JP2018109084A - Green phosphor, light emitting element and light emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a γ-AlON green phosphor having improved brightness, a light emitting element including the phosphor, and a light emitting device including the light emitting element.SOLUTION: A green phosphor has a host crystal having the same crystal structure as a cubic spinel AlON crystal, and in the host crystal, element M (where element M is at least one element selected from Mn, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Tm, Yb) and element A (where element A is at least one metal element other than element M and Al) are dissolved in a solid state. When D90, D10 and D50 are defined as particle sizes corresponding to 90%, 10%, and 50% in integral values of particle size distribution of the phosphor, a span value represented by the formula (span value)=(D90-D10)/D50 is 1.450 or more and 2.200 or less.SELECTED DRAWING: None

Description

The present invention relates to a green phosphor, and a light emitting element and a light emitting device using the phosphor. More specifically, the present invention relates to a green phosphor that is excellent in luminance and can be preferably used for an LED (also referred to as a light emitting diode) or an LD (also referred to as a laser diode), and a light emitting element and a light emitting device using the phosphor.

A white LED is a device that emits pseudo white light by a combination of a semiconductor light-emitting element and a phosphor. As a typical example, a combination of a blue LED and a YAG yellow phosphor is known. However, although this type of white LED is in the white region as its chromaticity coordinate value, it lacks the green light emission component and the red light emission component, so it has a low color rendering property for lighting applications, and is similar to a liquid crystal backlight. Such an image display device has a problem that color reproducibility is poor. Therefore, in order to compensate for the lack of light emitting components, a light emitting device combining a blue LED, a green phosphor and a red phosphor has been proposed. As a typical example of a phosphor emitting green light, a β sialon phosphor in which silicon nitride silicon, a part of nitrogen is aluminum, and β sialon in which oxygen is substituted to form a solid solution and an element serving as a luminescent center is further dissolved is known. It has been.

As other phosphors emitting green light, Patent Documents 1 and 2 disclose that an inorganic crystal having the same crystal structure as a cubic spinel AlON crystal (also referred to as γ-AlON) is a base crystal, for example, Mn A phosphor in which a combination of elements such as Mg or a combination of elements such as Mn, Eu and Mg, or Mn and Si is further dissolved in the base crystal (hereinafter also referred to as a γ-AlON phosphor) is disclosed. In principle, γ-AlON phosphors have a narrow emission spectrum half-width, and the emission peak wavelength of green phosphors is on the shorter wavelength side than the emission peak wavelength of β sialon phosphors. A light emitting device with higher efficiency and wider color reproducibility can be obtained. Patent Documents 3 and 4 also propose a light emitting device that combines a γ-AlON phosphor, a red phosphor, and a light source.

However, although the γ-AlON phosphor is more advantageous than the β sialon phosphor in terms of emission wavelength, there is a large variation in emission luminance when used as a light emitting device, and there remains room for improvement in this respect. Therefore, reduction in luminance variation of the γ-AlON phosphor has been expected in the industry so that a light emitting element and a light emitting device with stable luminance can be provided.

International Publication No. 2007/099862 Pamphlet JP 2009-096854 A JP 2009-218422 A JP 2010-093132 A

An object of the present invention is to provide a γ-AlON green phosphor having higher luminance, a light emitting element including the phosphor, and a light emitting device using the light emitting element.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have obtained a phosphor obtained by further dissolving a plurality of elements in a base crystal having the same crystal structure as that of a cubic spinel AlON crystal. When the range that the span value of the particles should satisfy is defined, it has been found that a phosphor with a higher luminance of the phosphor can be obtained, and the present invention has been completed.

That is, the present invention
(1) To a base crystal having the same crystal structure as that of a cubic spinel AlON crystal, an element M (wherein the element M is Mn, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Tm, Yb) D90, D10 and D50 are green phosphors in which one or more selected elements) and element A (wherein element A is one or more metal elements other than element M and Al) are solid-dissolved, When the integrated value of the particle size distribution of the phosphor is 90%, 10%, and 50%, respectively, the span value represented by the formula of (span value) = (D90−D10) / D50 is 1 A green phosphor characterized by being in the range of 450 to 2.200.
(2) The green phosphor described in (1) has a composition formula of MaAbAlcOdNe (where M is the element M, A is the element A, Al is aluminum, O is oxygen, and N is nitrogen, which satisfies a + b + c + d + e = 1). It is preferable that the green phosphor is 0.00001 ≦ a ≦ 0.1.
(3) The green phosphor described in (1) or (2) has a composition formula of MaAbAlcOdNe (where M is the element M, A is the element A, Al is aluminum, O is oxygen, and N is nitrogen, a + b + c + d + e) = 1), and a green phosphor satisfying 0.001 ≦ b ≦ 0.40 is preferable.
(4) In the green phosphor according to any one of (1) to (3), the element M is preferably Mn.
(5) In the green phosphor according to any one of (1) to (4), the element A preferably contains at least Mg.
(6) Moreover, this invention is a light emitting element containing the green fluorescent substance as described in any one of said (1)-(5).
(7) Moreover, this invention is a light-emitting device using the light emitting element of said (6) description.

By implementing the present invention, it is possible to obtain a green phosphor with more stable brightness than before, and for example, a blue LED that can excite the phosphor of the present invention. For example, a light emitting element such as a white LED including a phosphor emitting color (for example, a red phosphor), or a light emitting device using these light emitting elements can be provided. Examples of the light emitting device include a lighting device, a backlight device, an image display device, and a signal device.

Hereinafter, embodiments for carrying out the present invention will be described in detail.

By implementing the present invention, a base crystal having the same crystal structure as that of the cubic spinel AlON crystal is converted into an element M (where the element M is Mn, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Tm, A green phosphor in which one or more elements selected from Yb) and element A (wherein element A is one or more metal elements other than element M and Al) is obtained as a solid solution is obtained. More specifically, the base crystal having the same crystal structure as the cubic spinel type AlON crystal in the present invention includes a cubic spinel type AlON crystal, an AlON solid solution crystal, the AlON crystal, and the AlON solid solution crystal. It is a general term for crystals having the same crystal structure as the cubic spinel AlON crystal. The cubic spinel AlON crystal is more generally called γ-AlON. The AlON solid solution crystal is a crystal having the same crystal structure as that of the AlON but having an oxygen / nitrogen ratio different from that of the AlON or having other elements such as silicon and Mn added thereto. Furthermore, the crystal having the same crystal structure as the cubic spinel type AlON crystal is a crystal having the same crystal structure as that of the AlON, except that some or all of Al, O, and N are replaced with other elements. Among these, γ-AlON is the most typical crystal.

In this specification, for convenience, it is described that the main crystal structure of the phosphor is represented by, for example, γ-AlON. However, even if the raw materials are blended so as to obtain a phosphor having such a composition, impurities in the raw materials and firing The composition of the phosphor may fluctuate due to the influence of the atmosphere at the time. The composition of the green phosphor of the present invention is an expression including such a variation.

Whether or not the base crystal of the green phosphor of the present invention has the same crystal structure as γ-AlON can be confirmed by powder X-ray diffraction measurement. When the host crystal of the phosphor of the present invention does not have the same crystal structure as that of γ-AlON, the emission color is not green, and the fluorescence intensity is greatly reduced, which is not preferable. In the green phosphor of the present invention, the base crystal having the same crystal structure as that of γ-AlON is preferably a single-phase crystal, but contains a heterophasic crystal as long as the phosphor characteristics are not greatly affected. It doesn't matter. Presence / absence of heterogeneous crystals can also be determined by the presence / absence of peaks other than those due to the target crystal phase by powder X-ray diffraction measurement. In addition, elements in which the lattice constant is changed by partially replacing the constituent elements of γ-AlON with other elements are also included in the present invention.

The green phosphor of the present invention is obtained by adding Mn, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Tm to a base crystal having the same crystal structure as a cubic spinel AlON (ie, γ-AlON) crystal. , Yb is a phosphor in which one or more elements M selected from Yb are dissolved. The element M is an element that becomes the emission center of the phosphor, and Mn is particularly preferable in the green phosphor of the present invention.

The green phosphor of the present invention is a phosphor in which the element A is further dissolved in addition to the element M. The element A is one or more metal elements other than the elements M and Al, and preferably contains Mg.

In the green phosphor of the present invention, when D90, D10, and D50 are set to particle sizes corresponding to the integral values of the particle size distribution of the phosphor of 90%, 10%, and 50%, respectively, (span value) = (D90 -D10) A phosphor having a span value represented by a formula of D50) in a range of 1.450 to 2.200. If the span value is less than 1.450 or exceeds 2.200, the luminous efficiency of the phosphor tends to be low and the luminance tends to decrease.

The composition of the green phosphor of the present invention is expressed by MaAbAlcOdNe (where M is element M, A is element A, Al is aluminum, O is oxygen, N is nitrogen, and a + b + c + d + e = 1 is satisfied). It is preferable that 0.00001 ≦ a ≦ 0.1. If a is smaller than 0.00001, the luminance decreases because the number of elements M that are the emission centers is small. On the other hand, when a is larger than 0.1, the luminance is lowered by an interference phenomenon between elements M called concentration quenching.

The green phosphor of the present invention preferably satisfies 0.001 ≦ b ≦ 0.40 in the composition formula of the present invention. If b is out of this range, the host crystal of the phosphor becomes chemically unstable, and the ratio of the crystal phase other than the crystal phase represented by γ-AlON (that is, a different phase) increases, so that the luminance decreases.

The production method of the green phosphor of the present invention can be the same production method as the conventional production method of γ-AlON phosphor. Here, as a method for obtaining a crystal in which the element M and the element A are dissolved in the γ-AlON crystal according to one embodiment of the present invention, a powder in which raw materials that can constitute the crystal are mixed in a nitrogen atmosphere. Although the method of baking in a predetermined temperature range is illustrated, it does not specifically limit to this method.

The above-mentioned manufacturing method prepares a simple substance and / or a compound containing element M, element A, aluminum, oxygen, and nitrogen as a raw material of the green phosphor of the present invention, and a compound that can obtain a target phosphor In the manufacturing method including the preparation step of mixing the raw materials and the baking step of baking the raw material to obtain the green phosphor of the present invention. The simple substance or compound containing the element M is a metal containing the element M, an oxide, carbonate, nitride, fluoride, chloride, oxynitride of the element M, or a combination thereof. The simple substance or compound containing the element A is a metal containing the element A, an oxide of the element A, carbonate, nitride, fluoride, chloride, oxynitride, or a combination thereof. Further, the simple substance or compound containing aluminum is aluminum, an aluminum alloy, aluminum oxide, aluminum nitride, or a combination thereof. Oxygen and nitrogen, which are raw materials for the green phosphor of the present invention, can be supplied from the oxides and nitrides, and the atmospheric gas (nitrogen gas) in the furnace for sintering. Each of these raw materials is preferably in the form of a powder if it is solid, and is preferably mixed in advance before firing.

The raw material uniformly mixed in advance (hereinafter referred to as raw material mixed powder) is filled in a firing container and fired. The firing container is preferably made of a material that is sufficiently chemically and physically (mechanically) stable at least in a nitrogen atmosphere at the firing temperature and is difficult to react with the raw material mixed powder and its reaction product. Made of carbon and carbon.

The firing container filled with the raw material mixed powder is set in a firing furnace, and preferably fired in a nitrogen atmosphere of 1500 ° C. or higher and 2200 ° C. or lower. When the firing temperature is lower than 1500 ° C., the amount of unreacted residue increases, and when the firing temperature is higher than 2200 ° C., the host crystal of the target phosphor is decomposed, which is not preferable.

The firing time is selected within a time range in which a large amount of unreacted raw material remains, the phosphor particles do not grow sufficiently, or the practical productivity is not lowered. In a preferred embodiment of the present invention, the firing time may be 1 hour or more and 24 hours or less.

The pressure of the firing atmosphere is selected according to the firing temperature. The higher the atmospheric pressure, the higher the decomposition start temperature of the base crystal of the green phosphor of the present invention, but it is preferably less than 1 MPa in view of industrial productivity.

The state of the fired product obtained by firing the raw material mixed powder varies depending on the blending ratio of the raw material mixed powder and the firing conditions, such as powder, lump, and sintered body. When used as a phosphor, the fired product can have a predetermined particle size by combining crushing, pulverization and / or classification operations.

In the production of the green phosphor of the present invention, an acid treatment step for removing impurities in the phosphor and an annealing treatment step for improving the crystallinity of the phosphor are further provided. You may do it.

The green phosphor of the present invention can be used for a light emitting device including a light emitting source and the phosphor of the present invention. In particular, when an LED that emits ultraviolet light or visible light having a wavelength of 350 nm or more and 500 nm or less is used as a light source, and the phosphor of the present invention is irradiated, green light having a fluorescence peak at a wavelength of 510 nm to 550 nm is emitted. For this reason, for example, by using an ultraviolet LED or a blue LED as a light-emitting light source and forming a light-emitting element including a combination of the green phosphor of the present invention and a red phosphor, a white light-emitting element can be easily obtained. Can do.

Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples. However, the present invention is not limited to the description of these examples.

Example 1
As raw materials for the phosphor of Example 1, aluminum oxide powder (Al ₂ O ₃ , TM-DAR grade, manufactured by Daimei Chemical Co., Ltd.), aluminum nitride powder (AlN, E grade, manufactured by Tokuyama Co., Ltd.), magnesium oxide powder (MgO, manufactured by Wako Pure Chemical Industries, Ltd.), manganese oxide powder (MnO, manufactured by High Purity Chemical Laboratory), Mn: Mg: Al: O: N = 0.0179: 0.0625: 0.3482: 0 5089: 0.0625 dry mix for a molar ratio of 0.0625. The mixed raw materials were classified with a nylon sieve having a mesh size of 250 μm to obtain a uniform mixed powder. 13 g of the classified raw material mixed powder was filled in a cylindrical boron nitride container (N-1 grade, manufactured by Denka) with a lid.

The boron nitride container filled with the raw material mixed powder was quickly set in an electric furnace of a carbon heater, and the inside of the furnace was sufficiently evacuated to 0.1 Pa or less. While evacuating, heating was started at a heating rate of 300 ° C. per hour, and after reaching 1000 ° C., nitrogen gas was introduced into the furnace, and the atmospheric pressure in the furnace was set to 0.8 MPa. When the internal volume of the furnace was 1, the volume of nitrogen gas flowing into the furnace per minute was introduced at a ratio of 0.02, and the nitrogen gas was exhausted in parallel so that the pressure was constant. . Even after the start of the introduction of nitrogen gas, heating was continued at a heating rate of 300 ° C. per hour, the temperature was raised to 1900 ° C., and the raw material mixture was baked for 4 hours while maintaining the temperature of 1900 ° C.

After cooling for a predetermined time, a green lump was recovered from the inside of the boron nitride vessel recovered from the furnace. The lump was further crushed with a ball mill, and further crushed with a mortar and classified by a sieve. The phosphor of Example 1 was obtained.

The phosphors of Examples 2-3 and Comparative Examples 1-2 were produced under the same conditions as in Example 1 except that the conditions for classification operation with mortar grinding and sieving were changed.

(Confirmation of crystal structure)
Powder X-ray diffraction using CuKα rays was performed on the phosphor samples of Examples 1 to 3 and Comparative Examples 1 and 2 using an X-ray diffractometer (Ultima IV, manufactured by Rigaku Corporation). As for the obtained X-ray diffraction pattern, the same diffraction pattern as the AlON crystal was recognized in all samples, and it was confirmed that the main crystal phase had the same crystal structure as the AlON crystal.

(Span value measurement)
The particle size distributions of the phosphor samples of Examples 1 to 3 and Comparative Examples 1 and 2 were measured by a laser diffraction / scattering method using a particle size distribution measuring apparatus (Microtrack MT3000II, manufactured by Microtrack Bell). These span values are listed in Table 1.

(Measurement of fluorescence spectrum)
Fluorescence spectra were measured for the phosphor samples of Examples 1 to 3 and Comparative Examples 1 and 2 using a spectrofluorometer (F-7000, manufactured by Hitachi High-Technologies Corporation) corrected with rhodamine B and a substandard light source. did. For the measurement, a solid sample holder attached to the photometer was used, and a fluorescence spectrum at an excitation wavelength of 445 nm was obtained. As a result, the peak wavelength of the fluorescence spectrum was 520 nm for all samples.

(Evaluation of brightness)
The luminances of the green phosphors of Examples 1 to 3 and Comparative Examples 1 and 2 were calculated from the product of the fluorescence peak intensity at the peak wavelength of each fluorescence spectrum and the CIE standard relative luminous sensitivity. The results are shown in Table 1. The luminance is shown as a relative value when Example 1 is set to 100%. If the luminance is 95% or more, it is determined that the green phosphor exhibits excellent luminance.

From the results shown in Table 1, by implementing the present invention, it is possible to provide a γ-AlON green phosphor with higher luminance, a light emitting element including the phosphor, and a light emitting device using the light emitting element. It was shown that there is.

Claims (7)

A base crystal having the same crystal structure as that of a cubic spinel AlON crystal is converted into an element M (wherein the element M is selected from Mn, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Tm, and Yb). A green phosphor in which element A or more element) and element A (where element A is one or more metal elements other than element M and Al) are solid-solved, and D90, D10 and D50 are the phosphors. When the integrated value of the particle size distribution of the particles is 90%, 10%, and 50%, the span value represented by the formula of (span value) = (D90−D10) / D50 is 1.450 or more. 2. A green phosphor having a range of 200 or less. The composition formula is represented by MaAbAlcOdNe (where M is element M, A is element A, Al is aluminum, O is oxygen, N is nitrogen, and satisfies a + b + c + d + e = 1), and 0.00001 ≦ a ≦ 0.1 The green phosphor according to claim 1, wherein The composition formula is represented by MaAbAlcOdNe (where M is element M, A is element A, Al is aluminum, O is oxygen, N is nitrogen, and a + b + c + d + e = 1 is satisfied), 0.001 ≦ b ≦ 0.40 The green phosphor according to claim 1 or 2, wherein The green phosphor according to any one of claims 1 to 3, wherein the element M is Mn. The green phosphor according to any one of claims 1 to 4, wherein the element A contains at least Mg. The light emitting element containing the fluorescent substance as described in any one of Claims 1-5. A light-emitting device using the light-emitting element according to claim 6.