JP7706071B2 - Wavelength conversion device and projector - Google Patents

Description

The present invention relates to a wavelength conversion device, a projector using the same, and a phosphor ceramic member.

Wavelength conversion devices used in projectors are known in the art.

For example, Patent Document 1 discloses a wavelength conversion device that includes a substrate that is circular in plan view and a phosphor layer (phosphor ceramic member) that is provided along the circumferential direction of the substrate, and that can be rotated by a motor connected to the center of the substrate. In Patent Document 1, this wavelength conversion device functions as a reflective phosphor wheel in a projector, and the fluorescence emitted by the phosphor layer of this wavelength conversion device is used as the light (projected light) emitted by the projector.

JP 2019-66880 A

However, the conventional wavelength conversion devices, projectors, and phosphor ceramic members described above have a problem in that the light utilization efficiency is low. Therefore, the present invention provides a wavelength conversion device, projector, and phosphor ceramic member that has high light utilization efficiency.

A wavelength conversion device according to one aspect of the present invention is used in a projector, receives excitation light, and emits reflected light including fluorescence. The wavelength conversion device includes a substrate having a light reflecting surface, and a phosphor ceramic layer located above the light reflecting surface and including a first crystal phase having a garnet structure. The visible light reflectance of the light reflecting surface is 95% or more and 100% or less, the density of the phosphor ceramic layer is 97% or more and 100% or less of the theoretical density, and the film thickness of the phosphor ceramic layer is 50 μm or more and less than 120 μm.

A projector according to one aspect of the present invention includes an excitation light source that emits excitation light, and the above-mentioned wavelength conversion device that receives the excitation light and emits reflected light that includes fluorescent light.

The phosphor ceramic member according to one aspect of the present invention is a phosphor ceramic member used in a projector, and includes a first crystal phase having a garnet structure and a second crystal phase having a structure other than the garnet structure, the density of the phosphor ceramic member is 97% or more and 100% or less of the theoretical density, and the film thickness of the phosphor ceramic member is 50 μm or more and less than 300 μm.

The present invention provides a wavelength conversion device, projector, and phosphor ceramic member that have high light utilization efficiency.

FIG. 1 is a perspective view of a wavelength conversion device according to an embodiment. FIG. 2 is a cross-sectional view showing a cut surface of the wavelength conversion device taken along line II-II in FIG. FIG. 3 is a perspective view showing the appearance of the projector according to the embodiment. FIG. 4 is a schematic diagram showing an optical system of the projector according to the embodiment. FIG. 5A is a schematic diagram showing a wavelength conversion device and an aperture member according to an embodiment. FIG. 5B is a schematic diagram showing a wavelength conversion device and an aperture member according to a comparative example of the embodiment. FIG. 6 is a diagram showing the evaluation results of wavelength conversion devices according to examples and comparative examples of the embodiment. FIG. 7 is a diagram showing the evaluation results of the wavelength conversion device according to the embodiment. FIG. 8 is a perspective view of a wavelength conversion device according to the first modification. FIG. 9 is a cross-sectional view showing a cut surface of the wavelength conversion device taken along line IX-IX in FIG. FIG. 10 is an SEM image showing a cross section of a phosphor ceramic layer according to an example of the first modification. FIG. 11 is a diagram showing an evaluation result of a wavelength conversion device according to an example of the first modified example. FIG. 12 is a perspective view of a phosphor ceramic member according to the second modification.

The following describes in detail the wavelength conversion device and other aspects of the present invention using the drawings.

The embodiments described below are all comprehensive or specific examples. The numerical values, shapes, materials, components, component placement and connection, manufacturing process, and manufacturing process sequence shown in the following embodiments are merely examples and are not intended to limit the present invention. Furthermore, among the components in the following embodiments, components that are not described in an independent claim are described as optional components.

In addition, each figure is a schematic diagram and is not necessarily an exact illustration. Therefore, for example, the scales of each figure do not necessarily match. In addition, in each figure, substantially the same configuration is given the same reference numerals, and duplicate explanations are omitted or simplified.

In this specification, terms indicating the relationship between elements, such as parallel or perpendicular, terms indicating the shape of elements, such as circular or elliptical, and numerical ranges are not expressions that express only the strict meaning, but are expressions that include a substantially equivalent range, for example, a difference of about a few percent.

In addition, in this specification, "planar view" refers to the wavelength conversion device viewed along the perpendicular direction of the light reflecting surface of the substrate.

In addition, in this specification, the terms "above" and "below" in the configuration of a wavelength conversion device do not refer to the upward (vertically upward) and downward (vertically downward) directions in absolute spatial recognition, but are terms defined by the relative positional relationship based on the stacking order in the stacked structure. In addition, the terms "above" and "below" are applied not only to the case where two components are arranged with a gap between them and another component exists between the two components, but also to the case where two components are arranged closely together and the two components are in contact with each other.

In the present specification and drawings, the x-axis, y-axis, and z-axis refer to the three axes of a three-dimensional orthogonal coordinate system. In each embodiment, the two axes parallel to the light reflecting surface of the substrate are the x-axis and the y-axis, and the direction perpendicular to the light reflecting surface is the z-axis direction. In each embodiment described below, the positive direction of the z-axis may be referred to as the upward direction, and the negative direction of the z-axis may be referred to as the downward direction.

(Embodiment)
[Configuration of Wavelength Conversion Device]
First, the configuration of a wavelength conversion device 1 according to the present embodiment will be described with reference to the drawings. Fig. 1 is a perspective view of the wavelength conversion device 1 according to the present embodiment. Fig. 2 is a cross-sectional view showing a cut surface of the wavelength conversion device 1 taken along line II-II in Fig. 1.

As shown in Figures 1 and 2, the wavelength conversion device 1 is a device that includes a substrate 10 having a light-reflecting surface 13, a phosphor ceramic layer 20, and an anti-reflection layer 30.

In this embodiment, the wavelength conversion device 1 is used in a projector and is a phosphor wheel that receives excitation light L1 and emits reflected light including fluorescent light. The wavelength conversion device 1 has a disk shape, and a motor 4 that rotates is provided in the center of the wavelength conversion device 1 in a plan view. Therefore, the wavelength conversion device 1 is rotated by the motor 4 in the direction of the arrow shown in Figure 1 around the motor 4 as an axis.

Note that while FIG. 1 shows a configuration of a phosphor wheel equipped with a motor 4, the wavelength conversion device 1 does not have to be equipped with a motor 4. In other words, the wavelength conversion device 1 may be a fixed device that is not driven to rotate. With such a configuration, the wavelength conversion device 1 can be made small, making it possible to provide a compact projector.

The phosphor ceramic layer 20 is a layer located above the light reflecting surface 13 of the substrate 10. In this embodiment, since the wavelength conversion device 1 is a phosphor wheel, the phosphor ceramic layer 20 is a phosphor ring. The phosphor ceramic layer 20 is provided in a ring shape on a circumference that is equidistant from the center of rotation of the wavelength conversion device 1 (i.e., the location where the motor 4 is provided). In other words, the phosphor ceramic layer 20 is provided in a band shape along the circumferential direction in a plan view.

The phosphor ceramic layer 20 includes a first crystal phase having a garnet structure. More specifically, in this embodiment, the phosphor ceramic layer 20 is composed only of the first crystal phase having a garnet structure. That is, the phosphor ceramic layer 20 according to this embodiment does not include a crystal phase having a structure different from _{the garnet structure. The garnet structure is a crystal structure represented by the general formula A3B2C3O12 .} The element A includes rare earth elements such as _Ca , Y, _La , Ce, Pr, Nd, Sm, Eu, Gd, Tb, and Lu, the element B includes elements such as Mg, Al, Si, Ga, and Sc, and the element C includes elements such as Al, Si, and Ga. Such garnet structures include YAG (Yttrium Aluminum Garnet) _, LuAG (Lutetium Aluminum Garnet), _{Lu2CaMg2Si3O12} (Lutetium Calcium Magnesium Silicon Garnet), and _TAG (Terbium Aluminum Garnet) _. In this embodiment, the phosphor ceramic layer 20 is composed of _{a first} crystal phase _represented by (Y1 _{-xCe x} ) _3Al2Al3O12 (that is, (Y1 _{-xCe x ) 3Al5O12 )} (0.001≦x< _0.1 ), that is, YAG.

The first crystal phase constituting the phosphor ceramic layer 20 may be a solid solution of a plurality of garnet crystal phases having different chemical compositions. Such a solid solution may be _{a solid solution ((1-a)(Y1-xCe x)3Al5O12.a(Lu1-dCed)3Al2Al3O12 ( 0 < a < 1 )} ) of a garnet crystal phase represented by ( _{Y1 -xCe x ) 3Al2Al3O12 (} 0.001≦x<0.1) _{and a} garnet _crystal phase represented by ( _{Lu1 -dCed ) 3Al2Al3O12} (0.001≦ _d <0.1) _. Further, such a solid solution may be _{a solid solution} (( _{1-b)(Y1-xCex ) 3Al2Al3O12.b} (Lu1-zCez) _2CaMg2Si3O12 (0<b<1) ₎ of a garnet crystal phase represented by _{( Y1 -xCex ) 3Al2Al3O12} ( _0.001 ≦x<0.1) _{and a garnet} crystal phase represented by ( _{Lu1 - zCez} ) _2CaMg2Si3O12 (0.0015≦z<0.15). Since the _phosphor ceramic layer 20 is composed of _a solid solution of a plurality of garnet crystal phases having different chemical compositions, _the fluorescence spectrum of the fluorescence emitted by the phosphor ceramic layer 20 becomes broader, and the _green light component and the red light component increase. This makes it possible to provide a projector that emits projection light with a wide color gamut.

The first crystal phase constituting the phosphor ceramic layer 20 may contain a crystal phase whose chemical composition is different from that of the crystal phase expressed by the general formula A ₃ B ₂ C ₃ O ₁₂ described above. Such a crystal phase may be (Y _1-x Ce _x ) ₃ Al _{2 +} δ Al ₃ O ₁₂ (δ is a positive number) which is rich in Al compared to the crystal phase expressed by (Y _1-x Ce _x ) ₃ Al ₂ Al ₃ O ₁₂ (0.001≦x<0.1). Such a crystal phase may be (Y _1-x Ce _x ) ₃ + ζ Al ₂ Al ₃ O ₁₂ (ζ is a positive number) which is rich in Y compared to the crystal phase expressed by (Y _1-x Ce _x ) ₃ Al ₂ Al ₃ O ₁₂ (0.001≦x<0.1). These crystal phases have a different chemical composition from _the crystal phase expressed by _{the general formula A3B2C3O12 ,} but maintain the garnet structure. Since the phosphor ceramic layer 20 is composed of crystal phases with different chemical compositions, regions with different refractive indices are generated in the phosphor ceramic layer 20, so that the excitation light L1 and the fluorescent light are scattered more, and the light-emitting area of the phosphor ceramic layer 20 becomes smaller. Therefore, it is possible to provide a wavelength conversion device 1 and a projector with a smaller etendue and higher light utilization efficiency.

Furthermore, the phosphor ceramic layer 20 may contain a first crystal phase and a heterophase having a structure other than a garnet structure. When the phosphor ceramic layer 20 is composed of such a first crystal phase and a heterophase, regions with different refractive indices are generated in the phosphor ceramic layer 20, so that the excitation light L1 and the fluorescent light are scattered more, and the light-emitting area of the phosphor ceramic layer 20 becomes smaller. Therefore, it is possible to provide a wavelength conversion device 1 and a projector with a smaller etendue and higher light utilization efficiency.

The phosphor ceramic layer 20 made of YAG receives light incident from above the wavelength conversion device 1 as excitation light L1 and emits fluorescence. More specifically, light emitted from an excitation light source described below is irradiated onto the phosphor ceramic layer 20 as excitation light L1, causing the phosphor ceramic layer 20 to emit fluorescence as wavelength-converted light. In other words, the wavelength-converted light emitted from the phosphor ceramic layer 20 is light with a longer wavelength than the wavelength of the excitation light L1.

In this embodiment, the wavelength-converted light emitted from the phosphor ceramic layer 20 includes fluorescence, which is yellow light. The phosphor ceramic layer 20 absorbs light having a wavelength of 380 nm or more and 490 nm or less, and emits fluorescence, which is yellow light, having a fluorescence peak wavelength in the wavelength range of 490 nm or more and 580 nm or less. By making the phosphor ceramic layer 20 out of YAG, it is easy to realize a phosphor ceramic layer 20 that emits fluorescence having a fluorescence peak wavelength in the wavelength range of 490 nm or more and 580 nm or less.

The x-coordinate of the chromaticity diagram of the wavelength-converted light emitted from the phosphor ceramic layer 20 should be 0.415 or less, preferably 0.410 or less, and even better 0.408 or less. When the x-coordinate of the chromaticity diagram of the wavelength-converted light emitted from the phosphor ceramic layer 20 is within the above range, the temperature quenching of the phosphor ceramic layer 20 is reduced, and a phosphor ceramic layer 20 with high luminous efficiency can be achieved.

The density of the phosphor ceramic layer 20 may be 95% or more and 100% or less of the theoretical density, and more preferably 97% or more and 100% or less of the theoretical density. Here, the theoretical density is the density when the atoms in the layer are ideally arranged. In other words, the theoretical density is the density when it is assumed that there are no voids in the phosphor ceramic layer 20, and is a value calculated using the crystal structure. For example, when the density of the phosphor ceramic layer 20 is 99%, the remaining 1% corresponds to voids. In other words, the higher the density of the phosphor ceramic layer 20, the fewer the voids. When the density of the phosphor ceramic layer 20 is in the above range, the total amount of fluorescence emitted by the phosphor ceramic layer 20 increases, so that a wavelength conversion device 1 and a projector that emit a larger amount of light can be provided.

The density of the phosphor ceramic layer 20 may be 4.32 g/cm ³ or more and 4.55 g/cm ³ or less, and more preferably 4.41 g/cm ³ or more and 4.55 g/cm ³ or less. As shown in this embodiment, when the phosphor ceramic layer 20 is made of YAG, if the density of the phosphor ceramic layer 20 is in the above range, the density of the phosphor ceramic layer 20 is 95% or more and 100% or less and 97% or more and 100% or less of the theoretical density, respectively. When the density of the phosphor ceramic layer 20 is in the above range, the excitation light L1 absorbed by the phosphor ceramic layer 20 can be efficiently converted into fluorescence. In other words, a phosphor ceramic layer 20 with high luminous efficiency is realized.

The thickness of the phosphor ceramic layer 20 (length in the z-axis direction) is preferably 50 μm or more and less than 150 μm, and more preferably 50 μm or more and less than 120 μm. The thickness of the phosphor ceramic layer is more preferably 70 μm or more and less than 120 μm, and even more preferably 80 μm or more and less than 110 μm.

Furthermore, an anti-reflection layer 30 is located above the phosphor ceramic layer 20.

The anti-reflection layer 30 is a layer that prevents, or more specifically, suppresses, the reflection of the excitation light L1. The anti-reflection layer 30 reduces the reflectance of the excitation light L1 in the wavelength conversion device 1, and increases the amount of excitation light L1 that reaches the phosphor ceramic layer 20. As a result, the amount of excitation light L1 that can be absorbed by the phosphor ceramic layer 20 also increases, and the amount of fluorescence emitted by the phosphor ceramic layer 20 also increases. In other words, the provision of the anti-reflection layer 30 increases the amount of fluorescence emitted by the phosphor ceramic layer 20.

The anti-reflection layer 30 may be composed of, for example, a dielectric film or a fine uneven structure (so-called moth-eye structure) with a period smaller than the wavelength of light in the visible light region. When the anti-reflection layer 30 is composed of a dielectric film, it is preferable that the anti-reflection layer 30 contains an inorganic compound. _In this case, the anti-reflection layer 30 contains one _or more inorganic compounds selected from SiO2, _TiO2 , _Al2O3 , ZnO, _{Nb2O5 ,} MgF, etc.

In addition, although a configuration in which an anti-reflection layer 30 is provided is shown in Figures 1 and 2, the wavelength conversion device 1 does not necessarily have to include an anti-reflection layer 30.

The substrate 10 is a disk-shaped plate material, and is a base material that supports the phosphor ceramic layer 20 and the anti-reflection layer 30. The motor 4 is provided in the center of the substrate 10 in a plan view. As shown in FIG. 2, the substrate 10 has a substrate body 11 and a light-reflecting layer 12.

The substrate body 11 is preferably made of a material with high thermal conductivity. For example, the substrate body 11 is preferably made of a material with a higher thermal conductivity than the phosphor ceramic layer 20, but is not limited to this. Examples of the substrate body 11 include a glass substrate, a quartz substrate, a GaN substrate, a sapphire substrate, a Si substrate, and a metal substrate. The substrate body 11 may also be made of a resin such as a PEN (polyethylene naphthalate) film or a PET (polyethylene terephthalate) film. Furthermore, when the substrate body 11 is a metal substrate, the substrate body 11 is made of a metal material such as Al, Fe, and Ti.

In this embodiment, the substrate body 11 is a metal substrate made of Al. Since Al has high thermal conductivity and is lightweight, it is possible to improve the heat dissipation of the substrate body 11 and reduce the weight of the substrate body 11. The thickness of the substrate body 11 is, for example, 1.5 mm or less.

The substrate 10 also has a light-reflecting surface 13. The light-reflecting surface 13 is one surface of the substrate 10 on the side where the phosphor ceramic layer 20 is located. In this embodiment, the light-reflecting surface 13 is constituted by one surface included in the light-reflecting layer 12.

The light reflecting surface 13 is a surface that reflects the fluorescence emitted by the phosphor ceramic layer 20. The light reflecting surface 13 also reflects the excitation light L1 that was not converted to fluorescence in the phosphor ceramic layer 20. The light reflecting surface 13 reflects the fluorescence and the excitation light L1 that was not converted to fluorescence upward. In this embodiment, since the fluorescence and the excitation light L1 are light in the visible light region, the higher the visible light reflectance of the light reflecting surface 13, the less the loss of light. Specifically, the visible light reflectance of the light reflecting surface 13 may be 90% or more and 100% or less, and is preferably 95% or more and 100% or less. When the visible light reflectance of the light reflecting surface 13 is in the above range, the fluorescence and the excitation light L1 are reflected more upward, so that the guide of the fluorescence and the excitation light L1 in the lateral direction (i.e., the direction parallel to the light reflecting surface 13) is suppressed, and the light-emitting area is smaller. Therefore, a wavelength conversion device 1 and a projector having a smaller etendue and higher light utilization efficiency can be provided. In addition, the reflectance of the light of the light reflecting surface 13 in the wavelength region of 490 nm to 780 nm may be 90% to 100%, and preferably 95% to 100%. When the reflectance of the light of the light reflecting surface 13 in the wavelength region of 490 nm to 780 nm is in the above range, the fluorescence is reflected more upward, so that the lateral waveguiding of the fluorescence is suppressed and the light emission area is smaller. Therefore, it is possible to provide a wavelength conversion device 1 and a projector with a smaller etendue and higher light utilization efficiency. In this embodiment, the visible light region is a wavelength region of 380 nm to 780 nm.

The light reflecting layer 12 may be made of any material as long as it can reflect upward the fluorescent light and the excitation light L1 that has not been converted into fluorescent light. In this embodiment, the light reflecting layer 12 is a composite layer made of light scattering particles 121 and a binder 122 in which the light scattering particles 121 are dispersed. In other words, the light reflecting layer 12 has light diffusibility (light scattering properties) and reflects upward the fluorescent light and the excitation light L1 that has not been converted into fluorescent light due to light diffusion.

The light reflecting layer 12 diffuses light due to the difference in refractive index between the light scattering particles 121 and the binder 122. The light scattering particles 121 are, for example, fillers or white particles made of an inorganic compound or a resin material. More specifically, the light scattering particles 121 may be inorganic compounds such as SiO ₂ , TiO ₂ , Al ₂ O ₃ , ZnO, Nb ₂ O ₅ , ZrO ₂ and CaCO ₃ , or may be resin materials such as styrene resin and acrylic resin. The binder 122 may be made of a resin material such as an acrylic resin and a silicone resin that is light-transmitting.

By providing the light reflecting layer 12, the visible light reflectance of the light reflecting surface 13 can be increased. Furthermore, by forming the light reflecting layer 12 as a composite layer containing light scattering particles 121, the visible light reflectance of the light reflecting surface 13 can be further increased. In other words, the loss of light in the wavelength conversion device 1 can be further suppressed.

The light reflecting layer 12 may be a metal layer made of a metal having light reflectivity. For example, the metal is Ag, Al, or an alloy containing any of these. The light reflecting layer 12 may be formed of the metal by a dry process or a wet process. Even in such a case, the same effect as when the light reflecting layer 12 is made of a composite layer containing light scattering particles 121 is expected.

A bonding layer may be provided between the light reflecting layer 12 and the phosphor ceramic layer 20. This configuration allows the light reflecting layer 12 and the phosphor ceramic layer 20 to adhere more closely to each other, so that heat generated in the phosphor ceramic layer 20 can be more efficiently conducted to the substrate body 11 via the light reflecting layer 12. This allows for a highly efficient wavelength conversion device 1 with less temperature quenching of the phosphor ceramic layer 20. The bonding layer may be made of a transparent material such as a silicone-based resin or an epoxy-based resin. The thickness of the bonding layer may be 1 μm or more and less than 100 μm, and preferably 1 μm or more and less than 20 μm.

Note that although a configuration in which a light reflecting layer 12 is provided is shown in Figs. 1 and 2, the wavelength conversion device 1 does not have to include a light reflecting layer 12. In this case, the surface of the substrate body 11 becomes the light reflecting surface 13.

[Projector configuration]
The wavelength conversion device 1 configured as above is used in a projector 100 shown in Fig. 3 and Fig. 4. Fig. 3 is a perspective view showing the appearance of the projector 100 according to the present embodiment. Fig. 4 is a schematic diagram showing the optical system of the projector 100 according to the present embodiment. The configuration of the projector 100 according to the present embodiment will be described below with reference to Figs. 3 and 4.

As shown in Figures 3 and 4, the projector 100 according to this embodiment includes a light source 3, a dichroic mirror 5, a wavelength conversion device 1, a display element 6, a projection optical member 7, and a reflecting mirror 8.

The light source 3 is, for example, a semiconductor laser light source or an LED (Light Emitting Diode) light source, and is driven by a drive current to emit light of a predetermined color (wavelength).

In this embodiment, the light source 3 is a semiconductor laser light source. The semiconductor laser element included in the light source 3 is, for example, a GaN-based semiconductor laser element (laser chip) made of a nitride semiconductor material. In this embodiment, the light source 3, which is a semiconductor laser light source, is a multi-chip type light emitting device.

As an example, the light source 3 emits laser light in the near ultraviolet to blue range with a peak wavelength of 380 nm or more and 490 nm or less. More specifically, the light source 3 emits blue light with a peak wavelength of 445 nm. The light source 3 in this embodiment is an example of an excitation light source. The laser light emitted by the light source 3 reaches the dichroic mirror 5.

The dichroic mirror 5 is disposed at an angle of 45 degrees to the optical axis of the light source 3. The dichroic mirror 5 in this embodiment is a dichroic mirror that transmits part of the blue light, reflects the other part, and transmits the yellow fluorescent light.

In other words, the dichroic mirror 5 has the property of reflecting and transmitting light in the wavelength region of the laser light emitted from the light source 3. Therefore, a portion of the laser light emitted from the light source 3 passes through the dichroic mirror 5 without changing its direction of travel, and the other portion of the laser light is reflected by the dichroic mirror 5, has its direction of travel changed by 90°, and heads toward the wavelength conversion device 1.

Here, the other part of the laser light emitted from the light source 3 reaches the wavelength conversion device 1 as excitation light L1. The wavelength conversion device 1 receives the excitation light L1 and emits reflected light L2 containing fluorescence. More specifically, the reflected light L2 contains light that has been wavelength converted and reflected by the phosphor ceramic layer 20 and the light reflecting surface 13 of the wavelength conversion device 1. More specifically, the reflected light L2 contains yellowish fluorescence generated in the phosphor ceramic layer 20 and the excitation light L1, which is blue light that has not been converted to fluorescence in the phosphor ceramic layer 20. However, since the proportion of fluorescence in the reflected light L2 is high, the reflected light L2 is yellowish light.

The laser light that passes through the dichroic mirror 5 without changing its direction of travel reaches the reflecting mirror 8 as transmitted light L12, is specularly reflected by the reflecting mirror 8, and travels toward the other surface of the dichroic mirror 5. The transmitted light L12 is then reflected by the other surface of the dichroic mirror 5, its direction of travel is changed by 90°, and travels toward the display element 6.

The reflected light L2 also reaches the dichroic mirror 5. At this time, the dichroic mirror 5 is disposed at an angle of 45 degrees to the optical axis of the reflected light L2, and transmits yellow fluorescent light. Therefore, the traveling direction of the reflected light L2 that reaches the dichroic mirror 5 does not change.

As a result, as shown in Figure 4, the optical axis of the reflected light L2 and the optical axis of the transmitted light L12 coincide with each other and head toward the display element 6. At this time, the reflected light L2 is yellow light and the transmitted light L12 is blue light, so the light obtained by combining these lights is white light. In other words, the light heading toward the display element 6 from the dichroic mirror 5 is white light.

The white light, which is a mixture of the reflected light L2 and the transmitted light L12, travels toward the display element 6. If the reflected light L2 has a large etendue, the size of the reflected light L2 irradiated toward the display element 6 will be larger than the size of the display element 6. As a result, there will be a large amount of ineffective (i.e., unusable) light components that are not irradiated to the display element 6.

The display element 6 is a substantially planar element that controls the light (white light) that passes through the opening 2a and outputs it as an image. In other words, the display element 6 generates light for the image. Specifically, the display element 6 is a DLP (Digital Light Processing) having a DMD (Digital Micromirror Device). For example, the display element 6 may be a reflective liquid crystal panel. Note that a fly-eye lens, a polarization conversion element, a mirror rod, and the like may be provided between the display element 6 and the dichroic mirror 5.

The light for the image generated by the display element 6 is converted by the projection optical member 7 into projection light that is enlarged and projected onto the screen.

In the projector 100, only the light irradiated to the display element 6 is used as projection light. In other words, the smaller the etendue of the reflected light L2, the more light can be used as projection light by the projector 100.

[Optical behavior in wavelength conversion devices]
Here, the behavior of light in the wavelength conversion device 1 will be described using this embodiment and a comparative example.

Figure 5A is a schematic diagram showing a wavelength conversion device 1 and an aperture member 2 according to this embodiment. Figure 5B is a schematic diagram showing a wavelength conversion device 1x and an aperture member 2 according to a comparative example of this embodiment. For simplicity, the following description will be given using the aperture member 2, the wavelength conversion devices 1 and 1x, the excitation light L1, and the reflected light L2.

The aperture member 2 is a member for evaluating the etendue of the reflected light L2. The aperture member 2 is a light-absorbing member, and has an opening 2a in the center of the aperture member 2. If the proportion of light components passing through the opening 2a of the aperture member 2 is relatively high, the etendue of the reflected light L2 can be said to be small.

The wavelength conversion device 1x of the comparative example has the same configuration as the wavelength conversion device 1 of the present embodiment, except that the phosphor ceramic layer 20x is thicker (e.g., 200 μm) than the phosphor ceramic layer 20 of the present embodiment.

The phosphor ceramic layers 20 and 20x have a high density of 4.41 g/ ^cm3 or more and 4.55 g/ ^cm3 or less. That is, in the phosphor ceramic layers 20 and 20x, there are few voids and light scattering is unlikely to occur, so that light easily travels in the planar direction of the layer (i.e., the x-axis direction or the y-axis direction), and so-called light guiding is likely to occur.

First, the wavelength conversion device 1 according to this embodiment will be described with reference to FIG. 5A.

When the phosphor ceramic layer 20 according to the present embodiment is sufficiently thin (50 μm or more and 120 μm or less), the distance D in the planar direction of the layer (here, the x-axis direction) from when the excitation light L1 enters until the reflected light L2 exits can be made shorter. In other words, in this embodiment, the light emission area (light emission spot diameter) of the fluorescence of the phosphor ceramic layer 20 is sufficiently small. Therefore, as shown in FIG. 5A, the reflected light L2 reflected by the light reflecting surface 13 and exiting from the phosphor ceramic layer 20 easily passes through the opening 2a of the aperture member 2. As described above, the light that passes through the opening 2a can be used as light to be enlarged and projected onto the screen via the display element 6 and the projection optical member 7.

In other words, in this embodiment, the thickness of the phosphor ceramic layer 20 provided in the wavelength conversion device 1 is sufficiently thin, so that the fluorescent light emission area can be made sufficiently small. Therefore, since a large amount of light passes through the opening 2a of the aperture member 2, a large amount of light can be used as projection light for the projector 100. In other words, the above configuration realizes a wavelength conversion device 1 with high light utilization efficiency. Furthermore, by providing such a wavelength conversion device 1, a projector 100 with high light utilization efficiency is realized.

Next, a wavelength conversion device 1x according to a comparative example will be described with reference to FIG. 5B.

When the phosphor ceramic layer 20x in the comparative example is sufficiently thick (200 μm), the distance Dx in the planar direction of the layer from when the excitation light L1 enters until the reflected light L2x exits becomes longer. In other words, in the comparative example, the light emission area (light emission spot diameter) of the fluorescent light of the phosphor ceramic layer 20x becomes larger. Therefore, as shown in FIG. 5B, the reflected light L2x reflected by the light reflecting surface 13 and exiting from the phosphor ceramic layer 20x is likely to be blocked by the aperture member 2. Therefore, the wavelength conversion device 1x in the comparative example has low light utilization efficiency.

As described above, in this embodiment, the light reflecting layer 12 is provided, and the light reflecting layer 12 is further composed of a composite layer containing light scattering particles 121, so that the visible light reflectance of the light reflecting surface 13 can be further increased. This makes it possible to further suppress light loss in the wavelength conversion device 1, thereby realizing a wavelength conversion device 1 with high light utilization efficiency.

[Example]
Here, a manufacturing method and light utilization efficiency of the wavelength conversion devices according to Examples 1 to 3 of this embodiment and a comparative example will be described.

First, we will describe the manufacturing method for the phosphor ceramic layer.

_The phosphor ceramic layers according to Examples 1 to 3 and Comparative Example are all composed of _a first crystal phase represented by ( _{Y0.9953Ce0.0047} ) _{3Al5O12 .} Moreover, the phosphor ceramic layers according to Examples 1 to 3 and Comparative Example are all composed of a Ce3 ⁺ -activated phosphor.

The phosphor ceramic layers according to Examples 1 to 3 and the Comparative Example were made using the following three types of compound powder as raw materials: Y ₂ O ₃ (yttrium oxide, purity 3N, Nippon Yttrium Co., Ltd.), Al ₂ O ₃ (aluminum oxide, purity 3N, Sumitomo Chemical Co., Ltd.), and CeO ₂ (cerium oxide, purity 3N, Nippon Yttrium Co., Ltd.).

First, the raw materials were weighed out so as to obtain a compound having a stoichiometric composition of (Y _0.9953 Ce _0.0047 ) ₃ Al ₅ O _12. Next, the weighed raw materials and alumina balls (diameter 10 mm) were put into a plastic pot. The amount of the alumina balls was such that it filled about 1/3 of the volume of the plastic pot. Then, pure water was put into the plastic pot, and the raw materials and the pure water were mixed using a pot rotating device (BALL MILL ANZ-51S, manufactured by Nitto Chemical Co., Ltd.). This mixing was carried out for 12 hours. In this way, a slurry-like mixed raw material was obtained.

The slurry-like mixed raw material was dried using a dryer. Specifically, a Naflon (registered trademark) sheet was laid so as to cover the inner wall of a metal tray, and the mixed raw material was poured above the Naflon (registered trademark) sheet. The metal tray, the Naflon (registered trademark) sheet, and the mixed raw material were treated and dried for 8 hours in a dryer set at 150°C. Thereafter, the dried mixed raw material was collected, and the mixed raw material was granulated using a spray dryer. Note that polyvinyl alcohol was used as an adhesive (binder) during granulation.

The granulated mixed raw material was provisionally molded into a cylindrical shape using an electric hydraulic press (EMP-5, manufactured by Riken Seiki Co., Ltd.) and a cylindrical mold (outer diameter 58 mm, inner diameter 38 mm, height 130 mm). The pressure during molding was 5 MPa/ ^cm2 . Next, the molded body after the provisional molding was subjected to final molding using a cold isostatic pressing device. The pressure during final molding was 300 MPa. The molded body after final molding was subjected to a heat treatment (binder removal treatment) for the purpose of removing the adhesive (binder) used during granulation. The temperature of the heat treatment was 500°C. The heat treatment time was 10 hours.

The molded body after the heat treatment was sintered using a tubular atmosphere furnace. The sintering temperature was 1675°C. The sintering time was 4 hours. The sintering atmosphere was a mixed gas atmosphere of nitrogen and hydrogen. The outer diameter and inner diameter of the sintered product after sintering were 43 mm and 29 mm, respectively.

After firing, the cylindrical fired product was sliced using a multi-wire saw. The thickness of the sliced cylindrical fired product was approximately 700 μm.

The sliced fired product was polished using a polishing device to adjust the thickness of the fired product. This adjustment turned the fired product into a phosphor ceramic layer. The thickness of the phosphor ceramic layer was 53 μm in Example 1, 75 μm in Example 2, 106 μm in Example 3, and 206 μm in the comparative example.

The outer and inner diameters of the phosphor ceramic layers in Examples 1 to 3 and the Comparative Example were 43 mm and 29 mm, respectively. The phosphor ceramic layers in Examples 1 to 3 and the Comparative Example were also deep yellow in color.

Next, we will explain the evaluation of the phosphor ceramic layer.

First, the density of the phosphor ceramic layer according to Examples 1 to 3 and the Comparative Example was evaluated using the Archimedes method. The density of the phosphor ceramic layer according to Examples 1 to 3 and the Comparative Example was 4.49 g/cm ^3. The density of the phosphor ceramic layer according to Examples 1 to 3 and the Comparative Example was 98.7% of the theoretical density of Y ₃ Al ₅ O ₁₂ (4.55 g/cm ³ ). That is, the density of the phosphor ceramic layer according to Examples 1 to 3 and the Comparative Example was 97% or more and 100% or less of the theoretical density of Y ₃ Al ₅ O ₁₂ .

Next, we will describe the manufacturing method for the wavelength conversion device.

First, a disk-shaped substrate body (diameter 50 mm, thickness 0.5 mm) made of Al is prepared. Next, a light-reflecting layer containing a silicone-based resin with TiO2 _particles dispersed therein is applied to the substrate body using a dispenser device so as to have a circular shape (outer diameter 46 mm, inner diameter 30 mm). Here, the silicone-based resin contained in the light-reflecting layer also functions as an adhesive for bonding the phosphor ceramic layer and the substrate body.

The phosphor ceramic layer was then placed so as to overlap the circularly applied light-reflecting layer. Here, the phosphor ceramic layer was fixed with a metal jig so that the thickness of the light-reflecting layer was approximately 50 μm. The light-reflecting layer was then hardened by a heat treatment using a dryer. The heat treatment temperature was 150°C. The visible light reflectance of the light-reflecting surface, which is one surface included in the light-reflecting layer, was 95% or more.

In this way, wavelength conversion devices according to Examples 1 to 3 and Comparative Example were obtained, each of which includes a phosphor ceramic layer according to Examples 1 to 3 and Comparative Example, and a substrate.

Furthermore, we will explain the evaluation of wavelength conversion devices.

The wavelength conversion devices according to Examples 1 to 3 and Comparative Example were evaluated using an evaluation device for a reflective laser excitation type wavelength conversion device. Specifically, in the evaluation device, excitation light (laser light) is irradiated onto a rotated wavelength conversion device, and the fluorescent energy of the fluorescent light emitted from the wavelength conversion device is evaluated by a power meter. The wavelength, output, and irradiation spot diameter (1/e ² ) of the laser light were set to 455 nm, 70 W, and 1.2 mm, respectively. The laser light was a Gaussian beam. The rotation speed of the wavelength conversion device was set to 7200 rpm. The evaluation device was provided with an aperture member that blocks a part of the fluorescent light emitted from the wavelength conversion device. At this time, for example, the distance between the wavelength conversion device and the aperture member is 3 mm or more and 100 mm or less, and the opening of the aperture member is a circular hole with an opening diameter of 5 mm or more and 10 mm or less.

Figure 6 shows the evaluation results of the wavelength conversion devices according to Examples 1 to 3 of this embodiment and the Comparative Example. Specifically, Figure 6 shows the relative fluorescent energy value (after passing through the aperture), the relative fluorescent energy value (before passing through the aperture), and the coupling efficiency of the wavelength conversion devices according to Examples 1 to 3 and the Comparative Example.

Here, the relative value of the fluorescent energy (after passing through the opening) is the relative value of the fluorescent energy of the fluorescent light emitted by each wavelength conversion device after passing through the opening of the aperture member. The fluorescent energy of the fluorescent light emitted by the wavelength conversion device according to the comparative example after passing through the opening was set to 100%.

The relative fluorescent energy value (before passing through the opening) is the relative value of the fluorescent energy of the fluorescent light emitted by each wavelength conversion device before passing through the opening of the aperture member. The fluorescent energy of the fluorescent light emitted by the wavelength conversion device according to the comparative example after passing through the opening was set to 100%.

The binding efficiency is the ratio of the relative fluorescence energy value (after passing through the aperture) to the relative fluorescence energy value (before passing through the aperture). In other words, the binding efficiency is the value obtained by dividing the relative fluorescence energy value (after passing through the aperture) by the relative fluorescence energy value (before passing through the aperture).

In a projector, the fluorescent light that has passed through the opening is used as part of the projection light. In other words, the larger the relative fluorescent light energy value (after passing through the opening), the more fluorescent light can be used as projection light for the projector.

As shown in FIG. 6, the coupling efficiencies of the wavelength conversion devices according to Examples 1, 2, 3 and the Comparative Example were 85%, 86%, 84% and 81%, respectively. That is, the coupling efficiencies in the Examples were all higher than the coupling efficiency in the Comparative Example. The higher the coupling efficiency, the more light of the generated fluorescence passed through the opening, that is, as shown in FIG. 5A and FIG. 5B, the smaller the emission area of the fluorescence emitted by the wavelength conversion device. That is, the emission area of the fluorescence emitted by the wavelength conversion device according to Examples 1 to 3 is smaller than the emission area of the fluorescence emitted by the wavelength conversion device according to the Comparative Example, indicating that the wavelength conversion device according to the Examples has a high light utilization efficiency.

Also, as shown in FIG. 6, it is clear that by having the thickness of the phosphor ceramic layer in Examples 1 to 3 in the range of 50 μm or more and 120 μm or less, a sufficiently high coupling efficiency is achieved compared to the comparative example. In other words, by having the thickness of the phosphor ceramic layer 20 in the above-described embodiment in the range of 50 μm or more and 120 μm or less, a wavelength conversion device 1 with high light utilization efficiency is realized.

The relative fluorescent energy values (after passing through the opening) of the wavelength conversion devices according to Examples 1, 2, 3, and the Comparative Example were 103%, 106%, 105%, and 100%, respectively. That is, in all of Examples 1 to 3, the relative fluorescent energy values (after passing through the opening) were higher than the relative fluorescent energy values (after passing through the opening) in the Comparative Example. And, in Examples 1 to 3, the relative fluorescent energy values (after passing through the opening) of the wavelength conversion devices according to Example 2, in which the phosphor ceramic layer was 76 μm thick, and Example 3, in which the phosphor ceramic layer was 106 μm thick, were higher.

Also, as shown in FIG. 6, it is clear that the thickness of the phosphor ceramic layer in Examples 2 and 3 in the range of 70 μm or more and 120 μm or less results in a sufficiently high relative value of the fluorescent energy (after passing through the opening) compared to the comparative example. In other words, by having the thickness of the phosphor ceramic layer 20 in the above-described embodiment in the range of 70 μm or more and 120 μm or less, a wavelength conversion device 1 with higher light utilization efficiency is realized.

Furthermore, the relative fluorescence energy values (before passing through the opening) of the wavelength conversion devices according to Examples 1, 2, 3, and the Comparative Example were 121%, 124%, 125%, and 124%, respectively. The relative fluorescence energy value (before passing through the opening) of the wavelength conversion device according to Example 1, in which the phosphor ceramic layer is the thinnest at 53 μm, was lower than the relative fluorescence energy values (before passing through the opening) of the wavelength conversion devices according to Examples 2 and 3, and the Comparative Example. This is thought to be because in the wavelength conversion device according to Example 1, the phosphor ceramic layer was too thin to sufficiently absorb the laser light.

Here, we further explain the manufacturing method and light utilization efficiency of the wavelength conversion device according to Example 4 of this embodiment.

First, we will describe a method for manufacturing the phosphor ceramic layer provided in the wavelength conversion device according to Example 4 of this embodiment.

All of the phosphor ceramic layers according to Example 4 are composed of a first crystal phase represented by ( _{Y0.997Ce0.003} ) _{3Al5O12 .} Also, all of the phosphor ceramic layers according to Example 4 are composed of _a Ce3 ⁺ _-activated phosphor.

In Example 4, a fired product was obtained in the same manner as in Examples 1 to 3, except that the raw materials were weighed to obtain a compound having a stoichiometric composition of (Y _0.997 Ce _0.003 ) ₃ Al ₅ O _12. In other words, the phosphor ceramic layer according to Examples 1 to 3 and the phosphor ceramic layer according to Example 4 mainly differ in the composition ratio of Y and Ce.

The thickness of the phosphor ceramic layer in Example 4 was 103 μm.

The outer and inner diameters of the phosphor ceramic layer in Example 4 were 41 mm and 27 mm. The phosphor ceramic layer in Example 4 was deep yellow in color.

Next, we will explain the evaluation of the phosphor ceramic layer.

First, the density of the phosphor ceramic layer according to Example 4 was evaluated using the Archimedes method. The density of the phosphor ceramic layer according to Example 4 was 4.48 g/ ^cm3 . The density of the phosphor ceramic layer according to Example 4 was 98.4% of the theoretical density (4.55 _g ^/ _{cm3 )} of _Y3Al5O12 . That is, the density of the phosphor ceramic layer according to Example 4 was 97% or more and 100% or less of the theoretical density _{of Y3Al5O12} .

As described above, the phosphor ceramic layer 20 according to the present embodiment is composed of YAG having Ce ³⁺ and Ce ⁴⁺ , that is, the phosphor ceramic layer 20 contains Ce ³⁺ and Ce ⁴⁺ . Then, the Ce ³⁺ abundance ratio and the Ce ^{4+ abundance ratio of the phosphor ceramic layer according to Example 4 were evaluated using a hard X-ray XAFS device. Specifically, the XAFS spectrum of the phosphor ceramic layer according to Example 4 is obtained in the range of 5687 eV to 5777 eV using a hard X-ray XAFS device. The Ce 3+ abundance} ratio and the Ce ⁴⁺ abundance ratio were evaluated by performing fitting analysis of the reference spectrum of Ce ³⁺ and the reference spectrum of Ce ⁴⁺ on the obtained XAFS spectrum. Note that, in order to obtain the reference spectrum of Ce ³⁺ and the reference spectrum of Ce ⁴⁺ , CeO ₂ and CeF ₃ were evaluated under the same conditions.

Table 1 shows the Ce3 ⁺ abundance ratio and Ce4 ⁺ abundance ratio of the phosphor ceramic layer according to Example 4. As shown in Table 1, the Ce3 ⁺ abundance ratio and Ce4 ⁺ abundance ratio of the phosphor ceramic layer according to Example 4 were 78.3% and 21.7%, respectively. The phosphor ceramic layer according to Example 4 satisfied Ce3 ⁺ × 100%/(Ce3 ⁺ +Ce4 ⁺ ) ≧ 60%, that is, the Ce3 ⁺ abundance ratio was 60% or more.

Next, we will describe a method for manufacturing a wavelength conversion device according to Example 4.

First, a disk-shaped substrate body (diameter 50 mm, thickness 0.5 mm) made of Al coated with Ag as a light-reflecting layer is prepared. A screw hole is drilled in the center of this substrate body. Next, a phosphor ceramic layer is placed on this substrate body.

A disk-shaped first plate member (outer diameter 26.5 mm, thickness 100 μm) made of Al with a screw hole in the center is placed inside the phosphor ceramic layer. The phosphor ceramic layer is a phosphor ring, and the first plate member is placed inside the ring. Then, a disk-shaped second plate member (outer diameter 29 mm, thickness 200 μm) made of Al with a screw hole in the center is placed so as to overlap the phosphor ceramic layer and the first plate member. Then, the substrate body, the first plate member, and the second plate member are screwed together. In this way, the phosphor ceramic layer is fixed, and a wavelength conversion device is obtained. That is, in the wavelength conversion device of Example 4, the phosphor ceramic layer is sandwiched and fixed between the substrate body and the second plate member.

In this way, the phosphor ceramic layer and wavelength conversion device of Example 4 were obtained.

Furthermore, we will explain the evaluation of wavelength conversion devices.

The wavelength conversion device of Example 4 was evaluated in the same manner as Examples 1 to 3.

Figure 7 shows the evaluation results of the wavelength conversion device according to Example 4 of this embodiment. Specifically, Figure 7 shows the relative fluorescent energy value (after passing through the opening), the relative fluorescent energy value (before passing through the opening), and the coupling efficiency of the wavelength conversion device according to Example 4. For comparison, Figure 7 also shows the relative fluorescent energy value (after passing through the opening), the relative fluorescent energy value (before passing through the opening), and the coupling efficiency of the wavelength conversion devices according to Examples 1 to 3 and the comparative example.

Here, the relative value of the fluorescent energy (after passing through the opening) is the relative value of the fluorescent energy of the fluorescent light emitted by the wavelength conversion device after passing through the opening of the aperture member. Note that the fluorescent energy of the fluorescent light emitted by the wavelength conversion device according to the comparative example after passing through the opening was set to 100%.

The relative value of the fluorescent energy (before passing through the opening) is the relative value of the fluorescent energy of the fluorescent light emitted by the wavelength conversion device before passing through the opening of the aperture member. The fluorescent energy of the fluorescent light emitted by the wavelength conversion device according to the comparative example after passing through the opening was set to 100%.

The binding efficiency is the ratio of the relative fluorescence energy value (after passing through the aperture) to the relative fluorescence energy value (before passing through the aperture). In other words, the binding efficiency is the value obtained by dividing the relative fluorescence energy value (after passing through the aperture) by the relative fluorescence energy value (before passing through the aperture).

As shown in FIG. 7, the coupling efficiency of the wavelength conversion device according to Example 4 was 85%. As described above, the coupling efficiency of the wavelength conversion device according to the comparative example was 81%. In the wavelength conversion device according to Example 4, which has a higher coupling efficiency, more of the generated fluorescent light passes through the opening, and the fluorescent light emission area is smaller. For example, as shown in FIG. 5A and FIG. 5B, in the wavelength conversion device according to Example 4, more light passes through the opening 2a of the aperture member 2, and therefore more light can be used as projection light for the projector 100. In other words, the wavelength conversion device according to Example 4 shows a high light utilization efficiency.

Furthermore, the relative fluorescent energy value (after passing through the opening) and the relative fluorescent energy value (before passing through the opening) of the wavelength conversion device according to Example 4 were 108% and 128%, respectively. These values are higher than the relative fluorescent energy value (after passing through the opening) and the relative fluorescent energy value (before passing through the opening) of the wavelength conversion devices according to Examples 1 to 3.

As described above, in the phosphor ceramic layer according to Example 4, the Ce ³⁺ abundance ratio is 60% or more, and the Ce ⁴⁺ abundance ratio is less than 40%, which is small. Therefore, the non-luminous relaxation loss due to Ce ⁴⁺ is reduced, and the phosphor ceramic layer according to Example 4, in which the Ce ³⁺ abundance ratio is 60% or more, has high luminous efficiency. Therefore, by including such a phosphor ceramic layer, the wavelength conversion device according to Example 4 can improve the light utilization efficiency. Furthermore, when a projector includes such a wavelength conversion device 1, the light utilization efficiency of the projector can be improved. For example, a low power consumption projector can be realized.

In addition, the non-luminescent relaxation loss due to Ce4 ⁺ is reduced, which reduces heat generation in the phosphor ceramic layer according to Example 4. Therefore, in a projector including such a phosphor ceramic layer, the maximum input energy of the excitation light L1 can be increased, which means that a high-output projector can be realized.

(Variation 1)
The phosphor ceramic layer 20 according to the embodiment is composed of only the first crystal phase, but is not limited to this. Here, a wavelength conversion device 1a including a phosphor ceramic layer 20a including the first crystal phase and the second crystal phase will be described.

[Configuration of Wavelength Conversion Device]
First, the configuration of a wavelength conversion device 1a according to this modification will be described with reference to the drawings. Fig. 8 is a perspective view of the wavelength conversion device 1a according to this modification. Fig. 9 is a cross-sectional view showing a cut surface of the wavelength conversion device 1a taken along line IX-IX in Fig. 8.

The wavelength conversion device 1a according to this modification has the same configuration as the wavelength conversion device 1 according to the embodiment, except that it has a phosphor ceramic layer 20a. That is, as shown in Figs. 8 and 9, the wavelength conversion device 1a has a substrate 10 having a light reflecting surface 13, a phosphor ceramic layer 20a, and an anti-reflection layer 30.

In this modified example, the wavelength conversion device 1a is a phosphor wheel used in a projector that receives excitation light L1 and emits reflected light that includes fluorescent light.

The phosphor ceramic layer 20a includes a first crystal phase and a second crystal phase. More specifically, in this modified example, the phosphor ceramic layer 20a is composed of a first crystal phase and a second crystal phase.

The first crystal phase has the configuration described in the embodiment.

The second crystal phase is a crystal phase having a structure different from the garnet structure. In other words, the second crystal phase has a structure different from the structure of the first crystal phase. Therefore, the refractive index of the first crystal phase and the refractive index of the second crystal phase are different from each other.

When the phosphor ceramic layer 20a is observed in cross section, the area showing the first crystal phase is, for example, 10% to 99% when the entire area of the image showing the phosphor ceramic layer 20a is taken as 100%. Note that the area showing the first crystal phase is not limited to this, and may be, for example, 75% to 98%, or 85% to 95%. In other words, the phosphor ceramic layer 20a according to this modified example mainly contains the first crystal phase.

As an example, the second crystal phase in this modified example is a crystal phase having a perovskite structure, but is not limited to this and may be a crystal phase having a structure different from the garnet structure and the perovskite structure.

The perovskite structure is a crystal structure represented by the general formula _EFO3 . The element E is a rare earth element such as Ca, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, and Lu, and the element F is an element such as Mg, Al, Si, Ga, and Sc. An example of such a garnet structure is YAP (Yttrium Aluminum Perovskite). In this modification, the second crystal phase is represented by (Y1 _{- yCey} ) _AlO3 (0≦y<0.1), that is, YAP.

The second crystal phase may be a solid solution of multiple perovskite crystal phases with different chemical compositions.

The second crystal phase may include a crystal phase having a different chemical composition from the crystal phase represented by the general formula _EFO3 .

The phosphor ceramic layer 20a in this modified example is composed only of the first and second crystal phases, that is, it does not contain any crystal phases having a structure different from the garnet structure and the perovskite structure.

In this modified example, the material representing the second crystal phase is, by way of example, YAP, but is not limited to this. It is preferable to select a material representing the second crystal phase such that the difference between the refractive index of the material representing the second crystal phase and the refractive index of the material representing the first crystal phase having a garnet structure (here, YAG) is 0.05 or more and 0.5 or less. As a result, as described above, the refractive index of the first crystal phase and the refractive index of the second crystal phase are different from each other. It is more preferable that the difference between the refractive index of the material representing the second crystal phase and the refractive index of the material representing the first crystal phase is 0.06 or more and 0.3 or less, and even more preferable that it is 0.07 or more and 0.15 or less.

Furthermore, for example, when the second crystal phase in this modified example is a _crystal phase having a structure different from a _garnet structure and a _perovskite structure, the material exhibiting _{the second} crystal _phase may be _Al2O3 , _Y2O3 , _Y4Al2O9 , _Lu2O3 , _Lu4Al2O9 , _etc.

The phosphor ceramic layer 20a receives light incident from above the wavelength conversion device 1a as excitation light L1 and emits fluorescence. More specifically, light emitted from an excitation light source described below is irradiated onto the phosphor ceramic layer 20a as excitation light L1, causing the phosphor ceramic layer 20a to emit fluorescence as wavelength-converted light. In other words, the wavelength-converted light emitted from the phosphor ceramic layer 20a is light with a longer wavelength than the wavelength of the excitation light L1.

In this modified example, the wavelength-converted light emitted from the phosphor ceramic layer 20a includes yellow-based fluorescence. The phosphor ceramic layer 20a, for example, absorbs light having a wavelength of 380 nm or more and 490 nm or less, and emits yellow-based fluorescence having a fluorescent peak wavelength in the wavelength range of 490 nm or more and 580 nm or less. By making the phosphor ceramic layer 20a out of YAG and YAP, it is easy to realize a phosphor ceramic layer 20a that emits fluorescence having a fluorescent peak wavelength in the wavelength range of 490 nm or more and 580 nm or less.

The x-coordinate of the chromaticity diagram of the wavelength-converted light emitted from the phosphor ceramic layer 20a should be 0.415 or less, preferably 0.410 or less, and even better 0.408 or less. When the x-coordinate of the chromaticity diagram of the wavelength-converted light emitted from the phosphor ceramic layer 20a is the above value, the temperature quenching of the phosphor ceramic layer 20a is small, and a phosphor ceramic layer 20a with high luminous efficiency can be realized.

The density of the phosphor ceramic layer 20a may be 95% or more and 100% or less of the theoretical density, and more preferably 97% or more and 100% or less of the theoretical density. Here, the theoretical density is the density when the atoms in the layer are ideally arranged. In other words, the theoretical density is the density when it is assumed that there are no voids in the phosphor ceramic layer 20a, and is a value calculated using the crystal structure. For example, when the density of the phosphor ceramic layer 20a is 99%, the remaining 1% corresponds to voids. In other words, the higher the density of the phosphor ceramic layer 20a, the fewer the voids. When the density of the phosphor ceramic layer 20a is in the above range, the total amount of fluorescence emitted by the phosphor ceramic layer 20a increases, so that a wavelength conversion device 1a and a projector that emit a larger amount of light can be provided. The theoretical density is the theoretical density of the first crystal phase having a garnet structure.

The density of the phosphor ceramic layer 20a may be 4.32 g/cm ³ or more and 4.55 g/cm ³ or less, and more preferably 4.41 g/cm ³ or more and 4.55 g/cm ³ or less. As shown in this modification, when the phosphor ceramic layer 20a is made of YAG and YAP, if the density of the phosphor ceramic layer 20a is in the above range, the density of the phosphor ceramic layer 20a is 95% or more and 100% or less and 97% or more and 100% or less, respectively. When the density of the phosphor ceramic layer 20a is in the above range, the excitation light L1 absorbed by the phosphor ceramic layer 20a can be efficiently converted into fluorescence. In other words, a phosphor ceramic layer 20a with high luminous efficiency is realized.

The thickness of the phosphor ceramic layer 20a (length in the z-axis direction) is preferably 50 μm or more and less than 150 μm, and more preferably 50 μm or more and less than 120 μm. The thickness of the phosphor ceramic layer is more preferably 70 μm or more and less than 120 μm, and even more preferably 80 μm or more and less than 110 μm.

[Projector configuration]
The wavelength conversion device 1a configured as above is used in a projector, similarly to the wavelength conversion device 1 according to the embodiment. That is, the wavelength conversion device 1a according to this modification may be used instead of the wavelength conversion device 1 according to the embodiment.

[Example]
Here, a description will be given of a manufacturing method and light utilization efficiency in the wavelength conversion devices according to Examples 5 and 6. The wavelength conversion device according to Example 5 has the same configuration as the wavelength conversion device 1a according to this modification, and the wavelength conversion device according to Example 6 has the same configuration as the wavelength conversion device 1 according to the embodiment.

First, we will describe the manufacturing method of the phosphor ceramic layer provided in the wavelength conversion device of Examples 5 and 6.

_The phosphor ceramic layer according to Example 5 is mainly composed of a crystal phase (i.e., a first crystal phase) represented _by ( _{Y0.997Ce0.003} ) _{3Al5O12 .} As described above, the phosphor ceramic layer according to Example 5 also contains a second crystal phase. The phosphor ceramic layer according to Example 6 is composed of a crystal phase (i.e., a first crystal phase) represented by ( _{Y0.997Ce0.003} ) _{3Al5O12 .} The phosphor ceramic layers according to Examples ₅ and ₆ are both composed of a Ce3 ⁺ -activated phosphor.

The phosphor ceramic layers in Examples 5 and 6 were made using the same raw materials as those used in Examples 1 to 3.

First, the raw materials were weighed out so as to obtain a compound having a stoichiometric composition: (Y _0.997 Ce _0.003 ) ₃ Al ₅ O _12. Next, the raw materials were mixed in the same manner as in Examples 1 to 3 to obtain a mixed raw material in a slurry state.

Next, in Example 5, a granulated mixed raw material was obtained by a method that did not utilize a spray dryer. Specifically, 100 g of the mixed raw material dried using a dryer was put into an alumina mortar. Then, a solution in which polyvinyl alcohol was dissolved in water at a ratio of 0.5 wt % was made into a polyvinyl alcohol solution, and 18 mL of this polyvinyl alcohol solution was further put into the alumina mortar. Then, the mixed raw material and the polyvinyl alcohol solution were mixed using a pestle. Next, the mixture of the mixed raw material and the polyvinyl alcohol solution was sieved using a mesh with an opening of 512 μm. As a result, a mixture of the mixed raw material and the polyvinyl alcohol solution with a particle size of about 512 μm or less was obtained. Then, the mixture was treated for 30 minutes in a dryer set at 105 ° C., and the moisture was removed. In this way, the granulated mixed raw material used in Example 5 was obtained. Also, in Example 6, the mixed raw material was granulated in the same procedure as Examples 1 to 3, and a granulated mixed raw material was obtained.

The phosphor ceramic layers of Examples 5 and 6 were preformed in the same manner. Specifically, the granulated mixed raw material was preformed into a cylindrical shape using an electric hydraulic press (EMP-5, manufactured by Riken Seiki Co., Ltd.) and a cylindrical mold (outer diameter 66 mm, inner diameter 46 mm, height 130 mm). The pressure during molding was 5 MPa. Next, the molded body after the preform was molded into a final shape using a cold isostatic pressing device. The pressure during final molding was 300 MPa. The molded body after final molding was subjected to a heat treatment (binder removal treatment) in order to remove the adhesive (binder) used during granulation. The temperature of the heat treatment was 500°C. The heat treatment time was 10 hours.

The molded body after the heat treatment was sintered using a tubular atmosphere furnace. The sintering temperature was 1675°C. The sintering time was 4 hours. The sintering atmosphere was a mixed gas atmosphere of nitrogen and hydrogen. The outer diameter and inner diameter of the sintered product after sintering were 49 mm and 35 mm, respectively.

After firing, the cylindrical fired product was sliced using a multi-wire saw. The thickness of the sliced cylindrical fired product was approximately 700 μm.

In Examples 5 and 6, the fired product was heat-treated at a temperature of 1000°C or higher.

The sliced fired product was polished using a polishing device to adjust the thickness of the fired product. The thickness of the phosphor ceramic layer was 118 μm in Example 5 and 117 μm in Example 6.

The outer and inner diameters of the phosphor ceramic layers in Examples 5 and 6 were 49 mm and 35 mm, respectively. The phosphor ceramic layers in Examples 5 and 6 were deep yellow in color.

Next, we will explain the evaluation of the phosphor ceramic layer.

First, the density of the phosphor ceramic layer according to Examples 5 and 6 was evaluated using the Archimedes method. The densities of the phosphor ceramic layer according to Examples 5 and 6 were 4.48 g/ ^cm3 and 4.42 g/ ^cm3 , respectively. The densities of the phosphor ceramic layer according to Examples 5 and 6 were 98.4% and 97.1% of the theoretical density (4.55 g/ _cm3 ) _{of Y3Al5O12} , respectively. That is, the densities of the phosphor ceramic layer according to Examples 5 and 6 were 97% or more and ₁₀₀ % or _less of the theoretical density of _Y3Al5O12 .

Next, a scanning electron microscope (SEM) was used to evaluate the cross-sectional SEM image of the phosphor ceramic layer of Example 5.

Figure 10 is an SEM image showing a cross section of the phosphor ceramic layer according to Example 5 of this modified example. (a) of Figure 10 is an SEM image showing a wide cross section of the phosphor ceramic layer according to Example 5. The SEM image shown in (a) of Figure 10 corresponds to an image of the area surrounded by the dashed rectangle in the cross section shown in Figure 9. (b) of Figure 10 is an SEM image of an enlarged area surrounded by the dashed rectangle in (a) of Figure 10. (c) of Figure 10 is an SEM image of an enlarged area surrounded by the dashed rectangle in (a) of Figure 10.

Here, the phosphor ceramic layer in Example 5, that is, the phosphor ceramic layer 20a in this modified example, includes a single-phase portion and a mixed-phase portion that is separated from the single-phase portion. Figure 10(b) shows the single-phase portion, and Figure 10(c) shows the mixed-phase portion.

In this modified example, the darker areas in the SEM image in FIG. 10 correspond to the first crystal phase having a garnet structure, and the lighter areas correspond to the second crystal phase having a perovskite structure. Also, in the SEM image in FIG. 10, the darkest areas correspond to voids.

The single-phase portion contains only the first crystal phase of the first crystal phase having a garnet structure and the second crystal phase having a structure different from the garnet structure (here, a perovskite structure). More specifically, here, the single-phase portion contains only the first crystal phase, and does not contain any other crystal phases having a structure different from the garnet structure and the perovskite structure.

In addition, the mixed phase portion is provided with a mixture of both the first crystal phase and the second crystal phase. More specifically, the mixed phase portion is provided with a mixture of only the first crystal phase and the second crystal phase. Note that the mixed phase portion may be provided with a mixture of both the first crystal phase and the second crystal phase, as well as other crystal phases having structures different from the garnet structure and the perovskite structure.

In the mixed phase portion of Example 5, both the first crystal phase and the second crystal phase are mixed in a randomly intertwined structure, but this is not limited thereto, and both the first crystal phase and the second crystal phase may be mixed in a periodically arranged structure.

The phosphor ceramic layer in Example 5 includes multiple mixed phase parts. The regions surrounded by dotted lines in Figure 10(a) each correspond to a mixed phase part.

Each of the multiple mixed phase sections is surrounded by a single phase section. The shape of the single phase section and the multiple mixed phase sections can also be said to be an island-in-the-sea shape. In this case, the single phase section corresponds to the sea, and the multiple mixed phase sections correspond to the islands.

In addition, it is preferable that the mixed phase portion contains more of the second crystal phase than the first crystal phase. For example, the ratio of the first crystal phase to the second crystal phase in the mixed phase portion is as follows. When the phosphor ceramic layer according to Example 5 is cross-sectionally observed (for example, FIG. 10), the area showing the second crystal phase is, for example, 10% to 99% when the entire area of the image showing the mixed phase portion is 100%. Note that the area showing the second crystal phase is not limited to this, and may be, for example, 70% to 95% or 80% to 90%. In other words, the mixed phase portion according to this modified example mainly contains the second crystal phase.

In this way, the mixed phase portion is provided with a mixture of both a first crystal phase having a garnet structure and a second crystal phase having a perovskite structure. As described above, the refractive index of the first crystal phase and the refractive index of the second crystal phase are different from each other. Therefore, the refractive index of the single phase portion in which only the first crystal phase is provided is different from the refractive index of the mixed phase portion. In this modified example, the refractive index of YAG is 1.83 and the refractive index of YAP is 1.91, so the refractive index of the single phase portion is lower than the refractive index of the mixed phase portion.

Furthermore, the size of the mixed phase portion will be described. The size of the mixed phase portion refers to the length of the mixed phase portion in the longitudinal direction in the SEM image shown in Figure 10. The size of the mixed phase portion is, for example, the length indicated by the double-headed arrow in Figure 10. The size of the mixed phase portion is preferably 0.5 μm or more and less than 500 μm, more preferably 1 μm or more and less than 300 μm, and even more preferably 2 μm or more and less than 100 μm.

As described above, the phosphor ceramic layer (phosphor ceramic layer 20a) according to Example 5 contains the first crystal phase and the second crystal phase, and FIG. 10 shows that a single phase portion and a mixed phase portion are provided. On the other hand, the phosphor ceramic layer according to Example 6 is composed only of the first crystal phase. Therefore, it has been confirmed that the phosphor ceramic layer according to Example 6 does not have a mixed phase portion.

Next, we will describe the manufacturing method of the wavelength conversion device according to Examples 5 and 6.

First, a disk-shaped substrate body (diameter 50 mm, thickness 0.5 mm) made of Al coated with Ag as a light-reflecting layer is prepared. A screw hole is drilled in the center of this substrate body. Next, a phosphor ceramic layer is placed on this substrate body.

A disk-shaped third plate member (outer diameter 34.5 mm, thickness 100 μm) made of Al with a screw hole in the center is placed inside the phosphor ceramic layer. The phosphor ceramic layer is a phosphor ring, and the third plate member is placed inside the ring. Then, a disk-shaped fourth plate member (outer diameter 39 mm, thickness 200 μm) made of Al with a screw hole in the center is placed so as to overlap the phosphor ceramic layer and the third plate member. Then, the substrate body, the third plate member, and the fourth plate member are screwed together. In this way, the phosphor ceramic layer is fixed, and a wavelength conversion device is obtained. That is, in the wavelength conversion devices according to Examples 5 and 6, the phosphor ceramic layer is sandwiched and fixed between the substrate body and the fourth plate member.

Furthermore, we will explain the evaluation of wavelength conversion devices.

The wavelength conversion devices of Examples 5 and 6 were evaluated in the same manner as Examples 1 to 3.

Figure 11 shows the evaluation results of the wavelength conversion devices according to Examples 5 and 6 of this modified example. Specifically, Figure 11 shows the relative fluorescence energy value (after passing through the aperture), the relative fluorescence energy value (before passing through the aperture), and the coupling efficiency of the wavelength conversion devices according to Examples 5 and 6.

Here, the relative value of the fluorescent energy (after passing through the opening) is the relative value of the fluorescent energy of the fluorescent light emitted by each wavelength conversion device after passing through the opening of the aperture member. The fluorescent energy of the fluorescent light emitted by the wavelength conversion device according to Example 6 after passing through the opening was set to 100%.

The relative value of the fluorescent energy (before passing through the opening) is the relative value of the fluorescent energy of the fluorescent light emitted by each wavelength conversion device before passing through the opening of the aperture member. The fluorescent energy of the fluorescent light emitted by the wavelength conversion device according to Example 6 after passing through the opening was set to 100%.

The binding efficiency is the ratio of the relative fluorescence energy value (after passing through the aperture) to the relative fluorescence energy value (before passing through the aperture). In other words, the binding efficiency is the value obtained by dividing the relative fluorescence energy value (after passing through the aperture) by the relative fluorescence energy value (before passing through the aperture).

As shown in FIG. 11, the relative fluorescence energy values (after passing through the aperture) of the wavelength conversion devices according to Examples 5 and 6 were 101% and 100%, respectively. Furthermore, the relative fluorescence energy values (before passing through the aperture) of the wavelength conversion devices according to Examples 5 and 6 were 117% and 122%, respectively.

The coupling efficiency of the wavelength conversion device according to Example 5, which corresponds to the wavelength conversion device 1a according to this modified example, was 87%. The coupling efficiency of the wavelength conversion device according to Example 6, which corresponds to the wavelength conversion device 1 according to the embodiment, was 82%.

As described above, the phosphor ceramic layer (phosphor ceramic layer 20a) provided in the wavelength conversion device of Example 5 is composed of a first crystal phase and a second crystal phase that have different refractive indices.

This creates regions with different refractive indices in the phosphor ceramic layer 20a, making it easier for the excitation light L1 and the fluorescence to be scattered. As a result, light is suppressed from being guided in the planar direction of the layer shown in Figures 5A and 5B of the embodiment (i.e., the x-axis direction or the y-axis direction), and the light-emitting area of the phosphor ceramic layer 20a becomes smaller. Therefore, the coupling efficiency of the wavelength conversion device according to Example 5 is higher than that of the wavelength conversion device according to Example 6. In other words, a wavelength conversion device (wavelength conversion device 1a) according to Example 5 with a smaller etendue and higher light utilization efficiency is realized. When a projector is equipped with such a wavelength conversion device 1a, the light utilization efficiency of the projector can be further improved.

The phosphor ceramic layer 20a also includes a single phase portion and a mixed phase portion that is separate from the single phase portion. The single phase portion contains only the first crystal phase of the first and second crystal phases, while the mixed phase portion contains a mixture of both the first and second crystal phases. The refractive index of the single phase portion and the refractive index of the mixed phase portion are different from each other.

This creates areas of different refractive index in the phosphor ceramic layer 20a, making it easier for the excitation light L1 and the fluorescent light to be scattered. As a result, the light-emitting area of the phosphor ceramic layer 20a becomes even smaller. This results in a wavelength conversion device 1a with even smaller etendue and even higher light utilization efficiency.

In addition, when the size of the mixed phase portion is within the above range, the excitation light L1 and the fluorescent light are more likely to be scattered.

Furthermore, the phosphor ceramic layer 20a includes multiple mixed phase portions. Each of the multiple mixed phase portions is surrounded by a single phase portion.

This makes it easier for the excitation light L1 and the fluorescent light to be scattered. As a result, the light-emitting area of the phosphor ceramic layer 20a becomes even smaller. This results in a wavelength conversion device 1a with even smaller etendue and even higher light utilization efficiency.

The above results suggest that the coupling efficiency of the wavelength conversion device 1a is improved not only by the light guide suppression effect due to the thin thickness of the phosphor ceramic layer 20a, but also by the light guide suppression effect of the phosphor ceramic layer 20a itself. In other words, this suggests that the coupling efficiency of the wavelength conversion device 1a can be improved without controlling the thickness of the phosphor ceramic layer 20a.

In addition, the difference between the refractive index of the material representing the second crystal phase and the refractive index of the material representing the first crystal phase is 0.05 or more and 0.5 or less.

This makes it easier for the excitation light L1 and the fluorescent light to be scattered. As a result, the light-emitting area of the phosphor ceramic layer 20a becomes even smaller. This results in a wavelength conversion device 1a with even smaller etendue and even higher light utilization efficiency.

The second crystal phase is a crystal phase expressed by (Y _1-y Ce _y )AlO ₃ (0≦y<0.1).

This makes it easier to bring the difference between the refractive index of the material representing the second crystal phase and the refractive index of the material representing the first crystal phase within the above range.

(Variation 2)
Further, the phosphor ceramic layer 20b, which has a different structure from the phosphor ceramic layers 20 and 20a, will be described.

Figure 12 is a perspective view of the phosphor ceramic member of this modified example.

The phosphor ceramic member in this modified example is, as an example, a phosphor ceramic layer 20b having a layered shape.

The phosphor ceramic layer 20b is a component used in projectors, similar to the phosphor ceramic layers 20 and 20a shown in the embodiment and variant 1.

The phosphor ceramic layer 20b has the same configuration as the phosphor ceramic layer 20a according to Modification 1, except for the following one point: the abundance ratio of Ce ³⁺ is 60% or more.

That is, the phosphor ceramic layer 20b includes a first crystal phase having a garnet structure and a second crystal phase having a structure other than the garnet structure. The first crystal phase and the second crystal phase have different refractive indices. In this modified example, the first crystal phase and the second crystal phase are crystal phases represented by YAG and YAP, respectively, and the phosphor ceramic layer 20b also mainly includes the first crystal phase. The density of the phosphor ceramic member (phosphor ceramic layer 20b) may be 95% or more and 100% or less of the theoretical density, and it is better if it is 97% or more and 100% or less of the theoretical density. The film thickness of the phosphor ceramic member (phosphor ceramic layer 20b) does not need to be particularly limited, but if it is limited, it is better if it is 50 μm or more and less than 500 μm, and more preferably 50 μm or more and less than 300 μm. It is even better if the film thickness is 50 μm or more and less than 120 μm.

The phosphor ceramic member (phosphor ceramic layer 20b) has the above configuration. Therefore, when the phosphor ceramic layer 20b is used in a projector and is irradiated with excitation light, an area with a different refractive index is generated in the phosphor ceramic layer 20b, so that the excitation light and fluorescence are more scattered. As a result, the light guide in the planar direction of the layer shown in Figures 5A and 5B of the embodiment (i.e., the x-axis direction or the y-axis direction) is suppressed, and the light-emitting area of the phosphor ceramic layer 20b becomes smaller. Therefore, the phosphor ceramic member has a smaller etendue and a higher light utilization efficiency. When a projector has such a phosphor ceramic member (phosphor ceramic layer 20b), the light utilization efficiency of the projector can be further improved.

Furthermore, the phosphor ceramic layer 20b is composed of YAG and YAP having Ce3 ⁺ and Ce4 ⁺ , that is, the phosphor ceramic layer 20b contains Ce3 ⁺ and Ce4 ⁺ . Here, the phosphor ceramic layer 20b satisfies Ce3 ⁺ ×100%/( ^Ce3 ++Ce4 ⁺ )≧60%, that is, the abundance ratio of Ce3 ⁺ is 60% or more.

The phosphor ceramic layer 20b having a Ce3 ⁺ abundance ratio of 60% or more has a high luminous efficiency because the non-luminous relaxation loss due to Ce4 ⁺ is reduced. Furthermore, in a projector including such a phosphor ceramic layer 20b, the light utilization efficiency can be improved. For example, a projector with low power consumption can be realized.

In addition, the non-luminescent relaxation loss due to Ce ⁴⁺ is reduced, and thus the heat generation in the phosphor ceramic layer 20b is reduced. Therefore, in a projector including such a phosphor ceramic layer 20b, the maximum input energy of the excitation light can be increased, which means that a high-output projector can be realized.

Other Embodiments
Although the wavelength conversion device and the like according to the present invention have been described above based on the embodiments and modifications, the present invention is not limited to these embodiments and modifications. As long as they do not deviate from the gist of the present invention, various modifications conceived by a person skilled in the art to the embodiments and modifications, and other forms constructed by combining some of the components in the embodiments and modifications are also included in the scope of the present invention.

In the embodiment, the light source is a semiconductor laser light source, but the light source is not limited to this and may be an LED light source.

Furthermore, the above embodiment may be modified, substituted, added, omitted, etc. in various ways within the scope of the claims or their equivalents.

Reference Signs List 1 Wavelength conversion device 10 Substrate 11 Substrate body 12 Light reflecting layer 13 Light reflecting surface 20 Phosphor ceramic layer 30 Anti-reflection layer 100 Projector 121 Light scattering particles L1 Excitation light L2 Reflected light

Claims (13)

A wavelength conversion device for use in a projector, which receives excitation light and emits reflected light including fluorescent light,
A substrate having a substrate body and a light reflecting layer located above the substrate body and including a light reflecting surface;
a phosphor ceramic layer located above the light reflecting surface and including a first crystal phase having a garnet structure;
a bonding layer made of a transparent material and provided between the light reflecting layer and the phosphor ceramic layer;
The visible light reflectance of the light reflecting surface is 95% or more and 100% or less,
The density of the phosphor ceramic layer is 97% or more and 100% or less of the theoretical density,
The thickness of the phosphor ceramic layer is 50 μm or more and less than 120 μm,
When viewed from above, the light reflecting layer is provided so as to extend outside the outline of the phosphor ceramic layer ,
The phosphor ceramic layer further includes a second crystal phase having a structure different from a garnet structure,
The second crystalline phase has a randomly interwoven structure.
Wavelength conversion device. The wavelength conversion device according to claim 1 , wherein the phosphor ceramic layer has a thickness of 70 μm or more and less than 120 μm. The wavelength conversion device according to claim 1 , further comprising an anti-reflection layer located above the phosphor ceramic layer and preventing reflection of the excitation light. The wavelength conversion device of claim 1 , wherein the light reflecting layer comprises light scattering particles. The wavelength conversion device according to claim 1 , wherein the light reflecting layer comprises Ag. 6. The wavelength conversion device according to claim 1, wherein the phosphor ceramic layer is composed _of the first crystal phase represented by (Y1 _{-xCe x} ) _3Al5O12 ( _0.001 ≦x<0.1). 7. The wavelength conversion device according to claim 1, wherein the phosphor ceramic layer has a density of 4.41 g/cm ³ or more and 4.55 g/cm ³ or less. The phosphor ceramic layer includes a single phase portion and a mixed phase portion distinct from the single phase portion,
The single-phase portion is provided with only the first crystal phase of the first crystal phase and the second crystal phase,
The wavelength conversion device according to claim 1 , wherein the mixed phase portion is provided with a mixture of both the first crystal phase and the second crystal phase. the phosphor ceramic layer includes a plurality of the mixed phase portions,
The wavelength conversion device according to claim 8 , wherein each of the plurality of mixed phase portions is surrounded by the single phase portion. The wavelength conversion device according to claim 8 , wherein a difference between a refractive index of the material exhibiting the second crystal phase and a refractive index of the material exhibiting the first crystal phase is 0.05 or more and 0.5 or less. 11. The wavelength conversion device according to claim 8 , wherein the second crystal phase is a crystal phase expressed by (Y _1-y Ce _y )AlO ₃ (0≦y<0.1). The phosphor ceramic layer contains Ce3 ⁺ and Ce4 ⁺ ,
The wavelength conversion device according to claim 1 , which satisfies Ce ³⁺ × 100%/(Ce ³⁺ +Ce ⁴⁺ ) ≧ 60%. an excitation light source that emits excitation light;
A projector comprising: the wavelength conversion device according to any one of claims 1 to 12 , which receives the excitation light emitted from the excitation light source and emits reflected light including fluorescent light.

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