TW201510177A - Phosphor and illuminating device - Google Patents

Abstract

The present invention relates to a (Sr, Ca)AlSiN3 nitride phosphor which can realize high-luminance red light emission, and a light-emitting device which is excellent in color rendering properties and luminous efficiency by using the phosphor. The fluorescent system of the present invention is represented by the general formula: M1aM2bM3cM4dNeOf, M1 is one or more elements selected from the group consisting of Eu and Ce, and the M2 system Ca and Sr are essential and selected from the group consisting of Mg, Ca, Sr, Ba, and Zn. For the above-mentioned elements, M3 is one or more elements selected from the group consisting of Al, Ga, In, and Sc, and the M4-based Si is an element selected from one or more of Si, Ge, Sn, Ti, Zr, and Hf. N is nitrogen, O is oxygen, a~f is 0.00001≦a≦0.15, a+b=1, 0.5≦c≦1.5, 0.5≦d≦1.5, c+d=2, 2.5≦e≦3.0,0≦ f ≦ 0.5, and the half value width of the luminescence spectrum when excited by light of a wavelength of 455 nm is 72 nm or more and 86 nm or less.

Description

Phosphor and illuminating device

The present invention relates to a phosphor for an LED (Light Emitting Diode) or an LD (Laser Diode), and a light-emitting device using the same. More specifically, it relates to a (Sr, Ca)AlSiN ₃ -based nitride phosphor which can realize high-luminance red light, and a light-emitting device which is excellent in color rendering properties and luminous efficiency by using the phosphor.

In the case of white LEDs for illumination, a combination of a blue LED chip and a yellow phosphor to obtain approximate white light is widely spread. However, in the white LED of this mode, although the chromaticity coordinate value enters the white region, the object illuminated by the white LED is visually different from the object illuminated by the natural light because the luminescent component such as the red region is small. That is, the white LED does not perform well in the color rendering of the indicator of the visual naturalness of the object.

Therefore, by combining a red phosphor or an orange phosphor in addition to the yellow fluorescent light to compensate for the insufficient red component, the white LED having improved color rendering properties has been put into practical use. For example, Patent Document 1 discloses a light-emitting device comprising a yellow-emitting YAG phosphor and a red-emitting nitride and an oxynitride phosphor in order to compensate for a red component of a white LED.

However, when the color rendering property is to be improved, there is a tendency that the luminous efficiency is lowered. Therefore, in order to achieve a balance between color rendering properties and luminous efficiency, it is necessary to use a red phosphor having a higher luminance. Regarding such a high-intensity red phosphor, Patent Document 2 discloses an Eu ²⁺ -activated CaAlSiN ₃ . Further, this document describes that a phosphor having a light-emitting peak wavelength shifted to the short-wavelength side can be obtained by replacing a part of Ca with Sr. The emission wavelength of the Eu ²⁺ -activated (Sr,Ca)AlSiN ₃ -based nitride fluorescent system is shorter than that of the CaAlSiN ₃ -based nitride phosphor, and since the spectral component of the region with high visual sensitivity increases, it is used as a high-brightness white color. The red phosphor for LEDs is effective.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2004-071726

[Patent Document 2] International Publication No. 2005/052087

However, even in the case of (Sr, Ca)AlSiN ₃ -based nitride phosphors, those having a broad spectrum of light emission and exceeding a human visible range have a large spectral efficiency, and high luminance cannot be achieved.

Therefore, in order to realize a high-brightness white LED excellent in the balance between color rendering property and luminous efficiency in a white LED in which a semiconductor light-emitting element and a phosphor are combined, a red light having a high visual sensitivity is emitted with high luminance. Fluorescent body.

In order to solve the above problems, the inventors of the present invention have conducted a review of the composition range and synthesis conditions of (Sr, Ca)AlSiN ₃ activated by Eu ²⁺ , and found that the crystal lattice of the (Sr, Ca)AlSiN ₃ crystal phase is present. In a specific range, the half value of the luminescence spectrum can be narrowed to a desired range, and as a result, a red luminescence in which a luminescence spectrum in a wavelength band exceeding a human visible range is reduced and red light having a high luminosity can be emitted with high luminance can be obtained. And even completed the present invention.

That is, the main fluorescent system of the present invention is represented by the general formula: M1 _a M2 _b M3 _c M4 _d N _e O _f , M1 is selected from one or more elements of Eu and Ce, and M2 is Ca and Sr is set. It is necessary to select two or more elements selected from the group consisting of Mg, Ca, Sr, Ba, and Zn, and M3 is one or more elements selected from the group consisting of Al, Ga, In, and Sc, and M4-based Si is necessary and selected from Si and Ge. One or more elements of Sn, Ti, Zr and Hf, N is nitrogen, O is oxygen, a~f is 0.00001≦a≦0.15, a+b=1, 0.5≦c≦1.5, 0.5≦d≦1.5 C + d = 2, 2.5 ≦ e ≦ 3.0, 0 ≦ f ≦ 0.5, and the half value width of the luminescence spectrum when excited by light at a wavelength of 455 nm is 72 nm or more and 86 nm or less.

In the fluorescent system of the present invention, when the light has a peak in a range of 250 nm or more and 550 nm or less, and particularly blue light of 455 nm, the peak wavelength (λp) of the emission spectrum is red luminescent fluorescence of 600 nm or more and 635 nm or less. The half value width is limited to 72 nm or more and 86 nm or less. Therefore, in the field where the visibility is low, the amount of luminescence spectrum is small, and high-luminance red luminescence can be realized.

Moreover, the light-emitting device of the present invention can emit high-intensity white light excellent in balance between color rendering properties and luminous efficiency by using the phosphor.

1 is a flow chart showing a method of producing a phosphor of Example 1.

[Formation of the Invention]

The fluorescent system of the present invention is represented by the formula: M1 _a M2 _b M3 _c M4 _d N _e O _f . This formula represents a composition formula of a phosphor, and a to f are atomic ratios of respective elements calculated so that a+b=1.

M1 is an activator added to the parent crystal, that is, an element constituting the luminescent center ion of the phosphor, and is either or both of Eu or Ce. M1 can be selected according to the desired wavelength of light emission, preferably Eu.

When the amount of addition of M1 is too small, sufficient peak intensity of light emission cannot be obtained. When the amount of addition of M1 is too large, the concentration of extinction becomes large, and the peak intensity of light emission tends to be low. As a result, a phosphor having high luminance cannot be obtained. Therefore, the addition amount a of M1 is 0.00001 or more and 0.15 or less.

The M2 system Ca and Sr are essential and are selected from two or more elements of Mg, Ca, Sr, Ba, and Zn.

The content b of M2 satisfies a value of 1, which is a total of the content a of M1, that is, a value of a+b=1.

M3 is an element selected from the group consisting of Al, Ga, In, and Sc, and Al is preferable. When the content of M3 is too small, the desired phosphor crystals cannot be obtained, and if too much, there is a tendency that a heterogeneous phase occurs and the yield is lowered. Therefore, the content c of M3 is 0.5 or more and 1.5 or less.

M4 is one or more elements selected from the group consisting of Si, Ge, Sn, Ti, Zr, and Hf, and Si is preferable, and Si monomer is preferable. The content of M4 has passed When the amount is too small, the crystal of the phosphor of the object is not obtained, and when it is too large, the phase is out of phase and the yield tends to decrease. Therefore, the content d of M4 is 0.5 or more and 1.5 or less. Further, the total content of M3 and the content d of M4 are 2, that is, c + d = 2.

In the above formula, N is nitrogen and O is oxygen. The content e of N is 2.5 or more and 3.0 or less, preferably 2.7 or more and 3.0 or less. Further, the content f of O is 0 or more and 0.5 or less, preferably 0.3 or less.

In the phosphor of the present invention, the full width at half maximum (FWHM) is too narrow, and the color rendering property is lowered. When the width is too wide, the visual sensitivity is lowered. Therefore, the half value of the luminescence spectrum when excited by light having a wavelength of 455 nm is 72 nm or more and 86 nm or less. The lower limit of the half value width is preferably 75 nm, and the upper limit of the half value width is preferably 82 nm.

In the phosphor of the present invention, it is preferred that the main crystal phase is the same as the (Sr, Ca)AlSiN ₃ crystal. Whether the main crystal phase of the phosphor and the (Sr, Ca)AlSiN ₃ crystal have the same structure can be confirmed by X-ray powder diffraction. The crystal phase system existing in the phosphor is preferably a single crystal phase, but it does not matter if it has little influence on the characteristics of the phosphor. Regarding the out-of-phase having a low influence on the fluorescence characteristics, there are (Ca, Sr) ₂ Si ₅ N ₈ , α-SiAlON, and AlN. (Ca,Sr) ₂ Si ₅ N ₈ also contains a small amount of Al dissolved on the Si side and a small amount of O dissolved on the N side. The general formula is expressed as (Ca,Sr) ₂ (Si,Al) ₅ (N,O ) ₈ .

The amount of the heterogeneous phase is preferably 10% or less with respect to the strongest ray intensity of the crystal phase when the ray intensity of the other crystal phase is evaluated with respect to the X-ray powder diffraction method.

The skeleton structure of the (Sr, Ca)AlSiN ₃ crystal is a structure in which (Si,Al)-N ₄ tetrahedron is bonded and the Ca atom and the Sr atom are located in the gap. When a part of Ca ²⁺ or Sr ²⁺ is replaced by Eu ²⁺ acting as a luminescent center, it becomes a red phosphor. The composition of the phosphor is electrically neutral depending on the overall occupancy of Ca and Sr, the Si/Al ratio, and the N/O ratio.

The lattice around the Eu ²⁺ acting as the illuminating center affects the luminescence spectrum shape of the phosphor having the (Sr, Ca)AlSiN ₃ crystal as the main crystal phase, that is, the half value width (FWHM) of the luminescence peak.

In the phosphor of the present invention, the lattice constant a of the (Sr,Ca)AlSiN ₃ crystal which is preferable for achieving the above-mentioned half-value width is 9.795 or more and 9.812 or less, and the lattice constant b is 5.745 or more and 5.755 or less. The lattice constant c is 5.150 or more and 5.165 or less. When such a lattice constant is out of the above range, the red light-emitting body having a wide light-emitting spectrum and having a low visual sensitivity tends to cause lattice strain or crystal defects, and the light-emitting characteristics tend to be lowered.

The lattice constant of the crystal lattice changes depending on the occupancy ratio of Ca and Sr, the Si/Al ratio, the N/O ratio parameter, the firing temperature, and the like of the above composition.

Among them, the ratio of the atomic number of Sr to the total number of atoms of Ca and Sr (Sr/(Sr+Ca)) greatly affects the lattice constant of the crystal lattice.

In the (Sr, Ca)AlSiN ₃ crystal system, when the occupancy ratio (Sr/(Sr+Ca)) of Sr becomes large, the a, b, and c axes of the crystal lattice tend to increase, and especially the b and c axes are accompanied. The occupancy rate of Sr (Sr/(Sr+Ca)) increases linearly. When the occupancy ratio of Sr ²⁺ having a large ionic radius is increased, the lattice is elongated in the b and c directions, and it is considered that the lattice strain generated at this time is adjusted and relaxed in the a-axis direction.

When the occupancy ratio of Sr (Sr/(Sr+Ca)) is too large, it is difficult to maintain the (Sr, Ca)AlSiN ₃ crystal, and since a large amount of heterogeneous phases other than the target crystal are generated, the light-emitting characteristics are remarkably lowered. On the other hand, when the occupancy rate of Sr is too small, the luminescence spectrum is broadened, and the sensation of sensation tends to be low. Therefore, for example, when the element M2 contains Ca and Sr, the occupancy ratio of Sr (Sr/(Sr+Ca)) is preferably 0.85 or more and 0.95 or less, more preferably 0.88 or more and 0.94 or less.

Moreover, the inventors of the present invention investigated the relationship between the lattice constant of the (Sr, Ca)AlSiN ₃ crystal and the half value width (FWHM) of the luminescence peak in more detail, and found that even the Sr occupancy rate (Sr/(Sr+Ca)) It is certain that when the a-axis of the crystal lattice is increased due to a difference in firing temperature or the like, the half value width (FWHM) tends to be wide. In the case where there is a crystal defect or the like, the a-axis of the crystal lattice is increased, so that the light emission on the long wavelength side is increased by the lattice vibration, and the luminescence spectrum is broadened and the half value width is widened.

In the case of the phosphor of the present invention, when the peak wavelength (λp) of the luminescence spectrum is too short, yellowish light is emitted, and sufficient red luminescence cannot be obtained. Further, when the peak wavelength (λp) of the luminescence spectrum is too long, a band is emitted. The tendency of dark red and low red light. Therefore, it is preferable that the peak wavelength of the luminescence spectrum when excited by light having a wavelength of 455 nm is 600 nm or more and 635 nm or less. The peak wavelength can be adjusted by changing, for example, the occupancy ratio of Sr (Sr/(Sr+Ca)) or the like. Generally, when the content of Sr is increased, the peak wavelength tends to be short.

The fluorescent system of the present invention is preferably produced by a mixing step of a mixed raw material, a firing step of a raw material after the firing and mixing step, and a pulverizing step of the sintered body after the pulverizing and firing step. Further, it is preferred to add an acid treatment step and an annealing step. For the manufactured phosphor, The impurities remaining on the surface can be vaporized and removed by the acid treatment step, and the surface layer of the phosphor can be made more dense by the annealing step.

As described above, the fluorescent system of the present invention can emit red light having high visibility with high luminance because the half value width is limited to a specific range.

The light-emitting device of the present invention has the above-described phosphor and light-emitting element of the present invention.

As the light-emitting element, an ultraviolet LED, a blue LED, a single body of a phosphor lamp, or a combination of these may be used. The light-emitting element is preferably light having a wavelength of 250 nm or more and 550 nm or less, and more preferably a blue LED light-emitting element of 420 nm or more and 500 nm or less.

In the phosphor used in the light-emitting device, in addition to the phosphor of the present invention, a phosphor having other luminescent colors may be used in combination. In the case of phosphors of other luminescent colors, there are blue-emitting phosphors, green-emitting phosphors, yellow-emitting phosphors, and orange-emitting phosphors, and examples thereof include Ca ₃ Sc ₂ Si ₃ O ₁₂ : Ce, CaSc ₂ O ₄ :Ce, Y ₃ Al ₅ O ₁₂ :Ce, Tb ₃ Al ₅ O ₁₂ :Ce, (Sr,Ca,Ba) ₂ SiO ₄ :Eu, La ₃ Si ₆ N ₁₁ :Ce, Sr ₂ Si ₅ N ₈ :Eu, etc. The phosphor that can be used in combination with the phosphor of the present invention is not particularly limited, and can be appropriately selected in accordance with the brightness, color rendering, and the like required for the light-emitting device. By mixing the phosphor of the present invention with other phosphors of luminescent color, it is possible to realize white of various color temperatures of daylight white to bulb color.

In terms of light-emitting devices, there are illumination devices, backlight devices, image display devices, and signal devices.

In the light-emitting device of the present invention, by using the phosphor of the present invention, white light having excellent balance between luminous efficiency and color rendering properties and high luminance can be realized.

[Examples]

Hereinafter, the present invention will be described in more detail by way of the following examples. Table 1 shows the composition ratio, firing temperature, luminescent properties, and lattice constant of the phosphors of the examples and the comparative examples.

[Example 1]

As shown in FIG. 1, the mixing step of the fluorescent system of Example 1 by the mixing raw material, the firing step of the raw material after the firing mixing step, the pulverizing step of the sintered body after the pulverizing firing step, the acid treatment step, and the annealing The steps are made.

<mixing step>

In order to be α-type tantalum nitride powder (NP-400 grade, 1.0% by mass of Oxygen Chemical Industry Co., Ltd., oxygen content: 1.0% by mass), aluminum nitride powder (F grade of Tokuyama Co., Ltd., oxygen content 0.6 mass%) 22.65 mass%, and cerium oxide powder (RU grade of Shin-Etsu Chemical Co., Ltd.) was weighed in a manner of 0.78 mass%, and the raw material powder was fed into a V-type mixer. Dry mixing for 10 minutes. In order to make the sizes of the raw materials uniform, a nylon sieve made of 250 μm mesh in the mixed raw materials was used in the following steps.

In a glove box of a nitrogen atmosphere having a water content of 1 ppm or less and an oxygen content of 1 ppm or less, it is made into a calcium nitride powder (manufactured by High Purity Chemical Research Co., Ltd.: purity 2N) of 2.51% by mass and tantalum nitride powder ( High Purity Chemical Research Institute Co., Ltd.; purity 2N) 48.22% by mass method, and dry mixing with the above-mentioned raw materials that have passed through the sieve. The mesh was again sieved with a mesh of 250 μm mesh, and 300 g of the passed sieve was filled in a cylindrical boron nitride container (N-1 grade, manufactured by Electric Chemical Industry Co., Ltd.).

<Burning step>

The raw materials are placed in an electric furnace together with a container and fired. The firing was performed in an electric furnace using a carbon heater. After degassing to a vacuum, the temperature was raised at a rate of 5 ° C / min. From 500 ° C, a gas was introduced at a flow rate of 5 liters / min of nitrogen gas at 0.9 MPa. In a pressurized nitrogen atmosphere of G, heat treatment was carried out at 1800 ° C for 4 hours. After the end of the baking, the container was taken out and placed until room temperature. The obtained firing system is gradually agglomerated in a block shape.

<Smashing step>

The bulk sintered body was pulverized by a roller mill. Only the sieve which passed through the mesh of 150 μm among the pulverized synthetic powders was classified.

<acid treatment step>

The sieved synthetic powder was poured into 2.0 M hydrochloric acid so that the slurry concentration became 25% by mass, and the acid treatment was performed by immersion for 1 hour. After the acid treatment, the slurry was stirred for 1 hour while stirring the hydrochloric acid slurry.

The boiled synthetic powder was cooled to room temperature and filtered, and the acid treatment liquid was separated from the synthetic powder. The synthetic powder after separating the acid treatment liquid was placed in a dryer having a temperature of 100 ° C to 120 ° C for 12 hours, and classified only into a sieve having a mesh size of 150 μm among the dried synthetic powders.

< annealing step>

The synthetic powder after the acid treatment step was filled in a crucible made of alumina, heated in the air at a temperature elevation rate of 10 ° C /min, and heat-treated at 400 ° C for 3 hours. After the heat treatment, the film was allowed to stand at room temperature, and the phosphor of Example 1 was obtained.

The fluorescent system of Example 1 is represented by the general formula: M1 _a M2 _b M3 _c M4 _d N _e O _f , M1 is Eu, M2 is Sr and Ca, M3 is Al, M4 is Si, N is nitrogen, O is The content of oxygen, the content of each element a~f, and the occupation ratio of Sr (Sr/(Sr+Ca)) are the values shown in Table 1. Specifically, it is a phosphor represented by Eu _0.008 (Sr, Ca) _0.992 Al _1.0 Si _1.0 N _3.0 , a~f satisfies 0.00001≦a≦0.15, a+b=1, 0.5≦c≦1.5, 0.5≦ d≦1.5, c+d=2, 2.5≦e≦3.0, 0≦f≦0.5, and Sr/(Sr+Ca) is 0.90.

The half value of the luminescence spectrum when the phosphor was excited by light having a wavelength of 455 nm was 78 nm wide, and the peak wavelength was 620 nm. The half value width and the peak wavelength were measured using a fluorescence spectrophotometer (F-7000, manufactured by Hitachi Advanced Technology Co., Ltd.) which was corrected by Rose Red B and a sub-standard light source. The measurement was performed using a solid sample holder attached to a luminometer, and a fluorescence spectrum at an excitation wavelength of 455 nm was obtained.

X-ray powder diffraction using a CuKα line was performed on the phosphor of Example 1 using an X-ray diffraction apparatus (D8 ADVANCE, manufactured by Bruker AXS Co., Ltd.). The obtained X-ray diffraction pattern was confirmed to be a diffraction pattern of (Sr, Ca)AlSiN ₃ crystal phase and AlN having a slight heterogeneous phase. Each lattice constant of the (Sr,Ca)AlSiN ₃ crystal is a lattice constant a=9.806 Å, a lattice constant b=5.747 Å, and a lattice constant c=5.157 Å.

The relative brightness (%) is calculated from the product of the fluorescence spectrum and the standard sensibility. The other examples and comparative examples described below were also measured under the same conditions as in Example 1, and were presented in a relative value of 100% in Example 1. The acceptable value of the relative brightness is set to 90% or more.

[Examples 2 to 4]

In the second embodiment, the occupancy ratio of Sr (Sr/(Sr+Ca)) was changed in comparison with the phosphor of the first embodiment, and the occupancy ratio of Sr was changed in the examples 3 and 4 (Sr/(Sr+). Ca)) and firing temperature.

[Examples 5 to 8]

Compared with the phosphor of Example 1, the values of the contents a to d of the elements M1 to M4 were changed in the fifth embodiment, and the values of the contents a to d of the elements M1 to M4 and the value of Sr were changed in the sixth embodiment. Occupancy (Sr/(Sr+Ca)), the value of the content e of N was changed in Example 7, and the values of contents a, b, and f of M1, M2, and O were changed in Example 8.

[Comparative Examples 1 to 3]

In Comparative Examples 1 to 3, as shown in Table 1, the values of the contents a to f of the respective elements were the same as those of the phosphor of Example 1, but the occupancy ratio of Sr was changed (Sr/(Sr+). Ca)) or firing temperature.

It can be understood from Examples 1 to 8 that even if the content of the element, the occupancy rate of Sr, and the firing temperature are changed, the half value of the luminescence spectrum is limited. When it is 72 nm or more and 86 nm or less, it is still possible to obtain high-luminance red light emission. On the other hand, in the fluorescent systems of Comparative Examples 1 to 3, the half value width exceeded the above range and the relative brightness was remarkably lowered. In addition, it is confirmed that the above-mentioned half-value width system is in a range in which the lattice constant a is 9.795 or more and 9.812 or less, the lattice constant b is in the range of 5.745 or more and 5.755 or less, and the lattice constant c is in the range of 5.150 or more and 5.165 or less. Achieved. Further, although not described in the table, when the lattice constant a is less than 9.975, the half value width is outside the above range.

[Embodiment 9]

A general-type projectile-type white light-emitting device is manufactured by using a phosphor including the phosphor of Example 1, a phosphor that emits green light, a phosphor of a blue-emitting phosphor, and a blue light-emitting LED chip as a light-emitting element. . This light-emitting device was replaced with a phosphor of the first embodiment instead of the phosphor of the first embodiment, and had a high luminance.

By using the light-emitting device, a high-brightness backlight device, an image display device, and a signal device can be realized.

Claims (5)

A phosphor represented by the general formula: M1 _a M2 _b M3 _c M4 _d N _e O _f , M1 is selected from one or more elements of Eu and Ce, and M2 Ca and Sr are required and selected from the group consisting of Two or more elements of Mg, Ca, Sr, Ba, and Zn, M3 is one or more elements selected from the group consisting of Al, Ga, In, and Sc, and M4-based Si is required and selected from Si, Ge, Sn, and Ti. One or more elements of Zr and Hf, N is nitrogen, O is oxygen, a~f is 0.00001≦a≦0.15, a+b=1, 0.5≦c≦1.5, 0.5≦d≦1.5, c+d = 2, 2.5 ≦ e ≦ 3.0, 0 ≦ f ≦ 0.5, and the half value width of the luminescence spectrum when excited by light at a wavelength of 455 nm is 72 nm or more and 86 nm or less. The phosphor of claim 1, wherein the lattice constant a of the crystal lattice is 9.795 or more and 9.812 or less, the lattice constant b is 5.745 or more and 5.755 or less, and the lattice constant c is 5.150 or more and 5.165 or less. The phosphor of claim 1 or 2, wherein M1 is Eu, M2 is Ca and Sr, M3 is A1, M4 is Si, and the main crystalline phase is the same structure as (Sr, Ca)AlSiN ₃ crystal, and the M2 element The ratio of Sr (Sr/(Sr+Ca)) in the medium is 0.85 or more and 0.95 or less. The phosphor according to any one of claims 1 to 3, wherein the luminescence spectrum when excited by light having a wavelength of 455 nm is a peak wavelength of 600 nm or more and 635 nm or less. A light-emitting device having the phosphor and the light-emitting element according to any one of claims 1 to 4.