Patent Application
20080116422
1. Field of the Invention
The present invention relates to light emitting technology and more particularly, to a LED and its fluorescent powder and organic film layer. The LED has covered thereon an organic film layer containing a fluorescent powder that has added thereto Tb (terbium) ions, Ga (gallium) ions, Yb (ytterbium) ions and Lu (lutetium) ions. The fluorescent powder absorbs short-wave radiation λ=440˜480 nm from an InGaN semiconductor heterostructure and then radiates light of peak wavelength λ=525˜595 nm.
2. Description of the Related Art
In the development of lighting sources, white light is a blend of all the colors in the visual spectrum, resulting in the color white.
Blue light can be added to red light and green light to produce the impression of white light. Solid lighting sources of different colors can be made using this principle. Most white color solid lighting sources in production today are based on the following techniques.
One technique uses three solid lighting sources respectively based on AlInGaP, GaN and GaP to emit red, green and blue light subject to the control of an electric current through AlInGaP, GaN and GaP, enabling the red, green and blue colors of light to be mixed by a lens into white light.
Another technique uses two solid lighting sources respectively based on GaN and GaP to emit blue and yellow green light subject to the control of an electric current through GaN and GaP, enabling the red and yellow green colors of light to be mixed into white light.
In either of the aforesaid two techniques, when one solid lighting source fails, no white light can be obtained. Further, because the forward bias at one solid lighting source is different from that at the other solid lighting source, multiple control circuits are necessary, resulting in a high cost. These drawbacks are unfavorable factors in actual application.
Nichia Chemical Corp. developed a white LED in 1996 by covering an InGaN blue LED with phosphor, thereby mixing blue light and down-converted yellow light to create white light. However, the continuity of the spectrum distribution of the white light thus created is unlike sunlight. This design of white LED is simply suitable for the purpose of simple illumination.
A fourth method for producing white light was developed by Sumitomo Electric Industries, Ltd., Japan. According to this technique, a ZnSe-based white LED is made by introducing an i-ZnMgBeSe/p-ZnMgSe double cladding structure, which includes a very thin i-ZnMgBeSe layer for suppressing electron overflow and a p-ZnMgSSe layer for efficient p-type carrier concentration.
The present invention has been accomplished under the circumstances in view. The invention uses a blue color of solid lighting source to match with a specially prepared yellow orange color of fluorescent light for the production of white light.
It is the main object of the present invention to provide a fluorescent powder, which uses YAG (yttrium aluminum garnet) as the substrate and cerium as the excitant, and has added thereto Tb (terbium) ions, Ga (gallium) ions, Yb (ytterbium) ions and Lu (lutetium) ions. The fluorescent powder absorbs short-wave radiation λ=440˜480 nm from an InGaN semiconductor heterostructure and then radiates light of peak wavelength λ=525˜595 nm.
It is a object of the present invention to provide the fluorescent powder has the chemical formula of (Y1-x-y-z-p-qGdxTbyYbzLupCeq)3Al5O12.
A fluorescent powder for LED (light emitting diode) in accordance with the present invention can be but not limited to an inorganic fluorescent powder that uses YAG (yttrium aluminum garnet) as the substrate and Ce (cerium) as the excitant, and added with Tb (terbium) ions, Ga (gallium) ions, Yb (ytterbium) ions and Lu (lutetium) ions.
The substrate of the fluorescent powder is but not limited to YAG having the chemical composition of (Y1-x-y-z-p-qGdxTbyYbzLupCeq)3Al5O12 that uses Ce (cerium) as the excitant and radiates yellow-orange light. In the chemical formula (Y1-x-y-z-p-qGdxTbyYbzLupCeq)3Al5O12, x=0.05˜0.9, y=0.001˜0.3, Z=0.01˜0.05, p=0.01˜0.2, and q=0.0001˜0.2. Preferably, the content of the excitant is 0.07≦Ce/(Gd+Tb+Yb+Lu)≦0.20.
The concentration ratio between the active ions Ce+3 in the fluorescent powder and the concentration of Tb, Yb and Lu ions that are added to the YAG substrate is 0.09≦Ce/(Tb+Yb+Lu)≦0.23.
The fluorescent powder is a granulated fluorescent powder capable of absorbing short-wave radiation λ=440˜480 nm emitted by InGaN semiconductor heterostructure 1 (see
When the fluorescent powder is excited by the short-wave radiation of the semiconductor heterostructure 1, the afterflow luminance of the light being radiated by the fluorescent powder is relatively reduced within 120˜60 nanoseconds subject to increasing of the specific value (Gd+Ce)/(Y+Lu+Gd+Tb+Yb+Ce) within 0.005˜1.
Therefore, the fluorescent powder of the present invention has the following characteristics: It is based on the substrate of YAG (yttrium aluminum garnet), using Ce (cerium) as the excitant and having added thereto Th (terbium) ions, Ga (gallium) ions, Yb (ytterbium) ions and Lu (lutetium) ions to form a compound having the chemical formula of (Y1-x-y-z-p-qGdxTbyYbzLupCeq)3Al5O12 that absorbs short-wave radiation λ=440˜480 nm from InGaN semiconductor heterostructure 1 and then radiates light of peak wavelength λ=525˜595 nm in which the moving distance of the peak wave in the long-wave direction is relatively increased subject to increasing of the specific value (Gd+Ce)/(Y+Lu+Gd+Tb+Yb+Ce) within 0.05˜1.
The present invention uses a blue color of solid lighting source, which emitted short-wave radiation λ=440˜480 nm, to match with a specially prepared yellow orange color of fluorescent light, which absorbing short-wave radiation λ=440˜480 nm emitted by blue color of solid lighting source 1 (see
Although particular embodiments of the invention have been described in detail for purposes of illustration, various modifications and enhancements may be made without departing from the spirit and scope of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 095142974 | Nov 2006 | TW | national |
