Лако-красочные материалы — производство

2.3.1. Acylated Oxazine Leuco Dyes

Benzoyl leuco Basic Blue 3 (2) is a typical cyan leuco oxazine used in carbonless copy paper. To satisfy the requirements of new applications such as electrolytic recording and Color Dry Silver, new oxazine leucos have been
developed that can offer colors other than cyan such as red, purple, and blue violet.

The introduction of electron-withdrawing groups on the exocyclic amino groups of the oxazine dyes is one method employed to create a hypsochromic shift and obtain colors ranging from orange to violet.6 The redox potential of the new dyes is probably raised owing to the presence of the electron-withdrawing groups which leads to the nonacylated leuco oxazine dyes being stable enough to be isolated, as shown in Table 2.

The reductive acetylation of Brilliant Cresyl Blue (29) yields 1,9- dimethyl-4-acetamido-8-diethylaminoimidazophenoxazine (30) which gives a purple image in electrolytic recording.12 Other similar oxazine leucos (31-34) have also been developed for electrolytic recording.13 The leucos 33 and 34 produce blue violet images.

^H2 )=N

НзС Ac^Pyridine H3CV^4^NS>.

(H5c2)2N^^o^ANH] ^5c2)2n^^°^^n

(29) (30)

Table 2. Effect of Substituents on the Color of Oxazine Dyes