| 摘要 |
Substrate for printing and writing, which can be authenticated by heating, contains at least one metal salt (I), which is coloured in the moist state and has a different colour in the dry state. This is incorporated in or applied to the susbtrate in an amt. such that the colour of the substrate is practically the same as a substrate contg. no (I) at room temp. and can be changed reversibly by heating. (I) changes fromafrom a crystal form of one colour to a crystal form of a different colour and pref. is a Co-II salt, pref. contg. water, esp. Co sulphate, chloride, acetate, nitrate or acetylacetonate. (I) is used in an amt. of 0.1-4% w.r.t. the dry wt. of the substrate. The substrate also contains a desiccating salt (II), pref. NaCl, which reduces the temp. at which the colour change occurs.
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