JP2010241995A - beta-TYPE SIALON PHOSPHOR, METHOD FOR PRODUCING THE SAME AND APPLICATION OF THE SAME - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a phosphor usable for various light emitting devices such as a white light emitting diode (white LED) using a blue light emitting diode (blue LED) or ultraviolet light emitting diode (ultraviolet LED), and a light emitting device using the same. <P>SOLUTION: In the β-type sialon phosphor, a base material is a β-type sialon expressed by general formula: Si<SB>6-z</SB>Al<SB>Z</SB>O<SB>Z</SB>N<SB>8-Z</SB>, which forms a solid solution with Eu2+ as a light emitting center. In the β-type sialon phosphor, the lattice constant (a) of β-type sialon crystal is 0.7605-0.7610 nm and the lattice constant (c) is 0.2906-0.2911 nm, the content of Eu is 0.4-2 mass% and the content of the first transition metal is ≤5 ppm. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

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, as phosphors, those using silicate, phosphate, aluminate, and sulfide as a base material and using a transition metal or a rare earth metal as an emission center are widely known.

With the increase in output of white LEDs, demands for the 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.

Recently, phosphors having a strong covalent bond as a nitride or oxynitride base material have attracted attention as phosphors that have a small decrease in luminance due to temperature rise and are excellent in durability.

A typical example of the nitride or oxynitride phosphor is sialon which is a solid solution of silicon nitride. 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, β-type sialon has also been found to exhibit fluorescence characteristics by adding Mn, Ce, and Eu as emission centers (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, the solid solution range is very wide, and the molar ratio of (Si, Al) / (N, O) needs to be maintained at 3/4. In general, β-sialon can be obtained by heating by adding silicon oxide and aluminum nitride or adding aluminum oxide and aluminum nitride in addition to silicon 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 Pamphlet International Publication No. 2007/066673 Pamphlet

The conventional Eu-activated β-sialon phosphor has a trade-off relationship between the fluorescence emission efficiency and the spectrum width, and a white LED using the phosphor cannot obtain sufficient luminance when narrowed. When the luminous efficiency is increased, the color reproduction range is narrowed, and it is difficult to put it to practical use in applications such as a backlight light source of a liquid crystal display.

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

The phosphor of the present invention contains Eu ²⁺ as a luminescent center in a base crystal of a β-type sialon represented by the general formula: Si _6-z Al _z O _z N _8-z . 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 properties of β-sialon, the present inventor has not only determined the z-value from the crystal lattice size of β-sialon, but also the amount of Eu ²⁺ solid solution in the crystal. I found that I could estimate the size. 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.

Specifically, the present invention is as follows.
The invention according to claim 1 is a β-type sialon phosphor in which a β-type sialon represented by the general formula: Si _6-z Al _z O _z N _8-z is a base material, and Eu ²⁺ is solid-solved as an emission center. 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% by mass, and a first transition metal. It is a β-type sialon phosphor having a content of 5 ppm or less.

This β-sialon phosphor has an emission peak wavelength in a 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 is preferable.

In this β-type sialon phosphor, the cumulative volume fraction 90% diameter (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. It is preferable that

Another invention is a method for manufacturing a β-type sialon phosphor, which includes a β-type sialon represented by a general formula: Si _6-z Al _z O _z N _8-z as a base material, and an emission center. As a method for producing a β sialon phosphor in which Eu ²⁺ is dissolved, a raw material mixed powder containing silicon nitride powder containing Al and an inorganic compound containing Eu is heated to a temperature of 1850 to 2050 ° C. in a nitrogen atmosphere. A baking step for baking in a range, a heat treatment step for holding 1300 to 1500 ° C. for 1 to 100 hours in a rare gas atmosphere after the baking step, and 0.5 hours in a mixed acid of hydrofluoric acid and nitric acid at 60 ° C. or higher This is a method for producing a β-type sialon phosphor having an acid treatment step soaked.

In this production method, it is preferable that the content of the first transition metal obtained by synthesizing the silicon nitride powder by the metal silicon nitriding method is 10 ppm or less and that Al is contained in an amount of 0.1 to 2 wt%. .

In this production method, the silicon nitride powder preferably has a β ratio of 50% or more and a metal silicon content of 10% by mass or less.

Another invention is a light emitting device having an LED having a maximum emission wavelength intensity of 240 to 480 nm and the β-sialon phosphor described above stacked on the light emitting surface of the LED.

Another invention is a light emitting device having the light emitting element and a power source for supplying electricity to the light emitting element.

The phosphor of the present invention is excited in a wide wavelength range from ultraviolet to visible light, emits green light in a narrow band with high fluorescence emission efficiency, and is excellent as a green phosphor. This phosphor has little change in luminance with respect to changes in the usage environment, and can be used for various light emitting elements, particularly white LEDs using ultraviolet LEDs and blue LEDs as light sources, alone or in combination with other phosphors.

The figure which shows the fluorescence spectrum by the external excitation light of wavelength 455nm in Examples 1-3 and the comparative example 2.

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

β-sialon is synthesized by firing a mixture of silicon, aluminum nitride and oxide raw material powder at a high temperature. However, the obtained β-sialon is not a complete single phase, but inevitably forms a Si—Al—O—N glass phase, and in some cases, a heterogeneous phase such as 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 study results of the present inventors investigated the relationship between the lattice constant of the Eu ²⁺ solute contents and the β-sialon crystal, when z value is constant, the Eu ²⁺ is dissolved in β-sialon crystal, a-axis length It was found that only the c-axis length increased and the c-axis length hardly changed. This is presumed to be because Eu ²⁺ penetrates and dissolves in a large tunnel-like void in the c-axis direction existing in the β-type 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, it is preferable that the lattice constant c of the β-type sialon crystal is 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. When the lattice constant c exceeds 0.2911 nm, the true z value of the β-type sialon crystal increases. Since the fluorescence spectrum becomes broad, it 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 c is a lattice constant. a is preferably in the range of 0.7605 to 0.7610 nm. In order to realize this, the Eu content contained in the phosphor is preferably 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 a wavelength range of 520 to 540 nm by irradiating 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, when used as a powder, the 90% diameter (D90) in the volume-based integrated fraction is preferably 10 to 50 μm in the particle size distribution measured by the laser diffraction scattering method. In the phosphor of the present invention, the larger the primary particles, the higher the fluorescence intensity. Therefore, D90 is preferably 50 μm or more. By adjusting D90 to 50 μm or less, uniform mixing into the resin for sealing the LED is easy. In addition, the cause of the chromaticity variation of the LED and the color unevenness of the irradiated surface can be reduced, which is preferable.

Further, the phosphor of the present invention preferably has a 10% diameter (D10) of 2 μm or more. Particles of several μm or less have low crystallinity and not only low emission intensity of the phosphor itself, but also close to the wavelength of visible light, so an LED is assembled using a phosphor with a small content of such small particles. This is because it is possible to suppress light from being strongly scattered in the layer containing the phosphor, and to improve the light emission efficiency (light extraction efficiency) of the LED.

Next, a manufacturing method for obtaining the phosphor of the present invention will be described.

In the manufacturing method of the β-sialon phosphor manufacturing method which is another invention, it is preferable to use silicon nitride powder containing Al corresponding to the z value of β-sialon crystal synthesized by metal silicon nitriding. 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, but is not necessarily fine in the phosphor application of the present invention. There is no need, and the average particle diameter may be about 5 to 100 μm. Rather, 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. The Al content in the silicon nitride powder of the present invention is preferably 0.5 to 2% by mass in order to make the finally obtained β sialon lattice constant within the above range.

In the silicon nitride powder of the present invention, 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. About heating temperature, the range of 1850-2050 degreeC is preferable. 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 a 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.

As a specific processing example, a synthetic product is subjected to a sieve classification process 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 is used to remove the composite. 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. According to the inventor's study, the heat treatment of the phosphor is performed in order to further destabilize the low crystalline portion in the phosphor, and the atmosphere containing the constituent elements nitrogen and oxygen as little as possible is present. Effective and a noble 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 performed by heating at 60 ° C. or more for 5 minutes or more with a mixture of hydrofluoric acid and nitric acid is effective and preferable.

The β-sialon phosphor of the present invention is used in a light-emitting device composed of a light-emitting light source and a phosphor, and in particular by irradiating ultraviolet light or visible light containing a wavelength of 240 to 480 nm as an excitation source, Since the green band-emission light is emitted, white light can be easily obtained by combining an ultraviolet LED or a blue LED with a red phosphor and / or a blue phosphor as necessary.

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

Another light-emitting device according to the present invention includes at least one light-emitting light source and a phosphor mainly composed of the β-sialon according to the present invention. For example, an LED can be manufactured using a known method described in JP-A-5-152609, JP-A-7-99345, Japanese Patent No. 2927279, and the like. In this case, the light-emitting light source is preferably an ultraviolet LED or a blue LED that emits light having a wavelength of 240 to 480 nm, particularly preferably a blue LED that emits 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, such as CaAlSiN ₃ : Eu, to achieve color reproducibility. 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 when Examples 1 to 3 and Comparative Example 2 have an excitation wavelength of 455 nm.

<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 used for mixing, 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 (made by Denki Kagaku Kogyo Co., Ltd., “N-1” grade) with a lid of 60 mm in diameter and 30 mm in height, 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 heating in the heat treatment was from room temperature to 1200 ° C. at 20 ° C./min and from 1200 to 1500 ° C. at 0.5 ° C./min.

The obtained product was agglomerated, 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 spectrometer (CIROS-120, manufactured by Rigaku Corporation). went. The Al content of this powder was 0.52% by mass, and the first transition metal content was 8 ppm.

<Synthesis and evaluation of β-type sialon phosphor>
The Al-containing silicon nitride powder 98.03% by mass and Europium oxide powder (RU grade) 1.97% by mass produced 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, and β-type A raw material mixed powder for sialon phosphor was obtained. This raw material mixed powder is filled into a cylindrical boron nitride container with a lid of diameter 60 mm × height 30 mm (manufactured by Denki Kagaku Kogyo Co., Ltd., “N-1” grade) 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 of diameter 60 mm × height 30 mm (manufactured by Denki Kagaku Kogyo Co., Ltd., “N-1” grade), and in an atmospheric pressure argon atmosphere in an electric furnace of a carbon heater, 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 XRD measurement of this phosphor, the crystal phase was a β-type sialon single phase. The lattice constants of β-sialon were a = 0.7608 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) in the volume-based integrated fraction ) 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 in Appendix 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, the phosphor sample was irradiated, and the 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, an excitation wavelength of 405 nm and 455 nm, an XYZ table defined in JIS Z 8701 by a method according to JIS Z 8724 from data in the wavelength range of 415 to 780 nm and 465 to 780 nm, respectively. 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.

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 part, and the spectrum of 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 465 when the excitation light is 455 nm. Calculation was performed in the range of 800 nm. The external quantum efficiency (= Qem / Qex × 100), the absorption rate (= (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., phosphor of Example 1 and Si: Al The mixture was made to have the same Eu ratio, and β-sialon was synthesized by the same method 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 the case of Comparative 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 measuring the particle size distribution on this phosphor, the 10% diameter (D10) and the 90% diameter (D90) of the volume-based integrated fraction were 4.3 μm and 43.3 μm, respectively.

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 silicon powder and aluminum nitride powder, the purity of raw silicon powder, and the synthesis temperature of silicon nitride were as shown in Table 1, synthesis of silicon nitride powder and β-sialon were carried out in the same manner as in Example 1. Was fired and post-treated (heat treatment and acid treatment) to obtain a β-type sialon phosphor. In Examples 3 and 4 and Comparative Example 3, aluminum oxide powder was also added to adjust the amount of oxygen in β-sialon crystals.

Table 1 shows the β ratio calculated by XRD of 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 excitation wavelength.

Comparing Examples 1 to 3 and Comparative Example 3, 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 4, 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 5, 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-sialon phase except that a slight amount of metal 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 in the industry because the phosphor having the above characteristics can be stably provided.

Claims (8)

A β-type sialon represented by the general formula: Si _6-z Al _z O _z N _8-z is a base material, and is a β-type sialon phosphor in which Eu ²⁺ is solid-solved as an emission center, Β having 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 or less. Type sialon phosphor. 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. An integrated volume fraction 90% diameter (D90) in a particle size distribution measured by a laser diffraction scattering method is 10 to 50 μm, and a 10% diameter (D10) is 2 μm or more. (Beta) sialon fluorescent substance in any one of these. A β type sialon represented by the general formula: Si _6-z Al _z O _z N _8-z is a base material, and is a method for producing a β sialon phosphor in which Eu ²⁺ is solid-solved as an emission center, and contains Al. A raw material mixed powder containing silicon nitride powder and Eu-containing inorganic compound in a nitrogen atmosphere at a temperature range of 1850 to 2050 ° C., and after the baking step, in a rare gas atmosphere at 1300 to 1500 ° C. A method for producing a β-type sialon phosphor having 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 hours or longer. The β-type sialon fluorescence 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 wt% of Al. Body manufacturing method. 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. The light emitting element which has (beta) type | mold sialon fluorescent substance described in any one of Claims 1 thru | or 3 laminated | stacked on LED which has the maximum intensity | strength of light emission wavelength in 240-480 nm, and the light emission surface of LED. 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.