A composite film with ultra-low reflectivity and its preparation method and application

Abstract

The application relates to a composite film with ultralow reflectivity and a preparation method and application thereof, and the composite film with ultralow reflectivity comprises an absorption layer and a light matching layer which are alternately arranged on a copper substrate in sequence. The composite film is specially used for precise copper product parts, has high bonding force, and has a reflectivity less than 0.3% in a wavelength range of 400-800 nm.

Description

Technical Field

[0001] This invention relates to the field of metal blackening technology, specifically to a composite film with ultra-low reflectivity, its preparation method, and its application. Background Technology

[0002] Copper is abundant on Earth and possesses excellent electrical and thermal conductivity, making it widely used. In critical components of some instruments and meters, blackening the copper surface is often necessary to increase its light and heat absorption capabilities. Oxidation blackening of copper workpieces is a common method in the chemical conversion coating treatment of copper. Many blackening oxidants are available for copper, with persulfates and selenites being frequently used in existing technologies. However, persulfates have poor stability, resulting in a loose, easily peeling blackened film; selenites are toxic and can cause environmental pollution. In oxidation blackening applications, brass optical workpieces often require high blackness, matte finish, and low reflectivity; simultaneously, the presence of zinc in brass increases the difficulty of blackening.

[0003] Spraying light-absorbing materials onto copper surfaces, such as black paint, is currently quite practical. However, this black paint is composed of organic matter and begins to decompose and fade above 400°C. In vacuum conditions, it releases approximately 10% of its own weight in gas, some of which is highly corrosive and can easily corrode other components. Furthermore, the black paint layer is prone to cracking and peeling during repeated hot and cold cycles. Therefore, developing new blackening processes to improve adhesion and enhance the blackening effect is of great significance. Summary of the Invention

[0004] In view of this, the main objective of the present invention is to provide a composite film with ultra-low reflectivity, its preparation method and application. The composite film is specifically designed for precision copper workpieces, has high adhesion, and a reflectivity of less than 0.3% in the wavelength range of 400-800nm. After treatment by this method, the surface of the copper workpiece is uniform and delicate, and the blackening film has high adhesion.

[0005] The objective of this invention and the technical problem it solves are achieved by the following technical solution. This invention proposes a composite film with ultra-low reflectivity, comprising an absorption layer and a light matching layer alternately disposed on a copper substrate.

[0006] Preferably, in the aforementioned composite film with ultra-low reflectivity, the absorption layer is a copper sulfide layer; and the light matching layer is a magnesium fluoride layer or a silicon oxide layer.

[0007] Preferably, in the aforementioned composite film with ultra-low reflectivity, the alternation is performed at least three times.

[0008] Preferably, in the aforementioned composite film with ultra-low reflectivity, the alternation is performed three times; the film structure of the composite film is: a first copper sulfide layer | a first magnesium fluoride layer | a second copper sulfide layer | a second magnesium fluoride layer | a third copper sulfide layer | a third magnesium fluoride layer, with the thicknesses of each layer being 150-250 nm, 10-30 nm, 20-40 nm, 30-50 nm, 10-30 nm, and 50-150 nm, respectively.

[0009] Preferably, the aforementioned composite film with ultra-low reflectivity contains a plurality of copper nanowires with a size of 0.5-10 μm.

[0010] The objective of this invention and the technical problem it solves are achieved by the following technical solution. This invention proposes a method for preparing a composite film with ultra-low reflectivity, comprising the following steps: sequentially and alternately depositing an absorption layer and a light matching layer on a copper substrate.

[0011] Preferably, the aforementioned method for preparing a composite film with ultra-low reflectivity includes the following steps:

[0012] 1) Immerse the copper substrate in a mixed solution of NaOH and (NH4)2SO4, wash, and dry;

[0013] 2) Copper sulfide is deposited on the surface of a copper substrate to obtain an absorption layer; then magnesium fluoride or silicon oxide is deposited on the surface of the absorption layer to obtain a light matching layer; the composite film is obtained by repeating the process multiple times.

[0014] Preferably, the aforementioned method for preparing a composite film with ultra-low reflectivity includes the following steps:

[0015] 1) Immerse the cleaned and dried copper substrate in a mixed solution of NaOH and (NH4)2SO4 for 60s-180s. After immersion, remove the copper substrate, clean it, and blow it dry.

[0016] 2) Depositing copper sulfide on the surface of a copper substrate: bis(2,2,6,6-tetramethyl-3,5-heptanediol)copper is used as a solid copper source, the heating temperature of the solid copper source is 130℃, and hydrogen sulfide is used as a sulfur source. The reaction yields a copper sulfide layer at a temperature of 120–400℃. Then, depositing magnesium fluoride or silicon oxide on the surface of the copper sulfide layer: bis(2,2,6,6-tetramethyl-3,5-heptanedione)magnesium is used as a solid magnesium source, and hydrogen fluoride is used as a fluorine source. The heating temperature of the solid magnesium source is 100℃, and the reaction temperature is 120–400℃ to obtain a magnesium fluoride layer. Diisopropylaminosilane is used as a silicon source, and ozone is used as an oxygen source. The reaction temperature is 300–400℃ to obtain a silicon oxide layer. This process is repeated multiple times to obtain the composite film.

[0017] Preferably, in the aforementioned method for preparing a composite film with ultra-low reflectivity, in step 1), the concentration of NaOH in the mixed solution of NaOH and (NH4)2SO4 is 0.75 mol / L and the concentration of (NH4)2SO4 is 0.03 mol / L.

[0018] Preferably, in the aforementioned method for preparing a composite film with ultra-low reflectivity, in step 1), the cleaning includes sequentially ultrasonically cleaning with anhydrous ethanol and deionized water for 10-20 minutes each; the drying or blowing is performed by blowing with high-purity nitrogen for 30-60 seconds.

[0019] Preferably, in the aforementioned method for preparing a composite film with ultra-low reflectivity, in step 2), the number of cycles is at least three.

[0020] Preferably, in the aforementioned method for preparing the composite film with ultra-low reflectivity, in step 2), each cycle of the growth process includes a 0.5-2s copper bis(2,2,6,6-tetramethyl-3,5-heptanedioic acid) pulse, a 10-120s N2(g) purging, a 0.2-1s hydrogen sulfide pulse, and a 10-120s N2(g) purging; each cycle of the growth process includes a 0.5-2s magnesium bis(2,2,6,6,-tetramethyl-3,5-heptanedioic acid) pulse, a 10-120s N2(g) purging, a 0.2-1s hydrogen fluoride pulse, and a 10-120s N2(g) purging; and each cycle of the growth process includes a 0.2-1s diisopropylamino)silane pulse, a 10-120s N2(g) purging, a 0.5-2s ozone pulse, and a 10-120s N2(g) purging.

[0021] Preferably, in the aforementioned method for preparing a composite film with ultra-low reflectivity, in step 2), the alternating deposition method is atomic layer deposition.

[0022] The objective of this invention and the technical problem it solves are achieved by the following technical solution. This invention proposes a copper component, wherein the copper component, from the inside out, consists of a substrate, and alternating absorption layers and light matching layers.

[0023] Preferably, in the aforementioned copper component, the absorption layer is a copper sulfide layer; and the light matching layer is a magnesium fluoride layer.

[0024] Preferably, in the aforementioned copper component, the substrate is a brass component.

[0025] Preferably, the aforementioned copper components are arranged in alternation at least three times.

[0026] By employing the above technical solution, the composite film with ultra-low reflectivity, its preparation method, and its application provided by the present invention have at least the following advantages:

[0027] 1. This invention uses a solution method to prepare micro-nano structures such as copper nanowires on copper products. The method is simple and fast, and is especially suitable for samples with complex 3D structures such as copper mirror tubes and brass sheets. The micro-nano structures form a light-trapping surface through a large number of micro-pits and other microstructures. The length of the nanowires is 0.5-10μm, so that after light is incident, it is reflected and absorbed multiple times, and only a small amount of light is emitted, so that the reflectivity of the sample is reduced from 10% to less than 0.3%.

[0028] 2. This invention uses copper sulfide as the absorber layer. The expansion coefficients of the copper substrate and copper sulfide are similar, which improves the adhesion between the film and the substrate.

[0029] 3. The preparation method of the present invention combines atomic layer deposition technology with a simple chemical solution method. Compared with traditional preparation methods, it has the advantages of strong repeatability, high yield, high preparation efficiency, and suitability for large-scale preparation, and is especially suitable for application in the optical field.

[0030] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below. Attached Figure Description

[0031] Figure 1 This is a surface view of the untreated brass sheet in Comparative Example 1 of the present invention;

[0032] Figure 2 The images show the surface of the brass sheets after solution treatment in Examples 1-4 of this invention.

[0033] Figure 3 This is a surface view of the composite film with ultra-low reflectivity in Embodiment 1 of the present invention;

[0034] Figure 4 This is a schematic diagram of the structure of the composite film with ultra-low reflectivity in Embodiment 1 of the present invention;

[0035] Figure 5 This is a comparison of the reflectance spectra of the untreated sample in Comparative Example 1 and the solution-treated sample in Example 1 before and after coating.

[0036] Figure 6 This is a comparison of the reflectance spectra of the samples after solution treatment and coating in Examples 2-4 of the present invention. Detailed Implementation

[0037] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the following detailed description, in conjunction with preferred embodiments, details a composite film with ultra-low reflectivity proposed according to the present invention, its preparation method, and its specific implementation methods, structures, features, and effects. In the following description, different "embodiments" or "embodiments" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0038] Unless otherwise specified, all materials or reagents listed below are commercially available.

[0039] According to some embodiments of the present invention, a composite film with ultra-low reflectivity is provided, comprising an absorption layer and an optical matching layer alternately disposed on a copper substrate. The film structure is referenced to that of an antireflective film, and is composed of at least two alternating layers of high and low refractive indices: the high refractive index layer is selected from materials exhibiting absorption in the 400-800 nm wavelength range, i.e., an extinction coefficient k>0, as the absorption layer; the low refractive index layer is selected from materials exhibiting no light absorption in the 400-800 nm wavelength range as the optical matching layer. Considering the difference in the coefficient of thermal expansion between the copper substrate and the absorption film, the absorption layer is selected as a copper sulfide layer; to match the optical constant (refractive index) of copper sulfide, the optical matching layer is selected as a magnesium fluoride layer or a silicon oxide layer.

[0040] In the above technical solution, the alternation setting is performed at least three times. If it is less than three times, the reflectivity of the composite film will not reach the target value. Considering that too many alternations will complicate the process, it is optional that the alternation setting is performed three times.

[0041] In practice, the reflectivity of the sample varies depending on the film thickness. The reflectivity can be adjusted by changing the thickness. Therefore, the alternation is performed three times. The composite film structure can be configured as follows: first copper sulfide layer (150-250nm) | first magnesium fluoride layer (10-30nm) | second copper sulfide layer (20-40nm) | second magnesium fluoride layer (30-50nm) | third copper sulfide layer (10-30nm) | third magnesium fluoride layer (50-150nm). The composite film contains numerous irregular copper nanowires with a size of 0.5-10μm. Testing showed that the composite film has a reflectivity of 0.18%-0.29% between wavelengths of 400-800nm. If the size of the copper nanowire is less than 0.5 μm, the reflectivity will be high due to its small size; if the size of the copper nanowire is greater than 10 μm, the nanowire will be prone to breakage due to its large size, resulting in poor mechanical properties. Therefore, the size of the copper nanowire should be controlled between 0.5 and 10 μm.

[0042] Further preferred, such as Figure 4As shown, the composite membrane structure is as follows: first copper sulfide layer 1 (200nm) | first magnesium fluoride layer 2 (20nm) | second copper sulfide layer 3 (30nm) | second magnesium fluoride layer 4 (40nm) | third copper sulfide layer 5 (15nm) | third magnesium fluoride layer 6 (100nm). The morphology of the composite membrane is as follows. Figure 3 As shown, from Figure 3 As can be seen, the composite film contains a plurality of irregular copper nanowires with a size of 6 μm. Testing revealed that this optimized composite film exhibits the lowest reflectance (0.18%) in the wavelength range of 400-800 nm.

[0043] In addition, the copper substrate is selected as a brass component, such as a brass sheet with a size of 30mm x 30mm x 2mm; it can also be other copper components, such as a copper mirror barrel.

[0044] The aforementioned composite film with ultra-low reflectivity refers to a composite film with a reflectivity of less than 0.3% in the wavelength range of 400-800nm, for example, between 0.18% and 0.29%.

[0045] According to some embodiments of the present invention, a method for preparing a composite film with ultra-low reflectivity is also provided, comprising the following steps: sequentially and alternately depositing an absorption layer and a light matching layer on a copper substrate.

[0046] In some embodiments, optionally, the method includes the following steps:

[0047] 1) Immerse the cleaned and dried copper substrate in a mixed solution of NaOH and (NH4)2SO4 for 60-180 seconds. After immersion, remove the copper substrate, clean it, and dry it. Specifically, the concentration of NaOH in the mixed solution of NaOH and (NH4)2SO4 is 0.75 mol / L, and the concentration of (NH4)2SO4 is 0.03 mol / L. Immersing the copper substrate in the mixed solution of NaOH and (NH4)2SO4 is to reduce the reflectivity of the copper substrate. The cleaning includes ultrasonic cleaning with anhydrous ethanol and deionized water for 10-20 minutes each; the drying or blowing dry is done with high-purity nitrogen gas (purity 99.99%) for 30-60 seconds. The concentrations of NaOH and (NH4)2SO4 are fixed; only by adjusting the immersion time can the surface structure of the copper substrate be changed, thus indirectly affecting the reflectivity of the copper substrate.

[0048] 2) Deposition of copper sulfide on the surface of a copper substrate: The reaction temperature is set at 120–400 °C. Di(2,2,6,6-tetramethyl-3,5-heptanedioic acid)copper is used as the solid copper source, and the heating temperature of the solid copper source is 130 °C. Hydrogen sulfide is used as the sulfur source. The solid copper source reacts with the sulfur source to obtain a copper sulfide layer. Then, magnesium fluoride or silicon oxide is deposited on the surface of the copper sulfide layer: The reaction temperature is set at 120–400 °C. Bis(2,2,6,6-tetramethyl-3,5-heptanedioic acid)magnesium is used as the solid magnesium source, and hydrogen fluoride is used as the fluorine source. The heating temperature of the solid magnesium source is 100 °C. The solid magnesium source reacts with the fluorine source to obtain a magnesium fluoride layer. Alternatively, the reaction temperature is set at 300–400 °C. (Diisopropylamino)silane is used as the silicon source, and ozone is used as the oxygen source. The silicon source reacts with the oxygen source to obtain a silicon oxide layer. The number of deposition cycles is set to at least three. This invention allows for the control of precipitation rate and number of precipitation cycles to obtain copper sulfide and magnesium fluoride layers of target thickness.

[0049] In step 2) of the above preparation method, the growth process of each cycle includes a 0.5-2s copper bis(2,2,6,6-tetramethyl-3,5-heptanedioic acid) pulse, a 10-120s N2(g) purge, a 0.2-1s hydrogen sulfide pulse, and a 10-120s N2(g) purge; the growth process of each cycle includes a 0.5-2s magnesium bis(2,2,6,6-tetramethyl-3,5-heptanedioic acid) pulse, a 10-120s N2(g) purge, a 0.2-1s hydrogen fluoride pulse, and a 10-120s N2(g) purge; the growth process of each cycle includes a 0.2-1s diisopropylaminosilane pulse, a 10-120s N2(g) purge, a 0.5-2s ozone pulse, and a 10-120s N2(g) purge. Thus, by changing the pulse time, the thickness of the monolayer film can be changed.

[0050] In step 2) of the above preparation method, the alternating deposition method is selected as atomic layer deposition.

[0051] According to some embodiments of the present invention, a copper component is also provided, wherein the copper component comprises, from the inside out, a substrate, and alternating absorption layers and light matching layers; the absorption layer is a copper sulfide layer; the light matching layer is a magnesium fluoride layer or a silicon oxide layer; and the alternation is performed at least three times.

[0052] In specific implementation, the substrate is selected as a brass component, such as a brass sheet with a size of 30mm x 30mm x 2mm; it can also be other copper components, such as a copper mirror barrel.

[0053] The present invention will be further described below with reference to specific embodiments.

[0054] Example 1

[0055] like Figure 4 As shown, the film structure of this embodiment is: first copper sulfide layer 1 (200nm) | first magnesium fluoride layer 2 (20nm) | second copper sulfide layer 3 (30nm) | second magnesium fluoride layer 4 (40nm) | third copper sulfide layer 5 (15nm) | third magnesium fluoride layer 6 (100nm), and its morphology is as follows. Figure 3 As shown. From Figure 3 As can be seen, a number of irregular copper nanowires with a size of 6 μm are formed in the composite film.

[0056] This embodiment provides a method for preparing a composite film with ultra-low reflectivity, including the following steps:

[0057] (1) Prepare a mixed solution of NaOH and (NH4)2SO4, wherein the concentration of NaOH in the mixed solution is 0.75 mol / L and the concentration of (NH4)2SO4 is 0.03 mol / L;

[0058] (2) The cleaned and dried brass sheet (30mm x 30mm x 2mm, with a smooth surface and a morphology as shown) Figure 1 As shown in the figure, the brass sheet was used as a substrate and immersed in the above mixed solution for 100 seconds. After immersion, the brass sheet was removed, cleaned, and dried with high-purity nitrogen gas. The morphology of the dried brass sheet is shown in the figure. Figure 2 As shown. From Figure 2 As can be seen, a number of irregular copper nanowires with a size of 6 μm are formed in the composite film; the cleaning includes ultrasonic cleaning with anhydrous ethanol and deionized water for 15 min each, and the drying or blowing is carried out by blowing with high-purity nitrogen gas with a purity of 99.99% for 45 s.

[0059] (3) The dried brass sheet is placed in the reaction chamber of an atomic layer deposition (ALD) thin film system. A copper sulfide layer is prepared using ALD, with the reaction temperature set at 300°C. Di(2,2,6,6-tetramethyl-3,5-heptadecanoic acid) copper is selected as the solid copper source, and hydrogen sulfide is selected as the sulfur source. The heating temperature of the solid copper source is set at 130°C. Next, a magnesium fluoride layer is prepared, with the reaction temperature set at 300°C. Bis(2,2,6,6,-tetramethyl-3,5-heptadecanoic acid) magnesium is selected as the solid magnesium source, and hydrogen fluoride is selected as the fluorine source. The heating temperature of the solid magnesium source is set at 100°C. This process is repeated three times, resulting in a total of six layers, thus obtaining the composite film with ultra-low reflectivity, which is also the brass sheet product with the composite film.

[0060] In step 3) of the above preparation method, the growth process of each cycle includes a 1s bis(2,2,6,6-tetramethyl-3,5-heptanedioic acid)copper pulse, a 70s N2(g) purge, a 0.6s hydrogen sulfide pulse, and a 70s N2(g) purge; the growth process of each cycle includes a 1.2s bis(2,2,6,6,-tetramethyl-3,5-heptanedioic acid)magnesium pulse, a 70s N2(g) purge, a 0.6s hydrogen fluoride pulse, and a 70s N2(g) purge; the growth process of each cycle includes a 0.6s diisopropylaminosilane pulse, a 70s N2(g) purge, a 1.2s ozone pulse, and a 70s N2(g) purge.

[0061] The brass sheet product obtained above was tested using a spectrophotometer. The test results showed that the reflectance of the brass sheet product at a wavelength of 400-800 nm was 0.18%. Figure 5 .

[0062] Example 2

[0063] The film structure of this embodiment is as follows: first copper sulfide layer (200nm) | first silicon oxide layer (20nm) | second copper sulfide layer (30nm) | second silicon oxide layer (40nm) | third copper sulfide layer (15nm) | third silicon oxide layer (100nm); the morphology of the composite film in this embodiment is similar to that of the composite film in Example 1. A plurality of irregular copper nanowires with a size of 6μm are formed in the composite film.

[0064] This embodiment provides a method for preparing a composite film with ultra-low reflectivity, including the following steps:

[0065] (1) Prepare a mixed solution of NaOH and (NH4)2SO4, wherein the concentration of NaOH in the mixed solution is 0.75 mol / L and the concentration of (NH4)2SO4 is 0.03 mol / L;

[0066] (2) The cleaned and dried brass sheet (30mm x 30mm x 2mm, with a smooth surface and a morphology as shown) Figure 1 As shown in the figure, the brass sheet was used as a substrate and immersed in the above mixed solution for 100 seconds. After immersion, the brass sheet was removed, cleaned, and dried with high-purity nitrogen gas. The morphology of the dried brass sheet is shown in the figure. Figure 2 As shown. From Figure 2 As can be seen, a number of irregular copper nanowires with a size of 6 μm are formed in the composite film; the cleaning includes ultrasonic cleaning with anhydrous ethanol and deionized water for 15 min each, and the drying or blowing is carried out by blowing with high-purity nitrogen gas with a purity of 99.99% for 45 s.

[0067] (3) The dried brass sheet is placed in the reaction chamber of an atomic layer deposition (ALD) thin film system. A copper sulfide layer is prepared using ALD, with the reaction temperature set at 300°C. Di(2,2,6,6-tetramethyl-3,5-heptanoic acid) copper is selected as the solid copper source, and hydrogen sulfide is selected as the sulfur source. The heating temperature of the solid copper source is set at 130°C. Next, a silicon oxide layer is prepared, with the reaction temperature set at 300°C. Diisopropylaminosilane is selected as the silicon source, and ozone is selected as the oxygen source. The reaction yields silicon oxide. This process is repeated three times, resulting in a total of six layers, thus obtaining the composite film with ultra-low reflectivity, which is the brass sheet product with the composite film.

[0068] In step 3) of the above preparation method, the growth process of each cycle includes a 1s bis(2,2,6,6-tetramethyl-3,5-heptanoic acid)copper pulse, a 70s N2(g) purge, a 0.6s hydrogen sulfide pulse, and a 70s N2(g) purge; the growth process of each cycle includes a 0.6s diisopropylaminosilane pulse, a 70s N2(g) purge, a 1.2s ozone pulse, and a 70s N2(g) purge.

[0069] The brass sheet product obtained above was tested using a spectrophotometer. The test results showed that the reflectance of the brass sheet product at a wavelength of 400-800 nm was 0.29%. Figure 6 .

[0070] Example 3

[0071] The film structure of this embodiment is as follows: first copper sulfide layer 1 (250 nm) | first magnesium fluoride layer 2 (20 nm) | second copper sulfide layer 3 (40 nm) | second magnesium fluoride layer 4 (40 nm) | third copper sulfide layer 5 (30 nm) | third magnesium fluoride layer 6 (100 nm). The morphology of the composite film in this embodiment is similar to that of the composite film in Example 1. A plurality of irregular copper nanowires with a size of 6 μm are formed in the composite film.

[0072] This embodiment provides a method for preparing a composite film with ultra-low reflectivity, including the following steps:

[0073] (1) Prepare a mixed solution of NaOH and (NH4)2SO4, wherein the concentration of NaOH in the mixed solution is 0.75 mol / L and the concentration of (NH4)2SO4 is 0.03 mol / L;

[0074] (2) The cleaned and dried brass sheet (30mm x 30mm x 2mm, with a smooth surface and a morphology as shown) Figure 1 As shown in the figure, the brass sheet was used as a substrate and immersed in the above mixed solution for 100 seconds. After immersion, the brass sheet was removed, cleaned, and dried with high-purity nitrogen gas. The morphology of the dried brass sheet is shown in the figure. Figure 2 As shown. From Figure 2 As can be seen, a number of irregular copper nanowires with a size of 6 μm are formed in the composite film; the cleaning includes ultrasonic cleaning with anhydrous ethanol and deionized water for 15 min each, and the drying or blowing is carried out by blowing with high-purity nitrogen gas with a purity of 99.99% for 45 s.

[0075] (3) The dried brass sheet is placed in the reaction chamber of an atomic layer deposition (ALD) thin film system. A copper sulfide layer is prepared using ALD, with the reaction temperature set at 300°C. Di(2,2,6,6-tetramethyl-3,5-heptadecanoic acid) copper is selected as the solid copper source, and hydrogen sulfide is selected as the sulfur source. The heating temperature of the solid copper source is set at 130°C. Next, a magnesium fluoride layer is prepared, with the reaction temperature set at 300°C. Bis(2,2,6,6,-tetramethyl-3,5-heptadecanoic acid) magnesium is selected as the solid magnesium source, and hydrogen fluoride is selected as the fluorine source. The heating temperature of the solid magnesium source is set at 100°C. This process is repeated three times, resulting in a total of six layers, thus obtaining the composite film with ultra-low reflectivity, which is also the brass sheet product with the composite film.

[0076] In step 3) of the above preparation method, the growth process of each cycle includes a 2s bis(2,2,6,6-tetramethyl-3,5-heptanedioic acid)copper pulse, a 120s N2(g) purge, a 1s hydrogen sulfide pulse, and a 70s N2(g) purge; the growth process of each cycle includes a 1.2s bis(2,2,6,6,-tetramethyl-3,5-heptanedioic acid)magnesium pulse, a 70s N2(g) purge, a 0.6s hydrogen fluoride pulse, and a 70s N2(g) purge.

[0077] The brass sheet products obtained above were tested using a spectrophotometer. The test results showed that the reflectance of the brass sheet products in the wavelength range of 400-800 nm was 0.23%. Figure 6 .

[0078] Example 4

[0079] The film structure of this embodiment is as follows: first copper sulfide layer 1 (200 nm) | first magnesium fluoride layer 2 (30 nm) | second copper sulfide layer 3 (30 nm) | second magnesium fluoride layer 4 (50 nm) | third copper sulfide layer 5 (15 nm) | third magnesium fluoride layer 6 (150 nm). The morphology of the composite film in this embodiment is similar to that of the composite film in Example 1. A plurality of irregular copper nanowires with a size of 6 μm are formed in the composite film.

[0080] This embodiment provides a method for preparing a composite film with ultra-low reflectivity, including the following steps:

[0081] (1) Prepare a mixed solution of NaOH and (NH4)2SO4, wherein the concentration of NaOH in the mixed solution is 0.75 mol / L and the concentration of (NH4)2SO4 is 0.03 mol / L;

[0082] (2) The cleaned and dried brass sheet (30mm x 30mm x 2mm, with a smooth surface and a morphology as shown) Figure 1 As shown in the figure, the brass sheet was used as a substrate and immersed in the above mixed solution for 100 seconds. After immersion, the brass sheet was removed, cleaned, and dried with high-purity nitrogen gas (99.99% purity). The morphology of the dried brass sheet is shown in the figure. Figure 2 As shown. From Figure 2 As can be seen, a number of irregular copper nanowires with a size of 6 μm are formed in the composite film; the cleaning includes ultrasonic cleaning with anhydrous ethanol and deionized water for 15 min each, and the drying or blowing is carried out by blowing with high-purity nitrogen gas with a purity of 99.99% for 45 s.

[0083] (3) The dried brass sheet is placed in the reaction chamber of an atomic layer deposition (ALD) thin film system. A copper sulfide layer is prepared using ALD, with the reaction temperature set at 300°C. Di(2,2,6,6-tetramethyl-3,5-heptadecanoic acid) copper is selected as the solid copper source, and hydrogen sulfide is selected as the sulfur source. The heating temperature of the solid copper source is set at 130°C. Next, a magnesium fluoride layer is prepared, with the reaction temperature set at 300°C. Bis(2,2,6,6,-tetramethyl-3,5-heptadecanoic acid) magnesium is selected as the solid magnesium source, and hydrogen fluoride is selected as the fluorine source. The heating temperature of the solid magnesium source is set at 100°C. This process is repeated three times, resulting in a total of six layers, thus obtaining the composite film with ultra-low reflectivity, which is also the brass sheet product with the composite film.

[0084] In step 3) of the above preparation method, the growth process of each cycle includes a 1s bis(2,2,6,6-tetramethyl-3,5-heptanedioic acid)copper pulse, a 70s N2(g) purge, a 0.6s hydrogen sulfide pulse, and a 70s N2(g) purge; the growth process of each cycle includes a 2s bis(2,2,6,6,-tetramethyl-3,5-heptanedioic acid)magnesium pulse, a 120s N2(g) purge, a 1s hydrogen fluoride pulse, and a 120s N2(g) purge.

[0085] The brass sheet products obtained above were tested using a spectrophotometer. The test results showed that the reflectance of the brass sheet products at wavelengths of 400-800 nm was 0.21%. Figure 6 .

[0086] Comparative Example 1

[0087] The film structure of this comparative example is as follows: first copper sulfide layer (200 nm) | first magnesium fluoride layer (20 nm) | second copper sulfide layer (30 nm) | second magnesium fluoride layer (40 nm) | third copper sulfide layer (15 nm) | third magnesium fluoride layer (100 nm). The brass sheet, without being immersed in the above mixed solution of NaOH and (NH4)2SO4, has the following morphology. Figure 1 As shown.

[0088] This comparative example provides a method for preparing a composite membrane, including the following steps:

[0089] (1) A brass sheet (30mm x 30mm x 2mm) dried with 99.99% pure nitrogen gas for 45 seconds was placed in the reaction chamber of an atomic layer deposition (ALD) thin film system. A copper sulfide layer was prepared using ALD, with the reaction temperature set at 300℃. Di(2,2,6,6-tetramethyl-3,5-heptanediol) copper was selected as the solid copper source, hydrogen sulfide as the sulfur source, and the heating temperature of the solid copper source was set at 130℃. Next, a magnesium fluoride layer was prepared, with the reaction temperature set at 300℃. Bis(2,2,6,6,-tetramethyl-3,5-heptanedione) magnesium was selected as the solid magnesium source, hydrogen fluoride as the fluorine source, and the heating temperature of the solid magnesium source was set at 100℃. This process was repeated 3 times, resulting in a total of 6 layers, thus obtaining the composite film with ultra-low reflectivity, which is also the brass sheet product with the composite film.

[0090] In step 3) of the above preparation method, the growth process of each cycle includes a 1s bis(2,2,6,6-tetramethyl-3,5-heptanedioic acid)copper pulse, a 70s N2(g) purge, a 0.6s hydrogen sulfide pulse, and a 70s N2(g) purge; the growth process of each cycle includes a 1.2s bis(2,2,6,6,-tetramethyl-3,5-heptanedioic acid)magnesium pulse, a 70s N2(g) purge, a 0.6s hydrogen fluoride pulse, and a 70s N2(g) purge.

[0091] The brass sheet products obtained above were tested using a spectrophotometer. The test results showed that the reflectance of the brass sheet products at wavelengths of 400-800 nm was 1.8%. Figure 5 .

[0092] The reflectance data of Examples 1-4 and Comparative Example 1 are summarized in Table 1 below.

[0093] Table 1

[0094]

[0095] As shown in Table 1, the brass sheet samples with composite films described in Examples 1-4 of this invention have a reflectance of 0.18%-0.29% at a wavelength of 400-800 nm. In contrast, the brass sheet of Comparative Example 1, which was not soaked in the aforementioned mixed solution of NaOH and (NH4)2SO4, has a reflectance of 1.8% at a wavelength of 400-800 nm. This demonstrates that different thicknesses result in different reflectances. By adjusting the thickness of different layers, the reflectance of the brass sheet product can be adjusted.

[0096] A portion of the incident light passes through the third magnesium fluoride layer 6 and enters the third copper sulfide layer 5, where some is absorbed as it passes through the third copper sulfide layer 3. The unabsorbed portion continues downward, passing through the second magnesium fluoride layer 4 and entering the second copper sulfide layer 3, where it is further partially absorbed. The remaining unabsorbed light continues downward, passing through the first magnesium fluoride layer 2 and reaching the first copper sulfide layer 1 where it is absorbed. Overall, the light entering the composite film is continuously absorbed by the absorption layers between them; except for a small amount reflected out of the composite film, most of the light is absorbed.

[0097] Figure 5 This is a comparison of the reflectance spectra of the brass sheets before and after treatment with the solution and before and after coating according to the present invention. Figure 6 This is a comparison of the reflectance spectra of samples coated after solution treatment in Examples 2-4 of this invention. From... Figure 5 As can be seen, the reflectance of the brass sheet before coating was 15% without immersion in the solution, the reflectance of the brass sheet before coating was 5% with immersion in the solution, the reflectance of the brass sheet after coating (Comparative Example 1) was 1.8%, and the reflectance of the brass sheet after coating (Example 1) was 0.18%. Figure 5 As can be seen, the reflectance of the brass sheets after immersion in the solution in Examples 2, 3, and 4 is 0.29%, 0.23%, and 0.21%, respectively, all lower than that of Comparative Example 1. The brass sheet without immersion in the solution has a smooth surface. For objects with smooth surfaces, such as brass sheets without immersion in the solution, light will only undergo one reflection and absorption when incident on its surface. Even after depositing a light-absorbing film on the surface of the brass sheet, its absorption effect is still relatively limited. By treating the surface of the brass sheet with the immersion solution, a micro-irregular structure (copper nanowires) is formed on the surface of the brass sheet, resulting in a large number of irregular copper nanowires with a size of 6 μm in the final composite film. When light shines on this micro-irregular structure surface, multiple reflections and absorptions occur, further reducing the light "escaping" from the surface of the brass sheet, thereby improving the absorption effect and reducing the reflectance of the brass sheet.

[0098] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0099] The numerical range described in this invention includes all values ​​within this range, and also includes any range value composed of any two values ​​within this range. Different values ​​of the same indicator appearing in all embodiments of this invention can be arbitrarily combined to form a range value.

[0100] The technical features in the claims and / or specification of this invention can be combined, and the combination is not limited to the combinations obtained through reference in the claims. Technical solutions obtained by combining the technical features in the claims and / or specification are also within the scope of protection of this invention.

[0101] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A composite film with ultra-low reflectivity, characterized in that, The composite film comprises an absorption layer and a light matching layer alternately arranged on a brass substrate; the absorption layer is a copper sulfide layer; the light matching layer is a magnesium fluoride layer or a silicon oxide layer; the alternation is performed at least three times; the antireflective film structure is formed by alternating stacking of high-refractive-index absorption layers and low-refractive-index light matching layers; a plurality of copper nanowires with a length of 0.5-10 μm are formed in the composite film; the reflectivity of the composite film is ≤0.3% in the wavelength range of 400-800 nm.

2. The composite film with ultra-low reflectivity as described in claim 1, characterized in that, The alternation is performed three times; the composite membrane structure is as follows: first copper sulfide layer | first magnesium fluoride layer | second copper sulfide layer | second magnesium fluoride layer | third copper sulfide layer | third magnesium fluoride layer, with the thicknesses of each layer being 150-250nm, 10-30nm, 20-40nm, 30-50nm, 10-30nm, and 50-150nm respectively.

3. A method for preparing a composite film with ultra-low reflectivity as described in claim 1 or 2, characterized in that, Includes the following steps: 1) Immerse the brass substrate in a mixed solution of NaOH and (NH4)2SO4, wash and dry; the concentration of NaOH in the mixed solution of NaOH and (NH4)2SO4 is 0.75 mol / L and the concentration of (NH4)2SO4 is 0.03 mol / L. 2) Copper sulfide is deposited on the surface of a brass substrate to obtain an absorption layer; then magnesium fluoride or silicon oxide is deposited on the surface of the absorption layer to obtain a light matching layer; the composite film is obtained by at least three cycles.

4. The method for preparing a composite film with ultra-low reflectivity as described in claim 3, characterized in that, The method includes the following steps: 1) Immerse the cleaned and dried brass substrate in a mixed solution of NaOH and (NH4)2SO4 for 60s-180s. After immersion, remove the copper substrate, clean it, and blow it dry. The concentration of NaOH in the mixed solution of NaOH and (NH4)2SO4 is 0.75mol / L, and the concentration of (NH4)2SO4 is 0.03mol / L. 2) Depositing copper sulfide on the surface of a copper substrate: using bis(2,2,6,6-tetramethyl-3,5-heptanediol)copper as a solid copper source, heating the solid copper source at 130°C, using hydrogen sulfide as a sulfur source, and reacting at 120~400°C to obtain a copper sulfide layer; then depositing magnesium fluoride or silicon oxide on the surface of the copper sulfide layer: using bis(2,2,6,6,-tetramethyl-3,5-heptanedione)magnesium as a solid magnesium source, using hydrogen fluoride as a fluorine source, heating the solid magnesium source at 100°C, and reacting at 120~400°C to obtain a magnesium fluoride layer; or using diisopropylaminosilane as a silicon source, using ozone as an oxygen source, and reacting at 300~400°C to obtain a silicon oxide layer; cycling at least three times to obtain the composite film.

5. The method for preparing a composite film with ultra-low reflectivity as described in claim 3 or 4, characterized in that, In step 1), the cleaning includes ultrasonic cleaning with anhydrous ethanol and deionized water for 10-20 minutes each; drying or blowing is done by blowing with high-purity nitrogen for 30-60 seconds.

6. The method for preparing a composite film with ultra-low reflectivity as described in claim 3 or 4, characterized in that, In step 2), the growth process of each cycle includes a 0.5-2s copper bis(2,2,6,6-tetramethyl-3,5-heptanedioic acid) pulse, a 10-120s N2(g) purging, a 0.2-1s hydrogen sulfide pulse, and a 10-120s N2(g) purging; the growth process of each cycle includes a 0.5-2s magnesium bis(2,2,6,6-tetramethyl-3,5-heptanedioic acid) pulse, a 10-120s N2(g) purging, a 0.2-1s hydrogen fluoride pulse, and a 10-120s N2(g) purging; the growth process of each cycle includes a 0.2-1s diisopropylaminosilane pulse, a 10-120s N2(g) purging, a 0.5-2s ozone pulse, and a 10-120s N2(g) purging; the alternating deposition method is atomic layer deposition.

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