CN115148417A - Preparation method of silver nanowire conductive film - Google Patents

Abstract

The invention discloses a preparation method of a silver nanowire conductive film, which belongs to the technical field of flexible electronic materials and films. The method mainly adopts a soft nylon filter cloth material as a brushing medium, and adopts silver nanowire and polymer The mixed solution was used as a brush-on ink for film preparation. The advantages of the invention are: (1) simple and efficient operation, low equipment requirements, and easy realization; (2) short preparation period, simple preparation steps, high material utilization rate, low preparation cost, and good film repeatability; (3) preparation There is no agglomeration phenomenon in the thin film, and the thin film can maintain good morphology and performance; (4) It can realize large-area preparation and is compatible with different types of substrates; (5) The prepared conductive film has high transmittance and uniform square resistance. , suitable for the preparation of high-performance conductive films.

Description

A kind of preparation method of silver nanowire conductive film

technical field

The invention relates to the field of silver nanowire conductive films, in particular to a method for preparing silver nanowire conductive films by brush coating with filter cloth.

Background technique

Conductive films are widely used in optoelectronics and microelectronics, such as information display, information storage, energy conversion, bioelectronics and other devices. Silver nanowires (Ag NWs) are very promising flexible conductive materials because they exhibit superior optical transmittance and surface resistance compared to other conductive materials. Silver nanowires have high thermal and electrical conductivity, and their applications include transparent conductive films, biosensors, and surface-enhanced Raman scattering. At present, the main types of silver nanowire conductive films are spin coating, brush coating, bar coating, drop coating, vacuum filtration, dip coating, inkjet printing, and pulling.

In terms of preparing large-area silver nanowire conductive films, the rod coating method is a simple and easy process. Specifically, a Meyer rod is used as a coating tool to flatten the silver nanowire solution on the substrate to form a film. Ye rod can change the film thickness. However, in the process of preparing silver nanowire thin films by rod coating method, the Meyer rods are not in contact with the substrate, and rely on the liquid shear force to pull the solution to form a film. Therefore, it is difficult to precisely control the thickness of the film and the adhesion between the film layer and the substrate is poor. question.

The brush coating method is another simple and easy preparation method, which uses a brush or a writing brush to dip the silver nanowire solution on the surface of the substrate and brush to form a uniform silver nanowire film. The brush coating method has low requirements on equipment, high utilization rate of silver nanowire solution, and has the advantages of low cost and high performance. However, since the amount of silver nanowires stored in the bristles during the dipping process is not easy to control, and it is difficult to achieve continuous replenishment of the solution during the brushing process, the uniformity of the large-area silver nanowire conductive film cannot be guaranteed. For example, the patent with publication number CN105355262B provides a transparent conductive film and a preparation method thereof. By using a brush coating element treated with surfactant carboxylation, the silver nanowire paste is brushed on the transparent substrate, to a certain extent. It is ensured that the silver nanowires are uniformly and directionally arranged on the transparent substrate, and are firmly combined with the transparent substrate. After drying, a transparent conductive film with high light transmittance and good conductivity is obtained. However, its film preparation process is still based on manual brushing. The process of manual brushing is low in efficiency, consumes man-hours, labor-intensive, and has large performance differences between different electrode products, making it difficult to achieve standardized production;

Therefore, there is currently a lack of a low-cost method for preparing silver nano-films that can be produced automatically and sustainably under the premise of ensuring good performance of the electrode films.

SUMMARY OF THE INVENTION

In view of the deficiencies of the existing technology for preparing silver nanowire thin films such as the above rod coating or brush coating method, the present invention provides a preparation method of a silver nanowire conductive thin film, wherein filter cloth materials such as nylon filter cloth are folded in half as a coating tool , using a mixed solution of silver nanowires with a certain viscosity, and using the interaction between the pores of the filter cloth and the viscosity of the solution to control the outflow speed of the solution, so that the silver nanowire solution is uniformly coated on the surface of the substrate, aiming to solve the problem of using Defects of silver nanowire conductive thin films prepared by conventional blade coating method and brush coating method. The preparation method of the present invention realizes the preparation of a simple, low-cost, large-area, and relatively uniform thin film through the selection of the solvent and the optimization of the preparation conditions.

To achieve the above object, the present invention adopts the following technical solutions:

A preparation method of a silver nanowire conductive film, comprising the following steps:

The silver nanowire stock solution and dispersion liquid containing silver nanowires are mixed uniformly, and configured into a silver nanowire/dispersion liquid material mixed solution, hereinafter referred to as a mixed solution, wherein, the concentration range of the silver nanowires in the mixed solution is 2- 10mg/ml, the diameter of the silver nanowires ranges from 30-90nm; the dispersion liquid is prepared by dissolving the dispersion material in deionized water and fully dissolved, and the concentration range of the configured dispersion liquid is 3-7mg/ml; The dispersing material is any one of hydroxypropyl methylcellulose (HPMC), nitrocellulose plastic, cellulose acetate butyrate, cellulose acetate, methylcellulose, and polyaniline;

Clean the substrate, the substrate includes a glass sheet, a PET flexible substrate and a paper material; cut a filter cloth with a width larger than the substrate, and the filter cloth has a filter hole size of 50-150 μm;

After the syringe absorbs a certain amount of mixed solution, it is fixed on the syringe pump. The syringe is used to store the mixed solution of silver nanowires. The needle is in contact with the silver nanowire solution on the filter cloth. The syringe pump is used to push the syringe to supply the solution, and the syringe pump is controlled by the circuit board. The movement speed of the motor determines the liquid output of the syringe, and the movement time of the syringe pump is set by the size of the substrate;

After the filter cloth is folded in half, the sealing is fixed, and then the outer side of the sealing is fixed on the upper module of the movable platform. The upper module is fixed during the brushing process, and the needle of the syringe is inserted into the middle of the folded filter cloth, and it is necessary to ensure that the filter cloth is folded in half After the horizontal and vertical directions are flat;

Slowly move the filter cloth until the filter cloth is in horizontal contact with the substrate and then drop 1-2mm, place the substrate on the lower module of the movable platform, and control the movement of the substrate through the lower module, so that the filter cloth is brushed from the substrate at a constant speed, After brushing, the silver nanowire conductive film was annealed on a hot stage.

Preferably, the silver nanowire stock solution is weighed as the solute, wherein the mass fraction of the stock solution is 1-5wt%.

Preferably, the filter cloth is a nylon filter cloth, the length of the filter cloth is 4-6 cm, and the width is 1-2 cm greater than the width of the substrate;

Preferably, the process of dissolving the dispersing material in deionized water and fully dissolving it includes: weighing the dispersing material and dissolving it in deionized water, and stirring with a magnet for more than six hours after sealing to fully dissolve to obtain a dispersion liquid.

Preferably, the dispersing material is hydroxypropyl methylcellulose HPMC. In addition to reducing the aggregation of silver nanowires in the mixed solution, the HPMC can also form an HPMC protective layer on the surface of the final silver nanowire film to reduce the The roughness of the film surface.

Preferably, the substrate cleaning process includes: ultrasonically cleaning the substrate for at least 15 minutes, blowing it dry with N ₂ and conducting a hydrophilization treatment by a plasma cleaning machine; further preferably, the ultrasonic cleaning is performed sequentially by deionization. Ultrasonic cleaning with water, ethanol and isopropanol;

Preferably, a certain amount of silver nanowires is pre-dropped at the folded position of the filter cloth, and the pre-drop is to drain the mixed solution, so that the solution is spread evenly on the substrate along the direction of pre-drop; The volume of the silver nanowire mixture should ensure that the silver nanowire mixture does not drip from the filter cloth;

Preferably, the moving speed of the lower module of the movable platform is 20 cm/min, and the moving speed of the syringe pump pushing the syringe is 20-50 mm/s; Automatic brushing; Correspondingly, the speed at which the syringe pump pushes the syringe is set to 20-50mm/s, and the size of the syringe is 1-5ml;

Preferably, the final silver nanowire conductive film can be obtained by annealing on a hot stage at 100-120° C. for 5-10 min.

The present invention can control the viscosity of the solution by adding dispersing materials of different qualities, and the specific dissolving method is as follows: heating the required water to above 85° C., gradually adding the dispersing materials under constant stirring, the cellulose is gradually dispersed in the water, and swelled into a slurry. , stirring and cooling until the solution is transparent, that is, it has been dissolved completely;

Beneficial effects of the present invention:

In the preparation method of the silver nanowire conductive film provided by the present invention, a filter cloth is selected as a brushing tool, the viscosity of the solution is controlled by a dispersing material, and the silver nanowire solution is made of its excellent dispersing and glue-retaining ability, combined with the soft characteristics of the filter cloth. It can form a good contact with the substrate, and is suitable for all kinds of substrates. It can also generate strong shearing force during the brushing process; in addition, the filter holes on the filter cloth can filter the silver nanowire solution. Agglomerate, so that the silver nanowire conductive film obtained by brushing has better flatness and uniformity, and lower surface roughness of the film;

In the preparation method of the silver nanowire conductive film provided by the present invention, the filter cloth is preferably nylon filter cloth, which has the best flexibility; the silver nanowire network simply brushed shows smooth surface morphology and good electrical conductivity network, the filter cloth brushing method provided by the present invention itself is a simple and cost-effective preparation method of silver nanowire conductive thin film, with low material loss, ultra-low cost and no vacuum processing, high manufacturability and good Compatibility, etc.

The preparation method of the invention has the advantages of simple and efficient operation, low equipment requirements, and easy realization; the preparation method of the invention has the advantages of short preparation period, simple preparation steps, high material utilization rate, low preparation cost and good film repeatability; The prepared silver nanowire film has no agglomeration phenomenon, and the film can maintain good morphology and performance; the invention can realize large-area preparation, and is compatible with different types of substrates, including non-planar substrates; the conductive The film has good photoelectric properties and maintains uniform square resistance in a large area.

Description of drawings

Fig. 1 is the schematic diagram of the brushing method of the silver nanowire conductive film described in the embodiment of the present invention;

2 is a diagram of each position of the four-probe square resistance meter test described in Test Example 1 of the specific embodiment;

3 is a physical comparison diagram of a silver nanowire conductive film prepared on a glass substrate and a glass substrate in Example 1 of the present invention;

FIG. 4 is a physical view of the silver nanowire conductive films prepared in Examples 1-4 and Comparative Examples 1-2 of the present invention.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

Example 1

As shown in Figure 1, adopt the preparation method of a kind of silver nanowire conductive film of the present invention, the specific implementation process is as follows:

Step S1, take 0.4g of silver nanowire stock solution, the silver nanowire stock solution is purchased from Zhejiang Kechuang Material Technology Co., Ltd., the model is AW045, and the quality of the silver nanowire solute is 4mg;

In step S2, 40 mg of HPMC polymer was weighed and dissolved in 8 ml of deionized water to obtain an HPMC dispersion with a concentration of 5 mg/ml; 0.6 ml of the HPMC solution was added to the silver nanowire stock solution in step S1 to obtain a solution containing 5 mg/ml of HPMC. Silver nanowires and silver nanowires mixed solution of HPMC, the concentration of silver nanowires mixed solution is 4mg/ml at this time;

Step S3, suck 0.5ml of the silver nanowire mixed solution with the syringe 5, and fix it on the syringe pump 1;

Step S4, cutting a 6cm×6cm filter cloth 4 with a filter hole size of 150 μm as a brushing tool; the filter cloth is folded in half and sealed and fixed, and then the outer side of the seal is fixed on the upper module 6 of the movable platform, and the upper module 6 is brushed. In the process of fixing, the needle of the syringe is inserted into the middle of the filter cloth folded in half, and it is necessary to ensure that the filter cloth is flat in the horizontal and vertical directions after the filter cloth is folded in half;

Step S5, the glass substrate 3 with a size of 2cm×8cm is ultrasonically cleaned with deionized water, ethanol, and isopropanol for 15 minutes in turn, and after plasma cleaning treatment is performed to improve the hydrophilicity, it is placed on the 3D movable platform. On the lower module 2;

Step S6, pre-drop 30 μl of the silver nanowire mixed solution on the filter cloth, and adjust the height of the filter cloth 4 to make it contact with the glass substrate 3;

Step S7, start the movable platform and the syringe pump 1 of the 3D printer, control the module 2 below the platform to move in the Y-axis direction, the moving speed is 20cm/min, drive the glass substrate 3 to move, and realize automatic scraping;

Step S8, the silver nanowire conductive film is placed on a hot plate with a temperature of 120° C., and annealed for 10 minutes to form a film.

As shown in FIG. 3 , it is a physical comparison diagram of the silver nanowire conductive film prepared on the glass substrate in Example 1 of the present invention and the glass substrate.

Example 2

The preparation method of the conductive film in Example 2 is the same as that in Example 1, except that the size of the glass substrate used in step S5 is 5 cm×5 cm, and 50 μl of silver nanowire mixed solution is pre-dropped in step S6.

The testing method is the same as that in Example 1. After testing, the average square resistance of the film is 28.45Ω/sq, and the transmittance at 550 nm is 85.92%.

Example 3

The preparation method of the conductive film in Example 3 is the same as that in Example 1, the difference is that the substrate used in step S5 is a PET film. The testing method is the same as that in Example 1. After testing, the average square resistance of the film is 27.94Ω/sq, and the transmittance at 550 nm is 79.18%.

Example 4

The preparation method of the conductive film in Example 4 is the same as that in Example 1, except that the filter pore size of the filter cloth used in step S4 is 50 μm, and the substrate used in step 5) is A4 paper; the test method is the same as that in Example 1. After testing, the average square resistance of the film is 6.01Ω/sq,

Comparative Example 1

The preparation method of the conductive film in Comparative Example 1 is the same as that in Example 1, except that HPMC is not added in step S2, and only 0.6 ml of ethanol is weighed and mixed into the silver nanowire stock solution to obtain a silver nanowire solution.

The test method is the same as that in Example 1. After testing, the average square resistance of the film is 58.1Ω/sq, and the transmittance at 550nm is 87.18%.

Comparative Example 2

The preparation method of the conductive film in Comparative Example 2 is the same as that in Example 1, the difference is that the amount of HPMC used in step S2 is different. details as follows:

Weigh 120 mg of HPMC polymer and dissolve it in 8 ml of water to obtain a silver nanowire solution with a concentration of 15 mg/ml; using the solution obtained by mixing HPMC and silver nanowires with this concentration, a uniform film cannot be obtained by brushing on the substrate. The testing method is the same as that in Example 1. After testing, the average square resistance of the film is 6.86Ω/sq, and the transmittance at 550nm is 69.05%.

Comparative Example 3

The preparation method of the conductive film in Comparative Example 3 is the same as that in Example 1, except that the filter pore size of the filter cloth used in Step S3 is 38 μm. By using the filter cloth, the silver nanowires cannot smoothly penetrate through the filter holes, and the surface distribution of the prepared silver nanowire conductive film is uneven and has obvious scratches. The testing method is the same as that in Example 1. After testing, the average square resistance of the film is 85.68Ω/sq, and the transmittance at 550 nm is 89.13%.

Test Example 1

As shown in FIG. 4 , which is a physical diagram of the silver nanowire conductive films prepared in Examples 1-4 and Comparative Examples 1-3 of the present invention, a handheld four-probe square resistance tester was used to test all the examples and comparative examples. The prepared silver nanowire conductive film was tested. Four probes were placed directly on the prepared silver nanowire conductive film, and the uniformity of the square resistance was tested by moving the positions of the four probes. A total of 8 probes were selected for each test. The specific location is shown in Figure 2. The test results are shown in Table 1 below. After calculation, the average square resistance of the film is 27.15Ω/sq. After heating for 15 minutes, after the self-test of the instrument is completed, open the software to perform full-scale calibration with a clean glass substrate, set the test wavelength to 300-800nm, and finally select the transmittance curve to start the test. After the test, the average value of the film is The square resistance is 27.15Ω/sq, and the transmittance at 550nm is 85.13%.

Table 1 is a summary of the multi-point square resistance test of the silver nanowire conductive films prepared in each example and in the comparative example

Table 2 is a summary of the average square resistance and transmittance at 550 nm of the silver nanowire conductive films prepared in each example and comparative example.

Claims (10)

1. a preparation method of silver nanowire conductive film, is characterized in that, specifically comprises the following steps: The silver nanowire stock solution and dispersion liquid containing silver nanowires are mixed uniformly, and configured into a silver nanowire/dispersion liquid material mixed solution, hereinafter referred to as a mixed solution, wherein, the concentration range of the silver nanowires in the mixed solution is 2- 10mg/ml, the diameter of the silver nanowires ranges from 30-90nm; the dispersion liquid is prepared by dissolving the dispersion material in deionized water and fully dissolved, and the concentration range of the configured dispersion liquid is 3-7mg/ml; The dispersing material is any one of hydroxypropyl methylcellulose (HPMC), nitrocellulose plastic, cellulose acetate butyrate, cellulose acetate, methylcellulose, and polyaniline; Clean the substrate, the substrate includes a glass sheet, a PET flexible substrate and a paper material; cut a filter cloth with a width larger than the substrate, and the filter cloth has a filter hole size of 50-150 μm; After the syringe absorbs a certain amount of mixed solution, it is fixed on the syringe pump. The syringe is used to store the mixed solution of silver nanowires. The needle is in contact with the silver nanowire solution on the filter cloth. The syringe pump is used to push the syringe to supply the solution, and the syringe pump is controlled by the circuit board. The movement speed of the motor determines the liquid output of the syringe, and the movement time of the syringe pump is set by the size of the substrate; After the filter cloth is folded in half, the sealing is fixed, and then the outer side of the sealing is fixed on the upper module of the movable platform. The upper module is fixed during the brushing process, and the needle of the syringe is inserted into the middle of the folded filter cloth, and it is necessary to ensure that the filter cloth is folded in half After the horizontal and vertical directions are flat; Slowly move the filter cloth until the filter cloth is in horizontal contact with the substrate and then drop 1-2mm, place the substrate on the lower module of the movable platform, and control the movement of the substrate through the lower module, so that the filter cloth is brushed from the substrate at a constant speed, After brushing, the silver nanowire conductive film was annealed on a hot stage. 2 . The method for preparing a silver nanowire conductive film according to claim 1 , wherein the silver nanowire stock solution is weighed as a solute, wherein the mass fraction of the stock solution is 1-5wt%. 3 . 3 . The method for preparing a silver nanowire conductive film according to claim 1 , wherein the filter cloth is a nylon filter cloth. 4 . 4 . The method for preparing a silver nanowire conductive film according to claim 1 , wherein the length of the filter cloth is 4-6 cm, and the width is 1-2 cm greater than the width of the substrate. 5 . 5. The preparation method of a silver nanowire conductive film according to claim 1, wherein the dispersing material is dissolved in deionized water and the process of fully dissolving comprises: weighing the dispersing material and dissolving in deionized water, After sealing, magnetic stirring is carried out for more than six hours to make it fully dissolved to obtain a dispersion liquid. 6 . The method for preparing a silver nanowire conductive film according to claim 1 , wherein the substrate cleaning process comprises: ultrasonically cleaning the substrate for at least 15 minutes, drying with N 2 and cleaning by plasma. 7 . Machine for hydrophilic treatment. 7 . The method for preparing a silver nanowire conductive film according to claim 6 , wherein the ultrasonic cleaning is performed by using deionized water, ethanol, and isopropanol in sequence for ultrasonic cleaning. 8 . 8. the preparation method of a kind of silver nanowire conductive film according to claim 1, it is characterized in that, in filter cloth folding position pre-drop a certain amount of silver nanowires, described pre-drop the silver nanowire mixed solution The volume should ensure that the silver nanowire mixture does not drip from the filter cloth. 9 . The method for preparing a silver nanowire conductive film according to claim 1 , wherein the moving speed of the lower module of the movable platform is 20 cm/min; the different thicknesses are realized by the moving speed of the lower module. 10 . Automatic brushing of the silver nanowire conductive film; correspondingly, the movement speed of the syringe pump to push the syringe is set to 20-50mm/s, and the size of the syringe is 1-5ml. 10 . The method for preparing a silver nanowire conductive film according to claim 1 , wherein the final silver nanowire conductive film can be obtained by annealing on a hot stage at 100-120° C. for 5-10 minutes. 11 .

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