Light source having phosphor including divalent, trivalent and tetravalent elements

• US 7,884,539 B2
• Filed: 07/10/2008
• Issued: 02/08/2011
• Est. Priority Date: 07/09/2004
• Status: Active Grant

• Current Assignee: Citizen Electronics Company Limited
• Original Assignee: Dowa Electronics Materials Co. Ltd. (DOWA Holdings Company Limited), Nichia Corporation
• Inventors: Gotoh, Masahiro, Yamashita, Shuji, Nagatomi, Akira, Sakane, Kenji
• Primary Examiner(s): Won; Bumsuk
• Application Number:
  US12/216,774
• Publication Number:
  US 20080303412A1
• Time in Patent Office: 943 Days
• Field of Search: 313498-512, 252/301.R, 252/301.F
• US Class Current: 313/503
• CPC Class Codes: C09K 11/0883 Arsenides; Nitrides; Phosphides
• CPC Class Codes: C09K 11/77347 Silicon Nitrides or Silicon Oxynitrides
• CPC Class Codes: C09K 11/77348 Silicon Aluminium Nitrides or Silicon Aluminium Oxynitrides
• CPC Class Codes: Y02B 20/00 Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps

Abstract

A phosphor having an excitation band relative to lights in the wide range of wavelengths from ultraviolet to visible light, and having an emission spectrum in the red range and so on, with a wide half value width, and an LED and a light source using the phosphor and emitting white and other color lights with good color rendering properties are provided. Powdered raw materials of Ca₃N₂ (2N), CaO (2N), AlN (3N), Si₃N₄ (3N), and Eu₂O₃ (3N) are prepared, and the respective raw materials are mixed to have a mole ratio of the respective elements of Ca:Al:Si:Eu=0.985:1:1:0.015. The mixed raw materials are fired at 1000° C. or higher in an inert atmosphere for three hours, and thereafter pulverized to obtain a phosphor having a composition of CaAlSiN_2.83O_0.25:Eu, which is one example of the phosphor satisfying the above described object. Furthermore, by combining the phosphor with an appropriate LED or a light source emitting from ultraviolet light to visible light, the LED and the light source emitting white and other color lights with good color rendering properties can be obtained.

Claims

1. A phosphor emitting a light when a monochromatic excitation light in a range from 250 nm to 550 nm is irradiated thereon,

wherein a luminescence intensity at an excitation wavelength where an intensity of a spectrum of emitting the light by absorbing the excitation light becomes maximum is defined as P_H, a luminescence intensity at an excitation wavelength where the luminescence intensity becomes minimum is defined as P_L, and P_H/P_L≦

2, and

the phosphor is represented by a composition formula MmAaBbNn;

Z, where the element M is one or more kind of divalent elements, the element A is one or more kind of trivalent elements, the element B is one or more kind of tetravalent elements, N is nitrogen, and the element Z is an activator, satisfying n=(⅔

)m+a+(4/3)b and m=a=b=1.

2. The phosphor according to claim 1, wherein an emission maximum of the spectrum of emitting the light is in a range of 580 nm or more and 680 nm or less, and a half value width of the spectrum of emitting the light is 50 nm or more.

3. A light emitting diode, comprising:

a phosphor according to claim 2; and

a light emitting portion emitting any one of ultraviolet to green lights,

wherein said phosphor is light emitted by any one of the ultraviolet to green lights as an excitation source.

4. A light emitting diode, comprising:

a phosphor according to claim 1, and

a light emitting portion emitting any one of ultraviolet to green lights,

wherein said phosphor is light emitted by any one of the ultraviolet to green lights as an excitation source.

5. The light emitting diode according to claim 4, wherein the ultraviolet to green lights are lights of wavelengths from 250 nm to 550 nm.