JP2011225803A - Fluorescent material, method for manufacturing the same, and light-emitting device having the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fluorescent material which has a satisfactory band gap and is capable of light-emitting the highly intense blue-green luminescence by the excitation with a blue color that is light-emitted from an LED or an LD; a method for manufacturing it; and a light-emitting device using this.SOLUTION: This fluorescent material is expressed by compositional formula (1): ALSiON(wherein, A is an element which contains at least Ca and may contain one or more kinds of Ba, Sr, Mg, or Zn; L is an element which contains at least Eu and may contain one or more kinds of Ce, Pr, Yb, Tm, Tb, or Sm; x is a value satisfying 5.8≤x≤7.8; y is a value satisfying 0.001<y≤0.2; z is a value satisfying 6≤z≤10; b is a value satisfying 6≤b≤8; and c is a value satisfying 9≤c≤14), having a crystal structure of a cubic crystal system with a lattice constant of a (nm) satisfying 1.45<a<1.65.

Description

  The present invention relates to a phosphor, a manufacturing method thereof, and a light emitting device using the same, and more particularly to a blue-green phosphor, a manufacturing method thereof, and a light emitting device using the same.

A light-emitting device that emits white light using a blue light-emitting diode (LED) or blue laser (LD) as an excitation source is low in power consumption and long compared with conventional fluorescent lamps. Since it has a long life, it is used in various ways. 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 the LED and little deterioration by the 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 has been reported a light emitting diode or the like in which a phosphor that is excited by a blue LED and emits yellowish green is molded with at least one selected. 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, an oxynitride phosphor that emits blue-green to green fluorescence by light emission of a blue LED has been developed (Patent Documents 1-3). There is a demand for a phosphor that emits high-intensity blue-green fluorescence that can be excited by blue from an LED or LD and can further improve luminous efficiency, and a light-emitting device using the phosphor.

JP 2004-210921 A JP 2005-281700 A JP 2006-097034 A

  An object of the present invention is to provide a phosphor that has a sufficient band gap, is excited by blue light emitted from an LED or LD, and can emit high-intensity blue-green fluorescence. An object of the present invention is to provide a production method capable of producing a body easily and efficiently.

  In addition, the present invention is excellent in color rendering with blue from LED or LD as excitation light, can obtain white light with excellent color tone, has good luminous efficiency, and has sufficient luminous intensity, An object of the present invention is to provide a phosphor that can reduce power consumption and is suitable for illumination and a method for manufacturing the same, and to provide a light-emitting device using the phosphor.

  The present inventors have obtained a phosphor whose blue light energy emitted from an LED or LD approximates its excitation energy, has a sufficient band gap, and has a blue-green fluorescence wavelength emitted by excitation. We conducted intensive research to find out. As a result, it has been found that a phosphor having a specific element composition emits blue-green fluorescence having a high emission peak intensity due to blue light from ultraviolet light emitted from an LED or LD. Based on this finding, the present invention has been completed.

That is, the present invention provides a composition formula (1)
_{A x L y Si z O b} N c (1)
(In the formula, A represents an element that contains at least Ca, and may contain any one or more of Ba, Sr, Mg, or Zn, L contains at least Eu, Ce, Pr, Yb, An element that may contain one or more of Tm, Tb, or Sm is shown, x is 5.8 ≦ x ≦ 7.8, y is 0.001 <y ≦ 0.2, and z is 6 ≦ z ≦ 10, b is a numerical value satisfying 6 ≦ b ≦ 8, and c is a numerical value satisfying 9 ≦ c ≦ 14.) And the lattice constant a (nm) satisfies 1.45 <a <1.65. The present invention relates to a phosphor having a cubic crystal structure.

  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, and is excited by blue light emitted from an LED or LD, and can emit high-intensity blue-green fluorescence.

  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 is excellent in color rendering with blue light from LEDs and LDs as excitation light, can obtain white light with excellent color tone, has high luminous efficiency, and has sufficient luminous intensity. And can reduce power consumption and is suitable for illumination.

It is a figure which shows the X-ray-diffraction pattern which shows the crystal structure of the fluorescent substance of this invention. 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 PLE (excitation spectrum) and PL intensity (emission spectrum) of an example of the fluorescent substance of this invention. It is a figure which shows PLE (excitation spectrum) and PL intensity (emission spectrum) of an example of the fluorescent substance of this invention. It is a figure which shows the Rietveld analysis result of the X-ray-diffraction pattern which shows the crystal structure of the fluorescent substance of this invention. It is a figure which shows the crystal structure of the fluorescent substance of this invention.

The phosphor of the present invention has a composition formula (1)
_{A x L y Si z O b} N c (1)
(In the formula, A represents an element that contains at least Ca, and may contain any one or more of Ba, Sr, Mg, or Zn, L contains at least Eu, Ce, Pr, Yb, An element that may contain one or more of Tm, Tb, or Sm is shown, x is 5.8 ≦ x ≦ 7.8, y is 0.001 <y ≦ 0.2, and z is 6 ≦ z ≦ 10, b is a numerical value satisfying 6 ≦ b ≦ 8, and c is a numerical value satisfying 9 ≦ c ≦ 14.) And the lattice constant a (nm) satisfies 1.45 <a <1.65. It has a cubic crystal structure.

  The phosphor of the present invention contains Ca, Eu, Si, O, N, and may contain any one or two of Ba, Sr, Mg, or Zn as necessary, or Ce, Any one or more of Pr, Yb, Tm, Tb or Sm may be included. In formula (1), the total molar ratio x of Ca and Ba, Sr, Mg, or Zn contained as necessary satisfies 5.8 ≦ x ≦ 7.8. When the molar ratio x of these elements is in this range, the crystal structure of the phosphor represented by the formula (1) has a cubic system described later.

  Further, the total molar ratio y of Eu and Ce, Pr, Yb, Tm, Tb or Sm contained as necessary satisfies 0.001 <y ≦ 0.2. When the molar ratio y of these elements is within this range, the crystal structure of the phosphor represented by the formula (1) has a cubic system described later.

  Further, the molar ratio z of silicon atoms satisfies 6 ≦ z ≦ 10, the molar ratio b of oxygen atoms satisfies 6 ≦ b ≦ 8, and the molar ratio c of nitrogen atoms satisfies 9 ≦ c ≦ 14. If the molar ratio of these atoms is within this range, the crystal structure of the phosphor represented by the formula (1) has a cubic system described later.

  The phosphor represented by the formula (1) has a cubic crystal structure with a lattice constant a (nm) of 1.45 <a <1.65. By having such a cubic system, a phosphor that is excited by blue light and emits blue-green fluorescence efficiently and has excellent crystallinity is obtained. In such a phosphor, crystal lattice defects due to excitation light are obtained. It is possible to suppress the generation of phonons due to the above, and to inhibit the emission of fluorescence.

The phosphor represented by the composition formula (1) is composed of the composition formula (2).
A _{7-y Ly} Si ₁₀ O ₆ N ₁₄ (2)
(Wherein A, L, and y are the same as A, L, and y shown in Formula (1), respectively), and the lattice constant a (nm) is 1.5 <a <1.6. A phosphor having a cubic structure and a crystal structure of the space group Pa-3 (No. 205) is particularly preferable. The phosphor represented by the formula (2) has a cubic structure in which the lattice constant a (nm) is 1.5 <a <1.6 and has a crystal structure of the space group Pa-3 (No. 205) with the above composition. Have. By having such a cubic system, a phosphor that is excited by blue light and emits blue-green fluorescence efficiently and has excellent crystallinity is obtained. In such a phosphor, crystal lattice defects due to excitation light are obtained. It is possible to suppress the generation of phonons due to the above, and to inhibit the emission of fluorescence.

  The crystal structure was measured by powder X-ray diffraction measurement (RINT-2000; manufactured by Rigaku Corporation) in an X-ray diffraction pattern range of 10 ° to 130 °. A crystal system was determined from a diffraction peak extracted from the obtained diffraction pattern, and an optimized lattice constant value was obtained by a structure calculation program. As shown in FIG. 1, the phosphor represented by the formula (1) has diffraction peaks at 31.6 degrees, 32.7 degrees, and 33.7 degrees.

From this X-ray diffraction pattern, a diffraction pattern fitted by Rietveld analysis as shown in FIG. 7 is obtained by unknown structure analysis and Rietveld analysis. The fitting parameter R values (Rwp, Rp, RB, RF) all indicate 5% or less, indicating that the obtained crystal structure is appropriate. As a result of structural analysis, it is estimated that the crystal system is cubic, the space group Pa-3 (No. 205), and the unit cell is about 1.548 nm, and a specific crystal structure as shown in FIG. 8 is obtained. As for this crystal structure, all Si sites are composed of [Si (O, N) 4] polyhedral structure, and it is assumed that this base crystal has strong covalent bond, is strong, and is thermally stable. Can do. Table 1 shows the crystal structure data of Ca _6.988 Eu _0.012 Si ₁₀ O ₆ N ₁₄ obtained from FIG. 7 and FIG.

  The phosphors represented by the formulas (1) and (2) have a wide band gap excited by a wavelength of 300 to 500 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 blue light emitted from the LED or LD, and emits blue-green fluorescence having a wavelength of 450 to 600 nm.

  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, calcium oxide, barium oxide, strontium oxide, magnesium oxide, zinc oxide, europium oxide, silicon oxide, silicon nitride, or the like can be used. Further, in order to form a phosphor having a structure with excellent crystallinity, a flux material may be used to reduce defects in the crystal structure.

  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 1700 ° C, more preferably 1400 to 1600 ° C. The firing time can be, for example, 1 to 10 hours. As the atmosphere at the time of firing, nitrogen gas, a mixed gas of nitrogen and hydrogen, a reducing atmosphere such as ammonia is preferable, and nitrogen gas is particularly preferable.

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. Examples of the pressure of the firing atmosphere include 0.8 to 1.50 atm, and more preferably 0.85 to 1.1 atm. If the pressure at the time of baking is the said range, it can suppress that the crystal | crystallization is destroyed by the external force loaded in the case of pulverization, and the luminous efficiency of fluorescent substance is reduced. 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, as a light emitting device of the present invention, an LED element such as a light emitting diode having a semiconductor that emits light having a wavelength of 300 to 500 nm, an electroluminescence element, or 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, an LED element shown in the schematic configuration diagram of FIG. 2 can be given. The LED element shown in FIG. 2 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. For example, the surrounding transparent resin 14 and the phosphor-containing sheet 11 made of glass or the like are provided so as to cover the transparent resin. The LED chip 13 has a light emitting layer formed by laminating a semiconductor such as GaN on an Al ₂ O ₃ or SIO substrate, and the light emitting layer emits blue light from ultraviolet light of 300 to 500 nm. Is preferred. 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 sheet 11 provided on the upper surface of the transparent resin contains the phosphor represented by the formula (1). The sheet 11 is provided with a phosphor that emits fluorescence such as green, yellow, red, etc., if necessary, when the light emitted from the LED element is set to a desired wavelength, or when further color rendering is obtained. It can be included. For example, as a green light emitting phosphor, Y ₃ (Al, Ga) ₅ O ₁₂ : Ce, SrGa ₂ S ₄ : Eu, (Ba, Sr) ₂ SiO ₄ : Eu, Ca ₃ Sc ₂ Si ₃ O ₁₂ : Ce , CaSc ₂ O ₄ : Ce, Eu-activated β-sialon, (Sr, Ba) Si ₂ O ₂ N ₂ : Eu, Ba ₃ Si ₆ O ₁₂ N ₂ : Eu, BAM: Eu, Mn, etc. . As the yellow phosphor, (Y, Gd) ₃ Al ₅ O ₁₂ : Ce, Tb ₃ Al ₅ O ₁₂ ; Ce, CaGa ₂ S ₄ : Eu, (Sr, Ca, Ba) ₂ SiO ₄ : Eu, Eu activation Examples thereof include Ca-α-sialon, La ₃ Si ₆ N ₁₁ : Ce, and the like. As red phosphors, (Sr, Ca) S: Eu, (Ca, Sr) ₂ Si ₅ N ₈ : Eu, CaAlSiN ₃ : Eu, (Sr, Ba) ₃ SiO ₅ : Eu, K ₂ TiF ₆ : Mn Etc.

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

  In the LED element, when excitation light is emitted from the LED, the phosphor contained in the sheet is excited, and fluorescence including a blue-green region is emitted. These fluorescent light and blue light from the LED are diffused and mixed in the sheet, and white light with excellent color tone is emitted from the 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. 3, this type of FED apparatus includes a pair of glass-made anode substrate 31 and 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 through a transparent anode electrode 31a. The phosphor is provided with pixels such as a red phosphor, a blue-green phosphor, and a green phosphor alternately. It is formed. 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 phosphor is used as a blue-green phosphor, and a red phosphor and a green phosphor are appropriately selected in combination with the phosphor. 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.

  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.

  The FED device is provided with a conductive layer on the phosphor surface in order to avoid excessive electrons from the emitter being emitted and charging the phosphor surface to prevent collision between the phosphor and the electrons. You may make it suppress the abnormal discharge between the electron accumulate | stored on the surface and an emitter. The conductive layer can be formed by a method of coating a phosphor material with a conductive material containing transparent indium oxide that does not absorb in the visible light region or conductive fine particles such as zinc oxide.

  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. 4, 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 with red phosphors, blue-green phosphors, green phosphors, and the like. As the blue-green phosphor, the above-described phosphor is used, and in combination therewith, a red phosphor and a green phosphor can be appropriately selected. 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]
As powder raw materials, 3.08 g of CaCO ₃ , 1.92 g of Si ₃ N ₄ and 0.01 g of Eu ₂ O ₃ were weighed and mixed. The mixture was filled in a boron nitride crucible, set in an electric furnace, and fired at 1500 ° C. for 3 hours in a nitrogen reducing atmosphere of 0.9 atm. After firing, the product was gradually cooled, and the obtained fired product was pulverized, mixed, and washed to obtain a target phosphor of Ca _7-y Eu _y Si ₁₀ O ₆ N ₁₄ (y = 0.015).

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

[PLE measurement]
The obtained phosphor was measured with a fluorescence spectrophotometer (RF-5300PC: manufactured by Shimadzu Corporation) by changing the excitation wavelength and monitoring the emission peak wavelength of the phosphor in the atmosphere at room temperature. The wavelength range in which the phosphor can be excited has a peak near 330 nm and extends from 300 to 500 nm. The PLE intensity (excitation spectrum) with respect to the excitation light wavelength is indicated by a dotted line in FIG.

[PL measurement]
About the obtained fluorescent substance, it carried out by the fluorescence spectrophotometer (RF-5300PC: Shimadzu Corp. make) using the 365 nm as excitation light in air | atmosphere at room temperature atmosphere. The emission had a peak in the vicinity of 490 nm and ranged from 450 to 600 nm. The PL intensity (emission spectrum) of the obtained phosphor is shown by a solid line in FIG.

[Example 2]
The same procedure as in Example 1 was conducted except that 3.16 g of CaCO ₃ , 1.73 g of Si ₃ N ₄ , 0.01 g of Eu ₂ O ₃ and 0.11 g of SiO ₂ were weighed and used as powder raw materials. A phosphor was produced, and the target phosphor of Ca _7-y Eu _y Si ₁₀ O ₆ N ₁₄ (y = 0.003) was obtained. About the obtained fluorescent substance, PLE measurement and PL measurement were performed. FIG. 6 shows the PLE intensity as a dotted line and the PL intensity as a solid line.

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

Claims (6)

Composition formula (1)
_{A x L y Si z O b} N c (1)
(In the formula, A represents an element that contains at least Ca, and may contain any one or more of Ba, Sr, Mg, or Zn, L contains at least Eu, Ce, Pr, Yb, An element that may contain one or more of Tm, Tb, or Sm is shown, x is 5.8 ≦ x ≦ 7.8, y is 0.001 <y ≦ 0.2, and z is 6 ≦ z ≦ 10, b is a numerical value satisfying 6 ≦ b ≦ 8, and c is a numerical value satisfying 9 ≦ c ≦ 14.) And the lattice constant a (nm) satisfies 1.45 <a <1.65. A phosphor having a cubic crystal structure. Composition formula (2)
A _{7-y Ly} Si ₁₀ O ₆ N ₁₄ (2)
(Wherein A, L, and y are the same as A and L in formula (1)), and the cubic constant a (nm) satisfies 1.5 <a <1.6. The phosphor according to claim 1, wherein the phosphor has a crystal structure of a space group Pa-3 (No. 205).   The phosphor according to claim 1 or 2, which is excited by light having a wavelength of 300 to 460 nm.   The phosphor according to any one of claims 1 to 3, which emits light having a wavelength of 450 to 600 nm.   A light emitting device comprising the phosphor according to claim 1.   The method for producing a phosphor according to any one of claims 1 to 4, wherein the compound containing an element constituting the composition formula (1) is baked under a positive pressure.