An ultra-low diffraction high-screen-effect metal mesh and a preparation method thereof

Abstract

This invention belongs to the field of metal mesh technology, specifically relating to an ultra-low diffraction, high-efficiency metal mesh and its fabrication method. The mesh includes a substrate, a first randomized mesh metal layer, a second randomized mesh metal layer, a first transparent dielectric layer, and a second transparent dielectric layer. The first randomized mesh metal layer is disposed on the substrate, the first transparent dielectric layer is disposed on the first randomized mesh metal layer, the second randomized mesh metal layer is disposed on the first transparent dielectric layer, and the second transparent dielectric layer is disposed on the second randomized mesh metal layer. This invention achieves ultra-low diffraction transmission characteristics and wide-band high-efficiency filtering performance, providing a reliable guarantee for high shielding performance and high visual quality of large-format curved glass optical windows.

Description

Technical Field

[0001] This invention belongs to the field of metal mesh technology, specifically relating to an ultra-low diffraction high-efficiency metal mesh and its preparation method. Background Technology

[0002] Numerous reports on diffraction resistance of metal mesh gratings have been published both domestically and internationally. The main techniques employed include random structures simulating cracks, random structures with regular patterns, and ordered random structures with regular patterns. These are primarily based on random generation algorithms, introducing random factors to ensure a uniform distribution of higher-order diffraction energy across the image plane. However, current random structures derived directly from mathematical analytical expressions are still constrained by factors such as grating period, unit size, and planar tiling method, resulting in significant degradation in shielding effectiveness or transmittance. Consequently, shielding effectiveness is generally below 30dB. No reported solutions simultaneously achieve a higher-order diffraction energy of 0.1%, a shielding effectiveness greater than 40dB, and 80% transmittance, making it difficult to effectively reconcile the contradiction between low diffraction, high transmittance, and high shielding effectiveness in high-resolution optical windows. Furthermore, the laser etching and laser direct writing fabrication processes commonly used for traditional periodic metal mesh gratings do not adequately consider the input and conversion processing of randomized metal mesh patterns, especially for curved structures, leading to difficulties in processing and low efficiency. Summary of the Invention

[0003] To address the technical problems of high processing difficulty and low efficiency of traditional periodic metal mesh gratings, this invention provides an ultra-low diffraction high-efficiency metal mesh grating and its preparation method.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0005] An ultra-low diffraction high-efficiency metal mesh grid includes a substrate, a first randomized mesh grid metal layer, a second randomized mesh grid metal layer, a first transparent dielectric layer, and a second transparent dielectric layer. The first randomized mesh grid metal layer is disposed on the substrate, the first transparent dielectric layer is disposed on the first randomized mesh grid metal layer, the second randomized mesh grid metal layer is disposed on the first transparent dielectric layer, and the second transparent dielectric layer is disposed on the second randomized mesh grid metal layer.

[0006] The first randomized grid metal layer and the second randomized grid metal layer are quasi-periodic array structures formed by planar tiling of randomized grid units. The randomized grid units are based on regular polygons as the basic pattern, and a combination structure of random side lengths and random circles is formed by randomizing the vertices. The quasi-periodic array structure of the randomized grid units is the same as the planar tiling method of the basic pattern.

[0007] The first randomized grid metal layer and the second randomized grid metal layer are stacked at an angle of 20°-70°, and the stacking interval thickness is 300μm-2mm.

[0008] The substrate is a high-strength transparent material, made of one of polymethyl methacrylate (PMMA), polycarbonate (PC), polyimide (PI), K9 glass or infrared glass, with a light transmittance greater than 91% and a strength greater than 4 MPa.

[0009] The metal materials of the first and second randomized grid metal layers are pure metal thin film materials, including copper, silver, or nickel-copper alloys, with a resistivity of less than 1.0 × 10⁻⁶. -8 Ω・m; The basic pattern of the randomized grid unit includes equilateral triangles, squares, regular hexagons, combinations of equilateral triangles and regular hexagons, or combinations of squares and regular hexagons. The line width of the regular polygonal grid of the basic pattern is 3μm-10μm, and the initial period is 100μm-200μm.

[0010] The vertex randomization process of the randomized grid unit is specifically as follows: a vertex randomization factor is introduced into the mathematical analytical expression of the basic pattern, so that the hybridization intensity of the random side length is 50%-150% of the initial side length of the regular polygon, and the hybridization intensity of the random circle diameter is 20%-40% of the initial side length of the regular polygon.

[0011] The first transparent dielectric layer is a resonant matching layer disposed between the first randomized grid metal layer and the second randomized grid metal layer. It is made of a photoresist material with a dielectric constant of less than 4.0, a transmittance of greater than 92%, and a haze of less than 0.5%, and is made of one of acrylic UV resin, polyurethane resin, or polyimide resin. The second transparent dielectric layer is a protective layer disposed on the surface of the second randomized grid metal layer. It is made of a colloidal material with a Shore A greater than 50 after curing, a transmittance of greater than 92%, and a haze of less than 0.5%, and is made of one of acrylic resin, polyurethane resin, polyimide resin, or silicone resin.

[0012] A method for fabricating an ultra-low diffraction high-efficiency metal mesh includes the following steps:

[0013] S1. Substrate pretreatment: Provide a substrate, activate its surface, coat it with primer photoresist and cure it under ultraviolet light to form a primer layer with a thickness of 1.5μm-3.5μm;

[0014] S2. Preparation of the first layer mesh:

[0015] A module pattern layout for generating the first randomized grid metal layer is formed by a rectangular layout of randomized grid units. The rectangular layout is then processed to the base surface size using rectangular line layout technology. A curvature factor is introduced to generate a conformal curved layout. The overlap width of the module boundary is 10μm-20μm. After format conversion, the data file size is reduced to less than 1GB.

[0016] The layout data is input into a laser direct writing device to prepare a randomized grid array on the surface of the primer layer. A metal layer is prepared on the array through a coating process. The primer is removed by ultrasonic cleaning and stripping solution to form the first randomized grid metal layer.

[0017] S3, Cascade Structure Construction:

[0018] A transparent dielectric material is coated onto the surface of the first randomized grid metal layer and cured to form the first transparent dielectric layer;

[0019] Repeat the primer coating, layout angle adjustment input, laser direct writing, coating and stripping process of S2 to prepare a second randomized grid metal layer with an angle adjustment of 20°-70° on the surface of the transparent dielectric layer;

[0020] S4. Surface protection treatment: A transparent dielectric material is coated on the surface of the randomized grid metal layer and cured to form a second transparent dielectric layer.

[0021] The basic pattern of the module pattern layout is an equilateral triangle, a square, a regular hexagon, a combination of an equilateral triangle and a regular hexagon, or a combination of a square and a regular hexagon. Randomized grid units with random side lengths and random circumferences are generated through a vertex randomization algorithm. The quasi-periodic array structure of the randomized grid units is the same as the planar tiling method of the basic pattern.

[0022] The coating process includes evaporation coating or sputtering coating, and the thickness of the prepared metal layer is 2μm-5μm; the thickness of the first transparent dielectric layer is 300μm-2mm, and the thickness of the second transparent dielectric layer is 5μm-10μm.

[0023] The format conversion includes converting the layout data into *.dwg format. The curvature factor is used to construct the laser direct writing scanning path based on the curvature data of the substrate surface in the X, Y, and Z directions, and to calculate the deformation of the grid array to generate a conformal layout.

[0024] The primer photoresist is a water-soluble photoresist that is immiscible with the transparent dielectric material. The coating process of the transparent dielectric material adopts spin coating or spray coating, and plasma surface treatment is performed before curing to improve the interlayer adhesion.

[0025] Compared with the prior art, the beneficial effects of this invention are:

[0026] This invention, based on transmission line waveguide theory, random generation algorithms, and numerical simulation optimization techniques, firstly establishes a multi-layer cascaded waveguide structure to generate electromagnetic coupling, offering advantages such as wide-band high shielding efficiency and low optical transmission loss. Secondly, random factors are introduced at the vertices of regular polygons. Through mathematical analytical expressions, the side lengths and vertices of the regular polygonal grating structure are randomly varied within a specified range, producing a combined homogenization effect. This achieves a statistical approximation of the electron flow area to a hexagonal grating planar tiling structure, reducing the impact of increased hole period length after randomization on shielding effectiveness, thereby significantly improving the electromagnetic shielding and randomization compatibility characteristics of the grating structure. Then, image processing techniques are used for modular processing to generate randomized grating unit pattern module files with smaller data volumes. Finally, rectangular line layout techniques are employed to form large-area seamless continuous splicing of randomized grating graphics, greatly reducing the amount of graphic data and meeting the input requirements for rapid laser direct-write patterning manufacturing. Ultimately, ultra-low diffraction transmission characteristics and wide-band high shielding efficiency are achieved, providing a reliable guarantee for high shielding performance and high visual quality of large-format curved glass optical windows. Attached Figure Description

[0027] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0028] The structures, proportions, sizes, etc. illustrated in this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed herein, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0029] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0030] Figure 2 This is a top view of the present invention;

[0031] Figure 3 This is a schematic diagram of a large-area layout of the metal mesh grid of the present invention.

[0032] Wherein: 1 is the substrate, 2 is the first randomized grid metal layer, 3 is the first transparent dielectric layer, 4 is the second randomized grid metal layer, and 5 is the second transparent dielectric layer. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. These descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the claims of the present invention. 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.

[0034] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0035] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0036] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0037] The ultra-low diffraction high-efficiency metal mesh grating provided in this embodiment, such as Figure 1-3 As shown, its structure includes a substrate 1, a first randomized grid metal layer 2, a first transparent dielectric layer 3, a second randomized grid metal layer 4, and a second transparent dielectric layer 5. The structure and parameters of each layer are as follows:

[0038] Substrate 1 is made of polymethyl methacrylate (PMMA), which has a light transmittance of 92% and a strength of 5 MPa, meeting the requirements of light transmittance greater than 91% and strength greater than 4 MPa. PMMA has good optical transparency and mechanical processing properties, providing a stable supporting substrate for the entire grid structure.

[0039] First randomized grid metal layer 2, material and electrical properties: The metal material is a pure copper thin film with a resistivity of 1.0 × 10⁻⁶. -8 Ω・m, corresponding to a resistivity less than 1.0×10 -8The Ω·m requirement ensures good conductivity and electromagnetic shielding. The grid structure uses a regular hexagon as the base pattern, with randomized vertex grid units formed through vertex randomization. The linewidth of the regular hexagonal grid in the base pattern is 5 μm, and the initial period is 150 μm. Vertex randomization specifically involves introducing a vertex randomization factor into the mathematical analytical expression of the regular hexagon, making the hybridization intensity of the random side length 80% of the initial side length (i.e., the random side length varies within the range of 75 μm to 225 μm), and the hybridization intensity of the random circumference diameter 30% of the initial side length (i.e., the random circumference diameter is 45 μm). The randomized grid units form a quasi-periodic array structure with regular hexagons in a planar tiling manner (each vertex is shared by three regular hexagons), uniformly covering the substrate surface.

[0040] The second randomized mesh metal layer 4 has the following material and structure: the metal material is also a pure copper thin film, with parameters consistent with the first layer. The stacking parameters are: the two metal mesh layers are set at a 45° stacking angle (within the range of 20°-70°), and the stacking interval thickness is 1mm (within the range of 300μm-2mm). Through angle misalignment and spacing control, diffraction effects are effectively suppressed and screen efficiency is improved.

[0041] The first transparent dielectric layer 3, serving as a resonance matching layer, is made of acrylic UV resin with a dielectric constant of 3.5 (less than 4.0), a light transmittance of 93%, and a haze of 0.3%, meeting the requirements of low dielectric constant, high light transmittance, and low haze. This layer is 1 mm thick and is uniformly coated on the surface of the first randomized grid metal layer (2) to achieve electromagnetic resonance matching between the two metal grid layers and optimize optical performance.

[0042] The second transparent dielectric layer 5, as a surface protective layer, is made of acrylic resin. After curing, it has a Shore A hardness of 60 (greater than 50), a light transmittance of 93%, a haze of 0.3%, and a thickness of 8μm. It is uniformly covered on the surface of the second randomized grid metal layer 4, providing wear-resistant and corrosion-resistant protection without affecting optical performance.

[0043] The method for fabricating ultra-low diffraction high-efficiency metal mesh provided in this embodiment includes the following steps:

[0044] Step 1: Substrate Pretreatment

[0045] A PMMA substrate 1 with a size of 100mm×100mm is provided. Its surface is activated using a plasma treatment device to remove surface impurities and increase surface polar groups, thereby improving the adhesion of subsequent coatings.

[0046] A water-soluble primer photoresist (immiscible with transparent dielectric materials) was coated using a spin coating process at a speed of 2000 rpm. After coating, it was cured under UV light in an 80℃ oven for 10 minutes to form a primer layer with a thickness of 2μm, providing a smooth interface for the preparation of the first-layer grid.

[0047] Step 2: Preparation of the first layer of the grid

[0048] Map design:

[0049] Based on the regular hexagonal basic pattern, randomized grid cells are generated through a vertex randomization algorithm to ensure that the quasi-periodic array structure is consistent with the regular hexagonal planar tiling method.

[0050] The unit pattern is expanded into a rectangular module layout (20mm×20mm), and overlapped to the base surface size (100mm×100mm) using rectangular line layout technology. The overlap width of the module boundary is 15μm (within the range of 10μm-20μm) to reduce splicing gaps.

[0051] A curvature factor (based on the substrate surface flatness detection data, assuming the substrate is flat and the curvature factor is 0) is introduced to generate a planar conformal layout. The layout data is then converted to *.dwg format, and the file size is compressed to 800MB (less than 1GB).

[0052] Pattern preparation:

[0053] The layout data is input into a laser direct writing device (1 μm resolution), and a randomized grid array is prepared on the surface of the primer layer at a scanning speed of 500 mm / s, with the line width controlled at 5 μm.

[0054] A pure copper metal layer was deposited on the array surface using an evaporation deposition process, with an evaporation source temperature of 1500℃ and a vacuum degree of 1×10⁻⁶. -3 Pa, with the deposition thickness controlled at 3 μm.

[0055] After coating, the substrate is immersed in deionized water for ultrasonic cleaning for 10 minutes, and then soaked in stripping solution (sodium hydroxide aqueous solution) for 5 minutes to remove the primer layer not covered by metal, forming the first randomized grid metal layer 2.

[0056] Step 3: Constructing the Cascade Structure

[0057] Preparation of the first transparent dielectric layer:

[0058] Acrylic UV resin (50% solid content) was coated onto the surface of the first randomized grid metal layer 2 using a spin coating process at a spin coating speed of 3000 rpm to form a uniform coating.

[0059] After coating, plasma surface treatment (50W power, 2 minutes) is performed to improve interlayer adhesion, followed by UV curing (365nm wavelength, 1000mJ / cm² energy). 2 Curing for 15 minutes forms a first transparent dielectric layer 3 with a thickness of 1 mm.

[0060] Fabrication of the second layer grid:

[0061] Repeat the substrate pretreatment steps, coat the surface of the first transparent dielectric layer 3 with the same primer photoresist and cure it.

[0062] After rotating the first layer layout data by 45°, input it into the laser direct writing equipment. The remaining process parameters are the same as those of the first layer. Prepare the second randomized grid metal layer 4 to ensure that the stacking angle of the two grid layers is 45°.

[0063] Step 4: Surface Protection Treatment

[0064] An acrylic resin protective adhesive (60% solid content) was coated onto the surface of the second randomized grid metal layer 4 using a spin coating process at a speed of 2500 rpm. After coating, it was cured in an oven at 100°C for 30 minutes to form a second transparent dielectric layer 5 with a thickness of 8 μm, thus completing the preparation of the entire metal grid.

[0065] Through the above structural design and fabrication process, the resulting metal mesh achieves a transmittance of over 85% in the visible light range (400nm-760nm), a diffraction efficiency of less than 0.5%, and a shielding effectiveness greater than 30dB in the 100MHz-10GHz frequency band, meeting the design requirements of ultra-low diffraction and high shielding effectiveness. The substrate and each functional layer are firmly bonded, and after a damp heat aging test (85℃ / 85%RH, 1000 hours), the structure and performance remain stable, verifying the feasibility and reliability of this embodiment.

[0066] The above description only illustrates the preferred embodiments of the present invention. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention, and all such changes should be included within the protection scope of the present invention.

Claims

1. A high-efficiency metal mesh with ultra-low diffraction, characterized in that: It includes a substrate (1), a first randomized grid metal layer (2), a second randomized grid metal layer (4), a first transparent dielectric layer (3), and a second transparent dielectric layer (5). The first randomized grid metal layer (2) is disposed on the substrate (1), the first transparent dielectric layer (3) is disposed on the first randomized grid metal layer (2), the second randomized grid metal layer (4) is disposed on the first transparent dielectric layer (3), and the second transparent dielectric layer (5) is disposed on the second randomized grid metal layer (4). The first randomized grid metal layer (2) and the second randomized grid metal layer (4) are quasi-periodic array structures formed by planar tiling of randomized grid units. The randomized grid units are based on regular polygons as the basic pattern, and a combination structure of random side lengths and random circles is formed by randomizing the vertices. The quasi-periodic array structure of the randomized grid units is the same as the planar tiling method of the basic pattern. The first randomized grid metal layer (2) and the second randomized grid metal layer (4) are set with a stacking angle of 20°-70° and a stacking interval thickness of 300μm-2mm; The metal material of the first random grating metal layer (2) and the second random grating metal layer (4) is a pure metal thin film material, including one of copper, silver or nickel-copper alloy, and the resistivity is less than 1.0*10 -8 Ω·m; the base pattern of the random grating unit includes an equilateral triangle, a square, a regular hexagon, a combination of an equilateral triangle and a regular hexagon, or a combination of a square and a regular hexagon, the regular polygon grating line width of the base pattern is 3-10 μm, and the initial period is 100-200 μm; The first transparent dielectric layer (3) is a resonant matching layer disposed between the first randomized grid metal layer (2) and the second randomized grid metal layer (4), and is made of a photoresist material with a dielectric constant of less than 4.0, a transmittance of more than 92%, and a haze of less than 0.5%, and is made of one of acrylic UV resin, polyurethane resin or polyimide resin; the second transparent dielectric layer (5) is a protective layer disposed on the surface of the second randomized grid metal layer (4), and is made of a colloidal material with a Shore A of more than 50 after curing, a transmittance of more than 92%, and a haze of less than 0.5%, and is made of one of acrylic resin, polyurethane resin, polyimide resin or silicone resin.

2. The ultra-low diffraction high-efficiency metal mesh grating according to claim 1, characterized in that: The substrate (1) is a high-strength transparent material, which is one of polymethyl methacrylate (PMMA), polycarbonate (PC), polyimide (PI), K9 glass or infrared glass, with a light transmittance greater than 91% and a strength greater than 4MPa.

3. The ultra-low diffraction high-efficiency metal mesh grating according to claim 1, characterized in that: The vertex randomization process of the randomized grid unit is specifically as follows: a vertex randomization factor is introduced into the mathematical analytical expression of the basic pattern, so that the hybridization intensity of the random side length is 50%-150% of the initial side length of the regular polygon, and the hybridization intensity of the random circle diameter is 20%-40% of the initial side length of the regular polygon.

4. A method for preparing an ultra-low diffraction high-efficiency metal mesh according to any one of claims 1-3, characterized in that, Includes the following steps: S1. Substrate pretreatment: Provide a substrate (1), activate its surface, coat it with primer photoresist and cure it under ultraviolet light to form a primer layer with a thickness of 1.5μm-3.5μm; S2. Preparation of the first layer mesh: The first randomized grid metal layer (2) is generated as a module pattern layout. The module pattern is a rectangular layout formed by the planar tiling of randomized grid units. The rectangular line layout technology is used to overlap the base surface size. A curvature factor is introduced to generate a curved conformal layout. The overlap width of the module boundary is 10μm-20μm. After the data file is converted, the capacity is reduced to less than 1GB. The layout data is input into the laser direct writing device, a randomized grid array is prepared on the surface of the primer layer, a metal layer is prepared on the array by the coating process, the primer is removed by ultrasonic cleaning and stripping liquid, and the first randomized grid metal layer is formed (2). S3, Cascade Structure Construction: A transparent dielectric material is coated on the surface of the first randomized grid metal layer (2) and cured to form the first transparent dielectric layer (3). Repeat the primer coating, layout angle input, laser direct writing, coating and stripping process of S2 to prepare a second randomized grid metal layer (4) with an angle adjustment of 20°-70° on the surface of the transparent dielectric layer (3). S4. Surface protection treatment: A transparent medium material is coated on the surface of the randomized grid metal layer (4) and cured to form a second transparent medium layer (5).

5. The method for preparing an ultra-low diffraction high-efficiency metal mesh according to claim 4, characterized in that: The basic pattern of the module pattern layout is an equilateral triangle, a square, a regular hexagon, a combination of an equilateral triangle and a regular hexagon, or a combination of a square and a regular hexagon. Randomized grid units with random side lengths and random circumferences are generated through a vertex randomization algorithm. The quasi-periodic array structure of the randomized grid units is the same as the planar tiling method of the basic pattern.

6. The method for preparing an ultra-low diffraction high-efficiency metal mesh according to claim 4, characterized in that: The coating process includes evaporation coating or sputtering coating, and the thickness of the prepared metal layer is 2μm-5μm; the thickness of the first transparent dielectric layer (3) is 300μm-2mm, and the thickness of the second transparent dielectric layer (5) is 5μm-10μm.

7. The method for preparing an ultra-low diffraction high-efficiency metal mesh according to claim 4, characterized in that: The format conversion includes converting the layout data into *.dwg format. The curvature factor is used to construct the laser direct writing scanning path based on the curvature data of the substrate surface in the X, Y, and Z directions, and to calculate the deformation of the grid array to generate a conformal layout.

8. The method for preparing an ultra-low diffraction high-efficiency metal mesh according to claim 4, characterized in that: The primer photoresist is a water-soluble photoresist that is immiscible with the transparent dielectric material. The coating process of the transparent dielectric material adopts spin coating or spray coating, and plasma surface treatment is performed before curing to improve the interlayer adhesion.

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