JP2014197635A - LIGHT-EMITTING DEVICE AND β-SIALON PHOSPHOR USED FOR THE SAME - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a β-type sialon phosphor which is suitable for an LED and has high luminance, and to provide a light-emitting device using the same.SOLUTION: The light-emitting device comprises: a first phosphor which emits light in a blue or violet wavelength region; and a phosphor which absorbs at least part of light emitted from the first phosphor, converts its wavelength, and emits light. As the phosphor, a β-sialon phosphor whose surface is coated with a metal hydroxide is contained.

Description

  The present invention relates to a light emitting device using blue or purple as an excitation source and a phosphor having a β silicon nitride type structure used therefor. More specifically, the luminance of the powder is high, and the luminous efficiency when used as an LED is disclosed. The present invention relates to a β sialon phosphor capable of improving the brightness and a light emitting device using the same.

Recently, as phosphors having a small luminance drop due to temperature rise and excellent durability, attention has been paid to nitride and oxynitride phosphors having a stable crystal structure.
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. A β-sialon activated with a specific rare earth element is known to have useful fluorescence characteristics, and its application to a white LED or the like is being studied.

According to Patent Document 1, it has a specific range of electron spin density, is represented by the general formula Si _6-x Al _x O _x N _8-x (z is 0 to 4.2), and contains β-type containing Eu. A phosphor mainly composed of sialon is excited in a wide wavelength range from ultraviolet light to visible light, and emits green light having a main wavelength within a range of 520 nm to 550 nm with high efficiency. It is disclosed that it is excellent. It is also disclosed that this phosphor can be suitably used for various light emitting elements, particularly white LEDs using ultraviolet LEDs or blue LEDs as a light source, alone or in combination with other phosphors.

  Patent Document 1 also discloses a first step of generating Eu-containing β-type sialon and the obtained Eu-containing β-type sialon in a nitrogen atmosphere, vacuum, or a gas other than nitrogen as a main component. And a second step of reducing the crystal defect density by performing heat treatment at each optimum temperature and time in an inert atmosphere, and further performing acid treatment in some cases. The effect of this second step is to reduce the number of unpaired electrons and improve the luminous efficiency by, for example, decomposing unstable nitride or oxynitride phase with high crystal defect concentration. It is described.

On the other hand, various studies have been made in the past to coat the surface of a phosphor with a specific substance. For example, by coating the surface of the phosphor particles with a metal oxide or the like, the color shift of the luminescent color over time, the effect of suppressing the decrease in the luminous flux maintenance factor, the moisture proof effect, and the oxide etc. through the heat softening binder To improve phosphor film-forming properties by surface modification by adhering to the surface of phosphor particles, to improve anti-oxidation degradation by coating with phosphate compounds, and to coat phosphor with silica By doing so, the life deterioration is suppressed. However, in these prior art documents, coating the surface of the phosphor is chemical and physical by improving the change over time of the phosphor, such as deterioration and color shift, and modifying the surface of the phosphor. Emphasis is placed on improving chromaticity unevenness and luminance variation by changing the affinity, and there are few examples of studying improvement of the luminance of the phosphor by covering the surface of the phosphor. In particular, regarding nitride phosphors, Patent Document 2-4 discloses an example in which an oxide coating is provided on the surface of an α-sialon phosphor to improve light extraction efficiency. Patent Document 5 describes Lu3Al5O12. : Ce, BN / CaAlSiN3: An example in which a coating of oxide, pyrophosphate, etc. is provided on the surface of Eu phosphor. Patent Document 6 discloses that the surface of β sialon phosphor is coated with aluminum oxide and yttrium oxide by sol-gel method. A technique for improving the luminance of a phosphor by providing a magnesium oxide film is described.

  However, Patent Document 6 describes the theory, but does not show a result of actually improving luminance and the like using a phosphor. Moreover, until now, coating of hydroxide on the surface has not been carried out in practice. This is because water adsorbed on the surface of the phosphor has relatively high mobility and there is a concern that it may adversely affect the device. Generally, hydroxide is similar to oxide and is recognized as hydrated oxide. In many cases, it is difficult to select a hydroxide coating as a phosphor coating, and it will adversely affect the lifetime characteristics of the device. Consideration has been made that it does not exist on the body surface.

WO2008 / 062781 International Publication Pamphlet JP 2006-265506 A JP 2007-126536 A JP 2009-293035 A JP 2008-41796 A JP 2007-324475 A

  The β-sialon phosphor described in Patent Document 1 has little change in luminance and chromaticity over time and is suitable for use in a light-emitting device, but consumes less energy if it is brighter or the same brightness. Therefore, further improvement in luminance has been demanded in practical use.

  Therefore, as a result of intensive studies, the present inventors have also improved the β-type sialon phosphor itself. However, the brightness of the phosphor itself is improved by modifying the surface of the phosphor, and the excitation light from the LED Considering what kind of characteristics are necessary in order to be more efficient when the LED is used and extracted from the light conversion member, it has been hesitantly put into practical use as described above. Even in the case of a hydroxide coat, the hydroxyl group of the hydroxide, particularly the hydroxyl group on the surface of the nitride, forms a network with each other through hydrogen bonds, so that it does not easily desorb and move as water, adversely affecting the life characteristics. The present invention has been found.

That is, the gist of the present invention resides in the following (1) to (5).
(1) A first light emitter that emits light in a blue or violet wavelength range and a phosphor that absorbs at least a part of the light emitted from the first light emitter and converts the wavelength to emit light. In the light emitting device, the phosphor includes a β sialon phosphor whose surface is coated with a metal hydroxide.
(2) The light emitting device according to (1), wherein the phosphor has at least a β sialon phosphor and a phosphor having a peak between 580 nm and 660 nm, and the light emitting device emits white light.
(3) The phosphor having a peak between 580 nm and 660 nm is (Sr, Ca) AlSiN _3.
: The light emitting device according to (2), including Eu.
(4) The light emitting device according to any one of (1) to (3), wherein the light emitting device includes a blue (430-500 nm) phosphor.
(5) The light emitting device according to any one of (1) to (4), wherein the metal hydroxide is a metal hydroxide selected from at least La, Y, Zn, and Al.
(6) A β-sialon phosphor characterized in that the surface is coated with a metal hydroxide.

  The phosphor of the present invention has high brightness as a powder, and when used as a light-emitting device, it can have higher luminous efficiency than a light-emitting device using a conventional β-sialon phosphor. Therefore, by using the β sialon of the present invention, a light emitting device having high luminous efficiency can be realized.

FIG. 1 is an SEM photograph of the surface of the β sialon phosphor obtained in Example 1 of the present invention. FIG. 2 is an SEM photograph of the surface of the β sialon phosphor obtained in the comparative example of the present invention. FIG. 3 is a diagram showing an example of a typical structure of the light emitting device of the present invention.

Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and various modifications can be made within the scope of the gist of the present invention.
The light-emitting device of the present invention absorbs at least a part of light emitted from the first light-emitting body that emits light in the blue or violet wavelength range, and converts the wavelength to emit light. And a β-sialon phosphor having a surface coated with a metal hydroxide. The light-emitting device of the present invention can be used without any problem as long as it has any of the above-described features, even if it has any known shape.

The first light emitter used in the light emitting device of the present invention emits light in the blue or violet wavelength range. The first light emitter may be a semiconductor light emitting device, but may be a phosphor having a light emission peak wavelength of blue (about 420 to 480 nm), and in that case, ultraviolet light (380 nm or less) or purple light (light emission peak). It is only necessary to excite and emit light at a wavelength of 380 to 420 nm.
In the light emitting device of the present invention, the light of the first light emitter is used to excite the β sialon phosphor whose surface is coated with a metal hydroxide. At this time, other green phosphors can be used in combination depending on the emission spectrum of the desired light emitting device, but preferably 50% by weight or more, more preferably 75% by weight or more of the phosphor having a green emission peak. Is a β sialon phosphor. The β sialon phosphor whose surface is coated with the metal hydroxide will be described in detail separately.

More preferably, the light-emitting device of the present invention has a phosphor having a peak between 580 nm and 660 nm, and the light-emitting device emits white light by mixing these colors.
As the phosphor having a peak between 580 nm and 660 nm, various known phosphors can be used. Preferably, (Sr, Ca) ₂ Si ₅ N ₈ : Eu, (Sr, Ca) AlSi ₄ N _{7 is used.} :
Eu, α sialon phosphor, (La, Y) ₃ Si ₆ N ₁₁ : Ce phosphor, (Sr, Ca) AlSiN ₃ : Eu phosphor and the like can be preferably used, and most preferably, when the temperature rises This is a (Sr, Ca) AlSiN ₃ : Eu phosphor that produces a color shift in a direction that cancels the color shift direction of the β sialon phosphor of FIG.

In the light emitting element of the present invention, these light emitters or phosphors may be used as light emitting devices in various known forms.
An example of a typical structure is shown in FIG. The β sialon phosphor 2 coated with the metal hydroxide of the present invention on the first light emitter or the semiconductor light emitting device 1 for exciting the first light emitter, and other fluorescence if necessary The body 3 is arranged and sealed with the resin 4. Of course, the phosphors are not uniformly mixed in this way, but each phosphor is kneaded into a resin and molded into a laminate or a film as necessary on the semiconductor light emitting element 1 or the like. It may be placed.

Next, the β sialon phosphor having a surface coated with a metal hydroxide will be described.
There are mainly five reasons why the brightness of the β-sialon phosphor whose surface is coated with a metal hydroxide is increased.
When the surface of the phosphor is coated with a metal hydroxide, first, the surface of the phosphor becomes uneven, reflection of excitation light on the outer surface of the phosphor is suppressed, and the absorption rate of the phosphor is improved. It is considered that reflection of light converted by the phosphor on the surface of the phosphor is suppressed, light extraction efficiency is improved, and luminance is increased.

Second, since the refractive index of the metal hydroxide is different from the refractive index of the phosphor, the light extraction efficiency is increased.
Thirdly, since the material to be coated is a metal hydroxide, the surface is networked by strong hydrogen bonds, the lattice defects on the phosphor surface are repaired, and the luminance is improved. That is, the phosphor surface forms a dead layer with low luminous efficiency due to cracks and defects caused by physical stress in the dispersion process in addition to surface defects generated during firing.

In the dead layer, the light emission efficiency is lowered due to energy loss due to vibration in a state where the bond is broken.
Since hydroxide forms a strong network by hydrogen bonding, it is considered that suppressing this vibration suppresses a decrease in luminous efficiency and improves luminance.
In addition, the hydroxide that forms a strong network maintains its effect without the coating being peeled off in the resin or binder, and has no side effects such as an increase in viscosity due to the peeled surface coating.

Fourth, when the primary particles of the phosphor are aggregated to form secondary particles, light loss occurs at the primary particle interface, but coating the metal hydroxide improves the dispersibility of the phosphor and improves the particle interface. Can reduce light loss.
Fifth, covering the phosphor surface also improves deterioration and chromaticity change (color shift).

[Phosphor production method]
In the method for producing a β sialon phosphor used in the light emitting device of the present invention, a known method for producing a β sialon phosphor such as raw materials, firing conditions, washing, and classification may be used. The general formula of β sialon phosphor is represented by the following general formula.
_{S i6-x Al x O x} N 8-x: Eu y ··· [1]
(In the formula, x and y represent numbers satisfying 0 ≦ x ≦ 4.2 and 0.001 ≦ y ≦ 0.03, respectively.)

(Phosphor raw material)
As the phosphor raw material used in the method for producing the phosphor of the present invention, known materials can be used, for example, silicon nitride (Si ₃ N ₄ ), aluminum nitride (AlN), and silicon oxide (SiO ₂ ). And / or aluminum oxide (Al ₂ O ₃ ) and further Eu-containing compounds such as Eu metals, oxides, carbonates, chlorides, fluorides, nitrides or oxynitrides. Needless to say, β sialon or β sialon phosphor itself may be used as a raw material.

(Mixing process)
In the production method of the present invention, the phosphor raw materials are usually weighed so as to obtain the target composition and sufficiently mixed using a ball mill or the like to obtain a phosphor raw material mixture (mixing step).
Although it does not specifically limit as said mixing method, Specifically, the method of following (A) and (B) is mentioned.

(A) Dry pulverizer such as hammer mill, roll mill, ball mill, jet mill, etc., or pulverization using mortar and pestle, and mixer such as ribbon blender, V-type blender, Henschel mixer, or mortar and pestle And a dry mixing method in which the above phosphor raw materials are pulverized and mixed.
(B) A solvent or dispersion medium such as water is added to the phosphor material described above, and mixed using, for example, a pulverizer, a mortar and a pestle, or an evaporating dish and a stirring rod, to obtain a solution or slurry. A wet mixing method in which drying is performed by spray drying, heat drying, or natural drying.

  The mixing of the phosphor raw material may be either the wet mixing method or the dry mixing method, but in order to avoid contamination of the phosphor raw material with moisture, a dry mixing method or a wet mixing method using a water-insoluble solvent is more preferable. .

(Baking process)
Since the firing temperature varies depending on the desired phosphor composition, it cannot be generally specified, but in general, the phosphor can be stably obtained in a temperature range of 1800 ° C. or higher and 2200 ° C. or lower. A preferable firing temperature is preferably 1820 ° C. or higher, particularly preferably 1900 ° C. or higher, 2150 ° C. or lower is preferable, and 2100 ° C. or lower is particularly preferable.

The firing atmosphere in the firing step is arbitrary as long as the phosphor of the present invention is obtained, but is usually a nitrogen-containing atmosphere. Specific examples include a nitrogen atmosphere and a hydrogen-containing nitrogen atmosphere, and a nitrogen atmosphere is particularly preferable.
The oxygen content in the firing atmosphere is usually 10 ppm or less, preferably 5 ppm or less.

The rate of temperature increase is usually 2 ° C./min or more, preferably 3 ° C./min or more, and usually 20 ° C./min or less, preferably 15 ° C./min or less. If the rate of temperature rise is below this range, the firing time may be long. In addition, if the rate of temperature rise exceeds this range, the firing device, container, etc. may be damaged.
The firing time varies depending on the temperature, pressure and the like during firing, but is usually 10 minutes or longer, preferably 1 hour or longer, and usually 48 hours or shorter, preferably 36 hours or shorter, particularly preferably 24 hours or shorter.

The pressure during firing varies depending on the firing temperature and the like, but is usually 0.1 MPa or more, preferably 0.5 MPa or more, and the upper limit is usually 2 MPa or less, preferably 1.5 MPa or less. Of these, about 0.6 MPa to 1.2 MPa is industrially preferable in terms of cost and labor.
The obtained fired product is granular or massive. This is pulverized, pulverized and / or classified into a powder of a predetermined size.

(Heat treatment process)
It is preferable to heat-treat the phosphor obtained in the firing step at a temperature lower than the firing temperature (heat treatment step). This is to thermally decompose the impurity phase of oxynitride or the unstable oxynitride phase.
An appropriate heat treatment temperature varies depending on the atmosphere and the like, but a temperature range of 1200 ° C. or higher and 1550 ° C. or lower is preferable. The decomposition of the impurity phase tends to proceed at 1200 ° C. or higher, and the rapid decomposition of β-sialon can be suppressed at 1550 ° C. or lower.

Examples of the heat treatment atmosphere include a nitrogen atmosphere, a hydrogen-containing nitrogen atmosphere, an argon atmosphere, a hydrogen-containing argon atmosphere, and a vacuum atmosphere, and an argon atmosphere is preferable.
The pressure during the heat treatment varies depending on the heat treatment temperature and the like, but is usually 0.05 MPa or more, preferably 0.09 MPa or more, and the upper limit is usually 1 MPa or less, preferably 0.5 MPa or less. Of these, about 0.09 MPa to 0.3 MPa is industrially preferable in terms of cost and labor.

The heat treatment time varies depending on the temperature and pressure during the heat treatment, but is usually 10 minutes or longer, preferably 1 hour or longer, and usually 48 hours or shorter, preferably 24 hours or shorter.
In the production method of the present invention, it is more effective to perform the heat treatment after adjusting the fired product to a predetermined particle size. This is because even when the particle size adjustment is performed after the first firing with a small amount of the activator, the flux effect by the activator element is stronger than assumed at the second firing, and when the deviation from the target particle size occurs, This is because pulverization or the like may be necessary. In such a case, not only crystal defects formed during firing, but also crystal defects formed during pulverization and pulverization required for particle size adjustment can be removed.

(Washing process)
In general, β-type sialon phosphors tend to generate Si metal on the phosphor surface by thermal decomposition in a firing step or a heat treatment step. In order to improve the characteristics of the phosphor, it is necessary to remove this Si metal as much as possible. In the present invention, the cleaning method is not particularly limited as long as impurities can be removed. For example, cleaning can be performed using hydrofluoric acid and nitric acid. However, in consideration of safety, environmental load, and the like, (i) a solid at 20 ° C. and a solubility at 20 ° C. of 0.1. Using an aqueous solution A of fluoride of 01 g / water 100 ml or more and 400 g / water 100 ml or less, and (ii) an aqueous solution B containing at least one selected from the group consisting of nitric acid, sulfuric acid, hydrochloric acid, oxalic acid, and phosphoric acid To wash.

  In other words, hydrofluoric acid and nitric acid have been conventionally used as components of the mixed acid used in the cleaning process. However, in order to reduce the amount of hydrofluoric acid that is an acutely toxic substance, for example, sodium fluoride (melting point: A stable solid at 993 ° C.) and nitric acid. Thereby, impurities including the Si metal can be removed safely and efficiently, and the yield in the cleaning process can be improved, thereby improving industrial convenience. Compared with hydrofluoric acid, the aqueous solution A is safer for the human body, less burdens on the environment, and is easy to handle in work processes such as storage and transportation.

The solubility of the fluoride used in the aqueous solution A at 20 ° C. is usually 0.01 g / water 100 ml or more, preferably 0.1 g / water 100 ml or more, more preferably 0.5 g / water 100 ml or more, Usually, it is 400 g / 100 ml or less of water, preferably 100 g / 100 ml or less of water. Since it is solid at normal temperature, it is easy to handle and work and can be manufactured safely. Further, the aqueous solution A containing such a fluoride is corrosive with respect to impurities such as Si and SiO ₂ , so that these compounds can be removed by itself, but impurities such as Si and SiO ₂ are When coated with an impurity phase of nitride, it tends to be difficult to remove with the aqueous solution A alone, so at least one selected from the group consisting of nitric acid, sulfuric acid, hydrochloric acid, oxalic acid, and phosphoric acid By using together the aqueous solution B containing oxynitride, the impurity phase of oxynitride can be removed, and impurities such as Si and SiO ₂ can be efficiently removed.

Specific examples of the fluoride include LiF, NaF, KF, RbF, CsF, NH ₄ F, NaHF ₂ , KHF ₂ , RbHF ₂ , NH ₅ F ₂ , AlF ₃ , ZnF ₂ .4H ₂ O, ZrF. ₄ , Na ₂ TiF ₆ , K ₂ TiF ₆ , (NH ₄ ) ₂ TiF ₆ , Na ₂ SiF ₆ , K ₂ SiF ₆ , ZnSiF ₆ · 6H ₂ O, MgSiF ₆ · 6H ₂ O, Na ₂ ZrF ₆ , K ₂ ZrF ₆ , (NH ₄ ) ₂ ZrF ₆ , KBF ₄ , NH ₄ BF ₄ , Mg (BF ₄ ) ₂ .6H ₂ O, KPF ₆ , K ₃ AlF ₆ , Na ₃ AlF ₆ , SrF _2, etc. . Among those exemplified, NaF is preferable because of its moderately high solubility and low deliquescence.

The acid that can be used as the aqueous solution B is an inorganic acid other than hydrofluoric acid, and specifically, at least one selected from the group consisting of nitric acid, sulfuric acid, hydrochloric acid, oxalic acid, and phosphoric acid. (Hereinafter, these acids are referred to as “inorganic acids of aqueous solution B”). Of these, nitric acid is preferred because of its high oxidizing power.
The concentration of the inorganic acid in the aqueous solution B is generally 10% by weight or more, preferably 15% by weight or more, more preferably 20% by weight or more, and usually 70% by weight based on the total amount of the aqueous solution A and the aqueous solution B. % Or less. If the concentration of the inorganic acid in the aqueous solution B with respect to the total amount of the aqueous solution A and the aqueous solution B falls within the above range, the concentration of the inorganic acid in the aqueous solution B in the aqueous solution B is not particularly limited, and for example, dilute nitric acid or concentrated nitric acid is used. be able to.

As a combination of the aqueous solution A and the aqueous solution B, a combination of NaF and nitric acid is preferable. The dissolution treatment with these mixed aqueous solutions is preferable because Si can be quickly removed to improve the characteristics of the phosphor and workability and industrial convenience can be improved while reducing the environmental burden.
In the cleaning step of the present invention, the phosphor obtained in the firing step is immersed in a mixed solution of the aqueous solution A and the aqueous solution B. At this time, the mixing method is not particularly limited as long as the aqueous solution A and the aqueous solution B can be combined, and the aqueous solution B may be added to the aqueous solution A or the aqueous solution B.

Here, while it is immersed, it may be allowed to stand, but from the viewpoint of work efficiency, it is preferable to stir to such an extent that the cleaning time can be shortened. Moreover, although it normally works at room temperature, you may heat aqueous solution as needed.
The time for immersing the phosphor in the mixed solution of the aqueous solution A and the aqueous solution B varies depending on the stirring conditions and the like, but is usually 1 hour or more, preferably 2 hours or more, and usually 24 hours or less, preferably 12 Below time.

In the washing step, it is preferable to perform general water washing and filtration after the operation of immersing the phosphor in the mixed solution of the aqueous solution A and the aqueous solution B. As the cleaning medium in the water washing, water at room temperature (about 25 ° C.) is usually used, but it may be heated as necessary.
It is preferable to perform the water washing of the phosphor described above until the electrical conductivity of the supernatant liquid at the time becomes a predetermined value or less by performing the following water dispersion test on the washed phosphor. That is, the washed phosphor is pulverized or pulverized with a dry ball mill or the like, if necessary, and classified with a sieve or a water tank to adjust the particle size to a desired weight median diameter. Then, the phosphor particles having a specific gravity heavier than that of water are naturally precipitated by stirring and dispersing in water 10 times as much as the phosphor for a predetermined time, for example, 10 minutes, and then allowing to stand for 1 hour. The electrical conductivity of the supernatant liquid at this time is measured, and the above-described washing operation is performed as necessary until the electrical conductivity is usually 100 μS / cm or less, preferably 50 μS / cm or less, and most preferably 10 μS / cm or less. repeat.

  The water used for the water dispersion test of the phosphor is not particularly limited, but desalted water or distilled water is preferable in the same manner as the cleaning medium water, and the electrical conductivity is usually 0.01 μS / cm or more, preferably Is 0.1 μS / m or more, usually 10 μS / cm or less, preferably 1 μS / cm or less. The temperature of the water used for the water dispersion test of the phosphor is usually room temperature (about 25 ° C.).

The phosphor obtained by performing such washing has an electrical conductivity of usually 10 μS / cm or less of the supernatant obtained by dispersing the phosphor in water 10 times by weight and allowing it to stand for 1 hour.
In addition, the measurement of the electrical conductivity of the supernatant liquid in the water dispersion test of the phosphor can be performed using, for example, an electrical conductivity meter “ES-12” manufactured by Horiba, Ltd.
Moreover, after the said washing | cleaning process, it is made to use after making a fluorescent substance dry until there is no adhesion water. Further, if necessary, dispersion / classification treatment may be performed to loosen the aggregation.

(Phosphor coating process)
A metal hydroxide is adhered to the surface of the phosphor particles thus obtained. The method of attaching is not particularly limited, but preferably, the β-sialon phosphor produced as described above and a predetermined amount of metal hydroxide fine powder are mixed in a solvent to form a phosphor slurry. It can be produced by thoroughly mixing the slurry, followed by dehydration and drying. As the solvent used at this time, water is preferably used for handling, but an alcohol such as ethanol or an organic solvent such as acetone may be used. In addition, a solution containing a metal ion sufficient to chemically react with a hydroxide ion to form a metal hydroxide in the slurry of the phosphor, or a desired metal compound in a predetermined amount of water Was added to the phosphor slurry and mixed thoroughly, and an alkaline aqueous solution containing hydroxide ions such as aqueous ammonia and sodium hydroxide was added to the phosphor slurry to increase the pH of the slurry. It can also be produced by depositing and adhering hydroxide to the phosphor surface.

The metal used for the metal hydroxide used in the coating of the phosphor of the present invention includes alkali metals such as Rb, Cs, and K, alkaline earth metals such as Ca, Sr, Mg, and Ba, and Al, Y, La, Zn and the like are preferable. Among these, at least one metal hydroxide selected from Al, Y, La, and Zn is particularly preferable.
Further, when a metal hydroxide fine powder is used, it is preferable that the particle size is a submicron size of 1 μm or less from the viewpoint of difficulty of peeling and easy uniform adhesion.
Specifically, the average particle diameter of the attached metal hydroxide is preferably 1/10 or less with respect to the average particle diameter of the phosphor, and the lower limit is in the range of 1/50 or more. preferable.
In order to obtain the adhesion effect, the amount of metal hydroxide adhered depends on the particle size of the phosphor, but it is preferably 0.05% by weight or more, preferably 10% by weight or more. And this is not preferable because the brightness of the phosphor tends to decrease.

[Use of phosphor]
The phosphor obtained by the present invention can be used for any application using the phosphor. Moreover, although the phosphor obtained by the present invention can be used alone as the phosphor obtained by the present invention, two or more kinds of phosphors obtained by the present invention are used in combination or obtained by the present invention. It is also possible to use a phosphor mixture of any combination, such as a combination of a phosphor and another phosphor.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited to a following example, unless the summary is exceeded.

[Example 1]
_{Si 6-x Al x O x} N 8-x: when the Eu _y, x = 0.198, so that y = 0.0185, manufactured by Ube Industries, Ltd. α-type silicon nitride powder ( "SN-E10" grade oxygen Content 1.2% by mass, β phase content 4.5% by mass, carbon content less than 0.2% by mass) 95.2% by mass, Tokuyama aluminum nitride powder (“E” grade, oxygen content 0) 0.9 mass%, carbon content 0.03 mass%) 3.61 mass%, Shin-Etsu Chemical Co., Ltd. Europium Oxide Powder ("RU" grade) 0.81 mass%, Admatech Silicon Oxide (SO-E5) 0.35 mass% was weighed, and the above-mentioned raw materials were mixed until they were sufficiently uniform to obtain a “raw material mixture”.

The obtained phosphor raw material mixture was filled in a boron nitride crucible having an outer diameter of 9 cm and a height of 10 cm, and fired by holding it at 2050 ° C. for 12 hours in an atmosphere of nitrogen pressure of 0.95 MPa. Was made. Next, the fired powder was heat treated by holding it at 1450 ° C. for 12 hours under an atmosphere of argon pressure of 0.205 MPa, passing a nylon mesh (N-No. 305T, opening 48 μm), Obtained.

The obtained heat-treated powder was washed and dried to obtain a phosphor having chromaticity (x, y) = (0.359, 0.622).
The obtained phosphor was used as a core phosphor, 10 g of this phosphor was put into 100 ml of pure water, 0.53 ml of a 1 mol / l lanthanum nitrate aqueous solution was further added, and the mixture was sufficiently stirred to prepare a core phosphor slurry. Prepared. Next, 0.28% by weight of ammonia water is added until the pH of the core phosphor slurry reaches 10, and a precipitate of lanthanum hydroxide is generated in the phosphor slurry, and the phosphor slurry is sufficiently stirred. Then, after filtration, washing with water and dehydration were performed to obtain a phosphor of Example 1 in which 1.0% by weight of lanthanum hydroxide adhered to the surface of the phosphor.

The phosphor of Example 1 exhibited chromaticity (x, y) = (0.360, 0.621). Further, the relative luminance of the phosphor of Example 1 calculated with the luminance of the phosphor of Comparative Example 1 as 100% was 104%, and the luminance was improved compared to before the lanthanum hydroxide was attached to the phosphor surface.

[Example 2]
Using the phosphor core used in Example 1, 0.5 wt% lanthanum hydroxide was added to the phosphor in the same manner as in Example 1 except that the amount of lanthanum nitrate added was changed to 0.26 ml. The phosphor of Example 2 adhered to the surface was obtained.

The phosphor of Example 2 exhibited chromaticity (x, y) = (0.360, 0.621). Further, the relative luminance of the phosphor of Example 1 calculated with the luminance of the phosphor of Comparative Example 1 as 100% was 103%, and the luminance was improved from before the lanthanum hydroxide was attached to the phosphor surface.

[Example 3]
The phosphor used in Example 1 was used as a core phosphor, 10 g of this phosphor was put into 100 ml of pure water, and 1.00 ml of a 1 mol / l zinc nitrate aqueous solution was further added, and the mixture was sufficiently stirred to obtain core fluorescence. A body slurry was prepared. Next, 0.28% by weight of ammonia water is added until the pH of the core phosphor slurry reaches 10, and a precipitate of zinc hydroxide is generated in the phosphor slurry, and the phosphor slurry is sufficiently stirred. Then, after filtration, washing with water and dehydration were performed to obtain a phosphor of Example 3 in which 1.0% by weight of zinc hydroxide adhered to the surface of the phosphor.

The phosphor of Example 3 exhibited chromaticity (x, y) = (0.359, 0.622). Moreover, the relative luminance of the phosphor of Example 1 calculated with the luminance of the phosphor of Comparative Example 1 as 100% was 102%, and the luminance was improved before zinc hydroxide was attached to the phosphor surface.

[Comparative Example 1]
The phosphor core of Example 1 before attaching the lanthanum hydroxide was used as the phosphor of Comparative Example 1. The phosphor of Comparative Example 1 exhibited chromaticity (x, y) = (0.359, 0.622), and was used for comparison of light emission luminance of the present invention.

  As described above, the β sialon phosphor whose surface is coated with a metal hydroxide has a significantly improved luminance, and by using it as a light emitting device, a brighter light emitting device can be obtained. it can.

  The light emitting device of the present invention can be used in any field where light is used because of the high brightness of the phosphor used. For example, in addition to indoor and outdoor lighting, cellular phones, household appliances, outdoor It can be suitably used for an image display device of various electronic devices such as an installation display.

1: First light emitter or semiconductor light emitting device for exciting the first light emitter 2: β-sialon phosphor coated with metal hydroxide 3: Other phosphor 4: Resin 5: Gold wire 6: Connection member
7: Case body 8: Case electrode 9: Case heat sink

Claims (6)

  In a light-emitting device including a first light emitter that emits light in a blue or violet wavelength region, and a phosphor that absorbs at least part of the light emitted from the first light emitter, converts the wavelength, and emits light A light-emitting device comprising a β-sialon phosphor whose surface is coated with a metal hydroxide as the phosphor.   2. The light emitting device according to claim 1, wherein the phosphor has at least a β sialon phosphor and a phosphor having a peak between 580 nm and 660 nm, and the light emitting device emits white light. As a phosphor having a peak between 580 nm and 660 nm, (Sr, Ca) AlSiN ₃
The light emitting device according to claim 2, comprising: Eu.   The light-emitting device according to claim 1, wherein the light-emitting device includes a blue (430-500 nm) phosphor.   5. The light emitting device according to claim 1, wherein the metal hydroxide is a metal hydroxide selected from at least La, Y, Zn, and Al. A β-sialon phosphor having a surface coated with a metal hydroxide.