A light-uniform diffusion film, a preparation method and application thereof

Abstract

The application discloses a kind of light uniformity diffusion film, preparation method and application, first by dispersion polymerization method from acrylate monomer, silane coupling agent and initiator to obtain monodisperse polymer / silica hybrid microparticle, again by sol-gel method from tetraethoxysilane and silane coupling agent double bond modification obtains polymer / silica hybrid microparticle with vinyl, and it is added into polyester resin as hybrid particle and diffusion particle ratio inside by melt extrusion, double drawing light uniformity diffusion film is obtained, obtains film with high haze effect, the haze of light uniformity performance is more than 90%, light transmittance can be kept at 40% or more;Double bond structure can be combined with polyester resin to improve organic / inorganic phase compatibility, improve film mechanics performance.

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, takes a long time to process and has a low success rate, which 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 and 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 by 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 bond to improve the compatibility of organic / inorganic phases and improve the film mechanical properties.

[0006] The application is implemented by the following technical solutions:

[0007] 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%.

[0008] Further, the light-uniform diffusion film has a light transmittance value R≥40% and a haze≥90%.

[0009] The diffusion layer includes a first polyester resin, first diffusion particles, and hybrid particles.

[0010] 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.

[0011] The first diffusion particles include at least one of polymethyl methacrylate, silicon dioxide, calcium carbonate, titanium dioxide, and barium sulfate.

[0012] The average particle size of the first diffusion particles is distributed in a range of 3 μm-20 μm.

[0013] In some embodiments of the present application, the first diffusion particles are polymethyl methacrylate with a particle size of 3 μm and 20 μm.

[0014] The first polyester resin includes at least one of polyethylene terephthalate (PET) and polybutylene terephthalate.

[0015] The light-uniform layer includes a second polyester resin, second diffusion particles, hybrid particles, and an incompatible resin.

[0016] 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.

[0017] The second diffusion particles include at least one of polymethyl methacrylate, silicon dioxide, calcium carbonate, titanium dioxide, and barium sulfate.

[0018] Preferably, the second diffusion particles are polymethyl methacrylate microspheres or silicon dioxide microspheres.

[0019] The average particle size of the second diffusion particles is distributed in a range of 2 μm-5 μm.

[0020] The second polyester resin includes at least one of polyethylene terephthalate and polybutylene terephthalate.

[0021] The incompatible resin is a polyolefin-based resin, including at least one of polypropylene, polymethylpentene, cyclic polyolefin (COC / COP).

[0022] The hybrid particle is a double-bond modified polymer / silica hybrid microparticle, specifically, a monodisperse polymer / silica hybrid microparticle prepared by a dispersion polymerization method, and then modified by a double bond.

[0023] The monodisperse polymer / silica hybrid microparticle can be obtained by a dispersion polymerization method: under the action of a dispersion stabilizer, by polymerization reaction of an acrylate monomer, a silane coupling agent and an initiator under certain conditions.

[0024] Specifically, under a nitrogen atmosphere, the stabilizer and solvent are added to a four-necked glass flask reaction container equipped with a reflux condenser and a mechanical stirrer, then the acrylate monomer, the silane coupling agent and the initiator are added, stirred for 20 minutes to mix uniformly, the reaction temperature is controlled at 50-60°C, and the polymerization reaction is carried out at a 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.

[0025] The monodisperse polymer / silica hybrid microparticle can be obtained by a dispersion polymerization method: under the action of a dispersion stabilizer, by polymerization reaction of an acrylate monomer, a silane coupling agent and an initiator under certain conditions.

[0026] Specifically, under a nitrogen atmosphere, the stabilizer and solvent are added to a four-necked glass flask reaction container equipped with a reflux condenser and a mechanical stirrer, then the acrylate monomer, the silane coupling agent and the initiator are added, stirred for 20 minutes to mix uniformly, the reaction temperature is controlled at 50-60°C, and the polymerization reaction is carried out at a 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.

[0027] The amount of the acrylate monomer is 11-13wt% based on the total amount of the acrylate monomer, the silane coupling agent, the initiator and the solvent; the amount of the silane coupling agent is 0.6-0.7wt%; the amount of the initiator is 0.05-0.07wt%.

[0028] The amount of the stabilizer is 7.0-9.0wt% based on the total amount of the acrylate monomer and the silane coupling agent.

[0029] The stabilizer is polyvinylpyrrolidone (PVP) or sodium polystyrene sulfonate (NaPSS).

[0030] The solvent is a mixture of methanol and deionized water or a mixture of methanol and ethanol; in addition, the solvent can also be single methanol or ethanol.

[0031] 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.

[0032] In some embodiments of the present application, the solvent is a methanol / ethanol solvent mixture (10wt% ethanol), and hybrid particles with a particle size of about 5μm can be obtained;

[0033] In some embodiments of the present application, the solvent is methanol, and hybrid particles with a particle size of about 3.0μm can be obtained.

[0034] Further, the double bond modified polymer / silica hybrid microparticles are obtained by sol-gel method, specifically, the polymer particles are subjected to double bond surface modification 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.

[0035] The ratio of the mixed solution of methanol and water is methanol: water = 6-8:3 by mass fraction;

[0036] The amount of the mixture of the monodisperse polymer / silica hybrid microparticles, tetraethoxysilane and silane coupling agent is 1:1 by mass fraction.

[0037] Further, the amount of the mixture of tetraethoxysilane and silane coupling agent is tetraethoxysilane: silane coupling agent = 3-5:1 by mass fraction.

[0038] The acrylate monomer is one or more of methyl methacrylate, ethyl methacrylate, methyl acrylate, ethyl acrylate, and butyl acrylate.

[0039] The silane coupling agent is one or more of 3-(methacryloyloxy)propyltrimethoxysilane, 3-acryloyloxypropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, and vinyltrimethoxysilane;

[0040] As preferred, the silane coupling agent is 3-(methacryloyloxy)propyltrimethoxysilane or 3-acryloyloxypropyltrimethoxysilane.

[0041] The initiator is any one of azobisisobutyronitrile (AIBN), azobisisoheptyl nitrile, dimethyl azobisisobutyrate (AIBME).

[0042] In some embodiments of the present application, the monodisperse polymer / silica hybrid microparticle is a poly(MMA-co-TMSP) hybrid particle.

[0043] Further, the poly(MMA-co-TMSP) hybrid particle is polymerized with methyl methacrylate (MMA) as an acrylate monomer and 3-acryloxypropyltrimethoxysilane (TMSP) as a silane coupling agent.

[0044] In some embodiments of the present application, the double bond modified polymer / silica hybrid microparticle is a double bond modified poly(MMA-co-TMSP) hybrid particle; further, the double bond modified poly(MMA-co-TMSP) hybrid particle is obtained by sol-gel reaction of tetraethoxysilane (TEOS) and 3-acryloxypropyltrimethoxysilane (TMSP) on the poly(MMA-co-TMSP) hybrid particle.

[0045] In another aspect, a preparation method of a light-uniform diffusion film, the light-uniform diffusion film being obtained by melt extrusion and double-drawing process, specifically comprising the following preparation steps:

[0046] Step one, mixing

[0047] S1-1: according to the formula, the first diffusion particle, the first polyester resin, the hybrid particle are sequentially added into the stirrer, the stirring speed is 50-150 rpm, and the stirring time is 20-40 minutes, to obtain the diffusion layer (light-incident surface) mixture I;

[0048] S1-2: according to the formula, the second diffusion particle, the second polyester resin, the hybrid particle, and the incompatible resin are sequentially added into the stirrer, the stirring speed is 50-150 rpm, and the stirring time is 20-40 minutes, to obtain the light-uniform layer mixture II;

[0049] S1-3: according to the formula, the first diffusion particle, the first polyester resin, and the hybrid particle are sequentially added into the stirrer, the stirring speed is 50-150 rpm, and the stirring time is 20-40 minutes, to obtain the diffusion layer (adhesion surface) mixture III.

[0050] The formula of the diffusion layer (light-incident surface) and the formula of the diffusion layer (adhesion surface) are the same or different.

[0051] Step two, film preparation

[0052] S2-1: melt extrusion: the diffusion layer (light receiving surface) mixture I is added to the three-layer extruder A bin, melt extrusion A layer; the light homogenization layer mixture II is added to the three-layer extruder B bin, melt extrusion B layer; the diffusion layer (adhesion surface) mixture III is added to the three-layer extruder C bin, melt extrusion C layer; the melt is co-extruded through the die, and cast onto the casting roll to form a three-layer co-extruded casting sheet, and the casting roll temperature is 18-25 DEG C;

[0053] S2-2: traction, winding: the casting sheet is stretched in the longitudinal direction, the longitudinal stretching temperature is 66-85 DEG C, and the longitudinal stretching ratio is 2.6-4.1; the longitudinal stretching sheet is stretched in the transverse direction, the transverse stretching temperature is 112-126 DEG C, and the transverse stretching ratio is 3.8-4.8; the stretched film is shaped and cooled, the shaping temperature is 225-235 DEG C, and the cooling temperature is 40-50 DEG C; the cooled film is drawn and wound.

[0054] The third aspect is the application of the above-mentioned light homogenization diffusion film, which can be applied in the fields of backlight module, LED lighting and vehicle display.

[0055] Compared with the prior art, the present application has the following beneficial effects:

[0056] (1) The present application introduces hybrid particles in the diffusion layer and the light homogenization layer, and adjusts the three-layer haze by controlling the amount of hybrid particles and diffusion particles, so that the optical polyester film has high haze effect and exhibits excellent light homogenization performance;

[0057] (2) The hybrid particles are modified by double bond, which has vinyl group on the structure, and can be combined with polyester resin by covalent bond in the process of melt extrusion and double stretching to obtain optical film, on the one hand, promoting the uniform dispersion of particles in the resin; on the other hand, the generation of chemical bond can make the particles firmly adhere to the resin, and enhance the overall mechanical properties of the optical film material;

[0058] (3) The middle layer of the present application forms a bubble structure by incompatible resin, and the bubble technology forms a porous structure to realize light diffusion, and a certain amount of diffusion particles are added to realize light diffusion by uniform distribution of scattering particles, and the two synergistically further obtain light homogenization effect;

[0059] (4) The present application is an internal addition type light homogenization diffusion film, which is one-step formed by melt extrusion and double stretching process, has strong operability, shortens the production cycle and reduces the cost. BRIEF DESCRIPTION OF DRAWINGS

[0060] Figure 1 The structure diagram of the light homogenization diffusion film of the present application is shown in the figure.

[0061] Figure: 1-diffusion layer; 2-light homogenization layer.

[0062] Figure 2 Schematic diagram of preparation of double bond modified poly (MMA-co-TMSP) hybrid particles. DETAILED DESCRIPTION

[0063] The technical solutions of the present application will be described below in conjunction with examples.

[0064] In the following examples, the experimental methods are conventional methods, and are performed according to the techniques or conditions described in the literature in the art or according to the product instructions, unless otherwise specified.

[0065] In the following examples, the materials, reagents, etc. used, unless otherwise specified, can be obtained commercially.

[0066] Methyl methacrylate (MMA), analytical pure, Tianjin Chemical Reagent Factory.

[0067] 3-(acryloyloxy)propyl trimethoxysilane, purity 99%, Shanghai Maikelin Biochemical Science and Technology Co., Ltd.

[0068] Schematic diagram of preparation of double bond modified poly (MMA-co-TMSP) hybrid particles is shown in the accompanying Figure 2 The specific preparation steps are as follows:

[0069] S1: Preparation of poly (MMA-co-TMSP) hybrid particles: under nitrogen protection, 8 g of polyvinylpyrrolidone (PVP) and a methanol / ethanol solvent mixture (ethanol 10 wt%, 7.94 g) were added to a 250 mL four-necked glass flask equipped with a reflux condenser and a mechanical stirrer. Then, 11.88 g of methyl methacrylate (MMA), 0.63 g of 3-acryloyloxypropyl trimethoxysilane (TMSP) and 0.06 g of azobisisobutyronitrile were added to the flask; the mixture was stirred for 20 minutes until uniform, and the polymerization reaction was carried out at 55°C under stirring at a speed of 60 revolutions / minute, for 24 hours. The obtained particles were centrifuged with methanol at 3000 revolutions / minute for 10 minutes, the operation was repeated, and the purification was carried out for five times, then the particles were freeze-dried under vacuum to obtain poly (MMA-co-TMSP) hybrid particles, and the particle size was about 5 μm;

[0070] In addition, the solvent was adjusted to methanol, and the remaining steps were unchanged to obtain poly (MMA-co-TMSP) hybrid particles with a particle size of about 3 μm.

[0071] 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 that the particles were completely dispersed, concentrated ammonia water was added to the flask to adjust the pH of the system to the alkaline range (pH 8-10), and then a mixture of tetraethoxysilane (TEOS, 1.6 g) and 3-acryloxypropyltrimethoxysilane (TMSP, 0.4 g) was slowly dropped into the flask; the sol-gel reaction was carried out at room temperature for 4 hours, and the synthesized particles were centrifuged with methanol at a speed of 3000 rpm, washed six times, and then freeze-dried under vacuum.

[0072] Conventional silicone particles: commercially available polymethylsilsesquioxane particles, Ankos NX050, average particle size 5 μm; Ankos NX030, average particle size 3 μm, respectively.

[0073] Example 1

[0074] The present application provides a light uniformity diffusion film, comprising a diffusion layer and a light uniformity layer, the diffusion layer is located on both sides of the light uniformity layer, and the corresponding structural diagram is as shown in the accompanying Figure 1 The thickness of the light uniformity diffusion film is 300 μm, the single-layer thickness of the diffusion layer is 15 μm, and the thickness of the light uniformity layer is 270 μm.

[0075] The diffusion layer comprises a first polyester resin, first diffusion particles and hybrid particles; the light uniformity layer comprises a second polyester resin, second diffusion particles, hybrid particles and an incompatible resin, and specifically, the components of each layer are as follows:

[0076] Diffusion layer (light receiving surface & adhering surface):

[0077] 3 μm poly(methyl methacrylate): 5.0 parts;

[0078] 20 μm poly(methyl methacrylate): 1.5 parts;

[0079] 5 μm double bond modified poly(MMA-co-TMSP) hybrid particles: 0.5 parts;

[0080] Polyethylene terephthalate: 93 parts.

[0081] Light uniformity layer:

[0082] 3 μm poly(methyl methacrylate): 2.5 parts;

[0083] 3 μm double bond modified poly(MMA-co-TMSP) hybrid particles: 2.4 parts;

[0084] Incompatible resin (COC): 0.1 parts;

[0085] Polyethylene terephthalate: 95 parts.

[0086] According to the components of each layer described above, a light uniformity diffusion film is prepared:

[0087] Step one, mixing

[0088] S1-1: According to the formula, the first diffusion particle, the first polyester resin, the hybrid particle are added into the stirrer in turn, the speed is 120 rpm, and the stirring time is 30 minutes, to obtain the diffusion layer (light receiving surface) mixture I;

[0089] S1-2: According to the formula, the second diffusion particle, the second polyester resin, the hybrid particle, and the incompatible resin are added into the stirrer in turn, the speed is 120 rpm, and the stirring time is 30 minutes, to obtain the light uniformity layer mixture II;

[0090] S1-3: According to the formula, the first diffusion particle, the first polyester resin, the hybrid particle are added into the stirrer in turn, the speed is 120 rpm, and the stirring time is 30 minutes, to obtain the diffusion layer (adhesion surface) mixture III.

[0091] Step two, film preparation

[0092] S2-1: Melt extrusion: the diffusion layer (light receiving surface) mixture I is added to the three-layer extruder A bin, and the A layer is melt extruded; the light uniformity layer mixture II is added to the three-layer extruder B bin, and the B layer is melt extruded; the diffusion layer (adhesion surface) mixture III is added to the three-layer extruder C bin, and the C layer is melt extruded; the melt is co-extruded through the die, and cast onto the casting roll to form a three-layer co-extruded casting sheet, and the casting roll temperature is 18℃~25℃;

[0093] S2-2: Traction and winding: the casting sheet is stretched longitudinally, the longitudinal stretching temperature is 66℃~85℃, and the longitudinal stretching ratio is 2.6~4.1; the longitudinally stretched sheet is stretched transversely, the transverse stretching temperature is 112℃~126℃, and the transverse stretching ratio is 3.8~4.8; the stretched film is shaped and cooled, the shaping temperature is 225℃~235℃, and the cooling temperature is 40℃~50℃; the cooled film is drawn and wound.

[0094] Example 2

[0095] The light uniformity diffusion film is prepared as described in Example 1, the diffusion layer formula is adjusted, and the remaining steps remain unchanged, as follows:

[0096] Diffusion layer (light receiving surface & adhesion surface):

[0097] 3μm polymethyl methacrylate: 4.0 parts;

[0098] 20μm polymethyl methacrylate: 2 parts;

[0099] 5 pm double bond modified poly (MMA-co-TMSP) hybrid particles: 1 part;

[0100] Polyethylene terephthalate: 93 parts.

[0101] Diffusion layer:

[0102] 3 pm polymethyl methacrylate: 2.5 parts;

[0103] 3 pm double bond modified poly (MMA-co-TMSP) hybrid particles: 2.4 parts;

[0104] Incompatible resin (COC): 0.1 part;

[0105] Polyethylene terephthalate: 95 parts.

[0106] Example 3

[0107] The diffusion film as described in Example 1 was adjusted in the diffusion layer formulation, and the remaining steps were kept unchanged, as follows:

[0108] Diffusion layer (light receiving surface & adhering surface):

[0109] 3 pm polymethyl methacrylate: 3.0 parts;

[0110] 20 pm polymethyl methacrylate: 2 parts;

[0111] 5 pm double bond modified poly (MMA-co-TMSP) hybrid particles: 2 parts;

[0112] Polyethylene terephthalate: 93 parts.

[0113] Diffusion layer:

[0114] 3 pm polymethyl methacrylate: 2.5 parts;

[0115] 3 pm double bond modified poly (MMA-co-TMSP) hybrid particles: 2.4 parts;

[0116] Incompatible resin (COC): 0.1 part;

[0117] Polyethylene terephthalate: 95 parts.

[0118] Example 4

[0119] The diffusion film as described in Example 1 was adjusted in the diffusion layer formulation, and the remaining steps were kept unchanged, as follows:

[0120] Diffusion layer (light receiving surface & adhering surface):

[0121] 3 pm polymethyl methacrylate: 1.0 part;

[0122] 20 pm polymethyl methacrylate: 2 parts;

[0123] 5 pm double bond modified poly(MMA-co-TMSP) hybrid particles: 4 parts;

[0124] polyethylene terephthalate: 93 parts.

[0125] light uniformity layer:

[0126] 3 pm polymethyl methacrylate: 2.5 parts;

[0127] 3 pm double bond modified poly(MMA-co-TMSP) hybrid particles: 2.4 parts;

[0128] incompatible resin (COC): 0.1 parts;

[0129] polyethylene terephthalate: 95 parts.

[0130] Example 5

[0131] The light uniformity diffusion film was prepared as described in Example 1, adjusting the formulation of the diffusion layer, and the remaining steps were kept unchanged, as follows:

[0132] diffusion layer (light receiving surface & adhering surface):

[0133] 3 pm polymethyl methacrylate: 1.0 parts;

[0134] 20 pm polymethyl methacrylate: 1.0 parts;

[0135] 5 pm double bond modified poly(MMA-co-TMSP) hybrid particles: 5 parts;

[0136] polyethylene terephthalate: 93 parts.

[0137] light uniformity layer:

[0138] 3 pm polymethyl methacrylate: 2.5 parts;

[0139] 3 pm double bond modified poly(MMA-co-TMSP) hybrid particles: 2.4 parts;

[0140] incompatible resin (COC): 0.1 parts;

[0141] polyethylene terephthalate: 95 parts.

[0142] Example 6

[0143] The light uniformity diffusion film was prepared as described in Example 3, adjusting the formulation of the light uniformity layer, and the remaining steps were kept unchanged, as follows:

[0144] Diffusion layer (light incident & attachment surface):

[0145] 3 μιη PMMA: 3.0 parts;

[0146] 20 μιη PMMA: 2 parts;

[0147] 5 μιη double-bond modified poly(MMA-co-TMSP) hybrid particles: 2 parts;

[0148] Polyethylene terephthalate: 93 parts.

[0149] Uniform light layer:

[0150] 3 μιη PMMA: 1.5 parts;

[0151] 3 μιη double-bond modified poly(MMA-co-TMSP) hybrid particles: 3.4 parts;

[0152] Immiscible resin (COC): 0.1 parts;

[0153] Polyethylene terephthalate: 95 parts.

[0154] Example 7

[0155] The uniform light diffusion film as described in Example 6 was adjusted in the uniform light layer formulation, and the remaining steps were kept unchanged, as follows:

[0156] Diffusion layer (light incident & attachment surface):

[0157] 3 μιη PMMA: 3.0 parts;

[0158] 20 μιη PMMA: 2 parts;

[0159] 5 μιη double-bond modified poly(MMA-co-TMSP) hybrid particles: 2 parts;

[0160] Polyethylene terephthalate: 93 parts.

[0161] Uniform light layer:

[0162] 3 μιη PMMA: 3 parts;

[0163] 3 μιη double-bond modified poly(MMA-co-TMSP) hybrid particles: 1.9 parts;

[0164] Immiscible resin (COC): 0.1 parts;

[0165] Polyethylene terephthalate: 95 parts.

[0166] Example 8

[0167] The light-uniform diffusion film was prepared as described in Example 6, the light-uniform layer formulation was adjusted, and the remaining steps were kept unchanged, specifically as follows:

[0168] Diffusion layer (light-incident surface & adhering surface):

[0169] 3 μm polymethyl methacrylate: 3.0 parts;

[0170] 20 μm polymethyl methacrylate: 2 parts;

[0171] 5 μm double-bond modified poly (MMA-co-TMSP) hybrid particles: 2 parts;

[0172] Polyethylene terephthalate glycol: 93 parts.

[0173] Light-uniform layer:

[0174] 3 μm polymethyl methacrylate: 2 parts;

[0175] 3 μm double-bond modified poly (MMA-co-TMSP) hybrid particles: 2.8 parts;

[0176] Incompatible resin (COC): 0.1 part;

[0177] Polyethylene terephthalate glycol: 95 parts.

[0178] Example 9

[0179] The light-uniform diffusion film was prepared as described in Example 6, the light-uniform layer formulation was adjusted, and the remaining steps were kept unchanged, specifically as follows:

[0180] Diffusion layer (light-incident surface & adhering surface):

[0181] 3 μm polymethyl methacrylate: 3.0 parts;

[0182] 20 μm polymethyl methacrylate: 2 parts;

[0183] 5 μm double-bond modified poly (MMA-co-TMSP) hybrid particles: 2 parts;

[0184] Polyethylene terephthalate glycol: 93 parts.

[0185] Light-uniform layer:

[0186] 3 μm polymethyl methacrylate: 1.5 parts;

[0187] 3 μm double-bond modified poly (MMA-co-TMSP) hybrid particles: 2.4 parts;

[0188] Incompatible resin (COC): 2 parts;

[0189] Polyethylene terephthalate glycol: 95 parts.

[0190] Example 10

[0191] The light uniformity diffusion film was prepared as described in Example 1, adjusting the formulation of each layer, and the remaining steps were kept unchanged, as follows:

[0192] Diffusion layer (light-incident surface):

[0193] 3 μm polymethyl methacrylate: 4.0 parts;

[0194] 20 μm polymethyl methacrylate: 2.5 parts;

[0195] 5 μm double bond modified poly (MMA-co-TMSP) hybrid particles: 0.5 parts;

[0196] Polyethylene terephthalate: 93 parts.

[0197] Diffusion layer (adhesion surface):

[0198] 3 μm polymethyl methacrylate: 0 parts;

[0199] 10 μm polymethyl methacrylate: 0.5 parts;

[0200] 5 μm double bond modified poly (MMA-co-TMSP) hybrid particles: 0.5 parts;

[0201] Polyethylene terephthalate: 99 parts.

[0202] Light uniformity layer:

[0203] 3 μm polymethyl methacrylate: 1.5 parts;

[0204] 3 μm double bond modified poly (MMA-co-TMSP) hybrid particles: 0.4 parts;

[0205] Incompatible resin (COC): 0.1 parts;

[0206] Polyethylene terephthalate: 98 parts.

[0207] Example 11

[0208] The light uniformity diffusion film was prepared as described in Example 10, adjusting the formulation of the diffusion layer (adhesion surface) and the light uniformity layer, and the remaining steps were kept unchanged, as follows:

[0209] Diffusion layer (light-incident surface):

[0210] 3 μm polymethyl methacrylate: 4.0 parts;

[0211] 20 μm polymethyl methacrylate: 2.5 parts;

[0212] 5 μm double-bond modified poly(MMA-co-TMSP) hybrid particles: 0.5 parts;

[0213] Polyethylene terephthalate: 93 parts.

[0214] Diffusion layer (light-incident surface & attachment surface):

[0215] 3 μm poly(methyl methacrylate): 0.8 parts;

[0216] 10 μm poly(methyl methacrylate): 0.2 parts;

[0217] 5 μm double-bond modified poly(MMA-co-TMSP) hybrid particles: 1 part;

[0218] Polyethylene terephthalate: 98 parts.

[0219] Diffusion layer:

[0220] 3 μm poly(methyl methacrylate): 2.5 parts;

[0221] 3 μm double-bond modified poly(MMA-co-TMSP) hybrid particles: 2.4 parts;

[0222] Incompatible resin (COC): 0.1 part;

[0223] Polyethylene terephthalate: 95 parts.

[0224] Comparative Example 1

[0225] The diffusion film for light homogenization was prepared as described in Example 3, except that no hybrid particles were added to the light homogenization layer, and the remaining steps were kept unchanged, as follows:

[0226] Diffusion layer (light-incident surface & attachment surface):

[0227] 3 μm poly(methyl methacrylate): 3 parts;

[0228] 20 μm poly(methyl methacrylate): 2 parts;

[0229] 5 μm double-bond modified poly(MMA-co-TMSP) hybrid particles: 2 parts;

[0230] Polyethylene terephthalate: 93 parts.

[0231] Diffusion layer:

[0232] 3 μm poly(methyl methacrylate): 4.9 parts;

[0233] 3 μm double-bond modified poly(MMA-co-TMSP) hybrid particles: 0 parts;

[0234] Incompatible resin (COC): 0.1 part;

[0235] Polyethylene terephthalate: 95 parts.

[0236] Comparative Example 2

[0237] 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:

[0238] Diffusion layer (light-incident surface & adhering surface):

[0239] 3 μιη polymethyl methacrylate: 5 parts;

[0240] 20 μιη polymethyl methacrylate: 2 parts;

[0241] 5 μιη double-bond modified poly(MMA-co-TMSP) hybrid particles: 0 parts;

[0242] Polyethylene terephthalate: 93 parts.

[0243] Light-uniform layer:

[0244] 3 μιη polymethyl methacrylate: 2.5 parts;

[0245] 3 μιη double-bond modified poly(MMA-co-TMSP) hybrid particles: 2.4 parts;

[0246] Incompatible resin (COC): 0.1 parts;

[0247] Polyethylene terephthalate: 95 parts.

[0248] Comparative Example 3

[0249] 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:

[0250] Diffusion layer (light-incident surface & adhering surface):

[0251] 3 μιη polymethyl methacrylate: 4 parts;

[0252] 20 μιη polymethyl methacrylate: 3 parts;

[0253] 5 μιη double-bond modified poly(MMA-co-TMSP) hybrid particles: 0 parts;

[0254] Polyethylene terephthalate: 93 parts.

[0255] Light-uniform layer:

[0256] 3 μιη polymethyl methacrylate: 4.9 parts;

[0257] 3 pm double bond modified poly(MMA-co-TMSP) hybrid particles: 0 parts;

[0258] Incompatible resin (COC): 0.1 parts;

[0259] Polyethylene terephthalate: 95 parts.

[0260] Comparative Example 4

[0261] 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:

[0262] Diffusion layer (light-incident surface & adhering surface):

[0263] 3 pm poly(methyl methacrylate): 3 parts;

[0264] 20 pm poly(methyl methacrylate): 2 parts;

[0265] 5 pm silicone particles (polymethylsilsesquioxane): 2 parts;

[0266] Polyethylene terephthalate: 93 parts.

[0267] Light-uniform layer:

[0268] 3 pm poly(methyl methacrylate): 2.5 parts;

[0269] 3 pm double bond modified poly(MMA-co-TMSP) hybrid particles: 2.5 parts;

[0270] Incompatible resin (COC): 0 parts;

[0271] Polyethylene terephthalate: 95 parts.

[0272] Comparative Example 5

[0273] The light-uniform diffusion film was prepared as described in Example 3, except that the double bond modified poly(MMA-co-TMSP) hybrid particles were replaced with conventional silicone particles, and the remaining steps were unchanged, as follows:

[0274] Diffusion layer (light-incident surface & adhering surface):

[0275] 3 pm poly(methyl methacrylate): 3 parts;

[0276] 20 pm poly(methyl methacrylate): 2 parts;

[0277] 5 pm silicone particles (polymethylsilsesquioxane): 2 parts;

[0278] Polyethylene terephthalate: 93 parts.

[0279] Light-uniform layer:

[0280] 3 μm polymethyl methacrylate: 4.9 parts;

[0281] 3 μm silicone particles (polymethylsilsesquioxane): 0 parts;

[0282] Incompatible resin (COC): 0.1 parts;

[0283] Polyethylene terephthalate: 95 parts.

[0284] The performance of the light-uniform diffusion films obtained in Examples 1-11 and Comparative Examples 1-5 above was characterized:

[0285] (1) Brightness and brightness uniformity: The average brightness and brightness uniformity of the obtained sample 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;

[0286] (2) Light transmittance and haze: The haze and light 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";

[0287] (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.

[0288] The performance characterization results of the light-uniform diffusion films obtained in Examples 1-11 and Comparative Examples 1-5 are shown in Table 1.

[0289] Table 1 Performance characterization results of light-uniform diffusion films obtained in Examples 1-11 and Comparative Examples 1-5

[0290]

[0291] Examples 1-5 investigated the performance of the light-uniform diffusion films obtained by different ratios of hybrid particles and polymethyl methacrylate particles with different particle sizes, in which the proportion of double bond modified poly(MMA-co-TMSP) hybrid particles gradually increased. Examples 6-9 investigated the performance of the light-uniform diffusion films obtained by different ratios of hybrid particles and polymethyl methacrylate particles in the light-uniform layer, while Examples 10 and 11 were light-uniform diffusion films obtained by different formulations on the light-incident surface and the bonding surface of the diffusion layer. As can be seen from the data in Table 1, Examples 1-11 exhibited better overall performance than Comparative Examples 1-5, especially the optimization of light transmittance and haze, with haze > 90% and light transmittance maintained above 40%. At the same time, they exhibited good light-uniform effect, especially the brightness uniformity of Examples 4, 5, 6 and 8 was greater than 98%.

[0292] From the comparison of Example 3 and Comparative Examples 1-3 and Comparative Example 5, it can be seen that 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 double bond modified poly(MMA-co-TMSP) hybrid particles. On the one hand, poly(MMA-co-TMSP) hybrid particles are obtained by polymerization of acrylate monomers and silane coupling agents. The material itself has better compatibility with 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 poly(MMA-co-TMSP) hybrid particles provides a site for chemical bonding between the particles and the polyester, further promoting particle dispersion and improving the mechanical properties of the film.

[0293] In addition, the comparison of Example 3 and Comparative Example 4 shows that the addition of incompatible resins can significantly improve the film haze by synergistic effect of particles and cells, making the film material have higher light transmittance while effectively improving its haze performance, and further improving the light uniformity of the film. However, the comparison of Example 9 and Example 3 and Comparative Example 4 shows that too much amount of incompatible resins will affect the light transmittance of the film.

Claims

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

2. The light-uniformizing diffusion film according to claim 1, wherein The double bond modified polymer / silica hybrid microparticle preparation step comprises: dispersing the monodisperse polymer / silica hybrid microparticles in a mixed solution of methanol and water in a reaction vessel, and ultrasonic treatment to ensure complete dispersion, then adding NH4OH solution into the flask, and slowly dropping a mixture of tetraethoxysilane and silane coupling agent into the reaction vessel, and reacting at room temperature for 3-5 hours, and centrifuging, washing and freeze-drying under vacuum to obtain.

3. The light-uniformizing diffusion film according to claim 2, wherein The monodisperse polymer / silica hybrid microparticle preparation step comprises: under a nitrogen atmosphere, adding a stabilizer and a solvent into a reaction vessel, then adding acrylate monomers, silane coupling agents and initiators, controlling the reaction temperature to be 50-60°C, and performing a polymerization reaction at a stirring speed of 50-70 rpm for 22-26 hours; finally, centrifuging, purifying and freeze-drying under vacuum to obtain the microparticles.

4. The light-uniformizing diffusion film according to claim 3, wherein The stabilizer is polyvinylpyrrolidone or sodium polystyrene sulfonate; the initiator is any one of azobisisobutyronitrile, azobisisoheptyl nitrile and dimethyl azobisisobutyrate; and the solvent is methanol or ethanol, or a mixture of methanol / deionized water or a mixture of methanol / ethanol.

5. The light-uniformizing diffusion film according to claim 3, wherein The amount of the acrylate monomers is 11-13 wt% based on the total amount of the acrylate monomers, silane coupling agents, initiators and solvents; the amount of the silane coupling agents is 0.6-0.7 wt%; the amount of the initiators is 0.05-0.07 wt%; the amount of the stabilizer is 7.0-9.0 wt% of the total amount of the acrylate monomers and silane coupling agents; the amount of the monodisperse polymer / silica hybrid microparticles and the mixture of tetraethoxysilane and silane coupling agents is 1:1 by mass; the amount of the mixture of tetraethoxysilane and silane coupling agents is 3-5:1 by mass of tetraethoxysilane:silane coupling agent; and the ratio of the mixed solution of methanol and water is 6-8:3 by mass of methanol:water.

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

7. The light-uniformizing diffusion film according to claim 6, wherein The first or second polyester resin comprises at least one of polyethylene terephthalate, polybutylene terephthalate; the first or second diffusion particle comprises at least one of polymethyl methacrylate, silicon dioxide, calcium carbonate, titanium dioxide, barium sulfate; the average particle size of the first diffusion particle is distributed in 3-20 μm, and the average particle size of the second diffusion particle is distributed in 2-5 μm; the incompatible resin is a polyolefin resin, comprising at least one of polypropylene, polymethyl pentene, cyclic polyolefin.

8. The preparation method of a uniform light diffusion film according to any one of claims 1-7, characterized in that, The preparation steps include: Step one, mixing: S1-1: according to the formula, the first diffusion particle, the first polyester resin, and the hybrid particle are sequentially added to the stirrer, and uniformly stirred to obtain the light-incident surface diffusion layer mixture I; S1-2: according to the formula, the second diffusion particle, the hybrid particle, the second polyester resin, and the incompatible resin are sequentially added to the stirrer and uniformly stirred to obtain the light-uniform layer mixture II; S1-3: according to the formula, the first diffusion particle, the first polyester resin, and the hybrid particle are sequentially added to the stirrer and uniformly stirred to obtain the adhesion surface diffusion layer mixture III; Step two, film preparation: S2-1: melt extrusion: the light-incident surface diffusion layer mixture I is added to the three-layer extruder A bin, and the A layer is melt extruded; the light-uniform layer mixture II is added to the three-layer extruder B bin, and the B layer is melt extruded; the adhesion surface diffusion layer mixture III is added to the three-layer extruder C bin, and the C layer is melt extruded; the melt is co-extruded through the die, and cast onto the casting roll to form a three-layer co-extruded casting sheet, and the casting roll temperature is 18-25℃; S2-2: traction and winding: the casting sheet is longitudinally stretched, transversely stretched, shaped, cooled, pulled and wound to obtain the product.

9. The method of claim 8, wherein the light uniformity diffusion film is prepared by coating a solution of the light uniformity diffusion film on a substrate and drying the solution. 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 shaping temperature is 225-235℃, and the cooling temperature is 40-50℃.

10. Use of a uniform light diffusion film according to any one of claims 1 to 7, characterized in that, The light-uniform diffusion film can be applied to the backlight module, LED lighting, and vehicle display field.

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