JP4165406B2 - Phosphor - Google Patents

Description

  The present invention relates to a phosphor having an osmillite-type crystal structure, which emits blue to green light when excited by ultraviolet light to visible light.

  Phosphors are widely used in the fields of illumination devices such as fluorescent lamps, display devices such as PDP (Plasma Display Panel), and X-ray imaging tubes. For example, in a fluorescent lamp, a fluorescent film in which a mixture of phosphors such as blue, green, and red is applied to the inside of the tube is generally used, and the emission characteristics of the phosphor are related to the brightness (light flux) and color rendering of the lamp. It is known to have a great effect on sex.

Patent Documents 1 and 2 disclose examples of phosphors. Patent Document 1 discloses that a blue phosphor can be obtained by activating BaMgAl ₁₁ O ₁₇ having a magnetoplumbite type crystal structure with divalent europium. Patent Document 2 discloses that a green phosphor can be obtained by activating LaAl ₁₁ O ₁₈ having a magnetoplumbite-type crystal structure with trivalent terbium, or trivalent terbium and divalent manganese. Has been.
Shoko 52-22836 JP-A-2003-342566

However, in the conventional blue or green phosphor, when the amount of activator added such as europium or terbium is increased with respect to the matrix, a phenomenon called “concentration quenching” occurs, resulting in a decrease in emission luminance. there were. For example, in BaMgAl ₁₁ O ₁₇ , when 5% or more of the number of barium atoms is substituted with divalent europium, it is known that electron transfer occurs between the europium in the crystal and the emission luminance decreases. . Therefore, in order to obtain a phosphor with good emission luminance, the amount of substitution of divalent europium needs to be less than 5% of the number of barium atoms.

In addition, it is known that the emission wavelength shifts to the longer wavelength side when the amount of europium added to the base is increased. However, when the amount of divalent europium is suppressed by deriving from the above, the divalent europium is reduced. It has also been difficult to change the emission wavelength of the BaMgAl ₁₁ O ₁₇ phosphor in a wide range by controlling the amount of substitution. Therefore, when changing the emission wavelength of the BaMgAl ₁₁ O ₁₇ phosphor in a wide range, in general, a part of the barium atom has been replaced with strontium, calcium, etc. In such a method, the emission Although it is possible to change the wavelength in a wide range, the light emission luminance is lowered. In other words, the conventional BaMgAl ₁₁ O ₁₇ phosphor cannot change the emission wavelength in a wide range without lowering the emission luminance.
An object of the present invention is to provide a phosphor capable of changing the emission wavelength in a wide range without lowering the emission luminance.

  As a result of intensive studies to solve the above problems, the present inventors have developed a matrix having a specific crystal structure and composition that does not cause concentration quenching even when the activation amount of divalent europium is changed. The inventor has invented a novel phosphor.

That is, the phosphor of the invention according to claim 1 is characterized in that it has an osmyrite type crystal structure and has a chemical composition represented by the following general formula .
(A _1-a Eu _a ) _1-x Mg ₂ Al _6-2x Si _{9 + 2x} O ₃₀
(In the above general formula, A is at least one alkaline earth metal element selected from calcium, strontium and barium, respectively a and x 0 <a ≦ 1, 0 ≦ x ≦ 0. 2 )

The invention described in claim 2
The phosphor according to claim 1 ,
Furthermore, it is characterized in that it contains at least one kind of rare earth element serving as a coactivator with respect to Eu in the above general formula .

According to the phosphors according to claims 1 and 2 , a indicating the europium substitution amount can be selected in a wide range of 0 <a ≦ 1 without causing concentration quenching. That is, according to the phosphor according to the present invention, the emission wavelength can be changed in a wide range without lowering the emission luminance, and thus can be widely applied to fluorescent lamps, PDPs and the like.

Hereinafter, the best mode for carrying out the present invention will be described.
The phosphor according to the present invention is mainly composed of a matrix and an element for activating it (an element serving as a light emission center). In the present embodiment, the matrix and the luminescent center element will be described, respectively, and then a method for manufacturing the phosphor will be described.

(Maternal body)
The phosphor according to the present invention is a compound whose matrix has an osmillite crystal structure and whose chemical composition is represented by the following general formula (1).
(A _1-a Eu _a ) _1-x (Mg _1-b Mn _b ) ₂ Al _6-2x (Si _{1- (c + d)} Zr _c Ge _d ) _{9 + 2x} O ₃₀ (1)
In the general formula (1), A is at least one alkaline earth metal element selected from calcium, strontium, and barium, and a, b, c, d, and x are 0 <a ≦ 1, respectively. 0 ≦ b <1, 0 ≦ c <1, 0 ≦ d <1, 0 ≦ c + d <1, 0 ≦ x <1.

Preferably, in the compound represented by the general formula (1), b, c, and d may be 0, and the compound represented by the following general formula (2) may be the phosphor according to the present invention.
(A _1-a Eu _a ) _1-x Mg ₂ Al _6-2x Si _{9 + 2x} O ₃₀ (2)

More preferably, in the compound represented by the general formula (2), x may be 0, and the compound represented by the following general formula (3) may be the phosphor according to the present invention.
(A _1-a Eu _a ) Mg ₂ Al ₆ Si ₉ O ₃₀ (3)

(Osmillite crystal structure)
The osumilite crystal structure is represented by the following general formula (4).
(M ¹ ) _1-y (M ² ) ₂ (M ³ ) ₃ (M ⁴ ) ₁₂ O ₃₀ (4)
In the general formula (4), M ¹ is a metal element having an oxidation number of 1 or 2, M ² is a metal element having an oxidation number of 2, M ³ is a metal element having an oxidation number of 3, and M ⁴ is an oxidation. It is a metal element of number 3 or 4, and y is 0 ≦ y ≦ 1.

In this osmylite-type crystal structure, M ⁴ forms a ring represented by (M ⁴ ) ₁₂ O ₃₀ , and this ring is bonded by M ² and M ³ to form a strong network. ¹ is confined in a hole in the annular body represented by (M ⁴ ) ₁₂ O ₃₀ .

  The matrix of the phosphor according to the present invention is essential to have an osmillite type crystal structure. However, as long as the effect of the present invention is not impaired, an unrestricted crystal phase other than the osmillite type crystal structure is included. Also good. Although the osmylite type crystal structure has hexagonal symmetry, it is not limited to hexagonal crystals as long as the effects of the present invention are not impaired. An oblique crystal may be included.

In the phosphor according to the present invention, the matrix has an osmillite type crystal structure represented by the above general formula (4), and in particular, M ¹ , M ² , M ³ and M ⁴ are composed of combinations of the following elements: Then, the fluorescent substance with the favorable light emission luminance which is the object of the present invention can be obtained.
M ¹ ; at least one alkaline earth metal element selected from calcium, strontium and barium and europium M ² ; magnesium M ³ ; aluminum M ⁴ ; aluminum and silicon

In the phosphor according to the present invention, as M ¹ , in addition to at least one alkaline earth metal element selected from calcium, strontium and barium, divalent europium serving as a luminescent center as an activator is used. The inclusion is essential, but at least one rare earth element that serves as a co-activator for europium may be contained within a range that does not impair the effects of the present invention. That is, at least one alkaline earth metal element selected from calcium, strontium, and barium and / or a part of europium may be substituted with at least one rare earth element such as terbium, dysprosium, and cerium. . This substitution can produce a co-activation effect with europium and the substituted rare earth element, and is effective in changing the emission wavelength of the phosphor in a wide range.

In the phosphor according to the present invention, it is essential that magnesium is contained as M ² , but a part of magnesium may be substituted with an element such as manganese as long as the effects of the present invention are not impaired. This substitution can produce a co-activation effect with elements such as europium and manganese, and is effective in changing the emission wavelength of the phosphor in a wide range.

In the phosphor according to the present invention, it is essential that M ⁴ contains aluminum and silicon as M ⁴ , but even if a part of silicon is replaced with zirconium and / or germanium as long as the effect of the present invention is not impaired. Good. This substitution is effective in improving the acid resistance of the phosphor.

  In the general formulas (1) to (3), a represents the amount of substitution of europium with respect to A. In the phosphor according to the present invention, substitution of europium for A is possible in a wide range of 0 <a ≦ 1.0, and a is preferably 0.010 ≦ a ≦ 1.0. When a is in the range of 0.010 ≦ a ≦ 1.0, a phosphor with particularly good emission luminance can be obtained.

In the above general formulas (1) and (2), x represents the ratio of the number of atomic vacancies to the number of atomic positions present in the ring represented by (M ⁴ ) ₁₂ O ₃₀ . Within this ring, there are atomic positions that can be occupied by M ¹ atoms. At this atomic position, M ¹ atoms may be present, and atomic vacancies may be formed by the lack of M ¹ atoms.

In the osmylite type crystal structure, x can take a wide range of values of 0 ≦ x ≦ 1. When x is 0, all atomic positions existing in the ring represented by (M ⁴ ) ₁₂ O ₃₀ are occupied by M ¹ atoms, and when x is 1, M ¹ existing at the atomic positions. Although the number of atoms is 0, in the phosphor according to the present invention, it is necessary that 0 ≦ x <1. In order to obtain a phosphor with high emission intensity, it is particularly preferable that x is in the range of 0 ≦ x ≦ 0.5.

In the phosphor according to the present invention, even if a indicating the amount of substitution of europium with respect to A increases to 1.0, the mechanism by which the decrease in emission luminance due to concentration quenching is suppressed is not clear, but the matrix is an osmillite type Due to the crystal structure, europium is strongly separated by the (M ² ) ₂ (M ³ ) ₃ (M ⁴ ) ₁₂ O ₃₀ network containing the (M ⁴ ) ₁₂ O ₃₀ ring, and the electron transfer between europium Is insulated and concentration quenching is considered to be suppressed.

(Emission center element)
The phosphor according to the present invention contains europium as an element serving as a light emission center, and can emit light in blue to green by activating the matrix. In addition to europium, the luminescent center elements include terbium, scandium, titanium, vanadium, chromium, iron, cobalt, nickel, copper, zinc, gallium, germanium, strontium, yttrium, zirconium, niobium, molybdenum, technetium, and ruthenium. Palladium, silver, cadmium, indium, tin, barium, lanthanum, praseodymium, neodymium, promethium, samarium, gadolinium, dysprodium, holmium, erbium, thulium, ytterbium, lutetium, hafnium, tantalum, lead, bismuth, and the like.

(Production method)
Next, a method for manufacturing the phosphor according to the present invention will be described.
As a method for producing the phosphor according to the present invention, a thermal melting method, a solid phase method, a wet method, a spray pyrolysis method, and other known methods can be applied, but other methods may also be used. Can be manufactured. Here, an example of the manufacturing method of the phosphor according to the present invention is shown.

First, each compound containing the elements constituting the general formulas (1) to (3) is weighed and mixed so as to have a predetermined composition ratio corresponding to the constituent elements of the final product. For example, when producing Sr _0.4 Eu _0.6 Mg ₂ Al ₆ Si ₉ O ₃₀ , each compound containing strontium, europium, magnesium, aluminum, and silicon is changed to Sr: Eu: Mg: Al: Si = 0.4. : Weigh and mix so that 0.6: 2.0: 6.0: 9.0.

When each compound containing the constituent elements is weighed and mixed, the mixture is preferably fired at 1000 to 1600 ° C. for 1 to 12 hours in a reducing atmosphere or an inert atmosphere. As a result, a sintered body of the target phosphor can be obtained. In this firing process, the firing temperature can be lowered by using a reaction accelerator such as AlF ₃ , MgF ₂ , LiF, and NaF within a range that does not interfere with the effects of the present invention.

  After obtaining the fired body of the target phosphor, the fired body is pulverized and classified as necessary. As a result, a desired phosphor having a predetermined particle diameter can be obtained.

  According to the above phosphor, a indicating the europium substitution amount can be selected in a wide range of 0 <a ≦ 1 without causing concentration quenching. That is, according to the phosphor according to the present invention, the emission wavelength can be changed in a wide range without lowering the emission luminance, and thus can be widely applied to fluorescent lamps, PDPs and the like.

  Hereinafter, the phosphor according to the present invention will be described in detail through the present embodiment with reference to the drawings. However, the scope of the invention is not limited to this embodiment.

(Preparation of samples 1 to 7)
First, strontium nitrate, europium nitrate, magnesium nitrate, aluminum nitrate and sodium silicate were weighed and mixed at a predetermined molar ratio. Thereafter, the mixture was fired at 1300 ° C. for 5 hours in an argon atmosphere containing 4% by volume of hydrogen to obtain a sintered body. Thereafter, the obtained sintered body was pulverized, and the obtained phosphors were used as Samples 1 to 7. Table 1 shows the molar ratio of the raw materials of each sample 1 to 7 and the chemical composition of each sample 1 to 7.

(Preparation of samples 8 and 9)
In the preparation of Samples 1 to 7, samples 8 and 9 were obtained in accordance with the same manufacturing method as Samples 1 to 7 except that strontium nitrate as a raw material was replaced with calcium nitrate and barium nitrate, respectively. . Table 1 shows the molar ratio of the raw materials of Samples 8 and 9 and the chemical composition of Samples 8 and 9.

(Production of samples 10 to 12)
In the preparation of the above samples 1 to 7, the molar ratio of the raw materials was changed as appropriate (changed so that the value of x in the general formula (2) in the above embodiment was 0; 0.1; 0.2). Samples 10 to 12 were obtained according to the same production method as that of Samples 1 to 7 except for those described above. Table 1 shows the molar ratio of the raw materials of each sample 10-12 and the chemical composition of each sample 10-12.
In Table 1, the compound composition of sample 10 is 0 in the general formula (2) in the above embodiment, and the compound composition of sample 11 is x in the general formula (2) in the above embodiment. The compound composition of Sample 12 has a value of 0.1, and the value of x in the general formula (2) in the above embodiment is 0.2.

(X-ray diffraction patterns of samples 1 to 12)
For each of the produced samples 1 to 12, a powder X-ray diffraction experiment using an X-ray diffractometer RAD manufactured by Rigaku Corporation was performed, and an X-ray diffraction pattern was recorded. An X-ray diffraction diffraction pattern of SrMg ₂ Al ₆ Si ₉ O ₃₀ having an osmillite-type crystal structure is shown in the upper part of FIG. 1 as a control. The diffraction diffraction pattern is shown in the lower part of FIG. X-ray diffraction patterns similar to those of Sample 3 were obtained from Samples 1, 2, 4 to 12 other than Sample 3. From the X-ray diffraction patterns of Samples 1 to 12, it was confirmed that Samples 1 to 12 had an osmillite crystal structure (hexagonal crystal).

(Fluorescence characteristics of samples 1-12)
About each of the produced samples 1-12, the fluorescence spectrum between 400-600 nm of emission wavelengths by the excitation light of wavelength 365nm was measured with the fluorescence photometer made from HITACHI. Table 1 shows the measurement results (measurement values) for the center position of the emission peak and the emission intensity of each sample 1-12. The emission intensity of each sample 1-12 in Table 1 is relative intensity when the emission intensity at the emission peak wavelength of 519 nm of the commercially available phosphor SrAl ₂ O ₄ ; Further, from the measurement results of samples 1 to 12, the fluorescence spectra of samples 1, 3, 5, and 7 are shown in FIG. 2, the fluorescence spectra of samples 8 and 9 are shown in FIG. 3, and the fluorescence spectra of samples 10 to 12 are shown. 4 shows.

From each measurement result of the samples 1 to 7, even in the compound represented by the general formula (3) in the above embodiment, even if the substitution amount of europium is selected in a wide range of 0 <a ≦ 1.0, the emission luminance is It was confirmed that the emission wavelength varied in a wide range according to the amount of substitution of europium without decreasing. From each measurement result of the samples 8 and 9, even in the compound represented by the general formula (3) in the above embodiment, even if the alkaline earth metal element constituting A is calcium or barium, the emission luminance does not decrease. I was able to confirm that. From the measurement results of Samples 10 to 12, if the value of x is in the range of 0 ≦ x ≦ 0.2 in the compound represented by the general formula (2) in the above embodiment, the emission luminance does not decrease. I was able to confirm that.

₂ shows an X-ray diffraction pattern (upper stage) of SrMg ₂ Al ₆ Si ₉ O _{30 and} an X-ray diffraction pattern (lower stage) of Sample 3 in Examples. It is a fluorescence spectrum of sample 1,3,5,7 in an Example. It is a fluorescence spectrum of samples 8 and 9 in an example. It is a fluorescence spectrum of samples 10-12 in an example.

Claims (2)

A phosphor having an osmylite type crystal structure and a chemical composition represented by the following general formula .
(A _1-a Eu _a ) _1-x Mg ₂ Al _6-2x Si _{9 + 2x} O ₃₀
(However, in the above general formula, A is at least one alkaline earth metal element selected from calcium, strontium and barium, respectively a and x 0 <a ≦ 1, 0 ≦ x ≦ 0. 2 ) The phosphor according to claim 1 ,
Furthermore, the phosphor containing at least 1 sort (s) of rare earth elements used as a coactivator with respect to Eu in the said general formula .

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