Preparation method of high-heat-resistance silver nanowire film

Abstract

The invention provides a preparation method of a high-heat-resistance silver nanowire thin film, which comprises the following preparation steps of: S1, adsorbing a silver nanowire on the surface of a transparent substrate to form a transparent conductive thin film, namely a silver nanowire / glass transparent conductive thin film; s2, the silver nanowire / glass transparent conductive thin film is connected to a direct current negative electrode, a positive electrode is any one of graphite or a noble metal inert conductive material, and the voltage is 5-30 V; and S3, taking out the silver nanowire / glass transparent conductive thin film, washing the silver nanowire / glass transparent conductive thin film with deionized water, and drying the silver nanowire / glass transparent conductive thin film in a drying oven to obtain the high-heat-resistance transparent conductive thin film. The method has the beneficial effects that the very thin silicon dioxide shell layer is formed on the surface of the silver nanowire through electroplating, and the heat resistance of the surface of the silver nanowire is greatly improved through the silicon dioxide shell layer.

Description

Technical Field

[0001] The present invention relates to the technical field of thin film material preparation, and specifically to a method for preparing a high heat-resistant silver nanowire film. Background Art

[0002] Silver nanowires have excellent electrical conductivity, which makes them suitable for a variety of applications in the field of transparent electrodes, such as touch modules, flexible displays, heating and defogging of car windshields, etc. These applications require that the silver nanowires themselves have good current resistance, and high currents often cause silver nanowires to break. According to current papers, the breakage of silver nanowires caused by high currents is related to local Joule heat. Improving the heat resistance of silver nanowires is very helpful in improving the current resistance, especially for applications that require heating, such as heating and defogging films for car windshields.

[0003] In order to improve the heat resistance of silver nanowires, the current feasible solution is to use some oxides, such as zinc oxide (refer to the following document 1), silicon oxide (refer to the following document 2), tin oxide (refer to the following document 3), aluminum oxide (refer to the following document 4), molybdenum oxide (refer to the following document 5), etc. These oxides can be coated on the surface of silver nanowires to significantly improve the heat resistance of silver nanowires. Among them, silicon oxide has the best transparency, but silicon oxide cannot be obtained by electroplating in traditional theory (it is mentioned in the People's Education Edition of Chemistry for Senior High School Students that the silicon in sodium silicate is +4 valence, and the Si in silicon oxide is also +4 valence, and there is no valence change between the two components. Traditional theory does not support the electroplating of silicon dioxide).

[0004] 1. Mitigation of Electrical Failure of Silver Nanowires under, CurrentFlow and the Application for Long Lifetime Organic Light-Emitting Diodes, Adv.Electron. Mater. 2016, 1600167, Dustin Chen, Fangchao Zhao, Kwing Tong et al.

[0005] 2. Fused silver nanowires with silica sol nanoparticles for smooth, flexible, electrically conductive and highly stable transparent electrodes, RSC Adv., 2018, 8, 13466–13473, Shengchi Bai, Haifeng Wang, Hui Yang et al.

[0006] 3. Overcoming Temperature-Induced Degradation of Silver Nanowire Electrodes by an Ag@SnOx Core-Shell Approach, Adv. Electron. Mater. 2022, 8, 2100787, Violetta Kalancha, Albert These, Lilian Vog et al.

[0007] 4. Highly Flexible and Transparent Ag Nanowire Electrode Encapsulated with Ultra-Thin Al2O3: Thermal, Ambient, and Mechanical Stabilities, Scientific RepoRts, 7:41336, Byungil Hwang, YoungseoAn2, Hyangsook Lee et al.

[0008] 5. All-Solution-Processed Molybdenum Oxide-Encapsulated Silver Nanowire Flexible Transparent Conductors with Improved Conductivity and Adhesion, ACS Appl. Mater. Interfaces 2021, 13, 14470−14478, Shihui Yu, Xiaoyu Liu, Muying Wu et al.

[0009] To achieve the encapsulation of these oxides, there are currently the following three schemes:

[0010] 1) In the solution, the surface of the silver nanowires is coated with materials such as silicon dioxide through sol-gel. The drawback of this solution is that after the surface of the silver nanowires is coated with these materials and coated into a thin film, the conductivity of the silver nanowires will be greatly affected. Because these materials on the surface of the silver nanowires affect the overlap of the silver nanowires, it is difficult to form a conductive network;

[0011] 2) After the silver nanowires form a conductive film, they are evaporated by physical methods. This method has good results, but the equipment cost is high and it is difficult to produce in large quantities;

[0012] 3) The silver nanowire film is electroplated to form some protective shell structures, such as nickel plating. However, according to the metal activity series, the electroplating scheme can only form shells of a few elements.

[0013] In summary, in order to solve the above technical problems of the prior art:

[0014] The invention provides a method for preparing a highly heat-resistant silver nanowire film, in which a very thin silica shell is formed on the surface of the silver nanowire by electroplating, and the silica shell greatly improves the heat resistance of the surface of the silver nanowire;

[0015] This invention breaks through the limitations of traditional theory and realizes the electroplating of silicon dioxide on the surface of silver nanowires (traditional electrochemical theory does not support the electroplating of silicon dioxide, but the actual situation does produce an electroplating effect), thereby obtaining a highly heat-resistant silver nanowire film. Summary of the invention

[0016] In order to solve the above technical problems, the present invention provides a method for preparing a high heat-resistant silver nanowire film.

[0017] A method for preparing a highly heat-resistant silver nanowire film comprises the following preparation steps:

[0018] S1: Adsorbing silver nanowires on the surface of a transparent substrate to form a transparent conductive film, i.e., silver nanowire / glass transparent conductive film;

[0019] S2. Connect the silver nanowire / glass transparent conductive film to the negative electrode of direct current, and the positive electrode is any one of graphite or precious metal inert conductive materials, with a voltage of 5-30V;

[0020] S3: taking out the silver nanowire / glass transparent conductive film, washing it with deionized water, and drying it in an oven to obtain a highly heat-resistant transparent conductive film.

[0021] In this scheme, the voltage is 5-30V. Too high a voltage will produce the effect of electrolyzing water, but it does not affect the success of electroplating silicon dioxide. Silicate is used as an electrolyte, preferably sodium silicate, and other soluble silicates are also feasible.

[0022] As a further improvement of this scheme,

[0023] In S1, the silver nanowire has a diameter of 20 nanometers to 30 nanometers and a length of 20 to 40 micrometers.

[0024] As a further improvement of this scheme,

[0025] In S1, the silver nanowires are prepared into a silver nanowire dispersion having a concentration of 0.1 wt%.

[0026] As a further improvement of this scheme,

[0027] S2 also includes preparing a sodium silicate solution, and the specific preparation steps are: taking 5-50 grams of sodium silicate and dissolving it in 500 grams of water to obtain a sodium silicate solution, and pouring the sodium silicate solution into the electroplating tank.

[0028] As a further improvement of the present solution, the positive electrode of the electroplating tank is graphite, the negative electrode is a silver nanowire / glass transparent conductive film, and the electrode is in direct contact with the silver nanowire film.

[0029] As a further improvement of this solution, the substrate in S1 is any one of resin and glass.

[0030] As a further improvement of this solution, in S3, the drying temperature in the oven is 120-150°C.

[0031] As a further improvement of this solution, the electrolysis time is 3 to 20 minutes.

[0032] In this scheme, the electrolysis time is 3-20 minutes. Too long electroplating time does not bring negative effects. After a certain degree of electroplating, the reaction will not continue, and only the electrolysis of water will occur.

[0033] The beneficial effects of the present invention are:

[0034] The invention provides a method for preparing a highly heat-resistant silver nanowire film, in which a very thin silica shell is formed on the surface of the silver nanowire by electroplating, and the silica shell greatly improves the heat resistance of the surface of the silver nanowire;

[0035] This invention breaks through the limitations of traditional theory and realizes the electroplating of silicon dioxide on the surface of silver nanowires (traditional electrochemical theory does not support the electroplating of silicon dioxide, but the actual situation does produce an electroplating effect), thereby obtaining a silver nanowire film with high heat resistance (the temperature at which the conductive film fails is as high as 400°C). BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1For the present invention, the conductive film of Example 1 during the heating test was taken out and observed using a dark field microscope to observe the conductivity failure process.

[0037] Figure 2 This is a picture of the products prepared in Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 in the method for preparing the high heat-resistant silver nanowire film of the present invention. DETAILED DESCRIPTION

[0038] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0039] Example 1

[0040] 1. Take a silver nanowire dispersion with a diameter of 20 nm-30 nm and a length of 20-40 μm at a concentration of 0.1 wt %, apply it on the hydrophilic glass surface, and dry it in an oven at 135°C to obtain a silver nanowire / glass transparent conductive film.

[0041] 2. Take 50 grams of sodium silicate and dissolve it in 500 grams of water to obtain a sodium silicate solution. Pour the sodium silicate solution into the electroplating tank.

[0042] 3. The positive electrode of the electroplating tank is graphite, and the negative electrode is silver nanowire / glass transparent conductive film. The electrode can be in direct contact with the silver nanowire film.

[0043] 4. The electrolytic cell is powered on with a voltage of 10V.

[0044] 5. Take out the silver nanowire / glass transparent conductive film, rinse it with deionized water, and dry it in an oven at 135° C. to obtain a conductive film 1.

[0045] 7. Test electrical and optical properties.

[0046] Comparative Example 1: (The difference from Example 1 is whether power is turned on)

[0047] 1. Take a silver nanowire dispersion with a diameter of 20 nm-30 nm and a length of 20-40 μm at a concentration of 0.1 wt %, apply it on the hydrophilic glass surface, and dry it in an oven at 135°C to obtain a silver nanowire / glass transparent conductive film.

[0048] 2. Take 50 grams of sodium silicate and dissolve it in 500 grams of water to obtain a sodium silicate solution. Pour the sodium silicate solution into the electroplating tank.

[0049] 3. The positive electrode of the electroplating tank is graphite, and the negative electrode is silver nanowire / glass transparent conductive film. The electrode can be in direct contact with the silver nanowire film.

[0050] 4. Take out the silver nanowire / glass transparent conductive film, rinse it with deionized water, and dry it in an oven at 135° C. to obtain a conductive film 2.

[0051] 5. Test electrical and optical properties.

[0052] Comparative Example 2: (The difference from Example 1 is that there is no sodium silicate)

[0053] 1. Take a silver nanowire dispersion with a diameter of 20 nm-30 nm and a length of 20-40 μm at a concentration of 0.1 wt %, apply it on the hydrophilic glass surface, and dry it in an oven at 135°C to obtain a silver nanowire / glass transparent conductive film.

[0054] 2. Pour deionized water into the electroplating tank.

[0055] 3. The positive electrode of the electroplating tank is graphite, and the negative electrode is silver nanowire / glass transparent conductive film. The electrode can be in direct contact with the silver nanowire film.

[0056] 5. The electrolytic cell is powered on with a voltage of 10V.

[0057] 6. Take out the silver nanowire / glass transparent conductive film, rinse it with deionized water, and dry it in an oven at 135° C. to obtain a conductive film 3.

[0058] 7. Test electrical and optical properties.

[0059] Comparative Example 3: (To illustrate that electricity is ineffective without silicate ions, sodium chloride is used for comparison to show that sodium ions do not work)

[0060] 1. Take a silver nanowire dispersion with a diameter of 20 nm-30 nm and a length of 20-40 μm at a concentration of 0.1 wt %, apply it on the hydrophilic glass surface, and dry it in an oven at 135°C to obtain a silver nanowire / glass transparent conductive film.

[0061] 3. Take 50 grams of sodium chloride and dissolve it in 500 grams of water to obtain a sodium chloride solution. Pour the sodium silicate solution into the electroplating tank.

[0062] 4. The positive electrode of the electroplating tank is graphite, and the negative electrode is silver nanowire / glass transparent conductive film. The electrode can be in direct contact with the silver nanowire film.

[0063] 5. The electrolytic cell is powered on with a voltage of 10V.

[0064] 6. Take out the silver nanowire / glass transparent conductive film, rinse it with deionized water, and dry it in an oven at 135° C. to obtain a conductive film 4.

[0065] 7. Test electrical and optical properties.

[0066] The resistance test is a standard four-probe sheet resistance test: the device has four probes that touch the film simultaneously and read a number.

[0067] The conductive films 1 to 4 prepared in Example 1 and Comparative Examples 1 to 3 were subjected to performance tests, and the test results are as follows:

[0068] Table 1 Resistance before heating of conductive films 1 to 4 prepared in Examples and Comparative Examples 1 to 3

[0069] Place conductive film 1, conductive film 2, and conductive film 3 on a 160°C heating platform for 3 minutes and measure the sheet resistance. If the sheet resistance remains unchanged, continue to increase the temperature by 20°C until the film is no longer conductive. Record the temperature at which the conductive film fails to conduct electricity.

[0070] Table 2 Temperatures at which the conductive films 1 to 4 prepared in Examples and Comparative Examples 1 to 3 fail to conduct electricity

[0071] The transmittance of the conductive film 1, the conductive film 2 and the conductive film 3 before and after the electroplating treatment was tested respectively.

[0072] Table 3 Light transmittance of conductive films 1 to 4 prepared in Example 1 and Comparative Examples 1 to 3 before and after treatment

[0073] The haze of conductive film 1, conductive film 2 and conductive film 3 was tested before and after electroplating treatment.

[0074] Table 4 Haze of conductive films 1 to 4 prepared in Example 1 and Comparative Examples 1 to 3 before and after treatment

[0075] The temperature at which the conductive film fails to conduct electricity is 400° C. in Example 1 and 220° C. in the comparative example.

[0076] like Figure 1 As shown, the conductive film in the heating test process was taken out and observed with a dark field microscope to observe the conductivity failure process. The electroplated silicon dioxide limited the melting of the silver nanowires. The surface of the silver nanowires covered with silicon dioxide can limit the melting of the silver nanowires, which has been mentioned in the papers of the prior art. It’s just that the source of silicon dioxide is different, it can be sol-gel or evaporation. The present invention adopts the electroplating method to produce a high-heat-resistant silver nanowire film with performance that meets the requirements.

[0077] Dark field microscopy shows that the conductivity failure of silver nanowires during heating is mainly reflected in the melting of silver nanowires into particles and the inability to form a conductive network. The role of silicon dioxide limits the melting of silver nanowires.

[0078] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0079] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A method for preparing a highly heat-resistant silver nanowire film, characterized in that: The method comprises the following preparation steps: S1: Adsorbing silver nanowires on the surface of a transparent substrate to form a transparent conductive film, i.e., silver nanowire / glass transparent conductive film; S2. Connect the silver nanowire / glass transparent conductive film to the negative electrode of direct current, and the positive electrode is any one of graphite or precious metal inert conductive materials, with a voltage of 5-30V; S3: taking out the silver nanowire / glass transparent conductive film, washing it with deionized water, and drying it in an oven to obtain a highly heat-resistant transparent conductive film.

2. The method for preparing a highly heat-resistant silver nanowire film according to claim 1, characterized in that: In S1, the silver nanowire has a diameter of 20 nanometers to 30 nanometers and a length of 20 to 40 micrometers.

3. The method for preparing a highly heat-resistant silver nanowire film according to claim 2, characterized in that: In S1, the silver nanowires are prepared into a silver nanowire dispersion having a concentration of 0.1 wt%.

4. The method for preparing a highly heat-resistant silver nanowire film according to claim 2, characterized in that: S2 also includes preparing a sodium silicate solution, and the specific preparation steps are: taking 5-50 grams of sodium silicate and dissolving it in 500 grams of water to obtain a sodium silicate solution, and pouring the sodium silicate solution into the electroplating tank.

5. The method for preparing a highly heat-resistant silver nanowire film according to claim 4, characterized in that: The positive electrode of the electroplating tank is graphite, and the negative electrode is silver nanowire / glass transparent conductive film, which are connected by conductive silver paste.

6. The method for preparing a highly heat-resistant silver nanowire film according to claim 4, characterized in that: The substrate in S1 is any one of resin and glass.

7. The method for preparing a highly heat-resistant silver nanowire film according to claim 1, characterized in that: In S3, the drying temperature in the oven is 120-150°C.

8. The method for preparing a highly heat-resistant silver nanowire film according to claim 1, characterized in that: The electrolysis time is 3 to 20 minutes.

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