JP2008285606A - Phosphor, method for producing the same and light-emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a phosphor which has a sufficient band gap, emits yellow to red fluorescent lights, can sequentially change the color tone of the emitted fluorescent light from yellow to red by changing the molar ratio of the elements contained therein, can easily give objective yellow to red color tone, and is good in light-emitting efficacy in blue color LED and blue color LD, and to provide a method for producing the phosphor, by which the phosphor can easily and efficiently be produced. <P>SOLUTION: This phosphor is represented by composition formula (1): Y<SB>3-a-b</SB>Ce<SB>a</SB>L<SB>b</SB>Al<SB>5-c</SB>Si<SB>c</SB>O<SB>12-d</SB>N<SB>d</SB>(1) (wherein, L is one or more elements selected from Gd, La, Tb, Lu, and Sc; a, b, c and d are numerical values satisfying 0.01<a<0.50, 0.0≤b<2.5, 0.0<c<2.0 and 0.01<d<2.67, respectively). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a phosphor, a method for manufacturing the same, and a light emitting device using the same, and more particularly to a yellow to red phosphor and a light emitting device using the same.

A white light emitting diode (LED), a blue laser (LD), etc. is used as an excitation source and emits fluorescent light in the yellow region to achieve color rendering and emit white light. Compared to the above, the power consumption is low and the life is long. In addition, light-emitting devices using these LEDs can easily obtain light that does not contain unnecessary ultraviolet rays and infrared rays, so they can be used for various illuminations such as cultural assets and art works sensitive to ultraviolet rays, and objects that do not like heat irradiation. Is preferred. As a phosphor of such a light-emitting device, a so-called YAG: Ce-based phosphor such as (Y, Gd) ₃ (Al, Ga) ₅ O ₁₂ : Ce ³⁺ is used which has good luminous efficiency by LED and little deterioration by LED. ing. As this type of light emitting device, specifically, for _{example, (RE 1-x Sm x} ) 3 (Al y Ga 1-y) 5 O 12: represented by Ce, wherein, RE is, Y, from Gd There have been reported light emitting diodes (Patent Documents 1 to 3) and the like molded with phosphors that emit at least one selected from blue LEDs and emit yellowish green light. However, these light emitting diodes have a problem that a sufficient color rendering property cannot be obtained because they are white by complementary colors of blue and yellow.

In order to improve the color rendering in such a light emitting device, a phosphor that emits fluorescent light in a yellow to red region from a long wavelength by light emission of a blue LED has been developed. As such a phosphor, for example, an oxynitride phosphor (Patent Document 4) containing α-sialon as a main component with a reduced content of metal impurities other than the constituent components, a lanthanide metal or the like in a CaAlSiN ₃ crystal phase is used. A solid solution (Patent Document 5), a phosphor composed of an α sialon type compound containing a lanthanide metal or the like (Patent Document 6), and the like have been reported. In addition, an LED in which a non-particulate phosphor layer is formed on a blue LED (Patent Document 7) has been reported.

  In a white LED device using this type of sialon phosphor, a warm white color having a low color temperature tends to be obtained as compared with a white LED device using a YAG: Ce phosphor. However, in the phosphor, there is a difference between the excitation energy and the energy of light emitted from the blue LED, and further improvement in light emission efficiency is required.

In addition, a white LED (Patent Document 8) that combines an ultraviolet light emitting diode (UV-LED) and a blue, green, and red phosphor has been developed. There has been a demand for a phosphor that is excellent in color rendering and has a more approximate emission energy and excitation energy from a blue LED and can further improve the light emission efficiency.
Patent No. 2900928 Patent No. 29998696 Japanese Patent No. 2927279 JP 2004-238506 A JP 2005-235934 A JP 2006-265506 A JP 11-046015 A Special table 2000-509912

  The object of the present invention is to provide a sufficient band gap, emit yellow to red fluorescence, change the molar ratio of the elements contained therein, and sequentially modulate the color of the emitted fluorescence from yellow to red It is possible to easily obtain a desired yellow to red color tone, and to provide a phosphor having a high luminous efficiency by a blue LED or blue LD, which can be easily and efficiently manufactured. An object of the present invention is to provide a method for producing a phosphor that can be used. In addition, the problem of the present invention is that by changing the molar ratio of the elements constituting the phosphor, it is possible to adjust to a desired color tone, and it is excellent in color rendering, regardless of the other color tone phosphor to be combined. To provide a light-emitting device that can emit white light with excellent color tone, has high luminous efficiency, has sufficient luminous intensity, can reduce power consumption, and is suitable for illumination. is there.

  The inventors of the present invention approximated the energy of light emitted from a blue LED or the like and its excitation energy, had a sufficient band gap, and the fluorescence wavelength emitted by the excitation shifted from yellow to red on the longer wavelength side. We conducted intensive research to find phosphors. As a result, it has been found that a phosphor having a specific elemental composition emits fluorescent light in a yellow to red region having a high emission peak intensity due to light emission of a blue LED. Based on this finding, the present invention has been completed.

That is, the present invention provides a composition formula (1)
_{Y 3-ab Ce a L b} Al 5-c Si c O 12-d N d (1)
(In the formula, L represents one or more elements of Gd, La, Tb, Lu, or Sc, a is 0.01 <a <0.50, and b is 0.0 ≦ b <. 2.5 and c are numerical values satisfying 0.0 <c <2.0 and 0.01 <d <2.7.)

  The present invention also relates to a method for producing a phosphor, characterized in that a compound containing an element constituting the composition formula (1) is baked under a positive pressure.

  The present invention also relates to a light-emitting device using the phosphor.

  The phosphor of the present invention has a sufficient band gap, emits yellow to red fluorescence, changes the molar ratio of the elements contained therein, and sequentially changes the color of emitted fluorescence from yellow to red. It is possible to modulate, and it is easy to obtain a target yellow to red color tone, and the light emission efficiency by a blue LED or blue LD is good.

  In addition, the phosphor production method of the present invention can produce the phosphor easily and efficiently.

  In addition, the light emitting device of the present invention can be adjusted to a desired color tone by changing the molar ratio of the elements constituting the phosphor, and is excellent in color rendering, regardless of the other color tone phosphor to be combined. To provide a light-emitting device that can emit white light with excellent color tone, has high luminous efficiency, has sufficient luminous intensity, can reduce power consumption, and is suitable for illumination. It is in.

The phosphor of the present invention has a composition formula (1)
_{Y 3-ab Ce a L b} Al 5-c Si c O 12-d N d (1)
It is represented by In the formula, L represents one or more of Gd, La, Tb, Lu, or Sc, a is 0.01 <a <0.50, and b is 0.0 ≦ b <2.5. , C is a numerical value satisfying 0.0 <c <2.0 and 0.01 <d <2.7.

  The phosphor of the present invention contains Y, Ce, Al, Si, O, and N, and contains one or more of Gd, La, Tb, Lu, or Sc as necessary. In the phosphor, the molar ratio of Y and Ce and L, Al and Si, and O and N is 3: 5: 12. When the number of moles of all phosphors is 20, the molar ratio of Y is larger than 0.00 and smaller than 2.99, and the molar ratio of Ce is larger than 0.01 and smaller than 0.50. Preferably, the molar ratio of Y is larger than 0.5, and the molar ratio of Ce is larger than 0.02 and smaller than 0.3. When the number of moles of all phosphors is 20, the Al molar ratio is larger than 3.0 and smaller than 5.0, and the Si molar ratio is larger than 0.0 and smaller than 2.0. Preferably, the molar ratio of Al is larger than 4.0 and smaller than 4.99, and the molar ratio of Si is larger than 0.01 and smaller than 1.0. When the number of moles of all phosphors is 20, the molar ratio of O is larger than 9.33 and smaller than 11.99, and the molar ratio of N is larger than 0.01 and smaller than 2.67. Preferably, the molar ratio of O is larger than 10.0 and smaller than 11.95, and the molar ratio of N is larger than 0.05 and smaller than 2.00.

  It is preferable that these elements constitute crystals. In a phosphor excellent in crystallinity, generation of phonons due to crystal lattice defects caused by excitation light can be suppressed, and inhibition of fluorescence emission can be suppressed.

  The phosphor represented by the composition formula (1) has a wide band gap excited by light having a wavelength of 400 to 520 nm. Examples of an excitation source that emits excitation light having such excitation energy include a blue laser and a blue LED. Specific examples of the blue LED as the excitation source include InGaN.

  The phosphor is excited by the blue LED and emits red region fluorescence. YAG: emits fluorescence in the red region of 560 nm to 700 nm shifted to a longer wavelength than Ce fluorescence. The elements involved in red light emission are Si and N. By changing the element of the composition formula (1) within this composition range, the emission peak wavelength can be changed from yellow to the red region. It is easy to obtain a yellow to red color tone.

In order to produce the phosphor, there can be mentioned a method in which compounds containing respective elements are combined and fired under a positive pressure so as to correspond to the target elemental composition. As a raw material, an oxide or nitride of an element contained in the phosphor can be used. Specifically, yttrium oxide (Y ₂ O ₃ ), aluminum oxide (Al ₂ O ₃ ), aluminum nitride (AlN), silicon oxide (SiO ₂ ), silicon nitride (Si ₃ N ₄ ), cerium oxide (CeO ₂ ) Etc. can be used. Further, in order to form a phosphor having a structure with excellent crystallinity, it is preferable to use a flux material in order to reduce defects in the crystal structure. The flux material promotes the fusion of these elements when each metal oxide or the like is melted by firing, which will be described later, reduces crystal lattice defects, and enables formation of a phosphor having excellent crystallinity. A halide such as aluminum fluoride (AlF ₃ ) or ammonium chloride (NH ₄ Cl) can be used as the flux material. As usage-amount of a flux material, 1-5 mol% can be mentioned with respect to fluorescent substance.

  These raw materials are weighed and collected in accordance with the target composition formula, and thoroughly mixed in a dry or wet manner. In the case of wet mixing, it is preferable to use an alcohol such as ethanol or isopropyl alcohol, or an organic solvent such as acetone. These organic solvents and the weighed raw materials can be put in a ball mill made of ceramics together with balls made of alumina or zirconia and mixed for 1 to 24 hours. Thereafter, the organic solvent can be removed by drying to obtain a mixed raw material powder.

  The obtained mixed raw material powder is filled in a heat-resistant container such as a carbon crucible, a carbon tray, a boron nitride crucible, or a boron nitride tray and fired. The firing temperature is, for example, preferably 1300 to 1800 ° C, more preferably 1350 to 1750 ° C, and still more preferably 1400 to 1700 ° C. The firing time can be, for example, 3 to 10 hours. As the atmosphere at the time of firing, a reducing atmosphere such as a mixed gas of nitrogen and hydrogen, ammonia, or nitrogen gas is preferable. The mixed gas of nitrogen and hydrogen is preferably 10 to 90:90 to 10 in terms of the volume ratio of nitrogen and hydrogen, and nitrogen: hydrogen is preferably 1: 3.

The firing atmosphere of the mixed raw material powder is a positive pressure. By firing under a positive pressure, it is possible to suppress decomposition of nitrides such as Si ₃ N ₄ and obtain a phosphor having a desired composition. The pressure in the firing atmosphere is preferably 1.00 to 1.50 atm, more preferably 1.02 to 1.3 atm, and further preferably 1.05 to 1.2 atm. If the pressure at the time of firing is 1.50 atm or less, the phosphor as the target product is prevented from being completely sintered, and a strong pulverization force is applied at the time of powdering to destroy the crystal. It can suppress that the luminous efficiency of fluorescent substance falls. Firing can be performed multiple times by repeating cooling and refiring after firing. The obtained fired product is pulverized, washed, dried, sieved, and the like to obtain a powdered phosphor, which is suitable for an LED element or the like.

  The light emitting device of the present invention may be any as long as it uses the above phosphor. For example, the light emitting device of the present invention includes an LED element such as a light emitting diode having a semiconductor that emits light having a wavelength of 400 to 520 nm, an electroluminescent element, and a field emission type that emits light by directly colliding electrons from a cathode with a phosphor. Examples thereof include electron beam light emitting devices such as display (FED) and vacuum fluorescent display (VFD), and other fluorescent lamps such as cold cathode fluorescent lamps and hot cathode fluorescent lamps.

As an example of the light emitting device of the present invention, a white LED device shown in the schematic configuration diagram of FIG. 1 can be given. The white LED device shown in FIG. 1 mainly includes a casing 12 having a reflector function, an LED chip 13 fixed on a submount (not shown) fixed to the casing, and the LED chip 13. The transparent resin 14 that surrounds the phosphor and the phosphor-containing glass sheet 11 are provided so as to cover the transparent resin. The LED chip 13 preferably has a light emitting layer in which the above-described semiconductor or the like that emits blue light of 400 to 520 nm such as GaN is laminated on an Al ₂ O ₃ or SIO substrate. The LED of the LED chip is electrically connected to a power source (not shown) by wire-bonding its electrodes by wiring 15.

For example, an epoxy resin, a urea resin, a silicone resin, or the like, which is provided for protecting the LED chip, has excellent light transmission from the LED, and has resistance to the energy, is preferably used. The phosphor-containing glass sheet 11 provided on the upper surface of the transparent resin contains the phosphor 11a. The glass sheet 11 preferably contains a red phosphor or a green phosphor that emits green or red light using the LED as an excitation source. Examples of the red phosphor used here include SrS: Eu, CaS: Eu, CaAlSiN3: Eu, and the like , and examples of the green phosphor include (Ba, Sr) 2SiO4: Eu, SrGa2S4. : Eu, (Ba, Sr, Ca) Si2O2N2: Eu, β-sialon: Eu, and the like.

  Such a glass sheet can be formed into a thin film by melting and mixing a glass component constituting the glass and a phosphor. Further, the phosphor can be contained in the transparent resin.

  In the white LED device, when blue light is emitted from the LED, the phosphor contained in the glass sheet is excited, and fluorescent light from yellow to red region, red region wave, and green region is emitted. These fluorescent light and blue light from the LED are diffused and mixed in the glass sheet, and white light with excellent color tone is emitted from the glass sheet surface.

  As an example of the light emitting device of the present invention, a field emission display (field emission display: FED) device can be exemplified. As shown in the partial schematic cross-sectional view of FIG. 2, this type of FED apparatus includes a pair of an anode substrate 31 made of glass or the like and a cathode substrate 32, which are separated by a support frame (not shown) at intervals of several millimeters or less. Arranged in parallel, the inside is kept in a vacuum. The anode substrate 31 is provided with a phosphor 31b on the inner surface via a transparent anode electrode 31a. The phosphor is a yellow to red phosphor, a red phosphor, a green phosphor, a blue phosphor, or other pixels. Are formed alternately. Between each pixel of each of these phosphors, a light absorber made of a black conductive material that separates them may be provided. The above phosphors are used as yellow to red phosphors, and red phosphors and green phosphors selected in combination with them are specifically exemplified by the same phosphors as described above. be able to. On the other hand, an electron-emitting device (emitter) 32b made of a carbon film or the like is provided on the inner surface of the cathode substrate 32 via a cathode electrode 32a corresponding to each phosphor pixel. Each electron-emitting device is connected to a signal input terminal (not shown) provided on the support frame and is applied with a voltage by a wiring (not shown) formed on the cathode substrate. Furthermore, a conductive layer is provided on the phosphor surface to prevent the phosphor surface from being charged by the collision of excessive electrons from the emitter and impinging the collision between the phosphor and the electron, and accumulated on the phosphor surface. An abnormal discharge between the electrons and the emitter may be suppressed. The conductive layer can be formed by a method of coating the surface of the phosphor with a conductive material.

  In such an FED device, when a voltage is applied between the cathode electrode 32a and the anode electrode 31a, electrons are emitted from the electron-emitting device 32b, and the emitted electrons are attracted to the anode electrode 31a as indicated by an arrow A. Then, it collides with the phosphor 31b to generate fluorescence, and the generated fluorescence becomes white light and is emitted from the anode substrate 31 to the outside as indicated by an arrow B. By using the phosphor, white light with excellent color tone can be emitted.

  Further, as an example of the light emitting device of the present invention, a vacuum fluorescent display (vacuum fluorocent display: VFD) device can be exemplified. As this type of VFD device, as shown in the partial schematic cross-sectional view of FIG. 3, each wiring 42 provided on a substrate 41 made of glass or the like is connected through a through hole 44 provided in an insulator layer 43. Connected anodes 45 are provided, and phosphor layers 46a, 46b, and 46c are formed on each anode. The phosphor layers 46a, 46b, and 46c are alternately provided containing the yellow to red phosphors, red phosphors, green phosphors, and the like. The above phosphors are used as yellow to red phosphors, and the red phosphors and green phosphors selected in combination therewith are specifically the same phosphors as described above. It can be illustrated. A grid 47 is disposed above the phosphor layer so as to cover the phosphor layer, and the grid 47 is provided so as to be electrically connected to a terminal (not shown) provided on the substrate. Further, a filamentary cathode 48 is provided above the grid so as to be stretched on a support provided at both ends of the substrate, and these are provided in a container 49 that forms a vacuum space. Further, a conductive layer may be provided on the phosphor surface to suppress abnormal charging by suppressing charging of the phosphor surface. The conductive layer can be formed in the same manner as the conductive layer in the FED device.

  In such a vacuum fluorescent display device, display is performed by emitting light from the phosphor by applying electrons from the cathode to the phosphor, and there is little fluctuation in emission intensity due to environmental temperature, particularly low temperature, and the phosphor is contained. Thus, color rendering properties can be achieved and constant fluorescence can be continuously generated.

Hereinafter, the phosphor of the present invention will be described in more detail with reference to examples.
[Example 1]
Y ₂ O ₃ 19.53 g, Al ₂ O ₃ 13.95 g, Si ₃ N ₄ 0.96 g, CeO ₂ 0.61 g were used as powder raw materials, and these were put into a ceramic ball mill together with acetone and zirconia balls and mixed for 12 hours. . After the zirconia balls were removed from the mixed raw material liquid with a sieve and acetone was removed, the mixture was filled in a boron nitride crucible, set in an electric furnace, and baked at 1400 ° C. in a nitrogen reducing atmosphere at 1.1 atm for 3 hours. After firing, the product was gradually cooled, and the obtained fired product was pulverized and mixed. Thereafter, it was again fired at 1450 ° C. for 3 hours. The fired product was pulverized, mixed, and washed to obtain the target phosphor of Y _2.94 Ce _0.06 Al _4.95 Si _0.05 O _11.9 N _0.1 .

  About the obtained fluorescent substance, excitation light (Photoluminescence Excitation: PLE) measurement and photoluminescence (Photoluminescence: PL) measurement were performed as follows.

[PL measurement]
About the obtained fluorescent substance, 450 nm was used as excitation light, and it carried out by the fluorescence spectrophotometer (RF-5300PC: Shimadzu Corporation make) under the room temperature atmosphere in air | atmosphere. FIG. 4 shows the PL intensity (emission spectrum) of the obtained phosphor.

[PLE measurement]
The obtained phosphor was measured by changing the excitation wavelength and monitoring the emission peak wavelength of the phosphor in the atmosphere at room temperature. FIG. 5 shows the PLE intensity (excitation spectrum) with respect to the excitation light wavelength.

[White chromaticity]
FIG. 6 and Table 1 show CIE (Commission International de l'Eclairage) chromaticity coordinates of fluorescence emitted from the obtained phosphor. The CIE chromaticity coordinate of blue light corresponding to the excitation light of the blue LED is set to (0.130, 0.075), and in the same chromaticity diagram, the intersection of the line connecting the fluorescence coordinate and the blue light coordinate and the black body radiation Table 2 shows the chromaticity coordinates of white light obtained as follows. The color temperature of this white light and the average color rendering index were determined by the following method. The results are shown in Table 2.

[White LED device]
The emission intensity in a white LED device using the obtained phosphor and blue LED was measured. The results are shown in FIG.

[Examples 2 to 5]
A phosphor was prepared in the same manner as in Example 1 except that the amount of the powder raw material was changed so that a phosphor having the target composition was obtained, and PL measurement and PLE measurement were performed on the obtained phosphor. The chromaticity coordinates, color temperature, and average color rendering index of white light obtained from this were determined. The results are shown in FIGS.

[Comparative example]
Using YAG: Ce as the phosphor, PL measurement and PLE measurement were performed in the same manner as in Example 1, and the chromaticity coordinates, color temperature, and average color rendering index of white light obtained therefrom were obtained. The results are shown in FIGS. Furthermore, the emission intensity in the white LED device was measured in the same manner as in Example 1 except that the phosphor used was changed. The results are shown in FIG.

  In both Examples and Comparative Examples, the peak wavelength of the excitation light was 450 to 480 nm. Further, in the comparative example, the emission peak wavelength in PL measurement is near 550 nm, and in the example, the emission peak shifted to the long wavelength side. In addition, on the CIE chromaticity diagram, blue light corresponding to a blue LED and white light obtained from a phosphor have a high color temperature and average color rendering index in the comparative example, indicating that the blue color tone is strong. On the other hand, in the phosphors of the examples, both the color temperature and the average color rendering index are similar to those of the light bulb color or sunlight, indicating that the color tone is natural light. The actual light emission of the white LED coincided with the chromaticity of white light obtained from the black radiation on the chromaticity diagram.

  From the results, the phosphor represented by the composition formula (1) has good emission efficiency with respect to the excitation source, emits yellow to red fluorescence, and can be used alone without using other phosphors. It is clear that white light having a color tone similar to natural light can be obtained together with the LED and the like.

It is a figure which shows the schematic block diagram of the LED element as an example of the light-emitting device of this invention. It is a figure which shows the schematic sectional drawing of the FED apparatus as an example of the light-emitting device of this invention. It is a figure which shows the schematic block diagram of the VFD apparatus as an example of the light-emitting device of this invention. It is a figure which shows PL intensity (emission spectrum) of an example of the fluorescent substance of this invention. It is a figure which shows the PLE intensity | strength (excitation spectrum) of an example of the fluorescent substance of this invention. It is a figure which shows the CIE chromaticity diagram of an example of the fluorescent substance of this invention. It is a figure which shows the emitted light intensity of the white LED apparatus of an example of the fluorescent device of this invention.

Explanation of symbols

46a, 46b, 46c phosphor layers 11a, 31b phosphor

Claims (6)

Composition formula (1)
_{Y 3-ab Ce a L b} Al 5-c Si c O 12-d N d (1)
(In the formula, L represents one or more elements of Gd, La, Tb, Lu, or Sc, a is 0.01 <a <0.50, and b is 0.0 ≦ b <. 2.5 and c are phosphors represented by the following values: 0.0 <c <2.0 and 0.01 <d <2.7.   The phosphor according to claim 1, which is excited by light having a wavelength of 400 to 520 nm and emits yellow to red fluorescence.   3. The method for producing a phosphor according to claim 1, wherein the compound containing an element constituting the composition formula (1) is baked under a positive pressure. 4.   A light-emitting device using the phosphor according to claim 1.   5. The light emitting device according to claim 4, wherein the light emitting device is a white diode device having one or more phosphors selected from green phosphors and red phosphors.   5. The light-emitting device according to claim 4, wherein the light-emitting device is an electron beam light-emitting device having at least one phosphor selected from a green phosphor and a red phosphor.

Images