以分光色差儀進行綠色系閃玉顏色等級分類之研究

Preliminary study of green nephrite color grading with spectrophotometer

蔡佳容(Chia-Jung Tsai)

指導教授 ： 余炳盛

國立臺北科技大學/工程學院/材料科學與工程研究所/碩士(2008年)

https://doi.org/10.6841/NTUT.2008.00390

摘要

本研究使用分光色差儀量測，根據1976 CIE Lab 色度學方法，量化閃玉顏色的參數指標，確定其L、a、b值、色彩指數C、色差指數ΔE，以進行客觀之顏色分級。並探討樣品大小、粗糙度、上蠟及不同弧度等因素對量測之影響。
量測結果顯示，L值隨樣品粗糙度增加有上升的趨勢，而a、b值向原點趨近。而隨樣品遮蓋偵測孔面積減小，L值下降a、b值趨向原點。至於樣品上蠟則可使不同粗糙度之顏色趨於一致。此外，樣品弧度越大則L值下降，a、b值也趨向原點。
透過量測結果可將綠色系閃玉顏色分為A、B、C、D四個等級。A級L值大於36~40，彩度指數11以上；B級L值34~35，彩度指數6~11；C級L值31~33，彩度指數7~9；D級L值29~30，彩度指數4~8。CIE Lab色度學方法能有效地表明閃玉顏色的視覺特徵，可作為閃玉顏色評價的客觀依據。
本研究中並探討不同顏色等級閃玉之其他光譜性質。拉曼光譜量測結果可知，A級閃玉lattice mode振動模之波數均較其他B、C、D者為低，Si-O-Si bend、Si-O-Si stretch振動模之波數，由A級往B、C、D級有漸增之趨勢。各級閃玉之紅外線光譜無明顯差異。而以254 nm短波長的紫外線進行照射產生的螢光光譜，可在400~650 nm間觀察到寬幅的放射波段，其主要的峰值位於530 nm波段。

關鍵字

閃玉 ； 顏色分級 ； CIE Lab ； 分光色差儀

並列摘要

The spectrophotometer and 1976 CIE Lab colorimetry are adopted to quantify color of nephrite in L, a, b, C(color index) and ΔE(color differential index) for color grading. Several factors of sizes, roughnesses, waxing , and different radians of samples which may influence measurement were discussed in this study.
The result indicate L value increase and value a and b shifting to the origin of the coordinates, with the increasing of sample roughness. L value decreasing and value a and b shifting to the origin of the coordinates with smaller detecting area. Waxing treatment can make samples with different roughness show similar results on colorimetry measurement. Furthermore, L value decreasing and value a and b shifting to the origin of the coordinates with larger radian.
The result show that, the green nephrite could be categorized in four classes： A, B, C and D. L value of class A is higher than 34 and its color index is above 11; class B with L value between 34-35 and color index between 6-11; class C with L value between 31-33 and color index between 7-9; class D with L value between 29-30 and color index between 4-8. CIE Lab colorimetry is suitable for color index and vision feature of nephrite color description, and proper for nephrite color evaluation.
Several spectra are used for auxiliary measurement in the study. The Raman spectrum indicates the wave number of lattice vibration mode of class A is lower than that of class B, C and D. Wave number of Si-O-Si bending and stretching vibration modes increase slightly from class A to class B, C and D. Infrared spectra of all sample of different classes show no evidently different. Photoluminescence spectra with 254 nm ultraviolet source show board emission band lying between 400-650 nm with main peak at 530 nm.

並列關鍵字

Nephrite ； color grading ； CIE Lab ； spectrophotometer

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