Akihiro Fujita

OPTICAL CHARACTERISTICS OF PHOSPHORESCENT MATERIALS WITH WATER-BASED CERAMICS

A composite coating approach has been employed to produce phosphorescent materials for emergency exit signs. The coating consists of a reflecting undercoat, a middle coating comprising phosphorescent pigments in a water based ceramic, and a final transparent silica topcoat. The effects of size and amount of pigments in the ceramic based coating on the luminance of the materials was assessed and compared with the Japanese Industrial Standard for safety signboards (JIS Z9107). The luminance increased with the amount of pigment in the coating, and samples with more than 20% exceeded the standard. Luminance 10 times higher than the JIS standard was obtained with 50% phosphorescent pigments. The luminance increased initially with the number of applications of the ceramic based coating but there was no further increase for more than 4 applications. The water-based phosphorescent ceramics developed here are superior in optical characteristics and made entirely of inorganic materials. It is considered that these are excellent materials for phosphorescent emergency exit signs. In addition, the materials can be applied at room temperature for example to metal substrates or by silkscreen printing on tiles, and then calcined at low temperature. This type of processing makes them suitable for a whole range of applications.