Preparation method of micro-lens film layer

Abstract

The invention discloses a preparation method of a micro-lens film layer, and belongs to the technical field of optics. The preparation method of the micro-lens film layer comprises the following steps: preparing a positioning groove in the surface of a substrate; the positioning groove is filled with free radical polymerization type UV glue, and a glue layer is obtained; performing UV pre-curing on the adhesive layer in an aerobic environment to obtain an adhesive layer with a cured bottom and a liquid layer reserved on the surface; optical microspheres are sprayed to the surface of the adhesive layer in a dry mode, and the optical microspheres are limited in the positioning grooves; and completely curing the adhesive layer, and removing the optical microspheres in an unglued area after curing to obtain a single-layer micro-lens film layer. The single-layer micro-lens film layer prepared by the preparation method has a single-layer structure and a periodic array structure on the microstructure, has a relatively large height-width ratio, is flexible and adjustable in focal length, and has a good industrial application prospect.

Description

Technical Field

[0001] This invention belongs to the field of optical technology, and in particular relates to a method for preparing a microlens film. Background Technology

[0002] In recent years, with the miniaturization of display technology and optical devices, microlenses, as key optical components, have attracted much attention due to their unique advantages in improving display brightness and optimizing light efficiency. Microlens arrays typically consist of a series of micrometer-scale lens units, each corresponding to a single pixel of the display. They can precisely control light distribution by focusing or diffusing incident light. By optimizing the geometric design of microlenses, such as their radius of curvature and array density, more precise light control can be achieved while maintaining high brightness output, significantly improving display quality and energy efficiency. Currently, microlenses, with their small size, light weight, and ease of integration, can perform functions such as focusing, diverging, collimation, imaging, and light transmission in optical paths, and are widely used in fiber optic coupling, photonic devices, and integrated optical components.

[0003] In the field of OLED device research, the introduction of microlens arrays has become a key technological approach to improve display brightness. The successful implementation of this technology requires addressing the compatibility issues between microlens fabrication processes and OLED device manufacturing processes. The core challenge lies in the selection of refractive index-matching materials and the adaptation to high-precision micro / nano manufacturing technologies to maximize brightness enhancement. However, the practical application of this technology currently faces multiple bottlenecks, as follows:

[0004] On the one hand, the lagging development of high-refractive-index organic materials limits the light-gathering efficiency of microlenses, making it difficult to break through the theoretical upper limit of optical gain. On the other hand, the precision control and cost balance issues in micro-nano fabrication processes are significant, and large-scale manufacturing of complex structures still faces technical barriers, hindering the industrialization of high-brightness enhancement solutions. Among these, single-layer microlens arrays typically possess higher light utilization efficiency due to minimal reflection loss on the microlens surface, but fabricating microlens arrays with single-layer structures still requires overcoming significant technical obstacles. Furthermore, significant technical barriers also exist when fabricating microlens films on complex curved surfaces such as non-planar or flexible substrates.

[0005] Overall, existing microlens manufacturing technologies generally face common problems such as complex processes, high equipment costs, difficulties in yield control, and the inability to mass-produce complex structures. These problems not only increase the manufacturing cost of microlens films but also severely limit their further expansion in application. Therefore, breaking through the constraints of traditional material systems and process routes, and overcoming process bottlenecks through innovation in microlens array fabrication schemes, has become a core development direction for improving the brightness of OLED displays. Currently, there is an urgent need to provide a simple, low-cost method for fabricating single-layer microlens films with flexible adjustable focal length. Summary of the Invention

[0006] The main objective of this invention is to provide a method for preparing microlens films, thereby solving the problems of complex processes, high costs, limited light focusing efficiency, and difficulty in preparing single-layer structures in the prior art.

[0007] This invention provides a method for preparing a microlens film, the method comprising:

[0008] A positioning groove is prepared on the surface of the substrate;

[0009] The positioning groove is filled with a free radical polymerizable UV adhesive to obtain an adhesive layer;

[0010] The adhesive layer is UV pre-cured in an oxygen-rich environment to obtain an adhesive layer with a liquid layer remaining on the bottom cured surface.

[0011] Optical microspheres are dry-sprayed onto the surface of the adhesive layer, and the optical microspheres are confined in the positioning groove;

[0012] The adhesive layer is fully cured, and after curing, the optical microspheres in the uncoated areas are removed to obtain a single-layer microlens film.

[0013] This invention utilizes UV adhesives with a curing principle based on free radical polymerization, such as UV adhesives using acrylate monomers. Based on the oxygen inhibition phenomenon of such adhesives in an aerobic environment, a pre-cured adhesive layer with an ultra-thin liquid layer remaining on the bottom surface can be obtained. The UV adhesive cures based on free radical polymerization. Under UV irradiation, the photoinitiator decomposes to generate active free radicals, which then open the carbon-carbon double bonds of the acrylate monomers, initiating polymerization. Oxygen in the air (ground state triplet oxygen) has diradical properties and disrupts the polymerization process through three pathways: first, it quenches the excited-state photoinitiator, reducing the source of free radical generation; second, it combines with primary free radicals to generate low-activity peroxy radicals (ROO·); and third, it directly interrupts the polymer chain growth reaction, leading to a significant loss of surface free radicals. Since oxygen mainly diffuses and acts on the shallow surface of the adhesive layer, the typical phenomenon of "bottom curing, surface stickiness" occurs.

[0014] Furthermore, the positioning grooves prepared on the substrate surface constitute a positioning groove array, and the optical microspheres dry-sprayed into the positioning grooves also constitute a single-layer microlens array.

[0015] Furthermore, the thickness of the liquid layer is 1 / 10 to 1 / 2 of the diameter of the optical microspheres, thereby making the bonded optical microspheres present a single-layer structure in terms of microstructure, and forming a microlens film layer with a single-layer lattice structure at the target position of the substrate.

[0016] Furthermore, the substrate surface is washed with water or cleaned with Plasma before UV adhesive coating to ensure material cleanliness.

[0017] Furthermore, the optical microspheres are selected from at least one of silica microspheres, polystyrene microspheres, latex microspheres, and polymethyl methacrylate microspheres.

[0018] Furthermore, the optical microspheres include at least two different diameters, with the diameter of the optical microspheres ranging from 3 to 100 μm; in the microlens array, the optical microspheres in each row or column are spaced apart by different diameters and arranged in a regular manner, and correspondingly, the size of each positioning groove in the positioning groove array is set in the same way as the size of the arranged optical microspheres.

[0019] Further, the process of dry-spraying optical microspheres onto the surface of the adhesive layer includes:

[0020] Optical microspheres of different diameters were sequentially dry-sprayed onto the substrate surface in order of increasing diameter.

[0021] Furthermore, the dimensions of each positioning groove in the positioning groove array are the same as the dimensions of the corresponding optical microsphere, so that the corresponding optical microsphere falls exactly into the target positioning groove after dry spraying.

[0022] Furthermore, the filling height of the UV adhesive is lower than the height of the groove, and the filling amount of the UV adhesive is 50% to 80% of the groove capacity.

[0023] Furthermore, UV adhesive is used to fill the positioning groove using micro-nano direct writing, piezoelectric, or inkjet methods.

[0024] Furthermore, with the substrate inverted, optical microspheres are dry-sprayed onto the substrate surface using electrostatic, pneumatic, or ultrasonic methods to avoid large-area stacking of optical microspheres on the substrate.

[0025] Furthermore, this invention regulates the thickness of the pre-cured liquid layer by controlling the oxygen content of the environment and the UV curing energy during pre-curing. Preferably, the oxygen content of the aerobic environment is 0.01%~20%, and the UV energy during UV pre-curing and complete curing is 100mj / cm²~10000mj / cm². If the curing energy is too high, the adhesive layer will be completely cured or the thickness of the bottom cured layer will be too high, resulting in a liquid layer thickness that is too low to provide sufficient adhesion for the optical microspheres; if the curing energy is too low, the thickness of the cured layer at the bottom of the adhesive layer will be too low, resulting in a liquid layer thickness that is too high. In this case, the optical microspheres tend to stack and adhere to the surface of the liquid layer, easily forming a non-single-layer microlens film.

[0026] Furthermore, the complete curing of the adhesive layer, followed by the removal of the uncoated areas of the optical microspheres after curing, includes:

[0027] The adhesive layer is fully cured in an oxygen-free environment. After curing, the optical microspheres in the uncoated areas are removed using compressed air or ultrasound. The adhesion between the optical microspheres in the uncoated areas and the substrate is not strong, so they can be removed even under relatively small stress conditions.

[0028] Furthermore, the method also includes finally spraying a protective film onto the surface of the microlens and planarizing the surface.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) A single-layer microlens array can be obtained, and the optical structure of the single-layer microlens array has significant advantages: it only has a small amount of reflection loss on the surface of the microlens, the overall light utilization efficiency is high, and the light loss is usually controlled within 15%. In contrast, multi-layer structures (such as multi-layer microsphere films) have more optical interfaces, and the incident light needs to undergo multiple scattering and refraction between different layers. On the one hand, each interface contact will generate reflection loss, and some light will be reflected back to the light source side during the scattering process (forming ineffective light loss); on the other hand, impurities in the multi-layer adhesive and microspheres may aggravate light absorption, ultimately leading to a significantly larger overall light loss, usually reaching 20%-35%, which is much higher than the light loss level of a single-layer microlens array. This invention employs a UV adhesive filling combined with pre-curing, utilizing the oxygen inhibition phenomenon of the adhesive in an aerobic environment to obtain an ultrathin liquid layer on the adhesive surface. This ultrathin liquid layer is then used to achieve controllable adhesion of optical microspheres to its surface. By strictly controlling the pre-curing process parameters, the thickness of the liquid layer is stably controlled at 1 / 10 to 1 / 2 of the diameter of the optical microspheres, thereby enabling the bonded optical microspheres to exhibit a single-layer structure in terms of microstructure. This forms a microlens film layer with a single-layer structure and a periodically arranged lattice at the target position on the substrate.

[0031] (2) The single-layer microlens film layer uses optical microlenses of different diameters arranged at regular intervals to form a periodic array structure with a large aspect ratio. This can effectively improve the forward brightness of the display panel, enhance the light-gathering effect of the overall structure, improve the light energy utilization efficiency, and thus improve the visual effect and energy consumption performance of the display device.

[0032] (3) The focal length of the microlens array is flexibly adjustable. The focal length of the microlens array mainly depends on the size of the optical microsphere and the difference between the refractive index of the optical microsphere and the refractive index of the environment. By reasonably controlling the above parameters, the focal length of the microlens can be precisely designed and flexibly adjusted, thereby meeting the specific requirements of the focal length in different application scenarios and enhancing the adaptability and integration capability of the device in actual optical systems.

[0033] (4) The preparation process provided is simple, requires low equipment, is suitable for complex curved surface structures, and is easy to implement and scale up production. The microlens film preparation method of the present invention does not involve complex route design and high temperature and high pressure control, nor does it require high precision instruments and equipment. The preparation of a single-layer microlens array can be completed by conventional glue coating and ultraviolet curing, which greatly reduces the technical threshold and production cost and has good industrial application prospects. Attached Figure Description

[0034] Figure 1 A schematic diagram of the substrate and positioning groove structure;

[0035] Figure 2 This is a schematic diagram of the UV adhesive filling process;

[0036] Figure 3 This is a schematic diagram of the structure after the UV adhesive layer has been pre-cured;

[0037] Figure 4 This is a schematic diagram of the dry spraying of optical microspheres.

[0038] Figure 5 This is a schematic diagram of the microlens array substrate obtained after dry-spraying microspheres.

[0039] Figure 6 This is a schematic diagram of the microlens array substrate after planarization.

[0040] Figure 7 This is a schematic diagram of the actual structure of the positioning groove array;

[0041] Figure 8 This is a schematic diagram illustrating the UV adhesive filling process using a micro-nano direct-write printing solution.

[0042] Figure 9 This is a physical image of the microlens array substrate obtained after dry-spraying microspheres.

[0043] Figure 10This is a physical image of the microlens array substrate after planarization.

[0044] Explanation of reference numerals in the attached drawings: 1-substrate, 2-UV adhesive, 3-curing layer, 4-liquid layer, 5-optical microspheres, 6-electrostatic powder nozzle, 7-light-emitting unit, 8-positioning groove, 9-planarization layer. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0046] As described in the background section of this invention, the fabrication of microlens arrays still faces multiple bottlenecks in practical applications: on the one hand, the research and development of high-refractive-index organic materials lags behind, resulting in limited light-gathering efficiency of microlenses and difficulty in breaking through the theoretical upper limit of optical gain; on the other hand, the precision control and cost balance issues of micro-nano fabrication processes are significant, and large-scale manufacturing of complex structures still faces technical barriers, restricting the industrialization of high-brightness enhancement solutions. Among these, single-layer microlens arrays typically possess higher light utilization efficiency due to minimal reflection loss on the microlens surface, but fabricating microlens arrays with single-layer structures still requires overcoming significant technical obstacles. Furthermore, significant technical barriers exist when fabricating microlens films on complex curved surfaces such as non-planar or flexible substrates. Therefore, this invention aims to provide a simple, low-cost method for fabricating single-layer microlens films with flexible adjustable focal length.

[0047] This invention provides a method for preparing a microlens film, such as... Figure 1-6 As shown, the method includes:

[0048] A positioning groove is prepared on the surface of the substrate;

[0049] The positioning groove is filled with a free radical polymerizable UV adhesive to obtain an adhesive layer;

[0050] The adhesive layer is UV pre-cured in an oxygen-rich environment to obtain an adhesive layer with a liquid layer remaining on the bottom cured surface.

[0051] Optical microspheres are dry-sprayed onto the surface of the adhesive layer, and the optical microspheres are confined in the positioning groove;

[0052] The adhesive layer is fully cured, and after curing, the optical microspheres in the uncoated areas are removed to obtain a single-layer microlens film.

[0053] This invention utilizes a UV adhesive with a curing principle based on free radical polymerization, such as UV adhesives using acrylate monomers. Based on the oxygen inhibition phenomenon of this type of adhesive in an aerobic environment, a pre-cured adhesive layer with a certain thickness of ultra-thin liquid layer remaining on the bottom surface can be obtained. The UV adhesive cures based on free radical polymerization. Under UV light irradiation, the photoinitiator decomposes to generate active free radicals, which then open the carbon-carbon double bonds of the acrylate monomers, initiating polymerization. Oxygen in the air (ground state triplet oxygen) has diradical properties and disrupts the polymerization process through three pathways: first, it quenches the excited-state photoinitiator, reducing the source of free radical generation; second, it combines with primary free radicals to generate low-activity peroxy radicals (ROO·); and third, it directly interrupts the polymer chain growth reaction, leading to a significant loss of surface free radicals. Since oxygen mainly diffuses and acts on the shallow surface of the adhesive layer, the typical phenomenon of "bottom curing, surface stickiness" occurs.

[0054] In some specific embodiments, the positioning grooves prepared on the substrate surface constitute a positioning groove array, and the optical microspheres dry-sprayed into the positioning grooves also constitute a single-layer microlens array.

[0055] In some specific embodiments, the thickness of the liquid layer is 1 / 10 to 1 / 2 of the diameter of the optical microspheres, preferably 0.5 to 20 μm, so that the bonded optical microspheres present a single-layer structure in terms of microstructure, and a microlens film layer with a single-layer random lattice is formed at the target position of the substrate.

[0056] In some specific embodiments, the substrate surface is washed with water or cleaned with Plasma before UV adhesive coating to ensure material cleanliness.

[0057] In some specific embodiments, the optical microspheres may be selected from at least one of polymethyl methacrylate microspheres, silica microspheres, polystyrene microspheres, and latex microspheres. The optical microspheres include at least two different diameters, with diameters ranging from 3 to 100 μm. In the microlens array, the optical microspheres in each row or column are spaced at different diameters and arranged regularly. Correspondingly, the dimensions of each positioning groove in the positioning groove array are set according to the dimensions of the arranged optical microspheres. The focal length of the microlens mainly depends on the size of the optical microspheres and the difference between the refractive index of the optical microspheres and the refractive index of the environment. Here, the required refractive index difference can be calculated based on the actual focal length requirements and the size data of the optical microspheres, thereby selecting the corresponding filling layer material. The theoretical formula for calculating the lens focal length is as follows:

[0058]

[0059] Where f is the focal length of the lens, D is the diameter of the microsphere, n is the refractive index of the microsphere, and n0 is the refractive index of the filling layer.

[0060] In some specific embodiments, the process of dry-spraying optical microspheres onto the surface of the adhesive layer includes:

[0061] Optical microspheres of different diameters were sequentially dry-sprayed onto the substrate surface in order of increasing diameter.

[0062] In some specific embodiments, the size of each positioning groove in the positioning groove array is the same as the size of the corresponding optical microsphere, so that the corresponding optical microsphere falls exactly into the target positioning groove after dry spraying.

[0063] In some specific embodiments, the filling height of the UV adhesive is lower than the height of the groove, and the filling amount of the UV adhesive is 50% to 80% of the groove capacity.

[0064] In some specific embodiments, UV adhesive is used to fill the positioning groove using micro-nano direct writing, piezoelectric or inkjet methods.

[0065] In some specific embodiments, optical microspheres are dry-sprayed onto the substrate surface using electrostatic, pneumatic, or ultrasonic methods when the substrate is inverted, thus avoiding large-area stacking of optical microspheres on the substrate.

[0066] In some specific embodiments, the present invention regulates the thickness of the pre-cured liquid layer by controlling the oxygen content of the environment during pre-curing and the UV curing power. Preferably, the oxygen content of the aerobic environment is 0.01%~20%, the energy during UV pre-curing and complete curing is 100mj / cm²~10000mj / cm², and the curing time is 1~100s. Excessive curing energy will cause the adhesive layer to cure completely or the bottom cured layer to be too thick, resulting in a liquid layer thickness that is too thin and cannot provide sufficient adhesion for the optical microspheres. Conversely, insufficient curing energy will result in a thin bottom cured layer, leading to a liquid layer thickness that is too thick. In this case, the optical microspheres tend to overlap and adhere to the surface of the liquid layer, easily forming a non-single-layer microlens film. Therefore, by using UV adhesive filling combined with pre-curing and controlling the above key process parameters, the adhesive can form a liquid layer with a certain thickness on the bottom curing surface in an oxygen-rich environment. The thickness of the liquid layer can be controlled to be 1 / 10 to 1 / 2 of the diameter of the optical microspheres, ensuring that the bonded optical microspheres exhibit a single-layer structure in terms of microstructure.

[0067] In some specific embodiments, the complete curing of the adhesive layer and the removal of the optical microspheres from the uncoated areas after curing includes:

[0068] The adhesive layer is fully cured in an oxygen-free environment, such as a nitrogen atmosphere. After curing, the optical microspheres in the uncoated areas are removed using compressed air or ultrasound. The adhesion between the optical microspheres in the uncoated areas and the substrate is weak, so they can be removed even under relatively small stress conditions.

[0069] In some specific embodiments, the method further includes finally spraying a protective film onto the surface of the microlens array and planarizing the surface.

[0070] Example 1

[0071] (1) The surface of the substrate 1 to be printed is washed and cleaned with water to ensure the cleanliness of the material. Several light-emitting units 7 are provided on the upper part of the substrate 1.

[0072] (2) such as Figure 7 As shown, positioning grooves 8 of different sizes are prepared on the surface of substrate 1 using photolithography according to the actual needs of different sub-pixels. The positioning grooves 8 of different sizes (groove widths of 30μm, 20μm, and 5μm) are arranged at intervals according to a certain pattern to form a positioning groove array. Specifically, the positioning grooves 8 are used to separate each light-emitting unit 7.

[0073] (3) such as Figure 8 As shown, using the micro-nano direct-write printing scheme, the largest positioning groove 8 (30μm wide) is first filled with UV adhesive 2 based on acrylate monomers using dispensing, and the filling amount of UV adhesive 2 is 70% of the groove capacity;

[0074] The dispensing equipment includes a micro-dot array dispensing mechanism and a frame. An operating platform is mounted on the frame, and a fixed balance beam is supported on the operating platform. A drive device for moving the micro-dot array dispensing mechanism up and down is mounted on the fixed balance beam. The feed cylinders are fixed to the base at intervals by feed cylinder clamps, and the needles are arranged close together in an array. The micro-dot array dispensing mechanism is fixed to the drive shaft of the driving device via a substrate. The driving device controls the dot width and thickness of the dispensing. An inverted visual observation system is located below the dispensing assembly, used to detect the position of each flexible dispensing needle in the X, Y, and Z directions. A vertically mounted visual recognition system is located on the side of the dispensing assembly, used to identify, calibrate, and correct the dispensing start position. This system is linked to a height measurement and tracking system, used to scan and record values ​​in the sample printing area, compensating for vertical deviations in the sample, and simultaneously measuring the dispensing thickness. A real-time observation system is obliquely positioned above the front of the dispensing assembly, used to monitor the dispensing effect and status in real time. A multi-axis motion system is located on the operating platform, with a sample adsorption mechanism positioned directly below the micro-dot array dispensing mechanism. A rotating mechanism is located on the bottom of the sample adsorption mechanism, used to correct horizontal position deviations in the sample. A dispensing needle cleaning mechanism is located on the side of the sample adsorption mechanism. The multi-axis motion system includes an X-axis motion mechanism, a Y-axis motion mechanism, and a Z-axis motion mechanism. The X-axis and Y-axis motion mechanisms drive the sample to move horizontally, generating a printing path. The Z-axis motion mechanism drives the sample to move vertically, compensating for vertical deviations and controlling the dispensing thickness. The micro-dot array dispensing mechanism includes a base, a dispensing assembly fixed to the base, and an adjusting slide. The dispensing assembly includes several dispensing needles. The adjusting slide independently adjusts the position of each dispensing needle in the X, Y, and Z directions. The base is spaced apart by several feed cylinder clamps, gathering grooves, and needle limiting grooves. Along the feeding direction, the spacing between adjacent feed cylinder clamps, gathering grooves, and needle limiting grooves decreases sequentially. The feed cylinder is equipped with a fluid control system, which controls the dispensing flow rate of each dispensing needle.

[0075] (4) The adhesive layer is UV pre-cured in an oxygen-containing environment (oxygen content is 10%) with UV energy of 500mj / cm² and UV power of 100mW / cm². The curing time is 5s, and an adhesive layer with a cured layer 3 at the bottom and a liquid layer 4 with a thickness of 7μm on the surface can be obtained. The thickness of the adhesive layer is 50μm.

[0076] (5) Invert the substrate 1 and use an electrostatic powder sprayer 6 to dry spray PMMA optical microspheres 5 with a diameter of 30 μm onto the surface of the adhesive layer. The optical microspheres 5 are confined in the positioning groove 8.

[0077] (6) Place the substrate 1 in an oxygen-free environment for complete curing. After curing, use USC cleaning to clean the surface of the substrate 1 and remove the optical microspheres 5 in the uncoated areas.

[0078] (7) Repeat steps (3) to (6), and process the remaining pixel positions in the same way according to the order of the remaining positioning grooves 8 from largest to smallest. The diameters of the remaining optical microspheres 5 are 20μm and 15μm, respectively. The resulting microlens array is as follows: Figure 9 As shown;

[0079] (8) such as Figure 10 As shown, a full layer of adhesive film (the same UV adhesive as in step (3)) is sprayed onto the surface of the microlens array to perform surface planarization treatment to obtain a planarization layer 9, which is used to protect the microlens array. At the same time, by selecting the refractive index difference between the adhesive layer and the optical microsphere 5, the actual focal length of the microlens array can be controlled to obtain the final single-layer microlens array substrate.

[0080] Example 2

[0081] (1) The surface of the substrate 1 to be printed is washed and cleaned with water to ensure the cleanliness of the material. Several light-emitting units 7 are provided on the upper part of the substrate 1.

[0082] (2) Using photolithography, positioning grooves 8 of different sizes are prepared on the surface of substrate 1 according to the actual needs of different sub-pixels. The positioning grooves 8 of different sizes (groove width 10μm, 5μm, 2μm) are arranged at intervals according to a certain pattern to form a positioning groove array.

[0083] (3) Using the micro-nano direct writing printing scheme, firstly, UV adhesive 2 with acrylic ester monomers is used to fill the positioning groove 8 with the largest size (width 10μm). The filling amount of UV adhesive 2 is 70% of the groove capacity;

[0084] (4) The adhesive layer is UV pre-cured in an oxygen-containing environment (oxygen content is 20%) with UV energy of 500mj / cm² and UV power of 100mW / cm². The curing time is 5s, and an adhesive layer with a cured layer 3 at the bottom and a liquid layer 4 with a thickness of 1μm on the surface can be obtained. The thickness of the adhesive layer is 50μm.

[0085] (5) Invert the substrate 1 and use an electrostatic powder sprayer 6 to dry spray a PMMA optical microsphere 5 with a diameter of 10 μm onto the surface of the adhesive layer. The optical microsphere 5 is confined in the positioning groove 8.

[0086] (6) Place the substrate 1 in an oxygen-free environment for complete curing. After curing, use USC cleaning to clean the surface of the substrate 1 and remove the optical microspheres 5 in the uncoated areas.

[0087] (7) Repeat steps (3) to (6) and process the remaining pixel positions in the same way according to the order of the remaining positioning groove 8 from large to small. The diameters of the remaining optical microspheres 5 are 5μm and 2μm respectively.

[0088] (8) Finally, a full layer of adhesive film (the same UV adhesive as in step (3)) is sprayed onto the surface of the microlens array to perform surface planarization treatment to obtain a planarization layer 9, which is used to protect the microlens array. At the same time, by selecting the refractive index difference between the adhesive layer and the optical microsphere 5, the actual focal length of the microlens array can be controlled to obtain the final single-layer microlens array substrate.

[0089] Comparative Example

[0090] (1) The surface of the substrate 1 to be printed is washed and cleaned with water to ensure the cleanliness of the material. Several light-emitting units 7 are provided on the upper part of the substrate 1.

[0091] (2) Using photolithography, positioning grooves 8 of different sizes are prepared on the surface of substrate 1 according to the actual needs of different sub-pixels. The positioning grooves 8 of different sizes (groove width 10μm, 5μm, 2μm) are arranged at intervals according to a certain pattern to form a positioning groove array.

[0092] (3) Using the micro-nano direct writing printing scheme, firstly, UV adhesive 2 with acrylic ester monomers is used to fill the positioning groove 8 with the largest size (width 10μm). The filling amount of UV adhesive 2 is 70% of the groove capacity;

[0093] (4) The adhesive layer is UV pre-cured in an oxygen-containing environment (oxygen content is 20%) with UV energy of 100mj / cm² and UV power of 100mW / cm². The curing time is 1s. This yields an adhesive layer with a cured layer 3 at the bottom and a liquid layer 4 with a thickness of 15μm on the surface. The thickness of the adhesive layer is 50μm.

[0094] (5) Invert the substrate 1 and use an electrostatic powder sprayer 6 to dry spray a PMMA optical microsphere 5 with a diameter of 10 μm onto the surface of the adhesive layer. The optical microsphere 5 is confined in the positioning groove 8.

[0095] (6) Place the substrate 1 in an oxygen-free environment for complete curing. After curing, use USC cleaning to clean the surface of the substrate 1 and remove the optical microspheres 5 in the uncoated areas.

[0096] (7) Repeat steps (3) to (6) and process the remaining pixel positions in the same way according to the order of the remaining positioning groove 8 from large to small. The diameters of the remaining optical microspheres 5 are 5μm and 2μm respectively.

[0097] (8) Finally, a full layer of adhesive film (the same UV adhesive as in step (3)) is sprayed onto the surface of the microlens array to perform surface planarization treatment to obtain a planarization layer 9, and finally a non-single-layer microlens array substrate is obtained.

[0098] As can be seen, the microlens film preparation method of the present invention can obtain a single-layer microlens array substrate, overcoming significant technical obstacles. The optical structure of the single-layer microlens array has significant advantages: it only experiences a small amount of reflection loss on the microlens surface, resulting in high overall light utilization efficiency, with light loss typically controlled within 15%. In contrast, multi-layer microsphere films, due to the increased number of optical interfaces, require incident light to undergo multiple scattering and refractions between different layers. On the one hand, each interface contact generates reflection loss, and during scattering, some light is reflected back to the light source side (forming ineffective light loss); on the other hand, impurities in the multilayer adhesive and microspheres may exacerbate light absorption, ultimately leading to a significantly higher overall light loss, typically reaching 20%-35%, far exceeding the light loss level of a single-layer microlens array. This invention employs a UV adhesive filling combined with pre-curing. It utilizes the oxygen inhibition phenomenon of the adhesive in an aerobic environment to obtain an ultrathin liquid layer on the adhesive surface. This ultrathin liquid layer is then used to achieve controllable adhesion of optical microspheres to its surface. By strictly controlling the pre-curing process parameters, the thickness of the liquid layer is stably controlled at 1 / 10 to 1 / 2 of the diameter of the optical microspheres. This results in the bonded optical microspheres exhibiting a single-layer structure at the microscopic level, forming a microlens film with a periodic array of dots at the target location on the substrate. Furthermore, the single-layer microlens film of this invention uses optical microlenses of different diameters arranged at regular intervals to form a periodic array structure with a large aspect ratio. This effectively improves the forward brightness of the display panel, enhances the overall light-gathering effect, improves light energy utilization efficiency, and thus improves the visual effect and energy consumption performance of the display device. The focal length of the microlens array is flexibly adjustable. The focal length of the microlens array mainly depends on the size of the optical microsphere, the refractive index of the optical microsphere, and the refractive index of the environment. By reasonably controlling the above parameters, the focal length of the microlens can be precisely designed and flexibly adjusted, thereby meeting the specific focal length requirements of different application scenarios and enhancing the adaptability and integration capability of the device in actual optical systems.

[0099] Although embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations all fall within the scope defined by the present invention.

Claims

1. A method for producing a microlens film layer, characterized by, The method comprises the following steps: Preparation of positioning grooves on the surface of the substrate; Filling of the positioning grooves with radical polymerization type UV glue to obtain a glue layer; Pre-curing of the glue layer in an oxygen-containing environment to obtain a glue layer with a bottom solidified surface remaining liquid layer; Dry spraying of optical microspheres onto the surface of the glue layer, the optical microspheres being limited in the positioning grooves; Complete curing of the glue layer, and removal of the optical microspheres in the non-glued area after curing to obtain a single-layer microlens film layer.

2. The method for preparing the microlens film according to claim 1, characterized in that, The thickness of the liquid layer is 1 / 10-1 / 2 of the diameter of the optical microspheres.

3. The method for preparing the microlens film according to claim 1, characterized in that, The optical microspheres are selected from at least one of silica microspheres, polystyrene microspheres, latex microspheres and polymethyl methacrylate microspheres.

4. The method for preparing the microlens film according to claim 3, characterized in that, The optical microspheres include at least two different diameters of optical microspheres, and the different diameters of optical microspheres are distributed by step-by-step dry spraying.

5. The method for preparing the microlens film according to claim 4, characterized in that, The dry spraying of the optical microspheres onto the surface of the glue layer comprises the following steps: The different diameters of optical microspheres are dry sprayed onto the surface of the substrate in the order of large diameter first and small diameter last.

6. The method for preparing the microlens film according to claim 1, characterized in that, The size of the groove is the same as that of the optical microspheres, and the filling height of the UV glue is lower than the height of the groove.

7. The method for preparing the microlens film according to claim 1, characterized in that, The UV glue is filled in the positioning grooves by micro-nano direct writing, piezoelectric or inkjet.

8. The method for preparing the microlens film according to claim 1, characterized in that, The optical microspheres are dry sprayed onto the surface of the substrate by electrostatic, air pressure or ultrasonic method under the condition that the substrate is inverted.

9. The method for preparing the microlens film according to claim 1, characterized in that, The complete curing of the glue layer, and removal of the optical microspheres in the non-glued area after curing comprises the following steps: The complete curing of the glue layer is carried out in an oxygen-free environment, and the optical microspheres in the non-glued area are removed by compressed air or ultrasonic after curing.

10. The method for preparing the microlens film according to claim 1, characterized in that, The method further comprises the following step: Finally, a protective whole-layer glue film is sprayed on the surface of the microlens, and the surface is planarized.

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