Yellow light afterglow material and preparation method thereof as well as LED illuminating device using same

Abstract

The invention relates to a yellow light afterglow material and a preparation method thereof as well as an LED illuminating device using the same. The yellow light afterglow material comprises the chemical formula of aY.sub.2O.sub.3.bAl.sub.2O.sub.3.cSiO.sub.2:mCe.nB.xNa.yP, where a, b, c, m, n, x and y are coefficients, and a is not less than 1 but not more than 2, b is not less than 2 but not more than 3, c is not less than 0.001 but not more than 1, m is not less than 0.0001 but not more than 0.6, n is not less than 0.0001 but not more than 0.5, x is not less than 0.0001 but not more than 0.2, and y is not less than 0.0001 but not more than 0.5; wherein Y, Al and Si are substrate elements, and Ce, B, Na and P are activators. The yellow light afterglow material is prepared by the following steps: weighing oxides of elements or materials which can generate oxides at high temperature by molar ratio as raw materials, evenly mixing and then sintering the raw materials at 1200-1700 in a reducing atmosphere.

Claims

1. A method for preparing a compound having a chemical formula of aY.sub.2O.sub.3.bAl.sub.2O.sub.3.cSiO.sub.2:mCe.nB.xNa.yP, wherein a, b, c, m, n, x and y are coefficients, wherein a is not less than 1 but not more than 2, b is not less than 2 but not more than 3, c is not less than 0.001 but not more than 1, m is not less than 0.0001 but not more than 0.6, n is not less than 0.0001 but not more than 0.5, x is not less than 0.0001 but not more than 0.2, and y is not less than 0.0001 but not more than 0.5, wherein the method comprises the steps of: weighing oxides of elements or materials which can generate oxides at high temperature by molar ratio as raw materials; and evenly mixing and then sintering the raw materials at 1200-1700 C. in a reducing atmosphere for 1-8 h.

2. The method of claim 1, wherein a is not less than 1.3 but not more than 1.8, b is not less than 2.3 but not more than 2.7, c is not less than 0.001 but not more than 0.5, m is not less than 0.01 but not more than 0.3, n is not less than 0.01 but not more than 0.3, x is not less than 0.01 but not more than 0.1, and y is not less than 0.01 but not more than 0.5.

3. The method of claim 1, wherein a is not less than 1.3 but not more than 1.5, b is not less than 2.3 but not more than 2.5, c is not less than 0.01 but not more than 0.5, m is not less than 0.01 but not more than 0.3, n is not less than 0.1 but not more than 0.3, x is not less than 0.02 but not more than 0.1, and y is not less than 0.2 but not more than 0 3.

4. The method of claim 1, wherein a is 1.45, b is 2.5, c is 0.01, m is 0.24, n is 0.05, x is 0.1, and y is 0.2.

5. The method of claim 1, wherein a is 1.45, b is 2, c is 0.5, m is 0.01 , n is 0.3, x is 0.02, and y is 0.3.

6. The method of claim 1, wherein a is 1.5, b is 2.6, c is 0.01, m is 0.1, n is 0.05, x is 0.1, and y is 0.2.

7. The method of claim 1, wherein a is 1, b is 2.05, c is 0.01, m is 0.0001, n is 0.1, x is 0.002, and y is 0.01.

8. The method of claim 1, wherein a is 1.2, b is 2.2, c is 0.005, m is 0.05, n is 0.06, x is 0.0001, and y is 0.08.

9. The method of claim 1, wherein a is 1.85, b is 2.7, c is 0.12, m is 0.008, n is 0.0065, x is 0.05, and y is 0.004.

10. The method of claim 1, wherein a is 2, b is 2.95, c is 1, m is 0.2, n is 0.3, x is 0.04, and y is 0.04.

11. The method of claim 1, wherein a is 1.45, b is 2.5, c is 0.002, m is 0.6, n is 0.15, x is 0.03, and y is 0.3.

12. The method of claim 1, wherein a is 1.45, b is 2.5, c is 0.01, m is 0.3, n is 0.5, x is 0.01, and y is 0.0001.

13. The method of claim 1, wherein a is 1.75, b is 3, c is 0.01, m is 0.34, n is 0.02, x is 0.06, and y is 0.4.

14. The method of claim 1, wherein a is 1.15, b is 2, c is 0.014, m is 0.18, n is 0.25, x is 0.003, and y is 0.26.

15. The method of claim 1, wherein a is 1.4, b is 2.45, c is 0.02, m is 0.15, n is 0.0001, x is 0.2, and y is 0.5.

16. The method of claim 1, wherein the raw materials are sintered at a sintering temperature of 1400-1600 C.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic diagram of an LED basic module of a DC LED illuminating device;

(2) FIG. 2 is a schematic diagram of an LED basic module of an AC LED illuminating device;

(3) FIG. 3 is an excitation spectrum of sample 2;

(4) FIG. 4 is a photoluminescence spectrum of the sample 2;

(5) FIG. 5 is an afterglow spectrum of the sample 2; and

(6) FIG. 6 is a thermoluminescence spectrum of the sample 2.

(7) The invention will be further illustrated in detail through preferred embodiments in the form of examples. However, the following examples should not be construed as limit to the scope of the invention, and technologies realized based on the contents of the invention shall fall into the scope of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(8) The yellow light afterglow material of the invention comprises the following chemical formula: aY.sub.2O.sub.3.bAl.sub.2O.sub.3.cSiO.sub.2:mCe.nB.xNa.yP, where a, b, c, m, n, x and y are coefficients, and a is not less than 1 but not more than 2, b is not less than 2 but not more than 3, c is not less than 0.001 but not more than 1, m is not less than 0.0001 but not more than 0.6, n is not less than 0 0001 but not more than 0.5, x is not less than 0.0001 but not more than 0.2, and y is not less than 0.0001 but not more than 0.5. Preferably: a is not less than 1.3 but not more than 1.8, b is not less than 2.3 but not more than 23, c is not less than 0.001 but not more than 0.5, m is not less than 0.01 but not more than 0.3, n is not less than 0.01 but not more than 0.3, x is not less than 0.01 but not more than 0.1, and y is not less than 0.01 but not more than 0.5.

(9) More preferably a is not less than 1.3 but not more than 1.5, b is not less than 2.3 but not more than 2.5, c is not less than 0.01 but not more than 0.5, m is not less than 0.01 but not more than 0.3, n is not less than 0.1 but not more than 0.3, x is not less than 0.02 but not more than 0.1, and y is not less than 0.2 but not more than 0.3. Most preferably: 1.45Y.sub.2O.sub.3.2.5Al.sub.2O.sub.3.0.01SiO.sub.2: 0.24Ce.0.05B.0.1Na.0.2P or 1.45Y.sub.2O.sub.3.2.5Al.sub.2O.sub.3.0.5SiO.sub.2: 0.01Ce.0.3B.0.02Na.0.3P.

(10) The yellow light afterglow material of the invention uses trivalent Ce as luminescent ions, and B, Na and P as a defect center. When excited by ultraviolet light and visible light, the material of the invention emits bright yellow light afterglow.

(11) The yellow light afterglow material of the invention uses oxides of Y, Al, Si, Ce, Na, B and P or elementary substances and compounds which can generate the oxides at high temperature as raw materials.

(12) The preparation method of the yellow light afterglow material comprises the following steps: evenly mixing the raw materials by molar ratio, sintering the raw materials at 1200-1700 C. for 1-8 h in a reducing atmosphere once or several times, preferably at 1400-1600 C. for 2-5 h.

(13) Further, the yellow light afterglow material of the invention has excitation wavelength of 200-500 nm and the strongest emission wavelength of 530-570 nm. The material can store energy from ultraviolet light and/or visible light, and then emit yellow light afterglow at room temperature and emit thermoluminescence when heated, afterglow luminescent and thermoluminescence peak is 530-570 nm, and peak temperature of thermoluminescence is 60-350 C.

(14) Refer to FIG. 1 for schematic diagram of a basic module of a DC LED illuminating device using the yellow light afterglow material of the invention. As the LED illuminating device is at 60-200 in use, the luminance of the conventional YAG:Ce.sup.3+ luminescent powder will decrease due to higher temperature, therefore, the luminance of the LED illuminating device decreases and luminescence turns blue. As the material of the invention can generate thermoluminescence when heated, and emit yellow fluorescence when excited by blue light LED chips, white light LED illumination can be realized by blue light plus yellow light when the material of the invention is used in the LED illuminating device. However, as the material of the invention has thermoluminescence effect when the temperature of the device rises, and energy in the defect center will release in the form of luminescence when heated, the material can compensate temperature quenching generated by using the conventional YAG:Ce.sup.3+ luminescent powder when the device is at high operating temperature, maintaining the overall luminescence of the LED illuminating device in operation at a relatively stable level.

(15) Refer to FIG. 2 for schematic diagram of an LED basic module of an AC LED illuminating device using the yellow light afterglow material of the invention. It can be seen the figure that AC input can be realized by connecting two reverse LEDs in parallel. Luminescence realized by connecting two reverse LEDs in parallel also has periodic luminance change for periodicity of AC, affecting applications of the device. As the yellow light afterglow material of the invention has afterglow luminescence characteristics, when the material is to the AC LED illuminating device, afterglow of the luminescent powder can compensate LED luminescence due to current drop when current cycle changes, thus maintaining stable output of the device in AC cycle.

(16) The invention will be further described through preferred embodiments, but the following examples should not be construed as limit thereto. It should be understood by those skilled in the art that various modifications, replacements and changes can be made according to the technical thought of the invention.

EXAMPLES 1-12

(17) TABLE-US-00001 TABLE 1 Mixture ratio of sample materials (mol) Yttrium Cerium Boric Sodium Monoammonium Sample oxide Alumina Silica dioxide acid bicarbonate phosphate Reference 1.47 2.5 0 0.06 0 0 0 sample 1 1.5 2.6 0.01 0.1 0.05 0.1 0.2 2 1.45 2.5 0.01 0.24 0.05 0.1 0.2 3 1 2.05 0.001 0.0001 0.1 0.002 0.01 4 1.2 2.2 0.005 0.05 0.06 0.0001 0.08 5 1.85 2.7 0.12 0.008 0.0065 0.05 0.004 6 2 2.95 1 0.2 0.3 0.04 0.04 7 1.45 2.5 0.002 0.6 0.15 0.03 0.3 8 1.45 2.5 0.5 0.01 0.3 0.02 0.3 9 1.45 2.5 0.01 0.3 0.5 0.01 0.0001 10 1.75 3 0.01 0.34 0.02 0.06 0.4 11 1.15 2 0.014 0.18 0.25 0.003 0.26 12 1.4 2.45 0.02 0.15 0.0001 0.2 0.5

Test Example 1 Luminescence Temperature Characteristics of the Material of the Invention

(18) All samples and the reference sample in Table 1 were put in a temperature control heating device, and excited by an LED with emission wavelength of 460 nm. Luminance was read by a luminance meter at different temperatures. Refer to Table 2 for results.

(19) TABLE-US-00002 TABLE 2 Sample 25 C. 80 C. 150 C. 200 C. Reference 100 100 100 100 sample 1 99 105 110 110 2 105 110 115 110 3 94 103 110 115 4 93 108 105 108 5 93 103 106 106 6 95 105 105 108 7 90 102 106 105 8 102 106 110 111 9 106 108 110 109 10 99 110 105 106 11 90 102 103 105 12 98 105 110 110

(20) It can be seen from Table 2 that the luminance of the yellow light afterglow material of the invention is greater than that of current Y.sub.2.94 Ce.sub.0.06 Al.sub.5O.sub.12 luminescent powder at the operating temperature of the LED illuminating device (>80), thus being capable of solving temperature quenching problems of luminance of the existing DC LED illuminating devices.

Test Example 2 Afterglow Characteristics of the Material of the Invention

(21) All samples and the reference sample in Table 1 were excited by an LED with dominant emission wavelength of 460 nm for 15 minutes, and afterglow thereafter was tested by a glow tester equipped with a photomultiplier. Refer to Table 3 for results.

(22) TABLE-US-00003 TABLE 3 Luminance at 0 Luminance at 30 Luminance at 1 Sample second seconds minute Reference 0 0 0 sample 1 100 100 100 2 120 118 116 3 86 80 81 4 90 91 90 5 70 74 70 6 65 63 63 7 104 105 106 8 110 112 110 9 88 80 81 10 80 85 81 11 75 71 70 12 65 60 65

(23) Luminance values in Table 3 took sample 1 as a reference. Afterglow luminescence value of the reference sample below the lower limit of a testing instrument 1 mcd/m.sup.2, and can not be read, thus being recorded as 0.

(24) FIG. 3 is an excitation spectrum of sample 2, FIG. 4 is a photoluminescence spectrum of the sample 2, FIG. 3 and FIG. 4 show that the material of the invention emits yellow fluorescence when excited by ultraviolet to visible light. FIG. 5 is an afterglow spectrum of the sample 2, showing that afterglow luminescence of the material of the invention is yellow. FIG. 6 is a thermoluminescence spectrum of sample 2, showing that the material of the invention has thermoluminescence phenomenon when heated to above 60.

(25) As frequency of common AC is 50 Hz, that is, the period is 20 ms, the direction does not change, and change in current is 10 ms per semi-period. Table 5 provides afterglow luminance within 10 ms tested by a high speed CCD capable of taking 300 pictures per second when the sample 2 is excited by an LED with dominant emission wavelength of 460 nm for 15 minutes and the excitation stops. Refer to Table 4 for results.

(26) TABLE-US-00004 TABLE 4 3.33 ms 6.66 ms 9.99 ms Reference sample 2 1 1 Sample 2 1527 1510 1505

(27) It can be seen from Table 4 that the material of the invention has afterglow luminescence, while the existing Y.sub.2.94 Ce.sub.0.06 Al.sub.5O.sub.12 luminescent powder does not have afterglow luminescence. The figures in Table 4 show that the luminescent material of the invention has stronger afterglow luminescence within the AC cycle, and can effectively compensate luminescent intensity loss due to the current drop. The afterglow value of the reference sample is caused by instrument noise, and can be ignored.

(28) The figures in Tables 2 to 4 show that the material of the invention has the afterglow luminescence characteristics compared with the material Y.sub.2.94 Ce.sub.0.06 Al.sub.5O.sub.12 reported by documents, and the DC and/or AC LED illuminating device of the basic unit (as shown in FIG. 1 and FIG. 2) using the yellow light afterglow material of the invention has obvious novelty and creativity.