Light-emitting diode (LED) is a kind of electroluminescent solid devices. With the continuous innovation of technology and the guidance of national policies, the whole LED products are developing rapidly, and the LED packaging industry is developing synchronously.Among the packaging materials, silicone packaging materials have been recognized by the industry for their excellent performance, and become the fastest developing and most valuable packaging materials, showing a huge market value.

LED silicone packaging adhesive is a new type of high performance liquid silicone, also known as optical packaging.It maintains high transmittance in visible light region, has high absorption rate of ultraviolet light, and improves the light output rate and service life of lighting equipment.

    In recent years, due to the rapid development of the LED industry, the demand for LED packaging materials has been increasing.LED silicone packaging adhesives have become the leader in the field of LED packaging materials due to their excellent physical and chemical properties.With the intensification of the energy crisis, the LED industry will maintain continuous growth, therefore, the market potential of LED packaging materials is huge.High-power LED packaging materials require high transmittance and refractive index of raw materials.Phenyl silicone oil has become an important part of LED packaging adhesives.With the increase of the mole fraction of phenyl, the high temperature resistance, radiation resistance and refractive index of silicone materials are improved, and the importance of phenyl silicone oil in LED packaging adhesives is increasing. 

    The phenyl silicone oil used in LED packaging mainly includes vinyl methyl silicone oil and phenyl hydrosilicone oil.According to benzene content, phenyl silicone oil can be divided into low phenyl silicone oil (phenyl mole fraction 5%-10%), medium phenyl silicone oil (phenyl mole fraction 25%) and high phenyl silicone oil (phenyl mole fraction 45%).LED packaging gels for different uses have different requirements for phenyl content. High-power LED packaging gels generally require higher phenyl content to achieve a high refractive index and thus reduce the energy loss of the light source.

    End-vinyl methylphenyl silicone oil refers to the backbone that contains the end-group silicon atom of vinyl and methyl and phenyl silicone oil connected.Depending on the type of phenyl group, it can be classified as methylphenyl chain node type, diphenyl chain node type, and mixed type (containing both phenyl chains).

    Phenyl-containing silicone oil can be divided into terminal and side hydro-containing silicone oil, both of which have different uses.The former is mainly used as a diluent or chain extender for packaging glue, while the latter is mainly used as a concentrated crosslinking agent for packaging glue, playing the role of crosslinking center.A preparation method of phenyl containing hydrogen silicone oil is cationic polymerization, generally using sulfuric acid.In order to reduce the process flow, acid resin can also be used for catalytic polymerization, eliminating the neutralization of the catalyst step, direct filtration of acid resin, acid resin can be reused many times.

    Terminal vinyl methylphenyl silicone oil and hydrogen silicone oil containing phenyl are the basic raw materials for making high-refractive index LED packaging adhesives.With the rapid development of LED industry, LED packaging industry has unlimited potential, and the demand for phenyl silicone oil is also huge.In recent years, with the further improvement of the production technology of phenyl monomers and intermediates in China, the research of such products has made some progress, but compared with foreign products, there is still a certain gap, which needs to be improved urgently.At present, foreign organosilicon companies monopolize the preparation technology and market of high-index LED packaging adhesives.Phenyl materials are the key to the development and the focus of urgent research.