Provided is a light emitting device that is bright in both scotopic vision and photopic vision, and has reduced glare for humans.

The light emitting device includes a light emitting element having a dominant wavelength in a range of 430 nm or more and 500 nm or less, and a fluorescent material that is excited by light emitted from the light emitting element and has a light emission peak wavelength in a range of 507 nm or more and 660 nm or less, wherein the light emitting device emits light having a dominant wavelength in a range of 490 nm or more and 500 nm or less, wherein the light emitting device has an S/P ratio, which is the ratio of a luminous flux in photopic vision to a luminous flux in scotopic vision, being 6.5 or less, and wherein the light emitting device has a light emission intensity in the light emission peak wavelength of the light emitting element that is greater than that in the light emission peak wavelength of the fluorescent material.

An object is to provide a new type of near-infrared ray-emitting phosphor which exhibits excellent emission intensity. A near-infrared ray-emitting phosphor is represented by a general formula, (Y, Lu, Gd).sub.3-x-y (Ga,Al,Sc).sub.5O.sub.12:(Cr.sub.x,(Yb,Nd).sub.y) (0.05<x<0.3, 0≤y<0.3).

A plastic scintillating fiber according to an aspect of the present invention includes: an outermost peripheral layer containing a fluorescent substance that emits scintillation light when it is irradiated with at least one of neutron radiation and heavy-particle radiation; a core disposed inside the outermost peripheral layer and containing at least one type of fluorescent substance that absorbs the scintillation light and wavelength-converts the absorbed light into light having a wavelength longer than that of the absorbed light; and a cladding layer covering an outer peripheral surface of the core and having a refractive index lower than that of the core. A wavelength shifting fiber including the core and the cladding layer, and the outermost peripheral layer covering an outer peripheral surface of the wavelength shifting fiber are integrally formed.

This specification discloses methods of enhancing the stability and performance of Eu.sup.2+ doped narrow band red emitting phosphors. In one embodiment the resulting phosphor compositions are characterized by crystallizing in ordered structure variants of the UCr.sub.4C.sub.4 crystal structure type and having a composition of AE.sub.1−xLi.sub.3−2yAl.sub.1+y−zSi.sub.zO.sub.4−4y−zN.sub.4y+z:Eu.sub.x (AE=Ca, Sr, Ba, or a combination thereof, 0<x<0.04, 0≤y<1, 0<z<0.05, y+z≤1). It is believed that the formal substitution (Al,O).sup.+ by (Si,N).sup.+ reduces the concentration of unwanted Eu.sup.3+ and thus enhances properties of the phosphor such as stability and conversion efficiency.

A phosphor is specified. The phosphor has the general molecular formula:
(MA).sub.a(MB).sub.b(MC).sub.c(MD).sub.d(TA).sub.e(TB).sub.f(TC).sub.g(TD).sub.h(TE).sub.i(TF).sub.j(XA).sub.k(XB).sub.l(XC).sub.m(XD).sub.n:E.
In this case, MA is selected from a group of monovalent metals, MB is selected from a group of divalent metals, MC is selected from a group of trivalent metals, MD is selected from a group of tetravalent metals, TA is selected from a group of monovalent metals, TB is selected from a group of divalent metals, TC is selected from a group of trivalent metals, TD is selected from a group of tetravalent metals, TE is selected from a group of pentavalent elements, TF is selected from a group of hexavalent elements, XA is selected from a group of elements which comprises halogens, XB is selected from a group of elements which comprises O, S and combinations thereof, -E=Eu, Ce, Yb and/or Mn, XC=N and XD=C. The following furthermore hold true: a+b+c+d=t; e+f+g+h+i+j=u; k+l+m+n=v; a+2b+3c+4d+e+2f+3g+4h+5i+6j−k−2l−3m−4n=w; 0.8≤t≤1; 3.5≤u≤4; 3.5≤v≤4; (−0.2)≤w≤0.2 and 0≤m<0.875 v and/or v≥1>0.125 v.

According to one embodiment, a white light source includes a combination of a light emitting diode and phosphors. One of the phosphors is at least a cerium activated yttrium aluminum garnet-based phosphor. There is no light emission spectrum peak at which a ratio of a largest maximum value to a minimum value is greater than 1.9. The largest maximum value is largest among at least one maximum value present in a wavelength range of 400 nm to 500 nm in a light emission spectrum of white light emitted from the white light source. The minimum value is adjacent to the largest maximum value in a longer wavelength side of the light emission spectrum.

A light emitting device including a housing including walls defining a cavity having one side thereof opened, a light emitter to emit light having a peak wavelength in a blue wavelength band and including first and second light emitting chips, a reflective region in the housing to reflect light, and a wavelength conversion layer disposed on the light emitter and including a first wavelength converter and a second wavelength converter to emit light having different peak wavelengths from each other, in which the first wavelength converter has a first excitation peak wavelength and the second wavelength converter has a second excitation peak wavelength, and the second wavelength converter includes a fluoride-based red phosphor represented by A.sub.2MF.sub.6:Mn.sup.4+, where A is one of Li, Na, K, Ba, Rb, Cs, Mg, Ca, Se, and Zn, and M is one of Ti, Si, Zr, Sn, and Ge.

A β-sialon phosphor that is a solid solution of europium, in which D.sub.50 is 7.0 μm or more and 20.0 μm or less and (D.sub.50−D.sub.10)/D.sub.50 is 0.60 or less, where D.sub.50 is a 50% area diameter of primary particles of the β-sialon phosphor, and D.sub.10 is a 10% area diameter of the primary particles of the β-sialon phosphor. Primary particles are defined as single-crystal particles distinguished for each crystal orientation by identifying the crystal orientation of individual particles of the β-sialon phosphor by an electron backscatter diffraction image method. D.sub.50 and D.sub.10 are obtained by image analysis of the cross-sectional area of the primary particles.

Phosphors include a CaAlSiN.sub.3 family crystal phase, wherein the CaAlSiN.sub.3 family crystal phase comprises at least one element selected from the group consisting of Mn, Ce, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, and Yb.

[Object] An electric conductivity-measuring material which emits light according to electric conductivity of a measurement object; an electric conductivity-measuring film containing the material; and an electric conductivity-measuring device and an electric conductivity-measuring method using the electric conductivity-measuring film are provided. An electric resistivity-measuring material which emits light according to electric resistivity of a measurement object when electrons are made incident; an electric resistivity-measuring film containing the material; and an electric resistivity-measuring device and an electric resistivity-measuring method using the electric resistivity-measuring film are also provided. [Solution] An electric conductivity-measuring material is used, which contains at least one of a fluorescent substance, a luminescent substance, an electroluminescent substance, a fractoluminescent substance, a photochromic substance, an afterglow substance, a photostimulated luminescent substance and a mechanoluminescent substance.