| 摘要 |
PURPOSE:To provide a reversible thermochromic compsn. which does not corrode substrates, has excellent durability and is inexpensive, by combining a polyhydroxy compd., an alkali metal borate and a pH indicating colorant. CONSTITUTION:A polyhydroxy compd. such as allose or polyvinyl alcohol, an alkali metal borate such as Na2B4O7 or K2B2O4 and a pH indicating colorant in a weight ratio of 1:0.01-10:0.001-0.1 are blended together to obtain a reversible thermochromic compsn. which functions as follows. At ordinary temp. a complex of the polyhydroxy compd. with the alkali metal borate (more strictly, boron) is formed, the pH is low and the indicator indicates an acid color. At an elevated temp. said complex is dissociated, the pH is high and the indicator indicates an alkaline color. For example, when phenolphthalein is used as an indicator, the compsn. is colorless at ordinary temp. and turns into red at an elevated temp. |
