A high-durability ultra-wideband EMP shielding light window and a preparation method thereof

Abstract

The application relates to the technical field of optical windows, in particular to a high-durability ultra-wideband EMP shielding optical window and a preparation method thereof. The optical window comprises a transparent substrate, a metal grid and a transparent protective layer; the transparent substrate is provided with a micro-groove array on the surface; the metal grid is filled in the micro-groove, and the upper surface of the metal grid is flush with the surface of the transparent substrate; the transparent protective layer covers the surfaces of the transparent substrate and the metal grid; the metal grid is formed by printing and curing of conductive silver paste. The raw materials of the conductive silver paste include silver powder, an organic carrier, glass powder and an additive; the silver powder is a mixture of spherical silver powder and spheroid silver powder; the mass ratio of the spherical silver powder to the spheroid silver powder is 1:0.8-1.2. Through synergistic optimization of the structural design and the material formula, the comprehensive balance of shielding effectiveness (SE >= 89 dB), light transmittance (>= 40%) and environmental durability is realized.

Description

Technical Field

[0001] This invention relates to the field of optical window technology, and in particular to a high-durability ultra-wideband EMP shielded optical window and its preparation method. Background Technology

[0002] Optical windows are an important component of optical systems, widely used in architectural lighting, vehicle observation windows, military equipment observation ports, and optoelectronic equipment protective covers. Their core function is to provide physical protection and electromagnetic isolation for internal optical components or electronic equipment while ensuring optical transparency. With the development of electromagnetic pulse (EMP) weapons and strong electromagnetic interference sources, transparent optical windows have become a weak link in the coupling of electromagnetic energy into shielded cavities, posing a serious threat to the safety of internal precision optical instruments and electronic systems.

[0003] In existing technologies, transparent electromagnetic shielding windows mainly employ a composite structure in which a metal mesh film (MMF) is embedded in a transparent substrate. While this type of structure can achieve ultra-wideband (0.18-18 GHz) shielding effectiveness (SE>80 dB) under laboratory conditions, it faces severe environmental durability challenges in practical engineering applications: the metal mesh is prone to oxidation and corrosion when exposed to warm and humid environments, leading to increased surface resistance and decreased shielding performance; the multi-layer composite structure generates interfacial stress under extreme temperature cycling, triggering failure modes such as delamination and mesh deformation, significantly shortening its service life.

[0004] For the protection of metal mesh optical windows, existing technologies mainly fall into two structural categories:

[0005] The first type is the "sandwich" structure. For example, patent CN210075930U completely embeds a metal mesh grid inside a transparent polymer substrate, achieving environmental isolation through polymer encapsulation. However, this type of solution uses a flexible polymer as the substrate, whose coefficient of thermal expansion does not match that of a rigid optical system, making it unsuitable for rigid optical windows requiring high surface accuracy. Furthermore, the relatively thick polymer encapsulation layer causes additional absorption and scattering of visible light, affecting the transmittance and imaging quality of the optical system.

[0006] The second type is a multilayer film structure with a surface coating. For example, CN119342787A describes alternating deposition of high / low refractive index films on a substrate with an embedded metal mesh, achieving anti-reflection and protection through multilayer interference films. However, in this scheme, the metal mesh is still located near the substrate surface, and the protection mechanism of the multilayer film depends on the integrity of the overall coverage. During long-term environmental service, the interface between the film and the substrate is prone to corrosion and failure. In addition, the introduction of multilayer films changes the spectral characteristics of the optical window surface, which may have an adverse effect on optical systems in specific wavelength bands.

[0007] From the perspective of the structural integrity of optical components, none of the aforementioned existing technologies have solved the interface encapsulation problem between the metal mesh and the transparent substrate. When a metal mesh is embedded in a transparent substrate as a functional optical component, the integrity of its three-dimensional interface directly determines the long-term service reliability of the optical window. Atomic layer deposition (ALD) technology has been widely used in the field of optical coatings due to its excellent conformal coverage capability. However, there are still many technical problems to be solved in applying ALD technology to the conformal encapsulation of embedded metal meshes and combining it with a flush embedding structure of microgrooves to achieve synergistic optimization of the electromagnetic shielding function and environmental durability of the optical window. Existing technologies (such as sputtering) cannot form continuous, dense, and pinhole-free conformal coverage on the sidewalls and bottom corners of microgrooves, causing the interface to become the starting point of failure.

[0008] On the other hand, the preparation of 30μm linewidth metal meshes places extremely high demands on conductive pastes and printing processes. Conductive silver paste, as a functional material for the metal mesh in optical windows, directly affects the conductivity of the mesh and its bonding strength with the optical substrate through its curing properties. Changzhou Juhe New Material Co., Ltd. disclosed a conductive silver paste for narrow linewidth, low film thickness screen printing in patent CN117352206A, which balances printability and formability by introducing a combination of short-chain viscous resin, non-polar elastomer resin, and wetting solvent. However, this patent mainly targets silicon substrates and high-temperature sintering processes in the solar cell field. Its formulation exhibits significant performance degradation in low-temperature curing scenarios for optical substrates such as PET, and it lacks a refined design for the silver powder particle size distribution, making it difficult to meet the requirements of low sheet resistance (<0.1Ω / □) and high optical flatness for optical windows.

[0009] Therefore, developing an optical window structure that can achieve efficient EMP shielding, excellent environmental durability, and maintain high transparency and surface flatness, as well as a matching highly conductive silver paste suitable for low-temperature curing of optical substrates, is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0010] Based on the above, the present invention provides a high-durability ultra-wideband EMP shielded optical window and its preparation method.

[0011] To achieve the above objectives, the present invention provides the following solution:

[0012] One of the technical solutions of the present invention is a conductive silver paste, which, by mass parts, comprises the following raw material components: 80-90 parts of silver powder, 4-8 parts of organic carrier, 1.0-3.0 parts of glass powder, and 0.5-2 parts of additives;

[0013] The silver powder is a mixture of spherical silver powder and near-spherical silver powder, wherein the median particle size D50 of the spherical silver powder is 1.0 to 2.0 μm, the median particle size D50 of the near-spherical silver powder is 2.0 to 3.5 μm, and the mass ratio of spherical silver powder to near-spherical silver powder is 1:0.8 to 1.2.

[0014] The organic carrier comprises, by weight, 0.3-2.0 parts of short-chain adhesive resin, 0.2-2.5 parts of non-polar elastomer resin, and 1.0-5.0 parts of wetting solvent.

[0015] The second technical solution of the present invention is a method for preparing the above-mentioned conductive silver paste, comprising the following steps:

[0016] Short-chain viscous resin, non-polar elastomer resin, and wetting solvent are dissolved uniformly under heating conditions to obtain an organic carrier;

[0017] Add an auxiliary agent to the organic carrier and stir until homogeneous to obtain mixture A;

[0018] Mixing spherical silver powder and near-spherical silver powder yields a mixed silver powder;

[0019] The mixed silver powder, glass powder, and mixture A are mixed and pre-dispersed. The pre-dispersed slurry is then ground until the fineness is ≤8μm, and then filtered and degassed to obtain the conductive silver paste.

[0020] The third technical solution of the present invention is the application of the above-mentioned conductive silver paste in the preparation of EMP shielding optical windows.

[0021] The fourth technical solution of the present invention is a high-durability ultra-wideband EMP shielding window, comprising: a transparent substrate, a metal mesh, and a transparent protective layer;

[0022] The transparent substrate has a micro-groove array on its surface; the metal mesh fills the micro-grooves, and the upper surface of the metal mesh is flush with the surface of the transparent substrate; the transparent protective layer covers the surfaces of the transparent substrate and the metal mesh.

[0023] The metal mesh is formed by printing and curing the aforementioned conductive silver paste.

[0024] The fifth technical solution of the present invention is a method for preparing the above-mentioned high-durability ultra-wideband EMP shielding optical window, comprising the following steps:

[0025] A microgroove array is fabricated on the surface of a transparent substrate;

[0026] The conductive silver paste described above is filled into the microgrooves, cured to form a metal mesh, and its upper surface is flush with the surface of the transparent substrate.

[0027] A transparent protective layer is deposited on the surface of a transparent substrate and a metal mesh.

[0028] The sixth technical solution of this invention is the application of the above-mentioned high-durability ultra-wideband EMP shielded light window in the preparation of building lighting windows, vehicle observation windows, military equipment observation holes, or optoelectronic equipment protective covers.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) Integrated structure, significantly improved durability: Through the design of "flat embedding on substrate surface + conformal protective layer", the metal mesh is completely wrapped by the substrate and dense inorganic protective layer, eliminating the interface corrosion channel. As shown in Table 2, the shielding effectiveness of Example 1 of the present invention decreased by only 2.1dB after 1000h in a humid heat environment of 85℃ / 85%RH, which is much lower than that of Comparative Example 1 (8.7dB) and Comparative Example 2 (15.3dB); the corrosion area in the salt spray test was <1%, and the adhesion remained at level 5B, proving that its environmental durability is far superior to the prior art.

[0031] (2) Low sheet resistance with low temperature curing, meeting the requirements of narrow linewidth printing: By using the particle size distribution of spherical and near-spherical silver powder (D50=1.0~2.0μm and 2.0~3.5μm mixed, mass ratio 1:0.8~1.2), combined with the synergistic effect of short-chain viscous resin / non-polar elastomer resin / wetting solvent organic carrier, the silver paste can still achieve a sheet resistance of ≤0.10Ω / □ after low temperature curing at 130℃ (see Table 1 Preparation Examples 1-3), which is significantly better than silver paste Comparative Example 4 (polyhe formulation reproduction, 0.13Ω / □) and silver paste Comparative Example 5 (polyhe low temperature curing, 0.21Ω / □), and at the same time, high-precision printing with a linewidth of 30μm is achieved.

[0032] (3) Synergistic effect and excellent overall performance: Through the synergistic optimization of structural design and material formulation, this invention achieves a comprehensive balance of shielding effectiveness (SE≥89dB), light transmittance (≥40%), and environmental durability. Cross experiments of silver paste comparative examples 6-7 show that silver powder optimization and organic carrier optimization have a synergistic enhancement effect, and the combined effect of the two (preparation example 1) is better than the simple superposition of individual optimizations. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 This is a schematic diagram of the cross-section of the high-durability ultra-wideband EMP shielded optical window structure of the present invention.

[0035] Figure 2This is a schematic diagram of a metal mesh structure.

[0036] Figure 3 This is a typical SEM image of a microgroove.

[0037] Figure 4 Steel plates used for printing.

[0038] Figure 5 This is a flowchart of the process for preparing conductive silver paste.

[0039] Figure 6 This is a flowchart of the metal mesh printing and embedding process. Detailed Implementation

[0040] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0041] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0042] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0043] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0044] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0045] Unless otherwise specified, the "%" in this invention refers to a percentage by mass.

[0046] The first aspect of the present invention provides a conductive silver paste, comprising the following raw material components by mass: 80-90 parts silver powder, 4-8 parts organic carrier, 1.0-3.0 parts glass powder, and 0.5-2 parts additives;

[0047] The silver powder is a mixture of spherical silver powder and near-spherical silver powder, wherein the median particle size D50 of the spherical silver powder is 1.0-2.0 μm, the median particle size D50 of the near-spherical silver powder is 2.0-3.5 μm, and the mass ratio of spherical silver powder to near-spherical silver powder is 1:0.8-1.2. This invention improves the bulk density of silver powder by grading the size distribution of the silver powder, thereby obtaining low sheet resistance under low temperature curing conditions.

[0048] The organic carrier comprises, by weight, 0.3-2.0 parts of short-chain viscous resin, 0.2-2.5 parts of non-polar elastomer resin, and 1.0-5.0 parts of wetting solvent. In this invention, the short-chain viscous resin provides plasticity during silver paste printing, the non-polar elastomer resin enhances the adhesion between the silver paste and the substrate and reduces curing shrinkage stress, and the wetting solvent improves the silver paste's ability to fill microgrooves.

[0049] In a preferred embodiment of the present invention, the short-chain adhesive resin is ethyl cellulose or cellulose acetate butyrate, the non-polar elastomer resin is SEBS elastomer or SBS elastomer, and the wetting solvent is dodecyl alcohol ester or diethylene glycol monobutyl ether.

[0050] In a preferred embodiment of the present invention, the additives include a thixotropic agent and a dispersant, wherein the thixotropic agent is hydrogenated castor oil and the dispersant is polyvinylpyrrolidone.

[0051] A second aspect of the present invention provides a method for preparing the above-mentioned conductive silver paste, comprising the following steps:

[0052] Short-chain viscous resin, non-polar elastomer resin, and wetting solvent are dissolved uniformly under heating conditions to obtain an organic carrier;

[0053] Add an auxiliary agent to the organic carrier and stir until homogeneous to obtain mixture A;

[0054] Mixing spherical silver powder and near-spherical silver powder yields a mixed silver powder;

[0055] The mixed silver powder, glass powder, and mixture A are mixed and pre-dispersed. The pre-dispersed slurry is then ground until the fineness is ≤8μm, and then filtered and degassed to obtain the conductive silver paste.

[0056] The third aspect of the present invention provides the application of the above-mentioned conductive silver paste in the preparation of EMP shielded optical windows.

[0057] A fourth aspect of the present invention provides a high-durability ultra-wideband EMP shielding window, comprising: a transparent substrate, a metal mesh, and a transparent protective layer;

[0058] The transparent substrate has a micro-groove array on its surface; the metal mesh fills the micro-grooves, and the upper surface of the metal mesh is flush with the surface of the transparent substrate; the transparent protective layer covers the surfaces of the transparent substrate and the metal mesh.

[0059] The metal mesh is formed by printing and curing the aforementioned conductive silver paste.

[0060] In a preferred embodiment of the present invention, the depth of the microgroove is 1.2 to 2.0 times the thickness of the metal mesh (within this range, the microgroove depth ensures complete embedding of the metal mesh while avoiding filling difficulties and uneven coverage of the protective layer due to excessive groove depth); the linewidth of the metal mesh is 25 to 32 μm, and the thickness is 1.5 to 2.5 μm; the transparent protective layer is an atomic layer deposited Al2O3, TiO2, SiO2 monolayer film or nanolayer film (such as TiO2 / Al2O3 nanolayer), with a thickness of 50 to 200 nm; the transparent substrate is a glass substrate. The transparent protective layer covers the surface of the substrate after the metal mesh is embedded, encapsulating the metal mesh between the substrate and the protective layer; atomic layer deposition can achieve conformal coverage, ensuring complete encapsulation at the interface between the metal mesh and the substrate.

[0061] Preferably, the metal mesh is an asymmetric hexagonal mesh with the following geometric parameters: period p = 234 ± 20 μm, line width w = 30 ± 3 μm, and metal thickness t = 2 ± 0.5 μm.

[0062] The fifth aspect of this invention provides a method for preparing the above-mentioned high-durability ultra-wideband EMP shielding optical window, comprising the following steps:

[0063] A microgroove array is fabricated on the surface of a transparent substrate; the microgroove array is fabricated on the surface of the transparent substrate by a combination of photolithography mask and plasma etching process; the shape of the microgroove matches the line pattern of the metal mesh;

[0064] The conductive silver paste described above is filled into the microgrooves, cured to form a metal mesh, and its upper surface is flush with the surface of the transparent substrate.

[0065] A transparent protective layer is deposited on the surface of a transparent substrate and a metal mesh.

[0066] In a preferred embodiment of the present invention, the step of filling the microgrooves with conductive material includes: filling the microgrooves with conductive silver paste using screen printing, followed by curing and polishing to make the metal mesh flush with the substrate surface; the screen printing uses a 100% open steel plate with a line width of 28-32 μm and a plate thickness of 20-30 μm; the printing pressure is 0.2-0.4 MPa, the squeegee speed is 80-150 mm / s, and the spacing between the squeegee and the plate is 1-3 mm; the curing temperature is 120-150°C, and the curing time is 15-30 minutes; the transparent protective layer is prepared using atomic layer deposition (ALD) at a deposition temperature of 80-120°C.

[0067] The flushing can also be achieved through mechanical scraping or self-leveling after filling, based on precise control of the groove depth.

[0068] The sixth technical solution of this invention is the application of the above-mentioned high-durability ultra-wideband EMP shielded light window in the preparation of building lighting windows, vehicle observation windows, military equipment observation holes, or optoelectronic equipment protective covers.

[0069] Unless otherwise specified, the technical solutions described in this invention are all conventional solutions in the field, and the reagents or raw materials used are all purchased from commercial channels or are publicly available unless otherwise specified.

[0070] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0071] I. Preparation and Properties of Conductive Silver Paste (hereinafter referred to as: silver paste)

[0072] Preparation Example 1

[0073] The raw material composition of conductive silver paste, by mass parts, is as follows:

[0074] The composition includes 42.5 parts of spherical silver powder (D50=1.5μm) and 42.5 parts of near-spherical silver powder (D50=2.8μm) (i.e., a total of 85 parts of silver powder); the organic carrier consists of 1.2 parts of ethyl cellulose (molecular weight 30000, used as a short-chain adhesive resin), 1.0 part of SEBS elastomer (hydrogenated styrene-butadiene-styrene block copolymer, used as a non-polar elastomer resin), and 3.5 parts of dodecyl alcohol ester (used as a wetting solvent); 2.0 parts of glass powder; and 0.5 parts of additives (composed of 0.3 parts of hydrogenated castor oil and 0.2 parts of polyvinylpyrrolidone).

[0075] The preparation method of the above-mentioned conductive silver paste includes the following steps:

[0076] An organic carrier was obtained by dissolving 1.2 parts of ethyl cellulose (molecular weight 30,000), 1.0 part of SEBS elastomer (hydrogenated styrene-butadiene-styrene block copolymer), and 3.5 parts of alcohol ester dodecyl in a water bath at 70°C. After the organic carrier cooled to room temperature, 0.3 parts of hydrogenated castor oil and 0.2 parts of polyvinylpyrrolidone were added to obtain an organic carrier with additives. 42.5 parts of spherical silver powder (D50=1.5μm) and near-spherical silver powder (D50=2.8μm) were mixed to obtain a mixed silver powder. The organic carrier with additives, glass powder, and mixed silver powder were added to a planetary mixer for pre-dispersion (pre-dispersion at 200 rpm for 45 minutes). The pre-dispersion slurry was then transferred to a three-roll mill, and the roller spacing was adjusted to 20μm, 15μm, and 10μm, and the mill was repeatedly rolled 5 times until the fineness of the slurry was ≤8μm as measured by a scraper fineness meter. Finally, the slurry was filtered through a 200-mesh stainless steel sieve and degassed in a vacuum degassing machine for 30 minutes to obtain the finished conductive silver paste. The viscosity of this silver paste was 350 Pa·s (tested using a rotational viscometer at 25°C), and the solid content was approximately 87% (process route as follows). Figure 5 (As shown).

[0077] The silver paste prepared above was subjected to performance tests. The width and thickness of the cured lines after printing were measured using an optical microscope (on a PET substrate, curing temperature 130℃, curing time 20min). The sheet resistance was tested using a four-probe resistance tester. The edges, breaks, burrs, etc. of the lines were observed visually and under a 100x microscope. The adhesion was tested using 3M tape peel test according to ASTM D3359 standard. The print conformability was reflected by dividing the ratio of the cured line height to the line width by the aspect ratio of the stencil opening.

[0078] Preparation Example 2

[0079] The only difference from Preparation Example 1 is that the silver powder consists of 45 parts of spherical silver powder (D50=1.2μm) and 40 parts of near-spherical silver powder (D50=3.2μm) (total silver powder 85 parts); the other steps and parameters are the same as in Preparation Example 1.

[0080] Preparation Example 3

[0081] The only difference from Preparation Example 1 is that the organic carrier is composed of 1.0 part of cellulose acetate butyrate, 1.2 parts of SBS elastomer and 4.0 parts of diethylene glycol monobutyl ether (total organic carrier 6.2 parts); the remaining steps and parameters are the same as in Preparation Example 1.

[0082] Preparation Example 4

[0083] The only difference from Preparation Example 1 is that the silver powder consists of 42.5 parts of spherical silver powder (D50=1.0μm) and 42.5 parts of near-spherical silver powder (D50=2.0μm) (total silver powder 85 parts); the other steps and parameters are the same as in Preparation Example 1.

[0084] Preparation Example 5

[0085] The only difference from Preparation Example 1 is that the silver powder consists of 42.5 parts of spherical silver powder (D50=2.0μm) and 42.5 parts of near-spherical silver powder (D50=3.5μm) (total silver powder 85 parts); the other steps and parameters are the same as in Preparation Example 1.

[0086] Preparation Example 6

[0087] The only difference from Preparation Example 1 is that the silver powder consists of 47.2 parts of spherical silver powder (D50=1.5μm) and 37.8 parts of near-spherical silver powder (D50=2.8μm) (total silver powder of 85 parts, with a mass ratio of spherical silver powder to near-spherical silver powder of 1:0.8); the other steps and parameters are the same as in Preparation Example 1.

[0088] Preparation Example 7

[0089] The only difference from Preparation Example 1 is that the silver powder consists of 38.6 parts of spherical silver powder (D50=1.5μm) and 46.4 parts of near-spherical silver powder (D50=2.8μm) (total silver powder of 85 parts, with a mass ratio of spherical silver powder to near-spherical silver powder of 1:1.2); the rest of the steps and parameters are the same as in Preparation Example 1.

[0090] Preparation Example 8

[0091] The only difference from Preparation Example 1 is that the silver powder consists of 40 parts of spherical silver powder (D50=1.5μm) and 40 parts of near-spherical silver powder (D50=2.8μm) (total silver powder 80 parts); the organic carrier consists of 1.5 parts of ethyl cellulose, 1.2 parts of SEBS, and 4.5 parts of dodecyl alcohol ester (total organic carrier 7.2 parts); and 0.8 parts of additives (0.5 parts of hydrogenated castor oil + 0.3 parts of polyvinylpyrrolidone); the remaining steps and parameters are the same as in Preparation Example 1.

[0092] Preparation Example 9

[0093] The only difference from Preparation Example 1 is that the silver powder consists of 45 parts of spherical silver powder (D50=1.5μm) and 45 parts of near-spherical silver powder (D50=2.8μm) (total silver powder 90 parts); the organic carrier consists of 1.0 part of ethyl cellulose, 0.8 parts of SEBS, and 3.0 parts of dodecyl alcohol ester (total organic carrier 4.8 parts), and 0.7 parts of additives (0.4 parts of hydrogenated castor oil + 0.3 parts of polyvinylpyrrolidone); the remaining steps and parameters are the same as in Preparation Example 1.

[0094] Silver paste comparison example 1

[0095] The only difference from Preparation Example 1 is that all the silver powder used was spherical silver powder with a single particle size (D50=2.0μm) (total amount of silver powder 85 parts); the other steps and parameters were the same as in Preparation Example 1.

[0096] Silver paste comparison example 2

[0097] The only difference from Preparation Example 1 is that the organic carrier consists of 2.2 parts of ethyl cellulose (molecular weight 30,000) and 3.5 parts of dodecyl alcohol ester (as a wetting solvent) (total organic carrier 5.7 parts); the remaining steps and parameters are the same as in Preparation Example 1 (i.e., the organic carrier does not contain SEBS elastomer and the ethyl cellulose is increased to 2.2 parts).

[0098] Silver paste comparison example 3

[0099] The only difference from Preparation Example 1 is that the organic carrier consists of 2.5 parts of ethyl cellulose (molecular weight 30,000), 1.0 part of SEBS elastomer (hydrogenated styrene-butadiene-styrene block copolymer), and 3.5 parts of terpineol (total organic carrier 7 parts); the remaining steps and parameters are the same as in Preparation Example 1 (i.e., the organic carrier does not contain dodecyl alcohol ester, ethyl cellulose is increased to 2.5 parts, and terpineol is added as a substitute).

[0100] Silver paste comparison example 4

[0101] The only difference from Preparation Example 1 is that the raw material composition of the conductive silver paste is as follows: 85 parts silver powder (conventional spherical silver powder D50=1.8μm), 2 parts glass powder, 13 parts organic carrier (1.5 parts ethyl cellulose, 1.0 part SEBS, 3.0 parts dodecyl alcohol ester, and the remainder is terpineol).

[0102] Silver paste comparison ratio 5

[0103] The raw material composition of the conductive silver paste in Comparative Example 4 is the same as that in the silver paste, but the curing temperature is changed to 150℃ (that is, the only difference from Comparative Example 4 is that the curing temperature during the performance test is 150℃).

[0104] Silver paste comparison ratio 6

[0105] The difference from Preparation Example 1 is that the silver powder ratio of the present invention is used (42.5 parts of spherical D50=1.5μm + 42.5 parts of near-spherical D50=2.8μm), but the organic carrier adopts the Polyhe patented formula, which includes, by mass parts: 1.5 parts of ethyl cellulose, 1.0 part of SEBS elastomer, 3.0 parts of dodecyl alcohol ester and 0.2 parts of terpineol (total organic carrier is 5.7 parts). The amount of additives and glass powder added is the same as in Preparation Example 1 (i.e., 0.3 parts of hydrogenated castor oil, 0.2 parts of polyvinylpyrrolidone, and 2.0 parts of glass powder); the remaining steps and parameters are the same as in Preparation Example 1.

[0106] Silver paste comparison example 7

[0107] The difference from Preparation Example 1 is that Polyhe's patented silver powder (85 parts of conventional spherical silver powder with D50=1.8μm) was used, the organic carrier adopted the formulation of this invention (1.2 parts of ethyl cellulose + 1.0 part of SEBS + 3.5 parts of dodecyl alcohol ester), and the amount of additives and glass powder added was the same as in Preparation Example 1 (i.e., 0.3 parts of hydrogenated castor oil, 0.2 parts of polyvinylpyrrolidone, and 2.0 parts of glass powder); the remaining steps and parameters were the same as in Preparation Example 1.

[0108] Silver paste comparison ratio 8

[0109] The only difference from Preparation Example 1 is that the silver powder is made by mixing spherical silver powder (D50=0.8μm) and near-spherical silver powder (D50=4.0μm) in a mass ratio of 1:1, with a total amount of 85 parts of silver powder; the other steps and parameters are the same as in Preparation Example 1.

[0110] The performance test results of the silver pastes prepared in the above preparation examples and comparative examples are summarized in Table 1.

[0111] Table 1 Silver paste properties

[0112] Preparation Example 1 30.2 2.1 0.09 The edges are clear and there are no broken lines. 5B 95 Preparation Example 2 30.5 2.0 0.08 The edges are clear and there are no broken lines. 5B 93 Preparation Example 3 31.0 2.2 0.10 The edges are clear and there are no broken lines. 5B 94 Preparation Example 4 30.8 2.0 0.10 The edges are clear and there are no broken lines. 5B 94 Preparation Example 5 31.2 2.1 0.09 The edges are clear and there are no broken lines. 5B 93 Preparation Example 6 30.5 2.0 0.09 The edges are clear and there are no broken lines. 5B 94 Preparation Example 7 30.9 2.1 0.10 The edges are clear and there are no broken lines. 5B 94 Preparation Example 8 30.0 1.9 0.12 The edges are clear and there are no broken lines. 5B 92 Preparation Example 9 31.5 2.3 0.08 Slight burrs on the edges 4B 90 Silver paste comparison example 1 31.5 1.8 0.18 slight burrs 4B 82 Silver paste comparison example 2 33.5 1.9 0.15 Jagged edges, partially broken wire 3B 75 Silver paste comparison example 3 — — — Severely clogged screen, unable to print. — — Silver paste comparison example 4 32.0 1.9 0.13 Slight burrs on the edges 3B 85 Silver paste comparison ratio 5 33.5 1.7 0.21 The lines collapsed, and some lines broke. 2B 68 Silver paste comparison ratio 6 30.8 2.0 0.11 The edges are relatively clear 4B 90 Silver paste comparison example 7 31.2 1.9 0.12 Slight burrs on the edges 4B 88 Silver paste comparison ratio 8 32.5 1.8 0.17 Obvious burrs on the edges 3B 80

[0113] As shown in Table 1, the sheet resistance of Preparation Examples 1-7 of this invention is ≤0.10Ω / □, and the printing quality and adhesion are excellent. This proves that the synergistic effect of particle size distribution and organic carrier can achieve low sheet resistance and high precision under low temperature curing. Preparation Examples 4-7 verify that good performance can be obtained within the silver powder particle size range and ratio boundary defined by this invention. Preparation Examples 8 and 9 verify that acceptable performance (sheet resistance ≤0.12Ω / □) can be achieved within the range of silver powder content of 80%~92.5%, with the best overall performance at around 85%. However, Comparative Examples 4 and 5 cannot achieve low sheet resistance (≥0.13Ω / □) under low temperature curing and the printing quality decreases. Cross-validation of Comparative Examples 6 and 7 shows that silver powder optimization and organic carrier optimization have a synergistic effect, and the combination of the two has the best effect. Comparative Example 8 verifies that exceeding this range will lead to increased sheet resistance and decreased printing quality.

[0114] II. Preparation and Performance of Shielding Windows

[0115] The following examples all use the silver paste prepared in Preparation Example 1 to prepare the metal mesh, and follow the procedures outlined in the examples. Figure 6 The process shown completes the manufacturing of the entire optical window. A schematic cross-sectional view of the high-durability ultra-wideband EMP shielded optical window structure of this invention is shown below. Figure 1 As shown.

[0116] Example 1

[0117] This embodiment provides a specific method for preparing a high-durability ultra-wideband EMP shielded optical window, and details the materials used and the basis for their selection.

[0118] Step 1: Prepare the glass substrate: Select soda-lime glass with dimensions of 100mm × 100mm and a thickness of 3mm as the substrate. This glass has an average transmittance of approximately 90% in the visible light range and possesses good mechanical strength and chemical stability, making it suitable as a base material for observation windows in buildings or equipment. The glass substrate is then ultrasonically cleaned sequentially in acetone, ethanol, and deionized water for 15 minutes each to remove surface oil and particulate impurities, and then dried in a nitrogen atmosphere for later use.

[0119] Step 2, fabricating a microgroove array on the glass surface: Using standard photolithography, first, a layer of positive photoresist (model AZ4620) is spin-coated onto the cleaned glass surface at a spin speed of 3000 rpm for 30 seconds, then cured on a 100°C hot plate for 90 seconds. A photomask with an asymmetric hexagonal grid pattern (such as...) is then placed on the glass surface. Figure 2 (As shown) The substrate was aligned and placed on the photoresist, and exposed using a contact UV lithography machine at an exposure dose of 120 mJ / cm². After exposure, the glass substrate was immersed in a developer (2.38% tetramethylammonium hydroxide aqueous solution) for 60 seconds to dissolve the photoresist in the exposed area, leaving a grid-like photoresist pattern consistent with the mask pattern. The glass substrate with the photoresist mask was then placed in a plasma etching machine, using a CF4 / O2 mixed gas (CF4 flow rate 40 sccm, O2 flow rate 10 sccm) as the etching gas, etched under a reaction pressure of 5 Pa and an RF power of 200 W, with the etching time controlled at a preset depth of 8 minutes, ultimately forming a microgroove with a depth of 3 μm. After etching, residual photoresist was removed with acetone, rinsed with deionized water, and dried in nitrogen. The SEM image of the microgroove is shown below. Figure 3 As shown.

[0120] Step 3: Preparation of conductive silver paste: This embodiment uses a self-developed special silver paste, the formulation of which is based on a comprehensive consideration of 30μm linewidth printability and low-temperature curing conductivity. The specific preparation process is as follows: First, weigh 1.2g of ethyl cellulose (molecular weight approximately 30,000, as a short-chain adhesive resin), 1.0g of SEBS elastomer (hydrogenated styrene-butadiene-styrene block copolymer, as a non-polar elastomer resin), and 3.5g of alcohol ester dodecyl (as a wetting solvent), place them in a 100ml beaker, heat in a 70℃ water bath and magnetically stir for 2 hours to completely dissolve the resin and form a uniform and transparent organic carrier. After cooling the organic carrier to room temperature, add 0.3g of hydrogenated castor oil (as a thixotropic agent) and 0.2g of polyvinylpyrrolidone (as a dispersant), and stir evenly. Next, 42.5g of spherical silver powder (D50=1.5μm) and 42.5g of near-spherical silver powder (D50=2.8μm) were weighed and mixed to obtain 85g of mixed silver powder; 2.0g of silicate glass powder was also weighed. The organic carrier with added additives, glass powder, and mixed silver powder were sequentially added to a planetary mixer and pre-dispersed at 200rpm for 45 minutes. The pre-dispersed slurry was then transferred to a three-roll mill, and the roller spacing was adjusted sequentially to 20μm, 15μm, and 10μm, and repeatedly milled five times until the slurry fineness, tested with a scraper fineness meter, was ≤8μm. Finally, the slurry was filtered through a 200-mesh stainless steel sieve and degassed in a vacuum degassing machine for 30 minutes to obtain the finished conductive silver paste. The viscosity of this silver paste was 350Pa·s (tested using a rotational viscometer at 25℃), with a solid content of approximately 87%, making it suitable for high-precision screen printing.

[0121] Step 4, Print and fill the metal mesh: Use a custom high-precision 100% open steel plate (such as...) Figure 4As shown, the steel plate has a line width of 30μm, a thickness of 25μm, and an asymmetric hexagonal grid pattern with a period of 234μm. The steel plate is mounted on a high-precision screen printing machine (model: Dongguan Keqiao K-P2030), and the printing parameters are adjusted as follows: printing pressure 0.3MPa, squeegee speed 120mm / s, squeegee hardness 80 degrees, spacing between the squeegee and the plate 2mm, and the printing environment temperature controlled at 23±2℃. The prepared conductive silver paste is placed at one end of the steel plate. Before printing on a PET substrate, several trial prints are performed to ensure the silver paste evenly fills the screen openings. During the actual printing, the glass substrate is placed on the printing table, aligned, and the printing program is started. The silver paste fills the micro-grooves on the glass surface through the openings of the steel plate. After printing, the glass substrate is quickly transferred to a hot air circulating oven and cured at 130℃ for 20 minutes to allow the organic carrier in the silver paste to volatilize and the resin to crosslink, sintering the silver powder to form a conductive network. After curing, the glass surface is polished using a chemical mechanical polishing (CMP) machine to remove excess metal material outside the microgrooves and ensure that the upper surface of the metal mesh is precisely flush with the glass substrate surface. The polishing slurry used is an alumina suspension (0.5 μm particle size), and the polishing time is approximately 3 minutes. After polishing, the surface is ultrasonically cleaned with deionized water for 5 minutes and then dried with nitrogen. Measurements show that the resulting metal mesh has a linewidth of 30.2 μm and a thickness of 2.1 μm. A four-probe resistance meter was used to measure the sheet resistance, which was 0.09 Ω / □. Microscopic observation revealed clear lines with no breaks or burrs.

[0122] Step 5: Deposition of the transparent protective layer: The glass substrate is placed in the reaction chamber of an atomic layer deposition (ALD) apparatus. Trimethylaluminum and water are used as precursors, and deposition is performed at 100°C for 500 cycles to obtain a 50 nm thick Al₂O₃ protective layer. During deposition, the precursor pulse times are: trimethylaluminum 0.1 s, purge 10 s; water 0.1 s, purge 10 s. This protective layer uniformly covers the surface of the glass substrate and the metal mesh, forming a dense encapsulation layer. Thus, a high-durability embedded electromagnetic pulse shielding optical window (i.e., a high-durability ultra-wideband EMP shielding optical window, abbreviated as: the window) is obtained.

[0123] The performance of the optical window obtained in this embodiment was tested: Shielding effectiveness was measured in the 0.18-18 GHz frequency band according to the IEEE Std 299-2006 standard, with an average value of 89 dB; the average transmittance in the 380-780 nm range was 42% as measured by a spectrophotometer (including an integrating sphere); after placing the sample in an 85℃ / 85%RH environment for 1000 h, the shielding effectiveness decreased by only 2.1 dB; after 96 h in a 5% NaCl salt spray, the corrosion area was less than 1%, and the 3M tape peel adhesion test showed a grade of 5B. The results indicate that the optical window prepared in this embodiment possesses excellent shielding performance, optical transparency, and environmental durability.

[0124] Example 2

[0125] The only difference from Example 1 is that in step 5, the protective layer is replaced with a TiO2 / Al2O3 nanolayer. The deposition temperature is 100℃, and the deposition sequence is as follows: first deposit 10nm TiO2, then deposit 10nm Al2O3, with this bilayer as one cycle, alternating for 10 cycles, and the total thickness of the nanolayer is 100nm. The specific deposition parameters are: the TiO2 layer uses tetrakis(dimethylamino)titanium (TDMAT) and water as precursors; the TDMAT pulse time is 0.2s, followed by a 10s purge; the water pulse time is 0.1s, followed by a 10s purge; the pulse time ratio of TDMAT to water is 2:1; the TDMAT flow rate is 50 sccm; and the water flow rate is 50 sccm. The Al2O3 layer uses trimethylaluminum (TMA) and water as precursors. The TMA pulse time is 0.1s followed by 10s purging, and the water pulse time is 0.1s followed by 10s purging. The pulse time ratio of TMA to water is 1:1, the TMA flow rate is 40 sccm, and the water flow rate is 40 sccm.

[0126] Example 3

[0127] The only difference from Example 1 is that in step 2, the microgroove pattern is a square grid with a period of 200 μm, a line width of 25 μm, and an etching depth of 3 μm; in step 4, the metal grid filling is replaced by electroplating copper process instead of silver paste printing filling. The specific steps are as follows: (1) A seed layer is deposited in the microgroove using magnetron sputtering process. First, a Ti adhesion layer (thickness 30 nm) is deposited, and then a Cu conductive seed layer (thickness 150 nm) is deposited. The sputtering power is 150 W and the argon pressure is 0.5 Pa. (2) The metal is filled using electroplating copper process. The electroplating solution formula is: CuSO4·5H2O 150 g / L, H2SO4 80 g / L, and the additives are sodium polydisulfide dipropane sulfonate (SPS) 10 mg / L, polyethylene glycol (PEG, molecular weight 8000) 100 mg / L, Janus Green B (JGB) 5 mg / L, and the current density is 1.5. A / dm², electroplating time 10 minutes, to obtain a copper metal mesh with a thickness of about 2μm; (3) After electroplating, remove excess metal from the surface by chemical mechanical polishing so that the upper surface of the metal mesh is flush with the surface of the glass substrate.

[0128] Example 4

[0129] The only difference from Example 1 is that the depth of the microgroove in step 2 is 2.4 μm and the thickness of the metal mesh in step 4 is 2 μm; the other steps and parameters are the same as in Example 1.

[0130] Example 5

[0131] The only difference from Example 1 is that the depth of the microgroove in step 2 is 4.0 μm and the thickness of the metal mesh in step 4 is 2 μm; the other steps and parameters are the same as in Example 1.

[0132] Light Window Comparison Example 1

[0133] Referring to the structure of patent CN119342787A, this comparative example provides a surface multilayer film type shielding window. The preparation steps are as follows: (1) Prepare a 100μm thick PET film, clean and dry it; (2) Prepare a metal grid on the PET surface using a photolithography-development-sputtering-stripping process. The grid pattern is an asymmetric hexagonal grid with a line width of 30μm, a period of 234μm, a metal thickness of 2μm, and the metal material is silver; (3) Alternately deposit ITO film and SiO2 film on the surface of the metal grid: first deposit an ITO layer (thickness 20nm), then deposit a SiO2 layer (thickness 30nm). (nm), repeat the stacked structure 5 times, with a total thickness of 250nm. The deposition method is magnetron sputtering. The ITO target is In2O3 / SnO2 (90:10), the SiO2 target is high-purity SiO2, the sputtering power is 150W, the argon flow rate is 30sccm, the oxygen flow rate is 2sccm (only introduced during ITO deposition), and the deposition is carried out at room temperature. (4) The above PET film is bonded to a 3mm thick soda-lime glass substrate using optical adhesive (OCA). The bonding pressure is 0.2MPa, and the film is hot-pressed and cured under vacuum conditions at a temperature of 60℃ for 30 minutes to obtain the optical window comparative example 1 sample.

[0134] Light Window Comparison Example 2

[0135] The only difference from Example 1 is that step 5 is omitted.

[0136] Light Window Comparison Example 3

[0137] Referring to patent CN210075930U, this comparative example provides a "fully embedded" metal mesh shielded light window. The preparation steps are as follows: (1) Prepare two layers of PET film (both with a thickness of 100μm), clean and dry them; (2) Use screen printing technology to print conductive silver paste (using the silver paste of preparation example 1) on the surface of the lower PET film. The printing parameters are the same as step 4 of example 1. After printing, cure at 130℃ for 20 minutes to form a metal mesh with a line width of 30μm, a thickness of 2μm, and a period of 234μm; (3) Place the upper layer PET film is covered on the surface of metal grid and placed in a hot press for pressing. The hot pressing temperature is 150°C, the pressure is 1MPa, and the time is 10 minutes, so that the two PET films are melted and bonded at the gap of the metal grid, and the metal grid is completely embedded and encapsulated between the two PET films; (4) The above PET composite structure is bonded to a 3mm thick soda-lime glass substrate using optical adhesive (OCA). The bonding pressure is 0.2MPa, and the substrate is hot-pressed and cured under vacuum conditions at a temperature of 60°C for 30 minutes to obtain the light window comparative example 3 sample.

[0138] Light Window Comparison Example 4

[0139] The only difference from Example 1 is that the silver paste used for printing and filling the metal mesh is the silver paste prepared in Comparative Example 4; the other steps and parameters are the same as in Example 1.

[0140] Light Window Comparison Example 5

[0141] The only difference from Example 1 is that the silver paste used for printing and filling the metal mesh is the silver paste prepared in Silver Paste Comparative Example 5; the other steps and parameters are the same as in Example 1.

[0142] Light Window Comparison Example 6

[0143] The only difference from Example 1 is that the silver paste used for printing and filling the metal mesh is the silver paste prepared in Silver Paste Comparative Example 6; the other steps and parameters are the same as in Example 1.

[0144] Light Window Comparison Example 7

[0145] The only difference from Example 1 is that the silver paste used for printing and filling the metal mesh is the silver paste prepared in Silver Paste Comparative Example 7; the other steps and parameters are the same as in Example 1.

[0146] Light Window Comparison Example 8

[0147] The only difference from Example 1 is that the depth of the microgroove in step 2 is 1.5 μm and the thickness of the metal mesh in step 4 is 2 μm (the depth of the microgroove is only 0.75 times the thickness of the metal mesh); the other steps and parameters are the same as in Example 1.

[0148] Light Window Comparison Example 9

[0149] The only difference from Example 1 is that the depth of the microgroove in step 2 is 5 μm and the thickness of the metal mesh in step 4 is 2 μm (the depth of the microgroove is only 2.5 times the thickness of the metal mesh); the other steps and parameters are the same as in Example 1.

[0150] The optical windows prepared in the above embodiments and comparative optical windows were subjected to the following performance tests, and the overall performance is shown in Table 2.

[0151] Shielding effectiveness (SE) was measured in the 0.18-18GHz band according to IEEE Std 299-2006 standard; Optical transparency (OT) was measured using a spectrophotometer (including integrating sphere) to measure the average transmittance of 380-780nm; Environmental durability test (1) Resistance to damp heat: 85℃ / 85%RH, SE decay and appearance change were measured after 1000h; (2) Resistance to salt spray: 5% NaCl solution, corrosion was observed after 96h; (3) Adhesion: 3M tape peel test (ASTM D3359).

[0152] Table 2 Comparison of Overall Performance of Light Windows

[0153] Example 1 89 42 2.1 <1% 5B Example 2 91 40 1.8 <1% 5B Example 3 72 50 2.5 <1% 5B Example 4 86 42 2.5 <1% 5B Example 5 87 41 2.3 <1% 5B Light Window Comparison Example 1 78 45 8.7 5% 3B Light Window Comparison Example 2 88 45 15.3 25% 0B Light Window Comparison Example 3 65 38 5.6 3% 4B Light Window Comparison Example 4 82 41 6.2 4% 4B Light Window Comparison Example 5 70 40 12.5 12% 2B Light Window Comparison Example 6 85 41 4.0 2% 4B Light Window Comparison Example 7 83 42 4.5 3% 4B Light Window Comparison Example 8 75 40 10.2 8% 3B Light Window Comparison Example 9 76 38 9.8 7% 3B

[0154] As shown in Table 2, Examples 1, 2, 4, and 5 of this invention exhibit excellent performance in shielding effectiveness (≥86dB), light transmittance (≥40%), resistance to damp heat attenuation (≤2.5dB), salt spray resistance (<1% corrosion), and adhesion (5B), comprehensively outperforming the comparative examples of each light window. Example 3 uses an electroplated copper mesh, which has slightly lower shielding effectiveness (72dB), but improved light transmittance, making it still suitable for scenarios with higher light transmittance requirements.

[0155] Comparative Examples 1 (existing "surface multilayer film" structure) exhibited significant damp heat attenuation (8.7 dB), Comparative Example 2 (no protective layer) showed extremely poor weather resistance, and Comparative Example 3 (flexible sandwich) had low shielding effectiveness and insufficient durability. Comparative Examples 4-7, using different silver paste formulations, all performed worse than Example 1, demonstrating that the silver paste and structural design of this invention need to be synergistically optimized. Comparative Examples 8 and 9 show that a deviation of the microgroove depth from the range of 1.2-2 times leads to a significant decrease in weather resistance and adhesion, verifying the necessity of the depth range.

[0156] To demonstrate the preferred range of the process parameters of this invention, the curing temperature, curing time, and steel plate line width were changed separately based on Example 1 for verification. The results are as follows:

[0157] Curing temperature 120℃: sheet resistance 0.12Ω / □, adhesion 5B, good printing quality.

[0158] Curing temperature 150℃: sheet resistance 0.08Ω / □, adhesion 5B, but the fluidity of the silver paste increased slightly, and the linewidth increased to 31μm.

[0159] Curing time 15 minutes: sheet resistance 0.11Ω / □, adhesion 4B, incomplete curing leads to a slight decrease in adhesion.

[0160] Curing time 30 minutes: sheet resistance 0.09Ω / □, adhesion 5B, stable performance.

[0161] Steel plate line width 28μm: Printed line width 28.5μm, sheet resistance 0.10Ω / □.

[0162] The steel plate has a line width of 32μm; the printed line width is 32.8μm, and the sheet resistance is 0.09Ω / □. The line width is slightly increased but still within an acceptable range.

[0163] In summary, a curing temperature of 120-150℃, a curing time of 15-30 minutes, and a steel plate line width of 28-32μm can all achieve the required performance, with 130℃ / 20 minutes / 30μm being the optimal combination.

[0164] The high-durability ultra-wideband EMP shielding window provided by this invention is suitable for applications such as buildings, military vehicles, ships, and aircraft that have strict requirements for electromagnetic shielding and optical transparency and need to be exposed to harsh environments for extended periods. Its high durability, high shielding effectiveness, and good light transmittance can significantly improve the electromagnetic protection capabilities and service life of related equipment.

[0165] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A conductive silver paste, characterized in that, By weight, it includes the following raw material components: 80-90 parts silver powder, 4-8 parts organic carrier, 1.0-3.0 parts glass powder, and 0.5-2 parts additives; The silver powder is a mixture of spherical silver powder and near-spherical silver powder, wherein the median particle size D50 of the spherical silver powder is 1.0 to 2.0 μm, the median particle size D50 of the near-spherical silver powder is 2.0 to 3.5 μm, and the mass ratio of spherical silver powder to near-spherical silver powder is 1:0.8 to 1.

2. The organic carrier comprises, by weight, 0.3-2.0 parts of short-chain adhesive resin, 0.2-2.5 parts of non-polar elastomer resin, and 1.0-5.0 parts of wetting solvent.

2. The conductive silver paste according to claim 1, characterized in that, The short-chain adhesive resin is ethyl cellulose or cellulose acetate butyrate, the non-polar elastomer resin is SEBS elastomer or SBS elastomer, and the wetting solvent is dodecyl alcohol ester or diethylene glycol monobutyl ether.

3. The conductive silver paste according to claim 1, characterized in that, The additives include a thixotropic agent and a dispersant, wherein the thixotropic agent is hydrogenated castor oil and the dispersant is polyvinylpyrrolidone.

4. A method for preparing conductive silver paste according to any one of claims 1 to 3, characterized in that, Includes the following steps: Short-chain viscous resin, non-polar elastomer resin, and wetting solvent are dissolved uniformly under heating conditions to obtain an organic carrier; Add an auxiliary agent to the organic carrier and stir until homogeneous to obtain mixture A; Mixing spherical silver powder and near-spherical silver powder yields a mixed silver powder; The mixed silver powder, glass powder, and mixture A are mixed and pre-dispersed. The pre-dispersed slurry is then ground until the fineness is ≤8μm, and then filtered and degassed to obtain the conductive silver paste.

5. The application of the conductive silver paste as described in any one of claims 1 to 3 in the preparation of EMP shielding optical windows.

6. A high-durability ultra-wideband EMP shielding optical window, characterized in that, include: Transparent substrate, metal mesh, and transparent protective layer; The transparent substrate has a micro-groove array on its surface; the metal mesh fills the micro-grooves, and the upper surface of the metal mesh is flush with the surface of the transparent substrate; the transparent protective layer covers the surfaces of the transparent substrate and the metal mesh. The metal mesh is formed by printing and curing the conductive silver paste as described in any one of claims 1 to 3.

7. The high-durability ultra-wideband EMP shielding optical window according to claim 6, characterized in that, The depth of the microgroove is 1.2 to 2.0 times the thickness of the metal mesh; the linewidth of the metal mesh is 25 to 32 μm and the thickness is 1.5 to 2.5 μm; the transparent protective layer is an atomic layer deposited Al2O3, TiO2, SiO2 monolayer film or nano-stacked film with a thickness of 100 to 200 nm; the transparent substrate is a glass substrate.

8. A method for preparing a high-durability ultrawideband EMP shielding optical window according to claim 6 or 7, characterized in that, Includes the following steps: A microgroove array is fabricated on the surface of a transparent substrate; The conductive silver paste according to any one of claims 1 to 3 is filled into the microgroove, cured to form a metal mesh, and its upper surface is flush with the surface of the transparent substrate; A transparent protective layer is deposited on the surface of a transparent substrate and a metal mesh.

9. The preparation method according to claim 8, characterized in that, The step of filling the microgrooves with conductive material includes: filling the microgrooves with conductive silver paste using screen printing, followed by curing and polishing to make the metal mesh flush with the substrate surface; the screen printing uses a 100% open steel plate with a line width of 28-32 μm and a plate thickness of 20-30 μm; the printing pressure is 0.2-0.4 MPa, the squeegee speed is 80-150 mm / s, and the distance between the squeegee and the plate is 1-3 mm; the curing temperature is 120-150℃, and the curing time is 15-30 minutes; the transparent protective layer is prepared using atomic layer deposition (ALD) at a deposition temperature of 80-120℃.

10. The application of the high-durability ultra-wideband EMP shielded light window as described in claim 6 or 7 in the preparation of building skylights, vehicle observation windows, military equipment observation holes, or optoelectronic equipment protective covers.

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