Photopolymerization resins are extensively used across several industrial fields, such as optical waveguides, three-dimensional（3D）printing, inks, coatings, adhesives, and dental materials. Recently, photopolymerization has primarily been performed using ultraviolet（UV）or visible light sources. UV and visible light cannot penetrate deeply into biological and polymeric material while near-infrared（NIR）light is found to be capable of deeper penetration into such material compared to with UV light. Single-photon and two-photon absorption chromophore sensitized photopolymerization has been developed in the NIR region. An important application of photopolymerization is its use in micro- and nanooptics. This article introduces the NIR photopolymerization resins, and its application to optical devices.

Two types of biocompatible hydrophilic monomers were used to coat a block copolymer brush on polypropylene. In addition, we were able to achieve ultra-low friction with the friction coefficient of less than 0.01 in the specific molecular weight ratio of the two monomers, and to realize a coating of which friction coefficient is independent on sliding velocity. Furthermore, it was suggested that in addition to the known elements of molecular weight uniformity, sufficient film thickness, and molecular stretching conformation, surface roughness, Young’s modulus, loss modulus, and water content are involved in the ultra-low friction realization. In particular, surface roughness has a strong correlation with the friction coefficient for ultra-low friction, and the Young’s modulus and loss modulus in the sliding speed range（20～240 mm/min） in the use of general medical devices for the dependence of sliding velocity. It is desirable to select a material having a low loss modulus and apply a two-layer coating as shown in this study.