Electromagnetic shielding and infrared anti-reflection integrated window and manufacturing method thereof

Abstract

The invention relates to the technical field of infrared window processing and application, and provides an electromagnetic shielding and infrared anti-reflection integrated window and a manufacturing method thereof. The window comprises an infrared window substrate, and is characterized in that an embedded periodic square metal mesh is manufactured on a first surface of the infrared window substrate, and a periodic hole-shaped or conical infrared anti-reflection microstructure is manufactured on a second surface of the infrared window substrate; the manufacturing method of the window comprises the steps of spin coating of protective glue, processing of the mesh groove, vacuum coating, removal of the protective glue, processing of the infrared anti-reflection microstructure, cleaning treatment and the like. The problem that the electromagnetic shielding performance and the infrared transmission performance of a traditional infrared window are difficult to balance is effectively solved, the electromagnetic shielding performance and the infrared transmission performance are synchronously improved, meanwhile, high stability is achieved, and the requirement for the high-performance infrared window in the aerospace complex application environment is met.

Description

Technical Field

[0001] The present invention relates to the field of infrared window processing and application technology, and in particular to an electromagnetic shielding and infrared anti-reflection integrated window and a preparation method thereof. Background Art

[0002] The infrared window is a core functional component in the composite guidance system, which is crucial for the high-quality transmission of optoelectronic signals to ensure accurate guidance performance. In the modern battlefield environment, with the widespread application of electromagnetic interference and stealth technology, the infrared window in the composite guidance system faces more stringent performance requirements. Specifically, the infrared window needs to have the following characteristics: first, it must provide high transmittance to ensure high imaging quality and accurate detection of long-distance tiny targets; second, it needs to have efficient electromagnetic shielding capabilities to resist interference from external electromagnetic fields; finally, it should also have high strength, good thermal shock resistance, and physical and chemical stability in high temperature environments.

[0003] In the prior art, for example, the method reported by Zhang et al. of the Shanghai Institute of Optics and Precision Mechanics of the Chinese Academy of Sciences in the document “Double-layer metal mesh etched by femtosecond laser for high-performance electromagnetic interference shielding window”, by preparing a single / double-layer square lattice metal grid on a quartz glass substrate, although electromagnetic shielding is achieved to a certain extent, its transmittance is significantly reduced. Similarly, the random Cu-Ag metal grid prepared by the crack template method mentioned by Voronin et al. of the Russian Academy of Sciences in the document “Cu-Ag and Ni-Ag meshes based on cracked template as efficient transparent electromagnetic shielding coating with excellent mechanical performance”, although the shielding effectiveness is improved to a certain extent, the optical transmittance is low and the reliability is poor.

[0004] In the patent application (CN 117187755 A), although a method of coating a layer of infrared anti-reflection film on a metal grid is proposed to improve transmittance and electromagnetic shielding performance, the anti-reflection film used has problems such as thermal expansion failure, poor environmental adaptability and insufficient long-term stability, which limits its application in complex environments such as aerospace, military reconnaissance, and remote sensing detection.

[0005] In summary, the challenge facing current technology is how to ensure that the infrared window has both high infrared transmittance and high electromagnetic shielding performance, and to improve its environmental adaptability and long-term operation stability as much as possible. Therefore, developing an infrared window that can meet the optical performance requirements while maintaining good electromagnetic shielding effect and high stability has become a key issue that needs to be solved in the current technical field. Summary of the invention

[0006] In view of the above problems, the present invention proposes an integrated electromagnetic shielding and infrared anti-reflection window and a preparation method thereof, which can not only ensure the electromagnetic shielding performance and high transmittance performance in the infrared band, but also the embedded metal grid and the infrared anti-reflection microstructure on the surface have high temperature resistance, impact resistance and good mechanical properties.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] An electromagnetic shielding and infrared anti-reflection integrated window includes an infrared window substrate, characterized in that: an embedded periodic metal grid is manufactured on the first surface of the infrared window substrate, and a periodic infrared anti-reflection microstructure is manufactured on the second surface of the infrared window substrate; the metal grid is a square metal grid, including three key parameters of period p1, width w1, and thickness t; the infrared anti-reflection microstructure is a hole-type or cone-type structure, including three key parameters of period p2, width w2, and height h.

[0009] Furthermore, the material of the metal grid includes copper, silver, gold, nickel, and chromium.

[0010] Furthermore, the period p1 of the metal grid is 100-200 μm, the width w1 is 1-5 μm, and the thickness t is 1-5 μm.

[0011] Furthermore, the period p2 of the infrared anti-reflection microstructure is ≤λ0 / n0, the filling ratio f of the infrared window substrate within a unit period is approximately 0.51-0.53, and the structural aspect ratio is approximately 1:1; wherein λ0 is the minimum wavelength value of the anti-reflection infrared band, and n0 is the refractive index of the infrared window substrate.

[0012] The present invention also provides a method for preparing an electromagnetic shielding and infrared anti-reflection integrated window, comprising the following steps:

[0013] Step 1: Spin-coat a layer of protective glue on the first surface of the infrared window substrate, and bake and cure it to form a protective film;

[0014] Step 2: using a femtosecond laser Bessel beam to simultaneously ablate the protective glue layer and the window material on the first surface of the infrared window substrate to obtain periodic grid grooves;

[0015] Step 3: depositing a metal film layer in the formed grid groove by a vacuum coating process until the grid groove is just filled;

[0016] Step 4: removing the protective glue on the first surface of the infrared window substrate to obtain an embedded metal grid array;

[0017] Step 5: Protect the first surface of the infrared window substrate, and further directly write a periodic infrared anti-reflection microstructure on the second surface of the infrared window substrate using a femtosecond laser Bessel beam;

[0018] Step six: clean the entire infrared window through ultrasonic cleaning technology, and finally prepare an electromagnetic shielding and infrared anti-reflection integrated window.

[0019] The beneficial effects of the present invention are:

[0020] 1. The electromagnetic shielding and infrared anti-reflection integrated window prepared by the method of the present invention can meet the needs of complex application environments such as aerospace, military reconnaissance, and remote sensing detection: the embedded metal grid has excellent electromagnetic shielding performance and wear and scratch resistance; the infrared anti-reflection microstructure on the window surface achieves efficient improvement of the infrared transmittance of the window, and at the same time perfectly solves the problems of thermal expansion failure and insufficient stability of traditional anti-reflection film technology.

[0021] 2. In the preparation method of the electromagnetic shielding and infrared anti-reflection integrated window provided by the present invention, the femtosecond laser Bessel beam technology is used to process the mesh grooves and infrared anti-reflection microstructures, which can realize the manufacture of microstructures with high aspect ratio. In this process, the narrower the width of the metal mesh, the better the light transmittance, the higher the height, the better the electromagnetic shielding performance, and the higher the aspect ratio of the infrared anti-reflection microstructure, the better the anti-reflection performance, thereby further optimizing the electromagnetic shielding and infrared transmittance performance of the window. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the three-dimensional structure of the electromagnetic shielding and infrared anti-reflection integrated window according to an embodiment of the present invention.

[0023] Figure 2 4 is a top view of a metal grid according to an embodiment of the present invention.

[0024] Figure 3 1 is a top view of the infrared antireflection microstructure according to an embodiment of the present invention.

[0025] Figure 4 It is a flow chart of the preparation of the electromagnetic shielding and infrared anti-reflection integrated window according to an embodiment of the present invention.

[0026] Figure 5 It is the simulated electromagnetic shielding efficiency of the 2-18 GHz band of the embodiment of the present invention.

[0027] Figure 6 It is the simulated transmittance performance of the long-wave infrared (8-12 μm) of the embodiment of the present invention.

[0028] Explanation of the accompanying drawings: 1-infrared window substrate, 2-metal grid, 3-infrared anti-reflection microstructure. DETAILED DESCRIPTION

[0029] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings; it should be understood that the preferred embodiments are only for illustrating the present invention rather than for limiting the protection scope of the present invention.

[0030] Figure 1 It is a schematic diagram of the three-dimensional structure of the electromagnetic shielding and infrared anti-reflection integrated window of the embodiment of the present invention. As can be seen from the figure, the electromagnetic shielding and infrared anti-reflection integrated window of the present invention comprises an infrared window substrate 1, an embedded periodic metal grid 2 is manufactured on the first surface of the infrared window substrate 1, and a periodic infrared anti-reflection microstructure 3 is manufactured on the second surface of the infrared window substrate 1.

[0031] Figure 2 It is a top view of the metal grid 2. As can be seen from the figure, the shape of the metal grid is a square grid, which includes three key parameters: period p1, width w1, and thickness t. In addition, the materials of the metal grid include copper, silver, gold, nickel, and chromium. According to the requirements of the application scenario for electromagnetic shielding and infrared transmittance performance, by changing the key parameters and material properties of the metal grid, the coordinated regulation of electromagnetic shielding and infrared transmittance can be achieved.

[0032] Figure 3 It is a top view of the infrared anti-reflection microstructure 3. The infrared anti-reflection microstructure 3 can be a hole-type (or cone-type) structure, including three key parameters: period p2, width w2, and height h. In order to achieve better infrared anti-reflection performance: its structural period must satisfy: p2≤λ0 / n0; at the same time, the structural width w2 and height h need to be adjusted so that the filling ratio f of the infrared window substrate within a unit period is approximately 0.51-0.53, and the structural depth-to-width ratio is approximately 1:1; where λ0 is the minimum wavelength value of the anti-reflection infrared band, and n0 is the refractive index of the infrared window substrate. According to the refractive index n0 of the infrared window substrate 1 material and the minimum wavelength value λ0 of the anti-reflection infrared band, changing the key parameters of the infrared anti-reflection microstructure 3 can achieve a significant increase in the transmittance of the target anti-reflection infrared band.

[0033] As a possible implementation, Figure 4 A preparation method of an integrated electromagnetic shielding and infrared anti-reflection window is demonstrated, which can be described in detail as the following steps:

[0034] Step 1: Spin-coat a layer of protective glue on the first surface of the infrared window substrate 1, and bake and cure it to form a protective film;

[0035] Step 2: using a femtosecond laser Bessel beam to simultaneously ablate the protective glue layer and the window material on the first surface of the infrared window substrate to obtain periodic grid grooves;

[0036] Step 3: depositing a metal film layer in the formed grid groove by a vacuum coating process until the grid groove is just filled;

[0037] Step 4: removing the protective glue on the first surface of the infrared window substrate to obtain the embedded metal grid array 2;

[0038] Step 5: Protect the first surface of the infrared window substrate, and further directly write a periodic infrared anti-reflection microstructure 3 on the second surface of the infrared window substrate using a femtosecond laser Bessel beam;

[0039] Step six: clean the entire infrared window through ultrasonic cleaning technology, and finally prepare an electromagnetic shielding and infrared anti-reflection integrated window.

[0040] Example:

[0041] A schematic diagram of a three-dimensional structure according to an embodiment of the present invention is shown in FIG. Figure 1 As shown. The metal grid 2 is a square grid, embedded and distributed on the first surface of the infrared window substrate 1; the infrared anti-reflection microstructure 3 is a hole-shaped structure, periodically distributed on the second surface of the infrared window substrate 1. The materials and key parameters of the metal grid 2 and the infrared anti-reflection microstructure 3 are selected and optimized as follows:

[0042] The infrared anti-reflection window substrate 1 is a zinc sulfide window material with a thickness of 3 mm and a refractive index of about 2.2; the material of the metal grid 2 is copper; the target shielding band of the metal grid 2 is 2-18 GHz; the period p1 of the metal grid 2 is 100 μm, the width w1 is 3 μm, and the thickness t is 3 μm; the target anti-reflection band of the infrared anti-reflection microstructure 3 is long-wave infrared (8-12 μm); the period p2 of the infrared anti-reflection microstructure 3 is 3.6 μm, the width w2 is 3.5 μm, and the height h is 3.5 μm.

[0043] Figure 5 The simulated electromagnetic shielding efficiency of the integrated electromagnetic shielding and infrared anti-reflection window in the 2-18GHz band is given, which is higher than 30dB on average and can reach 54dB at most. It has efficient electromagnetic shielding capability and can resist interference from external electromagnetic fields.

[0044] Figure 6The simulated transmittance performance of zinc sulfide window substrate, electromagnetic shielding window (including metal grid) and integrated electromagnetic shielding and infrared anti-reflection window in long-wave infrared (8-12μm) is given. As can be seen from the figure, the infrared transmittance of the electromagnetic shielding window is reduced by about 4% compared with the zinc sulfide window substrate (74%); on the contrary, the integrated electromagnetic shielding and infrared anti-reflection window increases the infrared transmittance by an average of about 10% on the basis of ensuring the electromagnetic shielding performance, and the highest can reach 84%.

[0045] The above is only a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the concept described herein through the above teachings or the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art do not deviate from the spirit and scope of the present invention, and should be within the scope of protection of the claims attached to the present invention.

Claims

1. An electromagnetic shielding and infrared anti-reflection integrated window, comprising an infrared window substrate, characterized in that: An embedded periodic metal grid is manufactured on the first surface of the infrared window substrate, and a periodic infrared anti-reflection microstructure is manufactured on the second surface of the infrared window substrate; the metal grid is a square metal grid, including three key parameters: period p1, width w1, and thickness t; the infrared anti-reflection microstructure is a hole-type or cone-type structure, including three key parameters: period p2, width w2, and height h.

2. The electromagnetic shielding and infrared anti-reflection integrated window according to claim 1, characterized in that: The material of the metal grid includes copper, silver, gold, nickel and chromium.

3. The electromagnetic shielding and infrared anti-reflection integrated window according to claim 1, characterized in that: The metal grid has a period p1 of 100-200 μm, a width w1 of 1-5 μm, and a thickness t of 1-5 μm.

4. The electromagnetic shielding and infrared anti-reflection integrated window according to claim 1, characterized in that: The period p2 of the infrared anti-reflection microstructure is ≤λ0 / n0, the filling ratio f of the infrared window substrate within a unit period is approximately 0.51-0.53, and the structural aspect ratio is approximately 1:1; wherein λ0 is the minimum wavelength value of the anti-reflection infrared band, and n0 is the refractive index of the infrared window substrate.

5. A method for manufacturing an electromagnetic shielding and infrared anti-reflection integrated window, characterized in that: The manufacturing method comprises the following steps: Step 1: Spin-coat a layer of protective glue on the first surface of the infrared window substrate, and bake and cure it to form a protective film; Step 2: using a femtosecond laser Bessel beam to simultaneously ablate the protective glue layer and the window material on the first surface of the infrared window substrate to obtain periodic grid grooves; Step 3: depositing a metal film layer in the formed grid groove by a vacuum coating process until the grid groove is just filled; Step 4: removing the protective glue on the first surface of the infrared window substrate to obtain an embedded metal grid array; Step 5: Protect the first surface of the infrared window substrate, and further directly write a periodic infrared anti-reflection microstructure on the second surface of the infrared window substrate using a femtosecond laser Bessel beam; Step six: clean the entire infrared window through ultrasonic cleaning technology, and finally prepare an electromagnetic shielding and infrared anti-reflection integrated window.

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