Borate phosphor and white light illumination device utilizing the same

The invention provides borate phosphors composed of Ma(Mb)1-xBO3:(Mc)x, wherein Ma is Li, Na, K, Rb, Cs, or combinations thereof, Mb is Mg, Ca, Sr, Ba, Zn or combinations thereof, Mc is Y, La, Pr, Nd, Eu, Gd, Tb, Ce, Dy, Yb, Er, Sc, Mn, Zn, Cu, Ni, Lu, or combinations thereof, and 0≦x≦0.3. The borate phosphors emit visible light under the excitation of ultraviolet light or blue light, and may be further collocated with different colored phosphors to provide a white light illumination device.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a borate phosphor, and in particular relates to a white light illumination device utilizing the same.

2. Description of the Related Art

Commercially available white light illumination devices such as light emitting diodes (hereinafter LED), have gradually replaced conventional tungsten lamps or fluorescent lamps due to high luminescence efficiency and eco-friendliness. For white LEDs, the phosphor composition located within, is a critical factor determining luminescence efficiency, color rendering, color temperature, and lifespan of white LEDs.

In general, the excitation light source of conventional phosphors is a short wavelength ultraviolet light (UV) such as 147 nm, 172 nm, 185 nm, or 254 nm. The phosphors excited by the short wavelength UV have high light absorption and light transfer efficiency. Compared with phosphors excited by short wavelength UV, phosphors excited by long wavelength UV or visible light (350-470 nm) are rare.

In the field, conventional host materials in the phosphor are sulfides, nitrides, or oxides such as silicates or aluminates. Sulfides have high light transfer efficiency, but are unstable and easily degraded by moisture or oxygen. Meanwhile, nitrides are stable, but they are difficult to manufacture as nitrides require a high temperature/pressure condition, thus increasing costs and decreasing production yields. Compared the described phosphors, the borate phosphor of the invention has advantages such as low preparation temperature, high optical stability, and high chemical stability. Accompanied with blue-light or UV LED or laser diode, the borate phosphor may emit visible light. Furthermore, the borate phosphor may collocate with other suitable phosphors to emit different colors to complete a white light illumination device.

SUMMARY OF THE INVENTION

The invention further provides a white light illumination device comprising the borate phosphor as described as above and an excitation light source, wherein the excitation light source emits 200-400 nm UV or 400-470 nm blue light.

DETAILED DESCRIPTION OF THE INVENTION

The method for preparing the described aluminosilicate is sintering. First, the appropriate stoichiometry of reagents was weighted according to the element molar ratio of resulting borates. The reagents containing Li, Na, K, Rb, Cs, or combinations thereof can be chlorides such as (Li, Na, K, Rb, Cs)Cl. The reagents containing Mg, Ca, Sr, Ba, Zn, or combinations thereof can be oxides such as (Mg, Ca, Sr, Ba, Zn)O or carbonates such as (Mg, Ca, Sr, Ba)CO3. The reagents containing Y, La, Pr, Nd, Eu, Gd, Tb, Ce, Dy, Yb, Er, Sc, Mn, Zn, Cu, Ni, Lu, or combinations thereof can be chlorides such as EuCl2and the likes, fluorides such as CeF3and the likes, oxides such as Mn3O4, MnO2, Eu2O3, CeO2, and the likes, carbonates such as MnCO3and the likes, acetates such as Mn(CH3COO)2and the likes, and nitrates such as Ce(NO3)3and the likes. The boron containing reagents includes oxides such as boron oxide (B2O3) or boric acid (H3BO3). The described reagents were evenly mixed and grinded, and charged in a double-crucible. The double-crucible was then stuffed by graphite, and then heated in a high temperature furnace. After sintering at 700-1000° C. for several hours, washing, and heat drying, the described borate phosphors were prepared.

In one embodiment, the borate phosphor emits blue light after being excited by blue light or UV light. In this embodiment, the borate phosphors may collocate with a UV or blue light excitable yellow phosphor. Arranged with a UV excitation light source such as a light-emitting diode or laser diode, a white light emitting diode or white laser diode is completed. The described yellow phosphor includes Y3Al5O12:Ce3+(YAG), Tb3Al5O12:Ce3+(TAG), (Mg, Ca, Sr, Ba)2SiO4:Eu2+, and other suitable yellow phosphors. If the yellow phosphor is UV excitable, the yellow phosphor is directly excited by the excitation light source. If the yellow phosphor is blue light excitable, the yellow phosphor is indirectly excited by blue light. The blue light is emitted from the borate phosphor excited by the excitation light source. The combination and ratio of blue and yellow phosphors are optional in different applications of direct or indirect excitation.

For improving the color rendering, the described phosphors of the invention may collocate with a UV or blue light excitable red and green phosphors. Arranged with an ultraviolet excitation light source such as a light-emitting diode or laser diode, a white light emitting diode or white laser diode is completed. The red phosphor includes (Sr, Ca)S:Eu2+, (Y, La, Gd, Lu)2O3:(Eu3+, Bi3+), (Y, La, Gd, Lu)2O2S:(Eu3+, Bi3+), Ca2Si5N8:Eu2+, ZnCdS:AgCl, or other suitable red phosphors. The green phosphor includes BaMgAl10O17:(Eu2+,Mn2+), SrGa2S4:Eu2+, (Ca, Sr, Ba)Al2O4:(Eu2+, Mn2+), (Ca, Sr, Ba)4Al14O25:Eu2+, Ca8Mg(SiO4)4Cl2:(Eu2+, Mn2+), or other suitable green phosphors. Similar to yellow phosphor, the red and green phosphor can be divided into being directly or indirectly excitable. If the red or green phosphor is UV excitable, the red or green phosphor is directly excited by the excitation light source. If the red or green phosphor is blue light excitable, the red or green phosphor is indirectly excited by blue light. The blue light is emitted from the borate phosphor excited by the excitation light source. The combination and ratio of red, green, and blue phosphors are optional in different applications of direct or indirect excitation.

For the white light illumination device such as described, a white light emitting diode or white laser diode, and the blue/yellow or red/green/blue phosphors can be evenly mixed in preferable ratio and dispersed in an optical gel. The optical gel containing the phosphors may further seal a near UV excitation light source such as a chip of a light emitting diode or a laser diode. Note that if UV is selected as the excitation light source, a UV filter or other UV insulator should be arranged externally from the white light illumination device to protect user's eyes and skin.

EXAMPLES

0.5 mol of Li2CO3(0.1847 g, FW=73.89, commercially available from ALDRICH, 99.99%), 0.99 mol of CaCO3(0.4954 g, FW=100.086, commercially available from ALDRICH, 99.99%), 0.01 mol of CeO2(0.0086 g, FW=172.118, commercially available from STREM, 99.998%), and 1 mol of H3BO3(0.3092 g, FW=61.83, commercially available from STREM, 99.9995%) were weighted, evenly mixed and grinded, and charged in a double-crucible. The double-crucible was then stuffed by graphite, and then heated in a high temperature furnace. After sintering at 700-1000° C. for 10 hours, washing, filtering, and heat drying, pure phase of the borate phosphor LiCa0.99BO3:Ce0.01was prepared. The photoluminescence spectrum of the described product is shown inFIG. 1. The major peak of the excitation band is 356 nm, the major peak of the emission band is 413 nm, and the CIE coordination is (0.16, 0.03).

0.5 mol of Li2CO3(0.1847 g, FW=73.89, commercially available from ALDRICH, 99.99%), 0.99 mol of SrCO3(0.7308 g, FW=147.63, commercially available from ALDRICH, 99.9%), 0.01 mol of CeO2(0.0086 g, FW=172.118, commercially available from STREM, 99.998%), and 1 mol of H3BO3(0.3092 g, FW=61.83, commercially available from STREM, 99.9995%) were weighted, evenly mixed and grinded, and charged in a double-crucible. The double-crucible was then stuffed by graphite, and then heated in a high temperature furnace. After sintering at 700-1000° C. for 10 hours, washing, filtering, and heat drying, pure phase of the borate phosphor LiSr0.99BO3:Ce0.01was prepared. The photoluminescence spectrum of the described product is shown inFIG. 2. The major peak of the excitation band is 340 nm, the major peak of the emission band is 407 nm, and the CIE coordination is (0.16, 0.03).

0.5 mol of Li2CO3(0.1847 g, FW=73.89, commercially available from ALDRICH, 99.99%), 0.99 mol of BaCO3(0.9768 g, FW=187.338, commercially available from ALDRICH, 99.99%), 0.01 mol of CeO2(0.0086 g, FW=172.118, commercially available from STREM, 99.998%), and 1 mol of H3BO3(0.3092 g, FW=61.83, commercially available from STREM, 99.9995%) were weighted, evenly mixed and grinded, and charged in a double-crucible. The double-crucible was then stuffed by graphite, and then heated in a high temperature furnace. After sintering at 700-1000° C. for 10 hours, washing, filtering, and heat drying, pure phase of the borate phosphor LiBa0.99BO3:Ce0.01was prepared. The photoluminescence spectrum of the described product is shown inFIG. 3. The major peak of the excitation band is 323 nm, the major peak of the emission band is 382 nm, and the CIE coordination is (0.17, 0.05).

0.5 mol of Li2CO3(0.1847 g, FW=73.89, commercially available from ALDRICH, 99.99%), 0.99 mol of BaCO3(0.9768 g, FW=197.338, commercially available from ALDRICH, 99.99%), 0.005 mol of Eu2O3(0.0088 g, FW=351.92, commercially available from ALDRICH, 99.9%), and 1 mol of H3BO3(0.3092 g, FW=61.83, commercially available from STREM, 99.9995%) were weighted, evenly mixed and grinded, and charged in a double-crucible. The double-crucible was then stuffed by graphite, and then heated in a high temperature furnace. After sintering at 700-1000° C. for 10 hours, washing, filtering, and heat drying, pure phase of the borate phosphor LiBa0.99BO3:Eu0.01was prepared. The photoluminescence spectrum of the described product is shown inFIG. 4. The major peak of the excitation band is 350 nm, the major peak of the emission band is 495 nm, and the CIE coordination is (0.21, 0.38).

0.5 mol of Na2CO3(0.265 g, FW=105.99, commercially available from TEDLA, 99.8%), 0.99 mol of CaCO3(0.4954 g, FW=100.086, commercially available from ALDRICH, 99.99%), 0.01 mol of CeO2(0.0086 g, FW=172.118, commercially available from STREM, 99.998%), and 1 mol of H3BO3(0.3092 g, FW=61.83, commercially available from STREM, 99.9995%) were weighted, evenly mixed and grinded, and charged in a double-crucible. The double-crucible was then stuffed by graphite, and then heated in a high temperature furnace. After sintering at 700-1000° C. for 10 hours, washing, filtering, and heat drying, pure phase of the borate phosphor NaCa0.99BO3:Ce0.01was prepared. The photoluminescence spectrum of the described product is shown inFIG. 5. The major peak of the excitation band is 357 nm, the major peak of the emission band is 423 nm, and the CIE coordination is (0.16, 0.11).

0.5 mol of Na2CO3(0.2650 g, FW=105.99, commercially available from TEDLA, 99.8%), 0.99 mol of SrCO3(0.7308 g, FW=147.63, commercially available from ALDRICH, 99.9%), 0.01 mol of CeO2(0.0086 g, FW=172.118, commercially available from STREM, 99.998%), and 1 mol of H3BO3(0.3092 g, FW=61.83, commercially available from STREM, 99.9995%) were weighted, evenly mixed and grinded, and charged in a double-crucible. The double-crucible was then stuffed by graphite, and then heated in a high temperature furnace. After sintering at 700-1000° C. for 10 hours, washing, filtering, and heat drying, pure phase of the borate phosphor NaSr0.99BO3:Ce0.01was prepared. The photoluminescence spectrum of the described product is shown inFIG. 6. The major peak of the excitation band is 360 nm, the major peak of the emission band is 423 nm, and the CIE coordination is (0.15, 0.04).

0.5 mol of Na2CO3(0.2650 g, FW=105.99, commercially available from TEDLA, 99.8%), 0.99 mol of BaCO3(0.9768 g, FW=197.338, commercially available from ALDRICH, 99.99%), 0.01 mol of CeO2(0.0086 g, FW=172.118, commercially available from STREM, 99.998%), and 1 mol of H3BO3(0.3092 g, FW=61.83, commercially available from STREM, 99.9995%) were weighted, evenly mixed and grinded, and charged in a double-crucible. The double-crucible was then stuffed by graphite, and then heated in a high temperature furnace. After sintering at 700-1000° C. for 10 hours, washing, filtering, and heat drying, pure phase of the borate phosphor NaBa0.99BO3:Ce0.01was prepared. The photoluminescence spectrum of the described product is shown inFIG. 7. The major peak of the excitation band is 356 nm, the major peak of the emission band is 423 nm, and the CIE coordination is (0.16, 0.07).

0.5 mol of Na2CO3(0.2650 g, FW=105.99, commercially available from TEDLA, 99.8%), 0.98 mol of CaCO3(0.4904 g, FW=100.086, commercially available from ALDRICH, 99.99%), 0.02 mol of Eu2O3(0.0176 g, FW=351.92, commercially available from ALDRICH, 99.9%), and 1 mol of H3BO3(0.3092 g, FW=61.83, commercially available from STREM, 99.9995%) were weighted, evenly mixed and grinded, and charged in a double-crucible. The double-crucible was then stuffed by graphite, and then heated in a high temperature furnace. After sintering at 700-1000° C. for 10 hours, washing, filtering, and heat drying, pure phase of the borate phosphor NaCa0.98BO3:Eu0.02was prepared. The photoluminescence spectrum of the described product is shown inFIG. 8. The major peak of the excitation band is 341 nm, the major peak of the emission band is 509 nm, and the CIE coordination is (0.27, 0.33).

0.5 mol of Na2CO3(0.2650 g, FW=105.99, commercially available from TEDLA, 99.8%), 0.98 mol of SrCO3(0.7233 g, FW=147.63, commercially available from ALDRICH, 99.9%), 0.02 mol of Eu2O3(0.0176 g, FW=351.92, commercially available from ALDRICH, 99.9%), and 1 mol of H3BO3(0.3092 g, FW=61.83, commercially available from STREM, 99.9995%) were weighted, evenly mixed and grinded, and charged in a double-crucible. The double-crucible was then stuffed by graphite, and then heated in a high temperature furnace. After sintering at 700-1000° C. for 10 hours, washing, filtering, and heat drying, pure phase of the borate phosphor NaSr0.98BO3:Eu0.02was prepared. The photoluminescence spectrum of the described product is shown inFIG. 9. The major peak of the excitation band is 410 nm, the major peak of the emission band is 601 nm, and the CIE coordination is (0.51, 0.43).

0.5 mol of Na2CO3(0.2650 g, FW=105.99, commercially available from TEDLA, 99.8%), 0.98 mol of BaCO3(0.9670 g, FW=197.338, commercially available from ALDRICH, 99.99%), 0.02 mol of Eu2O3(0.0176 g, FW=351.92, commercially available from ALDRICH, 99.9%), and 1 mol of H3BO3(0.3092 g, FW=61.83, commercially available from STREM, 99.9995%) were weighted, evenly mixed and grinded, and charged in a double-crucible. The double-crucible was then stuffed by graphite, and then heated in a high temperature furnace. After sintering at 700-1000° C. for 10 hours, washing, filtering, and heat drying, pure phase of the borate phosphor NaBa0.98BO3:Eu0.02was prepared. The photoluminescence spectrum of the described product is shown inFIG. 10. The major peak of the excitation band is 347 nm, the major peak of the emission band is 507 nm, and the CIE coordination is (0.28, 0.44).

0.5 mol of K2CO3(0.3455 g, FW=138.21, commercially available from SHOWA, 99.8%), 0.99 mol of CaCO3(0.4954 g, FW=100.086, commercially available from ALDRICH, 99.99%), 0.01 mol of CeO2(0.0086 g, FW=172.118, commercially available from STREM, 99.998%), and 1 mol of H3BO3(0.3092 g, FW=61.83, commercially available from STREM, 99.9995%) were weighted, evenly mixed and grinded, and charged in a double-crucible. The double-crucible was then stuffed by graphite, and then heated in a high temperature furnace. After sintering at 700-1000° C. for 10 hours, washing, filtering, and heat drying, pure phase of the borate phosphor KCa0.99BO3:Ce0.01was prepared. The photoluminescence spectrum of the described product is shown inFIG. 11. The major peak of the excitation band is 370 nm, the major peak of the emission band is 429 nm, and the CIE coordination is (0.14, 0.06).

0.5 mol of K2CO3(0.3455 g, FW=138.21, commercially available from SHOWA, 99.8%), 0.99 mol of SrCO3(0.7308 g, FW=147.63, commercially available from ALDRICH, 99.9%), 0.01 mol of CeO2(0.0086 g, FW=172.118, commercially available from STREM, 99.998%), and 1 mol of H3BO3(0.3092 g, FW=61.83, commercially available from STREM, 99.9995%) were weighted, evenly mixed and grinded, and charged in a double-crucible. The double-crucible was then stuffed by graphite, and then heated in a high temperature furnace. After sintering at 700-1000° C. for 10 hours, washing, filtering, and heat drying, pure phase of the borate phosphor KSr0.99BO3:Ce0.01was prepared. The photoluminescence spectrum of the described product is shown inFIG. 12. The major peak of the excitation band is 353 nm, the major peak of the emission band is 415 nm, and the CIE coordination is (0.14, 0.03).

The borate phosphors of the examples have excellent emission brightness and color saturation, thereby being suitable to be applied as phosphor of white light illumination devices. Comparing with the Kasei KX661 (BaMgAl10O17:Eu2+, CIE coordination (0.15, 0.07), commercially available from Kasei), the borate phosphor NaSr0.99BO3:Ce0.01in Example 6 has similar emission brightness and better color saturation. The comparison of the photoluminescence spectrum between the borate and KX661 is shown inFIG. 13 and 14, respectively.