Preparation method of flexible anti-reflection surface based on femtosecond laser

Abstract

The invention provides a preparation method of a flexible anti-reflection surface based on femtosecond laser, which comprises the following steps: modifying a polyimide film, post-processing a processed sample, introducing laser into a galvanometer system, and carrying out secondary material processing through emergent light of a field lens so as to realize the effect of rapidly and efficiently processing a larger anti-reflection surface. And finally, the high-anti-reflection flexible surface combining super-hydrophobicity and anti-reflection is obtained. Therefore, the flexible anti-reflection surface is innovatively improved by virtue of the advantages of high precision machining, high peak power density, no need of post-treatment, high material adaptability and the like of femtosecond laser, and the machining efficiency is greatly improved; the average reflectivity of the prepared high-anti-reflection flexible surface at 450-1250nm is lower than 1%, the anti-reflection surface has good flexibility and can be applied to various complex curved surfaces, the surface reflectivity of the complex curved surfaces is reduced, and the high-anti-reflection flexible surface is applied to various equipment surfaces so as to realize infrared stealth.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of femtosecond laser processing, and particularly relates to a preparation method of a flexible anti-reflection surface based on a femtosecond laser. BACKGROUND

[0002] The anti-reflection surface has excellent light wave absorption capacity due to its special micro-nano structure, and has a good application prospect in the fields of solar cells, photodiodes and infrared stealth, and has become a research hotspot. It can improve the absorption of specific incident light waves and also shield part of the light waves. The anti-reflection performance is mainly the result of the interaction between the incident light and the micro-nano structure of the anti-reflection surface. At present, researchers mainly believe that when light is incident on the surface of the material, reflection, scattering, multiple internal reflection and complete interaction between light and the structure surface occur. In this process, the interface light scattering and absorption times increase, thereby reducing the reflected light and improving the light utilization rate.

[0003] At present, there are various methods for preparing anti-reflection surfaces, such as sol-gel method, 3D printing, chemical etching, etc. However, compared with the above methods, the photo-thermal effect of femtosecond laser is controllable, the heat deposition can be accurately adjusted, and the processing resolution is high, which makes it an important technical means for preparing anti-reflection surfaces. More importantly, femtosecond laser can accurately control the generation mode and range of micro-nano structures, so femtosecond laser has significant advantages in preparing anti-reflection surfaces.

[0004] Compared with rigid anti-reflection surfaces, flexible anti-reflection surfaces can be applied to various complex device surfaces, that is, the infrared stealth effect on curved surfaces can be realized to cope with different working conditions. However, the reflectivity of the flexible anti-reflection surface is still not as low as that of the rigid one. In terms of preparation method, the traditional method selects to introduce laser into the objective lens and then directly process the surface of the material. However, such processing method is time-consuming and the prepared surface is often small, which cannot meet the actual application requirements. SUMMARY

[0005] In order to solve the problems of long manufacturing time, rigid material and low reflectivity in the preparation process of anti-reflection surfaces, the application provides a preparation method of a flexible anti-reflection surface based on a femtosecond laser. The method adjusts the position of laser focusing by modifying a polyimide film and using a displacement table, processes in the defocusing condition, and performs post-processing on the sample, so as to realize the preparation of the anti-reflection surface.

[0006] The preparation method of the flexible anti-reflection surface based on the femtosecond laser comprises the following steps. Step one, fix the pretreated polyimide film on the lifting platform through the glass slide, then adjust the position of the lifting table in the vertical direction until the galvanometer system can obtain the upper surface of the polyimide film with the required definition, at this time the position of the upper surface of the polyimide film is the focal position of the galvanometer system; Step two, lowering the lifting platform in the vertical direction, wherein the distance of downward movement is greater than the thickness of the polyimide film, so that the upper surface of the polyimide film is in a defocused state in the galvanometer system; Step three, using the femtosecond laser system set according to the set laser parameters to perform secondary scanning on the polyimide film along the set track, and then performing post-processing on the sample obtained by the secondary scanning to obtain a super-hydrophobic flexible anti-reflection surface.

[0007] Further, the laser parameters used by the femtosecond laser system when performing the first scanning on the polyimide film are as follows: The laser wavelength is 1030 nm, the repetition frequency is 40 kHz, the defocusing amount is 0.5 mm, the scanning speed is 30 mm / s, and the scanning interval is 0.03 mm; The laser parameters used by the femtosecond laser system when performing the second scanning on the polyimide film are as follows: The laser wavelength is 1030 nm, the repetition frequency is 100 kHz, the scanning interval is 0.03-0.07 mm, the scanning speed is 10-30 mm / s, and the defocusing amount is -0.5-1 mm.

[0008] Further, if a flexible anti-reflection surface with a periodic sparse porous cluster structure is needed, then the secondary scanning is performed according to the track of non-continuous parallel scanning or continuous parallel scanning; If a flexible anti-reflection surface with a periodic micro-nano pillar array structure is needed, then the secondary scanning is performed according to the track of cross scanning; If a flexible anti-reflection surface with a scattered porous micro-nano structure is needed, then the secondary scanning is performed according to the track of back-type scanning.

[0009] Further, the pretreatment method of the polyimide film is as follows: Use a vernier caliper to cut the polyimide film into a 25x25mm square, and then use a GR-grade ethanol solution for 2 hours of immersion treatment of the cut polyimide film to clean and modify the impurities, thereby obtaining the final polyimide film. 2

[0010] Further, the method for post-processing the sample obtained by the secondary scanning is as follows: Ultrasonic water washing the sample for 20 minutes, and then placing it in a drying oven at 80 degrees Celsius for 20 minutes.

[0011] Further, the femtosecond laser system includes a femtosecond laser 1, a first mirror 2, a beam splitter 3, a second mirror 4, and a third mirror 5. ​The femtosecond laser emitted by the femtosecond laser 1 is incident on the first mirror 2 in a horizontal direction, and the femtosecond laser is introduced into the beam splitter 3 by the first mirror 2 for beam expansion, and then the expanded femtosecond laser is introduced into the galvanometer system through the second mirror 4 and the third mirror 5, and finally is incident on the upper surface of the polyimide film through the galvanometer system.

[0012] Further, the galvanometer system comprises an X mirror 6, a Y mirror 7, a field lens and an imaging system 8. The femtosecond laser emitted by the femtosecond laser system is sequentially focused on the upper surface of the polyimide film through the X mirror 6, the Y mirror 7, the field lens and the imaging system 8 for scanning ablation, wherein the X mirror 6 and the Y mirror 7 control the movement of the femtosecond laser by rotating in different directions, so that the femtosecond laser performs secondary scanning on the surface of the polyimide film according to the set trajectory; the field lens and the imaging system 8 are used for observing the surface topography of the polyimide film in real time.

[0013] Further, the field lens and the imaging system 8 comprise a red light source and an imaging unit, and the method for obtaining the surface topography of the polyimide film is: The polyimide film is illuminated by the built-in red light source, the illumination light source is reflected to the imaging unit through the polyimide film, and then the surface image of the polyimide film is transmitted to the external computer system through the imaging unit for real-time viewing.

[0014] Beneficial effects: 1. The preparation method of the flexible anti-reflective surface based on the femtosecond laser modifies the polyimide film and processes the sample after treatment, introduces the laser into the galvanometer system, and performs secondary processing on the material through the exit light of the field lens to realize the effect of rapidly and efficiently processing a larger anti-reflective surface, and finally obtains a high anti-reflective flexible surface combining super-hydrophobicity and anti-reflectivity; it can be seen that the flexible anti-reflective surface is innovatively improved by the advantages of high-precision processing, high peak power density, no post-processing and strong material adaptability of the femtosecond laser, and the galvanometer system further optimizes the slow processing speed of the femtosecond laser, greatly improving the processing efficiency; the average reflectivity of the prepared high anti-reflective flexible surface is less than 1% at 450-1250 nm, and the anti-reflective surface has good flexibility and can be applied to various complex curved surfaces, reduces the surface reflectivity of the complex curved surface, and is applied to various equipment surfaces to realize infrared stealth.

[0015] 2. The application provides a preparation method of a flexible antireflection surface based on a femtosecond laser, impurities of a polyimide film are removed and modified by using anhydrous ethanol, and the sample is subjected to secondary scanning by using four different scanning modes of a femtosecond laser and a galvanometer system, and then is subjected to ultrasonic water washing and drying treatment, so that a periodic sparse porous cluster-shaped micro-nano structure with strong light absorption capacity is prepared, and the prepared super-hydrophobic antireflection micro-nano structure can solve the problems of existing antireflection surfaces, such as rigidity, long processing cycle and high reflectivity.

[0016] 3. The application provides a preparation method of a flexible antireflection surface based on a femtosecond laser, a polyimide film is subjected to secondary scanning by using a femtosecond laser to generate a high-density micro-nano structure, the structure can not only limit light to be reflected multiple times when the light is incident, so as to reduce the reflectivity of the material surface, but also can make the surface become super-hydrophobic, so that the flexible antireflection surface can be applied to various working conditions and practical application ability is embodied.

[0017] 4. The application provides a preparation method of a flexible antireflection surface based on a femtosecond laser, an antireflection surface is prepared by using a femtosecond laser in one step, the preparation process is short in time consumption and good in effect, and the used material, a polyimide film, is low in cost and has potential for large-scale application. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 It is a schematic diagram of a laser manufacturing system of the application.

[0019] Figure 2 It is a schematic diagram of a high-antireflection surface manufacturing and spectrophotometer detection process of the application.

[0020] Figure 3 It is a schematic diagram of a high-antireflection surface pattern structure, an actual sample, a contact angle and a surface morphology of the application.

[0021] Figure 4 It is a reflectivity spectrum diagram of different processing modes obtained by using a spectrophotometer to detect a flexible high-antireflection surface.

[0022] Figure 5 It is a scanning electron microscope image under different scanning modes. Figure Four

[0023] It is a radar effect diagram of a tank model and a surrounding environment without using the application. Figure 6

[0024] It is an infrared stealth effect diagram of a flexible high-antireflection surface applied to a tank model surface. Figure 7

[0025] ​Among them, 1-femtosecond laser, 2-first reflecting mirror, 3-beam splitter, 4-second reflecting mirror, 5-third reflecting mirror, 6-X reflecting mirror, 7-Y reflecting mirror, 8-field mirror and imaging system, 9-polyimide film, 10-glass slide, 11-lifting platform, 12-computer control system. Detailed Implementation

[0026] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings.

[0027] To further reduce the reflectivity of material surfaces and address the limitations of application scenarios beyond the material itself, this invention provides a method for preparing a flexible anti-reflective surface based on femtosecond lasers, comprising: Step 1: Fix the pretreated polyimide film onto the lifting platform using a glass slide. Then, adjust the position of the lifting platform vertically until the galvanometer system can obtain the upper surface of the polyimide film with the required clarity. At this point, the position of the upper surface of the polyimide film is the focal point of the galvanometer system. For example, the pretreatment method for polyimide films can be: Use calipers to cut the polyimide film into 25x25mm pieces. 2 The polyimide film is cut into squares of a certain size and then soaked in GR-grade ethanol solution for 2 hours to remove impurities and modify it, thus obtaining the final polyimide film.

[0028] Step 2: Lower the lifting platform vertically, with the downward movement distance being greater than the thickness of the polyimide film, so that the upper surface of the polyimide film is in a defocused state in the galvanometer system; that is, by controlling the lifting platform to focus on the upper surface of the polyimide film, the defocusing operation is then performed. Step 3: Use a femtosecond laser system with set laser parameters to perform a second scan of the polyimide film along a set trajectory. Then, perform post-processing on the sample obtained from the second scan to obtain a superhydrophobic flexible anti-reflective surface, wherein the contact angle of the superhydrophobic structure is >150°.

[0029] The method for post-processing the samples obtained from the second scan is as follows: The sample was ultrasonically washed with water for 20 minutes, and then placed in a drying oven at 80 degrees Celsius for 20 minutes.

[0030] like Figure 1As shown, the femtosecond laser system includes a femtosecond laser (1), a first mirror (2), a beam splitter (3), a second mirror (4), and a third mirror (5); the galvanometer system includes an X-mirror (6), a Y-mirror (7), a field mirror, and an imaging system (8). The femtosecond laser emitted from the femtosecond laser (1) is incident on the first reflecting mirror (2) in the horizontal direction, and the femtosecond laser is introduced into the beam splitter (3) for beam expansion through the first reflecting mirror (2). The expanded femtosecond laser is then introduced into the galvanometer system through the second reflecting mirror (4) and the third reflecting mirror (5), and finally incident on the upper surface of the polyimide film through the galvanometer system.

[0031] The femtosecond laser emitted from the femtosecond laser system is sequentially focused onto the surface of the polyimide film by an X-mirror (6), a Y-mirror (7), and a field lens and imaging system (8) for scanning and ablation. The X-mirror (6) and Y-mirror (7) are rotated in different directions to control the movement of the femtosecond laser, allowing it to perform a secondary scan on the surface of the polyimide film along a set trajectory, thus achieving rapid processing. The field lens and imaging system (8) is used to observe the surface morphology of the polyimide film in real time. The field lens and imaging system (8) includes a red light source and an imaging unit. The method for obtaining the surface morphology of the polyimide film is as follows: The polyimide film is illuminated by a built-in red light source. The light source is reflected by the polyimide film to the imaging unit, which then transmits the surface image of the polyimide film to an external computer system for real-time viewing.

[0032] Furthermore, the laser parameters used by the femtosecond laser system for the first scan of the polyimide film are as follows: The laser wavelength is 1030nm, the repetition frequency is 40kHz, the defocusing amount is 0.5mm, the scanning speed is 30mm / s, the scanning interval is 0.03mm, and the laser power is 1W. The laser parameters used by the femtosecond laser system for the second scan of the polyimide film are as follows: The laser wavelength is 1030nm, the repetition frequency is 100kHz, the scanning interval is 0.03-0.07mm, the scanning speed is 10-30mm / s, the defocusing amount is -0.5-1mm, and the laser power is 1W.

[0033] Therefore, the method for the high anti-reflection flexible surface of the present invention can be summarized as follows: Before starting, cut the 0.2mm thick polyimide film into 25x25mm pieces. 2A square sample was prepared and then immersed in a GR-grade ethanol solution to remove surface impurities and modify the surface. During the preparation process, a femtosecond laser was used to perform a secondary scan of the polyimide film surface in a defocused state via a galvanometer system to obtain a superhydrophobic micro / nano structure. The defocusing distance needed to be greater than the material thickness to control the generation of the processing pattern only on the processing side. Finally, the sample was ultrasonically washed and dried to obtain a flexible anti-reflective surface with a reflectivity of 1%. The flexible anti-reflective surface of this invention can be attached to the surface of various materials to reduce surface reflectivity and achieve infrared stealth effect.

[0034] It should be noted that the micro-nano array structures generated by the four scanning methods vary with the scanning method. Parallel scanning and continuous scanning produce periodic sparse porous cluster structures, cross scanning produces periodic micro-nano columnar arrays, and back-shaped scanning produces relatively scattered porous micro-nano structures.

[0035] Therefore, if a flexible antireflective surface with a periodic, sparse, porous, clustered structure is required, a secondary scan is performed using either a discontinuous parallel scan or a continuous parallel scan trajectory. If a flexible antireflective surface with a periodic micro / nano columnar array structure is required, a secondary scan is performed using a cross-scan trajectory. If a flexible antireflective surface with a scattered porous micro / nano structure is required, a secondary scan is performed using a loop-shaped scan trajectory. The pore size of the micro / nano array is between 5 nm and 0.5 μm, and the period is 30 μm.

[0036] Furthermore, the relationship between the ablation diameter and pulse energy during laser ablation is as follows: D² = 2ω0² ln(E0) - 2ω0² ln(E th ) Where D is the diameter of the laser ablation spot, ω0 is the beam waist radius after laser focusing, E0 is the single pulse energy of the incident laser, and E th The damage threshold energy of the material.

[0037] The single-pulse energy E0 can be expressed by the following formula: E0 = u × A Where u is the energy density and A is the area affected by the laser.

[0038] Therefore, when other parameters remain constant, the ablation diameter D during femtosecond laser processing of polyimide can be controlled by changing the single-pulse energy E0 or the beam waist radius ω0, and the larger E0 or ω0 is, the larger D is. Furthermore, adjusting the laser repetition rate directly changes the level of E0; adjusting the scanning speed changes the level of u; adjusting the defocus amount changes the magnitude of ω0; and adjusting the scanning spacing overlaps the ablation areas, thereby deepening the ablation. The ablation diameter D of the material can be calculated using the above methods.

[0039] By changing the scanning method, the accumulation of laser energy on the material surface can be controlled, that is, the area A of laser action can be changed, affecting the thermal balance of the material within a unit time region, thereby changing the morphology of the micro-nano structures generated by ablation.

[0040] According to the trapping effect, the electron capture rate C n for: C n = B n n (N t - n t ) Among them B n N is the electron capture coefficient, n is the conduction band electron concentration, and N is the electron trapping coefficient. t n represents the total concentration of the trapped states. t This refers to the concentration of trapped states already occupied by electrons. When a semiconductor material is in a non-equilibrium state, its internal impurity energy levels accumulate non-equilibrium carriers through the trapping cross section. When external forces such as light disrupt the material's original thermal equilibrium, the impurity energy levels can capture and store non-equilibrium carriers, and the storage capacity can reach a level comparable to the concentration of conduction band or valence band carriers, thus forming a temporary accumulation of carriers. Parallel scanning, continuous scanning, cross-scanning, and loop scanning, by changing the thermal accumulation over a small area per unit time, regulate the formation process of micro- and nano-structures, and can generate considerable nanoscale porous structures, i.e., trapped states. Under constant conditions, the total concentration of trapped states, N, is... t The higher the value, the higher the electron capture rate C. n The higher the reflectivity, the greater the reduction in surface reflectivity of the sample.

[0041] Furthermore, the process flow used in this invention is as follows: Figure 2 As shown: First, the polyimide film is cleaned and modified using GR-grade anhydrous ethanol. After drying, it is firmly adhered to a glass slide. Then, CAD software is used to draw the following... Figure 3 (a) shows 22x22mm 2 A second scan was performed on the square linear scanning area; the processed sample was placed in an ultrasonic cleaner for ultrasonic water washing for 20 minutes, and then placed in a drying oven at 80 degrees Celsius for 20 minutes to obtain the desired result. Figure 3 (b) shows the flexible, highly anti-reflective surface.

[0042] The performance tests conducted on the flexible high anti-reflection surface in this embodiment are as follows: Figure 3 (c)(d) and Figure 4 As shown.

[0043] Contact angle test: Place the sample horizontally on the displacement stage of the contact angle measuring instrument and add a drop of 4μL distilled water using a dropper. Record the data using a computer. The sample surface contact angle reaches 154.5°. Figure 3(c) Compared to the 85° contact angle of polyimide film, the hydrophobicity is greatly improved.

[0044] Spectrophotometer detection: for polyimide films. Figure 4 The four scanning methods shown in the left figure were used for processing, and the processing parameters were as described in (2). The reflectance of the four samples was tested using UV-VIS-NIR spectrophotometry. The spectral range was set to 450-1250 nm, the sampling time was 0.2 s, and baseline processing was performed. The reflectance of the samples was as follows. Figure 4 As shown in the right figure, the excessively high reflectivity due to cross-scanning is mainly caused by the damage from two scans. Figure 3 (d) shows a fluffy, porous, layered structure. The reason why continuous scanning has a slightly lower reflectivity compared to parallel and loop scanning is mainly because debris is easily generated during the laser processing of polyimide. This debris cannot be removed in time and remains on the processed surface. Loop scanning further hinders the debris removal process, resulting in a higher reflectivity compared to parallel scanning. However, continuous scanning can better spread the debris in two directions instead of accumulating in one direction, thus resulting in a lower reflectivity compared to parallel scanning. The final processing scheme adopted was continuous scanning. Under this condition, the reflectivity of the flexible, high-anti-reflection surface is as low as 0.99% at 1000nm.

[0045] Scanning electron microscopy analysis: The surface morphology of the samples was analyzed using a Zeiss Gemini 300 scanning electron microscope. First, the samples were sputter-coated with gold to enhance conductivity, and then observed within the chamber. Figure 3 As shown in (d), the surface morphology of the polyimide surface formed by femtosecond laser processing effectively traps incident light. This structure not only significantly reduces surface reflectivity but also creates air gaps between the surface and water droplets, thus transforming the surface into a superhydrophobic structure. The surface morphologies of the four scanning methods are shown below. Figure 5 As shown, it can be observed that in continuous scanning ( Figure 5 The surface micro- and nano-structures obtained under (d) are the most abundant, proving that the anti-reflection performance of the material is the best at this time.

[0046] (4) Application of the present invention to flexible high anti-reflection surfaces, such as Figure 6 and Figure 7 As shown. The computer system and radar sensor used (emitting laser wavelength of 905nm) are as follows. Figure 6 (a) Scanning the surrounding environment and the car model. Figure 6 (b) Figure 6 (c) is obtained Figure 6(d) shows the radar signal pattern, where the upper blue horizontal line represents the stepped terrain, and the raised signal in the middle represents the vehicle's surface, indicating that the vehicle has been detected by radar. The flexible, high-anti-reflective surface of this invention is applied to one side of the vehicle's surface and placed in the same position as when not in use. Figure 7 (a) Figure 7 (b) Perform radar scanning to obtain Figure 7 (c) shows the radar signal diagram, which reveals that the surface of the vehicle to which the present invention is attached has become "invisible" within the radar detection range, indicating that the flexible high anti-reflection surface of the present invention has good infrared stealth capability.

[0047] In summary, this invention provides a method for preparing a flexible anti-reflective surface based on femtosecond laser. By using reagents for modification and taking advantage of the processing capabilities of femtosecond lasers for secondary scanning, the resulting highly anti-reflective flexible surface exhibits an average reflectivity of less than 1% at 450~1250nm. The prepared flexible anti-reflective surface possesses excellent flexibility and can be applied to various complex curved surfaces to reduce their surface reflectivity. It can also be applied to various stealth model surfaces to achieve infrared stealth effects.

[0048] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the appended claims.

Claims

1. A method for preparing a flexible anti-reflective surface based on femtosecond laser, characterized in that, include: Step 1: Fix the pretreated polyimide film onto the lifting platform using a glass slide. Then, adjust the position of the lifting platform vertically until the galvanometer system can obtain the upper surface of the polyimide film with the required clarity. At this point, the position of the upper surface of the polyimide film is the focal point of the galvanometer system. Step 2: Lower the lifting platform vertically, with the downward movement distance being greater than the thickness of the polyimide film, so that the upper surface of the polyimide film is in a defocused state in the galvanometer system; Step 3: Use a femtosecond laser system with set laser parameters to perform a second scan of the polyimide film along a set trajectory. Then, perform post-processing on the sample obtained from the second scan to obtain a superhydrophobic flexible anti-reflective surface.

2. The method for preparing a flexible anti-reflective surface based on a femtosecond laser as described in claim 1, characterized in that, The laser parameters used by the femtosecond laser system for the first scan of the polyimide film are as follows: The laser wavelength is 1030nm, the repetition frequency is 40kHz, the defocusing amount is 0.5mm, the scanning speed is 30mm / s, and the scanning interval is 0.03mm. The laser parameters used by the femtosecond laser system for the second scan of the polyimide film are as follows: The laser wavelength is 1030nm, the repetition frequency is 100kHz, the scanning interval is 0.03-0.07mm, the scanning speed is 10-30mm / s, and the defocusing amount is -0.5-1mm.

3. The method for preparing a flexible anti-reflective surface based on a femtosecond laser as described in claim 1, characterized in that, If a flexible anti-reflective surface with a periodic, sparse, porous, clustered structure is required, a secondary scan is performed according to a non-continuous parallel scan or a continuous parallel scan trajectory. If a flexible anti-reflective surface with a periodic micro-nano columnar array structure is required, a second scan is performed according to the cross-scan trajectory. If a flexible anti-reflective surface with scattered porous micro / nano structures is required, a secondary scan is performed following the loop scan trajectory.

4. The method for preparing a flexible anti-reflective surface based on femtosecond laser as described in claim 1, characterized in that, The pretreatment method for polyimide films is as follows: Use calipers to cut the polyimide film into 25x25mm pieces. 2 The polyimide film is cut into squares of a certain size and then soaked in GR-grade ethanol solution for 2 hours to remove impurities and modify it, thus obtaining the final polyimide film.

5. The method for preparing a flexible anti-reflective surface based on a femtosecond laser as described in claim 1, characterized in that, The post-processing method for the samples obtained from the second scan is as follows: The sample was ultrasonically washed with water for 20 minutes, and then placed in a drying oven at 80 degrees Celsius for 20 minutes.

6. The method for preparing a flexible anti-reflective surface based on a femtosecond laser as described in claim 1, characterized in that, The femtosecond laser system includes a femtosecond laser (1), a first mirror (2), a beam splitter (3), a second mirror (4), and a third mirror (5); The femtosecond laser emitted from the femtosecond laser (1) is incident on the first reflecting mirror (2) in the horizontal direction, and the femtosecond laser is introduced into the beam splitter (3) for beam expansion through the first reflecting mirror (2). The expanded femtosecond laser is then introduced into the galvanometer system through the second reflecting mirror (4) and the third reflecting mirror (5), and finally incident on the upper surface of the polyimide film through the galvanometer system.

7. The method for preparing a flexible anti-reflective surface based on a femtosecond laser as described in claim 1, characterized in that, The galvanometer system includes an X-mirror (6), a Y-mirror (7), a field lens, and an imaging system (8). The femtosecond laser emitted from the femtosecond laser system is sequentially focused onto the surface of the polyimide film by an X-mirror (6), a Y-mirror (7), a field lens, and an imaging system (8) for scanning and ablation. The X-mirror (6) and the Y-mirror (7) are rotated in different directions to control the movement of the femtosecond laser, so that the femtosecond laser performs a secondary scan on the surface of the polyimide film according to a set trajectory. The field lens and imaging system (8) is used to observe the surface morphology of the polyimide film in real time.

8. The method for preparing a flexible anti-reflective surface based on a femtosecond laser as described in claim 7, characterized in that, The field lens and imaging system (8) includes a red light source and an imaging unit. The method for obtaining the surface morphology of the polyimide film is as follows: The polyimide film is illuminated by a built-in red light source. The light source is reflected by the polyimide film to the imaging unit, which then transmits the surface image of the polyimide film to an external computer system for real-time viewing.

Images