Synthesis And Application Of Novel Naphthalimides Used As Negative Fluorescent Dichroic Dyes

In comparison with conventional twisted-nematic displays,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 extemal polarizers at all,so they can't lead to excessive energy loss of beaming light and low brightness.Especially,fluorescent dyes based on 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,proposed to be a less energy consuming display for portable electronics.In present work,three novel negative fluorescent dichroic dyes containing 4-phenyl-1,8-naphthalimide such as 4-(p-phenyl benzoate)-1,8-naphthalimides(BENA),4-{ p-[2'-(1'H-benzimidazole)]-phenyl}-1,8-naphthalimides(BIMZ) and 4-{p-[2'-(5'-phenyl-1',3',4'-oxadiazole)]-phenyl}-1,8-naphthalimides(BODZ) have been designed and synthesized,by changing functional groups on the 4'-position of the phenyl and length of alkyl chain,using 4-bromo-1,8-naphthalic anhydride as the raw material.Study on spectral characteristics of the three series dyes shows that the position of the fluorescence maximum occur in the visible region and the quantum yield of dyes are relatively high,up to 46.2%.The half-peak widths of 4-(p-phenyl benzoate)-1, 8-naphthalimides(BENA) and 4-{p-[2'-(5'-phenyl-1',3',4'-oxadiazole)]-phenyl}-1, 8-naphthalimides(BODZ) are 58 nm and 63 nm respectively,which indicate vivid blue fluorescence.So they are proposed to be applied further in the field of blue fluorescent dye. Based on polarized spectra,the fluorescence maximum in anisotropic solvent shows bathochromic shift or blue shift in some degree compared with isotropic solvent,and dichroic ratio and orientation order parameter are calculated.These dyes are of negative fluorescent dichroic characteristics,which are not reported.What's more,the length of BIMZ's fluorescence maximum is up to 481 nm,and the highest fluorescent order parameter is -0.42, with both of which can satisfy people's need on properties of dyes used for positive display.