ELECTROTHERMAL COLOR-VARYING INSTRUMENT

摘要

An electrothermal color-varying instrument for inducing color change. in a thermal color-varying layer provided in a toy, a picture book, a teaching aid, a writing board has an electrothermal heat-generating element serving as a heat source which is composed of a thermistor which has: (i) a positive temperature coefficient on the electrical resistance within a temperature range from 25.degree.C to 70.degree.C; (ii) a volume resistivity at 25.degree.C (p25) within a range of 9.8 x 10 -3 to 2.97 x 10 5 .OMEGA.~cm; and (iii) a ratio (p70/p25) of the volume resistivity at 70.degree.C to that at 25.degree.C within a range of ~ (p70/p25) ~ 400; and which is adapted to generate heat under the application of a voltage in a range of 0.8 to 40 V and is capable of temperature self-control whereby the saturated heating temperature is maintained at an arbitrary temperature within a range of 30.degree.C to 100.degree.C.