江戸時代後期の渡来唐桟布(とうざんふ)に用いられた橙色金属化合物染料の微細構造と木綿繊維内部の分布

Abstract

The microstructures and distribution of an orange dyestuff compound in the cotton fiber used for touzan fabric imported in the late Edo period have been investigated. The dyed fibers are taken off from the old fabric. The color of the fabric is measured with a spectrophotometer. To observe the distribution of nanometer-sized compound grains in the fiber, the cross section of the fiber is flattened by ion milling after mechanical polishing. The microstructures are observed by SEM and TEM. The composition and crystal structure are analyzed by EDX and XRD. The absorption edges at 590 nm (2.1 eV) and 720 nm (1.7 eV) are observed in the reflectance spectrum for an orange thread. The orange color is determined by the edge at 590 nm. The spectral luminous efficacy spectrum shows a peak at 574 nm. The dyestuff compound, Pb2CrO5, is detected by EDX and XRD. Although the film like compound covers the cotton fiber surface, the fine compound of 100~500 nm precipitates in the fiber. Most of these precipitates align along the fiber forming concentric circles; however, some precipitates distribute randomly. The preferential precipitation is observed at a crack in the fiber and a precipitation-free zone is also observed. The compound, Pb2CrO5, precipitates preferentially at a defect, which is possibly an amorphous structure, in the fiber. It is considered that the distribution of the precipitates indicates the defect structure of the fiber.