The new generation of folding screen mobile phones launched in the industry mainly emphasizes the foldability of the screen. After more than 100,000 foldings, the screen display can still be touched. So what is the core behind the flexible folding screen? Can ITO still occupy the field of touch screens? ITO (Indium Tin Oxide) as a cermet semiconductor material, its brittleness makes it necessary to choose glass to protect the internal conductors and sensors in use, at the same time it also limits the development of touch screens to be flexible.
Folding screens have gradually shifted their requirements for the internal construction materials of mobile phones. Similarly, touch screen materials also need to be flexible, and ITO can no longer meet the requirements. Therefore, flexible metal grids, silver nanowires AgNWs, carbon nanotubes, and new conductive materials such as graphene and conductive polymers have emerged.
However, the metal grids and silver nanowires that can be put into practical use at present have better effects. As shown above, silver nanowires are called heptathlons in all indicators. In addition to the excellent electrical conductivity of silver, nano-silver wires also have excellent light transmission and flex resistance due to the size effect at the nanometer level.
With the continuous discovery of new materials for conductive films and the introduction of new processes, nano-silver conductive films have the advantages of simple production process, low cost, high yield, and good stability. It is the best solution for the development of flexible touch to foldable and curling screen! So how did nano-silver wires come about?
The origin of nano silver wires
Nanowire is a ratio concept. The aspect ratio must be above 1000, and the diameter in the lateral direction must be below 100 nanometers. Inspired by the abalone shell, Angela Belcher, a Ph.D. in biochemistry at MIT, created nanostructures that can be used by humans. The manufacturing process originated from the 13th century silver nitrate refining method. In the 18th century, people began to apply collodion on clean glass as a solvent for the main material, then immersed in silver nitrate, and took it out to shoot while wet.
Manufacturing of nano silver wire conductive film
Synthesis of silver nanowires
The chemical synthesis methods of nano-silver wires are roughly divided into four categories: template method, electrochemical method, wet chemical method and polyol method. The template method requires a pre-made template. The quality and quantity of the pores determine the quality and quantity of the nanomaterials obtained. The electrochemical method pollutes the environment and has low efficiency. At present, a large number of methods for synthesizing silver nanowires are wet chemical method and polyol method.
The nature of nano-silver wire formation is the result of the selective adsorption of PVP on each crystal plane. Selective adsorption results in different crystal growth rates, enabling crystals to grow anisotropically into silver metal one-dimensional linear structures.
Nano silver wire conductive film
Nanowires are often referred to as one-dimensional materials, and coating into a film can form a two-dimensional network-woven structure. Chemical methods are used to grow nano-silver wires with a diameter of 25-300 nanometers and a length of 10-300um, and then produce nano-silver wire inks. Nano-silver wire inks are transferred to transparent substrates (PET, PMMA, PC, etc.) by RTOR process precision coating.
TP manufacturers can use traditional ITO yellow light process for etching, or laser laser, in addition to etching paste screen printing process, embossed graphic nano-conductive film, printing process and so on. The difficulty in manufacturing the nano-silver wire conductive film lies in the compatibility between the nano-silver conductive film and the silver glue, and it is necessary to ensure the conductivity and adhesion of the overlap.
Cambrios, a leading company in nanosilver wire, has developed nanosilver film and nanosilver ink (Ink) solutions. The silver used in the nano-silver wire conductive film and the indium ore used in ITO are not much different in raw material price, but in the stage of manufacturing the transparent conductive film, the amount of silver raw material added is only one percent of the transparent conductive film component First, the production cost is lower than that of ITO, and its flexibility is better than that of ITO.