| 摘要 |
PURPOSE:To obtain crystals of a fluoran compound, which give particularly a thermal recording paper with a non-image are improved in light resistance, by reacting a specified benzoic acid derivative with a specified diphenylamine derivative in the presence of a dehydration condensing agent, followed by alkalinization. CONSTITUTION:A benzoic acid derivative of formula I (wherein R2 is methyl or ethyl) is reacted with a diphenylamine derivative of formula II (wherein R3 is 1-4C lower alkyl) in the presence of a dehydration condensing agent, e.g. concentrated sulfuric acid or anhydrous aluminum chloride, and the reaction product is alkalinized to give a fluoran compound of formula III (wherein R1 is methyl or ethyl). Stable crystals of this compound can be obtained by depositing the obtained reaction product from the solution in an aromatic hydrocarbon solvent, an alcoholic solvent, a polar solvent or a mixture thereof, and then isolating the crystals. |
