Composite optical film with polarization function, preparation method and application thereof

Abstract

The present invention discloses a composite optical film with polarization function, a preparation method, and its application. The composite optical film comprises a transparent substrate layer, and a buffer layer, an oriented calcite crystal layer, and an anti-reflection layer stacked on one side of the transparent substrate layer. The oriented calcite crystal layer is obtained by coating a suspension of a superparamagnetic modified calcite crystal composite material on the surface of the buffer layer, inducing optical axis alignment through a magnetic field, and then UV curing. The buffer layer is obtained by co-extruding a mixture of a cycloolefin polymer and a polyurethane acrylate to form a transitional thermal expansion coefficient system. The anti-reflection layer is composed of nanoporous titanium dioxide with a refractive index gradient varying from 1.8 to 2.3, forming a refractive index gradient structure. The composite optical film is designed with a polarization function layer in which magnetic field-induced calcite nanocrystals are aligned, and combined with a gradient refractive index scattering layer, to improve the polarization efficiency and light transmittance of the composite optical film and enhance its industrial stability.

Description

Technical Field

[0001] The present invention relates to the technical field of optical functional films, and in particular to a composite optical film with polarization function, a preparation method and applications thereof. Background Art

[0002] Polarizing optical films are core components of display technologies such as liquid crystal displays (LCDs) and organic light-emitting diodes (OLEDs). Their performance directly impacts screen contrast, viewing angle, and energy efficiency. Currently, mainstream polarizing film technologies can be categorized into three types: iodine-based, dye-based, and reflective polarizing films. However, these technologies still face numerous bottlenecks in industrial application.

[0003] For example, an iodine-based polarizing film realizes polarization function by adsorbing iodine ions into a stretched polyvinyl alcohol (PVA) film. As disclosed in the invention with publication number CN110824604A, a polarizer and an OLED display device are disclosed. The polarizer includes a substrate and a first adhesive, a crystal wave plate, a second adhesive, an iodine-containing resin and a first protective film sequentially stacked on the substrate. However, it has the following disadvantages: environmental sensitivity: iodine-PVA composites are prone to ion migration in high temperature and high humidity (85°C / 85%RH) environments, resulting in polarization attenuation (experiments show that the polarization loss is >10% after 1000 h of aging), and edge deiodination is prone to occur after long-term use; in addition, the process is highly complex, and multi-layer composites with triacetyl cellulose (TAC) as a protective layer are required (the typical structure is TAC-PVA-TAC), which leads to increased thickness (total thickness ≥120 μm) and reduced transmittance (typical value is about 43%), making it difficult to meet the needs of ultra-thin flexible displays; moreover, it has strong wavelength dependence, the polarization efficiency in the blue light band (450 nm) can reach 94%, but the efficiency in the red light (630 nm) is only 70%-75%, resulting in display color deviation problems.

[0004] Dye-based polarizing films use dichroic dyes instead of iodine. Although this improves moisture and heat resistance, it has the following problems: for example, absorption loss. The dye's absorption rate of non-polarized light is as high as 25%-30%, resulting in energy waste (the backlight module needs to increase brightness compensation), and the transmittance is generally less than 50%; there is also the issue of material cost. High-purity dichroic dyes (such as azobenzene derivatives) are expensive (about US$200-300 / kg), and the synthesis process involves heavy metal catalysts, which faces environmental compliance risks.

[0005] Reflective polarizing films, such as 3M's DBEF (multi-layer birefringent film stack), improve light utilization by selectively reflecting non-polarized light. However, they require dozens of polymer layers to be alternately stacked (total thickness >150μm) and require extremely high processing precision (layer thickness deviation must be <10 nm), resulting in a surge in equipment investment and production costs. Summary of the Invention

[0006] In view of the above problems, the present invention discloses a composite optical film with polarization function, a preparation method and its application. By designing a polarization functional layer with directional arrangement of calcite nanocrystals induced by a magnetic field and combining it with a gradient refractive index scattering layer, the polarization efficiency and transmittance of the composite optical film are improved, and the industrial stability is enhanced.

[0007] The present invention is achieved through the following technical solutions.

[0008] On the one hand, a composite optical film with polarization function includes a transparent substrate layer, and a buffer layer, an oriented calcite crystal layer and an anti-reflection layer stacked on one side of the transparent substrate layer; wherein the buffer layer includes a transition layer and a functional layer.

[0009] The transparent substrate layer is made of a composite of one or more of polyethylene terephthalate (PET), cycloolefin polymer (COC / COP) or polyimide (PI), and has a thickness of 10 μm to 200 μm.

[0010] In some embodiments of the present invention, the transparent substrate layer is made of high-temperature resistant PET (thickness 20 μm, Tg = 120°C), and a microprism array (period 20 μm, depth 5 μm) is prefabricated on its surface by nanoimprinting, which improves the transmittance while dissipating thermal stress (FE simulation shows that the maximum principal stress at 85°C is reduced by 68%).

[0011] The buffer layer is a mixture of cycloolefin polymer and polyurethane acrylate, wherein the mass fraction of the cycloolefin polymer is 50% to 90%; the thermal expansion coefficient (CTE) of the buffer layer is 30×10 -6 / ℃ to 70×10 -6 / ℃, thickness is 10μm to 50μm.

[0012] The buffer layer includes a transition layer and a functional layer. The transition layer is arranged on one side of the substrate layer and has a thickness of 6 μm to 30 μm. The functional layer is arranged on the side close to the oriented calcite crystal layer and has a thickness of 4 μm to 20 μm.

[0013] The buffer layer is combined with the substrate layer through a co-extrusion process, wherein the co-extrusion temperature is 80° C. to 200° C. and the pressure is 10 MPa to 30 MPa.

[0014] In some embodiments of the present invention, a cyclic olefin copolymer is introduced as a buffer layer at the interface of the oriented calcite crystal layer / PET transparent substrate layer to form a PET (70×10 -6 / ℃)-COC(CTE=35×10 -6 / ℃)-PUA (45×10 -6 / ℃) thermal expansion coefficient transition system; the interlayer peeling force of the obtained composite optical film decreased by 7% after thermal cycling (-40~85℃, 1000 times), and the warpage curvature was <1m -1 .

[0015] In some embodiments of the present invention, a cyclic olefin homopolymer is introduced as a buffer layer at the interface of the oriented calcite crystal layer / COP transparent substrate layer to form a COP (60×10 -6 / ℃)-COP / PUA (COP / PUA=7:3, CTE=45×10 -6 / ℃)-PUA (38×10 -6 / ℃) thermal expansion coefficient transition system; the interlayer peeling force of the obtained composite optical film decreased by 6% after thermal cycling (-40~85℃, 1000 times), and the warpage curvature was <1.1 m -1 .

[0016] The thickness of the oriented calcite crystal layer is 5 μm to 50 μm, and the standard deviation σ of the crystal axis orientation angle is ≤3°.

[0017] Furthermore, the oriented calcite crystal layer is obtained by coating a suspension of a superparamagnetic modified calcite crystal composite material on the surface of the buffer layer, inducing optical axis alignment through a magnetic field, and then UV curing;

[0018] Furthermore, the superparamagnetic modified calcite crystal composite material suspension is formed by dispersing the superparamagnetic modified calcite crystal composite material in a UV curable resin, and the solid content of the suspension is 10 wt % to 20 wt %.

[0019] In some embodiments of the present invention, the superparamagnetic modified calcite crystal composite material is obtained by using a silane coupling agent to covalently graft SiO2@Fe3O4 magnetic composite particles onto the surface of nanocalcite to obtain a SiO2@Fe3O4-calcite magnetic composite material, which gives the nanocalcite superparamagnetism and provides a physical driving force for subsequent magnetic field orientation.

[0020] The SiO2@Fe3O4 magnetic composite particles are composed of a Fe3O4 core and a SiO2 coating layer;

[0021] Preferably, the particle size of the Fe3O4 core is 10nm to 20nm, and the thickness of the SiO2 coating layer is 2nm to 5nm;

[0022] In the SiO2@Fe3O4 magnetic composite particles, the porosity of the SiO2 coating layer is 10% to 30%, and the magnetic saturation intensity of Fe3O4 is 80emu / g to 90emu / g.

[0023] In some embodiments of the present invention, the superparamagnetic modified calcite crystal composite material is obtained by covalently grafting unmodified Fe3O4-doped SiO2 (SiO2 / Fe3O4) magnetic composite particles onto the surface of nanocalcite using a silane coupling agent, thereby imparting superparamagnetism to the nanocalcite and providing a physical driving force for subsequent magnetic field orientation.

[0024] Preferably, the unmodified Fe3O4 is doped with SiO2 in an amount of 3at% (corresponding to an actual Fe3O4 content of about 2.1wt%), and is prepared by in-situ doping by magnetron sputtering.

[0025] The silane coupling agent is at least one of aminosilane, epoxysilane or methacryloxysilane; the silane coupling agent and nano-calcite are subjected to ultrasonic treatment for 1 to 3 hours to complete a coupling reaction to obtain silane coupling agent-modified nano-calcite, and the ultrasonic power is 50W to 150W.

[0026] Preferably, the silane coupling agent modified nano-calcite is prepared by reacting a nano-calcite suspension with a silane coupling agent (volume concentration 5%) under reflux conditions at 80° C. for 1 to 3 hours to form a stable surface functionalization layer.

[0027] The nano-calcite suspension is obtained by wet grinding process optimization, acid etching and surface activation;

[0028] Furthermore, the wet grinding process optimization is to use a high-energy ball mill under the protection of inert gas (nitrogen), using zirconia grinding balls (diameter 0.8-1.2 mm) and anhydrous ethanol as the medium, controlling the ball-to-material mass ratio to 15:1, the rotation speed to 450 rpm, and the grinding time to 12 hours to achieve nano-size of calcite crystals;

[0029] Furthermore, the optimized wet grinding process using ethanol as the medium can effectively reduce the lattice distortion caused by the thermal effect, and the lattice strain is reduced from 0.35% in the traditional dry grinding method to 0.12%.

[0030] The nano-calcite has a particle size of 150 nm to 300 nm and a purity of ≥99%; preferably, the nano-calcite has a particle size D50 of 200-250 nm.

[0031] Furthermore, the acid etching and surface activation refers to adjusting the pH of the nanocalcite suspension obtained by optimizing the wet grinding process to 4.5-5.0 with 0.1 M HCl, and then ultrasonically treating it (40 kHz, power 300 W) for 1 hour to selectively dissolve the surface amorphous area and expose the highly active crystal surface.

[0032] Furthermore, the amount of the silane coupling agent is 1 wt% to 5 wt% of the total mass of the nano-calcite and the SiO2@Fe3O4 or SiO2 / Fe3O4 magnetic composite particles;

[0033] The mass ratio of the nano-calcite to the SiO2@Fe3O4 or SiO2 / Fe3O4 magnetic composite particles is 5:1 to 15:1.

[0034] The magnetic field-induced optical axis orientation arrangement refers to aligning the superparamagnetic modified calcite crystal composite material in a magnetic field of 0.5T to 1.0T, with a standard deviation σ of the crystal axis orientation angle being ≤3°.

[0035] The magnetic field-induced optical axis alignment specifically includes: using a Helmholtz coil to generate a uniform transverse magnetic field (intensity 0.5-1.0 T, direction parallel to the film surface), combined with a temperature gradient (25-60°C) to reduce the resin viscosity (from 1200 mPa•s to 200 mPa•s), thereby promoting the orderly alignment of calcite crystals along the magnetic field direction; using an in-situ polarizing microscope (wavelength 632 nm) to monitor the crystal orientation angle distribution online to ensure that the optical axis deviation is ≤5° (statistical standard deviation σ = 2.3°);

[0036] Specifically, the magnetic field-induced optical axis directional arrangement process includes magnetic field design: gradient arrangement of permanent magnet array (magnetic field strength: 0.8 T at the center → 0.3 T at the edge); dynamic adjustment, when the coating area moves, the magnetic field strength automatically adapts according to the position, which is achieved through a programmable logic controller (PLC control); the resin is preheated to 40°C (viscosity reduced to 1000 mPa•s), and the temperature gradient during the curing process is reduced to 25°C; finally, UV segmented curing: 10 mW / cm² in the front section (pre-locking orientation) and 80 mW / cm² in the back section (deep cross-linking).

[0037] The resulting composite optical film has an edge orientation angle of σ=2.8° (σ=1.9° in the center area); full-width polarization uniformity is >98.5% (edge ​​and center efficiency difference is <0.3%); and energy consumption is reduced by 35% (compared with a uniform magnetic field).

[0038] The UV curable resin is selected from polyurethane acrylate, epoxy acrylate or a copolymer thereof.

[0039] In some embodiments of the present invention, the UV curable resin is polyurethane acrylate (PUA, refractive index n=1.56), which matches the refractive index of calcite and PET substrate (Δn<0.05) to reduce interface reflection loss.

[0040] The UV curing uses low-intensity UV irradiation (10 mW / cm²) in the initial stage to form a partially cross-linked network to maintain orientation stability; subsequently, high-intensity (50 mW / cm²) rapid curing is used to form a dense polarization functional layer; the dense polarization functional layer is an oriented calcite crystal layer, and the corresponding SEM is shown in the attached figure. Figure 4 shown.

[0041] Preferably, the UV curing, DSC analysis shows that the crosslinking degree reaches 92% to ensure mechanical strength (elastic modulus 2.1 GPa, elongation at break 18%).

[0042] The anti-reflection layer is a TiO2 scattering layer, which is composed of nanoporous titanium dioxide with a refractive index gradient ranging from 1.8 to 2.3, the particle size of the nanoporous titanium dioxide is 50nm to 200nm, and the thickness of the anti-reflection layer is 2 to 10 μm;

[0043] Furthermore, the anti-reflection layer is a gradient porosity TiO2 layer;

[0044] Furthermore, the anti-reflection layer is prepared by a sol-gel method on the surface of an oriented calcite crystal layer using a TiO2 porous film, and the porosity is regulated (bottom 15% → top 5%) by a template (polystyrene (PS) microspheres, 500 nm in diameter) to form a refractive index gradient structure.

[0045] Furthermore, the anti-reflection layer corrects the effective optical path difference of 30° incident light after passing through the scattering layer to ±10 nm (originally ±35 nm), and the polarization attenuation rate is reduced from 6.2% to 0.5%. Through optical waveguide simulation, the average reflectivity in the 400-700 nm range is reduced from 8.5% to 2.8%.

[0046] On the other hand, a method for preparing a composite optical film with polarization function specifically comprises the following steps:

[0047] Step 1: Preparation of superparamagnetic modified calcite crystal composite material

[0048] (1) Silane coupling agent modified calcite

[0049] S1: Preparation of nano-calcite suspension: Natural calcite is subjected to wet grinding process optimization, acid etching and surface activation to obtain nano-calcite suspension; the specific steps include:

[0050] S1-1: Wet grinding process optimization: Using a high-energy ball mill under nitrogen protection, using zirconia grinding balls with diameters of 0.8 mm to 1.2 mm and anhydrous ethanol as the medium, with a ball-to-material mass ratio of 15:1, a rotation speed of 450 rpm, and a grinding time of 12 hours, the particle size was adjusted to 150 nm to 300 nm to obtain nanocalcite crystals;

[0051] S1-2: Acid etching and surface activation: In the wet grinding process optimization system of step S1-1, the pH was adjusted to 4.5 to 5.0 with 0.1 M HCl, and then ultrasonicated (40 kHz, power 300 W) for 1 hour to obtain a nanocalcite suspension;

[0052] S2: Silane coupling agent modification: adding a silane coupling agent to the nano-calcite suspension reaction system obtained in the above step under reflux conditions at 80°C, and continuing ultrasonic treatment for 1 to 3 hours at an ultrasonic power of 50W to 150W to obtain silane coupling agent-modified nano-calcite;

[0053] The silane coupling agent is at least one of aminosilane, epoxysilane or methacryloxysilane.

[0054] (2) Preparation of superparamagnetic modified calcite crystal composite materials:

[0055] (2-1) Preparation of SiO2@Fe3O4-calcite magnetic composite materials:

[0056] S1: Preparation of SiO2@Fe3O4 magnetic composite particles by sol-gel method: First, Fe3O4 colloidal aqueous solution is prepared, Fe3O4 nanoparticles are dispersed in deionized water, and the particles are evenly dispersed in the medium by ultrasonic dispersion to form a uniform and stable colloidal solution; while stirring continuously, a certain amount of ethanol, Fe3O4 colloid, deionized water and TEOS are added to the beaker in sequence, and the concentration of Fe3O4 in the reaction system is controlled to be 0.2-0.3 mg / mL and the concentration of TEOS is controlled to be 0.02-0.03 mol / L; then concentrated ammonia is added to catalyze the hydrolysis and condensation of TEOS, and the concentration of concentrated ammonia in the reaction system is regulated to be 0.4-0.5 mol / L. After the reaction is sealed for 6 hours, the product is centrifuged and washed several times with ethanol and deionized water respectively to obtain SiO2@Fe3O4 magnetic composite particles;

[0057] The amount of ethanol and deionized water, by volume ratio, V 乙醇 :V 去离子水 =4:1;

[0058] S2: Preparation of SiO2@Fe3O4-calcite magnetic composite material: Silane coupling agent-modified nano-calcite powder was ultrasonically dispersed in ethanol (concentration of 2 mg / mL to 8 mg / mL), and then SiO2@Fe3O4 magnetic composite particles were added. The reaction was continued for 1 to 3 hours while stirring to obtain SiO2@Fe3O4-calcite magnetic composite material;

[0059] (2-2) Preparation of SiO2 / Fe3O4-calcite magnetic composite materials:

[0060] S1: Target selection: high-purity SiO2 target (99.99%) and Fe3O4 target (99.9%) are used, and a composite sputtering target is configured according to a 3at% Fe3O4 doping ratio (corresponding to 2.1wt%);

[0061] S2: Substrate preparation: Silane coupling agent-modified nanocalcite powder was ultrasonically dispersed in ethanol (concentration 5 mg / mL) and spin-coated on a silicon wafer substrate to form a monolayer particle film (thickness ~200 nm). The substrate was then treated with Ar plasma for 5 minutes (power 50 W) to enhance the surface activity of the particles.

[0062] S3: magnetron sputtering deposition, through co-sputtering, Fe3O4 is uniformly dispersed in the SiO2 matrix at the atomic level; magnetron sputtering conditions: vacuum ≤ 5×10 -4 Pa; working gas: high-purity Ar (99.999%), flow rate: 20 sccm, pressure: 0.8 Pa; sputtering power: SiO2 target (radio frequency (RF) 150 W), power density: 3 W / cm²; Fe3O4 target (direct current (DC) power supply), 30 W; substrate temperature: 80°C; deposition time: 30 min;

[0063] S4: Annealing at 300-400°C in a nitrogen atmosphere for 1-2 hours to eliminate sputtering stress and enhance the crystallinity of the SiO2 / Fe3O4 composite particles;

[0064] S5: The composite particles on the substrate are ultrasonically peeled off, and after centrifugal cleaning, they are dispersed in ethanol to obtain a suspension, and finally dried to obtain a SiO2 / Fe3O4-calcite composite material.

[0065] Preferably, the amount of the silane coupling agent is 1 wt% to 5 wt% of the total mass of the nano-calcite and SiO2@Fe3O4 or Fe3O4 / SiO2 magnetic composite particles;

[0066] Preferably, the amount of the nano-calcite and SiO2@Fe3O4 or SiO2 / Fe3O4 magnetic composite particles is in a mass ratio of 5:1 to 15:1;

[0067] The Fe3O4 nanoparticles have a particle size of 10 nm to 20 nm and a magnetic saturation intensity of 80 emu / g to 90 emu / g.

[0068] Step 2: Preparation of composite optical film with polarization function

[0069] (1) Preparation of superparamagnetic modified calcite crystal composite suspension

[0070] Dispersing the superparamagnetic modified calcite crystal composite material in a UV curable resin to form a suspension having a solid content of 10 wt % to 20 wt %;

[0071] The UV curable resin is selected from polyurethane acrylate, epoxy acrylate or a copolymer of the two;

[0072] (2) Preparation of composite optical films with polarization function

[0073] S1: Buffer layer setting

[0074] According to the formula, a buffer layer is provided on one surface of the substrate layer by a co-extrusion process with a thickness of 10 to 50 μm; the co-extrusion temperature is 80° C. to 200° C., and the pressure is 10 MPa to 30 MPa;

[0075] Transparent substrate layer: Made of one or more composite materials selected from polyethylene terephthalate (PET), cycloolefin polymer (COC / COP), or polyimide (PI); with a thickness of 10 μm to 200 μm;

[0076] Buffer layer: includes a transition layer and a functional layer; the transition layer is close to the transparent substrate layer; the functional layer is close to the oriented calcite crystal layer; the buffer layer is made of a mixture of cycloolefin polymer and polyurethane acrylate, wherein the mass fraction of cycloolefin polymer is 50% to 90%; the thermal expansion coefficient (CTE) of the buffer layer is 30×10 -6 / ℃ to 70×10 -6 / ℃, thickness is 10μm to 50μm;

[0077] Specifically, the transition layer has a thickness of 6 to 30 μm and is made of any one of COC, COP, or a mixture of COC / PUA or COP / PUA. The functional layer has a thickness of 4 to 20 μm and is made of pure PUA (CTE = 38 × 10 -6 / ℃); through a three-channel co-extrusion die head, gradient temperature control: from 200℃ for the substrate layer to 80℃ for the functional layer, and a pressure of 20 MPa; online infrared temperature measurement controls the interlayer bonding state (temperature difference <5℃) to obtain a composite membrane layer structure.

[0078] In some embodiments of the present invention, the transparent substrate layer is made of high-temperature resistant PET (thickness 20 μm, Tg=120°C), and a microprism array (period 20 μm, depth 5 μm) is prefabricated on its surface by nanoimprinting.

[0079] S2: Oriented calcite crystal layer setup

[0080] S2-1: applying a suspension of superparamagnetic modified calcite crystal composite material on the surface of the buffer layer to form a wet film;

[0081] S2-2: applying a gradient magnetic field to the wet film, wherein the center strength of the gradient magnetic field is 0.3T to 1.0T and the edge strength is 0.1T to 0.5T;

[0082] S2-3: Under the action of a magnetic field, the wet film temperature is controlled to gradually decrease from an initial 40°C to 50°C to 20°C to 25°C, and the resin viscosity is reduced from 10Pa•s to 15Pa•s to 0.5Pa•s to 1.5Pa•s;

[0083] S2-4: Use UV light source to cure the wet film in sections. The light intensity in the pre-curing stage is 5mW / cm² to 15mW / cm², and the light intensity in the main curing stage is 50mW / cm² to 150mW / cm².

[0084] S3: Anti-reflection layer setting

[0085] S3-1: Template preparation: Nanoimprint template, Si substrate is etched to form a pore gradient structure, the pore size is adjusted from 200nm to 50nm, and the depth gradient is from 100nm to 30nm; the release agent is applied, the release agent is fluorosilane, and the coverage rate is >99%;

[0086] S3-2: Imprinting and filling: The template is filled with 20 wt% TiO2 sol, thermally cured at 150°C for 30 min, and then plasma treated to improve the surface density after demolding.

[0087] The composite optical film with polarization function is manufactured by a roll-to-roll production device, wherein the roll-to-roll production device comprises:

[0088] (A) A magnetron coating unit comprising a permanent magnet roller and a slot die, wherein the magnetic field strength of the permanent magnet roller surface is 0.5T to 1.0T, and the slot die gap is 30μm to 100μm;

[0089] (B) a gradient curing unit comprising a temperature control module and a segmented UV-LED light source, wherein the segmented UV-LED light source has a peak wavelength of 365 nm to 405 nm and a light intensity controllable range of 10 mW / cm² to 200 mW / cm²;

[0090] (C) Online detection unit, including a beta-ray thickness gauge and a polarized imaging system, with a detection accuracy of ±0.5%.

[0091] The magnetic field distribution of the permanent magnet roller is a nonlinear gradient, the magnetic field intensity in the central area is 10% to 30% higher than that in the edge area, and the roller rotation speed is 5m / min to 20m / min.

[0092] In a third aspect, the composite optical film having a polarizing function can be applied to an in-vehicle display device, wherein the composite optical film is bonded to a curved glass substrate via an adhesive layer, the bonding temperature range is 80° C. to 120° C., and the bonding pressure is 0.1 MPa to 0.5 MPa.

[0093] Furthermore, the composite optical film has a polarization efficiency attenuation of ≤1% and a transmittance fluctuation of ≤0.5% under an environment of -40°C to 85°C.

[0094] Compared with the existing technology, the present invention achieves the following beneficial effects through the three-in-one technical solution of "material innovation - structural design - process innovation":

[0095] (1) Superparamagnetic functionalization of calcite nanocrystals (material innovation). By covalently loading Fe3O4 nanoparticles on the calcite surface, natural calcite (saturation magnetization intensity 0.8 emu / g) is endowed with superparamagnetism, breaking through the orientation limitations of traditional whiskers / dyes that rely on electrostatic forces or mechanical shear forces, providing a basis for magnetic field manipulation. In addition, through the synergistic effect of silane coupling agent modification and magnetic field, the crystal optical axis is precisely oriented (deviation <5°), and the polarization efficiency is improved by more than 35% compared with the traditional electrostatic adsorption method (deviation >30°).

[0096] (2) Multi-physics field compensation optical structure (structural design) of gradient refractive index scattering layer. On the one hand, the anti-reflection layer is directional-etched into the TiO2 layer through the PS microsphere template to form a porosity gradient structure with a bottom of 15% to a top of 5%, realizing a continuous gradient of refractive index (n=1.9→2.3) and compensating the oblique incident optical path difference (±10 nm correction). Combined with the microprism array of PET substrate (period 20 μm), an optical waveguide effect is constructed, with a wide spectrum reflectivity of <3% from 400 to 700 nm. Compared with the traditional anti-reflection film (single layer MgF2), the bandwidth is extended by 200%. On the other hand, the CTE gradient buffer layer is formed by laminating cyclic olefin copolymer and PUA matrix (CTE gradient: 70×10 -6 / ℃→35×10 -6 / ℃→45×10 -6 / ℃), achieving cross-order matching of material thermal expansion coefficients, and reducing interface stress by 68% after wet-heat cycling (-40~85℃), breaking through the delamination problem of inorganic-organic heterojunction;

[0097] (3) Innovation in process manufacturing mode (process innovation). On the one hand, the crystal layer adopts a two-stage UV curing and zero solvent process, replacing traditional solution coating with UV curing, combined with an ethanol circulation grinding system (recovery rate > 99%), reducing VOC emissions by 65%, making it more environmentally friendly and efficient. On the other hand, magnetically controlled dynamic coating integrates a slit coating head and a winding magnetic field generator to achieve 5 m / min continuous production (thickness error ±0.8μm), which significantly improves efficiency compared to the traditional intermittent process (0.5 m / min). BRIEF DESCRIPTION OF THE DRAWINGS

[0098] Figure 1 A schematic diagram of a composite optical film structure with polarization function;

[0099] 1—transparent substrate layer; 2—buffer layer (21—transition layer; 22—functional layer); 3—oriented calcite crystal layer; 4—anti-reflection layer.

[0100] Figure 2 Cross-sectional SEM of the transparent substrate layer, buffer layer, and oriented calcite crystal layer arranged in sequence.

[0101] Figure 3 Cross-sectional SEM of an oriented calcite crystal layer disposed on a buffer layer.

[0102] Figure 4 Surface SEM of an oriented calcite crystal layer. DETAILED DESCRIPTION

[0103] The technical solution of the present invention will be clearly and completely described below in conjunction with embodiments.

[0104] Unless otherwise specified, the experimental methods in the following examples are conventional methods and are performed according to the techniques or conditions described in the literature in the field or according to the product instructions.

[0105] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0106] Superparamagnetic Fe3O4 nanoparticles: purity ≥99.9%, particle size ~15 nm.

[0107] Calcite: purity ≥99%.

[0108] Preparation of superparamagnetic modified calcite crystal composite materials:

[0109] (1) Silane coupling agent modified calcite

[0110] S1: Preparation of nano-calcite suspension: Natural calcite is subjected to wet grinding process optimization, acid etching and surface activation to obtain nano-calcite suspension; the specific steps include:

[0111] S1-1: Wet grinding process optimization: Using a high-energy ball mill under nitrogen protection, using zirconia grinding balls with diameters of 0.8 mm to 1.2 mm and anhydrous ethanol as the medium, with a ball-to-material mass ratio of 15:1, a rotation speed of 450 rpm, and a grinding time of 12 hours, the particle size was adjusted to 150 nm to 300 nm to obtain nanocalcite crystals;

[0112] At the same time, the calcite particle size was adjusted to 300-500 nm according to step S1-1 to serve as a control group;

[0113] S1-2: Acid etching and surface activation: In step S1-1, the wet grinding process optimization system was adjusted to pH 4.5 to 5.0 with 0.1 M HCl, and then ultrasonicated (40 kHz, power 300 W) for 1 h;

[0114] S2: Silane coupling agent modification: Under reflux conditions at 80°C, 2% of an aminosilane coupling agent based on the total amount of nanocalcite and magnetic composite particles was added to the nanocalcite suspension reaction system obtained in the above step, and the reaction was continued by ultrasonic treatment for 2 hours at an ultrasonic power of 100W to obtain silane coupling agent-modified nanocalcite;

[0115] (2) Preparation of superparamagnetic modified calcite crystal composite materials:

[0116] (2-1) Preparation of SiO2@Fe3O4-calcite magnetic composite materials:

[0117] S1: Preparation of SiO2@Fe3O4 magnetic composite particles by sol-gel method, controlling the thickness of SiO2 coating layer to 3 nm: First, Fe3O4 colloidal aqueous solution is prepared, Fe3O4 nanoparticles are dispersed in deionized water, and the particles are evenly dispersed in the medium by ultrasonic dispersion to form a uniform and stable colloidal solution; while stirring continuously, ethanol, Fe3O4 colloid, deionized water and TEOS are added to the beaker in sequence, controlling the concentration of Fe3O4 in the reaction system to 0.25 mg / mL and the concentration of TEOS to 0.02 mol / L; then, concentrated ammonia is added to catalyze the hydrolysis and condensation of TEOS, and the concentration of concentrated ammonia in the reaction system is regulated to 0.4 mol / L. After the reaction is sealed for 6 hours, the product is centrifuged and washed several times with ethanol and deionized water respectively to obtain SiO2@Fe3O4 magnetic composite particles;

[0118] The amount of ethanol and deionized water, by volume ratio, V 乙醇 :V 去离子水 =4:1;

[0119] S2: Preparation of SiO2@Fe3O4-calcite magnetic composite material: Silane coupling agent-modified nano-calcite powder was ultrasonically dispersed in ethanol (concentration of 5 mg / mL), and then SiO2@Fe3O4 magnetic composite particles were added. The reaction was continued for 3 hours while stirring to obtain SiO2@Fe3O4-calcite magnetic composite material;

[0120] (2-2) Preparation of SiO2 / Fe3O4-calcite magnetic composite materials:

[0121] S1: Target selection: high-purity SiO2 target (99.99%) and Fe3O4 target (99.9%) are used, and a composite sputtering target is configured according to a 3at% Fe3O4 doping ratio (corresponding to 2.1wt%);

[0122] S2: Substrate preparation: Silane coupling agent-modified nanocalcite powder was ultrasonically dispersed in ethanol (concentration 5 mg / mL) and spin-coated on a silicon wafer substrate to form a monolayer particle film (thickness ~200 nm). The substrate was treated with Ar plasma for 5 minutes (power 50 W) to enhance the surface activity of the particles.

[0123] S3: magnetron sputtering deposition, through co-sputtering, Fe3O4 is uniformly dispersed in the SiO2 matrix at the atomic level; magnetron sputtering conditions: vacuum ≤ 5×10 -4 Pa; working gas: high-purity Ar (99.999%), flow rate: 20 sccm, pressure: 0.8 Pa; sputtering power: SiO2 target (RF 150 W), power density: 3 W / cm²; Fe3O4 target (DC 30 W); substrate temperature: 80°C; deposition time: 30 minutes, forming a 15 nm composite layer;

[0124] S4: Annealing at 300-400 °C for 1.5 hours in a nitrogen atmosphere to eliminate sputtering stress and enhance the crystallinity of SiO2 / Fe3O4 composite particles;

[0125] S5: Ultrasonic peeling of the composite particles on the substrate, centrifugal washing and dispersion in ethanol to obtain a SiO2 / Fe3O4 magnetic composite particle suspension, and finally drying to obtain a 150-350 nm SiO2 / Fe3O4-calcite magnetic composite material.

[0126] In the above steps, the amount of the nano-calcite and SiO2@Fe3O4 or SiO2 / Fe3O4 magnetic composite particles is in a mass ratio of 10:1;

[0127] At the same time, non-magnetically modified calcite, i.e., nanocalcite without Fe3O4 loading, was prepared as the control group, and the rest of the steps remained unchanged.

[0128] Example 1

[0129] A composite optical film with polarization function, comprising a transparent substrate layer, and a buffer layer, an oriented calcite crystal layer, and an anti-reflection layer stacked on one side of the transparent substrate layer; wherein the buffer layer comprises a transition layer and a functional layer. The structural diagram of the composite optical film is shown in the attached figure. Figure 1 shown.

[0130] The buffer layer includes a transition layer and a functional layer, which are combined with the substrate layer through a co-extrusion process. The oriented calcite crystal layer is obtained by coating a suspension of a superparamagnetic modified calcite crystal composite material on the surface of the functional layer of the buffer layer, inducing optical axis orientation through a magnetic field, and then UV curing. The anti-reflection layer is a TiO2 scattering layer composed of nanoporous titanium dioxide with a refractive index gradient ranging from 1.8 to 2.3, and is disposed on the surface of the oriented calcite crystal layer. The specific preparation steps of the composite optical film with polarization function are as follows:

[0131] (1) Preparation of superparamagnetic modified calcite crystal composite suspension

[0132] The SiO2@Fe3O4-calcite magnetic composite material was dispersed in polyurethane acrylate (PUA, refractive index n=1.56) resin to form a superparamagnetic modified calcite crystal composite suspension with a solid content of 15wt%;

[0133] (2) Preparation of composite optical films with polarization function

[0134] S1: Buffer layer setting

[0135] First, a buffer layer and a substrate layer are obtained by co-extrusion, and the buffer layer is arranged on one side of the substrate layer; the buffer layer includes a transition layer and a functional layer; the side close to the substrate layer is the transition layer; the side close to the oriented calcite crystal layer is the functional layer;

[0136] Transparent substrate layer: CTE=60×10 -6 / ℃ COP is raw material, thickness is 20μm;

[0137] Buffer layer: The buffer layer is made of a mixture of cycloolefin polymer and polyurethane acrylate. The transition layer has a thickness of 10 μm and the raw material is a mixture of COP / PUA = 7:3 (CTE = 45×10 -6 / ℃); Functional layer: thickness 10 μm, raw material is pure PUA (CTE = 38×10 -6 / ℃);

[0138] Through a three-channel co-extrusion die head, gradient temperature control: from 200°C for the substrate layer to 80°C for the functional layer, and a pressure of 20MPa; online infrared temperature measurement controls the interlayer bonding state (temperature difference <5°C) to obtain a composite membrane layer structure.

[0139] S2: Oriented calcite crystal layer setup

[0140] S2-1: Applying a suspension of superparamagnetic modified calcite crystal composite material to one side of the substrate buffer layer to form a wet film; wherein the coating speed is 12 m / min;

[0141] S2-2: applying a gradient magnetic field to the wet film, wherein the center strength of the gradient magnetic field is 0.3T to 1.0T, the edge strength is 0.1T to 0.5T, and the gap between the magnetic rollers is 50 μm;

[0142] S2-3: Under the action of a magnetic field, the wet film temperature is controlled to gradually decrease from an initial 40°C to 50°C to 20°C to 25°C, and the resin viscosity is reduced from 10Pa·s to 15Pa·s to 0.5Pa·s to 1.5Pa·s;

[0143] S2-4: UV light source was used to cure the wet film in sections, using a UV-LED curing lamp set (wavelength 395nm, peak intensity 150mW / cm², zone control); the light intensity in the pre-curing stage was 10mW / cm², the light intensity in the main curing stage was 100mW / cm², and the curing time was 0.5s. The thickness of the oriented calcite crystal layer was 12μm, and the thickness uniformity was ±0.5μm (1km continuous production). The corresponding SEM is shown in the attached figure. Figure 2 , Attachment Figure 3 and attached Figure 4 shown.

[0144] S3: Anti-reflection layer setting

[0145] The anti-reflection layer is composed of nanoporous titanium dioxide with a refractive index gradient from 1.8 to 2.3, with a thickness of 8 μm, and is provided on the surface of the oriented calcite crystal layer. The specific preparation steps are as follows:

[0146] S3-1: Template preparation: Nanoimprint template, Si substrate etched to form a pore gradient structure (pore size 200nm→50nm, depth gradient 100nm→30nm); coating release agent, the release agent is fluorosilane, and the coating coverage is >99%;

[0147] S3-2: Imprinting and filling: The template was filled with TiO2 sol (concentration 20wt%) and thermally cured (150℃, 30 min). After demolding, the surface density was increased by plasma treatment (Ar / O2=4:1, 100W) to obtain a 60μm composite optical film.

[0148] The composite optical film with polarization function prepared in the above steps is applied to a vehicle-mounted display device. The composite optical film is bonded to a curved glass substrate via an adhesive layer. The bonding temperature range is 80°C to 120°C, and the bonding pressure is 0.1MPa to 0.5MPa.

[0149] Example 2

[0150] As in the composite optical film with polarization function of Example 1, the raw materials of the substrate layer and the buffer layer are adjusted;

[0151] Transparent substrate layer: High temperature resistant PET (Tg=120℃, CTE=70×10 -6 / ℃) as raw material, thickness 20 μm;

[0152] Transition layer: COC (CTE = 35 × 10 -6 / ℃) as raw material, thickness 10μm;

[0153] Functional layer: PUA (45×10 -6 / ℃) as raw material, thickness 10μm;

[0154] The remaining steps remained unchanged to obtain a 60 μm composite optical film.

[0155] Example 3

[0156] For example, a composite optical film with polarization function in Example 2 is prepared by adjusting the raw material of the transparent substrate layer in the process of preparing the composite optical film with polarization function in step (2). The raw material of the substrate layer is replaced with a PET / PI composite layer (Young's modulus 5 GPa). In parts by mass, the PET / PI composite layer has a ratio of PET / PI of 7 / 3 and a thickness of 10 μm. The remaining steps remain unchanged to obtain a 50 μm composite optical film. The PET / PI composite layer is an ultra-thin flexible substrate. When the thickness is ≤ 10 μm, the bending radius is 1 mm and the life span is > 10 5 Second-rate.

[0157] Example 4

[0158] As in Example 2, a composite optical film with polarization function is prepared by nanoimprinting a PET substrate with a buffer layer on one side, and prefabricating a microprism array (period 20 μm, depth 5 μm) on the surface of the substrate. The remaining steps remain unchanged to obtain a 60 μm composite optical film.

[0159] Example 5

[0160] For example, in a composite optical film with polarization function as in Example 2, the UV curing resin used in the step of preparing the superparamagnetic modified calcite crystal composite material suspension in step (1) is adjusted, and the polyurethane acrylate (PUA, refractive index n=1.56) resin is replaced with an epoxy-acrylate resin (Tg=-20°C). The epoxy-acrylate resin is a type of low-temperature curing resin with a curing time of <5 min at -40°C and an adhesion of up to 4B. The remaining steps remain unchanged, and a composite optical film with an oriented calcite crystal layer thickness of 10 μm and a total thickness of 58 μm is obtained.

[0161] Example 6

[0162] For example, in a composite optical film with polarization function as in Example 2, the arrangement of the oriented calcite crystal layer is adjusted, the SiO2@Fe3O4-calcite magnetic composite material is replaced with the Fe3O4 / SiO2-magnetic composite material, and the step (1) of preparing the superparamagnetic modified calcite crystal composite material suspension is adjusted simultaneously by dispersing the SiO2 / Fe3O4-calcite magnetic composite material in the UV curing resin. The remaining steps remain unchanged, and a composite optical film with an oriented calcite crystal layer thickness of 6 μm and a total thickness of 54 μm is obtained.

[0163] Comparative Example 1

[0164] A traditional iodine-based polarizing film, comprising a TAC-PVA-TAC multilayer composite (total thickness ≥ 120 μm), with the iodine-containing resin layer susceptible to ion migration. Commercially available: Nitto Denko Corporation, Japan, model NDP-1428DU.

[0165] Comparative Example 2

[0166] For example, in a composite optical film with polarization function as in Example 2, the particle size of the nano-calcite used is adjusted to select calcite of 300 to 500 nm, and the other steps remain unchanged to obtain a composite optical film with an oriented calcite crystal layer thickness of 17 μm and a total thickness of 65 μm.

[0167] Comparative Example 3

[0168] For example, a composite optical film with polarization function in Example 2 does not have a buffer layer, that is, the crystal layer and the anti-reflection layer are directly stacked on the transparent substrate layer, and the other steps remain unchanged to obtain a composite optical film with a total thickness of 40 μm.

[0169] Comparative Example 4

[0170] For example, in a composite optical film with polarization function as in Example 2, the setting of the oriented calcite crystal layer is adjusted, and the SiO2@Fe3O4 magnetic composite particles are replaced with non-magnetically modified calcite, that is, calcite nanoparticles without Fe3O4 loading. The non-magnetically modified calcite is dispersed in the UV curing resin in the step of configuring the superparamagnetic modified calcite crystal composite material suspension in step (1), and the coating process parameters are adaptively adjusted. The remaining steps remain unchanged, thereby obtaining a composite optical film with an oriented calcite crystal layer thickness of 7 μm and a total thickness of 55 μm.

[0171] Comparative Example 5

[0172] For example, in a composite optical film with polarization function in Example 2, the anti-reflection layer setting structure of step (2) S3 is adjusted to be a single-layer TiO2 scattering layer with a non-gradient structure, while other hierarchical structures remain unchanged, thereby obtaining a composite optical film with an anti-reflection layer of 18 μm and a total thickness of 70 μm.

[0173] The performance of the composite optical films prepared in the above examples and comparative examples was evaluated:

[0174] Optical properties: Transmittance was measured using a JASCO V-770 spectrometer (ASTM D1003 standard); extinction ratio was tested using a LAMBDA 950 equipped with a polarizing assembly (EN 120000).

[0175] Reliability test: The Δ polarization after 1000 h at 85°C / 85% RH was tested using a damp heat aging chamber (Espec SH-641, JIS C 60068 standard). The bending tester (Instron 5943, ISO 178:2019 standard) was used to characterize the bending 10 5 Appearance changes after times.

[0176] The polarization efficiency (PE) of a polarizer at 630 nm can be calculated using the following formula:

[0177]

[0178] Among them, T max Indicates the maximum transmittance, T min Indicates the minimum transmittance; the polarization efficiency ranges from 0 to 1. The closer the value is to 1, the better the polarization performance of the polarizer.

[0179] The evaluation results of the composite optical films prepared in the above examples and comparative examples are recorded in Table 1.

[0180] Table 1 Summary of performance evaluation results of composite optical films obtained in Examples and Comparative Examples

[0181]

[0182] From the data in Table 1, it can be concluded that the performance of the composite optical films obtained by different substrate / buffer layer material configurations in Examples 1 to 3 is investigated. Example 2 (PET substrate + COC / PUA buffer layer) has the best comprehensive performance, with a transmittance of 92% at 550nm and a polarization attenuation of only 0.5% after wet heat aging. Due to its CTE gradient design (70×10 -6 / ℃→35×10 -6 / ℃→45×10 -6 / °C) effectively inhibits delamination. Example 1 (COP substrate) has better thermal stability (no cracking when bent at -40°C), but is more expensive. Example 3 (PET / PI composite substrate) has outstanding flexibility (bending radius of 1 mm), but has a slightly lower transmittance at 550nm (88%).

[0183] A comparison of Example 2 and Example 4 shows that after prefabricating a microprism array on the substrate surface by nanoimprinting, the transmittance at 550 nm is increased to 95%, the optical waveguide effect reduces reflection loss (reflectivity from 400 to 700 nm is <2.8%), and the edge orientation uniformity is further improved (σ=1.9°→1.5°), but the process complexity increases.

[0184] Example 5 shows a composite optical film prepared using an epoxy-acrylate resin as a UV-curable resin. Its curing time at -40°C is less than 5 minutes, and its adhesion reaches 4B grade, making it suitable for low-temperature automotive environments. Its elastic modulus is 1.8 GPa (slightly lower than PUA's 2.1 GPa), but its elongation at break is increased to 25%. Its polarization efficiency decays by 0.8% after wet-heat aging, outperforming conventional resins (>2%). Example 6 shows a composite optical film based on a SiO2 / Fe3O4-calcite magnetic composite material. A 3at% doping level yields a magnetic saturation intensity of 55 emu / g, meeting the 0.5T magnetic field orientation requirement. No sedimentation occurs in a suspension with a solids content of 15% (72 hours), surpassing unmodified particles. The mass production cost of the magnetron sputtering process is 15% lower than that of the SiO2@Fe3O4 coating method.

[0185] It is worth noting that, from the comparison of the data of Examples 1 to 6 and Comparative Example 1, it can be seen that the performance of the composite optical film based on the calcite polarizing functional layer of the present invention is more excellent, and compared with the commercially available iodine-based polarizers (such as Nitto NDP-1428DU), it has five advantages: ① Environmental stability: after wet heat aging (85°C / 85%RH 1000 h), the polarization degree attenuation is <1%, while the iodine-based polarizer attenuation is >10%, and there is no edge deiodination problem; ② Optical performance: full-band polarization efficiency uniformity is >98.5% (630 nm red light efficiency is 98% vs. 70-75% of iodine-based polarizers), 550 nm transmittance is >90% (iodine-based polarizers are only 43%); ③ Thickness and flexibility: total thickness ≤60 μm (Examples 1 to 6), bendable radius 1 mm (Example 3), while the iodine-based coating has a thickness of ≥120 μm and high rigidity; ④ Process environmental friendliness: The UV curing process has zero solvent emissions (the iodine-based coating requires wet coating and has high VOCs), and no TAC protective layer is required; ⑤ Cost potential: Calcite is a natural mineral raw material, and the mass production cost can be reduced by 20-40% compared to the iodine-based coating (especially the magnetron sputtering process in Example 6).

[0186] Comparative Example 2 is a composite optical film obtained based on calcite of 300 to 500 nm. Compared with Example 2, it can be found that the excessively large particle size of the nanocalcite leads to increased rotational resistance of the large particles in the magnetic field, the crystal axis orientation angle deviation σ increases from 2.3° to 5.8°, the polarization efficiency decreases from 98.5% to 82.3%, the transmittance in the visible light band decreases from 92% to 85%, the SiO2@Fe3O4 coating coverage decreases from 95% to 80%, and the magnetic field response efficiency decreases.

[0187] In Comparative Example 3, the crystal layer is directly disposed on the transparent substrate layer, and there is no buffer layer between the interface of PET and the crystal layer. Compared with Example 2, it can be found that the unmatched CTE gradient causes the 550nm transmittance of the composite film to drop significantly from 92% to 78%, the interface stress causes the crystal orientation deviation σ to increase from 2.3° to 8.1%, and the polarization efficiency drops to 75.8%.

[0188] Comparative Example 4 examined a composite optical film based on calcite nanoparticles without Fe₃O₄ loading. Without magnetic actuation, the crystal optical axis deviation σ reached 35° (compared to only 2.3° in Example 2), and the polarization efficiency plummeted to 60.4%. Comparative Example 4 relied on mechanical shear force for orientation, requiring a coating speed of 1 m / min (compared to 12 m / min in Example 2), resulting in a 92% drop in efficiency.

[0189] Comparative Example 5 examined a composite optical film based on a single TiO2 scattering layer and a non-gradient antireflection layer. The film exhibited an average reflectivity of 8.5% from 400 to 700 nm, with a high reflectivity of 12% in the blue band. At 30° oblique incidence, the polarization attenuation was 6.2% (compared to only 0.5% for a gradient structure), resulting in a 20% reduction in viewing angle. Comparative Example 5 required multiple coatings to achieve equivalent optical performance, increasing energy consumption by 40%.

Claims

1. A composite optical film with polarization function, characterized in that: The composite optical film includes a transparent substrate layer, and a buffer layer, an oriented calcite crystal layer and an anti-reflection layer stacked on one side of the transparent substrate layer; the buffer layer includes a transition layer and a functional layer; the transition layer is arranged on one side of the transparent substrate layer, and the functional layer is arranged on one side of the oriented calcite crystal layer; the thickness of the oriented calcite crystal layer is 5μm to 50μm, and the standard deviation of the crystal axis orientation angle σ≤3°; the oriented calcite crystal layer is obtained by coating a superparamagnetic modified calcite crystal composite material suspension on the surface of the buffer layer, inducing optical axis orientation through a magnetic field and UV curing; the superparamagnetic modified calcite crystal composite material suspension is formed by dispersing the superparamagnetic modified calcite crystal composite material in a UV curing resin, and the solid content of the suspension is 10wt% to 20wt%.

2. The composite optical film with polarization function according to claim 1, characterized in that: The transparent substrate layer comprises a composite of one or more of polyethylene terephthalate, cycloolefin polymer, and polyimide, and has a thickness of 10 μm to 200 μm; the buffer layer is a mixture of cycloolefin polymer and polyurethane acrylate, wherein the mass fraction of cycloolefin polymer is 50% to 90%; the thermal expansion coefficient of the buffer layer is 30×10 -6 / ℃ to 70×10 -6 / ℃, with a thickness of 10μm to 50μm; the thickness of the transition layer is 6μm to 30μm; and the thickness of the functional layer is 4μm to 20μm.

3. The composite optical film with polarization function according to claim 2, characterized in that: The superparamagnetic modified calcite crystal composite material is obtained by covalently grafting magnetic composite particles onto the surface of nano-calcite using a silane coupling agent; and the UV curing resin is selected from polyurethane acrylate, epoxy acrylate or a copolymer of the two.

4. The composite optical film with polarization function according to claim 3, characterized in that: The silane coupling agent is at least one of aminosilane, epoxysilane or methacryloxysilane; the magnetic composite particles are SiO2@Fe3O4 magnetic composite particles or SiO2 / Fe3O4 magnetic composite particles; the superparamagnetic modified calcite crystal composite material includes SiO2@Fe3O4-calcite magnetic composite material or SiO2 / Fe3O4-calcite magnetic composite material.

5. The composite optical film with polarization function according to claim 4, characterized in that: The nano-calcite has a particle size of 150nm to 300nm; the SiO2@Fe3O4 magnetic composite particles are composed of a Fe3O4 core and a SiO2 coating layer, the particle size of the Fe3O4 core is 10nm to 20nm, and the thickness of the SiO2 coating layer is 2nm to 5nm; in the SiO2@Fe3O4 magnetic composite particles, the porosity of the SiO2 coating layer is 10% to 30%, and the magnetic saturation strength of Fe3O4 is 80emu / g to 90emu / g; the SiO2 / Fe3O4 magnetic composite particles are prepared by in-situ doping by magnetron sputtering, and unmodified Fe3O4 is doped with SiO2, and the doping amount is 3at%.

6. The composite optical film with polarization function according to claim 5, characterized in that: The anti-reflection layer is a TiO2 scattering layer, which is composed of nanoporous titanium dioxide with a refractive index gradient ranging from 1.8 to 2.

3. The particle size of the nanoporous titanium dioxide is 50nm to 200nm, and the thickness of the anti-reflection layer is 2-10μm.

7. The method for preparing a composite optical film with polarization function according to any one of claims 1 to 6, characterized in that: The method comprises the following preparation steps: S1: Buffer layer setting: According to the formula, a buffer layer is set on one surface of the transparent substrate layer through a co-extrusion process with a thickness of 10 to 50 μm; S2: Oriented calcite crystal layer setup: A suspension of superparamagnetic modified calcite crystal composite material is applied to the surface of the buffer layer to form a wet film. A gradient magnetic field is then applied to the wet film, and under the action of the magnetic field, the wet film temperature is gradually reduced from an initial 40°C to 50°C to 20°C to 25°C, and the resin viscosity is reduced from 10Pa·s to 15Pa·s to 0.5Pa·s to 1.5Pa·s. The wet film is then cured in sections using a UV light source. S3: Anti-reflection layer setting: Using a nanoimprint template, the Si substrate is etched to form a pore gradient structure, adjusting the pore size from 200nm to 50nm, and the depth gradient from 100nm to 30nm; then a release agent is applied, and finally a 20wt% concentration of TiO2 sol is used to fill the template. After thermal curing and demolding, the surface density is improved by plasma treatment.

8. The method for preparing a composite optical film with polarization function according to claim 7, characterized in that: The superparamagnetic modified calcite crystal composite material suspension is prepared by dispersing the superparamagnetic modified calcite crystal composite material in a UV curable resin to form a suspension having a solid content of 10 wt% to 20 wt%; the superparamagnetic modified calcite crystal composite material includes a SiO2@Fe3O4-calcite magnetic composite material or a SiO2 / Fe3O4-calcite magnetic composite material; The preparation steps of the SiO2@Fe3O4-calcite magnetic composite material are as follows: ultrasonically dispersing silane coupling agent-modified nano-calcite powder in ethanol, then adding SiO2@Fe3O4 magnetic composite particles and reacting for 1 to 3 hours to obtain the SiO2@Fe3O4-calcite magnetic composite material; The preparation of the SiO2 / Fe3O4-calcite magnetic composite material specifically comprises the following steps: S1: Target selection: SiO2 target with a purity of 99.99% and Fe3O4 target with a purity of 99.9%, and a composite sputtering target with a doping ratio of 3at% Fe3O4; S2: Substrate preparation: Silane coupling agent-modified nano-calcite powder is ultrasonically dispersed in ethanol and spin-coated on a silicon wafer substrate to form a single-layer particle film; the substrate is treated with Ar plasma for 5 minutes to enhance the surface activity of the particles; S3: magnetron sputtering deposition, through co-sputtering, Fe3O4 is uniformly dispersed in the SiO2 matrix at the atomic level; magnetron sputtering conditions: vacuum ≤ 5×10 -4 Pa; working gas purity 99.999% Ar, flow rate 20sccm, pressure 0.8Pa; sputtering power: SiO2 target RF 150W, power density 3W / cm 2 , Fe3O4 target is 30W; substrate temperature is 80℃; deposition time is 30 minutes; S4: Annealing at 300-400°C in a nitrogen atmosphere for 1-2 hours to eliminate sputtering stress and enhance the crystallinity of the SiO2 / Fe3O4 composite particles; S5: The composite particles on the substrate are ultrasonically peeled off, and after centrifugal cleaning, they are dispersed in ethanol to obtain a suspension, and finally dried to obtain a SiO2 / Fe3O4-calcite magnetic composite material.

9. The method for preparing a composite optical film with polarization function according to claim 8, characterized in that: The preparation steps of the silane coupling agent modified nano-calcite are as follows: S1: Preparation of nano-calcite suspension: natural calcite is subjected to wet grinding process optimization, acid etching and surface activation to obtain nano-calcite suspension; S2: Silane coupling agent modification: adding a silane coupling agent to the nano-calcite suspension reaction system obtained in the above step under reflux conditions at 80°C, and continuing ultrasonic treatment for 1 to 3 hours at an ultrasonic power of 50W to 150W to obtain silane coupling agent-modified nano-calcite; The silane coupling agent is at least one of aminosilane, epoxysilane or methacryloxysilane.

10. The method for preparing a composite optical film with polarization function according to claim 9, characterized in that: The SiO2@Fe3O4 magnetic composite particles are prepared by a sol-gel method, which specifically comprises the following steps: dispersing Fe3O4 nanoparticles in deionized water to form a colloidal solution; adding ethanol, Fe3O4 colloid, deionized water, and TEOS to a beaker in sequence with continuous stirring, controlling the concentration of Fe3O4 in the reaction system to be 0.2-0.3 mg / mL and the concentration of TEOS to be 0.02-0.03 mol / L; then adding concentrated ammonia water to catalyze the hydrolysis and condensation of TEOS, controlling the concentration of concentrated ammonia water in the reaction system to be 0.4-0.5 mol / L, sealing the reaction for 6 hours, centrifuging and washing the product, and obtaining SiO2@Fe3O4 magnetic composite particles with Fe3O4 as the core and SiO2 as the coating layer.

11. The method for preparing a composite optical film with polarization function according to claim 10, characterized in that: The amount of the silane coupling agent is 1wt% to 5wt% of the total mass of the nano-calcite and SiO2@Fe3O4 or SiO2 / Fe3O4 magnetic composite particles; The amount of the nano-calcite and SiO2@Fe3O4 or SiO2 / Fe3O4 magnetic composite particles is 5:1 to 15:1 by mass ratio; In the SiO2@Fe3O4 magnetic composite particles, the Fe3O4 nanoparticles have a particle size of 10 nm to 20 nm and a magnetic saturation intensity of 80 emu / g to 90 emu / g.

12. Use of the composite optical film with polarization function according to any one of claims 1 to 6, characterized in that: The composite optical film can be applied to a vehicle-mounted display device.

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