フェノール樹脂を用いた電気容量型湿度センサ

Abstract

Capacitive humidity sensors using polyphenol resin (PPR) were fabricated. Then, the humidity characteristics of PPR were compared with that of cellulose acetate butyrate (CAB).It is reported by several researchers that CAB is suitable to a humidity sensitizer of the capacitive humidity sensor.Relative humidity (RH) vs. capacitance (C) curves are almost linear for PPR 72 (phenylene content of 72%), and are non-linear for CAB and PPR 66 (phenylene content of 66%). For all materials, temperature coefficient of C-RH curve is less than 1%/°C. Especially the temperature coefficient is negligibly small for PPR 66. Hysteresis width against humidity cycles are 0.5%, 1.5%, 3% and 2% at maximum in RH equivalent for PPR 72, PPR 66, CAB 38 (butyryl content of 38%) and CAB 50 (butyryl content of 50%), respectively. The response duration time against humidity change is short enough at a relatively low humidity range for all materials. However, it takes 4 min, 4 min, 33 min and 28 min for -1% response in RH equivalent by increasing humidity from RH of 81.2% to RH of 90.7% for PPR 72, PPR 66, CAB 38 and CAB 50, respectively. The humidity sensors of PPR 72 and PPR 66 work stable in 3%. accuracy after kept in 90% RH of 80°C for 100 days. Furthermore, the sensors of PPR 66 can be used even after kept in 150°C for 100 days.