An audio sound is detected. The audio sound is determined to be indicative of a power source of a safety sensor waning. Based on the determination, first light is produced based on a reaction of one or more chemicals with second light from a light emitting diode (LED).

A phosphor including a crystal phase of an aluminate compound containing a metal element M constituting a luminescent center ion and aluminum, in which the crystal phase contains crystallites, and an average size of the crystallites is 2 to 100 ?m.

Provided are a method of producing an aluminate fluorescent material, an aluminate fluorescent material and a light emitting device. The production method includes heat-treating a mixture prepared by mixing a compound containing at least one alkaline earth metal element selected from the group consisting of Ba, Sr and Ca, a Mg-containing compound not acting as a flux, a Mn-containing compound, an Al-containing compound, a first flux containing at least one alkali metal element selected from the group consisting of Na, K, Rb and Cs, and a Mg-containing second flux to give an aluminate fluorescent material.

A method for producing a -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 m 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 m 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.

Disclosed is a method for manufacturing crystals of aluminates of one or more element(s) other than aluminium, referred to as A. The method includes: placing starting reagents, including at least one aluminium element source and a source of the element(s) A that has a degree of oxidation of between 1 and 6, in suspension in a liquid medium, forming a suspension referred to as the starting suspension; milling the starting suspension at 50 C., in a three-dimensional liquid medium ball mill for 5 minutes; recovering, at the outlet of the three-dimensional ball mill, a suspension referred to as the end suspension including the starting reagents in activated form or crystals of aluminate of the element(s) A generally in hydrated form; if required, calcination of the end suspension when it includes the starting reagents in activated form, to obtain generally non-hydrated crystals of aluminate of the element(s) A.

Provided are a method of producing an aluminate fluorescent material, an aluminate fluorescent material and a light emitting device. The production method includes heat-treating a mixture prepared by mixing a compound containing at least one alkaline earth metal element selected from the group consisting of Ba, Sr and Ca, a Mg-containing compound not acting as a flux, a Mn-containing compound, an Al-containing compound, a first flux containing at least one alkali metal element selected from the group consisting of Na, K, Rb and Cs, and a Mg-containing second flux to give an aluminate fluorescent material.

A hybrid photoluminescent display consumes little electrical power and provides for light emission/color in a desired color. The display includes a housing having openings forming a desired legend. White LEDs internal to the housing provide light for energizing photoluminescent material. A legend panel housed within the housing defines openings corresponding to the legend. Photoluminescent material is disposed within the openings of the legend panel. The photoluminescent material is selected to be energizable by light from the white light source, and to emit light primarily in a selected wavelength range corresponding to a desired legend color. A color is filter disposed adjacent the photoluminescent material on a side of the legend panel opposite the light source. The color filter is selected to selectively transmit substantially all light in the selected wavelength range, and to selectively not transmit substantially all light outside the selected wavelength range.

Provided is a light-emitting device including a light-emitting element having a peak emission wavelength in a range of from 400 nm to 470 nm, and a fluorescent member including a first fluorescent material including an aluminate that contains Mg, Mn, and at least one alkali earth metal selected from the group consisting of Ba, Sr, and Ca, a second fluorescent material having a different composition from the first fluorescent material, and a third fluorescent material. The first, second and third fluorescent materials have a peak emission wavelength in a range of from 510 nm to 525 nm, from 510 nm to 550 nm, and from 620 nm to 670 nm, respectively.

Provided is an aluminate fluorescent material having a high emission intensity and having a composition containing a first element that contains one or more of Ba and Sr, and a second element that contains Mg and Mn. In the composition, when a molar ratio of Al is 10, a total molar ratio of the first element is a parameter a, a total molar ratio of the second element is a parameter b, a molar ratio of Sr is a product of a parameter m and the parameter a, a molar ratio of Mn is a product of a parameter n and the parameter b. The parameters a and b satisfy 0.5<b<a0.5b+0.5<1.0, the parameter m satisfies 0m1.0, and the parameter n satisfies 0.4n0.7.

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.