JP2012092233A - Oxynitride phosphor and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oxynitride phosphor which is efficiently excited by near-ultraviolet or visible light, and a method for efficiently producing the oxynitride phosphor.SOLUTION: The oxynitride phosphor comprises: two or more elements selected from among B, Na, Mg, Al, K, Ca, Sc, Ti, V, Zn, Ga, Sr, Y, Zr, Nb, Ba, La, Hf and Ta; Si, O, N and a rare earth element as an activation element, and is represented by the chemical formula: (AM)SiONor the chemical formula: (AM)BSiON. In the formulae, the element A is one or more elements selected from among alkali metals and alkaline earth metals; the element M is B, Na, Mg, Al, K, Ca, Sc, Ti, V, Zn, Ga, Sr, Y, Zr, Nb, Ba, La, Hf or Ta other than the element A; and the element B is a tri- or tetravalent element.

Description

  The present invention relates to an oxynitride phosphor and a method for manufacturing the same, and more particularly, an ultraviolet-excited phosphor that emits high-intensity fluorescence in a light emission wavelength region of a near-ultraviolet light-emitting diode, an FED (electrolytic emission display), and an inorganic EL. The present invention relates to an oxynitride phosphor having a high fluorescence brightness to which a rare earth element is added as an activator that can be suitably used as a phosphor used in a display such as a display and a method for producing the same.

In recent years, the development of white LEDs has progressed, and it is expected as illumination replacing incandescent lamps and fluorescent lamps.
In a conventional white LED, a phosphor in which Ce is added to a YGA-based oxide known from the composition formula of (Y, Gd) ₃ (Al, Ga) ₅ O ₁₂ is dispersed in a blue LED sealing resin. The thing (refer patent documents 1-3) is known. Although these are used for the front light of a mobile phone or a simple lighting device, these white LEDs have poor color reproducibility and color rendering, and their improvement has been demanded.

Therefore, recently, as new phosphors, nitride phosphors such as CaAlSiN ₃ : Eu ²⁺ (Patent Document 4) and M ₂ Si ₅ N ₈ : Eu ²⁺ (Non-Patent Document 1), β sialon: Eu ²⁺ (Non-Patent Document) 2) Oxynitride phosphors such as α sialon: Eu ²⁺ (Non-Patent Documents 3 and 4) and Ba ₃ Si ₆ O ₁₂ N ₂ : Eu ²⁺ (Patent Document 5) have been developed.
These phosphors contain SiN ₄ , Si (N, O) ₄ , or AlN ₄ tetrahedra in the skeleton of the crystal structure, and are known to have excellent luminous efficiency temperature characteristics by having a strong skeleton. Yes.

As for the synthesis of oxynitride phosphors, the synthesis of sialon is popular, in which amorphous silicon, Al or AlN, and a metal oxide are mixed in a predetermined amount in Ar gas containing nitrogen gas or ammonia gas. A method of firing (Patent Document 6), Al ₂ O ₃ (including nitrates and sulfates that change to Al ₂ O ₃ during the firing process), CaO (carbonates and nitrates that change to CaO during the firing process, etc.) ), SiO ₂ (including carbonates and nitrates that change to SiO ₂ in the course of firing), and carbon (may be a compound containing carbon such as hydrocarbons) in a predetermined amount capable of producing α-sialon. A synthesis method (see Patent Document 7) is known in which a sample is collected and mixed at a ratio, and is placed in a carbon boat and subjected to a reductive nitridation reaction (hereinafter referred to as firing) for 1400 to 1600 ° C. for 30 minutes to 5 hours in a nitrogen stream. Have .

Further, as a method for synthesizing oxynitride glass using the sol-gel method, a borosilicate glass gel having a specific surface area of 300 to 500 m ² / g is heat-treated in NH ₃ at 400 to 750 ° C., and NH ₃ is used as a Lewis acid on the surface. It is known that they are bonded and fired at 900 ° C. (Non-patent Document 5).

Recently, as a method of synthesizing alkaline earth metal-added α sialon: Eu ²⁺ , a metal salt is made into an aqueous solution and mixed with SiO _2, and citric acid is added to the aqueous solution to heat it to gel, and the gel body is dried by heat. A precursor is formed by decomposing. A method has been proposed in which α sialon: Eu ²⁺ is synthesized by firing this precursor in a reducing atmosphere gas (mixed gas of hydrocarbon gas and ammonia) at 1300 to 1400 ° C. and further in nitrogen gas at 1700 ° C. (Patent Documents 8 and 9).

Japanese Patent No. 2900928 Japanese Patent No. 2927279 Japanese Patent No. 2998696 Japanese Patent No. 3837588 JP 2008-138156 A JP-A-62-222309 Japanese Patent Laid-Open No. 2001-026407 WO2006 / 132188 JP 2005-306692 A

H. A. Hoppe, et. al. , J .; Phys. Chem. Solids. 2000, vol. 61, pp. 2001 N. Hirosaki, et. al. Appl. Phys. Lett. , 2005, vol. 86, p. 211905 J. et al. W. H. van Krevel, et. al. , J .; Solid State Chem. , 2002, vol. 165, p. 19 R. -J. Xie, et. al. , J .; Am. Ceram. Soc. , 2002, vol. 85, p. 1229 Sakuo Sakuo, "Oxynitride Glass", Uchida Otsukuru, 1989, p. 49-52 P. Dorenbos, J. et al. Lumin. 2003, vol. 104, p. 239 P. Dorenbos, J. et al. Lumin. 2005, vol. 111, p. 89

Many minerals containing SiO ₂ exist in nature. Among them, B, Na, Mg, Al, K, Ca, Sc, Ti, V, Zn, Ga, Sr, Y, etc. can be obtained by adding a divalent or trivalent rare earth element. There is a silicate containing two or more elements selected from Zr, Nb, Ba, La, Hf, and Ta.
In general, the excitation energy of rare earth elements in oxides is large, and it is difficult to excite with near ultraviolet or visible light. It is said that nitrogen has lower electronegativity than oxygen and has high covalent bonding properties, so that the excitation energy of the phosphor is reduced (Non-Patent Documents 6 and 7). For this reason, it is considered that the excitation energy decreases when the silicate is partially nitrided.

  In addition, when the silicate is partially nitrided, the atomic position of oxygen, which is an anion, is replaced with a nitrogen atom. However, since oxygen and nitrogen have different valences, there is a problem that the substitution of nitrogen does not proceed because the charge balance is lost. As a countermeasure, it is necessary to substitute an appropriate atom at the cation atom position so as to balance the charge. Since the precursor before partial nitridation does not contain nitrogen, stoichiometrically there are vacancies corresponding to the nitrogen content. Therefore, when baked at high temperature and crystallized, other silicates are formed and nitriding becomes difficult. Therefore, it is desirable to be amorphous.

In addition, when raw material particles such as oxides and carbonates are mixed to form a vitreous as in the solid phase method, the diffusion rate is low particularly when SiO ₂ particles are used as a Si source for synthesizing silicate. Therefore, it cannot be nitrided at low temperatures.

  When using the sol-gel method or the citric acid gelation method, it is necessary to use an alkoxide such as tetraethoxysilane (TEOS) as the Si source and to synthesize it in a non-aqueous system because it does not mix with water. Further, tetraethoxysilane (TEOS) has a low boiling point, and thus has a problem that it is difficult to control the composition because it evaporates during heating and there is no appropriate Si source.

  In view of such circumstances, the present invention provides an oxynitride phosphor that is efficiently excited by near-ultraviolet light or visible light, and an efficient method for producing the oxynitride phosphor.

As a result of intensive studies to solve the technical problem, the present inventors have obtained B, Na, Mg, Al, K, Ca, Sc, Ti, V, Zn, Ga, Sr, Y, Zr, An oxynitride phosphor containing two or more elements selected from Nb, Ba, La, Hf, and Ta, Si, O, N, and a rare earth element as an activating element, general formula (A _1-x M _x ) An oxynitride phosphor represented by either SiO _n-y N _y or general formula (A _1-x M _x ) BSiO _m-y N _y is useful as a phosphor that is excited by near ultraviolet or visible light. I found out.

  As a method for producing such an oxynitride phosphor, a step of mixing a metal salt dissolved in water and a water-soluble silicon compound, and a mole of oxycarboxylic acid and metal element that is 3 to 8 times the number of moles of the metal element The obtained mixture solution was obtained by adding 6 times the number of moles or oxycarboxylic acid 3 to 8 times the number of moles of metal element and 6 to 12 times the number of moles of metal element. A step of producing a gel body by heating the mixed solution, and a precursor compound is obtained by heating the obtained gel body in an oxidizing atmosphere to decompose organic substances, and the precursor compound is obtained in a reducing nitriding atmosphere. It has been found that various problems can be solved by producing an oxynitride phosphor by heating, and the present invention has been completed.

  The first invention of the present invention is selected from B, Na, Mg, Al, K, Ca, Sc, Ti, V, Zn, Ga, Sr, Y, Zr, Nb, Ba, La, Hf, Ta An oxynitride phosphor containing two or more kinds of elements and rare earth elements as Si, O, N and an activating element, and represented by the following chemical formula 1 or chemical formula 2: It is a feature.

  The second invention of the present invention is selected from B, Na, Mg, Al, K, Ca, Sc, Ti, V, Zn, Ga, Sr, Y, Zr, Nb, Ba, La, Hf, Ta The oxynitride phosphor containing two or more kinds of elements and rare earth elements as Si, O, N, and an activation element is synthesized through the synthesis of the precursor compound. An oxynitride phosphor manufacturing method characterized by being an oxynitride formed by heating.

  According to a third aspect of the present invention, the precursor compound according to the second aspect comprises a step of mixing a metal salt dissolved in water and a water-soluble silicon compound, and three times the number of moles of the metal element of the metal salt. It is characterized in that it is formed through a step of preparing a gel body by adding 8 times oxycarboxylic acid, mixing and heating, and a step of decomposing organic matter by heating the obtained gel body in an oxidizing atmosphere. This is a method for manufacturing an oxynitride phosphor.

  According to a fourth aspect of the present invention, the precursor compound according to the second aspect comprises a step of mixing a metal salt dissolved in water and a water-soluble silicon compound, and three times the number of moles of the metal element of the metal salt. Steps for preparing a gel body by adding 8 times oxycarboxylic acid and 6 to 12 times the number of moles of metal element of the metal salt, mixing and heating, and oxidizing the obtained gel body It is a method for producing an oxynitride phosphor, which is formed through a step of decomposing an organic substance by heating in an atmosphere.

  According to the present invention, phosphors that are efficiently excited by near-ultraviolet light or visible light, that is, B, Na, Mg, Al, K, Ca, Sc, Ti, V, Zn, Ga, Sr, Y, Zr, Nb. An oxynitride phosphor containing two or more elements selected from Ba, La, Hf, and Ta, Si, O, N, and a rare earth element as an activation element can be provided.

  Further, according to the method for producing an oxynitride phosphor of the present invention, that is, a step of mixing a metal salt dissolved in water and a water-soluble silicon compound, and an oxycarboxylic acid having 3 to 8 times the number of moles of the metal element Solution containing 6 to 6 times the number of moles of metal element or mixed solution of 3 to 8 times the number of moles of metal element and 6 to 12 times the number of moles of metal element As a result, the obtained mixed solution is heated to produce a gel body, the gel body is heated in an oxidizing atmosphere to decompose an organic substance, and a precursor compound is produced. Further, the obtained precursor compound is reduced. By heating in a nitriding atmosphere, an oxynitride phosphor that is efficiently nitrided at a relatively low temperature can be produced.

It is a figure which shows an example of the processing container used for the baking pre-processing of a precursor compound. It is a spectrum diagram which shows the light emission characteristic of the oxynitride fluorescent substance produced in the Example (Example 1, Comparative Example 1). 2 is a spectrum diagram comparing the excitation characteristics of Example 1 and Comparative Example 1. FIG.

  The oxynitride phosphor according to the present invention includes B, Na, Mg, Al, K, Ca, Sc, Ti, V, Zn, Ga, Sr, Y, Zr, Nb, Ba, La, Hf, and Ta. It is an oxynitride phosphor containing two or more elements selected from the group consisting of Si, O, N, and rare earth elements, and is useful as a phosphor excited by near ultraviolet or visible light.

  In addition, the oxynitride phosphor according to the present invention includes B, Na, Mg, Al, K, Ca, Sc, Ti, V, Zn, Ga, Sr, Y, Zr, Nb, Ba, La, Hf, Ta oxide, carbonate, nitrate, acetate or chloride, or an aqueous solution thereof is dissolved in water to which oxycarboxylic acid is added. At this time, when chloride is used, it is necessary to use a salt that changes to an oxide when heated to 800 ° C. in the atmosphere. Also, since nitrates may react explosively, care must be taken during heating and firing.

The composition of the oxynitride phosphor according to the present invention needs to change the composition of the cation in accordance with the nitrogen substitution ratio from the silicate composition, but the general formula (A _1-x M _x ) SiO _n-y N _y , and the general formula _{(a 1-x M x)} bSiO m-y N , wherein the expressed is that either of _y.
For example, NaAlSiO ₄ introduces a cation having a large valence such as (Na _1-x Sr _x ) AlSiO _4−x N _x or (Na _1−x La _x ) AlSiO _4−2x N _2x to achieve charge balance. It is necessary to match.

In the case of ASiO _n , A is one or more elements made of an alkali metal or an alkaline earth metal, and (A _1−x M _x ) SiO _n− N N _y , where y = (M valence−A Valence) × x, and M valence> A valence.
In the case of ABSiO _m , (A _1−x M _x ) BSiO _m− N N _y , where y = (M valence−A valence) × x and M valence> A valence , A is one or more elements made of alkali metal or alkaline earth metal, B is one or more elements made of trivalent or tetravalent, or AB _1-x Si _{1 + x} O ₁ when B is trivalent It can also be _−x N _x .

Divalent Eu is suitably used as the rare earth element as the activation element, and it is considered that the rare earth element is basically substituted at the A atom position.
For example, in the case of bivalent Eu, it is as follows.
(A _1−x M _x ) _1−z Eu _z SiO _n− N N _y , where y = (valence of M−valence of A) × xx × (1−z) + z × (valence of Eu ( = 2) Valence of -A).

Next, a method for producing the oxynitride phosphor according to the present invention will be described.
[Production of water-soluble silicon compounds]
As the oxycarboxylic acid, citric acid, malic acid, tartaric acid and the like can be suitably used. Of these, citric acid is preferred. In the same manner, the rare earth salt is dissolved and added to the aqueous solution.
If the amount of oxycarboxylic acid added is less than 3 times the total number of moles of metal elements, the metal salt cannot be dissolved or gelled, and if it is more than 8 times, the viscosity of the aqueous solution will increase, making uniform mixing difficult and organic matter. Therefore, it is preferable that the residual amount is 3 to 8 times the total number of moles of metal elements.

Next, a water-soluble silicon compound having a stoichiometric composition is added to the mixed solution and stirred while heating. The heating temperature is preferably 50 to 120 ° C.
The water-soluble silicon can be produced by the following method. As raw materials, tetraethoxysilane (TEOS) and propylene glycol are weighed so as to have a molar ratio of 1: 4, and mixed at 80 ° C. for 1 hour. Stir for 1 hour. Distilled water is added to the stirring liquid to produce water-soluble silicon having a concentration of 1M.
Further, depending on the type of metal element used, glycol may be added and esterified with citric acid. As glycol, propylene glycol, ethylene glycol, or propylene glycol can be used. Propylene glycol is preferred because of its high safety.

  After the salt is completely dissolved, the liquid temperature is maintained at 50 to 250 ° C., more preferably 80 to 180 ° C., and the mixture is stirred until it becomes a viscous gel for polymerization. The stirring time is preferably 4 to 16 hours. Thereby, the gel body containing Eu uniformly is obtained. Subsequently, the obtained gel body is heated to 400 to 500 ° C., more preferably 440 to 460 ° C., and further heated to 500 to 800 ° C. in an electric furnace, and the gel body is thermally decomposed to be a precursor compound. (Oxide) is produced.

In addition, since the precursor compound (oxide) obtained may melt and become a glass body when directly nitriding at a high temperature, a double crucible containing carbon (graphite) as shown in FIG. A pre-calcination treatment for crystallization by calcination may be added, in which case the rare earth may be reduced together.
In FIG. 1, 1 is a processing container used for pre-firing treatment, 2 is a crucible, 2a is an outer crucible, 2b is an inner crucible, 3 is a calcined powder (precursor compound), 4 is a carbon sheet, and 5 is carbon (graphite). , 6 is a crucible lid.

  Next, the obtained precursor compound (oxide) was put into an alumina boat and baked in nitrogen gas containing ammonia. The firing temperature is preferably 900 ° C to 1400 ° C. Moreover, you may add the process which makes ammonia adsorb | suck at 600 to 800 degreeC.

  Hereinafter, description will be made using examples.

[Production of water-soluble silicon]
Pipette TEOS: 22.4 ml and propylene glycol: 29.3 ml into an Erlenmeyer flask. (PG: TEOS molar ratio 4: 1).
Next, 0.1 ml of HCl is added. Stir with a hot stirrer at 80 ° C. for 1 hr. After cooling, the contents were transferred to a volumetric flask and made up to a volume of 100 ml with pure water to obtain 1 M / L water-soluble silicon.

[Preparation of aqueous solution of each component]
Na nitrate: 0.1 mol was dissolved in 0.3 mol of citric acid, and the volume was adjusted to 100 ml to prepare a 1 M / L Na aqueous solution. Al nitrate: 0.1 mol was dissolved in water, and the volume was adjusted to 100 ml to prepare a 1 M / L aqueous solution of Al. Eu nitrate: 0.01 mol was dissolved in water and the volume was adjusted to 100 ml to prepare a 0.1 M / L Eu aqueous solution.
Nitrogen Sr: 0.1 mol was dissolved in 0.6 mol of citric acid, and the volume was adjusted to 100 ml to prepare a 1 M / L Sr aqueous solution. 1 mol of citric acid was dissolved in water and the volume was adjusted to 500 ml to prepare a 2 M / L aqueous citric acid solution.

[Production of gel body]
Each aqueous solution was mixed so that Na: Sr: Eu: Al = 0.895: 0.095: 0.01: 1, and a 2M aqueous citric acid solution was added so that the amount of citric acid was three times that of the metal element. added.
This was stirred at room temperature for 30 minutes, and water-soluble silicon was added so that Al: Si = 1: 1.
The mixture was further stirred for 30 minutes, and propylene glycol was added so as to be 10 times the total number of moles of metal elements. The gel was prepared by stirring at a temperature of 80 ° C. for 2 hours and at 120 ° C. for 12 hours for polymerization.

[Preparation of precursor compound]
The prepared gel was treated at 450 ° C. for 6 hours and then at 550 ° C. for 2 hours to decompose the organic matter, and then the obtained sample was placed in the double crucible containing carbon in FIG. 1 at 1200 ° C. for 2 hours. The precursor compound (oxide) was obtained by performing the heat treatment.

[Baking of precursor compound]
The prepared precursor compound (oxide) was put in an alumina boat and calcined in ammonia gas at 1200 ° C. for 4 hours.
By this step, an oxynitride phosphor of Na _0.895 Sr _0.095 Eu _0.01 AlSiO _3.895 N _0.105 was produced.
The nitriding treatment relating to the firing of the precursor compound may be repeated.
The emission characteristics of the obtained oxynitride phosphor are shown in FIG. 2 (curves indicated by “Example 1 (one nitriding treatment), (two nitriding treatments)”).

(Comparative Example 1)
Na _0.99 Eu _0.01 AlSiO _3.99 N _{0 in} the same manner as in Example 1 except that Sr was not added and Na: Sr: Eu: Al = 0.99: 0: 0.01: 1. _{A .01} oxynitride phosphor was produced.
The emission characteristics of the obtained oxynitride phosphor are shown in FIG. 2 (curve shown in “Comparative Example 1”).

FIG. 3 shows the result of comparison of the excitation characteristics of Example 1 and Comparative Example 1.
As is apparent from FIG. 3, the excitation characteristic extends to a long wavelength, and it can be seen that the nitriding effect is large in the oxynitride of the present invention.

DESCRIPTION OF SYMBOLS 1 Processing container 2 used for pre-processing Crucible 2a Outer crucible 2b Inner crucible 3 Calcined powder (precursor compound: oxide)
4 Carbon sheet 5 Graphite (carbon)
6 Crucible lid

Claims (4)

B, Na, Mg, Al, K, Ca, Sc, Ti, V, Zn, Ga, Sr, Y, Zr, Nb, Ba, La, Hf, Ta and two or more elements selected from Si, An oxynitride phosphor containing O, N and a rare earth element as an activation element,
It is an oxynitride phosphor represented by the following chemical formula 1 or chemical formula 2.
  Two or more elements selected from B, Na, Mg, Al, K, Ca, Sc, Ti, V, Zn, Ga, Sr, Y, Zr, Nb, Ba, La, Hf, Ta, and Si The oxynitride phosphor containing rare earth elements as O, N, and activator is an oxynitride formed by heating the precursor compound in a reducing nitridation atmosphere after synthesis of the precursor compound. There is provided a method for producing an oxynitride phosphor. The precursor compound is
Mixing a metal salt dissolved in water and a water-soluble silicon compound;
Adding oxycarboxylic acid 3 to 8 times the number of moles of the metal element of the metal salt, mixing and heating to produce a gel body;
Heating the obtained gel body in an oxidizing atmosphere to decompose organic matter,
The method for producing an oxynitride phosphor according to claim 2, wherein The precursor compound is
Mixing a metal salt dissolved in water and a water-soluble silicon compound;
Gel body obtained by adding oxycarboxylic acid 3 to 8 times the number of moles of the metal element of the metal salt and glycol 6 to 12 times the number of moles of the metal element of the metal salt, mixing and heating A step of producing
Heating the obtained gel body in an oxidizing atmosphere to decompose organic matter,
The method for producing an oxynitride phosphor according to claim 2, wherein