1-Two-Photon stereolithography process: In the two-photon SL (2p-SL) process, the photoinitiator requires two photons to strike it before it decomposes to form a free radical that can initiate polymerization.The effect of this two-photon requirement is to greatly increase the resolution of photopolymerization processes. This is true since only near the center of the laser is the irradiance high enough to provide the photon density necessary to ensure that two photons will strike the same photoinitiator molecule. Feature sizes of 0.2 mm have been achieved using 2p-SL.
Typical photopolymer materials can be used in 2p-SL machines. The most commonly used resin was SCR500 from Japan Synthetic Rubber Company, which was a common SL resin in Japan, where this research started during the 1990s. SCR500 is a mixture of urethane acrylate oligomers/monomers and common free radical generating photoinitiators. The absorption spectrum of the resin shows that it is transparent beyond 550 nm, which is a significant advantage since photons can penetrate the resin to a great depth (Dp is very large). One implication is that parts can be built inside the resin vat, not just at the vat surface, which eliminates the need for recoating.
(Additive Manufacturing Technologies,I. Gibson,D. W. Rosen,B. Stucker,P.96-97)
Ertan Toparlak
503091329
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