Light emitting element and lighting instrument

• US 20070159091A1
• Filed: 02/15/2005
• Published: 07/12/2007
• Est. Priority Date: 02/18/2004
• Status: Active Grant

• Current Assignee: National Institute for Materials Science
• Original Assignee: National Institute for Materials Science
• Inventors: Hirosaki, Naoto, Yamamoto, Hajime, Sakuma, Ken, Ueda, Kyota
• Granted Patent: US 7,573,190 B2
• Time in Patent Office: Days
• US Class Current: 313/512
• CPC Class Codes: C09K 11/0883 Arsenides; Nitrides; Phosphides
• CPC Class Codes: C09K 11/77348 Silicon Aluminium Nitrides or Silicon Aluminium Oxynitrides
• CPC Class Codes: H01L 2224/45144 Gold (Au) as principal constituent
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48247 connecting the wire to a bond pad of the item
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 33/502 Wavelength conversion materials
• CPC Class Codes: Y02B 20/00 Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps

Abstract

Conventional light emitting diode designs combined with blue light emitting diodes tend to lack in decorativeness and warmness. The present invention aims at providing a white light emitting diode for emitting white light with warmness at a higher luminance, and an intermediate color light emitting diode satisfying light emission in diversified color tones at a higher luminance.

The solving means resides in adoption of a fluorescent material which is configured to emit yellowish red or red light and which comprises a CaAlSiN₃ crystal phase including, dissolved therein in a solid state, one kind or two or more kinds of element(s) selected from Mn, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, in a manner that the fluorescent material is mixed with another fluorescent material configured to emit green, yellowish green, or yellow light, and that the mixedly obtained phosphor is combined with a semiconductor light emitting element configured to emit bluish purple or blue light, to thereby fabricate a white light emitting diode for emitting white light with warmness at a high efficiency.

Claims

1. A visible light emitting device, characterized in that said visible light emitting device includes at least:

a semiconductor light emitting element configured to emit bluish purple or blue light;

a support member formed with a depression for placing said semiconductor light emitting element therein, said depression having an inclined surface constituted as a visible wavelength light reflective surface;

terminals configured to supply electric power to said semiconductor light emitting element; and

a phosphor configured to absorb a part or the whole of light emitted from said light emitting element, and to emit fluorescence at a wavelength different from that of the absorbed light, the phosphor including X % of a first fluorescent material configured to emit green, yellowish green, or yellow light, and Y % of a second fluorescent material configured to emit yellowish red or red light, at a mixing ratio meeting a condition of 0≦

X<

100, 0<

Y<

100, and 0<

X+Y≦

100,

wherein said second fluorescent material comprises a CaAlSiN₃ crystal phase including, dissolved therein in a solid state, one kind or two or more kinds of element(s) selected from Mn, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu.

2. The light emitting device of claim 1, characterized in that said second fluorescent material contains at least Eu.

3. The light emitting device to emit arbitrary colors of claim 1, characterized in that said semiconductor light emitting element is a blue light emitting diode having a main emission wavelength of 380 nm to 485 nm,

said first fluorescent material is a phosphor powder having a main emission wavelength of 495 nm to 585 nm,

said second fluorescent material is a phosphor powder having a main emission wavelength of 585 nm to 780 nm, and said phosphor powders are mixed, dispersed in a resin, and mounted to cover said blue light emitting diode element.

5. The lighting apparatus of claim 4, characterized in that the light emitting device of any claim 1 is used as said light emitting device.

6. The lighting apparatus of claim 5, characterized in that each light source unit is optically connected with a light guiding member including a scattering element.

7. The lighting apparatus of claim 6, characterized in that said scattering element comprises air bubbles, and said light guiding member is a rod-like member made of transparent resin.

4. A lighting apparatus characterized in that said lighting apparatus includes three or more light source units, each light source unit including at least one light emitting device,

said light emitting device including at least:

a semiconductor light emitting element configured to emit bluish purple or blue light;

a support member formed with a depression for placing said semiconductor light emitting element therein, said depression having an inclined surface constituted as a visible wavelength light reflective surface;

terminals configured to supply electric power to said semiconductor light emitting element; and

a phosphor configured to absorb a part or the whole of light emitted from said light emitting element, and to emit fluorescence at a wavelength different from that of the absorbed light, the phosphor including at least one of a first fluorescent material configured to emit green, yellowish green, or yellow light, and a second fluorescent material configured to emit yellowish red or red light,

wherein each of said light source units or each of said light emitting device has a mixing ratio of said first fluorescent material to said second fluorescent material, which mixing ratio is different from those of the other light source units or other light emitting devices, in a manner that different light emission colors are visible, site by site of said lighting apparatus.