Synthesis, application and investigation of structure–thermal stability relationships of thermally stable water-soluble azo naphthalene dyes for LCD red color filters

A series of structurally isomeric water-soluble azo naphthalene dyes were synthesized, and their thermal properties were examined by thermogravimetric analysis and differential scanning calorimetry. Dye-based color filters were also fabricated using the synthesized dyes. Transmittance (98.9%) at 650 nm and a wide color gamut (62.8%) were achieved using one of the color filters. All the prepared dyes had a degradation temperature above 280 °C, which varied with the dye structure. The degradation temperatures of the dyes were presumed to be related to the intra- and inter-molecular interactions of the structural isomers. From quantum mechanics calculations, their intra-molecular interactions were similar. However, the degradation temperatures generally increased in proportion to their density. According to the molecular mechanics calculations, the different structures induced changes in electrostatic attraction, steric hindrance and linearity of the dyes, which in turn caused changes in their molecular packing geometry, density and degradation temperature.