JP2006137902A - Nitride phosphor, process for producing nitride phosphor and white light-emitting element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nitride phosphor that has an emission peak wavelength in a range of 600 nm or more, more specifically in a range of 620-650 nm and a high luminous intensity, to provide a process for producing the nitride phosphor and to provide a white light-emitting element. <P>SOLUTION: The nitride phosphor has a chemical composition represented by the formula (1) as shown below and has a peak emission wavelength in a range of 600-650 nm. Formula (1) is (Ca<SB>x</SB>Sr<SB>y</SB>Eu<SB>z</SB>)<SB>m/2</SB>Si<SB>12-(m+n)</SB>Al<SB>m+n</SB>O<SB>n</SB>N<SB>16-n</SB>wherein x+y+z=1; 0<y/(x+y)≤1; 0<z≤0.3; 0.6<m<3.0; and 0≤n≤1.5. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a nitride phosphor having a light emission peak in a long wavelength region of 600 to 650 nm or more and high emission intensity, a method for producing the nitride phosphor, and a white light emitting device.

Currently, a nitride-based phosphor that absorbs ultraviolet to blue light and exhibits a relatively long-wavelength yellow-orange fluorescent color is attracting attention as a phosphor suitable for a white light-emitting element. The white light emitting element converts a part of light emitted from a blue semiconductor light emitting element (blue LED) such as a GaN system with a photoluminescence phosphor, and converts the wavelength of the blue LED light into the wavelength converted light (mainly a yellow light emitting element). It is a light emitting element that emits a light emission color different from that of LED light, particularly white light, by mixing with light. Since such a light emitting element is small and has high power efficiency, it is used as various light sources such as a signal lamp, an in-vehicle illumination, a liquid crystal backlight, and a display board such as a station destination guide plate.
As a photoluminescence phosphor used in a white light emitting element in combination with a blue LED, an yttrium / aluminum / garnet phosphor activated with cerium (Ce) (hereinafter referred to as “YAG phosphor”). However, nitride phosphors that emit yellow to orange light are also expected as photoluminescent phosphors for white light-emitting elements that replace YAG phosphors.
On the other hand, the light emitted from the YAG phosphor is yellow-green to yellow, and when the YAG phosphor is used as a photoluminescence phosphor, the emission color of the white light emitting element becomes slightly bluish white. Although it is good for illumination, when it is used for illumination applications that require high color rendering properties, or when used as a backlight for a color liquid crystal display (LCD), the output light is insufficient for the red component. For this reason, it is desired to correct the emission color by supplementing the red component using a red light emitting phosphor having an emission peak wavelength of 600 nm or more, particularly 620 nm or more.
Therefore, it has been proposed to use the nitride phosphor together with the YAG phosphor. As such a nitride-based red phosphor, calcium (Ca) -α-sialon-based phosphors (see Patent Documents 1 to 3) are known.
JP 2002-363554 A JP 2003-124527 A JP 2003-203504 A

However, the Ca-α-sialon-based phosphors described in the above Patent Documents 1 to 3 are practical nitride fluorescent light whose emission peak wavelength is almost 500 to 600 nm and whose emission peak wavelength is longer than 600 nm. There is almost no body.
The present invention has been made in view of the above circumstances. A nitride phosphor having an emission peak wavelength at 600 nm or more, particularly 620 to 650 nm, and having high emission intensity, a method for producing the nitride phosphor, and a white light emitting element are provided. It is intended to provide.

In order to solve the above-mentioned problems, the present inventors have made extensive studies and found a novel nitride phosphor having an emission peak wavelength in the range of 600 to 650 nm and high emission intensity.
That is, the nitride phosphor of the invention described in claim 1 has a chemical composition represented by the following general formula (1).
_{(Ca x Sr y Eu z)} m / 2 Si 12- (m + n) Al m + n O n N 16-n ... (1)
(However, in the general formula (1), x + y + z = 1, 0 <y / (x + y) ≦ 1, 0 <z ≦ 0.3, 0.6 <m <3.0, 0 ≦ n ≦ 1.5. It is.

The invention according to claim 2 is the nitride phosphor according to claim 1,
The main crystal phase is an α-sialon structure or a mixed phase of an α-sialon structure and an orthorhombic crystal structure.

The invention according to claim 3 is a method for producing the nitride phosphor according to claim 1 or 2,
A compound of a metal element other than silicon constituting the nitride and silicon nitride are dissolved or dispersed in molten urea and / or a molten urea derivative to form a nitride precursor, and the nitride precursor is A nitride phosphor is produced by heating in an inert or reducing atmosphere.

  The white light emitting device according to claim 4 is a semiconductor light emitting device that emits blue light, and a phosphor that emits fluorescence in the green to yellow wavelength region by absorbing part of the light from the semiconductor light emitting device. And the nitride phosphor according to claim 1 or 2.

  The white light-emitting device according to claim 5 is a semiconductor light-emitting device that emits light in the ultraviolet to blue-violet region, and a phosphor that absorbs light from the semiconductor light-emitting device and emits blue fluorescence, or It comprises at least one of phosphors emitting green fluorescence, and the nitride phosphor according to claim 1 or 2.

The nitride phosphor according to the present invention has an emission peak wavelength in a long wavelength region of 600 to 650 nm, which has not been particularly practical, and exhibits high emission intensity. Further, it emits light by being excited by light in a wide wavelength region from the ultraviolet region to the yellow-green light region, and also by an electron beam or an electric field. Therefore, it is useful as a phosphor used for ordinary illumination, various display tubes, white LEDs, and the like. Particularly, those having an emission peak wavelength of 620 to 650 nm are suitable for red correction of white LEDs when used in combination with YAG.
Further, since the base material is α-sialon or a mixed phase of α-sialon and orthorhombic crystal, it is excellent in chemical, mechanical and thermal characteristics, and can be expected to be stable and long-life as a phosphor material. . As a result, it is possible to prevent thermal degradation of the red phosphor during the resin sealing process of the white LED.
Furthermore, according to the method for producing a nitride phosphor according to the present invention, a nitride precursor having a uniform composition can be formed by dissolving or dispersing each raw material in molten urea and / or a molten urea derivative. it can. Then, by heating such a nitride precursor in an inert or reducing atmosphere, a nitride phosphor having excellent characteristics and crystallinity with a uniform particle diameter can be obtained. Further, since nitriding and crystal growth of the raw material can be performed in the same reaction vessel, it can be efficiently produced by a simple process, and can be produced at normal pressure and at a relatively low temperature.

Hereinafter, the nitride phosphor according to the present invention, a white light emitting device as an application, and a method for producing the nitride phosphor will be described in detail.
(Nitride phosphor)
The nitride phosphor according to the present invention has a chemical composition represented by the following general formula (1).
_{(Ca x Sr y Eu z)} m / 2 Si 12- (m + n) Al m + n O n N 16-n ... (1)
(However, in the general formula (1), x + y + z = 1, 0 <y / (x + y) ≦ 1, 0 <z ≦ 0.3, 0.6 <m <3.0, 0 ≦ n ≦ 1.5. It is.

The present invention is a conventional Ca-α-sialon in which at least a part of Ca is substituted with Sr.
In the present invention, the emission peak wavelength is shifted to the long wavelength region by increasing the substitution amount of Sr for Ca, which is preferable.
On the other hand, Ca-α-sialon containing no Sr has an emission peak wavelength shorter than 600 nm, and thus is out of the scope of the present invention.
Thus, by controlling the composition ratio of the conventional α-sialon, particularly the addition amount of Ca and Sr, a nitride phosphor having an emission peak wavelength of 600 to 650 nm can be obtained. Particularly, the value of y / (x + y) representing the substitution amount of Sr with respect to Ca is preferably larger than 0.3, particularly 0.4 or more, because the emission wavelength is 620 nm or more.

  Furthermore, although it is considered that Al stabilizes the structure in the present invention, the emission intensity decreases conversely as the amount of Al added increases. In particular, it is necessary to satisfy m <3 since the emission intensity is low at m = 3.0 from the results of Examples described later.

The nitride phosphor has a crystal structure that changes depending on y / (x + y), which is the ratio of Sr and (Ca + Sr). When the amount of Sr added is small, the main crystal phase has an α-sialon crystal structure. As the amount of Sr added increases, the proportion of orthorhombic system increases, and the α-sialon crystal structure and the orthorhombic crystal structure coexist.
The nitride phosphor according to the present invention tends to have a longer emission wavelength and higher intensity as the main crystal phase has a higher orthorhombic ratio, and therefore the main crystal phase has an α-sialon crystal structure and an oblique structure. What mixed with the tetragonal crystal structure is preferable.

  The nitride phosphor of the present invention includes an element that acts as a coactivator such as a rare earth metal element, such as cerium (Ce), terbium (Tb), in order to adjust emission intensity, afterglow, and other fluorescence characteristics. ), Dysprodium (Dy), samarium (Sm), praseodymium (Pr), neodymium (Nd), erbium (Er), holmium (Ho), thulium (Tm), manganese (Mn), etc. may be appropriately doped. .

  The nitride phosphor according to the present invention emits fluorescence having an emission peak wavelength in the range of 600 nm or more, particularly 620 nm to 650 nm, which has never existed in the past, when excited by light in the ultraviolet to yellow-green light region, electron beam, or electric field. Long-wavelength red light emitting phosphor.

  Such nitride phosphors can be used as long-wavelength red phosphors, illumination phosphors such as lamps, and red phosphors for display tubes such as cold cathode tubes, CRTs, PDPs, FEDs, and inorganic ELs. Can be used as

Further, it is excited by ultraviolet light and visible light in a purple to yellow-green wavelength region, and these light can be converted into light having a longer wavelength, so that it is very effective for producing a white light emitting element.
Specifically, the blue LED absorbs part of the blue light from the LED, converts the wavelength and emits green to yellow light, and the nitride of the present invention as the second phosphor. By combining with a phosphor, a white light emitting device with excellent color balance can be obtained.
For example, a white light emitting device including a GaN-based or InGaN-based blue LED having a light emission peak wavelength of 400 nm to 460 nm and a YAG phosphor that emits yellow-green to yellow light when excited by blue light is used. The color rendering property and color sensitivity can be improved by adding the nitride phosphor of the present invention for the red component complementary color.
In addition, by combining the blue LED, the first phosphor that emits green light with the blue light, and the red light emitting nitride phosphor of the present invention, white light emission by mixing three primary colors of blue, green, and red light. An element can also be obtained.
Moreover, instead of blue LED, for example, a semiconductor element (ultraviolet LED) that emits light in an ultraviolet to blue-violet region having a peak wavelength of 360 to 400 nm is used, and the emitted light is absorbed to emit red, green, or blue fluorescence. A light emitting device that emits white light by mixing these three primary colors in combination with a photoluminescent phosphor that emits light is also known, but the nitride phosphor of the present invention is used as a red component of such a white light emitting device. You can also. In any case, since the nitride phosphor of the present invention can be excited by light in a wide wavelength region from ultraviolet light to yellow-green light, not only light from the blue LED but also light emitted by other phosphors. Because it also emits light, efficiency is high.
Furthermore, as a phosphor combined with an ultraviolet LED, a blue LED, or an LED emitting blue-green to green, the nitride phosphor of the present invention is used alone, and various light sources such as white light, purple, magenta, pink, and red are used. A light-emitting element that emits colored light can also be obtained.

(Nitride phosphor manufacturing method)
Next, a method for producing a nitride phosphor according to the present invention will be described.
As the method for producing a nitride phosphor according to the present invention, a known solid phase reaction method, spray pyrolysis method, liquid phase reaction method, and other methods can be applied, but the urea precursor shown below is used. This method is most preferable in that it has a uniform composition and is easy to obtain a nitride having a uniform particle size and good crystallinity. Furthermore, this method is preferable in that the raw material can be nitrided and grown in the same reaction vessel, and can be produced at normal pressure and at a relatively low temperature.
Hereinafter, an example of the method using the urea precursor suitably used in the present invention will be described. First, urea and / or a urea derivative (hereinafter sometimes referred to as “urea or the like”) is heated to a temperature equal to or higher than these melting points to be in a molten state. However, if the heating temperature is too high, another product may be formed. Therefore, urea or the like is dissolved, and a molten state is added even after adding a Ca compound, Sr compound, Eu compound, Al compound, or silicon nitride described later. It is preferable to set the temperature to such a level that can be maintained for a predetermined time. For example, when urea is used, its melting point is 132 ° C., so it is sufficient to heat it to a slightly higher temperature.

  As the urea derivative, various compounds such as urea compounds as carbamate compounds, urea complex compounds, and urea adduct compounds can be used as substitutes of various organic groups for nitrogen atoms in urea. As urea or the like, urea is preferably used from the viewpoints of availability, ease of handling, and the like.

  Next, a Ca compound, an Sr compound, an Eu compound, and an Al compound, which are constituent components of the final product, are dissolved in molten urea or the like, and silicon nitride is dispersed to form a nitride precursor. The Ca compound may be added according to the nitride phosphor to be produced, and is not necessarily essential. When the coactivator is doped, a predetermined amount of a metal element compound that acts as a coactivator is added and dissolved.

  A compound of a metal element other than silicon constituting the nitride, that is, a Ca compound, a Sr compound, an Eu compound, an Al compound, or a compound of a coactivator element is not particularly limited. For example, chloride, nitrate It is preferable to use a material that dissolves in molten urea or the like because the product becomes more uniform. When oxygen is introduced into the nitride, an oxide such as aluminum oxide or silicon oxide can also be used. As silicon nitride, either crystalline or amorphous silicon can be used as appropriate. For example, amorphous silicon nitride is considered preferable in terms of reactivity, but crystalline silicon nitride is advantageous in terms of easy availability, easy handling, and yield. is there.

The nitride precursor thus obtained is allowed to cool, for example, and dried to form a solid. This solid material is mechanically pulverized as necessary, and heated using a heating furnace to produce a nitride. As a heating furnace, well-known things, such as a batch furnace, a belt furnace, a tubular furnace, a rotary kiln, can be used.
However, it is necessary to perform heating under an inert atmosphere or a reducing atmosphere.
Further, the target product may be formed by one-step heating (firing) in an inert atmosphere or a reducing atmosphere, or the target nitride is obtained by heating (firing) in multiple stages. Also good. Various conditions such as the heating temperature and the heating time may be appropriately set according to the type of the desired product and the required characteristics. For example, in the case of one-stage heating, the temperature is in the range of 1200 to 1700 ° C. The conditions may be set from a range of 0.5 to 24 hours at a temperature of. In the case of two-stage heating, it is desirable to set the second stage heating temperature higher than the first stage heating temperature. For example, the first stage heating is performed at about 200 to 900 ° C. It is desirable that the temperature be within the range of 0.5 to 6 hours, and the second stage heating be performed at a temperature within the range of about 1200 to 1700 ° C. for about 0.5 to 24 hours. Multi-stage heating is advantageous in that a product with a more uniform composition can be obtained with good reproducibility.

  Also, as other heating means, the finely powdered and highly uniform crystallinity is obtained by heating the mechanically pulverized precursor powder desirably after adjusting the particle size and then dispersing in the gas phase. A nitride powder can be obtained.

Furthermore, a spray pyrolysis method may be used as another heating means. In this spray pyrolysis method, the liquid precursor is made into fine droplets using an atomizer such as an ultrasonic type or a two-fluid nozzle type or other atomizing means, and this is subjected to an inert atmosphere or a reducing atmosphere condition. Under heating, the precursor can be decomposed and reacted to obtain fine and uniform nitride powder.
In the above production example, the method of dissolving or dispersing each compound etc. in the molten urea etc. has been described, but the urea etc. and the compound etc. are mixed in advance and then heated to melt the urea etc. It doesn't matter.

EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated concretely, the embodiment of this invention is not limited to this.
Samples 1-14 were prepared according to the following method, and then the following measurements were performed for each sample 1-14 and evaluated.
[Preparation of Sample 1]
Urea was melted at 134 ° C. to obtain molten urea. In 30 g of this molten urea, 0.235 g of EuCl3 · 6H2O, 3.098 g of AlCl3 · 6H2O and 0.512 g of CaCl2 were added and dissolved. Further, 3 g of Si3N4 powder (Ube Industries SN-E10) was added, stirred, and uniformly dispersed. This was air-cooled while stirring to produce a solid nitride precursor having an element molar ratio of Ca: Eu: Si: Al = 0.9: 0.1: 10: 2. The obtained precursor was put in a carbon container, fired at 600 ° C. for 1 hour in an N ₂ atmosphere containing 4% of H _2, and then pulverized. This was put in a Mo container, held at 1200 ° C. for 6 hours in an N ₂ atmosphere containing 4% H _2, and then kept at 1550 ° C. for 6 hours and heated for a total of 24 hours to produce a nitride phosphor.

[Preparation of Samples 2 to 14]
Samples 2 to 14 were obtained in the same manner as Sample 1 by appropriately changing the molar ratio of the raw materials Ca, Sr, Eu, and Al in the preparation of Sample 1. SrCl ₂ .6H ₂ O was used as the Sr source. Table 1 shows the chemical composition of each sample 1-14.
Samples 1 to 7 have y / (x + y) that is a ratio of Sr and (Ca + Sr) in the general formula (1) changed, and samples 8 to 10 have the composition of sample 4 and the ratio of Eu. Z is changed within a range of 0.03 ≦ z ≦ 0.1. Samples 11 and 12 are different from Samples 1 to 10 in that the amount of Al added is changed to m = 3 and does not contain Sr. Similarly, Samples 13 and 14 are cases in which the amount of Al added is changed to m = 2.8, and Ca is not further contained. Samples 1, 11, and 12 are outside the scope of the present invention.

<< X-ray diffraction pattern >>
About the obtained phosphor powder (samples 1 to 14), an X-ray diffraction pattern was measured using a X-ray source of Cu-Kα rays using a powder X-ray diffractometer manufactured by Rigaku Corporation. FIG. 1 shows X-ray diffraction patterns of Samples 2 and 6 as representative ones. As shown in FIG. 1, it can be confirmed that when the amount of Sr is small, the α-sialon structure is the main phase, but as the Sr ratio increases, the crystal structure has a higher orthorhombic ratio. In addition, the crystal structures of other samples were similarly confirmed from the X-ray diffraction patterns, and are also shown in Table 1.

<Fluorescence characteristics>
About each sample 1-14, the fluorescence spectrum was measured in the range of 500 nm to 800 nm using 400 nm monochromatic light as an excitation light source using a spectrofluorometer (FP-6600 type) manufactured by JASCO Corporation. Table 1 shows the measurement results (measurement values) of the emission peak wavelength and emission intensity of each sample 1-14. The emission intensity in Table 1 is the relative intensity when the emission intensity at the emission peak wavelength of 594 nm of Sample 1 is taken as 100. FIG. 2 shows the fluorescence spectra of representative samples 1, 2, and 6. Further, FIG. 3 shows the results of measuring the excitation spectra at the respective emission peak wavelengths for these samples 1, 2, and 6 in the range of 250 nm to 580 nm.
Rhodamine B was used for correcting the excitation spectrum, and a xenon lamp and a tungsten lamp were used for correcting the fluorescence spectrum.

表１の結果から明らかなように、上記一般式（１）で表される窒化物蛍光体において、ｘ、ｙ、ｚ、ｍ、ｎの各パラメータが本発明の範囲内にある試料２〜１０、１３、１４は、６００〜６５０ｎｍの長波長域に発光ピークが見られ、発光強度も比較的高いものであった。一方、本発明の範囲外である試料１、１１、１２は、発光ピーク波長が６００ｎｍより短波長域に見られた。
また、試料１〜７から明らかなように、ＣａとＳｒの組成比においてＣａに対するＳｒの添加量を増加させることにより発光ピーク波長が長波長にシフトする傾向があった。この結果から、Ｓｒの添加量によって発光ピーク波長をコントロールできることがわかる。

As is apparent from the results in Table 1, in the nitride phosphor represented by the general formula (1), samples 2 to 10 in which the parameters x, y, z, m, and n are within the scope of the present invention. , 13 and 14 had a light emission peak in the long wavelength region of 600 to 650 nm and a relatively high light emission intensity. On the other hand, Samples 1, 11, and 12, which are outside the scope of the present invention, had an emission peak wavelength in the shorter wavelength region than 600 nm.
Further, as is clear from Samples 1 to 7, the emission peak wavelength tends to shift to a longer wavelength by increasing the amount of Sr added to Ca in the composition ratio of Ca and Sr. From this result, it is understood that the emission peak wavelength can be controlled by the addition amount of Sr.

It is an X-ray diffraction pattern of Samples 2 and 6. It is a fluorescence spectrum of samples 1, 2, and 6. It is an excitation spectrum of samples 1, 2, and 6.

Claims (5)

A nitride phosphor having a chemical composition represented by the following general formula (1) and having a peak emission wavelength in the range of 600 to 650 nm.
_{(Ca x Sr y Eu z)} m / 2 Si 12- (m + n) Al m + n O n N 16-n ... (1)
(However, in the general formula (1), x + y + z = 1, 0 <y / (x + y) ≦ 1, 0 <z ≦ 0.3, 0.6 <m <3.0, 0 ≦ n ≦ 1.5. It is. The nitride phosphor according to claim 1, wherein
A nitride phosphor, wherein the main crystal phase is an α-sialon structure or a mixed phase of an α-sialon structure and an orthorhombic crystal structure. A method for producing the nitride phosphor according to claim 1, comprising:
A compound of a metal element other than silicon constituting the nitride and silicon nitride are dissolved or dispersed in molten urea and / or a molten urea derivative to form a nitride precursor, and the nitride precursor is A method for producing a nitride phosphor, comprising producing a nitride phosphor by heating in an inert or reducing atmosphere.   3. A semiconductor light emitting device that emits blue light, a phosphor that absorbs part of light from the semiconductor light emitting device and emits fluorescence in a green to yellow wavelength region, and the nitride fluorescence according to claim 1. A white light emitting element comprising: a body.   A semiconductor light emitting device that emits light in the ultraviolet to blue-violet region, and at least one of a phosphor that emits blue fluorescence by absorbing light from the semiconductor light emitting device, or a phosphor that emits green fluorescence, A white light-emitting element comprising the nitride phosphor according to claim 1.

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