Authored By:
Taro Kenmochi
Kyoritsu Chemical
Chiyodaku, Tokyo, Japan
Summary
There is an increase in the number of optical sensors and cameras being integrated into electronics devices. These go beyond cell phone cameras into automotive sensors, wearables, and other smart devices. The applications can be lens bonding, waveguide imprinting, or other applications where the adhesive is in the optical pathway. To support these various optical applications, new materials with tailorable optical properties are required. There is often a mismatched refractive index between plastic lenses such as PC (Poly Carbonate), COP (Cyclo Olefin Polymer), COC (Cyclo Olefin Copolymer), PMMA (Poly Methyl Methacrylate), and UV curable liquid adhesive. A UV curable liquid adhesive is needed where you can alter the refractive index from 1.470 to 1.730, and maintain high optical performance as yellowness index, haze, and transmittance.
This wide range of refractive index possibilities provides optimized optical design. Using particular plastic lens must consider how chemical attack is occurring during the process. Another consideration is that before the UV curable liquid adhesive is cured, chemical raw component can attack the plastic lens which then cracks and delaminates. We will also show engineering and reliability data which defined root cause and provided how optical performance is maintained under different reliability conditions.
Conclusions
There are several sets of data shown which covers the lens lamination process, selection of liquid adhesives, and technical solutions. Using high refractive index liquid adhesive has limitations and tradeoffs for the adhesive's performance. There is no one way on how to solve the tradeoff of the adhesive’s performance however, if there are basic oligomer and monomers which are able to solve the tradeoffs, liquid adhesives have the opportunity to make very high refractive index liquid adhesive, and maintain current processability.
Initially Published in the SMTA Proceedings
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