Composite polarizing brightening privacy film and preparation method thereof

Abstract

The application discloses a composite polarizing brightening privacy-protection film and a preparation method thereof, relates to the technical field of vehicle-mounted display optical films, and aims to solve the problem of poor privacy-protection brightening effect of the existing technology, and comprises a modified PET base layer, a first black-and-white adhesive privacy-protection layer, a second black-and-white adhesive privacy-protection layer, a polarizing and brightening integrated layer and a weather-resistant protective layer arranged in sequence from an incident light surface to an outgoing light surface, wherein the first white adhesive privacy-protection layer and the second black adhesive privacy-protection layer are distributed in a staggered manner. The application is applicable to a central control screen, an instrument panel and a rear-row entertainment screen of a vehicle, and can synchronously realize the functions of preventing visual pollution, protecting privacy, brightening and high-definition display, and is resistant to extreme vehicle-mounted environments.

Description

Technical Field

[0001] This invention relates to a composite polarizing brightening privacy film and its preparation method, belonging to the field of automotive display optical thin film technology. Background Technology

[0002] With the trend towards larger in-vehicle screens and higher dashboard designs, managing screen light to reduce reflections and interference (light pollution) on the windshield at night has become increasingly important. Simultaneously, the widespread adoption of vehicle-to-everything (V2X) connectivity has created a pressing need to protect the driver's privacy when projecting their screen. However, traditional single-unit privacy film solutions have the following core drawbacks: Optical performance imbalance: The traditional single-layer black and white adhesive alternating coating grating structure has a light transmittance of only 50-70%. After the brightness enhancement film is superimposed, moiré patterns are generated due to refractive index mismatch, and the brightness drops sharply from the side viewing angle, resulting in a poor viewing experience for the driver and passenger. Uncontrolled light efficiency and energy consumption: Current technology cannot recover blocked light. Due to the lack of innovative designs for backlight recycling, it is impossible to achieve a 30%~40% improvement in light efficiency and backlight energy saving, making it difficult to meet the low power consumption requirements of modern display terminals (such as mobile phones, MNTs and automotive screens); Poor integration and process compatibility: Traditional solutions require multiple layers of individual film materials to be physically stacked in order to achieve privacy protection, polarization, and brightness enhancement. This not only increases the thickness of the display device, but also easily causes secondary reflections and optical interference (such as horizontal lines and surface roughness) between the interfaces of each layer, making it impossible to perfectly adapt to the bonding requirements of automotive curved screens, resulting in low mass production yield.

[0003] Existing privacy protection solutions have not achieved microscopic integration of privacy protection structure and polarization enhancement function, and have not solved the optical interference problems of backlight recycling and multi-layer bonding, thus failing to meet the high standards of modern displays and automotive-grade applications. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a composite polarized brightening privacy film and its preparation method, which is suitable for automotive central control screens, dashboards and rear entertainment screens. It can simultaneously achieve the functions of preventing visual pollution, protecting privacy, and enhancing high-definition display, and can withstand extreme in-vehicle environments.

[0005] To achieve the above objectives, the present invention is implemented using the following technical solution: On one hand, the present invention provides a composite polarizing and brightening privacy film, comprising a modified PET substrate layer, a first black and white adhesive privacy layer, a second black and white adhesive privacy layer, an integrated polarizing and brightening layer, and a weather-resistant protective layer arranged sequentially from the light-incident surface to the light-outceasing surface, wherein the first black and white adhesive privacy layer and the second black and white adhesive privacy layer are staggered.

[0006] Furthermore, the misalignment length between the second black and white adhesive privacy layer and the first black and white adhesive privacy layer ranges from 3.5 to 4.5 μm.

[0007] Furthermore, the thickness of the composite polarizing and brightening privacy film ranges from 0.40 to 0.50 mm, the thickness of the modified PET substrate layer ranges from 110 to 150 μm, the thickness of the first black and white adhesive privacy layer and the second black and white adhesive privacy layer ranges from 40 to 70 μm, the thickness of the integrated polarizing and brightening layer ranges from 30 to 60 μm, and the thickness of the weather-resistant protective layer ranges from 80 to 150 μm.

[0008] On the other hand, the present invention also provides a method for preparing a composite polarizing brightening privacy film, comprising: S1. Modify the PET substrate to obtain a modified PET base layer; S2. Apply black adhesive to the surface of the modified PET substrate, cure it with ultraviolet light to form a grating, fill the gaps in the grating with white adhesive, and cure it with ultraviolet light again to obtain the first black and white adhesive privacy layer. S3. Repeat S2 under the condition of grating misalignment to obtain the second black and white adhesive privacy layer; S4. Prepare an integrated polarization brightening layer and a weather-resistant protective layer; S5. The integrated polarization brightening layer is bonded to the top of the second black and white adhesive privacy layer using UV optical adhesive. After vacuum degassing, the weather-resistant protective layer is bonded to the top of the integrated polarization brightening layer using UV optical adhesive to obtain a composite polarization brightening privacy film.

[0009] Furthermore, the method for preparing the modified PET substrate layer includes: PET substrate, glass microspheres and antioxidants are melt-blended at 250~330℃, biaxially stretched and then cured by ultraviolet light to obtain a modified PET substrate layer. The glass microspheres constitute 3-5% of the mass of the PET substrate, and the antioxidant constitutes 0.1-0.3% of the mass of the PET substrate. And / or, the antioxidant is one or more of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, and 3,5-di-tert-butyl-4-hydroxybenzyl)isocyanurate; And / or, the parameters for the biaxial stretching molding include longitudinal stretching at 110~120℃ and 120~160 mm / s, and transverse stretching at 120~130℃ and 150~180 mm / s.

[0010] Furthermore, by mass percentage, it contains 50-80% hydroxyl acrylic resin, 8-12% tannin, 6-10% ferric chloride, 0.1-0.3% UV-327, 2-4% photoinitiator, and 16-20% acrylate monomer; The white glue ingredients include, by weight percentage, 3-5% polyurethane acrylate, 3-5% nano titanium dioxide, 4-8% dipropylene glycol diacrylate, 3-6% photoinitiator and 70-90% acrylic resin matrix.

[0011] Furthermore, the energy range of the ultraviolet curing is 800~1200 mJ / cm. 2 ; And / or, the width of the grating is in the range of 10~15μm, and the width of the grating gap is in the range of 30~45μm.

[0012] Furthermore, the integrated polarizing brightening layer is a composite structure of a microprism array and nano-aerogel, and its preparation method includes: Preparation of polyvinyl alcohol polarizing film; Microprism brightening layer prepared by UV imprinting; A polyvinyl alcohol polarizing film and a microprism brightening layer are combined and then bonded together with a protective layer to obtain an integrated polarizing and brightening layer.

[0013] Furthermore, the preparation method of the polyvinyl alcohol polarizing film includes: The polyvinyl alcohol film is immersed in pure water and swelled at 25~35℃ until its swelling rate reaches 150~250%, thus obtaining a swollen polyvinyl alcohol film. The swollen polyvinyl alcohol film was stained with iodine solution at 25~40℃ for 60~120s, wherein the concentration of the iodine solution was 0.1~0.5 mol / L to obtain the stained polyvinyl alcohol film. The dyed polyvinyl alcohol film was placed in a boric acid bath at 40-60℃ and stretched longitudinally to 3-5 times its original size. Then it was immersed in a 2-5 wt% boric acid solution for crosslinking for 30-60 seconds. After washing and drying, a polyvinyl alcohol polarizing film was obtained. And / or, the fabrication of the microprism brightening layer by UV imprinting includes: UV resin is coated on a PET substrate at a coating line speed of 5-15 m / min and a wet film thickness of 40-80 μm to obtain a resin layer. Under the conditions of roller pressing pressure of 0.3~1.0MPa and roller temperature of 25~50℃, the prism mold is pressed into the resin layer to form a prism structure; After UV curing the prism structure, the mold is peeled off to obtain a microprism brightening layer; And / or, the method of combining the polyvinyl alcohol polarizing film and the microprism brightening layer includes: Plasma or corona treatment was applied to the polyvinyl alcohol polarizing film and the microprism brightening layer. Under a linear velocity of 8~12m / min, UV-curable adhesive is applied to the surfaces to be bonded between the polyvinyl alcohol polarizing film and the microprism brightening layer, with the adhesive layer thickness controlled at 0.8~1.2μm. Polyvinyl alcohol polarizing film and microprism brightening layer are pressed together under tension of 5~15N, rolling pressure of 0.2~0.6MPa and 25~40℃, with a strength of 500~1500mJ / cm. 2 The polarizing and brightening integrated layer is obtained by curing under ultraviolet light and standing at 40~60℃ for 24~48h.

[0014] Furthermore, the method for preparing the weather-resistant protective layer includes: Polyvinylidene fluoride resin and polymethyl methacrylate resin were blended, and silicon-coated rutile nano-titanium dioxide, nano-silica, hindered amine light stabilizer and phosphite antioxidant were added to obtain the protective layer material. The protective layer base film is obtained by melt blending the protective layer material and then casting it into a film. The protective base film is subjected to gradient UV curing treatment to obtain a weather-resistant protective layer.

[0015] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: This invention adds an integrated polarization and brightness enhancement layer, which enables the backlight to be recycled and improves the light efficiency by 30-40%, which is equivalent to saving 30-40% of the backlight energy. The light is controlled by the louver structure formed by the first black and white adhesive privacy layer and the second black and white adhesive privacy layer to prevent reflection and interference, thus achieving the function of privacy without loss of brightness. The composite polarized brightening privacy film provided by this invention has a light transmittance of 86~91% (550nm) and a privacy viewing angle of ±30°, achieving a balance between privacy protection and high-definition display; it can withstand 1000 hours of dry temperature test at 105℃ without depolarization, and the light transmittance decreases by only 1.7% under dual 85℃ environment; it can withstand 100 cycles at -40~85℃ without warping or delamination. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of the composite polarizing brightening privacy film in one embodiment of the present invention; Figure 2 This is a schematic diagram showing the angular relationship between the polarization axis and the privacy grating of the composite polarizing brightening privacy film in one embodiment of the present invention; In the diagram: 1-Modified PET base layer, 2-First black and white adhesive privacy layer, 3-Second black and white adhesive privacy layer, 4-UV optical adhesive, 5-Polarization and brightening integrated layer, 6-Weather-resistant protective layer. Detailed Implementation

[0017] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention. Example 1

[0018] This invention provides a method for preparing a composite polarizing brightening privacy film, comprising the following steps: S1. 96.8 wt% polyethylene terephthalate (PET) base resin, 3 wt% glass microspheres and 0.2 wt% antioxidant 1010 are mixed evenly and then fed into a twin-screw extruder. The extruder temperature gradient is set to 270℃→280℃→290℃, the die temperature is 290℃, and melt blending extrusion is carried out under the conditions of screw speed of 250 r / min, material residence time of 6 min and system vacuum degree ≥-0.08 MPa to fully remove small molecules and water vapor. Modified PET thick sheets are obtained by casting.

[0019] Modified PET sheets were fed into a stretching machine for biaxial stretching. The stretching temperature for longitudinal stretching (MD) was 115℃, the stretching speed was 140 mm / s, and the stretching ratio was fixed at 3.0 times. The stretching temperature for transverse stretching (TD) was 125℃, the stretching speed was 165 mm / s, and the stretching ratio was fixed at 3.2 times. The biaxially stretched film was introduced into a heat-setting chamber and heat-set at 185°C and a relaxation rate of 5%. It was then rapidly cooled using a cooling roller at 45°C and cured by ultraviolet radiation to obtain a modified PET substrate layer. The modified PET substrate layer had a thickness of 35 μm and a coefficient of thermal expansion of 27 ppm / °C.

[0020] S2. By mass percentage, the black glue ingredients include: 60.0% hydroxyl acrylic resin, 10.0% tannin, 8.0% ferric chloride, 0.2% UV absorber UV-327, 3.0% photoinitiator 819, and 18.8% acrylate monomer. After uniformly mixing the above black glue components, the mixture is milled using a three-roll mill to a fineness ≤3μm to obtain a black glue coating with an optical density (OD) value of 3.6.

[0021] The black adhesive coating was applied to the surface of a modified PET substrate using a micro-grooving process, and the repeating interval period of the formed black adhesive grating structure was controlled to be 14 μm.

[0022] Subsequently, radiation curing is achieved by dynamically controlling the gradient changes in ultraviolet light intensity, irradiation time, and irradiation distance. During this process, the radiation energy received by the black glue grating layer decreases sequentially from the surface to the bottom layer, thereby guiding the curing degree to decrease layer by layer, ultimately forming a non-uniform gradient cured grating structure with a highly cross-linked and dense surface layer and a moderately flexible bottom layer.

[0023] By weight percentage, the white glue formulation includes: 4.0% polyurethane acrylate, 4.0% nano titanium dioxide, 6.0% dipropylene glycol diacrylate (TPGDA), 4.8% photoinitiator 1173, and 81.2% acrylic resin matrix. The white glue coating was prepared by uniformly grinding the above white glue components using a three-roll mill, and its reflectance was measured to be 89%.

[0024] White glue coating is applied to the gaps of the gradient curing grating. After the excess white glue is squeezed out using a mold, it is cured again with ultraviolet light. Finally, the first black and white glue privacy layer is constructed in the gaps of the grating.

[0025] S3. Repeat S2 under the condition of grating misalignment of 4μm to obtain the second black and white adhesive privacy layer.

[0026] S4. Prepare an integrated polarization brightening layer, including: Preparation of polyvinyl alcohol polarizing film: The polyvinyl alcohol film was immersed in pure water and swollen at 30°C for 45 seconds until its swelling rate reached 200%, thus obtaining a swollen polyvinyl alcohol film to open up the gaps between molecular chains and facilitate subsequent dyeing.

[0027] Swelling polyvinyl alcohol (PVA) films were stained with 0.3 mol / L iodine solution at 35°C for 90 seconds to obtain stained PVA films. Iodine molecules penetrated into the amorphous regions of PVA, forming iodine-iodide ion complexes, which imparted dichroism.

[0028] The dyed polyvinyl alcohol film was longitudinally stretched to 4 times its original size in a boric acid bath at 50°C. Stretching caused the polyvinyl alcohol molecular chains to align in the stretching direction, and the iodine complex was oriented accordingly, resulting in optical anisotropy. Then, it was immersed in a 3wt% boric acid solution for 45 seconds for crosslinking. Boric acid and the hydroxyl groups of polyvinyl alcohol underwent complexation and crosslinking, which fixed the orientation structure and improved the water resistance and mechanical strength of the film. The film was washed three times with pure water at 25°C to remove the surface iodine and boric acid, and then dried at 65°C for 8 minutes to obtain a polyvinyl alcohol polarizing film with a water content of <5%.

[0029] Preparation of microprism brightening layer by UV imprinting: UV resin was coated onto a PET substrate at a coating line speed of 10 m / min and a wet film thickness of 60 μm to obtain a resin layer.

[0030] Under rolling pressure of 0.6 MPa and rolling temperature of 27°C, a prism mold is pressed into the resin layer to form a prism structure. The mold parameters used in this embodiment are: apex angle 90°, spacing 50 μm, and height 40 μm.

[0031] Irradiation was performed using ultraviolet light with a wavelength of 365nm and a light intensity of 600mW / cm². 2The cumulative energy is 1400 mJ / cm³. 2 The prism structure was UV cured and cooled to 30°C before being peeled off from the mold to obtain the microprism brightening layer.

[0032] The polyvinyl alcohol polarizing film and the microprism brightening layer are subjected to plasma or corona treatment.

[0033] At a linear velocity of 10 m / min, UV-curable adhesive was applied to the surfaces to be bonded between the polyvinyl alcohol polarizing film and the microprism brightening layer, with the adhesive layer thickness controlled at 1.0 μm. Polyvinyl alcohol polarizing film and microprism brightening layer were laminated under tension of 10N, roller pressure of 0.4MPa and 30℃, with a yield of 1000mJ / cm. 2 Cured under ultraviolet light and then aged (standing at 50°C for 36 hours), and a protective layer (cellulose triacetate film) is attached to one side of the polyvinyl alcohol polarizing film to obtain an integrated polarization brightening layer.

[0034] S5. The polarizing brightening integrated layer is bonded to the second black and white adhesive privacy layer using UV optical adhesive, and then vacuum degassing is performed.

[0035] S6. Prepare a weather-resistant protective layer, including: By weight, 70 parts of polyvinylidene fluoride (PVDF) resin and 30 parts of weather-resistant polymethyl methacrylate (PMMA) resin were blended, and 3 parts of silicon-coated rutile nano-titanium dioxide and 2 parts of nano-silica (SiO2) were introduced as UV shielding fillers. At the same time, 0.5 parts of hindered amine light stabilizer (UV-944) and 0.3 parts of phosphite antioxidant (antioxidant 626) were added to obtain the protective layer material.

[0036] The above-mentioned protective layer material is fed into a twin-screw extruder for melt blending (feeding section (zone 1): 185-215℃, plasticizing section (zone 2): 205-230℃, homogenizing section (zone 3): 210-240℃, conveying section (zone 4): 215-245℃, die section: 220-250℃), and then the protective layer base film is obtained by casting film forming process.

[0037] Next, a gradient ultraviolet (UV) curing process (light intensity 500mW / cm²) was adopted. 2 Accumulated energy 1000 mJ / cm 2 Divided into three stages, each stage using 200 mJ / cm 2 The protective layer base film is subjected to single-sided radiation treatment by increasing the cumulative energy gradient; by controlling the gradient distribution of ultraviolet light radiation intensity and irradiation time, the cross-linking reaction inside the film is guided to decrease layer by layer from the surface to the inner layer, thereby forming a non-uniform gradient structure with dense cross-linking on the surface and flexible transition at the bottom layer inside the protective layer, thus obtaining a weather-resistant protective layer.

[0038] S7. The weather-resistant protective layer is bonded to the integrated polarizing and brightening layer using UV optical adhesive to obtain a composite polarizing and brightening privacy film, such as... Figure 1 As shown, its thickness is 0.45 mm.

[0039] The angular relationship between the polarization axis and the privacy grating of the composite polarizing brightening privacy film is as follows: Figure 2 As shown: the absorption axes of the upper and lower polarizers are parallel to each other, forming a horizontal axis and constituting the basic unit for polarization control; the privacy grille layer has a vertical grille direction, orthogonal to the absorption axes of the upper and lower polarizers, achieving a privacy effect by blocking obliquely emitted light; the reflection axis of the core reflective layer is vertical, orthogonal to the absorption axes of the upper and lower polarizers, and can reflect and recover light with specific polarization states, improving the brightness utilization rate from the front viewing angle. The overall structure, through the synergistic effect of polarization absorption, grille blocking, and polarization reflection, achieves screen privacy functionality while also ensuring front display brightness and optical contrast.

[0040] Comparative Example 1: The only difference between this comparative example and Example 1 is that steps S4 and S5 are omitted, i.e., the integrated polarization brightening layer is not included.

[0041] Comparative Example 2: The only difference between this comparative example and Example 1 is that steps S2 and S3 are omitted, i.e., the first black and white adhesive privacy layer and the second black and white adhesive privacy layer are not included.

[0042] The specific testing methods are as follows: Haze test: Haze meter.

[0043] Transmittance test: A spectrophotometer was used. The test steps included: calibrating the instrument and selecting the transmittance mode; taking an uncoated vehicle display screen as a blank control; attaching the high-transmittance privacy film with black and white adhesive layered onto a standard transparent substrate and placing it in the instrument's measuring hole; setting the test wavelength to 550nm; and taking the average value after three consecutive measurements.

[0044] Privacy viewing angle test: A viewing angle test fixture and a luminance meter are used. The test procedure includes: fixing the high-transmittance automotive privacy film with black and white adhesive layered onto the test fixture, facing the light source. Using the normal (0°) as a reference, slowly rotate the test fixture clockwise / counterclockwise. Observe the changes in brightness / contrast. When the screen contrast drops to 50% or the visibility becomes significantly blurred, stop rotating and record the left and right angles.

[0045] Heat shrinkage test: The privacy film was baked at 105℃ for 60 minutes, and the length before and after baking was measured to calculate the heat shrinkage rate.

[0046] Thermal expansion test: The change of the sample's dimensions (length or volume) with temperature is accurately measured using a thermomechanical analyzer at a temperature of 0~105℃ to obtain the coefficient of linear thermal expansion.

[0047] Double 85 Aging (Weather Resistance) Test: A constant temperature and humidity chamber was used. The test procedure included: placing the high-transmittance privacy film with black and white adhesive layered coating into the constant temperature and humidity chamber, setting the temperature to 85℃ and the relative humidity to 85%, and leaving it continuously for 1000 hours. After cooling to room temperature, the transmittance attenuation value was measured, and the calculation expression was as follows: Transmittance attenuation value = (Transmittance before aging - Transmittance after aging) / Transmittance before aging × 100% Test results: The privacy film of Example 1 has a haze of 30-40%, a light transmittance of 86-91%, a privacy angle of 25-35°, a thermal shrinkage rate of 0.06-0.3 in the transverse direction and 0.05-0.09 in the longitudinal direction, a linear thermal expansion coefficient of 60-70 in the transverse direction and 78-88 in the longitudinal direction, a light transmittance attenuation of ≤2% after 1000 hours in a dual 85 environment, and a relative brightness of 100%. All indicators are qualified.

[0048] The test data for Comparative Example 1 include: haze: 28–38%, transmittance: 28–35%, privacy angle: 25°–35°, thermal shrinkage rate: 0.06–0.3% laterally, 0.05–0.09% longitudinally, linear thermal expansion coefficient: 60–70 ppm / ℃ laterally, 78–88 ppm / ℃ longitudinally, transmittance decay after 1000 hours of dual 85 aging: ≤2%, and relative brightness: 75–85%. A comparison of the test data between Comparative Example 1 and Example 1 shows that Example 1, due to the polarization light recovery effect of the integrated polarization brightening layer, achieves a significant improvement in transmittance and mitigates the brightness loss problem. Furthermore, the haze changes are relatively small in both examples, indicating that the introduction of the integrated polarization brightening layer did not cause additional scattering defects.

[0049] The test data for Comparative Example 2 include: haze: 10-15%, light transmittance: 45-55%, privacy angle: no privacy effect (full-view visibility), thermal shrinkage rate: 0.06-0.3% in the transverse direction and 0.05-0.09% in the longitudinal direction, linear thermal expansion coefficient: 60-70 ppm / ℃ in the transverse direction and 78-88 ppm / ℃ in the longitudinal direction, aging at 85 for 1000 hours, light transmittance attenuation: ≤2%, and relative brightness: 110-120%. It can be clearly seen that the privacy effect of Example 1 is greatly improved, and the relative brightness is also improved.

[0050] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A composite polarizing and brightening privacy film, characterized in that, It includes a modified PET substrate layer, a first black and white adhesive privacy layer, a second black and white adhesive privacy layer, a polarizing and brightening integrated layer, and a weather-resistant protective layer arranged sequentially from the light-incident surface to the light-outceasing surface, wherein the first black and white adhesive privacy layer and the second black and white adhesive privacy layer are staggered.

2. The composite polarizing brightening privacy film according to claim 1, characterized in that, The misalignment length between the second black and white adhesive privacy layer and the first black and white adhesive privacy layer ranges from 3.5 to 4.5 μm.

3. The composite polarizing brightening privacy film according to claim 1, characterized in that, The thickness of the composite polarizing and brightening privacy film ranges from 0.40 to 0.50 mm; the thickness of the modified PET substrate layer ranges from 110 to 150 μm; the thickness of the first black and white adhesive privacy layer and the second black and white adhesive privacy layer ranges from 40 to 70 μm; the thickness of the integrated polarizing and brightening layer ranges from 30 to 60 μm; and the thickness of the weather-resistant protective layer ranges from 80 to 150 μm.

4. A method for preparing a composite polarizing brightening privacy film as described in any one of claims 1 to 3, characterized in that, include: S1. Modify the PET substrate to obtain a modified PET base layer; S2. Apply black adhesive to the surface of the modified PET substrate, cure it with ultraviolet light to form a grating, fill the gaps in the grating with white adhesive, and cure it with ultraviolet light again to obtain the first black and white adhesive privacy layer. S3. Repeat S2 under the condition of grating misalignment to obtain the second black and white adhesive privacy layer; S4. Prepare an integrated polarization brightening layer and a weather-resistant protective layer; S5. The integrated polarization brightening layer is bonded to the top of the second black and white adhesive privacy layer using UV optical adhesive. After vacuum degassing, the weather-resistant protective layer is bonded to the top of the integrated polarization brightening layer using UV optical adhesive to obtain a composite polarization brightening privacy film.

5. The method for preparing the composite polarizing brightening privacy film according to claim 4, characterized in that, The method for preparing the modified PET substrate layer includes: PET substrate, glass microspheres and antioxidants are melt-blended at 250~330℃, biaxially stretched and then cured by ultraviolet light to obtain a modified PET substrate layer. The glass microspheres constitute 3-5% of the mass of the PET substrate, and the antioxidant constitutes 0.1-0.3% of the mass of the PET substrate. And / or, the antioxidant is one or more of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, and 3,5-di-tert-butyl-4-hydroxybenzyl)isocyanurate; And / or, the parameters for the biaxial stretching molding include longitudinal stretching at 110~120℃ and 120~160 mm / s, and transverse stretching at 120~130℃ and 150~180 mm / s.

6. The method for preparing the composite polarizing brightening privacy film according to claim 4, characterized in that, The black glue ingredients include, by weight percentage, 50-80% hydroxyl acrylic resin, 8-12% tannin, 6-10% ferric chloride, 0.1-0.3% UV-327, 2-4% photoinitiator and 16-20% acrylate monomer; The white glue ingredients include, by weight percentage, 3-5% polyurethane acrylate, 3-5% nano titanium dioxide, 4-8% dipropylene glycol diacrylate, 3-6% photoinitiator and 70-90% acrylic resin matrix.

7. The method for preparing the composite polarizing brightening privacy film according to claim 4, characterized in that, The energy range of the ultraviolet curing is 800~1200 mJ / cm. 2 ; And / or, the width of the grating is in the range of 10~15μm, and the width of the grating gap is in the range of 30~45μm.

8. The method for preparing the composite polarizing brightening privacy film according to claim 4, characterized in that, The integrated polarization brightening layer is a composite structure of a microprism array and nano-aerogel, and its preparation method includes: Preparation of polyvinyl alcohol polarizing film; Microprism brightening layer prepared by UV imprinting; A polyvinyl alcohol polarizing film and a microprism brightening layer are composited, and a protective layer is attached to one side of the polyvinyl alcohol polarizing film to obtain an integrated polarizing and brightening layer.

9. The method for preparing the composite polarizing brightening privacy film according to claim 8, characterized in that, The method for preparing the polyvinyl alcohol polarizing film includes: The polyvinyl alcohol film is immersed in pure water and swelled at 25~35℃ until its swelling rate reaches 150~250%, thus obtaining a swollen polyvinyl alcohol film. The swollen polyvinyl alcohol film is stained with iodine solution at 25~40℃ for 60~120s, wherein the concentration of the iodine solution is 0.1~0.5mol / L to obtain the stained polyvinyl alcohol film. The dyed polyvinyl alcohol film was placed in a boric acid bath at 40-60℃ and stretched longitudinally to 3-5 times its original size. Then it was immersed in a 2-5 wt% boric acid solution for crosslinking for 30-60 seconds. After washing and drying, a polyvinyl alcohol polarizing film was obtained. And / or, the fabrication of the microprism brightening layer by UV imprinting includes: UV resin is coated on a PET substrate at a coating line speed of 5-15 m / min and a wet film thickness of 40-80 μm to obtain a resin layer. Under the conditions of roller pressing pressure of 0.3~1.0MPa and roller temperature of 25~50℃, the prism mold is pressed into the resin layer to form a prism structure; After UV curing the prism structure, the mold is peeled off to obtain a microprism brightening layer; And / or, the method of combining the polyvinyl alcohol polarizing film and the microprism brightening layer includes: Plasma or corona treatment was applied to the polyvinyl alcohol polarizing film and the microprism brightening layer. Under a linear velocity of 8~12m / min, UV-curable adhesive is applied to the surfaces to be bonded between the polyvinyl alcohol polarizing film and the microprism brightening layer, with the adhesive layer thickness controlled at 0.8~1.2μm. Polyvinyl alcohol polarizing film and microprism brightening layer are pressed together under tension of 5~15N, rolling pressure of 0.2~0.6MPa and 25~40℃, with a maximum temperature of 500~1500mJ / cm. 2 Cured under ultraviolet light and left to stand at 40~60℃ for 24~48 hours.

10. The method for preparing the composite polarizing brightening privacy film according to claim 4, characterized in that, The method for preparing the weather-resistant protective layer includes: Polyvinylidene fluoride resin and polymethyl methacrylate resin were blended, and silicon-coated rutile nano-titanium dioxide, nano-silica, hindered amine light stabilizer and phosphite antioxidant were added to obtain the protective layer material. The protective layer base film is obtained by melt blending the protective layer material and then casting it into a film. The protective base film is subjected to gradient UV curing treatment to obtain a weather-resistant protective layer.

Images