WO2019087814A1 - Fluorescent body - Google Patents
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- WO2019087814A1 WO2019087814A1 PCT/JP2018/038964 JP2018038964W WO2019087814A1 WO 2019087814 A1 WO2019087814 A1 WO 2019087814A1 JP 2018038964 W JP2018038964 W JP 2018038964W WO 2019087814 A1 WO2019087814 A1 WO 2019087814A1
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- 150000001768 cations Chemical class 0.000 claims abstract description 77
- 239000013078 crystal Substances 0.000 claims abstract description 74
- 150000001450 anions Chemical group 0.000 claims abstract description 60
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims description 116
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- 238000000295 emission spectrum Methods 0.000 claims description 22
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- -1 rare earth ions Chemical class 0.000 description 23
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- 238000005259 measurement Methods 0.000 description 16
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- 230000007423 decrease Effects 0.000 description 8
- 239000004065 semiconductor Substances 0.000 description 8
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 7
- 238000005090 crystal field Methods 0.000 description 7
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- 229910001416 lithium ion Inorganic materials 0.000 description 7
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- 239000011734 sodium Substances 0.000 description 7
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- OGPBJKLSAFTDLK-UHFFFAOYSA-N europium atom Chemical compound [Eu] OGPBJKLSAFTDLK-UHFFFAOYSA-N 0.000 description 6
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- NPYPAHLBTDXSSS-UHFFFAOYSA-N Potassium ion Chemical compound [K+] NPYPAHLBTDXSSS-UHFFFAOYSA-N 0.000 description 4
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 4
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical group [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 4
- 229910052791 calcium Inorganic materials 0.000 description 4
- 238000005384 cross polarization magic-angle spinning Methods 0.000 description 4
- 238000002284 excitation--emission spectrum Methods 0.000 description 4
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- 239000011574 phosphorus Substances 0.000 description 4
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- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 3
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 description 3
- 239000012190 activator Substances 0.000 description 3
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- 239000004570 mortar (masonry) Substances 0.000 description 3
- 150000004767 nitrides Chemical class 0.000 description 3
- 229910052700 potassium Inorganic materials 0.000 description 3
- 239000011591 potassium Substances 0.000 description 3
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- 238000000371 solid-state nuclear magnetic resonance spectroscopy Methods 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- BHPQYMZQTOCNFJ-UHFFFAOYSA-N Calcium cation Chemical compound [Ca+2] BHPQYMZQTOCNFJ-UHFFFAOYSA-N 0.000 description 2
- KRHYYFGTRYWZRS-UHFFFAOYSA-M Fluoride anion Chemical compound [F-] KRHYYFGTRYWZRS-UHFFFAOYSA-M 0.000 description 2
- FKNQFGJONOIPTF-UHFFFAOYSA-N Sodium cation Chemical compound [Na+] FKNQFGJONOIPTF-UHFFFAOYSA-N 0.000 description 2
- 229910001424 calcium ion Inorganic materials 0.000 description 2
- 125000002091 cationic group Chemical group 0.000 description 2
- 238000006073 displacement reaction Methods 0.000 description 2
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- 229910052736 halogen Inorganic materials 0.000 description 2
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- 238000001095 inductively coupled plasma mass spectrometry Methods 0.000 description 2
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- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 1
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 1
- 238000005004 MAS NMR spectroscopy Methods 0.000 description 1
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- RKTYLMNFRDHKIL-UHFFFAOYSA-N copper;5,10,15,20-tetraphenylporphyrin-22,24-diide Chemical compound [Cu+2].C1=CC(C(=C2C=CC([N-]2)=C(C=2C=CC=CC=2)C=2C=CC(N=2)=C(C=2C=CC=CC=2)C2=CC=C3[N-]2)C=2C=CC=CC=2)=NC1=C3C1=CC=CC=C1 RKTYLMNFRDHKIL-UHFFFAOYSA-N 0.000 description 1
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Images
Classifications
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
- C09K11/08—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials
- C09K11/70—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing phosphorus
- C09K11/72—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing phosphorus also containing halogen, e.g. halophosphates
- C09K11/73—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing phosphorus also containing halogen, e.g. halophosphates also containing alkaline earth metals
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L33/48—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor body packages
- H01L33/50—Wavelength conversion elements
Definitions
- the present invention relates to a phosphor.
- the above-described phosphor is added with a plurality of elements (eg, Eu 2+ and Mn 2+ ) as activators. Therefore, when this phosphor is irradiated with ultraviolet light, the light is absorbed by Eu 2+ to emit blue-green light with a wavelength of 450 to 520 nm, and Mn 2+ absorbs a part of the energy of excited Eu 2+ Emits orange-red light with a wavelength of 590 to 660 nm. As a result, light of two colors emitted from one kind of phosphor is added to obtain white light.
- elements eg, Eu 2+ and Mn 2+
- the emission lifetime of Eu 2+ as an activator is about 1 ⁇ s
- the emission lifetime of Mn 2+ is about 1 ms, so the luminance saturation of Mn 2+ occurs with the increase of the excitation light density, and the emission color Sometimes shifts blue.
- the present invention has been made in view of these circumstances, and an object thereof is to provide a novel phosphor.
- the phosphor according to an embodiment of the present invention has a perovskite crystal structure in which a light emitting site is represented by ABX 3 (A and B are cations and X is an anion), and a body of the perovskite crystal structure A single-phase phosphor in which the light emitting element is located at the central B site, and a part of the cation A of the light emission site ABX 3 and the light emission site ABX 3 has a smaller ion radius than the cation A.
- a plurality of light emissions with different peak wavelengths can be realized.
- the ionic radius I A of the cation located at the A site of the perovskite crystal structure is 15% or more larger than the ionic radius I B of the cation located at the B site.
- the cation A may be K + and the cation A ′ may be Na + or Li + .
- the cation B may be one or more cations selected from the group consisting of Eu 2+ , Ce 3+ , Sm 2+ and Yb 2+ . This facilitates 4f-5d transition.
- This phosphor has a perovskite crystal structure in which the light emission site is represented by ABX3 (A and B are cations and X is an anion), and the light emitting element is located at the B site which is the body center of the perovskite crystal structure
- a phosphor consisting of phases, the emission spectrum having a first peak in the violet to green wavelength range and a second peak in the yellow to red wavelength range.
- white light can be realized by light of a plurality of colors emitted by one kind of phosphor.
- novel phosphors can be provided.
- FIG. 6 (a) is a view schematically showing a six-coordinate BX 6 octahedron
- FIG. 6 (b) is a view for explaining the energy state of the 5d orbital in six-coordinate. It is the figure which showed typically the breadth of the divided
- FIG. 24A is a perspective view schematically showing the light emitting site (AA ′) BX 3
- FIG. 24B is a side view schematically showing the light emitting site (AA ′) BX 3
- FIG. 2 is a view showing an X-ray diffraction pattern of a phosphor according to Example 1;
- FIG. 2 is a view showing an excitation spectrum and an emission spectrum of a phosphor according to Example 1.
- FIG. 6 is a view showing an X-ray diffraction pattern of a phosphor according to Example 2.
- FIG. 6 is a diagram showing an excitation spectrum and an emission spectrum of a phosphor according to Example 2.
- FIG. 29 (a) schematically shows an energy diagram in which only potassium ion is coordinated to A site, and FIG. 29 (b) shows only potassium ion and sodium ion (lithium ion) coordinated to A site
- FIG. 6 schematically shows an energy diagram of FIG.
- the phosphor according to the present embodiment is a phosphor that is efficiently excited and emits light with ultraviolet light or short wavelength visible light. Specifically, it shows strong excitation with near-ultraviolet light or short-wavelength visible light of 420 nm or less, and the second emission spectrum has a first peak in the violet to green wavelength range and a second peak in the yellow to red wavelength range. And a peak of In addition, the phosphor according to the present embodiment realizes light emission by doping a host crystal of a halo oxide with an activator such as Eu 2+ ion.
- the phosphor according to the present embodiment is a phosphor that emits light in a wavelength range of at least yellow to red, which has a large Stokes shift (approximately 0.8 to 1.2 eV). Therefore, it is difficult to absorb visible light emitted from other phosphors such as blue, green and yellow.
- the Stokes shift refers to the energy difference between the excitation end wavelength and the peak wavelength of the emission spectrum.
- the excitation end wavelength indicates a wavelength at which the decrease in excitation intensity on the long wavelength side in the excitation spectrum starts to decrease sharply.
- a phosphor corresponding to light of a semiconductor light emitting device having a high excitation light density requires a fast excitation-emission cycle (short emission life).
- 4f-5d allowable transition which can make transition while maintaining the electron spin state is preferable.
- the elements capable of 4f-5d transition include rare earth elements of Eu 2+ , Ce 3+ , Sm 2+ , Yb 2+ and the like.
- the outer shell orbit of those rare earth elements is 6s, and the inner shell has a 4f orbit.
- an electron in the 4f orbital forms an excited state by transitioning to the 5d orbital located in the outer shell.
- the larger the spread of the electron cloud in the 5d orbit the lower the energy level of this orbit, and the higher the transition probability. That is, to efficiently absorb the light of the semiconductor light emitting element, it is necessary to lower the energy level of the 5d orbit. To that end, it is desirable to increase the crystal field splitting of the luminescent site.
- FIG. 1 is a diagram for explaining the mechanism of excitation and light emission depending on the state of the crystal. Excitation with low energy requires complex (or distorted low symmetry) light emitting site structure or covalent bonding.
- the 4f-5d transition with free ions requires an energy of 4.0 eV or more.
- no transition occurs in the light of the semiconductor light emitting element that emits near ultraviolet light having a wavelength of about 380 to 450 nm or visible light with a short wavelength. Therefore, to lower the 4f-5d transition energy, it is effective to dope the crystal and coordinate anions around rare earth ions.
- the 5d orbital is reduced in energy by two actions (center of gravity shift E c , crystal field splitting E cfs ) by coordination of anions.
- the center-of-gravity shift E c is the coordination of the anion to the rare earth element (cation), and due to the influence of the surrounding negative charge, the energy of all the 5 d orbitals is reduced.
- the effect is small when the anion to be coordinated is ionically bound and increases as the covalentity increases.
- the valence electrons contributing to the binding are shared by the anion and the cation.
- the negative charge of the covalent anion is less than the negative charge of the ionic bond. Therefore, the electrostatic repulsion of the electrons excited in the 5d orbital is reduced, and the electron cloud in the 5d orbital spreads widely, resulting in an effective decrease in transition energy. In other words, it can be understood that it is important to increase the covalent bond in order to increase the center-of-gravity shift.
- the crystal field splitting E cfs is that the degeneracy of five 5d orbitals is resolved by the steric structure in which the anion is coordinated to the rare earth element (cation), and the energy level (orbital level) of the 5d orbital is split.
- the 5d orbital that spreads in the direction in which the occupancy density of the anion is low has small electrostatic repulsion with the anion, and the electron cloud of the 5d orbital tends to spread (the energy level becomes low).
- the electrostatic repulsion becomes large and the energy level becomes high.
- Light emission occurs at the transition from the energy level to the ground state after the nonradiative transition from the high energy level 5d orbit to the low energy level 5d orbit. Therefore, a specific transition (emission color) occurs from one emission site, and the emission color of the 4f-5d transition phosphor is often monochromatic. In addition, a distorted ligand field is required to largely split the degeneracy of the 5d orbital.
- FIG. 2 is a diagram showing an example of an excitation spectrum and an emission spectrum of a general red phosphor based on nitride.
- a red phosphor that has become widespread in recent years is a phosphor based on nitrides such as CaAlSiN 3 : Eu and Ca 2 Si 5 N 8 : Eu. Since these phosphors increase the barycentric shift by enhancing the covalent bonding property, as shown in FIG. 2, the excitation band (excitation spectrum) is extended to the long wavelength side, and only the light in the ultraviolet region is It also absorbs blue, green and yellow visible light.
- FIG. 3 is a schematic view for explaining the Stokes shift.
- Stokes shift is caused by relaxation of the crystal structure in the excited state.
- the fluorophore is excited from the ground state 4f to the excited state 5d, the excited electron orbitals approach the coordinating anion.
- positions of light (small atomic weight) anions are shifted as compared to cations (rare earth elements).
- cations rare earth elements
- FIG. 4 is a schematic view showing coordination coordinates.
- the ordinate of the coordination coordinate indicates the energy level of the valence electron of the light emitting element
- the abscissa indicates the displacement between the light emitting element and the anion at which the energy level decreases most in the ground state of the crystal.
- the present inventors have considered the possibility of a phosphor having a new crystal structure that increases the Stokes shift, based on the above findings and considerations.
- the excitation / emission of the phosphor is caused by electron orbital transition in the luminescent center element. Therefore, as a phosphor in a high luminance light source such as a white LED, a light emitting element (for example, Eu 2+ or Ce 3+ ) having 4f-5d transition with high transition speed is desirable.
- a light emitting element for example, Eu 2+ or Ce 3+
- electrons in the 4f orbital in the inner shell of the 6s orbital absorb excitation energy and transition to the 5d orbital spreading in the outer shell of the 6s orbital. Light emission occurs from the 5d orbit back to the 4f orbit. Therefore, in order to show a large Stokes shift, it is important that the spread of the 5d orbit in the excited state is large.
- the spread of the 5d orbital is determined by the crystal structure around the light emitting element. Therefore, the inventors of the present invention have devised a crystal structure that increases the spread of the 5d orbital.
- FIG. 5 is a view showing a perovskite crystal structure.
- the perovskite crystal represented by the composition formula ABX 3 ideally has a cubic system unit cell, metal A at each vertex (A site) of the cubic crystal, and metal B at the body center site (B site) However, the anion X is arrange
- the anion X forming the BX 6 octahedron may be composed of two or more types of anions. Specifically, one of the anions X is oxygen. Another type of anion X is halogen. Among the halogens, fluorine is particularly preferred. In another form, another anion X other than oxygen may be nitrogen.
- the A site according to the present embodiment is occupied by a monovalent or divalent cation having a large ionic radius.
- the ionic radius I A of the cation located at the A site is larger than the ionic radius I B of the light emitting element located at the B site.
- the ion radius I A may be 10% or more larger than the ion radius I B , and preferably 15% or more.
- the cation occupying the A site may be a monovalent cation, a divalent cation, or both.
- the phosphor according to the present embodiment configured in this way can be excited at low energy, and the Stokes shift is also large.
- FIG. 6 (a) is a view schematically showing a six-coordinate BX 6 octahedron
- FIG. 6 (b) is a view for explaining the energy state of the 5d orbital in six-coordinate.
- a mixed ligand multiple ligands
- the general perovskite structure is represented by ABO 3 , and six oxygen ions are coordinated to the B site. Therefore, the B site has strong ionic bondability, high symmetry, and less distortion of the ligand field. Therefore, excitation is difficult with small energy such as light of the wavelength (380 to 450 nm) of a semiconductor light emitting element used for a white LED.
- two or more types of anions X are coordinated to the B site of the light emitting site to make the electron density involved in the binding of BX 6 octahedron nonuniform.
- crystal field splitting becomes large, and the excitation band falls to the energy level excited by light emission (low energy) of the semiconductor light emitting device used for the white LED.
- the energy level of t 2 g orbit than e g orbitals decreases.
- the energy level in the d xz and d yz directions is low, where the density of anions X is low.
- FIG. 7 is a view schematically showing the spread of the split orbit.
- the split d xz and d yz orbitals spread in the direction of the A site located at each vertex of the cubic crystal.
- the cation at the A site is charged to a positive charge.
- Electrons in d xz and d yz orbitals that have spread from the B site are attracted to the A site (the cation at the A site is not attracted by electrostatic attraction because the ion radius is large and the mass is large).
- the energy level of the d xz and d yz orbits decreases in the excited state because the electron cloud in the d xz and d yz orbits is greatly spread by electrostatic attraction. Therefore, the Stokes shift becomes large.
- the relaxation of the normal excited state is considered to occur as the coordination position of the anion is changed by the electrostatic repulsive force of the 5 d electron and the anion, and the structure of the ligand field is largely changed.
- the crystal structure of the present invention spreads the 5d orbital by the electrostatic attraction of 5d electrons and cations, the structural change of the ligand field is small. This is because the atomic weight of the cation is large and heavy, so it is difficult to move. Therefore, the phosphor according to the present embodiment exhibits stable temperature characteristics despite the large Stokes shift.
- a first phosphor for example, a red phosphor
- a second phosphor for example, a blue phosphor, a green phosphor, a yellow fluorescence
- a light emitting module provided with a body, an orange phosphor and the like, and a semiconductor light emitting element that emits light for exciting the first phosphor and the second phosphor exhibits the following effects.
- the absorption of the first phosphor according to the present embodiment is scarcely in the wavelength range longer than the emission wavelength of the semiconductor light emitting device, the color is mixed when mixed with the second phosphor of another emission color. It becomes difficult to cause a gap.
- the first phosphor according to the present embodiment does not cause relaxation of the excited state due to the movement of anions, so there is little change in the crystal structure due to excitation, and the temperature characteristics are large despite the large Stokes shift. It becomes good.
- a perovskite crystal structure which is a basic structure of the phosphor according to the present embodiment, will be described using a reference example.
- the elements constituting the crystal structure ABX 3 of the light-emitting site the cation A is K +, cations B is Eu 2+, anion X is O 2- and F - a.
- cation B In addition to Eu 2+ , Ce 3+ , Sm 2+ , Yb 2+ or the like may be added as cation B. This facilitates 4f-5d transition.
- a cation M constituting tetrahedral MO 4 which connects the perovskite structures of the light emitting site is P 5+ .
- M may be a trivalent to pentavalent metal element.
- FIG. 8 is a view showing an X-ray diffraction pattern of a phosphor according to a reference example.
- At least a part of the crystal contained in the phosphor according to the reference example has a diffraction angle 2 ⁇ of 31.0 ° to 33.0 in an X-ray diffraction pattern using a K ⁇ characteristic X-ray of Cu.
- the first diffraction peak P1 the second diffraction peak P2 and the third diffraction peak P3 exist in the range of °, and the diffraction intensity of the highest first diffraction peak P1 is 100, the second diffraction peak P2 and The diffraction intensity of the third diffraction peak P3 is 30 to 50.
- the fourth diffraction peak P4 whose diffraction intensity is 15 to 25 in the range of the diffraction angle 2 ⁇ of 27.0 ° to 29.0 °.
- the fifth diffraction peak P5 having a diffraction intensity of 15 to 25 is in the range of the diffraction angle 2 ⁇ of 41.0 ° to 43.0 °.
- the sixth diffraction peak P6 having a diffraction intensity of 10 to 15 is provided in the range of the diffraction angle 2 ⁇ of 29.0 ° to 31.0 °.
- the seventh diffraction peak P7 having a diffraction intensity of 10 to 15 is provided in the range of the diffraction angle 2 ⁇ of 36.0 ° to 39.0 °.
- the eighth diffraction peak P8 having a diffraction intensity of 5 to 10 is provided in the range of the diffraction angle 2 ⁇ of 13.0 ° to 15.0 °.
- the crystal system of the phosphor according to the present embodiment the brabe based on the data processing software (Rapid Auto: manufactured by Rigaku) from the X-ray diffraction pattern obtained by
- the lattices, space groups, and lattice constants were determined as follows.
- the phosphor of the reference example contains oxygen and fluorine in the anion.
- Oxygen and fluorine are elements adjacent to each other in the periodic table, and it is difficult to specify the occupied position only from the data of X-ray diffraction.
- solid-state NMR measurement of the sample concerning a reference example was performed.
- solid-state NMR the coupling state of an element having a spin quantum number of 1/2 can be grasped, and the coupling relation between 19 F and 31 P can be investigated.
- the measurement was performed using JNM-ECZ500R (manufactured by JEOL Ltd.) with a magnetic field strength of 11.7 T (500 MHz).
- About 50 ⁇ L of the sample was packed in a 3.2 mm measuring probe and measured at room temperature (about 23 ° C.).
- FIG. 9 is a diagram showing the results of resonance spectra measured without decoupling. As shown in FIG. 9, resonance spectra were confirmed at 0.64 ppm and 0.76 ppm. Next, a radio wave (470.6 MHz) corresponding to a gyromagnetic ratio of 19 F was irradiated to cancel the interaction of PF and to perform decoupling measurement.
- FIG. 10 is a diagram showing the result of the resonance spectrum in which the interaction of PF is eliminated and the decoupling measurement is performed. As shown in FIG. 10, the resonance spectrum changed to one broad signal. This result indicates that F interferes with the atomic vibration of P in some way, but it has not reached the judgment of the presence or absence of coupling.
- FIG. 11 is a diagram showing the results of 31 P ⁇ 19 F ⁇ CP-CPMAS measurement. As shown in FIG. 11, the maximum value of the signal intensity did not appear even if the contact time was extended to 20000 ⁇ s, and the signal intensity monotonously increased with the passage of the contact time. From this, it is understood that although fluorine is in the vicinity of phosphorus, fluorine and phosphorus are not directly bonded.
- Phosphorus tends to have a tetragonal coordination structure. From the results of the solid state NMR described above, it was determined that four oxygens were coordinated to phosphorus. Therefore, in structural analysis conducted on the basis of X-ray diffraction data of the reference example, structural analysis was performed on the assumption that the crystal is present in the form of (PO 4 ) 3- .
- FIG. 12 is a schematic view showing a crystal structure of the phosphor according to the present embodiment.
- the occupied position of the light emitting element Eu 2+ is the Ca site (see Table 1).
- the crystal structure shown in FIG. 12 shows the case of viewing from the b-axis direction.
- FIG. 13 is a diagram for explaining the crystal structure of the light emitting site.
- the Eu 2+ site has an octahedral structure in which six anions are coordinated.
- the breakdown of the anion is 4 oxygen ions and 2 fluorine ions.
- the structure of the octahedron EuO 4 F 2 is a cis structure in which two fluorine ions are adjacent to each other.
- the fluorine ions of the octahedron EuO 4 F 2 are linearly arranged in the b-axis direction of the present crystal, and connect the octahedron EuO 4 F 2 to each other in such a manner that the apexes of the octahedron EuO 4 F 2 are shared.
- the octahedron EuO 4 F 2 is connected zigzag in the b-axis direction centering on the fluorine ion (see FIG. 14).
- Each oxygen ion of octahedral EuO 4 F 2 shares a vertex with the PO 4 tetrahedron.
- FIG. 14 is a schematic view of the crystal structure of the phosphor shown in FIG. 12 as viewed from another direction.
- the fluoride ion and the PO 4 tetrahedron form octahedron EuO. 4 F 2 are arranged in a staggered pattern.
- the potassium ions line up to fill the houndstooth of octahedral EuO 4 F 2 .
- FIG. 15 is a view showing a light emitting site of the perovskite crystal structure according to the present embodiment.
- eight potassium ions are located at the top of the cubic lattice (A site).
- Oxygen ions and fluoride ions as anions of octahedral EuO 4 F 2 are located at the face center of the cubic lattice formed by potassium.
- europium (or calcium) ion is located in the body center of cubic lattice (B site).
- the ion radius of 1.55 ⁇ of potassium ions (K + ) occupying A sites is the ion radius 1 of europium ions (Eu 2+ ) occupying B sites. 32% larger than .17 ⁇ .
- the electron density of cis octahedron EuO 4 F 2 centering on divalent europium ion is biased to the fluorine side with high electronegativity. Because of this, the symmetry of the octahedral electron distribution is broken, and the degeneracy of the 5d orbital of the divalent europium ion is solved. As a result, valence electrons in the inner shell 4f orbit of divalent europium tend to transition to the d xz or d yz orbit of the 5 d orbit even at low energy.
- the direction of the d xz or d yz orbitals is the vertex direction of the cubic lattice constituting the perovskite structure.
- the position is occupied by the cation K + having a large ion radius.
- electrostatic attraction is generated between the electron cloud of the 5 d electron (d xz or d yz orbit) of Eu 2+ and the cation K + .
- the mass of the K + ions is large and it is difficult to move, so the spread of the d xz or d yz orbital electron cloud is large.
- the probability of the presence of electrons in the d xz or d yz orbitals increases, and the energy level decreases, thus exhibiting a large Stokes shift.
- FIG. 16 is a schematic view of the unit cell of the phosphor according to the present embodiment as viewed from the a-axis.
- FIG. 17 is a schematic view of a unit cell of the phosphor according to the present embodiment as viewed from the b axis.
- FIG. 18 is a schematic view of a unit cell of the phosphor according to the present embodiment as viewed from the c-axis.
- the unit cell contains atoms of the coordinates shown in Table 1.
- the a axis corresponds to coordinates (x, 0, 0)
- the b axis corresponds to (0, y, 0)
- the c axis corresponds to (0, 0, z).
- FIG. 19 is a diagram showing an excitation spectrum and an emission spectrum of a phosphor according to a reference example.
- the measurement of the excitation light emission spectrum was performed at room temperature using a multi-channel optical spectrometer (PMA C5966-31 (manufactured by Hamamatsu Photonics)).
- the emission spectrum was measured at 400 nm excitation.
- the excitation spectrum was measured by matching the monitor wavelength to the emission peak wavelength at 400 nm excitation.
- the excitation spectrum L1 of the phosphor according to the reference example has a peak wavelength ⁇ 1 in the range of 330 to 420 nm, more specifically in the range of 350 to 390 nm.
- the excitation end wavelength ⁇ e is about 420 nm, and the energy of the wavelength is 2.938 eV.
- the emission spectrum L2 of excitation light having a peak wavelength of 400 nm has a peak wavelength ⁇ 2 of 658 nm, a half width of 152 nm, and an energy of the peak wavelength ⁇ 2 of 1.884 eV. Therefore, the Stokes shift is 1.054 eV.
- the chromaticity coordinates (cx, cy) of the light emitted from this phosphor are (0.613, 0.384).
- the powder sample obtained in the reference example was subjected to compositional analysis using inductively coupled plasma mass spectrometry (ICP-MS) and ion chromatography. As a result, it was revealed that the composition ratio of the phosphor according to the reference example was KF ⁇ Ca 0.99 KPO 4 : Eu 2+ 0.01 .
- FIG. 20 is a diagram showing temperature characteristics of phosphor light emission according to a reference example.
- FIG. 17 shows the relative intensity of each temperature normalized with the emission intensity at 30 ° C. excited with light having a wavelength of 400 nm as 100%. Even though the maintenance rate of emission intensity at 150 ° C. was 90% or more at 30 ° C., and although the Stokes shift was large, good temperature characteristics could be confirmed.
- the inventors of the present invention have found that the light emission site of the perovskite structure of the reference example shifts to a bluish green color upon excitation with high energy (short wavelength).
- the anion for the emission center Eu of the phosphor according to the reference example has a cis octahedral structure of EuO 4 F 2 .
- anions are positioned in each crystal axis direction (see FIG. 6A).
- the phosphor according to the reference example when excited the phosphor according to the reference example in lower energy of about 3.10 eV (400 nm), lower the energy level of t 2 g orbit due to the crystal field splitting of the 5d orbital and 5d orbital in this direction spreads.
- FIG. 21 is a schematic view showing the spread of electron clouds in octahedron EuO 4 F 2 .
- the electrostatic attraction of the cation at the top of the perovskite cube does not act on the axially extended 5d orbital. Instead, electrostatic repulsion (repulsion) with the anion in the axial direction acts. Therefore, the spread of the 5d trajectory is suppressed, and the light emission shifts to the light on the short wavelength side.
- FIG. 22 is a view showing an emission spectrum in the case where the phosphor according to the reference example is irradiated with ultraviolet light of high energy. As shown in FIG. 22, in the phosphor according to the reference example, blue-green emission with a peak wavelength ⁇ 2 of the emission spectrum of 476 nm could be confirmed.
- FIG. 23 is a view showing a diffuse reflection spectrum of the phosphor according to the reference example. As indicated by line L1 in FIG. 23, it can be seen that most of the light of 420 nm or less is absorbed.
- the excitation spectrum L2 for red light emission (monitor wavelength 622 nm) and the excitation spectrum L3 for blue-green light emission (monitor wavelength 476 nm) are superimposed on this. From this, the excitation band of red light emission is at 330 to 420 nm, and the excitation band of blue-green light emission can be confirmed at around 250 to 320 nm. This indicates that one emission center changes the emission color due to the difference in excitation wavelength.
- the phosphor according to the reference example of the present embodiment emits red light with light of the first wavelength (for example, near-ultraviolet light or short-wavelength visible light with a peak wavelength of 380 to 450 nm)
- Light of a second wavelength for example, 200-350 nm forbidden ultraviolet light
- a shorter wavelength than light of a wavelength emits light with a color shorter than red (for example, blue to green at a wavelength of 450 nm to 550 nm).
- Example 1 As a result of the inventors of the present invention performing further studies based on the above findings, it has been realized that a phosphor of a single phase emitting plural colors of light (a plurality of lights having different peak wavelengths) is realized by the phosphor of the following configuration. . Specifically, the light emitting element is located in a body-centered become B site of the perovskite crystal structure (cubic), a phosphor composed of a single phase, and the light-emitting site ABX 3, the light-emitting site ABX 3 cation A Is a phosphor having a luminescent site (AA ') BX 3 substituted by a cation A' having a smaller ionic radius than the cation A.
- the light emitting element is located in a body-centered become B site of the perovskite crystal structure (cubic), a phosphor composed of a single phase, and the light-emitting site ABX 3, the light-emitting site ABX
- cations A and cation A ' there are two or more types of cations (cation A and cation A '), which constitute the A site serving as each vertex of the perovskite crystal structure.
- 95% to 99% of the cations constituting the A site may be occupied by ions larger by 15% or more than the ion radius of the cation B of the B site.
- 1 to 5% of the cations constituting the A site may be occupied by ions having an ion radius equal to or smaller than that of the cation B of the B site.
- the d xz and d yz orbitals split in the T2g direction are attracted to the cation A of the A site located at each vertex of the cubic crystal, and the electron cloud is widely spread by electrostatic attraction, so the energy levels of the d xz and d yz orbitals Decreases. As a result, it emits light of long wavelength (yellow to red).
- FIG. 24A is a perspective view schematically showing the light emitting site (AA ′) BX 3
- FIG. 24B is a side view schematically showing the light emitting site (AA ′) BX 3
- a gap is generated around the anion X located in the face center of the perovskite structure An anion X can move (see FIG. 24B). Therefore, allows energy relaxation, 5d orbital spreads E g direction.
- the phosphor according to Example 1 will be specifically described.
- the elements constituting the crystal structure AA'BX 3 of emission sites + cation A is K (0.975), + cation A 'is Na (0.025), cationic B eu 2+, anion X is O 2- and F - a.
- a cation M constituting tetrahedral MO 4 which connects the perovskite structures of the light emitting site is P 5+ .
- the phosphor according to Example 1 is manufactured by the following method. First, KF, NaF, and K 2 CO 3 powder are dried at 150 ° C. for 2 hours. And, in a glove box filled with dry N 2 , KF, K 2 CO 3 , NaF, CaHPO 4 , (NH 3 ) 2 HPO 4 , Eu 2 O 3 at a stoichiometric ratio of 0.950: 0.500: The mixture was precisely weighed to a ratio of 0.050: 0.960: 0.040: 0.020 (mol), and ground and mixed in an alumina mortar to obtain a raw material mixed powder. Thereafter, the same processing as in the reference example was performed to obtain a phosphor according to example 1.
- Example 1 The powder sample obtained in Example 1 was subjected to composition analysis in the same manner as in the reference example. As a result, it was revealed that the compositional ratio of the phosphor according to Example 1 was (K 1.95 , Na 0.05 ) Ca 0.96 PO 4 F: Eu 2 + 0.04 .
- FIG. 25 is a diagram showing an X-ray diffraction pattern of the phosphor according to Example 1. The measurement was performed using a device similar to Reference Example 1, with a sampling width of 0.02 °, and a scan speed of 2.0 ° / min.
- the obtained powder X-ray diffraction profile shows the same diffraction pattern as the phosphor of the reference example (K 2 Ca (PO 4 ) F: Eu 2+ ), and Rietveld analysis using the same crystal as a model, Rw 6 It converges to less than%, It turned out that it is crystal structure (Crystal system: monoclinic crystal, Bravais lattice: simple lattice, space group: P2 1 / m) of the crystal structure of the same system. In the following, the description overlapping with the reference example is appropriately omitted.
- the phosphor according to Example 1 has the same crystal structure (see FIGS. 12 to 18) as the phosphor according to the reference example from the measurement results described above, and a part of the A site is occupied by sodium ions. Are the main differences.
- Alkali ions (potassium ions, sodium ions) are arranged to fill in a zigzag grid of octahedral EuO 4 F 2 . It has a perovskite structure represented by a composition formula (AA ') BX 3 and attention is paid to the relationship between the alkali ions and octahedral EuO 4 F 2.
- alkali ions are located at the top of the cubic lattice (A site).
- Oxygen ions and fluorine ions as anions of octahedral EuO 4 F 2 are located at the face center of the cubic lattice composed of potassium or sodium.
- europium (or calcium) ion is located in the body center of cubic lattice (B site).
- the alkali ions occupying the A site the ion radius of 1.59 ⁇ of potassium ion (K + ) is 32% larger than the ion radius of 1.17 ⁇ of the europium ion (Eu 2+ ) occupying the B site.
- the ion radius of 1.32 ⁇ of sodium ion (Na + ) occupying A site is relatively close to the ion radius 1.17 of europium ion (Eu 2+ ) occupying B site.
- the mass of the K + ions is large and it is difficult to move, so the spread of the d xz or d yz orbital electron cloud is large.
- the probability of the presence of electrons in the d xz or d yz orbitals is increased, and the energy level is reduced, thus emitting red light.
- FIG. 26 is a diagram showing an excitation spectrum and an emission spectrum of the phosphor according to Example 1.
- the measurement of the excitation light emission spectrum was performed at room temperature using a multi-channel optical spectrometer (PMA C5966-31 (manufactured by Hamamatsu Photonics)).
- the emission spectrum L2 was measured at 400 nm excitation.
- the excitation spectra L1 and L1 ' were measured by matching the monitor wavelength to the emission peak wavelength (655 nm and 493 nm) at 400 nm excitation.
- the emission spectrum L2 of the phosphor according to Example 1 was white light in which blue green light having a peak wavelength ⁇ 2 ′ of 493 nm and red light having a peak wavelength ⁇ 2 of 655 nm were mixed.
- the fluorescent substance which concerns on Example 1 can implement
- single phase means that the material has a component (composition) that is uniform, and the basic crystal structure (perovskite structure in this embodiment) can also be said to be one type of substance.
- Other interpretations can be made without departing from the spirit of the present invention.
- the excitation spectrum L1 ' (measured in accordance with the emission peak wavelength 493 nm) of the phosphor according to Example 1 has a peak wavelength ⁇ 1' in the range of 300 to 420 nm, more specifically in the range of 300 to 350 nm.
- the excitation spectrum L1 (measured to match the emission peak wavelength of 655 nm) has a peak wavelength ⁇ 1 in the range of 300 to 420 nm, more specifically in the range of 350 to 400 nm.
- the chromaticity coordinates (cx, cy) of the light emitted from this phosphor are (0.434, 0.386).
- the profile of the excitation spectrum L1 is almost the same as that of the reference example in which all of the A sites are occupied by potassium ions.
- the excitation spectrum L1 shows a peak at around 300 nm and extends to around 400 nm showing red emission. Therefore, in emission spectrum L2 by excitation light including light with a wavelength of 400 nm, two emission peaks of blue-green emission and red emission are shown.
- Example 2 Next, the phosphor according to Example 2 will be specifically described. The description of the same configuration as that of the first embodiment will be appropriately omitted.
- the elements constituting the crystal structure AA'BX 3 of emission sites + cation A is K (of 0.99), + cation A 'is Li (0.01), cationic B eu 2+, anion X is O 2- and F - a.
- a cation M constituting tetrahedral MO 4 which connects the perovskite structures of the light emitting site is P 5+ .
- the phosphor according to Example 2 is manufactured by the following method. First, KF, LiF, K 2 CO 3 powder is dried at 150 ° C. for 2 hours. And, in a glove box filled with dry N 2 , KF, K 2 CO 3 , LiF, CaHPO 4 , (NH 3 ) 2 HPO 4 , and Eu 2 O 3 have a stoichiometric ratio of 0.98: 0.50: The mixture was precisely weighed to have a ratio of 0.020: 0.960: 0.040: 0.020 (mol), and ground and mixed in an alumina mortar to obtain a raw material mixed powder. Thereafter, the same processing as in the reference example was performed to obtain a phosphor according to example 2.
- Example 2 The powder sample obtained in Example 2 was subjected to composition analysis in the same manner as in the reference example. As a result, the composition ratio of the phosphor according to the second embodiment, (K 1.98, Li 0.02) Ca 0.96 PO 4 F: revealed a Eu 2+ 0.04.
- FIG. 27 is a diagram showing an X-ray diffraction pattern of the phosphor according to Example 2. The measurement was performed using a device similar to Reference Example 1, with a sampling width of 0.02 °, and a scan speed of 2.0 ° / min. The obtained powder X-ray diffraction profile showed a diffraction pattern similar to that of the phosphor of Example 1. In the following, description overlapping with the first embodiment will be omitted as appropriate.
- the phosphor according to Example 2 has the same crystal structure (see FIGS. 12 to 18) as the phosphor according to Example 1 from the above measurement results, and a part of the A site is occupied by lithium ions. Is the main difference.
- Alkali ions (potassium ions, lithium ions) are arranged to fill in a zigzag grid of octahedral EuO 4 F 2 . It has a perovskite structure represented by a composition formula (AA ') BX 3 and attention is paid to the relationship between the alkali ions and octahedral EuO 4 F 2.
- alkali ions are located at the apex of the cubic lattice (A site).
- Oxygen ions and fluoride ions as anions of octahedral EuO 4 F 2 are located at the face center of the cubic lattice composed of potassium or lithium.
- europium (or calcium) ion is located in the body center of cubic lattice (B site).
- the alkali ions occupying the A site the ion radius of 1.59 ⁇ of potassium ion (K + ) is 32% larger than the ion radius of 1.17 ⁇ of the europium ion (Eu 2+ ) occupying the B site.
- the ion radius of 0.92 ⁇ of the lithium ion (Li + ) occupying the A site is smaller than the ion radius 1.17 of the europium ion (Eu 2+ ) occupying the B site.
- the phosphor according to Example 2 having such a structure exhibits similar emission characteristics to Example 1 by the same emission mechanism as that of Example 1.
- FIG. 28 is a diagram showing an excitation spectrum and an emission spectrum of a phosphor according to Example 2.
- the measurement of the excitation emission spectrum is the same as in Example 1.
- the excitation spectra L1 and L1 ' were measured by matching the monitor wavelength to the emission peak wavelength (662 nm and 495 nm) at 400 nm excitation.
- the emission spectrum L2 of the phosphor according to Example 2 was white light in which blue green light having a peak wavelength ⁇ 2 ′ of 495 nm and red light having a peak wavelength ⁇ 2 of 662 nm were mixed.
- the fluorescent substance which concerns on Example 2 can implement
- the excitation spectrum L1 '(measured to match the emission peak wavelength of 495 nm) of the phosphor according to Example 2 has a peak wavelength ⁇ 1' in the range of 300 to 420 nm, more specifically in the range of 300 to 350 nm.
- the excitation spectrum L1 (measured to match the emission peak wavelength 662 nm) has a peak wavelength ⁇ 1 in the range of 300 to 420 nm, more specifically in the range of 350 to 400 nm.
- the chromaticity coordinates (cx, cy) of the light emitted from this phosphor are (0.424, 0.369).
- the profile of the excitation spectrum L1 is almost the same as that of the reference example in which all of the A sites are occupied by potassium ions.
- the excitation spectrum L1 shows a peak at around 300 nm and extends to around 400 nm showing red emission. Therefore, in emission spectrum L2 by excitation light including light with a wavelength of 400 nm, two emission peaks of blue-green emission and red emission are shown.
- the ionic radius (10 coordination) of monovalent metal ions is 1.59 ⁇ for potassium ions, 1.32 ⁇ for sodium ions, and 0.92 ⁇ for lithium ions.
- the ionic radius (six coordination) of the divalent metal ion is 1.00 ⁇ for calcium ions and 1.17 ⁇ for europium ions.
- the ionic radius of the europium ion is larger than the ionic radius of the calcium ion. Therefore, when the B site is occupied by europium ions, distortion occurs in the crystal lattice. Therefore, the distortion can be alleviated by replacing part of the potassium ions at the A site with sodium ions or lithium ions having an ion radius smaller than the ion radius of the potassium ions. Therefore, in order to minimize the total energy of the crystal and obtain a stable structure, Eu and Na (Li) tend to be doped at the same light emitting site in a pairwise manner.
- Fig. 29 (a) schematically shows an energy diagram in which only potassium ions are occupied at the A site
- Fig. 29 (b) shows energy in which only potassium ions and sodium ions (lithium ions) are occupied at the A site. It is the figure which showed the diagram typically.
- white light emission can be realized by mixing light of a plurality of colors having different peak wavelengths in the phosphor having a single crystal structure.
- the present invention was explained with reference to the above-mentioned embodiment and each example, the present invention is not limited to the above-mentioned embodiment and each example, but the embodiment and each example The present invention also includes those in which the configurations are appropriately combined or substituted. Further, it is also possible to appropriately rearrange the combination and order of processing in the embodiment and each embodiment based on the knowledge of the person skilled in the art, and add various modifications such as design changes to the embodiment and each embodiment. However, an embodiment in which such a modification is added can be included in the scope of the present invention.
- the present invention can be used for phosphors used in lighting devices and the like.
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Abstract
This fluorescent body is a fluorescent body which comprises a single phase and has a perovskite crystal structure having a light-emitting site represented by ABX3 (A, B are cations, and X is an anion), and in which a light-emitting element is located at a B site that is the body center of the perovskite crystal structure. The fluorescent body has: a light-emitting site ABX3; and a light-emitting site (AA')BX3 in which a part of the cation A of the light-emitting site ABX3 is substituted with a cation A' having a smaller ionic radius than the cation A.
Description
本発明は、蛍光体に関する。
The present invention relates to a phosphor.
近年、蛍光体や白熱電球の代替光源として白色発光ダイオード(LED)が普及してきている。このような白色LEDにおいても、従来の光源と同様に自然光に近い高い演色性が求められている。現在主流の白色LEDは、青色発光の半導体発光素子と黄色蛍光体とを組み合わせたものが一般的である。
In recent years, white light emitting diodes (LEDs) have become widespread as alternative light sources for phosphors and incandescent bulbs. Also in such a white LED, high color rendering property close to natural light is required as in the conventional light source. At present, mainstream white LEDs are generally a combination of a blue light emitting semiconductor light emitting element and a yellow phosphor.
しかしながら、青色光と黄色光とを合成した疑似白色では赤色成分が不足となるため、高い演色性を実現することは困難であった。そこで、青色波長領域から赤色波長領域にわたる非常に広い発光波長領域を有するMgAl2Si4O6N4を主相とする蛍光体が考案されている(特許文献1参照)。
However, it is difficult to realize high color rendering because pseudo white obtained by combining blue light and yellow light is insufficient in red component. Therefore, a phosphor having MgAl 2 Si 4 O 6 N 4 as a main phase having a very wide emission wavelength range ranging from the blue wavelength range to the red wavelength range has been devised (see Patent Document 1).
前述の蛍光体は、賦活剤として複数種の元素(例えば、Eu2+とMn2+)が添加されている。そのため、この蛍光体に紫外線が照射されると、その光をEu2+が吸収し、波長が450~520nmの青緑光を発するとともに、励起されたEu2+のエネルギの一部を更にMn2+が吸収し、波長が590~660nmの橙赤色光を発する。その結果、1種類の蛍光体から発する2色の光が加色され、白色光が得られる。
The above-described phosphor is added with a plurality of elements (eg, Eu 2+ and Mn 2+ ) as activators. Therefore, when this phosphor is irradiated with ultraviolet light, the light is absorbed by Eu 2+ to emit blue-green light with a wavelength of 450 to 520 nm, and Mn 2+ absorbs a part of the energy of excited Eu 2+ Emits orange-red light with a wavelength of 590 to 660 nm. As a result, light of two colors emitted from one kind of phosphor is added to obtain white light.
一方、賦活剤としてのEu2+の発光寿命が約1μsであるのに対して、Mn2+の発光寿命が約1msであるため、励起光密度の増大に伴いMn2+の輝度飽和が起こり、発光色がブルーシフトしてしまうことがある。
On the other hand, while the emission lifetime of Eu 2+ as an activator is about 1 μs, the emission lifetime of Mn 2+ is about 1 ms, so the luminance saturation of Mn 2+ occurs with the increase of the excitation light density, and the emission color Sometimes shifts blue.
本発明はこうした状況に鑑みてなされたものであり、その目的とするところは、新規な蛍光体を提供することにある。
The present invention has been made in view of these circumstances, and an object thereof is to provide a novel phosphor.
上記課題を解決するために、本発明のある態様の蛍光体は、発光サイトがABX3(A,Bはカチオン、Xはアニオン)で表されるペロブスカイト結晶構造を持ち、該ペロブスカイト結晶構造の体心となるBサイトに発光元素が位置した、単一相からなる蛍光体であって、発光サイトABX3と、発光サイトABX3のカチオンAの一部がカチオンAよりイオン半径が小さいカチオンA’で置換された発光サイト(AA’)BX3と、を有する。
In order to solve the above problems, the phosphor according to an embodiment of the present invention has a perovskite crystal structure in which a light emitting site is represented by ABX 3 (A and B are cations and X is an anion), and a body of the perovskite crystal structure A single-phase phosphor in which the light emitting element is located at the central B site, and a part of the cation A of the light emission site ABX 3 and the light emission site ABX 3 has a smaller ion radius than the cation A. And a luminescent site (AA ') BX 3 substituted with
この態様によると、ピーク波長が異なる複数の発光を実現できる。
According to this aspect, a plurality of light emissions with different peak wavelengths can be realized.
ペロブスカイト結晶構造のAサイトに位置するカチオンのイオン半径IAは、Bサイトに位置するカチオンのイオン半径IBよりも15%以上大きい。
The ionic radius I A of the cation located at the A site of the perovskite crystal structure is 15% or more larger than the ionic radius I B of the cation located at the B site.
カチオンAはK+、カチオンA’はNa+またはLi+であってもよい。
The cation A may be K + and the cation A ′ may be Na + or Li + .
カチオンBは、Eu2+、Ce3+、Sm2+及びYb2+からなる群より選択される1種以上のカチオンであってもよい。これにより、4f-5d遷移が容易となる。
The cation B may be one or more cations selected from the group consisting of Eu 2+ , Ce 3+ , Sm 2+ and Yb 2+ . This facilitates 4f-5d transition.
本発明の別の態様もまた、蛍光体である。この蛍光体は、発光サイトがABX3(A,Bはカチオン、Xはアニオン)で表されるペロブスカイト結晶構造を持ち、該ペロブスカイト結晶構造の体心となるBサイトに発光元素が位置した、単一相からなる蛍光体であって、発光スペクトルが、紫色から緑色の波長範囲にある第1のピークと、黄色から赤色の波長範囲にある第2のピークと、を有する。
Another aspect of the present invention is also a phosphor. This phosphor has a perovskite crystal structure in which the light emission site is represented by ABX3 (A and B are cations and X is an anion), and the light emitting element is located at the B site which is the body center of the perovskite crystal structure A phosphor consisting of phases, the emission spectrum having a first peak in the violet to green wavelength range and a second peak in the yellow to red wavelength range.
この態様によると、1種類の蛍光体が発する複数の色の光により白色光を実現できる。
According to this aspect, white light can be realized by light of a plurality of colors emitted by one kind of phosphor.
以上の構成要素の任意の組合せ、本発明の表現を製造方法、灯具や照明などの装置、発光モジュール、光源などの間で変換したものもまた、本発明の態様として有効である。
Arbitrary combinations of the above-described components, conversions of the expression of the present invention among manufacturing methods, devices such as lamps and lights, light emitting modules, light sources and the like are also effective as aspects of the present invention.
本発明によれば、新規な蛍光体を提供できる。
According to the present invention, novel phosphors can be provided.
以下、本発明を好適な実施の形態をもとに図面を参照しながら説明する。各図面に示される同一または同等の構成要素、部材、処理には、同一の符号を付するものとし、適宜重複した説明は省略する。また、実施の形態は、発明を限定するものではなく例示であって、実施の形態に記述されるすべての特徴やその組合せは、必ずしも発明の本質的なものであるとは限らない。
Hereinafter, the present invention will be described based on preferred embodiments with reference to the drawings. The same or equivalent components, members, and processes shown in the drawings are denoted by the same reference numerals, and duplicating descriptions will be omitted as appropriate. In addition, the embodiments do not limit the invention and are merely examples, and all the features and combinations thereof described in the embodiments are not necessarily essential to the invention.
本実施の形態に係る蛍光体は、紫外線または短波長可視光で効率良く励起され発光する蛍光体である。具体的には、420nm以下の近紫外光または短波長可視光で強い励起を示し、発光スペクトルが、紫色から緑色の波長範囲にある第1のピークと、黄色から赤色の波長範囲にある第2のピークと、を有する蛍光体である。また、本実施の形態に係る蛍光体は、ハロ酸化物の母体結晶にEu2+イオン等の賦活剤をドープすることで発光を実現している。
The phosphor according to the present embodiment is a phosphor that is efficiently excited and emits light with ultraviolet light or short wavelength visible light. Specifically, it shows strong excitation with near-ultraviolet light or short-wavelength visible light of 420 nm or less, and the second emission spectrum has a first peak in the violet to green wavelength range and a second peak in the yellow to red wavelength range. And a peak of In addition, the phosphor according to the present embodiment realizes light emission by doping a host crystal of a halo oxide with an activator such as Eu 2+ ion.
また、本実施の形態に係る蛍光体は、ストークスシフトが大きい(0.8~1.2eV程度)少なくとも黄色から赤色の波長範囲の光を発する蛍光体である。そのため、青色、緑色、黄色等の他の蛍光体が発する可視光が吸収されにくい。なお、ストークスシフトとは、励起端波長と発光スペクトルのピーク波長とのエネルギ差をいう。ここで、励起端波長とは、励起スペクトルにおける長波長側の励起強度の低下が急減し始める波長を示している。
The phosphor according to the present embodiment is a phosphor that emits light in a wavelength range of at least yellow to red, which has a large Stokes shift (approximately 0.8 to 1.2 eV). Therefore, it is difficult to absorb visible light emitted from other phosphors such as blue, green and yellow. The Stokes shift refers to the energy difference between the excitation end wavelength and the peak wavelength of the emission spectrum. Here, the excitation end wavelength indicates a wavelength at which the decrease in excitation intensity on the long wavelength side in the excitation spectrum starts to decrease sharply.
はじめに、本願発明に想到するまでの経緯について説明する。励起光密度の高い半導体発光素子の光に対応する蛍光体は、速い励起-発光のサイクル(発光寿命が短い)が必要となる。そのためには、電子スピン状態を維持したまま遷移できる4f-5d許容遷移が好適である。
First, the process of achieving the present invention will be described. A phosphor corresponding to light of a semiconductor light emitting device having a high excitation light density requires a fast excitation-emission cycle (short emission life). For that purpose, 4f-5d allowable transition which can make transition while maintaining the electron spin state is preferable.
4f-5d遷移が可能な元素は、Eu2+、Ce3+、Sm2+、Yb2+の希土類元素等が挙げられる。それらの希土類元素の外殻軌道は6sであり、その内殻に4f軌道がある。4f-5d遷移では、4f軌道の電子が外殻に位置する5d軌道に遷移することで、励起状態を形成する。このとき、5d軌道の電子雲の広がりが大きいほど、この軌道のエネルギレベルが下がり、遷移確率が高くなる。つまり、半導体発光素子の光を効率的に吸収するには、5d軌道のエネルギレベルを下げる必要がある。それには、発光サイトの結晶場分裂を大きくすることが望まれる。
The elements capable of 4f-5d transition include rare earth elements of Eu 2+ , Ce 3+ , Sm 2+ , Yb 2+ and the like. The outer shell orbit of those rare earth elements is 6s, and the inner shell has a 4f orbit. In the 4f-5d transition, an electron in the 4f orbital forms an excited state by transitioning to the 5d orbital located in the outer shell. At this time, the larger the spread of the electron cloud in the 5d orbit, the lower the energy level of this orbit, and the higher the transition probability. That is, to efficiently absorb the light of the semiconductor light emitting element, it is necessary to lower the energy level of the 5d orbit. To that end, it is desirable to increase the crystal field splitting of the luminescent site.
図1は、結晶の状態に応じた励起及び発光のメカニズムを説明するための図である。低エネルギで励起するには、複雑な(あるいは歪んだ対称性の低い構造の)発光サイト構造か、共有結合性が必要である。
FIG. 1 is a diagram for explaining the mechanism of excitation and light emission depending on the state of the crystal. Excitation with low energy requires complex (or distorted low symmetry) light emitting site structure or covalent bonding.
例えば、自由イオンでの4f-5d遷移には4.0eV以上のエネルギが必要である。その場合、波長が380~450nm程度の近紫外線または短波長可視光を発する半導体発光素子の光では遷移が発生しない。そこで、4f-5d遷移エネルギを下げるには、結晶中にドープし、希土類イオンの周りにアニオンを配位させることが有効である。5d軌道は、アニオンの配位により、2つの作用(重心シフトEc,結晶場分裂Ecfs)で低エネルギ化する。
For example, the 4f-5d transition with free ions requires an energy of 4.0 eV or more. In that case, no transition occurs in the light of the semiconductor light emitting element that emits near ultraviolet light having a wavelength of about 380 to 450 nm or visible light with a short wavelength. Therefore, to lower the 4f-5d transition energy, it is effective to dope the crystal and coordinate anions around rare earth ions. The 5d orbital is reduced in energy by two actions (center of gravity shift E c , crystal field splitting E cfs ) by coordination of anions.
重心シフトEcは、希土類元素(カチオン)にアニオンが配位することで、周りの負電荷の影響により、5つの5d軌道全体が低エネルギ化する。その効果は、配位するアニオンがイオン結合性の場合は小さく、共有結合性が増すと大きくなる。
The center-of-gravity shift E c is the coordination of the anion to the rare earth element (cation), and due to the influence of the surrounding negative charge, the energy of all the 5 d orbitals is reduced. The effect is small when the anion to be coordinated is ionically bound and increases as the covalentity increases.
イオン結合性の場合、結合に寄与する価電子はアニオン側に分布する。5d軌道に励起した電子は、マイナスチャージのアニオンと電気的反発が大きく、5d軌道の電子雲の広がり(遷移エネルギレベルの低下)は限定的になる。
In the case of ionic bonding, valence electrons contributing to bonding are distributed on the anion side. Electrons excited in the 5d orbital have large electrical repulsion with anions of negative charge, and the spread of the electron cloud in the 5d orbital (reduction of transition energy level) becomes limited.
共有結合性の場合、結合に寄与する価電子はアニオンとカチオンが共有する。共有結合性のアニオンのマイナスチャージは、イオン結合性のマイナスチャージより小さい。したがって、5d軌道に励起した電子の静電反発は小さくなり、5d軌道の電子雲は、大きく広がり、有効的な遷移エネルギの低下が起こる。つまり、重心シフトを大きくするには、共有結合性を高めることが重要であることがわかる。
In the case of covalent bonding, the valence electrons contributing to the binding are shared by the anion and the cation. The negative charge of the covalent anion is less than the negative charge of the ionic bond. Therefore, the electrostatic repulsion of the electrons excited in the 5d orbital is reduced, and the electron cloud in the 5d orbital spreads widely, resulting in an effective decrease in transition energy. In other words, it can be understood that it is important to increase the covalent bond in order to increase the center-of-gravity shift.
結晶場分裂Ecfsは、希土類元素(カチオン)にアニオンが配位した立体構造により、5つある5d軌道の縮退が解け、5d軌道のエネルギレベル(軌道準位)が分裂することである。アニオンの占有密度が低い方向(アニオンがない方向)に広がる5d軌道は、アニオンとの静電反発は小さく、5d軌道の電子雲は広がりやすい(エネルギレベルが低くなる)。一方、アニオンの占有密度が高い方向(アニオンが配位している方向)は、静電反発が大きくなり、エネルギレベルが高くなる。発光は、高いエネルギレベルの5d軌道から低いエネルギレベルの5d軌道に無輻射遷移をした後、そのエネルギレベルから基底状態に遷移する際に起こる。したがって、ひとつの発光サイトからは、特定の遷移(発光色)が生じ、4f-5d遷移の蛍光体の発光色は単色となることが多い。また、5d軌道の縮退を大きく分裂させるためには、歪んだ配位子場が必要になる。
The crystal field splitting E cfs is that the degeneracy of five 5d orbitals is resolved by the steric structure in which the anion is coordinated to the rare earth element (cation), and the energy level (orbital level) of the 5d orbital is split. The 5d orbital that spreads in the direction in which the occupancy density of the anion is low (the direction in which the anion is not present) has small electrostatic repulsion with the anion, and the electron cloud of the 5d orbital tends to spread (the energy level becomes low). On the other hand, in the direction in which the occupancy density of the anions is high (the direction in which the anions are coordinated), the electrostatic repulsion becomes large and the energy level becomes high. Light emission occurs at the transition from the energy level to the ground state after the nonradiative transition from the high energy level 5d orbit to the low energy level 5d orbit. Therefore, a specific transition (emission color) occurs from one emission site, and the emission color of the 4f-5d transition phosphor is often monochromatic. In addition, a distorted ligand field is required to largely split the degeneracy of the 5d orbital.
図2は、窒化物を母体とする一般的な赤色蛍光体の励起スペクトルおよび発光スペクトルの一例を示す図である。近年普及している赤色蛍光体は、CaAlSiN3:Eu、Ca2Si5N8:Eu等の窒化物を母体とする蛍光体である。これらの蛍光体は、共有結合性を高めることで、重心シフトを大きくしているため、図2に示すように、励起帯(励起スペクトル)は長波長側まで広がっており、紫外領域の光だけでなく青色、緑色、黄色の可視光まで吸収してしまう。
FIG. 2 is a diagram showing an example of an excitation spectrum and an emission spectrum of a general red phosphor based on nitride. A red phosphor that has become widespread in recent years is a phosphor based on nitrides such as CaAlSiN 3 : Eu and Ca 2 Si 5 N 8 : Eu. Since these phosphors increase the barycentric shift by enhancing the covalent bonding property, as shown in FIG. 2, the excitation band (excitation spectrum) is extended to the long wavelength side, and only the light in the ultraviolet region is It also absorbs blue, green and yellow visible light.
図3は、ストークスシフトを説明するための模式図である。ストークスシフトは、励起状態での結晶構造の緩和によって起こる。蛍光体が基底状態4fから励起状態5dに励起されたとき、励起した電子軌道は配位アニオンに近づく。このとき、静電反発により、カチオン(希土類)に比べ軽い(原子量が小さい)アニオンの位置がずれる。しかし、アニオンの周りには元々他のカチオンが存在するため、平衡位置までの移動となる。このようなアニオンの移動により、励起状態の結晶構造は、基底状態とは異なってくる。この励起状態での結晶構造変化(緩和1)が起こった後に、基底状態に戻り、それに伴い発光が起こる。
FIG. 3 is a schematic view for explaining the Stokes shift. Stokes shift is caused by relaxation of the crystal structure in the excited state. When the fluorophore is excited from the ground state 4f to the excited state 5d, the excited electron orbitals approach the coordinating anion. At this time, due to electrostatic repulsion, positions of light (small atomic weight) anions are shifted as compared to cations (rare earth elements). However, because there are other cations originally present around the anion, it will move to the equilibrium position. Such an anion transfer makes the crystal structure of the excited state different from that of the ground state. After the crystal structure change (relaxation 1) in this excited state occurs, the state returns to the ground state, and light emission occurs accordingly.
カチオンである発光元素は、図3に示すように、基底状態から励起されて励起状態となり、励起状態での結晶構造変化(緩和)後に発光する。この際、エネルギ状態が変化する。この変化は、一般には配位座標で表される。図4は、配位座標を示す模式図である。配位座標の縦軸は、発光元素の価電子のエネルギレベル、横軸は、結晶の基底状態で最もエネルギレベルが下がる発光元素-アニオン間の距離をゼロとし、その変位を示す。
As shown in FIG. 3, the light emitting element which is a cation is excited from the ground state to be in the excited state, and emits light after the crystal structure change (relaxation) in the excited state. At this time, the energy state changes. This change is generally expressed in coordination coordinates. FIG. 4 is a schematic view showing coordination coordinates. The ordinate of the coordination coordinate indicates the energy level of the valence electron of the light emitting element, and the abscissa indicates the displacement between the light emitting element and the anion at which the energy level decreases most in the ground state of the crystal.
発光元素の4f電子は、励起光を吸収した瞬間に、エネルギレベルが上がり、励起状態になる。励起状態では、配位アニオンとの静電反発を解消する緩和が起こり、平衡状態までエネルギレベルが下がる。その時点から発行が始まるため、励起エネルギより小さなエネルギの遷移、長波長シフトが起こる。このとき、考慮しなければならないのはフォノン振動である。変位が大きくなれば、フォノン振動が大きくなる。その場合、系のエネルギレベルが上昇する。また、温度が上昇し、励起状態でのフォノン振動により基底状態の振動レベルと等しくなると、非輻射遷移となる。一般にストークスシフトが大きくなると温度特性の低下が懸念されていた。
At the moment when 4f electrons of the light emitting element absorb the excitation light, the energy level rises and becomes an excited state. In the excited state, relaxation occurs to eliminate electrostatic repulsion with the coordination anion, and the energy level drops to the equilibrium state. Since the issuance starts from that point, a transition of energy smaller than the excitation energy, a long wavelength shift, occurs. At this time, it is phonon oscillation that must be taken into consideration. The greater the displacement, the greater the phonon vibration. In that case, the energy level of the system rises. In addition, when the temperature rises and becomes equal to the vibration level of the ground state due to phonon vibration in the excited state, non-radiative transition occurs. In general, when the Stokes shift becomes large, there is a concern that the temperature characteristic is lowered.
本願発明者らは、上記の知見や考察に基づいて、ストークスシフトを増大させる新しい結晶構造を有する蛍光体の可能性に想到した。
The present inventors have considered the possibility of a phosphor having a new crystal structure that increases the Stokes shift, based on the above findings and considerations.
蛍光体の励起/発光は、発光中心元素内の電子軌道遷移によって起こる。そのため、白色LEDのような高輝度光源における蛍光体には、遷移速度の速い4f-5d遷移をする発光元素(例えば、Eu2+、Ce3+)が望ましい。4f-5d遷移の励起は、6s軌道の内殻にある4f軌道の電子が励起エネルギを吸収し、6s軌道の外殻に広がる5d軌道に遷移する。発光は、5d軌道から4f軌道に戻ることで起こる。そのため、大きなストークスシフトを示すには、励起状態での5d軌道の広がりが大きくなることが重要となる。5d軌道の広がりは、発光元素周りの結晶構造によって決まる。そこで、本願発明者らは、5d軌道の広がりを大きくする結晶構造を考案した。
The excitation / emission of the phosphor is caused by electron orbital transition in the luminescent center element. Therefore, as a phosphor in a high luminance light source such as a white LED, a light emitting element (for example, Eu 2+ or Ce 3+ ) having 4f-5d transition with high transition speed is desirable. In the excitation of the 4f-5d transition, electrons in the 4f orbital in the inner shell of the 6s orbital absorb excitation energy and transition to the 5d orbital spreading in the outer shell of the 6s orbital. Light emission occurs from the 5d orbit back to the 4f orbit. Therefore, in order to show a large Stokes shift, it is important that the spread of the 5d orbit in the excited state is large. The spread of the 5d orbital is determined by the crystal structure around the light emitting element. Therefore, the inventors of the present invention have devised a crystal structure that increases the spread of the 5d orbital.
はじめに、本実施の形態に係る蛍光体が有する結晶構造の一つとして、ペロブスカイト結晶構造に着目した。図5は、ペロブスカイト結晶構造を示す図である。
First, attention was focused on the perovskite crystal structure as one of the crystal structures of the phosphor according to the present embodiment. FIG. 5 is a view showing a perovskite crystal structure.
組成式ABX3で表されるペロブスカイト結晶は、理想的には、立方晶系の単位格子をもち、立方晶の各頂点(Aサイト)に金属Aが、体心サイト(Bサイト)に金属Bが、立方晶の各面心サイト(Xサイト)にアニオンXが配置されている。また、金属Bには6つのアニオンXが配位し、BX6八面体を形成している。また、本実施の形態に係る発光サイトでは、Bサイトに4f-5d遷移する発光元素が位置している。このように、本実施の形態に係る蛍光体は、発光サイトがペロブスカイト結晶構造の新規な蛍光体である。
The perovskite crystal represented by the composition formula ABX 3 ideally has a cubic system unit cell, metal A at each vertex (A site) of the cubic crystal, and metal B at the body center site (B site) However, the anion X is arrange | positioned at each face-centered site (X site) of a cubic crystal. In addition, six anions X are coordinated to the metal B to form a BX 6 octahedron. In addition, in the light emitting site according to the present embodiment, a light emitting element having a 4f-5d transition is located at the B site. As described above, the phosphor according to the present embodiment is a novel phosphor having a perovskite crystal structure as the light emitting site.
BX6八面体を形成しているアニオンXは、2種類以上のアニオンからなっていてもよい。具体的には、アニオンXの一つは酸素である。また、他の一種のアニオンXは、ハロゲンである。ハロゲンの中では、特にフッ素が好ましい。また、別の形態としては、酸素以外のもう一種のアニオンXが窒素であってもよい。
The anion X forming the BX 6 octahedron may be composed of two or more types of anions. Specifically, one of the anions X is oxygen. Another type of anion X is halogen. Among the halogens, fluorine is particularly preferred. In another form, another anion X other than oxygen may be nitrogen.
本実施の形態に係るAサイトは、イオン半径の大きな1価または2価のカチオンが占有している。Aサイトに位置するカチオンのイオン半径IAは、Bサイトに位置する発光元素のイオン半径IBより大きい。また、イオン半径IAはイオン半径IBより10%以上大きくてもよく、好ましくは15%以上大きいとよい。なお、Aサイトを占有するカチオンは、1価のカチオンからなる場合、2価のカチオンからなる場合、または、その両者からなる場合が有り得る。このように構成された本実施の形態に係る蛍光体は、低エネルギでの励起が可能であり、ストークスシフトも大きくなっている。
The A site according to the present embodiment is occupied by a monovalent or divalent cation having a large ionic radius. The ionic radius I A of the cation located at the A site is larger than the ionic radius I B of the light emitting element located at the B site. In addition, the ion radius I A may be 10% or more larger than the ion radius I B , and preferably 15% or more. The cation occupying the A site may be a monovalent cation, a divalent cation, or both. The phosphor according to the present embodiment configured in this way can be excited at low energy, and the Stokes shift is also large.
図6(a)は、6配位のBX6八面体の模式的に示す図、図6(b)は、6配位における5d軌道のエネルギ状態を説明するための図である。低エネルギ励起のメカニズムにおいては、前述の6配位のBX6八面体の対称性を低下させるミックスリガンド(複数種の配位子)を有することが好ましい。一般のペロブスカイト構造はABO3で表され、Bサイトには6つの酸素イオンが配位している。したがって、Bサイトは、イオン結合性が強く、また、対称性が高く、配位子場の歪が少ない。そのため、白色LEDに用いられる半導体発光素子の波長(380~450nm)の光のような小さなエネルギでは励起が難しい。
FIG. 6 (a) is a view schematically showing a six-coordinate BX 6 octahedron, and FIG. 6 (b) is a view for explaining the energy state of the 5d orbital in six-coordinate. In the mechanism of low energy excitation, it is preferable to have a mixed ligand (multiple ligands) that reduces the symmetry of the aforementioned six-coordinated BX 6 octahedron. The general perovskite structure is represented by ABO 3 , and six oxygen ions are coordinated to the B site. Therefore, the B site has strong ionic bondability, high symmetry, and less distortion of the ligand field. Therefore, excitation is difficult with small energy such as light of the wavelength (380 to 450 nm) of a semiconductor light emitting element used for a white LED.
そこで、本実施の形態に係る蛍光体は、発光サイトのBサイトに2種以上のアニオンXを配位させることで、BX6八面体の結合に係わる電子密度を不均一にした。その結果、結晶場分裂が大きくなり、白色LEDに用いられる半導体発光素子の発光(低エネルギ)で励起されるエネルギレベルまで励起帯が下がってくる。このとき5d軌道の縮退は、軸方向にあるアニオンXとの静電反発を避けるように広がるため、eg軌道よりt2g軌道のエネルギレベルが下がる。t2g軌道の中でも、アニオンXの密度が低いdxz、dyz方向のエネルギレベルが下がる。
Therefore, in the phosphor according to the present embodiment, two or more types of anions X are coordinated to the B site of the light emitting site to make the electron density involved in the binding of BX 6 octahedron nonuniform. As a result, crystal field splitting becomes large, and the excitation band falls to the energy level excited by light emission (low energy) of the semiconductor light emitting device used for the white LED. Degeneracy of this time 5d orbit, since spread to avoid electrostatic repulsion between the anions X in the axial direction, the energy level of t 2 g orbit than e g orbitals decreases. Among the t 2g orbitals, the energy level in the d xz and d yz directions is low, where the density of anions X is low.
図7は、分裂した軌道の広がりを模式的に示した図である。図7に示すように、分裂したdxz、dyz軌道は、立方晶の各頂点に位置するAサイト方向に広がる。Aサイトのカチオンは正電荷にチャージしている。Bサイトから広がってきたdxz、dyz軌道の電子はAサイトに引き付けられる(Aサイトのカチオンは、イオン半径が大きく質量が大きいため、静電引力によって引き付けられない。)。
FIG. 7 is a view schematically showing the spread of the split orbit. As shown in FIG. 7, the split d xz and d yz orbitals spread in the direction of the A site located at each vertex of the cubic crystal. The cation at the A site is charged to a positive charge. Electrons in d xz and d yz orbitals that have spread from the B site are attracted to the A site (the cation at the A site is not attracted by electrostatic attraction because the ion radius is large and the mass is large).
dxz、dyz軌道の電子雲が静電引力によって大きく広がるため、dxz、dyz軌道のエネルギレベルは励起状態で低下する。そのため、ストークスシフトは大きくなる。通常の励起状態の緩和は、5d電子とアニオンの静電斥力によりアニオンの配位位置が変わり、配位子場の構造が大きく変化することで生じると考えられる。これに対して、本考案の結晶構造は5d電子とカチオンの静電引力により5d軌道を広げることから、配位子場の構造変化は少ない。このことは、カチオンの原子量が大きく重いため、動きづらいことが理由である。よって、本実施の形態に係る蛍光体は、ストークスシフトが大きいにも関わらず、安定した温度特性を示す。
The energy level of the d xz and d yz orbits decreases in the excited state because the electron cloud in the d xz and d yz orbits is greatly spread by electrostatic attraction. Therefore, the Stokes shift becomes large. The relaxation of the normal excited state is considered to occur as the coordination position of the anion is changed by the electrostatic repulsive force of the 5 d electron and the anion, and the structure of the ligand field is largely changed. On the other hand, since the crystal structure of the present invention spreads the 5d orbital by the electrostatic attraction of 5d electrons and cations, the structural change of the ligand field is small. This is because the atomic weight of the cation is large and heavy, so it is difficult to move. Therefore, the phosphor according to the present embodiment exhibits stable temperature characteristics despite the large Stokes shift.
本実施の形態に係る第1の蛍光体(例えば、赤色蛍光体)と、第1の蛍光体と異なる色の蛍光を発する第2の蛍光体(例えば、青色蛍光体、緑色蛍光体、黄色蛍光体、橙蛍光体等)と、第1の蛍光体および第2の蛍光体を励起する光を発する半導体発光素子と、を備えた発光モジュールは、以下の効果を奏する。
A first phosphor (for example, a red phosphor) according to the present embodiment and a second phosphor (for example, a blue phosphor, a green phosphor, a yellow fluorescence) emitting fluorescence of a color different from that of the first phosphor A light emitting module provided with a body, an orange phosphor and the like, and a semiconductor light emitting element that emits light for exciting the first phosphor and the second phosphor exhibits the following effects.
第1に、本実施の形態に係る第1の蛍光体の吸収が、半導体発光素子の発光波長より長い波長域においてほとんどないため、他の発光色の第2の蛍光体と混合した時に、色ずれを起こしにくくなる。第2に、本実施の形態に係る第1の蛍光体は、アニオンの移動による励起状態の緩和を起こさないため、励起による結晶構造変化が少なく、ストークスシフトが大きいにも関わらず、温度特性が良好となる。
First, since the absorption of the first phosphor according to the present embodiment is scarcely in the wavelength range longer than the emission wavelength of the semiconductor light emitting device, the color is mixed when mixed with the second phosphor of another emission color. It becomes difficult to cause a gap. Second, the first phosphor according to the present embodiment does not cause relaxation of the excited state due to the movement of anions, so there is little change in the crystal structure due to excitation, and the temperature characteristics are large despite the large Stokes shift. It becomes good.
(参考例)
はじめに、本実施の形態に係る蛍光体の基本構造となるペロブスカイト結晶構造について参考例を用いて説明する。参考例に係る蛍光体において、発光サイトの結晶構造ABX3を構成する元素は、カチオンAがK+、カチオンBがEu2+、アニオンXがO2-及びF-である。なお、Eu2+以外にカチオンBとしてCe3+、Sm2+、Yb2+等を添加してもよい。これにより、4f-5d遷移が容易となる。また、発光サイトのペロブスカイト構造同士をつなぐ四面体MO4を構成するカチオンMはP5+である。なお、Mは、3~5価の金属元素であってもよい。 (Reference example)
First, a perovskite crystal structure, which is a basic structure of the phosphor according to the present embodiment, will be described using a reference example. In the phosphor according to the reference example, the elements constituting the crystal structure ABX 3 of the light-emitting site, the cation A is K +, cations B is Eu 2+, anion X is O 2- and F - a. In addition to Eu 2+ , Ce 3+ , Sm 2+ , Yb 2+ or the like may be added as cation B. This facilitates 4f-5d transition. Further, a cation M constituting tetrahedral MO 4 which connects the perovskite structures of the light emitting site is P 5+ . M may be a trivalent to pentavalent metal element.
はじめに、本実施の形態に係る蛍光体の基本構造となるペロブスカイト結晶構造について参考例を用いて説明する。参考例に係る蛍光体において、発光サイトの結晶構造ABX3を構成する元素は、カチオンAがK+、カチオンBがEu2+、アニオンXがO2-及びF-である。なお、Eu2+以外にカチオンBとしてCe3+、Sm2+、Yb2+等を添加してもよい。これにより、4f-5d遷移が容易となる。また、発光サイトのペロブスカイト構造同士をつなぐ四面体MO4を構成するカチオンMはP5+である。なお、Mは、3~5価の金属元素であってもよい。 (Reference example)
First, a perovskite crystal structure, which is a basic structure of the phosphor according to the present embodiment, will be described using a reference example. In the phosphor according to the reference example, the elements constituting the crystal structure ABX 3 of the light-emitting site, the cation A is K +, cations B is Eu 2+, anion X is O 2- and F - a. In addition to Eu 2+ , Ce 3+ , Sm 2+ , Yb 2+ or the like may be added as cation B. This facilitates 4f-5d transition. Further, a cation M constituting tetrahedral MO 4 which connects the perovskite structures of the light emitting site is P 5+ . M may be a trivalent to pentavalent metal element.
参考例に係る蛍光体は以下の方法で製造される。はじめに、KF、K2CO3粉末を150℃、2時間乾燥する。そして、乾燥N2を充填したグローブボックス内で、KF、K2CO3、CaHPO4、(NH3)2HPO4、Eu2O3を化学量論比1.000:0.500:0.990:0.010:0.0050(mol)の割合となるように精秤し、アルミナ乳鉢中で粉砕混合し、原料混合粉末を得た。この原料混合粉末をアルミナ坩堝に入れ、1000℃で6時間焼成し、焼成粉末を得た。焼成する際の雰囲気は、N2/H2=95/5の混合ガス雰囲気である。そして、得られた焼成粉末を純水で洗浄し、参考例に係る蛍光体を得た。
The phosphor according to the reference example is manufactured by the following method. First, KF, K 2 CO 3 powder is dried at 150 ° C. for 2 hours. Then, in a glove box filled with dry N 2 , KF, K 2 CO 3 , CaHPO 4 , (NH 3 ) 2 HPO 4 , and Eu 2 O 3 have a stoichiometric ratio of 1.000: 0.500: 0. The mixture was precisely weighed to a ratio of 990: 0.010: 0.0050 (mol), and ground and mixed in an alumina mortar to obtain a raw material mixed powder. The raw material mixed powder was placed in an alumina crucible and fired at 1000 ° C. for 6 hours to obtain a fired powder. The atmosphere at the time of firing is a mixed gas atmosphere of N 2 / H 2 = 95/5. Then, the obtained fired powder was washed with pure water to obtain a phosphor according to a reference example.
[X線回折パターン]
次に、X線回折測定について説明する。まず、粉末X線回折装置(RINT UltimaIII:Rigaku製)により、CuのKα線を発するX線管球を用い、サンプリング幅0.01°、スキャンスピード0.05°/minの条件で粉末X線回折測定を行った。図8は、参考例に係る蛍光体のX線回折パターンを示す図である。 [X-ray diffraction pattern]
Next, X-ray diffraction measurement will be described. First, using a powder X-ray diffractometer (RINT Ultima III: manufactured by Rigaku), using powder X-ray tube emitting Kα rays of Cu, powder X-ray powder under conditions of sampling width 0.01 ° and scan speed 0.05 ° / min. Diffraction measurements were made. FIG. 8 is a view showing an X-ray diffraction pattern of a phosphor according to a reference example.
次に、X線回折測定について説明する。まず、粉末X線回折装置(RINT UltimaIII:Rigaku製)により、CuのKα線を発するX線管球を用い、サンプリング幅0.01°、スキャンスピード0.05°/minの条件で粉末X線回折測定を行った。図8は、参考例に係る蛍光体のX線回折パターンを示す図である。 [X-ray diffraction pattern]
Next, X-ray diffraction measurement will be described. First, using a powder X-ray diffractometer (RINT Ultima III: manufactured by Rigaku), using powder X-ray tube emitting Kα rays of Cu, powder X-ray powder under conditions of sampling width 0.01 ° and scan speed 0.05 ° / min. Diffraction measurements were made. FIG. 8 is a view showing an X-ray diffraction pattern of a phosphor according to a reference example.
図8に示すように、参考例に係る蛍光体に含まれる結晶の少なくとも一部が、CuのKα特性X線を用いたX線回折パターンにおいて、回折角2θが31.0°~33.0°の範囲に第1回折ピークP1、第2回折ピークP2及び第3回折ピークP3が存在し、最も強度の高い第1回折ピークP1の回折強度を100とした場合に、第2回折ピークP2および第3回折ピークP3の回折強度は30~50である。また、回折角2θが27.0°~29.0°の範囲に回折強度が15~25の第4回折ピークP4を有している。また、回折角2θが41.0°~43.0°の範囲に回折強度が15~25の第5回折ピークP5を有している。また、回折角2θが29.0°~31.0°の範囲に回折強度が10~15の第6回折ピークP6を有している。また、回折角2θが36.0°~39.0°の範囲に回折強度が10~15の第7回折ピークP7を有している。また、回折角2θが13.0°~15.0°の範囲に回折強度が5~10の第8回折ピークP8を有している。
As shown in FIG. 8, at least a part of the crystal contained in the phosphor according to the reference example has a diffraction angle 2θ of 31.0 ° to 33.0 in an X-ray diffraction pattern using a Kα characteristic X-ray of Cu. When the first diffraction peak P1, the second diffraction peak P2 and the third diffraction peak P3 exist in the range of °, and the diffraction intensity of the highest first diffraction peak P1 is 100, the second diffraction peak P2 and The diffraction intensity of the third diffraction peak P3 is 30 to 50. Further, it has a fourth diffraction peak P4 whose diffraction intensity is 15 to 25 in the range of the diffraction angle 2θ of 27.0 ° to 29.0 °. Further, the fifth diffraction peak P5 having a diffraction intensity of 15 to 25 is in the range of the diffraction angle 2θ of 41.0 ° to 43.0 °. In addition, the sixth diffraction peak P6 having a diffraction intensity of 10 to 15 is provided in the range of the diffraction angle 2θ of 29.0 ° to 31.0 °. In addition, the seventh diffraction peak P7 having a diffraction intensity of 10 to 15 is provided in the range of the diffraction angle 2θ of 36.0 ° to 39.0 °. Further, the eighth diffraction peak P8 having a diffraction intensity of 5 to 10 is provided in the range of the diffraction angle 2θ of 13.0 ° to 15.0 °.
また、参考例に係る蛍光体の粉末サンプルについて、測定により得られたX線回折パターンから、データ処理ソフト(Rapid Auto:Rigaku製)を用い、本実施の形態に係る蛍光体の結晶系、ブラベ格子、空間群、及び格子定数を以下の通り決定した。
結晶系:単斜晶
ブラベ格子:単純格子
空間群:P21/m
格子定数:
a=7.3161(4)Å
b=5.8560(6)Å
c=12.6434(1)Å
α=γ=90°
β=90.3200°
V=541.673782Å3 In addition, with respect to the powder sample of the phosphor according to the reference example, the crystal system of the phosphor according to the present embodiment, the brabe based on the data processing software (Rapid Auto: manufactured by Rigaku) from the X-ray diffraction pattern obtained by The lattices, space groups, and lattice constants were determined as follows.
Crystal system: Monoclinic Brave lattice: Simple lattice space group: P2 1 / m
Lattice constant:
a = 7.3161 (4) Å
b = 5.8560 (6) Å
c = 12.6434 (1) Å
α = γ = 90 °
β = 90.3200 °
V = 541.673782 Å 3
結晶系:単斜晶
ブラベ格子:単純格子
空間群:P21/m
格子定数:
a=7.3161(4)Å
b=5.8560(6)Å
c=12.6434(1)Å
α=γ=90°
β=90.3200°
V=541.673782Å3 In addition, with respect to the powder sample of the phosphor according to the reference example, the crystal system of the phosphor according to the present embodiment, the brabe based on the data processing software (Rapid Auto: manufactured by Rigaku) from the X-ray diffraction pattern obtained by The lattices, space groups, and lattice constants were determined as follows.
Crystal system: Monoclinic Brave lattice: Simple lattice space group: P2 1 / m
Lattice constant:
a = 7.3161 (4) Å
b = 5.8560 (6) Å
c = 12.6434 (1) Å
α = γ = 90 °
β = 90.3200 °
V = 541.673782 Å 3
その後、結晶構造解析ソフトを用い、原子座標を決定した。上記解析の結果、前述の結晶は、X線回折に広く用いられるX線回折データベースであるICDD(International Center for Diffraction Date)に登録されていない新規構造の結晶であることが判明した。
Thereafter, atomic coordinates were determined using crystal structure analysis software. As a result of the above analysis, it was found that the above-mentioned crystal is a crystal of a novel structure not registered in ICDD (International Center for Diffraction Date), which is an X-ray diffraction database widely used for X-ray diffraction.
なお、参考例の蛍光体は、アニオンに酸素とフッ素を含む。酸素とフッ素は周期表で隣り合わせの元素であり、X線回折のデータからだけではその占有位置を特定することは困難である。
The phosphor of the reference example contains oxygen and fluorine in the anion. Oxygen and fluorine are elements adjacent to each other in the periodic table, and it is difficult to specify the occupied position only from the data of X-ray diffraction.
そこで、Fの占有位置を把握するために、参考例に係るサンプルの固体NMR測定を行った。固体NMRでは、スピン量子数が1/2の元素の結合状態が把握でき、19Fと31Pの結合関係を調べられる。測定は、磁場強度11.7T(500MHz)のJNM-ECZ500R(日本電子製)を用い行った。3.2mmの測定プローブに約50μLのサンプルを詰め、室温(約23℃)で測定した。
Then, in order to grasp the occupied position of F, solid-state NMR measurement of the sample concerning a reference example was performed. In solid-state NMR, the coupling state of an element having a spin quantum number of 1/2 can be grasped, and the coupling relation between 19 F and 31 P can be investigated. The measurement was performed using JNM-ECZ500R (manufactured by JEOL Ltd.) with a magnetic field strength of 11.7 T (500 MHz). About 50 μL of the sample was packed in a 3.2 mm measuring probe and measured at room temperature (about 23 ° C.).
はじめに31PのDD-MAS(Dipolar Decoupling - Magic Angle Spinning)測定を行った。図9は、デカップリングなしで計測した共鳴スペクトルの結果を示す図である。図9に示すように、0.64ppmと0.76ppmに共鳴スペクトルを確認した。次に、19Fの磁気回転比に相当するラジオ波(470.6MHz)を照射し、P-Fの相互作用を消去してデカップリング測定した。図10は、P-Fの相互作用を消去してデカップリング測定した共鳴スペクトルの結果を示す図である。図10に示すように、共鳴スペクトルは1本のブロードな信号に変わった。この結果は、Pの原子振動にFが何らかの干渉をしていることを示しているが、カップリングの有無の判断に至らなかった。
First, DD-MAS (Dipolar Decoupling-Magic Angle Spinning) measurement of 31 P was performed. FIG. 9 is a diagram showing the results of resonance spectra measured without decoupling. As shown in FIG. 9, resonance spectra were confirmed at 0.64 ppm and 0.76 ppm. Next, a radio wave (470.6 MHz) corresponding to a gyromagnetic ratio of 19 F was irradiated to cancel the interaction of PF and to perform decoupling measurement. FIG. 10 is a diagram showing the result of the resonance spectrum in which the interaction of PF is eliminated and the decoupling measurement is performed. As shown in FIG. 10, the resonance spectrum changed to one broad signal. This result indicates that F interferes with the atomic vibration of P in some way, but it has not reached the judgment of the presence or absence of coupling.
次に、31P{19F}CP-CPMAS(Cross Polarization - Magic Angle Spinning)測定を行った。接触時間は50~20000μsで可変して計測した。図11は、31P{19F}CP-CPMAS測定の結果を示す図である。図11に示すように、接触時間を20000μsまで伸ばしても信号強度の極大値が現れず、接触時間の経過とともに単調に信号強度が増加した。このことから、フッ素はリンの近傍にあるが、フッ素とリンが直接結合していないことがわかる。
Next, 31 P { 19 F} CP-CPMAS (Cross Polarization-Magic Angle Spinning) measurement was performed. The contact time was measured at 50 to 20000 μs in a variable manner. FIG. 11 is a diagram showing the results of 31 P { 19 F} CP-CPMAS measurement. As shown in FIG. 11, the maximum value of the signal intensity did not appear even if the contact time was extended to 20000 μs, and the signal intensity monotonously increased with the passage of the contact time. From this, it is understood that although fluorine is in the vicinity of phosphorus, fluorine and phosphorus are not directly bonded.
リンはテトラゴナルな配位構造を取りやすい。前述の固体NMRの結果から、リンには4つの酸素が配位していると判断した。そこで、参考例のX線回折データを基に行う構造解析では、(PO4)3-の形で結晶中に存在するとして構造解析を行った。
Phosphorus tends to have a tetragonal coordination structure. From the results of the solid state NMR described above, it was determined that four oxygens were coordinated to phosphorus. Therefore, in structural analysis conducted on the basis of X-ray diffraction data of the reference example, structural analysis was performed on the assumption that the crystal is present in the form of (PO 4 ) 3- .
各元素と原子座標との関係を表1に示す。
The relationship between each element and atomic coordinates is shown in Table 1.
また、結晶構造解析の結果を図12に示す。図12は、本実施の形態に係る蛍光体の結晶構造を示す模式図である。発光元素Eu2+の占有位置はCaサイトになる(表1参照)。なお、図12に示す結晶構造は、b軸方向から見た場合を示している。
The results of crystal structure analysis are shown in FIG. FIG. 12 is a schematic view showing a crystal structure of the phosphor according to the present embodiment. The occupied position of the light emitting element Eu 2+ is the Ca site (see Table 1). The crystal structure shown in FIG. 12 shows the case of viewing from the b-axis direction.
図13は、発光サイトが有する結晶構造を説明するための図である。Eu2+サイトは、6個のアニオンが配位した八面体構造をしている。アニオンの内訳は、酸素イオン4個とフッ素イオン2個である。八面体EuO4F2の構造は、2つのフッ素イオンが互いに隣接した位置をとるcis型構造をしている。
FIG. 13 is a diagram for explaining the crystal structure of the light emitting site. The Eu 2+ site has an octahedral structure in which six anions are coordinated. The breakdown of the anion is 4 oxygen ions and 2 fluorine ions. The structure of the octahedron EuO 4 F 2 is a cis structure in which two fluorine ions are adjacent to each other.
八面体EuO4F2のフッ素イオンは、本結晶のb軸方向に直線状に並んでおり、八面体EuO4F2の頂点を共有する形で八面体EuO4F2同士をつなげている。その結果、八面体EuO4F2は、フッ素イオンを中心にb軸方向にジグザグにつながっている(図14参照)。八面体EuO4F2の各酸素イオンは、PO4四面体と頂点を共有している。
The fluorine ions of the octahedron EuO 4 F 2 are linearly arranged in the b-axis direction of the present crystal, and connect the octahedron EuO 4 F 2 to each other in such a manner that the apexes of the octahedron EuO 4 F 2 are shared. As a result, the octahedron EuO 4 F 2 is connected zigzag in the b-axis direction centering on the fluorine ion (see FIG. 14). Each oxygen ion of octahedral EuO 4 F 2 shares a vertex with the PO 4 tetrahedron.
図14は、図12に示す蛍光体の結晶構造を他の方向から見た模式図である。図14に示すように、b軸を中心にc軸を30°回転させた方向([303]又は[-303]方向)から結晶を見ると、フッ素イオンとPO4四面体によって、八面体EuO4F2が千鳥格子状に並んでいる。カリウムイオンは、八面体EuO4F2の千鳥格子の間を埋めるように並んでいる。カリウムイオンと八面体EuO4F2の関係に着目すると組成式ABX3で表されるペロブスカイト構造をしている。
FIG. 14 is a schematic view of the crystal structure of the phosphor shown in FIG. 12 as viewed from another direction. As shown in FIG. 14, when the crystal is viewed from the direction ([303] or [-303] direction) in which the c-axis is rotated 30 ° about the b-axis, the fluoride ion and the PO 4 tetrahedron form octahedron EuO. 4 F 2 are arranged in a staggered pattern. The potassium ions line up to fill the houndstooth of octahedral EuO 4 F 2 . Has a perovskite structure represented by a composition formula ABX 3 and attention is paid to the relationship between potassium ions and octahedral EuO 4 F 2.
図15は、本実施の形態に係るペロブスカイト結晶構造の発光サイトを示す図である。図15に示すように、8個のカリウムイオンは、立方格子の頂点部に位置する(Aサイト)。八面体EuO4F2のアニオンとしての酸素イオンおよびフッ素イオンは、カリウムが構成する立方格子の面心に位置する。そして、ユーロピウム(またはカルシウム)イオンは、立方格子の体心に位置する(Bサイト)。全てのAサイトがカリウムイオンのみで占められている場合を考慮すると、Aサイトを占めるカリウムイオン(K+)のイオン半径1.55Åは、Bサイトを占めるユーロピウムイオン(Eu2+)のイオン半径1.17Åに対し32%大きい。
FIG. 15 is a view showing a light emitting site of the perovskite crystal structure according to the present embodiment. As shown in FIG. 15, eight potassium ions are located at the top of the cubic lattice (A site). Oxygen ions and fluoride ions as anions of octahedral EuO 4 F 2 are located at the face center of the cubic lattice formed by potassium. And europium (or calcium) ion is located in the body center of cubic lattice (B site). Considering the case where all A sites are occupied only by potassium ions, the ion radius of 1.55 Å of potassium ions (K + ) occupying A sites is the ion radius 1 of europium ions (Eu 2+ ) occupying B sites. 32% larger than .17 Å.
2価のユーロピウムイオンを中心としたcis型八面体EuO4F2の電子密度は、電気陰性度の高いフッ素側に偏る。そのため、八面体の電子分布の対称性は崩れるため、2価ユーロピウムイオンの5d軌道の縮退が解ける。その結果、2価ユーロピウムの内殻4f軌道にある価電子は、低いエネルギでも5d軌道のdxzまたはdyz軌道に遷移しやすくなる。dxzまたはdyz軌道の方向は、ペロブスカイト構造を構成する立方格子の頂点方向になる。その位置には、イオン半径の大きなカチオンK+が占有している。その結果、Eu2+の5d電子(dxzまたはdyz軌道)の電子雲とカチオンK+の間に静電引力が生じる。このとき、K+イオンは質量が大きく動きにくいため、dxzまたはdyz軌道電子雲の広がりが大きくなる。その結果、dxzまたはdyz軌道の電子の存在確率は高くなり、エネルギレベルが下がるため、大きなストークスシフトを示す。
The electron density of cis octahedron EuO 4 F 2 centering on divalent europium ion is biased to the fluorine side with high electronegativity. Because of this, the symmetry of the octahedral electron distribution is broken, and the degeneracy of the 5d orbital of the divalent europium ion is solved. As a result, valence electrons in the inner shell 4f orbit of divalent europium tend to transition to the d xz or d yz orbit of the 5 d orbit even at low energy. The direction of the d xz or d yz orbitals is the vertex direction of the cubic lattice constituting the perovskite structure. The position is occupied by the cation K + having a large ion radius. As a result, electrostatic attraction is generated between the electron cloud of the 5 d electron (d xz or d yz orbit) of Eu 2+ and the cation K + . At this time, the mass of the K + ions is large and it is difficult to move, so the spread of the d xz or d yz orbital electron cloud is large. As a result, the probability of the presence of electrons in the d xz or d yz orbitals increases, and the energy level decreases, thus exhibiting a large Stokes shift.
[単位格子]
図12や図14に示す結晶構造の単位格子を以下に示す。図16は、本実施の形態に係る蛍光体の単位格子をa軸から見た模式図である。図17は、本実施の形態に係る蛍光体の単位格子をb軸から見た模式図である。図18は、本実施の形態に係る蛍光体の単位格子をc軸から見た模式図である。単位格子には、表1に示した座標の原子が含まれている。なお、a軸は座標(x,0,0)、b軸は(0,y,0)、c軸は(0,0,z)に対応する。 [Unit cell]
The unit cell of the crystal structure shown in FIG. 12 and FIG. 14 is shown below. FIG. 16 is a schematic view of the unit cell of the phosphor according to the present embodiment as viewed from the a-axis. FIG. 17 is a schematic view of a unit cell of the phosphor according to the present embodiment as viewed from the b axis. FIG. 18 is a schematic view of a unit cell of the phosphor according to the present embodiment as viewed from the c-axis. The unit cell contains atoms of the coordinates shown in Table 1. The a axis corresponds to coordinates (x, 0, 0), the b axis corresponds to (0, y, 0), and the c axis corresponds to (0, 0, z).
図12や図14に示す結晶構造の単位格子を以下に示す。図16は、本実施の形態に係る蛍光体の単位格子をa軸から見た模式図である。図17は、本実施の形態に係る蛍光体の単位格子をb軸から見た模式図である。図18は、本実施の形態に係る蛍光体の単位格子をc軸から見た模式図である。単位格子には、表1に示した座標の原子が含まれている。なお、a軸は座標(x,0,0)、b軸は(0,y,0)、c軸は(0,0,z)に対応する。 [Unit cell]
The unit cell of the crystal structure shown in FIG. 12 and FIG. 14 is shown below. FIG. 16 is a schematic view of the unit cell of the phosphor according to the present embodiment as viewed from the a-axis. FIG. 17 is a schematic view of a unit cell of the phosphor according to the present embodiment as viewed from the b axis. FIG. 18 is a schematic view of a unit cell of the phosphor according to the present embodiment as viewed from the c-axis. The unit cell contains atoms of the coordinates shown in Table 1. The a axis corresponds to coordinates (x, 0, 0), the b axis corresponds to (0, y, 0), and the c axis corresponds to (0, 0, z).
[励起スペクトルおよび発光スペクトル]
図19は、参考例に係る蛍光体の励起スペクトルおよび発光スペクトルを示す図である。励起発光スペクトルの測定は、マルチチャンネル光学分光器(PMA C5966-31(浜松ホトニクス製))を用いて室温で行った。発光スペクトルは400nm励起で測定した。励起スペクトルは、モニタ波長を400nm励起時の発光ピーク波長に合わせ、測定した。 [Excitation spectrum and emission spectrum]
FIG. 19 is a diagram showing an excitation spectrum and an emission spectrum of a phosphor according to a reference example. The measurement of the excitation light emission spectrum was performed at room temperature using a multi-channel optical spectrometer (PMA C5966-31 (manufactured by Hamamatsu Photonics)). The emission spectrum was measured at 400 nm excitation. The excitation spectrum was measured by matching the monitor wavelength to the emission peak wavelength at 400 nm excitation.
図19は、参考例に係る蛍光体の励起スペクトルおよび発光スペクトルを示す図である。励起発光スペクトルの測定は、マルチチャンネル光学分光器(PMA C5966-31(浜松ホトニクス製))を用いて室温で行った。発光スペクトルは400nm励起で測定した。励起スペクトルは、モニタ波長を400nm励起時の発光ピーク波長に合わせ、測定した。 [Excitation spectrum and emission spectrum]
FIG. 19 is a diagram showing an excitation spectrum and an emission spectrum of a phosphor according to a reference example. The measurement of the excitation light emission spectrum was performed at room temperature using a multi-channel optical spectrometer (PMA C5966-31 (manufactured by Hamamatsu Photonics)). The emission spectrum was measured at 400 nm excitation. The excitation spectrum was measured by matching the monitor wavelength to the emission peak wavelength at 400 nm excitation.
図19に示すように、参考例に係る蛍光体の励起スペクトルL1は、ピーク波長λ1が330~420nmの範囲、より詳述すると350~390nmの範囲にある。また、励起端波長λeは420nm程度であり、その波長のエネルギは2.938eVである。一方、ピーク波長が400nmの励起光による発光スペクトルL2は、ピーク波長λ2が658nmであり、半値幅が152nmであり、ピーク波長λ2のエネルギは1.884eVである。したがって、ストークスシフトは、1.054eVである。また、この蛍光体が発する光の色度座標(cx、cy)は、(0.613,0.384)である。
As shown in FIG. 19, the excitation spectrum L1 of the phosphor according to the reference example has a peak wavelength λ1 in the range of 330 to 420 nm, more specifically in the range of 350 to 390 nm. The excitation end wavelength λe is about 420 nm, and the energy of the wavelength is 2.938 eV. On the other hand, the emission spectrum L2 of excitation light having a peak wavelength of 400 nm has a peak wavelength λ2 of 658 nm, a half width of 152 nm, and an energy of the peak wavelength λ2 of 1.884 eV. Therefore, the Stokes shift is 1.054 eV. The chromaticity coordinates (cx, cy) of the light emitted from this phosphor are (0.613, 0.384).
参考例で得られた紛体サンプルは、誘導結合プラズマ質量分析(ICP-MS)およびイオンクロマトグラフィーを用いて組成分析を行った。その結果、参考例に係る蛍光体の組成比は、KF・Ca0.99KPO4:Eu2+
0.01であることが明らかになった。
The powder sample obtained in the reference example was subjected to compositional analysis using inductively coupled plasma mass spectrometry (ICP-MS) and ion chromatography. As a result, it was revealed that the composition ratio of the phosphor according to the reference example was KF · Ca 0.99 KPO 4 : Eu 2+ 0.01 .
図20は、参考例に係る蛍光体発光の温度特性を示す図である。図17は、波長が400nmの光で励起した30℃の発光強度を100%として規格化した各温度の相対強度を示す。150℃で発光強度の維持率が30℃比90%以上であり、ストークスシフトが大きいにもかかわらず、良好な温度特性が確認できた。
FIG. 20 is a diagram showing temperature characteristics of phosphor light emission according to a reference example. FIG. 17 shows the relative intensity of each temperature normalized with the emission intensity at 30 ° C. excited with light having a wavelength of 400 nm as 100%. Even though the maintenance rate of emission intensity at 150 ° C. was 90% or more at 30 ° C., and although the Stokes shift was large, good temperature characteristics could be confirmed.
[短波長励起による発光]
本願発明者らは、参考例のペロブスカイト構造の発光サイトは、高いエネルギ(短波長)で励起させると発光色が青緑色にシフトすることを見いだした。 [Light emission by short wavelength excitation]
The inventors of the present invention have found that the light emission site of the perovskite structure of the reference example shifts to a bluish green color upon excitation with high energy (short wavelength).
本願発明者らは、参考例のペロブスカイト構造の発光サイトは、高いエネルギ(短波長)で励起させると発光色が青緑色にシフトすることを見いだした。 [Light emission by short wavelength excitation]
The inventors of the present invention have found that the light emission site of the perovskite structure of the reference example shifts to a bluish green color upon excitation with high energy (short wavelength).
前述のように、参考例に係る蛍光体の発光中心Euに対するアニオンは、EuO4F2のcis型八面体構造を取る。つまり、各結晶軸方向にアニオンが位置することになる(図6(a)参照)。例えば、3.10eV(400nm)程度の低いエネルギで参考例に係る蛍光体を励起した場合、5d軌道の結晶場分裂によるt2g軌道のエネルギ準位が下がり、この方向に5d軌道が広がる。
As described above, the anion for the emission center Eu of the phosphor according to the reference example has a cis octahedral structure of EuO 4 F 2 . In other words, anions are positioned in each crystal axis direction (see FIG. 6A). For example, when excited the phosphor according to the reference example in lower energy of about 3.10 eV (400 nm), lower the energy level of t 2 g orbit due to the crystal field splitting of the 5d orbital and 5d orbital in this direction spreads.
一方、高いエネルギ4.13eV(300nm)で励起した場合、5d軌道の結晶場分裂によるエネルギ準位の高い軌道eg、つまり、アニオンが存在する軸方向に5d軌道の電子雲が広がる。図21は、八面体EuO4F2における電子雲の広がりを示す模式図である。軸方向に広がった5d軌道には、ペロブスカイト立方体の頂点位置にあるカチオンの静電引力は作用しない。代わりに、軸方向にあるアニオンとの静電反発力(斥力)が作用する。そのため、5d軌道の広がりは抑制され、発光は短波長側の光にシフトする。図22は、参考例に係る蛍光体に高いエネルギの紫外線を照射した場合の発光スペクトルを示す図である。図22に示すように、参考例に係る蛍光体では、発光スペクトルのピーク波長λ2が476nmの青緑色発光が確認できた。
On the other hand, when excited with a high energy of 4.13 eV (300 nm), an electron cloud of 5 d orbital spreads in an orbital e g with high energy level due to crystal field splitting of 5 d orbital, that is, an axial direction in which an anion exists. FIG. 21 is a schematic view showing the spread of electron clouds in octahedron EuO 4 F 2 . The electrostatic attraction of the cation at the top of the perovskite cube does not act on the axially extended 5d orbital. Instead, electrostatic repulsion (repulsion) with the anion in the axial direction acts. Therefore, the spread of the 5d trajectory is suppressed, and the light emission shifts to the light on the short wavelength side. FIG. 22 is a view showing an emission spectrum in the case where the phosphor according to the reference example is irradiated with ultraviolet light of high energy. As shown in FIG. 22, in the phosphor according to the reference example, blue-green emission with a peak wavelength λ2 of the emission spectrum of 476 nm could be confirmed.
次に、ひとつの発光元素が2色の発光を示す証拠として、参考例に係る蛍光体の拡散反射スペクトルを測定した。図23は、参考例に係る蛍光体の拡散反射スペクトルを示す図である。図23のラインL1が示すように、420nm以下の光のほとんどが吸収されていることがわかる。これに赤色発光の励起スペクトルL2(モニタ波長622nm)と青緑発光の励起スペクトル(モニタ波長476nm)L3を重ね合わせる。このことから、赤色発光の励起帯は330~420nmにあり、青緑発光の励起帯は250~320nm付近に確認できる。これは一つの発光中心が励起波長の違いで発光色を変えていることを表している。
Next, as evidence that one light emitting element emits light of two colors, the diffuse reflection spectrum of the phosphor according to the reference example was measured. FIG. 23 is a view showing a diffuse reflection spectrum of the phosphor according to the reference example. As indicated by line L1 in FIG. 23, it can be seen that most of the light of 420 nm or less is absorbed. The excitation spectrum L2 for red light emission (monitor wavelength 622 nm) and the excitation spectrum L3 for blue-green light emission (monitor wavelength 476 nm) are superimposed on this. From this, the excitation band of red light emission is at 330 to 420 nm, and the excitation band of blue-green light emission can be confirmed at around 250 to 320 nm. This indicates that one emission center changes the emission color due to the difference in excitation wavelength.
このように、本実施の形態の参考例に係る蛍光体は、第1の波長の光(例えば、ピーク波長が380~450nmの近紫外線または短波長可視光)で赤色発光するとともに、第1の波長の光よりも短波長の第2の波長の光(例えば、200~350nmの禁紫外線)で赤色より短波長側の色(例えば、波長が450nm~550nmの青色から緑色)で発光する。
As described above, the phosphor according to the reference example of the present embodiment emits red light with light of the first wavelength (for example, near-ultraviolet light or short-wavelength visible light with a peak wavelength of 380 to 450 nm) Light of a second wavelength (for example, 200-350 nm forbidden ultraviolet light) having a shorter wavelength than light of a wavelength emits light with a color shorter than red (for example, blue to green at a wavelength of 450 nm to 550 nm).
(実施例1)
以上の知見に基づき本願発明者が更なる検討を行った結果、以下の構成の蛍光体により複数色の光(ピーク波長が異なる複数の光)を発する単一相の蛍光体の実現に至った。具体的には、ペロブスカイト結晶構造(立方晶)の体心となるBサイトに発光元素が位置した、単一相からなる蛍光体であって、発光サイトABX3と、発光サイトABX3のカチオンAの一部がカチオンAよりイオン半径が小さいカチオンA’で置換された発光サイト(AA’)BX3と、を有する蛍光体である。 Example 1
As a result of the inventors of the present invention performing further studies based on the above findings, it has been realized that a phosphor of a single phase emitting plural colors of light (a plurality of lights having different peak wavelengths) is realized by the phosphor of the following configuration. . Specifically, the light emitting element is located in a body-centered become B site of the perovskite crystal structure (cubic), a phosphor composed of a single phase, and the light-emitting site ABX 3, the light-emitting site ABX 3 cation A Is a phosphor having a luminescent site (AA ') BX 3 substituted by a cation A' having a smaller ionic radius than the cation A.
以上の知見に基づき本願発明者が更なる検討を行った結果、以下の構成の蛍光体により複数色の光(ピーク波長が異なる複数の光)を発する単一相の蛍光体の実現に至った。具体的には、ペロブスカイト結晶構造(立方晶)の体心となるBサイトに発光元素が位置した、単一相からなる蛍光体であって、発光サイトABX3と、発光サイトABX3のカチオンAの一部がカチオンAよりイオン半径が小さいカチオンA’で置換された発光サイト(AA’)BX3と、を有する蛍光体である。 Example 1
As a result of the inventors of the present invention performing further studies based on the above findings, it has been realized that a phosphor of a single phase emitting plural colors of light (a plurality of lights having different peak wavelengths) is realized by the phosphor of the following configuration. . Specifically, the light emitting element is located in a body-centered become B site of the perovskite crystal structure (cubic), a phosphor composed of a single phase, and the light-emitting site ABX 3, the light-emitting site ABX 3 cation A Is a phosphor having a luminescent site (AA ') BX 3 substituted by a cation A' having a smaller ionic radius than the cation A.
ペロブスカイト結晶構造の各頂点となるAサイトを構成するカチオンは、前述のように2種類(カチオンAおよびカチオンA’)以上ある。また、Aサイトを構成するカチオンの95%~99%は、BサイトのカチオンBのイオン半径より15%以上大きいイオンが占めているとよい。また、Aサイトを構成するカチオンの1~5%は、BサイトのカチオンBのイオン半径と同等か、又は、小さいイオン半径のイオンが占有していてもよい。
As described above, there are two or more types of cations (cation A and cation A '), which constitute the A site serving as each vertex of the perovskite crystal structure. In addition, 95% to 99% of the cations constituting the A site may be occupied by ions larger by 15% or more than the ion radius of the cation B of the B site. In addition, 1 to 5% of the cations constituting the A site may be occupied by ions having an ion radius equal to or smaller than that of the cation B of the B site.
発光サイトABX3においては、全てのAサイトにカチオンBのイオン半径より大きいカチオンAが占有しているため、ペロブスカイト構造の面心に位置するアニオンXは、Aサイトの4つのカチオンAに挟まれる形で固定されている。そのため、5d軌道とアニオンの静電反発が大きいため、低いエネルギで蛍光体を励起した場合、5d軌道の結晶場分裂によるt2g軌道のエネルギ準位が下がり、T2g方向に5d軌道の電子雲が広がる。
In the light-emitting site ABX 3, because the larger the cation A than the ionic radius of the cation B in all the A-site is occupied, the anion X which is located on the surface center of the perovskite structure is sandwiched four cations A of the A site It is fixed in shape. Therefore, since electrostatic repulsion 5d orbital and anions is large, when excited the phosphor with a low energy, lower the energy level of t 2 g orbit due to the crystal field splitting of the 5d orbital, the electron cloud of the 5d orbital T2g direction spread.
T2g方向に分裂したdxz、dyz軌道は、立方晶の各頂点に位置するAサイトのカチオンAに引き付けられ、静電引力により電子雲が大きく広がるため、dxz、dyz軌道のエネルギレベルが低下する。その結果、長波長(黄色から赤色)発光をする。
The d xz and d yz orbitals split in the T2g direction are attracted to the cation A of the A site located at each vertex of the cubic crystal, and the electron cloud is widely spread by electrostatic attraction, so the energy levels of the d xz and d yz orbitals Decreases. As a result, it emits light of long wavelength (yellow to red).
一方、発光サイト(AA’)BX3では異なる発光形態となる。図24(a)は、発光サイト(AA’)BX3を模式的に示した斜視図、図24(b)は、発光サイト(AA’)BX3を模式的に示した側面図である。発光サイト(AA’)BX3においては、Aサイトの一部にカチオンAよりイオン半径が小さなカチオンA’が占有しているため、ペロブスカイト構造の面心に位置するアニオンXの周りに隙間が生じ(図24(b)参照)、アニオンXが移動できる。そのため、エネルギ緩和が可能になり、Eg方向に5d軌道が広がる。
On the other hand, the light emission site (AA ′) BX 3 has a different light emission form. FIG. 24A is a perspective view schematically showing the light emitting site (AA ′) BX 3 , and FIG. 24B is a side view schematically showing the light emitting site (AA ′) BX 3 . In the light emitting site (AA ′) BX 3 , since a part of the A site is occupied by the cation A ′ having a smaller ion radius than the cation A, a gap is generated around the anion X located in the face center of the perovskite structure An anion X can move (see FIG. 24B). Therefore, allows energy relaxation, 5d orbital spreads E g direction.
Eg方向に広がった5d軌道には、ペロブスカイト立方体の頂点位置にあるカチオンの静電引力は作用しない。代わりに、軸方向にあるアニオンXとの静電反発力(斥力)が作用する。この時、アニオンXはAサイトに占有するイオン半径の小さなカチオンA’側に移動することができ、静電反発力を緩和した状態ができる。その結果、静電反発力で抑制された5d軌道から、短波長(紫色から緑色)発光をする。
The 5d orbital spread in E g direction, the electrostatic attraction of the cation in the vertex positions of the perovskite cube does not act. Instead, electrostatic repulsion (repulsion) with the anion X in the axial direction acts. At this time, the anion X can move to the side of the cation A ′ having a smaller ion radius occupied at the A site, and the electrostatic repulsion can be relaxed. As a result, it emits short wavelength (purple to green) light from the 5d orbit suppressed by electrostatic repulsion.
次に、実施例1に係る蛍光体について具体的に説明する。実施例1に係る蛍光体において、発光サイトの結晶構造AA’BX3を構成する元素は、カチオンAがK+(0.975)、カチオンA’がNa+(0.025)、カチオンBがEu2+、アニオンXがO2-及びF-である。また、発光サイトのペロブスカイト構造同士をつなぐ四面体MO4を構成するカチオンMはP5+である。
Next, the phosphor according to Example 1 will be specifically described. In the phosphor according to Embodiment 1, the elements constituting the crystal structure AA'BX 3 of emission sites, + cation A is K (0.975), + cation A 'is Na (0.025), cationic B eu 2+, anion X is O 2- and F - a. Further, a cation M constituting tetrahedral MO 4 which connects the perovskite structures of the light emitting site is P 5+ .
実施例1に係る蛍光体は以下の方法で製造される。はじめに、KF、NaF、K2CO3粉末を150℃、2時間乾燥する。そして、乾燥N2を充填したグローブボックス内で、KF、K2CO3、NaF、CaHPO4、(NH3)2HPO4、Eu2O3を化学量論比0.950:0.500:0.050:0.960:0.040:0.020(mol)の割合となるように精秤し、アルミナ乳鉢中で粉砕混合し、原料混合粉末を得た。その後は、参考例と同様の処理を行い実施例1に係る蛍光体を得た。実施例1で得られた紛体サンプルは、参考例と同様の方法で組成分析を行った。その結果、実施例1に係る蛍光体の組成比は、(K1.95,Na0.05)Ca0.96PO4F:Eu2+
0.04であることが明らかになった。
The phosphor according to Example 1 is manufactured by the following method. First, KF, NaF, and K 2 CO 3 powder are dried at 150 ° C. for 2 hours. And, in a glove box filled with dry N 2 , KF, K 2 CO 3 , NaF, CaHPO 4 , (NH 3 ) 2 HPO 4 , Eu 2 O 3 at a stoichiometric ratio of 0.950: 0.500: The mixture was precisely weighed to a ratio of 0.050: 0.960: 0.040: 0.020 (mol), and ground and mixed in an alumina mortar to obtain a raw material mixed powder. Thereafter, the same processing as in the reference example was performed to obtain a phosphor according to example 1. The powder sample obtained in Example 1 was subjected to composition analysis in the same manner as in the reference example. As a result, it was revealed that the compositional ratio of the phosphor according to Example 1 was (K 1.95 , Na 0.05 ) Ca 0.96 PO 4 F: Eu 2 + 0.04 .
図25は、実施例1に係る蛍光体のX線回折パターンを示す図である。測定は、参考例1と同様の装置を用い、サンプリング幅0.02°、スキャンスピード2.0°/minで行った。
FIG. 25 is a diagram showing an X-ray diffraction pattern of the phosphor according to Example 1. The measurement was performed using a device similar to Reference Example 1, with a sampling width of 0.02 °, and a scan speed of 2.0 ° / min.
得られた粉末X線回折プロファイルは、参考例の蛍光体(K2Ca(PO4)F:Eu2+)と同様の回折パターンを示し、同結晶をモデルにリートベルト解析を行った結果、Rw6%以下に収束し、同系の結晶構造(結晶系:単斜晶、ブラベ格子:単純格子、空間群:P21/m)であることが判明した。以下では、参考例と重複する記載については適宜説明を省略する。
The obtained powder X-ray diffraction profile shows the same diffraction pattern as the phosphor of the reference example (K 2 Ca (PO 4 ) F: Eu 2+ ), and Rietveld analysis using the same crystal as a model, Rw 6 It converges to less than%, It turned out that it is crystal structure (Crystal system: monoclinic crystal, Bravais lattice: simple lattice, space group: P2 1 / m) of the crystal structure of the same system. In the following, the description overlapping with the reference example is appropriately omitted.
実施例1に係る蛍光体は、前述の測定結果から参考例に係る蛍光体と同様の結晶構造(図12乃至図18参照)を有しており、Aサイトの一部をナトリウムイオンが占めている点が主な相違点である。
The phosphor according to Example 1 has the same crystal structure (see FIGS. 12 to 18) as the phosphor according to the reference example from the measurement results described above, and a part of the A site is occupied by sodium ions. Are the main differences.
アルカリイオン(カリウムイオン,ナトリウムイオン)は、八面体EuO4F2の千鳥格子の間を埋めるように並んでいる。アルカリイオンと八面体EuO4F2の関係に着目すると組成式(AA’)BX3で表されるペロブスカイト構造をしている。
Alkali ions (potassium ions, sodium ions) are arranged to fill in a zigzag grid of octahedral EuO 4 F 2 . It has a perovskite structure represented by a composition formula (AA ') BX 3 and attention is paid to the relationship between the alkali ions and octahedral EuO 4 F 2.
図15に示すように、8個のアルカリイオンは、立方格子の頂点部に位置する(Aサイト)。八面体EuO4F2のアニオンとしての酸素イオンおよびフッ素イオンは、カリウムまたはナトリウムが構成する立方格子の面心に位置する。そして、ユーロピウム(またはカルシウム)イオンは、立方格子の体心に位置する(Bサイト)。Aサイトを占めるアルカリイオンのうちカリウムイオン(K+)のイオン半径1.59Åは、Bサイトを占めるユーロピウムイオン(Eu2+)のイオン半径1.17Åに対し32%大きい。一方、Aサイトを占めるナトリウムイオン(Na+)のイオン半径1.32Åは、Bサイトを占めるユーロピウムイオン(Eu2+)のイオン半径1.17に比較的近い。
As shown in FIG. 15, eight alkali ions are located at the top of the cubic lattice (A site). Oxygen ions and fluorine ions as anions of octahedral EuO 4 F 2 are located at the face center of the cubic lattice composed of potassium or sodium. And europium (or calcium) ion is located in the body center of cubic lattice (B site). Of the alkali ions occupying the A site, the ion radius of 1.59 Å of potassium ion (K + ) is 32% larger than the ion radius of 1.17 Å of the europium ion (Eu 2+ ) occupying the B site. On the other hand, the ion radius of 1.32 Å of sodium ion (Na + ) occupying A site is relatively close to the ion radius 1.17 of europium ion (Eu 2+ ) occupying B site.
例えば、ペロブスカイト構造の8個あるAサイトの全てをカリウムイオンが占有している場合、2価ユーロピウムの内殻4f軌道にある価電子は、低いエネルギでも5d軌道のdxzまたはdyz軌道に遷移しやすくなる。dxzまたはdyz軌道の方向は、ペロブスカイト構造を構成する立方格子の頂点方向になる。その位置には、イオン半径の大きなカチオンK+が占有している。その結果、Eu2+の5d電子(dxzまたはdyz軌道)の電子雲とカチオンK+の間に静電引力が生じる。このとき、K+イオンは質量が大きく動きにくいため、dxzまたはdyz軌道電子雲の広がりが大きくなる。その結果、dxzまたはdyz軌道の電子の存在確率は高くなり、エネルギレベルが下がるため、赤色発光を示す。
For example, when all eight A sites of the perovskite structure are occupied by potassium ions, valence electrons in the inner shell 4f orbital of divalent europium transition to d xz or d yz orbital of 5 d orbital even at low energy. It becomes easy to do. The direction of the d xz or d yz orbitals is the vertex direction of the cubic lattice constituting the perovskite structure. The position is occupied by the cation K + having a large ion radius. As a result, electrostatic attraction is generated between the electron cloud of the 5 d electron (d xz or d yz orbit) of Eu 2+ and the cation K + . At this time, the mass of the K + ions is large and it is difficult to move, so the spread of the d xz or d yz orbital electron cloud is large. As a result, the probability of the presence of electrons in the d xz or d yz orbitals is increased, and the energy level is reduced, thus emitting red light.
一方、ペロブスカイト構造の8個あるAサイトをカリウムイオンだけでなくナトリウムイオンも占有している場合、2価ユーロピウムの内殻4f軌道にある価電子は、励起光照射により、5d軌道のEg方向(軸方向:dx
2
-y
2又はdz
2軌道の方向)に遷移が可能となる。これは、Aサイトの一部に小さなカチオンが占有した場合、面心のアニオンの周りに隙間が生じ、アニオンの移動によるエネルギ緩和が生じるからである。軸方向に広がった5d軌道には、ペロブスカイト立方体の頂点位置にあるカチオンの静電引力は作用しない。代わりに、軸方向にあるアニオンとの静電反発力(斥力)が作用する。そのため、5d軌道の広がりは抑制され、発光波長は短波側にシフトし、青緑色発光が確認できる。
On the other hand, when the eight certain A site of the perovskite structure is occupied also sodium ions as well as potassium ions, the valence electrons in the inner shell 4f orbit of divalent europium, by the excitation light irradiation, E g direction of 5d orbital A transition is possible (in the direction of the axis: the direction of d x 2- y 2 or d z 2 trajectory). This is because when a small cation occupies a part of the A site, a gap is formed around the anion of the face center, and energy relaxation occurs due to the movement of the anion. The electrostatic attraction of the cation at the top of the perovskite cube does not act on the axially extended 5d orbital. Instead, electrostatic repulsion (repulsion) with the anion in the axial direction acts. Therefore, the spread of the 5d trajectory is suppressed, the emission wavelength shifts to the short wavelength side, and bluish green emission can be confirmed.
図26は、実施例1に係る蛍光体の励起スペクトルおよび発光スペクトルを示す図である。励起発光スペクトルの測定は、マルチチャンネル光学分光器(PMA C5966-31(浜松ホトニクス製))を用いて室温で行った。発光スペクトルL2は400nm励起で測定した。励起スペクトルL1,L1’は、モニタ波長を400nm励起時の発光ピーク波長(655nmおよび493nm)に合わせ、測定した。
FIG. 26 is a diagram showing an excitation spectrum and an emission spectrum of the phosphor according to Example 1. The measurement of the excitation light emission spectrum was performed at room temperature using a multi-channel optical spectrometer (PMA C5966-31 (manufactured by Hamamatsu Photonics)). The emission spectrum L2 was measured at 400 nm excitation. The excitation spectra L1 and L1 'were measured by matching the monitor wavelength to the emission peak wavelength (655 nm and 493 nm) at 400 nm excitation.
図26に示すように、実施例1に係る蛍光体の発光スペクトルL2は、ピーク波長λ2’が493nmの青緑色光と、ピーク波長λ2が655nmの赤色光が混色した白色光であった。このように、実施例1に係る蛍光体は、単一相からなる1種類の蛍光体が発する複数の色の光により白色光を実現できる。ここで、「単一相」とは、材質が均一な成分(組成)を持ち、基本的な結晶構造(本実施の形態ではペロブスカイト構造)も1種類の物質ということができる。なお、本願発明の趣旨を逸脱しない範囲で他の解釈も成立し得る。
As shown in FIG. 26, the emission spectrum L2 of the phosphor according to Example 1 was white light in which blue green light having a peak wavelength λ2 ′ of 493 nm and red light having a peak wavelength λ2 of 655 nm were mixed. Thus, the fluorescent substance which concerns on Example 1 can implement | achieve white light by the light of the several color which 1 type of fluorescent substance which consists of single phase emits. Here, “single phase” means that the material has a component (composition) that is uniform, and the basic crystal structure (perovskite structure in this embodiment) can also be said to be one type of substance. Other interpretations can be made without departing from the spirit of the present invention.
実施例1に係る蛍光体の励起スペクトルL1’(発光ピーク波長493nmに合わせて測定)は、ピーク波長λ1’が300~420nmの範囲、より詳述すると300~350nmの範囲にある。また、励起スペクトルL1(発光ピーク波長655nmに合わせて測定)は、ピーク波長λ1が300~420nmの範囲、より詳述すると350~400nmの範囲にある。また、この蛍光体が発する光の色度座標(cx、cy)は、(0.434,0.386)である。
The excitation spectrum L1 '(measured in accordance with the emission peak wavelength 493 nm) of the phosphor according to Example 1 has a peak wavelength λ1' in the range of 300 to 420 nm, more specifically in the range of 300 to 350 nm. The excitation spectrum L1 (measured to match the emission peak wavelength of 655 nm) has a peak wavelength λ1 in the range of 300 to 420 nm, more specifically in the range of 350 to 400 nm. The chromaticity coordinates (cx, cy) of the light emitted from this phosphor are (0.434, 0.386).
励起スペクトルL1のプロファイルは、Aサイトの全てをカリウムイオンが占有している参考例のそれとほぼ同じである。一方、励起スペクトルL1’は、300nm付近にピークを示し、赤色発光を示す400nm付近まで延びている。よって、波長が400nmの光を含む励起光による発光スペクトルL2では、青緑発光と赤色発光の2つの発光ピークを示すことになる。
The profile of the excitation spectrum L1 is almost the same as that of the reference example in which all of the A sites are occupied by potassium ions. On the other hand, the excitation spectrum L1 'shows a peak at around 300 nm and extends to around 400 nm showing red emission. Therefore, in emission spectrum L2 by excitation light including light with a wavelength of 400 nm, two emission peaks of blue-green emission and red emission are shown.
(実施例2)
次に、実施例2に係る蛍光体について具体的に説明する。なお、実施例1と同様の構成については説明を適宜省略する。実施例2に係る蛍光体において、発光サイトの結晶構造AA’BX3を構成する元素は、カチオンAがK+(0.99)、カチオンA’がLi+(0.01)、カチオンBがEu2+、アニオンXがO2-及びF-である。また、発光サイトのペロブスカイト構造同士をつなぐ四面体MO4を構成するカチオンMはP5+である。 (Example 2)
Next, the phosphor according to Example 2 will be specifically described. The description of the same configuration as that of the first embodiment will be appropriately omitted. In the phosphor according to the second embodiment, the elements constituting the crystal structure AA'BX 3 of emission sites, + cation A is K (of 0.99), + cation A 'is Li (0.01), cationic B eu 2+, anion X is O 2- and F - a. Further, a cation M constituting tetrahedral MO 4 which connects the perovskite structures of the light emitting site is P 5+ .
次に、実施例2に係る蛍光体について具体的に説明する。なお、実施例1と同様の構成については説明を適宜省略する。実施例2に係る蛍光体において、発光サイトの結晶構造AA’BX3を構成する元素は、カチオンAがK+(0.99)、カチオンA’がLi+(0.01)、カチオンBがEu2+、アニオンXがO2-及びF-である。また、発光サイトのペロブスカイト構造同士をつなぐ四面体MO4を構成するカチオンMはP5+である。 (Example 2)
Next, the phosphor according to Example 2 will be specifically described. The description of the same configuration as that of the first embodiment will be appropriately omitted. In the phosphor according to the second embodiment, the elements constituting the crystal structure AA'BX 3 of emission sites, + cation A is K (of 0.99), + cation A 'is Li (0.01), cationic B eu 2+, anion X is O 2- and F - a. Further, a cation M constituting tetrahedral MO 4 which connects the perovskite structures of the light emitting site is P 5+ .
実施例2に係る蛍光体は以下の方法で製造される。はじめに、KF、LiF、K2CO3粉末を150℃、2時間乾燥する。そして、乾燥N2を充填したグローブボックス内で、KF、K2CO3、LiF、CaHPO4、(NH3)2HPO4、Eu2O3を化学量論比0.98:0.50:0.020:0.960:0.040:0.020(mol)の割合となるように精秤し、アルミナ乳鉢中で粉砕混合し、原料混合粉末を得た。その後は、参考例と同様の処理を行い実施例2に係る蛍光体を得た。実施例2で得られた紛体サンプルは、参考例と同様の方法で組成分析を行った。その結果、実施例2に係る蛍光体の組成比は、(K1.98,Li0.02)Ca0.96PO4F:Eu2+
0.04であることが明らかになった。
The phosphor according to Example 2 is manufactured by the following method. First, KF, LiF, K 2 CO 3 powder is dried at 150 ° C. for 2 hours. And, in a glove box filled with dry N 2 , KF, K 2 CO 3 , LiF, CaHPO 4 , (NH 3 ) 2 HPO 4 , and Eu 2 O 3 have a stoichiometric ratio of 0.98: 0.50: The mixture was precisely weighed to have a ratio of 0.020: 0.960: 0.040: 0.020 (mol), and ground and mixed in an alumina mortar to obtain a raw material mixed powder. Thereafter, the same processing as in the reference example was performed to obtain a phosphor according to example 2. The powder sample obtained in Example 2 was subjected to composition analysis in the same manner as in the reference example. As a result, the composition ratio of the phosphor according to the second embodiment, (K 1.98, Li 0.02) Ca 0.96 PO 4 F: revealed a Eu 2+ 0.04.
図27は、実施例2に係る蛍光体のX線回折パターンを示す図である。測定は、参考例1と同様の装置を用い、サンプリング幅0.02°、スキャンスピード2.0°/minで行った。得られた粉末X線回折プロファイルは、実施例1の蛍光体と同様の回折パターンを示した。以下では、実施例1と重複する記載については適宜説明を省略する。
FIG. 27 is a diagram showing an X-ray diffraction pattern of the phosphor according to Example 2. The measurement was performed using a device similar to Reference Example 1, with a sampling width of 0.02 °, and a scan speed of 2.0 ° / min. The obtained powder X-ray diffraction profile showed a diffraction pattern similar to that of the phosphor of Example 1. In the following, description overlapping with the first embodiment will be omitted as appropriate.
実施例2に係る蛍光体は、前述の測定結果から実施例1に係る蛍光体と同様の結晶構造(図12乃至図18参照)を有しており、Aサイトの一部をリチウムイオンが占めている点が主な相違点である。
The phosphor according to Example 2 has the same crystal structure (see FIGS. 12 to 18) as the phosphor according to Example 1 from the above measurement results, and a part of the A site is occupied by lithium ions. Is the main difference.
アルカリイオン(カリウムイオン,リチウムイオン)は、八面体EuO4F2の千鳥格子の間を埋めるように並んでいる。アルカリイオンと八面体EuO4F2の関係に着目すると組成式(AA’)BX3で表されるペロブスカイト構造をしている。
Alkali ions (potassium ions, lithium ions) are arranged to fill in a zigzag grid of octahedral EuO 4 F 2 . It has a perovskite structure represented by a composition formula (AA ') BX 3 and attention is paid to the relationship between the alkali ions and octahedral EuO 4 F 2.
8個のアルカリイオンは、立方格子の頂点部に位置する(Aサイト)。八面体EuO4F2のアニオンとしての酸素イオンおよびフッ素イオンは、カリウムまたはリチウムが構成する立方格子の面心に位置する。そして、ユーロピウム(またはカルシウム)イオンは、立方格子の体心に位置する(Bサイト)。Aサイトを占めるアルカリイオンのうちカリウムイオン(K+)のイオン半径1.59Åは、Bサイトを占めるユーロピウムイオン(Eu2+)のイオン半径1.17Åに対し32%大きい。一方、Aサイトを占めるリチウムイオン(Li+)のイオン半径0.92Åは、Bサイトを占めるユーロピウムイオン(Eu2+)のイオン半径1.17よりも小さい。
Eight alkali ions are located at the apex of the cubic lattice (A site). Oxygen ions and fluoride ions as anions of octahedral EuO 4 F 2 are located at the face center of the cubic lattice composed of potassium or lithium. And europium (or calcium) ion is located in the body center of cubic lattice (B site). Of the alkali ions occupying the A site, the ion radius of 1.59 Å of potassium ion (K + ) is 32% larger than the ion radius of 1.17 Å of the europium ion (Eu 2+ ) occupying the B site. On the other hand, the ion radius of 0.92 Å of the lithium ion (Li + ) occupying the A site is smaller than the ion radius 1.17 of the europium ion (Eu 2+ ) occupying the B site.
このような構造の実施例2に係る蛍光体は、実施例1と同様の発光メカニズムにより、実施例1と類似の発光特性を示す。
The phosphor according to Example 2 having such a structure exhibits similar emission characteristics to Example 1 by the same emission mechanism as that of Example 1.
図28は、実施例2に係る蛍光体の励起スペクトルおよび発光スペクトルを示す図である。励起発光スペクトルの測定は、実施例1と同様である。励起スペクトルL1,L1’は、モニタ波長を400nm励起時の発光ピーク波長(662nmおよび495nm)に合わせ、測定した。
FIG. 28 is a diagram showing an excitation spectrum and an emission spectrum of a phosphor according to Example 2. The measurement of the excitation emission spectrum is the same as in Example 1. The excitation spectra L1 and L1 'were measured by matching the monitor wavelength to the emission peak wavelength (662 nm and 495 nm) at 400 nm excitation.
図28に示すように、実施例2に係る蛍光体の発光スペクトルL2は、ピーク波長λ2’が495nmの青緑色光と、ピーク波長λ2が662nmの赤色光が混色した白色光であった。このように、実施例2に係る蛍光体は、単一相からなる1種類の蛍光体が発する複数の色の光により白色光を実現できる。
As shown in FIG. 28, the emission spectrum L2 of the phosphor according to Example 2 was white light in which blue green light having a peak wavelength λ2 ′ of 495 nm and red light having a peak wavelength λ2 of 662 nm were mixed. Thus, the fluorescent substance which concerns on Example 2 can implement | achieve white light by the light of the several color which 1 type of fluorescent substance which consists of single phases emits.
実施例2に係る蛍光体の励起スペクトルL1’(発光ピーク波長495nmに合わせて測定)は、ピーク波長λ1’が300~420nmの範囲、より詳述すると300~350nmの範囲にある。また、励起スペクトルL1(発光ピーク波長662nmに合わせて測定)は、ピーク波長λ1が300~420nmの範囲、より詳述すると350~400nmの範囲にある。また、この蛍光体が発する光の色度座標(cx、cy)は、(0.424,0.369)である。
The excitation spectrum L1 '(measured to match the emission peak wavelength of 495 nm) of the phosphor according to Example 2 has a peak wavelength λ1' in the range of 300 to 420 nm, more specifically in the range of 300 to 350 nm. The excitation spectrum L1 (measured to match the emission peak wavelength 662 nm) has a peak wavelength λ1 in the range of 300 to 420 nm, more specifically in the range of 350 to 400 nm. The chromaticity coordinates (cx, cy) of the light emitted from this phosphor are (0.424, 0.369).
励起スペクトルL1のプロファイルは、Aサイトの全てをカリウムイオンが占有している参考例のそれとほぼ同じである。一方、励起スペクトルL1’は、300nm付近にピークを示し、赤色発光を示す400nm付近まで延びている。よって、波長が400nmの光を含む励起光による発光スペクトルL2では、青緑発光と赤色発光の2つの発光ピークを示すことになる。
The profile of the excitation spectrum L1 is almost the same as that of the reference example in which all of the A sites are occupied by potassium ions. On the other hand, the excitation spectrum L1 'shows a peak at around 300 nm and extends to around 400 nm showing red emission. Therefore, in emission spectrum L2 by excitation light including light with a wavelength of 400 nm, two emission peaks of blue-green emission and red emission are shown.
(発光サイト(AA’)BX3におけるカチオンA’とカチオンBとの選択性)
1価の金属イオンのイオン半径(10配位)は、カリウムイオンが1.59Å、ナトリウムイオンが1.32Å、リチウムイオンが0.92Åである。2価の金属イオンのイオン半径(6配位)は、カルシウムイオンが1.00Å、ユーロピウムイオンが1.17Åである。 (Selectivity of cation A 'and cation B in luminescent site (AA') BX 3 )
The ionic radius (10 coordination) of monovalent metal ions is 1.59 Å for potassium ions, 1.32 Å for sodium ions, and 0.92 Å for lithium ions. The ionic radius (six coordination) of the divalent metal ion is 1.00 Å for calcium ions and 1.17 Å for europium ions.
1価の金属イオンのイオン半径(10配位)は、カリウムイオンが1.59Å、ナトリウムイオンが1.32Å、リチウムイオンが0.92Åである。2価の金属イオンのイオン半径(6配位)は、カルシウムイオンが1.00Å、ユーロピウムイオンが1.17Åである。 (Selectivity of cation A 'and cation B in luminescent site (AA') BX 3 )
The ionic radius (10 coordination) of monovalent metal ions is 1.59 Å for potassium ions, 1.32 Å for sodium ions, and 0.92 Å for lithium ions. The ionic radius (six coordination) of the divalent metal ion is 1.00 Å for calcium ions and 1.17 Å for europium ions.
前述のように、ユーロピウムイオンのイオン半径は、カルシウムイオンのイオン半径よりも大きい。そのため、Bサイトをユーロピウムイオンが占有している場合、結晶格子に歪みが生じる。そのため、Aサイトのカリウムイオンの一部が、カリウムイオンのイオン半径よりも小さいイオン半径を有するナトリウムイオンやリチウムイオンで置換されることで、その歪みを緩和できる。したがって、結晶のトータルエネルギを最少にして安定構造を取るためには、EuとNa(Li)はペア性をもって同一の発光サイトにドープされやすい。
As mentioned above, the ionic radius of the europium ion is larger than the ionic radius of the calcium ion. Therefore, when the B site is occupied by europium ions, distortion occurs in the crystal lattice. Therefore, the distortion can be alleviated by replacing part of the potassium ions at the A site with sodium ions or lithium ions having an ion radius smaller than the ion radius of the potassium ions. Therefore, in order to minimize the total energy of the crystal and obtain a stable structure, Eu and Na (Li) tend to be doped at the same light emitting site in a pairwise manner.
上述の各実施例では、ドープ量がEu>Na(Li)であるため、ペロブスカイトを構成するAサイトが全てKで占有される発光サイトと、Aサイトがカリウムイオンとナトリウムイオンとで占有される発光サイトが生じる。図29(a)は、Aサイトにカリウムイオンのみが占有したエネルギダイアグラムを模式的に示した図、図29(b)は、Aサイトにカリウムイオン及びナトリウムイオン(リチウムイオン)のみが占有したエネルギダイアグラムを模式的に示した図である。
In each of the above-described embodiments, since the doping amount is Eu> Na (Li), the light emitting site where all the A sites constituting the perovskite are occupied by K, and the A site are occupied by the potassium ions and sodium ions Luminescent sites are generated. Fig. 29 (a) schematically shows an energy diagram in which only potassium ions are occupied at the A site, and Fig. 29 (b) shows energy in which only potassium ions and sodium ions (lithium ions) are occupied at the A site. It is the figure which showed the diagram typically.
図29(a)、図29(b)に示す励起、発光プロセスにより、一つの結晶構造からなる蛍光体において、ピーク波長が異なる複数色の光の混色による白色発光が実現できる。
By the excitation and light emission process shown in FIGS. 29A and 29B, white light emission can be realized by mixing light of a plurality of colors having different peak wavelengths in the phosphor having a single crystal structure.
以上、本発明を上述の実施の形態や各実施例を参照して説明したが、本発明は上述の実施の形態や各実施例に限定されるものではなく、実施の形態や各実施例の構成を適宜組み合わせたものや置換したものについても本発明に含まれるものである。また、当業者の知識に基づいて実施の形態や各実施例における組合せや処理の順番を適宜組み替えることや各種の設計変更等の変形を実施の形態や各実施例に対して加えることも可能であり、そのような変形が加えられた実施の形態も本発明の範囲に含まれうる。
As mentioned above, although the present invention was explained with reference to the above-mentioned embodiment and each example, the present invention is not limited to the above-mentioned embodiment and each example, but the embodiment and each example The present invention also includes those in which the configurations are appropriately combined or substituted. Further, it is also possible to appropriately rearrange the combination and order of processing in the embodiment and each embodiment based on the knowledge of the person skilled in the art, and add various modifications such as design changes to the embodiment and each embodiment. However, an embodiment in which such a modification is added can be included in the scope of the present invention.
本発明は、照明装置等に用いられる蛍光体に利用できる。
The present invention can be used for phosphors used in lighting devices and the like.
Claims (5)
- 発光サイトがABX3(A,Bはカチオン、Xはアニオン)で表されるペロブスカイト結晶構造を持ち、該ペロブスカイト結晶構造の体心となるBサイトに発光元素が位置した、単一相からなる蛍光体であって、
前記発光サイトABX3と、前記発光サイトABX3のカチオンAの一部がカチオンAよりイオン半径が小さいカチオンA’で置換された発光サイト(AA’)BX3と、を有することを特徴とする蛍光体。 A single-phase fluorescence that has a perovskite crystal structure in which the light emission site is represented by ABX 3 (A and B are cations and X is an anion) and the light emitting element is located at the B site that is the body center of the perovskite crystal structure Being a body
The light emitting site ABX 3 and the light emitting site (AA ′) BX 3 in which a part of the cation A of the light emitting site ABX 3 is substituted with a cation A ′ smaller in ion radius than the cation A Phosphor. - 前記ペロブスカイト結晶構造のAサイトに位置するカチオンのイオン半径IAは、Bサイトに位置するカチオンのイオン半径IBよりも15%以上大きいことを特徴とする請求項1に記載の蛍光体。 The phosphor according to claim 1, characterized in that the ion radius I A of the cation located at the A site of the perovskite crystal structure is 15% or more larger than the ion radius I B of the cation located at the B site.
- 前記カチオンAはK+、前記カチオンA’はNa+またはLi+であることを特徴とする請求項1または2に記載の蛍光体。 The phosphor according to claim 1 or 2, wherein the cation A is K + and the cation A 'is Na + or Li + .
- 前記カチオンBは、Eu2+、Ce3+、Sm2+及びYb2+からなる群より選択される1種以上のカチオンであることを特徴とする請求項1乃至3のいずれか1項に記載の蛍光体。 The phosphor according to any one of claims 1 to 3, wherein the cation B is at least one cation selected from the group consisting of Eu 2+ , Ce 3+ , Sm 2+ and Yb 2+. .
- 発光サイトがABX3(A,Bはカチオン、Xはアニオン)で表されるペロブスカイト結晶構造を持ち、該ペロブスカイト結晶構造の体心となるBサイトに発光元素が位置した、単一相からなる蛍光体であって、
発光スペクトルが、紫色から緑色の波長範囲にある第1のピークと、黄色から赤色の波長範囲にある第2のピークと、を有する蛍光体。 A single-phase fluorescence that has a perovskite crystal structure in which the light emission site is represented by ABX 3 (A and B are cations and X is an anion) and the light emitting element is located at the B site that is the body center of the perovskite crystal structure Being a body
A phosphor having an emission spectrum having a first peak in the violet to green wavelength range and a second peak in the yellow to red wavelength range.
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