0062] Comparative Example 3 uses only submicron-sized MMA to prepare a single-size scatterer. Even with the field-induced process, its haze (92.5%) and viewing angle (±70°) are still much lower than those of Example 1. This shows that a single-size scatterer cannot simultaneously and efficiently control the full spectrum of light.

[0063] In Example 1, nanoscale TiO2 and submicron-scale PMMA microspheres constitute a "bidirectional heterogeneous light scatterer," which works synergistically through Rayleigh scattering and Mie scattering mechanisms, respectively. Test data shows that this design produces a synergistic effect of "1+1>2," increasing haze to 96.5% and expanding the viewing angle to ±85° with minimal transmittance loss, achieving an unexpected effect of "wavelength band management" of light.

[0064] Although Comparative Example 4 had a slightly higher transmittance (93.5%), its haze (88.0%) was severely insufficient, and its viewing angle (±60°) was also the worst. This indicates that the low scatterer content cannot provide sufficient light uniformity, and the product cannot meet the requirements of high-performance displays.

[0065] In contrast, Example 1 increases the total content of scatterers to an effective range (approximately 45% in this example) and solves the resulting process challenges through the unique method of this invention, thereby achieving comprehensive optimization of overall performance. Furthermore, the variations in Examples 2, 3, and 4 (changing the induction method, adjusting the ratio, and increasing the thickness) all yielded excellent performance data with different focuses (transmittance 91.5%-93.0%, haze 95.8%-97.8%, viewing angle ±82°-±88°). This fully demonstrates that the technical solution of this invention is not a narrow "point solution," but a "platform technology" with good process tolerance and design flexibility. Technicians can make adjustments within the scope of the principles and parameters provided by this invention to meet the specific needs of different application scenarios, which further reflects its industrial practical value.

[0066] Based on the data in the table above, Example 1 is preferred.

[0067] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A high-performance diffusion film, characterized in that: It includes a transparent base film and a functional coating disposed on at least one side of the transparent base film; the functional coating includes a cured resin and a bidirectional heterogeneous light scatterer generated in situ and dispersed within the cured resin; The bidirectional heterogeneous light scatterer includes a first scattering particle with a refractive index of n1 and a second scattering particle with a refractive index of n2, wherein |n1-n2|≥0.05, the number-average particle size of the first scattering particle is 20nm-50nm, the number-average particle size of the second scattering particle is 200nm-500nm, and the mass ratio of the first scattering particle to the second scattering particle is 1:5 to 5:

1. The bidirectional heterogeneous light scatterer in the functional coating accounts for 30%-80% of the cured resin by mass.

2. The ultra-high performance diffusion film as described in claim 1, characterized in that: The cured resin is formed by mixing and curing a prepolymer, which serves as a solid solvent, with an active monomer. The prepolymer is selected from at least one of modified acrylate resin, polyurethane acrylate resin, and epoxy acrylate resin. The active monomer is selected from at least one of isobornyl acrylate, tripropylene glycol diacrylate, and 1,6-hexanediol diacrylate. The mass ratio of the prepolymer to the active monomer is 100:10 to 100:

50.

3. The ultra-high performance diffusion film as described in claim 2, characterized in that: The first scattering particle is at least one of nano-titanium dioxide, nano-zirconia, and nano-zinc oxide, and the second scattering particle is at least one of cross-linked polymethyl methacrylate microspheres, cross-linked polystyrene microspheres, and silica microspheres.

4. The ultra-high performance diffusion film as described in claim 1, characterized in that: The bidirectional heterogeneous light scatterer is partially ordered or gradient distributed within the functional coating. This distribution pattern is formed by applying an external field before the coating liquid cures, so that the brightness half-peak width angle of the diffusion film in the horizontal direction is greater than or equal to ±80°.

5. The ultra-high performance diffusion film as described in claim 1, characterized in that: The transparent base film is a polyethylene terephthalate film, a polycarbonate film, or a cyclic olefin polymer film, with a thickness of 25μm-250μm; the thickness of the functional coating is 3μm-30μm.

6. A method for preparing an ultra-high performance diffusion film as described in any one of claims 1-5, characterized in that, Includes the following steps: S1. Preparation of coating solution: Mix the prepolymer, active monomer, first scatterer precursor, second scatterer precursor and photoinitiator as solid solvent, and stir at 40℃-60℃ for 2-4 hours to form a uniform and transparent coating solution. Wherein, the first scatterer precursor is a metal alkoxide that can be hydrolyzed to generate the first scattering particle, and the second scatterer precursor is a polymer monomer or prepolymer that can be polymerized to generate the second scattering particle. S2. Coating and Field Induction: The coating solution is coated onto the surface of a transparent base film to form a wet film. Subsequently, an external field treatment is applied to the wet film. The external field has a wavelength of 300nm-400nm and an intensity of 5mW / cm. 2 -50mW / cm 2 The ultraviolet light field, or the thermal field with a temperature of 40℃-70℃, is used for processing for 10 seconds to 300 seconds; S3. In-situ curing and molding: The wet film after step S2 is cured. During the curing process, the first scattering precursor and the second scattering precursor react in situ to generate the first scattering particle and the second scattering particle, respectively, thereby forming the functional coating and obtaining the ultra-high performance diffusion film.

7. The method for preparing the ultra-high performance diffusion film as described in claim 6, characterized in that: In step S1, based on a total mass of 100 parts for the prepolymer and the active monomer, the amount of the first scatterer precursor added is 5-30 parts, the amount of the second scatterer precursor added is 10-50 parts, and the amount of the photoinitiator added is 0.5-5 parts.

8. The method for preparing the ultra-high performance diffusion film as described in claim 6, characterized in that: In step S2, a microgravure coating method is used. The coating thickness of the wet film is controlled by the cell depth and coating speed of the microgravure roller. The cell depth is 5μm-35μm and the coating speed is 5m / min-30m / min.

9. The method for preparing the ultra-high performance diffusion film as described in claim 6, characterized in that: In step S3, the curing process is ultraviolet curing with a curing energy of 300 mJ / cm². 2 -1500mJ / cm 2 Alternatively, it can be thermosetting, with a curing temperature of 80℃-120℃ and a curing time of 1 minute-10 minutes.

10. The method for preparing the ultra-high performance diffusion film as described in claim 6, characterized in that: In step S2, the external field treatment is an ultraviolet light field, the irradiation direction of which is tilted at an angle of 15°-75° to the normal direction of the transparent base film; or the external field treatment is a thermal field, and the environment in which the wet film is located has a temperature gradient along the film surface direction, the temperature gradient being 1℃ / cm-5℃ / cm.

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