Wavelength conversion member and light-emitting device

Abstract

A wavelength conversion member of the present invention includes a phosphor plate including an inorganic base material and a phosphor dispersed in the inorganic base material, and a reflective multilayer film which is formed on one surface of the phosphor plate and in which a plurality of inorganic material films having different refractive indexes is laminated, the wavelength conversion member being configured so that in L*a*b* color coordinates on the surface of the reflective multilayer film formed on the one surface of the phosphor plate when measured in accordance with JIS Z 8781-4, the a* value satisfies -20 to 0, and / or the b* value satisfies 20 to 60.

Description

Technical Field

[0001] The present invention relates to a wavelength conversion member and a light emitting device.

Background Art

[0002] Various developments have been made on light emitting devices so far. As this type of technology, for example, the technology described in Patent Document 1 is known. Patent Document 1 describes a semiconductor light emitting element, a plate-shaped light wavelength conversion member (fluorescent ceramics) provided so as to face the light emitting surface of the semiconductor light emitting element and converting the wavelength of the light emitted by the semiconductor light emitting element, and at least one of the surface facing the semiconductor light emitting element and the side surface of the surface of the plate-shaped light wavelength conversion member. A light emitting device including a filter layer formed on the surface to transmit the light emitted from the semiconductor light emitting element and reflect the light wavelength-converted by the light wavelength conversion member is described (Claim 1 of Patent Document 1, paragraph 0037, etc.).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, as a result of the study by the present inventor, it has been found that there is room for improvement in terms of light emission intensity in the light wavelength conversion member having the filter layer described in Patent Document 1 on the excitation light irradiation surface side.

Means for Solving the Problems

[0005] The inventor further studied and found that by forming a reflective multilayer film on the excitation light irradiation surface side of a phosphor plate containing an inorganic base material and a phosphor dispersed in the inorganic base material, and appropriately controlling the color tone on the surface of the reflective multilayer film in this laminated state, the light emission intensity in the phosphor plate can be increased. Based on such findings, through further intensive research, it was found that by adopting a reflective multilayer film in which the a * , , , , , , * , a * b * color coordinates are used and the a * value and / or the b * value is within a predetermined range, the light emission intensity of the phosphor plate when excitation light is irradiated through such a reflective multilayer film can be improved, and the present invention has been completed.

[0006] According to one aspect of the present invention, the following wavelength conversion member and a light emitting device using the same are provided. 1. A wavelength conversion member comprising: a phosphor plate including an inorganic base material and a phosphor dispersed in the inorganic base material; and a reflective multilayer film formed on the surface on one side of the phosphor plate and having a plurality of inorganic films with different refractive indexes laminated thereon, wherein in the L * a * b * color coordinates measured in accordance with JIS Z 8781-4 on the surface of the reflective multilayer film formed on the one side of the phosphor plate, the a * value is -20 or more and 0 or less, and / or the b * value satisfies 20 or more and 60 or less. 2. The wavelength conversion member according to 1., wherein in the diffuse reflection spectrum on one side of the phosphor plate on which the reflective multilayer film is formed, the diffuse reflectance at 450 nm is 35% or less. 3. The wavelength conversion member according to 1. or 2., wherein A wavelength conversion member wherein, in the diffuse reflectance spectrum on one side of the phosphor plate on which the reflective multilayer film is formed, the diffuse reflectance at 600 nm is 82% or more. 4. A wavelength conversion member described in any one of 1. to 3., A wavelength conversion member wherein, when blue excitation light is irradiated from one side on which the reflective multilayer film is formed, the emission spectrum detected from the other side of the phosphor plate located opposite the reflective multilayer film has a peak wavelength in the range of 580 nm to 620 nm. 5. A wavelength conversion member described in any one of 1. to 4., A wavelength conversion member wherein the Rsm measured on one side of the phosphor plate in accordance with JIS B 0031:1994 is 60 μm or less. 6. A wavelength conversion member described in any one of items 1 to 5, A wavelength conversion member comprising a reflective multilayer film having a periodic stacked structure in which at least one of a high refractive index inorganic film and a low refractive index inorganic film is stacked with substantially the same thickness. 7. The wavelength conversion member described in 6. A wavelength conversion member comprising an asymmetric laminated structure in which the reflective multilayer film is arranged adjacent to the periodic laminated structure, and at least one of the high refractive index inorganic film and the low refractive index inorganic film is laminated with different thicknesses. 8. A wavelength conversion member described in any one of 1. to 7., A wavelength conversion member comprising one of the following phosphors: an α-type sialon phosphor, a (Ba,Sr,Ca)2Si5N8 phosphor, a mixture of a YAG phosphor and a SCASN phosphor, and a SCASN phosphor. 9. A wavelength conversion member described in any one of 1. to 7., A wavelength conversion member wherein the inorganic matrix material includes alumina or a spinel-based compound. 10. A light-emitting device comprising a wavelength conversion member described in any one of items 1 to 9, and a light source. 11. The light-emitting device described in 10. A light-emitting device that serves as a turn signal. [Effects of the Invention]

[0007] According to the present invention, a wavelength conversion member with excellent light emission intensity and a light-emitting device using the same are provided. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic cross-sectional view showing an example of the configuration of the wavelength conversion member of this embodiment. [Figure 2] This is a schematic cross-sectional view showing an example of the configuration of the light-emitting device of this embodiment. [Figure 3] These are SEM images of Example 2 and Comparative Example 3. [Modes for carrying out the invention]

[0009] Embodiments of the present invention will be described below with reference to the drawings. In all drawings, similar components are denoted by the same reference numerals, and their descriptions are omitted as appropriate. Also, the drawings are schematic diagrams and do not correspond to the actual dimensional ratios.

[0010] The outline of the wavelength conversion member of this embodiment will be described.

[0011] The wavelength conversion member of this embodiment comprises a phosphor plate containing an inorganic matrix and a phosphor dispersed in the inorganic matrix, and a reflective multilayer film formed on one surface of the phosphor plate, which is made up of multiple inorganic films with different refractive indices stacked on top of each other.

[0012] The reflective multilayer film functions as a dichroic filter layer, utilizing optical interference to transmit light in a specific wavelength range (blue excitation light emitted from the light source) and reflect light in the remaining wavelength range (luminescence emitted from the phosphor after the blue excitation light has been wavelength-converted). This makes it possible to efficiently extract the luminescence emitted from the phosphor from the other side of the phosphor plate.

[0013] The wavelength conversion member of this embodiment uses L as an indicator of color on the surface of the reflective multilayer film formed on one side of the phosphor plate. * a* b * Using color coordinates, the a within it * value and / or b * The value must be within a specified range. L * a * b * Color coordinates can be measured in accordance with JIS Z 8781-4. L * a * b * The color coordinates are measured on, firstly, the surface of the reflective multilayer film formed on one side of the phosphor plate (i.e., the reflective multilayer film surface on one side of the phosphor plate), and secondly, the surface on the other side of the phosphor plate opposite the reflective multilayer film (the exposed surface of the phosphor plate if no functional film such as a reflective film is formed). The wavelength conversion member of this embodiment has L on the reflective multilayer film surface. * a * b * The color coordinates are configured to satisfy the following first condition, or the L of the reflective multilayer surface relative to the exposed surface. * a * b * The difference in color coordinates is configured to satisfy the second condition below. This further increases the emission intensity of the wavelength conversion member. Although the detailed mechanism is unclear, it is thought that because the layered structure of the reflective multilayer film can be formed on one surface of the phosphor plate while maintaining an appropriate state, the reduction in the dichroic filtering ability due to the reflective multilayer film can be sufficiently suppressed, thereby improving the emission intensity.

[0014] L * a * b * The first condition for color coordinates is a * The value is between -20 and 0, and / or b * The value satisfies the condition of being between 20 and 60. In the first condition above, a * The value is -20 or greater and 0 or less, preferably -15 or greater and 0 or less, more preferably -10 or greater and -1 or less. On the other hand, b *The value is 20 to 60, preferably 23 to 58, and more preferably 25 to 55. Also, L * The value is, for example, 80 or more and 100 or less, preferably 85 or more and 100 or less, and more preferably 90 or more and 99 or less.

[0015] L on the reflective multilayer surface * a * b * The values ​​are L1 * Value, a1 * Value, b2 * The value is L on the other side of the phosphor plate opposite the reflective multilayer film (the exposed surface of the phosphor plate if no other functional layer is formed). * a * b * The values ​​are L2 * Value, a2 * Value, b2 * Set this as the value. L * a * b * The second condition for the color coordinates is (a1 * Value -a2 * The value) is -30 or greater and -7 or less, and / or (b1 * Value -b2 * The value satisfies the condition that it is between 0 and 50 (inclusive). In the second condition above, (a1 * Value -a2 * The value is -30 or more and -7 or less, preferably -25 or more and -8 or less, more preferably -20 or more and -9 or less. On the other hand, (b1 * Value -b2 * The value is 0 to 50, preferably 5 to 45, and more preferably 10 to 40. Also, (L1 * Value -L2 * The value is, for example, 0 to 20, preferably 0 to 15, and more preferably 1 to 10.

[0016] In this embodiment, for example, by appropriately selecting the type and amount of each component contained in the reflective multilayer film, the manufacturing method of the reflective multilayer film, etc., the L of the reflective multilayer film is * a * b* It is possible to control the value. Among these, for example, grinding and polishing one surface of the phosphor plate (the surface on which the reflective multilayer film is formed) using a grinding wheel or abrasive grains of a predetermined grit size, and appropriately selecting the layered structure of the reflective multilayer film, are ways to control the L of the reflective multilayer film. * a * b * These are elements used to set the value to a desired numerical range.

[0017] The wavelength conversion member of this embodiment can be used in light-emitting devices for various applications, but for example, it can be used in vehicle lighting fixtures and lighting fixtures for non-vehicle applications. Among vehicle lighting fixtures, it is preferable to use it in turn signals (sometimes called turn signals, turn lamps, or hazard lamps). Vehicles include automobiles, motorcycles, and railway vehicles.

[0018] The configuration of the wavelength conversion member in this embodiment will be described in detail.

[0019] Figure 1 is a schematic cross-sectional view showing an example of the configuration of the wavelength conversion member 10. The wavelength conversion member 10 comprises a phosphor plate 20 and a reflective multilayer film 30 formed on one surface 21 of the phosphor plate 20. An excitation light source is placed on the side of the reflective multilayer film 30 that is formed on the wavelength conversion member 10, and excitation light is irradiated onto it.

[0020] (Phosphor plate) The phosphor plate 20 is composed of a plate-shaped composite in which phosphors are dispersed in an inorganic matrix. The composite material constituting the phosphor plate contains a mixture of phosphor and an inorganic matrix. Specifically, it may have a structure in which the phosphor is dispersed in a sintered product of the compounds constituting the inorganic matrix. This phosphor may be uniformly dispersed in the inorganic matrix in a particulate state.

[0021] The inorganic matrix may be the main component in the composite. In this case, the matrix content may be, for example, 50 vol% or more, preferably 60 vol% or more, on a volume basis, relative to the composite.

[0022] The inorganic base material may be composed of a sintered product of at least one of a sintered product of Al2O3, a sintered product of SiO2, and a spinel-based compound M 2x Al 4-4x O 6-4x (where M is at least one of Mg, Mn, and Zn, and 0.2 < x < 0.6). These may be used alone or in combination of two or more. Among these, from the viewpoints of thermal properties and transparency, the base material may be composed of a sintered product containing alumina or a spinel-based compound.

[0023] [[ID=[]]

[0024] The sintered product of SiO2 may be composed of a glass matrix. As the glass matrix, silica glass or the like is used.

[0025] The sintered product containing a spinel-based compound is usually obtained by mixing and sintering a powder of a metal oxide represented by the general formula MO (M is at least one of Mg, Mn, and Zn) and a powder of Al2O3. Spinel, stoichiometrically, has a composition represented by x = 0.5 (that is, the general formula MAl2O4). However, depending on the ratio of the amount of MO and the amount of Al2O3 in the raw materials, a spinel-based compound having a non-stoichiometric composition in which MO or Al2O3 is excessively solid-dissolved is obtained. The sintered body containing the spinel-based compound represented by the above general formula is relatively transparent. Therefore, excessive scattering of light in the phosphor plate is suppressed. Further, from the viewpoint of transparency, it is preferable to use a spinel-based compound in which M in the above general formula is Mg. [[ID=[]]

[0026] [[ID=[]] ​The phosphor can be any known phosphor depending on the application, but may include at least one of the following: α-type sialon phosphor, (Ba,Sr,Ca)2Si5N8 phosphor, a mixture of YAG phosphor and SCASN phosphor, and SCASN phosphor.

[0027] For example, when blue excitation light with a wavelength of 450 nm is irradiated from one side 21 where the reflective multilayer film 30 is formed, the emission spectrum detected from the other side 22 of the phosphor plate 20 located opposite the reflective multilayer film 30 is measured. By using the phosphor plate 20 containing the phosphor exemplified above, it is possible to configure the emission spectrum so that the peak wavelength is in the range of 580 nm to 620 nm. Furthermore, an α-type sialon phosphor may be used from the viewpoint of controlling the peak wavelength to 585 nm to 605 nm, a (Ba,Sr,Ca)2Si5N8 phosphor may be used from the viewpoint of controlling the peak wavelength to 605 nm to 620 nm, a mixture of YAG phosphor and SCASN phosphor may be used from the viewpoint of controlling the peak wavelength to 580 nm to 620 nm, and a SCASN phosphor may be used from the viewpoint of controlling the peak wavelength to around 620 nm. Furthermore, when using YAG phosphor alone as the phosphor, the peak wavelength will be approximately 540-570 nm.

[0028] As the α-type sialon phosphor, one containing an α-type sialon phosphor that contains the element Eu represented by the following general formula (1) is used. (M) m(1-x) / p (EU) mx / 2 (Si) 12-(m+n) (Al) m+n (O) n (N) 16-n ·General formula (1)

[0029] In the above general formula (1), M represents one or more elements selected from the group consisting of Li, Mg, Ca, Y, and lanthanide elements (excluding La and Ce), p represents the valence of the M element, 0 < x < 0.5, 1.5 ≤ m ≤ 4.0, and 0 ≤ n ≤ 2.0. n may be, for example, 2.0 or less, 1.0 or less, or 0.8 or less. Generally, the one with M being Ca is called a Ca-α type sialon phosphor.

[0030] The solid solution composition of α-type sialon is such that m Si-N bonds in the unit cell of α-type silicon nitride (Si 12 N 16 ) are replaced by Al-N bonds, and n Si-N bonds are replaced by Al-O bonds. In order to maintain electrical neutrality, m / p cations (M, Eu) penetrate and dissolve into the crystal lattice and are represented as in the above general formula. In particular, when Ca is used as M, α-type sialon is stabilized in a wide composition range, and by replacing a part of it with Eu as the luminescence center, a phosphor that is excited by light in a wide wavelength range from ultraviolet to blue and exhibits visible light emission from yellow to orange can be obtained.

[0031] Due to the second crystal phase different from α-type sialon and the inevitably present amorphous phase, the solid solution composition of α-type sialon cannot be strictly defined. α-type sialon may contain β-type sialon, aluminum nitride or its polytypoid, Ca2Si5N8, CaAlSiN3, etc. as other crystal phases.

[0032] As a method for producing α-type sialon phosphor, there is a method of heating and reacting a mixed powder composed of silicon nitride, aluminum nitride, and a compound of the penetrating and dissolving element in a high-temperature nitrogen atmosphere. In the heating process, a part of the constituent components forms a liquid phase, and substances move in this liquid phase to generate an α-type sialon solid solution. The α-type sialon phosphor after synthesis is formed by sintering a plurality of equiaxed primary particles to form massive secondary particles. The primary particles in the present embodiment refer to the smallest particles in which the crystal orientation within the particles is the same and can exist independently.

[0033] As the (Ba,Sr,Ca)2Si5N8 phosphor, a phosphor doped with Eu element is used.

[0034] As an example of an SCASN phosphor, a phosphor in which the element Eu is activated in a matrix crystal of alkaline earth silicatride represented by (Sr,Ca)AlSiN3 is used.

[0035] The lower limit of the average particle diameter of the phosphor is preferably 1 μm or more, and more preferably 2 μm or more. This can increase the luminescence intensity. The upper limit of the average particle diameter of the phosphor is preferably 30 μm or less, and more preferably 20 μm or less. The average particle diameter of the phosphor is the dimension of the secondary particles mentioned above. By setting the average particle diameter to 5 μm or more, the transparency of the composite can be further increased. On the other hand, by setting the average particle diameter of the phosphor to 30 μm or less, the occurrence of chipping can be suppressed when cutting the phosphor plate with a dicer or the like.

[0036] Here, the average particle diameter of the phosphor refers to the particle diameter D50 at which 50% of the cumulative passing fraction (cumulative passing fraction) from the small particle size side is obtained in the volume-based particle size distribution obtained by the laser diffraction scattering particle size distribution method (Beckman Coulter, LS13-320).

[0037] The lower limit of the phosphor content is, for example, 5 vol% or more, preferably 10 vol% or more, and more preferably 15 vol% or more, in 100 vol% of the composite constituting the phosphor plate 20. This makes it possible to increase the luminescence intensity of the thin phosphor plate. It also makes it possible to improve the light conversion efficiency of the phosphor plate. On the other hand, the upper limit of the phosphor content is, for example, 60 vol% or less, preferably 50 vol% or less, and more preferably 40 vol% or less, of 100 vol% of the composite. This suppresses a decrease in the thermal conductivity of the phosphor plate.

[0038] The thickness of the phosphor plate 20 can be appropriately set depending on the application. The lower limit of the thickness of the phosphor plate 20 is, for example, 50 μm or more, preferably 80 μm or more, and more preferably 100 μm or more. The upper limit of the thickness of the phosphor plate 20 is, for example, 1 mm or less, preferably 500 μm or less, and more preferably 300 μm or less. By keeping it within this range, the light extraction efficiency can be improved and the luminescence intensity can be increased.

[0039] The planar shape of the phosphor plate 20, as viewed from a direction perpendicular to one surface 21, may be circular or rectangular. By making the planar shape of the phosphor plate 20 circular during transport, the occurrence of chipping and cracking at the corners can be suppressed compared to the case of a rectangular shape, thereby improving durability and transportability.

[0040] The surface of one side 21 of the phosphor plate 20 may be configured such that the upper limit of Rsm, measured according to JIS B 0031:1994, is, for example, 60 μm or less, preferably 55 μm or less, and more preferably 50 μm or less. On the other hand, the lower limit of Rsm is not particularly limited, but may be 1 μm or more. Here, Rsm refers to the average length from a convex point to an adjacent concave point on the surface. The other surface 22 of the phosphor plate 20 may be configured such that Rsm satisfies the above numerical range, but it does not have to.

[0041] (Reflective multilayer film) The reflective multilayer film 30 is composed of a dielectric multilayer film in which multiple inorganic films with different refractive indices are stacked. In other words, the reflective multilayer film 30 is composed of a stacked film in which high refractive index inorganic films and low refractive index inorganic films are alternately stacked. Examples of materials for high refractive index inorganic films include titanium oxide, niobium oxide, lanthanum oxide, tantalum oxide, yttrium oxide, gadolinium oxide, tungsten oxide, hafnium oxide, aluminum oxide, and silicon nitride. Examples of materials for low refractive index inorganic films include silicon dioxide.

[0042] The number of inorganic film layers in the reflective multilayer film 30 is not particularly limited, but may be, for example, 2 to 100 layers, preferably 10 to 60 layers.

[0043] The thickness of the reflective multilayer film 30 is not particularly limited, but may be, for example, 0.1 to 20 μm, preferably 0.5 μm to 5 μm.

[0044] The reflective multilayer film 30 may have a periodic stacked structure in which at least one of a high refractive index inorganic film and a low refractive index inorganic film, or each of both, is stacked with substantially the same thickness. In a periodic stacked structure, the thicknesses of the high-refractive-index inorganic film and the low-refractive-index inorganic film do not need to be approximately the same; they may be different. "Approximately the same" means that their thicknesses are within a range of ±10% of each other. The periodic stacked structure may be located near the center of the reflective multilayer film 30. Furthermore, the total number of layers of high-refractive-index inorganic films and low-refractive-index inorganic films in the periodic stacked structure may be, for example, 4 to 30 layers, or 6 to 20 layers.

[0045] The thickness of each inorganic layer can be measured from a graph created by plotting the brightness using a STEM cross-sectional image of the reflective multilayer film 30.

[0046] Furthermore, the reflective multilayer film 30 may include an asymmetrical stacked structure arranged adjacent to one or both of the periodic stacked structures. In the asymmetrical stacked structure, at least one of the high refractive index inorganic film and the low refractive index inorganic film, or each of both, is stacked with different thicknesses. However, in an asymmetrical stacked structure, the thicknesses of the high-refractive-index inorganic film and the low-refractive-index inorganic film do not need to be approximately the same; they may be different.

[0047] The reflective multilayer film 30 having a periodic stacked structure or a stacked structure comprising a periodic stacked structure and an asymmetric stacked structure has a high transmittance of blue excitation light and a high reflectance of the emission of phosphors whose peak wavelength is in the range of 580 nm to 620 nm, thereby further improving the efficiency of light extraction in the wavelength conversion member 10.

[0048] In the diffuse reflectance spectrum on one side 21 of the phosphor plate 20 on which the reflective multilayer film 30 is formed, the diffuse reflectance at 450 nm is, for example, 35% or less, preferably 30% or less, and more preferably 25% or less. This increases the transmittance of blue excitation light.

[0049] In the diffuse reflectance spectrum on one side 21 of the phosphor plate 20 on which the reflective multilayer film 30 is formed, the diffuse reflectance at 600 nm is, for example, 82% or more, preferably 85% or more, and more preferably 90% or more. This makes it possible to increase the reflectance of the emission of phosphors whose peak wavelength is in the range of 580 nm to 620 nm.

[0050] An example of the manufacturing process for the wavelength conversion member 10 of this embodiment will be described.

[0051] The method for manufacturing the wavelength conversion member 10 of this embodiment includes the steps of forming a phosphor plate 20 and forming a reflective multilayer film 30 on one surface 21 of the phosphor plate 20. An example of the process for forming the phosphor plate 20 may include, for example, a step of obtaining a mixture containing a metal oxide and a phosphor (1), and a step of firing the obtained mixture (2). The process is not limited to steps (1) and (2). For example, a phosphor plate may be formed by melting a metal oxide and mixing phosphor particles into the resulting molten material.

[0052] In step (1), the phosphor or metal oxide powder used as raw material is preferably of the highest possible purity, and the impurities of elements other than the constituent elements are preferably 0.1% or less, and more preferably 0.01% or less.

[0053] Various dry and wet methods can be applied to the mixing of the raw material powders, but a method is preferred that minimizes the pulverization of the phosphor particles used as raw materials and minimizes the introduction of impurities from the equipment during mixing.

[0054] As the metal oxide raw material for the phosphor, a mixture containing at least one of Al2O3 powder, SiO2 powder, and spinel raw material powder may be used. These may be used individually or in combination of two or more. The metal oxide can be in the form of a fine powder, and its average particle size may be, for example, 1 μm or less.

[0055] Alumina powder (Al2O3) may be used as the metal oxide raw material.

[0056] The upper limit of the BET specific surface area of ​​alumina powder is, for example, 10.0 m². 2 Less than or equal to / g, preferably 9.0m 2 / g or less, more preferably 8.0m 2 / g or less, more preferably 6.0m 2 The amount is less than / g. This suppresses the blackening of the phosphor plate. On the other hand, the lower limit of the BET specific surface area of ​​alumina powder is, for example, 0.1 m². 2 / g or more, preferably 0.5m 2 / g or more, more preferably 1.0m 2 / g or more, more preferably 2.0m 2 The concentration is 1 / g or higher. This enhances the sinterability of the alumina powder, allowing for the formation of a dense composite.

[0057] In step (2), the mixture of alumina powder and phosphor powder may be fired at, for example, 1300°C to 1650°C. A heating temperature of 1500°C to 1600°C is more preferable in the sintering process. A higher firing temperature is preferable for densifying the composite, but if the firing temperature is too high, the phosphor and alumina will react and the luminescence intensity of the phosphor plate will decrease, so the above range is preferable. Furthermore, when the firing temperature is in the high-temperature range of approximately 1600°C to 1650°C, the holding time for maintaining this temperature is, for example, 20 minutes or less, preferably 15 minutes or less. This increases the luminescence intensity of the phosphor plate.

[0058] Glass powder (powder containing SiO2) may be used as the metal oxide raw material. As the glass powder, SiO2 powder (silica powder) or general glass raw materials can be used. These can be used individually or in combination of two or more.

[0059] Spinel raw material powder may be used as the metal oxide raw material. Here, "spinel raw material powder" refers to, for example, (i) the general formula M mentioned above. 2x Al 4-4x O 6-4x (ii) a powder containing a spinel compound represented by the formula, and / or (ii) a mixture of a powder of a metal oxide represented by the general formula MO (where M is at least one of Mg, Mn, or Zn) and a powder of Al2O3.

[0060] In step (2), the spinel raw material powder may be fired at, for example, 1300°C to 1650°C. A heating temperature of 1500°C to 1600°C is more preferable in the sintering process. A higher firing temperature is preferable for densifying the composite, but if the firing temperature is too high, the luminescence intensity of the phosphor plate will decrease, so the above range is preferable. Furthermore, when the firing temperature is in the high-temperature range of approximately 1600°C to 1650°C, the holding time for maintaining this temperature is, for example, 20 minutes or less, preferably 15 minutes or less. This increases the luminescence intensity of the phosphor plate.

[0061] In the above manufacturing method, the firing method may be either atmospheric pressure sintering or pressure sintering, but pressure sintering, which is easier to densify than atmospheric pressure sintering, is preferred in order to suppress the deterioration of the phosphor's properties and obtain a dense composite.

[0062] Examples of pressurized sintering methods include hot press sintering, discharge plasma sintering (SPS), and hot isotropic press sintering (HIP). In the case of hot press sintering and SPS sintering, the pressure is 10 MPa or higher, preferably 30 MPa or higher, and 100 MPa or lower, preferably 80 MPa or lower. To prevent oxidation of the phosphor, the firing atmosphere should preferably be a non-oxidizing inert gas such as nitrogen or argon, or a vacuum atmosphere.

[0063] Thus, a phosphor plate 20 is obtained. Surface treatment is applied to at least one surface 21 (the surface on which the reflective multilayer film 30 is formed) of the obtained phosphor plate 20, or to both surfaces 21 and 22. Surface treatments include, for example, grinding using diamond grinding wheels, lapping, polishing, and other similar processes.

[0064] On the other surface 22 of the wavelength conversion member 10, there may be an exposed surface on which the reflective multilayer film 30 is not formed, or a known functional layer such as an anti-reflective layer may be formed.

[0065] Next, as an example of the process for forming the reflective multilayer film 30, a method can be used in which the high refractive index inorganic film material and the low refractive index inorganic film material are alternately deposited on one surface 21 of the phosphor plate 20. For example, a reflective multilayer film 30 can be formed by alternately depositing titanium dioxide (a material for high refractive index inorganic films) and silicon dioxide (a material for low refractive index inorganic films) and controlling the film thickness of each layer.

[0066] For film formation, known methods can be used, including vacuum deposition such as thermal deposition, ion-assisted deposition, and ion plating deposition, as well as sputtering methods such as DC sputtering, ion beam sputtering, and magnetron sputtering.

[0067] The light-emitting device of this embodiment will now be described.

[0068] Figure 2 is a schematic cross-sectional view showing an example of the configuration of the light-emitting device 1. The light-emitting device 1 comprises the wavelength conversion member 10 described above and the light-emitting element 3 (light source).

[0069] The light-emitting element 3 can be a blue LED that emits blue light, such as a group III nitride semiconductor light-emitting element. The group III nitride semiconductor light-emitting element comprises an n layer, a light-emitting layer, and a p layer, and is composed of a group III nitride semiconductor such as AlGaN, GaN, or InAlGaN-based materials.

[0070] The light-emitting element 3 mounted on the substrate 2 only needs to be positioned on the side of the wavelength conversion member 10 where the reflective multilayer film 30 is formed. The light-emitting element 3 and the wavelength conversion member 10 may be arranged in direct contact, or they may be arranged with a space between them. The space may be filled with a light-transmitting material or the like, or it may consist of an air gap.

[0071] The base material 2 may have various structures depending on the application, for example, it may have a structure that accommodates a light-emitting element 3. The wavelength conversion member 10 is placed in the opening of this housing structure. The material of base material 2 is not particularly limited, but ceramics may be used. The electrical connection between the substrate 2 and the light-emitting element 3 may be of the flip-chip type or the wire bonding type.

[0072] The embodiments of the present invention have been described above, but these are merely examples, and various other configurations can be adopted. Furthermore, the present invention is not limited to the embodiments described above, and modifications, improvements, etc., within the scope that can achieve the objectives of the present invention are included in the present invention. [Examples]

[0073] The present invention will be described in detail below with reference to examples, but the present invention is not limited in any way to the descriptions of these examples. <Preparation of spinel-based phosphor plates> The phosphor plate was manufactured using the following procedure. (1) Ca-α type Sialon phosphor (Alonbright YL-600B, manufactured by Denka Co., Ltd., median diameter 15 μm), and as spinel raw material powder, MgO (MgO: magnesium oxide manufactured by Fujifilm Wako Pure Chemical Industries, average particle size 0.2 μm, purity 99.9%) and Al2O3 (manufactured by Sumitomo Chemical Co., Ltd., AA-03, BET specific surface area: 5.2 m²) 2 The raw materials ( / g) were wet-mixed in ethanol solvent for 30 minutes using a polyethylene pot and an alumina ball. The resulting slurry was filtered by suction to remove the solvent and then dried. The mixed raw materials were then passed through a nylon mesh sieve with a mesh size of 75 μm to break down agglomeration and obtain a raw material mixed powder. The amount of α-sialon phosphor was adjusted so that when all of the spinel raw material powder had reacted to form spinel, the amount of α-sialon phosphor in the phosphor plate was 30% by volume (the remainder being MgO and Al2O3). The ratio of MgO to Al2O3 in the spinel raw material powder was set to a mass ratio of MgO:Al2O3=21:79 (in molar terms, Mg:Al=1:3).

[0074] (2) The raw material mixture powder was filled into the hot press jig. Specifically, about 10 g of the raw material mixture powder was filled into a carbon die with an inner diameter of 30 mm, into which a carbon lower punch was set. Then, a carbon upper punch was set and the raw material powder was sandwiched between them. A 0.127mm thick carbon sheet (GRAFOIL, manufactured by GraTech) was placed between the raw material mixture powder and the carbon jig to prevent sticking.

[0075] (3) A hot press jig filled with the raw material mixture powder was placed in a multi-purpose high-temperature furnace (High Multi 5000, manufactured by Fuji Denpa Kogyo Co., Ltd.) equipped with a carbon heater. The furnace was evacuated to a vacuum of 0.1 Pa or less, and while maintaining the reduced pressure, the upper and lower punches were pressurized with a pressing pressure of 55 MPa. While maintaining the pressurized state, the temperature was raised to 1600°C at a rate of 5°C per minute. After reaching 1600°C, heating was stopped, and the furnace was slowly cooled to room temperature and the pressure was released. Thereafter, a fired product with an outer diameter of 30 mm was recovered, and the surface, back surface, and side surface were ground using a surface grinding machine and a cylindrical grinding machine. As a result, a spinel-based phosphor plate in the shape of a disc with a thickness of 2.5 to 3.0 mm and a diameter of 25 mm was obtained.

[0076] (Examples 1 - 2, Comparative Examples 1 - 2) Using a surface grinding machine, after grinding the obtained spinel-based phosphor plate until its thickness reached approximately 1.0 mm, using a polishing machine, while keeping the polishing rotation speed constant, the grain size of the abrasive grains and the polishing time were adjusted, and polishing was performed until the thickness reached approximately 0.2 mm. As the polishing conditions using the polishing machine, in the order of Comparative Example 2, Comparative Example 1, Example 2, and Example 1, polishing using finer-grained abrasive grains was added, the polishing time was lengthened, or both were performed.

[0077] (Comparative Example 3) A product obtained by grinding the obtained spinel-based phosphor plate using a surface grinding machine until its thickness reached approximately 0.2 mm was used.

[0078] (Production of Alumina-Based Phosphor Plate) 7.857 g of alumina powder (manufactured by Sumitomo Chemical Co., Ltd., AA - 03, BET specific surface area: 5.2 m 2 / g) and 2.833 g of Ca-α type sialon phosphor powder (Alonbright YL - 600B, manufactured by Denka Co., Ltd., median diameter 15 μm) were weighed and dry-mixed using an agate mortar. After mixing, the raw materials were passed through a nylon mesh sieve with a mesh opening of 75 μm to break up the agglomerates, and a raw material mixed powder was obtained. Incidentally, the mixing ratio calculated from the true densities of the raw materials (alumina: 3.97 g / cm 3 , Ca-α type sialon phosphor: 3.34 g / cm 3 ) was alumina:Ca-α type sialon phosphor = 70:30 vol%.

[0079] Approximately 11g of raw material mixture powder was filled into a 30mm inner diameter carbon die with a carbon lower punch set inside, and a carbon upper punch was then set in place, sandwiching the raw material powder between the two. A 0.127mm thick carbon sheet (GRAFOIL, manufactured by GraTech) was placed between the raw material mixture powder and the carbon jig to prevent adhesion.

[0080] A hot press jig filled with this raw material mixture powder was placed in a multi-purpose high-temperature furnace with a carbon heater (Fuji Denpa Kogyo Co., Ltd., High Multi 5000). The furnace was evacuated to a vacuum of 0.1 Pa or less, and while maintaining the reduced pressure, the upper and lower punches were pressurized with a pressing pressure of 55 MPa. While maintaining the pressurized state, the temperature was raised to 1600°C at a rate of 5°C per minute. After reaching 1600°C, heating was immediately stopped, and the furnace was slowly cooled to room temperature and the pressure was released (firing process). Subsequently, the fired material with an outer diameter of 30 mm was recovered, and its surface, back surface, and sides were ground using a surface grinder and a cylindrical grinder. This resulted in obtaining a disc-shaped alumina-based phosphor plate with a thickness of 2.5 to 3.0 mm and a diameter of 25 mm.

[0081] (Example 3, Comparative Example 4) Using a surface grinding machine, the obtained spinel-based phosphor plate was ground to a thickness of approximately 1.0 mm. Then, using a polishing machine, while keeping the polishing rotation speed constant, the grit size of the abrasive grains and the polishing time were adjusted to polish the plate to a thickness of approximately 0.2 mm. The polishing conditions using the polishing machine were as follows: Comparative Example 4 and Example 3 were followed by either adding polishing with finer abrasive particles, increasing the polishing time, or both.

[0082] (Comparative Example 5) The spinel-based phosphor plate obtained was ground using a surface grinder until its thickness was approximately 0.2 mm.

[0083] The Rsm of one surface (the surface where the reflective multilayer film is formed) of the phosphor plate in each of the obtained examples and comparative examples was measured using a surface roughness meter (Mitutoyo SJ-400) in accordance with JIS B 0031:1994. The results are shown in Table 1. In Table 1, "-" indicates that measurement was not performed.

[0084] [Table 1]

[0085] <Deposition of reflective multilayer films> For each example and comparative example obtained, titanium dioxide (TiO2) and silicon dioxide (SiO2) were alternately vacuum-deposited onto one side of the phosphor plate (the surface for forming the reflective multilayer film) using the same deposition conditions, thereby forming a total of 28 layers (total thickness approximately 2.6 μm) of reflective multilayer film. Based on the above, a wavelength conversion component was manufactured in which a reflective multilayer film was formed on one surface of a phosphor plate.

[0086] Figure 3(a) shows the SEM image of Example 2, and Figure 3(b) shows the SEM image of Comparative Example 3. In Figure 3, gray represents SiO2 and black represents TiO2.

[0087] Furthermore, for the reflective multilayer film formed on the phosphor plate of Example 2, a STEM cross-sectional image was obtained, and the thickness of each layer was measured from a figure created by plotting the brightness using that image. The results are shown in Table 2. From the results in Table 2, it was found that the reflective multilayer film of Example 2 has a layered structure in which asymmetrical layered structures, periodic layered structures, and asymmetrical layered structures are arranged in that order. Similar layered structures were also confirmed in the reflective multilayer films on the phosphor plates of Examples 1 and 3.

[0088] [Table 2]

[0089] <Color> In each example and comparative example of the wavelength conversion member, the color of the surface of the reflective multilayer film on one side of the phosphor plate (reflective multilayer film surface) and the surface on the other side of the phosphor plate (exposed surface) were measured using a JASCO UV-Vis spectrophotometer (V-550) equipped with an integrating sphere device (ISV-469). Base correction was performed using a standard whiteboard (Labsphere, Spectralon). Set the wavelength conversion component and perform measurements on the measurement surface (the surface of the reflective multilayer film or the exposed surface of the phosphor plate) in the wavelength range of 300 to 850 nm, and determine the color (L) in accordance with JIS Z 8781-4:2013. * a * , b * The result was calculated. The results are shown in Table 3.

[0090] [Table 3]

[0091] The obtained wavelength conversion components were evaluated against the following evaluation criteria.

[0092] <Diffuse reflectance> For each example and comparative example of the wavelength conversion member, the reflective multilayer film formation surface was measured using an ultraviolet-visible-infrared spectrophotometer (JASCO Corporation, V-550). After base correction was performed on a standard whiteboard (Labsphere, Spectralon), the diffuse reflectance spectrum at wavelengths from 250 nm to 850 nm was measured, and the diffuse reflectance (%) at each wavelength (450 nm and 600 nm) was calculated based on the obtained diffuse reflectance spectrum. The results are shown in Table 4.

[0093] [Table 4]

[0094] <Evaluation of optical properties> In each example and comparative example of the wavelength conversion member, the emission intensity before and after the formation of the reflective multilayer film was measured. Specifically, a jig was prepared to house an excitation light source (blue LED: peak wavelength 450 nm) in the aperture. The phosphor plate was positioned so that one side (exposed side or side with reflective multilayer film formation) faced the excitation light source, and the phosphor plate was placed to cover the opening of the jig. Then, using a total luminous flux measurement system (HalfMoon / φ1000mm integrating sphere system, manufactured by Otsuka Electronics Co., Ltd.), after applying current to the excitation light source and holding it for 90 seconds, the emission spectrum of the light emitted from the other side of the phosphor plate (the side opposite to the side irradiated by the excitation light) was measured. Table 5 shows the relative values ​​of the peak intensity of the emission spectrum, normalized to the emission intensity before the formation of the reflective multilayer film in Comparative Example 3, with the normalized value set to 1.0.

[0095] [Table 5]

[0096] Compared to Comparative Examples 1 to 5, the wavelength conversion members of Examples 1 to 3 showed superior emission intensity because the fluorescence intensity (relative value) after forming a reflective multilayer film on the phosphor plate was improved.

[0097] This application claims priority based on Japanese Patent Application No. 2022-149926, filed on 21 September 2022, and incorporates all of its disclosures herein. [Explanation of Symbols]

[0098] 1. Light-emitting device 2 Base material 3 Light-emitting elements 10 Wavelength conversion member 20 Phosphor Plates 21 one side 22 Other side 30 reflective multilayer film

Claims

1. A phosphor plate comprising an inorganic matrix and a phosphor dispersed in the inorganic matrix, A wavelength conversion member comprising a reflective multilayer film formed on one side surface of the phosphor plate, wherein a plurality of inorganic films with different refractive indices are laminated together, The L on the surface of the reflective multilayer film formed on one side of the phosphor plate, measured in accordance with JIS Z 8781-4. ＊ a ＊ b ＊ In color coordinates, a ＊ The value is between -20 and 0, and b ＊ It is configured such that the value is between 20 and 60. A wavelength conversion member wherein, when blue excitation light is irradiated from one side on which the reflective multilayer film is formed, the emission spectrum detected from the other side of the phosphor plate located opposite the reflective multilayer film has a peak wavelength in the range of 580 nm to 620 nm.

2. A wavelength conversion member according to claim 1, A wavelength conversion member wherein, in the diffuse reflectance spectrum on one side of the phosphor plate on which the reflective multilayer film is formed, the diffuse reflectance at 450 nm is 35% or less.

3. A wavelength conversion member according to claim 1 or 2, A wavelength conversion member wherein, in the diffuse reflectance spectrum on one side of the phosphor plate on which the reflective multilayer film is formed, the diffuse reflectance at 600 nm is 82% or more.

4. A wavelength conversion member according to claim 1 or 2, A wavelength conversion member wherein the Rsm measured on one side of the phosphor plate according to JIS B 0031:1994 is 60 μm or less.

5. A wavelength conversion member according to claim 1 or 2, A wavelength conversion member comprising a reflective multilayer film having a periodic stacked structure in which at least one of a high refractive index inorganic film and a low refractive index inorganic film is stacked with substantially the same thickness.

6. A wavelength conversion member according to claim 5, A wavelength conversion member comprising an asymmetric laminated structure in which the reflective multilayer film is arranged adjacent to the periodic laminated structure, and at least one of the high refractive index inorganic film and the low refractive index inorganic film is laminated with different thicknesses.

7. A wavelength conversion member according to claim 1 or 2, The aforementioned phosphor is an α-type sialon phosphor, (Ba, Sr, Ca) ２ Si ５ N ８ A wavelength conversion member comprising a phosphor, a mixture of a YAG phosphor and a SCASN phosphor, and a SCASN phosphor.

8. A wavelength conversion member according to claim 1 or 2, A wavelength conversion member wherein the inorganic matrix material includes alumina or a spinel-based compound.

9. A light-emitting device comprising a wavelength conversion member according to claim 1 or 2 and a light source.

10. A light-emitting device according to claim 9, A light-emitting device that serves as a turn signal.

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