Fujifilm Corp developed a film-type mirror whose reflectance is as high as that of a glass mirror.
The reflectance of the film-type mirror is 95%. Its thickness is 100μm, and its weight is about 1/30-1/20 that of a normal mirror that uses glass as a base, Fujifilm said. The company plans to commercialize the new mirror in three years at the earliest as a product for concentrating light for solar thermal power generation and as a reflecting plate for LED lighting devices.
To make the mirror, Fujifilm formed a functional resin layer (thickness: about 0.3μm) on a 75μm-thick polyethylene terephthalate (PET) resin sheet by applying a resin that hardens when exposed to heat or light. Then, silver (Ag) plating was applied to form a reflective layer that is about 0.1μm thick. Furthermore, a transparent protective layer was attached to it.
The functional resin layer, which becomes a base for Ag plating, promotes the crystal growth of Ag, helping realize the high reflectance, Fujifilm said. The mirror can be manufactured by roll-to-roll method, and the company has already prototyped a 70cm-wide 30m-long film-type mirror.
The film-type mirror features not only the slimness but excellent resistances to light, heat and moisture. After a 180W/m2 light was continuously shed on the mirror for 1,000 hours by using a xenon (Xe) lamp under a temperature of 50°C and a humidity of 50% to evaluate its resistance to light, the reflectance of the mirror was still 95%. So, Fujifilm confirmed that the mirror has a high durability even in hot and humid conditions.
When the mirror was placed under a temperature of 70°C and a humidity of 85% for more than 2,000 hours, its reflectance did not deteriorate.