JP2013139525A - Ultraviolet phosphor, and methods for manufacturing light source and ultraviolet phosphor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultraviolet phosphor having both a high light emission intensity and chemical stability.SOLUTION: The ultraviolet phosphor has a perovskite structure in which a luminescent center is Gd; a sensitizing ion is Pr: and a base body is YLnAlO, wherein Ln is one or two elements selected from La and Lu. The ultraviolet phosphor is preferably represented by a composition formula (YLn)GdPrAlO, wherein x is 0.005 to 0.20, y is 0.00 to 0.20, and z is 0.0 to 0.30.

Description

  The present invention relates to an ultraviolet phosphor, a light source using the same, and a method for producing the ultraviolet phosphor.

Several ultraviolet rays are used to excite phosphors for fluorescent lamps and plasma displays, and the ultraviolet rays (UV) are classified by wavelength. UV-A has a wavelength range of 315 to 380 nm, UV-B has a wavelength range of 280 to 315 nm, UV-C has a wavelength range of 200 to 280 nm, and vacuum ultraviolet light (VUV) has a wavelength range of less than 200 nm.

In fluorescent lamps, 254 nm UV-C emitted from mercury atoms is excitation light, and even in black light emitting UV-A, UV-C emitted from the same mercury atoms is excitation light. . Furthermore, UV-C emitted from mercury atoms is directly used in germicidal lamps. Considering the environment and reducing the use of mercury in the future, it is possible that not only the visible light source of fluorescent lamps but also the ultraviolet light source cannot be used.

On the other hand, VUV emitted from Xe atoms / molecules is used in plasma displays, and Xe excimer lamps that directly emit VUV are also commercially available. Although it is expected to be an ultraviolet light source that does not use mercury, it is generally difficult to handle such as the wavelength is too short to excite many existing phosphors and VUV is absorbed in the atmosphere. There is.

In view of such a background, attention is paid to Gd ³⁺ ions that emit UV-B near 310 nm, and development of an ultraviolet light source using a phosphor to which Gd ³⁺ is added is underway. A method of converting from VUV to UV-B in combination with an Xe excimer lamp, a method of obtaining UV-B directly by being incorporated in an EL device, and the like have been reported. (See Prior Art Document 1, Non-Patent Documents 1 and 2) In particular, since the latter is a thin film device, there is a merit that a thin and light source can be obtained. However, an existing reported phosphor is a fluoride. There are problems with chemical weakness. Further, there is a problem that it is difficult to obtain a high-quality thin film because the crystal structure of the phosphor is not related to the crystal structure of the substrate. Therefore, it is expected to develop a phosphor that exhibits strong emission intensity, is easy to be made into a device, and is chemically stable.

Japanese Patent Application No. 2009-504863

H. Yoshida et al. , Journal of Luminescence, 2007, Vol. 122-123, 488-491 N. Miura et al. , Japan Journal of Applied Physics, 1991, Vol. 30 L1815-L1816

The problem to be solved is that the phosphor added with the conventional Gd ³⁺ does not have high emission intensity and chemical stability sufficiently, and it is difficult to obtain a high-quality phosphor thin film in combination with the substrate. Is a point.

Ultraviolet phosphor according to the present invention is a light emitting center ^{Gd 3+,} a sensitizing ions ^{Pr 3+,} a perovskite structure matrix consists of _{Y 1-z Ln z AlO 3} , Ln is the La and Lu It is characterized by being one or two elements selected from among them.

The ultraviolet phosphor according to the present invention are preferably represented by the composition formula _{(Y 1-z Ln z)} 1-x-y Gd x Pr y AlO 3, x is .00-.20, y Is 0.00 to 0.20, and z is 0.0 to 0.30.

  Moreover, the light source which concerns on this invention is equipped with the fluorescent layer containing said ultraviolet fluorescent substance, It is characterized by the above-mentioned.

    Further, the method for producing an ultraviolet phosphor according to the present invention is a method for producing the aforementioned ultraviolet phosphor by a solid phase reaction,

Y ₂ O ₃ , Ln oxide, Al oxide, Gd ₂ O ₃ , Pr oxide, Y: Ln: Gd: Pr: Al = 0.30 to 1.00: 0.00 to 0.30: 0 Compounding so as to have a molar ratio of 0.00 to 0.20: 0.00 to 0.20: 1 to obtain a mixed powder;
And baking the mixed powder at a temperature of 1000 to 1600 ° C. for 1 to 10 hours at least once in an air atmosphere.

In the method for producing an ultraviolet phosphor according to the present invention, preferably, the Al oxide is γ-Al ₂ O ₃ , the Pr oxide is Pr ₆ O ₁₁ or Pr ₂ O ₃ , and the Ln oxide is It is characterized by being La ₂ O ₃ or Lu ₂ O ₃ .

Ultraviolet oxide phosphor according to the present invention is a light emitting center ^{Gd 3+,} sensitizing ions are ^{Pr 3+,} a perovskite structure matrix consists of _{Y 1-z Ln z AlO 3} , Ln is La and 1 or 2 elements selected from Lu.
For this reason, since the ultraviolet phosphor exhibits high emission intensity and is an oxide, it has chemical stability and can produce a high-quality thin film on a perovskite single crystal substrate. The ultraviolet phosphor is in the vicinity of a fluorescence wavelength of 310 nm and is preferable as a phosphor for an ultraviolet light source.
Moreover, since the light source which concerns on this invention is equipped with the fluorescent layer containing said ultraviolet fluorescent substance, the effect of an ultraviolet fluorescent substance can be acquired suitably. In particular, since it is easy to obtain a high-quality thin film, it is suitable for application to a light-emitting device using the above-mentioned ultraviolet phosphor. Also, the method for producing an ultraviolet phosphor according to the present invention uses the above-described ultraviolet phosphor as a solid phase. A process for producing by reaction,
Y ₂ O ₃ , Ln oxide, Al oxide, Gd ₂ O ₃ , Pr oxide, Y: Ln: Gd: Pr: Al = 0.30 to 1.00: 0.00 to 0.30: 0 Compounding so as to have a molar ratio of 0.00 to 0.20: 0.00 to 0.20: 1 to obtain a mixed powder;
Since the mixed powder includes a step of baking at least 1 to 10 hours at a temperature of 1000 to 1600 ° C. in an air atmosphere, the above-described ultraviolet phosphor can be suitably obtained.

FIG. 1 is a diagram showing an X-ray diffraction pattern of a phosphor with x = 0.10 and y = 0.03 among the phosphors of Example 1. FIG. 2 is a diagram showing an emission spectrum of the phosphor of Example 1. FIG. FIG. 3 is a graph showing the Pr concentration dependence of the fluorescence intensity of the phosphor of Example 1. FIG. 3 is a graph showing the Gd concentration dependency of the fluorescence intensity of the phosphor of Example 2. FIG. 5 is a graph showing a comparison of fluorescence intensities between the phosphors of Examples 1 and 2 and commercially available phosphors (LaPO ₄ : Tb ³⁺ , Ce ³⁺ ). 6 is a graph showing the Ln concentration dependency of the fluorescence intensity of the phosphor of Example 3. FIG. FIG. 7 is a graph showing the Ln concentration dependence of the lattice constant of the phosphor of Example 3. FIG. 8 is a diagram showing the crystal structure of the matrix of the deep red phosphor according to the present embodiment.

    Embodiments of the present invention will be described below.

Ultraviolet oxide phosphor according to the present invention is a light emitting center ^{Gd 3+,} sensitizing ions are ^{Pr 3+,} a perovskite structure matrix consists of _{Y 1-z Ln z AlO 3} , Ln is La and 1 or 2 elements selected from Lu.
In the perovskite structure described above, it is well known to those skilled in the art that the number of Os represented by ABO ₃ actually varies slightly from 3, and the present invention includes this range of fluctuation.
The ultraviolet phosphor is preferably represented by the composition formula _{(Y 1-z Ln z)} 1-x-y Gd x Pr y AlO 3, x is 0.005 to 0.20, y is 0.00 -0.20, z is 0.0-0.30, It is characterized by the above-mentioned.

Here, the purpose of including Pr ³⁺ in the matrix is to increase Gd ³⁺ emission intensity. The phenomenon in which the energy absorbed in the Pr ³⁺ 4d orbitals is effectively transferred to Gd ³⁺ is known in some phosphors, and also in the ultraviolet phosphor according to the present invention, the combination of these additives and the matrix Then, the phenomenon works effectively and increases the Gd ³⁺ emission intensity.

On the other hand, the purpose of including La ³⁺ and Lu ³⁺ in the matrix is to change the lattice constant of the perovskite structure of the matrix in a state where no significant change is made in the Gd ³⁺ emission intensity. La ³⁺ and Lu ³⁺ have no energy level involved in light emission, and do not have a factor that directly inhibits light emission of Gd ³⁺ . On the other hand, the ionic radii (9-coordinates) of La ³⁺ and Lu ³⁺ are 1.216 and 1.032 そ れ ぞ れ, respectively, and La ³⁺ is larger and Lu ³⁺ is smaller than the ionic radius 1.075 Ｙ of Y ³⁺ . Thereby, La ³⁺ and Lu ³⁺ can be replaced with Y of the parent YAlO ₃ to increase or decrease the lattice constant of the parent. It becomes possible to produce a high-quality thin film and device by making the lattice constant correspond to a commercially available single crystal substrate, such as SrTiO ₃ or LaAlO ₃ .

FIG. 8 shows the crystal structure of the matrix of the ultraviolet phosphor according to the present embodiment.
The base oxide YAlO ₃ of the present invention has a slightly distorted crystal structure as compared with a general cubic perovskite structure ABO _3, and has four times the number of atoms in the unit cell of FIG. In the matrix, the A site of the perovskite structure is occupied by Y having a large ionic radius (1.075 Å), and the B site is occupied by Al having a small ionic radius (0.535 Å).
The additive has an ionic radius (9-coordinate) of Gd ³⁺ of 1.107 mm, which is sufficiently larger than Al ³⁺ and close to the ionic radius of Y ³⁺ , so that it replaces the A site and becomes the emission center. For the same reason, Pr ³⁺ having an ionic radius of 1.179Å replaces the A site and becomes a sensitized ion of Gd ³⁺ emission. As described above, La ³⁺ and Lu ³⁺ also replace the A site to enable control of the matrix lattice constant.

Gd ³⁺ emits ultraviolet light having a wavelength of about 310 nm due to the 4f-4f transition. ^{Pr 3+} sensitizing ions, than the 4f orbit (start state) relating to the emission of ^{Gd 3+} has a 5d orbital to a higher energy side, causing strong optical absorption than the trajectory of the ^{Gd 3+} in its orbit. The absorbed light energy is efficiently transferred to Gd ³⁺ in the phosphor matrix of the present invention, and promotes ultraviolet emission of Gd ³⁺ . On the other hand, in La ³⁺ and Lu ³⁺ , the 4f orbits are completely open or closed, and their 5d orbits are on the higher energy side than the 4f orbits (starting state) of Gd ³⁺ as in Pr ^3+. , Not involved in luminescence.
Therefore, in the present embodiment, Pr ³⁺ is used as a sensitizer, and La ³⁺ or Lu ³⁺ is used for the purpose of controlling the lattice constant for device formation.

The method for producing an ultraviolet phosphor according to the present embodiment is a method for producing an ultraviolet phosphor by a solid phase reaction, and includes Y ₂ O ₃ , Ln oxide, Al oxide, Gd ₂ O ₃ , and Pr oxide. Y: Ln: Gd: Pr: Al = 0.30 to 1.00: 0.00 to 0.30: 0.00 to 0.20: 0.00 to 0.20: 1 So that the mixed powder is obtained, and the mixed powder is calcined at a temperature of 1000 to 1600 ° C. once or more for 1 to 10 hours in an air atmosphere.
It is a preferred embodiment to use γ-Al ₂ O ₃ as the Al oxide, Pr ₆ O ₁₁ or Pr ₂ O ₃ as the Pr oxide, and La ₂ O ₃ or Lu ₂ O ₃ as the Ln oxide. .

These raw materials are weighed so as to have a predetermined molar ratio, and using an agate mortar, for example, 500 parts by mass of ethanol is added to 100 parts by mass of the raw material and wet-mixed. The mixed powder obtained after drying is fired at least once under the above conditions. If the impurity phase remains and a single phase cannot be obtained by one firing, it is preferable to repeat the process of pulverization, mixing and firing again to reduce the impurity phase as much as possible.

The ultraviolet phosphor according to the present embodiment is excellent in chemical stability because it does not contain fluorine, and has high emission intensity at a wavelength of 310 nm by excitation with ultraviolet rays of 150 to 250 nm.
Next, the light source according to the present embodiment includes a fluorescent layer including the ultraviolet phosphor according to the present embodiment. The fluorescent layer containing the ultraviolet phosphor can be a thin film on a single crystal or, for example, a silicon resin sheet containing the ultraviolet phosphor.
Thus, it can be directly applied to a UV-B light source in combination with an excimer lamp. Further, it can be applied to a surface emitting light source that directly emits UV-B by voltage application.
In addition, these UV-B light sources are used in light and thin air purifiers by combining with a photocatalyst. It can also be applied to the treatment of skin diseases by irradiating the skin. Furthermore, it can be used as an illumination or display element by combining with a highly efficient visible phosphor.

An inorganic oxide phosphor represented formula _{(Y 1-z Ln z)} experiments _{1-x-y Gd x Pr} y AlO 3 of the present invention was performed. In addition, this invention is not limited to the Example demonstrated below.

Example 1
Experiment of Example 1 of the formula (Y _0.90-y Gd _0.10 Pr _y ) AlO ₃ representing the inorganic oxide phosphor of the present invention was conducted. In Example 1, the Ln concentration z is fixed to 0.00 and the Gd concentration x is fixed to 0.10, and the Pr concentration changes as y = 0.01, 0.03, 0.05, 0.07, and 0.10. I let you. Y ₂ O ₃ and γ-Al ₂ O ₃ were used as base materials, and Gd ₂ O ₃ and Pr ₆ O ₁₁ were used as materials for the substances to be added. A predetermined amount of each raw material was weighed, wet-mixed using an agate mortar, and fired twice at 1400 ° C. for 6 hours. The atmosphere of the electric furnace during firing was air.
FIG. 1 shows an X-ray diffraction pattern of a sample of the inorganic oxide phosphor obtained in Example 1. In Example 1, the simulation pattern calculated from the crystal structure was almost the same regardless of the Pr concentration. The impurity slightly as the hetero-phase _Y 3 _Al 5 _{O 12} and _Y 4 _Al 2 _{O 9} appeared. These heterogeneous phases have little influence on the fluorescence intensity.
FIG. 2 is an emission spectrum obtained by measuring the inorganic oxide phosphor of Example 1 with an excitation wavelength of 215 nm using a fluorometer. The inorganic oxide phosphor of Example 1 showed the maximum fluorescence intensity at an excitation wavelength of about 215 nm. A sharp peak appeared in the emission spectrum, and its wavelength was about 314 nm. This is emission of ultraviolet light, and when the Pr concentration is changed, the spectral shape does not change significantly, but the spectral intensity changes greatly.
FIG. 3 shows the Pr concentration dependence of the emission relative intensity of the inorganic oxide phosphor of Example 1. The optimum Pr concentration of the inorganic oxide phosphor of Example 1 was y = 0.03.

(Example 2)
Experiment of Example 2 of the formula (Y _0.97-x Gd _x Pr _0.03 ) AlO ₃ representing the inorganic oxide phosphor of the present invention was conducted. In Example 2, the Ln concentration z is fixed to 0.00 and the Pr concentration y is fixed to 0.03, and the Gd concentrations are x = 0.005, 0.01, 0.03, 0.05, 0.07, 0. .10 and changed. Y ₂ O ₃ and γ-Al ₂ O ₃ were used as base materials, and Gd ₂ O ₃ and Pr ₆ O ₁₁ were used as materials for the substances to be added. A predetermined amount of each raw material was weighed, wet-mixed using an agate mortar, and fired twice at 1400 ° C. for 6 hours. The atmosphere of the electric furnace during firing was air.
The X-ray diffraction pattern of the inorganic oxide phosphor sample obtained in Example 2 was almost the same as the pattern calculated from the crystal structure regardless of the Gd concentration. The impurity slightly as the hetero-phase _Y 3 _Al 5 _{O 12} and _Y 4 _Al 2 _{O 9} appeared. These heterogeneous phases have little influence on the fluorescence intensity.
The inorganic oxide phosphor of Example 2 showed the maximum fluorescence intensity at an excitation wavelength of about 215 nm, and the emission spectrum was measured with a fluorometer at an excitation wavelength of 215 nm. The inorganic oxide phosphor of Example 2 showed a sharp peak as in Example 1, and its wavelength was about 314 nm. It was an ultraviolet light emission, and even if the Gd concentration changed, the spectral shape did not change significantly.
FIG. 4 shows the Gd concentration dependence of the emission relative intensity of the inorganic oxide phosphor of Example 2. The optimum Gd concentration of the inorganic oxide phosphor of Example 2 was x = 0.07.
FIG. 5 is an emission spectrum of the inorganic oxide phosphor having the optimum composition obtained in Example 2. The emission wavelength of the phosphor is 314 nm and the optimum excitation wavelength is 215 nm. The relative emission intensity at the optimum excitation wavelength compared to the commercially available phosphor LaPO4: Tb, Ce is 1.3 times the peak top as shown in FIG. It became.

(Examples 3 and 4)
Example 3 and of the formula _{(Y 1-z La z)} 0.90 Gd 0.07 Pr 0.03 AlO 3 representing an inorganic oxide phosphor of the present invention _{(Y 1-z Lu z)} 0.90 Gd The experiment of Example 4 of _0.07 Pr _0.03 AlO ₃ was performed.
In Examples 3 and 4, the Gd concentration x is fixed to 0.07 and the Pr concentration y is fixed to 0.03, and the La or Lu concentration is z = 0.00, 0.05, 0.10, 0.20, 0 .30, 0.40, 0.50. Y ₂ O ₃ and La ₂ O ₃ or Lu ₂ O ₃ and γ-Al ₂ O ₃ were used as base materials, and Gd ₂ O ₃ and Pr ₆ O ₁₁ were used as raw materials for the substance to be added. Further, after weighing a predetermined amount of each of the raw materials, wet mixing was performed using an agate mortar, and the mixture was fired twice at 1400 ° C. for 6 hours. The atmosphere of the electric furnace during firing was air.
The X-ray diffraction patterns of the inorganic oxide phosphor samples obtained in Examples 3 and 4 were almost the same as the patterns calculated from the crystal structure when the concentrations of La and Lu were low. The impurity slightly as the hetero-phase _Y 3 _Al 5 _{O 12} and _Y 4 _Al 2 _{O 9} appeared. These heterogeneous phases have little influence on the fluorescence intensity. When the concentration of La or Lu was high, the diffraction peak of the impurity phase increased and the abundance of the impurity phase increased.
The inorganic oxide phosphors of Examples 3 and 4 showed the maximum fluorescence intensity at an excitation wavelength of about 215 nm, and the emission spectrum was measured with a fluorometer at an excitation wavelength of 215 nm. The inorganic oxide phosphor of Example 2 showed a sharp peak as in Example 1, and its wavelength was about 314 nm. It was an ultraviolet light emission, and even if the Gd concentration changed, the spectral shape did not change significantly.
FIG. 6 shows the La or Lu concentration dependence of the emission relative intensity of the inorganic oxide phosphors of Examples 3 and 4. In the low concentration region, the emission intensity does not change so much and only slightly decreases. However, in the high concentration region where z = 0.30 or more, the impurity phase increases, and thus the emission intensity significantly decreases.
FIG. 7 shows the La or Lu concentration dependence of the lattice constant of the inorganic oxide phosphors of Examples 3 and 4. Although the crystal structure of the phosphor is orthorhombic, it is shown in terms of a lattice constant _ap of a cubic perovskite structure for easy comparison. By adding La, the lattice constant increased to about 3.72 、, and by adding Lu, it decreased to about 3.705 格子.

Claims (5)

The emission center is Gd ³⁺ , the sensitizing ion is Pr ³⁺ , and the matrix is a perovskite structure consisting of Y _1-z Ln _z AlO ₃ , where Ln is one or two elements selected from La and Lu Is an ultraviolet phosphor. Is represented by a composition formula _{(Y 1-z Ln z)} 1-x-y Gd x Pr y AlO 3, x is 0.005 to 0.20, y is 0.00-.20, z is 0.0 The ultraviolet phosphor according to claim 1, which is ˜0.30.     A light source comprising a fluorescent layer containing the ultraviolet phosphor according to claim 1. A method for producing the ultraviolet phosphor according to any one of claims 1 to 3 by a solid phase reaction,
Y ₂ O ₃ , Ln oxide, Al oxide, Gd ₂ O ₃ , Pr oxide, Y: Ln: Gd: Pr: Al = 0.30 to 1.00: 0.00 to 0.30: 0 Compounding so as to have a molar ratio of 0.00 to 0.20: 0.00 to 0.20: 1 to obtain a mixed powder;
Firing the mixed powder at a temperature of 1000 to 1600 ° C. in an air atmosphere at least once for 1 to 10 hours;
A method for producing an ultraviolet phosphor, comprising: The Al oxide is γ-Al ₂ O ₃ , the Pr oxide is Pr ₆ O ₁₁ or Pr ₂ O ₃ , and the Ln oxide is La ₂ O ₃ or Lu ₂ O _3. Item 5. A method for producing an ultraviolet phosphor according to Item 4.