Study of color deterioration of fluorescent dyestuffs under white LEDs illumination

Research Project

Project/Area Number	18K01098
Research Category	Grant-in-Aid for Scientific Research (C)
Allocation Type	Multi-year Fund
Section	一般
Review Section	Basic Section 03060:Cultural assets study-related
Research Institution	Independent Administrative Institution National Institutes for Cultural Heritage Tokyo National Research Institute for Cultural Properties
Principal Investigator	YOSHIDA NAOTO 独立行政法人国立文化財機構東京文化財研究所, 保存科学研究センター, 保存環境研究室付 (80370998)
Project Period (FY)	2018-04-01 – 2021-03-31
Project Status	Completed (Fiscal Year 2020)
Budget Amount *help	¥2,860,000 (Direct Cost: ¥2,200,000、Indirect Cost: ¥660,000) Fiscal Year 2020: ¥650,000 (Direct Cost: ¥500,000、Indirect Cost: ¥150,000) Fiscal Year 2019: ¥650,000 (Direct Cost: ¥500,000、Indirect Cost: ¥150,000) Fiscal Year 2018: ¥1,560,000 (Direct Cost: ¥1,200,000、Indirect Cost: ¥360,000)
Keywords	染料 / LED / 展示照明 / 白色LED / 変退色 / 有機性文化財材料 / LED展示照明 / 有機染料 / 博物館照明 / 文化財材料 / 劣化
Outline of Final Research Achievements	The following findings were obtained through experiments and verifications using samples of yellow dyestuffs on silk fabric. (1) Even with the same white LED, the higher the color temperature, that is, the greater the contribution of blue light, the greater the amount of fluorescence with respect to the reflected light. (2) By long-term irradiation experiments in different wavelength bands, it was confirmed that the shorter the wavelength of the irradiation light, the faster the discoloration / fading rate. (3) Furthermore, it was demonstrated that with dyes having low light resistance, discoloration and fading and changes in the reflection spectrum become remarkable when light is irradiated on the wavelength side shorter than the absorption peak.
Academic Significance and Societal Importance of the Research Achievements	国内では、博物館等における展示照明の白色LED化が急速に進んでいる。一方で、展示物の変退色抑制を主眼とした照度基準や積算照度基準は、従来光源であるハロゲンランプや蛍光ランプの時代に提示されたものであり、これらとは発光原理、発光特性（分光分布）などが異なる白色LED光にそのまま適用されることが適切かどうかの実証的研究はないままであった。今回の研究では、特に白色LED光に特長的な狭い波長帯での鋭い発光ピークに着目し、特定波長帯での黄色染料への照射試験により、波長帯による相対的な変退色、色差増大の差を染料の吸収特性との関連で明らかにし、白色LED時代の安全な展示に資する知見を得た。