| 摘要 |
This invention involves thermographic imaging systems. The thermographic system under consideration comprises a leuco dye, a nitrate salt, and, optionally, an acid and stabilizing compound. Dyes in their reduced leuco form can provide the basis of color image forming systems. However, the leuco form of a given dye can often revert spontaneously to the colored form of the dye during manufacture unless the structure of the dye is altered to promote stability. In this invention, which involves stabilization of the leuco dye, the stabilized leuco dye contains a phenazine nucleus with naphthoyl substituents on the 10-position and, optionally on one or both of the 3- and 7-positions through an amino group. In their oxidized form, the leuco dyes of this invention provide access to a range of red and magenta colors which exhibit greater stability when subjected to light and temperatures characteristic of the stage of overhead projectors than that exhibited by previously available leuco dyes of this color range. |
