JP2007262417A - Fluorescent substance - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lighting equipment and an image display device each using a green fluorescent substance which has higher green brightness than those of conventional rare earth element-activated sialon fluorescent substances and has more excellent durability than those of conventional oxide fluorescent substances. <P>SOLUTION: This fluorescent substance used in a lighting equipment having a luminous light source and a fluorescent substance or in an image display device having an exciting source and a fluorescent substance is characterized by having a β type Si<SB>3</SB>N<SB>4</SB>crystal structure-having nitride or oxynitride crystal phase obtained by solid-dissolving a metal element M (M is one or more element selected from Mn, Ce, and Eu) in β type Si<SB>3</SB>N<SB>4</SB>crystal structure-having nitride or oxynitride crystal, and emitting fluorescent light having peaks in a wavelength range of 500 to 600 nm by irradiating with a luminous light source or an exciting source. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a phosphor having a β-type Si ₃ N ₄ crystal structure.
More specifically, the application relates to a phosphor having a property of the phosphor, that is, a phosphor that emits green fluorescence having an emission peak at a wavelength of 500 nm to 600 nm.

The phosphor is used for a fluorescent display tube (VFD), a field emission display (FED), a plasma display panel (PDP), a cathode ray tube (CRT), a white light emitting diode (LED), and the like.
In any of these applications, in order to make the phosphor emit light, it is necessary to supply the phosphor with energy for exciting the phosphor, and the phosphor is not limited to vacuum ultraviolet rays, ultraviolet rays, electron beams, blue light, etc. When excited by a high energy excitation source, it emits visible light.
However, the phosphor has a problem that the luminance of the phosphor is reduced as a result of being exposed to the excitation source as described above, and there is a demand for a phosphor having no luminance reduction.
For this reason, sialon phosphors have been proposed as phosphors with little reduction in luminance instead of phosphors such as conventional silicate phosphors, phosphate phosphors, aluminate phosphors, and sulfide phosphors.

An example of this sialon phosphor is manufactured by a manufacturing process generally described below.
First, silicon nitride (Si ₃ N ₄ ), aluminum nitride (AlN), and europium oxide (Eu ₂ O ₃ ) are mixed at a predetermined molar ratio, and the temperature is 1700 ° C. in nitrogen at 1 atm (0.1 MPa). And is fired by a hot press method (for example, see Patent Document 1).
It has been reported that α sialon activated by Eu ions obtained in this process becomes a phosphor that emits yellow light of 550 to 600 nm when excited by blue light of 450 to 500 nm.

Furthermore, JEM phase _{(LaAl (Si 6-z Al} z) N 10-z O z) as host crystals, blue phosphor is activated with Ce (see Patent Document _{2), La 3 Si 8 N} 11 O 4 There are known blue phosphors (see Patent Document 3) in which Ce is activated with Ca as a base crystal (see Patent Document 3), and red phosphors in which Eu is activated with CaAlSiN ₃ as a host crystal (see Patent Document 4).

  However, phosphors that emit light in green as well as blue and yellow have been required for applications such as white LEDs and plasma displays using ultraviolet LEDs as an excitation source.

JP 2002-363554 A Japanese Patent Application No. 2003-208409 Japanese Patent Application No. 2003-346013 Japanese Patent Application No. 2003-394855

As another sialon phosphor, a phosphor in which a rare earth element is added to β-type sialon (see Patent Document 5) is known, and those activated by Tb, Yb, and Ag emit green light from 525 nm to 545 nm. It is shown to be a phosphor.
However, since the synthesis temperature is as low as 1500 ° C., the activating element is not sufficiently dissolved in the crystal and remains in the grain boundary phase, so that a high-luminance phosphor has not been obtained.

JP-A-60-206889

  The present invention is intended to meet such demands, and provides a green phosphor that has a higher green luminance than conventional rare earth activated sialon phosphors and is more durable than conventional oxide phosphors. This is the issue.

In the present inventors, under such circumstances, M (where M is one or more elements selected from Mn, Ce, and Eu) and Si, Al, O, and N elements are added. As a result of diligent research on the nitrides contained, phosphors having a specific composition region range, a specific solid solution state, and a specific crystal phase become phosphors having an emission peak at a wavelength in the range of 500 nm to 600 nm. I found.
That is, a nitride or oxynitride having a β-type Si ₃ N ₄ crystal structure is used as a base crystal, and M (where M is one or more elements selected from Mn, Ce, and Eu) is an emission center It was found that the solid solution crystal added as a phosphor having a light emission having a peak at a wavelength in the range of 500 nm to 600 nm.
In particular, β-sialon synthesized at a temperature of 1820 ° C. or higher with the addition of an Eu compound has good color purity with a peak at a wavelength of 500 nm to 550 nm as Eu dissolves in the crystal of β-sialon. I found green fluorescence.

The β-type Si ₃ N ₄ crystal structure has a symmetry of P6 ₃ or P6 ₃ / m and is defined as a structure having the ideal atomic position shown in Table 1 (see Non-Patent Document 1).
Nitride or oxynitride having this crystal structure includes β-type Si ₃ N ₄ , β-type Ge ₃ N ₄ and β-type sialon (Si _6-z Al _z O _z N _{8-z where} 0 <z <4 .2) is known.
In addition, β-sialon does not dissolve the metal element in the crystal at a synthesis temperature of 1700 ° C. or less, and the metal oxide added as a sintering aid or the like forms a glass phase at the grain boundary and remains. It has been known.
In the case of incorporating a metal element into a sialon crystal, α-sialon described in Patent Document 1 is used.
Table 1 shows crystal structure data based on the atomic coordinates of β-type silicon nitride.

CHONG-MIN WANG and 4 others "Journal of Materials Science" 1996, 31, 5281-5298

β-type Si ₃ N ₄ and β-type sialon have been studied as heat-resistant materials, and there is a description of using optically active elements in this crystal as a solid solution and using the solid solution as a phosphor. Patent Document 5 only examines specific elements.

According to Patent Document 5, only when Tb, Yb, or Ag is added as a phosphor having an emission peak at a wavelength in the range of 500 nm to 600 nm is reported.
However, the phosphor added with Tb has an excitation wavelength of 300 nm or less and cannot be used for white LED applications, and has a problem that an afterimage remains because it has a long emission lifetime and is not suitable for display applications.
Further, Yb or Ag added has a problem of low luminance.
Further, until the present invention, there has been no study of using a crystal having a β-type Si ₃ N ₄ structure as a phosphor.
Namely, a phosphor having a β-type Si ₃ N ₄ crystal structure in which a specific metal element is dissolved and having a high luminance green light emission when excited by ultraviolet rays, visible light, electron beams or X-rays. The present inventors have found for the first time an important discovery that they can be used as
As a result of further earnest studies based on this knowledge, the present inventors have obtained a phosphor exhibiting a high-luminance light emission phenomenon in a specific wavelength region by adopting the configurations described in (1) to (47) below. Succeeded in providing.
The configuration is as described below.

(1) The phosphor of the present invention includes a metal element M (where M is one selected from the group consisting of Mn, Ce and Eu) in a nitride or oxynitride crystal containing at least Si and Al. It includes a crystal phase in which two or more kinds of elements) are dissolved, and emits fluorescence having a peak in a wavelength range of 500 nm to 600 nm by irradiating an emission light source.

The phosphor of the present invention contains, as a main component, a nitride or oxynitride crystal phase solid solution having a β-type Si ₃ N ₄ crystal structure. The emission intensity in the wavelength region of ˜600 nm is high, and it is excellent as a green phosphor.
Even when exposed to a light emitting source or an excitation source, this phosphor does not decrease in luminance. By using this phosphor, VFD, FED, PDP, CRT, white LED, etc. having excellent performance can be obtained. can get.

In addition, when the phosphor of the present invention is used for a lighting fixture, it is appropriate to use ultraviolet light or visible light that includes the phosphor of the present invention and whose light emission source has a wavelength of 100 nm to 500 nm.
When the phosphor of the present invention is used for an image display device, it is appropriate to irradiate an excitation source.
The image display device is preferably a fluorescent display tube (VFD), a field emission display (FED), a plasma display panel (PDP), or a cathode ray tube (CRT).

  Hereinafter, it demonstrates in detail based on the Example of this invention.

First, the phosphor used in the lighting apparatus and image display device of the present invention (hereinafter referred to as “the phosphor of the present invention”) will be described.
The phosphor of the present invention comprises a solid solution of a crystal phase of nitride or oxynitride having a β-type Si ₃ N ₄ crystal structure (hereinafter referred to as β-type Si ₃ N _{4 group} crystal) as a main component. It is.
The β-type Si ₃ N _{4 group} crystal can be identified by X-ray diffraction or neutron diffraction, and in addition to a substance exhibiting the same diffraction as that of pure β-type Si ₃ N ₄ , the constituent element is different from other elements. A β-type Si ₃ N _{4 group} crystal whose lattice constant has been changed by replacing it is also a β-type Si ₃ N _{4 group} crystal.

Here, the crystal structure of pure β-type Si ₃ N ₄ belongs to a hexagonal system having symmetry of P6 ₃ or P6 ₃ / m, and is defined as a structure having an ideal atomic position in Table 1 (non-patent) Reference 1) Crystal.
In an actual crystal, the position of each atom varies by about ± 0.05 from the ideal position depending on the type of atom occupying each position.
The lattice constants are a = 0.7595 nm and c = 0.90223 nm, but the constituent Si is replaced by an element such as Al, N is replaced by an element such as O, or a metal such as Eu. The lattice constant changes as the element dissolves, but the atomic position given by the crystal structure, the sites occupied by the atoms, and their coordinates does not change significantly.
Therefore, given the lattice constant and the plane index of pure β-type Si ₃ N ₄ , the position (2θ) of the diffraction peak by X-ray diffraction is uniquely determined.
And when the lattice constant calculated from the X-ray diffraction result measured for the new substance and the diffraction peak position (2θ) data calculated using the surface index in Table 4 coincide, the crystal structure is the same. Can be identified.

A nitride or oxynitride crystal having a β-type Si ₃ N ₄ crystal structure is not specified if the crystal structure is the same, but β-type Si ₃ N ₄ , β-type Ge ₃ N ₄ , β-type C ₃ N ₄ and solid solutions thereof.
As a solid solution, the position of Si in the β-type Si ₃ N ₄ crystal structure may be replaced with elements of C, Si, Ge, Sn, B, Al, Ga, and In, and the position of N may be replaced with elements of O and N. it can.
Further, the substitution of these elements includes not only one kind but also substitution of two or more kinds of elements at the same time.
Among these crystals, particularly high brightness is obtained by β-type Si ₃ N ₄ and β-type sialon (Si _6-z Al _z O _z N _8-z , where 0 <z <4.2). .

In the phosphor of the present invention, from the point of fluorescence emission, the crystal phase of nitride or oxynitride having a β-type Si ₃ N ₄ crystal structure, which is a constituent component thereof, contains a high purity and as much as possible, preferably a single phase. However, it may be composed of a mixture with other crystalline phase or amorphous phase as long as the characteristics are not deteriorated.
In this case, the content of the crystal phase of nitride or oxynitride having a β-type Si ₃ N ₄ crystal structure is preferably 50% by mass or more in order to obtain high luminance.
The main component of the phosphor of the present invention is that the content of the crystal phase of nitride or oxynitride having a β-type Si ₃ N ₄ crystal structure is 50% by mass or more.

A nitride or oxynitride crystal having a β-type Si ₃ N ₄ crystal structure is used as a base crystal, and a metal element M (where M is one or more elements selected from Mn, Ce, and Eu) is used. When dissolved in the base crystal, these elements function as luminescent centers and exhibit fluorescence characteristics.
Among the elements of M, Eu is particularly excellent in green light emission characteristics.
Further, a β-type sialon crystal containing Eu, that is, a material containing Al and Eu in the crystal is particularly excellent in green emission characteristics.

By irradiating the phosphor of the present invention with a light emission source or an excitation source, fluorescence having a peak in a wavelength range of 500 nm to 600 nm is emitted.
An emission spectrum having a peak in this range emits green light.
In particular, in a sharply shaped spectrum having a peak in the wavelength range of 500 nm to 550 nm, the emitted color is an (x, y) value on the CIE chromaticity coordinates, and 0 ≦ x ≦ 0.3, 0.6 It takes a value of ≦ y ≦ 0.83 and is green with good color purity.

The luminescent light source or excitation source of a phosphor, 100 nm or more 500nm or less wavelengths of light and an electron beam (vacuum ultraviolet rays, deep ultraviolet, ultraviolet, near ultraviolet, blue visible light from violet), using X-ray when high brightness Emits fluorescence.

Although not particularly specified the type of composition as long as crystal of nitride or oxynitride having the β-Si ₃ N ₄ crystal structure in the phosphor of the present invention, with β-Si ₃ N ₄ crystal structure at the following composition A phosphor having a high content of nitride or oxynitride crystals and high luminance can be obtained.

The composition in the following range is preferable as a composition for obtaining a phosphor having a high content ratio of nitride or oxynitride crystals having a β-type Si ₃ N ₄ crystal structure and high brightness.
M (where M is one or more elements selected from Mn, Ce, Eu), A (where A is an element of C, Si, Ge, Sn, B, Al, Ga, In) And X (where X is one or two elements selected from O and N), represented by a composition formula M _a A _b X _c (where a + b + c = 1), a, b , C are 0.00001 ≦ a ≦ 0.1 (i) 0.38 ≦ b ≦ 0.46 (Ii) 0.54 ≦ c ≦ 0.62... (Iii) A value satisfying all the conditions of (iii) is selected.
a represents the amount of the element M to be the emission center, and it is preferable that the atomic ratio be 0.00001 or more and 0.1 or less.
If the a value is smaller than 0.00001, the number of Ms as the emission center is small, and the emission luminance is lowered.
If it is greater than 0.1, concentration quenching occurs due to interference between M ions, and the luminance decreases.
b is the amount of the metal element constituting the host crystal, and it is preferable that the atomic ratio be 0.38 or more and 0.46 or less.
Preferably, b = 0.429 is good.
When the b value is out of this range, the bonds in the crystal become unstable, the generation rate of crystal phases other than the β-type Si ₃ N ₄ structure increases, and the green emission intensity decreases.
c is the amount of the nonmetallic element constituting the host crystal, and it is preferable that the atomic ratio be 0.54 or more and 0.62 or less.
Preferably, c = 0.571 is good.
If the c value is out of this range, the bonds in the crystal become unstable, the generation rate of crystal phases other than the β-type Si ₃ N ₄ structure increases, and the green emission intensity decreases.

When β-sialon is used as a base crystal, a phosphor having high luminance can be obtained with the following composition.
M (where M is one or more elements selected from Mn, Ce, Eu) and Al, Si, O, N elements, and a composition formula M _a Si _b1 Al _b2 O _c1 N _c2 (where a + b ₁ + b ₂ + c ₁ + c ₂ = 1), and a, b ₁ , b ₂ , c ₁ , c ₂ are 0.00001 ≦ a ≦ 0.1. (I) 0.28 ≦ b ₁ ≦ 0.46 (ii) 0.001 ≦ b ₂ ≦ 0.3 (Iii) 0.001 ≦ c ₁ ≦ 0.3 (iv) 0.44 ≦ c ₂ ≦ 0.62 ... (v) Selected from values that satisfy all of the above conditions.
a represents the amount of the element M to be the emission center, and it is preferable that the atomic ratio be 0.00001 or more and 0.1 or less.
If the a value is smaller than 0.00001, the number of Ms as the emission center is small, and the emission luminance is lowered.
If it is greater than 0.1, concentration quenching occurs due to interference between M ions, and the luminance decreases.
b ₁ is the amount of Si, and it is preferable that the atomic ratio be 0.28 or more and 0.46 or less.
b ₂ is the amount of Al, it is preferable to be 0.001 to 0.3 in atomic ratio.
Further, the sum of the values of b ₁ and b ₂ is preferably 0.41 or more and 0.44 or less, and more preferably 0.429.
If the b ₁ and b ₂ values are out of this range, the rate of formation of crystal phases other than β-sialon increases, and the green emission intensity decreases.
c ₁ is the amount of oxygen, and it is preferable that the atomic ratio be 0.001 or more and 0.3 or less.
c ₂ is the amount of nitrogen, it is preferable to be 0.44 or more 0.62 or less in atomic ratio.
The sum of the values of c ₁ and c ₂ is preferably 0.56 or more and 0.59 or less.
Preferably, c = 0.571 is good.
If the c ₁ and c ₂ values are out of this range, the rate of generation of crystal phases other than β-sialon increases, and the green emission intensity decreases.

When β-sialon is used as the host crystal and Eu is used as the emission center, a phosphor with particularly high luminance can be obtained with the following composition.
Eu _a Si _b1 Al _b2 O _c1 N _c2 (in the formula, a + b ₁ + b ₂ + c ₁ + c ₂ = 1), and a, b ₁ , b ₂ , c ₁ and c ₂ are 0.00001 ≦ a ₁ ≦ 0.1 (i) 0.28 ≦ b ₁ ≦ 0.46 (ii) 0.001 ≦ b ₂ ≦ 0.3 (iii) 0.001 ≦ c ₁ ≦ 0.3 (iv) 0.44 ≦ c ₂ ≦ 0.62... (V) Selected from values that satisfy all the above conditions.
b ₁ is the amount of Si, and it is preferable that the atomic ratio be 0.28 or more and 0.46 or less.
b ₂ is the amount of Al, it is preferable to be 0.001 to 0.3 in atomic ratio.
Further, the sum of the values of b ₁ and b ₂ is preferably 0.41 or more and 0.44 or less, and preferably 0.429.
If the b ₁ and b ₂ values are out of this range, the rate of formation of crystal phases other than β-sialon increases, and the green emission intensity decreases.
c ₁ is the amount of oxygen, and it is preferable that the atomic ratio be 0.001 or more and 0.3 or less.
c ₂ is the amount of nitrogen, it is preferable to be 0.54 or more 0.62 or less in atomic ratio.
The sum of the values of c ₁ and c ₂ is preferably 0.56 or more and 0.59 or less.
Preferably, c = 0.571 is good.
If the c ₁ and c ₂ values are out of this range, the rate of generation of crystal phases other than β-sialon increases, and the green emission intensity decreases.

Further, these compositions may contain other elements as impurities as long as the characteristics are not deteriorated.
Impurities that degrade the light emission characteristics include Fe, Co, Ni, and the like. When the total of these three elements exceeds 500 ppm, the light emission luminance decreases.

As described above, the phosphor of the present invention is preferably composed of a single phase of a crystal phase of nitride or oxynitride having a β-type Si ₃ N ₄ crystal structure as a crystal phase, but the characteristics are not deteriorated. It can also be composed of a mixture with other crystalline phase or amorphous phase within the range.
In this case, the content of the crystal phase of nitride or oxynitride having a β-type Si ₃ N ₄ crystal structure is preferably 50% by mass or more in order to obtain high luminance.
The ratio of the content is determined by X-ray diffraction measurement, based on the ratio of the strength of the strongest peak in each of the crystal phase of nitride or oxynitride having a β-type Si ₃ N ₄ crystal structure and the other crystal phase. Can be sought.

In a phosphor composed of a mixture with another crystal phase or an amorphous phase, it can be a mixture with a conductive inorganic substance.
When the phosphor of the present invention is excited with an electron beam in a VFD, PDP, or the like, it is preferable that the phosphor has a certain degree of conductivity so that electrons do not accumulate on the phosphor and escape to the outside.
As the conductive substance, an oxide, an oxynitride, a nitride, or a mixture thereof containing one or more elements selected from Zn, Ga, In, and Sn can be given.
Among these, indium oxide and indium-tin oxide (ITO) are preferable because they have little decrease in fluorescence intensity and high conductivity.

The form of the phosphor of the present invention is not particularly defined, but when used as a powder, a single crystal having an average particle size of 50 nm or more and 20 μm or less is preferable because high luminance is obtained.
Furthermore, a single crystal having an average aspect ratio (a value obtained by dividing the length of the major axis of the particle by the length of the minor axis) of 1.5 or more and 20 or less has higher luminance.
When the average particle diameter is larger than 20 μm, the dispersibility deteriorates when applied to a lighting fixture or an image display device, and color unevenness occurs, which is not preferable.
If it is smaller than 50 nm, the powder is agglomerated and the operability is deteriorated.
In the case of single crystal particles having an average aspect ratio (value obtained by dividing the length of the major axis of the particle by the length of the minor axis) of 1.5 or more, the emission luminance is particularly high.
This is because when a crystal having a β-type silicon nitride structure grows at a high temperature, a relatively large amount of a metal element such as Eu is incorporated into the crystal, and there are few crystal defects that hinder fluorescence and transparency. Therefore, the luminance is high.
However, when the aspect ratio exceeds 20, needle crystals are formed, which is not preferable from the environmental viewpoint.
In that case, it is good to grind | pulverize by the manufacturing method of this invention.

  Although the manufacturing method of the phosphor of the present invention is not particularly specified, the following method can be given as an example.

By firing a mixture of metal compounds, a composition of M _a Si _b Al _c O _d N _e (where M is one or more elements selected from Mn, Ce, Eu) can be formed. The raw material mixture is fired in a nitrogen atmosphere.
Since the optimum firing temperature differs depending on the composition, it cannot be defined unconditionally, but in general, a green phosphor can be stably obtained in a temperature range of 1820 ° C. or higher and 2200 ° C. or lower.
When the firing temperature is lower than 1820 ° C., the element M serving as the light emission center is not dissolved in the crystal of nitride or oxynitride having the β-type Si ₃ N ₄ crystal structure, and the oxygen content is high in the grain boundary phase. Therefore, light emitted from the oxide glass as a host is emitted, and light having a low wavelength such as blue is emitted, and green fluorescence cannot be obtained.
In Patent Document 5, the firing temperature is 1550 ° C., and the element M remains at the grain boundary.
That is, in Patent Document 5, even when the same Eu is used as the activator element, the emission wavelength is blue of 410 to 440 nm, which is essentially different from the emission wavelength of 500 to 550 nm of the phosphor of the present invention.
Further, when the firing temperature is 2200 ° C. or higher, a special apparatus is required, which is not industrially preferable.
Among the elements M serving as the emission center, Eu is preferable because high luminance can be obtained.

The mixture of the metal compound is preferably a mixture of a metal compound containing M selected from M metal, oxide, carbonate, nitride, or oxynitride, silicon nitride, and aluminum nitride.
In addition to being able to obtain a highly pure synthetic product with high reactivity, these have the advantage that they are produced as industrial raw materials and are easily available.

In order to improve the reactivity at the time of baking, the inorganic compound which produces | generates a liquid phase at the temperature below a calcination temperature can be added to the mixture of a metal compound as needed.
As the inorganic compound, those that generate a stable liquid phase at the reaction temperature are preferable. Fluoride, chloride, iodide, bromide, or phosphate of the elements Li, Na, K, Mg, Ca, Sr, Ba Is suitable.
Furthermore, these inorganic compounds may be added alone or in combination of two or more.
Among these, calcium fluoride is suitable because it has a high ability to improve the reactivity of synthesis.
The amount of the inorganic compound added is not particularly limited, but the effect is particularly great when it is 0.1 parts by weight or more and 10 parts by weight or less with respect to 100 parts by weight of the mixture of the starting metal compound.
When the amount is less than 0.1 part by weight, the reactivity is not improved, and when the amount exceeds 10 parts by weight, the luminance of the phosphor decreases.
When these inorganic compounds are added and baked, the reactivity is improved, grain growth is promoted in a relatively short time, and a single crystal having a large grain size grows, thereby improving the luminance of the phosphor.
Furthermore, the brightness of the phosphor is improved by reducing the content of the inorganic compound contained in the reaction product obtained by firing by washing with a solvent that dissolves the inorganic compound after firing.
Examples of such a solvent include water, ethanol, sulfuric acid, hydrofluoric acid, and a mixture of sulfuric acid and hydrofluoric acid.

The nitrogen atmosphere is preferably a gas atmosphere in a pressure range of 0.1 MPa to 100 MPa.
More preferably, it is 0.5 MPa or more and 10 MPa or less.
When silicon nitride is used as a raw material, heating to a temperature of 1820 ° C. or higher is not preferable if the nitrogen gas atmosphere is lower than 0.1 MPa because the raw material is thermally decomposed.
When it is higher than 0.5 MPa, it hardly decomposes.
10 MPa is sufficient, and if it exceeds 100 MPa, a special apparatus is required, which is not suitable for industrial production.

According to a method in which a metal compound in the form of powder or aggregate is filled in a container in a state where the bulk density is kept at 40% or less and then baked, particularly high luminance can be obtained.
When a fine powder having a particle size of several μm is used as a starting material, the mixture of metal compounds after the mixing step has a form in which fine powder having a particle size of several μm is aggregated to a size of several hundred μm to several mm (powder). Called aggregates).
In the present invention, the powder aggregate is fired in a state where the bulk density is maintained at a filling rate of 40% or less.
That is, in normal sialon production, firing is performed after the hot press method or mold forming and the powder is filled at a high filling rate. However, in the present invention, mechanical force is applied to the powder. Without using a mold or the like in advance, a mixture of powder agglomerates having the same particle size is filled into a container or the like with a bulk density of 40% or less.
If necessary, the powder aggregate can be granulated to an average particle size of 500 μm or less using a sieve or air classification, and the particle size can be controlled.
Moreover, you may granulate directly in the shape of 500 micrometers or less using a spray dryer etc.
Further, when the container is made of boron nitride, there is an advantage that there is little reaction with the phosphor.

Firing while maintaining the bulk density at 40% or less is that when the firing is performed in a state where there is a free space around the raw material powder, the crystals of the reaction product grow in the free space, so that the crystals contact each other. This is because a crystal with fewer surface defects can be synthesized.
Thereby, a fluorescent substance with high brightness is obtained.
If the bulk density exceeds 40%, densification occurs partially during firing, resulting in a dense sintered body that hinders crystal growth and lowers the brightness of the phosphor.
Moreover, a fine powder cannot be obtained.
Further, the size of the powder aggregate is particularly preferably 500 μm or less because of excellent grindability after firing.

Next, a powder aggregate having a filling rate of 40% or less is fired under the above conditions.
The furnace used for firing is a metal resistance heating resistance heating method or a graphite resistance heating method because the firing temperature is high and the firing atmosphere is nitrogen, and an electric furnace using carbon as a material for the high temperature part of the furnace is suitable. It is.
As the firing method, a sintering method in which mechanical pressure is not applied from the outside, such as an atmospheric pressure sintering method or a gas pressure sintering method, is preferable because firing is performed while maintaining a high bulk density.

When the powder aggregate obtained by firing is firmly fixed, it is pulverized by a pulverizer usually used in factories such as a ball mill and a jet mill.
Among these, ball milling makes it easy to control the particle size.
The balls and pots used at this time are preferably made of a silicon nitride sintered body or a sialon sintered body.
Particularly preferably, a ceramic sintered body having the same composition as the phosphor used as the product is preferable.
Grinding is performed until the average particle size becomes 20 μm or less.
The average particle size is particularly preferably 20 nm or more and 5 μm or less.
When the average particle diameter exceeds 20 μm, the fluidity of the powder and the dispersibility in the resin are deteriorated, and the light emission intensity becomes uneven depending on the part when the light emitting device is formed in combination with the light emitting element.
When the thickness is 20 nm or less, the operability for handling the powder is deteriorated.
If the desired particle size cannot be obtained only by grinding, classification can be combined.
As a classification method, sieving, air classification, precipitation in a liquid, or the like can be used.

Acid treatment may be performed as one method of pulverization classification.
In many cases, the powder aggregate obtained by firing is firmly fixed in a grain boundary phase in which a single crystal of nitride or oxynitride having a β-type Si ₃ N ₄ crystal structure is mainly composed of a small amount of glass phase. It has become a state.
In this case, when immersed in an acid having a specific composition, the grain boundary phase mainly composed of the glass phase is selectively dissolved, and the single crystal is separated.
As a result, each particle is not a single crystal aggregate, but is obtained as a single particle of nitride or oxynitride single crystal having a β-type Si ₃ N ₄ crystal structure.
Since such particles are composed of a single crystal with few surface defects, the luminance of the phosphor is particularly high.

Examples of the acid effective for this treatment include hydrofluoric acid, sulfuric acid, hydrochloric acid, and a mixture of hydrofluoric acid and sulfuric acid.
Among them, a mixture of hydrofluoric acid and sulfuric acid has a high glass phase removal effect.

Although fine phosphor powder is obtained by the above steps, heat treatment is effective for further improving the luminance.
In this case, the powder after firing or the powder whose particle size has been adjusted by pulverization or classification can be heat-treated at a temperature of 1000 ° C. or higher and lower than the firing temperature.
At a temperature lower than 1000 ° C., the effect of removing surface defects is small.
Above the firing temperature, the pulverized powders are fixed again, which is not preferable.
Although the atmosphere suitable for the heat treatment varies depending on the composition of the phosphor, one or two or more mixed atmospheres selected from nitrogen, air, ammonia, and hydrogen can be used. Particularly, the nitrogen atmosphere is effective for defect removal. It is preferable because it is excellent.

The nitride obtained as described above has a broad excitation range from ultraviolet to visible light, and has a green peak in the range of 500 nm to 600 nm, compared to normal oxide phosphors and existing sialon phosphors. Is suitable for the lighting apparatus and the image display device of the present invention.
In addition, since it does not deteriorate even when exposed to high temperatures, it has excellent heat resistance, and excellent long-term stability in an oxidizing atmosphere and moisture environment.

The lighting fixture of this invention is comprised using the light-emitting light source and the fluorescent substance of this invention at least.
Examples of lighting fixtures include LED lighting fixtures and fluorescent lamps.
The LED lighting apparatus can be manufactured by using the phosphor of the present invention by a known method as described in JP-A-5-152609, JP-A-7-99345, JP-A-2927279, and the like.
In this case, it is desirable that the light emitting light source emits light having a wavelength of 330 to 500 nm, and among them, an ultraviolet (or purple) LED light emitting element or LD light emitting element of 330 to 420 nm and a blue LED or LD light emitting element of 420 to 500 nm are preferable. .

  These light emitting elements include those made of nitride semiconductors such as GaN and InGaN, and can be light emitting light sources that emit light of a predetermined wavelength by adjusting the composition.

In addition to the method of using the phosphor of the present invention alone in a lighting fixture, a lighting fixture emitting a desired color can be configured by using it together with a phosphor having other light emission characteristics.
As an example of this, an ultraviolet LED or LD light emitting element of 330 to 420 nm, a blue phosphor excited at this wavelength and having an emission peak at a wavelength of 420 nm or more and 500 nm or less, and red fluorescence having an emission peak at a wavelength of 600 nm or more and 700 nm or less. Body and the green phosphor of the present invention.
Examples of such blue phosphor include BaMgAl ₁₀ O ₁₇ : Eu, and examples of red phosphor include CaSiAlN ₃ : Eu described in Japanese Patent Application No. 2003-394855.
In this configuration, when the phosphors are irradiated with ultraviolet rays emitted from the LED or LD, light of three colors of red, green, and blue is emitted, and a white lighting device is obtained by mixing these.

As another method, there is a combination of a 420 to 500 nm blue LED or LD light emitting element, a red phosphor having an emission peak at a wavelength of 600 nm to 700 nm and excited by this wavelength, and the phosphor of the present invention.
Examples of such a red phosphor include CaSiAlN ₃ : Eu described in Japanese Patent Application No. 2003-394855.
In this configuration, when blue light emitted from the LED or LD is applied to the phosphor, light of two colors, red and green, is emitted, and the blue light of the LED or LD itself is mixed to produce a white or reddish bulb. It becomes a color lighting fixture.

As another method, there is a combination of a blue LED or LD having a wavelength of 420 to 500 nm, a yellow or orange phosphor having an emission peak at a wavelength of 550 to 600 nm when excited at this wavelength, and the phosphor of the present invention. .
Examples of such a yellow or orange phosphor include (Y, Gd) ₂ (Al, Ga) ₅ O ₁₂ : Ce described in JP-A-9-218149 and α-sialon described in JP-A 2002-363554. : Eu can be mentioned.
Among these, Ca-α-sialon in which Eu is dissolved is good because the emission luminance is high.
In this configuration, when blue light emitted from the LED or LD is irradiated onto the phosphor, yellow or orange light and green light are emitted, and the blue light of the LED or LD itself is mixed to produce white light. It becomes a lighting fixture.
Further, by changing the blending amount of the two types of phosphors, it is possible to adjust to light of a wide range of pale light, white, and reddish bulb color.

The image display device of the present invention is composed of at least an excitation source and the phosphor of the present invention, and includes a fluorescent display tube (VFD), a field emission display (FED), a plasma display panel (PDP), a cathode ray tube (CRT), and the like. .
The phosphor of the present invention has been confirmed to emit light by excitation of vacuum ultraviolet rays of 100 to 190 nm, ultraviolet rays of 190 to 380 nm, electron beams, etc., and in combination of these excitation sources and the phosphor of the present invention, An image display apparatus as described above can be configured.

  Next, the present invention will be described in more detail with reference to the following examples, which are disclosed as an aid for easy understanding of the present invention, and the present invention is limited to these examples. It is not a thing.

Example 1; raw material powder: silicon nitride powder having an average particle size of 0.5 μm, oxygen content of 0.93% by weight, α-type content of 92%, specific surface area of 3.3 m ² / g, oxygen content of 0.79 % Aluminum nitride powder, purity 99.9% europium oxide powder was used.
To _obtain compounds represented by the composition formula Eu _0.00296 Si _0.41395 Al _0.01334 O _0.00444 N _0.56528 (Table 2 shows the design composition, and Table 3 shows the mixed composition and firing temperature of the raw material powder). The silicon nitride powder, the aluminum nitride powder, and the europium oxide powder were weighed to 94.77 wt%, 2.68 wt%, and 2.556 wt%, respectively. It mixed for 2 hours with the wet ball mill using the ball | bowl made from a silicon sintered compact, and n-hexane.
N-Hexane was removed by a rotary evaporator to obtain a dry product of the mixed powder.
The obtained mixture was pulverized using an agate mortar and pestle and then passed through a 500 μm sieve to obtain a powder aggregate having excellent fluidity.
When this powder aggregate was naturally dropped into a boron nitride crucible having a diameter of 20 mm and a height of 20 mm, the bulk density was 30% by volume.
The bulk density was calculated from the weight of the charged powder aggregate and the internal volume of the crucible.
Next, the crucible was set in a graphite resistance heating type electric furnace.

In the firing operation, first, the firing atmosphere is evacuated by a diffusion pump, heated from room temperature to 800 ° C. at a rate of 500 ° C. per hour, introduced with nitrogen having a purity of 99.999% by volume at 800 ° C. and a pressure of 1 MPa, The temperature was raised to 1900 ° C. at 500 ° C. per hour and held at 1900 ° C. for 8 hours.
First, the synthesized sample using an agate mortar, and ground to a powder, was carried out the powder X-ray diffraction measurement using a K _alpha line of Cu (XRD).
As a result, the obtained chart shows the pattern shown in FIG. 1, has a β-type silicon nitride structure, and contains Al and O in the composition analysis, so that β-type sialon is generated. all right.
The fired body thus obtained was roughly pulverized and then pulverized with a silicon nitride mortar and pestle.
When the particle size distribution was measured, the average particle size was 4 μm.

The composition analysis of this powder was performed by the following method.
First, 50 mg of a sample was put in a platinum crucible, 0.5 g of sodium carbonate and 0.2 g of boric acid were added and heated to melt, and then dissolved in 2 ml of hydrochloric acid to prepare a measurement solution having a constant volume of 100 ml.
The amount of Si, Al, Eu, and Ca in the powder sample was quantified by ICP emission spectroscopic analysis of this liquid sample.
In addition, 20 mg of a sample was put into a tin capsule, and this was put into a nickel basket, and oxygen and nitrogen in the powder sample were quantified using a LECO TC-436 type oxygen-nitrogen analyzer.
Furthermore, in order to quantify the amount of impurities of trace components in the powder, 50 mg of a sample and 50 mg of graphite powder were mixed and packed in a graphite electrode, and B, Fe, The amount of impurities of Ca, Mg, Al, and Cr was quantified.
The measurement results by ICP emission spectrometry and oxygen-nitrogen analyzer were as follows: Eu: 2.16 ± 0.02 mass%, Si: 55.6 ± 0.1 mass%, Al: 1.64 ± 0.1 mass%, N: 38.0 ± 0.1 mass%, O: 2.1 ± 0.1 mass%.
The composition (in atomic number display) of the synthesized inorganic compound calculated from the analysis results of all elements is Eu _0.00290 Si _0.40427 Al _0.01210 O _0.02679 N _0.55391 .
Compared with the design composition shown in Table 2 (Eu _0.00296 Si _0.41395 Al _0.01334 O _0.00444 N _0.56528 ), the oxygen content is particularly high.
This is because the impurity oxygen contained in the silicon nitride and aluminum nitride used as raw materials.

The sialon composition of the present invention is ideally a composition of Si _6-z Al _z O _z N _8-z (where 0 <z <4.2), but a part of N in this composition is substituted with O. Those obtained are included in the scope of the invention, and even in this case, a green phosphor with high luminance can be obtained.
Impurity elements detected by CID-DCA emission spectroscopic analysis are as follows: Y is 0.009 mass%, B is 0.001 mass%, Fe is 0.003 mass%, Ca is 0.001 mass% or less, Mg Was 0.001 mass% or less, and Cr was 0.001 mass% or less.
The form of this powder was observed with a scanning electron microscope (SEM).
As shown in FIG. 2, it was confirmed to be a needle-like crystal having a minor axis of 100 to 500 nm and a major axis of about 4 μm.
This form of crystal indicates that the crystal has grown in free space via the gas phase or liquid phase, which is essentially different from synthesis at a low temperature of 1800 ° C. or lower.
The form of the powder was observed with a transmission electron microscope (TEM) (FIGS. 3A and 3B).
As shown in FIG. 3A, the particle is a single crystal having no grain boundary phase and is characterized by few defects in the particle.
In addition, according to high-resolution observation (FIG. 3-2), there is an amorphous phase of 0.7 nm on the surface of the single crystal particles, but there are no other amorphous and crystalline phases. Was confirmed.
This amorphous phase is silicon oxide resulting from oxidation of the particle surface.

In order to investigate the presence of Eu in the particles, the spectrum of Eu was measured using an electron energy loss analyzer (EELS) attached to the TEM (FIG. 3-3).
The spectrum showing the electronic state of Eu is almost the same at the particle surface (chart (a) in FIG. 3-3) and the center of the particle (chart (b) in FIG. 3-3). It was confirmed that the spectrum was the same as that of europium (Eu ₂ O ₃ ; chart (c) in FIG. 3-3).
That is, it was confirmed that Eu exists in the grains and is not unevenly distributed in the amorphous surface phase.
The uniformity of the powder was observed with an SEM equipped with a cathodoluminescence (CL) detector, and the cathodoluminescence image (CL image) was evaluated.
This device detects visible light generated by irradiating an electron beam and obtains it as a photographic image that is two-dimensional information, thereby clarifying which wavelength of light is emitted at which location. .

By observation of the emission spectrum of FIG. 4-1, it was confirmed that this phosphor was excited by an electron beam and emitted green light having a wavelength of 530 nm.
Further, according to the CL image (FIG. 4-2) in which several tens of particles were observed, it was confirmed that there was no portion where a specific portion emitted light, and the inside of the particles emitted green light uniformly.
In addition, it was confirmed that there were no particles that emitted particularly intense light, and that all tens of particles emitted uniformly green.
Note that the portion observed white in the CL image is a portion emitting light of 530 nm, and the white light is displayed in black and white color display, indicating that the green emission is stronger.

When the observation results of the above XRD chart, SEM image, TEM image, EELS spectrum, and CL image are combined, this powder has (1) β-sialon having a β-type Si ₃ N ₄ structure as a base crystal, and Eu has (2) Composition is Eu _0.00290 Si _0.40427 Al _0.01210 O _0.02679 N _0.55391 , and (3) Eu is uniformly in the β-sialon crystal. Distributed, (4) does not form other phases such as second phase and grain boundary phase, is a single phase substance, (5) each particle is a single crystal, (6 ) It was confirmed that each particle emitted light uniformly.
A phosphor having such characteristics has not been reported in the past, and was first discovered by the present inventors.
As a result of irradiating the powder with a lamp emitting light having a wavelength of 365 nm, it was confirmed that the powder emitted green light.
As a result of measuring the emission spectrum and excitation spectrum (FIG. 5) of this powder using a fluorescence spectrophotometer, this powder has an excitation spectrum peak at 303 nm and a peak at 535 nm green light in the emission spectrum by excitation at 303 nm. It was found to be a certain phosphor.
The peak emission intensity was 3948 counts.
Since the count value varies depending on the measuring device and conditions, the unit is an arbitrary unit.
That is, the comparison can be made only in the present example and the comparative example measured under the same conditions.
The CIE chromaticity of light emitted by excitation at 303 nm was green with x = 0.32 and y = 0.64.

Examples 2 to 24 were further performed based on the same method and procedure as in Example 1.
The design composition and the mixed composition of the raw material powder are summarized in Tables 2 and 3.

Examples 2 to 24: Using the same raw material powder as in Example 1, predetermined amounts of silicon nitride powder, aluminum nitride powder and europium oxide powder were weighed to obtain the composition shown in Table 2, and the silicon nitride sintered body was manufactured. And a ball made of a silicon nitride sintered body and n-hexane were mixed for 2 hours by a wet ball mill.
N-Hexane was removed by a rotary evaporator to obtain a dry product of the mixed powder.
The obtained mixture was pulverized using an agate mortar and pestle and then passed through a 500 μm sieve to obtain a powder aggregate having excellent fluidity.
The powder aggregate was naturally dropped into a boron nitride crucible having a diameter of 20 mm and a height of 20 mm.
Next, the crucible was set in a graphite resistance heating type electric furnace.
In the firing operation, first, the firing atmosphere is evacuated by a diffusion pump, heated from room temperature to 800 ° C. at a rate of 500 ° C. per hour, introduced with nitrogen having a purity of 99.999% by volume at 800 ° C. and a pressure of 1 MPa, The temperature was raised to 1900 ° C. or 2000 ° C. at 500 ° C. per hour and held at that temperature for 2 hours.
All the fired products thus obtained contained 50 mass% or more of β-type Si ₃ N ₄ or β-type sialon, and were subjected to fluorescence spectroscopic measurement. A phosphor emitting green with a peak at a wavelength between ˜550 nm was obtained.
Table 4 below collectively shows the optical characteristics of the above examples and comparative examples disclosed below.

Comparative Examples 1 to 5: Inorganic compound powders were prepared in the same manner as in Examples 2 to 24 except for the compositions and firing temperatures shown in Tables 2 and 3.
Comparative Example 1 has a composition close to that of Example 14, but does not contain Eu.
The inorganic compound obtained by baking at 2000 ° C. for 2 hours is β-sialon with z = 0.5, but does not emit any light even when excited with light in the range of 200 nm to 500 nm because it does not contain Eu.
Comparative Example 2 has a composition close to that of Example 20, but does not contain Al.
The inorganic compound obtained by firing at 2000 ° C. for 2 hours is β-Si ₃ N ₄ , but under these conditions, Eu did not dissolve in the grains but remained in the grain boundary glass phase, and as shown in FIG. The emission of was not shown.
Comparative Examples 3 to 5 have the same composition as Examples 16 to 18, respectively, but the firing temperature is low.
The inorganic compound obtained by firing at 1800 ° C. for 2 hours is β-sialon with z = 1, but since the firing temperature is low, most of Eu remains as a grain boundary phase without being dissolved in the grains. When excited with, it emitted blue light as shown in FIG. 7 and did not show green light.

Next, a lighting fixture using the nitride phosphor of the present invention will be described.
FIG. 8 shows a schematic structural diagram of a white LED as a lighting fixture.
A blue LED 2 having a wavelength of 460 nm is used as a light emitting element, and the phosphor of Example 1 of the present invention and Ca having a composition of Ca _0.75 Eu _0.25 Si _8.625 A1 _3.375 O _1.125 N _14.875. -Α-sialon: a structure in which a yellow phosphor of Eu is dispersed in a resin layer and covered on the blue LED 2.
When an electric current is passed through the conductive terminal, the LED 2 emits light of 460 nm, and this light excites the yellow phosphor and the green phosphor to emit yellow and green light, and the LED light and yellow and green are mixed. It functions as a lighting device that emits white light.
Since this lighting fixture has a green component as compared with the case of using a single yellow phosphor, the color rendering property is high.

The lighting apparatus produced by the mixing | blending design different from the said mixing | blending is shown.
First, a blue LED having a wavelength of 460 nm is used as the light emitting element, and the phosphor of Example 1 of the present invention and the red phosphor (CaSiAlN ₃ : Eu) are dispersed in a resin layer and covered with an ultraviolet LED.
When a current is passed through the conductive terminal, the LED emits light of 460 nm, and this light excites the red phosphor and the green phosphor to emit red and green light.
The blue light emitted from the LED itself and the light from these phosphors are mixed to function as an illumination device that emits white light.

The lighting apparatus produced by the mixing | blending design different from the said mixing | blending is shown.
First, a 380 nm ultraviolet LED is used as a light emitting element, and the phosphor of Example 1 of the present invention, a blue phosphor (BaMgAl ₁₀ O ₁₇ : Eu), and a red phosphor (CaSiAlN ₃ : Eu) are dispersed in a resin layer. The structure is made to cover the ultraviolet LED.
When a current is passed through the conductive terminal, the LED emits light of 380 nm, and this light excites the red phosphor, the green phosphor, and the blue phosphor to emit red, green, and blue light.
These lights are mixed to function as a lighting device that emits white light.

Next, a design example of an image display device using the nitride phosphor of the present invention will be described.
FIG. 9 is a principle schematic diagram of a plasma display panel as an image display device.
The green phosphor, red phosphor (Y (PV) O ₄ : Eu), and blue phosphor (BaMgAl ₁₀ O ₁₇ : Eu) of Example 1 of the present invention are applied to the inner surfaces of the respective cells 11, 12, and 13. ing.
When the electrodes 14, 15, 16, and 17 are energized, vacuum ultraviolet rays are generated by Xe discharge in the cell, thereby exciting the phosphors to emit red, green, and blue visible light, and this light is emitted from the protective layer 20, It is observed from the outside through the dielectric layer 19 and the glass substrate 22 and functions as an image display.

  The nitride phosphor of the present invention emits green light different from that of conventional sialon and oxynitride phosphors, and further, since the luminance of the phosphor is less lowered when exposed to a light emission source or excitation source, By using a nitride phosphor, it is possible to obtain the lighting apparatus and image display device of the present invention such as VFD, FED, PDP, CRT, white LED, etc., which have excellent performance, and will be greatly utilized in material design in various display devices in the future. Can be expected to contribute to industrial development.

X-ray diffraction chart of the inorganic compound of Example 1 The figure which shows the scanning electron microscope (SEM) image of the inorganic compound of Example 1 The figure which shows the transmission electron microscope (TEM) image of the inorganic compound of Example 1. The figure which showed the transmission electron microscope (TEM) image of the inorganic compound of Example 1 in high resolution The figure which shows the observation spectrum of intra-particle Eu by the electron beam energy loss analyzer (EELS) attached to TEM. Emission spectrum showing emission characteristics of inorganic compound of Example 1 The figure which shows the image observed with the cathodoluminescence detector (CL) of the inorganic compound of Example 1. Excitation spectrum and emission spectrum by fluorescence measurement of Example 1 Emission spectrum of Comparative Example 2 Emission spectra of Comparative Examples 3-5 Schematic of the lighting fixture (LED lighting fixture) by this invention. 1 is a schematic view of an image display device (plasma display panel) according to the present invention.

Explanation of symbols

1. A mixture of the green phosphor of the present invention (Example 1), a red phosphor and a blue phosphor, or a mixture of the green phosphor of the present invention (Example 1) and a red phosphor, or the green of the present invention A mixture of a phosphor (Example 1) and a yellow phosphor.
2. LED chip.
3, 4. Conductive terminal.
5). Wire bond.
6). Resin layer.
7). container.
8). Red phosphor.
9. Green phosphor.
10. Blue phosphor.
11, 12, 13. UV light emitting cell.
14, 15, 16, 17. electrode.
18, 19. Dielectric layer.
20. Protective layer.
21,22. Glass substrate.

Claims (1)

  A metal element M (wherein M is one or more elements selected from the group consisting of Mn, Ce and Eu) is dissolved in a nitride or oxynitride crystal containing at least Si and Al. A phosphor having a peak in a wavelength range of 500 nm to 600 nm by irradiating a light source.