An optical member includes a first light guide member having an elongated shape and comprising an end surface and a lateral surface extending in a longitudinal direction from the end surface; and a wavelength conversion layer disposed on the lateral surface of the first light guide member and containing a phosphor.

A phosphor in which at least some of an element M in a phosphor host crystal represented by M.sub.α(L,A).sub.βX.sub.γ is substituted with Eu as an activation material. M represents one or more (including at least Sr) of Mg, Ca, Sr, Ba, and Zn, L represents one or more of Li, Na, and K, A represents one or more of Al, Ga, B, In, Sc, Y, La, and Si, X represents one or more (except that X represents only N) of O, N, F, and Cl, α, β, γ, and δ satisfy 8.70≤α+β+γ+δ≤9.30, 0.00<α≤1.30, 3.70≤β≤4.30, 3.70≤γ≤4.30, and 0.00<δ≤1.30. In a fluorescence spectrum obtained by irradiation with light having a wavelength of 260 nm, when a fluorescence intensity at a wavelength of 569 nm is represented by I.sub.0 and a fluorescence intensity at a wavelength of 617 nm is represented by I.sub.1, I.sub.1/I.sub.0 is 0.01 or more and 0.4 or less.

In a surface modification method for fluoride luminescent materials, an inorganic coating layer A.sub.xMF.sub.y coated substrate A.sub.xMF.sub.y:Mn.sup.4+ is mixed with an organic solution containing a metal phosphate, an alkoxysilane, an organic carboxylic acid or an organic amine. The solution is evaporated to give the organic-inorganic coating layer coated surface-modified fluoride luminescent material. The phosphor photoluminescence intensity and quantum efficiency of the modified phosphors can be maintained at 85%-95% under high temperature and high humidity conditions. After being coated with the inorganic coating layer, the surface defects of the phosphor are reduced, and the photoluminescence intensity and quantum yield of the phosphor are increased by 5%-15%. After being coated with the organic coating layer, the photoluminescence intensity of the phosphor is reduced <3%.

A method for producing a γ-AlON fluorescent material, comprising: preparing a first mixture containing a compound containing Mn, a compound containing Li, a compound containing Mg, an aluminum oxide, and an aluminum nitride, in which the amount of fluorine is 150 ppm by mass or less relative to the total amount of the first mixture excluding fluorine, and subjecting the first mixture to a first heat treatment to obtain a first calcined product having an average particle diameter D1, as measured according to a Fisher Sub-Sieve Sizer method, of 10.0 μm or more; and preparing a second mixture containing the first calcined product, a compound containing Mn, a compound containing Li, a compound containing Mg, an aluminum oxide, and an aluminum nitride, in which the amount of fluorine is 150 ppm by mass or less relative to the total amount of the second mixture excluding fluorine, and subjecting the second mixture to a second heat treatment to obtain a second calcined product having an average particle diameter D2, as measured according to the Fisher Sub-Sieve Sizer method, of 16.0 μm or more, wherein the second mixture contains the first calcined product in an amount of more than 20% by mass and 82% by mass or less.

A head-mounted display to be mounted on a head of the user includes a display panel to display an image, a lighting device to supply light to the display device, the lighting device including at least one light source including a blue light emitting element emitting blue light, and a red phosphor to emit red light when excited by the blue light from the blue light emitting element, the red phosphor including a complex fluoride red phosphor and a nitride red phosphor having a content ratio smaller than that of the complex fluoride red phosphor, a lighting controller to control driving of the light source in synchronization with the image display by the display device so that a one-frame display period in the display device includes a turn-on period and a turn-off period, and a lens.

A head-mounted display to be mounted on a head of the user includes a display panel to display an image, a lighting device to supply light to the display device, the lighting device including at least one light source including a blue light emitting element emitting blue light, and a red phosphor to emit red light when excited by the blue light from the blue light emitting element, the red phosphor including a complex fluoride red phosphor and a nitride red phosphor having a content ratio smaller than that of the complex fluoride red phosphor, a lighting controller to control driving of the light source in synchronization with the image display by the display device so that a one-frame display period in the display device includes a turn-on period and a turn-off period, and a lens.

Embodiments of the invention include a light source and a wavelength converting structure disposed in a path of light emitted by the light source. The wavelength converting structure includes a first phosphor that emits infrared light and a second phosphor that emits visible light. In some embodiments, the light source emits first light, the second phosphor absorbs the first light and emits second light, and the first phosphor absorbs the first light and emits third light and absorbs the second light and emits fourth light.

Synthesizing a color stable Mn.sup.4+ doped phosphor by contacting a gaseous fluorine-containing oxidizing agent with a precursor of: A.sub.aB.sub.bC.sub.cD.sub.dX.sub.x:Mn.sup.4+; A.sub.aiB.sub.biC.sub.ciD.sub.dX.sub.xY.sub.d:Mn.sup.4+; A.sup.1.sub.3G.sub.2mnMn.sub.mMg.sub.nLi.sub.3F.sub.12O.sub.p; or AZF.sub.4:Mn.sup.4+. Where A is Li, Na, K, Rb, Cs, or a combination; B is Be, Mg, Ca, Sr, Ba, or a combination; C is Sc, Y, B, Al, Ga, In, Tl, or a combination; D is Ti, Zr, Hf, Rf, Si, Ge, Sn, Pb, or a combination; X is F or a combination of F and one of Br, Cl, and I; Y is O, or a combination of O and one of S and Se; A.sup.1 is Na or K, or a combination; G is Al, B, Sc, Fe, Cr, Ti, In, or a combination; Z is La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc, Y, In, or a combination.

A material represented by the following formula (I)
(M).sub.8M.sub.6M.sub.6O.sub.24(X,S).sub.2:Mformula (I).
Also disclosed is an ultraviolet radiation sensing material, an X-radiation sensing material, a device and a method for determining the intensity of ultraviolet radiation.

Provided are a light-emitting instrument, and an image display device utilizing an AlON phosphor and having wide color gamut. The light-emitting instrument includes an emission source emitting light having a wavelength from 410 nm to 470 nm and a phosphor or a light-transmitting body where the phosphor is dispersed, and the phosphor includes an inorganic compound where an AlON crystal, an AlON solid solution crystal, or an inorganic crystal having a crystal structure identical to AlON includes at least Mn, an A element (a monovalent metal element) it necessary, a D element (a divalent metal element) if necessary, an E element (a monovalent anion) if necessary, and a G element (one or more elements other than Mn, the A, Al, O, N, the D, or the E) if necessary, and emits fluorescence having a peak wavelength from 515 nm to 541 nm upon irradiation of an excitation source.