A color temperature tunable LED-filament includes an elongated light-transmissive substrate; a first array of LED chips on a front face of the substrate; a second array of LED chips on the front face of the substrate; a first photoluminescence layer covering the first array of LED chips; a second photoluminescence layer covering the second array of LED chips; and a circuit arrangement enabling independent power control to the first and second LED arrays or relative power control to the first and second array of LED chips to control the color temperature of light generated by the LED-filament.

Disclosed are a preparation method for manganese-doped red phosphor, a device and a backlight module including the product. The method includes: 1) mixing A.sub.2BF.sub.6 polycrystalline particles with mill balls; 2) mixing A.sub.2BF.sub.6 powder obtained after ball-milling with a hydrofluoric acid for secondary crystallization; 3) filtering out solid particles in A.sub.2BF.sub.6 and hydrofluoric acid solution after the secondary crystallization; 4) performing ion exchange between A.sub.2BF.sub.6 particles and A.sub.2BF.sub.6; and 5) filtering out solid particles to obtain a filter cake, and performing drying treatment to obtain manganese-doped red phosphor.

Provided is a fluoride phosphor that has a good external quantum efficiency and is suitable for stably producing white LEDs. The fluoride phosphor has a composition represented by a general formula (1) and a repose angle of 30° or more and 60° or less. general formula: A.sub.2M.sub.(1-n)F.sub.6:Mn.sup.4+.sub.n (1), wherein 0<n≤0.1, the element A is one or more alkali metal elements including at least K, and the element M is a simple substance of Si, a simple substance of Ge, or a combination of Si and one or more elements selected from the group consisting of Ge, Sn, Ti, Zr, and Hf.

The present invention provides a method for producing a fluoride fluorescent material, comprising: contacting a fluoride particles represented by the following general formula (I):
K.sub.2[M.sub.1−aMn.sup.4+.sub.aF.sub.6]  (I)
wherein M is at least one member selected from the group consisting of elements belonging to Groups 4 and 14 of the Periodic Table, and a satisfies the relationship: 0<a<0.2; with a solution containing alkaline earth metal ions in the presence of a reducing agent to form an alkaline earth metal fluoride and less than tetravalent manganese ions on the surface of the fluoride particles.

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.

To provide a semiconductor light emitting device which is capable of accomplishing a broad color reproducibility for an entire image without losing brightness of the entire image. A light source provided on a backlight for a color image display device has a semiconductor light emitting device comprising a solid light emitting device to emit light in a blue or deep blue region or in an ultraviolet region and phosphors, in combination. The phosphors comprise a green emitting phosphor and a red emitting phosphor. The green emitting phosphor and the red emitting phosphor are ones, of which the rate of change of the emission peak intensity at 100 C. to the emission intensity at 25 C., when the wavelength of the excitation light is 400 nm or 455 nm, is at most 40%.

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.

The present invention relates to a metal fluoride red phosphor and an application of the phosphor as a light emitting element, the metal fluoride red phosphor having a tetragonal crystal structure of a novel composition, and emitting light in the red color wavelength by being excited by ultraviolet rays or a blue excitation source, thereby being usefully applicable to a light emitting element such as a light emitting diode, a laser diode, a surface emitting laser diode, an inorganic electroluminescence element, and an organic electroluminescence element.

An LED-filament includes a light-transmissive substrate; a first array of LED chips on a front face of the substrate; a second array of LED chips on the front face of the substrate; a first photoluminescence arrangement covering the first array of LED chips; and a second photoluminescence arrangement covering the second array of LED chips; where the first array of LED chips and the first arrangement generate light of a first color temperature and the second array of LED chips and the second arrangement generate light of a second color temperature.