Fumed silica (also known as pyrogenic silica, colloidal silicon dioxide) is an inorganic nano-oxide (non-metal) of white fluffy appearance. Among nano-powder materials, fumed silica is one that has seen large-scale production and widest application at the earliest time. It is widely used in fields such as production of silicone rubber, sealants, adhesives, plastics, unsaturated polyesters, paints and inks as well as electrical and electronic industries, green tire production, construction and aerospace industries. With the development of information technology and the electronics industry, fumed silica also plays an important role in the field of display technologies for smart devices.
Today, mobile phones, wearable devices, smart TVs, etc. have become the main tools for people to entertain themselves and communicate with others, and the screens of these devices have become the primary window for man-machine interactions. In this case, screen display technology has become a key area of concern for users and the industry. After years of development, screen display technology has undergone several upgrades, from the initial CRT to LCD, LED and finally the currently popular OLED technology.
(Principle of OLED technology)
OLED (Organic Light Emitting Diode) refers to a type of organic semiconductors that emit light in response to electric currents. Compared with traditional liquid crystal display technology, this new display technology has many more advantages, including lighter and thinner build, self-luminous properties, wide viewing angle, high definition, fast response, low energy consumption, low temperature resistance and excellent shock resistance, and it has potential to reduce relevant manufacturing cost and be used in flexible screens and various environmentally friendly designs. Based on the above advantages, OLED is recognized by the industry as the most ideal and promising new display technology. In particular, it can be used to realize magic-like flexible designs, making it possible to manufacture stunning foldable TVs and computers.
(OLED folding screen for mobile phone)
(OLED curved TV)
However, upon the advert of OLED technology, the service life of OLED devices could not meet the application requirements, and one of the technical difficulties that had led to this issue was electronic packaging technology and materials.
At present, silicone modified epoxy resins are widely used in Japan, US and European countries, the principle of which to improve the internal toughness of the molecule while reducing the internal stress of the epoxy resin through the blending, copolymerization or grafting reaction of the two materials, thereby improving the high temperature resistance of the material and the waterproof, oil and oxygen resistance of the silicone. But this method requires a long curing time (a few hours to a few days). To speed up the curing reaction, it is required to increase the temperature (60 ℃ to 100 ℃ or more) or the amount of curing agent used, resulting in increased costs and making it difficult to meet the requirements of large-scale production lines for packaging materials (short curing time and room temperature packaging).
(OLED packaging process)
Fumed silica boasts a variety of excellent properties, including large specific surface area, high surface energy, strong surface adsorption, high chemical purity, good dispersion performance, thermal resistance, electrical resistivity and stability, as well as better properties in respect of reinforcement, dispersion, thickening and thixotropy. And its application in the production of silicone rubber and composite materials is supported by mature technologies. By fully dispersing surface bioactive fumed silicas in the matrix of encapsulant made of silicone modified epoxy resins, we can greatly reduce the time required for curing of the packaging materials (2.0-2.5h), and lower the curing temperature down to the level of normal room temperature, therefore significantly improving the sealing performance of OLED devices and extending their service lives.
The addition of fumed silica enables the electronic packaging process which used to have special environment requirements to be completed under room temperature, which helps to significantly reduce production costs. In addition, the use of fumed silica also helps to shorten the curing time of the packaging material, therefore allowing for greatly improved production efficiency and lower production costs. In summary, the application of fumed silica should be conducive to promoting the popularization of the new generation OLED display technology.