JP5170247B2 - Li-containing α-sialon phosphor, method for producing the same, lighting apparatus, and image display device - Google Patents

Description

  The present invention relates to an optical functional material having a function of converting part of irradiated light into light having a wavelength different from that, and a method for manufacturing the same. Specifically, the present invention relates to a sialon-based phosphor activated with a rare earth metal element suitable for an ultraviolet to blue light source. The present invention also relates to a method for producing the sialon phosphor, a light emitting device and an image display device using the same.

  In recent years, blue light emitting diodes (LEDs) have been put into practical use, and white LEDs using the blue LEDs have been vigorously developed. White LEDs have lower power consumption and longer life than existing white light sources, and are therefore being used for backlights for liquid crystal panels, indoor and outdoor lighting devices, and the like.

  The white LED currently being developed is obtained by applying YAG (yttrium, aluminum, garnet) doped with Ce on the surface of a blue LED. However, the fluorescence wavelength of YAG doped with Ce is in the vicinity of 530 nm. If this fluorescent color and the light of a blue LED are mixed to form white light, white light with strong bluish light is obtained, and good white color cannot be obtained.

  On the other hand, it is known that an α-sialon-based phosphor activated with a rare earth element generates fluorescence having a longer wavelength than that of Ce-doped YAG (see Patent Document 1). When a white LED is configured using such sialon fluorescence, a white LED with a light bulb color having a lower color temperature than a white LED using YAG can be produced.

In Non-Patent Document 1, when the composition formula of the sialon-based phosphor is expressed by M _x Si _{12- (m + n)} Al _{m + n On} N _16-n , the maximum intensity is obtained when m = 2.8. The peak wavelength of is around 595 nm. This fluorescent wavelength is suitable for a white LED having a low color temperature such as a light bulb color. However, white LEDs having higher color temperatures such as daylight white and daylight with higher color temperatures cannot be produced.

  Daylight white and daylight colors are widely used not only for lighting but also for backlights of liquid crystal display devices, and societal needs are greater than those of light bulbs. Therefore, it is desired to shorten the wavelength of the fluorescence of the sialon phosphor. However, as can be seen from Non-Patent Document 1, in the α-sialon phosphor containing Ca, the fluorescence intensity decreases when the fluorescence wavelength is shorter than 595 nm. Therefore, it has been difficult to produce a sialon-based phosphor that emits short-wavelength fluorescence suitable for producing a high-brightness daylight white or daylight color LED in combination with a blue LED.

  In order to solve this, Patent Document 2 discloses a Li (lithium) -containing α-sialon-based phosphor. This sialon can emit fluorescence having a shorter wavelength than the Ca-containing α-sialon phosphor. However, in the present invention, the Li-containing α-sialon-based phosphor is obtained in a pressurized atmosphere of 1 MPa of nitrogen, and the cost is low in that the manufacturing process is complicated and a manufacturing apparatus that can withstand high-temperature and high-pressure nitrogen gas is used. It is produced by such a method. In the above sialon composition formula, x1 representing the Li content is an abnormally large value of 1.2 ≦ x1 ≦ 2.4, and a Li-containing α-sialon phosphor having a desired composition is reproducible. Difficult to make well.

  As a report of Li-containing α-sialon-based phosphor, there is Patent Document 3 in addition to Patent Document 2, but the emission wavelength of the disclosed Li-containing α-sialon-based phosphor is 585 nm, and The composition of the Li-containing α-sialon phosphor is different. With such an emission wavelength, a daylight white or daylight color LED cannot be obtained even when combined with a blue light emitting diode.

  Furthermore, in the invention of the cited document 2, no consideration is given to the form and aggregation state of the particles. In Patent Document 2, a Li-containing α-sialon-based phosphor is produced using crystalline silicon nitride. In the case of a Ca-containing α-sialon-based phosphor, when crystalline silicon nitride is used, secondary particles in which small primary particles are strongly aggregated (fused) are formed. Such an example can be seen in FIGS. The same can be said for the Li-containing α-sialon phosphor.

  The particle form and aggregation state of the phosphor powder affect the light scattering and absorption, and therefore the fluorescence intensity. Furthermore, it affects the physical properties of the slurry when the phosphor is applied. The physical properties of the slurry are important factors in the product manufacturing process.

  The influence on the fluorescence intensity will be further described. In the phosphor, regardless of the primary particle size and the secondary particle, when the particle size becomes about submicron, light scattering increases and absorption decreases, and fluorescence intensity decreases. As a method of avoiding this, it is conceivable to produce large secondary particles by agglomerating primary particles of submicrons. However, when such a powder is pulverized or handled in various ways, the submicron primary particles fall off, and as a result, it is difficult to avoid the influence of the primary particles. Further, in the case of secondary particles in which small primary particles are aggregated, fine irregularities are generated on the surface of the secondary particles, which may cause light scattering and decrease the fluorescence intensity.

  In addition, when the aggregation of the secondary particles is strong, strong pulverization is required, and impurities are mixed from the pulverizer. A phosphor is not suitable for strong pulverization because its characteristics are greatly deteriorated when a small amount of a light absorbing component is added.

  On the other hand, when the particle size is several tens of microns or more, when producing a product such as a white LED, it causes color unevenness and the like, and it becomes impossible to produce a product with stable quality. On the other hand, in order to obtain a high-quality phosphor, that is, a phosphor having high fluorescence intensity, highly crystalline particles are required. From these points, it is preferable that the primary particles are large crystals. The reason is that when the crystal size is reduced, the fluorescence intensity is lowered due to the influence of surface defects.

  Considering the above conditions, it can be said that a phosphor having good characteristics is preferably a powder in which primary particles without aggregation are distributed in a range of 1 μm to 20 μm and particles having a larger size in this particle size range.

  In Patent Documents 5 and 6, the size of primary particles of Ca-containing α-sialon phosphors is already known. However, in Patent Documents 5 and 6, the primary particles of Li-containing α-sialon phosphors are still sufficiently examined. Has not been made. Despite the disclosure of Patent Documents 5 and 6, with regard to the growth of primary particles of Li-containing α-sialon, Li is an element that easily evaporates, and a substance related to Li is a compound having a relatively low melting point. Because it is easy to make, it cannot be considered the same as Ca-containing α-sialon.

  In phosphors, a technique using a flux is widely used as a technique for adjusting the morphology of primary particles. Even in Li-containing α-sialon, it is conceivable to use a flux in order to enlarge the primary particles. In Patent Document 2, as fluxes, Li, Na, K, Mg, Ca, Sr, Ba, Al, Eu fluorides, chlorides, iodides, bromides, phosphates, particularly lithium fluoride, fluoride Although calcium and aluminum fluoride are pointed out, the effect is not specifically shown, but only a general technique is shown.

JP 2002-363554 A WO2007 / 004493 A1 JP 2004-67837 A JP 2006-152069 A JP 2006-52337 A JP 2006-321921 A

J. et al. Phys. Chem. B 2004, 108, 12027-12031

  The present invention has been made to solve the above-described problems of sialon-based phosphors. A white light emitting diode of daylight or daylight color is produced in combination with a blue LED with high fluorescence intensity. An object of the present invention is to provide a phosphor that emits a fluorescent color that can be used.

  The present invention also provides a Li-containing α-sialon phosphor powder having high fluorescence intensity and excellent properties as a phosphor powder by controlling the primary particles of Li-containing α-sialon. For the purpose. Such Li-containing α-sialon can be combined with an ultraviolet to blue LED to produce a highly efficient daylight white or daylight white light emitting diode.

  The present invention also provides an illumination device such as a white LED that emits a daylight white or daylight color using an ultraviolet or blue LED as a light source by providing a Li-containing α-sialon-based phosphor with high fluorescence intensity. Objective.

  It is another object of the present invention to achieve high brightness and color tone stabilization of an image evaluation apparatus having an excitation source such as an electron beam.

  Furthermore, an object of the present invention is to provide a novel method for producing a sialon-based phosphor capable of emitting a fluorescent color as described above with high intensity and with high yield.

  The present inventors have conducted detailed research on an α-sialon-based phosphor containing Li and Eu (europium), and can be produced in an atmosphere of atmospheric nitrogen gas and have a specific composition and Li-containing α-sialon. The present inventors have found that it is possible to shorten the wavelength of the fluorescent light and the excellent fluorescent intensity in the phosphors.

  In addition, when the present inventors use a nitrogen-containing silane compound and / or amorphous silicon nitride powder as a starting material, the primary particle size is large, the primary particles are less aggregated, and the cohesive force is weak. It has been found that a Li-containing α-sialon phosphor can be obtained. Moreover, it has higher fluorescence intensity than that produced using crystalline silicon nitride.

  Furthermore, the present inventors have found that it is possible to obtain Li-containing α-sialon having a large primary particle size in an α-sialon-based phosphor containing Li and Eu. Furthermore, with this method, it was found that a Li-containing α-sialon-based phosphor powder that emits fluorescence of a shorter wavelength can be obtained, and that the fluorescence intensity is higher than that produced by a normal method. .

Thus, the present invention provides the following.
General formula (1)
Li _x Eu _y Si _{12- (m + n)} Al _{(m + n) On + δ} N _16-n-δ (1)
(Wherein the average valence of Eu is a, x + ya + δ = m; 0.45 ≦ x <1.2, 0.001 ≦ y ≦ 0.2, 0.9 ≦ m ≦ 2.5, 0. 5 ≦ n ≦ 2.4 and δ> 0.) The present invention relates to a Li-containing α-sialon-based phosphor.

  Preferably, in the present invention, the δ is 0.05 to 1.2, and the ratio x / m of the x and m is in the range of 0.4 to 0.9. The present invention relates to a contained α-sialon phosphor. Furthermore, in a preferred aspect of the present invention, the x is 0.82 ≦ x <1.2, and the x / m is in the range of 0.5 to 0.9. It is an α-sialon phosphor.

  Furthermore, in the Li-containing α-sialon phosphor of the present invention, the x is 0.91 ≦ x <1.2, and the x / m is in the range of 0.6 to 0.9. preferable. In addition, the present invention relates to the Li-containing α-sialon-based phosphor, which emits fluorescence having a peak wavelength of 560 nm to 580 nm when incident excitation light is incident.

  Moreover, this invention relates to the lighting fixture comprised from the light emission source and the fluorescent substance containing the said Li containing alpha-sialon type fluorescent substance. The light emitting source is preferably an LED that emits light having a wavelength of 330 to 500 nm. Moreover, one aspect | mode of the lighting fixture of this invention is characterized by the said fluorescent substance containing the fluorescent substance which emits red of 600 nm-650 nm further.

  The present invention also relates to an image display device comprising an excitation source and a phosphor containing the Li-containing α-sialon phosphor. One embodiment of the image display device of the present invention is characterized in that the excitation source is an electron beam, an electric field, vacuum ultraviolet, or ultraviolet.

  In addition, the present invention provides a silicon nitride powder and / or a nitrogen-containing silane compound, an aluminum source-containing material, a nitride of Li, an oxynitride, an oxide, or a precursor that becomes an oxide by thermal decomposition. A material and a precursor material that becomes Eu nitride, oxynitride, oxide, or oxide by thermal decomposition, rather than the desired Li-containing α-sialon phosphor composition represented by the general formula (1) The Li-containing α-sialon-based phosphor is characterized by being weighed and mixed so as to have an excessive composition of lithium, and fired at 1400 to 1800 ° C. in an inert gas atmosphere containing nitrogen. It relates to a manufacturing method. In the method for producing a Li-containing α-sialon-based phosphor of the present invention, it is preferable that the Li-containing α-sialon-based phosphor after firing is subjected to acid cleaning.

  The present invention also relates to a method for producing the Li-containing α-sialon-based phosphor, wherein amorphous silicon nitride powder is used as the silicon nitride powder.

In one preferred embodiment, the present invention is an Li-containing α-sialon-based phosphor represented by the general formula (1), which is an average primary particle diameter measured by image analysis of a scanning electron micrograph. The present invention relates to a Li-containing α-sialon-based phosphor powder having an aspect ratio of 2 or less and an average particle diameter D _particle of 1 μm or more and 3.0 μm or less.

  Further, according to the present invention, in this aspect, in the particles measured by image analysis of a scanning electron micrograph, primary particles of 0.8 μm or more are present in an area ratio of 70% or more. The present invention relates to a contained α-sialon phosphor powder. In the present invention, the frequency distribution curve in the particle size distribution curve measured with a laser diffraction / scattering type particle size distribution measuring device is a single peak, and the median diameter is 4 to 15 μm. The present invention relates to α-sialon phosphor powder.

  In this aspect, the present invention also relates to the Li-containing α-sialon-based phosphor powder, wherein the 10% diameter in the particle size distribution curve is 1.5 μm or more and the 90% diameter is 15 μm or less.

  Moreover, this invention relates to the said Li containing alpha-sialon type | system | group fluorescent substance powder which discharge | releases fluorescence with a peak wavelength of 560 nm to 580 nm by injecting excitation light in this aspect.

  Moreover, this invention relates to the lighting fixture comprised in this aspect from the light emission source and the fluorescent substance containing the said Li containing alpha-sialon type | system | group fluorescent substance powder. It is preferable that the light emitting source is an LED that emits light having a wavelength of 330 to 500 nm. Further, as another form of the phosphor, a phosphor emitting red light of 600 nm to 650 nm may be contained.

  Further, according to the present invention, in this embodiment, the amorphous silicon nitride powder and / or the nitrogen-containing silane compound, the aluminum source material containing AlN, the nitride of Li, the oxynitride, the oxide, or the thermal decomposition And a precursor material that becomes an oxide of Eu, a precursor material that becomes an oxide by pyrolysis, and a desired Li-containing α- represented by the general formula (1) Li-containing, characterized in that lithium is weighed and mixed so as to have a lithium-excess composition rather than a sialon-based phosphor composition, and fired at 1400 to 1800 ° C. in an inert gas atmosphere containing nitrogen. The present invention relates to a method for producing an α-sialon phosphor powder.

  In another preferred embodiment, the present invention is an Li-containing α-sialon-based phosphor represented by the general formula (1), which is an aspect of primary particles measured by image analysis of a scanning electron micrograph. Provided is a Li-containing α-sialon-based phosphor particle having a ratio of 3 or less and a minor axis length of greater than 3 μm.

  Furthermore, this aspect of the present invention includes a theoretical amount of amorphous silicon nitride powder and / or a nitrogen-containing silane compound and an aluminum source material containing AlN, and a nitride of Li having the composition of the general formula (1). , Oxynitride, oxide, or precursor material that becomes oxide by thermal decomposition, Eu nitride, oxynitride, oxide, or precursor material that becomes oxide by thermal decomposition, and the theory Excess Li oxide not included in the amount, or precursor material that becomes oxide by thermal decomposition is mixed and fired at 1500 to 1800 ° C. in an inert gas atmosphere containing normal pressure nitrogen. And a method for producing the above Li-containing α-sialon-based phosphor powder.

In this aspect of the invention, preferably, the amount of excess Li oxide not included in the theoretical amount, or the precursor metal lithium that becomes an oxide by thermal decomposition, is the theoretical amount of product Li. It is 0.1-1.25 mol with respect to 1 mol of the contained α-sialon phosphor.
This aspect of the present invention relates to a luminaire comprising a light emitting source and a phosphor containing the Li-containing α-sialon phosphor represented by the general formula (1). The light emitting source is an LED that emits light having a wavelength of 330 to 500 nm.

  The Li-containing α-sialon-based phosphor of the present invention shows high fluorescence intensity that has not been obtained conventionally by adjusting the Li content of the product and having a specific composition, and using an ultraviolet or blue LED as a light source, An illumination device such as a white LED that emits a daylight white color or a daylight color can be provided.

  According to a preferred embodiment of the present invention, Li-containing α-sialon-based phosphor particles having a specific particle form are obtained by using amorphous silicon nitride and / or a nitrogen-containing silane compound as a raw material, and the product contains Li. By adjusting the amount to obtain Li-containing α-sialon-based phosphor particles having a specific composition, it is possible to obtain a phosphor exhibiting high fluorescence intensity that has not been obtained conventionally.

  According to another preferred embodiment of the present invention, an unconventional Li-containing α-sialon phosphor having a large primary particle size can be obtained. The Li-containing α-sialon phosphor of the present invention has high fluorescence intensity and excellent characteristics as a phosphor powder.

  Further, by using these phosphor powders obtained by the present invention, it is possible to provide a high-luminance illumination device such as a white LED that emits a daylight white color or a daylight color using an ultraviolet or blue LED as a light source. .

1A and 1B are SEM photographs showing the state of an embodiment of the powder after acid treatment of Example 2 and Example 6. FIG. FIG. 1A is a SEM of Li-containing α-sialon phosphor powder prepared using amorphous silicon nitride as a raw material, and FIG. 1B is an SEM of Li-containing α-sialon phosphor powder prepared using crystalline silicon nitride as a raw material. It is a photograph.
2A and 2B are SEM photographs showing one embodiment of the phosphor powder after pulverization of Example 2 and Example 6. FIG. FIG. 2A is an SEM photograph of Li-containing α-sialon phosphor powder produced using amorphous silicon nitride as a raw material, and FIG. 2B is a Li-containing α-sialon phosphor produced using crystalline silicon nitride as a raw material. It is a SEM photograph of powder.
3A and 3B are enlarged photographs of FIGS. 2A and 2B.
4A is a particle size distribution (frequency distribution curve) of the Li-α-sialon phosphor powder of the present invention obtained in Example 2, and FIG. 4B is Example 6 using crystalline silicon nitride as a raw material. It is a particle size distribution figure of the obtained fluorescent substance powder.
5 is an SEM photograph of the powder obtained in Example 11. FIG.

The present invention will be described in detail below.
In the present invention, the Li-containing α-sialon-based phosphor has the general formula (1)
Li _x Eu _y Si _{12- (m + n)} Al _{(m + n) On + δ} N _16-n-δ (1)
Indicated by Here, when the average valence of Eu is a, x + ya + δ = m (where δ> 0).

  The Li-containing α-sialon phosphor of the present invention is characterized by the Li content. That is, the present inventors found that the Li-containing α-sialon-based phosphor fired in a normal pressure inert gas atmosphere containing nitrogen has a large Li content in the charged composition and the composition of the obtained composite. I found out that there was a difference. Li is an element that easily evaporates, and evaporation occurs during firing. As a result, the Li content of the Li-containing α-sialon-based phosphor obtained after the acid cleaning decreases. The evaporation of Li is particularly noticeable in firing under normal pressure or reduced pressure, and by examining in detail the correlation between the charged composition and the composition of the resulting composite, in the composition formula of the Li-containing α-sialon, In the case where δ is 0.05 to 1.2 and the ratio x / m of x to m is in the range of 0.4 to 0.9, the X-ray diffraction pattern shows almost single-phase Li It has been found that a phosphor identified as the containing α-sialon phosphor can be obtained. This is the first time that the present invention has shown that excellent fluorescence intensity and shorter fluorescence wavelength can be achieved in the Li composition region of the Li-containing α-sialon phosphor of the present invention.

  In this invention, after baking at 1400-2000 degreeC in the inert gas atmosphere of a 0.08-0.9MPa pressure, a Li containing alpha-sialon type fluorescent substance is synthesize | combined by acid washing. As a firing atmosphere, it is preferable to carry out at normal pressure under nitrogen atmosphere. In particular, the production cost of the Li-containing α-sialon phosphor can be reduced by performing synthesis in an inert gas atmosphere containing nitrogen at normal pressure. The present inventors synthesized Li-containing α-sialon-based phosphors having various compositions in a nitrogen atmosphere at normal pressure, and have compositional characteristics on the fluorescence characteristics of the Li-containing α-sialon-based phosphors obtained after acid cleaning. I found. As a result, it became possible for the first time to synthesize a Li-containing α-sialon-based phosphor capable of achieving both excellent fluorescence intensity and shorter fluorescence wavelength by firing in a nitrogen atmosphere at normal pressure.

Furthermore, the Li-containing α-sialon phosphor of the present invention is expressed as x + ya + δ = m (where δ> 0) as described above, and is characterized in that x + ya is smaller than m. Here, a is the average valence of Eu, but the valence of Eu varies depending on the temperature and the oxygen partial pressure in the atmosphere. Since trivalent is stable at room temperature, only Eu ₂ O ₃ is known as an Eu oxide. However, since the divalent becomes more stable when the temperature is higher, Eu is higher at higher temperatures in a nitrogen atmosphere. It is believed that it is reduced to a divalent form and is dissolved as Eu ^{2+ in} the crystal lattice of α-sialon. As disclosed in paragraph 0065 on page 14 of Patent Document 2 (WO2007 / 004493), in the literatures and patent publications that have been reported in the past, Eu is divalent, and α-sialon has a composition formula. Is assembled. For this reason, in the composition of the Li-containing α-sialon of the present invention, δ is calculated assuming that the valence of Eu is divalent.

  In conventional sialons, the amount of metal dissolved in all is m / [metal valence], and the composition of Li-containing α-sialon phosphors in the prior art satisfies the relational expression x + ya = m. Was. On the other hand, in the case of the Li-containing α-sialon phosphor of the present invention, the content of Al is higher than that of the conventional composition, and the chemical composition is characterized by being represented by the general formula (1). When x + ya is smaller than m, the ratio of Si atoms and Al atoms constituting the Li-containing α-sialon phosphor changes, and at the same time, the ratio of oxygen atoms and the ratio of nitrogen atoms also changes.

It is also conceivable that a charge shift occurs due to a composition change of constituent atoms in such a Li-containing α-sialon phosphor. In this case, it is also conceivable that the charge balance is compensated by defects generated in the Li-containing α-sialon phosphor. The α-sialon crystal lattice has a network consisting of cations (Si, Al) -anions (O, N) -cations (Si, Al) -anions (O, N)- Metal elements such as Li and Eu enter and dissolve in the gaps. When vacancies are generated at the cation sites, the proportion of oxygen or nitrogen atoms at the anion sites is relatively increased. Conversely, when vacancies are generated at the anion sites, oxygen at the anion sites is relatively increased. Or since the ratio of nitrogen atoms decreases, the chemical composition is more generally expressed by the following formula (2).
Li _x Eu _y Si _{12- (m + n)} Al _{(m + n) On + εN 16-n-φ} (2)
Here, when the average valence of Eu is a, x + ya + δ = m and δ = 3φ−2ε. Here, (n + ε) represents the number of oxygen atoms that occupy the anion site, and (16−n−φ) represents the number of nitrogen atoms that occupy the anion site. However, δ> 0, −δ / 2 ≦ ε ≦ δ / 2, and −δ / 3 ≦ φ ≦ δ / 3.

  If an attempt is made to synthesize a sialon such that x + ya and m coincide with each other by increasing Li in the raw material, a heterogeneous phase is generated, and a single-phase Li-containing α-sialon-based phosphor cannot be obtained. The Li-containing α-sialon-based phosphor obtained by the method of the present invention is obtained from the finding that x + ya and m do not coincide with each other to become a stable sialon. Focusing on matching x + ya and m is not preferable because it leads to cost increase such as synthesis in high-pressure nitrogen gas and the reproducibility is poor.

  As a result of the study by the present inventors, the composition that becomes a single-phase Li-containing α-sialon phosphor is 0.45 ≦ x <1.2 in the general formula (1) of the Li-containing α-sialon phosphor. More preferably, the range is 0.82 ≦ x <1.2. More preferably, it is the range of 0.91 <= x <1.2. When x is smaller than 0.45, the fluorescence intensity is lowered, and when 1.2 or more, a heterogeneous phase is generated, and a single-phase α-sialon phosphor cannot be obtained. In particular, the composition range that can achieve both shorter wavelength and fluorescence intensity is 0.82 ≦ x <1.2. The fluorescence wavelength shifts to a shorter wavelength as the Li content increases, and can be changed in the range of 560 nm to 580 nm at the peak wavelength.

  In addition, the Li-containing α-sialon phosphor of the present invention is characterized by δ> 0, and in particular, δ is 0.05 to 1.2, and the ratio of x to m is x / m. It is more preferable that it is 0.5 to 0.9 because the fluorescence intensity increases. More preferably, δ is 0.05 to 1.0 and the x / m ratio is 0.6 to 0.9.

  Eu is an element that becomes a light-emitting source when dissolved in a Li-containing α-sialon-based phosphor. In general formula (1), y is preferably 0.001 ≦ y ≦ 0.2. Bright phosphors cannot be obtained because the number of light emitting sources with y less than 0.001 decreases, and sialon that emits short-wavelength fluorescence cannot be obtained when y is greater than 0.2. A more preferable range is 0.01 ≦ y ≦ 0.15, and a further preferable range is 0.01 ≦ y ≦ 0.1.

  m and n are 0.9 ≦ m ≦ 2.5 and 0.5 ≦ n ≦ 2.4. m is a value determined to maintain electrical neutrality when the metal element is dissolved in sialon, and m = x + ya + δ. a is the average valence of Eu. Here, in the network composed of cations (Si, Al) —anions (O, N) —cations (Si, Al) —anions (O, N) — constituting α-sialon, intrusion and solid solution occurred. The number of Al atoms substituted by Si atoms in excess of the number of substituted Al atoms at the cation site corresponding to the number of metal elements (Li and Eu) is expressed as δ (in the present invention, δ> 0). ). If m is smaller than 0.9, the solid solution amount of the metal elements (Li and Eu) is so small that it is difficult to stabilize the sialon crystal, so that the fluorescence intensity of the phosphor may be lowered. When the m value is larger than 2.5, a crystal phase other than sialon is easily generated. 0.9 ≦ m ≦ 2.5 is preferable. n is a value related to the substitutional solid solution amount of oxygen in the Li-containing α-sialon phosphor. If the n value is smaller than 0.5 or (n + δ) is smaller than 0.55, the solid solution amount of the metal elements (Li and Eu) is small, and the sialon crystal is difficult to stabilize, so that the fluorescence intensity may decrease. is there. When the n value is larger than 2.4 or (n + δ) is larger than 3.2, a crystal phase other than sialon is easily generated. More preferable ranges are 1.0 ≦ m ≦ 2.1, 1.4 ≦ n ≦ 2.4, 1.8 ≦ n + δ ≦ 3.1, and still more preferable ranges are 1.1 ≦ m ≦ 2. 0, 1.55 ≦ n ≦ 2.3, 1.9 ≦ n + δ ≦ 3.0.

  The heterogeneous phase here is a heterogeneous phase identified by a diffraction pattern of X-ray diffraction, and does not include components that do not appear in X-ray diffraction, such as glass.

  Next, a method for producing the sialon phosphor powder of the present invention will be described.

  The Li-containing α-sialon-based phosphor powder of the present invention includes a silicon nitride powder, a substance serving as an aluminum source containing AlN, a Li nitride, an oxynitride, an oxide, or a precursor that becomes an oxide by thermal decomposition. And a precursor material that becomes an oxide of Eu nitride, oxynitride, oxide, or thermal decomposition into a composition containing more lithium than the desired Li-containing α-sialon-based phosphor composition. Weighing and mixing so that the mixture can be obtained by firing at 1400 to 2000 ° C. in an inert gas atmosphere containing nitrogen at normal pressure. The obtained powder is washed with an acid solution to remove the glass component adhering to the surface, and finally, a phosphor powder substantially composed of a single phase of a Li-containing α-sialon phosphor is obtained. Can be obtained.

  The reason for increasing the Li compound of the raw material is to prevent Li from evaporating and preventing the Li from the resulting Li-containing α-sialon phosphor from becoming too small.

As the raw material silicon nitride powder, crystalline silicon nitride, nitrogen-containing silane compound and / or amorphous silicon nitride powder may be used.
As the nitrogen-containing silane compound, silicon diimide (Si (NH) ₂ ), silicon nitrogen imide (Si ₂ N ₂ NH), or the like can be used. Further, these compounds may be used by mixing with silicon nitride powder.

  The nitrogen-containing silane compound and / or amorphous silicon nitride powder as the main raw material may be obtained by a known method, for example, by vaporizing silicon halide such as silicon tetrachloride, silicon tetrabromide, silicon tetraiodide and ammonia in the gas phase. A Si—N—H system precursor compound such as silicon diimide produced by reacting in a liquid phase can be obtained by thermal decomposition at 600 to 1200 ° C. in a nitrogen or ammonia gas atmosphere. The crystalline silicon nitride powder is obtained by firing the obtained nitrogen-containing silane compound and / or amorphous silicon nitride powder at 1300 ° C to 1550 ° C. Crystalline silicon nitride can also be obtained by nitriding metal silicon directly in a nitrogen atmosphere, but this method requires a pulverization step to obtain a fine powder, so impurities can easily enter. It is preferable to employ a method of decomposing a precursor that easily obtains a pure powder.

  The nitrogen-containing silane compound and / or amorphous silicon nitride powder and crystalline silicon nitride powder have an oxygen content of 1 to 5% by mass. Those having an oxygen content of 1 to 3% by mass are more preferable. When the oxygen content is less than 1% by mass, the formation of an α-sialon phase due to the reaction in the firing process becomes extremely difficult, and the remaining crystal phase of the starting material and the generation of AlN porotype such as 21R are not preferable. On the other hand, when the oxygen content is 5% by mass or more, the α-sialon production reaction is promoted, but the production rate of β-sialon and oxynitride glass increases.

The nitrogen-containing silane compound and / or amorphous silicon nitride powder preferably has a specific surface area of 80 to 600 m ² / g. A thing of 340-500 m < ² > / g is still more preferable. For crystalline silicon ^nitride, it is preferable to use a material having a specific surface area of 1m ² / g~15m 2 / g.

Examples of the aluminum source include aluminum oxide, metal aluminum, and aluminum nitride. Each of these powders may be used alone or in combination. As the aluminum nitride powder, a general one having an oxygen content of 0.1 to 8% by mass and a specific surface area of 1 to 100 m ² / g can be used.

  Examples of precursor substances that are converted to oxides by thermal decomposition of Li and Eu include metal salts such as carbonates, oxalates, citrates, basic carbonates, and hydroxides.

  In the present invention, it is preferable that the amount of metal impurities other than the constituent components of the Li-containing α-sialon phosphor is 0.01% by mass or less. In particular, for nitrogen-containing silane compounds and / or amorphous silicon nitride powder and / or crystalline silicon nitride with a large amount of addition, and aluminum oxide and AlN, the content of metal impurities is preferably 0.01% by mass or less, preferably Is 0.005% by mass or less, more preferably 0.001% by mass. The metal impurity content in the case of the oxide of the metal Li oxide or the precursor material that becomes an oxide by thermal decomposition and the metal Eu oxide or the precursor material that becomes an oxide by thermal decomposition is 0. It is preferable to use one having a mass of 0.01% by mass or less.

  The method for mixing each of the starting materials is not particularly limited. For example, a method known per se, for example, a dry mixing method, a wet mixing in an inert solvent that does not substantially react with each component of the starting material, and then the solvent is added. A removal method or the like can be employed. As the mixing device, a V-type mixer, a rocking mixer, a ball mill, a vibration mill, a medium stirring mill, or the like is preferably used. However, since the nitrogen-containing silane compound and / or amorphous silicon nitride powder is extremely sensitive to moisture and moisture, it is necessary to mix the starting materials in a controlled inert gas atmosphere. .

  The mixture of starting materials is fired at 1400 to 1800 ° C., preferably 1500 to 1700 ° C. in a nitrogen-containing inert gas atmosphere at normal pressure, and the target Li-containing α-sialon-based phosphor powder is obtained. Examples of the inert gas include helium, argon, neon, and krypton. In the present invention, these gases and a small amount of hydrogen gas can be mixed and used. When the firing temperature is lower than 1400 ° C., it takes a long time to produce the desired Li-containing α-sialon phosphor powder, which is not practical. Moreover, the production | generation ratio of Li containing alpha-sialon type | system | group fluorescent substance phase in production | generation powder also falls. If the firing temperature exceeds 1800 ° C., an undesirable situation occurs in which silicon nitride and sialon undergo sublimation decomposition and free silicon is produced.

  There are no particular restrictions on the heating furnace used for firing the powder mixture. For example, a batch-type electric furnace, rotary kiln, fluidized firing furnace, pusher-type electric furnace, or the like using a high-frequency induction heating system or a resistance heating system is used. be able to. For the firing crucible, a BN crucible, a silicon nitride crucible, a graphite crucible, or a silicon carbide crucible can be used. In the case of a graphite crucible, the inner wall is preferably covered with silicon nitride, boron nitride or the like.

  The Li-containing α-sialon phosphor thus obtained has a glass layer attached to the surface, and in order to obtain a phosphor with higher fluorescence intensity, it is preferable to remove the glass layer. For removal of the glass layer on the surface of the phosphor particles, cleaning with an acid is easiest. In other words, the sialon particles are placed in an acid solution selected from sulfuric acid, hydrochloric acid or nitric acid to remove the glass layer on the surface. The concentration of the acid solution is 0.1 N to 7 N, preferably 1 N to 3 N. If the concentration is excessively high, the oxidation proceeds remarkably and good fluorescence characteristics cannot be obtained. 5 wt% of sialon phosphor powder is added to the acid solution of which the concentration is adjusted, and the solution is kept for a desired time while stirring. After washing, the solution containing the sialon phosphor powder is filtered, washed with water, washed away with acid, and dried.

  In one preferred embodiment, the Li-containing α-sialon phosphor of the present invention is characterized by the size and crystal form of the particles constituting the phosphor, in addition to the compositional features described above.

  The Li-containing α-sialon-based phosphor powder of this aspect of the present invention is manufactured using the compositional characteristics having the above Li content, and using amorphous silicon nitride powder and / or nitrogen-containing silane compound as raw materials. A desired Li-containing α-sialon phosphor of the above general formula (1), comprising amorphous silicon nitride powder and / or nitrogen-containing silane compound, Al source, Li source, and Eu source. It is obtained by weighing and mixing lithium so as to have an excessive composition rather than the composition, and firing in a normal pressure inert gas atmosphere containing nitrogen.

  By using an amorphous silicon nitride powder and / or a nitrogen-containing silane compound as raw materials, the Li-containing α-sialon-based phosphor powder of this aspect of the present invention has the following characteristics of particle morphology and aggregation state. Have. 1A and 1B are scanning electron microscope (SEM) photographs showing the state of powder after acid treatment of Li-containing α-sialon-based phosphor particles obtained in Examples 2 and 6 of this aspect of the present invention. is there. A part of the secondary particles in which the primary particles are fused and aggregated are observed. FIG. 1A is an SEM photograph of Li-containing α-sialon phosphor particles using amorphous silicon nitride as a raw material, and FIG. 1B is an SEM photograph of Li-containing α-sialon phosphor particles using crystalline silicon nitride as a raw material. is there. In FIG. 1A, it turns out that it consists of 1-2 micrometers particle | grains. These are self-shaped primary particles of Li-containing α-sialon phosphor particles. FIG. 1B shows that the particles are 0.5 to 1.3 μm. As will be described later, these particles are secondary particles in which crystals of several Li-containing α-sialon-based phosphor particles are aggregated, and crystals exhibiting a self-form are hardly seen.

SEM photographs of representative examples of the particles that have been pulverized and made available as phosphor powder are shown in FIGS. 2A, 2B, 3A, and 3B. FIG. 2B is an SEM photograph of Li-containing α-sialon-based phosphor powder prepared using amorphous silicon nitride of FIG. 2A as a raw material, and FIG. 2B is a Li-containing α-sialon-based fluorescence using crystalline silicon nitride as a raw material. It is a SEM photograph of body particles. 3A and 3B are enlarged photographs of FIGS. 2A and 2B. In the Li-containing α-sialon-based phosphor powder produced using the amorphous silicon nitride of FIG. 2A as a raw material, there are many primary particles of hexagonal columnar and hexagonal pyramid with a particle size of 1 to 1.5 μm, and fine There are almost no particles. The size of the primary particle diameter varies depending on the composition and firing conditions, but within the scope of the present invention, the average particle diameter D _particle was 1.0 to 3.0 μm from the results of image analysis of SEM photographs. In order to produce a material having an average particle size larger than this, a remarkably long firing process is required, which is not practical. In addition, when the average particle size is 0.5 μm or less, there is no difference from that produced from a crystalline material. Moreover, as can be seen from the SEM photograph, the aspect ratio of the particles constituting the Li-containing α-sialon phosphor powder of the present invention is 2 or less. FIG. 2B is an SEM photograph of Li-containing α-sialon phosphor particles using crystalline silicon nitride as a raw material.

  The Li-containing α-sialon phosphor powder of this aspect of the present invention is characterized by being large primary particles, and there is little fusion / aggregation between the primary particles. However, not all particles do so, and the generation of small particles also occurs. In a preferred embodiment of the present invention, as a result of the measurement, the existing area of particles of 0.8 μm or more was 70% or more with respect to the total area of all particles in the measurement range. It is considered that the larger the area, the better the phosphor, and the smaller the area, the lower the fluorescence intensity.

  In the case where the crystalline silicon nitride of FIG. 2B is used as a raw material, self-shaped primary particles do not exist. As can be seen from FIG. 3B, the large particles of 1 to 1.3 μm are those in which the primary particles of about 0.5 μm are closely fused. There are many fine crystals of 0.5 μm or less. In such powders, light scattering by small particles increases and the fluorescence intensity decreases.

  2A and 2B appear as a difference in particle size distribution. FIG. 4A shows the particle size distribution (frequency distribution curve) of the Li-containing α-sialon phosphor powder of this embodiment of the present invention measured by a laser diffraction / scattering particle size distribution measuring apparatus, and FIG. 4B shows crystalline silicon nitride. The particle size distribution when used is shown. This frequency distribution curve is obtained by dividing the section of sufficiently large particles (approximately 1000 μm) and sufficiently small particles (approximately 0.02 μm) into 80 equal sections on a log scale, and calculating the frequency based on the volume of the particles. is there. FIG. 4A shows the particle size distribution of a single peak (hitoyama) having a peak in the vicinity of 5 μm. Such a particle size distribution is very preferable as a phosphor. Since the Li-containing α-sialon phosphor powder of this aspect of the present invention is weakly fused and agglomerated, a powder showing a single peak with a median diameter of 4 to 15 μm can be obtained by weak grinding. The shape of a human mountain peak is important. This is because the median diameter can be changed depending on the degree of pulverization, but the peak shape depends on the size of the primary particles in the secondary particles.

  On the other hand, when crystalline silicon nitride is used as a raw material, the particle size distribution becomes a particle size distribution curve showing a peak of 1.5 μm and two peaks (Futama) of 15 μm, and amorphous silicon nitride is used as a raw material. This indicates that the obtained powder characteristics are excellent. As can be seen from FIG. 3B, in this case, small primary particles aggregate to form large secondary particles. Since these particles are broken powder, it is considered that the above-mentioned two peaks have occurred.

  Here, the cause of the difference in the form and aggregation state of particles when amorphous silicon nitride and / or nitrogen-containing silane compound and crystalline silicon nitride are used as raw materials will be described.

  Nucleation and growth of Li-containing α-sialon phosphor particles are considered to occur in a Li—Al—Si—O—N glass phase generated in the raw material in the process of increasing the temperature. Amorphous silicon nitride or nitrogen-containing silane compound is an ultrafine powder having a particle size of about several nm to 10 nm and is extremely bulky. Since this is the main component, the other components can be uniformly dispersed therein, and a fine glass phase is considered to be uniformly formed at a low temperature. It is considered that the component of the Li-containing α-sialon-based phosphor dissolves in this glass phase, and nucleation and growth proceed in stages. For this reason, it is considered that Li-containing α-sialon-based phosphor particles having a large particle diameter and exhibiting a self-shape grow. Coupled with the bulkiness, each particle grows independently, so that fusion and aggregation hardly occur.

  On the other hand, the particle size of crystalline silicon nitride is about 0.2 μm even if it is fine, and the particle size is very large compared to the above-mentioned amorphous silicon nitride or nitrogen-containing silane compound. For this reason, uniform contact with Li, Al, O, and N forming the glass phase cannot be ensured. For this reason, it is thought that a glass phase produces | generates locally. Moreover, it is thought that there are few glass grains to produce | generate. Since the silicon nitride present has a large particle diameter, the raw material does not dissolve in the glass phase, but the surface of the silicon nitride particles is present to cover the glass, and the reaction to the Li-containing α-sialon phosphor proceeds. In such an existence mode of the glass phase, a large number of crystal nuclei share the glass phase, and the growth proceeds competitively or simultaneously. As a result, secondary particles are considered to be secondary particles in which primary particles are strongly fused and aggregated.

  Next, a method for producing the Li-containing α-sialon phosphor powder of this preferred embodiment of the present invention will be described. The Li-containing α-sialon-based phosphor powder of this aspect of the present invention includes an amorphous silicon nitride powder and / or a nitrogen-containing silane compound, a substance serving as an aluminum source containing AlN, a nitride of Li, and an oxynitride , Oxide or precursor material that becomes oxide by thermal decomposition and Eu nitride, oxynitride, oxide, or precursor material that becomes oxide by thermal decomposition, a desired Li-containing α-sialon It can be obtained by weighing and mixing so that lithium is in excess of the phosphor composition, and firing the mixture at 1400 to 2000 ° C. in an inert gas atmosphere containing nitrogen. . The obtained powder is washed with an acid solution to remove glass components and the like attached to the surface, and finally, a phosphor powder substantially composed of a Li-containing α-sialon phosphor can be obtained. it can.

The method for producing the Li-containing α-sialon-based phosphor powder of this embodiment uses amorphous silicon nitride powder and / or nitrogen-containing silane compound as the silicon nitride powder, not the crystalline silicon nitride powder, among the raw materials. Except for the above, it may be the same as the method for producing the Li-containing α-sialon phosphor powder of the present invention described above.
As a raw material nitrogen-containing silane compound, silicon diimide (Si (NH) ₂ ), silicon nitrogen imide (Si ₂ N ₂ NH), or the like can be used. Further, a mixture of a nitrogen-containing silane compound and amorphous silicon nitride powder may be used.

  The particles of the Li-containing α-sialon-based phosphor according to another preferred embodiment of the present invention are Li-containing α-sialon-based phosphors having a composition represented by the general formula (1). The aspect ratio of primary particles measured by image analysis is 3 or less, and the length of the minor axis is larger than 3 μm. A preferable upper limit of the length of the short axis is 5 μm. Such Li-containing α-sialon phosphor particles have high fluorescence intensity.

  The Li-containing α-sialon-based phosphor powder of this aspect of the present invention includes the above-described Li-content α-sialon composition, an amorphous silicon nitride powder and / or a nitrogen-containing silane compound as raw materials, and oxidation. It is characterized by being manufactured by adding excessively a raw material that forms lithium oxide and / or lithium oxide at a high temperature, amorphous silicon nitride powder and / or nitrogen-containing silane compound, Al source, Li source, , Eu source, a desired Li-containing α-sialon-based phosphor composition of the above general formula (1) is weighed, and further, a Li oxide or a precursor material that is converted into an oxide by thermal decomposition. Is added and mixed, and is fired in an inert gas atmosphere containing nitrogen.

  FIG. 5 is a scanning electron microscope (SEM) photograph showing the state of the powder after acid treatment of Li-containing α-sialon-based phosphor particles obtained in the example of this aspect of the present invention. A part of the secondary particles in which the primary particles are weakly fused are observed.

  FIG. 5 shows Li-containing α-sialon-based phosphor particles prepared using a raw material in which amorphous silicon nitride is excessively added with an oxide of Li or a precursor substance that becomes an oxide by thermal decomposition.

  In FIG. 5, the form (self-form) of the primary particles of the Li-containing α-sialon phosphor can be clearly confirmed. In these powders, the short axis of the primary particles contains particles larger than 3 μm.

  The cause of the difference in primary particle morphology and aggregation state as shown in FIG. 5 will be described. Nucleation and growth of Li-containing α-sialon phosphor particles are considered to occur in a Li—Al—Si—O—N glass phase generated in the raw material during the temperature rising process.

  First, the cause of the difference in the size of the primary particles will be described. In the case where amorphous silicon nitride and / or a nitrogen-containing silane compound is used and no excess lithium oxide is used, the size of the primary particles is small. On the other hand, when excess lithium oxide is used, the size of the primary particles increases. This is due to the difference in the amount of glass phase. That is, when excess lithium oxide is used, the glass phase to be generated increases. As the glass phase increases, the degree of supersaturation of sialon in the glass decreases and the amount of nuclei produced decreases. For this reason, the amount of the raw material supplied to one nucleus increases, and the size of the crystal increases.

Next, as described above, the state of particle aggregation will be described. When produced using crystalline silicon nitride, the resulting phosphor powder is significantly aggregated. On the other hand, when amorphous silicon nitride and / or nitrogen-containing silane compound is used, aggregation is reduced.
Amorphous silicon nitride and / or nitrogen-containing silane compound is an ultrafine powder having a particle size of several nanometers to about 10 nm, and this is the main raw material of sialon. Therefore, the raw material of sialon using amorphous silicon nitride is Very bulky. In this, other raw materials are uniformly dispersed and come into contact with the ultrafine silicon nitride raw material. For this reason, it is thought that a fine glass phase is uniformly formed at low temperature. And since the raw material is bulky, it will be in the state separated spatially. When nucleation and growth occur in such a glass phase, the resulting powder is less agglomerated.

  On the other hand, in the case of crystalline silicon nitride, the particle diameter is very large compared with amorphous silicon nitride and / or nitrogen-containing silane compound, and is about 0.2 μm. Since silicon nitride is large, it is considered that the reaction to sialon proceeds in such a manner that the glass covers the surface of the silicon nitride particles rather than the raw material being dissolved in the glass phase. In addition, the sialon raw material using crystalline silicon nitride is small in volume and cannot sufficiently separate the glass phase spatially as in the case of using amorphous silicon nitride and / or a nitrogen-containing silane compound. When the reaction to sialon proceeds in such a state, the primary particles become secondary particles that are strongly fused and aggregated with each other.

In this aspect of the present invention, the lithium oxide added in excess and the raw material that produces lithium oxide at high temperatures serve as a kind of flux, but are generally added for the purpose of aligning crystals. It is very different from conventional flux. The reason is the following two points.
(1) In the synthesis of Li-containing α-sialon at normal pressure shown in this aspect of the present invention, the evaporation of Li increases. When sialon is produced without supplementing Li, Li-containing α-sialon which is largely lacking in lithium is obtained. Such sialon has many defects and is not preferable as a phosphor. In order to solve this, the lack of Li can be compensated by adding lithium oxide or a raw material that forms lithium oxide at a high temperature.
(2) An important feature of the Li-containing α-sialon-based phosphor is that it emits fluorescence having a shorter wavelength than that of the Ca-containing α-sialon-based phosphor. In this study, it was also clarified that lithium oxide or a raw material that forms lithium oxide at a high temperature is effective for shortening the fluorescence wavelength. This seems to be due to oxygen being supplied from the added reagent.
As described above, the lithium oxide and the raw material that generates lithium oxide at high temperature in this aspect of the present invention are different from the usual flux that simply controls the morphology of the primary particles of the crystal, unlike the Li-containing α-sialon. There is an effect of essentially improving the fluorescence characteristics.

  In general, when producing a sialon phosphor, it is not preferable to use lithium oxide or a raw material that forms lithium oxide at a high temperature as a flux. Since the flux becomes an unnecessary component after obtaining the phosphor, it is preferably removed after synthesis. For this reason, it is common to select substances that can be easily removed by water or acid. Considering this point, a halogen compound such as barium fluoride is selected. Lithium oxide is a component that is less soluble than halogen compounds, and is difficult to remove after synthesis. For this reason, it is a raw material that is difficult to employ as a flux. Therefore, the inventors examined using fluoride as a flux, but with fluoride, it was not possible to obtain a Li-containing α-sialon-based phosphor composed of primary particles of good shape.

  In addition, the fluorescence intensity is lower than when lithium oxide or a raw material that forms lithium oxide at a high temperature is added. This is probably because the evaporation of Li cannot be compensated. From the above study, it has been concluded that lithium oxide or a raw material that forms lithium oxide at a high temperature is suitable as an effective flux for the Li-containing α-sialon phosphor.

  The method of adding the lithium oxide of this aspect of the present invention or the raw material that forms lithium oxide at high temperature is considered to be effective for Li-containing α-sialon of all compositions of the present invention, and Li-containing α-sialon. The composition of the system phosphor can be the composition described above.

  Lithium oxide added excessively relative to the Li-containing α-sialon-based phosphor powder raw material (that is, the theoretical amount of lithium oxide to be Li-containing α-sialon to be generated), or a raw material that forms lithium oxide at a high temperature Is an amount of metal Li, and is preferably 0.1 mol or more and 1.25 mol or less with respect to 1 mol of Li-containing α-sialon to be produced. When the amount is less than 0.1 mol, the effect of enlarging the crystal cannot be obtained sufficiently. On the other hand, when the amount exceeds 1.25 mol, the amount of heterogeneous production increases and the fluorescence intensity decreases. A more preferable range is 0.15 mol or more and 0.8 mol or less.

  Next, a method for producing the Li-containing α-sialon phosphor powder of this embodiment of the present invention will be described. The Li-containing α-sialon-based phosphor powder of the present invention includes an amorphous silicon nitride powder and / or a nitrogen-containing silane compound, a substance serving as an aluminum source containing AlN, a Li nitride, an oxynitride, and an oxide. Measure the desired Li-containing α-sialon with a precursor material that becomes oxide by thermal decomposition and a precursor material that becomes Eu nitride, oxynitride, oxide, or oxide by thermal decomposition. Further, an excessive amount of Li oxide or / and a precursor material that becomes an oxide by thermal decomposition is added to and mixed with this powder, and the mixture is mixed at 1500 to 1800 ° C. in an inert gas atmosphere of 0.08 to 0.1 MPa. It can be obtained by firing. As the firing atmosphere, it is more preferable to carry out at normal pressure in a nitrogen atmosphere. In particular, the production cost of the Li-containing α-sialon phosphor can be reduced by performing synthesis in an inert gas atmosphere containing nitrogen at normal pressure.

  The method for producing the Li-containing α-sialon-based phosphor powder of this aspect uses an amorphous silicon nitride powder and / or a nitrogen-containing silane compound, and the amount of Li-containing α-sialon represented by the general formula (1) In addition to the raw material, it can be basically the same as described above, except that an oxide of Li or a precursor substance that becomes an oxide by thermal decomposition is excessively added.

  An excessive amount of Li oxide or a precursor substance that becomes Li oxide by thermal decomposition is added, and precursor substances that become Li oxide by thermal decomposition include each of carbonate, oxalate, and citric acid. Mention may be made of metal salts such as salts, basic carbonates and hydroxides.

  The mixture of starting materials is fired at 1500 to 1800 ° C., preferably 1550 to 1700 ° C. in a nitrogen-containing inert gas atmosphere at normal pressure or reduced pressure to obtain the target Li-containing α-sialon phosphor powder. Examples of the inert gas include helium, argon, neon, and krypton. In the present invention, these gases and a small amount of hydrogen gas can be mixed and used. When the firing temperature is lower than 1500 ° C., it takes a long time to produce the desired Li-containing α-sialon phosphor powder, which is not practical. Moreover, the production | generation ratio of Li containing alpha-sialon type | system | group fluorescent substance phase in production | generation powder also falls. If the firing temperature exceeds 1800 ° C., an undesirable situation occurs in which silicon nitride and sialon undergo sublimation decomposition and free silicon is produced. The firing time is preferably 1 to 48 hours. In particular, a calcination time of 1 to 24 hours at a calcination temperature of 1600 to 1700 ° C. is most preferable because phosphor particles excellent in particle shape and composition can be obtained.

The Li-containing α-sialon-based phosphor powder activated by rare earth elements of the present invention emits fluorescence having a peak wavelength of 560 nm to 580 nm by entering excitation light. In this preferred embodiment of the present invention, the Li-containing α-sialon-based phosphor powder activated with a rare earth element emits fluorescence having a dominant wavelength of 570 nm to 574 nm when incident upon excitation light.
The Li-containing α-sialon phosphors activated with rare earth elements of the present invention are all kneaded with a transparent resin such as an epoxy resin or an acrylic resin by a known method to produce a coating agent. A light emitting diode whose surface is coated with an agent can be used as a light emitting element in various lighting fixtures.

  In particular, a light emission source having a peak wavelength of excitation light in the range of 330 to 500 nm is suitable for a Li-containing α-sialon phosphor. In the ultraviolet region, the luminous efficiency of the Li-containing α-sialon-based phosphor is high, and a light-emitting element with good performance can be configured. In addition, even a blue light source has high luminous efficiency, and a combination of yellow fluorescence and blue excitation light of a Li-containing α-sialon phosphor can form a good daylight to daylight light emitting element.

  Further, in combination with a red phosphor having a wavelength of 600 nm to 650 nm for color tone adjustment, the daylight white or daylight emission color can be controlled to a warm light bulb color region. Such a light-emitting element having a light bulb color can be widely used for general household lighting.

  In addition, any of the Li-containing α-sialon phosphors activated by rare earth elements of the present invention can be used to make an image display element using a Li-containing α-sialon phosphor. In this case, the light-emitting element described above can be used, but it is also possible to directly emit light by exciting the Li-containing α-sialon-based phosphor using an excitation source such as an electron beam, an electric field, or ultraviolet light. For example, it can be used on the principle of a fluorescent lamp. Such a light emitting element can also constitute an image display device.

Below, a specific example is given and this invention is demonstrated in more detail.
(Examples 1-8)
Lithium carbonate powder, lithium nitride powder, europium oxide powder, aluminum nitride powder, and amorphous silicon nitride powder obtained by reacting silicon tetrachloride with ammonia, or having a specific surface area of about 9.2 m ² / g Crystalline silicon nitride was weighed to have the composition shown in Table 1. Table 1 shows the raw material composition in mol%, and Table 2 shows the raw material composition in weight%. A nylon ball for stirring and a weighed powder were placed in a container and mixed by a vibration mill for 1 hour in a nitrogen atmosphere. After mixing, the powder was taken out and filled into a boron nitride crucible. The packing density at this time was about 0.5 g / cm ³ when crystalline silicon nitride was used, and about 0.18 g / cm ³ when amorphous silicon nitride was used. This was set in a resistance heating furnace, and under a normal pressure nitrogen gas flow atmosphere, from room temperature to 1000 ° C. for 1 hour, from 1000 ° C. to 1250 ° C. for 2 hours, from 1250 ° C. to the target temperature shown in Table 3 Was heated at a temperature increase schedule of 200 ° C./h to obtain phosphor powder. Since the obtained powder was weakly sintered lump, this was lightly crushed using an agate mortar until it became a powder without large lump, immersed in 2N-nitric acid solution for 5 hours, stirred and acidified. Treatment was performed, and the obtained powder was dried at a temperature of 110 ° C. for 5 hours to obtain a powder.

  The X-ray diffraction pattern of this powder was measured, and the crystal phase was identified. As a result, in all Examples, it was confirmed that the Li-containing α-sialon-based phosphor was almost obtained. Next, composition analysis of the obtained powder was performed. Oxygen and nitrogen contained in the Li-containing α-sialon-based phosphor were measured with a simultaneous oxygen / nitrogen analyzer manufactured by LECO, and for Li, the sample was subjected to pressurized acid decomposition with nitric acid and hydrofluoric acid. Then, sulfuric acid was added and concentrated by heating until white smoke was generated, and hydrochloric acid was added and dissolved by heating. Then, quantitative analysis was performed by ICP-AES method using SPS5100 type manufactured by SII Nanotechnology. For Si, the sample was melted by heating with sodium carbonate and boric acid, then dissolved in hydrochloric acid, and quantitative analysis was performed according to the coagulation weight method. About Li and Eu, the filtrate obtained by the pre-processing of the quantitative analysis of Si was collect | recovered, and the quantitative analysis by ICP-AES was performed. The results are shown in Table 3. These powders were further evaluated for fluorescence peak wavelength and peak intensity using FP-6500 with an integrating sphere manufactured by JASCO Corporation. The excitation wavelength of the fluorescence spectrum was 450 nm. The results are shown in Table 4. Note that 2 was used as the Eu valence a in calculating δ.

  Next, with respect to Example 2 using amorphous silicon nitride as a raw material and Example 6 using crystalline silicon nitride, a scanning electron microscope of S4800 manufactured by Hitachi High-Technologies Corporation and JSM-7000F manufactured by JEOL Ltd. The particle morphology was observed by (SEM). The observation was performed on the particle form after acid treatment (FIG. 1A, FIG. 1B), and then the classified product obtained by removing extremely large particles and small particles from the powder so that it could be used as a phosphor (FIG. 2A, 2B, 3A and 3B). Specifically, fine particles were removed by passing the powder through a 20 μm sieve and the water ratio.

  Based on the SEM photograph, the area of each particle was determined using image analysis software ImageJ, the particle diameter corresponding to a circle was determined from the area, and the average particle diameter was determined. The results are shown in Table 4. In addition, about 20 average primary particles were extracted by visual observation, and the average particle size was also obtained. The result was almost the same as the average value of the equivalent circle diameter described above. The average particle diameter of Li-containing α-sialon using amorphous silicon nitride was 1 to 3 μm. The aspect ratio was 2 or less in all examples. In the case of using amorphous silicon nitride as a raw material, primary particles can be clearly distinguished, but in the case of using crystalline silicon nitride, the primary particles are secondary particles that are closely fused and aggregated. Therefore, image analysis was difficult. Therefore, about 20 average primary particles were extracted by visual observation, and the average particle size was obtained. The results are shown in Table 4. The primary particle size was about 0.5 μm, much smaller than that using amorphous silicon nitride.

  Moreover, about the particle | grains of the analysis area | region, the ratio of 0.8 micrometer or more particle | grains was calculated | required. The area of all the particles in the measurement region and the area of particles of 0.8 μm or more were obtained, and the ratio was calculated. The results are shown in Table 4. The area ratio was 70% or more for all samples.

For the classified product of Example 2, the particle size distribution was measured using a laser diffraction / scattering particle size distribution measuring apparatus LA-910 manufactured by Horiba. The measurement method is as follows. A blank medium was measured by placing a dispersion medium containing 0.03 wt% of SN Dispersant manufactured by San Nopco into a flow cell. Next, a sample was added to a dispersion medium having the same composition, and ultrasonic dispersion was performed for 60 minutes. Measurement was performed by adjusting the amount of the sample so that the transmittance of the solution was 95% to 70%. The measurement result was corrected with the blank measurement result measured in advance, and the particle size distribution was obtained. SEM photographs of this powder are shown in FIGS. 2A and 3A. The result of the particle size distribution measurement is shown in FIG. 4A. The frequency distribution curve showed a good curve for a person. Table 10 shows D10, D50, and D90. It was 1.52 m < ² > / g when the specific surface area of this powder was measured by Shimadzu Corporation flowsorb 2300 type. Furthermore, the classified products of Example 4 were also measured for D10, D50, and D90. The frequency distribution curve showed a good curve for a person.

Further, the particle size distribution of Example 6 was measured. SEM photographs of this powder are shown in FIGS. 2B and 3B. The measurement result of the particle size distribution is shown in FIG. 4B. The frequency distribution curve is a Futyama curve. Table 10 shows D10, D50, and D90. It was 2.50 m < ² > / g when the specific surface area of this powder was measured by Shimadzu Corporation flowsorb 2300 type. Further, D10, D50, and D90 were measured for the classified product of Example 7. The frequency distribution curve is a Futyama curve. D90 of Example 7 exceeded 20 μm, which is considered to be because fine particles and large particles aggregated during the measurement.

  When producing Li-containing α-sialon-based phosphor powder using crystalline silicon nitride, small primary particles are fused and aggregated into a powder composed of secondary particles. , It becomes small particles of secondary particles and large secondary particles. In such a powder, scattering is increased by fine particles, the fluorescence intensity is lowered, and the particle size distribution is also relatively deteriorated.

(Comparative Example 1)
With the composition shown in Table 1, phosphor powders were produced in the same manner as in Example 1. Furthermore, identification of the crystal phase and composition analysis were performed in the same manner as in Example 1. As a result of analysis of the crystal phase, the powder was composed of a single phase containing Li-containing α-sialon phosphor. The analyzed composition is shown in Table 3. The Li-containing α-sialon phosphor having an x value of 0.39. The fluorescence intensity of this Li-containing α-sialon phosphor powder was low. From this, it became clear that when the x value is smaller than 0.45, good fluorescence intensity cannot be obtained.

(Comparative Example 2)
With the composition shown in Table 1, phosphor powders were produced in the same manner as in Example 1. Furthermore, identification of the crystal phase and composition analysis were performed in the same manner as in Example 1. As a result of analysis of the crystal phase, it was a powder composed of a Li-containing α-sialon phosphor and a slight heterogeneous phase. The analyzed composition is shown in Table 3. In addition, since there were few heterogeneous phases and most were Li containing alpha-sialon fluorescent substance, the heterogeneous phase was disregarded and it calculated. It was a Li-containing α-sialon phosphor having an x value of 0.9 and δ of −0.2. The fluorescence intensity of this Li-containing α-sialon phosphor powder was low. From this, it is clear that good fluorescence intensity cannot be obtained when δ is smaller than 0.

(Comparative Example 3)
A phosphor powder was prepared in the same manner as in Example 1 except that crystalline silicon nitride having a specific surface area of about 9.2 m ² / g was used as the silicon nitride raw material with the composition shown in Table 1, and the acid cleaning was similarly performed. Went. Furthermore, identification of the crystal phase and composition analysis were performed in the same manner as in Example 1. As a result of analysis of the crystal phase, it was a powder composed of a Li-containing α-sialon phosphor and a slight heterogeneous phase. The analyzed composition is shown in Table 3. In addition, since there were few heterogeneous phases and most were Li containing alpha-sialon fluorescent substance, the heterogeneous phase was disregarded and it calculated. The Li-containing α-sialon phosphor having an x value of 0.82 and δ of 0.0. The fluorescence intensity ratio was as small as 68.

Example 9
The phosphor of Example 2 and the epoxy resin were mixed at a weight ratio of 20: 100 to prepare a phosphor paste. This was applied to a blue light emitting diode (wavelength 470 nm) attached to the electrode, heated at 120 ° C. for 1 hour, and further heated at 150 ° C. for 12 hours to cure the epoxy resin. The obtained light emitting diode was turned on, and it was confirmed that it was white of daylight color.

(Example 10)
The phosphor of Example 2 and a separately prepared red phosphor CaAlSiN ₃ were mixed to adjust the color tone of the phosphor. The results are shown in Table 5. According to the change of the color tone shown in Table 5, it was possible to produce a white LED in the range of daylight color to light bulb color in combination with a blue LED.

(Example 11)
Lithium carbonate powder, europium oxide powder, aluminum nitride powder, aluminum oxide powder, and amorphous silicon nitride powder obtained by reacting silicon tetrachloride with ammonia are x = 0.85, y = 0.2, m = 1.25 and n = 1.0, and as an excessive additive, lithium carbonate was added in an amount of 0.63 mol in terms of metallic Li to 1 mol of Li-containing α-sialon. A nylon ball for stirring and a weighed powder were placed in a container and mixed by a vibration mill for 1 hour in a nitrogen atmosphere. After mixing, the powder was taken out and filled into a boron nitride crucible. The packing density at this time was about 0.18 g / cm ³ . This was set in a resistance heating furnace and heated from room temperature to 1000 ° C. for 1 hour, from 1000 ° C. to 1250 ° C. for 2 hours and from 1250 ° C. to 200 ° C./h to 1600 ° C. in a normal pressure nitrogen gas flow atmosphere. did. The holding time was 3 hours to obtain a phosphor powder. Since the obtained powder was a weakly sintered lump, it was lightly crushed using an agate mortar until it became a powder without a large lump. Subsequently, it was immersed in a 2N-nitric acid solution for 5 hours and stirred for acid treatment. The obtained powder was dried at a temperature of 110 ° C. for 5 hours.

The composition of the obtained powder was analyzed in the same manner as in Example 1. As a result, x = 0.64, y = 0.10, m = 0.91, n = 2.12, x / m = 0.70, and δ = 0.07.
Furthermore, the particle | grain form of the obtained powder was observed using the scanning electron microscope (SEM) of JSM-7000F by JEOL. The results are shown in FIG. As shown in FIG. 5, Li-containing α-sialon of primary particles having an average aspect ratio of 1.3 μm or more, a short axis length of 3.3 μm, and a short axis length of greater than 3 μm. Li-containing α-sialon phosphor powder containing phosphor particles could be obtained.

  The X-ray diffraction pattern of this powder was measured, and the crystal phase was identified. Note that Cu Kα was used as an X-ray source. As a result, it was confirmed that the main peak was Li-containing α-sialon. The X-ray was scanned precisely to obtain the lattice constant. As a result, they were hexagonal, a = 7.812Å, and c = 5.666Å.

  Next, the fluorescence characteristics will be described. Considering the case of actually using a phosphor as a sample, a classified product from which extremely large particles and small particles were removed was adopted. Specifically, a large particle lump was removed through a 20 μm sieve, and extremely fine particles were removed by a water ratio.

The fluorescence characteristics were measured using an FP-6500 with an integrating sphere manufactured by JASCO Corporation. It was 270% on the same scale as Table 4.
(Example 12)
As the raw material, the amorphous silicon nitride powder was replaced with silicon diimide, and the raw material was weighed and mixed with the same composition as in Example 2. The mixed powder was filled in a silicon nitride crucible. The packing density at this time was 0.09 g / cm ³ . This was set in a resistance heating furnace, and under normal pressure nitrogen gas flow atmosphere, from room temperature to 800 ° C for 1 hour, from 800 ° C to 1000 ° C for 2 hours, from 1000 ° C to 1250 ° C for 2 hours, 1250 ° C To 1650 ° C. with a temperature increase schedule of 200 ° C./h to obtain phosphor powder. The obtained powder was processed in the same manner as in Example 2 and the composition was analyzed. As a result, x = 0.90, y = 0.03, m = 1.13, n = 2.23, x / m = 0.80, and δ = 0.17. The fluorescence peak wavelength was 572 nm, and the fluorescence intensity was 293% when represented by the intensity ratio in Table 4.

Claims (18)

General formula (1)
Li _x Eu _y Si _{12- (m + n)} Al _{(m + n) On + δ} N _16-n-δ (1)
(Wherein the average valence of Eu is a, x + ya + δ = m; 0.45 ≦ x <1.2, 0.001 ≦ y ≦ 0.2, 0.9 ≦ m ≦ 2.5, 0. 5 ≦ n ≦ 2.4, δ> 0.) A Li-containing α-sialon-based phosphor.   The Li-containing α- according to claim 1, wherein the δ is 0.05 to 1.2, and the ratio x / m between the x and m is in the range of 0.4 to 0.9. Sialon phosphor.   3. The Li-containing α-sialon-based fluorescence according to claim 2, wherein x is 0.82 ≦ x <1.2, and x / m is in a range of 0.5 to 0.9. body.   The Li-containing α-sialon-based phosphor according to claim 1, wherein when the excitation light is incident, fluorescence having a peak wavelength of 560 nm to 580 nm is emitted. The average aspect ratio of primary particles measured by image analysis of a scanning electron micrograph is 2 or less, and the powder has an average particle diameter D _particle of 1 µm to 3.0 µm. 1. The Li-containing α-sialon phosphor according to 1.   6. The Li-containing α-sialon-based fluorescence according to claim 5, wherein in the particles measured by image analysis of a scanning electron micrograph, primary particles of 0.8 μm or more are present in an area ratio of 70% or more. body.   The Li-containing α- according to claim 5, wherein the frequency distribution curve in the particle size distribution curve measured with a laser diffraction / scattering particle size distribution analyzer is a single peak and the median diameter is 4 to 15 µm. Sialon phosphor.   The Li-containing α-sialon-based phosphor according to claim 5, wherein the 10% diameter in the particle size distribution curve is 1.5 µm or more and the 90% diameter is 15 µm or less.   2. The Li-containing α according to claim 1, wherein the primary particle aspect ratio measured by image analysis of a scanning electron micrograph is a powder having an aspect ratio of 3 or less and a minor axis length of more than 3 μm. -Sialon phosphor.   Silicon nitride powder and / or nitrogen-containing silane compound, AlN-containing aluminum source material, Li nitride, oxynitride, oxide, or precursor material that becomes an oxide by thermal decomposition, Eu nitridation Lithium is in excess of the composition of the Li-containing α-sialon-based phosphor represented by the general formula (1) with the oxide, oxynitride, oxide, or precursor material that becomes oxide by thermal decomposition. 2. Production of Li-containing α-sialon-based phosphor according to claim 1, characterized by being weighed and mixed so as to have a composition, and calcined at 1400 to 1800 ° C. in an inert gas atmosphere containing nitrogen. Method.   The method for producing a Li-containing α-sialon-based phosphor according to claim 10, wherein the Li-containing α-sialon-based phosphor after the baking is acid-washed.   An amorphous silicon nitride powder and / or a nitrogen-containing silane compound, a material that becomes an aluminum source containing AlN, a nitride of Li, an oxynitride, an oxide, or a precursor material that becomes an oxide by thermal decomposition, Eu nitride, oxynitride, oxide, or precursor material that becomes oxide by thermal decomposition is more lithium than the composition of the Li-containing α-sialon-based phosphor represented by the general formula (1). The Li-containing α-sialon-based fluorescence according to claim 5, wherein the Li-containing α-sialon-based fluorescent material is weighed and mixed so as to have an excessive composition, and fired at 1400 to 1800 ° C. in an inert gas atmosphere containing nitrogen. Body manufacturing method.   A theoretical amount of amorphous silicon nitride powder and / or a nitrogen source silane compound and an aluminum source material containing AlN, a Li nitride, an oxynitride, an oxide, and a composition of the general formula (1) Or a precursor material that becomes an oxide by thermal decomposition, a nitride of Eu, an oxynitride, an oxide, or a precursor material that becomes an oxide by thermal decomposition, and an excessive amount not included in the theoretical amount, The oxide of Li or the precursor substance which becomes an oxide by thermal decomposition is mixed and calcined at 1500 to 1800 ° C. in an inert gas atmosphere containing nitrogen at normal pressure. A method for producing the Li-containing α-sialon phosphor as described.   The amount of excess Li oxide not included in the theoretical amount, or the metallic lithium of the precursor material that becomes an oxide by thermal decomposition, is 1 mol of Li-containing α-sialon-based phosphor of the theoretical amount of the product. The method for producing a Li-containing α-sialon phosphor according to claim 13, wherein the content is 0.1 to 1.25 mol.   The lighting fixture comprised from a light emission source and the fluorescent substance containing Li containing alpha-sialon type | system | group fluorescent substance of Claim 1, 5 or 9.   The lighting apparatus according to claim 15, wherein the light source is an LED that emits light having a wavelength of 330 to 500 nm.   The lighting device according to claim 16, wherein the phosphor further contains a phosphor emitting red light of 600 nm to 650 nm.   An image display device comprising an excitation source and a phosphor containing the Li-containing α-sialon phosphor according to claim 1, 5 or 9.