Light emitting device with blue light LED and phosphor components

• US 7,026,756 B2
• Filed: 10/03/2003
• Issued: 04/11/2006
• Est. Priority Date: 07/29/1996
• Status: Expired due to Fees

• Current Assignee: Nichia Corporation
• Original Assignee: Nichia Kagaku Kogyo Kabushiki Kaisha
• Inventors: Shimizu, Yoshinori, Moriguchi, Toshio, Sakano, Kensho, Noguchi, Yasunobu
• Primary Examiner(s): Santiago, Mariceli
• Assistant Examiner(s): RIELLEY, ELIZABETH A
• Application Number:
  US10/677,382
• Publication Number:
  US 20040090180A1
• Time in Patent Office: 921 Days
• Field of Search: 313/512, 313/503, 313/504, 313/506, 438/25
• US Class Current: 313/503
• CPC Class Codes: C09K 11/7767 Chalcogenides
• CPC Class Codes: C09K 11/7774 Aluminates
• CPC Class Codes: G02B 6/0023 provided by one optical element, or plurality thereof, placed between the light guide and the light source, or around the light source
• CPC Class Codes: G02B 6/0025 Diffusing sheet or layer; Prismatic sheet or layer
• CPC Class Codes: G02B 6/0051 Diffusing sheet or layer
• CPC Class Codes: G02B 6/0073 Light emitting diode [LED]
• CPC Class Codes: H01J 29/20 characterised by the luminescent material
• CPC Class Codes: H01L 2224/45015 being circular
• CPC Class Codes: H01L 2224/45124 Aluminium (Al) as principal constituent
• CPC Class Codes: H01L 2224/45144 Gold (Au) as principal constituent
• CPC Class Codes: H01L 2224/45147 Copper (Cu) as principal constituent
• CPC Class Codes: H01L 2224/45169 Platinum (Pt) 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 2224/48257 connecting the wire to a die pad of the item
• CPC Class Codes: H01L 2224/48465 the other connecting portion not on the bonding area being a wedge bond, i.e. ball-to-wedge, regular stitch
• CPC Class Codes: H01L 2224/73265 Layer and wire connectors
• CPC Class Codes: H01L 24/45 of an individual wire connector
• 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 2924/00012 Relevant to the scope of the group, the symbol of which is combined with the symbol of this group
• 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 2924/01019 : Potassium [K]
• CPC Class Codes: H01L 2924/01021 : Scandium [Sc]
• CPC Class Codes: H01L 2924/01067 : Holmium [Ho]
• CPC Class Codes: H01L 2924/01068 : Erbium [Er]
• CPC Class Codes: H01L 2924/12036 : PN diode
• CPC Class Codes: H01L 2924/12041 : LED
• CPC Class Codes: H01L 2924/12042 : LASER
• CPC Class Codes: H01L 2924/15747 : Copper [Cu] as principal constituent
• CPC Class Codes: H01L 2924/181 : Encapsulation
• CPC Class Codes: H01L 2924/20751 : larger or equal to 10 microns less than 20 microns
• CPC Class Codes: H01L 2924/20752 : larger or equal to 20 microns less than 30 microns
• CPC Class Codes: H01L 2924/20753 : larger or equal to 30 microns less than 40 microns
• CPC Class Codes: H01L 2924/20754 : larger or equal to 40 microns less than 50 microns
• CPC Class Codes: H01L 2924/3011 : Impedance
• CPC Class Codes: H01L 2924/3025 : Electromagnetic shielding
• CPC Class Codes: H01L 2933/0091 : Scattering means in or on the semiconductor body or semiconductor body package H01L33/22 takes precedence
• CPC Class Codes: H01L 33/50 : Wavelength conversion elements
• CPC Class Codes: H01L 33/501 : characterised by the materials, e.g. binder
• CPC Class Codes: H01L 33/502 : Wavelength conversion materials
• CPC Class Codes: H01L 33/504 : Elements with two or more wavelength conversion materials
• CPC Class Codes: H01L 33/56 : Materials, e.g. epoxy or silicone resin
• CPC Class Codes: H05B 33/14 : characterised by the chemical or physical composition or the arrangement of the electroluminescent material , or by the simultaneous addition of the electroluminescent material in or onto the light source
• CPC Class Codes: Y02B 20/00 : Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps

Abstract

A light emitting device includes a light emitting component having an active layer of a semiconductor and a phosphor capable of absorbing a part of light emitted from the light emitting component and emitting light of wavelength different from that of the absorbed light, wherein the light emitting component is a LED which has an active layer constituting a gallium nitride based semiconductor containing Indium and is capable of emitting a blue color light with a peak wavelength within the range from 420 to 490 nm. The phosphor is a garnet fluorescent material activated with cerium which is capable of absorbing a part of the blue color light and thereby emitting light having a broad emission spectrum with a peak wavelength existing around the range from 510 to 600 nm and a tail continuing into the region from 700 to 750 nm.

Claims

1. A light emitting device which comprises a light emitting component having an active layer of a semiconductor and a phosphor capable of absorbing a part of light emitted from the light emitting component and emitting light of wavelength different from that of the absorbed light, wherein:

a) said light emitting component is an LED which has an active layer comprising a gallium nitride based semiconductor containing Indium and is capable of emitting a blue color light which spectrum has a peak wavelength within the range from 420 to 490 nm,

b) said phosphor is a garnet fluorescent material activated with cerium which is capable of absorbing a part of the blue color light which spectrum has the peak wavelength within the range from 420 to 490 nm and thereby emitting light having a broad emission spectrum comprising a peak wavelength existing around the range from 510 to 600 nm and a tail continuing beyond 700 nm, and

c) said emission spectrum emitted from the garnet fluorescent material activated with cerium and a spectrum of an unabsorbed light passed through said the garnet fluorescent material from said LED are capable of overlapping each other to make a continuous combined spectrum.

2. A light emitting device according to claim 1, wherein the light color of the combined spectrum is white.

3. A light emitting device according to claim 1, wherein the phosphor comprises two or more kinds of the garnet fluorescent materials activated with cerium.

4. A light emitting device according to claim 3, wherein the two or more kinds of the garnet fluorescent materials activated with cerium including different compositions of Y and Al.

5. A light emitting device according to claim 1, wherein the phosphor includes a first fluorescent material represented by a formula Y₃(Al_1-sGa_s)₅O₁₂:

Ce and a second fluorescent material represented by a formula Re₃Al₅O₁₂;

Ce, where O≦

s≦

1 and Re is at least one selected from Y, Gd and La.

6. A light emitting device according to claim 1, wherein the light color of the combined spectrum corresponds to a point on a straight line connecting points of chromacity genrated by the LED and the fluorescent material.

7. A light emitting device according to claim 1, wherein the emission spectrum of said phosphor comprises a peak wavelength existing around the range from 530 to 570 mm and a tail continuing beyond 700 nm.