Copper film structure and transparent antenna

Abstract

The application discloses a copper film structure and a transparent antenna. The copper film structure comprises a copper foil substrate layer, a first blackening layer and a second blackening layer. The copper foil substrate layer comprises a first surface and a second surface arranged oppositely. The first blackening layer is formed on the first surface and is arranged to reduce the gloss of the first surface, so that the gloss of the first surface is reduced to less than a preset gloss value. The second blackening layer is formed on the second surface and is arranged to reduce the gloss of the second surface, so that the gloss of the second surface is reduced to less than the preset gloss value. The technical scheme can effectively improve the problem that the existing transparent antenna is difficult to balance between high conductivity and low visual visibility.

Description

Technical Field

[0001] This application relates to the field of antenna technology, and more specifically, to a copper film structure and a transparent antenna. Background Technology

[0002] In related technologies, as wireless communication technology evolves towards 5G / 6G, transparent antennas have become a research hotspot due to their ability to integrate with carriers such as architectural glass and automotive windows. Existing transparent antenna materials mainly include transparent conductive films (such as ITO and graphene) and metal meshes. However, these technologies suffer from the following problems: First, there is a significant contradiction between conductivity and transmittance. Materials such as ITO have high transmittance but high sheet resistance, resulting in low antenna radiation efficiency and difficulty meeting the low-loss requirements of high-frequency bands. Second, the visual stealth effect is poor. Although traditional copper metal meshes have good conductivity, their high metallic luster produces significant reflection under illumination, creating a strong visual contrast with the transparent background and ruining the visual effect of transparency or stealth. Third, the structure is complex and costly. To reduce visual visibility, complex multi-layer lamination or multi-step photolithography processes are often required, increasing production costs and reducing yield. Summary of the Invention

[0003] The purpose of this application is to provide a copper film structure and a transparent antenna, which aims to improve the problem that existing transparent antennas cannot achieve both high conductivity and low visual visibility.

[0004] To achieve this objective, embodiments of this application provide a copper film structure, which includes a copper foil substrate layer, a first blackening layer, and a second blackening layer, wherein... The copper foil substrate layer includes a first surface and a second surface disposed opposite to each other; The first blackening layer is formed on the first surface and is configured to reduce the gloss of the first surface, such that the gloss of the first surface is reduced to less than a preset gloss value. The second blackening layer is formed on the second surface and is configured to reduce the gloss of the second surface, such that the gloss of the second surface is reduced to less than a preset gloss value.

[0005] Optionally, in some embodiments of this application, the copper foil substrate layer is an ultrathin copper foil formed by electroplating or rolling processes, and the thickness of the ultrathin copper foil is 1 μm to 10 μm; and / or, The copper foil substrate layer is a dense conductive layer formed by a single process, so that the conductivity of the copper foil substrate layer is not less than 95% of the conductivity of pure copper.

[0006] Optionally, in some embodiments of this application, the first blackening layer is a metal oxide layer or a nickel-zinc alloy layer formed on the first surface by a surface treatment process; and / or, The second blackening layer is a metal oxide layer or a nickel-zinc alloy layer formed on the second surface through a surface treatment process.

[0007] Optionally, in some embodiments of this application, the thickness of the first blackening layer and the thickness of the second blackening layer are both 5 nm to 500 nm, and the first blackening layer and the second blackening layer are configured such that the increase in surface resistance of the copper foil substrate layer does not exceed 5%.

[0008] Optionally, in some embodiments of this application, the preset gloss value is 25 to 35.

[0009] Optionally, in some embodiments of this application, the copper film structure is etched to form a mesh structure, the linewidth of the mesh structure is 2μm to 15μm, and the mesh period of the mesh structure is 50μm to 300μm.

[0010] In addition, to achieve this purpose, the present application also provides a transparent antenna, which includes a transparent dielectric substrate and an antenna conductive layer. The antenna conductive layer is attached to the surface of the transparent dielectric substrate, and the antenna conductive layer is formed by photolithography etching process to form a preset antenna pattern from the copper film structure of any of the above.

[0011] Optionally, in some embodiments of this application, the preset antenna pattern is selected from one or more of a microstrip patch antenna, a dipole antenna, or a grid ground plane antenna.

[0012] Optionally, in some embodiments of this application, the material of the transparent dielectric substrate is selected from any one of glass, polyethylene terephthalate, polyimide, and polymethyl methacrylate.

[0013] Optionally, in some embodiments of this application, both sides of the antenna conductive layer are black or dark gray, and the reflectivity of the antenna conductive layer in the visible light band is less than 10%, so that the antenna conductive layer visually blends into the background of the transparent dielectric substrate.

[0014] The copper film structure and transparent antenna provided in this application, through the aforementioned structural configuration, utilize the formation of corresponding blackening layers (i.e., a first blackening layer and a second blackening layer) on both sides of the copper foil substrate layer, significantly reducing the gloss of the copper foil substrate layer surface. This design allows the copper film structure to maintain the excellent conductivity of the copper foil itself while effectively absorbing ambient light and eliminating metallic reflection through the blackening layers, thus achieving a balance between high conductivity and low visual visibility. When this copper film structure is applied to a transparent antenna as the antenna conductive layer, it allows the antenna conductive layer to be visually concealed in the background, achieving excellent optical stealth characteristics while ensuring the high gain and radiation efficiency of the transparent antenna. Therefore, this technical solution effectively improves the problem of existing transparent antennas struggling to balance high conductivity and low visual visibility. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] The structures, proportions, sizes, etc., shown in the accompanying drawings are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed in the specification, and are not intended to limit the implementation conditions of this application. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size should still fall within the scope of the technical content disclosed in this application, provided that they do not affect the effects and purposes that this application can produce.

[0017] Figure 1 This is a schematic diagram of a copper film structure according to an embodiment of this application; Figure 2 This is another schematic diagram of the copper film structure according to an embodiment of this application; Figure 3 This is a schematic diagram of the transparent antenna structure according to an embodiment of this application; Figure 4 for Figure 3 The diagram shows a cross-sectional view of the transparent antenna.

[0018] Illustrations: 10. Copper film structure; 11. Copper foil substrate layer; 12. First blackening layer; 13. Second blackening layer; 20. Transparent antenna; 21. Transparent dielectric substrate; 22. Antenna conductive layer. Detailed Implementation

[0019] To make the inventive objectives, features, and advantages of this application more apparent and understandable, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0020] In the description of this application, it should be understood that the terms "upper," "lower," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. It should be noted that when a component is considered to be "connected" to another component, it can be directly connected to the other component or there may be a component centrally located at the same time.

[0021] The technical solution of this application will be further described below with reference to the accompanying drawings and specific embodiments.

[0022] Please see Figures 1 to 2 As shown, in one embodiment, this application provides a copper film structure 10, which specifically includes a copper foil substrate layer 11, a first blackening layer 12, and a second blackening layer 13. The copper foil substrate layer 11 includes a first surface and a second surface disposed opposite to each other. The first blackening layer 12 is formed on the first surface and is configured to reduce the gloss of the first surface to a value less than a preset gloss value. The second blackening layer 13 is formed on the second surface and is configured to reduce the gloss of the second surface to a value less than a preset gloss value.

[0023] It should be noted that the copper film structure 10 of this application embodiment is mainly used in the fabrication of transparent antennas 20, especially suitable for scenarios where transparent antennas 20 need to be integrated onto transparent carriers such as architectural glass, car windows, and electronic device displays, particularly as a conductive functional layer in transparent antennas 20. This copper film structure 10 can be directly bonded to the surface of various transparent dielectric substrates 21, and the required antenna pattern can be formed through subsequent patterning processes (such as etching). In specific applications, the copper foil substrate layer 11 undertakes the main functions of current transmission and signal radiation, and its excellent conductivity ensures the radiation efficiency of the antenna; while the first blackening layer 12 and the second blackening layer 13 are located on both sides of the copper foil substrate layer 11, used to eliminate the metallic luster and specular reflection of the copper foil itself. Regardless of which side of the copper film structure 10 faces the observer, the blackening layer can effectively absorb ambient light, eliminating the original golden hue and specular reflection of the copper foil substrate layer 11, so that the final antenna pattern can visually "hide" into the background, achieving a light stealth effect. Furthermore, the presence of the blackening layer does not affect the bonding strength between the copper film structure 10 and the transparent dielectric substrate 21, nor does it hinder the subsequent photoresist coating and patterning processes. Those skilled in the art should understand that the copper film structure 10 can be laminated or bonded to the transparent dielectric substrate 21 in a roll-to-roll or sheet-to-sheet manner. The specific processing method can be determined according to actual production conditions and is not limited here.

[0024] Furthermore, the glossiness mentioned above specifically refers to the quantitative characterization of a material surface's ability to reflect visible light, typically expressed using the lightness index (L value) in the internationally recognized CIELAB color space. The L value generally ranges from 0 to 100, where L=0 represents pure black (completely non-reflective), and L=100 represents pure white (completely diffuse reflection). In this application, glossiness (L value) is the core indicator for measuring the blackening effect of the copper film structure 10. The lower the L value, the darker the surface color and the lower the reflectivity, visually closer to black or dark gray, thus less noticeable against a transparent background. Those skilled in the art can use a standard colorimeter (such as a spectrophotometer) under D65 standard light source (daylight conditions with a color temperature of approximately 6500K) and a 10° observation angle to measure the surface of the copper film structure 10 and directly read the L value. The L-value of ordinary copper foil without blackening treatment is usually high (e.g., between 60 and 80), exhibiting a distinct metallic golden hue and mirror-like reflection effect. However, the copper film structure 10, after undergoing double-sided blackening treatment according to this application, has an L-value lowered to below a preset gloss value (e.g., 25-35), appearing as a dull black or dark gray, significantly reducing visual visibility. The preset gloss value (i.e., the L-value threshold) can be set according to the stealth requirements of specific application scenarios. For example, for high-requirement architectural glass or display applications, the L-value threshold (i.e., the preset gloss value) can be set relatively low (e.g., 25-30); for general automotive applications, the L-value threshold (i.e., the preset gloss value) can be set relatively high (e.g., 30-35). As long as the L-value of the double-sided blackened copper film structure 10 is lower than the preset gloss value, the expected optical stealth effect can be considered achieved.

[0025] In this way, the copper film structure 10 of this embodiment, through the above-described structural configuration, significantly reduces the gloss of the surface of the copper foil substrate layer 11 by forming corresponding blackening layers (i.e., the first blackening layer 12 and the second blackening layer 13) on both sides of the copper foil substrate layer 11. This design allows the copper film structure 10 to maintain the excellent conductivity of the copper foil body while effectively absorbing ambient light and eliminating metallic reflection using the blackening layers, thus achieving a balance between high conductivity and low visual visibility. When the copper film structure 10 is applied to the transparent antenna 20 as the antenna conductive layer 22, it allows the antenna conductive layer 22 to be visually hidden from the background, achieving excellent optical stealth characteristics while ensuring the high gain and radiation efficiency of the transparent antenna 20.

[0026] In some examples, such as Figure 1As shown, the copper foil substrate layer 11 is an ultra-thin copper foil formed by electroplating or rolling processes, with a thickness of 1μm to 10μm. This ensures that the copper foil substrate layer 11 has sufficient mechanical strength and conductive cross-sectional area to support antenna signal transmission, while also providing good flexibility for subsequent patterning and bonding with the transparent dielectric substrate 21. Furthermore, the thinner thickness helps reduce the visual abruptness of the metal lines, further enhancing the optical stealth effect.

[0027] It should be noted that the thickness of the copper foil substrate layer 11 in this example can be selected within the above range according to specific application scenarios and performance requirements. When the thickness approaches 1 μm, the copper film structure 10 has the best flexibility and the lowest material cost, making it suitable for flexible transparent antennas 20 or applications with high bending performance requirements. When the thickness approaches 10 μm, the copper film structure 10 has lower surface resistance (i.e., better conductivity) and better mechanical strength, making it suitable for high-frequency antennas that need to carry high power or have extremely high conductivity requirements. Regardless of the thickness selected within this range, the surface of the copper foil substrate layer 11 should be flat and free of defects such as pinholes and cracks to ensure the uniform formation of the subsequent blackening layer and the integrity of the antenna pattern after etching. In addition, copper foil formed by electroplating usually has higher tensile strength and hardness, while copper foil formed by rolling has better ductility and lower internal stress. Those skilled in the art can choose the appropriate process type according to actual needs.

[0028] In some examples, such as Figure 1 As shown, the copper foil substrate layer 11 is a dense conductive layer formed through a single process, ensuring that the conductivity of the copper foil substrate layer 11 is not less than 95% of that of pure copper. This ensures that the core conductivity of the copper film structure 10 is close to that of pure copper, with a sheet resistance of less than 0.1 Ω / □, far superior to traditional ITO or graphene films. This effectively reduces the conductor loss of the transparent antenna 20 and improves radiation efficiency, making it particularly suitable for loss-sensitive millimeter-wave bands.

[0029] It should be noted that the "dense conductive layer formed by a single process" in this example refers to the copper foil substrate layer 11 being directly formed by a single independent process such as electroplating or rolling, which is different from the composite stacking process of "seed layer + electroplating thickening". Copper foil formed by a single process has a more uniform internal grain structure and fewer lattice defects, thus its conductivity is closer to the theoretical value of pure copper. Composite processes, due to the bonding between different interfaces, often generate additional interface resistance or lattice mismatch, thereby reducing the overall conductivity. This example limits the conductivity to no less than 95% of the conductivity of pure copper, which is an optimal range derived from actual test data. Within this range, the antenna gain and radiation efficiency of the copper film structure 10 are significantly improved compared to existing transparent antenna 20 materials. Those skilled in the art can measure the sheet resistance of the copper foil substrate layer 11 using the four-probe method, then convert it to conductivity based on its thickness, and compare it with the standard conductivity of pure copper (approximately 5.8 × 10⁻⁶). 7 The conductivity (S / m) was compared to verify whether the above conductivity requirements were met.

[0030] In some examples, such as Figure 1 As shown, the first blackening layer 12 is a metal oxide layer or a nickel-zinc alloy layer formed on the first surface through a surface treatment process. In this way, the dark color and low reflectivity of the metal oxide (such as copper oxide, cobalt oxide) or nickel-zinc alloy can be used to effectively reduce the gloss of the copper foil substrate layer 11. At the same time, these materials have strong adhesion to the copper foil substrate layer 11 and have good environmental corrosion resistance.

[0031] It should be noted that the formation of the metal oxide layer or nickel-zinc alloy layer in this example should ensure that the film is dense, uniform, and firmly adhered to the copper foil substrate layer 11. The metal oxide layer can be a copper oxide (such as CuO) or other transition metal oxides. In the nickel-zinc alloy layer, the mass ratio of nickel to zinc is preferably between 6:4 and 8:2 to obtain the best dark color effect and corrosion resistance. The thickness of this blackening layer should be controlled within the nanometer range (e.g., 5 nm-500 nm) to avoid excessively increasing the surface resistance of the copper film structure 10. Those skilled in the art can confirm the elemental composition of the blackening layer using energy dispersive spectroscopy (EDS) or X-ray photoelectron spectroscopy (XPS), and test the film adhesion using the cross-cut adhesion test or tape peeling method.

[0032] In some examples, such as Figure 1 As shown, the second blackening layer 13 is a metal oxide layer or a nickel-zinc alloy layer formed on the second surface through a surface treatment process. In this way, double-sided blackening treatment of the copper foil substrate layer 11 is achieved, so that no matter which side of the copper film structure 10 faces the observer, it can present a low-reflection dark appearance, providing greater flexibility for the installation direction and viewing angle of the transparent antenna 20.

[0033] It should be noted that the second blackening layer 13 and the first blackening layer 12 in this example can be made of the same material or different materials. For example, the side facing the observer (e.g., the second blackening layer 13) can be made of a material with deeper blackness and better light absorption, while the side attached to the substrate (e.g., the transparent dielectric substrate 21) (e.g., the first blackening layer 12) can focus more on the adhesion to the substrate or the maintenance of conductivity while ensuring the blackening effect. Regardless of whether the same or different materials are used, the thickness uniformity and adhesion of the blackening layers on both sides should meet the requirements of subsequent processing and use.

[0034] In some examples, the surface treatment processes mentioned above can be selected from one or more of chemical oxidation, electrochemical oxidation, physical vapor deposition, or electroless plating. This provides a variety of feasible industrial preparation routes, facilitating flexible selection based on different production conditions, cost requirements, and quality indicators.

[0035] It should be noted that the different surface treatment processes in this example have their own characteristics and applicable scenarios. Chemical oxidation is simple to operate, convenient, and suitable for batch processing; a black oxide layer is formed on the surface by immersing the copper foil in an alkaline solution containing an oxidant. Electrochemical oxidation controls the oxidation reaction with an applied current, making it easier to control the film thickness and uniformity, but requires specialized power supply equipment and electrode systems. Physical vapor deposition (such as magnetron sputtering) produces high-purity films with precise thickness control and minimal thermal impact on the copper foil substrate layer 11, but requires significant equipment investment and has relatively low production efficiency. Chemical plating can deposit metal layers such as nickel-zinc alloys on the copper surface, making it suitable for treating complex shapes or porous surfaces. Those skilled in the art can select the appropriate process based on actual production scale, cost budget, and performance requirements. Regardless of the process used, the final blackened layer should meet the requirements of a gloss level lower than the preset gloss value, good adhesion, and minimal impact on conductivity.

[0036] In some examples, such as Figure 1 As shown, the aforementioned first blackening layer 12 and / or second blackening layer 13 can also be replaced with a composite conductive coating containing nano-sized carbon black particles or graphene particles. In this way, by utilizing the black light-absorbing properties and excellent conductivity of carbon black or graphene itself, the blackening effect can be achieved while further reducing or maintaining the surface resistance of the copper foil substrate layer 11, which is beneficial for maintaining the high-frequency performance of the transparent antenna 20.

[0037] It should be noted that the composite conductive coating in this example is typically formed on the surface of the copper foil substrate layer 11 by coating or electrophoretic deposition. The particle size of the carbon black or graphene particles is preferably 10nm-100nm to ensure a uniform matte surface and avoid uneven coating or localized reflections caused by particle agglomeration. Appropriate amounts of dispersants and binders can also be added to the composite conductive coating to ensure that the carbon black or graphene particles are uniformly distributed and firmly adhered to the surface of the copper foil substrate layer 11. When using this alternative, care should be taken to control the thickness of the composite conductive coating to avoid a significant increase in surface resistance or a decrease in flexibility due to an excessively thick coating.

[0038] In some examples, such as Figure 1 As shown, the aforementioned first blackening layer 12 and / or second blackening layer 13 can also be replaced by a roughening layer with a light-trapping microstructure formed by chemical etching, and a dark passivation layer deposited on the roughening layer. Thus, by first etching a micron or nanometer-scale uneven structure (i.e., a roughening layer) onto the surface of the copper foil substrate layer 11, incident light is effectively absorbed through multiple reflections and scattering (i.e., light-trapping effect). Then, a dark passivation layer is deposited on the roughening layer to further reduce reflectivity and improve corrosion resistance. The synergy of these two processes achieves an excellent blackening effect.

[0039] It should be noted that the etching solution in this example can be a micro-etching system (such as a sodium persulfate-sulfuric acid system, ferric chloride-hydrochloric acid system, etc.). By controlling the etching time, temperature, and etching solution concentration, pyramidal, honeycomb, or irregular light-trapping microstructures can be formed on the surface of the copper foil substrate layer 11. The roughened surface should be thoroughly cleaned to remove residual etching solution and reaction products. The dark passivation layer can be made of materials such as black nickel, black chromium, or black cobalt, and formed on the surface of the roughened layer by electrodeposition or chemical deposition. This passivation layer can not only further reduce reflectivity but also effectively protect the roughened structure, preventing it from being worn or oxidized during subsequent processing or use. When using this alternative, care should be taken not to over-roughen the surface, so as not to affect the mechanical properties of the copper foil substrate layer 11 or increase the edge burrs of the etched antenna pattern.

[0040] In some examples, such as Figure 1 As shown, the thickness of the first blackening layer 12 and the thickness of the second blackening layer 13 are both between 5 nm and 500 nm, and the first blackening layer 12 and the second blackening layer 13 are configured such that the increase in surface resistance of the copper foil substrate layer 11 does not exceed 5%. In this way, while ensuring excellent blackening effect (L value is lower than the preset gloss value), the negative impact of blackening treatment on conductivity is minimized, so that the copper film structure 10 can take into account both low optical reflectivity and high conductivity, which is especially suitable for high-frequency transparent antenna 20 applications that are sensitive to conductor loss.

[0041] It should be noted that the thickness of the blackening layers (i.e., the first blackening layer 12 and the second blackening layer 13) in this example is closely related to the surface treatment process and material type used. When the thickness approaches 5 nm, the blackening layer is extremely thin, and its impact on the surface resistance of the copper foil substrate layer 11 is almost negligible. However, its blackening effect may not be fully realized, requiring the use of highly absorbent materials (such as nano-sized carbon black or graphene) to ensure sufficiently low gloss. When the thickness approaches 500 nm, the blackening layer can provide a deeper color and lower reflectivity. However, if the thickness continues to increase, the surface resistance of the copper foil substrate layer 11 may increase significantly due to the increased resistance of the blackening layer material itself or the increased internal stress of the film. Limiting the thickness to the range of 5 nm to 500 nm, and optimizing the material composition of the blackening layer within this range (such as using a nickel-zinc alloy with relatively good conductivity or a composite conductive coating containing graphene), the increase in surface resistance of the copper foil substrate layer 11 due to double-sided blackening treatment is controlled to within 5%. This is the preferred range verified in practice. Those skilled in the art can use a four-probe resistance meter to measure the surface resistance of the same copper foil sample before and after the blackening treatment, and calculate the percentage increase in resistance to verify whether the above requirements are met. In addition, due to the skin effect in high-frequency signal transmission, the signal current is mainly concentrated within the skin depth of the conductor surface. For millimeter-wave bands (such as 28GHz and 39GHz), the skin depth is only at the submicron level. At this time, the additional influence of the blackening layer (5nm-500nm) on signal transmission is minimal, and the antenna radiation efficiency is mainly determined by the highly conductive copper foil body (i.e., copper foil substrate layer 11).

[0042] In some examples, the aforementioned preset gloss value can specifically be between 25 and 35. This makes the surface of the copper film structure 10 appear as a dull black or dark gray, which is closer to the human eye's visual perception of a transparent background (such as glass, PET film, etc.). When the copper film structure 10 is processed into an antenna pattern with fine linewidth and appropriate grid period, the human eye will have difficulty distinguishing the existence of the antenna pattern at normal viewing distance, thereby achieving an excellent "visual invisibility" effect.

[0043] It should be noted that gloss (lightness index L value) is the core quantitative indicator for measuring the blackening effect of the copper film structure 10. The lower the L value, the darker the surface color and the lower the reflectivity. In this example, the preset gloss value is preferably in the range of 25 to 35, which is based on a large number of experimental tests and human visual perception evaluation. Specifically, when the L value is higher than 35, the surface of the copper film structure 10 still has a relatively obvious metallic gray hue, which is easily detected by the naked eye on a transparent background, resulting in poor stealth effect. When the L value is lower than 25, although the stealth effect is better, further reducing the L value often requires increasing the thickness of the blackening layer or adopting more complex processing technology. This may cause the surface resistance of the blackening layer to the copper foil substrate layer 11 to increase by more than 5%, thereby affecting the high-frequency performance of the transparent antenna 20. Therefore, setting the preset gloss value to 25 to 35 is the preferred range for balancing optical stealth effect and conductivity performance. As a more specific preferred value, when the preset gloss value is set to 30, the copper film structure 10 can achieve satisfactory optical stealth effects in most application scenarios (such as architectural glass, automotive windows, and electronic device displays). Simultaneously, the impact of the blackening treatment on surface resistance is controllable, ensuring sufficient radiation efficiency of the transparent antenna 20. Those skilled in the art should understand that this preset gloss value can be appropriately adjusted according to the different requirements for stealth effect and conductivity in specific application scenarios. For example, for high-end display applications with extremely high stealth requirements, a target value between 25 and 30 can be selected, while for millimeter-wave antenna applications with more stringent conductivity requirements, a target value between 30 and 35 can be selected. As long as the L value of the copper film structure 10 after double-sided blackening treatment is lower than the selected preset threshold, the expected design requirements can be considered met. Furthermore, when measuring the L value, a standard colorimeter (such as a spectrophotometer) should be used. Multiple measurements should be taken on the copper film surface under D65 standard light source and 10° observation angle conditions, and the average value should be taken to ensure the accuracy and representativeness of the data.

[0044] In some examples, such as Figure 2 As shown, the copper film structure 10 can be formed into a grid structure through an etching process. The linewidth of the grid structure is 2μm to 15μm, and the grid period is 50μm to 300μm. Thus, when this copper film structure 10 is processed into the conductive layer of the transparent antenna 20, the grid structure allows most of the light to pass through, ensuring the overall transparency of the antenna. At the same time, the finer linewidth further reduces the visual visibility of the metal lines. Combined with the double-sided blackening treatment, the conductive layer becomes almost invisible on the transparent substrate, achieving a technical effect that combines high light transmittance with low visual obtrusiveness.

[0045] It should be noted that the linewidth and grid period of the mesh structure in this example are two interrelated key parameters, which together determine the theoretical aperture ratio of the antenna (i.e., the proportion of the light-transmitting area to the total area). The aperture ratio can be estimated using the formula (1 - linewidth / period)². The finer the linewidth and the larger the period, the higher the aperture ratio and the better the light transmission. However, excessively fine linewidths increase the difficulty and cost of the etching process, while excessively large grid periods may affect the current continuity on the antenna surface, thus adversely affecting radiation performance. In this example, the linewidth is limited to 2μm to 15μm and the grid period is limited to 50μm to 300μm, which is an optimal range derived after comprehensively considering light transmission, process feasibility, and antenna electrical performance. Specifically, when the linewidth approaches 2μm, high-precision photolithography equipment and optimized etching processes are required, which is suitable for high-end applications with extremely high requirements for light transmission and stealth effects. When the linewidth approaches 15μm, the process tolerance is higher, which is suitable for applications that are more cost-sensitive or require a larger conductive cross-sectional area. When the grid period approaches 50 μm, the grid is relatively dense, which is beneficial for forming a more uniform current distribution and is suitable for antenna designs in higher frequency bands. When the grid period approaches 300 μm, the aperture ratio is higher and the light transmittance is better, which is suitable for mid-to-low frequency antennas where transparency is a priority. The grid shape can be any of square, rhombus, or hexagonal (honeycomb). Different grid shapes have slightly different aperture ratios under the same linewidth and feature size, but all can achieve the technical effects described in this example. Those skilled in the art can select a suitable combination of linewidth and grid period within the above range according to the specific antenna operating frequency band, light transmittance requirements, and fabrication conditions. After selection, the grid structure is fabricated using a standard photolithography etching process. Specifically, the photolithography etching method involves first coating a photoresist on the surface of the copper film structure 10, then exposing and developing it to form the required grid pattern, then removing the copper areas not protected by the photoresist using a chemical etching solution, and finally removing the residual photoresist to obtain the conductive layer of the transparent antenna 20 with a grid structure.

[0046] In one embodiment, such as Figure 3 and Figure 4 As shown, this application embodiment also provides a transparent antenna 20, which includes a transparent dielectric substrate 21 and an antenna conductive layer 22. The antenna conductive layer 22 is attached to the surface of the transparent dielectric substrate 21, and the antenna conductive layer 22 is formed by photolithography etching process to form a preset antenna pattern from the copper film structure 10 in the above embodiment.

[0047] It should be noted that the transparent antenna 20 in this application embodiment is mainly used in various scenarios that require simultaneous visual transparency and wireless communication functionality. Specifically, the transparent antenna 20 can be integrated into building glass curtain walls or windows to achieve indoor 5G / 6G signal coverage or IoT communication for smart buildings. In this case, the transparent antenna 20 is attached to the glass surface in a nearly invisible state, without affecting the building's aesthetic appearance. The transparent antenna 20 can also be integrated into the windshield, side windows, or sunroof of a car to achieve vehicle-to-everything (V2X) communication, satellite navigation, or in-vehicle entertainment system signal transmission. In this case, the transparent antenna 20 does not obstruct the driver's and passengers' view, ensuring driving safety and aesthetics. The transparent antenna 20 can also be integrated below the display screen of electronic devices such as smartphones, tablets, and smartwatches to achieve wireless communication or wireless charging functions. In this case, the transparent antenna 20 is hidden within the display area, does not occupy the device's bezel space, and is conducive to achieving a higher screen-to-body ratio.

[0048] In this transparent antenna 20, the copper film structure 10, after being formed into a preset antenna pattern through photolithography etching, is attached to the surface of the transparent dielectric substrate 21 as the antenna conductive layer 22 using optical adhesive or pressure-sensitive adhesive. The copper foil substrate layer 11 undertakes the core functions of current conduction and electromagnetic wave radiation, and its high conductivity ensures that the transparent antenna 20 has low conductor loss and high radiation efficiency. The second blackening layer 13 (the side facing the observer) in the double-sided blackening layer effectively absorbs ambient light, eliminating the metallic reflection of the copper foil substrate layer 11, making the preset antenna pattern visually imperceptible. The first blackening layer 12 (the side attached to the transparent dielectric substrate 21) is also dark, avoiding reflection when viewed from the other side (such as indoors or inside a vehicle). This transparent antenna 20 can be connected to the RF front-end circuit via a coaxial cable or flexible printed circuit board, and its specific feeding method depends on the design of the preset antenna pattern and the actual application requirements. Those skilled in the art will understand that the transparent dielectric substrate 21 itself can be an independent carrier (such as a single piece of glass or plastic sheet) or part of the final product (such as architectural glass itself or cover glass of electronic devices), and this application does not limit this.

[0049] In this way, the transparent antenna 20 of this application embodiment, through the above-described structural configuration, utilizes the antenna conductive layer 22 made of the double-sided blackened copper film structure 10 in the above embodiment. While ensuring the excellent conductivity of the copper foil substrate layer 11, the light absorption effect of the double-sided blackened layer significantly reduces the visual visibility of the metal lines. Thus, the transparent antenna 20 simultaneously achieves high radiation efficiency and high optical transparency, effectively overcoming the technical difficulty of balancing high conductivity and low visual visibility in existing transparent antenna 20 materials. This provides an ideal solution for seamlessly integrating the transparent antenna 20 onto various transparent carriers.

[0050] In some examples, such as Figure 3 and Figure 4 As shown, the antenna conductive layer 22 is formed by photolithography etching of a copper film structure 10 to create a preset antenna pattern. The preset antenna pattern is selected from one or more of a microstrip patch antenna, a dipole antenna, or a grid ground plane antenna. In this way, the appropriate antenna pattern type can be flexibly selected according to different application scenarios, frequency band requirements, and radiation characteristics, enabling this transparent antenna 20 to adapt to diverse wireless communication systems.

[0051] It should be noted that the different types of antenna patterns in this example have their own characteristics and applicable scenarios. Among them, the microstrip patch antenna, composed of a radiating patch and a ground plane, has the advantages of low profile, light weight, and easy conformal design, making it suitable for applications requiring directional radiation, such as base station antennas on building exteriors or vehicle-mounted communication antennas. Its radiating patch can be etched using the copper film structure 10 of this application, and the ground plane can also use a grid-like copper film structure 10 to maintain overall light transmittance. The dipole antenna has omnidirectional radiation characteristics and a simple structure, making it suitable for scenarios requiring signal reception and transmission coverage in multiple directions, such as indoor distribution systems or IoT terminal devices. The grid-ground plane antenna refers to a microstrip antenna with a grid-like ground plane structure. Both its ground plane and radiating patch are transparent, maximizing antenna transparency, making it suitable for applications with extremely high light transmittance requirements, such as antennas below electronic device displays. Those skilled in the art can select one or more of the most suitable combinations from the above antenna pattern types based on the specific operating frequency band (e.g., Sub-6GHz or millimeter-wave band), the size of the installation space, the required radiation pattern, and the light transmittance requirements. When using a combination of multiple antenna patterns (e.g., integrating multiple dipole antennas of different frequency bands on the same transparent substrate), sufficient isolation should be maintained between the antenna patterns to avoid mutual interference.

[0052] In some examples, such as Figure 3 and Figure 4 As shown, the material of the transparent dielectric substrate 21 is selected from any one of glass, polyethylene terephthalate, polyimide, and polymethyl methacrylate. Thus, a suitable substrate material can be flexibly selected according to the specific application requirements for rigidity, flexibility, temperature resistance, and cost, thereby broadening the applicability of this transparent antenna 20.

[0053] It should be noted that the transparent dielectric substrates 21 made of different materials in this example have different characteristics and applicable scenarios. Glass, with its high rigidity, high light transmittance, good weather resistance, and scratch resistance, is suitable for applications requiring long-term environmental exposure, such as architectural glass integrated antennas or automotive windshield antennas. Polyethylene terephthalate (PET) has good flexibility and transparency, and is relatively inexpensive, making it suitable for manufacturing flexible transparent antennas 20, such as antennas that can be attached to curved car windows or bent glass surfaces. Polyimide (PI) has excellent high-temperature resistance (withstanding temperatures above 300°C), making it suitable for manufacturing flexible circuit boards requiring high-temperature processes (such as reflow soldering), but its light transmittance is relatively low, and it is usually light yellow. Polymethyl methacrylate (PMMA), commonly known as acrylic, has high light transmittance (up to 92%) and good processing performance, but its surface hardness is relatively low, making it suitable for indoor applications or applications where scratch resistance requirements are not high. Furthermore, the thickness of the transparent dielectric substrate 21 can be selected according to actual mechanical strength requirements, typically between 0.05mm and 5mm. For example, the thickness of a flexible thin film substrate can be 0.05mm-0.2mm, and the thickness of a rigid glass substrate can be 0.5mm-5mm. Those skilled in the art can select the most suitable substrate material based on the specific application's requirements for flexibility, temperature resistance, light transmittance, and cost.

[0054] In some examples, such as Figure 3 and Figure 4 As shown, both sides of the antenna conductive layer 22 are black or dark gray, and the reflectivity of the antenna conductive layer 22 in the visible light band is less than 10%, making the antenna conductive layer 22 visually blend into the background of the transparent dielectric substrate 21. In this way, an excellent visual fusion effect is achieved, and the antenna pattern is almost invisible on the transparent dielectric substrate 21, thereby maintaining the appearance integrity of the carrier to the maximum extent without affecting the communication function.

[0055] It should be noted that in this example, "reflectivity less than 10%" means that the total reflectivity (including specular and diffuse reflection) of the surface of the antenna conductive layer 22 in the visible light band (wavelength range of approximately 380nm to 780nm) is less than 10%. This value can be measured using a UV-Vis-NIR spectrophotometer with an integrating sphere accessory. The level of this reflectivity directly determines the degree of visual perception of the antenna pattern by the human eye: the lower the reflectivity, the less ambient light is reflected from the antenna surface, and the more difficult it is for the human eye to distinguish it from a transparent background. Ordinary copper foil without blackening treatment typically has a reflectivity of over 60% in the visible light band, exhibiting a distinct metallic luster; however, this application, through double-sided blackening treatment, can reduce this reflectivity to below 10%, making the surface of the antenna conductive layer 22 appear as a dull black or dark gray. At the same time, the microstructure (such as micro-roughness) of the blackened layer surface can scatter the remaining reflected light in the form of diffuse reflection, further reducing directional specular reflection. During specific measurements, care should be taken to treat the back of the sample with an anti-reflective coating (e.g., attaching a black light-absorbing film) to avoid interference from back reflections on the measurement results. When the antenna conductive layer 22 is etched into a fine-linewidth (e.g., 2μm-15μm) grid structure with an appropriate grid period (e.g., 50μm-300μm), the human eye can hardly distinguish the lines at normal viewing distances (e.g., 30cm-50cm). The black or dark gray lines overlap with the background objects seen through the transparent dielectric substrate 21, making the antenna conductive layer 22 visually "integrate" into the background, thus achieving an optical stealth effect. It should be noted that the technical effect of a reflectivity of less than 10% is achieved through the selection of materials for the double-sided blackening layer (e.g., metal oxides, nickel-zinc alloys, composite coatings containing carbon black or graphene, etc.) and structural design (e.g., light-trapping microstructures). The specific implementation method has been described in detail in the embodiment of the copper film structure 10 and will not be repeated here.

[0056] In summary, the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit it. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A copper film structure, characterized by, The copper film structure includes a copper foil substrate layer, a first blackening layer, and a second blackening layer, wherein, The copper foil substrate layer includes a first surface and a second surface disposed opposite to each other; The first blackening layer is formed on the first surface and is configured to reduce the gloss of the first surface, such that the gloss of the first surface is reduced to less than a preset gloss value. The second blackening layer is formed on the second surface and is configured to reduce the gloss of the second surface, such that the gloss of the second surface is reduced to less than a preset gloss value.

2. The copper film structure of claim 1, wherein, The copper foil substrate layer is an ultra-thin copper foil formed by electroplating or rolling processes, and the thickness of the ultra-thin copper foil is 1 μm to 10 μm; and / or, The copper foil substrate layer is a dense conductive layer formed by a single process, so that the conductivity of the copper foil substrate layer is not less than 95% of the conductivity of pure copper.

3. The copper film structure of claim 1, wherein, The first blackening layer is a metal oxide layer or a nickel-zinc alloy layer formed on the first surface through a surface treatment process; and / or, The second blackening layer is a metal oxide layer or a nickel-zinc alloy layer formed on the second surface through a surface treatment process.

4. The copper film structure of claim 1, wherein, The thickness of the first blackening layer and the thickness of the second blackening layer are both 5 nm to 500 nm, and the first blackening layer and the second blackening layer are configured such that the increase in surface resistance of the copper foil substrate layer does not exceed 5%.

5. The copper film structure of claim 1, wherein, The preset gloss value is 25 to 35.

6. The copper film structure according to any one of claims 1 to 5, characterized in that The copper film structure is etched to form a mesh structure with a linewidth of 2μm to 15μm and a mesh period of 50μm to 300μm.

7. A transparent antenna, characterized by The transparent antenna includes a transparent dielectric substrate and an antenna conductive layer. The antenna conductive layer is attached to the surface of the transparent dielectric substrate, and the antenna conductive layer is formed by photolithography etching of a copper film structure as described in any one of claims 1 to 6 to create a preset antenna pattern.

8. The transparent antenna of claim 7, wherein, The preset antenna pattern is selected from one or more of microstrip patch antennas, dipole antennas, or grid ground plane antennas.

9. The transparent antenna of claim 7, wherein, The material of the transparent dielectric substrate is selected from any one of glass, polyethylene terephthalate, polyimide, and polymethyl methacrylate.

10. The transparent antenna of claim 7, wherein, Both sides of the antenna conductive layer are black or dark gray, and the reflectivity of the antenna conductive layer in the visible light band is less than 10%, so that the antenna conductive layer visually blends into the background of the transparent dielectric substrate.

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