Dodging diffusion film, preparation method and application

Abstract

The invention discloses a uniform light diffusion film, and a preparation method and application thereof. The preparation method comprises the following steps: firstly, preparing monodisperse polymer / silicon dioxide hybrid particles from an acrylate monomer, a silane coupling agent and an initiator through a dispersion polymerization method; polymer / silicon dioxide hybrid particles with vinyl are obtained through double-bond modification of tetraethoxysilane and a silane coupling agent through a sol-gel method and serve as hybrid particles and diffusion particles, the hybrid particles and the diffusion particles are proportionally added into polyester resin, the uniform light diffusion film is obtained through melt extrusion and double drawing, and the uniform light diffusion film with the high fog effect, the excellent uniform light performance and the good light diffusion effect is obtained. The haze is greater than 90%, and the light transmittance can be kept above 40%; meanwhile, a double-bond structure can be combined with polyester resin through chemical bonds, so that the organic / inorganic phase compatibility is improved, and the film-forming mechanical property is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of optical films, and particularly relates to a light-uniformizing diffusion film, a preparation method and application. BACKGROUND

[0002] Driven by liquid crystal display, LED lighting, vehicle-mounted display, emerging application fields and the trend of domestic substitution, the performance requirements of optical films are increasingly stringent. Conventional diffusion films have been difficult to meet the relevant needs. In order to further uniformly distribute light, reduce brightness unevenness and glare, improve diffusion uniformity, ensure uniform distribution of light in space, and avoid local over-brightness or over-darkness; in addition, while maintaining high light transmittance, the haze is optimized to make the light soft and uniform, and the best balance between light transmittance and haze is achieved. Light-uniformizing films emerge as the times require.

[0003] Current light-uniformizing film structure design is complex. For example, the invention disclosed in the publication No. CN119126431A discloses a light-uniformizing film, a backlight module, a display device and a preparation method of the light-uniformizing film, which specifically comprises: a substrate layer, a first haze layer, a second haze layer, and a double haze structure stacked on the first haze layer and the second haze layer, so that the light-uniformizing film has multiple haze. The double haze structure has a complex microstructure design, which is difficult to process with a mold, has a long processing time and a low success rate, and seriously affects the roll-to-roll production efficiency and cost of the light-uniformizing film product. The invention disclosed in the publication No. CN117805950A discloses an optical polyester film, which is an internal additive light-uniformizing film. The optical polyester film adopts a three-layer structure, combines reflective particles, diffusion particles and silicone particles, solves the problems of insufficient brightness, stereoscopic effect and weather resistance of existing projection films, and realizes high brightness, high haze, excellent scratch resistance and weather resistance; however, the addition of multiple types of particles in a large amount may cause problems such as poor compatibility of organic / inorganic phases, uneven dispersion of particles and poor film mechanical properties during melt extrusion and stretching.

[0004] In view of this, the present application is proposed. SUMMARY

[0005] The application discloses a light-uniformizing diffusion film, a preparation method and application. The light-uniformizing diffusion film is an internal additive optical film, which is obtained through melt extrusion and bidirectional stretching. The preparation process is simple and operable. In addition, the addition of double-bond modified monodisperse polymer / silica hybrid particles enables the film to have high haze effect and excellent light-uniformizing performance. The double-bond structure can be combined with polyester resin by chemical bonds to improve the compatibility of organic / inorganic phases and improve the film mechanical properties.

[0006] The application is implemented by the following technical solutions: In one aspect, a light-uniform diffusion film includes a diffusion layer and a light-uniform layer; the thickness of the light-uniform diffusion film is 100-500 μm, the single-layer thickness of the diffusion layer is 5-50 μm, the thickness ratio of the diffusion layer is 10-20%, and the thickness ratio of the light-uniform layer is 80-90%.

[0007] Further, the light-uniform diffusion film has a light transmittance value R≥40% and a haze≥90%.

[0008] The diffusion layer includes a first polyester resin, first diffusion particles, and hybrid particles. The first polyester resin accounts for 92-99% by mass, the first diffusion particles account for 0.5-7.0% by mass, and the hybrid particles account for 0.5-6.5% by mass.

[0009] The first diffusion particles include at least one of polymethyl methacrylate, silicon dioxide, calcium carbonate, titanium dioxide, and barium sulfate. The average particle size of the first diffusion particles is distributed in a range of 3 μm-20 μm. In some embodiments of the present application, the first diffusion particles are polymethyl methacrylate with a particle size of 3 μm and 20 μm.

[0010] The first polyester resin includes at least one of polyethylene terephthalate (PET) and polybutylene terephthalate.

[0011] The light-uniform layer includes a second polyester resin, second diffusion particles, hybrid particles, and an incompatible resin. The second polyester resin accounts for 94.5-98% by mass, the second diffusion particles account for 1.5-3.0% by mass, the hybrid particles account for 0.4-3.9% by mass, and the incompatible resin accounts for 0.1-2.0% by mass.

[0012] The second diffusion particles include at least one of polymethyl methacrylate, silicon dioxide, calcium carbonate, titanium dioxide, and barium sulfate. Preferably, the second diffusion particles are polymethyl methacrylate microspheres or silicon dioxide microspheres.

[0013] The average particle size of the second diffusion particles is distributed in a range of 2 μm-5 μm. The second polyester resin includes at least one of polyethylene terephthalate and polybutylene terephthalate.

[0014] The incompatible resin is a polyolefin resin, including at least one of polypropylene, polymethyl pentene, and cyclic polyolefin (COC / COP).

[0015] The hybrid particles are double bond modified polymer / silica hybrid microparticles, specifically, monodisperse polymer / silica hybrid microparticles are prepared by dispersion polymerization method, and then modified by double bond to obtain, and the particle size is 2.5 ~ 7.5 µm.

[0016] The monodisperse polymer / silica hybrid microparticles can be obtained by dispersion polymerization method: under the action of dispersion stabilizer, acrylic ester monomer, silane coupling agent and initiator are polymerized under certain conditions to obtain.

[0017] Specifically, under the nitrogen atmosphere, the stabilizer and solvent are added to the four-necked glass flask reaction container equipped with reflux condenser and mechanical stirrer, then the acrylic ester monomer, silane coupling agent and initiator are added, stirred for 20 minutes to mix uniformly, the reaction temperature is controlled at 50 ~ 60 ℃, and the polymerization reaction is carried out at the stirring speed of 50 ~ 70 rpm for 22 ~ 26 hours; finally, the obtained microparticles are purified 4 ~ 6 times by centrifugation at 3000 rpm for 10 minutes with methanol, and freeze-dried under vacuum.

[0018] The monodisperse polymer / silica hybrid microparticles can be obtained by dispersion polymerization method: under the action of dispersion stabilizer, acrylic ester monomer, silane coupling agent and initiator are polymerized under certain conditions to obtain.

[0019] Specifically, under the nitrogen atmosphere, the stabilizer and solvent are added to the four-necked glass flask reaction container equipped with reflux condenser and mechanical stirrer, then the acrylic ester monomer, silane coupling agent and initiator are added, stirred for 20 minutes to mix uniformly, the reaction temperature is controlled at 50 ~ 60 ℃, and the polymerization reaction is carried out at the stirring speed of 50 ~ 70 rpm for 22 ~ 26 hours; finally, the obtained microparticles are purified 4 ~ 6 times by centrifugation at 3000 rpm for 10 minutes with methanol, and freeze-dried under vacuum.

[0020] The amount of acrylic ester monomer is 11 ~ 13wt% based on the total amount of acrylic ester monomer, silane coupling agent, initiator and solvent; the amount of silane coupling agent is 0.6 ~ 0.7wt%; the amount of initiator is 0.05 ~ 0.07wt%.

[0021] The amount of stabilizer is 7.0 ~ 9.0wt% based on the total amount of acrylic ester monomer and silane coupling agent.

[0022] The stabilizer is polyvinylpyrrolidone (PVP) or sodium polystyrene sulfonate (NaPSS).

[0023] The solvent is a mixture of methanol / deionized water or a mixture of methanol / ethanol; in addition, the solvent can also be single methanol or ethanol.

[0024] The solvent has certain influence on the final particle size, and with the increase of the content of the poor solvent in the monomer mixture, the particle size after dispersion polymerization is reduced.

[0025] In some embodiments of the present application, the solvent is a methanol / ethanol solvent mixture (ethanol 10wt%), and the hybrid particles with a particle size of about 5 μm can be obtained. In some embodiments of the present application, the solvent is methanol, and the hybrid particles with a particle size of about 3.0 μm can be obtained.

[0026] Further, the double bond modified polymer / silica hybrid microparticles are obtained by a sol-gel method, specifically, the double bond surface modification of the polymer particles is carried out in a round bottom flask reaction container, first, the monodisperse polymer / silica hybrid microparticles are re-dispersed in a mixed solution of methanol and water, ultrasonic treatment ensures complete dispersion of the particles, then, NH4OH solution is added to the flask, and a mixture of tetraethoxysilane (TEOS) and silane coupling agent is slowly dropped into the flask; the sol-gel reaction is carried out at room temperature for 3-5 hours. The synthesized particles are centrifuged with methanol at a speed of 3000 rpm for six times, and then freeze-dried under vacuum conditions.

[0027] The ratio of the mixed solution of methanol and water is methanol: water = 6-8:3 by mass fraction; The amount of the mixture of the monodisperse polymer / silica hybrid microparticles, tetraethoxysilane and silane coupling agent is 1:1 by mass fraction.

[0028] Further, the amount of the mixture of tetraethoxysilane and silane coupling agent is 3-5:1 by mass fraction.

[0029] The acrylate monomer is one or more of methyl methacrylate, ethyl methacrylate, methyl acrylate, ethyl acrylate, and butyl acrylate.

[0030] The silane coupling agent is one or more of 3-(methacryloyloxy)propyltrimethoxysilane, 3-acryloyloxypropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, and vinyltrimethoxysilane. As a preferred, the silane coupling agent is 3-(methacryloyloxy)propyltrimethoxysilane or 3-acryloyloxypropyltrimethoxysilane.

[0031] The initiator is any one of azobisisobutyronitrile (AIBN), azobisisoheptyl nitrile, and dimethyl azobisisobutyrate (AIBME).

[0032] In some embodiments of the present application, the monodisperse polymer / silica hybrid microparticles are poly(MMA-co-TMSP) hybrid particles. Further, the poly(MMA-co-TMSP) hybrid particles are obtained by polymerization of methyl methacrylate (MMA) as an acrylate monomer and 3-acryloxypropyltrimethoxysilane (TMSP) as a silane coupling agent.

[0033] In some embodiments of the present application, the double-bond modified polymer / silica hybrid microparticles are double-bond modified poly(MMA-co-TMSP) hybrid particles; further, the double-bond modified poly(MMA-co-TMSP) hybrid particles are obtained by sol-gel reaction of tetraethoxysilane (TEOS) and 3-acryloxypropyltrimethoxysilane (TMSP) on poly(MMA-co-TMSP) hybrid particles.

[0034] In another aspect, a preparation method of a uniform light diffusion film, the uniform light diffusion film being obtained by melt extrusion and double-drawing process, specifically comprising the following preparation steps: Step one, mixing S1-1: according to the formula, the first diffusion particles, the first polyester resin, and the hybrid particles are sequentially added into a stirrer, the stirring speed is 50-150 rpm, and the stirring time is 20-40 minutes, to obtain a diffusion layer (light-incident surface) mixture I; S1-2: according to the formula, the second diffusion particles, the second polyester resin, the hybrid particles, and the incompatible resin are sequentially added into a stirrer, the stirring speed is 50-150 rpm, and the stirring time is 20-40 minutes, to obtain a uniform light layer mixture II; S1-3: according to the formula, the first diffusion particles, the first polyester resin, and the hybrid particles are sequentially added into a stirrer, the stirring speed is 50-150 rpm, and the stirring time is 20-40 minutes, to obtain a diffusion layer (adhesion surface) mixture III.

[0035] The formula of the diffusion layer (light-incident surface) and the formula of the diffusion layer (adhesion surface) are the same or different.

[0036] Step two, film preparation S2-1: melt extrusion: the diffusion layer (light-incident surface) mixture I is added into the A bin of a three-layer extruder, to melt extrude the A layer; the uniform light layer mixture II is added into the B bin of the three-layer extruder, to melt extrude the B layer; the diffusion layer (adhesion surface) mixture III is added into the C bin of the three-layer extruder, to melt extrude the C layer; the melt is co-extruded through a die, and is cast onto a casting roll, to form a three-layer co-extruded casting sheet, and the casting roll temperature is 18-25°C; S2-2: traction, winding: the cast piece is longitudinally stretched, the longitudinal stretching temperature is 66-85 DEG C, the longitudinal stretching ratio is 2.6-4.1; the longitudinally stretched piece is transversely stretched, the transverse stretching temperature is 112-126 DEG C, the transverse stretching ratio is 3.8-4.8; the stretched film is shaped and cooled, the shaping temperature is 225-235 DEG C, the cooling temperature is 40-50 DEG C; the cooled film is tractioned and wound.

[0037] In a third aspect, the application discloses the application of the light uniformity diffusion film, and the light uniformity diffusion film can be applied to the fields of backlight modules, LED lighting and vehicle-mounted display.

[0038] Compared with the prior art, the application has the following beneficial effects: (1) The hybrid particles are introduced into the diffusion layer and the light uniformity layer, and the three-layer haze is adjusted by controlling the amount of the hybrid particles and the diffusion particles, so that the optical polyester film has high haze effect and exhibits excellent light uniformity performance; (2) The hybrid particles are modified by a double bond, so that the structure has a vinyl group, and the hybrid particles can be combined with the polyester resin by a covalent bond in the process of melt extrusion and double drawing of the optical film, on the one hand, the particles are uniformly dispersed in the resin; on the other hand, the chemical bond can firmly adhere the particles to the resin, and the overall mechanical properties of the optical film material are enhanced; (3) The middle layer in the application forms a bubble structure by incompatible resins, the bubble technology forms a porous structure to realize light diffusion, and a certain amount of diffusion particles are added, and light diffusion is realized by uniform distribution of the scattering particles, and the two synergistically further obtain the light uniformity effect; (4) The light uniformity diffusion film of the application is an internal addition type light uniformity diffusion film, which is one-step formed by melt extrusion and double drawing process, has strong operability, shortens the production cycle and reduces the cost. BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1 The application discloses a light uniformity diffusion film structure schematic diagram. Figure legend: 1-diffusion layer; 2-light uniformity layer.

[0040] Figure 2 The preparation schematic diagram of the double bond modified poly (MMA-co-TMSP) hybrid particles. DETAILED DESCRIPTION

[0041] The technical solutions of the application will be described clearly and completely in combination with the embodiments.

[0042] In the following examples, the experimental methods are conventional methods, and are carried out according to the techniques or conditions described in the literature in the art or according to the product instructions, unless otherwise specified.

[0043] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0044] Methyl methacrylate (MMA), analytical grade, Tianjin Chemical Reagent Factory.

[0045] 3-(acryloyloxy)propyltrimethoxysilane, 99% purity, Shanghai Maclean Biochemical Technology Co., Ltd.

[0046] A schematic diagram of the preparation of double-bond modified poly(MMA-co-TMSP) hybrid particles is attached. Figure 2 As shown, the specific preparation steps are as follows: S1: Preparation of poly(MMA-co-TMSP) hybrid particles: Under nitrogen protection, 8 g of polyvinylpyrrolidone (PVP) and a methanol / ethanol solvent mixture (10 wt% ethanol, 7.94 g) were added to a 250 mL four-necked glass flask equipped with a reflux condenser and a mechanical stirrer. Subsequently, 11.88 g of methyl methacrylate (MMA), 0.63 g of 3-acryloyloxypropyltrimethoxysilane (TMSP), and 0.06 g of azobisisobutyronitrile were added to the flask; the mixture was stirred for 20 minutes until homogeneous, and the polymerization reaction was carried out at 55 °C with a stirring speed of 60 rpm for 24 hours. The resulting particles were centrifuged with methanol at 3000 rpm for 10 minutes, and the operation was repeated five times for purification. Then, the particles were freeze-dried under vacuum to obtain poly(MMA-co-TMSP) hybrid particles with a particle size of approximately 5 μm. In addition, by changing the solvent to methanol while keeping the other steps unchanged, the particle size of the poly(MMA-co-TMSP) hybrid particles was approximately 3 μm.

[0047] S2: Preparation of double-bond modified poly(MMA-co-TMSP) hybrid particles: Poly(MMA-co-TMSP) hybrid particles (2 g) were ultrasonically dispersed in a mixed solution of methanol (140 g) and water (60 g) for 30 minutes. After ensuring complete dispersion of the particles, concentrated ammonia was added to the flask to adjust the pH of the system to the alkaline range (pH 8-10). Then, a mixture of tetraethoxysilane (TEOS, 1.6 g) and 3-acryloyloxypropyltrimethoxysilane (TMSP, 0.4 g) was slowly added dropwise to the flask. The sol-gel reaction was carried out at room temperature for 4 hours. The synthesized particles were centrifuged with methanol at 3000 rpm, washed six times, and then freeze-dried under vacuum.

[0048] Conventional silicone particles: Commercially available polymethylsilsesquioxane particles, Ancos NX050, with an average particle size of 5μm; Ancos NX030, with an average particle size of 3μm.

[0049] Example 1 The application provides a light-uniform diffusion film, comprising a diffusion layer and a light-uniform layer, the diffusion layer is located on both sides of the light-uniform layer, and a corresponding structural schematic diagram is as shown in the accompanying Figure 1 The thickness of the light-uniform diffusion film is 300 μm, the single-layer thickness of the diffusion layer is 15 μm, and the thickness of the light-uniform layer is 270 μm.

[0050] The diffusion layer comprises a first polyester resin, first diffusion particles and hybrid particles; the light-uniform layer comprises a second polyester resin, second diffusion particles, hybrid particles and an incompatible resin, and the components of each layer are as follows: Diffusion layer (light-incident surface & adhering surface): 3 μm poly (methyl methacrylate): 5.0 parts; 20 μm poly (methyl methacrylate): 1.5 parts; 5 μm double-bond modified poly (MMA-co-TMSP) hybrid particles: 0.5 parts; Polyethylene terephthalate: 93 parts.

[0051] Light-uniform layer: 3 μm poly (methyl methacrylate): 2.5 parts; 3 μm double-bond modified poly (MMA-co-TMSP) hybrid particles: 2.4 parts; Incompatible resin (COC): 0.1 parts; Polyethylene terephthalate: 95 parts.

[0052] According to the components of each layer, the light-uniform diffusion film is prepared: Step one, mixing S1-1: according to the formula, the first diffusion particles, the first polyester resin and the hybrid particles are sequentially added into a stirrer, the rotating speed is 120 rpm, and stirring is performed for 30 minutes to obtain the diffusion layer (light-incident surface) mixture I; S1-2: according to the formula, the second diffusion particles, the second polyester resin, the hybrid particles and the incompatible resin are sequentially added into a stirrer, the rotating speed is 120 rpm, and stirring is performed for 30 minutes to obtain the light-uniform layer mixture II; S1-3: according to the formula, the first diffusion particles, the first polyester resin and the hybrid particles are sequentially added into a stirrer, the rotating speed is 120 rpm, and stirring is performed for 30 minutes to obtain the diffusion layer (adhering surface) mixture III.

[0053] Step two, film preparation S2-1: Melt extrusion: Add diffusion layer (light-facing surface) mixture I to chamber A of the three-layer extruder and melt extrude layer A; add smoothing layer mixture II to chamber B of the three-layer extruder and melt extrude layer B; add diffusion layer (adhesive surface) mixture III to chamber C of the three-layer extruder and melt extrude layer C; the melt is co-extruded through the die and cast onto the casting roll to form a three-layer co-extruded sheet, with the casting roll temperature being 18℃~25℃; S2-2: Traction and winding: The cast sheet is longitudinally stretched at a temperature of 66℃~85℃ and a stretching ratio of 2.6~4.1; the longitudinally stretched sheet is then transversely stretched at a temperature of 112℃~126℃ and a stretching ratio of 3.8~4.8; the stretched film is then shaped and cooled at a temperature of 225℃~235℃ and a cooling temperature of 40℃~50℃; the cooled film is then traction and winding.

[0054] Example 2 As described in Example 1, the light-diffusing film with the diffusion layer formulation adjusted while keeping the other steps unchanged is as follows: Diffuser layer (light-facing side & bonding side): 3μm polymethyl methacrylate: 4.0 parts; 20μm polymethyl methacrylate: 2 parts; 5μm double-bond modified poly(MMA-co-TMSP) hybrid particles: 1 part; Polyethylene terephthalate: 93 parts.

[0055] homogenizing layer: 3μm polymethyl methacrylate: 2.5 parts; 3μm double-bond modified poly(MMA-co-TMSP) hybrid particles: 2.4 parts; Incompatible resin (COC): 0.1 parts; Polyethylene terephthalate: 95 parts.

[0056] Example 3 As described in Example 1, the light-diffusing film with the diffusion layer formulation adjusted while keeping the other steps unchanged is as follows: Diffuser layer (light-facing side & bonding side): 3μm polymethyl methacrylate: 3.0 parts; 20μm polymethyl methacrylate: 2 parts; 5μm double-bond modified poly(MMA-co-TMSP) hybrid particles: 2 parts; Polyethylene terephthalate: 93 parts.

[0057] homogenizing layer: 3μm polymethyl methacrylate: 2.5 parts; 3 pm double bond modified poly (MMA-co-TMSP) hybrid particles: 2.4 parts; Incompatible resin (COC): 0.1 part; Polyethylene terephthalate: 95 parts.

[0058] Example 4 The light uniformity diffusion film was prepared as described in Example 1, with the diffusion layer formulation adjusted, and the remaining steps unchanged, as follows: Diffusion layer (light receiving surface & adhering surface): 3 pm poly (methyl methacrylate): 1.0 part; 20 pm poly (methyl methacrylate): 2 parts; 5 pm double bond modified poly (MMA-co-TMSP) hybrid particles: 4 parts; Polyethylene terephthalate: 93 parts.

[0059] Light uniformity layer: 3 pm poly (methyl methacrylate): 2.5 parts; 3 pm double bond modified poly (MMA-co-TMSP) hybrid particles: 2.4 parts; Incompatible resin (COC): 0.1 part; Polyethylene terephthalate: 95 parts.

[0060] Example 5 The light uniformity diffusion film was prepared as described in Example 1, with the diffusion layer formulation adjusted, and the remaining steps unchanged, as follows: Diffusion layer (light receiving surface & adhering surface): 3 pm poly (methyl methacrylate): 1.0 part; 20 pm poly (methyl methacrylate): 1.0 part; 5 pm double bond modified poly (MMA-co-TMSP) hybrid particles: 5 parts; Polyethylene terephthalate: 93 parts.

[0061] Light uniformity layer: 3 pm poly (methyl methacrylate): 2.5 parts; 3 pm double bond modified poly (MMA-co-TMSP) hybrid particles: 2.4 parts; Incompatible resin (COC): 0.1 part; Polyethylene terephthalate: 95 parts.

[0062] Example 6 The light uniformity diffusion film was prepared as described in Example 3, with the light uniformity layer formulation adjusted, and the remaining steps unchanged, as follows: Diffusion layer (light receiving surface & adhering surface): 3 pm PMMA: 3.0 parts; 20 pm PMMA: 2 parts; 5 pm double bond modified poly (MMA-co-TMSP) hybrid particles: 2 parts; Polyethylene terephthalate: 93 parts.

[0063] Uniform light layer: 3 pm PMMA: 1.5 parts; 3 pm double bond modified poly (MMA-co-TMSP) hybrid particles: 3.4 parts; Incompatible resin (COC): 0.1 parts; Polyethylene terephthalate: 95 parts.

[0064] Example 7 The uniform light diffusion film as described in Example 6, adjusting the uniform light layer formula, the rest of the steps remain unchanged, as follows: Diffusion layer (light receiving surface & adhering surface): 3 pm PMMA: 3.0 parts; 20 pm PMMA: 2 parts; 5 pm double bond modified poly (MMA-co-TMSP) hybrid particles: 2 parts; Polyethylene terephthalate: 93 parts.

[0065] Uniform light layer: 3 pm PMMA: 3 parts; 3 pm double bond modified poly (MMA-co-TMSP) hybrid particles: 1.9 parts; Incompatible resin (COC): 0.1 parts; Polyethylene terephthalate: 95 parts.

[0066] Example 8 The uniform light diffusion film as described in Example 6, adjusting the uniform light layer formula, the rest of the steps remain unchanged, as follows: Diffusion layer (light receiving surface & adhering surface): 3 pm PMMA: 3.0 parts; 20 pm PMMA: 2 parts; 5 pm double bond modified poly (MMA-co-TMSP) hybrid particles: 2 parts; Polyethylene terephthalate: 93 parts.

[0067] Uniform light layer: 3 pm PMMA: 2 parts; 3 μm double-bond modified poly(MMA-co-TMSP) hybrid particles: 2.8 parts; Incompatible resin (COC): 0.1 parts; Polyethylene terephthalate: 95 parts.

[0068] Example 9 The light-uniformizing diffusion film as described in Example 6 was adjusted in the light-uniformizing layer formulation, and the remaining steps were kept unchanged, specifically as follows: Diffusion layer (light-incident surface & adhering surface): 3 μm poly(methyl methacrylate): 3.0 parts; 20 μm poly(methyl methacrylate): 2 parts; 5 μm double-bond modified poly(MMA-co-TMSP) hybrid particles: 2 parts; Polyethylene terephthalate: 93 parts.

[0069] Light-uniformizing layer: 3 μm poly(methyl methacrylate): 1.5 parts; 3 μm double-bond modified poly(MMA-co-TMSP) hybrid particles: 2.4 parts; Incompatible resin (COC): 2 parts; Polyethylene terephthalate: 95 parts.

[0070] Example 10 The light-uniformizing diffusion film as described in Example 1 was adjusted in the formulation of each layer, and the remaining steps were kept unchanged, specifically as follows: Diffusion layer (light-incident surface): 3 μm poly(methyl methacrylate): 4.0 parts; 20 μm poly(methyl methacrylate): 2.5 parts; 5 μm double-bond modified poly(MMA-co-TMSP) hybrid particles: 0.5 parts; Polyethylene terephthalate: 93 parts.

[0071] Diffusion layer (adhering surface): 3 μm poly(methyl methacrylate): 0 parts; 10 μm poly(methyl methacrylate): 0.5 parts; 5 μm double-bond modified poly(MMA-co-TMSP) hybrid particles: 0.5 parts; Polyethylene terephthalate: 99 parts.

[0072] Light-uniformizing layer: 3 μm poly(methyl methacrylate): 1.5 parts; 3 μm double-bond modified poly(MMA-co-TMSP) hybrid particles: 0.4 parts; Incompatible resin (COC): 0.1 part; Polyethylene terephthalate: 98 parts.

[0073] Example 11 The light uniformity diffusion film was prepared as described in Example 10, adjusting the formulation of the diffusion layer (light-incident surface) and the light uniformity layer (adhesion surface), and the remaining steps were kept unchanged, as follows: Diffusion layer (light-incident surface): 3 μm polymethyl methacrylate: 4.0 parts; 20 μm polymethyl methacrylate: 2.5 parts; 5 μm double-bond modified poly (MMA-co-TMSP) hybrid particles: 0.5 parts; Polyethylene terephthalate: 93 parts.

[0074] Diffusion layer (adhesion surface): 3 μm polymethyl methacrylate: 0.8 parts; 10 μm polymethyl methacrylate: 0.2 parts; 5 μm double-bond modified poly (MMA-co-TMSP) hybrid particles: 1 part; Polyethylene terephthalate: 98 parts.

[0075] Light uniformity layer: 3 μm polymethyl methacrylate: 2.5 parts; 3 μm double-bond modified poly (MMA-co-TMSP) hybrid particles: 2.4 parts; Incompatible resin (COC): 0.1 part; Polyethylene terephthalate: 95 parts.

[0076] Comparative Example 1 The light uniformity diffusion film was prepared as described in Example 3, without adding hybrid particles to the light uniformity layer, and the remaining steps were kept unchanged, as follows: Diffusion layer (light-incident surface & adhesion surface): 3 μm polymethyl methacrylate: 3 parts; 20 μm polymethyl methacrylate: 2 parts; 5 μm double-bond modified poly (MMA-co-TMSP) hybrid particles: 2 parts; Polyethylene terephthalate: 93 parts.

[0077] Light uniformity layer: 3 μm polymethyl methacrylate: 4.9 parts; 3 μm double-bond modified poly (MMA-co-TMSP) hybrid particles: 0 parts; Incompatible resin (COC): 0.1 part; Polyethylene terephthalate: 95 parts.

[0078] Comparative Example 2 The light-uniform diffusion film was prepared as described in Example 3, except that no hybrid particles were added to the diffusion layer, and the remaining steps were unchanged, as follows: Diffusion layer (light-incident surface & adhering surface): 3 μιη polymethyl methacrylate: 5 parts; 20 μιη polymethyl methacrylate: 2 parts; 5 μιη double-bond modified poly(MMA-co-TMSP) hybrid particles: 0 parts; Polyethylene terephthalate: 93 parts.

[0079] Light-uniform layer: 3 μιη polymethyl methacrylate: 2.5 parts; 3 μιη double-bond modified poly(MMA-co-TMSP) hybrid particles: 2.4 parts; Incompatible resin (COC): 0.1 part; Polyethylene terephthalate: 95 parts.

[0080] Comparative Example 3 The light-uniform diffusion film was prepared as described in Example 3, except that no hybrid particles were added to each layer, and the remaining steps were unchanged, as follows: Diffusion layer (light-incident surface & adhering surface): 3 μιη polymethyl methacrylate: 4 parts; 20 μιη polymethyl methacrylate: 3 parts; 5 μιη double-bond modified poly(MMA-co-TMSP) hybrid particles: 0 parts; Polyethylene terephthalate: 93 parts.

[0081] Light-uniform layer: 3 μιη polymethyl methacrylate: 4.9 parts; 3 μιη double-bond modified poly(MMA-co-TMSP) hybrid particles: 0 parts; Incompatible resin (COC): 0.1 part; Polyethylene terephthalate: 95 parts.

[0082] Comparative Example 4 The light-uniform diffusion film was prepared as described in Example 3, except that no incompatible resin was added to the light-uniform layer, and the remaining steps were unchanged, as follows: Diffusion layer (light-incident surface & adhering surface): 3 μιη polymethyl methacrylate: 3 parts; 20 μιη polymethyl methacrylate: 2 parts; 5 μm silicone particles (polymethylsilsesquioxane): 2 parts; Polyethylene terephthalate: 93 parts.

[0083] Light uniformity layer: 3 μm polymethyl methacrylate: 2.5 parts; 3 μm double bond modified poly (MMA-co-TMSP) hybrid particles: 2.5 parts; Incompatible resin (COC): 0 parts; Polyethylene terephthalate: 95 parts.

[0084] Comparative Example 5 The light uniformity diffusion film as described in Example 3, the double bond modified poly (MMA-co-TMSP) hybrid particles were adjusted to conventional silicone particles, and the remaining steps were kept unchanged, as follows: Diffusion layer (light receiving surface & adhering surface): 3 μm polymethyl methacrylate: 3 parts; 20 μm polymethyl methacrylate: 2 parts; 5 μm silicone particles (polymethylsilsesquioxane): 2 parts; Polyethylene terephthalate: 93 parts.

[0085] Light uniformity layer: 3 μm polymethyl methacrylate: 4.9 parts; 3 μm silicone particles (polymethylsilsesquioxane): 0 parts; Incompatible resin (COC): 0.1 parts; Polyethylene terephthalate: 95 parts.

[0086] The performance of the light uniformity diffusion films obtained in Examples 1-11 and Comparative Examples 1-5 above was characterized as follows: (1) Brightness and brightness uniformity: The average brightness and brightness uniformity of the obtained samples were tested with a BM-7A brightness colorimeter according to GB / T 43979-2024. The higher the brightness uniformity, the more uniform the light output. (2) Transmittance and haze: The haze and transmittance of each group of film materials were tested with an NDH2000 type haze meter according to ASTM D1003 "Standard Test Method for Haze and Transmittance of Transparent Plastics". (3) Mechanical property test: Film sample strips of 15 cm long and 15 mm wide were taken, 3 strips in MD / TD direction, and a universal material testing machine was used to test the tensile strength under the conditions of gauge length 100 cm and speed 100 mm / min, and the average value was taken.

[0087] The performance characterization results of the light uniformity diffusion films obtained in Examples 1-11 and Comparative Examples 1-5 are shown in Table 1.

[0088] Table 1 Performance characterization results of the light-uniform diffusion films obtained in Examples 1-11 and Comparative Examples 1-5

[0089] Examples 1-5 investigated the performance of the light-uniform diffusion films obtained by gradually increasing the proportion of the double-bond modified poly(MMA-co-TMSP) hybrid particles in different proportions of the poly(methyl methacrylate) particles with different particle sizes. Examples 6-9 investigated the performance of the light-uniform diffusion films obtained by different proportions of the hybrid particles in the light-uniform layer and the poly(methyl methacrylate) particles. Examples 10 and 11 were light-uniform diffusion films obtained by different formulations of the light-incident surface and the adhering surface of the diffusion layer. As can be seen from the data in Table 1, Examples 1-11 exhibited better comprehensive performance than Comparative Examples 1-5, especially the optimization of the adaptation of the light transmittance and the haze, with a haze > 90% and a light transmittance that can be maintained at > 40%. At the same time, they exhibited better light-uniform effect, especially the brightness uniformity of Examples 4, 5, 6, and 8 was > 98%.

[0090] As can be seen from the comparison of Example 3 with Comparative Examples 1-3 and Comparative Example 5, the addition of hybrid particles can significantly improve the brightness uniformity of the film and the mechanical strength of the film material. This is mainly due to the introduction of the double-bond modified poly(MMA-co-TMSP) hybrid particles. On the one hand, the poly(MMA-co-TMSP) hybrid particles are obtained by polymerization of acrylate monomers and silane coupling agents, and the material itself has better compatibility with the conventional inorganic particles and the main resin of the film material due to its organic / inorganic hybrid nature. On the other hand, the vinyl group in the structure of the poly(MMA-co-TMSP) hybrid particles provides a site for the chemical bonding of the particles and the polyester, further promoting the dispersion of the particles and improving the mechanical properties of the film.

[0091] In addition, the comparison of Example 3 with Comparative Example 4 can find that the addition of incompatible resins can significantly improve the film haze, making the film material have a higher light transmittance while effectively improving its haze performance, thereby improving the light-uniform effect of the film. However, the comparison of Example 9 with Example 3 and Comparative Example 4 can find that too much addition of incompatible resins can affect the light transmittance of the film.

Claims

1. A light-diffusing film, comprising a diffusion layer and a light-diffusing layer, wherein the diffusion layer is located on both sides of the light-diffusing layer, characterized in that, The diffusion layer comprises a first polyester resin, first diffusion particles, and hybrid particles; by mass, the first polyester resin comprises 92-99%, the first diffusion particles comprise 0.5-7.0%, and the hybrid particles comprise 0.5-6.5%; the homogenizing layer comprises a second polyester resin, second diffusion particles, hybrid particles, and incompatible resin; by mass, the second polyester resin comprises 94.5-98%, the second diffusion particles comprise 1.5-3.0%, the hybrid particles comprise 0.4-3.9%, and the incompatible resin comprises 0.1-2.0%; the hybrid particles are double-bond modified polymer / silica hybrid microparticles, which are first prepared by dispersion polymerization from acrylate monomers, silane coupling agents, and initiators to obtain monodisperse polymer / silica hybrid microparticles, and then obtained by sol-gel method from tetraethoxysilane and silane coupling agent double bond modification, with a particle size of 2.5-7.5 µm.

2. The light-diffusing film according to claim 1, characterized in that, The preparation steps of the double bond modified polymer / silica hybrid microparticles include: dispersing monodisperse polymer / silica hybrid microparticles in a methanol and water mixture in a reaction vessel, sonicating to ensure complete dispersion, then adding NH4OH solution to a flask, and then slowly dripping a mixture of tetraethoxysilane and silane coupling agent into the reaction vessel, reacting at room temperature for 3 to 5 hours, centrifuging and washing the synthesized particles, and freeze-drying them under vacuum.

3. The light-diffusing film according to claim 2, characterized in that, The preparation steps of the monodisperse polymer / silica hybrid microparticles include: adding stabilizer and solvent to a reaction vessel under a nitrogen atmosphere, followed by adding acrylate monomer, silane coupling agent and initiator, controlling the reaction temperature at 50-60℃ and carrying out the polymerization reaction at a stirring speed of 50-70 rpm for 22-26 hours; finally, centrifuging and purifying the obtained microparticles, and freeze-drying them under vacuum.

4. The light-diffusing film according to claim 3, characterized in that, The stabilizer is polyvinylpyrrolidone or sodium polystyrene sulfonate; the initiator is any one of azobisisobutyronitrile, azobisisoheptanenitrile, and dimethyl azobisisobutyrate; the solvent is methanol or ethanol, or a mixture of methanol / deionized water or a mixture of methanol / ethanol.

5. The light-diffusing film according to claim 3, characterized in that, The amount of acrylate monomer, silane coupling agent, initiator, and solvent is 11-13 wt%; the amount of silane coupling agent is 0.6-0.7 wt%; the amount of initiator is 0.05-0.07 wt%; the amount of stabilizer is 7.0-9.0 wt% of the total amount of acrylate monomer and silane coupling agent; the ratio of monodisperse polymer / silica hybrid microparticles to tetraethoxysilane and silane coupling agent mixture is 1:1 by mass; the ratio of tetraethoxysilane to silane coupling agent mixture is 3-5:1 by mass; and the ratio of methanol to water mixture is 6-8:3 by mass.

6. The light-diffusing film according to claim 3, characterized in that, The acrylate monomer is one or more of methyl methacrylate, ethyl methacrylate, methyl acrylate, ethyl acrylate, and butyl acrylate; the silane coupling agent is one or more of 3-(methacryloyloxy)propyltrimethoxysilane, 3-acryloyloxypropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, and vinyltrimethoxysilane.

7. The light-diffusing film according to claim 6, characterized in that, The first or second polyester resin includes at least one of polyethylene terephthalate and polybutylene terephthalate; the first or second diffused particles include at least one of polymethyl methacrylate, silica, calcium carbonate, titanium dioxide, and barium sulfate; the average particle size of the first diffused particles is distributed between 3 μm and 20 μm, and the average particle size of the second diffused particles is distributed between 2 μm and 5 μm; the incompatible resin is a polyolefin resin, including at least one of polypropylene, polymethylpentene, and cyclic polyolefins.

8. A method for preparing a uniform light diffusion film according to any one of claims 1 to 7, characterized in that, The preparation steps include the following: Step 1, Mixing: S1-1: According to the formula, add the first diffusion particles, the first polyester resin, and the hybrid particles to the mixer in sequence, and mix evenly to obtain the light-facing diffusion layer mixture I; S1-2: According to the formula, add the second diffusion particles, the hybrid particles, the second polyester resin, and the incompatible resin to the mixer in sequence, and mix evenly to obtain the light-diffusing layer mixture II; S1-3: According to the formula, add the first diffusion particles, the first polyester resin, and the hybrid particles to the mixer in sequence, and mix evenly to obtain the bonding surface diffusion layer mixture III; Step 2, Film Forming: S2-1: Melt Extrusion: Add the light-facing diffusion layer mixture I to chamber A of the three-layer extruder and melt-extrude layer A; add the light-diffusing layer mixture II to chamber B of the three-layer extruder and melt-extrude layer B; add the bonding surface diffusion layer mixture III to chamber C of the three-layer extruder and melt-extrude layer C; the melt is co-extruded through the die head and cast onto the casting roller to form a three-layer co-extruded sheet. The temperature of the casting roller is 18℃~25℃; S2-2: Traction and Winding: The casting sheet is stretched longitudinally and laterally, shaped, cooled, traction, and wound to obtain the final product.

9. The method for preparing a uniform light diffusion film according to claim 8, characterized in that, The longitudinal stretching temperature is 66℃~85℃, and the longitudinal stretching ratio is 2.6~4.1; the transverse stretching temperature is 112℃~126℃, and the transverse stretching ratio is 3.8~4.8; the setting temperature is 225℃~235℃, and the cooling temperature is 40℃~50℃.

10. The application of a uniform light diffusion film as described in any one of claims 1 to 7, characterized in that, The light diffusion film can be applied to backlight modules, LED lighting, and automotive displays.

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