A random metal grid and its preparation method

Abstract

The present invention relates to the technical field of magnetic shielding materials, and specifically discloses a random metal grid and a preparation method thereof. The method comprises: uniformly mixing a diluent and a photoresist to obtain a photoresist solution; ultrasonically spraying the photoresist solution on a substrate at 60°C-90°C to obtain an ultrasonic spraying substrate; plating a metal film on the ultrasonic spraying substrate, cleaning, and obtaining a random metal grid; wherein the diluent is a mixture of acetone and N-methylpyrrolidone; and the spraying distance between the photoresist solution and the substrate is 50mm-70mm. The metal grid prepared by the method can significantly reduce the influence of high-order stray light on imaging quality through the design of random patterns, and has the characteristics of high electromagnetic shielding efficiency and transmittance. The preparation method provided by the present invention is simple to operate and can be realized in large-scale industrial production.

Description

Technical Field

[0001] The invention relates to the technical field of magnetic shielding materials, and in particular to a random metal grid and a preparation method thereof. Background Art

[0002] With the intelligent development of weapons and equipment in complex electromagnetic combat environments, infrared optoelectronic equipment has become one of the core systems of intelligent perception. The infrared window is located at the forefront of the infrared optoelectronic system and is a key component of the structure / function integration of the infrared optoelectronic imaging system. Due to its special position and the observation function that must be realized, it has become the focus of electromagnetic shielding of equipment. The metal grid prepared on the optical window can take into account the high transmittance characteristics of the infrared band, and at the same time can effectively shield other background electromagnetic wave interference outside the infrared band to achieve stealth effect. It is also one of the most effective ways to achieve electromagnetic stealth of weapons and equipment.

[0003] At present, the widely used methods for preparing metal grids are mainly realized by laser direct writing, vacuum coating technology or photolithography development, vacuum coating technology. Although the above methods have been applied in mass production, photolithography development is only suitable for the production of planar metal grids and is highly dependent on equipment; the curved electromagnetic shielding metal grid films made based on laser direct writing technology are usually periodic square grid patterns. For example, the existing control algorithm for adjusting the angular velocity and the graphic structure of the grid formed by the intersection of periodic latitudes and longitudes have realized the laser direct writing of the grid on the concave spherical surface with a constant exposure amount, but this method needs to rely on a more accurate control algorithm, the equipment is expensive, and it is not suitable for engineering applications. Moreover, in actual use, the metal grid with periodic longitude and latitude lines cannot avoid the influence of stray light caused by high-order diffraction, thereby affecting the imaging sensitivity and accuracy of the infrared detection system. Therefore, it is urgent to provide a curved random metal grid to solve the existing problems. At present, some researchers have used the crack template method to prepare a curved random metal grid structure. However, the template is removed mainly by mechanical grinding, which will damage the metal grid to a certain extent and affect its performance. In addition, this method also uses toxic substances such as chloroform, which causes pollution. Therefore, it is urgent to provide a random metal grid with excellent performance to solve the problems of poor electromagnetic shielding performance, low transmittance and low imaging quality of the existing metal grid optical window. Summary of the invention

[0004] In view of the above problems, the present invention provides a random metal grid and a preparation method thereof. The metal grid prepared by the method can significantly reduce the influence of high-order stray light on imaging quality through the design of random patterns, and has high electromagnetic shielding efficiency and transmittance. The preparation method provided by the present invention is simple to operate and can realize large-scale industrial production.

[0005] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solutions:

[0006] A method for preparing a random metal grid comprises the following steps:

[0007] S1, mixing a diluent and a photoresist evenly to obtain a photoresist solution;

[0008] S2, ultrasonically spraying the photoresist solution on a substrate at 60° C.-90° C. to obtain an ultrasonically sprayed substrate;

[0009] S3, plating a metal film on the ultrasonic spray-coated substrate, and cleaning it to obtain a random metal grid;

[0010] The diluent is a mixture of acetone and N-methylpyrrolidone;

[0011] The spraying distance between the photoresist solution and the substrate is 50 mm to 70 mm.

[0012] Compared with the prior art, the random metal grid provided by the present invention can decompose the photoresist solution into micron-level droplets of uniform size by ultrasonic spraying, and spray the droplets on a substrate to form a coating with a random pattern, which is beneficial to the preparation of the random metal grid; the inventors have found through a large number of experiments that when the temperature of ultrasonic spraying, the spraying distance between the photoresist solution and the substrate during ultrasonic spraying, and the specific composition of the diluent are further limited, the specific temperature and the specific distance jointly control the volatilization rate of acetone and N-methylpyrrolidone. By limiting the specific volatilization rate, it can be ensured that the photoresist is also doped with a small amount of diluent when sprayed on the substrate, and it is ensured that it has a certain continuity, thereby forming ... The experiment further found that when the temperature of ultrasonic spraying, the spraying distance between the photoresist solution and the substrate during ultrasonic spraying, and the specific composition of the diluent are outside the parameter range provided by the present invention, the volatilization rate of the diluent will change. When the volatilization rate is too fast, the photoresist ultrasonically sprayed on the substrate is doped with less diluent and has poor fluidity, thereby forming a granular pattern on the substrate. When the volatilization rate is too slow, the photoresist ultrasonically sprayed on the substrate is doped with more diluent and has strong fluidity, forming a complete thin film on the substrate. All of the above situations will affect the comprehensive performance of the metal grid. Furthermore, the present invention chooses to plate a metal film on the ultrasonically sprayed substrate so that the prepared metal grid has randomness, which can significantly reduce the influence of high-order stray light on imaging quality and obtain higher electromagnetic shielding efficiency and transmittance.

[0013] Preferably, in S1, the mass ratio of acetone to N-methylpyrrolidone in the diluent is (7-9):(0.6-0.8).

[0014] By limiting the preferred diluent ratio, it is advantageous to further improve the performance of the random metal grid.

[0015] Preferably, in S1, the mass ratio of the photoresist to the diluent is 1:(7.6-9.8).

[0016] Preferably, in S1, the photoresist is photoresist AZ6130.

[0017] Preferably, before step S2, the method further includes pretreatment of the substrate, wherein the pretreatment method is to wipe the substrate with acetone and anhydrous ethanol.

[0018] As a preferred embodiment, the mass ratio of acetone to anhydrous ethanol is 4:6.

[0019] Preferably, in S2, the humidity of the chamber during the ultrasonic spraying is 45%-55%.

[0020] Preferably, in S2, the flow rate of the ultrasonic spraying is 3 mL / min-8 mL / min.

[0021] Preferably, in S2, the ultrasonic spraying is performed 2-5 times.

[0022] The preferred ultrasonic spraying flow rate and number can make the spacing between the random patterns prepared on the substrate reach 15 μm-25 μm, thereby improving the electromagnetic shielding efficiency and light transmittance of the random metal grid.

[0023] Preferably, in S2, one ultrasonic spraying is completed when the photoresist solution is sprayed all over the substrate during ultrasonic spraying.

[0024] Preferably, in S2, after the ultrasonic spraying is completed, the sample needs to be baked.

[0025] Further preferably, during the baking, the carrier gas flow rate is 0.1 MPa-0.5 MPa, the temperature is 90° C.-150° C., and the time is 1 min-5 min.

[0026] Preferably, in S3, the metal film includes a chromium film and a gold film in order from bottom to top.

[0027] Further preferably, the thickness of the gold film is 400nm-500nm.

[0028] Further preferably, the thickness of the chromium film is 40nm-60nm.

[0029] Preferably, in S3, the metal film is prepared by a vacuum evaporation coating method.

[0030] The process parameters of the vacuum evaporation coating are as follows: the vacuum degree of the vacuum chamber is 6.0×10 -4 Pa-5.0×10 -3Pa, temperature is 150℃-250℃, operating speed is 15r / min-25r / min, vacuum insulation time is 20min-40min, and cooling time after plating is 20min-30min.

[0031] Preferably, in S3, the line width of the random metal grid is 15 μm-25 μm.

[0032] Preferably, in S3, the cleaning is to use acetone to ultrasonically clean the plated substrate.

[0033] The preparation method of the random metal grid provided by the present invention is simple to operate and can realize large-scale industrial production. The random metal grid can be flexibly produced in large quantities on a substrate according to actual needs, which can reduce the influence of high-order stray light on imaging quality, and ultimately obtain higher electromagnetic shielding efficiency and high transmittance.

[0034] The present invention also provides a random metal grid, which is prepared by the above-mentioned random metal grid preparation method. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the drawings without creative work.

[0036] Figure 1 This is a coating image of a substrate after ultrasonic spraying provided in Example 1 of the present invention;

[0037] Figure 2 An imager photo of the random metal grid provided in Example 1 of the present invention;

[0038] Figure 3 This is a coating image of a substrate after ultrasonic spraying provided in Example 5 of the present invention;

[0039] Figure 4 This is a coating image of a substrate after ultrasonic spraying provided in Example 6 of the present invention;

[0040] Figure 5 This is a coating image of a substrate after ultrasonic spraying provided in Example 7 of the present invention;

[0041] Figure 6 This is a coating image of a substrate after ultrasonic spraying provided in Example 8 of the present invention;

[0042] Figure 7 This is a coating image of the substrate after ultrasonic spraying provided in Comparative Example 1 of the present invention;

[0043] Figure 8This is a coating image of the substrate after ultrasonic spraying provided in Comparative Example 2 of the present invention;

[0044] Fig. 9 This is a coating image of the substrate after ultrasonic spraying provided in Comparative Example 3 of the present invention;

[0045] Fig.10 This is a coating image of the substrate after ultrasonic spraying provided in Comparative Example 4 of the present invention;

[0046] Fig.11 This is a diagram showing the electromagnetic shielding effectiveness test of the random metal mesh grid provided in Example 1 of the present invention;

[0047] Fig.12 A test diagram of the transmittance of a random metal mesh grid provided in Example 1 of the present invention;

[0048] Fig.13 This is a diagram showing the electromagnetic shielding effectiveness test of the random metal mesh grid provided in Example 5 of the present invention;

[0049] Fig.14 A test diagram of the transmittance of a random metal mesh grid provided in Example 5 of the present invention;

[0050] Fig.15 This is a diagram showing the electromagnetic shielding effectiveness test of the random metal mesh grid provided in Example 6 of the present invention;

[0051] Fig.16 A test diagram of the transmittance of a random metal mesh grid provided in Example 6 of the present invention;

[0052] Fig.17 This is a diagram showing the electromagnetic shielding effectiveness test of the random metal mesh grid provided in Example 7 of the present invention;

[0053] Fig.18 A test diagram of the transmittance of a random metal mesh grid provided in Example 7 of the present invention;

[0054] Fig.19 This is a diagram showing the electromagnetic shielding effectiveness test of a random metal mesh grid provided in Example 8 of the present invention;

[0055] Fig. 20 This is a test diagram of the transmittance of the random metal mesh grid provided in Example 8 of the present invention;. DETAILED DESCRIPTION

[0056] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0057] Example 1

[0058] This embodiment provides a method for preparing a random metal grid, comprising the following steps:

[0059] S1, mixing a diluent and a photoresist uniformly to obtain a photoresist solution; wherein the diluent is a mixture of acetone and N-methylpyrrolidone in a mass ratio of 9:0.8, and the mass ratio of the photoresist to the diluent is 1:9.8;

[0060] S2, using a mixture of acetone and anhydrous ethanol in a mass ratio of 4:6 to wipe a substrate with a size of 150nm×150nm, placing the cleaned substrate in a glue sprayer, controlling the chamber humidity to 45%, the heating plate temperature to 60°C, setting the spraying distance between the substrate and the nozzle to 50mm, the X-axis spacing to 70mm, the X-axis glue spraying speed to 200mm / s, the Y-axis spacing to 6mm, the Y-axis glue spraying speed to 70mm / s, the ultrasonic glue spraying flow rate to 3mL / min, spraying twice, baking after ultrasonic spraying, controlling the carrier gas flow rate to 0.1MPa, the baking temperature to 90°C, and the baking time to 1min, to obtain an ultrasonic sprayed substrate;

[0061] S3, a metal film is plated on the ultrasonic spraying substrate by vacuum evaporation coating method, the metal film is a chromium film with a thickness of 60nm and a gold film with a thickness of 400nm from the ultrasonic spraying substrate, and the plating parameters are: vacuum degree of 6.0×10 - 4 Pa, temperature is 150℃, operating speed is 25r / min, vacuum holding time is 20min, cooling time after plating is 20min, and the substrate after plating is ultrasonically cleaned with acetone to obtain a random metal grid.

[0062] Use an imager to detect random metal grids on the substrate surface, such as Figure 2 As shown, the line width of the random metal grid is 19 μm.

[0063] Example 2

[0064] This embodiment provides a method for preparing a random metal grid, comprising the following steps:

[0065] S1, mixing a diluent and a photoresist evenly to obtain a photoresist solution; wherein the diluent is a mixture of acetone and N-methylpyrrolidone in a mass ratio of 7:0.6, and the mass ratio of the photoresist to the diluent is 1:7.6;

[0066] S2, using a mixture of acetone and anhydrous ethanol in a mass ratio of 4:6 to wipe a fairing with a diameter of 90nm and a radius of curvature of 60mm, placing the cleaned fairing in a glue sprayer, controlling the chamber humidity to 50%, the heating plate temperature to 90°C, setting the spraying distance between the fairing and the nozzle to 70mm, the X-axis spacing to 70mm, the X-axis spraying speed to 200mm / s, the Y-axis spacing to 6mm, the Y-axis spraying speed to 70mm / s, the ultrasonic glue spraying flow rate to 8mL / min, spraying 5 times, baking after ultrasonic spraying, controlling the carrier gas flow rate to 0.5MPa, the baking temperature to 150°C, and the baking time to 5min, to obtain an ultrasonic sprayed fairing;

[0067] S3, a metal film is plated on the ultrasonic spray fairing by a vacuum evaporation coating method, and the metal film is a chromium film with a thickness of 40nm and a gold film with a thickness of 500nm from the ultrasonic spray substrate in sequence, and the plating parameters are: vacuum degree of 5.0×10 - 3 Pa, temperature is 250℃, operating speed is 15r / min, vacuum holding time is 40min, cooling time after plating is 30min, and acetone is used to ultrasonically clean the plated substrate to obtain a random metal grid.

[0068] The random metal grid on the surface of the fairing is inspected using an imager, and the line width of the random metal grid is 22μm.

[0069] Example 3

[0070] This embodiment provides a method for preparing a random metal grid, comprising the following steps:

[0071] S1, mixing a diluent and a photoresist uniformly to obtain a photoresist solution; wherein the diluent is a mixture of acetone and N-methylpyrrolidone in a mass ratio of 7:0.8, and the mass ratio of the photoresist to the diluent is 1:7.8;

[0072] S2, using a mixture of acetone and anhydrous ethanol in a mass ratio of 4:6 to wipe a fairing with a diameter of 90nm and a radius of curvature of 60mm, placing the cleaned fairing in a glue sprayer, controlling the chamber humidity to 55%, the heating plate temperature to 70°C, setting the spraying distance between the substrate and the nozzle to 60mm, the X-axis spacing to 70mm, the X-axis spraying speed to 200mm / s, the Y-axis spacing to 6mm, the Y-axis spraying speed to 70mm / s, the ultrasonic glue spraying flow rate to 5mL / min, spraying 3 times, baking after ultrasonic spraying, controlling the carrier gas flow rate to 0.3MPa, the baking temperature to 100°C, and the baking time to 2min, to obtain an ultrasonic sprayed substrate;

[0073] S3, a metal film is plated on the ultrasonic spraying substrate by a vacuum evaporation coating method, wherein the metal film is a chromium film with a thickness of 50 nm and a gold film with a thickness of 450 nm from the ultrasonic spraying substrate in sequence, and the plating parameters are: vacuum degree of 6.0×10 - 4 Pa, temperature is 200℃, operating speed is 20r / min, vacuum holding time is 30min, cooling time after plating is 25min, and the substrate after plating is ultrasonically cleaned with acetone to obtain a random metal grid.

[0074] The random metal grid on the surface of the fairing is inspected using an imager, and the line width of the random metal grid is 15 μm.

[0075] Example 4

[0076] This embodiment provides a method for preparing a random metal grid, comprising the following steps:

[0077] S1, mixing a diluent and a photoresist uniformly to obtain a photoresist solution; wherein the diluent is a mixture of acetone and N-methylpyrrolidone in a mass ratio of 9:0.6, and the mass ratio of the photoresist to the diluent is 1:9.6;

[0078] S2, using a mixture of acetone and anhydrous ethanol in a mass ratio of 4:6 to wipe a substrate with a size of 150nm×150nm, placing the cleaned substrate in a glue sprayer, controlling the chamber humidity to 50%, the heating plate temperature to 70°C, setting the spraying distance between the substrate and the nozzle to 60mm, the X-axis spacing to 70mm, the X-axis spraying speed to 200mm / s, the Y-axis spacing to 6mm, the Y-axis spraying speed to 70mm / s, the ultrasonic glue spraying flow rate to 7mL / min, spraying 4 times, baking after ultrasonic spraying, controlling the carrier gas flow rate to 0.3MPa, the baking temperature to 110°C, and the baking time to 3min, to obtain an ultrasonic sprayed substrate;

[0079] S3, a metal film is plated on the ultrasonic spraying substrate by a vacuum evaporation coating method, wherein the metal film is a chromium film with a thickness of 55 nm and a gold film with a thickness of 460 nm from the ultrasonic spraying substrate in sequence, and the plating parameters are: vacuum degree of 6.0×10 - 4 Pa, temperature is 200℃, operating speed is 20r / min, vacuum holding time is 35min, cooling time after plating is 22min, and acetone is used to ultrasonically clean the plated substrate to obtain a random metal grid.

[0080] The random metal grid on the surface of the fairing is inspected using an imager, and the line width of the random metal grid is 25 μm.

[0081] Example 5

[0082] This embodiment provides a method for preparing a metal grid, which is different from Embodiment 1 in that:

[0083] The ultrasonic spraying flow rate was reduced to 2 mL / min, and the other preparation methods were the same as those in Example 1.

[0084] Example 6

[0085] This embodiment provides a method for preparing a metal grid, which is different from Embodiment 1 in that:

[0086] The ultrasonic spraying flow rate was increased to 10 mL / min, and the other preparation methods were the same as those in Example 1.

[0087] Example 7

[0088] This embodiment provides a method for preparing a metal grid, which is different from Embodiment 1 in that:

[0089] The number of ultrasonic spraying was increased to 6 times, and the other preparation methods were the same as those in Example 1.

[0090] Example 8

[0091] This embodiment provides a method for preparing a metal grid, which is different from Embodiment 1 in that:

[0092] The number of ultrasonic spraying times was reduced to 1, and the other preparation methods were the same as those in Example 1.

[0093] Comparative Example 1

[0094] This comparative example provides a method for preparing a metal grid, which is different from Example 1 in that:

[0095] N-methylpyrrolidone was replaced by an equal amount of 1,4-butyrolactone, and the other preparation methods were the same as those in Example 1.

[0096] Comparative Example 2

[0097] This comparative example provides a method for preparing a metal grid, which is different from Example 1 in that:

[0098] N-methylpyrrolidone was replaced by an equal amount of acetone, and the other preparation methods were the same as those in Example 1.

[0099] Comparative Example 3

[0100] This comparative example provides a method for preparing a metal grid, which is different from Example 1 in that:

[0101] The spraying distance between the substrate and the nozzle was set to 90 mm, and the other preparation methods were the same as those in Example 1.

[0102] Comparative Example 4

[0103] This comparative example provides a method for preparing a metal grid, which is different from Example 1 in that:

[0104] The spraying distance between the substrate and the nozzle was set to 40 mm, and the other preparation methods were the same as those in Example 1.

[0105] The electromagnetic shielding effectiveness is tested according to GJB8820-2015. Specifically, a signal source and a transmitting antenna form a signal transmitting system, and a spectrum analyzer and a receiving antenna form a signal receiving system. The transmitting antenna and the receiving antenna are in vertical polarization mode and aligned with the center of the test window for testing.

[0106] The transmittance is tested according to Article 6.3 of JC / T 185-2013 (2017) "Optical Quartz Glass".

[0107] Depend on Figure 1-2 11-12, it can be seen that the random pattern in the coating after spraying obtained in Example 1 of the present invention has a certain spacing, the line width of the prepared metal grid is 19μm, and the distance between the grid lines of the grid is appropriate, which can simultaneously have high electromagnetic shielding effectiveness and transmittance, and its electromagnetic shielding effectiveness is 20dB, and the transmittance is 86%; in Example 5, due to the reduction of the flow rate of ultrasonic spraying, the photoresist and diluent sprayed per unit time are less, Figure 3 , 13 -14, it can be seen that the photoresist spacing is large, the line width is large, and the distance between the grid lines is small, resulting in a high shielding efficiency of the metal grid, reaching 24dB, and a low transmittance of 82%; in Example 6, due to the increase in ultrasonic spray flow, Figure 4 , 15 -16, it can be seen that the photoresist is more adhered, resulting in a long distance between the grid lines in the metal grid, resulting in the electromagnetic shielding efficiency of the metal grid being too low, as low as 17dB, and the transmittance is high, reaching 88%; in Example 7, the number of spraying times was increased, Figure 5 , 17 -18, it can be seen that the photoresist adhesion is large, the line width is reduced, and the distance between the grid lines is too large, resulting in the electromagnetic shielding efficiency of the metal grid being too low, as low as 15dB, and the transmittance is relatively high, reaching 90%; Example 8 can be seen that when the number of spraying times is reduced, Figure 6 , 19 -20, it can be seen that the spacing between the photoresists is large, the line width increases, and the grid line spacing decreases, resulting in a relatively high electromagnetic shielding performance of the metal grid, reaching 22dB, and a low transmittance, as low as 84%; Comparative Example 1-2 changes the composition of the diluent, Figure 7-8It can be seen that after replacing the diluent, the photoresist has strong fluidity, and a nearly complete thin film coating is formed on the substrate, and a metal grid cannot be prepared; in Comparative Example 3, the volatilization rate of the diluent is changed due to the long spraying distance between the substrate and the nozzle. Fig. 9 It can be seen that the mobile phase of the photoresist is deteriorated, thereby forming a granular pattern on the substrate, and the metal grid cannot be further prepared; in Comparative Example 4, the volatilization rate of the diluent is changed due to the close spraying distance between the substrate and the nozzle. Fig.10 It can be seen that the photoresist has good fluidity and forms a nearly complete thin film coating on the substrate, but it is impossible to prepare a metal grid.

[0108] The test performance of the metal grids prepared in Examples 2-4 can achieve the same technical effect as that of Example 1.

[0109] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modification, equivalent substitution or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a random metal grid, characterized in that: The following steps are involved: S1, mixing a diluent and a photoresist evenly to obtain a photoresist solution; S2, ultrasonically spraying the photoresist solution on a substrate at 60° C.-90° C. to obtain an ultrasonically sprayed substrate; S3, plating a metal film on the ultrasonic spray-coated substrate, and cleaning it to obtain a random metal grid; The diluent is a mixture of acetone and N-methylpyrrolidone; The spraying distance between the photoresist solution and the substrate is 50 mm to 70 mm.

2. The method for preparing a random metal grid according to claim 1, characterized in that: In S1, the mass ratio of acetone to N-methylpyrrolidone in the diluent is (7-9):(0.6-0.8).

3. The method for preparing a random metal grid according to claim 1, characterized in that: In S1, the mass ratio of the photoresist to the diluent is 1:(7.6-9.8).

4. The method for preparing a random metal grid according to claim 1, characterized in that: In S2, the humidity of the chamber during the ultrasonic spraying is 45%-55%.

5. The method for preparing a random metal grid according to claim 1, characterized in that: In S2, the flow rate of the ultrasonic spraying is 3 mL / min-8 mL / min.

6. The method for preparing a random metal grid according to claim 1, characterized in that: In S2, the ultrasonic spraying is performed 2-5 times.

7. The method for preparing a random metal grid according to claim 1, characterized in that: In S3, the metal film includes a chromium film and a gold film in order from bottom to top.

8. The method for preparing a random metal grid according to claim 7, characterized in that: The thickness of the gold film is 400nm-500nm; and / or The thickness of the chromium film is 40nm-60nm.

9. The method for preparing a random metal grid according to claim 1, characterized in that: In S3, the line width of the random metal grid is 15 μm-25 μm.

10. A random metal grid, characterized in that: The random metal grid is prepared by the preparation method of any one of claims 1 to 9.

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