JP2013249375A - Phosphor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nitride phosphor improved in luminance than conventional products.SOLUTION: A nitride phosphor is expressed by general formula (1): LnSiN:Z on the surface of which at least one selected from a group consisting of calcium phosphate, potassium silicate and sodium silicate covers by 0.3 mmol/100 g or more. In general formula (1), Ln is a rare earth element except elements used as an augmenting agent; Z is an augmenting agent; x satisfies 2.7≤x≤3.3; y satisfies 5.4≤y≤6.6; and n satisfies 10≤n≤12.

Description

  The present invention relates to a nitride phosphor, and more particularly, to a nitride phosphor having a brightness improved by coating compared to before coating.

  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 a large output, the luminance decreases as the phosphor temperature rises, so-called temperature quenching is large, and more excellent color reproduction range and color rendering properties are required. When excitation is performed with light of about 420 nm, 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 as a promising candidate, for example, a fluorescent material in which La ₃ Si ₆ N ₁₁ described in Patent Document 1 is used as a base and an activator is added. The body (hereinafter referred to as LSN phosphor) has been developed. Compared with conventional YAG phosphors, this phosphor has a small decrease in luminance even when the temperature rises, and can emit sufficient light even when excited with near ultraviolet rays. In combination with phosphors such as blue and red, it is expected to produce a light-emitting device that achieves both high color rendering and high efficiency.

  It is also known that the phosphor is usually coated on the surface in order to improve its dispersibility and handling property when mixed with a resin or to protect the phosphor. Such a coat generally adheres to the surface of the phosphor, and the coating substance itself generally does not emit light, so that it is an obstructive factor in terms of the light emission characteristics of the phosphor. Therefore, when the phosphor is coated, the amount of coating is determined by comparing the expected effect of the coating with the effect of inhibiting the phosphor emission so as not to disturb the light emission characteristics.

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

The LSN phosphor described in Patent Document 1 has a small decrease in luminance even when the temperature is increased as compared with a conventional YAG phosphor, and can emit sufficient light even when excited by near ultraviolet rays.
However, phosphors are required to obtain higher luminance with less energy, and further improvements in luminance, internal quantum efficiency, and external quantum efficiency are required. That is, an object of the present invention is to provide a nitride phosphor having improved brightness, internal quantum efficiency, and external quantum efficiency compared to conventional products.

The present inventor has been studying the coating of the LSN phosphor, and the luminance of the phosphor is usually lowered by the coating, but when the specific substance is coated in a specific amount, the luminance of the phosphor is surprisingly increased. The present invention has been found.
The gist of the present invention is as follows.
[1] A nitride phosphor represented by the following general formula (1):
A nitride phosphor having a surface coated with 0.3 mmol / 100 g or more of at least one selected from the group consisting of calcium phosphate, potassium silicate, and sodium silicate.

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.)

  According to the present invention, 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.
(Surface coat of phosphor)
The phosphor of the present invention has at least one selected from the group consisting of an appropriate amount of calcium phosphate and / or potassium silicate and sodium silicate on the surface of the phosphor represented by the specific general formula (1) described later. Coated.

The reason why the brightness is improved by such a coating is speculative, but the coating substance of the present invention adheres to the surface in an appropriate amount so that the efficiency of taking in the excitation light into the phosphor, taking out the light emission, etc. I guess because of the improvement.
The coat used in the present invention is to coat at least one selected from the group consisting of calcium phosphate and / or potassium silicate and sodium silicate.
Of these, calcium phosphate and / or potassium silicate are preferable, and calcium phosphate is particularly preferable.

  The coating amount is 0.3 mmol or more, that is, 0.3 mmol / 100 g or more, more preferably 1 mmol / 100 g, and further preferably 3 mmol / 100 g or more per 100 g of the phosphor. The upper limit is not particularly limited as long as the effect of improving luminance, which is the effect of the present invention, is obtained, but as a guideline, it is preferably 20 mmol / 100 g or less, more preferably 10 mmol / 100 g or less. If too much coating is applied, the brightness may decrease.

The method of coating is not particularly limited, but from the viewpoint of easy uniform coating, a coating substance is deposited in a liquid phase medium, adsorbed on the phosphor surface, and fixed in a drying step. Is preferable because it is easy and uniform.
Exemplifying a specific method, the phosphor before coating is sufficiently dispersed in 2 to 10 times the amount of ion-exchanged water, and then the coating substance itself or a substance capable of obtaining a coating substance by reaction Is put into ion-exchanged water, and stirring or pH adjustment is performed to precipitate the target coating substance or to adsorb it on the phosphor surface.

Thereafter, the coating substance is fixed to the surface of the phosphor by drying or the like.
More specifically, the case where the coating is performed by generating a coating substance by reaction using the case where calcium phosphate coating is performed will be described. First, a water-soluble calcium salt solution (for example, calcium nitrate solution) is added to the phosphor in dispersed water as much as necessary for the coating amount. After stirring, a water-soluble phosphate solution (for example, phosphoric acid) is added. Sodium solution) cations (Ca)
And a phosphate ion (PO ₄ ) in a molar ratio of about 3: 2 and stirred. The phosphor of the present invention can be obtained by subjecting this to dehydration, drying, and if necessary, sieving to loosen the dry agglomeration.

A case where the coating substance itself is directly poured into water and coated on the phosphor surface will be described using the case where potassium silicate coating is performed. First, water glass (potassium silicate solution) is added to the water in which the phosphor is dispersed, and an amount necessary for the coating amount is added. Preferably, the mixture is stirred for 30 minutes or more, and then allowed to stand for 1 hour or more. Was adsorbed. The phosphor of the present invention can be obtained by performing the steps after the dehydration in the same manner as in the case of coating by generating a coating substance by reaction.

(Type of phosphor)
The phosphor used in 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 z 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 z are set in a range of 2.7 ≦ x ≦ 3.3, 5.4 ≦ y ≦ 6.6, 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 1 μm or more, especially 5 μm or more, and usually 50 μm or less, especially 30 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)
(material)
The phosphor of the present invention is coated in the step of producing the phosphor. If the part is remove | excluded, it can manufacture with the manufacturing method of well-known patent document 1 and patent document 2. FIG.

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”). It is preferable to produce a “alloy for production”) by a method having a step of firing in the presence of a flux. The phosphor of the present invention can be produced using a part or all of the raw material as an alloy for producing a phosphor. The production method of this 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)
If the composition of the metal element contained in the phosphor production alloy matches the composition of the metal element contained in the crystal phase represented by the above formula (1), only the phosphor production alloy needs to be fired. . On the other hand, if a phosphor manufacturing alloy is not used or the composition does not match, a phosphor manufacturing alloy having a different composition, a simple 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. The specific type may be appropriately selected from these metal compounds in consideration of the reactivity to the target product and the low generation amount of NO _x , SO _{x and the} like during firing, etc. 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 fired in the presence of a flux and nitrided to obtain the base of the phosphor of the present invention. Here, the firing is preferably performed in a hydrogen-containing nitrogen gas atmosphere as described later.
(flux)
In the firing step, it is preferable that a flux coexists in the reaction system from the viewpoint of growing good crystals.

The type of flux is not particularly limited, for _example, NH 4 Cl, _NH 4 ammonium halides such as F · _HF; alkali metal carbonate such as _{NaCO 3, LiCO 3; LiCl,} NaCl, KCl, CsCl, LiF, NaF, Alkali metal halides such as KF and CsF; Alkaline earth metal halides such as CaCl ₂ , BaCl ₂ , SrCl ₂ , CaF ₂ , BaF ₂ , SrF ₂ , MgCl ₂ , 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 metal or alkaline earth metal borate compounds; Li ₃ PO ₄ , NH ₄ H ₂ PO phosphate compounds such as _4; aluminum halide such as AlF _3; ZnCl 2, zinc halides, such as ZnF ₂ Periodic Table Group 15 element compound such as _Bi 2 _{O 3;;} zinc compounds such as zinc oxide _{Li 3 N, Ca 3 N 2} , Sr 3 N 2, Ba 3 N 2, alkali metals such as BN, alkaline earth metal Alternatively, a nitride of a Group 13 element can be given.

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, only 1 type may be used for a flux and it may use 2 or more types together by arbitrary combinations and a ratio.
Further, MgF ₂ can be cited as a suitable flux, but CeF ₃ , LaF ₃ , YF ₃ , GdF _{3 and the} like can also be suitably used. Among these, YF ₃ , GdF _3, etc. have the effect of changing the chromaticity coordinates (x, y) of the emission color.

Further, as the cation-side element constituting the flux, carbonates, chlorides, fluorides, and the like of Rb and Cs that are difficult to be incorporated into the LSN phosphor due to the size of the ionic radius are preferable.
The amount of flux used varies depending on the type of raw material, the material of the flux, etc., and is arbitrary, but is usually 0.01% by weight or more, preferably 0.1% by weight or more, more preferably 0.8% by weight based on the whole raw material. A suitable range is 3% by weight or more, usually 20% by weight or less, preferably 10% by weight or less. If the amount of flux used is too small, the effect of the flux may not appear. If the amount of flux used is too large, the flux effect will be saturated, or it will be incorporated into the host crystal and change the emission color, brightness. It may cause a drop or deterioration of the firing furnace.

(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 heating 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 a “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 nitriding treatment 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.

  The nitriding treatment is performed by heating the phosphor raw 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 pressure. A state is good. 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. The nitriding conditions are described in detail in the above-mentioned Patent Document 1, Patent Document 2, and the like regarding the heating rate during the nitriding reaction, the preliminary nitriding method, the firing temperature, the holding time, and the like. Based on this, it may be manufactured.

(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 crushing of secondary particles, for example, the same as these in a container such as 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.

Hydrofluoric acid, ammonium fluoride (NH ₄ F), ammonium hydrogen fluoride (NH ₄ HF ₂ ), sodium hydrogen fluoride, potassium hydrogen fluoride, etc. for the purpose of removing the amorphous phase as an impurity phase An acidic aqueous solution containing can be used. Among these, NH ₄ HF ₂ aqueous solution is preferable. The concentration of the NH ₄ HF ₂ aqueous solution is usually 1% to 30% by weight, preferably 5% to 25% by weight. Moreover, these chemicals can be appropriately mixed and used as necessary. These acidic aqueous solutions are preferably temperature-controlled as necessary.

Moreover, it is preferable to wash with water after washing in an alkaline aqueous solution or an acidic aqueous solution.
By the above-described washing process, the luminance, emission intensity, absorption efficiency, and object color of the phosphor can be improved.
As an example of the washing step, the fired product after washing is stirred in a 10% by weight 10% by weight NH ₄ HF ₂ aqueous solution for 1 hour, then dispersed in water and left to stand for 1 hour. It is preferable to carry out washing until the pH of the resulting supernatant is neutral (about pH 5-9). This is because if the supernatant is biased to basic or acidic, the liquid medium or the like may be adversely affected when mixed with the liquid medium or the like described later.

In order to remove impurities generated during acid cleaning, a method of cleaning with a second type of liquid after cleaning with a first type of liquid, or a method of cleaning with a liquid in which two or more substances are mixed Is also preferable. As an example of the former, after washing with an NH ₄ HF ₂ aqueous solution, washing with hydrochloric acid and finally washing with water can be mentioned. As an example of the latter, there can be mentioned a step of washing with water after washing with a mixed aqueous solution of NH ₄ HF ₂ and HNO ₃ .

  The degree of washing can also be expressed by the electrical conductivity of the supernatant obtained by dispersing the washed phosphor in 10 times the weight ratio of water and allowing it to stand for 1 hour. The electrical conductivity is preferably as low as possible from the viewpoint of light emission characteristics. However, in consideration of productivity, the washing treatment is usually repeated until it is 10 mS / m or less, preferably 5 mS / m or less, more preferably 4 mS / m or less. It is preferable.

  The electrical conductivity is determined by stirring the particles in water 10 times the weight of the phosphor for a predetermined time (for example, 10 minutes) and then allowing the particles to stand for 1 hour to naturally settle particles having a specific gravity greater than that of water. What is necessary is just to measure the electrical conductivity of a supernatant liquid, for example using the electrical conductivity meter "EC METER CM-30G" by a Toa Decay company. Although there is no restriction | limiting in particular as water used for a washing process and the measurement of electrical conductivity, Demineralized water or distilled water is preferable. Among them, those having particularly low electric conductivity are preferable, and those having a conductivity of usually 0.0064 mS / m or more, and usually 1 mS / m or less, preferably 0.5 mS / m or less are used. The electrical conductivity is usually measured at room temperature (about 25 ° C.).

(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 with good dispersibility having a volume average system of about 10 μm 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)
In the phosphor of the present invention, special water having a strong hydrogen bond is present on the phosphor surface, and the luminance can be further improved. Such a phosphor containing special adsorbed water can be obtained by leaving the phosphor produced through the above steps in the presence of steam, preferably in the presence of water vapor, and subjecting it to steam heat treatment.

  When adsorbed water is present on the phosphor surface by placing the phosphor in the presence of vapor, 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 it is 200 degrees C or less, More preferably, it is 150 degrees C or less. 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.

  When adsorbed water is present on the phosphor surface by placing the phosphor in the presence of vapor, the humidity (relative humidity) is usually 50% or more, preferably 80% or more, and 100%. Particularly preferred. 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.

Further, when adsorbed water is present on the phosphor surface by placing the phosphor in the presence of vapor, the pressure is usually normal pressure or higher, preferably 0.12 MPa or higher, more preferably 0.3 MPa or higher, 10 MPa or less, preferably 1 MPa or less, more preferably 0.5 MPa or less. If the pressure is too low, the effect due to the presence of adsorbed water on the phosphor surface tends to be difficult to obtain. If the pressure is too high, the treatment apparatus becomes large, and there may be a problem in work safety.

  When adsorbed water is present on the phosphor surface by placing the phosphor in the presence of vapor, the time for holding the phosphor in the presence of the vapor is not uniform depending on the temperature, humidity and pressure, Usually, the higher the temperature, the higher the humidity, and the higher the pressure, the shorter the holding time. 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 having a strong hydrogen bond of the present invention in a high temperature, high pressure and high humidity environment. In particular, the adsorbed water can be present on the phosphor surface in a short time. 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.

More preferable conditions are described below. The pressure is preferably 0.2 MPa or more, more preferably 0.3 MPa or more, and usually 10 MPa or less, preferably 1 MPa or less,
More preferably, it is 0.5 MPa or less. The steam is preferably saturated steam (steam when the gas phase and the liquid phase coexist in equilibrium under a certain pressure). Further, the phosphor is preferably kept for 1 hour or longer, more preferably 1.5 hours or longer, and usually 12 hours or shorter, preferably 5 hours or shorter, more preferably 3 hours or shorter.

The phosphor may be put in an autoclave after being put in a container made of alumina or magnet, for example. At this time, steps such as acid cleaning, classification and surface treatment may be performed on the phosphor in advance, but the effect can be obtained even if the phosphor after firing is used as it is.
(Surface coat)
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.

  A suitable surface coating method and the like are as described in the column of (Surface coating of phosphor) at the beginning of the column of the mode for carrying out the invention.

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.
(Luminance)
The luminance 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 by a spectrum measuring device in the wavelength range of 380 nm to 800 nm under the condition of excitation light of 455 nm, and the visibility of each wavelength was multiplied by this to obtain a total value. In the examples, the luminance of the LSN phosphor not coated is expressed as a ratio, where 100 is the luminance.

(Particle size measurement)
The particle size was measured by an electrical detection band method using COULTER MULTISIZER II (Beckman Coulter, Inc.). The aperture size used was 100 μm, and the phosphor was ultrasonically dispersed in water before measurement.
Next, an actual phosphor manufacturing method will be described.

(Preparation of pre-coat phosphor)
The LSN phosphor serving as the core before coating was prepared by the following procedure.
(Preparation of raw materials)
An alloy of La: Si = 1: 1 (molar ratio), Si ₃ N ₄ , and CeF ₃ are La: Si = 3: 6 (molar ratio) and CeF ₃ / (alloy + Si ₃ N ₄ ) = 6 wt%. Weighed out. The raw materials were prepared by mixing the weighed raw materials with a ball mill. The operations from weighing to blending were performed 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 temperature in the furnace was raised to 1550 ° C., held at 1550 ° C. for 8 hours, and then the temperature reduction was started.

(Washing process)
The fired phosphor was passed through a nylon mesh sieve, pulverized with a ball mill, stirred in 1N hydrochloric acid for 1 hour or more, and then washed with water. Then, it dehydrated, dried with a 120 degreeC hot air dryer, and collect | recovered fluorescent substance through the sieve of a nylon mesh.
(Example)
Example 1
5 g of LSN phosphor prepared by the above method (composition formula La ₃ Si ₆ N ₁₁ : Ce, volume median particle size is 50 μm) is put into 6 times the amount of deionized water and stirred with a stirrer for about 15 minutes. Distributed. To this, 0.57 ml of 20 wt% calcium nitrate tetrahydrate aqueous solution was added and stirred for 10 minutes, and then 1.23 ml of 10 wt% trisodium phosphate dodecahydrate aqueous solution was added and stirred for 15 minutes, followed by filtration. It dehydrated using a bottle and a Buchner funnel and dried at 120 ° C. for 30 minutes or more to obtain a phosphor having a surface coated with calcium phosphate. The coating amount of calcium phosphate is 3.2 mmol / 100 g.

(Example 2)
The same procedure as in Example 1 was performed until the phosphor was dispersed, and 0.18 ml of water glass ((KO · nSiO ₂ · xH ₂ O) manufactured by Tokyo Ohka Co., Ltd.) was added thereto and stirred for 30 minutes. The phosphor was allowed to stand for 60 minutes, and the phosphor was recovered in the same manner as in Example 1 to obtain a phosphor having a surface coated with potassium silicate.

(Comparative Example 1)
The phosphor without coating used in Example 1 is referred to as Comparative Example 1.
(Comparative Example 2)
As an example showing that the effect of improving luminance cannot be obtained with other general coatings, yttrium carbonate coating was performed on the LSN phosphor. Specifically, the first reagent to be added after dispersion of the phosphor and the amount of the yttrium nitrate 0.61M are 0.46 ml, and the second reagent and the amount to be added are 0.10 g of ammonium bicarbonate. Except that, a phosphor having a surface coated with yttrium carbonate was obtained in the same manner as in Example 1. The coating amount of yttrium carbonate is 2.8 mmol / 100 g.

(Evaluation)
The phosphors produced in Examples 1 and 2 of the present invention, the phosphor not subjected to the coating of Comparative Example 1 and the phosphor coated with yttrium carbonate produced in Comparative Example 2 were used using MCPD-7000 manufactured by Otsuka Electronics. The luminance when excited at 455 nm was measured. Table 1 shows the results of evaluating the results with relative values with the luminance of Comparative Example 1 as 100.
Surprisingly, the brightness is improved by about 3% regardless of the surface being covered with the coating substance.

  According to the present invention, a phosphor having high luminance and high efficiency can be provided, and particularly when used for a white LED, it can be suitably used for illumination and a backlight of a display.

Claims (1)

A nitride phosphor represented by the following general formula (1), the surface of which is coated with at least one selected from the group consisting of calcium phosphate, potassium silicate, and sodium silicate by 0.3 mmol / 100 g or more. Nitride phosphor.
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.)