JP6970658B2 - Fluorescent material, light emitting element and light emitting device - Google Patents

Description

The present invention relates to a fluorescent substance. The present invention also relates to a light emitting device including a phosphor. Further, the present invention relates to a light emitting device including a light emitting element.

Conventionally, as a phosphor emitting orange light, the general _{formula: Ca x Eu y Si 12- (} m + n) Al (m + n) is represented by O _n N _16-n, to stabilize the crystal structure ^{A Ca-α-sialon fluorescent substance using Ca 2+} as a metal ion is known, and high luminous efficiency is obtained (see Patent Document 1). In the ^{light emitting device provided with the α-sialon phosphor using Ca 2+} , there was no problem that the luminous efficiency of the light emitting device was lowered when used for a long time.

On the other hand, in recent years, improvement of brightness and shortening of wavelength of fluorescence spectrum have been studied, and ^{Li-α sialone phosphors using Li +} as metal ions for stabilizing the crystal structure have been proposed (Patent Documents 2 to 2). 4). As a result, the brightness of the light-emitting device was improved and the wavelength was shortened by providing the Li-α-sialon phosphor as compared with the light-emitting device using the Ca-α-sialon phosphor. There was a new problem that the light emission efficiency of the light emitting device was lowered due to the deterioration of the resin which is the encapsulant of the LED package, which is considered to be caused by the ionization of the impurity element contained in the phosphor (see Patent Document 5). ..

On the other hand, in Patent Documents 6 to 7, the CASN-based fluorophore, which is an oxynitride-based phosphor similar to α-sialon, which is a kind of red-emitting phosphor, has a halogen element that is not an element constituting the crystal phase. It is also known that elements other than the elements constituting the crystal phase do not necessarily have an adverse effect, as it has been reported that high emission efficiency can be obtained.

Japanese Unexamined Patent Publication No. 2002-363554 International Publication No. 2007/004493 International Publication No. 2010/018873 Japanese Unexamined Patent Publication No. 2010-202738 Japanese Unexamined Patent Publication No. 2009-224754 Japanese Unexamined Patent Publication No. 2010-18771 Special Table 2012-512307 Gazette

As described above, although various studies have been made to improve the characteristics of the Li-α sialone-based phosphor, there is still room for improvement in the decrease in luminous efficiency due to long-term use. An object of the present invention is to provide a light emitting device having high fluorescence intensity and little decrease in luminous efficiency even after long-term use, and a phosphor for that purpose.

In one aspect, the present invention is an Eu-activated Li-α sialone-based phosphor, which has an F content of 20% by mass or less and a total content of P and Na of 10% by mass or less, and is a total crystal. It is a phosphor in which the ratio of α-sialon crystals to the phase is 95% by mass or more.

In one embodiment of the phosphor according to the present invention, the total content of P and Na is 5 mass ppm or less.

In another embodiment of the phosphor according to the present invention, the Li content is 1.8% by mass or more and 3% by mass or less.

In still another embodiment of the phosphor according to the present invention, the Eu content is 0.1% by mass or more and 1.5% by mass or less.

In still another embodiment of the phosphor according to the present invention, the O content is 0.4% by mass or more and 1.3% by mass or less.

In still another embodiment of the phosphor according to the present invention, the average primary particle size is 7 μm or more and 35 μm or less.

In another aspect, the present invention is a light emitting element having a phosphor according to the present invention and a light emitting light source for irradiating the phosphor with excitation light.

In one embodiment of the light emitting device according to the present invention, the light emitting light source is a light emitting diode or a laser diode.

In another embodiment of the light emitting device according to the present invention, the luminous flux retention rate is 95% or more when left at a temperature of 85 ° C. and a relative humidity of 85% and left at 150 mA for 1000 hours.

In yet another aspect, the present invention is a light emitting device including a light emitting element according to the present invention.

In the present invention, the content of F, Na and P in the Eu-activated Li-α-sialone-based phosphor is reduced while increasing the ratio of α-sialon crystals to the total crystal phase. By using the phosphor according to the present invention, it is possible to obtain a light emitting device having high fluorescence intensity and little decrease in luminous efficiency even after long-term use.

In one aspect, the present invention relates to an EU-activated Li-α sialone-based fluorophore. The Eu-activated Li-α sialone-based phosphor is generally expressed by the following equation: Li _x Eu _y Si _{12- (m + n)} Al _{m + n On} N _16-n (x + y ≦ 2, m = x + 2y). It is a fluorescent substance having a compound. In the phosphor, a part of the Si—N bond of the α-silicon nitride crystal is replaced with the Al—N bond and the Al—O bond, and Li and Eu invade the voids in the crystal so as to maintain the electrical neutrality. It is a solid solution, and the m value and n value correspond to the substitution rates for Al—N bond and Al—O bond, respectively.

^{The reason why Li +} is used in the present invention is not for the conventional purpose of shortening the wavelength, but for obtaining a higher fluorescence intensity than that of ^{Ca 2+.} The solid solution composition range of α-type sialon is limited not only by the number of solid solution sites of the stabilized cation described above, but also by the thermodynamic stability according to the stabilized cation. In ^{the case of Li +} , the range of m value that can maintain the α-type sialon structure is 0.5 or more and 2 or less, and the range of n value is 0 or more and 0.5 or less. If the Li content in the phosphor of the present invention is too small, the progress of grain growth in the phosphor firing step tends to be very slow, and it tends to be difficult to obtain large particles having high fluorescence intensity. If the Li content is too large, LiSi ₂ N ₃ It is preferable that it is 1.8% by mass or more and 3% by mass or less because it tends to generate another phase such as. The Li content can be adjusted by blending the raw materials of the phosphor. Specifically, it is adjusted by increasing or decreasing the blending ratio of lithium nitride or lithium oxide as a Li-containing raw material.

Eu content in the phosphor of the present invention is too small tends to fluorescence intensity is low contribution is decreased to emission, fluorescence intensity due to concentration quenching of fluorescence by energy transfer between too much and Eu ²⁺ Since it tends to be low, it is preferably 0.1% by mass or more and 1.5% by mass or less. The Eu content can be adjusted by blending the raw materials of the phosphor. Specifically, it is adjusted by increasing or decreasing the blending ratio of europium oxide and europium nitride, which are raw materials containing Eu.

The oxygen (O) content in the phosphor of the present invention is preferably 0.4% by mass or more and 1.3% by mass or less. This is because a fluorescent substance having an excessively low oxygen content has little growth of crystal grains in the manufacturing process and a high fluorescence intensity cannot be obtained. If the oxygen content is too high, the fluorescence spectrum becomes broadened, which is sufficient. This is because the fluorescence intensity cannot be obtained.

In order to obtain a phosphor having a small decrease in luminous efficiency even after long-term use, the content of F among the impurity elements of the phosphor is preferably 20% by mass or less, preferably 10% by mass or less. It is more preferably 5 mass ppm or less, and it can be, for example, 1 to 20 mass ppm. As will be described later, it is effective to acid-treat the fluorophore in order to increase the proportion of α-sialon crystals in the fluorophore to improve the light emission characteristics, but F is an element that is easily mixed during the acid treatment. It is difficult to sufficiently improve the light emitting characteristics only by the acid treatment, and it is important to remove F after the acid treatment in order to obtain excellent maintenance of the luminous efficiency.

Further, in order to suppress the decrease in luminous efficiency of the light emitting device provided with the phosphor and to reduce the occurrence of electrical defects even after long-term use, it is desirable to further control the total contents of P and Na. .. Specifically, the total content of P and Na is preferably 10 mass ppm or less, more preferably 5 mass ppm or less, still more preferably 2 mass ppm or less, for example, 1 to 5 It can be mass ppm. As will be described later, in order to increase the proportion of α-sialon crystals in the phosphor and improve the emission characteristics, it is effective to remove the fine powder of the phosphor by classification. For the classification, a wet classification using sodium hexametaphosphate as a dispersant can be adopted, but in this method, P and Na are easily mixed. Therefore, in this case, it is difficult to sufficiently improve the light emission characteristics only by classification, and it is important to remove Na and P after the classification in order to obtain excellent maintenance of luminous efficiency. In the classification step, in order to further control the P content and Na content and reduce the burden on the cleaning step after the classification step, wet classification using an alkaline solvent may be adopted, or dry classification may be used. ..

In the phosphor of the present invention, for the purpose of finely adjusting the fluorescence characteristics, a part of Li of the general formula is selected from the group consisting of Mg, Ca, Y and lanthanide elements (excluding La, Ce and Eu). It may be substituted with one or more substitution elements while maintaining electrical neutrality. Therefore, in one embodiment of the Eu-activated Li-α sialone-based phosphor, Li is partially substituted with one or more of such substitution elements.

As long as the fluorescence characteristics are not affected, the phosphor of the present invention uses not only α-sialon single phase but also crystal phases such as silicon nitride, aluminum nitride, silicon nitride lithium and their solid solutions as the crystal phase existing in the phosphor. It is also possible to include it. However, in general, the proportion of α-sialon in the phosphor is preferably 95% by mass or more, more preferably 97% by mass or more, still more preferably 98% by mass or more, for example, 95 to 99% by mass. can.

If the average primary particle size of the phosphor of the present invention is too small, the fluorescence intensity tends to be low, and if it is too large, the chromaticity of the emission color when the phosphor is mounted on the light emitting surface of the LED may vary or emit light. Since color unevenness tends to occur, it is preferably 7 μm or more and 35 μm or less. The average primary particle diameter here refers to the volume-based median diameter (D50) by the laser diffraction / scattering method.

The phosphor according to the present invention can be produced by going through a raw material mixing step, a firing step, an acid treatment step and a washing step. After the acid treatment step, the classification step is preferably carried out before, after, or both before and after the washing step, and more preferably, the classification step is carried out before or both before and after the washing step.

First, raw materials for phosphors other than lithium nitride powder such as silicon nitride powder, aluminum nitride powder, and europium oxide are mixed in a desired ratio. The mixing is preferably carried out by wet mixing in consideration of industrial productivity. After wet mixing, the solvent is removed, dried and crushed to obtain a premixed powder. This premixed powder is mixed with lithium nitride powder in a desired ratio to obtain a raw material mixed powder. Mixing is preferably performed in a nitrogen atmosphere or the like in order to suppress hydrolysis.

By firing the raw material mixed powder, it is possible to obtain Eu-activated Li-α sialon. The crucible used for firing is preferably made of a material that is stable in a high temperature atmosphere, and is preferably made of boron nitride, carbon, or a refractory metal such as molybdenum or tantalum. The firing atmosphere is not particularly limited, but is usually carried out in an inert gas atmosphere or a reducing atmosphere. Only one type of inert gas or reducing gas may be used, or two or more types may be used in any combination and ratio. Examples of the inert gas or reducing gas include hydrogen, nitrogen, argon, ammonia and the like, and among these, it is preferable to use a nitrogen atmosphere. The pressure of the firing atmosphere is selected according to the firing temperature. The higher the atmospheric pressure, the higher the decomposition temperature of the phosphor, but in consideration of industrial productivity, it is preferable to carry out the process under a pressure of about 0.02 to 1.0 MPa with a gauge pressure. If the calcination temperature is lower than 1650 ° C., crystal defects and unreacted residual amount of the mother crystal increase, and if it exceeds 1900 ° C., the mother body is decomposed, which is not preferable. Therefore, the firing temperature is preferably 1650 to 1900 ° C. If the calcination time is short, there are many crystal defects and unreacted residual amount of the mother crystal, and if the calcination time is long, it is not preferable in consideration of industrial productivity. Therefore, it is preferably 2 to 24 hours. The obtained Eu-activated Li-α sialon may be classified into a desired particle size, if necessary.

Since the Eu-activated Li-α sialon obtained by calcination generally has a low crystal ratio of α sialon, it is difficult to exhibit excellent fluorescence intensity. Therefore, it is preferable to increase the crystal ratio of α-sialon by acid treatment with a mixed solution of hydrofluoric acid and nitric acid.

As described above, if the particle size of the phosphor is too small, the fluorescence intensity tends to be low. Therefore, in order to obtain a high-luminance phosphor, it is necessary to carry out a classification step for removing fine powder after the acid treatment step. preferable. The classification step may be either wet or dry, but the phosphor is placed in a mixed solvent of ion-exchanged water and sodium hexametaphosphate as a dispersant, or in a mixed basic solvent of ion-exchanged water and aqueous ammonia. The elutriation classification that stands still or the dry classification is preferable.

The crystal ratio of α-sialon can be increased by undergoing acid treatment and classification steps, but if acid treatment with a mixed solution of hydrofluoric acid and nitric acid or elutriation classification treatment with sodium hexametaphosphate is performed, F, Impurities such as Na and P adhere to the phosphor, and on the contrary, they become impurities and cause a decrease in light emission efficiency after long-term use. Therefore, after performing acid treatment or elutriation classification treatment, it is effective to remove impurities by dispersing and washing the phosphor with an ultrasonic homogenizer in a solvent such as ion-exchanged water.

In another aspect, the present invention is a light emitting device having a light emitting light source and a fluorescent substance, and the fluorescent substance is the above-mentioned fluorescent substance. As the light emitting light source, a monochromatic LED or LD having a peak intensity of emission wavelength of 240 nm or more and 480 nm or less is preferable. Monochromatic light with a peak wavelength of 240 nm or more and 480 nm or less is the wavelength range of blue LEDs most often used in actual use, and Li-α sialon has high fluorescence intensity when excited at a wavelength in this range. This is because it emits light.

In one embodiment, the light emitting device according to the present invention can have a luminous flux retention rate of 95% or more when left at 150 mA for 1000 hours under the conditions of a temperature of 85 ° C. and a relative humidity of 85%, which is preferable. Can be 97% or more, more preferably 98% or more, for example 95 to 99%.

In yet another aspect, the present invention is a light emitting device including this light emitting element. Examples of the light emitting device include an information display device used outdoors such as a signal and an outdoor display device, and a lighting device that replaces an automobile headlight, an incandescent lamp, and a fluorescent lamp.

The light emitting device including the phosphor and the LED according to the present invention can be manufactured, for example, as follows. First, the fluorophore according to the present invention is mixed with a sealing material to prepare a slurry. For example, the slurry can be prepared by mixing at a ratio of 30 to 50 parts by mass with respect to 100 parts by mass of the encapsulant. Examples of the sealing material include thermoplastic resins, thermosetting resins, photocurable resins and the like. Specifically, for example, a methacrylic resin such as methyl polymethacrylic acid; a styrene resin such as polystyrene and a styrene-acrylonitrile copolymer; a polycarbonate resin; a polyester resin; a phenoxy resin; a butyral resin; a polyvinyl alcohol; an ethyl cellulose and a cellulose acetate. , Cellulose-based resin such as cellulose acetate butyrate; epoxy resin; phenol resin; silicone resin and the like. Further, an inorganic material such as a solution obtained by hydrolyzing and polymerizing a solution containing a metal alkoxide, a ceramic precursor polymer or a metal alkoxide by a sol-gel method, or an inorganic material obtained by solidifying a combination thereof, for example, a siloxane bond can be obtained. It is also possible to use an inorganic material having. Further, if the sealing portion can be externally attached without directly touching the LED chip (for example, an external cap, a dome-shaped sealing portion, etc.), molten glass can also be used. As the encapsulant, one type may be used, or two or more types may be used in any combination and ratio.

Among the encapsulants, it is preferable to use a resin having thermosetting property and fluidity at room temperature for the reason of dispersibility and moldability. As the resin having thermosetting property and fluidity at room temperature, for example, a silicone resin is used. For example, manufactured by Toray Dow Corning Co., Ltd., trade names: JCR6175, OE6631, OE6635, OE6636, OE6650 and the like can be mentioned.

Next, 3 to 4 μL of the above slurry is injected into a top view type package on which a blue LED chip having a peak wavelength of 460 nm is mounted. The top view type package infused with this slurry is heated at a temperature in the range of 140 to 160 ° C. for 2 to 2.5 hours to cure the slurry. In this way, it is possible to manufacture a light emitting device that absorbs light having a wavelength in the range of 420 to 480 nm and emits light having a wavelength exceeding 480 nm and 800 nm or less.

Examples of the present invention will be described with reference to the table while comparing with the comparative examples.

<Example 1 (reference example) >
The method for producing the fluorescent substance of Example 1 will be described. The phosphor was produced by going through a raw material mixing step and a firing step.

(Mixing process)
The raw materials for the phosphor of Example 1 are Si ₃ N ₄ (E10 grade manufactured by Ube Industries, Ltd.), AlN (F grade manufactured by Tokuyama Corporation), Eu ₂ O ₃ (RU grade manufactured by Shin-Etsu Chemical Co., Ltd.), and Li ₃ N powder. (Purity 99.5% by mass manufactured by Matterion, -60 mesh). These raw materials were _{weighed so as to have a mol ratio of Si 3} N ₄ : AlN: Eu ₂ O ₃ = 84.5: 14.8: 0.64 and mixed to obtain a premixed powder.

The ratio of the number of moles of the premixed powder to the premixed powder under a nitrogen atmosphere ( _{total number of moles of Si 3} N ₄ , Al N, and Eu ₂ O ₃ ): the _{number of moles of Li 3} N = 94.1: 5.9. The mixture was mixed so as to obtain a mixed raw material powder.

(Baking process)
The raw material mixed powder is filled in a boron nitride crucible in a glove box, and fired in a pressurized nitrogen atmosphere with a gauge pressure of 0.8 MPa at 1800 ° C. for 8 hours in an electric furnace of a carbon heater to activate Eu. Li-α sialon was obtained.

This EU-activated Li-α sialon was pulverized by a dry crusher using a roll mill and a jet mill, and classified into those which were pressed against a sieve having a mesh size of 45 μm and passed through.

(Acid treatment process)
The EU-activated Li-α sialon after classification was acid-treated with a mixed solution of hydrofluoric acid and nitric acid (80 ° C.).

(Washing process)
Impurities were removed by mixing the phosphor after the acid treatment step in a solvent such as ion-exchanged water and dispersing it with an ultrasonic homogenizer for 5 minutes. Then, suction filtration was performed.

<Example 2>
In Example 2, the following steps were added before the washing step in the manufacturing method of Example 1.

(Wet classification process)
The fluorescent substance after the acid treatment step was allowed to stand in a mixed solvent of ion-exchanged water and sodium hexametaphosphate as a dispersant for 10 minutes to remove fine powder. By the above steps, the fluorescent substance of Example 2 was produced.

<Example 3>
Example 3 is a phosphor produced under the same conditions as in Example 2 except that it was dispersed for 1 hour during the washing step with an ultrasonic homogenizer by the production method of Example 2.
<Example 4>
Example 4 is a phosphor produced under the same conditions as in Example 2 except that it was dispersed for 2 hours during the washing step with an ultrasonic homogenizer by the production method of Example 2.
<Example 5>
In Example 5, the phosphor after the acid treatment step in the production method of Example 2 is washed with a mixed solvent of ion-exchanged water and sodium hexametaphosphate as a dispersant, and then the ion-exchanged water and ammonia water are mixed. The phosphor was prepared under the same conditions as in Example 2 except that the washing treatment was changed to a basic solvent.
<Example 6>
Example 6 is a fluorescent substance produced under the same conditions as in Example 5 except that the washing step was performed before the wet classification step in the production method of Example 5.

<Comparative example 1>
Comparative Example 1 was manufactured by the same manufacturing method except that the acid treatment step and the cleaning step were omitted in the manufacturing step of Example 1.

<Comparative Example 2>
Comparative Example 2 was manufactured by the same manufacturing method except that the cleaning step was omitted in the manufacturing step of Example 1.

<Comparative Example 3>
Comparative Example 3 was manufactured by the same manufacturing method except that the acid treatment step and the cleaning step were omitted in the manufacturing step of Example 2.

<Comparative Example 4>
Comparative Example 4 was manufactured by the same manufacturing method except that the cleaning step was omitted in the manufacturing process of Example 2.

<Comparative Example 5>
Comparative Example 5 was manufactured by the same manufacturing method except that the acid treatment step was omitted in the manufacturing method of Example 2.

<Comparative Example 6>
Comparative Example 6 was manufactured by the same manufacturing method except that the cleaning step was omitted in the manufacturing method of Example 5.

<Comparative Example 7>
The difference between Comparative Example 7 and Comparative Example 4 is that a Ca-α-sialon-based phosphor was produced by using calcium nitride powder (Ca ₃ N _{2 ) as a raw material for lithium nitride (Li 3 N).} The premixed powder ratio was a molar ratio of silicon nitride powder: aluminum nitride powder: europium oxide powder = 71.6: 25.8: 2.6 (molar ratio). This premixed powder was placed in a glove box under a nitrogen atmosphere and mixed with calcium nitride powder to obtain a raw material mixed powder. The mixing ratio was the number of moles of the premixed powder ( _{total number of moles of Si 3} N ₄ , Al N, and Eu ₂ O ₃ ): the number of moles of the calcium nitride powder = 87.1: 12.9.

(Light emitting element manufacturing process)
Each of the phosphors according to the examples and comparative examples after the cleaning step is mixed at a ratio of 30 parts by mass with 100 parts by mass of a silicone resin (manufactured by Toray Dow Corning Co., Ltd., trade name: JCR6175, etc.) to form a slurry. Was adjusted. Then, 3 to 4 μL of the above slurry was injected into a top view type package on which a blue LED chip having a peak wavelength of 460 nm was mounted. The top view type package in which the slurry was injected was heated at 150 ° C. for 2 hours to cure the slurry, and a light emitting device was manufactured.

Table 1 shows the evaluation of each fluorescent substance according to Examples and Comparative Examples. Table 1 shows the impurity content (unit: mass ppm), median diameter (unit: μm), ratio of α-sialon crystals to the total crystal phase (unit: mass%), and peak wavelength (unit: mass%) for Examples and Comparative Examples. nm), fluorescence intensity (unit:%), and luminous flux retention rate (unit:%) of the LED are shown.

(Identification of crystal phase and ratio of α-sialon crystals to total crystal phase)
For each of the phosphors according to the examples and comparative examples, the crystal phase was identified by powder X-ray diffraction (XRD) using CuKα ray using an X-ray diffractometer (Ultima IV manufactured by Rigaku Co., Ltd.). The X-ray diffraction patterns of the phosphors obtained in Examples 1 to 6 and Comparative Examples 1 to 6 showed the same diffraction pattern as the α-sialon crystal, and it was confirmed that the main crystal phase was α-sialon. .. Further, the mass ratio of the α-sialon crystal to the total crystal phase was calculated based on the diffraction pattern of the α-sialon and the diffraction pattern of the impurity crystal phase. On the other hand, the diffraction pattern of α-sialon was also observed in Comparative Example 7, and it was confirmed that the main crystal phase was α-sialon.

(Impurity content)
The contents of phosphorus, sodium and fluorine were analyzed by an ICP emission spectrophotometer (CIROS-120, manufactured by Rigaku Co., Ltd.) after eluting 0.5 g of a phosphor / 25 ml of water at 100 ° C. for 12 hours and filtering. ..

(Mesian diameter (D50))
The median diameter (D50) (average primary particle diameter) of each of the phosphors according to the examples and comparative examples was measured as follows. First, a mixture of hydrofluoric acid (concentration of 46 to 48 g / 100 ml) and nitric acid (concentration of 60 g / 100 ml) at a ratio of 1: 1 was diluted 4-fold with distilled water to prepare a treatment liquid. This treatment liquid was heated to 80 ° C., and while stirring, the fluorescent substance of Example or Comparative Example was added in an amount of 20 g or less to 100 ml of the treatment liquid and dispersed. The fluorophore was allowed to stand for 1 hour after dispersion, and the insoluble powder was recovered by decantation. The recovered insoluble powder was washed with water and dried. For the insoluble powder after drying, the particle size distribution was measured with a laser diffraction / scattering type particle size distribution measuring device (LS 13 320 manufactured by Beckman Coulter Co., Ltd.), and the cumulative 50% of the volume-based particle size was set to the median size (D50). And said.

(Chemical composition)
Further, as a result of analyzing the fluorescent substance by the ICP emission spectroscopic analyzer (CIROS-120, manufactured by Rigaku Co., Ltd.), the Li content of the fluorescent substance of Example 1 and Comparative Example 6 was 1.8% by mass or more 3 The Eu content was in the range of 0.1% by mass or more and 1.5% by mass or less, and the O content was in the range of 0.4% by mass or more and 1.3% by mass or less. ..

(Peak wavelength)
Fluorescence measurements were performed on each of the phosphors according to the examples and comparative examples using a spectrofluorescence meter (F-7000, manufactured by Hitachi High-Technologies Corporation) corrected by Rhodamine B and a substandard light source. The solid sample holder attached to the photometer was used for the measurement, and the fluorescence spectrum and the peak wavelength at the excitation wavelength of 455 nm were measured.

(Fluorescence intensity)
The fluorescence intensity was calculated from the product of the fluorescence spectrum intensity and the CIE standard luminosity. The unit is arbitrary because it changes depending on the measuring device and conditions, and the comparison was made relative to each other in the examples and comparative examples measured under the same conditions. As a reference, the fluorescence intensity of Example 4 was set to 100%. 85% or more is a passing value.

(Luminous flux retention rate of light emitting element (durability evaluation of light emitting element))
Next, the change in luminous flux was measured for the light emitting device provided with the phosphor particles according to the examples and the comparative examples. To measure the change in luminous flux, the light emitting element is left at a temperature of 85 ° C. and a high temperature and high humidity of 85% relative humidity at 150 mA for a predetermined time, and then a total luminous flux measurement system (Half Moon: HH41-0773 manufactured by Otsuka Electronics Co., Ltd.). Using -1), the change in luminous flux of the fluorescence emitted from the light emitting element was measured. It should be noted that this shows the ratio of the luminous flux value for each energization time when the ratio immediately after the start of energization is 100% as the luminous flux retention rate, and is preferably 95% or more after 1000 hours have elapsed.

From Table 1, the Li-α sialone-based phosphors of Examples 1 to 6 had a lower impurity content and a higher proportion of α-sialon crystals as compared with Comparative Examples. As a result, a high fluorescence intensity can be obtained, the luminous efficiency does not decrease even after long-term use, and the light emitting device has few electrical defects. Since the light emitting element using the phosphor according to Examples 1 to 6 has a very small amount of the impurity element contained in the phosphor, it suppresses the occurrence of curing inhibition of the resin due to the impurity element of the phosphor. Therefore, the possibility of causing an electrical abnormality such as a short circuit is extremely small, and the life is long.

On the other hand, in Comparative Example 1, although the contents of fluorine, sodium and phosphorus were small, the proportion of α-sialon crystals was low, so that the fluorescence intensity was low. In Comparative Example 2, the sodium and phosphorus contents were low, but the fluorine content was high and the luminous flux retention rate was low. In Comparative Example 3, the fluorine content was low, but the sodium and phosphorus contents were high, the luminous flux retention rate was low, and the proportion of α-sialon crystals was also low. In Comparative Example 4, the luminous flux retention rate was low because the contents of phosphorus, sodium, and fluorine were high. In Comparative Example 5, the contents of phosphorus, sodium, and fluorine were low, but the proportion of α-sialon crystals was low. Therefore, the luminous flux retention rate is lower than that of the invention example. In Comparative Example 6, the sodium and phosphorus contents were low, but the fluorine content was high, and the luminous flux retention rate was low. Therefore, the luminous flux retention rate is lower than that of the invention example. In Comparative Example 7, the luminous flux retention rate was high despite the high contents of fluorine, sodium and phosphorus. That is, the presence of the impurity element does not necessarily have an adverse effect, and the deterioration of the characteristics due to the presence of the impurity element is peculiar to the Li-α sialone-based phosphor.

Claims (10)

An Eu-activated Li-α sialon-based phosphor having an F content of 1 mass ppm or more and 20 mass ppm or less, and a total content of P and Na of 1 mass ppm or more and 10 mass ppm or less. A phosphor in which the ratio of α-sialon crystals to the crystal phase is 97% by mass or more and 99% by mass or less. The fluorescent substance according to claim 1, wherein the total content of P and Na is 5 mass ppm or less. The fluorescent substance according to claim 1 or 2, wherein the Li content is 1.8% by mass or more and 3% by mass or less. The fluorescent substance according to any one of claims 1 to 3, wherein the Eu content is 0.1% by mass or more and 1.5% by mass or less. The fluorescent substance according to any one of claims 1 to 4, wherein the O content is 0.4% by mass or more and 1.3% by mass or less. The fluorescent substance according to any one of claims 1 to 5, wherein the average primary particle size is 7 μm or more and 35 μm or less. A light emitting device having the phosphor according to any one of claims 1 to 6 and a light emitting light source for irradiating the phosphor with excitation light. The light emitting element according to claim 7, wherein the light emitting light source is a light emitting diode or a laser diode. The light emitting device according to claim 7 or 8, wherein the luminous flux retention rate is 95% or more when the light flux is left at 150 mA for 1000 hours under the conditions of a temperature of 85 ° C. and a relative humidity of 85%. A light emitting device including the light emitting element according to any one of claims 7 to 9.