A layer of silver film with a thickness of 150 μ m was prepared on PET film using chemical silver plating method

PET silver plated filmA layer of silver film with a thickness of 150 μ m was prepared on PET film using chemical silver plating method. The silver plating process and chemical silver plating process were studied, and the silver plated film was tested. Studied the thickness, composition, anti-static properties, barrier properties, and heat resistance of silver plated film layers. The results showed that using immersion method for silver electroplating resulted in a silver layer thickness of approximately 120 μ m; The chemical silver plating method uses silver plating solution and silver plating process, with a coating thickness of 150 μ m in a vacuum environment. After 3 hours of heat treatment at 400 ℃, the silver film has good heat resistance and anti-static properties; For PET silver plated film, its barrier properties, barrier ratio, and mechanical properties improve with increasing film thickness; When the thickness of the coating layer reaches 300 μ m, the adhesion between the silver film and PET film will significantly decrease, and the mechanical adhesion between the silver layer and PET film will also significantly decrease. The silver plated film still has excellent mechanical properties, with significantly higher elongation at break, tensile strength, and bending strength than the non silver plated film. Therefore, adoptingChemical silver plating processThe PET silver plated film prepared has good application prospects.

PET has excellent mechanical properties, chemical corrosion resistance, and has a wide range of applications in many aspects. However, PET itself has poor transparency and thermal stability, and is prone to photochromic phenomena under light, heat, or humid conditions. Due to the excellent mechanical properties of PET materials, people have started to modify their surfaces by coating them with various metal alloys, metal oxides, and other materials for processing.

The most widely used technique currently is silver plating, which generally involves depositing a layer of metal or silver film on the surface of a silver film prepared by chemical platingAlloy thin filmThe silver plating process is easy to automate due to the deposition and coating of silver layers, resulting in high production efficiency and low cost. Therefore, the chemical silver plating method is widely used in the preparation of various thin film materials.

It is generally believed that silver plated films have good mechanical properties, barrier properties, thermal stability, and other characteristics. However, for some special applications, due to limitations such as cost and processing conditions, the chemical silver plating method cannot be widely used to prepare silver plated films at present.

This article adoptsChemical silver platingThe method of depositing a layer of silver film with a thickness of 150 μ m on PET film was used to test and analyze the thickness, composition, mechanical properties, etc. of the silver plated film layer, providing a theoretical basis for the application of PET silver plated film in the field of optical devices.

The process of silver plating film

(1) Cleaning: Use acetone or chloroform to remove dust, oil stains, and metal surface oxides from the film. Clean the film on the glass surface with acetone and the oil film on the surface with ammonia water.

(2) Activation is a key step in chemical silver plating. Firstly, disperse the silver paste in sulfuric acid, then mix it evenly with the active agent, and add a small amount of surfactant and additives. After stirring evenly, immerse the solution on the surface of the PET film. The immersion time should be controlled between 2-4 minutes, as prolonged immersion can lead to the formation of gaps between the silver paste and PET film. If the immersion time is too short, the silver paste cannot be dispersed on the surface of the film, and the film layer is prone to detachment.

(3) Activation is the process of vacuum drying impregnated PET film at a certain temperature and pressure. There are various vacuum drying methods used, including atmospheric pressure drying and pressure drying; Vacuum drying is the process of vacuum drying the impregnated film at 400-500 ℃.

(4) Chemical silver plating: After thorough mixing of silver paste and catalyst, immerse the film into the silver paste to allow the silver paste in the solution to adsorb onto the film. When the temperature reaches 150 ℃ (heating time of about 2 minutes), a uniform silver layer is deposited on the surface of the film. Then place the film at 250-300 ℃ for 1 minute to allow the film layer to cool naturally to room temperature.

(5) Silver plating: Remove residual acetone and chloroform from the surface of the pre plated silver film using acetone or chloroform, then clean with ammonia water, and finally dry at a certain temperature or naturally dry. The suitable temperature for chemical silver plating is 15-30 ℃, and silver wire shedding may occur below 15 ℃.

Silver plating pretreatment

Adopting immersion method for silver electroplating, the main salt content in the plating solution is 12g/L, the reducing agent dosage is 15g/L, the chelating agent dosage is 30g/L, and the temperature is 80 ℃. In order to increase the deposition rate of silver, improve the adhesion between the coating layer and the substrate, and enhance the corrosion resistance of the silver film, this study carried out acid washing treatment on PET film. The experimental results show that for the process of immersion silver electroplating, the thickness of the silver layer is about 120 μ m, and the adhesion between the silver layer and the PET film is poor; For the process of using chemical silver plating, the coating thickness can reach about 150 μ m, and the adhesion between the silver layer and PET film is good.

Preparation using chemical silver plating processPET silver plated filmThe diffusion rate of silver ions is affected by factors such as the pre-treatment method before plating and the concentration of reducing agents in the plating solution. This study used immersion method for silver electroplating. Transfer the silver plated PET film onto a glass slide, add 5g/L hydroxylamine hydrochloride (HCl), 20g/L boric acid (BHBA), and 15g/L copper sulfate solution, stir at room temperature for 5 minutes, then remove the glass slide and soak it in boiling water for about 10 minutes. Through X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM) observation, it was found that the amount of silver nitrate precipitation was low, and the silver layer was dense and uniform.

Silver plating process flow

(1) Pre treat the PET film to be silver plated at 60-80 ℃, and reduce the metal elements on the film layer through oxidation-reduction reactions in the air to form a silver film.

(2) Place the pre processed PET film on a chemical silver plating workbench containing silver plating solution, and use a vacuum pump to evacuate the silver plating solution, allowing it to react at a lower temperature in a vacuum environment.

(3) Silver will be consumed during the reaction process, and when the film thickness reaches 150 μ m, the bonding force between the silver film and the PET film becomes weak. At this point, the silver plating workbench is evacuated, and the current regulating device of the chemical silver plating machine is used to adjust the concentration of silver ions in the plating solution to meet the process requirements. Then fix the current regulating device of the chemical silver plating machine, and evacuate the silver plating worktable to a higher vacuum state for reaction.

(4) When the coating thickness reaches 100 μ m, the chemical silver plating machine is evacuated using a vacuum pump to reduce the concentration of silver ions in the plating solution to below 10 μ g/ml. Then heat treat it to achieve the bonding force between the silver plating layer and the PET film.

precautions

1. Chemical silver plating is a chemical raw material, and the use of organic solvents such as alcohol and acetone to clean equipment is strictly prohibited.

2. Avoid splashing water during operation.

3. It is strictly prohibited to pour silver plating solution into other solutions to prevent the silver plating solution from deteriorating.

4. If other substances need to be added to the silver liquid for some reason, the silver liquid should be checked for deterioration in advance.

5. Preparation of Silver Liquid: Mix 50g/L of purified water and deionized water in a 5:1 ratio, filter, and store the resulting solution at room temperature for at least six months before use.

6. Keep the equipment dry and dry the silver plated board. The drying temperature is around 80 ℃, and the drying time is 1-2 hours.

7. Before electroplating, the grounding condition of the equipment must be checked. If there is no grounding, the resistance value should be measured with a resistance tester first, which should be above 4 ohms (i.e. 5-10 Ω); After inspection, it can only be used if there are no issues.

8. After silver plating, the equipment needs to undergo vacuum testing to ensure that the vacuum degree meets the usage requirements before it can be turned on and operated; Blow the inlet pipe of the vacuum pump with dry compressed air to achieve a pressure of 0.07 MPa inside the pipe.

conclusion

The silver plating process has brought enormous development space for the application of PET film, but further research is needed to investigate its effects on the composition, anti-static properties, and barrier properties of the silver layer.

2. The silver plating solution contains a certain proportion of organic solvents, and the gases generated by their volatilization can easily cause the organic components in the silver plating layer to dissolve, resulting in discoloration and other phenomena in the silver plated film. Therefore, the content of organic solvents in the silver plating solution should be controlled, and the deposition concentration of other components in the silver plating solution on the surface of PET film should be increased as much as possible.

    3. PET silver plated filmThe barrier properties, barrier ratio, and mechanical properties improve with the increase of coating thickness. When the thickness of the coating layer is 150 μ m, its barrier properties, barrier rate, and mechanical properties are optimal; When the thickness of the coating layer reaches 300 μ m, the adhesion between the silver film and PET film significantly decreases, and the mechanical adhesion between the silver layer and PET film also significantly decreases. Therefore, the mechanical properties of the silver plated film are no longer better than those of the non silver plated film.

4. The chemical silver plating method has certain limitations: firstly, the thickness of the coating layer is difficult to control, and secondly, the process is complex and costly. Therefore, the chemical silver plating technology needs further development. PET silver coating with uniform thickness, controllable thickness, good heat resistance and stable performance can be prepared by electrochemical deposition or sol-gel method, and can be widely used in electronic, optical and film materials fields.