Source: http://www.google.com/patents/US8058793?dq=5920316
Timestamp: 2015-11-30 22:38:38
Document Index: 432230487

Matched Legal Cases: ['Application No. 2002', 'Application No. 2002', 'Application No. 2002', 'Application No. 2002', 'Application No. 2002', 'Application No. 2002', 'Application No. 2002', 'Application No. 2002', 'Application No. 2002']

Patent US8058793 - Nitride phosphor and production process thereof, and light emitting device - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inAdvanced Patent SearchPatentsTo provide a phosphor containing a comparatively much red component and having high light emitting efficiency, high brightness and further high durability, the nitride phosphor is represented by the general formula LXMYN((2/3)X+(4/3)Y):R or LXMYOZN((2/3)X+(4/3)Y−(2/3)Z):R (wherein L is at least one...http://www.google.com/patents/US8058793?utm_source=gb-gplus-sharePatent US8058793 - Nitride phosphor and production process thereof, and light emitting deviceAdvanced Patent SearchPublication numberUS8058793 B2Publication typeGrantApplication numberUS 12/453,534Publication dateNov 15, 2011Priority dateMar 22, 2002Fee statusPaidAlso published asCA2447288A1, CA2447288C, CN1522291A, CN100430456C, EP1433831A1, EP1433831A4, US7258816, US7297293, US7556744, US7597823, US7964113, US8076847, US20040135504, US20060038477, US20080089825, US20090072708, US20090230840, US20090284132, US20090309485, WO2003080764A1Publication number12453534, 453534, US 8058793 B2, US 8058793B2, US-B2-8058793, US8058793 B2, US8058793B2InventorsHiroto Tamaki, Masatoshi Kameshima, Motokazu Yamada, Takahiro Naitou, Kazuhiko SakaiOriginal AssigneeNichia CorporationExport CitationBiBTeX, EndNote, RefManPatent Citations (52), Non-Patent Citations (25), Referenced by (1), Classifications (72), Legal Events (2) External Links: USPTO, USPTO Assignment, EspacenetNitride phosphor and production process thereof, and light emitting device
US 8058793 B2Abstract
1. A light emitting device comprising a light emitting element, a first phosphor which absorbs at least the portion of light from said light emitting element and emits light having a different wave length, and a second phosphor which absorbs at least the portion of light from said light emitting element and emits light having a different wave length, wherein the peak wave length of luminescence spectrum which said light emitting element has is situated at a longer wave length side than the peak wave length of excitation spectrum which the first phosphor has and the peak wave length of excitation spectrum which the second phosphor has.
2. The light emitting device according to claim 1; wherein the peak wave length of luminescence spectrum of the light emitting element is shifted toward shorter wavelength side in accordance with the increase of electric current density.
3. The light emitting device according to claim 1; wherein said first phosphor and said second phosphor have a nearly equal change of luminescence intensity in accordance with the change of ambient temperatures of the first phosphor and the second phosphor.
4. The light emitting device according to claim 3; wherein the change of ambient temperatures of the first phosphor and the second phosphor is caused by the change of the input electric current to said light emitting element.
5. The light emitting device according to claim 1; wherein the peak wave length of luminescence spectrum of said light emitting element is in a range of 350 nm to 530 nm.
6. The light emitting device according to claim 1; wherein said first phosphor has a higher excitation efficiency at the short wavelength side of said wave length change than the long wavelength side within a range of the wave length change of the light emitting element which is generated at changing the electric current density of the light emitting element.
7. The light emitting device according to claim 1; wherein said first phosphor has the peak wave length of excitation spectrum which the first phosphor has at the short wavelength side of said wave length change within a range of the wave length change of the light emitting element which is generated at changing the electric current density of the light emitting element.
8. The light emitting device according to claim 1; wherein said first phosphor contains a yttrium-aluminum-garnet-base phosphor which contains Y and Al, and contains at least one of elements selected from the group consisting of Lu, Sc, La, Gd, Tb, Eu and Sm and at least one of elements selected from the group consisting of Ga and In and is activated by at least one of elements selected from the rare earth elements.
9. The light emitting device according to claim 1; wherein the difference between the peak wave length of excitation spectrum which said first phosphor has and the peak wave length of excitation spectrum which said light emitting element has is 40 nm or less.
10. The light emitting device according to claim 1; wherein said second phosphor has a higher excitation efficiency at the short wavelength side of said wave length change than the long wavelength side within a range of the wave length change of the light emitting element which is generated at changing the electric current density of the light emitting element.
11. The light emitting device according to claim 1; wherein said second phosphor contains a nitride-base phosphor which contains N, and contains at least one of elements selected from the group consisting of Be, Mg, Ca, Sr, Ba and Zn and at least one elements selected from the group consisting of C, Si, Ge, Sn, Ti, Zr and Hf, and is activated by at least one of elements selected from the rare earth elements.
12. The light emitting device according to claim 1; wherein said light emitting device is the light source of a back light for a liquid crystal display or a light source for illumination.
This application is a divisional of U.S. application Ser. No. 11/905,725, filed Oct. 3, 2007, which is a divisional of U.S. application Ser. No. 11/252,111, filed Oct. 18, 2005, now U.S. Pat. No. 7,297,293, which is a divisional of U.S. application Ser. No. 10/478,598, filed Nov. 24, 2003, now U.S. Pat. No. 7,258,816, which is the US national phase of international application PCT/JP03/03418, filed in English on 20 Mar. 2003, which designated the US. PCT/JP03/03418 claims priority to JP Application No. 2002-080879 filed 22 Mar. 2002, JP Application No. 2002-126566 filed 26 Apr. 2002, JP Application No. 2002-148555 filed 23 May 2002, JP Application No. 2002-167166 filed 7 Jun. 2002, JP Application No. 2002-187647 filed 27 Jun. 2002, JP Application No. 2002-226855 filed 5 Aug. 2002, JP Application No. 2002-348386 filed 29 Nov. 2002, JP Application No. 2002-348387 filed 29 Nov. 2002 and JP Application No. 2002-351634 filed-3 Dec. 2002. The entire contents of these applications are incorporated herein by reference.
Under these circumstances, in the pamphlet of International Open Patent No. 01/40403, there is disclosed an MxSiyNz:Eu nitride phosphor (wherein M is at least one of alkali earth metals at least selected from a group of Ca, Sr, Ba and Zn. z=(2/3)x+(4/3)y) which increased a red component in comparison with a conventional phosphor.
However, the nitride phosphor disclosed in the pamphlet of International Open Patent No. 01/40403 obtains a slightly reddish white color light, for example, by combination with a blue light emitting diode, but the improvement of brightness is further required.
In order to solve the above-mentioned problems, the nitride phosphor related to the present invention is a nitride phosphor (base nitride phosphor) which is represented by the general formula LXMYN((2/3)X+(4/3)Y):R or LXMYOZN((2/3)X+(4/3)Y−(2/3)Z):R (wherein L is at least one or more selected from the Group II Elements consisting of Mg, Ca, Sr, Ba and Zn, M is at least one or more selected from the Group IV Elements in which Si is essential among C, Si and Ge, and R is at least one or more selected from the rare earth elements in which Eu is essential among Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er and Lu.), and absorbs at least the portion of light having the first luminescence spectrum in which a peak wave length is 500 nm or less and emits light having the second luminescence spectrum which has at least one or more of peaks at a range of 520 to 780 nm; and further contains the elements (hereinafter, referred to as different elements) below.
The nitride phosphor which is represented by the general formula LXMYN((2/3)X+(4/3)Y):R or LXMYOZN((2/3)X+(4/3)Y−(2/3)Z):R is a nitride phosphor which emits light having the second luminescence spectrum which has a peak wave length at a yellow to red region and the like when light having the first luminescence spectrum which has a peak wave length at an ultra violet to blue region is irradiated. The luminescence intensity can be changed by containing the second different element in said nitride phosphor, without changing the color tone. The nitride phosphor having desired brightness can be provided thereby. Further, the adjustment of the brightness can be easily carried out.
The first production process of the nitride phosphor of the present invention is characterized in including the first step which mixes in a wet process the oxide of R(R has at least one or more selected from the rare earth element in which Eu is essential among Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er and Lu.) with a compound in which there are contained at least one or more of elements selected from the Group I Element consisting of Li, Na, K, Rb, Cs, Cu, Ag and Au, the Group III Element consisting of B, Al, Ga and In, the Group IV Element consisting of Ti, Zr, Hf, Sn and Pb, the Group V Element consisting of V, Nb, Ta, P, Sb and Bi, the Group VI Element consisting of Cr, Mo, W and S, the Group VII Element consisting of Re and the Group VIII Element consisting of Fe, Co, Ir, Ni, Pd, Pt and Ru; the second step of firing the mixture obtained by the first step; the third step in which the mixture obtained by the second step is mixed with at least any one of the nitride of L (L has at least one or more selected from the Group II Element consisting of Mg, Ca, Sr, Ba and Zn), the nitride of M and the oxide of M (M has at least one or more selected from the Group IV Element in which Si is essential among C, Si and Ge); and the fourth step of firing the mixture obtained from the third step in reductive atmosphere. The nitride phosphor having high brightness can be provided thereby. Further, the nitride phosphor having desired luminescence properties can be provided by the elements added.
The typical one of the above-mentioned fourth nitride phosphor is a nitride phosphor consisting of Si, N and at least any one of elements of Cs and Sr which is activated by Eu. In the typical example of the nitride phosphor, the portion of Eu can be substituted with at least one or more of the rare earth elements selected from a group consisting of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er and Lu. The portion of at least any one of elements of Ca and Sr can be substituted with at least one or more of the Group II Elements selected from a group consisting of Be, Mg, Ba and Zn. The portion of Si can be substituted with at least one or more of the Group IV Elements selected from a group consisting of C, Ge, Sn, Ti, Zr and Hf.
The fifth nitride phosphor related to the present invention is a nitride phosphor which is represented by the general formula LXMYN((2/3)X+(4/3)Y):R or LXMYOZN((2/3)X+(4/3)Y−(2/3)z):R (wherein L is at least one or more of the Group II Elements selected from a group consisting of Be, Mg, Ca, Sr, Ba and Zn. R is at least one or more of the rare earth elements selected from a group consisting of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er and Lu. X, Y and Z are 0.5≦X≦3, 1.5≦Y≦8, and 0<Z≦3); and said nitride phosphor is characterized in containing 1 ppm or more and 10000 ppm or less of B. The improvement of the luminescence properties such as luminescence brightness, quantum efficiency and the like can be designed thereby.
Further, the eighth nitride phosphor related to the present invention is characterized in being an L-M-O—N:Eu, WR (wherein L contains at least one or more selected from a group of II valency consisting of Be, Mg, Ca, Sir, Ba and Zn. M contains at least one or more selected from a group of IV valency consisting of C, Si, Ge, Sn, Ti, Zr and Hf. O is oxygen. N is nitrogen. Eu is europium. WR is the rare earth element.). In the eighth phosphor, an oxide can be used as a raw material. Further, when the phosphor is produced, it is considered that oxygen is contained in a composition, but in the eighth nitride phosphor related to the present invention, a phosphor having high luminescence efficiencies can be provided even when oxygen is contained in the composition during the firing step.
In the seventh to tenth nitride phosphors related to the present invention, it is preferable that at least one or more among Y, La, Ce, Pr, Nd, Gd, Tb, Dy, Ho, Er and Lu are contained as the above-mentioned WR. The phosphor having high luminescence efficiencies can be provided by using Y, La, Ce, Pr, Nd, Gd, Tb, Dy, Ho, Er and Lu among the rare earth element being a co-activator. It is considered that Y, La, Gd, Lu and the like have no luminescence center, therefore this is caused by the flux effect. Further, Pr, Dy, Tb, Ho, Er and the like among the rare earth element have the luminescence center, and it is considered that this is caused by the sensitization effect and the sensitization effect.
Further, Mn is preferably added in the seventh to tenth phosphors related to the present invention. When the Sr—Ca—Si—N:Eu, WR-base phosphor in which Mn or a Mn compound was added at production process is used, the luminescence efficiencies such as luminescence brightness, quantum efficiency and energy efficiency was improved than the Sr—Ca—Si—N:Eu, WR-base phosphor in which Mn was not added. This is considered because the Mn or a Mn compound accelerates the diffusion of Eu2+ being an activator and enlarges the particle diameter, and crystallinity was improved. Further, this is considered because Mn works as a sensitizer in the phosphor in which Eu2+ is an activator and the increase of the luminescence intensity of the Eu2+ activator was carried out.
Oxides or hydroxy oxide products such as MnO2, Mn2O3, Mn3O4 and MnOOH as the Mn added in the above-mentioned seventh to tenth phosphors are usually added, but it is not limited to these, a Mn metal, a Mn nitride, an imide, an amide or other inorganic salts thereof. Further, a condition in which it is previously contained in other raw material may be well. Further, with respect to the above-mentioned seventh to tenth phosphors, O is contained in the composition. It is considered that O is introduced from various Mn compounds being a raw material, or accelerates the effects of Eu diffusion, particle growth and the improvement of crystallinity. Namely, with respect to the effect of the Mn addition, similar effect is obtained even if a Mn compound is changed to a metal, nitride and oxide, and the effect of a case of using an oxide is rather great. As a result, a phosphor in which a trace amount of O is contained in the composition of the phosphor is produced. Even if a compound not containing oxygen in the Mn compound is used, O is introduced by other raw material such as Eu2O3, atmosphere and the like, and the above mentioned problems are solved thereby even if a compound containing oxygen is not used.
The above-mentioned seventh to tenth phosphors are preferably a mean particle diameter of 3 μm or more. The phosphors of Sr—Ca—Si—N:Eu, WR-base, Sr—Si—N:Eu, WR-base, and Ca—Si—N:Eu, WR-base are a mean particle diameter of about 1 to 2 μm, but the above-mentioned silicon nitride to which Mn was added can be a mean particle diameter of 3 μm or more. According to the difference of the particle diameter, there are advantages that the larger the particle diameter is, the more the luminescence brightness of the phosphor is improved, and the light take-out efficiency in a light emitting device is raised, etc.
The third light emitting device related to the present invention is a light emitting device which has at least a light emitting element which emits light having the first luminescence spectrum and a phosphor which absorbs at least the portion of light of the above-mentioned first luminescence spectrum and emits light having the second luminescence spectrum which is different from the above-mentioned first luminescence spectrum; and the above-mentioned phosphor is characterized in using any one of the seventh to tenth phosphors related to the present invention. The light emitting device which emits light being a different color from the color which the light emitting device has can be provided thereby. For example, the light emitting device which emits light of a white color by combining blue and yellow, red and blue green, green and red purple and the like which are in the relation of a complementary color. However, it is not limited to the white color, but the light emitting device having a desired luminescence color can be provided. Specifically, there can be constituted the light emitting device which emits a warm color-base white color which is slightly reddish by mixing blue light which is emitted from a blue light emitting element and yellow red light which was emitted by the wave length conversion by the phosphor, by using the blue light emitting element which has the first luminescence spectrum nearby 440 to 480 nm and using the Sr—Ca—Si—N:Eu, WR-base phosphor which carries out the wave length conversion of the portion of light of said first luminescence spectrum and emits light of the second luminescence spectrum at 600 to 660 nm.
The phosphor used for the third light emitting device related to the present invention is not limited to one kind, and a combination of 2 or more of phosphors having different peak wave lengths can be used. For example, the Sr—Ca—Si—N:Eu, WR-base phosphor has a luminescence spectrum nearby 650 nm, and on the contrary, the Sr—Si—N:Eu, WR-base phosphor has a luminescence spectrum nearby 620 nm. The phosphor having peak wave length at a desired position within a wave length range of 620 to 650 nm can be produced. The light emitting device using the phosphor which combined 2 kind of phosphors can make a luminescence color different from a light emitting device using only one phosphor. The light emitting device having a desired luminescence color can be provided thereby.
The twelfth phosphor related to the present invention is characterized in being a Sr—Si—N:R-base silicon nitride phosphor comprises Mn wherein R is one or more rare earth elements in which Eu is essential. In case of the silicon nitride of this system, luminescence efficiency is more improved by adding Mn at a production step than a case of not adding Mn. The effect which Mn exerts to the Sr—Si—N:Eu-base silicon nitride is similar as the above description, and this is considered because the Mn accelerates the diffusion of Eu2+ being an activator and enlarges the particle diameter, and crystallinity was improved. Further, this is considered because Mn works as a sensitizer in the phosphor in which Eu2+ is an activator and the increase of the luminescence intensity of the Eu2+ activator was carried out. The Sr—Si—N:R-base silicon nitride phosphor related to the present invention has a composition and luminescence spectrum different from the above-mentioned Sr—Ca—Si—N:R-base silicon nitride phosphor, and has a peak wave length nearby 610 to 630 nm.
Mn which is added to the silicon nitride constituting the above-mentioned eleventh to thirteenth phosphors is usually added by oxides or hydroxy oxide products such as MnO2, Mn2O3, Mn3O4 and MnOOH, but it is not limited to these, and may be a Mn metal, a Mn nitride, an imide, an amide or other inorganic salts thereof. Further, a condition in which it is previously contained in other raw material may be well. Further, O is contained in the composition of the above-mentioned silicon nitride. It is considered that O is introduced from various Mn compounds being a raw material, or accelerates the effects of Eu diffusion, particle growth and the improvement of crystallinity. Namely, with respect to the effect of the Mn addition, a similar effect is obtained even if a Mn compound is changed to a metal, nitride and oxide. The effect of a case of using an oxide is rather great. As a result, the phosphor in which a trace amount of O is contained in the composition of silicon nitride is produced. Accordingly, the base nitride phosphor are Sr—Ca—Si—O—N:R, Sr—Si—O—N:R and Ca—Si—O—N:R. Thus, even if a compound not containing oxygen in the Mn compound is used, O is introduced by other raw material such as Eu2O3, atmosphere and the like, and Eu diffusion, particle growth and the improvement of crystallinity are accelerated by Mn even if a compound containing oxygen is not used.
In the above-mentioned silicon nitride, it is preferable that there are contained at least one or more selected from a group consisting of Mg, Sr, Ca, Ba, Zn, B, Al, Cu, Mn, Cr and Ni. The luminescence efficiencies such as luminescence brightness and quantum efficiency can be improved by containing at least the component constituting elements such as Mn and B in the above-mentioned silicon nitride. The reason is considered to be that the particle diameter of powder becomes homogeneous and big by containing the component constituting elements such as Mg and B in the above-mentioned base nitride phosphor, and crystallinity is remarkably improved. The wave length of the first luminescence spectrum can be converted at high efficiency by improving the crystallinity, and the phosphor having good luminescence efficiencies which has the second luminescence spectrum is obtained. Further, the afterglow property of the phosphor can be arbitrarily adjusted. The afterglow property is important in a display device such as a display and PDP on which displays are continuously and repeatedly carried out. Accordingly, the afterglow can be suppressed by slightly containing B, Mg, Cr, Ni, Al and the like in the base nitride phosphor of the phosphor. Thus, the phosphor related to the present invention can be used for a display device such as a display. Further, even if oxides such as MnO2, Mn2O3, Mn3O4 and H3BO3 are added for adding B and the like, the luminescence properties are not lowered, and it is considered that O plays also an important role in the diffusion process as described above. Thus, the particle diameter of the phosphor, crystallinity and energy transmission passage are changed by containing the component constituting elements such as Mg and B in the above-mentioned silicone nitride, absorption, reflection and scattering are changed, and the luminescence properties in a light emitting device such as luminescence and take-out of light, afterglow and the like are changed. In other word, the phosphor utilized for a light emitting device is optimized by utilizing this.
With respect to the Sr—Ca—Si—N:R-base silicon nitride, the molar ratio of Sr to Ca is preferably Sr:Ca=1 to 9:9 to 1. In particular, for the Sr—Ca—Si—N:Eu-base silicon nitride, the molar ratio of Sr t