Micro-nano composite structure super black film, preparation method and application thereof

Abstract

This invention provides a micro / nano composite structure ultra-black thin film, its preparation method, and its application. The micro / nano composite structure ultra-black thin film comprises: a flexible light-absorbing substrate layer; a micro / nano composite structure layer disposed on at least one surface of the flexible light-absorbing substrate layer, the micro / nano composite structure layer comprising a micrometer-scale protrusion array, and the surface of the micrometer-scale protrusion array having a nanometer-scale structure; and a low-refractive-index antireflective protective layer covering the micro / nano composite structure layer, and covering the micrometer-scale protrusion array and the nanometer-scale structure on its surface. This invention achieves comprehensive performance of high absorption, low reflection, lightweight, flexibility, and stability across a wide wavelength range through the intrinsic absorption of the flexible light-absorbing substrate, the multiple reflection and light-trapping effect of the micrometer-scale protrusion structure, the gradient antireflective effect of the nanometer-scale structure, and the interface antireflective and structural protection effects of the low-refractive-index antireflective protective layer.

Description

Technical Field

[0001] This invention relates to the fields of optical absorption materials, micro / nano structured functional thin films and low-reflection interfaces, and particularly to a micro / nano composite structure ultra-black thin film, its preparation method and application. Background Technology

[0002] Stray light suppression is one of the key technologies in high-sensitivity optical systems. In space telescopes, space cameras, remote sensing payloads, spectrometers, and infrared detectors, stray light from outside the imaging path can reduce imaging contrast, increase background noise, and affect the detection accuracy of weak signal targets. Therefore, high-absorption, low-reflection black matting materials are widely used in the inner walls of optical systems, light shields, light-blocking rings, light traps, light-blocking sheets, and various light-absorbing components.

[0003] In recent years, space optical systems, flexible optoelectronic devices, and deployable structures have been rapidly developing towards lighter weight, greater flexibility, wider wavelength response, and higher reliability. However, traditional black coatings and matting materials face many bottlenecks in this trend. Existing black light-absorbing materials mainly include black organic or inorganic coatings, black anodic oxide layers, carburized polymer films, spray-applied matting coatings, and light-absorbing layers based on metal or inorganic nanostructures. Although these materials have alleviated the stray light problem to some extent, they still reveal the following key shortcomings in practical applications: (i) their absorption performance is limited across a wide band, especially in the ultraviolet, near-infrared, and mid-far-infrared bands, where the absorption rate is low and it is difficult to meet the requirements of multispectral and full-spectrum detection; (ii) the extinction materials have high density or large thickness, which is not conducive to the lightweight and compact integration of the system; (iii) the surface micro-nano structures are easily damaged or detached under friction, vibration, bending, cleaning, or environmental stress, resulting in a decrease in absorption performance; (iv) the bonding force between some materials and flexible substrates is insufficient, making them unsuitable for foldable, rollable, or curved surface attachment structures, which limits their application in new flexible optical systems; (v) their weather resistance (such as resistance to ultraviolet radiation, thermal cycling, and moisture erosion) still needs to be improved, and they cannot meet the stability requirements for long-term service in the space environment.

[0004] Therefore, there is an urgent need to develop an ultra-black thin film with a well-defined hierarchical structure to achieve ultra-black light absorption performance with wide wavelength, wide angle, and high stability, and to make it suitable for fields such as space optics, flexible electronics, display, sensing, thermal control, and photoelectric detection. Summary of the Invention

[0005] In view of the problems existing in the prior art, the present invention provides a micro-nano composite structure ultra-black thin film, its preparation method and application, which can achieve comprehensive performance of high absorption, low reflection, lightweight, flexibility and stability over a wide band. It can be used in fields such as light absorption, extinction, stray light suppression, thermal control absorption, photoelectric detection, display devices, flexible electronic devices, sensor devices and space optical systems.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a micro-nano composite structure ultra-black thin film, the micro-nano composite structure ultra-black thin film comprising:

[0008] Flexible light-absorbing substrate layer;

[0009] A micro-nano composite structure layer is disposed on at least one surface of the flexible light-absorbing substrate layer. The micro-nano composite structure layer includes a micron-scale protrusion structure array, and the surface of the micron-scale protrusion structure array has a nano-scale structure.

[0010] A low-refractive-index antireflective protective layer is applied to the micro-nano composite structure layer and covers the micron-scale protrusion array and the nanoscale structure on its surface.

[0011] This invention provides an ultra-black thin film composed of a flexible light-absorbing substrate, a micro / nano composite structure layer, and a low-refractive-index anti-reflection protective layer. The flexible light-absorbing substrate provides intrinsic absorption and mechanical support; the micron-scale protrusion array extends the incident light propagation path and enhances multiple reflections; the nanoscale structure forms an equivalent gradient refractive index interface; and the low-refractive-index anti-reflection protective layer further reduces interface reflection and improves the mechanical and environmental stability of the micro / nano structure. This results in a comprehensive performance profile of wide wavelength range, high absorption, low reflection, lightweight, flexibility, and durability.

[0012] As a preferred embodiment of the present invention, the flexible light-absorbing substrate layer comprises a polymer film containing light-absorbing components.

[0013] Preferably, the polymer film includes any one or a composite film of at least two of polyimide film, polyetheretherketone film, polyetherimide film or polyphenylene sulfide film, and preferably a polyimide film.

[0014] The flexible light-absorbing substrate layer of the present invention is preferably a black polyimide film, which enables the resulting ultra-black film to be bent, rolled, folded or attached to a curved substrate, and is suitable for lightweight light-shielding components, unfoldable structures and flexible optoelectronic devices.

[0015] Preferably, the light-absorbing component includes any one or a combination of at least two of carbon black, graphite, graphene, carbon nanotubes, or carbonized polymers.

[0016] Preferably, the mass content of the light-absorbing component in the polymer film containing the light-absorbing component is 1%-60%, such as 1%, 10%, 20%, 30%, 40%, 50% or 60%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0017] Preferably, the average thickness of the flexible light-absorbing substrate layer is 15-60 μm, such as 15 μm, 22 μm, 27 μm, 32 μm, 37 μm, 42 μm, 47 μm, 52 μm or 60 μm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0018] As a preferred technical solution of the present invention, the protrusion structure in the micron-level protrusion structure array includes any one or a combination of at least two of the following: conical, cylindrical, hemispherical, or pyramidal shapes.

[0019] Preferably, the average height of the protrusion structure is 7-29 μm, such as 7 μm, 9 μm, 11 μm, 13 μm, 15 μm, 17 μm, 19 μm, 21 μm, 23 μm, 25 μm, 27 μm or 29 μm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0020] Preferably, the bottom feature size of the protrusion structure is 20-50 μm, such as 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm or 50 μm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0021] When the bottom of the protruding structure of this invention is circular, the characteristic dimension refers to the diameter; when the bottom is polygonal, the characteristic dimension refers to the side length; and when it is an irregular shape, it refers to the length of the line connecting the two furthest points.

[0022] As a preferred technical solution of the present invention, the nanoscale structure includes a nanoscale villous structure and / or a nanoscale porous structure.

[0023] Preferably, the average thickness of the nanoscale structure is 0.5-1.5 μm, such as 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm or 1.5 μm, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0024] Preferably, the nanoscale structure is distributed at any one or at least two of the gaps in the sidewalls, top, or bottom of the micron-scale protrusion structure.

[0025] As a preferred embodiment of the present invention, the refractive index of the low-refractive-index antireflective protective layer is lower than that of the flexible light-absorbing substrate layer.

[0026] Preferably, the average thickness of the low refractive index antireflective protective layer is 10 nm-2 μm, such as 10 nm, 50 nm, 500 nm, 1 μm, 1.5 μm or 2 μm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0027] Preferably, the low refractive index antireflective protective layer comprises any one or a combination of at least two of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, magnesium fluoride, indium tin oxide, polydimethylsiloxane, acrylate, or fluorosilicone acrylate.

[0028] The low-refractive-index antireflective protective layer of the present invention provides conformal coverage for the micron-scale protrusion structure array and the nanoscale structure on its surface.

[0029] In a second aspect, the present invention provides a method for preparing the micro / nano composite structure ultrablack thin film described in the first aspect, the method comprising:

[0030] A micro-nano composite structure layer is formed on at least one side surface of the flexible light-absorbing substrate layer. The micro-nano composite structure layer includes a micron-scale protrusion structure array, and the surface of the micron-scale protrusion structure array has a nano-scale structure.

[0031] A low-refractive-index anti-reflection protective layer is formed on the surface of the micro-nano composite structure layer, and the low-refractive-index anti-reflection protective layer covers the micron-scale protrusion structure array and the nano-scale structure on its surface to obtain the ultra-black film of the micro-nano composite structure.

[0032] As a preferred technical solution of the present invention, the micro-nano composite structure layer is formed by an etching process.

[0033] The micro-nano composite structure layer of the present invention can also be formed by template imprinting, hot pressing, micro-nano replication process or a combination thereof.

[0034] Preferably, the etching process includes laser etching.

[0035] The etching process of this invention also includes plasma etching, ion beam etching, reactive ion etching, mechanical etching, or a combination thereof.

[0036] Preferably, the laser etching includes ultraviolet nanosecond laser etching.

[0037] This invention uses ultraviolet nanosecond laser etching technology to directly construct micro-nano composite structures on the surface of flexible light-absorbing substrates, without the need for complex templates or high-temperature deposition processes. The process is highly controllable and suitable for patterning and large-area fabrication.

[0038] If the present invention employs ultraviolet nanosecond laser etching technology, the specific etching process includes: First, the cleaned polymer film (such as a polyimide black film) is fixed on the moving stage of the ultraviolet nanosecond laser equipment. By precisely controlling the laser etching method and related parameters—including the number of etching passes, etching line spacing, current, frequency, scanning speed, and pulse width—the surface of the polymer film (such as the polyimide black film) is systematically structured. Then, the etched film is adhered to the sample stage of a spin coater. A low-refractive-index resin is dropped onto the film surface using a pipette, and spin-coated at a set speed to achieve uniform coverage. Finally, curing is performed under elevated temperature conditions to obtain the desired ultra-black film. The flexible, lightweight ultra-black film prepared by the above method has a micron-scale protrusion structure array on its surface. This structure can form multiple reflection and absorption paths for incident light, thereby significantly improving light absorption performance. Simultaneously, the low-refractive-index resin layer coated on the film surface not only further reduces surface reflection but also protects the micro / nano structure and enhances the film's environmental adaptability.

[0039] The current for ultraviolet nanosecond laser etching described in this invention is 2-8 A, such as 2 A, 3 A, 4 A, 5 A, 6 A, 7 A or 8 A, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable. The preferred current is 4 A.

[0040] The frequency of ultraviolet nanosecond laser etching described in this invention is 30-50 kHz, such as 30 kHz, 40 kHz or 50 kHz, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable, with 30 kHz being the preferred frequency.

[0041] The pulse width of the ultraviolet nanosecond laser etching described in this invention is 12-20 ns, such as 12 ns, 15 ns, 18 ns or 20 ns, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable. The preferred pulse width is 20 ns.

[0042] The scanning speed of the ultraviolet nanosecond laser etching described in this invention is 200-1000 mm·s. -1 For example, 200 mm·s -1 500 mm·s -1 or 1000 mm·s -1 The values ​​are not limited to those listed; other unlisted values ​​within this range also apply. A scanning speed of 200 mm / s is preferred. -1 .

[0043] The flexible light-absorbing substrate of the present invention requires pretreatment, which involves ultrasonic treatment in a cleaning agent. The cleaning agent includes any one or a combination of at least two of deionized water, ethanol, petroleum ether, or acetone. The ultrasonic treatment time is 5-10 minutes, for example, 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes, or 10 minutes, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0044] Preferably, the scanning method of the laser etching includes any one or a combination of at least two of the following: unidirectional parallel scanning, bidirectional orthogonal scanning, multidirectional cross scanning, or arrayed point scanning.

[0045] This invention can form groove-like structures, tetrahedral array structures, or trihedral array structures on the membrane surface through the different scanning methods described above. A bidirectional orthogonal scanning method is preferred to prepare a regular tetrahedral array.

[0046] Preferably, the number of laser etching repetitions is 10-35 times, for example, 10 times, 11 times, 13 times, 15 times, 17 times, 19 times, 21 times, 23 times, 25 times, 27 times, 29 times, 31 times, 33 times, or 35 times, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, with 35 times being the preferred number.

[0047] This invention limits the number of laser etching repetitions to the above range, which can ensure high light absorption performance while taking into account processing efficiency. If the number of repetitions is too few, the etching depth will be insufficient, making it difficult to achieve effective extinction; if the number of repetitions is too many, the processing time will be extended, and the improvement in light absorption performance will not be significant.

[0048] Preferably, the laser etching line spacing is 20-100 μm, for example, it can be 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm or 100 μm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable. Preferably, it is 20-50 μm, and more preferably 20 μm.

[0049] This invention limits the laser etching line scan spacing to the above-mentioned range, which can ensure high light absorption performance while taking into account processing efficiency. If the line scan spacing is too large, the resulting cone structure will be blunt and more plateau areas will be generated, thereby increasing specular reflection and reducing light absorption performance. If the line scan spacing is too small, it will increase the number of line scans, prolong the processing time, and have limited effect on further improving light absorption performance; or the laser beam energy may overlap, destroying the cone structure.

[0050] As a preferred technical solution of the present invention, the low refractive index antireflective protective layer is formed by spin coating, spraying, dip coating, blade coating, drop coating, chemical vapor deposition, physical vapor deposition, atomic layer deposition, sol-gel coating or a combination thereof.

[0051] The spin coating process used in this invention is preferably performed using a spin coater with a spin coater speed of 1000-5000 rpm, such as 1000 rpm, 2000 rpm, 3000 rpm, 4000 rpm or 5000 rpm, but not limited to the listed values. Other unlisted values ​​within this range are also applicable. Preferably, the spin coater speed is 3000 rpm.

[0052] After depositing a low-refractive-index antireflective protective layer, the resulting film is cured in an oven at a temperature controlled between 70-90 °C, such as 70 °C, 80 °C, or 90 °C, for a time of 3-8 h, such as 3 h, 4 h, 5 h, 6 h, 7 h, or 8 h.

[0053] Preferably, the raw materials for forming the low refractive index antireflective protective layer include any one or a combination of at least two of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, magnesium fluoride, indium tin oxide, polydimethylsiloxane, acrylate, or fluorosilicone acrylate.

[0054] The raw materials for forming the low refractive index antireflective protective layer of the present invention also include amorphous fluorinated resin AF2400. The amorphous fluorinated resin AF2400 is prepared by mixing resin AF2400 and solvent. The resin is amorphous fluorinated resin AF2400, the solvent is FC-40, and the resin concentration is 0.01%-1%, such as 0.01%, 0.1%, or 1%, but not limited to the listed values. Other unlisted values ​​within this range are also applicable. Preferably, the resin concentration is 1%.

[0055] The polydimethylsiloxane of this invention is prepared by mixing a prepolymer, a curing agent, and a solvent. The prepolymer is Dow Corning 184 silicone rubber component A, the curing agent is Dow Corning 184 silicone rubber component B, and the solvent is petroleum ether. The mass ratio of the prepolymer to the curing agent is (8-15):1, for example, 8:1, 10:1, 12:1, or 15:1, but not limited to the listed values; other unlisted values ​​within this range are also applicable. The resin concentration is 0.1%-5%, for example, 0.1%, 1%, 2.5%, or 5%. Preferably, the mass ratio of the prepolymer to the curing agent is 10:1, and the resin concentration is 1%. The mixing method is vacuum degassing and stirring. The specific process of vacuum degassing and stirring is as follows: stirring at a rate of 200-1000 rpm (e.g., 200 rpm, 500 rpm, 800 rpm, or 1000 rpm, etc.) for 2-5 minutes under normal pressure, and then stirring at a rate of 1500-2000 rpm (e.g., 1500 rpm, 1800 rpm, or 2000 rpm, etc.) under a vacuum of 20-60 kPa (e.g., 20 kPa, 40 kPa, or 60 kPa, etc.) for 3-5 minutes.

[0056] As a preferred embodiment of the present invention, the refractive index of the low-refractive-index antireflective protective layer is less than 1.5.

[0057] Thirdly, the present invention provides an application of the micro-nano composite structure ultra-black thin film as described in the first aspect, wherein the micro-nano composite structure ultra-black thin film is used for light absorption, extinction, stray light suppression, low-reflection interface construction, thermal control absorption, photoelectric detection, display devices, flexible electronic devices, sensor devices or space optical systems.

[0058] Compared with existing technical solutions, the present invention has at least the following beneficial effects:

[0059] (1) The micro-nano composite structure ultra-black film provided by the present invention is composed of a flexible light-absorbing substrate layer, a micro-nano composite structure layer and a low refractive index anti-reflection protective layer, forming a clear multi-level functional structure, which is conducive to simultaneously achieving intrinsic absorption, geometric light trapping, gradient anti-reflection and structural protection.

[0060] (2) The micro-nano composite structure ultra-black film provided by the present invention can enhance the multiple reflections and propagation path extension of incident light inside the structure. The nanoscale structure can reduce interface reflection, and the low refractive index anti-reflection protective layer can further improve optical coupling, thereby significantly improving the broadband absorption performance. Attached Figure Description

[0061] Figure 1 This is a schematic diagram of the micro-nano composite structure ultra-black thin film of the present invention;

[0062] Figure 2This is a schematic diagram of laser etching according to the present invention;

[0063] Figure 3 This is a scanning electron microscope (SEM) image of the cross-section of the micro / nano composite structure ultra-black thin film of Embodiment 1 of the present invention;

[0064] Figure 4 These are ultraviolet-visible-near-infrared reflectance curves of ultra-black films with micro-nano composite structures in some embodiments and comparative examples of the present invention. Detailed Implementation

[0065] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0066] It should be clarified that any use of the process provided in the embodiments of the present invention or any substitution or change of conventional data falls within the protection and disclosure scope of the present invention.

[0067] Example 1

[0068] This embodiment provides a micro-nano composite structure ultra-black thin film, characterized in that the micro-nano composite structure ultra-black thin film comprises:

[0069] Flexible light-absorbing substrate (black polyimide film containing ~40% carbon black material by mass, with an average thickness of 22 μm);

[0070] A micro-nano composite structure layer is disposed on one side surface of the flexible light-absorbing substrate layer. The micro-nano composite structure layer includes a pyramid-shaped array of micron-sized protrusions (the average height of the protrusions is 28 μm and the bottom side length is 30 μm), and the surface of the array of micron-sized protrusions has a nano-scale structure (nano-scale villous structure with an average thickness of 1 μm). The nano-scale structure is distributed in the gaps between the sidewalls, top, and bottom of the micron-sized protrusions.

[0071] A low-refractive-index antireflective protective layer (composed of amorphous fluorine resin AF2400) is applied to the micro-nano composite structure layer, with an average thickness of approximately 10 nm, and covers the micron-scale protrusion structure array and the nanoscale structure on its surface. The refractive index of the low-refractive-index antireflective protective layer is lower than that of the flexible light-absorbing substrate layer.

[0072] This embodiment also provides a method for preparing a micro / nano composite structure ultrablack thin film, the preparation method comprising:

[0073] (1) First, the polyimide black film is pretreated by placing the film in an ethanol solution and cleaning it under ultrasonic action for 5 min to remove surface impurities. Then, it is dried in an oven at 80 °C for 20 min.

[0074] (2) Adjusting the parameters of the ultraviolet nanosecond laser to etch the polyimide black film:

[0075] The cleaned polyimide black film is adhered and fixed onto the moving stage of the ultraviolet nanosecond laser equipment. The laser etching method is precisely controlled to be a bidirectional orthogonal scan, such as... Figure 2 As shown;

[0076] The etching parameters were adjusted as follows: 35 etching passes, 20 μm etching line spacing, 4 A current, 30 kHz frequency, 20 ns pulse width, and 200 mm·s scan speed. -1 This yielded micron-scale protrusion arrays and nano-scale structures.

[0077] (3) Spin-coating the low-refractive resin onto the surface of the nanoscale structure obtained by etching in step (2):

[0078] First, prepare the low-refractive resin. In this example, we use 1% AF2400 low-refractive resin, which can be directly taken from the purchased low-refractive resin without any further processing.

[0079] The etched film was attached to the stage of the spin coater, and resin was transferred onto the film surface. The spin coater rotated at 2000 rpm for 30 seconds.

[0080] (4) Place the homogenized film in an oven and cure it at 80 °C for 6 h to obtain the micro-nano composite structure ultra-black film.

[0081] Example 2

[0082] This embodiment provides a micro-nano composite structure ultra-black thin film, characterized in that the micro-nano composite structure ultra-black thin film comprises:

[0083] Flexible light-absorbing substrate (black polyimide film containing ~40% carbon black material by mass, with an average thickness of 22 μm);

[0084] A micro-nano composite structure layer is disposed on one side surface of the flexible light-absorbing substrate layer. The micro-nano composite structure layer includes a pyramid-shaped array of micron-sized protrusions (the average height of the protrusions is 28 μm and the bottom side length is 20 μm), and the surface of the array of micron-sized protrusions has a nano-scale structure (nano-scale porous structure with an average thickness of 0.5 μm). The nano-scale structure is distributed in the sidewalls, top, and bottom gaps of the micron-sized protrusions.

[0085] A low-refractive-index antireflective protective layer (composed of polydimethylsiloxane PDMS) is applied to the micro-nano composite structure layer, with an average thickness of 10 nm, and covers the micron-scale protrusion structure array and the nanoscale structure on its surface. The refractive index of the low-refractive-index antireflective protective layer is lower than that of the flexible light-absorbing substrate layer.

[0086] This embodiment also provides a method for preparing a micro / nano composite structure ultrablack thin film, the preparation method comprising:

[0087] (1) First, the black polyimide film is pretreated by placing it in an ethanol solution and cleaning it under ultrasonic action for 10 min to remove surface impurities. Then, it is dried in an oven at 80 ℃ for 20 min.

[0088] (2) Etching of the black polyimide film by adjusting the parameters of the ultraviolet nanosecond laser:

[0089] The cleaned black polyimide film is attached and fixed to the moving stage of the ultraviolet nanosecond laser equipment, and the laser etching mode is precisely controlled to be bidirectional orthogonal scanning.

[0090] The etching parameters were adjusted as follows: 35 etching passes, 20 μm etching line spacing, 4 A current, 30 kHz frequency, 20 ns pulse width, and 200 mm·s scan speed. -1 This yielded micron-scale protrusion arrays and nano-scale structures.

[0091] (3) Spin-coating the low-refractive resin polydimethylsiloxane (PDMS) onto the nanoscale structure surface obtained by etching in step (2):

[0092] First, prepare the low-refractive resin: Weigh out 1 g of Dow Corning 184 silicone rubber component A and Dow Corning silicone rubber component B at a mass ratio of 10:1; then add 99 g of petroleum ether to adjust the mass fraction of the solution to 1%; then mix in a high-speed degassing mixer at 2000 rpm for 5 min.

[0093] (4) Place the homogenized film in an oven and cure it at 80 °C for 6 h to obtain the micro-nano composite structure ultra-black film.

[0094] Example 3

[0095] This embodiment provides a method for preparing a micro-nano composite structure ultra-black thin film. The only difference between the preparation method of the micro-nano composite structure ultra-black thin film and that of Embodiment 1 is that the number of etching steps is changed to 5, while the rest are the same as in Embodiment 1.

[0096] Example 4

[0097] This embodiment provides a method for preparing a micro-nano composite structure ultra-black thin film. The only difference between the preparation method of the micro-nano composite structure ultra-black thin film and that of Embodiment 1 is that the number of etching cycles is changed to 10, while the rest are the same as in Embodiment 1.

[0098] Example 5

[0099] This embodiment provides a method for preparing a micro-nano composite structure ultra-black thin film. The only difference between the preparation method of the micro-nano composite structure ultra-black thin film and that of Embodiment 1 is that the number of etching cycles is changed to 20, while the rest are the same as in Embodiment 1.

[0100] Example 6

[0101] This embodiment provides a method for preparing a micro-nano composite structure ultra-black thin film. The only difference between the preparation method of the micro-nano composite structure ultra-black thin film and that of Embodiment 1 is that the number of etching cycles is changed to 30, while the rest are the same as those of Embodiment 1.

[0102] Example 7

[0103] This embodiment provides a method for preparing a micro-nano composite structure ultra-black thin film. The only difference between the preparation method of the micro-nano composite structure ultra-black thin film and that of Embodiment 1 is that the number of etching cycles is changed to 40, while the rest are the same as those of Embodiment 1.

[0104] Example 8

[0105] This embodiment provides a method for preparing a micro-nano composite structure ultra-black thin film. The only difference between the preparation method of the micro-nano composite structure ultra-black thin film and that of Embodiment 1 is that the etching line scan spacing is changed to 10 μm, and all other aspects are the same as those of Embodiment 1.

[0106] Example 9

[0107] This embodiment provides a method for preparing a micro-nano composite structure ultra-black thin film. The only difference between the preparation method of the micro-nano composite structure ultra-black thin film and that of Embodiment 1 is that the etching line scan spacing is changed to 30 μm, and all other aspects are the same as those of Embodiment 1.

[0108] Example 10

[0109] This embodiment provides a method for preparing a micro-nano composite structure ultra-black thin film. The only difference between the preparation method of the micro-nano composite structure ultra-black thin film and that of Embodiment 1 is that the etching line scan spacing is changed to 40 μm, and all other aspects are the same as those of Embodiment 1.

[0110] Example 11

[0111] This embodiment provides a method for preparing a micro-nano composite structure ultra-black thin film. The only difference between the preparation method of the micro-nano composite structure ultra-black thin film and that of Embodiment 1 is that the etching line scan spacing is changed to 50 μm, and all other aspects are the same as those of Embodiment 1.

[0112] Example 12

[0113] This embodiment provides a method for preparing a micro-nano composite structure ultra-black thin film. The only difference between the preparation method of the micro-nano composite structure ultra-black thin film and that of Embodiment 1 is that the etching line scan spacing is changed to 100 μm, and all other aspects are the same as those of Embodiment 1.

[0114] Comparative Example 1

[0115] This comparative example provides a method for preparing a micro-nano composite structure ultra-black thin film. The only difference between this method and Example 1 is that the low-refractive resin is not spin-coated; all other aspects are the same as in Example 1.

[0116] Comparative Example 2

[0117] This comparative example provides a method for preparing a micro-nano composite structure ultra-black thin film. The only difference between this method and Example 1 is that the polyimide black film is not etched and the low-refractive resin is not spin-coated after pretreatment. All other aspects are the same as in Example 1.

[0118] Performance testing

[0119] The performance of the micro-nano composite structure ultra-black thin films provided in the examples and comparative examples was tested. The cone size was analyzed by scanning electron microscopy (SEM), and the reflectance in the ultraviolet-visible-near-infrared bands was measured by spectrophotometer to calculate the average value. The results are shown in Table 1.

[0120]

[0121] In the table, "-" indicates no data.

[0122] As can be seen from Table 1, the micro-nano composite structure ultra-black thin film provided by the present invention has the characteristics of wide-band high absorption, low reflection (0.23%), and thinness. It can be widely used in stray light suppression of space optical systems, extinction of spacecraft surfaces, light shielding structures of space cameras and telescopes, light absorption structures of detector inner walls, light absorption structures inside spectrometers, lightweight light shielding components, deployable flexible optical structures, and thermally controlled absorption surfaces.

[0123] A comparative analysis of Examples 1 and 3-7 shows that, with a fixed linear scanning spacing of 20 μm, the cone height increases with the number of etching passes (i.e., cumulative laser energy). Simultaneously, the cone height exhibits a significant negative correlation with the average reflectivity. This phenomenon stems from its inherent optical mechanism: the increased cone height elongates the light propagation path within it, intensifying the multiple scattering effect and thus achieving more efficient capture and absorption of incident light. However, too many etching passes lead to insufficient etching depth, making effective extinction difficult; too few etching passes result in prolonged processing time and minimal improvement in light absorption performance.

[0124] A comprehensive comparison of Examples 1 and 8-12 shows that when the line spacing gradually increases from 20 μm to 50 μm, the bottom dimension exhibits a 1:1 linear response characteristic, while the top dimension also shows a positive correlation. As the line spacing increases, the area of ​​the top plateau increases, leading to enhanced specular reflection and ultimately an increase in overall reflectivity. However, excessively large line spacing results in a blunter cone structure and a greater number of plateau areas, increasing specular reflection and reducing light absorption performance. Insufficient line spacing leads to an increase in the number of line scans, prolonging processing time, with limited further improvement in light absorption performance; alternatively, laser beam energy overlap may occur, damaging the cone structure.

[0125] Comparative Examples 1-2 and Comparative Example 1 Figure 4 It can be seen that coating with low-refractive-index resin significantly reduces surface reflection of the thin film, and the lower the refractive index, the more obvious the anti-reflection effect. The ultra-black thin film without resin coating has the highest reflectivity, indicating that the anti-reflection layer plays a key role in suppressing specular reflection and enhancing broadband absorption. The principle is that refractive index matching effectively reduces interfacial light loss, thereby further improving the overall absorption efficiency. Furthermore, the micro / nano composite structure constructed on the surface plays a crucial role in improving the light absorption performance of the material. Comparing with Comparative Examples 1-2, it can be seen that this micro / nano structure can effectively extend the propagation path of incident light within the material, significantly reducing reflection loss through multiple reflections and scattering. This further confirms the effectiveness and advantages of the laser etching process proposed in this paper in achieving efficient light capture.

[0126] The present invention has been illustrated with the above embodiments to illustrate its detailed structural features. However, the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the components used in the present invention, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A micro / nano composite structure ultra-black thin film, characterized in that, The micro-nano composite structure ultrablack thin film includes: Flexible light-absorbing substrate layer; A micro-nano composite structure layer is disposed on at least one surface of the flexible light-absorbing substrate layer. The micro-nano composite structure layer includes a micron-scale protrusion structure array, and the surface of the micron-scale protrusion structure array has a nano-scale structure. A low-refractive-index antireflective protective layer is applied to the micro-nano composite structure layer and covers the micron-scale protrusion array and the nanoscale structure on its surface.

2. The micro / nano composite structure ultrablack thin film according to claim 1, characterized in that, The flexible light-absorbing substrate layer includes a polymer film containing light-absorbing components; Preferably, the polymer film comprises any one or a composite film of at least two of polyimide film, polyetheretherketone film, polyetherimide film or polyphenylene sulfide film, and preferably a polyimide film; Preferably, the light-absorbing component includes any one or a combination of at least two of carbon black, graphite, graphene, carbon nanotubes, or carbonized polymers; Preferably, the mass content of the light-absorbing component in the polymer film containing the light-absorbing component is 1%-60%; Preferably, the average thickness of the flexible light-absorbing substrate layer is 15-60 μm.

3. The micro / nano composite structure ultrablack thin film according to claim 1 or 2, characterized in that, The protrusion structures in the micron-scale protrusion structure array include any one or a combination of at least two of the following: conical, cylindrical, hemispherical, or pyramidal shapes. Preferably, the average height of the protrusion structure is 7-29 μm; Preferably, the bottom feature size of the protrusion structure is 20-50 μm.

4. The micro-nano composite structure ultra-black thin film according to any one of claims 1 to 3, characterized in that, The nanoscale structure includes a nanoscale villous structure and / or a nanoscale porous structure. Preferably, the average thickness of the nanoscale structure is 0.5-1.5 μm; Preferably, the nanoscale structure is distributed at any one or at least two of the gaps in the sidewalls, top, or bottom of the micron-scale protrusion structure.

5. The micro / nano composite structure ultrablack thin film according to any one of claims 1 to 4, characterized in that, The refractive index of the low-refractive-index antireflective protective layer is lower than that of the flexible light-absorbing substrate layer; Preferably, the average thickness of the low-refractive-index antireflective protective layer is 10 nm-2 μm; Preferably, the low refractive index antireflective protective layer comprises any one or a combination of at least two of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, magnesium fluoride, indium tin oxide, polydimethylsiloxane, acrylate, or fluorosilicone acrylate.

6. A method for preparing a micro / nano composite structure ultrablack thin film according to any one of claims 1 to 5, characterized in that, The preparation method includes: A micro-nano composite structure layer is formed on at least one side surface of the flexible light-absorbing substrate layer. The micro-nano composite structure layer includes a micron-scale protrusion structure array, and the surface of the micron-scale protrusion structure array has a nano-scale structure. A low-refractive-index anti-reflection protective layer is formed on the surface of the micro-nano composite structure layer, and the low-refractive-index anti-reflection protective layer covers the micron-scale protrusion structure array and the nano-scale structure on its surface to obtain the ultra-black film of the micro-nano composite structure.

7. The preparation method according to claim 6, characterized in that, The micro-nano composite structure layer is formed by an etching process; Preferably, the etching process includes laser etching; Preferably, the laser etching includes ultraviolet nanosecond laser etching; Preferably, the scanning method of the laser etching includes any one or a combination of at least two of the following: unidirectional parallel scanning, bidirectional orthogonal scanning, multidirectional cross scanning, or arrayed point scanning; Preferably, the laser etching is repeated 10-35 times, more preferably 35 times; Preferably, the laser etching line spacing is 20-100 μm, more preferably 20-50 μm, and even more preferably 20 μm.

8. The preparation method according to claim 6 or 7, characterized in that, The low-refractive-index anti-reflection protective layer is formed by spin coating, spraying, dip coating, blade coating, drop coating, chemical vapor deposition, physical vapor deposition, atomic layer deposition, sol-gel coating or a combination thereof. Preferably, the raw materials for forming the low refractive index antireflective protective layer include any one or a combination of at least two of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, magnesium fluoride, indium tin oxide, polydimethylsiloxane, acrylate, or fluorosilicone acrylate.

9. The preparation method according to any one of claims 6 to 8, characterized in that, The refractive index of the low-refractive-index antireflective protective layer is less than 1.

5.

10. An application of the micro-nano composite structure ultrablack thin film according to any one of claims 1 to 5, characterized in that, The micro-nano composite structure ultra-black thin film is used for light absorption, extinction, stray light suppression, low-reflection interface construction, thermal control absorption, photoelectric detection, display devices, flexible electronic devices, sensor devices, or space optical systems.

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