The Chemistry of Leuco Triarylmethanes

Photostabilization of Leuco Dyes: Counter-ion Effect on the Light Fastness of Color Formers

“…The colored materials 4 and 6 derived from color formers 3 and 5 showed red color (λmax 490, 522 and 555 nm) and black color (λmax 446 and 586 nm) respectively, as illustrated in Fig. 6, but their light fastness properties are as poor as dye 1 [1].…”

“…The colored material 8 derived from color former 7 showed pink color (λmax 520 and 559 nm), as illustrated in Fig. 7, but its light fastness property is as poor as dyes 1, 3 and 5 [1].…”

“…The chemistry of color formers has recently become of importance, particularly in connection with the rapid development of information recording systems and thermochromic systems for a diverse range of applications [1][2][3]. Thermal recording systems using heatsensitive paper have been widely used in facsimiles, wordprocessors, printers and point of sale labels, etc.…”

“…Furthermore, a heat-sensitive recording method has been used in prepaid cards. These information recording systems have recently become more common in our daily life [1]. In the systems, the image is recorded by the color-forming reactions upon heating.…”

“…The thermochromism centers around the interaction of color former and developer which occurs in a low-melting hydrophobic medium : the color of pigment changes when heated above its melting point and returns instantaneously on cooling and solidification [3]. But, functional dyes of this type gradually fade and so improved light fastness is currently being sought [1].…”