JP7807643B2 - Nitride phosphor, light-emitting device, lighting fixture and street light - Google Patents

Description

The present invention relates to nitride phosphors and light-emitting devices.

HID lamps, such as high-pressure mercury lamps, metal halide lamps, and high-pressure sodium lamps, are often used as light sources for lighting fixtures installed outdoors, such as street lamps and road lighting, because they have a longer lifespan and are more efficient than incandescent bulbs. Light sources using these lamps contain mercury as a luminous material, and in accordance with the Minamata Convention on Mercury, there is a demand for them to be replaced with lighting fixtures that use safer luminous materials.

Indoor and automotive lighting devices use light-emitting devices that combine light-emitting diodes (LEDs) and phosphors. Light-emitting devices used as light sources for outdoor lighting fixtures are required to emit light containing red, similar to the light emitted from HID lamps. For example, Patent Document 1 discloses a nitride phosphor that uses (Ba, Sr, Ca) ₂ Si ₅ N ₈ as a host crystal and europium as an activator element, as a phosphor having an emission peak wavelength in the range of 570 nm to 670 nm.

Special Publication No. 2003-515655

A light emitting device may be required to have temperature characteristics that enable it to maintain its luminous intensity even when the temperature rises.
An object of one aspect of the present invention is to provide a nitride phosphor and a light-emitting device that have good temperature characteristics.

The first aspect is a nitride phosphor having a composition included in a composition formula represented by the following formula (1), and having an emission peak wavelength in the range of 585 nm or more and 610 nm or less in an emission spectrum when irradiated with light having an emission peak wavelength in the range of 350 nm or more and 500 nm or less, and having an emission intensity when the irradiated excitation light is blocked as a reference intensity, and having a decay time of 2.49 μs or more at which the emission intensity becomes 1/10 of the reference intensity.
(Ba _v Sr _w Eu _x ) ₂ Si ₅ N _8-y (1)
(In formula (1), v, w, x, and y satisfy 0.50≦v≦0.919, 0.08≦w≦0.50, 0.001≦x≦0.030, 0.9<v+w+x≦1.0, and 0≦y≦0.5, respectively.)

The second aspect is a light-emitting device comprising a wavelength conversion member containing the nitride phosphor according to the first aspect and a light-emitting element having an emission peak wavelength in the range of 350 nm to 500 nm, with the wavelength conversion member disposed on top of the light-emitting element.

One aspect of the present invention provides a nitride phosphor and a light-emitting device with excellent temperature characteristics.

FIG. 1 is a diagram showing an area A1 in the xy chromaticity coordinate system of the CIE 1931 chromaticity diagram. FIG. 2 is a schematic cross-sectional view showing an example of a light emitting device according to the first configuration example. FIG. 3 is a schematic perspective view showing an example of a light emitting device according to the second configuration example. FIG. 4 is a schematic cross-sectional view showing an example of a light emitting device according to the second configuration example. FIG. 5 is a schematic perspective view showing an example of a light emitting device according to the third configuration example. FIG. 6 is a schematic cross-sectional view showing an example of a light emitting device according to the third configuration example. FIG. 7 is a diagram showing an example of a street light. FIG. 8 is a diagram showing the emission spectrum of a nitride phosphor. FIG. 9 is a graph showing the relationship between the luminous energy (%) and the decay time (μs) of nitride phosphors.

Embodiments of the present invention are described below with reference to the drawings. However, the embodiments described below are merely examples for embodying the technical concept of the present invention, and the present invention is not limited to the nitride phosphors and light-emitting devices described below. Furthermore, the components set forth in the claims are in no way limited to those in the embodiments. In particular, the dimensions, materials, shapes, relative positions, etc. of the components described in the embodiments are merely illustrative examples and are not intended to limit the scope of the present invention unless otherwise specified. The relationship between color names and chromaticity coordinates, and the relationship between light wavelength ranges and color names of monochromatic light, etc., conforms to JIS Z8110. In this specification, when multiple substances corresponding to each component are present in the composition, the content of each component in the composition refers to the total amount of those multiple substances present in the composition, unless otherwise specified.

The nitride phosphor according to the first embodiment has a composition included in the composition formula represented by formula (1) below, and has an emission peak wavelength in the range of 585 nm or more and 610 nm or less in the emission spectrum when irradiated with light having an emission peak wavelength in the range of 350 nm or more and 500 nm or less, and has a decay time of 2.49 μs or more at which the emission intensity becomes 1/10 of the reference intensity, with the emission intensity when the irradiated excitation light is blocked as a reference intensity.
(Ba _v Sr _w Eu _x ) ₂ Si ₅ N _8-y (1)
(In formula (1), v, w, x, and y satisfy 0.50≦v≦0.919, 0.08≦w≦0.50, 0.001≦x≦0.030, 0.9<v+w+x≦1.0, and 0≦y≦0.5, respectively.)

The nitride phosphor has a composition represented by the formula (1) and exhibits a decay time (hereinafter sometimes referred to as the "1/10 decay time") of 2.49 μs or longer, where the emission intensity when the irradiated excitation light is blocked is taken as the reference intensity. This decay time is thought to be related to defects in the crystalline structure that constitutes the nitride phosphor. For a nitride phosphor having a composition represented by the formula (1), a 1/10 decay time of 2.49 μs or longer indicates that the crystalline structure that constitutes the nitride phosphor contains few defects. When nitride phosphors absorb light, electrons transition from the ground state to an excited state energy level, and the electrons that transition to the excited state energy level transition back to the ground state while emitting light, thereby emitting fluorescence. When defects exist in the crystalline structure of a nitride phosphor, not only excited state energy levels but also defect-related energy levels are formed. Transitions in the excited state energy levels of nitride phosphors can also occur at defect-related energy levels. Therefore, it is believed that the rate at which the luminescence intensity of the nitride phosphor decreases after the excitation light is cut off also increases, i.e., the 1/10 decay time decreases. For a nitride phosphor having a composition included in the composition formula represented by formula (1), a 1/10 decay time of 2.49 μs or more indicates that the crystal structure contains few defects that change the electron transition. A nitride phosphor with few such defects can maintain a good crystal structure even with increasing temperature, with little change in luminescence energy and good temperature characteristics. On the other hand, for a nitride phosphor, a 1/10 decay time of less than 2.49 μs is presumed to contain defects in the crystal structure that change the transition of the electron energy levels in the nitride phosphor, which affects the 1/10 decay time. A nitride phosphor containing such defects in its crystal structure is presumed to be unable to maintain its crystal structure with increasing temperature, resulting in a significant change in luminescence energy and a deterioration in temperature characteristics. Luminescence energy refers to the integrated value of a specific wavelength range in the emission spectrum of a phosphor or light-emitting device. The emission spectrum represents the magnitude of luminescence intensity at a certain wavelength; the higher the luminescence energy, the greater the luminescence intensity. When the ambient temperature changes, if the change in the luminous energy of the nitride phosphor is small, i.e., if the luminous energy retention rate is high, the change in luminous intensity is also small and the temperature characteristics are good. The nitride phosphor may have a 1/10 decay time of 2.50 μs or more, 2.51 μs or more, 2.55 μs or more, or 2.60 μs.

To improve the temperature characteristics of nitride phosphors having a composition included in the composition formula represented by formula (1), v in formula (1) is 0.050 or more (0.50≦v), preferably 0.55 or more (0.55≦v), and more preferably 0.60 or more (0.60≦v). v in formula (1), which represents the composition of the nitride phosphor, is 0.919 or less (v≦0.919), preferably 0.90 or less (v≦0.90), more preferably 0.85 or less (v≦0.85), even more preferably 0.80 or less (v≦0.80), and may be less than 0.80 (v<0.80), 0.78 or less (v≦0.78), or 0.77 or less (v≦0.77). In the formula (1) representing the composition of the nitride phosphor, w is 0.08 or greater (0.08≦w), preferably 0.10 or greater (0.10≦w), more preferably 0.105 or greater (0.105≦w), and even more preferably 0.12 or greater (0.12≦w). In the formula (1) representing the composition of the nitride phosphor, w is 0.50 or less (w≦0.50), may be 0.45 or less (w≦0.45), or may be 0.40 or less (w≦0.40).

In order to improve the temperature characteristics of a nitride phosphor having a composition included in the composition formula represented by formula (1), it is preferable that v and w in formula (1) satisfy 0.50≦v<0.80 and 0.12<w≦0.50, respectively. It is more preferable that v and w in formula (1) satisfy 0.55≦v≦0.78 and 0.13≦w≦0.45, respectively, and even more preferable that they satisfy 0.60≦v≦0.77 and 0.15≦w≦0.40, respectively.

In order to improve the temperature characteristics of a nitride phosphor having a composition included in the composition formula represented by formula (1), x in formula (1) is preferably 0.001 or greater (0.001≦x) and 0.002 or greater (0.002≦x). x in formula (1), which represents the composition of the nitride phosphor, is preferably 0.030 or less (x≦0.030) and 0.020 or less (x≦0.020), more preferably 0.018 or less (x≦0.018), and even more preferably 0.015 or less (x≦0.015). In the product of the variable x, which represents the molar ratio of Eu, an activator element, in a nitride phosphor having a composition included in the composition formula expressed by the above formula (1), and 2, when the value of the variable x is small within a range in which the luminescence characteristics can be maintained, the number of defects in the crystal structure of the nitride phosphor that change the transition of electron energy levels decreases, and the 1/10 decay time of the nitride phosphor becomes 2.49 μs or longer.

Nitride phosphors having a composition included in the composition formula represented by formula (1) preferably have a 1/10 decay time of 2.91 μs or less. A 1/10 decay time of 2.91 μs or less indicates few crystal defects, maintains luminescence characteristics even with increasing temperature, and has good temperature characteristics. If the 1/10 decay time of a nitride phosphor exceeds 2.91 μs, this indicates a change in the transition of the electron energy levels of the phosphor, which is presumed to affect temperature characteristics. For example, in a composition included in the composition formula represented by formula (1), if the product of the variable w, which represents the molar ratio of Sr, and 2 exceeds 0.50, the 1/10 decay time of the nitride phosphor will exceed 2.91 μs, and there is a risk of a decrease in luminescence intensity when a light-emitting device containing the nitride phosphor is used for an extended period of time. For example, in the composition contained in the composition formula expressed by the above formula (1), when the product of the variable x, which represents the molar ratio of Eu, and 2 becomes larger than 0.030, the 1/10 decay time of the nitride phosphor increases beyond 2.91 μs, and concentration quenching occurs due to an excessively large molar ratio of Eu, which is an activator element, which may result in a decrease in emission intensity and a decrease in temperature characteristics.

A nitride phosphor having a composition included in the composition formula represented by formula (1) has a peak emission wavelength in the range of 585 nm to 610 nm in its emission spectrum, and may have a peak emission wavelength in the range of 590 nm to 605 nm, or may have a peak emission wavelength in the range of 595 nm to 600 nm. When the peak emission wavelength in the emission spectrum of the nitride phosphor is in the range of 585 nm to 610 nm, even if all the phosphors contained in the light-emitting device are nitride phosphors (100% by mass) having a composition included in the composition formula represented by formula (1), the light will emit light of a color similar to that emitted by an HID lamp. Even when used as a light source for lighting fixtures used outdoors, such as street lamps and road lighting, the light will emit light of a color similar to that of the light sources of lighting fixtures conventionally used outdoors.

A nitride phosphor having a composition included in the composition formula represented by formula (1) above may have an emission spectrum full width at half maximum within the range of 60 nm to 95 nm, 65 nm to 90 nm, 70 nm to 85 nm, or 75 nm to 83 nm. In this specification, full width at half maximum refers to the wavelength width that is 50% of the emission intensity at the emission peak wavelength exhibiting the maximum emission intensity in the emission spectrum. If the full width at half maximum in the emission spectrum of a nitride phosphor falls within the above range, the color purity of the emitted light is high, and even when used as a light source for lighting fixtures used outdoors, such as street lamps and road lighting, it can emit light with a color tone substantially equivalent to that of light sources used in lighting fixtures conventionally used outdoors.

The nitride phosphor having a composition included in the composition formula represented by formula (1) preferably has a volume average particle size, as measured by laser diffraction/scattering particle size distribution measurement, in the range of 10 μm to 40 μm, more preferably 15 μm to 38 μm, even more preferably 20 μm to 35 μm, and may be 30 μm or greater. When a nitride phosphor has a volume average particle size in the range of 10 μm to 40 μm, it easily absorbs excitation light and easily converts the wavelength of the absorbed light. The volume average particle size, as measured by laser diffraction/scattering particle size distribution measurement, refers to the particle size at which the cumulative volume frequency from the small diameter side reaches 50% in the volume-based particle size distribution measured using scattered light from a laser beam irradiated onto the particles.

A nitride phosphor having a composition included in the composition formula represented by formula (1) above preferably has an internal quantum efficiency of 85% or more when excited with light having a wavelength of 450 nm. It is more preferable that the nitride phosphor have an internal quantum efficiency of 90% or more, and even more preferably 91% or more, when excited with light having a wavelength of 450 nm. The nitride phosphor has a composition included in the composition formula represented by formula (1) above, has a 1/10 decay time of 2.49 μs or more, and has few crystal defects, resulting in high luminescence characteristics with an internal quantum efficiency of 85% or more.

2. Method for manufacturing nitride phosphors. The method for manufacturing nitride phosphors preferably includes the steps of: using compounds containing each element contained in the composition formula represented by formula (1) as raw materials, and obtaining a raw material mixture by weighing and mixing each compound so that the elements contained in each compound are contained in the composition formula represented by formula (1); subjecting this raw material mixture to a first heat treatment to obtain a raw material fired product; and mixing this raw material fired product with each compound so that the elements contained in each compound are contained in the composition formula represented by formula (1); and subjecting this mixture to a second heat treatment to obtain a fired product having a composition contained in the composition formula represented by formula (1). In this specification, the heat treatment of a raw material mixture that does not contain a fired product having a composition contained in the composition formula represented by formula (1) is referred to as the first heat treatment. In this specification, the heat treatment of a mixture containing a fired product having a composition contained in the composition formula represented by formula (1) and the raw material compound is referred to as the second heat treatment. The second heat treatment may be repeated multiple times. For details of the method for manufacturing nitride phosphors, see, for example, the disclosure of JP 2021-46516 A.

Raw Material Mixture Examples of raw material compounds include nitrides, fluorides, hydrides, oxides, carbonates, and chlorides. Examples of raw material compounds include _Ba3N2 , _BaF2 , _BaH2 , _EuN , EuF3, _EuH3 , _Si3N4 , _SiO2 , Si(NH) ₂ , _Si2N2NH , and Si( _NH2 ) ₄ . When the resulting nitride phosphor contains Sr, examples of raw materials include _Sr2N , _SrN , _Sr3N2 , _SrF2 , and _{SrH2 .} It is more preferable that at least one of the raw material compounds is _a nitride. By using a nitride as a raw material, it is possible to suppress the formation of _a raw material fired product with a composition other than the desired composition. The raw material mixture may contain a flux. By including a flux in the raw material mixture, the reaction between the raw material compounds is further promoted, and the solid-state reaction proceeds more uniformly, resulting in a phosphor with larger particle size and better luminescence properties. It is preferable to use a halide as the flux, whose heat treatment temperature for obtaining the phosphor is the same as the temperature at which the liquid phase of the compound is formed.

First Heat Treatment The obtained raw material mixture is subjected to a first heat treatment in a nitrogen-containing atmosphere to obtain a raw material fired product that will become a phosphor. In this specification, the fired product obtained by the first heat treatment of the raw material mixture may be referred to as a raw material fired product. The heat treatment temperature is preferably in the range of 1300°C or higher and 2100°C or lower, more preferably in the range of 1500°C or higher and 2000°C or lower, and may be 1600°C or higher or 1950°C or lower. If the heat treatment temperature is in the range of 1300°C or higher and 2100°C or lower, thermal decomposition is suppressed, and a raw material fired product for obtaining a phosphor having the desired composition is obtained.

The heat treatment atmosphere may be any atmosphere containing nitrogen. The nitrogen-containing atmosphere preferably contains nitrogen gas at 70 vol% or more, more preferably 80 vol% or more, and even more preferably 90 vol% or more. The nitrogen-containing atmosphere is preferably a reducing atmosphere. The reducing atmosphere is more preferably an atmosphere containing reducing hydrogen gas. The atmosphere containing nitrogen and reducing hydrogen gas preferably contains hydrogen gas at 1 vol% or more, more preferably 5 vol% or more, and even more preferably 10 vol% or more.
The pressure of the nitrogen-containing atmosphere is preferably a pressurized atmosphere of 0.1 MPa to 200 MPa in gauge pressure. By using a pressurized atmosphere, decomposition of the crystal structure can be suppressed, and a decrease in luminescence intensity can be suppressed. The pressure of the heat treatment atmosphere is more preferably 0.1 MPa to 100 MPa in gauge pressure, even more preferably 0.5 MPa to 10 MPa in gauge pressure, and from the viewpoint of ease of production, even more preferably 1.0 MPa or less.
The heat treatment time can be appropriately selected depending on the heat treatment temperature and the pressure of the atmosphere during the heat treatment, and is preferably 0.5 hours or more and 20 hours or less. Even when multi-stage heat treatment is performed, the heat treatment time for each stage is preferably 0.5 hours or more and 20 hours or less in order to suppress decomposition of the fired product.

Post-Processing After First Heat Treatment The raw material fired product obtained by the heat treatment may be subjected to post-treatments such as pulverization, wet dispersion, solid-liquid separation, drying, and classification. Solid-liquid separation can be carried out by industrially commonly used methods such as filtration, suction filtration, pressure filtration, centrifugation, and decantation. Drying can be carried out by industrially commonly used devices such as a vacuum dryer, a hot air heating dryer, a conical dryer, and a rotary evaporator. Classification can be carried out by industrially commonly used methods such as wet classification such as sedimentation classification, mechanical classification, hydraulic classification, and centrifugal classification, and sieving classification.

Mixture The mixture contains a fired product having a composition included in the composition formula represented by formula (1) including the raw material fired product, and a compound containing an element included in the composition formula represented by formula (1). In this specification, a fired product having a composition included in the composition formula represented by formula (1) including the raw material fired product may be simply referred to as a fired product. A mixture containing the fired product and raw material compounds is obtained by mixing the fired product and the elements contained in each compound so that they are included in the composition formula represented by formula (1). The mixture may contain a flux, as with the raw material mixture.

Second Heat Treatment The obtained mixture is preferably subjected to a second heat treatment separately from the first heat treatment to obtain a fired product having a composition included in the composition formula represented by formula (1). The heat treatment temperature, atmosphere, pressure, and time of the second heat treatment can be in the same ranges as those of the first heat treatment. The second heat treatment may be performed multiple times, and when performed multiple times, it may be referred to as the "first second heat treatment,""second second heat treatment,""third second heat treatment," etc.

Post-Processing of Second Heat Treatment The fired product obtained by the second heat treatment may be subjected to post-treatments such as pulverization, wet dispersion, solid-liquid separation, drying, classification, etc., in the same manner as the raw fired product obtained by the first heat treatment.

Light-emitting device The light-emitting device according to the second embodiment is a light-emitting device comprising: a wavelength conversion member containing a nitride phosphor having a composition included in the composition formula represented by formula (1) and having the 1/10 decay time of 2.49 μs or more; and a light-emitting element having an emission peak wavelength in the range of 350 nm or more and 500 nm or less, in which the wavelength conversion member is disposed above the light-emitting element (on the light emission side).

The light-emitting device preferably emits light within an area A1 defined by the first line connecting the first and second points, the second line connecting the second and third points, the third line connecting the third and fourth points, and the fourth line connecting the fourth point and the first point, where the chromaticity coordinates (x, y) in the xy chromaticity coordinate system of the CIE 1931 chromaticity diagram are (x = 0.510, y = 0.400) as the first point, (x = 0.510, y = 0.440) as the second point, (x = 0.600, y = 0.400) as the third point, and (x = 0.600, y = 0.360) as the fourth point, in the xy chromaticity coordinate system of the CIE 1931 chromaticity diagram.

Light sources used for outdoor lighting fixtures include HID lamps, halogen lamps, and LED-based light-emitting devices, depending on their luminous flux and energy characteristics. The light-emitting device preferably emits orange to reddish light within the aforementioned region A1 in the xy chromaticity coordinate system of the CIE 1931 chromaticity diagram. Light emitted from the light-emitting device within region A1 has a color similar to that of HID lamps such as high-pressure mercury lamps, metal halide lamps, and high-pressure sodium lamps. Light-emitting devices emitting light within region A1, when used as the light source for outdoor lighting fixtures such as street lamps and road lighting, emit light with a color similar to that of the various lamps mentioned above. Figure 1 shows region A1 in the xy chromaticity coordinate system of the CIE 1931 chromaticity diagram. The light-emitting device preferably emits light within region A1, which is enclosed by the straight lines connecting points 1 and 2, points 2 and 3, points 3 and 4, and points 4 and 1 in Figure 1. The light-emitting device emits light within region A1 in Figure 1, and the light within region A1 has an emission color ranging from orange to red.

The light-emitting device preferably emits light whose correlated color temperature is in the range of 1200K to 2000K inclusive on the CIE 1931 chromaticity diagram and whose color deviation duv from the blackbody radiation locus measured in accordance with JIS Z8725 is in the range of -0.020 to 0.020 inclusive. When the correlated color temperature of the light emitted from the light-emitting device is in the range of 1200K to 2000K inclusive, the emitted color is similar to that of light emitted by HID lamps such as high-pressure mercury lamps, metal halide lamps, and high-pressure sodium lamps. When used as a light source for lighting fixtures used outdoors, such as street lamps and road lighting, the light-emitting device emits light with a color similar to that of the light sources of lighting fixtures conventionally used outdoors. Furthermore, the light-emitting device emits light having a correlated color temperature in the range of 1200K to 2000K inclusive on the chromaticity diagram of the CIE 1931 color system, and a color deviation duv in the range of -0.020 to 0.020 inclusive from the blackbody radiation locus (duv = 0.000) measured in accordance with JIS Z8725. For example, even when used as the light source for a lighting fixture used outdoors, the light emitted from the light-emitting device produces light that gives the irradiated object a natural color tone. When the color deviation of the mixed color light emitted from the light-emitting device is Duv = 0, there is no deviation from the blackbody radiation locus and the light approximates the blackbody radiation locus. For example, Figure 2 of JP 2019-207995 A can be seen as an example of the range of color deviation duv from the blackbody radiation locus in the CIE 1931 color system chromaticity diagram measured in accordance with JIS Z8725, where duv = -0.020 to 0.020 inclusive.

Color deviation duv is the deviation of light emitted from a light-emitting device from the blackbody radiation locus, and is measured in accordance with JIS Z8725. Light-emitting devices preferably emit light with a color deviation duv, which is the deviation from the blackbody radiation locus at temperatures between 1200K and 2000K, in the range of -0.010 to +0.010, and more preferably with a duv in the range of -0.008 to +0.008. When light is emitted with a color deviation duv, which is the deviation from the blackbody radiation locus at 1950K or less, of more than plus or minus (±) 0.020, the color of the illuminated object may deviate from its natural color.

The light-emitting device emits light with a correlated color temperature that is similar to or slightly lower than that of light emitted by, for example, a high-pressure sodium lamp. If the correlated color temperature of the light emitted by the light-emitting device is 1200K or higher and 2000K or lower, even when the light-emitting device is used as the light source for outdoor lighting fixtures such as street lights and road lighting that use high-pressure sodium lamps as their light source, the light emitted will have a color tone roughly equivalent to that of the light source of lighting fixtures traditionally used outdoors. The correlated color temperature of the light emitted from the light-emitting device may be 1950K or lower, 1920K or lower, or 1900K or lower. The correlated color temperature of the light emitted from the light-emitting device may be 1200K or higher, 1500K or higher, 1500K or higher, or 1700K or higher.

The luminous flux of a light-emitting device emitted at an ambient temperature of 25°C is defined as 100% of the reference luminous flux, and the luminous flux of the light-emitting device emitted at ambient temperatures of 150°C or higher is preferably 55% or more of the reference luminous flux, or alternatively, 56% or more, or 58% or more of the reference luminous flux. The ratio of the luminous flux of the light-emitting device emitted at an ambient temperature of 150°C to the reference luminous flux of 100% of the reference luminous flux of the light-emitting device at an ambient temperature of 25°C is sometimes referred to as the luminous flux maintenance factor. If the luminous flux maintenance factor of the light-emitting device emitted at an ambient temperature of 150°C is 55% or more of the reference luminous flux of 100% of the reference luminous flux of the light-emitting device at an ambient temperature of 25°C, then even when the ambient temperature rises to 150°C, the degradation of the light-emitting device's luminous characteristics is suppressed, the temperature characteristics are good, and reliability requirements are met. The luminous flux of a light-emitting device can be measured from an emission spectrum measured, for example, using a spectrometer, similar to the measurement method in the examples described below.

Light-emitting element The light-emitting element has an emission peak wavelength in the range of 350 nm to 500 nm. The emission peak wavelength of the light-emitting element is preferably in the range of 380 nm to 490 nm, more preferably in the range of 400 nm to 480 nm, even more preferably in the range of 410 nm to 470 nm, and even more preferably in the range of 420 nm to 460 nm. The full width at half maximum of the emission peak having the emission peak wavelength in the emission spectrum of the light-emitting element is preferably 30 nm or less, more preferably 25 nm or less, and even more preferably 20 nm or less. For example, it is preferable to use a semiconductor light-emitting element using a nitride-based semiconductor as the light-emitting element. This makes it possible to obtain a light-emitting device that is highly efficient, has high output linearity relative to input, and is stable and resistant to mechanical shock.

Wavelength conversion member The light emitting device includes a wavelength conversion member containing a nitride phosphor having a composition included in the composition formula represented by formula (1) and having a 1/10 decay time of 2.49 μs or longer. The wavelength conversion member may contain only a nitride phosphor having a composition included in the composition formula represented by formula (1). The phosphor contained in the wavelength conversion member may be a nitride phosphor in which 100 mass% of the phosphor contained in the wavelength conversion member has a composition included in the composition formula represented by formula (1) and has a 1/10 decay time of 2.49 μs or longer. The nitride phosphor has an emission peak wavelength in the range of 585 nm to 610 nm in the emission spectrum of the nitride phosphor. The light emitting device has a composition included in the composition formula expressed by the formula (1) and is provided with a wavelength conversion member containing a nitride phosphor having a 1/10 decay time of 2.49 μs or more, so that the light emitting device emits light of a color similar to that emitted by an HID lamp, and even when used as a light source for a lighting fixture used outdoors, for example, the light emitting device emits light that has a natural color for the object it illuminates.

The content of the nitride phosphor contained in the wavelength conversion member varies depending on the form of the light emitting device, etc. The content of the nitride phosphor contained in the wavelength conversion member may be an amount that emits light within the aforementioned region A1 in the xy chromaticity coordinates of the CIE 1931 chromaticity diagram. The content of the nitride phosphor contained in the wavelength conversion member may be an amount that emits light whose correlated color temperature is between 1200 K and 2000 K inclusive on the CIE 1931 chromaticity diagram and whose color deviation duv from the blackbody radiation locus measured in accordance with JIS Z8725 is between -0.020 and 0.020 inclusive. For example, the total amount of the nitride phosphor contained in the wavelength conversion member may be between 10 and 900 parts by mass, between 15 and 850 parts by mass, or between 20 and 800 parts by mass, per 100 parts by mass of the translucent material.

The wavelength conversion member preferably includes a nitride phosphor having a composition within the composition formula represented by formula (1) and a 1/10 decay time of 2.49 μs or longer, and a translucent material. The translucent material varies depending on the form of the light-emitting device, etc. Examples of the translucent material include at least one selected from the group consisting of resin, glass, and inorganic materials. The resin is preferably at least one selected from the group consisting of epoxy resin, silicone resin, phenolic resin, and polyimide resin. Examples of the inorganic material include at least one selected from the group consisting of aluminum oxide and aluminum nitride.

The wavelength conversion member may, as necessary, include a nitride phosphor having a composition represented by the following formula (2): In the formula representing the phosphor composition, the part before the colon (:) represents the molar ratio of each element in 1 mole of the host crystal and phosphor composition, and the part after the colon (:) represents an activator element.
Sr _q Ca _s Al _t Si _u N _v :Eu (2)
(In formula (2), q, s, t, u, and v satisfy the following conditions: 0≦q<1, 0<s≦1, q+s≦1, 0.9≦t≦1.1, 0.9≦u≦1.1, and 2.5≦v≦3.5, respectively.)
Furthermore, the wavelength conversion member may, as necessary, include at least one selected from the group consisting of, for example, a first fluoride phosphor represented by the following formula (3) and a second fluoride phosphor having a composition represented by the following formula (4) which is different in composition from that of the following formula (3):
A _c [M ² _1-b Mn ⁴⁺ _b F _d ] (3)
(In formula (3), A includes at least one element selected from the group consisting of K ⁺ , Li ⁺ , Na ⁺ , Rb ⁺ , Cs ⁺ and NH ₄ ⁺ , of which K ⁺ is preferred. ^{M 2} includes at least one element selected from the group consisting of Group 4 elements and Group 14 elements, of which Si and Ge are preferred. b satisfies 0<b<0.2, c is the absolute value of the charge of the [M ² _1-b Mn ⁴⁺ _b F _d ] ion, and d satisfies 5<d<7.)
A'_c' [M ² '_1-b' Mn ⁴⁺ _b' F _d' ] (4)
(In formula (4), A' includes at least one element selected from the group consisting of K ⁺ , Li ⁺ , Na ⁺ , Rb ⁺ , Cs ⁺ and NH ₄ ⁺ , of which K ⁺ is preferred. M ² ' includes at least one element selected from the group consisting of Group 4 elements, Group 13 elements and Group 14 elements, of which Si and Al are preferred. b' satisfies 0<b'<0.2, c' is the absolute value of the charge of the [M ² '_1-b' Mn ⁴⁺ _b' F _d' ] ion, and d' satisfies 5<d'<7.)

In addition to the phosphor and translucent material, the wavelength conversion member may contain fillers, colorants, and light diffusing materials as needed. Examples of fillers include silicon dioxide, barium titanate, titanium oxide, and aluminum oxide. The total content of components other than the phosphor and translucent material contained in the wavelength conversion member can be in the range of 0.01 to 50 parts by weight, 0.1 to 45 parts by weight, or 0.5 to 40 parts by weight, per 100 parts by weight of the translucent material.

An example of a light-emitting device will be described with reference to the drawings. Figure 2 is a schematic cross-sectional view showing a light-emitting device of a first configuration example.

As shown in FIG. 2, the light-emitting device 100 comprises a light-emitting element 10 having an emission peak wavelength in the range of 350 nm to 500 nm, and a first phosphor 71, which is a nitride phosphor having a composition included in the composition formula represented by formula (1) and which emits light upon excitation by light from the light-emitting element.

The light-emitting device 100 includes a molded body 41, a light-emitting element 10, and a wavelength conversion member 21. The molded body 41 is integrally formed by molding a first lead 2, a second lead 3, and a resin portion 42 containing a thermoplastic resin or a thermosetting resin. The molded body 41 forms a recess with a bottom and side surfaces, and the light-emitting element 10 is placed on the bottom surface of the recess. The light-emitting element 10 has a pair of positive and negative electrodes, which are electrically connected to the first lead 2 and the second lead 3 via wires 60, respectively. The light-emitting element 10 is covered with a wavelength conversion member 21. The wavelength conversion member 21 includes, for example, a phosphor 70 that converts the wavelength of light from the light-emitting element 10 and a translucent material. The wavelength conversion member 21 also functions as a sealing member that covers the light-emitting element 10 and the phosphor 70 in the recess of the molded body 41. The phosphor 70 includes a first phosphor 71 that is excited by light from the light-emitting element and has an emission peak wavelength in the range of 585 nm to 610 nm. The first lead 2 and second lead 3 connected to a pair of positive and negative electrodes of the light-emitting element 10 each have a portion exposed toward the outside of the light-emitting device 100. Power can be supplied from the outside via these first lead 2 and second lead 3, causing the light-emitting device 100 to emit light.

A method for manufacturing a light emitting device according to a first configuration example will now be described. For details, the disclosure of JP 2010-062272 A can be referenced. The method for manufacturing a light emitting device preferably includes a molded body preparation step, a light emitting element arrangement step, a wavelength conversion member composition arrangement step, and a resin package formation step. When an aggregate molded body having a plurality of recesses is used as the molded body, the resin package formation step may be followed by a singulation step in which the molded body is separated into individual resin packages of each unit area.

In the molded body preparation step, a plurality of leads are integrally molded using a thermosetting resin or a thermoplastic resin to prepare a molded body having a recess with a side surface and a bottom surface. The molded body may be a molded body made of an aggregate base including a plurality of recesses.
In the light-emitting element placement step, the light-emitting element is placed on the bottom surface of the recess in the molded body, and the positive and negative electrodes of the light-emitting element are connected to the first lead and the second lead by wires.
In the step of placing the composition for a wavelength conversion member, the composition for a wavelength conversion member is placed in the recess of the molded body.
In the resin package molding process, the wavelength conversion material composition placed in the recesses of the molded body is cured to form a resin package, and a light emitting device is manufactured. When a molded body made of an aggregate base having multiple recesses is used, after the resin package formation process, the aggregate base having multiple recesses is separated into individual resin packages in each unit area in a singulation process, and individual light emitting devices are manufactured. In this way, the light emitting device of the first configuration example shown in Figure 2 can be manufactured.

Figure 3 is a schematic perspective view showing a light-emitting device of a second configuration example. Figure 4 is a schematic cross-sectional view showing a light-emitting device of a second configuration example.

As shown in Figures 3 and 4, the light-emitting device 300 comprises a support 1, a light-emitting element 10 arranged on the support 1, a wavelength conversion member 22 containing a phosphor 70 arranged on the upper surface of the light-emitting element 10, and a light-reflecting member 43 arranged on the support 1 to the side of the wavelength conversion member 22 and the light-emitting element 10. If necessary, a sealing member 50 may be provided on the upper surface of the wavelength conversion member 22. The sealing member 50 has a lens portion 51 that is circular in a plan view and semispherical in a cross section, and a flange portion 52 that extends outward from the lens portion 51. The lens portion 51 is circular in a plan view and semispherical in a cross section. The flange portion 52 also extends outward from the lens portion 51.

The wavelength conversion member 22 is larger than the light-emitting element 10 in plan view. A translucent member 30 is provided between the side surface of the light-emitting element 10 and the light-reflecting member 43, contacting the side surface of the light-emitting element 10 and a portion of the wavelength conversion member 22. The translucent member 30 includes a translucent joining member 32 provided between the light-emitting element 10 and the wavelength conversion member 22. The translucent joining member 32 can be an adhesive that joins the light-emitting element 10 and the wavelength conversion member 22. A portion of the translucent joining member 32 may extend into the corner formed by the side surface of the light-emitting element 10 and the main surface of the wavelength conversion member 22 facing the light-emitting element 10. As shown in FIG. 4, the cross-sectional shape of the extended translucent joining member 32 can be an inverted triangle extending toward the light-reflecting member 43. The translucent member 30 and the translucent joining member 32 can be made of a translucent resin. The support 1 is a member for mounting the light-emitting element 10, the sealing member 50, etc. on its upper surface. The support body 1 comprises an insulating base material and a conductive member 4, such as a wiring pattern, on the surface of which the light-emitting element is mounted. The light-reflecting member 43 is a member for covering the translucent member 30, the translucent bonding member 32, and the wavelength conversion member 22. For details of the light-emitting device of the second configuration example and the manufacturing method of the light-emitting device of the second configuration example described below, see, for example, the disclosure of Japanese Patent Application Laid-Open No. 2020-57756.

The wavelength conversion member of the light emitting device of the second configuration example includes a phosphor and a translucent material, similar to the wavelength conversion member of the light emitting device of the first configuration example. The wavelength conversion member is excited by light from the light emitting element and has an emission peak wavelength in the range of 585 nm to 610 nm, and includes a first phosphor that is a nitride phosphor having a composition within the composition formula represented by formula (1). The wavelength conversion member may not include any phosphors other than the first phosphor. The phosphor contained in the wavelength conversion member may include only a nitride phosphor having a composition within the composition formula represented by formula (1). The phosphor contained in the wavelength conversion member may be a first phosphor that is a nitride phosphor having a composition within the composition formula represented by formula (1), of 100% by mass of the phosphor contained in the wavelength conversion member. The translucent material may be the same as the translucent material used in the wavelength conversion member of the light emitting device of the first configuration example. Furthermore, the wavelength conversion member of the light emitting device of the second configuration example may contain, in addition to the phosphor and translucent material, a filler, colorant, and light diffusing material as needed, similar to the wavelength conversion member of the light emitting device of the first configuration example.

2. Method for manufacturing the light emitting device of the second configuration example An example of a method for manufacturing the light emitting device of the second configuration example will be described. The method for manufacturing the light emitting device of the second configuration example includes a step of arranging the light emitting elements, a step of preparing the wavelength conversion member, a step of forming the light transmissive member and the light transmissive joining member, a step of arranging the light reflecting member, and a step of arranging the sealing member, and may also include a singulation step of separating each unit area.

The light-emitting element placement process involves flip-chip mounting the light-emitting element on a pre-prepared support. The wavelength conversion member preparation process involves curing a wavelength conversion member composition containing a phosphor and a translucent material to form it into a plate, sheet, or layer, and then dividing it into pieces sized to be placed on the light-emitting element, thereby preparing a plate-, sheet-, or layer-shaped wavelength conversion member. The translucent member and translucent joining member formation process involves applying a translucent adhesive to the top surface of the light-emitting element, and joining the wavelength conversion member to the top surface of the light-emitting element. Any adhesive that protrudes from the interface between the light-emitting element and the wavelength conversion member extends from the side of the light-emitting element to the periphery of the wavelength conversion member, forming a fillet-like shape and then curing, thereby forming the translucent member and translucent joining member. The light-reflecting member placement process involves applying and curing a white resin on the top surface of the support so as to cover the side surfaces of the wavelength conversion member and the translucent member, and then placing the light-reflecting member. Finally, a sealing member is placed on the top surfaces of the wavelength conversion member and the light-reflecting member. This allows the light-emitting device of the second configuration example to be manufactured.

Figure 5 is a schematic perspective view showing a light-emitting device of a third configuration example. Figure 6 is a schematic cross-sectional view showing a light-emitting device of a third configuration example.

As shown in Figures 5 and 6, the light-emitting device 400 has an approximately rectangular parallelepiped exterior shape. The light-emitting device 400 includes a light-emitting element 10, a covering member 44, and a wavelength conversion member 23 containing phosphor 70. A translucent member 33 is provided between the side surface of the light-emitting element 10 and the covering member 44, contacting the side surface of the light-emitting element 10 and a portion of the wavelength conversion member 23. The translucent member 33 can be an adhesive that bonds the light-emitting element 10 and the wavelength conversion member 23. The covering member 44 is arranged to cover the lower surface of the light-emitting element 10, the electrodes 12p and 12n, the side surfaces of the translucent member 33, and the lower surface of the wavelength conversion member 23. The covering member 44 is light-reflective and directly or indirectly covers the side surface of the light-emitting element 10. The outer surface of the covering member 44, together with the side surface of the wavelength conversion member 23, constitutes the side surface of the light-emitting device 400. It is preferable that the outer surface of the covering member 44 and the side surface of the wavelength conversion member 23 are flush with each other. The covering member 44 covers the pair of positive and negative electrodes 12p, 12n of the light-emitting device 400 so that at least a portion of each is exposed. The lower surface of the covering member 44 forms part of the lower surface of the light-emitting device 400. For details of the light-emitting device of the third configuration example and its manufacturing method, please refer to the disclosure of Japanese Patent Application Laid-Open No. 2019-9429, for example.

3. Manufacturing Method of Light-Emitting Device of Third Configuration Example An outline of a manufacturing method of a light-emitting device of the third configuration example will be described. The manufacturing method of the light-emitting device of the third configuration example includes a step of preparing a wavelength conversion member, a step of arranging a light-transmitting member and a light-emitting element, a step of forming the light-transmitting member, and a step of forming a covering member, and may include a step of exposing electrodes after the step of forming the covering member, and may also include a step of separating into each unit region.

In the wavelength conversion member preparation process, a wavelength conversion member composition containing a phosphor and a translucent material is cured and formed into a plate, sheet, or layer. In the translucent member and light-emitting element arrangement process, a translucent adhesive is applied to the upper surface of the wavelength conversion member, and the light-emitting element is then arranged. In the translucent member formation process, the adhesive that protrudes from the interface between the light-emitting element and the wavelength conversion member extends from the side of the light-emitting element to the periphery of the wavelength conversion member, forming a fillet shape and then curing to form the translucent member. In the covering member formation process, a covering member is formed on the wavelength conversion member so as to embed the light-emitting element. By removing a portion of the covering member, the electrodes of the light-emitting element are exposed. If necessary, each unit area is cut into individual pieces. This allows the light-emitting device of the third configuration example to be manufactured.

Lighting fixtures can include at least one of the above-described light-emitting devices. The lighting fixture is configured with the above-described light-emitting device and may further include a reflective member, a protective member, an accessory device for supplying power to the light-emitting device, and the like. The lighting fixture may include multiple light-emitting devices. When the lighting fixture includes multiple light-emitting devices, the multiple light-emitting devices may be the same, or may include multiple light-emitting devices of different configurations. The lighting fixture may also include a driving device that can individually drive the multiple light-emitting devices and adjust the brightness of each individual light-emitting device. The lighting fixture may be used in any of a direct-mounted type, a recessed type, a hanging type, and the like. The lighting fixture may be a lighting fixture intended for outdoor installation such as a street light, a port, or a tunnel, or may be a lighting fixture intended for outdoor use such as a headlight, a flashlight, or a portable lantern using an LED, or may be a lighting fixture installed indoors or near an outdoor location such as a window.

Street Lights Street lights can include at least one of the light-emitting devices described above. FIG. 7 is a diagram showing an example of a street light. The street light 1000 includes a pole P installed on a sidewalk W or a roadway C and a support portion S for a light-emitting device Le. The support portion S includes a light-transmitting portion T that covers the periphery of the light-emitting device Le and is made of acrylic, polycarbonate, glass, or the like and transmits at least a portion of the light emitted by the light-emitting device Le. The street light 1000 can illuminate low places from high places using the light-emitting device Le installed on the support portion S that is integrated with the pole P. The street light is not limited to the example shown in FIG.

Streetlights can be pole-type streetlights with a pole that allows the support height to be set as desired, or bracket-type streetlights that support the support with a bracket instead of a pole, floodlights that illuminate from below, or landscape-integrated streetlights that are incorporated into landscape materials such as pillars or blocks.

The present invention will be explained in more detail below using examples. The present invention is not limited to these examples.

Nitride Phosphor Example 1
The raw materials used in the first heat treatment _{were Ba3N2 as} a compound containing Ba, _SrNu as a compound containing Sr (u is equivalent to 2/3, a mixture of _Sr2N and SrN), EuN as a compound containing Eu, _{and Si3N4} as a compound containing Si.

The raw material mixture was obtained by weighing and mixing each compound in a glove box with a nitrogen atmosphere containing essentially 100% nitrogen by volume so that the molar ratio of Ba:Sr:Eu:Si was 1.29:0.70:0.01:5.00.

The resulting raw material mixture was filled into a crucible and subjected to a first heat treatment at 1800°C for 5 hours in a nitrogen atmosphere containing essentially 100% nitrogen by volume, with a gas pressure of 0.92 MPa gauge pressure (1.02 MPa absolute pressure), to obtain a raw material sintered product. Because the resulting raw material sintered product may contain agglomerated particles, it was wet dispersed, sedimentation-classified, dehydrated, dried, and further sieved and classified using a sieve with a mesh size of approximately 10 μm to obtain a powdered raw material sintered product having a composition within the composition formula represented by formula (1) above.

The raw materials used in the first second heat treatment were the raw material fired product obtained in the first heat treatment, _Ba3N2 as a Ba-containing _compound , _SrNu as a Sr-containing compound (u is equivalent to 2/3, a mixture of _Sr2N and SrN), EuN as a Eu-containing compound, and _Si3N4 as a _Si -containing compound.

The starting composition was a mixture of the above compounds adjusted so that the molar ratio of Ba:Sr:Eu:Si was 1.29:0.70:0.01:5.00, and the raw material fired product obtained by the first heat treatment. The total amount of the compounds was 100 mass%, and the raw material fired product and the compounds were weighed and mixed in a glove box in a nitrogen atmosphere containing substantially 100% by volume of nitrogen, so that the content of the raw material fired product was 10 mass%.
The resulting first mixture was filled into a crucible and subjected to a first second heat treatment at 1770°C for 5 hours in a nitrogen atmosphere containing substantially 100% by volume of nitrogen, with a gas pressure of 0.92 MPa (absolute pressure of 1.02 MPa) at a gauge pressure of 1770°C to obtain a first fired product. Since the resulting first fired product may contain agglomerated particles, it was subjected to wet dispersion, sedimentation classification, dehydration, drying, and further sieving and classification using a sieve with an opening of approximately 15 µm to obtain a powdered first fired product having a composition included in the composition formula represented by formula (1).

Second and Third Second Heat Treatments The second second heat treatment was carried out in the same manner as the first second heat treatment described above, except that the obtained first fired product was replaced with the raw material fired product and sieved and classified using a sieve with a mesh size of approximately 25 μm, and a second fired product having a composition included in the composition formula represented by formula (1) was obtained.
The obtained second fired product was replaced with the raw material fired product, and a third second heat treatment was carried out in the same manner as the first second heat treatment described above, except that the heat treatment temperature was set to 1500°C for 10 hours and sieving classification was carried out using a sieve with an opening of approximately 35 μm, thereby obtaining a third fired product having a composition included in the composition formula represented by formula (1). The obtained third fired product was obtained as the nitride phosphor of Example 1.

Example 2
The nitride phosphor of Example 2 was obtained in the same manner as Example 1, except that the feed composition of the raw material mixture subjected to the first heat treatment was such that the molar ratio of Ba:Sr:Eu:Si was 1.58:0.40:0.02:5.00, and the feed compositions of the mixtures subjected to the first to third second heat treatments were the same as the feed composition of the raw material mixture.

Comparative Example 1
The nitride phosphor of Comparative Example 1 was obtained in the same manner as in Example 1, except that the feed composition of the raw material mixture subjected to the first heat treatment was set to a molar ratio of Ba:Sr:Eu:Si of 1.84:0.12:0.04:5.00, and the feed compositions of the mixtures subjected to the first to third second heat treatments were set to the same as the feed composition of the raw material mixture.

A composition analysis was performed on the nitride phosphors of Examples 1 and 2, and the nitride phosphor of Comparative Example 1.

Composition Analysis Composition analysis was performed on the nitride phosphors according to Examples 1 and 2 and the nitride phosphor according to Comparative Example 1 by ICP optical emission spectrometry using an inductively coupled plasma optical emission spectrometer (manufactured by Perkin Elmer), and the molar ratio of each element in 1 mole of the nitride phosphor composition was determined. The results are shown in Table 1. The molar ratio values shown in Table 1 are values calculated from the analysis results, assuming the molar ratio of Si to be 5. Table 1 also lists the values of v, w, x, and y in the composition formula represented by formula (1) above, based on the molar ratio of each element in 1 mole of the nitride phosphor composition.

Regarding the analyzed composition of each nitride phosphor, the nitride phosphors of Examples 1 and 2 had a composition included in the composition formula represented by formula (1) above. For the nitride phosphor of Comparative Example 1, in the composition formula represented by formula (1) above, the product of the variable w representing the molar ratio of Sr and 2 was less than 0.08, and the nitride phosphor did not have a composition included in the composition formula represented by formula (1) above.

The nitride phosphors of Examples 1 and 2, and the nitride phosphor of Comparative Example 1 were evaluated as follows. The results are shown in Table 2.

Volume Average Particle Size The volume average particle size at a cumulative frequency of 50% on a volume basis was measured for the nitride phosphors according to Examples 1 and 2 and the nitride phosphor according to Comparative Example 1 using a laser diffraction/scattering particle size distribution analyzer (MASTER SUZER 2000, manufactured by MALVERN).

Emission characteristics (emission peak wavelength, full width at half maximum, internal quantum efficiency)
For the nitride phosphors according to Examples 1 and 2, and the nitride phosphor according to Comparative Example 1, excitation light with an emission peak wavelength of 450 nm was irradiated onto each nitride phosphor using a quantum efficiency measurement device (QE-2000, manufactured by Otsuka Electronics Co., Ltd.), and the emission spectrum was measured at room temperature (25°C ± 5°C). From the emission spectrum of each nitride phosphor, the emission peak wavelength (nm) at which the emission intensity was maximum and the full width at half maximum (FWHM) (nm) were determined. Furthermore, the internal quantum efficiency (%) was determined from the emission spectrum of each nitride phosphor. FIG. 8 shows the emission spectra of the nitride phosphors according to Examples 1 and 2, and the nitride phosphor according to Comparative Example 1.

Temperature characteristic evaluation (phosphor)
The nitride phosphors according to Examples 1 and 2, and the nitride phosphor according to Comparative Example 1 were excited with light from an excitation light source having an emission peak wavelength of 450 nm at 25°C (room temperature) and 300°C, and their emission spectra were measured using a spectrofluorometer (F-4500, manufactured by Hitachi High-Tech Science Corporation). For each nitride phosphor, the energy value of the emission spectrum measured at 25°C was measured, and the emission energy of the nitride phosphor according to Comparative Example 1 was defined as 100%, and the emission energy of the nitride phosphors according to Examples 1 and 2 was calculated as relative emission energy (%). Furthermore, the emission energy value of the emission spectrum of each nitride phosphor measured at 25°C was defined as 100%, and the emission energy value of the emission spectrum of each nitride phosphor measured at 300°C was calculated, and the temperature characteristics were evaluated as the emission energy maintenance rate (%) with temperature change. The energy value was calculated from the integral value of the emission spectrum in the wavelength range of 470 nm to 730 nm at each temperature.

1/10 Decay Time For the nitride phosphors according to Examples 1 and 2, and the nitride phosphor according to Comparative Example 1, excitation light having an emission peak wavelength of 442 nm was irradiated onto each nitride phosphor, and the time when the irradiated excitation light was shut off was set as the reference time. The time over which the emission intensity of each nitride phosphor changed from the time when the excitation light was shut off was measured using a compact fluorescence lifetime analyzer (Quantaurus-Tau, manufactured by Hamamatsu Photonics K.K.). The emission intensity when the excitation light was shut off was set as 100%, and the time when the emission intensity became 1/10 of that when the excitation light was shut off was measured as the 1/10 decay time. Fig. 9 shows a graph showing the relationship between emission energy (%) and decay time (µs) for the nitride phosphors according to Examples 1 and 2, and the nitride phosphor according to Comparative Example 1.

As shown in Tables 1 and 2, the nitride phosphors of Examples 1 and 2 had compositions contained in the composition formula represented by formula (1) above, and had luminescence characteristics with an internal quantum efficiency of 90% or more.

As shown in Table 2 and Figure 8, the nitride phosphors of Examples 1 and 2 and the nitride phosphor of Comparative Example 1 had emission peak wavelengths in the range of 585 nm or more and 610 nm or less.

As shown in Table 2 and Figure 9, the nitride phosphors of Examples 1 and 2 had a 1/10 decay time of 2.49 μs or more, and even when the temperature rose to 300°C, the luminescence energy retention rate was 60% or more, maintaining luminescence intensity and exhibiting good temperature characteristics. Furthermore, the nitride phosphor of Example 1 had a longer 1/10 decay time than the nitride phosphor of Example 2, and even when the temperature rose to 300°C, the luminescence energy retention rate was higher, exhibiting good temperature characteristics.

The nitride phosphor of Comparative Example 1 had a 1/10 decay time of 2.48 μs, which was shorter than the 1/10 decay time of Examples 1 and 2. Furthermore, when the temperature rose to 300°C, the luminous energy retention rate was 37.4%, which was lower than the luminous energy retention rates of Examples 1 and 2, and the temperature characteristics were not improved compared to Examples 1 and 2.

Example of Light-Emitting Device Example 1-1
The light emitting device of the second configuration example was manufactured. For the light emitting device of the second configuration example, see FIGS.

Light-emitting element placement process: A ceramic substrate made of aluminum nitride was used as the support 1. The light-emitting element 10 used was a light-emitting element 10 in which nitride-based semiconductor layers with an emission peak wavelength of 450 nm were stacked. The light-emitting element 10 had a planar shape of approximately 1.0 mm square and a thickness of approximately 0.11 mm. The light-emitting element was placed so that the light-emitting surface faced the sealing member, and was flip-chip mounted using bumps made of Au conductive member 4.

Wavelength Conversion Member Preparation Process Silicone resin was used as the translucent material constituting the wavelength conversion member 22. The nitride phosphor of Example 1 shown in Table 1 was used as the first phosphor. The phosphor contained in the wavelength conversion member was the first phosphor alone. The wavelength conversion member composition was blended so that the correlated color temperature of the mixed light of the light from the light emitting element 10 and the light from the first phosphor was approximately 1800 K per 100 parts by mass of the translucent material. The wavelength conversion member composition was blended with 2 parts by mass of aluminum oxide as a filler per 100 parts by mass of silicone resin. Next, the prepared wavelength conversion member composition was heated at 180°C for 2 hours to harden it into a sheet shape, thereby preparing individualized sheet-like wavelength conversion members 22 having a planar shape approximately 1.6 mm square, approximately 0.1 mm larger in length and width than the planar shape of the light emitting element 10, and a thickness of approximately 150 μm.

Step of forming light-transmitting member and light-transmitting joining member A light-transmitting adhesive, phenyl silicone resin, was applied to the upper surface of the light-emitting element 10, and the wavelength conversion member 22 was joined thereto. Further, a light-transmitting adhesive was applied to the interface between the light-emitting element 10 and the wavelength conversion member 22 and cured at 150°C for 4 hours, thereby forming a light-transmitting member 30 and a light-transmitting joining member 32 that were hardened in a fillet shape so as to extend from the side surface of the light-emitting element 10 to the periphery of the wavelength conversion member 22.

Light-reflecting member arrangement process A composition for a light-reflecting member was prepared, which contained dimethyl silicone resin and titanium oxide particles with an average particle size (catalog value) of 0.28 μm, with 60 parts by mass of titanium oxide particles per 100 parts by mass of dimethyl silicone resin. The composition for a light-reflecting member, which is a white resin, was arranged on the upper surface of support 1 so as to cover the side surfaces of wavelength conversion member 22 and light-transmitting member 30, and was cured to form light-reflecting member 43.

Sealing member placement process Finally, a sealing member 50 was placed, which was formed by curing a phenyl silicone resin and had a lens portion 51 that was circular in plan view and semispherical in cross section, and a flange portion 52 that extended outward from the outer periphery of the lens portion 51, and a light-emitting device 300 of a second configuration example was manufactured, which emits light with a correlated color temperature of around 1800K.

Example 2-1
A light emitting device of a second configuration example was manufactured in the same manner as in Example 1-1, except that the nitride phosphor according to Example 2 in Table 1 was used as the first phosphor.

Comparative Example 1-1
A light emitting device of a second configuration example was manufactured in the same manner as in Example 1-1, except that the nitride phosphor according to Comparative Example 1 in Table 1 was used as the first phosphor.

The following measurements were performed on each light-emitting device. The results are shown in Table 3.

Emission spectrum of the light-emitting device (chromaticity coordinates (x, y), correlated color temperature (K), color deviation duv, relative luminous flux (%))
The emission spectrum of each light-emitting device was measured using an optical measurement system combining a spectrophotometer (PMA-12, manufactured by Hamamatsu Photonics KK) and an integrating sphere.
From the emission spectrum of each light-emitting device, the chromaticity coordinates (x, y) on the CIE chromaticity diagram of CIE 1931, and the correlated color temperature (K) and color deviation duv were measured in accordance with JIS Z8725. The luminous flux of the light-emitting device according to Comparative Example 1-1 was set to 100%, and the luminous flux of the light-emitting devices according to Examples 1-1 and 2-1 was expressed as a relative value (relative luminous flux (%)).

Temperature characteristic evaluation (light emitting device)
For the light-emitting devices according to Examples 1-1 and 2-1, and each light-emitting device according to Comparative Example 1-1, at temperatures of 25 ° C. (room temperature) and 150 ° C., each light-emitting device was placed in a thermostatic chamber (PG-2, manufactured by ESPEC Corporation) for 1 hour (1 hour after the thermostatic chamber set temperature was reached), and a spectrophotometer (PMA-12 C10027-02, manufactured by Hamamatsu Photonics K.K.) was used to apply a voltage with a pulse width of 0.05 msec and a pulse period of 5 msec, and the emission spectrum was measured. For each light-emitting device, the luminous flux of each light-emitting device measured at 25 ° C. was taken as 100%, and the luminous flux value of each light-emitting device measured at 150 ° C. was determined, and the temperature characteristics were evaluated as the luminous flux maintenance rate (%) of the light-emitting device during temperature change.

The light-emitting devices of Examples 1-1 and 2-1 and the light-emitting device of Comparative Example 1-1 emitted orange to red light within the above-mentioned region A1.

The light-emitting devices of Examples 1-1 and 2-1, and the light-emitting device of Comparative Example 1-1 all emitted light with a correlated color temperature in the range of 1200K to 2000K inclusive on the CIE 1931 chromaticity diagram, and with a color deviation duv from the blackbody radiation locus measured in accordance with JIS Z8725 in the range of -0.020 to 0.020 inclusive.

The light-emitting devices of Examples 1-1 and 2-1 had a higher relative luminous flux than the light-emitting device of Comparative Example 1-1. Furthermore, the light-emitting devices of Examples 1-1 and 2-1, which used the nitride phosphors of Examples 1 and 2, which had a 1/10 decay time of 2.49 μs or longer, had a luminous flux maintenance rate of 55% or higher even when the temperature rose to 150°C, and also had good temperature characteristics as light-emitting devices.

The light-emitting device of one embodiment of the present invention can be used as a light source for lighting fixtures intended for outdoor use, such as street lights, lighting fixtures installed outdoors in ports and tunnels, headlights, flashlights, and portable lanterns that use LEDs, as well as for lighting fixtures installed indoors in locations close to the outdoors, such as near entrances and windows.

1: Support, 2: First lead, 3: Second lead, 4: Conductive member, 10: Light-emitting element, 12p, 12n: Electrodes, 21, 22, 23: Wavelength conversion member, 30, 33: Light-transmitting member, 32: Light-transmitting joining member, 41: Molded body, 42: Resin portion, 43: Light-reflecting member, 44: Covering member, 50: Sealing member, 51: Lens portion, 52: Flange portion, 60: Wire, 70: Phosphor, 71: First phosphor, 72: Second phosphor, 100, 300, 400: Light-emitting device, 1000: Street light, C: Roadway, Le: Light source, P: Pole, S: Support portion, T: Light-transmitting portion, W: Sidewalk.

Claims (9)

A nitride phosphor having a composition included in a composition formula represented by the following formula (1), and having an emission peak wavelength in the range of 585 nm or more and 610 nm or less in an emission spectrum when irradiated with light having an emission peak wavelength in the range of 350 nm or more and 500 nm or less, and having a decay time of 2.49 μs or more at which the emission intensity becomes 1/10 of the reference intensity, where the emission intensity when the irradiated excitation light is blocked is taken as a reference intensity.
(Ba _v Sr _w Eu _x ) ₂ Si ₅ N _8-y (1)
(In formula (1), v, w, x, and y satisfy the following relationships: 0.50≦v≦ 0.78 , 0.13 ≦w≦0.50, 0.001≦x≦ 0.018 , 0.9<v+w+x≦1.0, and 0≦y≦0.5, respectively.) The nitride phosphor according to claim 1 , wherein the decay time is 2.91 μs or less. 3. The nitride phosphor according to claim 1, wherein the volume average particle size measured by a laser diffraction/scattering particle size distribution measurement method is in the range of 10 μm to 40 μm. 4. The nitride phosphor according to claim 1, which has an internal quantum efficiency of 85% or more when excited with light having a wavelength of 450 nm. 5. A light emitting device comprising: a wavelength conversion member containing the nitride phosphor according to claim 1; and a light emitting element having an emission peak wavelength in the range of 350 nm to 500 nm, wherein the wavelength conversion member is disposed on the light emitting element. 6. The light emitting device according to claim 5, wherein in the xy chromaticity coordinate system of the CIE 1931 chromaticity diagram, chromaticity coordinates (x, y) are (x=0.510, y=0.400) as a first point, (x=0.510, y=0.440) as a second point, (x=0.600, y=0.400) as a third point, and (x=0.600, y=0.360) as a fourth point, and the light emitting device emits light within a region defined by a first line connecting the first point and the second point, a second line connecting the second point and the third point, a third line connecting the third point and the fourth point, and a fourth line connecting the fourth point and the first point . 6. The light emitting device according to claim 5, which emits light having a correlated color temperature in the range of 1200 K or more and 2000 K or less on the CIE 1931 chromaticity diagram, and a color deviation duv from the blackbody radiation locus measured in accordance with JIS Z8725 in the range of -0.020 or more and 0.020 or less. A lamp comprising the light-emitting device according to any one of claims 5 to 7. A street light comprising the light emitting device according to any one of claims 5 to 7.