Electromagnetic shielding film with metal grid and preparation method thereof

Abstract

The invention provides an electromagnetic shielding film with a metal grid and a preparation method of the electromagnetic shielding film. The preparation method comprises the following steps: S1, pulling a substrate material placed in a crack solution, and drying to obtain a crack film; s2, in a vacuum state, a connecting layer material and a metal layer material are sequentially deposited on the crack film, then pressure maintaining treatment is carried out, and a film coating sample is obtained after cooling; and S3, carrying out photoresist removal treatment on the coated sample to obtain the electromagnetic shielding film with the metal grid structure. According to the preparation method, through preparation of the crack film, the connecting layer and the metal layer, the effects of simple process and low preparation cost are achieved, and the problems that a traditional photoetching process is complex, high in cost and not suitable for preparation of a large-area transparent conductive film and batch production are solved; in addition, the electromagnetic shielding film prepared by the method has relatively high transparency, excellent conductivity and relatively good electromagnetic shielding effectiveness.

Description

Technical Field

[0001] The present invention belongs to the technical field of preparation of optical coating materials and optical films, and particularly relates to an electromagnetic shielding film with a metal grid and a preparation method thereof. Background Art

[0002] Due to its unique high transparency and excellent electrical conductivity, metal mesh transparent electromagnetic shielding film has a wide range of applications in various fields, such as electronic displays, new energy, automotive, and smart wearable devices. Metal mesh transparent electromagnetic shielding film has a huge market demand and currently faces a significant shortage, showing broad market prospects.

[0003] The existing technology uses traditional photolithography technology for preparation. The main process is: substrate selection - photoresist coating - mask preparation - exposure - development - metal film deposition - etching - desizing - cleaning - performance testing. Its advantages are: it can prepare high-precision, high-resolution metal grid transparent conductive films, which are suitable for applications with high performance requirements; disadvantages: the preparation process of this method is cumbersome, the photolithography process cost is high, it is not conducive to large-scale production, and it will generate a large amount of waste gas and wastewater, which has a certain impact on the environment.

[0004] Therefore, there is an urgent need for a method for preparing an electromagnetic shielding film with a metal grid, which has the characteristics of convenient process, is conducive to large-scale production, and the prepared electromagnetic shielding film has high transparency, excellent conductivity and good electromagnetic shielding effectiveness. Summary of the Invention

[0005] To overcome the drawbacks of existing preparation methods, which are unfavorable for large-scale production and resultant electromagnetic shielding films with poor transparency, conductivity, and electromagnetic shielding effectiveness, the present invention provides an electromagnetic shielding film comprising a metal grid and a preparation method thereof. This preparation method, through the preparation of a cracked thin film, a connecting layer, and a metal layer, achieves a simple process and low production costs. This overcomes the problems of traditional photolithography processes, which are complex and costly and unsuitable for the preparation of large-area transparent conductive films and mass production. Furthermore, the electromagnetic shielding film produced by this method exhibits high transparency, excellent conductivity, and good electromagnetic shielding effectiveness.

[0006] The present invention achieves the above technical effects through the following technical solutions:

[0007] The present invention provides a method for preparing an electromagnetic shielding film with a metal grid structure, which includes the following steps: S1, pulling a base material placed in a crack solution, and obtaining a crack film after drying; the pulling speed is greater than or equal to 55μm / s; S2, under a vacuum state, depositing a connecting layer material and a metal layer material on the crack film in sequence, and then performing a pressure holding treatment, and obtaining a coating sample after cooling; the connecting layer material is at least one of Cr, SiO2 and Al2O3; S3, performing a degumming treatment on the coating sample to obtain an electromagnetic shielding film with a metal grid structure; the degumming treatment includes placing the coating sample in an ultrasonic cleaning device containing an organic solvent for ultrasonic treatment.

[0008] In the present invention, by using a specific material as the connecting layer, the adhesion between the metal layer and the base layer can be effectively improved, thereby improving the mechanical strength of the electromagnetic shielding film.

[0009] In some embodiments, in step S1, the substrate material includes quartz glass, sapphire, or thermoplastic polyester.

[0010] In a specific embodiment, the type of the quartz glass includes K9, JGS1, JGS2 or JGS3.

[0011] In a specific embodiment, the thermoplastic polyester comprises PET.

[0012] In some embodiments, in step S1, the crack solution includes water-based acrylic resin.

[0013] In the present invention, the pattern on the cracked film can be observed by a metallographic microscope, and the crack depth on the cracked film can be tested by a step profiler to obtain crack period, width and depth data.

[0014] In step S1 of the present invention, “pulling the base material placed in the crack solution” is conventionally understood in the art, and refers to “directly pulling the base material from the crack solution”.

[0015] In step S1 of the present invention, the pulling equipment adopts a PTL-MMB02 vertical pulling machine.

[0016] In the present invention, when the pulling speed is low, such as less than 55 μm / s, the crack period, depth, and width are all large. Large crack period and width can reduce the electromagnetic shielding effectiveness of the electromagnetic shielding film. A large crack depth hinders subsequent film deposition, preventing deposited particles from reaching the crack bottom, resulting in gaps and breakpoints. When the pulling speed is greater than or equal to 55 μm / s, the crack period, depth, and width tend to stabilize.

[0017] In some embodiments, in step S1, the pulling speed is 55-80 μm / s; under this condition, the crack period, depth, and width change slightly and are basically stable.

[0018] In a specific embodiment, the pulling speed is 60-80 μm / s.

[0019] In one embodiment, the pulling speed is 60 μm / s.

[0020] In some embodiments, in step S1, the substrate material is placed in the crack solution for a holding time of 5-30 minutes.

[0021] In some embodiments, in step S1, the base material undergoes a first cleaning treatment, and the first cleaning treatment step includes: cleaning in an ultrasonic cleaning device for 10 minutes and then centrifuging and drying.

[0022] In some embodiments, in step S1, the diameter of the base material is within 200 mm. The base material of this size can correspond to the above-mentioned pulling speed and can obtain a crack film with corresponding crack period, depth, and width.

[0023] In some embodiments, in step S1, the drying time is 8-15 hours.

[0024] In step S2 of the present invention, the deposition equipment may include a 1300 type vacuum coating machine equipped with a dual electron gun, a quartz crystal monitoring system, and a cryogenic pump and a dry pump oil-free exhaust system.

[0025] In some embodiments, in step S2, the vacuum degree in the vacuum state is 2.0×10 -4 Pa and above.

[0026] In step S2 of the present invention, the connection layer and the metal layer may be sequentially deposited on one side of the crack to form a single-sided structure.

[0027] In some embodiments, in step S2, the connection layer and the metal layer are sequentially deposited on both sides of the crack film to form a double-sided structure of "metal layer-connection layer-base layer-connection layer-metal layer".

[0028] In step S2 of the present invention, the deposition method includes electron beam evaporation.

[0029] In some embodiments, in step S2, the deposition temperature is 70-90°C.

[0030] In one embodiment, in step S2, the deposition temperature is 80°C.

[0031] In some embodiments, in step S2, the deposition rate of the connecting layer material is 0.5-2 nm / s.

[0032] In a specific embodiment, the deposition rate of the connecting layer material is 1-1.2 nm / s.

[0033] In one embodiment, the deposition rate of the connecting layer material is 1.2 nm / s.

[0034] In some embodiments, in step S2, the deposition rate of the metal layer material is 0.5-2 nm / s.

[0035] In a specific embodiment, the deposition rate of the metal layer material is 1.3-1.5 nm / s.

[0036] In one embodiment, the deposition rate of the connecting layer material is 1.5 nm / s.

[0037] In some embodiments, in step S2, in the coating sample, the thickness of the connection layer formed by depositing the connection layer material is 25-50 nm.

[0038] In a specific embodiment, the thickness of the connecting layer is 30-40 nm.

[0039] In one embodiment, the thickness of the connecting layer is 40 nm.

[0040] In some embodiments, in step S2, in the coating sample, the thickness of the metal layer formed by depositing the metal layer material is 350-500 nm.

[0041] In a specific embodiment, the thickness of the metal layer is 450-500 nm.

[0042] In one embodiment, the thickness of the metal layer is 450 nm.

[0043] In some embodiments, in step S2, the metal layer material includes Ag, Al, Au or Cu.

[0044] In some embodiments, in step S2, the pressure maintaining treatment time is 20-40 minutes.

[0045] In some embodiments, in step S2, after the pressure holding treatment is completed, vacuuming and heating are stopped.

[0046] In some embodiments, in step S2, the cooling method includes natural cooling.

[0047] In some embodiments, in step S2, the end temperature of the cooling is room temperature; "room temperature" is commonly understood in the art, i.e., 20-25°C.

[0048] In the present invention, the cracked film in step S1 has glue formed after the base material dries, and needs to be de-glueed before a metal mesh can be formed; otherwise, the glue will fill the metal mesh. However, the traditional static sol-gel technology can only be used when the thickness of the metal deposition is very thin relative to the depth of the gap. In comparison, the ultrasonic dissolution method can solve the problem of de-glueing the cracked film when the thickness of the metal layer is large.

[0049] In some embodiments, in step S3, after the desizing process, the coated sample is subjected to a second cleaning process.

[0050] In a specific embodiment, the power of the ultrasonic treatment is 20-200W.

[0051] In a specific embodiment, the ultrasonic treatment time is 5-60 min.

[0052] In a specific embodiment, the organic solvent includes propylene glycol butyl ether.

[0053] In a specific embodiment, the second cleaning process includes: placing the film-coated sample after the debonding process in an acetone solution, taking it out, and drying it with nitrogen.

[0054] The present invention also provides an electromagnetic shielding film having a metal grid structure, which is prepared by the preparation method described above. The electromagnetic shielding film comprises a base layer, a connecting layer and a metal layer stacked in sequence.

[0055] In some embodiments, the electromagnetic shielding film includes a first metal layer, a first connection layer, a base layer, a second connection layer, and a second metal layer stacked in sequence.

[0056] In some embodiments, the substrate material includes quartz glass, sapphire, or thermoplastic polyester; the connecting layer material is at least one of Cr, SiO2, and Al2O3; and the metal layer material includes Ag, Al, Au, or Cu.

[0057] In the present invention, the thickness of the base material can be determined according to usage requirements.

[0058] In some embodiments, the connecting layer has a thickness of 25-50 nm.

[0059] In some embodiments, the thickness of the metal layer is 350-500 nm.

[0060] In some embodiments, the electromagnetic shielding film has an average transmittance of greater than 70% in the 400-700 nm wavelength range.

[0061] In some embodiments, the electromagnetic shielding film has a square resistance of 3 to 4 Ω / square.

[0062] In some embodiments, the electromagnetic shielding effectiveness of the electromagnetic shielding film is greater than 60 dB.

[0063] In one embodiment of the present invention, water-based acrylic resin is used as the crack material, and a crack film is prepared by a pulling method; then, a connecting layer and a metal film layer are prepared by vacuum evaporation technology, and finally, an ultrasonic wave combined with propylene glycol butyl ether organic solvent is used to remove the crack material to obtain an electromagnetic shielding film with a metal grid structure.

[0064] The beneficial technical effects of the present invention include at least one of the following:

[0065] 1. The preparation method of the present invention has a simple process and low manufacturing cost, and is suitable for large-scale industrial production. It solves the problems of traditional photolithography process being complex, high cost, and unsuitable for preparing large-area transparent conductive films and mass production.

[0066] 2. The electromagnetic shielding film prepared by the preparation method of the present invention has high transparency, excellent conductivity and good electromagnetic shielding effectiveness; specifically, the average transmittance in the 400-700nm band is above 70%, the square resistance is 3-4Ω / square, and the electromagnetic shielding effectiveness is above 60dB.

[0067] 3. The electromagnetic shielding film with a metal grid of the present invention can be widely used in various transparent electromagnetic shielding windows. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] Figure 1 This is a front test image of the cracked film in step 2 of Example 1 of the present invention;

[0069] Figure 2 This is a backside test image of the cracked film in step 2 of Example 1 of the present invention;

[0070] Figure 3 Schematic diagram of the cross-sectional structure of the electromagnetic shielding film according to Example 1 of the present invention;

[0071] Figure 4 This is a SEM image of the Cr-Cu electromagnetic shielding film of Example 1 of the present invention;

[0072] Figure 5 This is an EDS image of the Cr-Cu electromagnetic shielding film of Example 1 of the present invention;

[0073] Figure 6The electromagnetic shielding effectiveness test results of the Cr-Cu electromagnetic shielding film of Example 1 of the present invention;

[0074] Figure 7 The graphs of the pulling speed and the crack cycle during the preparation of the electromagnetic shielding films of Examples 1-3 and Comparative Examples 1-5 are shown;

[0075] Figure 8 The graphs show the pulling speed and crack size distribution during the preparation of the electromagnetic shielding films of Examples 1-3 and Comparative Examples 1-5. DETAILED DESCRIPTION

[0076] The present invention is further illustrated by way of examples below, but the present invention is not limited to the scope of the examples. Experimental methods in the following examples where specific conditions are not specified were performed according to conventional methods and conditions, or selected according to the product specifications.

[0077] Example 1

[0078] This embodiment provides an electromagnetic shielding film having a metal grid and a method for preparing the same. The deposition process in the method uses a 1300 vacuum coating machine equipped with a dual electron gun, a quartz crystal monitoring system, and a cryopump and dry pump oil-free exhaust system.

[0079] The preparation method specifically comprises the following steps:

[0080] Step 1: Cleaning: Use an ultrasonic cleaner to clean the quartz glass JGS1 (base material) for 10 minutes, and then use a high-speed centrifugal dryer to dry it;

[0081] Step 2: Preparation of a crack film: The cleaned quartz glass JGS1 is placed in a crack solution of an aqueous acrylic resin for 15 minutes. The substrate is slowly pulled upward at a speed of 60 μm / s using a pulling device (e.g., a PTL-MMB02 vertical puller) to obtain a crack film. The crack film is then dried in a cool place for 10 hours. The crack solution undergoes self-decomposition to obtain a crack film with random cracks.

[0082] The crack film was measured using a metallographic microscope (20x). Figure 1 and Figure 2 As shown, Figure 1 and Figure 2 These are the test images of the front and back of the cracked film obtained in this step. It can be seen that the crack patterns on both sides are basically the same, the crack morphology is clean, and the lines between the crack networks are well connected.

[0083] Step 3, coating: Place the cracked film on the sample holder of the 1300 vacuum coating machine, evacuate the vacuum chamber, and heat the cracked film to 80°C; when the vacuum degree reaches 2.0×10-4 At Pa, deposition treatment was started on both sides of the film: first, a 40nm thick Cr film was deposited at a rate of 1.2nm / s as a connecting layer; second, a 450nm thick Cu film was deposited on the Cr film at a rate of 1.5nm / s as a metal film to obtain a coated sample;

[0084] Step 4, pressure holding: After the deposition process is completed, maintain it for 30 minutes (to allow the coated sample to fully stabilize), then stop vacuuming and heating, start cooling naturally, and take out the sample when it reaches room temperature;

[0085] Step 5, degumming: Place the coated sample in an ultrasonic cleaning machine, add propylene glycol butyl ether organic solvent, ultrasonic power 50W, ultrasonic for 20 minutes to complete the degumming;

[0086] Step 6, cleaning: placing the sample after degumming in an acetone solution for 30 minutes to remove the remaining surface impurities, and drying with nitrogen to obtain an electromagnetic shielding film with a metal grid structure.

[0087] Figure 3 The figure is a schematic cross-sectional view of the electromagnetic shielding film of this embodiment. The electromagnetic shielding film comprises a first metal layer, a first connecting layer, a base layer, a second connecting layer, and a second metal layer stacked in sequence. The base layer is made of quartz glass JGS1; the first and second connecting layers are made of Cr with a thickness of 40 nm; and the first and second metal layers are made of Cu with a thickness of 450 nm. Based on the materials of the connecting layer and the metal layer, this electromagnetic shielding film is also referred to as a Cr-Cu electromagnetic shielding film.

[0088] Effect Example 1

[0089] This effect example tests the light transmittance, electrical conductivity and electromagnetic shielding effectiveness of the electromagnetic shielding film with a metal grid of Example 1.

[0090] (1) Transmittance test: Using a UV-visible-near infrared spectrophotometer (manufacturer: PE company, model: lambda1050+), set the test wavelength to 400-700nm and the sampling interval to 1nm; the transmittance of the electromagnetic shielding film with metal grid in the visible light range is measured as follows: Figure 4 As shown, Figure 4 : is a SEM image of the Cr-Cu electromagnetic shielding film. It can be seen that the average transmittance of the electromagnetic shielding film of Example 1 in the 400-700 nm wavelength range is 72.7%.

[0091] (2) Conductivity test: Use a four-probe instrument (brand: KLA-Filmetrics, model: R50 / 54) to test the square resistance of the A and B sides of the Cr-Cu electromagnetic shielding film. The test results are as follows: Figure 5 As shown, Figure 5 The EDS image of the Cr-Cu electromagnetic shielding film shows that the square resistance of both the front and back surfaces of the electromagnetic shielding film is (3.4±0.4) Ω / square, demonstrating good electrical conductivity.

[0092] (3) Electromagnetic shielding effectiveness test: The electromagnetic shielding effectiveness test of the prepared Cr-Cu electromagnetic shielding film was carried out on one or both sides in the Ku band (12-18 GHz) using the waveguide method. Figure 6 As shown in the figure, the electromagnetic shielding effectiveness of the electromagnetic shielding film is above 60dB, with an average of about 65dB; among them, the shielding effectiveness at 12.4GHz is 54dB, which may be a test error.

[0093] Examples 2-3

[0094] This set of examples discloses an electromagnetic shielding film having a metal grid and a method for preparing the same. The only difference from Example 1 is that in step 2, the substrate is pulled at speeds of 70 μm / s and 80 μm / s; otherwise, all other conditions are the same as in Example 1.

[0095] Comparative Examples 1 to 5

[0096] This comparative example discloses an electromagnetic shielding film having a metal grid and a method for preparing the same. The only difference between this comparative example and Example 1 is that, in step 2, the substrate pulling speed is 10 μm / s, 20 μm / s, 30 μm / s, 40 μm / s, and 50 μm / s; otherwise, all other conditions are the same as in Example 1.

[0097] Figure 7 The curves of pulling speed and crack cycle of Examples 1-3 and Comparative Examples 1-5 are shown; Figure 8 The curves of the pulling speed and crack size distribution of Examples 1-3 and Comparative Examples 1-5 are shown in FIG. Figure 7 and 8 It can be seen that when the pulling speed is low (less than or equal to 50μm / s), the period, depth and width of the crack are all large; when the period and width of the crack are both large, the electromagnetic shielding effect of the electromagnetic shielding film will decrease; when the depth of the crack is large, it is not conducive to the subsequent film deposition, and the deposited particles cannot reach the bottom of the crack smoothly, which will cause defects and breakpoints at the bottom of the crack.

Claims

1. A method for preparing an electromagnetic shielding film having a metal grid structure, characterized in that: It includes the following steps: S1. Pulling the base material placed in the crack solution to obtain a crack film after drying; the pulling speed is greater than or equal to 55 μm / s; S2. Depositing a connecting layer material and a metal layer material on the cracked film in sequence under vacuum, then performing a pressure-maintaining treatment, and obtaining a coating sample after cooling; the connecting layer material is at least one of Cr, SiO2, and Al2O3; S3. Performing a degumming treatment on the film-coated sample to obtain an electromagnetic shielding film having a metal grid structure; the degumming treatment comprises placing the film-coated sample in an ultrasonic cleaning device containing an organic solvent for ultrasonic treatment.

2. The preparation method according to claim 1, wherein Step S1 satisfies at least one of the following conditions: ① The substrate material includes quartz glass, sapphire or thermoplastic polyester; ② The crack solution includes water-based acrylic resin; ③ The pulling speed is 55-80 μm / s; ④ The substrate material is placed in the crack solution for a retention time of 5-30 minutes; ⑤ The base material undergoes a first cleaning process, wherein the first cleaning process comprises: cleaning in an ultrasonic cleaning device for 10 minutes and then centrifuging and drying; ⑥ The diameter of the base material is within 200 mm; ⑦ The drying time is 8-15 hours.

3. The preparation method according to claim 2, wherein Step S1 satisfies at least one of the following conditions: ① The type of quartz glass includes K9, JGS1, JGS2 or JGS3; ② The thermoplastic polyester includes PET; ③ The pulling speed is 60 to 80 μm / s.

4. The preparation method according to claim 1, wherein Step S2 satisfies at least one of the following conditions: ① The vacuum degree under the vacuum state is 2.0×10 -4 Pa and above; ② The connection layer and the metal layer are sequentially deposited on both sides of the crack film; ③ The deposition temperature is 70-90°C; ④ The deposition rate of the connecting layer material is 0.5-2 nm / s; ⑤ The deposition rate of the metal layer material is 0.5-2 nm / s; ⑥ In the coating sample, the thickness of the connecting layer formed by depositing the connecting layer material is 25-50 nm; ⑦ In the coating sample, the thickness of the metal layer formed by depositing the metal layer material is 350-500 nm; ⑧The metal layer material includes Ag, Al, Au or Cu.

5. The preparation method according to claim 4, wherein Step S2 satisfies at least one of the following conditions: ① The deposition rate of the connecting layer material is 1-1.2 nm / s; ② The deposition rate of the metal layer material is 1.3-1.5 nm / s; ③ The thickness of the connecting layer is 30-40 nm; ④ The thickness of the metal layer is 450-500nm.

6. The preparation method according to claim 1, wherein Step S2 satisfies at least one of the following conditions: ① The pressure holding treatment time is 20-40 minutes; ② After completing the pressure holding treatment, stop vacuuming and heating; ③ The cooling method includes natural cooling; ④ The terminal temperature of the cooling is room temperature.

7. The preparation method according to claim 1, wherein In step S3, after the degumming treatment, the coated sample is subjected to a second cleaning treatment; the degumming treatment or the second cleaning treatment satisfies at least one of the following conditions: ① The power of the ultrasonic treatment is 20-200W; ② The ultrasonic treatment time is 5-60min; ③ The organic solvent includes propylene glycol butyl ether; ④ The second cleaning process includes: placing the coated sample after the degumming process in an acetone solution, taking it out and blowing it dry with nitrogen.

8. An electromagnetic shielding film having a metal grid structure, characterized in that: It is prepared by the preparation method according to any one of claims 1 to 7, and the electromagnetic shielding film comprises a base layer, a connecting layer and a metal layer stacked in sequence.

9. The electromagnetic shielding film according to claim 8, wherein The electromagnetic shielding film satisfies at least one of the following conditions: ① The electromagnetic shielding film comprises a first metal layer, a first connecting layer, a base layer, a second connecting layer and a second metal layer stacked in sequence; ② The substrate material includes quartz glass, sapphire or thermoplastic polyester; the connecting layer material is at least one of Cr, SiO2 and Al2O3; the metal layer material includes Ag, Al, Au or Cu; ③ The thickness of the connecting layer is 25-50nm; ④ The thickness of the metal layer is 350-500nm.

10. The electromagnetic shielding film according to claim 8, wherein The electromagnetic shielding film satisfies at least one of the following conditions: ① The electromagnetic shielding film has an average transmittance of more than 70% in the 400-700nm band; ② The square resistance of the electromagnetic shielding film is 3 to 4 Ω / square; ③ The electromagnetic shielding effectiveness of the electromagnetic shielding film is above 60dB.

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