Silicone resin for LED packaging

Characteristics of silicone materials
The main chain of organosilicon polymer is Si-O bond, and organic groups are connected to silicon atoms, which can be composed of R3 sio1 / 2 (m), R3 SiO2 / 2 (d), R3 SiO3 / 2 (T) and R3 SiO2 (q) in a certain proportion; The Si-O bond energy is higher, which makes it have better high temperature resistance or radiation resistance, and the Si-O bond angle is larger, which makes the molecular chain of the material soft. Silicone materials have excellent properties in heat resistance and yellowing resistance. Silicone materials are easy to modify, and functional groups with high refractive index, such as sulfur, benzene, phenol and epoxy, can be introduced into the side chain to improve the refractive index of packaging materials and the luminous efficiency of LED.

Synthesis of silicone resin

According to its refractive index, it can be divided into two types: low refractive index (1.4) and high refractive index (1.5). The main one with refractive index of 1.4 is methyl silicone material, and the main one with refractive index of 1.53 is phenyl silicone material. As the greater the refractive index of silicone material, the higher the light efficiency, so we should try to improve the refractive index of silicone material.

Silicone resin is usually prepared by hydrolysis and polycondensation of organosilane in the presence of solvent. The synthetic raw materials are chlorosilane or alkoxysilane. The specific process is as follows: first, the silane is hydrolyzed to silanol under certain conditions; second, the silanol itself is polycondensated; third, the silicone resin is obtained by washing neutralization, concentration and removal of small molecules. For example, Xu Xiaoqiu first hydrolyzed methylphenyldiethoxysilane to form methylphenyl ring at high temperature, and then synthesized colorless and transparent phenylvinyl silicone oil with refractive index above 1.5 through anionic ring opening polymerization. Wu Tao et al. Prepared vinyl terminated methylphenyl silicone oil by anionic ring opening polymerization from cyclic methylphenyl siloxane containing dimethylsiloxane and vinyl double head in the presence of basic catalyst. Wu Chuan et al. Polymerized octamethylcyclotetrasiloxane (D4) or mixed ring of 1,3,5,7-tetramethylcyclotetrasiloxane (D4H) and methylphenyl in toluene to prepare crosslinking agent silicone hydrogen silicone oil. The molar ratio of pH to Si is 0.30-0.60, the mass fraction of active hydrogen is 0-0.5%, the refractive index is 1.39-1.51 (25 ℃), and the dynamic viscosity is 100-550 MPa · s. Wang Xiaolu et al. Synthesized phenylvinyl transparent silicone resin by solvent-free method; Vinyl trimethoxysilane, hydroxyl terminated polydimethylsiloxane, Diphenyldimethoxysilane and phenyltrimethoxysilane were used as raw materials, and hydrochloric acid solution was used as catalyst to carry out hydrolysis condensation reaction to synthesize transparent silicone resin with high refractive index and fluidity at room temperature. In order to reduce the surface tension of LED packaging adhesive and make it easy to vacuum defoaming, Yang xiongfa prepared transparent vinyl silicone oil containing methyl trifluoropropyl siloxane and methyl phenyl siloxane. Huang ronghua et al. Synthesized phenyl vinyl silicone resin by using methyl vinyl chlorosilane, phenyl chlorosilane, methyl chlorosilane and phenyl chlorosilane as raw materials, using methyl sealing agent and vinyl sealing agent to seal the end, and then using 0. 45 pore size μ The results show that the residual hydrochloric acid particles can be effectively removed and the transparency of the product can be improved.