Wavelength conversion member and optical member

Abstract

To provide a wavelength conversion member capable of reducing a light diameter of emission light with respect to a light diameter of incident light.SOLUTION: A wavelength conversion member according to an embodiment of the present disclosure includes phosphor particles, a translucent filler, and a translucent binder having voids.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a wavelength conversion member and an optical member. [Background technology]

[0002] Light-emitting devices are known that include a light-emitting diode (LED) or a laser diode (LD) and a wavelength conversion member containing a phosphor that converts the wavelength of light emitted from the LED or LD. Such light-emitting devices are used as light sources for, for example, in-vehicle lighting, general lighting, backlights for liquid crystal display devices, projectors, etc.

[0003] As a wavelength conversion member provided in a light emitting device, for example, Patent Document 1 discloses a sintered body containing crystal aggregate grains and an aluminum oxide phase. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2024-31839 Summary of the Invention [Problem to be solved by the invention]

[0005] Such wavelength conversion members are required to reduce the spot diameter of incident laser light, particularly in light emitting devices using LDs.

[0006] Therefore, an object of one embodiment of the present disclosure is to provide a wavelength conversion member that can reduce the diameter of emitted light relative to the diameter of incident light. [Means for solving the problem]

[0007] A wavelength conversion member according to an embodiment of the present disclosure includes phosphor particles, a translucent filler, and a translucent binder having voids. [Effects of the Invention]

[0008] According to the wavelength conversion member according to an embodiment of the present disclosure, the diameter of the emitted light can be made smaller than the diameter of the incident light. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 2 is a schematic cross-sectional view of a wavelength conversion member according to one embodiment. [Figure 2] FIG. 2 is a partially enlarged view of FIG. [Figure 3] FIG. 1 is a schematic cross-sectional view of an optical member according to an embodiment. [Figure 4] FIG. 1 is a diagram showing a schematic configuration of an example of a light emitting device. [Figure 5] 10 is a diagram showing the relationship between the distance from the measurement center of emitted light and relative luminance in the wavelength conversion member of Example 1. FIG. [Figure 6] 10 is a diagram showing the relationship between the distance from the measurement center of the emitted light and the relative luminance in the wavelength conversion member of Example 2. FIG. [Figure 7] 10 is a diagram showing the relationship between the distance from the measurement center of emitted light and relative luminance in the wavelength conversion member of Comparative Example 1. FIG. [Figure 8] FIG. 10 is a diagram showing an SEM observation image of the wavelength conversion member of Example 3. DETAILED DESCRIPTION OF THE INVENTION

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following describes the preferred embodiments of the present invention with reference to the accompanying drawings. The same reference numerals appearing in multiple drawings indicate the same or equivalent parts or components.

[0011] Furthermore, the embodiments shown below are illustrative of wavelength conversion members, optical members, etc., embodying the technical concepts of the present invention, and are not intended to limit the present invention. Furthermore, unless otherwise specified, the dimensions, materials, shapes, relative positions, etc. of the components described below are intended for illustrative purposes only and are not intended to limit the scope of the present invention. Furthermore, the content described in one embodiment may also be applied to other embodiments and modified examples. Furthermore, the size and positional relationships of components shown in the drawings may be exaggerated for clarity. Furthermore, to avoid overly complex drawings, schematic diagrams may be used in which some elements are omitted, or end views may be used as cross-sectional views showing only the cut surface.

[0012] <Wavelength conversion material> FIG. 1 is a schematic cross-sectional view of a wavelength conversion member according to one embodiment, and FIG. 2 is a partially enlarged view of FIG. 1. The wavelength conversion member 1 of this embodiment is, for example, a flat-plate-shaped member as shown in FIG. 2. As shown in FIG. 2, the wavelength conversion member 1 includes phosphor particles 2, a translucent filler 3, and a translucent binder 5 having voids 4. Here, the voids 4 refer to voids formed in the translucent binder 5, which is a continuous phase (single phase state) made of the translucent binder 5, and refer to spaces surrounded by the translucent binder 5. A gas (e.g., air) is disposed in the voids 4. The voids 4 are formed by a chemical reaction during the formation of the translucent binder 5, and do not include voids formed by the boundaries between granular materials, for example. With this configuration, the wavelength conversion member 1 can reduce the diameter of emitted light relative to the diameter of incident light.

[0013] The transmittance of the wavelength conversion member 1 for light with a wavelength of 550 nm is preferably greater than 0% and less than 0.4%, more preferably greater than 0% and less than 0.2%, even more preferably greater than 0% and less than 0.2%, and most preferably greater than 0% and less than 0.1%. Here, the transmittance refers to the value measured using a spectrophotometer for a wavelength conversion member 1 with a thickness of 0.3 mm. Since the transmittance of the wavelength conversion member 1 for light with a wavelength of 550 nm is greater than 0% and less than 0.4%, the wavelength conversion member 1 can be suitably used in light emitting devices, such as light sources for projectors, that have a configuration in which light incident on a first main surface of the wavelength conversion member 1 is reflected and emitted from the first main surface.

[0014] The particle size of the phosphor particles 2 is preferably 10 μm to 20 μm, more preferably 12 μm to 18 μm, and even more preferably 14 μm to 16 μm. Here, the particle size of the phosphor particles 2 refers to the volume-average particle size measured using a particle size distribution analyzer using a capillary electrical resistance method (electrical detection zone method) based on the Coulter principle, and the median diameter corresponding to 50% of the cumulative volume from the short diameter side of the particle size distribution. When the particle size of the phosphor particles 2 is 10 μm to 20 μm, the phosphor particles 2 are less likely to overlap with each other, increasing the probability that translucent filler 3 is present around them. This suggests that light wavelength-converted by the phosphor particles 2 is more likely to be diffusely reflected at the translucent filler 3 interface. Therefore, when the particle size of the phosphor particles 2 is within the above range, the wavelength conversion member 1 can further reduce the diameter of the emitted light relative to the diameter of the incident light.

[0015] In the cross section, the area ratio of the phosphor particles 2 is preferably smaller than the area ratio of the light-transmitting filler 3. The area ratio can be calculated by the following method. The cross section of the wavelength conversion member 1 is observed using a scanning electron microscope (SEM), and the obtained SEM image is subjected to boundary blurring and binarization processing, and the area ratio of the light-transmitting filler 3 to the total area of ​​the observation field is calculated. The area of ​​the observation field is, for example, 0.015 mm 2 It can be said that:

[0016] Since the area ratio of the phosphor particles 2 is smaller than the area ratio of the translucent filler 3, the phosphor particles 2 are less likely to overlap with each other, and the probability that translucent filler 3 is present in the surrounding area increases, so it is thought that the light whose wavelength is converted by the phosphor particles 2 is more likely to be diffusely reflected at the interface of the translucent filler 3.

[0017] In the cross section, the area ratio of the phosphor particles 2 is preferably 10% or more and 22% or less, more preferably 12% or more and 19% or less, and even more preferably 14% or more and 16% or less.

[0018] The material constituting the phosphor particles 2 is, for example, an yttrium-aluminum-garnet phosphor (e.g., (Y,Gd)3(Al,Ga)5O 12 : Ce, (Y, Gd, Ce)3Al5O 12 ), lutetium aluminum garnet phosphors (e.g., Lu3(Al,Ga)5O 12 :Ce), terbium aluminum garnet phosphors (e.g., Tb3(Al,Ga)5O 12 :Ce), CCA-based phosphors (e.g., Ca 10 (PO4)6Cl2:Eu), SAE-based phosphors (e.g., Sr4Al 14 O 25 :Eu), chlorosilicate phosphors (e.g., Ca8MgSiO 16 Cl2:Eu), silicate-based phosphors (e.g., (Ba,Sr,Ca,Mg)2SiO4:Eu), β-sialon-based phosphors (e.g., (Si,Al)3(O,N)4:Eu) or α-sialon-based phosphors (e.g., Ca(Si,Al) 12 (O,N) 16 oxynitride phosphors such as (La,Y)3Si6N 11:Ce), BSESN-based phosphors (e.g., (Ba,Sr)2Si5N8:Eu), SLA-based phosphors (e.g., SrLiAl3N4:Eu), CASN-based phosphors (e.g., CaAlSiN3:Eu), or SCASN-based phosphors (e.g., (Sr,Ca)AlSiN3:Eu), etc., nitride-based phosphors, KSF-based phosphors (e.g., K2SiF6:Mn), KSAF-based phosphors (e.g., K2(Si 1-x Al x )F 6-x :Mn where x satisfies 0 < x < 1), or fluoride-based phosphors such as MGF-based phosphors (e.g., 3.5MgO·0.5MgF2·GeO2:Mn), quantum dots having a perovskite structure (e.g., (Cs,FA,MA)(Pb,Sn)(F,Cl,Br,I)3 where FA and MA represent formamidinium and methylammonium, respectively), II-VI group quantum dots (e.g., CdSe), III-V group quantum dots (e.g., InP), or quantum dots having a chalcopyrite structure (e.g., (Ag,Cu)(In,Ga)(S,Se)2), etc.

[0019] The shape of the translucent filler 3 is preferably columnar. Columnar includes cylindrical and prismatic shapes. The shape of the translucent filler 3 may be fibrous. When the shape of the translucent filler 3 is columnar, the binding between the translucent filler 3 and the translucent binder 5 becomes stronger, so that the wavelength conversion member 1 can improve its mechanical strength.

[0020] When the shape of the translucent filler 3 is columnar, the diameter of the translucent filler 3 is preferably 5 μm or more and 15 μm, more preferably 7 μm or more and 13 μm or less, and even more preferably 9 μm or more and 11 μm or less. Here, the diameter of the translucent filler 3 means the distance (major axis) between the two farthest points on the bottom surface or cross-section. When the diameter of the translucent filler 3 is 5 μm or more and 15 μm, the binding between the translucent filler and the translucent binder 5 becomes stronger, so that the wavelength conversion member 1 can improve its mechanical strength.

[0021] The aspect ratio of the light-transmitting filler 3 is preferably 1.0 or more and 35 or less, more preferably 10 or more and 35 or less, and even more preferably 20 or more and 35 or less. When the aspect ratio of the light-transmitting filler 3 is 1.0 or more and 35 or less, the bond between the light-transmitting filler 3 and the light-transmitting binder 5 becomes stronger, and the mechanical strength of the wavelength conversion member 1 can be improved.

[0022] The aspect ratio of the light-transmitting filler 3 can be calculated by the following method. The light-transmitting filler 3 is observed using a scanning electron microscope (SEM), and the length of the major axis and the length of the minor axis are measured point by point on the obtained SEM image using image analysis software, and the ratio of the length of the major axis to the length of the minor axis (aspect ratio) is calculated. Then, the average value of the aspect ratios of 100 light-reflecting materials is calculated.

[0023] In cross section, the length of the major axis of the light-transmitting filler 3 is preferably greater than the particle size of the phosphor particle 2 .

[0024] The refractive index of the light-transmitting filler 3 at a wavelength of 550 nm is preferably 1.40 or more and 1.46 or less, more preferably 1.40 or more and 1.45 or less, and even more preferably 1.40 or more and 1.44 or less. When the refractive index of the light-transmitting filler 3 at a wavelength of 550 nm is 1.40 or more and 1.46 or less, the wavelength conversion member 1 can make the diameter of the emitted light smaller than the diameter of the incident light.

[0025] In the cross section, the area ratio of the light-transmitting filler 3 is preferably 35% or more and 85% or less, more preferably 45% or more and 75% or less, and even more preferably 55% or more and 65% or less. When the area ratio of the light-transmitting filler 3 in the cross section is 35% or more and 85% or less, the wavelength conversion member 1 can sufficiently diffuse and reflect the light whose wavelength has been converted by the phosphor particles 2 by the light-transmitting filler 3.

[0026] In the cross section, the area ratio of the translucent filler 3 is preferably 35% or more and 85% or less, and the area ratio of the phosphor particles 2 is preferably 10% or more and 22% or less. With this configuration, the wavelength conversion member 1 can more sufficiently diffuse and reflect light whose wavelength has been converted by the phosphor particles 2 by the translucent filler 3.

[0027] Examples of materials constituting the light-transmitting filler 3 include silica (silicon dioxide) and alumina (aluminum oxide). Among these, the light-transmitting filler 3 preferably contains silica. Specifically, the light-transmitting filler 3 is preferably a glass filler.

[0028] The refractive index at a wavelength of 550 nm of the light-transmitting binder 5 excluding the voids 4 is preferably higher than the refractive index at a wavelength of 550 nm of the light-transmitting filler 3. This enables the wavelength conversion member 1 to make the diameter of the emitted light smaller than the diameter of the incident light.

[0029] Specifically, the refractive index at a wavelength of 550 nm of the portion of the light-transmitting binder 5 excluding the voids 4 is preferably greater than 1.46 and less than 1.50, more preferably greater than 1.47 and less than 1.50, and even more preferably greater than 1.48 and less than 1.50. This makes it possible for the wavelength conversion member 1 to make the diameter of the emitted light smaller than the diameter of the incident light.

[0030] The light-transmitting binder 5 preferably contains silica and an alkali metal. This allows the wavelength conversion member 1 to improve the reflectance of incident light, and therefore the wavelength conversion member 1 can be suitably used in a light-emitting device configured to reflect light incident on the first main surface of the wavelength conversion member 1 and emit it from the first main surface. Furthermore, the wavelength conversion member 1 can improve its heat resistance against the heat of incident light.

[0031] Examples of the alkali metal include potassium, sodium, lithium, etc. Among these, the alkali metal is preferably potassium or sodium.

[0032] The translucent binder 5 may contain an alkali metal silicate. Examples of the alkali metal silicate include potassium silicate, sodium silicate, and lithium metasilicate.

[0033] In the cross section, the area ratio of the light-transmitting binder 5 is preferably 8% or more and 24% or less, more preferably 10% or more and 21% or less, and even more preferably 12% or more and 18% or less.

[0034] The light-transmitting binder 5 is preferably porous. Here, "porous" means that there are a plurality of voids 4, and for example, the area ratio of the voids 4 is 4% or more and 18% or less. This allows the wavelength conversion member 1 to make the diameter of the emitted light smaller than the diameter of the incident light.

[0035] In the cross section, the area ratio of the voids 4 is preferably 4% or more and 18% or less, more preferably 6% or more and 15% or less, and even more preferably 8% or more and 12% or less.

[0036] An example of a method for manufacturing the wavelength conversion member 1 of this embodiment will be described. The method for manufacturing the wavelength conversion member 1 of this embodiment includes a step of mixing phosphor particles 2, a translucent filler 3, silica powder, and an alkali metal aqueous solution to prepare a mixture, and a step of heating the mixture.

[0037] In the step of preparing the mixture, the concentration of the alkali metal aqueous solution is preferably 1 mol / L or more and 10 mol / L or less, and more preferably 3 mol / L or more and 5 mol / L or less. When the concentration of the alkali metal aqueous solution is 3 mol / L or more and 5 mol / L or less, a porous light-transmitting binder 5 can be formed. The alkali metal aqueous solution is, for example, a potassium hydroxide solution or a sodium hydroxide solution.

[0038] In the step of heating the mixture, the mixture is heated to harden the mixture and form the wavelength conversion material 1. The wavelength conversion material 1 contains an alkali metal silicate produced by a reaction between silica contained in the mixture and an alkali metal aqueous solution. Furthermore, when the mixture hardens, the water in the alkali metal aqueous solution evaporates, forming voids 4.

[0039] The step of heating the mixture includes, for example, a preliminary curing step in which the mixture is cured at a first temperature T1 and a main curing step in which the mixture is cured at a second temperature T2 higher than the first temperature T1. The preliminary curing step involves heating the mixture at a first temperature T1 of 80°C or higher and 100°C or lower for 10 minutes to 2 hours. The main curing step involves heating the mixture at a second temperature T2 of 150°C or higher and 250°C or lower for 10 minutes to 3 hours.

[0040] <Optical components> Fig. 3 is a schematic cross-sectional view of an optical member 10 according to one embodiment. As shown in Fig. 3, the optical member 10 includes a substrate 8 and a wavelength conversion member 1 disposed on the substrate 8. Because the optical member 10 includes the wavelength conversion member 1, the diameter of the emitted light can be made smaller than the diameter of the incident light. Examples of materials that can be used to form the substrate 8 include aluminum, iron, copper, and stainless steel.

[0041] The wavelength conversion member 1 can be used in a light emitting device such as a light source for a projector by combining it with a light source.

[0042] A light emitting device using the wavelength conversion member 1 or the optical member 10 described above will be described. The light emitting device includes the wavelength conversion member 1 and an excitation light source. The light emitting device may include the optical member 10 having the wavelength conversion member 1 and an excitation light source.

[0043] The excitation light source is preferably a semiconductor light-emitting element made of an LED chip or an LD chip. The semiconductor light-emitting element can be made of a nitride-based semiconductor. By using a semiconductor light-emitting element as the excitation light source, a light-emitting device can be obtained that is highly efficient, has high output linearity relative to input, and is stable and resistant to mechanical shocks.

[0044] The wavelength conversion member 1 converts 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 semiconductor light emitting element preferably emits light in a wavelength range of, for example, 350 nm or more and 500 nm or less. The wavelength conversion member 1 preferably converts the wavelength of excitation light from the semiconductor light emitting element to emit output light having an emission peak wavelength of 500 nm or more and less than 650 nm.

[0045] The light emitting element is preferably an LD. The excitation light emitted from the LD, which serves as the excitation light source, is incident on the wavelength conversion member 1, and the light whose wavelength has been converted by the phosphor particles 2 contained in the wavelength conversion member 1 is condensed 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 image information to form color image light. The excitation light emitted from the LD, which serves as the excitation light source, may be incident on the wavelength conversion member 1 through an optical system such as a dichroic mirror or a collimating optical system.

[0046] FIG. 4 is a schematic diagram showing the configuration of an example of a light emitting device 100. Arrows in FIG. 4 schematically represent the optical paths of light. The light emitting device 100 preferably includes an excitation light source 101 which is a light emitting element, a collimator lens 102, three condenser lenses 103, 105, and 106, a dichroic mirror 104, a rod integrator 107, and a wavelength conversion member 1. In the example shown in FIG. 4, the wavelength conversion member 1 is applied to the light emitting device 100 as the optical member 10.

[0047] It is preferable to use an LD as the excitation light source 101. The excitation light source 101 may use a plurality of LDs, or may be one in which a plurality of LDs are arranged in an array or matrix.

[0048] The collimator lens 102 may be a collimator lens array in which a plurality of collimator lenses are arranged in an array. The laser light emitted from the excitation light source 101 is converted into approximately parallel light by the collimator lens 102, collected by the condenser lens 103, passes through the dichroic mirror 104, and is further collected by the condenser lens 105.

[0049] The laser light condensed by condenser lens 105 is wavelength-converted by optical member 10 including wavelength conversion member 1 and substrate 8, and light having an emission peak wavelength in a desired wavelength range is emitted from the wavelength conversion member 1 side of optical member 10. The wavelength-converted light emitted from optical member 10 is condensed by condenser lens 106, made incident on rod integrator 107, and emitted from light emitting device 100. [Example]

[0050] The embodiment will be described in more detail below by way of examples.

[0051] <Fabrication of wavelength conversion material> Example 1 First, we used (Y, Gd, Ce)3Al5O with a particle size of 15 μm as phosphor particles. 12 A mixture was prepared by mixing 1.22g of phosphor particles (manufactured by Nichia Corporation), 9.38g of a glass filler (manufactured by Nitto Boseki Co., Ltd.) as a translucent filler, which was columnar, i.e., fibrous, with a diameter of 10μm and an aspect ratio of 15, and 2.5g of silica powder (manufactured by Denka Co., Ltd.) with an average particle size and median diameter of 0.4μm as one of the translucent binder materials, with a potassium hydroxide solution of 5.8mol / L concentration. The particle size of the phosphor particles and the aspect ratio of the translucent filler were measured by the methods described above.

[0052] The mixed powder and potassium hydroxide solution were mixed to the extent that a uniform viscosity was obtained, and then the mixture was defoamed and stirred using a stirring / defoaming machine capable of stirring under reduced pressure.

[0053] Next, the mixture was heated at a first temperature of 90°C under a pressure of 1 MPa for 1 hour for provisional curing, and then heated at a second temperature of 200°C under a pressure of 1 MPa for 2 hours for full curing, thereby obtaining a wavelength conversion member of Example 1.

[0054] Example 2 A wavelength conversion member of Example 2 was obtained in the same manner as in Example 1, except that a potassium hydroxide solution with a concentration of 12 mol / L was used as the potassium hydroxide solution.

[0055] Example 3 A wavelength conversion member of Example 3 was obtained in the same manner as in Example 1, except that a potassium hydroxide solution with a concentration of 3 mol / L was used as the potassium hydroxide solution.

[0056] Example 4 A wavelength conversion member of Example 4 was obtained in the same manner as in Example 1, except that a potassium hydroxide solution with a concentration of 9 mol / L was used as the potassium hydroxide solution.

[0057] (Comparative Example 1) Phosphor particles (Y, Gd, Ce)3Al5O 12 (manufactured by Nichia Corporation) was filled into the mold and subjected to 5 MPa (51 kgf / cm 2 A cylindrical compact was formed under a pressure of 176 MPa. The obtained compact was placed in a packaging container, vacuum-packed, and subjected to cold isostatic pressing at 176 MPa using a cold isostatic pressing device (manufactured by Kobe Steel, Ltd. (KOBELCO)) to obtain a compact. The obtained compact was then heated and degreased at 700°C in a nitrogen atmosphere.

[0058] The compact obtained by molding was fired in a firing furnace (manufactured by Marusho Denki Co., Ltd.) in an air atmosphere (101.325 kPa, oxygen concentration: approximately 20% by volume) at a temperature of 1560°C for 6 hours to obtain a sintered body as the wavelength conversion member of Comparative Example 1.

[0059] <Evaluation of the beam diameter ratio (beam diameter of outgoing light / beam diameter of incoming light)> Each wavelength conversion member of the example and comparative example was irradiated with laser light having a wavelength of 450 nm from an LD so that the diameter of the incident light was 0.6 mm on the first main surface onto which the laser light was incident.

[0060] Then, the luminance of the light emitted from each wavelength conversion member of the Examples and Comparative Examples was measured using a color luminance meter, and the position showing the maximum luminance in the obtained emission spectrum was set as the center (measurement center), and the distances (mm) from the measurement center to two positions showing luminance that was 10 / 100 of the maximum luminance in the emission spectrum (10 / 100 luminance) were measured as absolute values.

[0061] The sum of the absolute values ​​of the distances (mm) from the measurement center to two positions where the brightness is 10 / 100 of the maximum brightness was measured as the diameter of the light emitted from the first principal surface. Since the diameter of the incident laser light on the first principal surface is constant, a smaller diameter of the light emitted from the first principal surface indicates a smaller diameter of the emitted light relative to the diameter of the incident light (beam diameter ratio).

[0062] FIG. 5 is a graph showing the relationship between the distance from the measurement center of the emitted light and the relative luminance in the wavelength conversion member of Example 1, FIG. 6 is a graph showing the relationship between the distance from the measurement center of the emitted light and the relative luminance in the wavelength conversion member of Example 2, and FIG. 7 is a graph showing the relationship between the distance from the measurement center of the emitted light and the relative luminance in the wavelength conversion member of Comparative Example 1. The emission luminance of the light emitted from each wavelength conversion member of the Examples and Comparative Examples was measured using a color luminance meter, and the emission spectra shown in FIGS. 5 to 7 were obtained. The beam diameters of the emitted light from the first principal surfaces of the wavelength conversion members of Example 1, Example 2, and Comparative Example 1 were 0.36 mm, 0.52 mm, and 0.69 mm, respectively. The beam diameter ratios of the emitted light from the first principal surfaces of the wavelength conversion members of Example 1, Example 2, and Comparative Example 1 were 0.5:0.8:1.0.

[0063] From the above, it was confirmed that the wavelength conversion members of Example 1 and Example 2 had a smaller beam diameter ratio (beam diameter of emitted light / beam diameter of incident light) than the wavelength conversion member of Comparative Example 1. Furthermore, when the wavelength conversion members of Example 1 and Example 2 were compared, it was confirmed that the wavelength conversion member of Example 1, which used a lower concentration of potassium hydroxide solution as a transparent binder material, had a smaller beam diameter ratio.

[0064] <Area ratio evaluation> The cross sections of the wavelength conversion members of Examples 1 to 4 were observed using a scanning electron microscope (SEM). Fig. 8 is a diagram showing an SEM image of the wavelength conversion member of Example 3. As shown in Fig. 8, it was confirmed that the wavelength conversion members of Examples 1 to 4 were composed of phosphor particles, a translucent filler, and a translucent binder having voids. In Fig. 8, the white parts are phosphor particles, the gray elongated parts are the translucent filler, and the parts other than the phosphor particles and the translucent filler are the translucent binder. The black parts are voids.

[0065] For the wavelength conversion members of Examples 3 and 4, the obtained SEM images were subjected to boundary blurring and binarization using image analysis software (ImageJ), and the area ratio to the total area of ​​the observation field was calculated. 2 The evaluation results of the area ratio are shown in Table 1.

[0066] [Table 1]

[0067] As shown in Table 1, the area ratio of the phosphor particles was smaller than the area ratio of the light-transmitting filler in the wavelength conversion members of Example 3 and Example 4. In addition, the area ratio of the voids in the wavelength conversion member of Example 3, in which the concentration of the potassium hydroxide solution used as the transparent binder material was low, was larger than the area ratio of the voids in the wavelength conversion member of Example 4.

[0068] <Transmittance measurement> Using a spectrophotometer ("U-2910," manufactured by Hitachi High-Tech Science Corporation), light from the light source was converted to monochromatic light with a wavelength of 550 nm using a spectroscope, and the intensity of the converted light with a wavelength of 550 nm was measured and used as the incident light intensity. The light with a wavelength of 550 nm was then incident on the 0.3 mm thick wavelength conversion members of Example 1, Example 2, and Comparative Example 1, and the intensity of the light exiting the wavelength conversion member on the side opposite to the incident side was measured and used as the transmitted light intensity. The ratio of the transmitted light intensity to the incident light intensity was measured as the transmittance for light with a wavelength of 550 nm based on the following formula (1): In formula (1), I0 is the incident light intensity, and I is the transmitted light intensity at each wavelength. Transmittance (%)=I / I0×100 (1)

[0069] As a result of measuring the transmittance, the transmittance of the wavelength conversion member of Example 1 was 0.1%, the transmittance of the wavelength conversion member of Example 2 was 0.2%, and the transmittance of the wavelength conversion member of Comparative Example 1 was 0.4%.

[0070] <Refractive index measurement> A potassium silicate solution (approximately 50% concentration, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was applied to a glass slide and allowed to slowly evaporate the water in the atmosphere, forming a potassium silicate film in the area excluding the voids in the translucent binder. The potassium silicate film of this sample was free of voids due to the slow evaporation of water. The refractive index of this sample was measured at a wavelength of 550 nm using a refractive index measuring device ("2010M," manufactured by Nippon Metricon Co., Ltd.) based on the Cauchy dispersion equation, resulting in a refractive index of 1.47. Meanwhile, the refractive index of silicon dioxide (silica) at a wavelength of 550 nm is known to be 1.46. Therefore, the refractive index of the area excluding the voids in the translucent binder at a wavelength of 550 nm was confirmed to be higher than the refractive index of the silica used as the translucent filler at a wavelength of 550 nm.

[0071] (Aspects of the present invention) The present invention includes the following aspects. <Aspect 1> The wavelength conversion member includes phosphor particles, a light-transmitting filler, and a light-transmitting binder having voids. <Aspect 2> In the wavelength conversion member according to aspect 1, the refractive index of the portion of the translucent binder excluding the voids at a wavelength of 550 nm is higher than the refractive index of the translucent filler at a wavelength of 550 nm. <Aspect 3> In the wavelength conversion member according to aspect 1 or 2, the refractive index at a wavelength of 550 nm of the portion of the light-transmitting binder excluding the voids is greater than 1.46 and equal to or less than 1.50. <Aspect 4> Aspect 4. The wavelength conversion member according to any one of Aspects 1 to 3, wherein the refractive index of the light-transmitting filler at a wavelength of 550 nm is 1.40 or more and 1.46 or less. <Aspect 5> In the wavelength conversion member according to any one of aspects 1 to 4, the area ratio of the phosphor particles is smaller than the area ratio of the light-transmitting filler in the cross section. <Aspect 6> The wavelength conversion member according to any one of aspects 1 to 5, wherein, in a cross section, the area ratio of the translucent filler is 35% or more and 85% or less, and the area ratio of the phosphor particles is 10% or more and 22% or less. <Aspect 7> 7. The wavelength conversion member according to any one of aspects 1 to 6, wherein the light-transmitting filler has a columnar shape. <Aspect 8> Aspect 7 is the wavelength conversion member according to aspect 7, wherein the diameter of the light-transmitting filler is 5 μm or more and 15 μm or less. <Aspect 9> Aspect 9 is the wavelength conversion member according to aspect 8, wherein the aspect ratio of the light-transmitting filler is 1.0 or more and 35 or less. <Aspect 10> 10. The wavelength conversion member according to any one of aspects 1 to 9, wherein the particle diameter of the phosphor particles is 10 μm or more and 20 μm or less. <Aspect 11> 11. The wavelength conversion member according to any one of aspects 1 to 10, wherein the transmittance for light with a wavelength of 550 nm is greater than 0% and less than 0.4%. <Aspect 12> 12. The wavelength conversion member according to any one of aspects 1 to 11, wherein the light-transmitting filler contains silica. <Aspect 13> 13. The wavelength conversion member according to any one of aspects 1 to 12, wherein the light-transmitting filler is a glass filler. <Aspect 14> 14. The wavelength conversion member according to any one of aspects 1 to 13, wherein the light-transmitting binder contains silica and an alkali metal. <Aspect 15> 15. The wavelength conversion member according to any one of aspects 1 to 14, wherein the alkali metal is potassium or sodium. <Aspect 16> 16. The wavelength conversion member according to any one of aspects 1 to 15, wherein the light-transmitting binder is porous. <Aspect 17> An optical member including: a substrate; and the wavelength conversion member according to any one of aspects 1 to 16, disposed on the substrate. [Explanation of symbols]

[0072] 1 Wavelength conversion material 2. Phosphor particles 3. Translucent filler 4 void 5. Translucent binder 8 PCB 10 Optical components

Claims

1. A wavelength conversion member comprising phosphor particles, a light-transmitting filler, and a light-transmitting binder having voids.

2. The wavelength conversion member according to claim 1 , wherein a refractive index of the portion of the translucent binder excluding the voids at a wavelength of 550 nm is higher than a refractive index of the translucent filler at a wavelength of 550 nm.

3. 3. The wavelength conversion member according to claim 2, wherein a refractive index at a wavelength of 550 nm of the portion of the light-transmitting binder excluding the voids is greater than 1.46 and equal to or less than 1.

50.

4. The wavelength conversion member according to claim 3 , wherein the refractive index of the light-transmitting filler at a wavelength of 550 nm is 1.40 or more and 1.46 or less.

5. The wavelength conversion member according to claim 4 , wherein an area ratio of the phosphor particles is smaller than an area ratio of the light-transmitting filler in a cross section.

6. 6. The wavelength conversion member according to claim 5, wherein, in a cross section, an area ratio of the translucent filler is 35% or more and 85% or less, and an area ratio of the phosphor particles is 10% or more and 22% or less.

7. The wavelength conversion member according to claim 6 , wherein the transparent filler has a columnar shape.

8. The wavelength conversion member according to claim 7 , wherein the diameter of the light-transmitting filler is 5 μm or more and 15 μm or less.

9. The wavelength conversion member according to claim 8 , wherein the aspect ratio of the light-transmitting filler is 1.0 or more and 35 or less.

10. The wavelength conversion member according to claim 9 , wherein the particle diameter of the phosphor particles is 10 μm or more and 20 μm or less.

11. The wavelength conversion member according to claim 10 , wherein the transmittance for light with a wavelength of 550 nm is greater than 0% and less than 0.4%.

12. The wavelength conversion member according to claim 11 , wherein the light-transmitting filler includes silica.

13. The wavelength conversion member according to claim 12 , wherein the light-transmitting filler is a glass filler.

14. The wavelength conversion member according to claim 13 , wherein the translucent binder contains silica and an alkali metal.

15. The wavelength conversion member according to claim 14 , wherein the alkali metal is potassium or sodium.

16. The wavelength conversion member according to claim 15 , wherein the light-transmitting binder is porous.

17. An optical member comprising: a substrate; and the wavelength conversion member according to claim 1 disposed on the substrate.

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