White Illumination Characteristics of ZnS-Based Phosphor Materials Excited by InGaN-Based Ultraviolet Light-Emitting Diode
Abstract
White illumination characteristics of ZnS-based phosphor materials exited by an In(x)Ga(1-x)N-based single quantum well (SQW) -structure ultraviolet (UV) light-emitting diode (LED) have extensively been investigated. in order to evaluate white luminescence, two kinds of ZnS-based white phosphors have been employed. When an UV LED was operated at a current of 10 mA, chromaticity (x,y), color temperature (Tc) and general color rendering index (Ra) of the white luminescence are obtained to be (x, y)=(0.29 0.33), Tc-7700 K and Ra=70, respectively, for ZnS:Ag + (Zn,Cd)S:Cu,Al phosphors, whilst (x, y)-(O.31, 0.34), Tc-6900 K and Ra=83, respectively for white phosphor material including ZnS:Cu,Al, Sr and Y materials. The value of chromaticity slightly changed with increasing forward current of the UV light source. As a result, it is possible to obtain stable white luminescence spectrum. The dependence of the luminescence brightness on the thickness of phosphor shows a tendency to saturate for reflection brightness. but for transmission brightness its dependence has a peak due to light scattering effect. The reflection brightness was higher than the transmission brightness. It is revealed that the white luminescence light of stable chromaticity and high brightness using reflection light can be obtained.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 01, 2000
- Accession Number
- ADP011310
Entities
People
- Kenji Murakami
- Masahiko Yoshino
- Tsunemasa Taguchi
Organizations
- Yamaguchi University