| 摘要 |
<p>A thermal recording sheet has a paper or plastics support coated with a layer which color-forms on heating containing essentially (a) an electron- donating colorless dye as particles of volume average size not exceeding 2.0 mu m and (b) particles of an electron acceptor. The particles are formed by ball milling or sand milling the colorless dye (chromogen), e.g. by using balls of size 1 to 5 mm, in an aqueous solution of a protective colloid, e.g. polyvinyl alcohol. The dispersions are mixed together and with other coating components e.g. pigment and binder. The chromogen can be a triaryl methane, diphenyl methane, xanthene, thiazine or spiro compound. The electron acceptor can be a phenolic or aromatic carboxylic acid derivative, especially a bisphenol. The fine particle size of the chromogen gives rapid color forming with adequate color density with short heat pulses of 2 ms.</p> |
