What is the stress effect of glasses?
In the field of materials science, stress is an important concept. Resin lens production, as an important application direction in this field, involves relevant knowledge of lens materials in its production process. Nowadays, the mainstream lenses on the market are mainly made of resin materials. During the production process, the generation of lens stress is inevitable. It is particularly worth noting that the stress effect of lenses cannot be directly identified by the naked eye. Only with the help of specialized optical detection equipment, stress meters, can effective monitoring be carried out.
During the production process, lenses generally may experience two types of internal stress phenomena: orientation stress and shrinkage stress. Both of these stresses will have certain impacts on the quality and performance of the lenses, so they need to be given sufficient attention.
① Orientation stress: During the molding process of resin materials, the molecular chains are subjected to high pressure and high shear force, causing them to undergo drastic changes. Residual orientation stress is generated because the molecular chains of the material are frozen before they fully return to the disordered and relaxed state of their natural state. This is particularly evident in PC materials.
In simple terms: The lens is made of resin material. During the molding process, the liquid lens transforms into a solid one, presenting an incompletely uniform feature, which generates certain internal stress. This internal stress is manifested as the pressure exerted by the areas with higher density on those with lower density.
② Shrinkage stress: During the production process of resin materials, as the molecular chains transition from melting to cooling, due to differences in product wall thickness or cooling waterways, it may lead to a non-uniform distribution of cooling temperatures. Furthermore, this temperature difference will lead to different degrees of contraction in different parts.
