Wavelength conversion member and light-emitting device

Abstract

To provide a wavelength conversion member and a light-emitting device having high luminescence efficiency. [Solution] A wavelength conversion member 110 comprising a ceramic composite 111 containing a phosphor having an emission peak wavelength in the range of 510 nm to 570 nm, and a translucent thin film 112 disposed on the ceramic composite 111, wherein the thickness of the translucent thin film 112 is in the range of 50 nm to 140 nm, the thickness of the ceramic composite 111 is in the range of 80 μm to 800 μm, and when measured from the translucent thin film 112 side, the first reflectance of light with a wavelength of 450 nm incident at an incident angle of 0° is 7% or less, the second reflectance of light with a wavelength of 550 nm incident at an incident angle of 0° is 7% or less, and the sum of the first reflectance and the second reflectance is 10% or less.

Description

[Technical Field]

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

[0002] Light-emitting devices are known that include light-emitting diodes (LEDs) or laser diodes (LDs) and wavelength conversion components containing phosphors that convert the wavelength of light emitted from the light-emitting elements of the LEDs or LDs. Such light-emitting devices are used as light sources for applications such as automobiles, general lighting, backlights for liquid crystal displays, and projectors.

[0003] For example, Patent Document 1 discloses porous optoceramics as a diffuse-reflecting wavelength conversion member that converts excitation light having a first wavelength into light having a second wavelength, at least partially. Patent Document 1 also discloses that for porous optoceramics, the diffuse reflectance based on a pre-measured diffuse reflectance standard is 0.7 to 1 at 600 nm. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2017-197774 [Overview of the project] [Problems that the invention aims to solve]

[0005] One aspect of this embodiment aims to provide a wavelength conversion member and a light-emitting device having higher luminescence efficiency. [Means for solving the problem]

[0006] The first aspect is a wavelength conversion member including a ceramic composite containing a phosphor having an emission peak wavelength within a range of 510 nm or more and 570 nm or less, and a translucent thin film disposed on the ceramic composite, where the thickness of the translucent thin film is within a range of 50 nm or more and 140 nm or less, the thickness of the ceramic composite is within a range of 80 μm or more and 800 μm or less, when measured from the side of the translucent thin film, the first reflectance of light with a wavelength of 450 nm incident at an incident angle of 0° is 7% or less, the second reflectance of light with a wavelength of 550 nm incident at an incident angle of 0° is 7% or less, and the sum of the first reflectance and the second reflectance is 10% or less.

[0007] The second aspect is a light emitting device including a light emitting element having an emission peak wavelength within a range of 380 nm or more and 500 nm or less, and the wavelength conversion member that is irradiated with light from the light emitting element and performs wavelength conversion.

Advantages of the Invention

[0008] According to one aspect of the present invention, it is possible to provide a wavelength conversion member and a light emitting device having higher luminous efficiency.

Brief Description of the Drawings

[0009] [Figure 1] FIG. 1 is a schematic view showing the configuration of the side surface of the wavelength conversion member. [Figure 2] FIG. 2 is a schematic perspective view of the wavelength conversion member schematically showing the incident angle of light with respect to the wavelength conversion member. [Figure 3] FIG. 3 is a schematic view showing the configuration of an example of the light emitting device. [Figure 4] FIG. 4 is a schematic view showing the configuration of a plane of an example of a wavelength conversion device including the wavelength conversion member. [Figure 5] FIG. 5 is a schematic view showing the configuration of a side surface of an example of a wavelength conversion device including the wavelength conversion member. [Figure 6] FIG. 6 is a diagram showing the reflection spectrum of the wavelength conversion member. [Figure 7] FIG. 7 is a diagram showing the reflection spectrum of the wavelength conversion member. [Figure 8] Figure 8 shows the reflection spectrum of the wavelength conversion component. [Figure 9] Figure 9 shows the reflection spectrum of the wavelength conversion component. [Figure 10] Figure 10 shows the reflection spectrum of the wavelength conversion member. [Figure 11] Figure 11 shows the transmission spectrum of the wavelength conversion component. [Modes for carrying out the invention]

[0010] The wavelength conversion member and light-emitting device will be described below based on embodiments. However, the embodiments shown below are illustrative examples for realizing the technical concept of the present invention, and the present invention is not limited to the wavelength conversion member and light-emitting device described below. The relationship between color names and chromaticity coordinates, and the relationship between the wavelength range of light and the color names of monochromatic light will conform to JIS Z8110.

[0011] Wavelength conversion component The wavelength conversion member comprises a ceramic composite containing a phosphor having an emission peak wavelength in the range of 510 nm to 570 nm, and a translucent thin film disposed on the ceramic composite, wherein the thickness of the translucent thin film is in the range of 50 nm to 140 nm, the thickness of the ceramic composite is in the range of 80 μm to 800 μm, and when measured from the translucent thin film side, the first reflectance of light with a wavelength of 450 nm incident at an incident angle of 0° is 7% or less, the second reflectance of light with a wavelength of 550 nm incident at an incident angle of 0° is 7% or less, and the sum of the first and second reflectances is 10% or less. Figure 1 is a schematic diagram showing the side configuration of the wavelength conversion member. Figure 2 is a schematic perspective view of the wavelength conversion member, also showing examples of the angle of incidence of light on the wavelength conversion member. The wavelength conversion member 110 comprises a ceramic composite 111 and a translucent thin film 112 disposed on the ceramic composite. Furthermore, the planar shape of the wavelength conversion member 110 is not limited to a rectangle as shown in Figure 2, but may also be an annular shape as shown in Figure 4, which will be described later. While the wavelength conversion member and light-emitting device may be described based on the drawings, the drawings are schematic diagrams showing the configuration of the wavelength conversion member or light-emitting device, and the wavelength conversion member and light-emitting device are not limited to the shape and size shown in the drawings.

[0012] As shown in Figures 1 and 2, the wavelength conversion member 110 comprises a ceramic composite 111 containing a phosphor and a translucent thin film 112. When measured from the translucent thin film 112 side, the first reflectance of light with a wavelength of 450 nm incident at an incident angle of 0° is 7.0% or less, the second reflectance of light with a wavelength of 550 nm incident at an incident angle of 0° is 7.0% or less, and the sum of the first and second reflectances is 10.0% or less. Therefore, the wavelength conversion member has a low reflectance of incident light, allowing sufficient excitation light to be incident into the ceramic composite. The wavelength conversion member also has a low reflectance of the wavelength-converted light, so the phosphor contained in the ceramic composite efficiently absorbs the incident light and converts its wavelength, allowing the wavelength conversion member to emit light with high luminescence efficiency. The reflectance at a specific wavelength can be determined by measuring the reflectance of borosilicate crown optical glass (hereinafter also referred to as "BK7") using a microspectroscopy measuring device (e.g., manufactured by Olympus Corporation). The measured reflectance of BK7 is set to 100%, and the reflectance of the wavelength conversion member is measured from the translucent thin film side. From the reflectance of the wavelength conversion member, the first reflectance for light at a wavelength of 450 nm and the second reflectance for light at a wavelength of 550 nm can be calculated. If the reflectance of BK7 is 100% for light incident at an incident angle of 0°, and the reflectance measured from the translucent thin film side of the wavelength conversion member incident at an incident angle of 0° is, for example, 70%, then when the reflectance of BK7 for light at a wavelength of 450 nm (measured value) is 4.1%, the first reflectance of the wavelength conversion member for light at a wavelength of 450 nm can be calculated as 2.87% by dividing the product of 4.1% and 70% by 100. The first reflectance of the wavelength conversion member may be 6.5% or less, 6.0% or less, or 5.8% or less. The first reflectance of the wavelength conversion member is usually 0.1% or more, may be 0.3% or more, or may be 0.5% or more. The second reflectance of the wavelength conversion member may be 6.0% or less, 5.0% or less, or may be 4.5% or less. The second reflectance of the wavelength conversion member is usually 0.1% or more, may be 0.3% or more, or may be 0.5% or more. The sum of the first and second reflectances of the wavelength conversion member may be 9.0% or less, or may be 8.5% or less. The sum of the first and second reflectances of the wavelength conversion member is 0.2% or more, may be 0.6% or more, or may be 1.0% or more.

[0013] In this specification, reflectance, including the first and second reflectances, refers to specular reflectance. Specular reflectance refers to light reflected such that the angle of incidence and the angle of reflection are equal. Here, diffuse reflectance refers to the reflection of incident light in various directions (various reflection angles). Total internal reflection refers to the light obtained by adding specular and diffuse reflection. In this specification, the reflectance of light incident at an incident angle of 0° is expressed as a percentage when the case where all light incident at an incident angle of 0° is reflected at a reflection angle of 0° is taken as 100%. An example of an incident angle of 0° for the wavelength conversion member 110 is schematically shown in Figure 2. An incident angle of 0° (θ=0°) refers to an angle perpendicular to the translucent thin film 112 of the wavelength conversion member 110. The direction of an incident angle of 0° refers to a direction parallel to the optical axis z of the wavelength conversion member.

[0014] The wavelength conversion member is preferably a so-called reflective type, in which the incident surface that receives light from the outside and the exit surface that emits light to the outside are the same surface. The incident surface of light preferably includes the surface on which the translucent thin film is arranged. The wavelength conversion member may also be provided with a light reflector on the side opposite to the translucent thin film.

[0015] Preferably, the wavelength conversion member has a first transmittance of 20% or more for light with a wavelength of 450 nm and a second transmittance of 20% or more for light with a wavelength of 550 nm. When the wavelength conversion member has a first transmittance of 20% or more for light with a wavelength of 450 nm, sufficient excitation light is incident on the wavelength conversion member, and the phosphor contained in the ceramic composite absorbs the incident excitation light, enabling wavelength conversion. Furthermore, when the wavelength conversion member has a second transmittance of 20% or more for light with a wavelength of 550 nm, the phosphor contained in the ceramic composite can emit the wavelength-converted light with high luminous efficiency. The first transmittance of the wavelength conversion member may be 22% or more, 23% or more, or 24% or more. The first transmittance of the wavelength conversion member may be 40% or less, or 35% or less. The second transmittance of the wavelength conversion member may be 22% or more, 25% or more, or 30% or more. The second transmittance of the wavelength conversion member may be 50% or less, or 45% or less. Transmittance can be calculated by using a spectrophotometer (for example, one manufactured by Hitachi High-Tech Science Co., Ltd.) to convert the light from a light source into monochromatic light of a specific wavelength using a spectrometer, and measuring the light intensity of the converted light of that specific wavelength to obtain the incident light intensity. This light of that specific wavelength is then incident on a wavelength conversion member, and the light intensity of the light emitted from the wavelength conversion member is measured to obtain the transmitted light intensity. The ratio of the transmitted light intensity to the incident light intensity is then defined as the transmittance. In other words, transmittance can be calculated based on the following equation (1). In equation (1), I0 is the incident light intensity and I is the transmitted light intensity.

[0016]

number

[0017] The transmittance of a wavelength conversion component is defined as the ratio of the transmitted light intensity emitted from the ceramic composite side (opposite the transparent thin film side) to the incident light intensity incident from the transparent thin film side at an incident angle of 0°.

[0018] Preferably, the wavelength conversion member has a minimum reflectivity wavelength of 730 nm or less for light incident at an incident angle of 0°, within the range of 380 nm to 830 nm. If the wavelength of the minimum reflectivity of the wavelength conversion member is 730 nm or less, the reflection of the excitation light incident on the wavelength conversion member can be suppressed, allowing sufficient excitation light to be incident into the ceramic composite. The excitation light is absorbed by the phosphor contained in the ceramic composite, and the wavelength-converted light can be emitted from the wavelength conversion member without reflection by the wavelength conversion member. For light incident at an incident angle of 0°, the wavelength at which the minimum reflectivity of the wavelength conversion member occurs within the range of 380 nm to 830 nm may be 720 nm or less, or 715 nm or less. The wavelength at which the minimum reflectivity of the wavelength conversion member occurs within the range of 380 nm to 830 nm may be 380 nm or more.

[0019] ceramic composite The thickness of the ceramic composite is in the range of 80 μm to 800 μm, but may also be in the range of 90 μm to 700 μm, 100 μm to 600 μm, or 120 μm to 500 μm. The ceramic composite contains a phosphor having an emission peak wavelength in the range of 510 nm to 570 nm, and converts the wavelength of incident light, which is then emitted from the wavelength conversion member. If the thickness of the ceramic composite is in the range of 80 μm to 800 μm, the phosphor contained in the ceramic composite efficiently absorbs the incident light and converts its wavelength, allowing for the emission of light with high luminescence efficiency.

[0020] The refractive index of the ceramic composite is preferably in the range of 1.76 to 1.85, and may also be in the range of 1.77 to 1.83. If the refractive index of the ceramic composite is within these ranges, the wavelength conversion member can sufficiently inject excitation light into the ceramic composite, and the light whose wavelength has been converted by the phosphor contained in the ceramic composite can be emitted from the wavelength conversion member with high luminescence efficiency. The refractive index of the ceramic composite may be the refractive index of the phosphor constituting the ceramic composite.

[0021] The relative density of the ceramic composite is preferably 90% or higher, more preferably 92% or higher, even more preferably 94% or higher, particularly preferably 95% or higher, and may also be 99% or lower, or 98% or lower. When the relative density of the ceramic composite is within the range of 90% to 99%, there are fewer voids, the transmittance of light at a wavelength of 450 nm and 550 nm is increased, the absorption of excitation light of the phosphors contained in the ceramic composite is enhanced, wavelength conversion is performed efficiently, and light with high luminescence efficiency can be emitted from the wavelength conversion member.

[0022] The relative density of the ceramic composite can be calculated from the apparent density and true density of the ceramic composite using the following formula (2).

[0023]

number

[0024] The apparent density of the ceramic composite is the value obtained by dividing the mass of the ceramic composite by the volume of the ceramic composite, and can be calculated by the following formula (3). The true density of the ceramic composite may be the true density of the phosphor constituting the ceramic composite.

[0025] [Number]

[0026] The porosity of the ceramic composite can be the value obtained by subtracting the relative density of the ceramic composite from 100.

[0027] Phosphor The phosphor contained in the ceramic composite may be any phosphor that emits fluorescence having an emission peak wavelength within the range of 510 nm or more and 570 nm or less, and preferably contains at least one phosphor selected from the group consisting of rare earth aluminate phosphors, silicate phosphors, and β-sialon phosphors, and more preferably contains a rare earth aluminate phosphor.

[0028] The rare earth aluminate phosphor preferably has a composition represented by the following formula (I). (Ln 1 1-a Ce a )3(Al c Ga b )5O 12 (I) (In the above formula (I), Ln 1 is at least one first rare earth element selected from the group consisting of Y, Gd, Lu, and Tb, and a, b, and c are numbers satisfying 0 < a ≤ 0.22, 0 ≤ b ≤ 0.4, 0 < c ≤ 1.1, and 0.9 ≤ b + c ≤ 1.1.)

[0029] The silicate phosphor preferably has a composition represented by the following formula (II). Ca d Eu e Mg f Si4O g Cl h (II) (In formula (II), d, e, f, g, and h are numbers satisfying 7.0 ≤ d ≤ 7.94, 0.01 ≤ e ≤ 1.0, 7.70 ≤ d + e ≤ 7.95, 0.9 ≤ f ≤ 1.1, 15.6 ≤ g ≤ 16.1, and 1.90 < h ≤ 2.00, respectively.)

[0030] The β-sialon phosphor preferably has a composition represented by the following formula (III). Si 6-z Al z O z N 8-z :Eu (0 < z ≤ 4.2) (III)

[0031] Method for producing a ceramic composite Ceramic composites can be manufactured by drying a slurry-like raw material mixture obtained by mixing raw material particles in a liquid to obtain a powdered raw material mixture, molding the raw material mixture by press molding methods such as die pressing and / or cold isostatic pressing (CIP), and then heating and degreasing the resulting molded body as needed, followed by firing to obtain a sintered body. The sintered body obtained after firing may be annealed. The resulting sintered body may be processed by cutting it to a desired size or thickness. After processing the sintered body, the cut surface may be treated by methods such as sandblasting, mechanical grinding, dicing, or chemical etching. The firing temperature for the molded body may be in the range of 1300°C to 1800°C, 1400°C to 1790°C, or 1450°C to 1780°C. The firing of the molded body is preferably carried out in an oxygen-containing atmosphere, and the oxygen content in the atmosphere may be 5% by volume or more, or it may be in an air atmosphere. The temperature for heat degreasing should be within the range of 500°C to 1000°C. The temperature for annealing should be lower than the firing temperature, and should be within the range of 1000°C to 1600°C. Annealing is preferably performed in a reducing atmosphere, which may be an atmosphere containing at least one noble gas selected from the group consisting of helium, neon, and argon, or nitrogen gas, and hydrogen gas or carbon monoxide gas. As an example of a method for manufacturing ceramic composites, refer to the disclosure in Japanese Patent Application No. 2020-135121.

[0032] Translucent thin film The translucent thin film is placed on top of the ceramic composite. In the case of a reflective wavelength conversion member that includes a surface where the light incident surface and the light exit surface are the same surface, it is preferable to place the translucent thin film on the surface that is the light incident side and the surface that is the light exit side. By providing a translucent thin film on top of the ceramic composite, the reflectivity of the surface of the wavelength conversion member to which light is incident can be reduced, and light with high luminous efficiency can be emitted from the wavelength conversion member.

[0033] The thickness of the translucent thin film is in the range of 50 nm to 140 nm, but may also be in the range of 55 nm to 130 nm, or 125 nm or less. By placing the translucent thin film on top of the ceramic composite, the refractive index difference between air and the ceramic composite is reduced, sufficient excitation light is incident into the ceramic composite, and light with high luminescence efficiency can be emitted from the wavelength conversion member. In this specification, the thickness of the translucent thin film refers to the physical film thickness of the translucent thin film.

[0034] The translucent thin film may be a single layer made of a single material, or it may be a multilayer film comprising at least two layers: a first layer and a second layer made of a material different from the material constituting the first layer. When the translucent thin film is a single layer made of a single material, the material forming the translucent thin film may be a fluoride or silicon dioxide containing at least one element selected from the group consisting of alkali metal elements, alkaline earth metal elements, and group 13 metal elements. Examples of fluorides include MgF2, CaF2, SrF2, AlF3, Na3AlF6, and Na5Al3F 14 Examples include LiF, NaF, and KF. Fluorides include MgF2, CaF2, SrF2, AlF3, Na3AlF6, and Na5Al3F 14 Preferably, it contains at least one selected from the group consisting of NaF and LiF. The light-transmitting thin film is preferably made of magnesium fluoride.

[0035] When the translucent thin film is made of silicon dioxide, it is preferable that the thickness of the translucent thin film made of silicon dioxide is in the range of 80 nm to 130 nm. By placing such a translucent thin film on top of a ceramic composite, the refractive index difference between air and the ceramic composite can be reduced, making the first reflectance at 450 nm and the second reflectance at 550 nm 7% or less, and the sum of the first and second reflectances 10% or less.

[0036] If the translucent thin film is a multilayer film, it comprises at least two layers: a first layer made of fluoride or silicon dioxide containing at least one element selected from the group consisting of alkali metals, alkaline earth metals, and Group 13 metallic elements, and a second layer made of an oxide containing at least one element selected from the group consisting of aluminum, niobium, tantalum, titanium, and zirconium. If there are two or more layers, the first and second layers may be alternately stacked to form a multilayer film. The refractive indices of the first layer and the second layer are different. The fluoride used can be the same as that used in a single-layer translucent thin film. If the translucent thin film is a multilayer film, commercially available optical multilayer films may be used.

[0037] When the translucent thin film is a single layer, the refractive index of the translucent thin film is preferably in the range of 1.3 to 1.5, but may also be in the range of 1.32 to 1.48, or in the range of 1.33 to 1.47. If the refractive index of the translucent thin film is in the range of 1.3 to 1.5, the refractive index difference between air and the ceramic composite is reduced, the first reflectance for 450 nm light and the second reflectance for 550 nm light are each set to 7% or less, and the sum of the first and second reflectances is set to 10% or less, allowing sufficient excitation light to be incident into the ceramic composite and enabling the emission of highly luminous light from the wavelength conversion member. The refractive index of magnesium fluoride is 1.38, and the refractive index of silicon dioxide is 1.47. When the translucent thin film is a single layer made of magnesium fluoride, the refractive index of the translucent thin film can be the refractive index of magnesium fluoride. If the translucent thin film is a single layer made of silicon dioxide, the refractive index of the translucent thin film can be the refractive index of silicon dioxide.

[0038] Method for manufacturing a light-transmitting thin film When the translucent thin film is a single layer, it can be manufactured by chemical vapor deposition or physical vapor deposition. Examples of physical vapor deposition methods include electron beam deposition, resistance heating deposition, ion plating, and sputtering. Preferably, the translucent thin film is formed on the light-emitting surface of a ceramic composite by resistance heating deposition or sputtering using fluoride or silicon dioxide as the raw material in a vacuum atmosphere at a temperature between 25°C and 400°C. If the translucent thin film is a multilayer film, the raw materials for the first layer and the raw materials for the second layer may be formed in this order on the light-emitting surface of the ceramic composite by electron beam (EB) heating deposition in a vacuum atmosphere at a temperature of 25°C to 400°C.

[0039] As described above, the wavelength conversion component can be used in combination with an excitation light source to form a light-emitting device, such a device can be used, for example, as a light source for a projector.

[0040] Light-emitting device A light-emitting device using the aforementioned wavelength conversion member will now be described. The light-emitting device comprises a wavelength conversion member and an excitation light source, and the excitation light source can be a light-emitting element having an emission peak wavelength in the range of 380 nm to 500 nm.

[0041] The light-emitting element is preferably a semiconductor light-emitting element consisting of an LED chip or an LD chip. Nitride semiconductors can be used for the semiconductor light-emitting element. By using a semiconductor light-emitting element as an excitation light source, a stable light-emitting device can be obtained that is highly efficient, has high linearity of output to input, and is resistant to mechanical shock. The rare-earth aluminate sintered body can convert the wavelength of light emitted from the semiconductor light-emitting element, making it possible to configure a light-emitting device that emits wavelength-converted mixed-color light. The light-emitting element may have an emission peak wavelength in the range of 380 nm to 500 nm, or in the range of 400 nm to 480 nm, or in the range of 420 nm to 460 nm.

[0042] The light-emitting element is more preferably a laser diode. The excitation light emitted from the laser diode, which is the excitation light source, is incident on a wavelength conversion member, and the light whose wavelength has been converted by the phosphor contained in the ceramic composite of the wavelength conversion member is focused and separated into red light, green light, and blue light by a plurality of optical systems such as a lens array, a polarization conversion element, and a color separation optical system, and modulated according to the image information to form color image light. The excitation light emitted from the laser diode as the excitation light source may also be incident on the wavelength conversion member through an optical system such as a dichroic mirror or a collimating optical system.

[0043] Figure 3 is a schematic diagram showing an example configuration of the light-emitting device 100. The arrows in Figure 3 schematically represent the optical path of the light. The light-emitting device 100 preferably includes an excitation light source 101 which is a light-emitting element, a collimating lens 102, three condenser lenses 103, 105 and 106, a dichroic mirror 104, a rod integrator 107, and a wavelength conversion device 120 including a wavelength conversion member. It is preferable to use a laser diode for the excitation light source 101. The excitation light source 101 may use multiple laser diodes, or multiple laser diodes may be arranged in an array or matrix. The collimating lens 102 may be a collimating lens array in which multiple collimating lenses are arranged in an array. The laser light emitted from the excitation light source 101 becomes substantially parallel light by the collimating lens 102, is focused by the condenser lens 103, passes through the dichroic mirror 104, and is further focused by the condenser lens 105. The laser light focused by the condenser lens 105 is wavelength-converted by a wavelength conversion device 120, which includes a wavelength conversion member 110 and a light reflector 122, and light having an emission peak wavelength in a desired wavelength range is emitted from the wavelength conversion member 110 side of the wavelength conversion device 120. The wavelength-converted light emitted from the wavelength conversion device 120 is focused by the condenser lens 106 and incident on the rod integrator 107, and light with improved uniformity of illuminance distribution in the illuminated area is emitted from the light-emitting device 100.

[0044] Figure 4 is a schematic diagram showing the planar configuration of an example of a wavelength conversion device 120. In Figure 3, the wavelength conversion device 120 is shown in a side view as one of the components constituting the light-emitting device 100. The wavelength conversion device 120 comprises at least a wavelength conversion member 110. The wavelength conversion device 120 comprises a disc-shaped wavelength conversion member 110 and may also include a rotation mechanism 121 for rotating the wavelength conversion member 110. The rotation mechanism 121 is connected to a drive mechanism such as a motor and can dissipate heat by rotating the wavelength conversion member 110.

[0045] Figure 5 is a schematic diagram showing the side configuration of an example of the wavelength conversion device 120, which was shown in Figure 3 as a side view as one of the components constituting the light-emitting device 100. The wavelength conversion device 120 is equipped with a light reflector 122 on the side opposite to the side where the translucent thin film 112 of the ceramic composite 111 of the wavelength conversion member 110 is located. Note that the light reflector 122 can be omitted if sufficient light from the ceramic composite 111 can be emitted to the side where the translucent thin film 112 is located. The light reflector 122 may be used not only as a component that reflects light from the ceramic composite 111 to the side where the translucent thin film 112 is located, but also as a heat dissipation component that transfers heat generated in the ceramic composite 111 and dissipates it to the outside. [Examples]

[0046] The embodiments will be described in detail below with reference to examples. The present invention is not limited to these embodiments.

[0047] Manufacturing of ceramic composite A Preparation of raw material mixture Specific surface area 20 m² using the BET method 2 Yttrium oxide particles per gram, specific surface area 5.5 m² by BET method. 2 Aluminum oxide particles / g, specific surface area 125m² by BET method. 2 The molar ratio of elements Y, Al, and Ce contained in each oxide particle of cerium oxide particles is Y 2.99 Ce0.01 Al 5.1 O 12 The materials were weighed to achieve the composition shown. To a total of 100 parts by mass of yttrium oxide particles, aluminum oxide particles, and cerium oxide particles, 4 parts by mass of a dispersant (Floren G-700, Kyoeisha Chemical Co., Ltd.) was added, and then 50 parts by mass of ethanol was added to prepare the raw material mixture.

[0048] stirring The raw material mixture was stirred in a wet ball mill for 15 hours to prepare a slurry-like raw material mixture in which yttrium oxide particles, aluminum oxide particles, and cerium oxide particles were uniformly mixed.

[0049] dry The resulting slurry-like raw material mixture was dried in an air atmosphere at 130°C for 10 hours to obtain a raw material mixture powder.

[0050] molding The resulting raw material mixture powder is filled into a mold and subjected to 5 MPa (51 kgf / cm²). 2 A cylindrical molded body with a diameter of 26 mm and a thickness of 10 mm was formed using the pressure of ). The obtained molded body was placed in a packaging container, vacuum-packed, and subjected to CIP at 176 MPa using a cold isostatic pressurizing device (manufactured by Kobe Steel, Ltd. (KOBELCO)) to obtain a molded body.

[0051] Heat degreasing The resulting molded body was degreased by heating at 700°C under a nitrogen atmosphere.

[0052] firing The resulting molded bodies were fired in a firing furnace (manufactured by Marusho Electric Co., Ltd.) to obtain rare earth aluminate sintered bodies. The firing conditions were an air atmosphere (101.325 kPa, oxygen concentration: approximately 20 vol%), a temperature of 1580°C, and a firing time of 6 hours.

[0053] Machining and surface treatment The obtained sintered body was cut to the appropriate shape and size using a wire saw, and then the surface of the cut pieces was polished with a surface grinder to obtain ceramic composite A. The true density of rare earth aluminate phosphor A was 4.6 g / cm³. 3 Therefore, the true density of the rare-earth aluminate phosphor A was taken as the true density of the ceramic composite A. The relative density of the ceramic composite A calculated based on equations (2) and (3) above was 97.0%. The refractive index of the rare-earth aluminate phosphor A was 1.82, and the refractive index of the ceramic composite A was taken as 1.82.

[0054] Manufacturing of ceramic composite A' Yttrium oxide particles, aluminum oxide particles, and cerium oxide particles are used, and the molar ratio of each element Y, Al, and Ce contained in each oxide particle is Y 2.99 Ce 0.01 Al 5.1 O 12 Ceramic composite A' was obtained in the same manner as ceramic composite A, except that the composition was measured to be as shown. The true density of ceramic composite A' is 4.6 g / cm³. 3 The refractive index of the rare earth aluminate phosphor A' is 1.82, and the refractive index of the ceramic composite A' was set to 1.82.

[0055] Manufacturing of ceramic composite B Yttrium oxide particles, aluminum oxide particles, and cerium oxide particles are used, and the molar ratio of each element Y, Al, and Ce contained in each oxide particle is Y 2.99 Ce 0.01 Al 5.1 O 12 Except for weighing to achieve the composition shown, ceramic composite B consisting of rare earth aluminate phosphor B was obtained in the same manner as ceramic composite A. The true density of rare earth aluminate phosphor B is 4.6 g / cm³. 3 Therefore, the true density of the rare-earth aluminate phosphor B was taken as the true density of the ceramic composite B. The relative density of the ceramic composite B calculated based on equations (2) and (3) above was 97.5%. The refractive index of the rare-earth aluminate phosphor B was 1.82, and the refractive index of the ceramic composite B was taken as 1.82.

[0056] Manufacturing of ceramic composite C Specific surface area 12 m² using the BET method 2 Lutetium oxide particles per gram, specific surface area 11.8 m² by BET method. 2 Aluminum oxide particles / g, specific surface area 125m² by BET method. 2 The molar ratio of Lu, Al, and Ce contained in each oxide particle of cerium oxide particles is Lu 2.987 Ce 0.013 Al5O 12 A ceramic composite C consisting of rare earth aluminate phosphor C was obtained in the same manner as for ceramic composite A, except that the composition was measured to be as shown. The true density of rare earth aluminate phosphor C was 6.69 g / cm³. 3 Therefore, the true density of the rare-earth aluminate phosphor C was taken as the true density of the ceramic composite C. The relative density of the ceramic composite C calculated based on equations (2) and (3) above was 97.7%. The refractive index of the rare-earth aluminate phosphor C was 1.85, and the refractive index of the ceramic composite C was taken as 1.85.

[0057] Wavelength conversion members of Examples A-1 to A-7 A ceramic composite A with a thickness of 200 μm and magnesium fluoride as the deposition material are placed inside the deposition apparatus, and the pressure inside the deposition apparatus is set to 1.0 × 10⁻⁶ -4 Under reduced pressure to Pa, a microheater was used to deposit a translucent thin film (MgF2 film) on ceramic composite A at a temperature of 300°C, using resistance heating deposition to achieve the physical film thicknesses shown in Table 1. Wavelength conversion members A-1 to A-7 with each physical film thickness were obtained. The refractive index of the translucent thin film is 1.38, which is the refractive index of MgF2.

[0058] Wavelength conversion component of comparative example a-1 A ceramic composite A with a thickness of 200 μm that does not form a translucent thin film was used as the wavelength conversion member in Comparative Example a-1.

[0059] Wavelength conversion component of comparative example a-2 A wavelength conversion member of Comparative Example a-2 was obtained in the same manner as in Examples A-1 to A-7, except that a translucent thin film (MgF2 film) with a thickness of 149 nm, exceeding 140 nm as shown in Table 1, was formed on a ceramic composite A with a thickness of 200 μm.

[0060] Wavelength conversion members of Examples A-8 to A-11 Wavelength conversion members of Examples A-8 to A-11 were obtained in the same manner as in Examples A-1 to A-7, except that a translucent thin film (MgF2 film) was formed on ceramic composite A' having the thicknesses shown in Table 2, so that the physical film thickness was as shown in Table 2. The refractive index of the translucent thin film is 1.38, which is the refractive index of MgF2.

[0061] Wavelength conversion component of Comparative Example a-3 The wavelength conversion member of Comparative Example a-3 was obtained in the same manner as in Examples A-8 to A-11, except that a translucent thin film (MgF2 film) with a physical film thickness of 87 nm was formed on a ceramic composite A' with a thickness exceeding 800 μm (1000 μm).

[0062] Wavelength conversion members of Examples B-1 to B-4 Using a ceramic composite B with a thickness of 200 μm and silicon dioxide, a translucent thin film (SiO2 film) was formed on the ceramic composite B at an output of 500 W using a magnetron sputtering apparatus, so that the physical film thickness was as shown in Table 3, thereby obtaining wavelength conversion members B-1 to B-4 with each physical film thickness. The refractive index of the translucent thin film is 1.47, which is the refractive index of SiO2.

[0063] Wavelength conversion component of comparative example b-1 A ceramic composite B with a thickness of 200 μm that does not form a translucent thin film was used as the wavelength conversion member in Comparative Example b-1.

[0064] Wavelength conversion members of Examples C-1 and C-2 Using a ceramic composite C with a thickness of 150 μm and silicon dioxide, a translucent thin film (SiO2 film) was formed on the ceramic composite C at an output of 500 W using a magnetron sputtering apparatus, so that the physical film thickness was as shown in Table 4, thereby obtaining wavelength conversion members C-1 and C-2 with the respective physical film thicknesses. The refractive index of the translucent thin film is 1.47, which is the refractive index of SiO2.

[0065] Wavelength conversion component of comparative example c-1 A ceramic composite C with a thickness of 150 μm that does not form a translucent thin film was used as the wavelength conversion member in comparative example c-1.

[0066] The following evaluations were performed on each wavelength conversion member in the examples and comparative examples. The results are shown in Tables 1 to 4. In Tables 1 to 4, the symbol "-" indicates the absence of a translucent thin film.

[0067] Physical thickness of translucent thin films The thickness of the translucent thin film was calculated using the following equation (4) based on the optical properties (control wavelength λ, refractive index n) of each wavelength conversion component. In equation (4) of TIFF2026083242000005.tif16155, d is the film thickness, λ is the control wavelength, and n is the refractive index. Equation (4) is based on page 61 of "Basic Theory of Optical Thin Films - Fresnel Coefficient, Characteristic Matrix -" by Mitsunobu Kohiyama, published by Optronics Co., Ltd., February 25, 2011, first edition with augmentation and revision. The control wavelength λ used was the emission peak wavelength of the rare-earth aluminate phosphor contained in each ceramic composite.

[0068] Relative luminous efficiency (%) For each wavelength conversion member in the examples and comparative examples, a laser beam with a wavelength of 450 nm was irradiated from a laser diode so that the incident beam diameter was 2.2 mm, and the beam was incident on the wavelength conversion member from the translucent thin film side. The radiant flux of the light emitted from the translucent thin film side, which is the same surface as the surface on which the laser beam was incident, was measured using an integrating sphere. The radiant flux of the wavelength conversion member according to Comparative Example a-1 was set to 100%, and the radiant flux measured for each sample of the wavelength conversion member according to Examples A-1 to A-11, Comparative Example a-2, and Comparative Example a-3 was expressed as the relative luminous efficiency (%) relative to the radiant flux of Comparative Example a-1. Similarly, the radiant flux of Comparative Example b-1 was set to 100%, and the radiant flux measured for each sample of the wavelength conversion member according to Examples B-1 to B-4 was expressed as the relative luminous efficiency (%) relative to the radiant flux of Comparative Example b-1. Furthermore, the radiant flux of Comparative Example c-1 was set to 100%, and the radiant flux of each wavelength conversion member sample from Examples C-1 and C-2 was measured relative to the radiant flux of Comparative Example c-1 and expressed as relative luminous efficiency (%).

[0069] First transmittance (%) and second transmittance (%) Using a spectrophotometer (manufactured by Hitachi High-Tech Science Co., Ltd.), the light from the light source was converted into monochromatic light with a wavelength of 450 nm using a spectrometer. The light intensity of the converted 450 nm light was measured and recorded as the incident light intensity. Light with a wavelength of 450 nm was incident on the wavelength conversion member from the translucent thin film side, and the light intensity of the light emitted from the ceramic composite side of the wavelength conversion member was measured and recorded as the transmitted light intensity. The ratio of the transmitted light intensity to the incident light intensity was calculated based on formula (1) and measured as the first transmittance of 450 nm light. The second transmittance was measured in the same manner as the first transmittance, except that the light was converted into monochromatic light with a wavelength of 550 nm.

[0070] Transmission spectrum Using a spectrophotometer (manufactured by Hitachi High-Tech Science Co., Ltd.), the light from the light source was converted into monochromatic light of each wavelength by a spectrometer. The light intensity of the converted light wavelengths was defined as the incident intensity. Light of each wavelength was incident on the wavelength conversion member from the translucent thin film side, and the light intensity of the light emitted from the ceramic composite side of the wavelength conversion member was measured to define the transmitted light intensity. The ratio of the transmitted light intensity to the incident intensity was calculated based on formula (1) above, and the transmittance of each wavelength was expressed as a transmission spectrum. Figure 11 shows the transmission spectra of each wavelength conversion member for Examples A-2, A-8 to A-11, and Comparative Examples a-1 and a-3.

[0071] First reflectance (%), second reflectance (%), and the sum of the first and second reflectances. Using a microspectroscopy measuring device (manufactured by Olympus Corporation), the reflectance of BK7 was measured for light incident at an incident angle of 0°, and the measured reflectance of BK7 was set to 100%. The reflectance of light incident from the transparent thin film side at an incident angle of 0° was measured from the transparent thin film side of the wavelength conversion member, and the first reflectance for light with a wavelength of 450 nm and the second reflectance for light with a wavelength of 550 nm were calculated. For example, if the reflectance measured from the transparent thin film side of the wavelength conversion member incident at an incident angle of 0° is 70% relative to the reflectance of BK7 for light incident at an incident angle of 0° (measured value), and the reflectance of BK7 for light with a wavelength of 450 nm (measured value) is 4.1%, then the first reflectance of the wavelength conversion member for light with a wavelength of 450 nm was calculated as 2.87% by dividing the product of 4.1% and 70% by 100. Furthermore, the sum of the first and second reflectances (hereinafter also referred to as the "sum of reflectances") was calculated.

[0072] Reflectance spectrum, wavelength of minimum reflectance Using a microspectroscopy measuring device (manufactured by Olympus Corporation), the reflectance of BK7 for light of each wavelength incident at an incident angle of 0° was measured. The reflectance of BK7 for light of each wavelength was set to 100%. The reflectance of light of each wavelength incident from the transparent thin film side of the wavelength conversion member at an incident angle of 0° was measured from the transparent thin film side of the wavelength conversion member, and the reflectance of light of each wavelength was calculated from the reflectance of BK7 and expressed as a reflection spectrum. The wavelength of minimum reflectance was measured from the reflection spectrum of each wavelength conversion member. Figures 6, 8 to 10 show the reflection spectra of each wavelength conversion member in the examples and comparative examples.

[0073] Reflectance spectrum and minimum reflectance wavelength of the wavelength conversion member according to Example A-1 To measure the reflectance of the wavelength conversion member according to Example A-1 below 380 nm, the following measurements were taken. Instead of a ceramic composite with a thickness of 200 μm, quartz with a thickness of 200 μm was used, and a translucent thin film with the same physical thickness as Example A-1 was formed on this quartz in the same manner as in Example A-1, to prepare sample A-1'. Using a spectrophotometer U-4100 (manufactured by Hitachi High-Tech Corporation), the amount of light at each wavelength that directly reached the integrating sphere from the light source was set to 100%. The bilateral reflectance of light at each wavelength incident from the translucent thin film side of sample A-1' at an incident angle of 5° was measured and expressed as a reflectance spectrum. The reflectance spectrum of sample A-1' was taken as the reflectance spectrum of Example A-1. The wavelength of minimum reflectance was measured from the reflectance spectrum of sample A-1' and taken as the wavelength of minimum reflectance of Example A-1. Figure 7 shows the reflectance spectrum of the wavelength conversion member according to Example A-1.

[0074] [Table 1]

[0075] [Table 2]

[0076] [Table 3]

[0077] [Table 4]

[0078] The wavelength conversion members of Examples A-1 to A-11, Examples B-1 to B-4, and Examples C-1 to C-2 had a ceramic composite thickness in the range of 80 μm to 800 μm, a translucent thin film thickness in the range of 50 nm to 140 nm, a first reflectance and a second reflectance of 7% or less, and a sum of reflectances of 10% or less. The wavelength conversion members of each example all showed higher relative luminous efficiency compared to the wavelength conversion members of Comparative Examples a-1, b-1, or c-1, which did not have a translucent thin film. The wavelength conversion members of each example all showed a first transmittance and a second transmittance of 20% or more.

[0079] Figures 6 and 7 show the reflectance spectra of the reflectance (%) against wavelength of the wavelength conversion members according to Examples A-1 to A-7 and Comparative Examples a-1 to a-2. The wavelength conversion members according to Examples A-1 to A-7 had a minimum reflectance wavelength of 730 nm or less. The wavelength conversion member according to Comparative Example a-1, which does not have a translucent thin film, had a first reflectance exceeding 7% and a sum of reflectances exceeding 10%. The wavelength conversion member according to Comparative Example a-2, which has a translucent thin film thickness exceeding 140 nm to 149 nm, also had a first reflectance exceeding 7% and a sum of reflectances exceeding 10%. In addition, although the minimum reflectance of the wavelength conversion member according to Comparative Example a-2 is not shown in Figure 6, it is presumed that the wavelength of the minimum reflectance of the wavelength conversion member according to Comparative Example a-2 exceeds 730 nm. Because the first reflectance of the wavelength conversion members according to Examples A-1 to A-7 is less than 7%, the intensity of the excitation light incident on the ceramic composite becomes larger, resulting in higher relative luminous efficiency. Furthermore, since the wavelength conversion members according to Examples A-1 to A-7 also have a second reflectance at a wavelength of 550 nm that is less than 7%, the wavelength-converted light is efficiently emitted from the wavelength conversion member, resulting in a higher relative luminescence efficiency than the wavelength conversion member according to Comparative Example a-2.

[0080] Figure 8 shows the reflectance spectra of the reflectance (%) against wavelength of the wavelength conversion members according to Examples A-8 to A-11 and the wavelength conversion members according to Comparative Examples a-1 and a-3. The wavelength of minimum reflectance for the wavelength conversion members according to Examples A-8 to A-11 and the wavelength conversion member according to Comparative Example a-3 was 730 nm or less. The wavelength conversion members according to Examples A-8 to A-11 had higher transmittance and higher relative luminous efficiency than the wavelength conversion member according to Comparative Example a-3, in which the thickness of the ceramic composite was greater than 800 μm and less than or equal to 1000 μm, as shown in Table 2 and Figure 11 described later.

[0081] Figure 9 shows the reflectance spectra of the reflectance (%) against wavelength of the wavelength conversion members according to Examples B-1 to B-4 and the wavelength conversion member according to Comparative Example b-1. The wavelength of the minimum reflectance of the wavelength conversion members according to Examples B-1 to B-4 was 730 nm or less. The wavelength conversion member according to Comparative Example b-1, which does not have a translucent thin film, had a first reflectance and a second reflectance each exceeding 7%, and the sum of the reflectances also exceeded 10%.

[0082] Figure 10 shows the reflectance spectra of the reflectance (%) against wavelength of the wavelength conversion members according to Examples C-1 and C-2 and the wavelength conversion member according to Comparative Example c-1. The wavelength of the minimum reflectance of the wavelength conversion members according to Examples C-1 and C-2 was 730 nm or less. The wavelength conversion member according to Comparative Example c-1, which does not have a translucent thin film, had a first reflectance and a second reflectance that each exceeded 7%, and the sum of the reflectances also exceeded 10%.

[0083] Figure 11 shows the transmission spectra of the transmittance (%) for wavelengths of the wavelength conversion members according to Examples A-2, A-8 to A-11 and Comparative Examples a-1 and a-3, each with different ceramic composite thicknesses. In the transmission spectra within the wavelength range of 380 nm to 780 nm, the transmittance tends to decrease as the thickness of the ceramic composite increases. For the wavelength conversion member according to Comparative Example a-3, where the thickness of the ceramic composite exceeds 800 μm and is 1000 μm, both the first transmittance at a wavelength of 450 nm and the second transmittance at a wavelength of 550 nm were less than 20%. [Industrial applicability]

[0084] The wavelength conversion member and light-emitting device relating to this disclosure can be used as an in-vehicle light source, a lighting device for general lighting, a backlight for a liquid crystal display device, or a light source for a projector. [Explanation of Symbols]

[0085] 100: Light-emitting device, 101: Excitation light source, 102: Collimating lens, 103, 105 and 106: Condenser lens, 104: Dichroic mirror, 107: Rod integrator, 110: Wavelength conversion member, 111: Ceramic composite, 112: Translucent thin film, 120: Wavelength conversion device, 121: Rotating mechanism, 122: Light reflector.

Claims

1. A ceramic composite containing a phosphor having an emission peak wavelength in the range of 510 nm to 570 nm, The ceramic composite comprises a translucent thin film disposed on the ceramic composite, The thickness of the translucent thin film is in the range of 50 nm to 140 nm, and the thickness of the ceramic composite is in the range of 80 μm to 800 μm. A wavelength conversion member in which, when measured from the side of the translucent thin film, the first reflectance of light with a wavelength of 450 nm incident at an incident angle of 0° is 7% or less, the second reflectance of light with a wavelength of 550 nm incident at an incident angle of 0° is 7% or less, and the sum of the first reflectance and the second reflectance is 10% or less.

2. The wavelength conversion member according to claim 1, wherein the wavelength of the minimum reflectance within the range of 380 nm to 830 nm of light incident at an incident angle of 0°, measured from the side of the translucent thin film, is 730 nm or less.

3. The wavelength conversion member according to claim 1 or 2, wherein the refractive index of the translucent thin film is in the range of 1.3 or more and 1.5 or less.

4. The wavelength conversion member according to any one of claims 1 to 3, wherein the refractive index of the ceramic composite is in the range of 1.76 or more and 1.85 or less.

5. The wavelength conversion member according to any one of claims 1 to 4, wherein the light-transmitting thin film is made of magnesium fluoride.

6. The wavelength conversion member according to any one of claims 1 to 4, wherein the translucent thin film is made of silicon dioxide, and the thickness of the translucent thin film made of silicon dioxide is in the range of 80 nm to 130 nm.

7. The wavelength conversion member according to any one of claims 1 to 6, wherein the phosphor is a rare earth aluminate phosphor.

8. The wavelength conversion member according to claim 7, wherein the rare earth aluminate phosphor has a composition represented by the following formula (I). (Ln) １ １－ａ Yes ａ ) ３ (Al) ｃ Ga ｂ ) ５ O １２ (I) (In the above formula (I), Ln １ is at least one selected from the group consisting of Y, Gd, Lu, and Tb, and a, b, and c satisfy 0 < a ≤ 0.22, 0 ≤ b ≤ 0.4, 0 < c ≤ 1.1, and 0.9 ≤ b + c ≤ 1.1.)

9. A light-emitting device comprising: a light-emitting element having an emission peak wavelength in the range of 380 nm to 500 nm; and a wavelength conversion member according to any one of claims 1 to 8, which is irradiated with light from the light-emitting element and performs wavelength conversion.

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