Pyridone azo dyes usually exist in hydrazone form. The proton of imino group (δ3.2-4.0). The proton lifetime (τA) and activation energy (E0) can be determined by means of nuclear magnetic double resonance. It is discovered that the exchange rate (ka) and E0 are related to structure of the dyes, pH values, temperature, property of the solvents used and relative content of water in the solution. In this paper, the effect of dye structure on τA and E0 has been investigated under similar experiment conditions. It is shown that the ka can be promoted by both the electron-withdrawing substituents in diazo and coupling components. Alkali in the solution can accelerate ka and decrease E0. The colour change mechanism and different pK values of the dyes have also been further explained in this paper.

Key words: ACTIVATION ENERGY, PYRIDINONE, AZO DYES, DISSOCIATION