Synthesis And Properties Of Novel Derivatives Of Naphthalene As Negative Dichroic Fluorescent Dyes

"Guest-Host" liquid crystal displays have many advantages, such as displaying information in excellent colour, good contrast ratio, a large viewing angle, high brightness and the need for only one or no external polarizers which greatly increased the light efficiency of backlights. Recently, fluorescent dye based GH-LCDs, which show dichroic characteristics excited by polarized light, combine the excellent hues and high brightness levels of emissive displays with the desirable features of LCDs, have been proposed as a less energy consuming display for portable electronics. Therefore, it has important significance to develope dichroic fluorescent dyes which have good performance.In this paper, three novel fruorescent dichroic dyes such as derivatives of 4-amino-N-substituted-1,8-naphthalimides(A) and 4-(p-hexyloxy benzoyloxy)-N-alkyl-1,8-naphthalimides (B) have been designed and synthesized, by changing functional groups on the 4-position of the naphthalimides and length of alkyl chain. Then the derivatives of 4-amino-1,8-dicyanonaphthalene have been designed and synthesized.The porperties of dyes have been characterized by spectral measurements. The results indicated that three dyes have good dichroism, strong emission in visible region and high fluorescence quantum yield, which accord with the design principle of fluorescent dichroic dyes. The fluorescence emission maximum of dyes A was at 509nm, they have vivid yellow-green fluorescence, high fluorescence quantum yield (up to 0.74). The dyes A have negative fluorescent dichroism which have not been reported, the order parameter of fluorescence is about-0.40. The fluorescence emission maximum of dyes B was at 404nm, they have vivid blue fluorescence, high fluorescence quantum yield (up to 0.70). The dyes B have also negative fluorescent dichroism, the order parameter of fluorescence was about-0.37. The fluorescence emission maximum of dyes C was at 474nm, they have vivid blue fluorescence, high fluorescence quantum yield (up to 0.67). The dyes C have also negative fluorescent dichroism, the order parameter of fluorescence is about-0.37. The introduction of ester group in the core unit could increase the dichroism of dyes by comparing dyes A and B. And the introduction of fluorine atom can improve the dichroism of dyes.