Wavelength conversion sheet, light-emitting device, and method for manufacturing a wavelength conversion sheet

Abstract

The objective is to provide a wavelength conversion sheet with improved durability, a light-emitting device, and a method for manufacturing a wavelength conversion sheet. [Solution] A wavelength conversion sheet according to one embodiment of the present disclosure comprises a first translucent layer having an inorganic film on its upper surface, and a wavelength conversion layer disposed on the inorganic film, wherein the wavelength conversion layer includes a first wavelength conversion section comprising a plurality of phosphor particles positioned apart from each other on the inorganic film and an inorganic compound film covering the plurality of phosphor particles, and a second wavelength conversion section comprising quantum dots separated from the plurality of phosphor particles via the inorganic compound film.

Description

Technical Field

[0001] The present disclosure relates to a wavelength conversion sheet, a light-emitting device, and a method for manufacturing a wavelength conversion sheet.

Background Art

[0002] Patent Document 1 discloses a quantum dot sheet having an inorganic dielectric layer and quantum dots distributed at predetermined positions within the inorganic dielectric layer.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present disclosure is to provide a wavelength conversion sheet, a light-emitting device, and a method for manufacturing a wavelength conversion sheet with improved durability.

Means for Solving the Problems

[0005] A wavelength conversion sheet according to an embodiment of the present disclosure includes a first light-transmissive layer having an inorganic film on an upper surface, and a wavelength conversion layer disposed on the inorganic film. The wavelength conversion layer includes a first wavelength conversion unit including a plurality of phosphor particles positioned to be separated from each other on the inorganic film, and an inorganic compound film covering the plurality of phosphor particles, and a second wavelength conversion unit including quantum dots separated from the plurality of phosphor particles through the inorganic compound film.

[0006] A light-emitting device according to one embodiment of the present disclosure comprises a light-emitting element that emits light having an emission peak wavelength in the range of 380 nm to 480 nm, and a wavelength conversion sheet disposed above the light-emitting element, wherein the wavelength conversion sheet comprises a first translucent layer having an inorganic film on its upper surface, and a wavelength conversion layer disposed on the inorganic film, wherein the wavelength conversion layer comprises a first wavelength conversion section including a plurality of phosphor particles positioned apart from each other on the inorganic film and an inorganic compound film covering the plurality of phosphor particles, and a second wavelength conversion section including quantum dots separated from the plurality of phosphor particles via the inorganic compound film.

[0007] A method for manufacturing a wavelength conversion sheet according to one embodiment of the present disclosure includes the steps of: preparing a first translucent layer having an inorganic film on its upper surface; forming a first wavelength conversion section on the inorganic film; and forming a second wavelength conversion section on the first wavelength conversion section, wherein the step of forming the first wavelength conversion section includes the first step of arranging a plurality of phosphor particles on the inorganic film so as to be spaced apart from each other; and the second step of forming an inorganic compound film using atomic layer deposition to coat the phosphor particles with the inorganic compound film, wherein the step of forming the second wavelength conversion section includes the step of arranging quantum dots so as to be spaced apart from the plurality of phosphor particles via the inorganic compound film. [Effects of the Invention]

[0008] According to one embodiment of the present disclosure, it is possible to provide a wavelength conversion sheet with improved durability, a light-emitting device, and a method for manufacturing a wavelength conversion sheet. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic top view showing a light-emitting device according to an embodiment. [Figure 2] This is a schematic cross-sectional view showing the cross-section of the light-emitting device along line II-II in Figure 1. [Figure 3] This is a schematic cross-sectional view showing the cross-section of a wavelength conversion sheet in the XZ plane. [Figure 4]Figure 3 is a partially cross-sectional view of the wavelength conversion sheet, showing an enlarged view of region IV. [Figure 5] This is a schematic top view showing the phosphor particles within the wavelength conversion sheet. [Figure 6] This is a schematic cross-sectional view showing an example of a method for manufacturing a wavelength conversion sheet according to the embodiment. [Figure 7] This is a schematic cross-sectional view showing an example of a method for manufacturing a wavelength conversion sheet according to the embodiment. [Figure 8] This is a schematic cross-sectional view showing an example of a method for manufacturing a wavelength conversion sheet according to the embodiment. [Figure 9] This is a schematic cross-sectional view showing an example of a method for manufacturing a wavelength conversion sheet according to the embodiment. [Figure 10] This is a schematic cross-sectional view showing an example of a method for manufacturing a wavelength conversion sheet according to the embodiment. [Figure 11] This is a schematic cross-sectional view showing an example of a method for manufacturing a wavelength conversion sheet according to the embodiment. [Modes for carrying out the invention]

[0010] The light-emitting device and wavelength conversion sheet according to the embodiments of this disclosure will be described in detail below with reference to the drawings. However, the embodiments shown below are illustrative of the light-emitting device and wavelength conversion sheet for realizing the technical concept of the embodiments and are not limited thereto. Furthermore, the dimensions, materials, shapes, relative arrangements, etc. of the components described in the embodiments are not intended to limit the scope of this disclosure to those described therein, unless otherwise specified, but are merely illustrative examples. Note that the size, positional relationships, etc. of the members shown in each drawing may be exaggerated for clarity of explanation. Also, in the following description, the same name and reference numerals indicate the same or similar members, and detailed explanations will be omitted as appropriate. In some cases, end view diagrams showing only the cut surface will be used as cross-sectional views.

[0011] In the diagrams shown below, directions may be indicated by the X, Y, and Z axes. The X, Y, and Z axes are mutually orthogonal. In the X-axis direction, the direction the arrow is pointing is denoted as the +X direction or +X side, and the opposite direction of the +X direction is denoted as the -X direction or -X side. In the Y-axis direction, the direction the arrow is pointing is denoted as the +Y direction or +Y side, and the opposite direction of the +Y direction is denoted as the -Y direction or -Y side. In the Z-axis direction, the direction the arrow is pointing is denoted as the +Z direction or +Z side, and the opposite direction of the +Z direction is denoted as the -Z direction or -Z side. Directions parallel to the X and Y axes may be referred to as "in-plane directions". Directions parallel to the Z axis may be referred to as "thickness directions". In addition, the dimension in the thickness direction of each component may be referred to as "thickness". Here, in this specification, "average thickness" means the arithmetic mean of the thicknesses at any three locations measured using a measuring means such as a reflectance spectrometer.

[0012] In the Z-axis direction, the surface of the object viewed from the +Z direction or the +Z side is defined as the "top surface," and the surface of the object viewed from the -Z direction or the -Z side is defined as the "bottom surface." In this specification, a top view means viewing the object from the +Z direction or the +Z side in the Z-axis direction. However, these are for illustrative purposes only and do not restrict the orientation when using the light-emitting device and wavelength conversion sheet. The orientation of the light-emitting device and wavelength conversion sheet is arbitrary. In the embodiments shown below, parallel to the X-axis, Y-axis, and Z-axis directions includes the object having an inclination within ±10° with respect to these directions. In the embodiments, orthogonality may include an error of ±10° or less with respect to 90°.

[0013] In this disclosure, unless otherwise specified, polygons such as rectangles shall be referred to as polygons, including shapes with rounded corners, chamfers, bevels, or other processing applied to their corners. Furthermore, shapes with processing applied not only to the corners (ends of the sides) but also to the middle parts of the sides shall also be referred to as polygons. In other words, shapes that retain a polygonal base but have undergone partial processing shall be included in the interpretation of "polygon" as described in this disclosure.

[0014] Moreover, not only for polygons, but the same also applies to terms representing specific shapes such as trapezoids, circles, concavities and convexities, etc. The same also applies to terms regarding each side forming the shape. That is, even if a side has been processed at a corner or an intermediate portion, the processed portion is included in the interpretation of "side".

[0015] Moreover, "cover" or "coat" includes not only cases of direct contact, but also cases of indirectly covering, for example, via other members. Also, "arrange" includes not only cases of direct contact, but also cases of indirectly arranging, for example, via other members.

[0016] [Embodiment] <Light-emitting device 1> Referring to FIGS. 1 and 2, an example of the overall configuration of the light-emitting device 1 according to the embodiment will be described. FIG. 1 is a top view schematically showing the light-emitting device 1 according to the embodiment. FIG. 2 is a cross-sectional view schematically showing a cross-section of the light-emitting device 1 taken along line II-II of FIG. 1. The light-emitting device 1 is used, for example, as a backlight in various displays such as liquid crystal displays. In this case, various members constituting the display such as a diffusion plate, a prism sheet, and a liquid crystal panel are arranged, for example, above the light-emitting device 1 (+Z side). However, the use of the light-emitting device 1 is not limited to the backlight of the display.

[0017] As shown in FIGS. 1 and 2, the light-emitting device 1 includes a light-emitting element 2 and a wavelength conversion sheet 10. As shown in FIG. 2, the light-emitting device 1 can further include a substrate 3 and a light-reflective member 4. In the example shown in FIG. 2, the upper surface of the wavelength conversion sheet 10 defines the upper surface of the light-emitting device 1. Also, the lower surface of the substrate 3 defines the lower surface of the light-emitting device 1. However, the positional relationship among the light-emitting element 2, the wavelength conversion sheet 10, the substrate 3, and the light-reflective member 4 is not limited to the example shown in FIG. 2. When the light-emitting device 1 is used as a backlight of a display, members such as a diffusion plate and a prism sheet may be arranged between the light-emitting element 2 and the wavelength conversion sheet 10 in the Z-axis direction.

[0018] The light-emitting element 2 is a semiconductor light-emitting element such as an LED (Light Emitting Diode) or an LD (Laser Diode). The light-emitting device 1 may be equipped with multiple light-emitting elements 2. In the example shown in Figure 2, the multiple light-emitting elements 2 are arranged between the wavelength conversion sheet 10 and the substrate 3 in the Z-axis direction. Alternatively, the multiple light-emitting elements 2 may be arranged in a matrix along the X-axis and Y-axis directions, for example. However, the position and arrangement direction of the light-emitting elements 2 are not limited to the example shown in Figure 2. The light-emitting elements 2 may be arranged outside the outer edge of the wavelength conversion sheet 10 in a top view, for example. In this case, the light-emitting device 1 may further be equipped with optical members such as a light-reflecting sheet and a light-guiding member for guiding the light emitted by the light-emitting elements 2 to the wavelength conversion sheet 10.

[0019] The light-emitting element 2 comprises a semiconductor structure and a positive and negative pair of electrodes. The semiconductor structure includes a first semiconductor layer having a first conductivity type, an active layer, and a second semiconductor layer having a second conductivity type different from the first conductivity type. The first semiconductor layer, the active layer, and the second semiconductor layer are stacked in this order along the Z-axis. One of the first and second semiconductor layers is an n-type semiconductor layer. The other of the first and second semiconductor layers is a p-type semiconductor layer. The active layer may have a single quantum well (SQW) structure or a multiple quantum well (MQW) structure including multiple well layers.

[0020] In the semiconductor structure, the first semiconductor layer, the active layer, and the second semiconductor layer are each composed of, for example, a nitride semiconductor. Nitride semiconductors are made of In x Al y Ga 1-x-yThe semiconductor comprises all compositions in which the composition ratios x and y are varied within their respective ranges in the chemical formula N(0≦x, 0≦y, x+y≦1). The emission peak wavelength range of the light emitted by the active layer is 380 nm to 480 nm. That is, the light-emitting element 2 emits light having an emission peak wavelength in the range of 380 nm to 480 nm. Examples of light having an emission peak wavelength in the range of 380 nm to 480 nm include violet light and blue light.

[0021] A positive and negative pair of electrodes are arranged, for example, at positions spaced apart from each other on the underside of a semiconductor structure. One electrode of the positive and negative pair is electrically connected to a first semiconductor layer. The other electrode of the positive and negative pair is electrically connected to a second semiconductor layer. Examples of materials constituting the positive and negative pair of electrodes include metals such as gold (Au), silver (Ag), copper (Cu), aluminum (Al), nickel (Ni), rhodium (Rh), titanium (Ti), platinum (Pt), palladium (Pd), molybdenum (Mo), chromium (Cr), and tungsten (W), as well as alloys containing these metals.

[0022] The wavelength conversion sheet 10 absorbs at least a portion of the light emitted by the light-emitting element 2 and emits light of a different wavelength than the absorbed light. In other words, in the light-emitting device 1, the light-emitting element 2 acts as an excitation light source for the wavelength conversion sheet 10. The mixed light from the wavelength conversion sheet 10 excited by the light emitted by the light-emitting element 2 and the light emitted by the light-emitting element 2 that has passed through the wavelength conversion sheet 10 is emitted from the top surface of the light-emitting device 1.

[0023] The wavelength conversion sheet 10 is positioned above the light-emitting element 2. In the example shown in Figure 2, the wavelength conversion sheet 10 overlaps with the light-emitting element 2 in the Z-axis direction. However, the wavelength conversion sheet 10 only needs to be positioned above the light-emitting element 2; it does not necessarily need to overlap with the light-emitting element 2 in the Z-axis direction. Details of the wavelength conversion sheet 10 will be explained separately with reference to Figures 3 to 5.

[0024] As shown in Figure 2, the substrate 3 supports the light-emitting element 2. The substrate 3 is, for example, a semiconductor substrate such as silicon, a ceramic substrate such as aluminum nitride, and a resin substrate such as glass epoxy. The substrate 3 has wiring sections, such as top wiring, which serve as electrical circuits for supplying power from an external power source to the light-emitting element 2. The positive and negative electrodes of the light-emitting element 2 are electrically connected to the top wiring of the substrate 3. The substrate 3 may also include integrated circuits for controlling the light-emitting operation of multiple light-emitting elements 2. Examples of integrated circuits include electronic circuits such as ASICs (Application Specific Integrated Circuits).

[0025] The light-reflective member 4 reflects the light emitted by the light-emitting element 2, for example, upward. In the example shown in Figure 2, the light-reflective member 4 covers the sides of the light-emitting element 2 while exposing the top surface of the light-emitting element 2. The light-reflective member 4 may include, for example, a substrate made of a resin material such as a thermosetting resin, and a light-reflective filler.

[0026] Examples of thermosetting resins constituting the base material of the light-reflective member 4 include epoxy resin, modified epoxy resin, silicone resin, modified silicone resin, silicone-modified epoxy resin, epoxy-modified silicone resin, polyimide resin, modified polyimide resin, and unsaturated polyester. Examples of fillers contained in the light-reflective member 4 include inorganic particles such as titanium dioxide, zinc oxide, magnesium oxide, magnesium carbonate, magnesium hydroxide, calcium carbonate, calcium hydroxide, calcium silicate, magnesium silicate, barium titanate, barium sulfate, aluminum hydroxide, aluminum oxide, zirconium oxide, silicon oxide, and boron nitride. The reflectance of the light-reflective member 4 is preferably 70% or more, more preferably 80% or more, and even more preferably 90% or more, relative to the emission peak wavelength of the light emitted by the light-emitting element 2.

[0027] <Wavelength Conversion Sheet 10> Referring to Figures 3 to 5, an example of the configuration of the wavelength conversion sheet 10 according to the embodiment will be described. Figure 3 is a schematic cross-sectional view showing a cross-section of the wavelength conversion sheet 10 in the XZ plane. Figure 4 is a magnified partial cross-sectional view of the wavelength conversion sheet 10 within region IV shown in Figure 3. Figure 5 is a schematic top view showing the phosphor particles 311 within the wavelength conversion sheet 10.

[0028] As shown in Figure 3, the wavelength conversion sheet 10 comprises a first translucent layer 20 and a wavelength conversion layer 30. The wavelength conversion sheet 10 may further comprise a second translucent layer 40. In the example shown in Figure 3, the lower surface of the first translucent layer 20 defines the lower surface of the wavelength conversion sheet 10. The upper surface of the second translucent layer 40 defines the upper surface of the wavelength conversion sheet 10. The wavelength conversion layer 30 is positioned between the first translucent layer 20 and the second translucent layer 40 in the Z-axis direction.

[0029] The wavelength conversion sheet 10 has a rectangular shape when viewed from above. However, the shape of the wavelength conversion sheet 10 when viewed from above is not limited to a rectangle. The average thickness of the wavelength conversion sheet 10 is, for example, 50 μm or more and 500 μm or less. More preferably, the average thickness of the wavelength conversion sheet 10 is 100 μm or more and 400 μm or less. By having an average thickness of 50 μm or more and 500 μm or less of the wavelength conversion sheet 10, the area in which the light emitted by the light-emitting element 2 is transmitted without being absorbed can be reduced, and the average thickness of the wavelength conversion sheet 10 can be reduced. In other words, unevenness of light emission within the plane of the wavelength conversion sheet 10 can be reduced, and the wavelength conversion sheet 10 can be made thinner. However, the average thickness of the wavelength conversion sheet 10 is not limited to this.

[0030] (First transparent layer 20) The first light-transmitting layer 20 is, for example, light-transmitting to light emitted by the light-emitting element 2. Here, in this specification, "light-transmitting" refers to the property of having a transmittance of at least 60%, preferably 80%, to light emitted by the light-emitting element 2. The average thickness of the first light-transmitting layer 20 does not exceed the average thickness of the wavelength conversion sheet 10, for example, 25 μm or more and 200 μm or less. However, the average thickness of the first light-transmitting layer 20 is not limited to this.

[0031] The first translucent layer 20 is a support that supports the wavelength conversion layer 30. Preferably, the first translucent layer 20 has gas barrier properties that suppress the transmission of gases such as oxygen gas into the interior of the wavelength conversion sheet 10. The gas barrier properties of the first translucent layer 20 reduce the degradation of the phosphor particles 311 and quantum dots 321 contained in the wavelength conversion layer 30. This improves the durability of the wavelength conversion sheet 10.

[0032] As shown in Figure 3, the first translucent layer 20 has an inorganic film 21 on its upper surface. Preferably, the inorganic film 21 is an oxide film. Having the inorganic film 21 on the upper surface of the first translucent layer 20 can further improve the gas barrier properties of the first translucent layer 20. This can further reduce the degradation of the phosphor particles 311 and quantum dots 321 contained in the wavelength conversion layer 30, and further improve the durability of the wavelength conversion sheet 10.

[0033] The first translucent layer 20 further comprises a substrate 22, which is the base material of the first translucent layer 20. As shown in Figure 3, the upper surface of the substrate 22 is covered with an inorganic film 21. Examples of materials constituting the inorganic film 21 include silicon oxide, aluminum oxide, magnesium oxide, tantalum oxide, zirconium oxide, titanium oxide, indium tin oxide, silicon nitride, aluminum nitride, and titanium nitride. Examples of materials constituting the substrate 22 include thermoplastic resins such as polyester (e.g., polyethylene terephthalate, polyethylene naphthalate), cellulose triacetate, cellulose diacetate, cellulose acetate butyrate, polyamide, polyimide, polyethersulfone, polysulfone, polypropylene, polymethylpentene, polyvinyl chloride, polyvinyl acetal, polyetherketone, polymethyl methacrylate, polycarbonate, and polyurethane.

[0034] (Wavelength conversion layer 30) The wavelength conversion layer 30 includes a first wavelength conversion section 31 and a second wavelength conversion section 32. In the example shown in Figure 3, the first wavelength conversion section 31 is located on the inorganic film 21 of the first translucent layer 20. The second wavelength conversion section 32 is located on the first wavelength conversion section 31.

[0035] Preferably, the maximum length H1 of the wavelength conversion layer 30 in the thickness direction does not exceed the average thickness of the wavelength conversion sheet 10, and is between 20 μm and 150 μm. By having a maximum length H1 of the wavelength conversion layer 30 in the thickness direction of 20 μm or more and 150 μm or less, unevenness of emission within the plane of the wavelength conversion layer 30 can be reduced, and the wavelength conversion layer 30 can be made thinner. However, the maximum length H1 of the wavelength conversion layer 30 in the thickness direction exceeds the maximum length H2 of the phosphor particles 311 contained in the first wavelength conversion section 31, and the maximum length of the quantum dots 321 contained in the second wavelength conversion section 32.

[0036] The first wavelength conversion unit 31 includes a plurality of phosphor particles 311 and an inorganic compound film 312. As shown in Figure 3, the plurality of phosphor particles 311 are positioned on the inorganic film 21 so as to be separated from each other. It is preferable that all phosphor particles 311 included in the first wavelength conversion unit 31 do not come into contact with neighboring phosphor particles 311 and are positioned at approximately the same location in the Z-axis direction. This reduces the average thickness of the first wavelength conversion unit 31 and prevents the plurality of phosphor particles 311 from being unevenly distributed on the inorganic film 21. As a result, the first wavelength conversion unit 31 can be made thinner and unevenness of emission within the plane of the first wavelength conversion unit 31 can be reduced. In the example shown in Figure 3, the plurality of phosphor particles 311 are arranged at approximately equal intervals in the X-axis direction. However, the spacing between adjacent phosphor particles 311 is arbitrary. In the example shown in Figure 3, the lower surface of the phosphor particles 311 is in contact with the inorganic film 21.

[0037] As shown in Figure 4, the maximum length H2 of the phosphor particles 311 in the thickness direction is preferably 20 μm or more and 150 μm or less, and does not exceed the average thickness of the wavelength conversion sheet 10. By having the maximum length H2 of the phosphor particles 311 in the thickness direction be 20 μm or more and 150 μm or less, the amount of light transmitted through the phosphor particles 311 without being excited by the phosphor particles 311 can be reduced, and the first wavelength conversion section 31 can be made thinner. This makes it possible to make the first wavelength conversion section 31 thinner while ensuring the effect of reducing unevenness of emission within the plane of the first wavelength conversion section 31. However, the maximum length H2 of the phosphor particles 311 in the thickness direction is less than the maximum length H1 of the wavelength conversion layer 30 in the thickness direction.

[0038] It is preferable that each of the multiple phosphor particles 311 is composed of a phosphor that is excited by short-wavelength excitation light such as violet or blue light from the visible spectrum. In other words, it is preferable that each of the multiple phosphor particles 311 is composed of a phosphor that is excited by light emitted by the light-emitting element 2. An example of a phosphor that is excited by short-wavelength excitation light from the visible spectrum is a rare-earth metal complex. By using a rare-earth metal complex as the phosphor that constitutes the phosphor particles 311, the phosphor particles 311 can emit long-wavelength light such as orange or red light from the visible spectrum. However, the phosphor that constitutes the phosphor particles 311 is not limited to a rare-earth metal complex. An example of another phosphor is a KSF-based phosphor (e.g., K2SiF6:Mn).

[0039] Rare earth metal complexes can include, for example, a rare earth metal and a β-diketonate ligand that coordinates to the rare earth metal. Furthermore, the rare earth metal complex may optionally contain one or more ligands different from the β-diketonate ligand. Examples of rare earth metals include lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu). Furthermore, the other components of the rare earth metal complex may be the same as those described in, for example, Japanese Patent Publication No. 2019-31446 and Japanese Patent Publication No. 2022-73204.

[0040] In particular, the phosphor particles 311 preferably contain a europium complex containing Eu as a rare earth metal. By including a europium complex in the phosphor particles 311, the luminescence properties such as the external quantum efficiency of the phosphor particles 311 can be enhanced. Furthermore, by including a europium complex in the phosphor particles 311, it is possible to obtain light with a sharp emission peak on the long wavelength side in the emission spectrum of the light emitted by the phosphor particles 311.

[0041] The phosphor particles 311 preferably have a flattened shape. Specifically, as shown in Figures 4 and 5, it is preferable that the maximum length W1 of the wavelength conversion layer 30 of the phosphor particles 311 in the in-plane direction is greater than the maximum length H2 of the phosphor particles 311 in the thickness direction. By having the maximum length W1 of the wavelength conversion layer 30 of the phosphor particles 311 greater than the maximum length H2 of the thickness direction, the area of ​​the surface of the phosphor particles 311 that faces the light-emitting element 2, such as the bottom surface, can be relatively increased. In other words, the light-receiving area of ​​the phosphor particles 311 that receives light emitted by the light-emitting element 2 can be increased. This makes it possible to reduce the amount of light that is transmitted through the phosphor particles 311 without being excited by them. As a result, unevenness in light emission within the plane of the first wavelength conversion section 31 can be reduced.

[0042] The ratio of the maximum length H2 of the phosphor particles 311 in the thickness direction to the maximum length W1 of the wavelength conversion layer 30 is preferably 0.01 or more and 0.8 or less. Furthermore, the ratio of the maximum length H2 of the phosphor particles 311 in the thickness direction to the maximum length W1 of the wavelength conversion layer 30 is more preferably 0.05 or more and 0.7 or less, and even more preferably 0.1 or more and 0.6 or less. By having a ratio of 0.01 or more and 0.8 or less to the maximum length W1 of the wavelength conversion layer 30 of the phosphor particles 311 in the thickness direction, unevenness of emission in the plane of the first wavelength conversion section 31 can be further reduced, and the first wavelength conversion section 31 can be made thinner.

[0043] When precipitating the europium complex from the raw material solution, a flattened powder can be obtained. Therefore, by including the europium complex in the phosphor particles 311, the amount of light transmitted through the phosphor particles 311 can be further reduced.

[0044] The inorganic compound film 312 coats a plurality of phosphor particles 311. By coating the plurality of phosphor particles 311 with the inorganic compound film 312, each of the plurality of phosphor particles 311 can be fixed onto the inorganic film 21 of the first translucent layer 20 while keeping adjacent phosphor particles 311 separated. Furthermore, by coating the plurality of phosphor particles 311 with the inorganic compound film 312, the phosphor particles 311 can be protected from oxygen and moisture. Examples of materials constituting the inorganic compound film 312 include silicon oxide, aluminum oxide, magnesium oxide, tantalum oxide, zirconium oxide, titanium oxide, and indium tin oxide. The inorganic compound film 312 may have the same composition as the inorganic film 21 and / or inorganic film 41. In the example shown in Figure 3, the inorganic compound film 312 coats the plurality of phosphor particles 311 all at once. However, the inorganic compound film 312 may also coat the plurality of phosphor particles 311 individually. In other words, the inorganic compound film 312 can coat multiple phosphor particles 311 collectively or individually. Here, "coating collectively" refers to a state in which one inorganic compound film 312 coats multiple phosphor particles 311 together. Also, "coating individually" refers to a state in which multiple inorganic compound films 312, separated from each other, coat multiple phosphor particles 311 individually. In other words, "coating individually" refers to a state in which one inorganic compound film 312 coats one phosphor particle 311 for multiple phosphor particles 311.

[0045] The inorganic compound film 312 can cover the portion of the upper surface of the inorganic film 21 that does not overlap with the phosphor particles 311. However, the upper surface of the inorganic film 21 may include portions that are not covered by the inorganic compound film 312.

[0046] The thickness of the inorganic compound film 312 is preferably 0.1 μm or more and 5.0 μm or less. A thickness of 0.1 μm or more and 5.0 μm or less ensures protection for the phosphor particles 311 and allows for a thinner first wavelength conversion section 31. Furthermore, a thickness of 0.1 μm or more and 5.0 μm or less improves the adhesion of the phosphor particles 311 to the inorganic film 21.

[0047] In the example shown in Figure 4, a portion 312a of the inorganic compound film 312 is located between the phosphor particles 311 and the inorganic film 21 in the thickness direction (Z-axis direction). That is, the inorganic compound film 312 can cover a portion of the bottom surface in addition to the top and side surfaces of the phosphor particles 311. By positioning a portion 312a of the inorganic compound film 312 between the phosphor particles 311 and the inorganic film 21, the phosphor particles 311 and the inorganic film 21 can be fixed together via the inorganic compound film 312. This further improves the adhesion force of the phosphor particles 311 to the inorganic film 21. However, the configuration of the inorganic compound film 312 is not limited to the example shown in Figure 4. The inorganic compound film 312 only needs to cover at least the top and side surfaces of the phosphor particles 311, and the bottom surface of the phosphor particles 311 may be exposed.

[0048] The second wavelength conversion unit 32 includes quantum dots 321. Here, quantum dots are semiconductor crystal particles with particle sizes ranging from a few nanometers to several tens of nanometers. When the size of a material is reduced to the nanometer order, electrons can only exist in a limited state within the material. Therefore, the electronic state in the quantum dot becomes discrete, and the band gap energy changes depending on the particle size.

[0049] The quantum dot 321 absorbs light emitted by the light-emitting element 2, for example, and emits light with a wavelength corresponding to the bandgap energy of the quantum dot 321. Therefore, the emission wavelength of the quantum dot 321 can be controlled by controlling the particle size, crystal composition, etc. of the quantum dot 321. As the quantum dot 321, for example, quantum dots described in Japanese Patent Publication No. 2012-212862, Japanese Patent Publication No. 2010-177656, International Publication No. 2018 / 159699, International Publication No. 2019 / 160094, International Publication No. 2020 / 162622, International Publication No. 2022 / 191032, International Publication No. 2023 / 176509, etc. can be used.

[0050] The quantum dot 321 is preferably excited by short-wavelength excitation light, such as violet or blue light, from the visible light spectrum. Furthermore, it is preferable that the emission peak wavelength of the light emitted by the quantum dot 321 differs from the emission peak wavelength of the light emitted by the phosphor particles 311. Green light is an example of light emitted by the quantum dot 321. This allows for different emission colors of the light emitted by the light-emitting element 2, the light emitted by the phosphor particles 311, and the light emitted by the quantum dot 321. As a result, the color gamut of the light extracted from the light-emitting device 1 can be broadened. However, the light emitted by the quantum dot 321 is not limited to green light.

[0051] Examples of quantum dots 321 include 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), group II-VI quantum dots (e.g., CdSe), group III-V quantum dots (e.g., InP), or quantum dots having a chalcopyrite structure (e.g., (Ag,Cu)(In,Ga)(S,Se)2). Quantum dots 321 may further include surface modification parts that modify the surface of the underlying semiconductor crystal grains.

[0052] The second wavelength conversion unit 32 may further include a curing resin 322 that holds the quantum dots 321. The curing resin 322 may be a cured product of a photocurable composition described later. By holding the quantum dots 321 in the curing resin 322, aggregation of the quantum dots 321 within the second wavelength conversion unit 32 can be suppressed. This reduces unevenness in light emission within the plane of the second wavelength conversion unit 32.

[0053] The photocurable composition that forms the cured resin 322 may include, for example, a (meth)acrylic compound. The (meth)acrylic compound may be a monofunctional (meth)acrylic compound having one (meth)acryloyl group in one molecule, or a polyfunctional (meth)acrylic compound having two or more (meth)acryloyl groups in one molecule. As the (meth)acrylic compound, one type may be used alone, two or more types may be used in combination, or monofunctional (meth)acrylic compounds and polyfunctional (meth)acrylic compounds may be used in combination. Here, the (meth)acrylic compound includes acrylic compounds, methacrylic compounds, and mixtures thereof. As the (meth)acrylic compound, for example, the (meth)acrylic compounds described in International Publication No. 2023 / 176509, etc., can be used.

[0054] As shown in Figure 3, the quantum dots 321 are separated from the multiple phosphor particles 311 via the inorganic compound film 312. By separating the quantum dots 321 from the multiple phosphor particles 311 via the inorganic compound film 312, degradation of both the phosphor particles 311 and the quantum dots 321 due to contact can be suppressed. This improves the durability of the wavelength conversion sheet 10. Furthermore, because the quantum dots 321 are separated from the multiple phosphor particles 311 via the inorganic compound film 312, degradation of the phosphor particles 311 and quantum dots 321 can be suppressed even if the average thickness of the first translucent layer 20 and the second translucent layer 40 sandwiching the wavelength conversion layer 30 in the Z-axis direction is reduced. In other words, the wavelength conversion sheet 10 can be made thinner, and its durability can be improved.

[0055] (Second transparent layer 40) As shown in Figure 3, the second light-transmitting layer 40 is placed on the wavelength conversion layer 30. The second light-transmitting layer 40 is transparent to, for example, light emitted by the light-emitting element 2, light emitted by the phosphor particles 311, and light emitted by the quantum dots 321.

[0056] Preferably, the second translucent layer 40, like the first translucent layer 20, has gas barrier properties that suppress the transmission of gases such as oxygen gas into the interior of the wavelength conversion sheet 10. Because the second translucent layer 40 has gas barrier properties, the first translucent layer 20 and the second translucent layer 40, each possessing gas barrier properties, sandwich the wavelength conversion layer 30. This suppresses the degradation of the phosphor particles 311 and quantum dots 321 contained in the wavelength conversion layer 30, thereby improving the durability of the wavelength conversion sheet 10.

[0057] As shown in Figure 3, the second translucent layer 40 may have an inorganic film 41 on its lower surface. The inorganic film 41 is preferably an oxide film. By having the inorganic film 41 on the lower surface of the second translucent layer 40, the gas barrier properties of the second translucent layer 40 can be further improved. This further reduces the degradation of the phosphor particles 311 and quantum dots 321 contained in the wavelength conversion layer 30, and further improves the durability of the wavelength conversion sheet 10.

[0058] The second translucent layer 40 further comprises a substrate 42, which is the base material of the second translucent layer 40. As shown in Figure 3, the lower surface of the substrate 42 is covered with an inorganic film 41. The average thickness of the second translucent layer 40 does not exceed the average thickness of the wavelength conversion sheet 10, and is, for example, between 25 μm and 200 μm. However, the average thickness of the second translucent layer 40 is not limited to this.

[0059] The material constituting the inorganic film 41 may be the same as the oxide listed as a material usable as the inorganic film 21 of the first translucent layer 20. Furthermore, the material constituting the substrate 42 may be the same as the thermoplastic resin listed as a material usable as the substrate 22 of the first translucent layer 20.

[0060] <Manufacturing method for wavelength conversion sheet 10> Next, an example of a method for manufacturing the wavelength conversion sheet 10 according to the embodiment will be described with reference to Figures 6 to 11. Figures 6 to 11 are schematic cross-sectional views showing an example of a method for manufacturing the wavelength conversion sheet 10. However, the method for manufacturing the wavelength conversion sheet 10 is not limited to the example shown in Figures 6 to 11.

[0061] The method for manufacturing the wavelength conversion sheet 10 includes the steps of: preparing a first translucent layer 20 having an inorganic film 21 on its upper surface; forming a first wavelength conversion section 31 on the inorganic film 21; and forming a second wavelength conversion section 32 on the first wavelength conversion section 31. The method for manufacturing the wavelength conversion sheet 10 may further include the step of placing a second translucent layer 40 on the second wavelength conversion section 32. The step of preparing the first translucent layer 20 having an inorganic film 21 on its upper surface will be hereinafter referred to as the "step of preparing the first translucent layer 20". The step of forming the first wavelength conversion section 31 on the inorganic film 21 will be hereinafter referred to as the "step of forming the first wavelength conversion section 31". The step of forming the second wavelength conversion section 32 on the first wavelength conversion section 31 will be hereinafter referred to as the "step of forming the second wavelength conversion section 32". The step of placing the second translucent layer 40 on the second wavelength conversion section 32 will be hereinafter referred to as the "step of placing the second translucent layer 40".

[0062] Referring to Figure 6, an example of the process for preparing the first translucent layer 20 will be described. As shown in Figure 6, the process for preparing the first translucent layer 20 includes forming an inorganic film 21 that covers the upper surface of the substrate 22 of the first translucent layer 20. The method for forming the inorganic film 21 is, for example, the CVD (Chemical Vapor Deposition) method. However, the method for forming the inorganic film 21 is not limited to the CVD method. In addition, in the process for preparing the first translucent layer 20, a commercially available first translucent layer 20 having a substrate 22 and an inorganic film 21 formed on the substrate 22 may be prepared.

[0063] An example of the process for forming the first wavelength conversion section 31 will be described with reference to Figures 7 to 9. The process for forming the first wavelength conversion section 31 is performed after the process for preparing the first translucent layer 20. The process for forming the first wavelength conversion section 31 includes a first step and a second step.

[0064] First, the first step is performed. The first step is to arrange a plurality of phosphor particles 311 on the inorganic film 21 so that they are spaced apart from each other. The first step may also include placing a holding member 311h on the inorganic film 21 to hold the plurality of phosphor particles 311 in a spaced-apart state, and then removing the holding member 311h using ozone gas. Here, the holding member 311h is, for example, a member made of resin.

[0065] An example of arranging a holding member 311h, which holds multiple phosphor particles 311 separated from each other, on an inorganic film 21 is described. After the first translucent layer 20 is brought into the chamber, a fluid corresponding to the holding member 311h is applied to the inorganic film 21 of the first translucent layer 20, for example, using a spin coating method. The fluid corresponding to the holding member 311h contains multiple phosphor particles 311. As shown in Figure 7, by applying the fluid corresponding to the holding member 311h onto the inorganic film 21, the multiple phosphor particles 311 held by the holding member 311h can be arranged on the inorganic film 21.

[0066] Next, an example of removing the retaining member 311h using ozone gas will be described. After placing the multiple phosphor particles 311 held by the retaining member 311h onto the inorganic film 21, the temperature inside the chamber is raised. After the temperature inside the chamber reaches a predetermined temperature, ozone gas is supplied into the chamber and the retaining member 311h is exposed to the ozone gas. At this time, since the temperature inside the chamber has been raised, the ozone gas contains active species such as atomic oxygen. By exposing the retaining member 311h to ozone gas, the retaining member 311h is decomposed by the active species. As a result, the retaining member 311h is removed. Meanwhile, as shown in Figure 8, the multiple phosphor particles 311 maintain a state of separation from each other on the inorganic film 21.

[0067] Next, the second step is performed. The second step involves forming an inorganic compound film 312 using atomic layer deposition and coating the phosphor particles 311 with the inorganic compound film 312. In the second step, as shown in Figure 9, a portion 312a of the inorganic compound film 312 is formed between the phosphor particles 311 and the inorganic film 21 in the thickness direction (Z-axis direction), and the phosphor particles 311 can be fixed to the inorganic film 21 via the portion 312a of the inorganic compound film 312. In the example shown in Figure 9, a portion of the lower surface of the phosphor particles 311 is in contact with the inorganic film 21. Therefore, the portion of the lower surface of the phosphor particles 311 that is not in contact with the inorganic film 21 is fixed to the inorganic film 21 via the portion 312a of the inorganic compound film 312. In the example shown in Figure 9, "forming a portion 312a of the inorganic compound film 312 between the phosphor particles 311 and the inorganic film 21 in the thickness direction (Z-axis direction)" means forming a portion 312a of the inorganic compound film 312 between the portion of the lower surface of the phosphor particles 311 that is not in contact with the inorganic film 21 and the inorganic film 21 in the thickness direction (Z-axis direction). Also, in the example shown in Figure 9, "fixing the phosphor particles 311 to the inorganic film 21 via a portion 312a of the inorganic compound film 312" means fixing the phosphor particles 311 to the inorganic film 21 via a portion 312a of the inorganic compound film 312 located between the portion of the lower surface of the phosphor particles 311 that is not in contact with the inorganic film 21 and the inorganic film 21. After the first and second steps, a first laminate 9M including a first wavelength conversion section 31 laminated on the first translucent layer 20 can be obtained, as shown in Figure 9.

[0068] When depositing an inorganic compound film 312 using atomic layer deposition, multiple types of raw material gases, each containing elements that constitute the inorganic compound film 312, are supplied into the chamber. By using atomic layer deposition, the unevenness of the film thickness of the inorganic compound film 312 can be reduced, and a conformal thin film of the inorganic compound film 312 can be deposited. Furthermore, by using atomic layer deposition, a portion 312a of the inorganic compound film 312 can be deposited between the phosphor particles 311 and the inorganic film 21 in the thickness direction (Z-axis direction). In other words, by using atomic layer deposition, the bottom surface of the phosphor particles 311 can be coated with the inorganic compound film 312 in addition to the top and side surfaces. This improves the adhesion between the phosphor particles 311 and the inorganic film 21. However, the method for depositing the inorganic compound film 312 containing a portion 312a is not limited to atomic layer deposition.

[0069] Referring to Figure 10, an example of the process for forming the second wavelength conversion section 32 will be described. The process for forming the second wavelength conversion section 32 includes arranging quantum dots 321 so as to be separated from a plurality of phosphor particles 311 via an inorganic compound film 312, as shown in Figure 10.

[0070] For example, a raw material solution containing a photocurable composition, which is the raw material for quantum dots 321 and cured resin 322, is applied to the inorganic compound film 312 of the first laminate 9M shown in Figure 9. Then, the applied raw material solution is cured by irradiating it with ultraviolet light, for example, to cure the photocurable composition. As a result, a second laminate 10M including a second wavelength conversion section 32 laminated on the first wavelength conversion section 31 can be obtained, as shown in Figure 10. That is, a wavelength conversion layer 30 is formed. However, the step of forming the second wavelength conversion section 32 is not limited to this.

[0071] Referring to Figure 11, an example of the process for placing the second translucent layer 40 will be described. As shown in Figure 11, the process for placing the second translucent layer 40 involves first forming an inorganic film 41 that covers the lower surface of the substrate 42 of the second translucent layer 40, then transporting the second translucent layer 40 so that the inorganic film 41 faces the second wavelength conversion section 32, and placing it on the second laminate 10M. Furthermore, the second translucent layer 40 may be heat-pressed to fix the inorganic film 41 and the second wavelength conversion section 32. This allows the wavelength conversion sheet 10 to be manufactured as shown in Figure 11. The method for forming the inorganic film 41 is, for example, the CVD (Chemical Vapor Deposition) method. The method for transporting the second translucent layer 40 is arbitrary. In addition, in the process for placing the second translucent layer 40, a commercially available second translucent layer 40 having a substrate 42 and an inorganic film 41 formed on the substrate 42 may be placed on the second laminate 10M.

[0072] The wavelength conversion sheet 10 is manufactured through these processes. The manufacturing method of the wavelength conversion sheet 10 may include steps other than those for preparing the first translucent layer 20, forming the first wavelength conversion section 31, forming the second wavelength conversion section 32, and arranging the second translucent layer 40.

[0073] Although preferred embodiments have been described in detail above, the invention is not limited to the embodiments described above, and various modifications and substitutions can be made to the embodiments described above without departing from the scope of the claims.

[0074] The aspects of this disclosure are, for example, as follows:

[0075] <Item 1> A first translucent layer having an inorganic film on its upper surface, A wavelength conversion layer disposed on the inorganic film, Equipped with, The wavelength conversion layer is A first wavelength conversion unit comprising a plurality of phosphor particles positioned apart from each other on the inorganic film, and an inorganic compound film coating the plurality of phosphor particles, A second wavelength conversion unit including quantum dots that separate from a plurality of phosphor particles via the inorganic compound film, A wavelength conversion sheet, including...

[0076] <Item 2> Further comprising a second translucent layer disposed on the wavelength conversion layer, The wavelength conversion sheet described in item 1 above.

[0077] <Item 3> A portion of the inorganic compound film is located between the phosphor particles and the inorganic film in the thickness direction. The wavelength conversion sheet described in item 1 or item 2 above.

[0078] <Item 4> The maximum length of the phosphor particles in the thickness direction is 20 μm or more and 150 μm or less. A wavelength conversion sheet as described in any one of the above items <1> to <3>.

[0079] <Item 5> The maximum length in the thickness direction of the wavelength conversion layer is greater than the maximum length in the thickness direction of the phosphor particles, and is between 20 μm and 150 μm. A wavelength conversion sheet as described in any one of the above items <1> to <4>.

[0080] <Item 6> The thickness of the inorganic compound film is 0.1 μm or more and 5.0 μm or less. A wavelength conversion sheet as described in any one of items 1 to 5 above.

[0081] <Item 7> The phosphor particles contain a europium complex, A wavelength conversion sheet as described in any one of the above items <1> to <6>.

[0082] <Item 8> The ratio of the maximum length of the phosphor particles in the thickness direction to the maximum length of the phosphor particles in the in-plane direction of the wavelength conversion layer is 0.01 or more and 0.8 or less. A wavelength conversion sheet as described in any one of the above items <1> to <7>.

[0083] <Item 9> A light-emitting element that emits light having an emission peak wavelength in the range of 380 nm to 480 nm, A wavelength conversion sheet is positioned above the light-emitting element, Equipped with, The aforementioned wavelength conversion sheet is A first translucent layer having an inorganic film on its upper surface, A wavelength conversion layer disposed on the inorganic film, Equipped with, The wavelength conversion layer is A first wavelength conversion unit comprising a plurality of phosphor particles positioned apart from each other on the inorganic film, and an inorganic compound film coating the plurality of phosphor particles, A second wavelength conversion unit including quantum dots that separate from a plurality of phosphor particles via the inorganic compound film, A light-emitting device, including a light-emitting device.

[0084] <Item 10> A step of preparing a first translucent layer having an inorganic film on its upper surface, The steps include forming a first wavelength conversion section on the inorganic film, The process involves forming a second wavelength conversion unit on the first wavelength conversion unit, Includes, The process of forming the first wavelength conversion section includes a first step of arranging a plurality of phosphor particles on the inorganic film so that they are spaced apart from each other, and a second step of forming an inorganic compound film using atomic layer deposition and coating the phosphor particles with the inorganic compound film. A method for manufacturing a wavelength conversion sheet, comprising the step of forming the second wavelength conversion section, which includes the step of arranging quantum dots so as to be separated from a plurality of phosphor particles via the inorganic compound film.

[0085] <Item 11> In the second step, a portion of the inorganic compound film is formed between the phosphor particles and the inorganic film in the thickness direction, and the phosphor particles are fixed to the inorganic film via the portion of the inorganic compound film. A method for manufacturing the wavelength conversion sheet described in item 10 above.

[0086] <Item 12> The first step includes placing a holding member that holds a plurality of phosphor particles separated from each other on the inorganic film, and then removing the holding member using ozone gas. A method for manufacturing a wavelength conversion sheet as described in item 10 or item 11 above.

[0087] <Item 13> The phosphor particles contain a europium complex, A method for manufacturing a wavelength conversion sheet according to any one of items 10 to 12 above.

[0088] <Item 14> The ratio of the length of the phosphor particles in the thickness direction to the maximum length of the phosphor particles in the in-plane direction of the wavelength conversion layer including the first wavelength conversion section and the second wavelength conversion section is 0.01 or more and 0.8 or less. A method for manufacturing a wavelength conversion sheet according to any one of items 10 to 13 above. [Explanation of Symbols]

[0089] 1. Light-emitting device 2 light-emitting elements 3 circuit boards 4. Light-reflective material 10 Wavelength Conversion Sheet 20 First transparent layer 21 Inorganic film 22 Base material 30 wavelength conversion layer 31 First Wavelength Conversion Section 311 Phosphorescent particles 311h Retaining member 312 Inorganic compound membrane 312a Part of an inorganic compound film 321 quantum dots 322 Cured resin 40 Second transparent layer

Claims

1. A first translucent layer having an inorganic film on its upper surface, A wavelength conversion layer disposed on the inorganic film, Equipped with, The wavelength conversion layer is A first wavelength conversion unit comprising a plurality of phosphor particles positioned apart from each other on the inorganic film, and an inorganic compound film coating the plurality of phosphor particles, A second wavelength conversion unit including quantum dots that separate from a plurality of phosphor particles via the inorganic compound film, A wavelength conversion sheet, including...

2. The wavelength conversion layer further comprises a second light-transmitting layer disposed on the wavelength conversion layer. The wavelength conversion sheet according to claim 1.

3. A portion of the inorganic compound film is located between the phosphor particles and the inorganic film in the thickness direction. A wavelength conversion sheet according to claim 1 or claim 2.

4. The maximum length of the phosphor particles in the thickness direction is 20 μm or more and 150 μm or less. A wavelength conversion sheet according to claim 1 or claim 2.

5. The maximum length in the thickness direction of the wavelength conversion layer is greater than the maximum length in the thickness direction of the phosphor particles, and is between 20 μm and 150 μm. A wavelength conversion sheet according to claim 1 or claim 2.

6. The thickness of the inorganic compound film is 0.1 μm or more and 5.0 μm or less. A wavelength conversion sheet according to claim 1 or claim 2.

7. The aforementioned phosphor particles contain a europium complex. A wavelength conversion sheet according to claim 1 or claim 2.

8. The ratio of the maximum length of the phosphor particles in the thickness direction to the maximum length of the phosphor particles in the in-plane direction of the wavelength conversion layer is 0.01 or more and 0.8 or less. A wavelength conversion sheet according to claim 1 or claim 2.

9. A light-emitting element that emits light having an emission peak wavelength in the range of 380 nm to 480 nm, A wavelength conversion sheet is positioned above the light-emitting element, Equipped with, The aforementioned wavelength conversion sheet is A first translucent layer having an inorganic film on its upper surface, A wavelength conversion layer disposed on the inorganic film, Equipped with, The wavelength conversion layer is A first wavelength conversion unit comprising a plurality of phosphor particles positioned apart from each other on the inorganic film, and an inorganic compound film coating the plurality of phosphor particles, A second wavelength conversion unit including quantum dots that separate from a plurality of phosphor particles via the inorganic compound film, A light-emitting device, including a light-emitting device.

10. A step of preparing a first translucent layer having an inorganic film on its upper surface, The steps include forming a first wavelength conversion section on the inorganic film, The process involves forming a second wavelength conversion unit on the first wavelength conversion unit, Includes, The process of forming the first wavelength conversion section includes a first step of arranging a plurality of phosphor particles on the inorganic film so that they are spaced apart from each other, and a second step of forming an inorganic compound film using atomic layer deposition and coating the phosphor particles with the inorganic compound film. A method for manufacturing a wavelength conversion sheet, comprising the step of forming the second wavelength conversion section, which includes the step of arranging quantum dots so as to be separated from a plurality of phosphor particles via the inorganic compound film.

11. In the second step, a portion of the inorganic compound film is formed between the phosphor particles and the inorganic film in the thickness direction, and the phosphor particles are fixed to the inorganic film via the portion of the inorganic compound film. A method for manufacturing a wavelength conversion sheet according to claim 10.

12. The first step includes placing a holding member that holds a plurality of phosphor particles separated from each other on the inorganic film, and then removing the holding member using ozone gas. A method for manufacturing a wavelength conversion sheet according to claim 10 or claim 11.

13. The aforementioned phosphor particles contain a europium complex. A method for manufacturing a wavelength conversion sheet according to claim 10 or claim 11.

14. The ratio of the length of the phosphor particles in the thickness direction to the maximum length of the phosphor particles in the in-plane direction of the wavelength conversion layer including the first wavelength conversion section and the second wavelength conversion section is 0.01 or more and 0.8 or less. A method for manufacturing a wavelength conversion sheet according to claim 10 or claim 11.

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