Preparation method of light diffusion film based on nanoscale polymer microspheres
By using SMA oligomers as emulsifiers and a soap-free emulsion polymerization process, nanoscale polymer microsphere light diffusion films were prepared, solving the problems of poor compatibility between inorganic particles and resins and emulsifier residues. This improved the stability and optical performance of the light diffusion films, resulting in environmental and economic benefits.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HARBIN INST OF TECH
- Filing Date
- 2026-03-18
- Publication Date
- 2026-04-21
AI Technical Summary
Existing light diffusion film preparation processes suffer from problems such as poor compatibility between inorganic particles and resin matrix, agglomeration, large size of organic polymer microspheres leading to rough light scattering, uneven local brightness, and excessive haze. Furthermore, residual emulsifiers in traditional emulsion polymerization processes affect optical performance.
Styrene-maleic anhydride (SMA) oligomers were used as emulsifiers, combined with soap-free emulsion polymerization, to prepare nanoscale polymer microspheres and resins, forming stable microsphere morphologies. These microspheres were then coated onto a base film in an aqueous system, avoiding the residue of small molecule emulsifiers.
This technology improves the structural stability and optical performance of light diffusion films, achieving a balance between light transmittance and haze, while reducing the use of organic solvents, thus offering environmental and economic benefits.
Smart Images
Figure CN121899962A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of light diffusion film technology, specifically relating to a method for preparing a light diffusion film using nanoscale polymer microspheres as diffusion particles. Background Technology
[0002] Light diffusion films are typically placed between the light source and the display panel. Their function is to transform point or line light sources into uniform surface light sources, thereby improving the brightness uniformity of the display or lighting system. They play an indispensable role in the display and lighting industries, including LCD TVs, laptop screens, lightbox billboards, and decorative lighting. The most important components of a light diffusion film are diffusion particles and resin. Its working principle is that when light passes through diffusion particles and resin with different refractive indices, it undergoes multiple scattering and refractions, thus scattering the point or line light source into a surface light source.
[0003] There are two main processes for preparing light diffusion films: dry extrusion and wet coating. Dry extrusion involves mixing diffusion particles with resin, melting the mixture, and then extruding it. After post-treatment, a light diffusion film is formed. This method has high production efficiency, but requires high extrusion temperatures, and the system has high viscosity in the molten state, resulting in weak molecular diffusion and a tendency for localized particle agglomeration. Therefore, wet coating is more commonly used in industrial production. Specifically, it involves preparing a solution of diffusion particles and resin, which is then coated onto a base film.
[0004] However, current wet coating processes require the use of large amounts of organic solvents, which can pollute the environment. Moreover, the diffusion particles are usually inorganic particles and organic polymer microspheres, such as silica, titanium dioxide, alumina, polymethyl methacrylate (PMMA), and polystyrene (PS). Among these, some inorganic particles have poor compatibility with the resin matrix, and are prone to agglomeration or sedimentation during the film formation process. Organic polymer microspheres are usually micron-sized, and their light scattering method is relatively rough, which can easily cause uneven local brightness or excessive haze, thus affecting the display clarity.
[0005] Emulsion polymerization is a polymerization process in which monomers polymerize into molecular chains within micelles formed by surfactants, i.e., emulsifiers. It typically uses water as the dispersion medium, making it environmentally friendly, and the polymer naturally forms nanoscale microspheres in water. However, the emulsifiers used in conventional emulsion polymerization processes act as plasticizers during the drying and dehydration process, causing latex particles to break down due to compression during drying and lose their microspherical morphology. On the other hand, although acrylate resins are commonly used in light-diffusing films, the emulsifiers used in the preparation of traditional acrylate emulsions are difficult to remove, and their residues in the coating, particularly small-molecule surfactants, can significantly affect its optical properties. In summary, traditional small-molecule emulsifiers simultaneously limit the application of emulsion products in both diffusion particles and resins. Summary of the Invention
[0006] To address the aforementioned problems, this invention provides a method for preparing a light diffusion film based on nanoscale polymer microspheres.
[0007] A method for preparing a light diffusion film based on nanoscale polymer microspheres is specifically carried out according to the following steps:
[0008] I. Preparation of polymer microspheres:
[0009] ① Mix the emulsifier with water, then adjust the pH of the solution to between 7 and 9, then heat and stir, and cool to room temperature to obtain the SMA solution;
[0010] ② Add initiator and monomer to SMA solution, stir and heat to 71℃~76℃, react for a period of time, raise the temperature to 81℃~86℃, keep warm, cool to room temperature to obtain polymer microspheres.
[0011] II. Resin Preparation:
[0012] ① Mix the monomer with water, then add the initiator and stir until the mixture is homogeneous to obtain a soap-free polymethyl methacrylate emulsion;
[0013] ② Stir the soap-free polymethyl methacrylate emulsion evenly, then heat it to 71℃~76℃. After reacting for a period of time, raise the temperature to 81℃~86℃, then keep it at the temperature and cool it to room temperature to obtain the resin.
[0014] 3. Mix the polymer microspheres with the resin evenly, then coat them onto the base film and dry to obtain a light diffusion film based on nanoscale polymer microspheres.
[0015] Compared with the prior art, the present invention has the following advantages:
[0016] I. This invention addresses the problem that latex particles in traditional emulsions are prone to melting and collapsing during the drying and film-forming process, making it difficult to maintain the microsphere morphology. It uses styrene-maleic anhydride (SMA) oligomers as emulsifiers. Compared with traditional small molecule emulsifiers, SMA oligomers can be stably adsorbed on the surface of polymer particles, forming a stable interface structure with a certain rigidity on the outer layer of the particles. This effectively inhibits the mutual diffusion and fusion between polymer molecular chains during the emulsion drying process, allowing the latex particles to maintain a relatively independent microsphere morphology after film formation.
[0017] II. To improve the compatibility between the diffusion particles (polymer microspheres) and the resin matrix, this invention selects an emulsion, which is also an aqueous system, as the film-forming resin, and further employs a soap-free emulsion polymerization process to prepare the resin, thereby avoiding the adverse effects of small molecule emulsifier residues on the optical performance of the light diffusion film. The light diffusion film thus obtained has the advantages of structural stability and a balance between light transmittance and haze. In addition, this invention uses an aqueous system as the coating liquid to prepare the light diffusion film. Unlike existing inventions, the aqueous system is inexpensive, environmentally friendly, economical, and effectively reduces the emission of organic gases. Attached Figure Description
[0018] Figure 1 The image shows the microstructure of the light diffusion film based on nanoscale polymer microspheres prepared in Example 1.
[0019] Figure 2 The image shows the microstructure of the light diffusion film prepared for Comparative Example 1. Detailed Implementation
[0020] The technical solution of the present invention will be further described below with reference to the embodiments, but it is not limited thereto. Any modifications or equivalent substitutions to the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention should be covered within the protection scope of the present invention.
[0021] Specific Implementation Method 1: This implementation method is a method for preparing a light diffusion film based on nanoscale polymer microspheres, specifically completed according to the following steps:
[0022] I. Preparation of polymer microspheres:
[0023] ① Mix the emulsifier with water, then adjust the pH of the solution to between 7 and 9, then heat and stir, and cool to room temperature to obtain the SMA solution;
[0024] ② Add initiator and monomer to SMA solution, stir and heat to 71℃~76℃, react for a period of time, raise the temperature to 81℃~86℃, keep warm, cool to room temperature to obtain polymer microspheres.
[0025] II. Resin Preparation:
[0026] ① Mix the monomer with water, then add the initiator and stir until the mixture is homogeneous to obtain a soap-free polymethyl methacrylate emulsion;
[0027] ② Stir the soap-free polymethyl methacrylate emulsion evenly, then heat it to 71℃~76℃, react for a period of time, then raise the temperature to 81℃~86℃, keep it at the temperature, and cool it to room temperature to obtain the resin.
[0028] 3. Mix the polymer microspheres with the resin evenly, then coat them onto the base film and dry to obtain a light diffusion film based on nanoscale polymer microspheres.
[0029] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that: in step one ①, the emulsifier is mixed with water, and then 25% ammonia water is added to adjust the pH of the solution to between 7 and 9; the emulsifier mentioned in step one ① is a styrene-maleic anhydride (SMA) oligomer, i.e., an alternating copolymer of styrene and maleic anhydride, with a molecular weight of 1000-3000. The other steps are the same as in Specific Implementation Method One.
[0030] Specific Implementation Method 3: This implementation method differs from Specific Implementation Method 1 or 2 in that the mass of the emulsifier mentioned in step 1① is 6.0% to 8.5% of the mass of water. The other steps are the same as in Specific Implementation Method 1 or 2.
[0031] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that: the initiator mentioned in step one ② is potassium persulfate; the monomer mentioned in step one ② is styrene or methyl methacrylate. The other steps are the same as in Specific Implementation Methods One to Three.
[0032] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that: the mass of the initiator mentioned in step one ② is 0.5% to 2.0% of the monomer mass; the reaction time mentioned in step one ② is 3 to 5 hours; and the heat preservation time is 1 to 2 hours. Other steps are the same as in Specific Implementation Methods One to Four.
[0033] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that: the total mass of the initiator and monomer mentioned in step one (②) is 30% to 40% of the mass of the SMA solution; the average particle size of the polymer microspheres mentioned in step one (②) is 90 nm to 140 nm. Other steps are the same as in Specific Implementation Methods One to Five.
[0034] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One to Six in that: the monomer mentioned in step two① is methyl methacrylate; the initiator mentioned in step two① is potassium persulfate. The other steps are the same as in Specific Implementation Methods One to Six.
[0035] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One to Seven in that: the mass of the initiator mentioned in step two ① is 0.5% to 2.0% of the monomer mass; the mass of the monomer in step two ① is 10% to 20% of the water mass. The other steps are the same as in Specific Implementation Methods One to Seven.
[0036] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in that: the reaction time in step two (②) is 6-8 hours; the heat preservation time is 1-2 hours; the base film in step three is a PET film; and the PET film is a PET film after corona treatment. Other steps are the same as in Specific Implementation Methods One to Eight.
[0037] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Methods One to Nine in that: the mass of the polymer microspheres in step three is 5% to 10% of the resin mass; the drying temperature in step three is 100°C; and the coating thickness in step three is 12 to 20 micrometers. Other steps are the same as in Specific Implementation Methods One to Nine.
[0038] The beneficial effects of the present invention are verified using the following embodiments:
[0039] Example 1: A method for preparing a light diffusion film based on nanoscale polymer microspheres, specifically completed according to the following steps:
[0040] I. Preparation of polymer microspheres:
[0041] ① Mix the emulsifier with water, then add 25% ammonia water to make the pH of the solution 7, then heat and stir until the emulsifier is completely dissolved, cool to room temperature to obtain SMA solution;
[0042] The emulsifier mentioned in step 1① is styrene-maleic anhydride (SMA) oligomer, which is an alternating copolymer of styrene and maleic anhydride with a molecular weight of 1000.
[0043] The mass of the emulsifier mentioned in step 1① is 8.5% of the mass of water;
[0044] ② Add initiator and monomer to SMA solution, stir and heat to 71°C, react for 4 hours, raise temperature to 86°C, keep warm for 2 hours, cool to room temperature to obtain polymer microspheres.
[0045] The initiator mentioned in step 1② is potassium persulfate;
[0046] The monomer mentioned in step 1② is methyl methacrylate;
[0047] The mass of the initiator mentioned in step 1② is 1% of the monomer mass;
[0048] The total mass of the initiator and monomer mentioned in step 1② is 35% of the mass of the SMA solution;
[0049] The average particle size of the polymer microspheres mentioned in step 1② is 90nm~140nm;
[0050] II. Resin Preparation:
[0051] ① Mix the monomer with water, then add the initiator and stir until the mixture is homogeneous to obtain a soap-free polymethyl methacrylate emulsion;
[0052] The monomer mentioned in step 2① is methyl methacrylate;
[0053] The initiator mentioned in step 2① is potassium persulfate;
[0054] The mass of the initiator mentioned in step 2① is 1% of the monomer mass;
[0055] In step two①, the mass of the monomer is 10% of the mass of water;
[0056] ② Stir the soap-free polymethyl methacrylate emulsion evenly, then heat it to 71°C and react for 8 hours. Then raise the temperature to 86°C and keep it at that temperature for 2 hours. Cool it to room temperature to obtain the resin.
[0057] 3. Mix the polymer microspheres with the resin evenly, then coat them onto the base film using a 12-micron coating rod, and then place the coated base film in an oven at 100°C until it is completely dry to obtain a light diffusion film based on nanoscale polymer microspheres.
[0058] The base film mentioned in step three is a corona-treated PET film with a thickness of 50 micrometers;
[0059] The mass of the polymer microspheres mentioned in step three is 10% of the mass of the resin.
[0060] Example 2: The difference between this example and Example 1 is that the mass of the polymer microspheres in step three is 5% of the resin mass. All other steps and parameters are the same as in Example 1.
[0061] Example 3: The difference between this example and Example 1 is that the monomer mentioned in step 1, ② is styrene. All other steps and parameters are the same as in Example 1.
[0062] Comparative Example 1: The difference between this example and Example 1 is that the emulsifier mentioned in step 1① is sodium dodecyl sulfonate. All other steps and parameters are the same as in Example 1.
[0063] The test results of the light diffusion films obtained in Examples 1-3 and Comparative Example 1 are shown in Table 1:
[0064] Table 1
[0065]
[0066] In Examples 1 and 2 of this invention, PMMA emulsions prepared using styrene-maleic anhydride (SMA) as emulsifiers were used to prepare diffusion particles (polymer microspheres). Soap-free PMMA emulsions were used as the resin. Both the particles and the resin are aqueous emulsions with similar molecular structures, resulting in excellent compatibility. To ensure good spreadability of the aqueous emulsion on a PET film, a corona-treated PET film was used. In Comparative Example 1, the coating liquid on the untreated PET film could not spread and shrank into small droplets, thus failing to form a uniform film structure. However, the coating liquid on the corona-treated PET film spread into a film shape and maintained high haze and transmittance. In contrast, when using emulsions with traditional emulsifiers as light diffusion films for diffusion particles, the molecular chains diffuse and fuse during drying, causing particle boundaries to disappear and forming a continuous phase with almost no effective scattering centers. Therefore, although higher transmittance is achieved, it has no effect on improving haze.
[0067] Figure 1 The image shows the microstructure of the light diffusion film based on nanoscale polymer microspheres prepared in Example 1.
[0068] Figure 2 The image shows the microstructure of the light diffusion film prepared in Comparative Example 1.
[0069] Characterization of the microstructure reveals that the latex microsphere morphology in the light diffusion film based on nanoscale polymer microspheres prepared in this invention is preserved, and the surface is coated with a continuous phase. This is because the emulsifier used in this invention is SMA, which has a certain molecular rigidity and can prevent the molecular chains from diffusing and fusing during the drying process. In contrast, the emulsifier on the surface of the latex particles in the film emulsion of Comparative Example 1 fused with each other during the drying process, and the molecular chains diffused to form a continuous phase, destroying the microsphere morphology and failing to achieve the light diffusion effect.
Claims
1. A method for preparing a light diffusion film based on nanoscale polymer microspheres, characterized in that... The preparation method is specifically carried out according to the following steps: I. Preparation of polymer microspheres: ① Mix the emulsifier with water, then adjust the pH of the solution to between 7 and 9, then heat and stir, and cool to room temperature to obtain the SMA solution; ② Add initiator and monomer to SMA solution, stir and heat to 71℃~76℃, react for a period of time, raise the temperature to 81℃~86℃, keep warm, cool to room temperature to obtain polymer microspheres. II. Resin Preparation: ① Mix the monomer with water, then add the initiator and stir until the mixture is homogeneous to obtain a soap-free polymethyl methacrylate emulsion; ② Stir the soap-free polymethyl methacrylate emulsion evenly, then heat it to 71℃~76℃, react for a period of time, then raise the temperature to 81℃~86℃, keep it at the temperature, and cool it to room temperature to obtain the resin.
3. Mix the polymer microspheres with the resin evenly, then coat them onto the base film and dry to obtain a light diffusion film based on nanoscale polymer microspheres.
2. The method for preparing a light diffusion film based on nanoscale polymer microspheres according to claim 1, characterized in that... In step 1①, the emulsifier is mixed with water, and then 25% ammonia is added to adjust the pH of the solution to be between 7 and 9. The emulsifier mentioned in step 1① is an alternating copolymer of styrene and maleic anhydride with a molecular weight of 1000-3000.
3. The method for preparing a light diffusion film based on nanoscale polymer microspheres according to claim 1, characterized in that... The mass of the emulsifier mentioned in step 1① is 6.0% to 8.5% of the mass of water.
4. The method for preparing a light diffusion film based on nanoscale polymer microspheres according to claim 1, characterized in that... The initiator mentioned in step 1② is potassium persulfate; the monomer mentioned in step 1② is styrene or methyl methacrylate.
5. The method for preparing a light diffusion film based on nanoscale polymer microspheres according to claim 1, characterized in that... The initiator mentioned in step 1② has a mass of 0.5% to 2.0% of the monomer mass; the reaction time mentioned in step 1② is 3 to 5 hours; and the heat preservation time is 1 to 2 hours.
6. The method for preparing a light diffusion film based on nanoscale polymer microspheres according to claim 1, characterized in that... The total mass of the initiator and monomer mentioned in step 1② is 30%~40% of the mass of the SMA solution; the average particle size of the polymer microspheres mentioned in step 1② is 90nm~140nm.
7. The method for preparing a light diffusion film based on nanoscale polymer microspheres according to claim 1, characterized in that... The monomer mentioned in step 2① is methyl methacrylate; the initiator mentioned in step 2① is potassium persulfate.
8. The method for preparing a light diffusion film based on nanoscale polymer microspheres according to claim 1, characterized in that... The mass of the initiator mentioned in step 2① is 0.5% to 2.0% of the monomer mass; the mass of the monomer in step 2① is 10% to 20% of the water mass.
9. The method for preparing a light diffusion film based on nanoscale polymer microspheres according to claim 1, characterized in that... The reaction time in step 2② is 6h~8h; the heat preservation time is 1h~2h; the base film in step 3 is a PET film; the PET film is a PET film after corona treatment.
10. The method for preparing a light diffusion film based on nanoscale polymer microspheres according to claim 1, characterized in that... The polymer microspheres mentioned in step three have a mass of 5% to 10% of the resin mass; the drying temperature mentioned in step three is 100°C; and the coating thickness mentioned in step three is 12 micrometers to 20 micrometers.