TWI688464B - Bionic brightness-enhancing film, its preparation method and applied optical element - Google Patents

Abstract

The invention relates to a bionic brightness enhancing film, a method for manufacturing the same, and an optical element using the same, which includes a polystyrene nanosphere synthesis step, a non-compact single-layer nanosphere array template preparation step, and a transparent brightness enhancement layer preparation step. The synthesis step of polystyrene nanospheres is synthesized by emulsification polymerization without emulsifier into polystyrene nanosphere suspension. The preparation step of the non-compact single-layer nanosphere array template is to assemble and arrange the polystyrene nanospheres in the polystyrene nanosphere suspension on the substrate surface into a single-layer non-compact nanosphere array by (LB) deposition method template. The preparation step of the transparent brightness enhancement layer is to make the nanosphere array template into a template with a sub-wavelength structure through the nanoimprint lithography technology, and then print the template on the application part after turning the mold to make the application part transparent and brighten The layer can be used to imitate the transparent brightness enhancement layer made by imitating the surface of grasshopper's wings, in addition to effectively reducing the difference in refractive index between the packaging material and the air, and improving the luminous efficiency of the LED.

Description

Bionic brightness-enhancing film, its preparation method and applied optical element

The invention relates to a bionic brightness enhancing film, a method for manufacturing the same, and optical elements for its application, in particular to a bionic brightness enhancing film technology that can be made by imitating a transparent brightness enhancing layer made on the surface of grasshopper wings.

In the global trend of energy saving and carbon reduction, how to improve the utilization rate of photovoltaic elements and reduce energy consumption becomes particularly important in the case of tight energy supply. Light-Emitting Diode (LED) is a lighting element with characteristics of small volume, fixed light wavelength, low power consumption, etc., and is widely used. However, due to the influence of the LED on the structure and the encapsulation resin, the total reflection often occurs at the interface of different materials, and the light cannot be effectively exported, resulting in only about 15% of its external quantum efficiency. According to Fresnel theory, light reflection occurs at the interface between two substances with different refractive indices. It can be seen from formula (1) that when light enters another medium with a refractive index of n _g from a medium with a refractive index of n ₁ , the reflection phenomenon may be caused due to the mismatch of the refractive indexes.

R(%)=[(n ₁ -n _g )/(n ₁ +n _g )] ² (1)

There are many methods to reduce the reflection at the interface to improve the luminous efficiency of the photovoltaic element. For example, at present, the surface of the lens is mostly sputtered (Sputtering deposition) with multiple layers of materials with different refractive index differences of about 0.1 to make an optical film to improve its anti-reflection effect, but the process of making a multilayer film by sputtering Complex, low yield and high cost. And besides splashing In addition to the plating deposition method, destructive interference (Destructive interference) can also be used to achieve the purpose of anti-reflection. However, when destructive interference is used to solve the problem of anti-reflection, it is usually only possible to destroy light of a specific wavelength and light with a wavelength close to it. None of the above methods can effectively overcome the loss of light output caused by the reflection of the photoelectric element at the interface.

Scientists also observed the firefly's light emitter under the electron microscope and found that the scaly surface has a periodic zigzag array structure, and applied it to the OLED, and found that it can effectively increase its luminous flux. In addition, we also found that there are similar nanopapillary periodic arrays on the transparent wings of grasshoppers. From the electron micrographs, it can be observed that the distance of the papillary arrays on the surface of grasshoppers is about 225nm, and the height is about 270nm (see Figure 1) ). Since its structural period is smaller than the wavelength of visible light, it can be regarded as a sub-wavelength structure.

In order to survive in a constantly changing environment, insects have evolved unique body structures after millions or even billions of years. In nature, the compound eye of a nocturnal moth is composed of thousands of hexagonal small eyes with a diameter of about 20 to 30 nm, and the corneal surface of each small eye has a regularly arranged nanopapillary array (Corneal nipple array) structure to prevent the reflection caused by compound eyes from being discovered by natural enemies. This kind of nanopapillary array was discovered by Miller and Bernhard et al. in 1962. This kind of nano-level special arrangement can be regarded as a sub-wavelength structure (SWS). Then in 1991, Southwell first proposed to design a periodic anti-reflective array based on the principle of moth-eye effect, and used this method to explore its refractive index changes. It is mentioned that in order to avoid the occurrence of diffraction, the period of the anti-reflection array needs to be less than the wavelength of visible light, that is, to reach the sub-wavelength structure. The appropriate structural period can be calculated by formula (2), where p is the period of the sub-wavelength structure, l is the wavelength to be anti-reflected, and n _s is the refractive index of the material of the sub-wavelength structure.

Mainly because the distance between nanopillars is less than half of the visible wavelength. When the light wave encounters such a structure, the light wave will gradually and continuously change along the depth axis according to the gradient refractive index theory. It is like the light passing through layers of materials with similar refractive index, so that light incident at any angle can be almost absorbed by the sub-wavelength structure. The sub-wavelength structure can effectively suppress the reflected light of different wavelengths, such as ultraviolet light, visible light, infrared light, etc., resulting in extremely low reflectivity. Formula (3) is the equivalent refractive index of the sub-wavelength structure obtained by deriving the effective medium theory. Wherein, n _eff is the equivalent refractive index, f is the sub-wavelength structure occupies the fill factor (Fill factor), n _a is the refractive index of the material times the wavelength, n _b is the refractive index of air.

In the present invention, the patent information retrieval system of the Republic of China conducts a cross-search on keywords such as "brightening film", "light guide film" and other keywords, and discusses the differences of related patents. The related patents are as follows:

1. Patent name: Light-emitting device and display (Patent Publication No. I570965) The light-emitting device disclosed in this invention includes a substrate, a light source assembly, a light extraction layer, and first optical particles. The light source assembly includes a light emitting element and a packaging structure. The light emitting element is provided on the substrate. The light emitting element has a light emitting surface, and the packaging structure is disposed on the light emitting surface. The light extraction layer is provided in the packaging structure of the light source assembly. The light extraction layer has opposing first and second surfaces, and the second surface faces the light source assembly. The first optical particles are embedded in the light extraction layer and protrude from the first surface. The first optical particle has a first refractive index, the light extraction layer has a second refractive index, and the packaging structure has a third refractive index. The first refractive index is greater than empty The refractive index of gas, and the second refractive index is greater than the first refractive index and the third refractive index. According to the light-emitting device and the display including the light-emitting device disclosed in the present invention, when the light generated by the light source assembly exits from the light extraction layer to the outside of the light-emitting device, part of the light first enters the first optical particles from the light extraction layer, and then The first optical particles are incident outside the light emitting device. Since the second refractive index of the light extraction layer is greater than the first refractive index of the first optical particles, and the first refractive index is greater than the refractive index of air, the light emitting device has a relatively gentle refractive index change on the first surface, which helps to avoid When light enters the outside of the light emitting device from the light extraction layer, it is totally reflected, which further improves the light extraction efficiency of the light emitting device. The light extraction method of this study is different from the surface sub-wavelength structure of the present invention using the imitating cicada wings.

2. Patent name: Method of manufacturing light guide film (Patent Publication No. I582475) This invention relates to a method of manufacturing light guide film. A lightguide is a film that provides substantial total internal reflection of light between its upper and lower surfaces. The light is incident on the edge of the film from one or more light sources (the edge is perpendicular to the upper and lower surfaces of the film). The light guide film can be used as a backlight unit when the upper and lower surfaces include a textured profile to scatter light from the light guide film. The textured surface redirects light out of the light guide film by refraction and/or total reflection. The invention provides a method for manufacturing a light guide film, comprising: (a) providing a light guide film having an upper surface and a lower surface, and the light supply is substantially total internal reflection between the upper surface and the lower surface; (b) Applying a flowable and curable material to at least the lower surface to form a pattern; (c) applying a surface texture to the material; and (d) curing the material so that it is obtained on the light guide film The surface textured pattern can extract light from the light guide film. The material applied in step (b) may include a curable resin. It may include scattering nanoparticles (eg, TiO ₂ ) to promote scattering. It may include ultraviolet light-regulating leaching additives, such as active ingredients such as UV absorbers or phosphorescent agents. It can be applied to high-resolution printing processes, such as inkjet printing or screen printing. The amount of the material can vary with the entire surface. In particular, the material may be applied only to the portion where the light guide film extracts light. Before step (b), a surface modifier such as polymer or oligomer can be applied to the surface. The effect of such surface modification may be to flatten, change the surface energy, or modify or match the refractive index. The texture applied in step (c) can be configured to match the pattern of the material to enhance light scattering. The texture can be uniformly distributed on the entire surface, or can change along with the entire surface, so as to effectively produce uniform illumination or produce patterns in which the illumination changes. The texture may include a randomly roughened profile or periodic geometric microstructures, such as: prismatic, pyramidal, conical, and/or microlens shaped. Step (c) may include, for example, reel-to-reel embossing or stamping embossing. In order to provide two opposite textured surfaces, the optional features described above can be performed on the upper and lower surfaces of the light guide film in steps (b), (c) and (d). The manufacturing method of the light guide film in this study is different from the method and the light guide structure of the invention for making the brightness enhancement film by micro-nano imprinting.

3. Patent name: Illumination device with microstructure brightness enhancement film (Patent Publication No. I452231) This invention relates to an appliance capable of illuminating, in particular to an illumination device with microstructure brightness enhancement film. At present, generally existing planar light sources project a light source field shape of Lambertian, namely Lambertian light source. The divergence angle of the light emitted by the planar light source is large, which is easy to cause the shortcomings of poor luminous efficiency and low central luminous intensity. When used in lighting devices, such as rear lights, multiple OLEDs (organic light-emitting diodes) are required to achieve The requirements of the regulations on the brightness of lighting will greatly increase the manufacturing cost. The technical means used in this invention is to provide a lighting device with a microstructure brightness enhancement film, including: a housing; a planar light source, which is fixed in the housing and is provided with a top surface; and a microstructure brightness enhancement film, It is fixed on the housing and located above the top surface of the planar light source; the microstructure brightness enhancement film is a thin sheet that can transmit light and is provided with a top, a bottom surface and a Fresnel Concentration part, the bottom surface of the microstructure brightness enhancement film is a plane, the Fresnel light concentration part is located on the top of the microstructure brightness enhancement film, the Fresnel light concentration part is provided with a center and an outer periphery, The cross-sectional shape of the Fresnel condensing part in the vertical direction is zigzag, and from the center toward the outer periphery, there are more than two periodic changes, wherein a first condensing is formed in the part of the first cycle Light zone, the first condensing zone includes a plurality of surrounding serrations, the plurality of serrations are adjacent to each other and are distributed around the center; a second condensing zone is formed in the part of the second cycle The second light-concentrating area surrounds and is adjacent to the first light-concentrating area; the arrangement order and cross-sectional shape of the saw teeth of the second light-concentrating area are the same as the first light-concentrating area; and a reflector is fixed to the shell The body and surrounding the plane light source. The microstructure brightness enhancement film of this patent is different from the present invention by imitating the subwavelength structure brightness enhancement film of the wing surface structure of the grasshopper.

In view of the fact that the above patents have indeed not been perfected, there is still a need for further improvement. The reason is that after continuous research and development, the inventors have finally developed a set of books that are different from the above-mentioned conventional technologies. invention.

The main purpose of the present invention is to provide a bionic brightening film, its manufacturing method and the optical element used therefor, mainly by imitating the transparent brightening layer made by imitating the surface of grasshopper wings, in addition to effectively reducing the refraction between the packaging material and the air In addition to the rate difference, it can effectively improve the luminous efficiency of the light-emitting diode or the light-transmitting ability of other optical components. The technical means to achieve the main purpose of the invention include a polystyrene nanosphere synthesis step, a non-compact single-layer nanosphere array template preparation step and a transparent brightness enhancement layer preparation step. The synthesis step of polystyrene nanospheres is synthesized by emulsification polymerization without emulsifier into polystyrene nanosphere suspension. The preparation step of the non-compact single-layer nanosphere array template is to use the Langmuir-Blodgett (LB) deposition method to deposit the polystyrene nanosphere suspension in The polystyrene nanospheres are assembled on the surface of the substrate to form a single-layer non-compact nanosphere array template. The preparation step of the transparent brightness enhancement layer is to make the nanosphere array template into a template with a sub-wavelength structure through the nanoimprint lithography technology, and then print the template on the application part after turning the mold to make the application part transparent and brighten Floor.

10‧‧‧Super substrate

11‧‧‧Nano ball array template

12‧‧‧LB slot

13‧‧‧Nano ball

14‧‧‧ PDMS mold kernel

15‧‧‧UV optical curing adhesive

20‧‧‧Application

21‧‧‧Transparent brightening layer

Fig. 1 (a) is an electron microscope photograph of the papillary array on the surface of the grasshopper's wings 1um per treaty; (b) is an electron microscope photograph of the papillary array on the surface of the grasshopper's wings 100um per treaty.

Fig. 2 (a) is a schematic flow chart of the preparation steps of the non-compact single-layer nanosphere array template of the present invention; (b) is a schematic flowchart of the front stage of the preparation step of the transparent brightening layer of the present invention; (c) is a transparent brightening layer of the present invention Schematic diagram of the latter stage of the preparation step.

Fig. 3 is a schematic diagram of the particle size distribution of the nanomicrospheres of the present invention, wherein the diameter is (a) 197nm; (b) 255nm; (c) 300nm.

FIG. 4 is an electron microscope photograph of nanospheres of the present invention having different sizes and outer diameters, where (a) is a photograph before oxygen plasma etching; (b) is a photograph after oxygen plasma etching; (c) is (b) The electron microscope image of the cross section.

FIG. 5 is a longitudinal cross-sectional view of the surface morphology of the sub-wavelength structure obtained by the AFM observation after the mode is copied by the present invention.

FIG. 6 is a comparison diagram of the reflection and transmission spectra of the glass covered by the BEL structure of the present invention.

Fig. 7(a) is the EL spectrum of a general white light bulb; Fig. 7(b)(c)(d) is derived from nanospheres with a particle size of 197, 255, and 300 nm, respectively, and is made of glass with a BEL structure. (a) Schematic diagram of the luminescence spectrum measured on the surface of the same white LED bulb.

In order to enable your reviewing committee to further understand the overall technical features of the present invention and the technical means to achieve the purpose of the invention, specific examples and drawings are used to explain in detail: According to the knowledge, the light-emitting diode (Light-Emitting Diode, (LED) Because of low power consumption and long life, it is widely used. However, due to the fact that reflection or total reflection will often occur at the interface of different materials on the structure to reduce its light extraction rate, how to improve the luminous efficiency of LEDs is particularly important in the era of energy efficiency. In nature, in order to avoid being preyed by natural enemies, grasshoppers have formed a special sub-wavelength array structure on their wings after a long period of evolution, which can effectively reduce the reflection on the surface of the wings and avoid the enemy. Therefore, the present invention is a TMPTA brightening layer printed with a polystyrene nanosphere with a particle size of 255nm. In addition to effectively reducing the reflectance to 0.87%, and maintaining the highest transmissivity of optical transmission to 96.9%, it can also emit light from the LED. Strength increased by 55%. The process technology provided by the present invention can still be applied to the development of micro-precision industry and optoelectronic industry in the future.

Please refer to Figures 1 to 4 for the implementation of the main purpose of the invention, which includes the following steps:

(a) Synthesis step of polystyrene nanospheres: It is synthesized by emulsification polymerization without emulsifier into polystyrene nanosphere suspension.

(b) Preparation of non-compact single-layer nanosphere array template: Langmuir-Blodgett (LB) deposition method is used to deposit polystyrene nanospheres 13 in polystyrene nanosphere suspension on a substrate 10 (such as light transmission The glass) surface is assembled and arranged into a single layer of non-compact nano-ball array template 11.

(c) Preparation step of the transparent brightness enhancement layer 21: the nano-ball array template 11 is made into a nano-ball array template 11 with a sub-wavelength structure through the nanoimprint lithography technology, and then the nano-ball array template 11 Printed on an application piece 20 after the mold is turned over, so that a transparent brightness enhancement layer 21 with low reflection and high light transmission characteristics is formed on the application piece 20.

Specifically, in the above synthesis step of polystyrene nanosphere 13, add 35~45mg (preferably 40mg) sodium sulfonate (4-SSrenesulfonic acid sodium salt hydrate, NaSS; Alfa Aesar) into the four-necked reaction flask Comonomer, 5~15g (preferably 8g) styrene monomer (styrene, St; Sigma-Aldrich), 75~95mg (preferably 87mg) potassium persulfate (KPS; JTBaker) It is a starter and 70~90g (preferably 80g) of deionized water (deionized water), using a mechanical stirring device at a speed of 280~320rpm (preferably 300rpm) evenly mixed, and then with a condensing reflux device under nitrogen environment continuous After reacting for about 1 day, the prepared polystyrene nanosphere suspension is centrifuged at a speed of 5500-6500 rpm (preferably 6000 rpm) for 15-25 minutes (preferably 20 minutes) at a rotation speed of the permeable centrifuge. Subsequently, the upper layer liquid is taken out to obtain a polystyrene nanosphere suspension with a uniform particle size.

Specifically, in the above preparation step of the non-compact single-layer nanosphere array template 11, the substrate 10 is immersed in 40~60ml (preferably 50ml) of 0.25M sodium hydroxide aqueous solution for 15~25 minutes (preferably 20 minutes) Hydrophilic modification, after the modification is completed, rinse with ionized water and soak in deionized water for use; in order to spread polystyrene nanospheres on the water surface of LB tank 12, the present invention chooses 60 %Ethanol (Merck) aqueous solution is used as a dispersing solvent, mix it into the polystyrene nanosphere suspension after polymerization, and then pour 180~220ml of secondary ionized water into the self-assembled LB (Langmuir-Blodgett) tank 12 In the process, the modified hydrophilic substrate 10 is placed obliquely on the edge of the baffle of the LB tank 12, and the polystyrene nanospheres are suspended on the surface of the hydrophilic substrate 10 by using a peristaltic pump to make the polystyrene nanospheres 13 Disperse uniformly at the gas-liquid interface by means of diffusion, so that the originally randomly distributed polystyrene nanospheres 13 are extruded through a self-assembled arrangement to form a single layer of tight arrangement. Among them, in order to shrink the particle size of the nanospheres 13 in the single-layer closely-arranged polystyrene array A non-close-packed array structure is formed as a subsequent sub-wavelength structure template 11. The present invention utilizes an oxygen plasma treatment (Plasma Cleaner, PCD) with a power of 40 W and an oxygen flow rate of 0.7 sccm 150, All Real Tech.) respectively performing oxygen plasma etching on the polymerized polystyrene nano-balls 13 with compact single-layer array templates 11 of different sizes, as shown in FIG. 2(a). After the etching process, the nano-balls 13 can be reduced, and the nano-balls 13 can be spaced.

Specifically, in the above step of preparing the brightness enhancement layer, silicone oil (Sigma-Aldrich), curing agent (curing agent), polydimethylsiloxane (PDMS; Sylgard 184, Dow Corning) are used After mixing the base agent in a mass ratio of 1.5~2.5:1:9~11 (preferably 2:1:10), put it in a refrigerator at a temperature of about 4 degrees Celsius for about 25~35 Minutes (preferably 30 minutes) to defoam, slowly cast it on the surface of the nano-ball array template 11 of the non-compact array, and then place it in a vacuum oven at 50~70℃ (preferably 60℃) Bake for 1.5~2.5 hours (preferably 2 hours), demold after curing to obtain the cavity-shaped PDMS mold core 14, the process is shown in Figure 2(b); then the UV optical curing adhesive 15( trimethylolpropane Triacrylate, TMPTA; shirakawa) uniformly drip on the surface of the application 20, and then cover the concave PDMS mold 14 on the ultraviolet optical curing adhesive 15 of the application 20, and use 1.5~2.5kg/cm ² (preferably Pressure of 2kg/cm ² ), and finally irradiated with ultraviolet light (Philips Actinic BL TL 8W, 365nm, 5mW/cm ² ) for 30 to 50 minutes (preferably 40 minutes) to cure and remove After the mold, an application 20 (such as a light-transmitting glass substrate) having a sub-wavelength structure on the surface is obtained.

In a more specific embodiment of the present invention, the above-mentioned application 20 is an optical element, which is a transparent cover of a light emitting diode LED; or a glass substrate of a display; or a glass substrate of a solar cell.

The invention utilizes dynamic light scattering particle size analysis and interface potential analyzer (Zetasizer; 3000HS, Malvern Instruments) measured the average particle size of the synthesized polystyrene nanospheres 13. Field Emission Scanning Electron Microscope (FE-SEM; JSM-7610F, JEOL) was used to observe the arrangement of tight and non-compact polystyrene single-layer nanosphere 13 arrays. The surface morphology, depth and period of the subwavelength array were measured with an atomic force microscope (Atomic Force Microscopy, AFM, DI 3100, Digital Instruments). Using UV-Vis Spectrophotometer (Cary 50, Varian) to measure the transmission and reflection spectrum of the completed TMPTA brightening film. Luminance and other characteristics of the finished brightness enhancing film are measured by high-resolution fiber optic spectrometer (HR2000+CG-UV-NIR).

In order to produce a SWS structure with better height and width, the present invention synthesizes three polystyrene nanospheres 13 with different sizes. The average particle size measured by a dynamic light scattering particle size analyzer is 197, 255, and 300 nm, respectively, and the dispersion coefficient (Polydispersity Index, PdI) of the particle size of the nanosphere 13 is 0.021, 0.012, and 0.009, respectively. The diameter of the nanosphere 13 is quite uniform, as shown in Fig. 3(a)(b)(c).

In order to explore the effect of oxygen plasma treatment time on the particle size of nanosphere 13, the SEM photo of Figure 4(a) is a single-layer closely-arranged array formed after self-assembly deposition by Langmuir-Blodgett (LB) device. The average particle diameter of the balls 13 is about 197, 255, and 300 nm, respectively. Oxygen plasma treatment can effectively reduce the size of the polystyrene nanospheres 13 to 175, 224, and 247 nm, respectively, so that the spacing between the nanospheres 13 is generated, as shown in FIG. 4(b). If the nanosphere 13 is too small, the surface morphology after the oxygen plasma etching will show an irregular shape, as shown in FIG. 4(b), which will reduce the optical anti-reflection capability of the sub-wavelength structure. 4(c) is a cross-sectional view corresponding to FIG. 4(b).

FIG. 5 is an AFM observation of the surface morphology of the sub-wavelength structure and the corresponding longitudinal cross-sectional view obtained after the over-mold replication. Fig. 5 (a), (b), (c) is a brightness enhancement film with a convex-shaped array replicated by a TMPTA material on a nano-array die made of nano-particles with a particle size of 197, 255, and 300 nm, respectively. The corresponding height (h) and width (d) are about 175nm and 113nm, 235nm and 221nm, 247nm and 287nm, and its aspect ratio is 1.54, 1.06 and 0.86 respectively. Among them, the nano-array made of polystyrene nano-balls 13 with a particle size of 255 nm is etched by oxygen plasma to reduce the particle size, and it is easier for PDMS sol to penetrate into the gap between the nano-balls 13 In order to make the height and width of the sub-wavelength structure obtained by the subsequent mold reversal closer to the height-to-width ratio of the papillary array structure on the wings of the cicada (Figure 1(c), about 1.20).

Fig. 6 (a), (b)-(i)(ii)(iii) is a glass with BEL structure covered by nanospheres 13 with a particle size of 197, 255 and 300 nm, and (v) is bare glass , The corresponding optical minimum reflectance and maximum transmittance are 1.63, 0.87, 1.34, 4.00%, and 92.1, 96.9, 95.6, 90.0%, respectively. From Fig. 6(a,b)(ii), it can be observed that the BEL structure made with nanospheres 13 with a particle size of 255 nm can effectively increase the glass penetration to the maximum (96.9%) and at the same time, it can optically The reflectivity is minimized (0.87%). According to research by Hadobas et al., it is found that the anti-reflection effect will become more obvious as the aspect ratio of the SWS structure increases [19]. Although the BEL film derived from the 197nm nanosphere 13 is the one with the highest aspect ratio (1.54) among the three, it is easy to cause stacking due to the smaller diameter of the nanosphere 13 during the oxygen plasma etching process And displacement, making it impossible to form a more perfect periodic arrangement, (see the SEM photo of Figure 4 (b)), resulting in the failure to reach the expected maximum.

Fig. 7(a) is the EL spectrum of a general white LED (Huankwun, 150cd/m ² ) bulb, and its luminous intensity value is about 0.99, while FIG. 7(b)(c)(d) is based on the particle size of 197, The luminescence spectrum measured by the 255 and 300 nm nanospheres 13 derived from the BEL structure glass covered on the surface of the same white LED bulb as in FIG. 7(a), the intensity values are 1.16, 1.36, 1.53, respectively. The brightening layer of BEL structure made of nano-balls with a diameter of 255nm 13 can increase the luminous value of LED from 0.99 to 1.53, which is about 55% enhanced. In addition, we have also observed that the LED emission spectrum does not shift with or without the brightness enhancement layer. The sub-wavelength structure array can effectively reduce the light reflection at the interface and improve its optical penetration. The improvement of the anti-reflection ability can be explained by the change of the fill factor and equivalent refractive index of the sub-wavelength structure in the equivalent medium theory, which is explained in conjunction with formula (2) and formula (4).

In formula (4), f is the fill factor in the sub-wavelength structure, A is the area occupied by the array of nanospheres 13 with sub-wavelength structure, A _unit is the area of the unit cell, and a ₁ and a ₂ are oxygen, respectively The diameter of the nanosphere 13 before and after plasma treatment, where the a ₁ value can be obtained from the SEM photograph (see FIG. 4(a)), respectively 197, 255, and 300 nm; the a ₂ value can be obtained from the SEM image (see FIG. 4 (b)) It is known that they are 175, 224, and 247 nm, respectively. FIG. 8 is a schematic diagram showing the change in the particle size of the nanosphere 13 formed by closely aligning the hexagonal structure before and after oxygen plasma treatment.

Substituting a ₁ and a ₂ into formula (4), the fill factor f of the brightness enhancement film derived from 197, 255, and 300 nm nanospheres 13 can be obtained as 0.7157, 0.6998, and 0.6148, respectively. Subsequent substituting f value into formula (3) can get n _eff respectively 1.3301, 1.3226, 1.2819. If the above data and the refractive index of glass (n=1.50) are substituted into formula (1), the corresponding theoretical values of reflectivity can be obtained as approximately 0.36, 0.39, 0.61%. It can be seen from Table 1 that the larger the sphere diameter of the nanosphere 13 array, the smaller the corresponding fill factor and the higher the reflectance. The theoretical value of the reflectance is different from the experimental value. The possible reasons are as follows: First, the nanosphere 13 is etched by oxygen plasma to cause its surface to be roughened, resulting in its shape no longer being a perfect spherical shape; second The theoretical value of the reflectivity is derived from the fill factor, but the fill factor only calculates the change in the projected area of the sphere and does not take into account the change in the height of the sphere. Since the anti-reflection structure manufactured by the present invention only covers one side of the glass substrate 10, if this structure can be replicated on both sides of the glass substrate 10, its light transmittance must be increased [20]. The bionic transparent brightening layer 21 made by the sub-wavelength structure on the surface of the grasshopper's wings can effectively reduce the difference in refractive index between the glass substrate 10 and the air, and improve the luminous efficiency of the LED. The process technology of the brightness enhancement layer provided by the present invention will have considerable development potential in the future application in the solid-state lighting, display and solar cell industries. The invention utilizes polystyrene nano-balls 13 and oxygen plasma etching technology and self-assembly device to rapidly produce periodic single-layer non-compact nano-ball 13 arrays, and combines with nano-imprint technology to successfully prepare imitation grass Transparent brightening layer 21 of cicada wings. By making the bionic structure, in addition to effectively reducing the reflectivity at the interface to 0.87%, it can also improve the luminous efficiency of the LED by 55% without shifting the luminescence spectrum. The brightening layer manufacturing technology provided by the present invention has the functions of improving optical penetration, avoiding reflection and anti-reflection, etc. In addition to being applicable to the lighting industry, in the future, glass substrates and solar cells of displays (LED or OLED) Optical components such as glass substrates, optical components such as biological detection instruments, sights and telescopes, and the production of films or related optical components for the display panels of smart mobile phones, tablet computers and wearable watches are also of great application value and development. potential.

The above is only a feasible embodiment of the present invention and is not intended to limit the patent scope of the present invention. Any equivalent implementation of other changes based on the content, features and spirit described in the following claims should be Included in the patent scope of the present invention. The structural features of the invention specifically defined in the claim are not found in similar items, and are practical and progressive. They have met the requirements of the invention patent. You have filed an application in accordance with the law, and I would like to ask the Jun Bureau to approve the patent in accordance with the law to maintain this. The applicant's legal rights and interests.

10‧‧‧ substrate

11‧‧‧Nano ball array template

12‧‧‧LB slot

13‧‧‧Nano ball

14‧‧‧ PDMS mold kernel

15‧‧‧UV optical curing adhesive

20‧‧‧Application

21‧‧‧Transparent brightening layer

Claims (6)

A bionic brightening film manufacturing method, which includes the following steps: (a) polystyrene nanosphere synthesis step: emulsification polymerization without emulsifier is used to synthesize polystyrene nanosphere suspension; wherein, it is used in the reaction bottle Add 35~45mg of sodium sulfonate comonomer, 5~15g of styrene monomer, 75~95mg of potassium persulfate as the starter and 70~90g of deionized water, using a mechanical stirring device at a speed of 280~320rpm evenly Stirring, and continuous reaction under a nitrogen environment with a condensing reflux device for about 1 day, then centrifuge the prepared polystyrene nanoparticle suspension through a centrifuge at a speed of 5500-6500rpm for 15-25 minutes, and then The polystyrene nanosphere suspension with uniform particle size can be obtained by taking out the upper layer liquid; (b) Preparation step of non-compact single-layer nanosphere array template: the polystyrene nanoparticles are deposited by Langmuir-Blodgett (LB) deposition method The polystyrene nanospheres in the rice ball suspension are assembled on a substrate surface and arranged into a single layer of non-compact nanosphere array template; wherein, the substrate is immersed in 40~60ml of 0.25M sodium hydroxide aqueous solution 15 ~25 minutes for hydrophilic modification, after the modification is completed, rinse with ionized water, and soak in deionized water for use, use ethanol aqueous solution as a dispersion solvent, mix it into the polystyrene nanosphere suspension after polymerization In the solution, pour 180~220ml of secondary ionized water into the self-assembled LB tank, and then slant the modified hydrophilic substrate on the edge of the LB tank baffle, use a peristaltic pump to transfer the polystyrene Suspended droplets of rice spheres on the surface of the hydrophilic substrate, so that the polystyrene nanospheres are evenly dispersed in the gas-liquid interface by diffusion, so that the originally disordered polystyrene nanospheres are squeezed through the self-assembly arrangement Press to form a single layer of tight arrangement; then use oxygen plasma with a power of 40W and an oxygen flow rate of 0.7sccm to perform oxygen plasma etching on the nanosphere array template, so that the average particle size of the polystyrene nanospheres is originally 255nm is reduced to about 224nm, and the polystyrene nanospheres are formed with a gap; and (c) transparent brightening layer preparation step: the nanosphere array template is made by nanoimprint lithography technology A template with a sub-wavelength structure, and then printing the template on an application part to form a transparent brightening layer with low reflection and high light transmission characteristics on the application part; The main agent of the agent and polydimethylsiloxane is mixed in a mass ratio of 1.5~2.5: 1:9~11, and then placed in the refrigerator for 25~35 minutes to defoam and then slowly Cast on the surface of the nano-ball array template of the non-compact array, and then place it in a vacuum oven at 50~70℃ for 1.5~2.5 hours, and release it after curing to obtain a concave PDMS mold core, and The UV optical curing adhesive is evenly covered on the surface of the application, and then the PDMS mold cavity is covered on the UV optical curing adhesive of the application, and the pressure is imprinted with a pressure of 1.5~2.5kg/cm ² . Finally, it is irradiated with ultraviolet light for 30 to 50 minutes to cure and release the mold to obtain the application part with a sub-wavelength structure on the surface. An optical element using the bionic brightness enhancement layer prepared by the method according to claim 1, wherein the optical element is the application part. An optical element using the bionic brightness enhancement layer as described in claim 2, wherein the optical element is a glass substrate of a display. An optical element using the bionic brightness enhancement layer as described in claim 2, wherein the optical element is a glass substrate of a solar cell. An optical element using the bionic brightness enhancement layer as described in claim 2, wherein the optical element is a film for a display panel of a smart mobile phone, a tablet computer, or a wearable watch. An optical element using the bionic brightness enhancement layer according to claim 2, wherein the optical element is an optical element of a biological detection instrument, a sight, or a telescope.

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