HUMIDITY INDICATOR, AND COATING MATERIAL FOR HUMIDITY INDICATOR

摘要

Provided is a humidity indicator which sharply responds to a humidity increase and which changes in color so that the indicator is colorless at low humidities and has a color at high humidities. The humidity indicator is produced by: coating a support with a coating material for humidity indicators which comprises an electron-donating color-assuming compound, an acidic compound that is solid at ordinary temperature, polyvinylpyrrolidone, and water and in which the weight ratio of the polyvinylpyrrolidone to the water is 0.45-1.86; and drying the applied coating material to form a coating film.