JP5870655B2 - Nitride phosphor and manufacturing method thereof - Google Patents

Description

  The present invention relates to a nitride phosphor, and more particularly, to a phosphor having a higher luminance than conventional ones.

  In recent years, with the trend of energy saving, the demand for lighting and backlights using LEDs is increasing. The LED used here is a white light emitting LED in which a phosphor is arranged on an LED chip that emits light of blue or near ultraviolet wavelength. As such a type of white light emitting LED, a LED using a YAG (yttrium aluminum garnet) phosphor that emits yellow light using blue light from the blue LED chip as excitation light on a blue LED chip is often used. .

However, when YAG phosphors are used under high output, the brightness decreases as the temperature of the phosphors increases, so-called temperature quenching is large, and more excellent color reproduction range and color rendering are sought. (Normally, a range including about 350 to 420 nm of violet as a term for blue excitation is read as near ultraviolet rays), there is a problem that the luminance is remarkably lowered. In order to solve these problems, nitride phosphors that emit yellow light have been studied, and La ₃ Si ₆ N ₁₁ phosphors described in, for example, Patent Documents 1 and 2 (lanthanum other lanthanum) are considered as promising candidates. This type of phosphor is hereinafter collectively referred to as LSN phosphor, including the case where it is replaced with metal. Patent Document 1 describes in its [0248] paragraph and Patent Document 2 in its [0131] to [0136] paragraphs, a method for producing LSN phosphors using various fluxes. . The most preferred flux is described as magnesium fluoride.

International Publication No. 2008/132754 International Publication No. 2010/114061 Pamphlet

The LSN phosphors described in Patent Documents 1 and 2 have a small decrease in luminance even when the temperature is increased as compared with conventional YAG phosphors, and sufficient light emission can be obtained even when excited by near ultraviolet rays. .
However, phosphors are required to obtain higher luminance with less energy, and further improvement in luminance is required. That is, an object of the present invention is to provide a nitride phosphor having improved brightness compared to the conventional products.
Moreover, in the manufacture of the phosphor, in many cases, the characteristics of the phosphor tend to be improved by increasing the firing time. This is thought to be due to the improvement in crystallinity due to defects in the crystal that escape to the surface due to thermal motion, or atoms that have entered the wrong site in the crystal structure are replaced with the elements that should be. It is done. However, in the case of industrial production, it is necessary to mass-produce in as short a time as possible and to maintain high quality, and there is a demand for a production method with sufficiently high brightness even when firing in a short time. .

  As a result of intensive studies, the present inventors can obtain a phosphor with extremely high luminance when an LSN phosphor is manufactured using a flux containing rubidium (Rb), which is not usually used. I came up with it. Specifically, when an LSN phosphor is manufactured using a flux containing rubidium, it is manufactured using a flux containing the aforementioned magnesium fluoride, which is known to be suitable for manufacturing an LSN phosphor. It has been found that a phosphor having a luminance exceeding that of the LSN phosphor can be obtained in a relatively short time, and has reached the present invention.

The present inventors speculate that the use of this rubidium-containing flux results in a phosphor having a brightness superior to that of using a conventionally known magnesium fluoride or the like. doing.
Magnesium fluoride works very well as a flux but is not without side effects. Magnesium ions contained in magnesium fluoride are ions having an ionic radius smaller than that of the lanthanum ions constituting the matrix, so they are easily replaced with La constituting LSN, or enter the crystal lattices and remain as impurities. This causes the crystal lattice to be distorted, the crystallinity is lowered, and the non-radiation radiation is caused to lower the luminance of the phosphor. On the other hand, in the flux containing rubidium, rubidium ions are very large (the ionic radius of Shannon's 6-coordinated La ³⁺ is 117 pm, the ionic radius of Rb ⁺ is 166 pm). There are almost no side effects to reduce. This means that almost no rubidium is detected from an LSN phosphor obtained by firing with a flux containing Rb, even after the LSN phosphor is sufficiently washed and the phosphor is dissolved and subjected to elemental analysis. , Appearing briefly. In addition, since the rubidium compound has a relatively low melting point, it can be considered that the effect as a flux can be obtained from a low temperature. For example, taking fluoride as an example, the melting points of RbF = 775 ° C., MgF ₂ = 1250 ° C., LaF ₃ = 1493 ° C., LiF = 842 ° C. and Rb are significantly lower. When these are considered together, when a phosphor is produced using a compound containing rubidium as a flux, rubidium does not remain in the matrix and has a low melting point, and thus a phosphor with high brightness can be obtained in a short time. Conceivable.

The present invention is as follows.
[1] A raw material containing an element constituting the nitride phosphor represented by the following general formula (1) is prepared, and at least selected from the raw material, a rubidium halide, a carbonate, a nitrate, and a hydroxide A method for producing a nitride phosphor represented by the following general formula (1), wherein one kind of rubidium compound is mixed and the obtained mixture is fired.
Ln _x Si _y N _n : Z (1)
(In General Formula (1), Ln is a rare earth element excluding an element used as an activator, Z is an activator, x satisfies 2.7 ≦ x ≦ 3.3, and y is 5.4 ≦ y ≦ 6.6 is satisfied, and n is 1.
0 ≦ n ≦ 12 is satisfied. )
[2] The method for producing a nitride phosphor according to [1], wherein the rubidium compound includes at least one selected from rubidium fluoride, rubidium chloride, and rubidium carbonate.
[3] The amount of the rubidium compound used is a charge molar ratio of rubidium when the amount of silicon in the phosphor is 6 mol [1] or [2] A method for producing a nitride phosphor as described in 1. above .

  According to the present invention, a nitride phosphor with improved luminance can be provided. In addition, a method for manufacturing a nitride phosphor with improved luminance can be provided.

  Hereinafter, the present invention will be described with reference to embodiments and examples. However, the present invention is not limited to the following embodiments and examples, and may be arbitrarily modified without departing from the gist of the present invention. Can be implemented.

(Rubidium compound used in the present invention)
The phosphor production method of the present invention is characterized by using a compound containing rubidium. This rubidium-containing compound acts as a flux during phosphor production. As described above, when an LSN phosphor is manufactured using a flux containing rubidium, it is manufactured using a flux containing magnesium fluoride, which is known to be suitable for manufacturing an LSN phosphor. Compared with the LSN phosphor, a phosphor with higher luminance can be obtained. In addition, such a high-luminance phosphor can be obtained in a relatively short time.

Examples of the compound containing rubidium include rubidium fluoride such as rubidium fluoride, rubidium chloride, and rubidium bromide, rubidium carbonate, rubidium nitrate, rubidium hydroxide, halides, carbonates, nitrates, and hydroxides. It is preferable to include at least one selected from those, more preferably at least one of rubidium halide or rubidium carbonate, and most preferably selected from rubidium fluoride, rubidium chloride, and rubidium carbonate. Including at least one kind.
A combination of these fluxes can also be used. In that case, considering the melting point, the effect of the flux can be obtained continuously by using two or more types having different melting points.

The amount of use varies depending on the type of raw material, the material of the flux, etc., and is arbitrary. For example, it may be used within a range well known to those skilled in the art described in Patent Documents 1 and 2. In particular, in the case of the present invention, the amount of the rubidium compound used is preferably 0.1 or more and 2.0 or less in terms of the charged molar ratio of rubidium when the amount of silicon in the phosphor is 6 mol, Preferably, it is 0.1 or more and 0.8 or less.
If the amount of the compound containing rubidium is too small so that the molar ratio is less than 0.1, the effect of the present invention may not appear. If the amount of the compound containing rubidium is too large, the flux effect May be saturated, coarse crystals may be easily formed, or luminance may be reduced. In the first place, if a phosphor having the same characteristics can be obtained, a smaller flux is preferable in terms of cost and waste. In particular, when the anion paired with rubidium is halogen, if the amount of flux is too large, the firing furnace may be deteriorated.

  Furthermore, in the present invention, it is most preferable to use only a compound containing rubidium as a flux to be used, but other fluxes may be used in combination as long as the effect is not impaired. When a flux other than a compound containing rubidium is used in combination, the amount used is preferably less than that of a compound containing rubidium. Further, the flux other than the compound containing rubidium preferably has a lower melting point than the compound containing rubidium. This is because the flux acting on the high temperature side acts at a higher temperature during firing, so that it is considered that the amount of solid solution by substitution or penetration into the phosphor matrix is likely to increase.

(Flux that can be used in combination)
In the present invention, a flux that can be used in combination as a flux other than the compound containing rubidium is not particularly limited, but examples thereof include ammonium halides such as NH ₄ Cl and NH ₄ F · HF; Na ₂ CO ₃ , Li ₂ CO Alkali metal carbonates such as ₃ ; alkali metal halides such as LiCl, NaCl, KCl, CsCl, LiF, NaF, KF, and CsF; CaCl ₂ , BaCl ₂ , SrCl ₂ , CaF ₂ , BaF ₂ , SrF ₂ , MgCl ₂ Alkaline earth metal halides such as MgF ₂ ; alkaline earth metal oxides such as BaO; boron oxides such as B ₂ O ₃ , H ₃ BO ₃ , Na ₂ B ₄ O ₇ , boric acid and alkali metals or borate compound of an alkaline earth _{metal; Li 3 PO 4, NH 4} H 2 PO phosphate compounds such as _4; AlF ₃ halogenated such as aluminum Um; ZnCl _2, zinc halides, such as ZnF _2, zinc compounds such as zinc oxide; Periodic Table Group 15 element compound such as _{Bi 2 O 3; Li 3 N} , Ca 3 N 2, Sr 3 N 2, Ba 3 Examples thereof include alkali metals such as N ₂ and BN, alkaline earth metals, and nitrides of Group 13 elements.

Furthermore, as the flux, for example, halides of rare earth elements such as LaF ₃ , LaCl ₃ , GdF ₃ , GdCl ₃ , LuF ₃ , LuCl ₃ , YF ₃ , YCl ₃ , ScF ₃ , ScCl ₃ , La ₂ O ₃ , Gd Examples thereof include oxides of rare earth elements such as ₂ O ₃ , Lu ₂ O ₃ , Y ₂ O ₃ , and Sc ₂ O ₃ .
The flux is preferably a halide, and specifically, for example, an alkali metal halide, an alkaline earth metal halide, a Zn halide, or a rare earth element halide is preferable. Of the halides, fluorides and chlorides are preferred.

Here, it is preferable to use an anhydride for the above-mentioned flux having deliquescence. Moreover, about the flux used together, you may use 2 or more types together by arbitrary combinations and a ratio.
Particularly suitable fluxes to be used in combination are MgF ₂ , CeF ₃ , LaF ₃ , YF ₃ , GdF _{3 and the} like. Of these, YF ₃ , GdF _3, etc. have the effect of changing the chromaticity coordinates (x, y) of the emitted color.

(Type of phosphor)
The phosphor of the present invention is a phosphor represented by the following general formula (1).
Ln _x Si _y N _n : Z (1)
In the general formula (1), Ln is a rare earth element excluding an element used as an activator, Z is an activator, x satisfies 2.7 ≦ x ≦ 3.3, and y is 5.4 ≦ y ≦ 6.6 is satisfied, and n satisfies 10 ≦ n ≦ 12.
The Ln is preferably a rare earth element containing 80 mol% or more of La, more preferably a rare earth element containing 95 mol% or more of La, and even more preferably La.
As elements other than La contained in Ln, it is considered that any rare earth element can be used without any problem. However, yttrium, gadolinium, etc., which are often substituted even in the case of other phosphors, are preferable. Is preferable because the ionic radius is close and the charges are equal.

The activator Z preferably contains either Eu or Ce, more preferably contains 80 mol% or more of Ce, more preferably contains 95 mol% or more of Ce, and most preferably is Ce. .
The molar ratio of elements, that is, the ratio of x, y, and n is 3: 6: 11 as a stoichiometric composition, and it can be used as a phosphor even if there is an excess or deficiency of about 10%. Therefore, the values of x, y, and n are set in the ranges of 2.7 ≦ x ≦ 3.3, 5.4 ≦ y ≦ 6.6, and 10 ≦ n ≦ 12, respectively.

  Although the phosphor of the present invention is represented by the above general formula (1), it is preferable to use alkaline earth metal elements such as calcium and strontium and aluminum for the purpose of changing the chromaticity point. Substitutions of part of the site are not excluded from the scope of the present invention. For example, substitution with calcium, yttrium, gadolinium, and strontium can be used when increasing the emission wavelength, and can be preferably exemplified. These elements are also replaced simultaneously with other elements in order to satisfy the law of conservation of charge. As a result, the sites of Si and N may be partially replaced with oxygen, and such phosphors are also preferably used. can do.

(Particle size of phosphor)
The phosphor of the present invention preferably has a volume median diameter in the range of usually 0.1 μm or more, especially 0.5 μm or more, and usually 35 μm or less, especially 25 μm or less. When the volume median diameter is too small, the luminance is lowered and the phosphor particles tend to aggregate. On the other hand, when the volume median diameter is too large, there is a tendency for coating unevenness and blockage of a dispenser to occur. For this reason, the said range is preferable. The volume median diameter can be measured by, for example, the above-mentioned Coulter counter method, and as a typical apparatus, it can be measured using “Multisizer” manufactured by Beckman Coulter, Inc.

(Phosphor production method)
(Preparation of raw materials)
The phosphor of the present invention can be produced by the production methods described in known Patent Document 1 and Patent Document 2 except that a compound containing rubidium, which is a feature of the present invention, is added.

For example, a phosphor precursor can be prepared as a raw material, the phosphor precursors can be mixed as necessary, and the mixed phosphor precursor can be baked (baking step).
Among these production methods, a method of using an alloy as at least a part of the raw material, more specifically, an alloy containing at least the Ln element, the Z element and the Si element in the above formula (1) (hereinafter referred to as “phosphor”). May be referred to as “manufacturing alloy”) by a method having a step of firing in the presence of a compound containing rubidium. The phosphor of the present invention can be prepared by using a part or all of the raw material as an alloy for producing a phosphor. The production method of the raw material alloy is described in detail in Patent Document 2, Methods that can be used as needed, such as grinding and classification, are described in detail.

Of the above production methods, the firing step is preferably performed in a hydrogen-containing nitrogen gas atmosphere. Furthermore, it is preferable to wash the resulting fired product with an acidic aqueous solution after firing.
The phosphors of the general formula (1) can be suitably prepared by using such methods in combination as necessary.

(Mixing of raw materials)
When using an alloy for producing a phosphor, an alloy for producing a phosphor is acceptable if the composition of the contained metal element matches the composition of the metal element contained in the crystal phase represented by the above formula (1). It is only necessary to bake. On the other hand, when a phosphor manufacturing alloy is not used or the composition does not match, a phosphor manufacturing alloy having a different composition, a single metal, a metal compound, etc. are mixed with the phosphor manufacturing alloy. Then, the composition of the metal element contained in the raw material is adjusted so as to coincide with the composition of the metal element contained in the crystal phase represented by the above formula (1), and firing is performed.

There is no restriction | limiting in the metal compound used other than the alloy for fluorescent substance manufacture, For example, nitride, an oxide, a hydroxide, carbonate, nitrate, a sulfate, oxalate, carboxylate, a halide etc. are mentioned. Specific types may be appropriately selected from these metal compounds in consideration of reactivity to the target product and low generation amount of NO _x , SO _x, etc. during firing. From the viewpoint that the phosphor is a nitrogen-containing phosphor, it is preferable to use a nitride and / or an oxynitride. Among them, it is preferable to use a nitride because it also serves as a nitrogen source.

Specific examples of nitrides and oxynitrides include nitrides of elements constituting phosphors such as LaN, Si ₃ N ₄ , and CeN, and phosphors such as La ₃ Si ₆ N ₁₁ and LaSi ₃ N _5. Examples include elemental composite nitrides.
In addition, the nitride described above may contain a trace amount of oxygen. Although the ratio (molar ratio) of oxygen / (oxygen + nitrogen) in the nitride is arbitrary as long as the phosphor of the present invention is obtained, it is usually 5% or less, preferably 1 when oxygen derived from adsorbed moisture is not included. % Or less, more preferably 0.5% or less, still more preferably 0.3% or less, and particularly preferably 0.2% or less. If the proportion of oxygen in the nitride is too large, the luminance may be lowered.

(Baking process)
The obtained raw material can be mixed with a flux containing rubidium and baked in the presence thereof to obtain the matrix of the phosphor of the present invention. Here, the firing is preferably performed in a hydrogen-containing nitrogen gas atmosphere as described later.

(Baking conditions)
The raw material mixture is usually filled in a crucible, tray or other container and placed in a heating furnace capable of controlling the atmosphere. At this time, the material of the container is preferably a material having low reactivity with the metal compound, and examples thereof include boron nitride, silicon nitride, carbon, aluminum nitride, molybdenum, and tungsten. Among these, molybdenum and boron nitride are preferable because of their excellent corrosion resistance. In addition, said material may use only 1 type and may use 2 or more types together by arbitrary combinations and a ratio.
Here, the shape of the baking container to be used is arbitrary. For example, the bottom surface of the firing container may be a round shape, an elliptical shape such as an ellipse, or a polygonal shape such as a triangle or a quadrangle. The height of the firing container is arbitrary as long as it enters the heating furnace, and is low. But it can be expensive. Among these, it is preferable to select a shape with good heat dissipation.

  And the fluorescent substance of this invention can be obtained by baking a raw material mixture. However, the raw material mixture is preferably baked in a state where the volume filling rate is maintained at 40% or less. The volume filling rate can be obtained by (bulk density of mixed powder) / (theoretical density of mixed powder) × 100 [%].

  The firing container filled with the phosphor raw material mixture is placed in a firing apparatus (hereinafter sometimes referred to as “heating furnace”). The firing apparatus used here is optional as long as the effects of the present invention can be obtained, but an apparatus capable of controlling the atmosphere in the apparatus is preferable, and an apparatus capable of controlling the pressure is also preferable. For example, a hot isostatic press (HIP), a resistance heating vacuum pressurizing atmosphere heat treatment furnace, and the like are preferable.

Further, it is preferable to circulate a gas containing nitrogen in the baking apparatus and sufficiently replace the inside of the system with this nitrogen-containing gas before the start of heating. If necessary, a nitrogen-containing gas may be circulated after the system is evacuated.
Examples of the nitrogen-containing gas used in the firing include a gas containing a nitrogen element, such as nitrogen, ammonia, or a mixed gas of nitrogen and hydrogen. Moreover, only 1 type may be used for nitrogen-containing gas and it may use 2 or more types together by arbitrary combinations and a ratio. Among these, the nitrogen-containing gas is preferably nitrogen gas containing hydrogen (hydrogen-containing nitrogen gas). In addition, the mixing ratio of hydrogen in the hydrogen-containing nitrogen gas is preferably 4% by volume or less outside the explosion limit, which is preferable from the viewpoint of safety.

Firing is performed by heating the phosphor material in a state filled with hydrogen gas or in a state where it is circulated, and the pressure at that time is somewhat reduced from atmospheric pressure, atmospheric pressure or pressurized state. But it ’s okay. However, in order to prevent oxygen from being mixed in the atmosphere, the pressure is preferably set to atmospheric pressure or higher. If the pressure is less than atmospheric pressure, if the heating furnace is not hermetically sealed, a large amount of oxygen may be mixed and a high-quality phosphor may not be obtained. The pressure of the hydrogen-containing nitrogen gas is preferably at least 0.1 MPa as a gauge pressure. Or it can also heat under the high pressure of 20 Mpa or more. Moreover, 200 MPa or less is preferable.
Thereafter, a gas containing nitrogen is circulated to sufficiently replace the inside of the system with this gas. If necessary, the gas may be circulated after the system is evacuated.

  Incidentally, the metal nitriding reaction is usually an exothermic reaction. Therefore, when the phosphor is manufactured by the alloy method, the alloy may be melted again by the reaction heat that is rapidly released, and the surface area may be reduced. If the surface area is reduced in this way, the reaction between gaseous nitrogen and the alloy may be delayed. For this reason, it is generally preferable in the alloy method to maintain a reaction rate at which the alloy does not melt because a high-performance phosphor can be stably produced. In particular, firing is performed at a low rate of 1.5 ° C./min or less in a firing temperature range where the generation of nitriding heat is intense at 1150 to 1400 ° C., at least in a temperature range where an exothermic peak rises. preferable. The upper limit of the heating rate is usually 1.5 ° C./min or less, preferably 0.5 ° C./min or less, more preferably 0.1 ° C./min or less. Moreover, there is no restriction | limiting in particular in a lower limit, What is necessary is just to determine from the economical viewpoint as industrial production. Here, the exothermic peak is an exothermic peak obtained by TG-DSC (thermogravimetric / differential heat) measurement.

As described above, in order to stably manufacture a high-performance phosphor, it is necessary to suppress the temperature rise of the firing temperature as much as possible, and firing takes a long time. In the method for producing an LSN phosphor of the present invention, An effect that cannot be predicted from the prior art that a phosphor with high brightness can be obtained even by firing in a short time with a large increase in the firing temperature.
In the production method of the present invention, a phosphor having a high luminance can be obtained even when the temperature raising rate is 2 ° C./min or more on average from the start of heating to the maximum temperature.

This method can suppress rapid generation of nitriding heat during firing, particularly when an alloy is used, suppresses local temperature rise, and provides a good phosphor, and does not generate nitriding heat. By setting the other temperature region to a high temperature increase rate, an efficient phosphor with a shortened overall firing time can be manufactured.
In the present invention, a compound containing rubidium is used as a flux, but the heating rate is slowed at the melting point of the compound containing rubidium or a temperature range slightly exceeding the melting point (for example, around melting point + 50 ° C. or less). Or by adding a step of maintaining a constant temperature, the crystallinity of the obtained phosphor can be further improved.
Further, when a compound containing rubidium is decomposed during firing to obtain an effect as a flux, the temperature is similarly increased at a decomposition temperature or a temperature range slightly exceeding the decomposition temperature (for example, within the decomposition temperature + 50 ° C. or less). There is a possibility that the same effect of improving crystallinity can be obtained even if a step of slowing down or maintaining a constant temperature is included.

The firing temperature varies depending on the composition of the phosphor-producing alloy, but is usually 1000 ° C. or higher and 1800 ° C. or lower, and more preferably 1400 ° C. or higher and 1700 ° C. or lower. Moreover, said temperature refers to the furnace temperature in the case of a baking process, ie, the preset temperature of a baking apparatus.
The heating time (holding time at the maximum temperature) during the nitriding treatment may be a time required for the reaction between the phosphor raw material and nitrogen, but is usually 1 minute or more, preferably 10 minutes or more, more preferably 30 minutes or more, More preferably 60 minutes or more. If the heating time is shorter than 1 minute, the nitriding reaction may not be completed and a phosphor having high characteristics may not be obtained. The upper limit of the heating time is determined from the viewpoint of production efficiency, and is usually 50 hours or less, preferably 24 hours or less.

In the production method of the present invention, when the phosphor production alloy is used, the above-described nitriding treatment may be performed after preliminary nitriding (primary nitriding) as necessary. Specifically, preliminary nitridation is performed by heating the phosphor-producing alloy for a predetermined time in a predetermined temperature range in a nitrogen-containing atmosphere. By introducing such a primary nitriding step, the reactivity of the alloy and nitrogen in the subsequent nitriding treatment can be controlled, and there is a possibility that the phosphor can be industrially produced easily from the alloy.
In addition, the nitriding treatment may be repeated a plurality of times as necessary. In this case, the conditions for the first firing (primary firing) and the firing conditions after the second firing (secondary firing) are as described above. The conditions after the secondary firing may be the same as or different from the primary firing.
Thus, the phosphor of the present invention having a nitride or oxynitride as a base can be obtained by nitriding the phosphor material.

(Post-processing process)
In the manufacturing method of this invention, you may perform another process as needed other than the process mentioned above. For example, after the above baking process, a pulverization process, a cleaning process, a classification process, a surface treatment process, a drying process, and the like may be performed as necessary.

(Crushing process)
In the pulverization step, for example, a pulverizer such as a hammer mill, a roll mill, a ball mill, a jet mill, a ribbon blender, a V-type blender or a Henschel mixer, or a pulverization using a mortar and pestle can be used. At this time, in order to suppress the destruction of the generated phosphor crystal and proceed with the intended treatment such as secondary particle crushing, for example, the same as these in a container of alumina, silicon nitride, ZrO ₂ , glass, etc. It is preferable to carry out a ball mill treatment for about 10 minutes to 24 hours by putting a ball such as the above material or iron cored urethane. In this case, you may use 0.05 weight%-2weight% of dispersing agents, such as alkali phosphates, such as organic acid and hexametaphosphoric acid.

(Washing process)
In the cleaning step, the phosphor surface can be formed with, for example, water such as deionized water, an organic solvent such as ethanol, or an alkaline aqueous solution such as ammonia water.
For example, hydrochloric acid, nitric acid, sulfuric acid, aqua regia, hydrofluoric acid and sulfuric acid for purposes such as removing the flux used, removing the impurity phase adhering to the phosphor surface and improving the light emission characteristics. An acidic aqueous solution containing an inorganic acid such as a mixture thereof; an organic acid such as acetic acid can also be used.
These methods are described in detail in Patent Documents 1 and 2, and may be performed in accordance with the description.

(Classification process)
The classification step can be performed, for example, by performing water sieving, or using various classifiers such as various air classifiers and vibration sieves. In particular, when dry classification using a nylon mesh is used, a phosphor having a volume average diameter of about 10 μm and good dispersibility can be obtained.
In addition, when dry classification using nylon mesh and water tank treatment are used in combination, a phosphor with good dispersibility having a volume median diameter of about 20 μm can be obtained.

  Here, in the water sieving or elutriation treatment, phosphor particles are usually dispersed in an aqueous medium at a concentration of about 0.1 wt% to 10 wt%. In order to suppress deterioration of the phosphor, the pH of the aqueous medium is usually 4 or more, preferably 5 or more, and usually 9 or less, preferably 8 or less. Further, when obtaining the volume median type phosphor particles as described above, in the water sieving and elutriation treatment, for example, particles of 50 μm or less are obtained, and then particles of 30 μm or less are obtained. Is preferable from the viewpoint of balance between work efficiency and yield. Moreover, as a minimum, it is preferable to perform the process which sifts a thing normally 1 micrometer or more, Preferably 5 micrometers or more.

(Drying process)
The phosphor thus washed is dried at about 100 ° C. to 200 ° C. You may perform the dispersion | distribution process (for example, mesh pass etc.) of the grade which prevents dry aggregation as needed.

(Steam heat treatment process)
The phosphor of the present invention can be subjected to steam heat treatment by leaving the phosphor produced through the above steps in the presence of steam, preferably in the presence of water vapor. By performing this heating step, the luminance of the phosphor can be further improved.

  When the steam heat treatment step is provided, the temperature is usually 50 ° C. or higher, preferably 80 ° C. or higher, more preferably 100 ° C. or higher, and usually 300 ° C. or lower, preferably 200 ° C. or lower, more preferably 150 ° C. or lower. is there. If the temperature is too low, the effect due to the presence of adsorbed water on the phosphor surface tends to be difficult to obtain, and if it is too high, the surface of the phosphor particles may be roughened.

  The humidity (relative humidity) in the steam heat treatment step is usually 50% or more, preferably 80% or more, and particularly preferably 100%. If the humidity is too low, the effect due to the presence of adsorbed water on the phosphor surface tends to be difficult to obtain. Note that the liquid phase may coexist in the gas phase having a humidity of 100% as long as the effect of forming the adsorbed water layer is obtained.

  The pressure in the steam heat treatment step is usually normal pressure or higher, preferably 0.12 MPa or higher, more preferably 0.3 MPa or higher, and usually 10 MPa or lower, preferably 1 MPa or lower, more preferably 0.5 MPa or lower. If the pressure is too low, the effect of the steam heat treatment process tends to be difficult to obtain. If the pressure is too high, the processing apparatus becomes large, and there may be a problem of work safety.

  The holding time of the phosphor in the presence of the vapor is not uniform depending on the temperature, humidity, and pressure, but the holding time is usually shorter as the temperature is higher, the humidity is higher, and the pressure is higher. That's it. Specific ranges of time are usually 0.5 hours or more, preferably 1 hour or more, more preferably 1.5 hours or more, and usually 200 hours or less, preferably 100 hours or less, more preferably 12 hours. Hereinafter, it is more preferably 5 hours or less.

As a specific method for performing the steam heating step while satisfying the above-mentioned conditions, a method of placing the autoclave under high humidity and high pressure can be exemplified. Here, in addition to the autoclave or instead of using the autoclave, an apparatus that can be subjected to high temperature and high humidity conditions such as a pressure cooker may be used. As the pressure cooker, for example, TPC-412M (manufactured by ESPEC Co., Ltd.) can be used. According to this, the temperature is 105 ° C. to 162.2 ° C. and the humidity is 75 to 100% (however, the temperature condition The pressure can be controlled to 0.020 MPa to 0.392 MPa (0.2 kg / cm ^{2 to} 4.0 kg / cm ² ).

  If the vapor heating process is carried out while holding the phosphor in the autoclave, it is possible to form a special water layer in a high temperature, high pressure and high humidity environment. It can be present on the phosphor surface. As specific conditions, the phosphor is preferably placed in an environment where the pressure is normal pressure (0.1 MPa) or more and steam exists for 0.5 hours or more.

(Surface treatment process)
When manufacturing a light-emitting device using the phosphor of the present invention, in order to further improve the weather resistance such as moisture resistance, or to improve the dispersibility of the phosphor in the phosphor-containing portion of the light-emitting device to be described later If necessary, surface treatment such as partially covering the surface of the phosphor with a different substance may be performed. The surface treatment may be performed before the steam heat treatment step or after the steam heat treatment step, which prevents the presence of special adsorbed water by the steam heat treatment or removes the adsorbed water. If the surface treatment is not effective, both treatments can be performed simultaneously without any problem.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to the following examples, and can be arbitrarily changed without departing from the gist of the present invention. Can be implemented.
In addition, the measurement of the light emission characteristic etc. of the fluorescent substance of an Example and a comparative example was performed with the following method.

(Emission spectrum)
The emission spectrum was measured using a 150 W xenon lamp as an excitation light source and MCPD7000 (manufactured by Otsuka Electronics Co., Ltd.) as a spectrum measuring device. The emission intensity of each wavelength was measured with a spectrum measuring device in the wavelength range of 380 nm to 800 nm under the condition of excitation light of 455 nm, and an emission spectrum was obtained.

(Chromaticity coordinates, relative luminance)
The chromaticity coordinates of the x, y color system (CIE 1931 color system) are obtained from the data in the wavelength region of 480 nm to 780 nm of the emission spectrum obtained by the above-mentioned method, according to JIS Z8724. The chromaticity coordinates x and y in the prescribed XYZ color system were calculated. The relative luminance is expressed as a relative value when the Y value in the XYZ color system is set to 100 when YAG (product number: P46-Y3) manufactured by Kasei Optonics Co., Ltd. is excited with light having a wavelength of 455 nm.
Next, an actual phosphor manufacturing method will be described.

<Example 1>
(Preparation of raw materials)
La: Si = 1: 1 (molar ratio) alloy, Si ₃ N ₄ , and CeF ₃ should be La: Si = 3: 6 (molar ratio) and CeF ₃ / (alloy + Si ₃ N ₄ ) = 6 wt%. Weighed out. Here, RbF is used as the flux, and the ratio of the total F amount to the Si amount F: Si = 0.75: 6 (molar ratio: that is, the charged molar ratio of rubidium when the amount of silicon in the phosphor is 6 mol is 0. .75). The weighed raw materials were mixed in a mortar, and then the raw materials were prepared through a nylon mesh sieve. The operations from weighing to preparation were carried out in a glove box in a nitrogen atmosphere with an oxygen concentration of 1% or less.

(Baking process)
The prepared raw material was filled in a Mo crucible and set in an electric furnace. After evacuating the inside of the apparatus, the furnace temperature was raised to 120 ° C., and after confirming that the furnace pressure was vacuum, the hydrogen-containing nitrogen gas (nitrogen: hydrogen = 96: 4 (volume ratio)) was increased. It was introduced until atmospheric pressure was reached. Thereafter, the furnace temperature was raised to 1550 ° C. in 44 hours, held at 1550 ° C. for 8 hours, and then the temperature reduction was started, and the firing treatment was finished to obtain a phosphor.

(Washing process)
The fired phosphor was passed through a nylon mesh sieve, stirred in 1N hydrochloric acid for 1 hour or longer, then washed with water and dehydrated. Then, it dried with a 120 degreeC hot air dryer, and collect | recovered fluorescent substance through the sieve of a nylon mesh. Table 1 shows the color coordinates and luminance of the obtained phosphor.

<Comparative Example 1>
A phosphor was prepared in the same manner as in Example 1 except that no flux was used. Table 1 shows the color coordinates and luminance of the obtained phosphor.

<Comparative Example 2>
A phosphor was prepared in the same manner as in Example 1 except that MgF ₂ , which is one of the most preferable fluxes in the known literature and used in the examples, was used. The amount of flux is
The molar ratio of F to Si was adjusted to that in Example 1. The same applies to the following comparative examples. Table 1 shows the color coordinates and luminance of the obtained phosphor.

<Comparative Example 3>
Except for using LiF (melting point 843 ° C.), which has a melting point relatively close to RbF (melting point 848 ° C.) used in the example as a flux, and is described in known literature as being used for an LSN phosphor. In the same manner as in Example 1, a phosphor was prepared. Table 1 shows the color coordinates and luminance of the obtained phosphor.

<Comparative Example 4>
Use LaF ₃ consisting of La and halogen, which are elements of the matrix composition of the phosphor as the flux, reduce the amount of lanthanum supplied from the LaF ₃ flux and the amount of alloy used, and the insufficient Si will increase silicon nitride Prepared a phosphor in the same manner as in Example 1. Table 1 shows the color coordinates and luminance of the obtained phosphor.

<Example 2>
A phosphor was prepared in the same manner as in Example 1 except that the furnace temperature was changed to 1550 ° C. for 13 hours in the firing step. Table 1 shows the color coordinates and luminance of the obtained phosphor.

<Comparative Example 5>
A phosphor was prepared in the same manner as in Example 2 except that no flux was used. Table 1 shows the color coordinates and luminance of the obtained phosphor.

<Comparative Example 6>
A phosphor was prepared in the same manner as in Example 2 except that MgF ₂ was used as the flux. Table 1 shows the color coordinates and luminance of the obtained phosphor.

<Comparative Example 7>
A phosphor was prepared in the same manner as in Example 2 except that LiF was used as the flux. Table 1 shows the color coordinates and luminance of the obtained phosphor.

<Comparative Example 8>
A phosphor was prepared in the same manner as in Example 2 except that LaF ₃ was used as the flux, the amount of lanthanum supplied from the LaF ₃ flux and the amount of alloy used were reduced, and the insufficient Si increased silicon nitride. Table 1 shows the color coordinates and luminance of the obtained phosphor.

From this result, it can be seen that a phosphor containing rubidium can obtain a phosphor having a higher luminance than when using the MgF ₂ flux, which has been most suitable in the past in Patent Documents 1 and 2, etc. In addition, when baking is performed in a short time using a flux other than the flux containing rubidium, the brightness is reduced as compared with the case where baking is performed for a long time, but the rubidium of the present invention. When the flux containing is used, it can be seen that sufficient brightness is obtained by short-time firing.

  According to the present invention, a high-intensity LSN phosphor can be provided, and particularly when used for white LEDs, it can be suitably used for illumination and display backlights. In addition, the production method of the present invention can produce a high-luminance phosphor in a shorter time than before.

Claims (3)

A raw material containing an element constituting the nitride phosphor represented by the following general formula (1) is prepared, and at least one selected from the raw material, a rubidium halide, a carbonate, a nitrate, and a hydroxide A method for producing a nitride phosphor represented by the following general formula (1), comprising mixing a rubidium compound and firing the obtained mixture.
Ln _x Si _y N _n : Z (1)
(In General Formula (1), Ln is a rare earth element excluding an element used as an activator, Z is an activator, x satisfies 2.7 ≦ x ≦ 3.3, and y is 5.4 ≦ y ≦ 6.6 is satisfied, and n satisfies 10 ≦ n ≦ 12.)   The method for producing a nitride phosphor according to claim 1, wherein the rubidium compound includes at least one selected from rubidium fluoride, rubidium chloride, and rubidium carbonate.   3. The nitride according to claim 1, wherein the amount of the rubidium compound used is 0.1 to 2.0 in terms of a charged molar ratio of rubidium when the amount of silicon in the phosphor is 6 mol. A method for producing a phosphor.