Yellow light emitting device with high luminance

• US 7,825,578 B2
• Filed: 02/28/2007
• Issued: 11/02/2010
• Est. Priority Date: 03/01/2006
• Status: Active Grant

• Current Assignee: Nichia Corporation
• Original Assignee: Nichia Corporation
• Inventors: Kihara, Takeshi, Aoyagi, Kenichi, Aihara, Masato, Miki, Hitomi, Takashima, Suguru, Kishimoto, Tomohisa
• Primary Examiner(s): Ton; Toan
• Assistant Examiner(s): Hanley; Britt D
• Application Number:
  US11/711,766
• Publication Number:
  US 20070205711A1
• Time in Patent Office: 1,343 Days
• Field of Search: 313483-512
• US Class Current: 313/502
• 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 2224/48465 the other connecting portion not on the bonding area being a wedge bond, i.e. ball-to-wedge, regular stitch
• CPC Class Codes: H01L 25/167 comprising optoelectronic devices, e.g. LED, photodiodes
• 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 33/44 characterised by the coatings, e.g. passivation layer or anti-reflective coating
• CPC Class Codes: H01L 33/502 Wavelength conversion materials

Abstract

An object of the present invention is to provide a light emitting device which emits light of deep yellowish color with high luminance. The light emitting device of the present invention comprises a light emitting element having a peak emission wavelength shorter than 490 nm, a fluorescent material for wavelength conversion which absorbs light from the light emitting element and emits light of a wavelength longer than that of the light from the light emitting element, and a filter which cuts off a part of a mixed light produced by mixing the light of the light emitting element and the light of the fluorescent material, wherein the light transmitted through the filter has a chromaticity coordinate on the chromaticity diagram according to CIE 1931 plotted in a region defined by a first point (x=0.450, y=0.450), a second point (x=0.250, y=0.650), a third point (x=0.350, y=0.750) and a fourth point (x=0.250, y=0.750) and in the region defined by a closed curve consisting of the monochromatic locus and the purple boundary.

Claims

1. A light emitting device comprising:

a light emitting element having a peak emission wavelength shorter than 490 nm;

a fluorescent material for wavelength conversion which absorbs light emitted by said light emitting element and emits light of a wavelength longer than that of the light from said light emitting element; and

a filter which cuts off a part of a mixed light produced by mixing the light from said light emitting element and the light from said fluorescent material,

wherein said filter transmits light of wavelengths shorter than 480 nm at a rate of about 10% or less if a maximum transmittance of light of wavelengths ranging from 495 nm to 730 nm is assumed to be 100%,

wherein the mixed light before passing said filter has a ratio of an intensity of a peak emission wavelength of said fluorescent material to an intensity of peak emission wavelength of said light emitting element that is about 1.0 or higher and not higher than about 20,

wherein the mixed light before passing said filter consists of a light component having a peak emission wavelength of said light emitting element and a light component having a peak emission wavelength of said fluorescent material, and has a y value of a chromaticity coordinate on the chromaticity diagram according to CIE 1931 not lower than 0.400, and

wherein the light transmitted through the filter has chromaticity coordinates on the chromaticity diagram according to CIE 1931 plotted in a region defined by a first point (x=0.450, y=0.450), a second point (x=0.250, y=0.650), a third point (x=0.250, y=0.750) and a fourth point (x=0.550, y=0.450) and in a region defined by a closed curve consisting of the monochromatic locus and the purple boundary.

2. The light emitting device according to claim 1, wherein the fluorescent material is at least one member selected from among alkaline earth metal element aluminate fluorescent material, alkaline earth element silicate, alkaline earth element thiogallate, rare earth element aluminate, and oxide-nitride-based fluorescent material.