Ultrathin flexible brightness enhancement film and roll-to-roll production process thereof

Abstract

The invention relates to the technical field of flexible display, and particularly discloses an ultrathin flexible brightness enhancement film and a roll-to-roll production process thereof. The ultrathin flexible brightness enhancement film comprises a PET / PI base material layer with the thickness of 20-50 [mu] m, a gradient brightening layer of 5-15 [mu] m; a 1-3 [mu] m anti-reflection layer; a 0.5-3 [mu] m composite protective layer; the preparation method comprises the steps of base material unwinding, plasma activating treatment, gradient coating of a PMMA solution containing nanoparticles, synchronous imprinting of the prism array and deposition of the anti-reflection layer, partitioned ultraviolet curing, electrostatic spraying of the protection layer, online detection and anti-adhesion winding. The ultrathin flexible brightness enhancement film can be used for a flexible display device, and has the advantages of low reflectivity, high brightness gain and excellent mechanical flexibility; in addition, the preparation method has the advantages of high-efficiency and low-cost large-scale production through a roll-to-roll continuous process.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of flexible display, more particularly, it relates to a kind of ultra-thin flexible brightness enhancement film and its roll-to-roll production process. BACKGROUND

[0002] In recent years, with the rapid development of flexible display technology, the application demand of ultra-thin flexible display device in the field of smart phone, wearable device, folding screen computer and the like is increasing day by day;As a key optical component in flexible display module, brightness enhancement film can significantly improve the brightness, contrast and viewing angle uniformity of display device by regulating light path propagation and reflection characteristics, thereby reducing power consumption and optimizing visual experience.

[0003] Traditional brightness enhancement film usually adopts single-layer coating structure with uniform refractive index, or only realizes light path regulation through surface prism array. Such design has limited ability to suppress the scattering and reflection of incident light, especially under complex ambient light, reflection loss leads to display picture contrast ratio decline, poor visibility, which cannot meet the dual requirements of high brightness and low reflectivity of flexible display device. SUMMARY

[0004] In order to solve the problem of high light reflection loss and insufficient light extraction efficiency of traditional brightness enhancement film in flexible display application, the present application provides an ultra-thin flexible brightness enhancement film and its roll-to-roll production process.

[0005] The ultra-thin flexible brightness enhancement film and its roll-to-roll production process provided by the present application adopt the following technical scheme: In a first aspect, the present application provides an ultra-thin flexible brightness enhancement film, which adopts the following technical scheme: An ultra-thin flexible brightness enhancement film, comprising, in sequence: A substrate layer: PET film or PI film with a thickness of 20-50 μm, the surface of the substrate layer is subjected to plasma activation treatment; A gradient brightness enhancement layer: with a thickness of 5-15 μm, composed of at least two layers of resin with a refractive index difference >0.15, the resin contains nano-silicon dioxide with a particle size of 20-50 nm and polymethyl methacrylate; An anti-reflection layer: a composite layer of magnesium fluoride and titanium dioxide with a thickness of 1-3 μm, the surface of the anti-reflection layer is provided with a nanostructure with a period of 100-200 nm; A composite protective layer: a polycarbonate and silica nanoparticle reinforced layer with a thickness of 0.5-3 μm, the surface of the composite protective layer has an asymmetric prism array with an apex angle of 45°-65°, the surface pencil hardness is 3H-5H and the water contact angle is >120°.

[0006] By adopting the technical scheme, due to the multi-layer structure design and material optimization, including plasma activation treatment of the substrate layer, refractive index difference control of the gradient brightening layer, nano-structure period design of the anti-reflection layer, asymmetric prism array and hydrophobicity enhancement of the composite protective layer, an ultra-thin flexible brightening film is obtained, which has high brightness gain, low reflectivity, high mechanical strength and hydrophobic self-cleaning property, and meets the strict requirements of flexible display devices on optical performance and reliability.

[0007] Preferably, the gradient brightening layer comprises a high-refractive-index resin layer and a low-refractive-index resin layer, the high-refractive-index resin has a refractive index of 1.60-1.70, the low-refractive-index resin comprises 10-20% by mass of nano-silicon dioxide, and the thickness difference between adjacent resin layers is 0.8-2 μm.

[0008] By adopting the technical scheme, due to the alternating stacking design of the high-refractive-index resin layer and the low-refractive-index resin layer, and the optimization of the thickness difference between adjacent layers and the mass fraction of nano-silicon dioxide, a light waveguide structure matched with the substrate layer is formed, and the total reflection loss of light at the interface between layers is reduced.

[0009] Preferably, the asymmetric prism array has an inclination angle α of 55°±5°, an inclination angle β of 35°±5°, and |α-β|≥15°, and the prism height is 3-12 μm.

[0010] By adopting the technical scheme, due to the inclination angle α and β design of the asymmetric prism array and the optimization of the prism height, the reflection glare of ambient light is reduced, and the outdoor display application requirement is met.

[0011] Preferably, the anti-reflection layer has a refractive index of 1.3-1.5, and the ratio of the depth to the width of the surface nano-structure is 1:1 to 1:1.5.

[0012] By adopting the technical scheme, due to the anti-reflection layer with a refractive index of 1.3-1.5 and the nano-structure with a depth to width ratio of 1:1 to 1:1.5, the reflectivity is further inhibited, and the light extraction efficiency is improved.

[0013] Preferably, the silica nano-particles in the protective layer have a particle size of 20-50 nm, and the mass fraction of the silica nano-particles is 5-8%.

[0014] By adopting the technical scheme, due to the silica nano-particles with a particle size of 20-50 nm, which is much smaller than the wavelength of visible light, the light scattering is effectively reduced; and due to the silica nano-particles with a mass fraction of 5-8%, which ensures sufficient mechanical enhancement effect and avoids the decrease in flexibility or poor processing performance caused by too high particle concentration.

[0015] In a second aspect, the application provides a roll-to-roll production process of an ultra-thin flexible brightness enhancement film, which adopts the following technical solution: A roll-to-roll production process of an ultra-thin flexible brightness enhancement film, comprising the following steps: S1, substrate unwinding: unwinding the PET film or PI film at a speed of 10-30 m / min; S2, plasma treatment: treating the surface of the substrate with a mixture of argon and oxygen gas under a vacuum degree of 0.1-10 Pa, a power density of 50-200 W / m 2 , and a treatment time of 10-30 s; S3, gradient coating: coating a polymethyl methacrylate solution containing nanosilica on the substrate layer through a slot coating device; S4, synchronous forming: simultaneously performing the following steps under a temperature of 80-150°C: using a nickel template to form an asymmetric prism array by imprinting; and depositing a mixed solution of magnesium fluoride and titanium dioxide by double-stage spin coating; S5, ultraviolet curing: using zoned radiation curing, a front zone radiation energy of 800-1200 mJ / cm 2 , and a rear zone radiation energy of 1200-1500 mJ / cm 2 ; S6, electrostatic spraying: spraying a polycarbonate solution containing silica nanoparticles; S7, online detection: using a combination of a CCD camera and a white light interference monitoring system for detection; S8, anti-blocking winding: winding after spraying an anti-blocking agent.

[0016] By adopting the above technical solution, since the steps of substrate unwinding, plasma treatment, gradient coating, synchronous forming, ultraviolet curing, electrostatic spraying, online detection, and anti-blocking winding are sequentially performed, and the process parameters of each step are optimized, the production cycle is greatly shortened, the yield stability is improved, and an efficient and reliable process path is provided for large-scale production of flexible display devices.

[0017] Preferably, in step S3, the polymethyl methacrylate solution contains 10-20% nanosilica by mass fraction, the solution concentration is 5-10%, and the coating speed is 1-5 m / min.

[0018] By adopting the above technical solution, since 10-20% nanosilica by mass fraction is used, the high refractive index of the nanosilica and the PMMA substrate form a refractive index gradient, significantly enhancing the light scattering effect.

[0019] Preferably, in step S4, the nickel template imprinting pressure is 0.5-2 MPa, and the pressure maintaining time is 5-15 s; in the two-stage spin coating, the first-stage rotation speed is 1000-2000 r / min, the second-stage rotation speed is 2000-3000 r / min, and the total spin coating time is 30-60 s.

[0020] By adopting the above technical scheme, the optical performance consistency of the brightness enhancement film is further ensured, and the long-term reliability requirement of the flexible display device is met.

[0021] Preferably, in step S6, the voltage of the electrostatic spraying is 5-10 kV; the mass fraction of the silica nanoparticles in the polycarbonate solution is 5-8%, and the particle size of the nanoparticles is 20-50 nm.

[0022] By adopting the above technical scheme, since the electrostatic spraying voltage is 5-10 kV, the polycarbonate solution forms a uniform charge distribution on the surface of the substrate, reducing the peeling and defects of the coating; since the mass fraction of the silica nanoparticles is 5-8% and the particle size is 20-50 nm, the polycarbonate solution forms a surface composite protective layer, thereby improving the wear resistance, enhancing the hydrophobic self-cleaning property, and reducing the adhesion of fingerprints and water stains.

[0023] Preferably, in step S8, the anti-blocking agent has a particle size of 0.1-0.5 μm, the coverage of the anti-blocking agent on the surface of the rolled material is 30-60%, and the rolling tension is controlled to be 5-15 N.

[0024] By adopting the above technical scheme, since the anti-blocking agent has a particle size of 0.1-0.5 μm, the sub-micron particle size can form a uniform isolation layer on the surface of the rolled material, reducing the structural damage and optical performance decline caused by adhesion.

[0025] In summary, the present application has the following beneficial effects: 1. Since the present application adopts at least two gradient brightness enhancement layers with a refractive index difference greater than 0.15, the design combines the periodic nanostructure on the surface of the anti-reflection layer and the asymmetric prism array, achieving a synergistic effect of significantly reducing light reflection loss and improving light extraction efficiency.

[0026] 2. In the present application, an asymmetric prism array with an apex angle of 45°-65° and an absolute value of inclination angle difference of not less than 15° is preferably adopted, which, in combination with the composite protective layer enhanced by polycarbonate and silica nanoparticles of a specific particle size, achieves high wear resistance and long-term hydrophobicity with stable maintenance of the film layer pencil hardness of 3H-5H and the water contact angle of more than 120°.

[0027] 3、The method of the application, by synchronously performing the integrated molding process of imprinting and double-stage spin coating, combining plasma-activated substrate surface and partitioned ultraviolet radiation curing, and through electrostatic spraying control of nanoparticle dispersion and anti-adhesion winding parameter regulation, thus obtaining the production stability improvement of interlayer adhesion force strengthening, uniform thermal stress distribution and significantly reduced defect rate. DETAILED DESCRIPTION

[0028] The application will be further described in detail below in combination with embodiments.

[0029] Technical ideas: The traditional brightness enhancement film uses a single-layer resin structure, the refractive index gradient is insufficient, and the light is significantly lost by total reflection at the interface; the symmetrical prism array has limited regulation ability for multi-angle incident light; the anti-reflection layer and the protective layer deposited in steps are prone to interlayer separation during bending due to the difference in thermal expansion coefficient; and the substrate thermal deformation and interlayer misalignment caused by independent process steps result in the displacement of the film layer structure during continuous winding.

[0030] The application solves the above problems by the following technical means: 1. Material design: introducing 20-50 nm particle size range of nano-silicon dioxide in the gradient brightness enhancement layer, by controlling its mass fraction in polymethyl methacrylate resin, a stack structure with a refractive index difference between adjacent layers greater than 0.15 is constructed; 2. Optical structure optimization: using an asymmetric prism array with an inclination angle α = 55° ± 5°, β = 35° ± 5° and | α - β | ≥ 15°, and a prism height of 3-12 μm; 3. Process integration: synchronously performing nickel template imprinting and double-stage spin coating at a temperature of 80-150°C, and combining plasma-activated substrate and partitioned ultraviolet curing to realize interlayer stress cooperative release.

[0031] The application provides an ultrathin flexible brightness enhancement film and a roll-to-roll production process thereof. The ultrathin flexible brightness enhancement film and the roll-to-roll production process thereof provided by the embodiments of the application will be described in detail below.

[0032] According to a first aspect of the application, the application provides an ultrathin flexible brightness enhancement film, which adopts the following technical scheme: An ultrathin flexible brightness enhancement film, comprising, in sequence: A substrate layer: a PET film or a PI film with a thickness of 20-50 μm, the surface of the substrate layer being subjected to plasma activation treatment; A gradient brightness enhancement layer: with a thickness of 5-15 μm, composed of at least two layers of resin with a refractive index difference >0.15, the resin containing 20-50 nm particle size of nano-silicon dioxide and polymethyl methacrylate; Anti-reflection layer: a composite layer of magnesium fluoride and titanium dioxide with a thickness of 1-3 μm, and a nanostructure with a period of 100-200 nm on the surface of the anti-reflection layer; Composite protective layer: a polycarbonate and silica nanoparticle reinforced layer with a thickness of 0.5-3 μm, and an asymmetric prism array with an apex angle of 45°-65° on the surface of the composite protective layer, and a pencil hardness of 3H-5H and a water contact angle > 120° on the surface.

[0033] Specifically, the substrate layer is a PET film or a PI film with a thickness of 20-50 μm, and the surface of the substrate layer is treated by plasma activation to enhance the adhesion between layers and improve the surface wettability, thereby improving the stability of the combination of the substrate layer and the subsequent functional layer, and preventing the separation between layers of the brightness enhancement film during bending or use. The gradient brightness enhancement layer is composed of at least two layers of resin with a refractive index difference of more than 0.15, and the thickness of the gradient brightness enhancement layer is 5-15 μm. The resin contains nano-silica with a particle size of 20-50 nm and polymethyl methacrylate, which reduces the total reflection loss of light at the interface and improves the light extraction efficiency. Thus, the optical performance of the brightness enhancement film is significantly enhanced, and the brightness enhancement film can provide higher brightness gain in display applications. The anti-reflection layer is a composite layer of magnesium fluoride and titanium dioxide with a thickness of 1-3 μm, and a nanostructure with a period of 100-200 nm is arranged on the surface of the anti-reflection layer, which reduces the reflectivity of light and improves the transmittance of light. Thus, the display device surface reflection is reduced, and the display clarity is improved, especially in strong light environment, the visibility is still good. The composite protective layer is a polycarbonate and silica nanoparticle reinforced layer with a thickness of 0.5-3 μm, and an asymmetric prism array with an apex angle of 45°-65° is arranged on the surface of the composite protective layer, and the surface pencil hardness is 3H-5H and the water contact angle is greater than 120°. Thus, the mechanical strength of the film layer is enhanced, the wear resistance and hydrophobicity are improved, the internal structure of the brightness enhancement film is protected from external damage, and the service life is prolonged. At the same time, the brightness enhancement film can still maintain good performance stability in a humid environment.

[0034] The gradient brightness enhancement layer comprises a high refractive index resin layer and a low refractive index resin layer. The high refractive index resin has a refractive index of 1.60-1.70, and the low refractive index resin contains 10-20% of nano-silica by mass fraction. The thickness difference between adjacent resin layers is 0.8-2 μm.

[0035] Specifically, by setting the high refractive index resin layer and the low refractive index resin layer in the gradient brightening layer, and controlling the thickness difference of the adjacent resin layers, the effect of constructing a multi-stage refractive index gradient and optimizing the light propagation path is achieved. The high refractive index layer can enhance the deflection ability of light, and the addition of nano-silicon dioxide in the low refractive index layer further adjusts the refractive index and enhances the light scattering effect, and the synergistic effect of the two reduces the reflection loss of light at the interface between the layers; and further, the effect of significantly improving the optical efficiency of the brightening film is achieved, so that the light realizes more efficient transmission and deflection in the multi-layer structure, thereby providing higher brightness gain and more uniform light distribution in display applications. At the same time, the precise control of the thickness difference of the adjacent resin layers helps to eliminate stress concentration between the layers, and improves the mechanical stability and bending reliability of the film layer.

[0036] The tilt angle α of the asymmetric prism array is 55°±5°, the tilt angle β is 35°±5°, and |α-β|≥15°, and the prism height is 3-12 μm.

[0037] Specifically, by setting the tilt angle α of the asymmetric prism array to 55°±5°, the tilt angle β to 35°±5°, and ensuring that |α-β|≥15°, and controlling the prism height to be 3-12 μm, the effect of multi-angle control of light deflection path and optimization of light field distribution is achieved. The asymmetric tilt angle design makes the prism have differentiated deflection ability for light of different incident angles, wherein the α angle enhances the convergence effect of light at normal viewing angle, and the β angle improves the utilization rate of light at oblique viewing angle, and the synergistic effect of the two can cover a wider viewing angle range. The control of the prism height of 3-12 μm further enhances the accurate control of the light path difference, and at the same time avoids the structural fragility caused by too high prism or the insufficient optical efficiency caused by too low prism.

[0038] The refractive index of the anti-reflection layer is 1.3-1.5, and the depth-to-width ratio of the surface nanostructure is 1:1 to 1:1.5.

[0039] Specifically, by setting the refractive index of the anti-reflection layer and controlling the depth-to-width ratio of the surface nanostructure, the effect of double optimization of light reflection suppression is achieved. The low refractive index anti-reflection layer can reduce the interface reflectivity and reduce the loss of light at the interface between the brightening film and air; and the specific ratio design of the depth and width of the nanostructure forms a sub-wavelength periodic structure, which causes diffraction and interference effect of incident light on the surface of the nanostructure, further weakens the reflection light intensity, and at the same time enhances the uniformity of the transmitted light; the synergistic effect of the nano-scale structure and the low refractive index material can effectively suppress the reflectivity in a wide wavelength band.

[0040] The particle size of the silicon dioxide nanoparticles in the protective layer is 20-50 nm, and the mass fraction of the silicon dioxide nanoparticles is 5-8%.

[0041] Specifically, by controlling the particle size of the silicon dioxide nanoparticles to be 20-50 nm, the mechanical strength and optical transparency of the polycarbonate substrate are enhanced. This particle size range can achieve uniform dispersion of the nanoparticles in the substrate, avoiding the decrease in light transmittance caused by too large particles or the agglomeration problem caused by too small particles; by controlling the mass fraction of the silicon dioxide nanoparticles to be 5-8%, the balance between the hardness and flexibility of the protective layer is optimized.

[0042] According to the second aspect of the present application, the present application provides a roll-to-roll production process of an ultra-thin flexible brightness enhancement film, which adopts the following technical scheme: A roll-to-roll production process of an ultra-thin flexible brightness enhancement film, comprising the following steps: S1, unwinding the substrate: unwinding the PET film or PI film at a speed of 10-30 m / min; S2, plasma treatment: treating the surface of the substrate with a mixed gas of argon and oxygen under a vacuum degree of 0.1-10 Pa, a power density of 50-200 W / m 2 , and a treatment time of 10-30 s; S3, gradient coating: coating a polymethyl methacrylate solution containing nano-silicon dioxide on the substrate layer by a slot coating device; S4, synchronous forming: simultaneously performing the following steps under a temperature of 80-150°C: forming an asymmetric prism array by using a nickel template for imprinting; and depositing a mixed solution of magnesium fluoride and titanium dioxide by two-stage spin coating; S5, ultraviolet curing: curing by partitioned radiation, a front zone radiation energy of 800-1200 mJ / cm 2 , and a rear zone radiation energy of 1200-1500 mJ / cm 2 ; S6, electrostatic spraying: spraying a polycarbonate solution containing silicon dioxide nanoparticles; S7, online detection: detecting by combining a CCD camera and a white light interference monitoring; S8, anti-blocking winding: winding after spraying an anti-blocking agent.

[0043] Specifically, by unwinding the PET film or PI film at a speed of 10-30 m / min, the substrate is stably supplied and the production line rhythm is controlled, thereby ensuring the continuity of the subsequent process and the production efficiency, and avoiding the substrate tension fluctuation or process delay caused by too fast or too slow unwinding speed; by treating the surface of the substrate with a mixed gas of argon and oxygen under a vacuum degree of 0.1-10 Pa, a power density of 50-200 W / m 2, the processing time is 10-30s, which plays a role in cleaning the surface of the substrate, improving the surface wettability and interlayer adhesion, and further enhances the stability of the substrate layer and the subsequent functional layer, ensuring that the brightness film is not prone to interlayer separation during bending or use, and improving the spreading and uniformity of the coating liquid; the PMMA solution containing nano-silicon dioxide is coated on the substrate layer through a slot coating device, which plays a role in forming a gradient brightening layer and provides a basis for subsequent optimization of optical performance; and further achieves the effect of controlling the thickness and uniformity of the gradient brightening layer, ensuring that the brightness film has high light extraction capability under different wavebands; under the temperature of 80-150°C, the following steps are performed simultaneously: using a nickel template to form an asymmetric prism array by imprinting; a mixed solution of magnesium fluoride and titanium dioxide is deposited by double-stage spin coating, which plays a role in simultaneously constructing an optical structure and an anti-reflection layer; and further achieves the effects of simplifying the process flow and improving the production efficiency, while ensuring the structural precision and optical performance of the asymmetric prism array and the anti-reflection layer, reducing light reflection loss, and improving brightness gain; by using partitioned radiation curing, the front area radiation energy is 800-1200mJ / cm 2 , and the rear area radiation energy is 1200-1500mJ / cm 2 , which plays a role in gradually curing the coating and reducing curing stress; and further achieves the effects of ensuring complete coating curing and avoiding curing cracks or interlayer peeling, while improving the mechanical strength and optical stability of the coating; by spraying a polycarbonate solution containing silicon dioxide nanoparticles, a composite protective layer is formed, which enhances the mechanical strength and hydrophobicity of the brightness film; and further achieves the effects of improving the surface hardness, wear resistance and hydrophobicity of the brightness film, prolonging the service life of the brightness film, while maintaining its optical transparency; by using a combination of CCD camera and white light interference monitoring for detection, the surface quality and structural precision of the brightness film are monitored in real time; and further achieves the effects of timely discovering and correcting defects or deviations in the production process, ensuring that the optical performance and mechanical performance of the brightness film meet the design requirements, and improving the product yield; by spraying an anti-adhesion agent and then winding, the brightness film is prevented from sticking or being damaged during the winding process; and further achieves the effects of protecting the surface quality of the brightness film, facilitating subsequent processing or application, while improving the winding efficiency and flatness of the roll.

[0044] In step S3, the PMMA solution contains 10-20% nano-silicon dioxide by mass fraction, and the solution concentration is 5-10%; the coating speed is 1m-5m / min.

[0045] Specifically, by controlling the mass fraction of nano-silicon dioxide to be 10-20%, the synergistic effect of enhancing the mechanical strength and optical scattering performance of the PMMA matrix is achieved; by controlling the PMMA solution concentration to be 5-10%, the effect of balancing the coating process and coating performance is achieved.

[0046] In step S4, the nickel template imprinting pressure is 0.5-2 MPa, and the pressure holding time is 5-15 s; in the two-stage spin coating, the first-stage rotation speed is 1000-2000 r / min, and the second-stage rotation speed is 2000-3000 r / min, and the total spin coating time is 30-60 s.

[0047] Specifically, by controlling the imprinting pressure to be 0.5-2 MPa, the function of accurately copying the asymmetric prism array structure of the nickel template on the surface of the substrate is achieved; by controlling the pressure holding time to be 5-15 s, the function of ensuring complete curing and stable forming of the prism array structure is achieved; by controlling the first-stage rotation speed to be 1000-2000 r / min, the function of preliminarily spreading the mixed solution of magnesium fluoride and titanium dioxide and forming a uniform coating is achieved; by controlling the second-stage rotation speed to be 2000-3000 r / min, the function of further flattening the coating and reducing surface defects is achieved; by controlling the total spin coating time to be 30-60 s, the function of balancing the coating quality and production efficiency is achieved.

[0048] In step S6, the voltage of the electrostatic spraying is 5-10 kV; the mass fraction of the silica nanoparticles in the polycarbonate solution is 5-8%, and the particle size of the nanoparticles is 20-50 nm.

[0049] Specifically, by controlling the voltage of the electrostatic spraying to be 5-10 kV, the function of electrifying the polycarbonate solution and uniformly spraying it on the surface of the substrate is achieved; by controlling the mass fraction of the silica nanoparticles to be 5-8%, the function of synergistically enhancing the mechanical strength and hydrophobicity of the polycarbonate coating is achieved; by controlling the particle size of the silica nanoparticles to be 20-50 nm, the function of forming a micro-nano composite structure in the polycarbonate coating and enhancing the optical transparency and mechanical strength is achieved.

[0050] In step S8, the particle size of the anti-adhesion agent is 0.1-0.5 μm, the coverage of the anti-adhesion agent on the surface of the rolled material is 30-60%, and the rolling tension is controlled to be 5-15 N.

[0051] Specifically, by controlling the particle size of the anti-adhesion agent to be 0.1-0.5 μm, the function of forming a micro-protrusion structure on the surface of the brightening film and reducing the interlayer contact area is achieved; by controlling the coverage of the anti-adhesion agent to be 30-60%, the function of balancing the anti-adhesion effect and the surface optical performance is achieved; by controlling the rolling tension to be 5-15 N, the function of ensuring the rolling flatness and avoiding interlayer slipping or film material tensile deformation is achieved.

[0052] In order to better understand the above technical solutions, the technical solutions of the present application will be described clearly and completely in conjunction with the embodiments.

[0053] The experimental methods used below are conventional methods unless otherwise specified. The materials, reagents, methods and instruments used, unless specifically stated, are conventional materials, reagents, methods and instruments in the art, which can be obtained by commercial channels or prepared according to the literature methods by those skilled in the art.

[0054] Example 1 The embodiment of the present application provides a kind of ultra-thin flexible brightness enhancement film, including sequentially laminated: Substrate layer: the PET film with thickness of 50 μm, surface is treated by plasma activation; Gradient brightness enhancement layer: thickness is 15 μm, by three layers of refractive index difference >0.15 composite, resin includes the nano-silica with particle size of 50 nm and polymethyl methacrylate; Anti-reflection layer: the fluorinated magnesium and titanium dioxide composite layer with thickness of 3 μm, surface is equipped with nanometer structure of period 200 nm; Composite protective layer: the polycarbonate and silica nanoparticle reinforced layer with thickness of 3 μm, surface has the asymmetric prism array with vertex angle 65 °, pencil hardness 5H, water contact angle >120 ° The roll-to-roll production process of the above-mentioned one kind of ultra-thin flexible brightness enhancement film, comprising the following steps: S1, substrate unwinding: PET film is unwound at a speed of 30 m / min; S2, plasma treatment: argon-oxygen mixed gas, vacuum degree 10 Pa, power density 200 W / m 2 , time 10 s; S3, gradient coating: slot coating polymethyl methacrylate solution containing 20% nano-silica, solution concentration is 10%, coating speed is 5 m / min; S4, synchronous forming: synchronous execution under temperature 150 °C: Nickel template imprinting, pressure 2 MPa, pressure maintaining 5 s; Two-stage spin coating: first stage 2000 r / min, second stage 3000 r / min, total time 30 s; S5, ultraviolet curing: using partition radiation curing, front zone radiation energy 1200 mJ / cm 2 , rear zone radiation energy 1500 mJ / cm 2 ; S6, electrostatic spraying: voltage 10 kV, the mass fraction of silica nanoparticles in sprayed polycarbonate solution is 8%, particle size is 50 nm; S7, online detection: using CCD camera and white light interference monitoring combined detection; S8, anti-blocking winding: spraying 0.5 μm anti-blocking agent, the coverage range of anti-blocking agent on the surface of winding material is 60%, and the winding tension is controlled at 15 N.

[0055] Example 2 The embodiment of the present application provides a kind of super-thin flexible brightness enhancement film, including sequentially laminated: Substrate layer: the PI film with the thickness of 35 μm, surface is treated by plasma activation; Gradient brightening layer: the thickness is 10 μm, by two refractive index difference >0.15 resin complex, resin includes the nano-silica with the particle size of 35 nm and polymethyl methacrylate; Anti-reflection layer: the fluorinated magnesium and titanium dioxide complex layer with the thickness of 2 μm, surface is equipped with the nanometer structure of period 150 nm; Composite protective layer: the polycarbonate and silica nanoparticle reinforced layer with the thickness of 1.8 μm, surface has the asymmetric prism array with the vertex angle of 55 °, pencil hardness 4H, water contact angle >120 ° The roll-to-roll production process of the above-mentioned super-thin flexible brightness enhancement film, comprising the following steps: S1, substrate unwinding: PI film is unwound at a speed of 20 m / min; S2, plasma treatment: argon-oxygen mixed gas, vacuum degree 5 Pa, power density 125 W / m 2 , time 20 s; S3, gradient coating: slot coating polymethyl methacrylate solution containing 15% nano-silica, solution concentration 7.5%, coating speed is 3 m / min; S4, synchronous forming: synchronous execution under the temperature of 115 °C: Nickel template imprinting, pressure 1.25 MPa, pressure maintaining 10 s; Double-stage spin coating: first stage 1500 r / min, second stage 2500 r / min, total time 45 s; S5, ultraviolet curing: adopts partition radiation curing, front zone radiation energy 1000 mJ / cm 2 , rear zone radiation energy 1350 mJ / cm 2 ; S6, electrostatic spraying: voltage 7.5 kV, the mass fraction of silica nanoparticles in sprayed polycarbonate solution is 6.5%, and the particle size is 35 nm; S7, online detection: CCD camera and white light interference monitoring combined detection are used; S8, anti-blocking winding: 0.3 μm anti-blocking agent is sprayed, the coverage range of anti-blocking agent on the surface of winding material is 45%, and the winding tension is controlled to be 10 N.

[0056] Example 3 The embodiment of the present application provides a kind of super-thin flexible brightness enhancement film, including sequentially laminated: Substrate layer: PET film with thickness of 20 μm, surface treated by plasma activation; Gradient brightening layer: 5 μm thick, composed of two layers of resins with refractive index difference >0.15, the resins containing 20 nm nano-silica and polymethyl methacrylate; Anti-reflection layer: 1 μm thick composite layer of magnesium fluoride and titanium dioxide, surface provided with periodic 100 nm nano-structure; Composite protective layer: 0.5 μm thick layer of polycarbonate and silica nanoparticle reinforced layer, surface provided with asymmetric prism array with 45° vertex angle, pencil hardness 3H, water contact angle >120°.

[0057] The roll-to-roll production process of the above-mentioned ultra-thin flexible brightening film includes the following steps: S1, substrate unwinding: PET film unwound at a speed of 10 m / min; S2, plasma treatment: argon-oxygen mixed gas, vacuum degree 0.1 Pa, power density 50 W / m 2 , time 30 s; S3, gradient coating: slot coating of polymethyl methacrylate solution containing 10% nano-silica, solution concentration 5%, coating speed 1 m / min; S4, synchronous forming: synchronous execution at a temperature of 80°C: Nickel template imprinting, pressure 0.5 MPa, pressure holding time 15 s; Two-stage spin coating: first stage 1000 r / min, second stage 2000 r / min, total time 60 s; S5, ultraviolet curing: using zoned radiation curing, front zone radiation energy 800 mJ / cm 2 , back zone radiation energy 1200 mJ / cm 2 ; S6, electrostatic spraying: voltage 5 kV, silica nanoparticle mass fraction in sprayed polycarbonate solution 5%, particle size 20 nm; S7, online detection: combined detection using CCD camera and white light interference monitoring; S8, anti-blocking winding: spraying of 0.1 μm anti-blocking agent, anti-blocking agent coverage on the surface of the wound material in the range of 30%, winding tension controlled at 5 N.

[0058] The key performance comparison table of Examples 1-3 is shown in Table 1.

[0059] Table 1:

[0060] Conclusion: According to the data in Table 1, Example 2 has the best comprehensive performance by a specific combination of parameters, and the brightness gain is 48.2%, which is 14.5% higher than that of Example 1 and 24.5% higher than that of Example 3, thereby solving the problem of efficiency decay of traditional brightness enhancement films under oblique incidence of light.

[0061] Comparative Example 1 The comparative example of the present application provides a conventional ultra-thin brightness enhancement film, which comprises, in sequence: a substrate layer: a PET film with a thickness of 35 μm, which is not subjected to plasma activation treatment; a brightness enhancement layer: a polymethyl methacrylate layer with a thickness of 10 μm, which does not contain nanoparticles; an anti-reflection layer: a magnesium fluoride single layer with a thickness of 2 μm, which has no nanostructure on the surface; a protective layer: a UV hardened resin layer with a thickness of 1.8 μm, which has a symmetric prism array with a top angle of 90° on the surface A roll-to-roll production process of the above-mentioned conventional ultra-thin brightness enhancement film comprises the following steps: S1, substrate unwinding: unwinding the PET film at a speed of 20 m / min; S3, coating: coating the polymethyl methacrylate solution on the substrate layer by a slot coating device, the solution concentration is 10%, and the coating speed is 3 m / min; S4, step-by-step forming: firstly performing anti-reflection layer deposition: spin coating the magnesium fluoride solution at a speed of 1500 r / min for 30 s; then performing imprinting: imprinting the prism array at 120 °C using a nickel template, the pressure is 1 MPa, and the pressure holding time is 10 s; S5, ultraviolet curing: single-zone radiation curing is adopted, and the radiation energy is 1200 mJ / cm 2 ; S6, electrostatic spraying: spraying the UV hardened resin solution under the condition of a voltage of 7.5 kV; S7, online detection: CCD camera detection is adopted; S8, anti-blocking winding: the winding tension is controlled at 10 N.

[0062] Note: In the present comparative example, the plasma treatment and gradient coating are omitted, and the anti-reflection layer and the protective layer are processed step by step.

[0063] Comparative Example 2 The comparative example of the present application provides a brightness enhancement film, which comprises, in sequence: a substrate layer: a PI film with a thickness of 35 μm, which is subjected to plasma activation treatment on the surface; a brightness enhancement layer: a single-layer polymethyl methacrylate layer with a thickness of 10 μm, which contains 15% of nano-silicon dioxide with a particle size of 35 nm by mass fraction; Anti-reflective layer: 2 pm thick MgF2 / TiO2 composite layer with 150 nm period nanostructure on the surface; Composite protective layer: 1.8 pm thick polycarbonate / silica nanoparticle reinforced layer with asymmetric prism array of 55° tip angle on the surface, pencil hardness 4H, water contact angle > 120°.

[0064] The roll-to-roll production process of the above-mentioned brightness enhancement film comprises the following steps: S1, substrate unwinding: unwinding the PI film at a speed of 20 m / min; S2, plasma treatment: treating the surface of the substrate with a mixed gas of argon and oxygen under a vacuum degree of 5 Pa, power density 125 W / m 2 , time 20 s; S3, single-layer coating: coating a polymethyl methacrylate solution containing 15% nanosilica on the substrate layer by a slot coating device, solution concentration 7.5%, coating speed 3 m / min; S4, step forming: Nickel template imprinting: imprinting to form an asymmetric prism array at 115°C, pressure 1.25 MPa, pressure holding time 10 s; Anti-reflective layer independent preparation: pre-depositing a MgF2 / TiO2 composite layer by magnetron sputtering, sputtering power 1.5 kW, argon flow rate 50 sccm, substrate temperature 80°C; S5, ultraviolet curing: using zoned radiation curing, front zone radiation energy 1000 mJ / cm 2 , back zone radiation energy 1350 mJ / cm 2 ; S6, electrostatic spraying: voltage 7.5 kV, spraying a polycarbonate solution containing 6.5% silica nanoparticles with a particle size of 35 nm; S7, online detection: using a combination of a CCD camera and a white light interference monitoring for detection; S8, anti-adhesion winding: spraying 0.3 pm anti-adhesion agent, coverage rate 45%, winding tension 10 N.

[0065] Comparative Example 3 The comparative example of the present application provides a brightness enhancement film, and each layer is stacked with the structure of Example 2.

[0066] The roll-to-roll production process of the above-mentioned brightness enhancement film comprises the following steps: S1, substrate unwinding: unwinding the PI film at a speed of 20 m / min; S2, plasma treatment: treating the surface of the substrate with a mixed gas of argon and oxygen under a vacuum degree of 5 Pa, power density 300 W / m 2 , time 20 s; S3, Gradient coating: PMMA solution with 15% nano-silica was coated on the substrate layer by slot-die coating device, solution concentration 7.5%, coating speed 3 m / min; S4, Synchronous forming: Synchronously executed at temperature 115 °C environment: Nickel template imprinting to form asymmetric prism array, pressure 1.25 MPa, pressure holding time 10 s; Two-stage spin coating to deposit MgF2 and TiO2 mixed solution: first stage speed 1500 r / min, second stage speed 2500 r / min, total time 45 s; S5, UV curing: using partition radiation curing, front zone radiation energy 1000 mJ / cm 2 , back zone radiation energy 1350 mJ / cm 2 ; S6, Electrostatic spraying: voltage 7.5 kV, the mass fraction of silica nanoparticles in the sprayed polycarbonate solution is 12%, and the particle size is 35 nm; S7, Online detection: using CCD camera and white light interference monitoring combined detection; S8, Anti-adhesion winding: spraying 0.3 μm anti-adhesion agent, coverage rate 45%, winding tension control at 20 N.

[0067] The key performance comparison table of Comparative Examples 1-3 and Example 2 is shown in Table 2.

[0068] Table 2:

[0069] It can be seen from Example 2 and Comparative Example 1 in combination with Table 2 that, due to the absence of gradient brightening layer and plasma treatment, the optical performance of Comparative Example 1 is greatly attenuated. The brightness gain is reduced to 28.5%, the reflectivity is increased to 4.3%, the light extraction efficiency is lost by 32.3%; the interlayer adhesion is reduced to level 3, the substrate interface is not activated, resulting in film layer falling area > 15%; the step-by-step processing process causes the mismatch of thermal expansion coefficient 2.3 ppm / °C, the winding misalignment amount reaches 0.82 mm / 100 m, and the defect density is increased to 0.35 / m 2 , confirming that plasma interface activation and gradient structure are the core guarantee of optical-mechanical performance.

[0070] It can be seen from the combination of Example 2 and Comparative Example 2 and Table 2 that the single-layer brightening structure and the magnetic control sputtering step-by-step process of Comparative Example 2 exposes two technical bottlenecks: the brightness gain is only 35.2%, and the interface reflection loss of the single-layer structure increases by 40%; the high-temperature sputtering process increases the energy consumption by 65%, causing thermal deformation of the substrate; the step-by-step processing causes the interlayer thermal stress to be > 150 MPa, the bending life to decrease to 73600 times, and the SEM to show a significant increase in interface microcracks. This shows that the synchronous forming process and the multi-layer refractive design have irreplaceability in suppressing optical loss and thermal stress.

[0071] It can be seen from the combination of Example 2 and Comparative Example 3 and Table 2 that the parameters of Comparative Example 3 are out of limits, causing a cascade failure: 300W / m 2 The plasma treatment causes the PET molecular chain to break, the light transmittance to decay by > 1.5%, and the reflectance to increase to 2.9%; the 12% silicon dioxide content causes the spraying liquid viscosity to be > 120 cP, the droplet particle size Dv50 to increase to 23 μm, and the haze increase to be 1.15%; the 20N winding tension causes the substrate elongation to exceed the safety threshold of 0.5%, the microcrack density to be > 120 / mm 2 , and the bending life to decrease to 81200 times. The accurate control of the process parameter threshold is a key constraint condition for stable mass production.

[0072] The specific embodiments are merely an explanation of the present application, and are not a limitation of the present application. Those skilled in the art can make modifications to the embodiments without creative contribution after reading the present specification, and the modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. An ultrathin flexible brightening film, characterized in that: Including those stacked in sequence: Substrate layer: PET or PI film with a thickness of 20-50 μm, the surface of which is subjected to plasma activation treatment; Gradient brightening layer: with a thickness of 5-15μm, composed of at least two layers of resin with a refractive index difference >0.15, wherein the resin contains nano-silica with a particle size of 20-50nm and polymethyl methacrylate; Anti-reflective layer: a composite layer of magnesium fluoride and titanium dioxide with a thickness of 1-3 μm, wherein the surface of the anti-reflective layer is provided with a nanostructure with a period of 100-200 nm; Composite protective layer: a polycarbonate and silica nanoparticle reinforcing layer with a thickness of 0.5-3μm, the surface of the composite protective layer has an asymmetric prism array with a vertex angle of 45°-65°, a surface pencil hardness of 3H-5H and a water contact angle >120°.

2. The ultrathin flexible brightening film according to claim 1, characterized in that: The gradient brightening layer comprises a high refractive index resin layer and a low refractive index resin layer. The high refractive index resin has a refractive index of 1.60-1.70, and the low refractive index resin contains 10-20% by mass of nano-silica. The thickness difference between adjacent resin layers is 0.8-2 μm.

3. The ultrathin flexible brightening film according to claim 1, characterized in that: The asymmetric prism array has a tilt angle α = 55° ± 5°, a tilt angle β = 35° ± 5° and |α - β| ≥ 15°, and the prism height is 3-12 μm.

4. The ultrathin flexible brightening film according to claim 1, characterized in that: The antireflective layer has a refractive index of 1.3-1.5, and the depth-to-width ratio of its surface nanostructure is 1:1 to 1:1.

5.

5. The ultrathin flexible brightening film according to claim 1, characterized in that: The silica nanoparticles in the protective layer have a particle size of 20-50 nm and a mass fraction of 5-8%.

6. A roll-to-roll production process for an ultrathin flexible brightening film, characterized in that, The ultrathin flexible brightening film according to any one of claims 1-5 comprises the following steps: S1. Substrate unwinding: Unwind the PET film or PI film at a speed of 10-30m / min; S2. Plasma treatment: The substrate surface is treated with a mixture of argon and oxygen gas under a vacuum of 0.1-10 Pa, with a power density of 50-200 W / m2 and a treatment time of 10-30 s. S3, Gradient Coating: A polymethyl methacrylate solution containing nano-silica is coated onto the substrate layer using a slit coating device; S4. Synchronous molding: Simultaneous execution at a temperature of 80-150℃: Asymmetric prism array is formed by imprinting with a nickel template; a mixed solution of magnesium fluoride and titanium dioxide is deposited by two-stage spin coating. S5. UV curing: Partitioned radiation curing is adopted, with radiation energy of 800-1200mJ / cm2 in the front zone and 1200-1500mJ / cm2 in the rear zone. S6. Electrostatic spraying: Spraying a polycarbonate solution containing silica nanoparticles; S7. Online inspection: Detection is carried out using a combination of CCD camera and white light interferometry monitoring; S8. Anti-adhesion winding: Wind up after spraying anti-adhesion agent.

7. The roll-to-roll production process of an ultrathin flexible brightening film according to claim 6, characterized in that: In step S3, the polymethyl methacrylate solution contains 10-20% by mass of nano-silica, and the solution concentration is 5-10%; the coating speed is 1m-5m / min.

8. The roll-to-roll production process of an ultrathin flexible brightening film according to claim 6, characterized in that: In step S4, the nickel template imprinting pressure is 0.5-2MPa, and the holding time is 5-15s; in the two-stage spin coating, the first stage rotation speed is 1000-2000r / min, the second stage rotation speed is 2000-3000r / min, and the total spin coating time is 30-60s.

9. The roll-to-roll production process of an ultrathin flexible brightening film according to claim 6, characterized in that: In step S6, the voltage of the electrostatic spraying is 5-10kV; the mass fraction of silica nanoparticles in the polycarbonate solution is 5-8%, and the particle size of the nanoparticles is 20-50nm.

10. The roll-to-roll production process of an ultrathin flexible brightening film according to claim 6, characterized in that: In step S8, the anti-blocking agent has a particle size of 0.1-0.5μm, the anti-blocking agent has a coverage rate of 30-60% on the surface of the winding material, and the winding tension is controlled at 5-15N.

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