Development of surfactant-free anti-fogging coating for automotive headlamps 2019-01-1439
Recently, the design of automotive headlamps becomes diversified and complicated according to customer needs. Hence, structural complexity of the headlamps is also increased. Complex structure of the headlamps inevitably causes a disturbance of air circulation. For this reason, inadvertent micro-sized water droplets, called fogging, are condensed on the inner surface of headlamp lens due to temperature difference between the inner and outer lens surface. To circumvent fogging inside of the headlamp lens, an anti-fogging coating is indispensable. Conventionally, the diverse surfactants have been adopted as a substantial material of the anti-fogging coating. However, the usage of the surfactants would cause undesirable side effect such as a water mark arising from vapor condensation, which is an important issue that must be fully resolved.
In this study, we developed the innovative anti-fogging coating material for excluding conventional surfactant. To this end, crosslinkable hydrophilic-hydrophobic random copolymer was newly utilized. The detailed experimental procedure was followed: (1) Thermosetting resin composed of hydrophobic monomer (methacrylic acid and methyl methacrylate), hydrophilic monomer (ADEKA™ Resoap ER-10, Adeka Corp.), and crosslinker was synthesized. It should be note that hydrophilic monomer has high water absorption capability. (2) Additional solvent and catalyst were mixed with the resin to dilute the resin and accelerate polymerization, respectively. (3) The diluted resin was transparently coated via air spray on the inner surface of headlamp lens. After the coating process, the efficiency of anti-fogging effect was evaluated based on industrial standard of Hyundai motor group (HMG) and the optimal monomers ratio was carried out. Consequently, not only anti-fogging effect was significantly improved but also the water mark was not observed completely. In addition, a ~40% cost reduction was also accomplished.