WO2012046288A1 - β-SIALON PHOSPHOR, METHOD FOR PRODUCING SAME, AND USE OF SAME - Google Patents

Abstract

[Problem] To provide an Eu-activated β-SiAlON phosphor which has high fluorescence emission efficiency and short fluorescence peak wavelength and is capable of achieving narrow band emission. [Solution] Provided is a β-SiAlON phosphor which is obtained using a β-SiAlON represented by general formula of Si_6-zAl_zO_zN_8-z as a matrix material and solid-solving Eu²⁺ hereinto as the luminescence center. The β-SiAlON crystals have a lattice constant a of 0.7605-0.7610 nm, a lattice constant c of 0.2906-0.2911 nm, an Eu content of 0.4-2% by mass and a first transition metal content of not more than 5 ppm.

Description

β-type sialon phosphor, method for producing the same, and use thereof

The present invention relates to a phosphor that can be used in various light emitting devices such as a blue light emitting diode (blue LED (Light Emitting Diode)) or a white light emitting diode (white LED) using an ultraviolet light emitting diode (ultraviolet LED). The present invention relates to a light emitting device using the same.

In Patent Document 1, a combination of a semiconductor light-emitting element that emits blue to violet short-wavelength visible light and a phosphor allows white light to be emitted by mixing the light emitted from the semiconductor light-emitting element and the light wavelength-converted by the phosphor. A white LED for obtaining the above is disclosed.

On the other hand, phosphors using silicates, phosphates, aluminates, and sulfides as the base material and using transition metals or rare earth metals as the emission center are widely known.

With the increase in output of white LEDs, demands for heat resistance and durability of phosphors are increasing. However, when the above-mentioned conventionally known phosphors are used, the phosphors are deteriorated due to a decrease in luminance of the phosphors due to an increase in the operating environment temperature or a long time exposure to blue light or ultraviolet light excitation sources. As a result, there is a problem in that the luminance of the white LED is reduced and color deviation occurs.

As a phosphor having a small decrease in luminance due to temperature rise and excellent durability, a phosphor using nitride or oxynitride having a strong covalent bond as a base material has recently attracted attention.

As a typical phosphor using nitride or oxynitride as a base material, sialon which is a solid solution of silicon nitride can be cited. Similar to silicon nitride, sialon has two types of crystal systems, α-type and β-type. For example, α-sialon activated with divalent Eu ions as the emission center is reported to be a phosphor that emits yellow light having an emission peak wavelength of 550 to 600 nm when excited in a wide wavelength range from ultraviolet to blue. (Patent Document 2).

In addition, it has been found that β-type sialon also exhibits fluorescence characteristics by adding Mn, Ce, and Eu as the emission center (Patent Document 3).

β-type sialon is a solid solution of β-type silicon nitride in which Al is substituted at the Si position and O is substituted at the N position. Since there are two formula atoms in the unit cell (unit cell), the general formula is expressed as “Si _6-z Al _z O _z N _8-z ”. Here, the composition z is 0 to 4.2, and the solid solution range is very wide. The molar ratio of (Si, Al) / (N, O) needs to be maintained at 3/4. β-sialon is generally obtained by heating silicon nitride with silicon oxide and aluminum nitride, or aluminum oxide and aluminum nitride.

When Eu ²⁺ is contained in the β-sialon crystal, the phosphor is excited by ultraviolet to blue light and emits green light of 520 to 550 nm, and can be used as a green light emitting component of a light emitting device such as a white LED. This Eu ²⁺ -activated β-sialon has a relatively sharp emission spectrum among the phosphors activated by Eu ²⁺ , and is particularly the back of a liquid crystal display panel that requires blue, green, and red narrow-band light emission. It is a phosphor suitable for a green light emitting component of a light source.

It has been reported that β-sialon phosphors synthesized by firing at high temperatures can reduce crystal defects and significantly improve fluorescence characteristics by post-treatment such as heat treatment and acid treatment under predetermined conditions. (Patent Document 4). However, in this case, as the luminous efficiency increases, the fluorescence peak becomes longer or broader.

Patent Document 5 reports that the fluorescence emission is narrowed by reducing the amount of oxygen solid solution in the β-sialon crystal. As a method for synthesizing β-sialon having a low oxygen solid solution amount, Examples include a method of nitriding elemental metal powder and a method of heating nitride and oxide raw materials in a reducing nitriding atmosphere. However, in this case, the emission efficiency of the β-type sialon phosphor is extremely low, and it is difficult to put it to practical use.

Japanese Patent No. 2927279 Japanese Patent No. 3668770 JP 2005-255895 A International Publication No. 2008/062781 International Publication No. 2007/066673

Conventional Eu-activated β-sialon phosphors have a trade-off relationship between fluorescence emission efficiency and spectrum width. Therefore, a white LED using this cannot obtain a sufficient luminance when the band is narrowed. On the other hand, when the luminous efficiency is increased, the color reproduction range becomes narrow, particularly in a backlight light source of a liquid crystal display. In use, there is difficulty in providing for practical use.

The present invention has been made in view of the above-described problems, and an object of the present invention is to provide an Eu-activated β-sialon phosphor that has a high fluorescence emission efficiency, a short fluorescence peak wavelength, and can realize narrow-band emission.

The phosphor of the present invention has a β-type sialon represented by the general formula: Si _6-z Al _z O _z N _8-z as a base crystal, and Eu ²⁺ as a luminescent center in solid solution. As shown in Patent Document 5, narrow-band light emission is realized by lowering the amount of oxygen solid solution in the β-type sialon crystal, that is, lowering the z value of the above equation.

As a result of extensive research on the z value, crystal structure, composition and fluorescence characteristics of β-sialon, the present inventor determined not only the z value but also the Eu ²⁺ solid solution amount in the crystal from the crystal lattice size of β-sialon. I found what I could estimate. As a result, it has been found that the β-sialon phosphor manufactured by the conventional method has a reduced z value, the amount of Eu ²⁺ actually dissolved in the β-sialon crystal is reduced, and the luminous efficiency is lowered.
Furthermore, the crystal system of silicon nitride powder, which is the main raw material of β-type sialon, optimization of impurities, and post-treatment of the synthesized phosphor under predetermined conditions can increase the amount of Eu ²⁺ solid solution even at low z values. The inventors have obtained the knowledge that high luminous efficiency can be maintained and narrow band emission can be realized, and the present invention has been achieved.

That is, the present invention is a beta-SiAlON represented by the general formula _{Si 6-z Al z O z} N 8-z as a host material, a beta-SiAlON phosphor solid solution ^{Eu 2+} as a luminescent center, beta Type sialon crystal has a lattice constant a of 0.7605 to 0.7610 nm, a lattice constant c of 0.2906 to 0.2911 nm, an Eu content of 0.4 to 2 mass%, and a first transition metal content of 5 ppm. The following β-sialon phosphor is provided.
This β-type sialon phosphor has an emission peak wavelength in the wavelength range of 520 to 540 nm when irradiated with an excitation source, and its chromaticity is CIExy chromaticity coordinates, 0.28 ≦ x ≦ 0.33, 0 .62 ≦ y ≦ 0.67.
In this β-type sialon phosphor, the 90% cumulative volume fraction (D90) in the particle size distribution measured by the laser diffraction scattering method is 10 to 50 μm, and the 10% diameter (D10) is 2 μm or more. Is preferred.

The present invention also provides a method for producing a β sialon phosphor in which β sialon represented by the general formula Si _6-z Al _z O _z N _8-z is used as a base material and Eu ²⁺ is used as a luminescence center in solid solution. A firing step of firing a raw material mixed powder containing silicon nitride powder containing Al and an inorganic compound containing Eu in a nitrogen atmosphere at a temperature range of 1850 to 2050 ° C., and 1300 to 1500 ° C. in a rare gas atmosphere. And a heat treatment step of holding for 1 to 100 hours, and an acid treatment step of immersing in a mixed acid of hydrofluoric acid and nitric acid at 60 ° C. or higher for 0.5 hour or longer. .
In this production method, it is preferable to use a silicon nitride powder having a first transition metal content synthesized by a metal silicon nitriding method of 10 ppm or less and containing 0.1 to 2% by mass of Al. . The silicon nitride powder preferably has a β ratio of 50% or more and a metal silicon content of 10% by mass or less.

Furthermore, the present invention provides a light emitting device having an LED having a maximum emission wavelength intensity of 240 to 480 nm and the β-sialon phosphor laminated on the light emitting surface of the LED, and the light emitting device and the light emitting device. There is also provided a light emitting device having a power source for supplying electricity.

According to the present invention, an Eu-activated β-sialon phosphor capable of realizing narrow-band light emission with high fluorescence emission efficiency and a short fluorescence peak wavelength is provided.

6 is a drawing-substituting graph showing fluorescence spectra of external excitation light having a wavelength of 455 nm for β-sialon phosphors according to Examples 1 to 3 and Comparative Example 2. FIG.

1. β-Sialon Phosphor The phosphor of the present invention is obtained by solid-dissolving Eu ^{2+ as the} emission center in a base crystal of β-sialon represented by the general formula: Si _6-z Al _z O _z N _8-z. .

Β-type sialon is synthesized by mixing silicon and aluminum nitride and oxide raw material powders and firing at high temperature. However, the obtained β-sialon is not a complete single phase, but inevitably forms a Si—Al—ON glass phase, and in some cases, a heterogeneous phase such as an AlN polytypoid or α-sialon is generated. End up. Therefore, it is difficult to grasp an accurate z value by a raw material blend composition or a composition analysis of a synthetic powder. In particular, in a region where the z value is low for the purpose of narrowing the band, dissociation between the charged composition and composition analysis values and the actual solid solution composition is remarkable.

In β-type sialon, Al is dissolved in the Si position of β-type silicon nitride, and O is dissolved in the N position. Therefore, the a-axis (= b-axis) length and c-axis of the hexagonal crystal increase as the amount of the solid solution increases. The length increases.

According to the examination results of the present inventors who investigated the relationship between the amount of Eu ²⁺ solid solution and the lattice constant of β-type sialon crystal, when Eu ²⁺ is dissolved in β-type sialon crystal when z value is constant, It was found that only the length increased and the c-axis length hardly changed. It is estimated that for Eu ²⁺ is penetrated solid solution in a large tunnel-like voids in the c-axis direction present in the β-sialon crystal.

Accordingly, the lattice constant of the β-type sialon crystal is a parameter that sensitively reflects the z value and the Eu ²⁺ solid solution amount. In the phosphor of the present invention, the lattice constant c of the β-type sialon crystal is preferably in the range of 0.2906 to 0.2911 nm. When the lattice constant c is smaller than 0.2906 nm, the solid solubility limit of Eu ²⁺ is lowered and sufficient fluorescence intensity cannot be obtained. On the other hand, if the lattice constant c exceeds 0.2911 nm, the fluorescence spectrum becomes broad due to an increase in the true z value of the β-type sialon crystal, which is not preferable. The amount of Eu ²⁺ solid solution in the β-type sialon crystal is preferably as large as possible. However, since the solid solution limit depends on the z value, in the phosphor of the present invention, the lattice constant a is 0.7605 to 0.7610 nm. It is preferable to be in the range. In order to realize this, the Eu content contained in the phosphor is preferably set to 0.4 to 2% by mass.

From the viewpoint of fluorescence emission, it is desirable that the phosphor contains a β-sialon crystal phase with a high purity and as much as possible. If possible, it is preferably composed of a single phase of β-sialon crystal. Even a mixture containing an amorphous phase and another crystal phase may be included as long as the characteristics are not deteriorated. In particular, the phosphor of the present invention having a low z value is very sensitive to first transition metal impurities such as Fe, Ni, Co, etc., and the content thereof is preferably 5 ppm or less, although the reason is not clear.

The phosphor of the present invention emits green light having a peak wavelength in the wavelength range of 520 to 540 nm when irradiated with an excitation source. The fluorescence spectrum of the β-sialon phosphor activated by Eu ²⁺ has a feature that even if the z value is increased, the wavelength at the rising edge of the spectrum hardly changes and the fluorescence component on the long wavelength side increases. That is, when the z value is increased, the peak wavelength is gradually shifted to the longer wavelength side, and the half width of the spectrum is increased. As a result, the x value on the CIE chromaticity coordinate increases and the y value decreases. In addition to the z value, another factor that affects the shape of the fluorescence spectrum is the crystallinity of β-type sialon. Even at a low z-value, when the crystallinity of β-type sialon is low, the half width of the spectrum increases. The phosphor of the present invention having a low z value and high crystallinity of the β-type sialon crystal has a narrow half-value width and 0.28 ≦ x ≦ 0.33, 0 in terms of (x, y) value on the CIE chromaticity coordinates. .62 ≦ y ≦ 0.67.

Regarding the form of the phosphor of the present invention, when used as a powder, the 90% diameter (D90) in the volume-based cumulative fraction is 10 to 50 μm in the particle size distribution measured by the laser diffraction scattering method. Is preferred. The phosphor of the present invention is preferable because D90 is adjusted to 50 μm or less so that uniform mixing with the resin for sealing the LED is facilitated, and the cause of the chromaticity variation of the LED and the uneven color of the irradiated surface can be reduced. .

Furthermore, the phosphor of the present invention preferably has a 10% diameter (D10) of 2 μm or more. Particles smaller than a few μm have low crystallinity and not only low emission intensity of the phosphor itself, but also close to the wavelength of visible light. By setting D10 to be 2 μm or more, an LED can be assembled using a phosphor with a small content of such small particles, and it is possible to suppress the strong scattering of light within the layer containing the phosphor. Luminous efficiency (light extraction efficiency) can be improved.

2. Method for Producing β-Sialon Phosphor Next, a method for producing the phosphor of the present invention will be described.

In the method for producing a β-type sialon phosphor of the present invention, it is preferable to use silicon nitride powder containing Al corresponding to the z value of the β-type sialon crystal synthesized by the metal silicon nitriding method. In the silicon nitride powder of the present invention, it is preferable to reduce impurity elements other than Si, Al, and N as much as possible, and it is particularly preferable that the content of the first transition metal is 10 ppm or less.
In β-sialon having a low z composition, excessive oxygen promotes the formation of a heterogeneous phase, so that it is necessary to reduce the amount of impurity oxygen in the silicon nitride raw material. From such a viewpoint, a silicon nitride raw material powder obtained by direct nitridation of silicon powder having a high purity and a small amount of impurity oxygen is preferable.
Silicon nitride powder by direct nitriding is synthesized by a known method. For example, after silicon powder is heated and nitrided in a nitrogen-containing atmosphere at a temperature of 1200 ° C. or higher, the resulting nitride is pulverized, pulverized, classified, and subjected to pulverization processes such as classification and acid treatment. Can be produced. Since silicon nitride powder obtained by the conventional direct nitriding method is mostly used for sintering, it is a fine powder having an average particle size of submicron to several microns. However, it is not always fine for use in the phosphor of the present invention. The average particle size may be about 5 to 100 μm, but it is important to suppress the contamination of impurities in the pulverization process due to excessive grinding as much as possible.

Furthermore, since β-sialon in the phosphor of the present invention has a small amount of Al solid solution, a small amount of Al is uniformly distributed in the final firing step by adding a predetermined amount of Al in the nitriding stage of silicon powder. Thus, a solid solution having a uniform composition is obtained. Examples of the method of adding Al include a method of directly adding aluminum powder, aluminum nitride powder, aluminum oxide powder and the like to silicon powder before nitriding, and a method of using an alloy powder of silicon and aluminum as a direct nitriding raw material. Regarding the presence form of Al in the Al-containing silicon nitride powder as the phosphor raw material, it may exist as a heterogeneous phase not dissolved in silicon nitride as long as it is uniformly dispersed. Regarding the Al content in the silicon nitride powder of the present invention, in order to make the β-sialon lattice constant finally obtained within the above range, it is 0.1-2% by mass, preferably 0.5-2% by mass. It is preferable.

In the silicon nitride powder, unreacted silicon may remain if it is 10% by mass or less. If the free silicon exceeds 10% by mass, silicon remains even at a high temperature for synthesizing the phosphor. Since silicon absorbs light in a wide wavelength range from ultraviolet to visible, if it is present in the phosphor, the luminance is greatly reduced.

According to the study of the present inventor, the silicon nitride powder of the present invention has a β-phase content ratio (β ratio = β amount / (α amount + β amount) of two types of crystal systems (α, β). ) by increasing, since it can be effectively dissolved the Eu ²⁺ in the β-sialon crystal when β-sialon synthesis, it is preferable that the β ratio is 50% or more.

The reason why the solid solution of Eu ²⁺ can be promoted by increasing the β ratio is considered as follows.
The solid solution of Eu ^{2+ in} the β-type sialon crystal is accompanied by the growth of β-type sialon through a liquid phase mainly composed of an oxide present in a minute amount at a high temperature in the phosphor synthesis process. And proceed. The α phase of silicon nitride has a significantly higher dissolution rate in the liquid phase than the β phase, and has a faster grain growth rate. Originally, Eu ²⁺ hardly dissolves in the β-type sialon crystal, and if the grain growth rate is too high, it is considered that it cannot be sufficiently dissolved. Therefore, it is considered that the solid solution of Eu ²⁺ could be promoted by increasing the β phase ratio and decreasing the grain growth rate.

The β-type sialon phosphor of the present invention is synthesized by heating a raw material mixed powder composed of the above-mentioned Al-containing silicon nitride powder and a compound containing Eu in a nitrogen atmosphere. The heating temperature is preferably in the range of 1850 to 2050 ° C. If the heating temperature is 1850 ° C. or higher, Eu ²⁺ can enter the β-type sialon crystal, and a phosphor having sufficient luminance can be obtained. Further, if the heating temperature is 2050 ° C. or less, it is not necessary to suppress the decomposition of β-sialon by applying a very high nitrogen pressure, and a special apparatus is not required for this purpose, which is industrially preferable. .

When the β-type sialon phosphor is produced, the composite is granular or massive. This is combined with pulverization, pulverization and / or classification operations to obtain a powder of a predetermined size. In order to use suitably as a fluorescent substance for LED, as above-mentioned, it is necessary to set it as predetermined D10 and D90.

Specific examples of treatment include a method of subjecting the synthesized product to sieve classification with an opening of 20 to 45 μm to obtain a powder that has passed through the sieve, or a general pulverizer such as a ball mill, a vibration mill, or a jet mill. The method of using and grind | pulverizing to a predetermined particle size is mentioned. In the latter method, excessive pulverization not only generates fine particles that easily scatter light, but also generates crystal defects on the particle surface, causing a decrease in luminous efficiency. According to the study by the present inventors, the powder obtained by the treatment only by sieve classification and the pulverization treatment by the jet mill pulverizer without the pulverization treatment finally showed high luminous efficiency.

The phosphor obtained by the above method is further subjected to the following treatment to improve the fluorescence characteristics.
That is, the β-sialon phosphor obtained by the above method is heat-treated in a rare gas atmosphere and then heat-treated with a mixed acid of hydrofluoric acid and nitric acid. The heat treatment of the phosphor is performed in order to further destabilize the low crystalline portion in the phosphor. According to the study of the present inventor, the atmosphere containing nitrogen and oxygen, which are constituent elements of the phosphor, is minimized. Since it is effective, a rare gas atmosphere is selected. Heat treatment only produces a destabilized phase, and removal of this phase significantly improves the fluorescence properties. The heat treatment temperature is preferably in the range of 1300 to 1500 ° C. If it is 1300 degreeC or more, a low crystalline part can be destabilized, and if it is 1500 degrees C or less, decomposition | disassembly of (beta) -sialon can be suppressed. For removing the destabilizing phase, a known technique such as dissolution removal with acid or alkali can be employed. Among them, a dissolution treatment carried out by heating with a mixture of hydrofluoric acid and nitric acid at 60 ° C. or higher for 5 minutes or longer, preferably 0.5 hours or longer is effective and preferable.

3. Light-Emitting Element and Light-Emitting Device The β-type sialon phosphor of the present invention is used in a light-emitting device composed of a light-emitting light source and a phosphor, and particularly uses ultraviolet light or visible light containing a wavelength of 240 to 480 nm as an excitation source. By irradiating, it emits a narrow band of green light, so it is easily laminated by stacking it on the light emitting surface of an ultraviolet LED or blue LED and combining it with a red phosphor and / or a blue phosphor as necessary. White light is obtained.

In addition, since β-sialon phosphors have a low luminance decrease at high temperatures, light emitting devices using the same have a low luminance decrease and chromaticity deviation, do not deteriorate even when exposed to high temperatures, have excellent heat resistance, and an oxidizing atmosphere. In addition, since it has excellent long-term stability in a moisture environment, it has a feature of high brightness and long life.

The light-emitting device is configured using at least one light-emitting light source and a phosphor mainly composed of β-sialon of the present invention. For example, an LED can be manufactured using a known method described in JP-A-5-152609, JP-A-7-99345, JP-A-2927279, and the like. In this case, the emission light source is preferably an ultraviolet LED or a blue LED emitting light having a wavelength of 240 to 480 nm, particularly preferably a blue LED emitting light having a wavelength of 440 to 470 nm. Examples of these light emitting elements include GaN and InGaN. The light emitting light source that emits light of a predetermined wavelength can be obtained by adjusting the composition.

In the light emitting device, in addition to the method of using the phosphor of the present invention alone, a light emitting device that emits a desired color can be configured by using in combination with a phosphor having other light emission characteristics. In particular, the green narrow-band phosphor of the present invention uses a blue LED as an excitation source, and is combined with a red phosphor having an emission wavelength peak of 600 to 700 nm, for example, CaAlSiN ₃ : Eu, so that color reproducibility is achieved. It is suitable for a white LED for backlight of an excellent image display device.

Next, an Example is described in detail, comparing with a comparative example, using a table | surface and a figure. FIG. 1 is a graph showing fluorescence spectra of external excitation light having a wavelength of 455 nm for β-sialon phosphors according to Examples 1 to 3 and Comparative Example 2.
[Example 1]

<Synthesis and evaluation of Al-containing silicon nitride powder>
High purity chemical silicon powder (purity 99.999% or more, -75 μm) 98.81% by mass and Tokuyama aluminum nitride powder (E grade) 1.19% by mass, V type mixer (Tsutsui Rika Instruments Co., Ltd.) “S-3”) was mixed, and a sieve having an opening of 250 μm was passed through to remove aggregates to obtain a raw material mixed powder.

The raw material mixed powder is filled into a cylindrical boron nitride container with a lid of 60 mm in diameter and 30 mm in height (“N-1” grade, manufactured by Denki Kagaku Kogyo Co., Ltd.) and pressurized to 0.5 MPa in an electric furnace of a carbon heater. Heat treatment was performed at 1500 ° C. for 8 hours in a nitrogen atmosphere. The heating rate during the heat treatment was such that room temperature to 1200 ° C. was 20 ° C./min, and 1200 to 1500 ° C. was 0.5 ° C./min.

The obtained product was in the form of a lump, and this was pulverized by a high-speed stamp mill (manufactured by Nippon Ceramic Science Co., Ltd., ANS-143PL, light and hammer made of alumina). The pulverized powder was classified with a sieve having an opening of 45 μm, and the powder of 45 μm or less was used as a silicon nitride powder for phosphor synthesis. In addition, the sieve passing rate with an opening of 45 μm was about 40%.

The obtained silicon nitride powder was subjected to powder X-ray diffraction measurement (XRD) using an X-ray diffractometer (manufactured by Rigaku Corporation, ULTIMA IV). The crystal phases present were three phases of β-type silicon nitride, α-type silicon nitride and metal silicon. The obtained powder X-ray diffraction pattern was subjected to Rietveld analysis by the analysis program JADE manufactured by Rigaku Corporation. As a result, the β ratio (the ratio indicated by the β phase in the silicon nitride crystal) was 90.2% and the metal silicon was 0. It was 8 mass%.

Next, for the Al content, the powder was dissolved by the alkali melting method, and for the impurity content by the pressure acid decomposition method, and then analyzed by an ICP emission spectroscopic analyzer (manufactured by Rigaku Corporation, CIROS-120). went. The Al content of this powder was 0.46% by mass, and the first transition metal content was 2 ppm.

<Synthesis and evaluation of β-type sialon phosphor>
98.03% by mass of the Al-containing silicon nitride powder and 1.97% by mass of Europium oxide powder (RU grade) manufactured by Shin-Etsu Chemical Co., Ltd. are dry-mixed in an alumina mortar, and further passed through a sieve having an opening of 250 μm. A raw material mixed powder for sialon phosphor was obtained. This raw material mixed powder is filled into a cylindrical boron nitride container (“N-1” grade, manufactured by Denki Kagaku Kogyo Co., Ltd.) with a lid having a diameter of 60 mm and a height of 30 mm, and 0.8 MPa in an electric furnace of a carbon heater. Heat treatment was performed at 2000 ° C. for 8 hours in a pressurized nitrogen atmosphere. The obtained product was a green loosely agglomerated lump, which could be easily unwound by hand wearing clean rubber gloves. In this way, after carrying out mild crushing, it was passed through a sieve having an opening of 45 μm. In this state, the sieve passing rate with an opening of 45 μm was about 90%.

The above powder is filled in a cylindrical boron nitride container with a lid having a diameter of 60 mm and a height of 30 mm (“N-1” grade, manufactured by Denki Kagaku Kogyo Co., Ltd.) in an atmospheric pressure argon atmosphere in a carbon heater electric furnace. Heat treatment was performed at 1400 ° C. for 8 hours. The color of the obtained powder changed from green before processing to dark green. The obtained powder did not shrink at all due to sintering or the like, and all passed through a sieve having an opening of 45 μm. The powder thus obtained was heat-treated at 75 ° C. in a 1: 1 mixed acid of 50% hydrofluoric acid and 70% nitric acid. During the treatment, the suspension changed from dark green to bright green. Thereafter, filtration, washing and drying were performed to obtain a phosphor powder.

As a result of performing XRD measurement on this phosphor, the crystal phase was a single β-sialon phase. The lattice constant of β-type sialon was a = 0.7606 nm and c = 0.2908 nm. The Al and Eu contents determined by ICP emission spectroscopic analysis were 0.49 and 0.77% by mass, respectively, and the first transition metal content was less than 5 ppm.

Next, as a result of particle size distribution measurement by laser diffraction / scattering method using a particle size distribution measuring apparatus (LS-230 type, manufactured by Beckman Coulter, Inc.), a 10% diameter (D10 ) Was 6.7 μm, and the 90% diameter (D90) was 38.4 μm. The adjustment of the sample for measuring the particle size distribution was in accordance with the silicon nitride measurement conditions shown in Table 1 of JIS R 1629-1997.

The light emission characteristics of the phosphor were evaluated as follows. The phosphor powder was filled with a concave cell so that the surface was smooth, and an integrating sphere was attached. Monochromatic light that was split into a predetermined wavelength from a light emitting light source (Xe lamp) was introduced into the integrating sphere using an optical fiber. Using this monochromatic light as an excitation source, a phosphor sample was irradiated, and a spectrophotometer (MCPD-7000, manufactured by Otsuka Electronics Co., Ltd.) was used to measure the spectrum of the fluorescence and reflected light of the sample. In this example, near-ultraviolet light having a wavelength of 405 nm and blue light having a wavelength of 455 nm were used as monochromatic light.

In the obtained fluorescence spectrum, for the excitation wavelengths of 405 nm and 455 nm, an XYZ table defined by JIS Z 8701 is obtained from data in the wavelength range of 415 to 780 nm and 465 to 780 nm, respectively, according to JIS Z 8724. The chromaticity coordinates CIEx and CIEy in the color system were calculated. When the excitation wavelength was 405 nm, the chromaticity CIEx and CIEy were 0.312 and 0.655, respectively, and when the excitation wavelength was 455 nm, the chromaticity CIEx and CIEy were 0.318 and 0.651, respectively.

The luminous efficiency was determined as follows. First, a standard reflector (Spectralon manufactured by Labsphere, Inc.) having a reflectance of 99% is set on the sample portion, and the spectrum of the excitation light is measured. When the excitation wavelength is 405 nm, excitation is performed in the wavelength range of 400 to 415 nm. When the wavelength was 455 nm, the number of excitation light photons (Qex) was calculated from the spectrum in the wavelength range of 450 to 465 nm. Next, a phosphor was set in the sample portion, and the number of excited reflected light photons (Qref) and the number of fluorescent photons (Qem) were calculated from the obtained spectrum data. The number of excitation reflected light photons is in the same wavelength range as the number of excitation light photons, and the number of fluorescent photons is in the wavelength range of 415 to 800 nm when the excitation wavelength is 405 nm, and from 465 to when the excitation light is 455 nm. Calculation was performed in the range of 800 nm. The external quantum efficiency (= Qem / Qex × 100), the absorptance (= (Qex−Qref) × 100), and the internal quantum efficiency (= Qem / (Qex−Qref) × 100) are obtained from the obtained three types of photons. Asked. Absorption rate, internal quantum efficiency, and external quantum efficiency are 83.2%, 59.2%, and 49.3%, respectively, when excited by near-ultraviolet light having a wavelength of 405 nm. When excited by blue light having a wavelength of 455 nm Were 73.1%, 56.6%, and 41.3%, respectively.

[Comparative Example 1]
Α-type silicon nitride powder (SN-E10 grade) manufactured by Ube Industries, Ltd., aluminum nitride powder (F grade) manufactured by Tokuyama Co., Ltd. and europium oxide powder (RU grade) manufactured by Shin-Etsu Chemical Co., Ltd., and the phosphor of Example 1 and Si: Al The mixture was made to have the same Eu ratio, and β-sialon was synthesized in the same manner as in Example 1. The obtained product was a green hard aggregate, and a reddish brown precipitate was formed on the surface thereof. As in Example 1, this product was difficult to be pulverized by mild disintegration. Therefore, the mixture was pulverized with an alumina mortar until it passed through a sieve having an opening of 150 μm, and further classified with a sieve having an opening of 45 μm. The powder that passed through the sieve was subjected to heat treatment and acid treatment in the same manner as in Example 1 to obtain a β-type sialon phosphor.

As a result of XRD measurement of this phosphor, the crystal phase was a β-type sialon single phase.
The lattice constants of β-sialon were a = 0.7604 nm and c = 0.2909 nm.
The Al and Eu contents determined by ICP emission spectroscopic analysis were 0.46 and 0.22% by mass, respectively, and the first transition metal content was less than 5 ppm. Compared to Example 1, both the Eu content particularly decreased.

As a result of performing particle size distribution measurement on this phosphor, the 10% diameter (D10) in the volume-based integrated fraction was 4.3 μm, and the 90% diameter (D90) was 43.3 μm.

Absorption rate, internal quantum efficiency, external quantum efficiency, CIEx and CIEy when excited with near-ultraviolet light having a wavelength of 405 nm of this phosphor are 56.4%, 69.5%, 39.2%, and 0.304, respectively. 0.655 and 45.1%, 68.4%, 30.9%, 0.314, and 0.650 when excited with blue light having a wavelength of 455 nm. Compared to Example 1, the amount of Eu dissolved in β-sialon was small, and the external absorption efficiency was low, so the external quantum efficiency was low.

[Examples 2 to 4, Comparative Examples 2 to 4]
Except that the mixing ratio of the silicon powder and the aluminum nitride powder, the purity of the raw silicon powder, and the silicon nitride synthesis temperature are as shown in Table 1, synthesis of the silicon nitride powder and β The type sialon was fired and post-treated (heat treatment and acid treatment) to obtain a β-type sialon phosphor. In Example 3 and Comparative Example 2, aluminum oxide powder was also added to adjust the oxygen content of the β-type sialon crystal.

Table 1 shows the β ratio calculated by XRD of the silicon nitride powder, the amount of metal silicon, the Al content and the first transition metal content determined by ICP. “Table 2” shows the lattice constant, composition, impurity content and particle size distribution of the obtained β-sialon phosphor, and “Table 3” shows the emission characteristics.

Comparing Examples 1 to 3 and Comparative Example 2, as the amount of Al in the silicon nitride raw material powder increases, the lattice constant c of the β-type sialon phosphor increases, and the fluorescence spectrum broadens as shown in FIG. It was found that the chromaticity shifts to the red side.

As shown in Comparative Example 3, when a raw material powder with a large amount of first transition metal impurities is used, or when a silicon nitride raw material with a large amount of metal silicon is used as in Comparative Example 4, acid treatment, etc. It has been found that even when the high purity treatment is performed, the first transition metal impurities and metal silicon remain in the phosphor to some extent, and the light emission characteristics are deteriorated.

As shown in “Table 1”, the crystal phase of the obtained phosphor was only a β-type sialon phase except that a slight amount of metallic silicon was detected in Comparative Example 4 as a result of XRD measurement.

The β-type sialon phosphor of the present invention is excited at a wide wavelength range from ultraviolet to blue light, and exhibits high luminance and narrow band green light emission. Therefore, as a phosphor of a white LED using blue or ultraviolet light as a light source. It can be used suitably, and can be used suitably especially for an image display apparatus.

Furthermore, since the phosphor of the present invention has little decrease in luminance at high temperatures and is excellent in heat resistance and moisture resistance, when applied to the above-mentioned image display device field, the luminance and luminescent color with respect to changes in the use environment temperature. It exhibits small characteristics and excellent long-term stability.

Furthermore, the method for producing a phosphor of the present invention is very useful industrially because it can stably provide the phosphor having the above characteristics.

Claims (8)

1. A β-type sialon phosphor having a β-type sialon represented by the general formula Si _6-z Al _z O _z N _8-z as a base material and Eu ²⁺ as a luminescence center in a solid solution,
   The β-type sialon crystal has a lattice constant a of 0.7605 to 0.7610 nm, a lattice constant c of 0.2906 to 0.2911 nm, an Eu content of 0.4 to 2 mass%, and a first transition metal content of Β-type sialon phosphor of 5 ppm or less.
2. By irradiating the excitation source, it has an emission peak wavelength in the wavelength range of 520 to 540 nm, and its chromaticity is CIExy chromaticity coordinates, 0.28 ≦ x ≦ 0.33, 0.62 ≦ y ≦ 0.67. The β-sialon phosphor according to claim 1, wherein
3. 3. The integrated volume fraction 90% diameter (D90) in a particle size distribution measured by a laser diffraction scattering method is 10 to 50 μm, and the 10% diameter (D10) is 2 μm or more. (Beta) sialon fluorescent substance in any one of these.
4. A method for producing a β sialon phosphor in which a β-type sialon represented by the general formula Si _6-z Al _z O _z N _8-z is used as a base material, and Eu ²⁺ is solid-solved as an emission center,
   A firing step of firing a raw material mixed powder containing silicon nitride powder containing Al and an inorganic compound containing Eu in a nitrogen atmosphere at a temperature range of 1850 to 2050 ° C .;
   A heat treatment step of holding at 1300 to 1500 ° C. for 1 to 100 hours in a rare gas atmosphere;
   And an acid treatment step of immersing in a mixed acid of hydrofluoric acid and nitric acid at 60 ° C. or higher for 0.5 hour or longer. A method for producing a β-type sialon phosphor.
5. The β-type according to claim 4, wherein the silicon nitride powder is a silicon nitride powder having a first transition metal content of 10 ppm or less synthesized by a metal silicon nitriding method and containing 0.1 to 2% by mass of Al. A method for producing a sialon phosphor.
6. 6. The method for producing a β-type sialon phosphor according to claim 4, wherein the silicon nitride powder has a β ratio of 50% or more and a metal silicon content of 10% by mass or less.
7. 4. A light emitting device having an LED having a maximum emission wavelength intensity of 240 to 480 nm and the β-sialon phosphor according to claim 1 laminated on a light emitting surface of the LED.
8. A light-emitting device comprising: the light-emitting element according to claim 7; and a power source for supplying electricity to the light-emitting element.

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