Development of Surfactant-Free Anti-Fogging Coating for Automotive Headlamps

Recently, the design of automotive headlamps has become diversified and complicated according to customer needs. Hence, structural complexity of the headlamps has also increased. Complex structure of the headlamps inevitably causes a disturbance in 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 surfaces. To circumvent fogging inside of the headlamp lens, an anti-fogging coating is indispensable. Conventionally, diverse surfactants have been adopted as substantial material for the anti-fogging coating. However, the usage of the surfactants causes undesirable side effect such as water mark arising from vapor condensation, which is an important issue that must be fully resolved. In this study, we developed an innovative anti-fogging coating material without using conventional surfactant. For this purpose, crosslinkable hydrophilic-hydrophobic random copolymer was utilized. The detailed experimental procedure is as follows: (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 noted 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. Consequently, not only anti-fogging effect was significantly improved but also the water mark disappeared completely. In addition, cost reduction of approximately 40% was also accomplished.