The Reseach Of UV-curable Material On Light Emitting Diodes Encapsulation

The UV curable materials were investigated which encapsulated inthe SMD LED cup. The UV-Vis spectroscopy, thermal gravimetricanalysis, differential scanning instrument were used to examine the antithermal aging yellowing properties and the thermal stability of the UVcurable materials. The adhesion and curing rate of the materials on theSMD LED cup were also paid attention. The role of the antioxidantsplays in the aspect of anti aging yellow for the UV curing system werealso investigated, and the conclusions for all investigations are following:(1) The thermal aging yellowing is relative with the thermaldecomposition. In the free radical UV curing system, the ether bond inthe acrylate monomer is prone to yellowing during thermal aging. Theyellowing tendency order of the monomers is HDDA> TMPTA>TPGDA> TMP9EOTA> TMP15EOTA.(2) The antioxidants can be applied to the UV curing system toreduce the thermal aging yellowing. There is a synergy effect betweenIrganox-1076/Irgafos-168and Irganox-1010/Irgafos-168which maybecome weaker after an aging time.(3) The anti-yellowing ability of the main antioxidant is relative with the number and activity of hydroxyl on it, so the activity of hydroxyl onthe main antioxidant can tell the anti thermal aging yellowing ability ofthe main antioxidant.(4) The yellowing caused during light curing stage may increase theyellowing index and which may result in the material get a worseyellowing during the late thermal aging.(5) The photo-initiator has an important affect to the thermalyellowing property of the UV curing materials, especially in the mixedinitiator system.The research also found that the complex initiation UV-curablesystem shows a good adhesion, faster curing rate and a smaller yellowingwhich is more suitable for application in the LED UV curingencapsulation. In addition to this subject, the use of antioxidants to reducethermal aging yellowing in the complex initiation UV-curable material, abetter anti-yellowing cationic initiator may need to improve the antithermal aging yellowing ability of the complex initiation UV-curable inthe further research of the UV curing LED encapsulation.