TW202201108A - Wavelength conversion element, projector, and phosphor ceramic member including a substrate, and a phosphor ceramic layer located above a light reflecting surface and containing the first crystal phase with garnet structure - Google Patents

Abstract

The present invention provides a wavelength conversion element having a high light utilization efficiency, a projector, and a phosphor ceramic member. The wavelength conversion element 1 is used in the projector 100 to receive excitation light L1 and emits reflected light L2 including fluorescent light, and includes: a substrate 10 having a light reflecting surface 13; and a phosphor ceramic layer 20 located above a light reflecting surface 13 and containing a first crystal phase with garnet structure. The visible light reflectance of the light reflecting surface 13 is 95% or more and 100% or less. The density of the phosphor ceramic layer 20 is 97% or more and 100% or less of the theoretical density. The film thickness of the phosphor ceramic layer 20 is 50 [mu]m or more and less than 120 [mu]m.

Description

Wavelength conversion element, projector and phosphor ceramic member

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

In the past, a wavelength conversion element for use in projectors has been known.

For example, the wavelength conversion element disclosed in Patent Document 1 includes a substrate that is circular in plan view, and a phosphor layer (phosphor ceramic member) provided along the circumferential direction of the substrate, and can be connected to the center of the substrate by a motor. while rotating. In Patent Document 1, the wavelength conversion element functions as a reflection-type fluorescent wheel of a projector, and the fluorescent light emitted by the phosphor layer of the wavelength conversion element is used as light (projection light) emitted by the projector. [Previously known technical literature] [Patent Literature]

Patent Document 1: Japanese Patent Laid-Open No. 2019-66880

[Problems to be Solved by the Invention]

However, the above-mentioned conventional wavelength conversion elements, projectors and phosphor ceramic components have problems such as low utilization efficiency of light. Therefore, the present invention provides a wavelength conversion element, a projector, and a phosphor ceramic member with high light utilization efficiency. [Technical means to solve problems]

A wavelength conversion element of one aspect of the present invention is used in a projector, receives excitation light, and emits reflected light including fluorescent light, comprising: a substrate having a light reflecting surface; and a phosphor ceramic layer on the light reflecting surface The top of the phosphor ceramic layer contains the first crystal phase with 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 of the theoretical density and less than 100%; the The film thickness of the phosphor ceramic layer is 50 μm or more and less than 120 μm.

Furthermore, a projector according to an aspect of the present invention includes: an excitation light source that emits excitation light; and the wavelength conversion element that receives the excitation light and emits reflected light including fluorescent light.

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

According to the present invention, a wavelength conversion element, a projector and a phosphor ceramic member with high light utilization efficiency can be provided.

Hereinafter, the wavelength conversion element and the like according to the embodiments of the present invention will be described in detail with reference to the drawings.

In addition, the implementation forms described below are all comprehensive or specific cases. The numerical values, shapes, materials, components, arrangement positions and connection forms of components, processes, and order of processes shown in the following embodiments are all examples, and are not intended to limit the present invention. In addition, among the components concerning the following embodiment, the components which are not described in the independent claim are demonstrated as arbitrary components.

In addition, each figure is a schematic diagram, and is not strictly a diagram. Therefore, for example, the scale or the like does not necessarily have to be the same among the figures. In addition, in each figure, the same code|symbol is attached|subjected to the substantially same structure, and the overlapping description is abbreviate|omitted or simplified.

In this specification, terms indicating the relationship between elements, such as parallel or orthogonal, and terms indicating the shape of elements such as circle or ellipse, and numerical ranges are not only expressions in a strict sense, but also mean Substantially equivalent ranges are included, for example, representations of differences of the order of a few percent.

In addition, in this specification, "planar view" means the case where a wavelength conversion element is seen along the perpendicular direction of the light reflection surface which a board|substrate has.

In addition, in this specification, the terms "upper" and "lower" in the structure of the wavelength conversion element do not refer to the upper (vertical upper) and lower (vertical lower) of the absolute spatial perception, but refer to the stacked layers in the stacked structure. A term specified by relative positional relationship on the basis of order. In addition, the terms "above" and "below" are not only applicable to the case where two components are arranged with a gap between each other and another component exists between the two components, but also when the two components are arranged in close contact with each other. When two components are brought into contact.

In addition, in this specification and the drawings, the x-axis, the y-axis, and the z-axis represent 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 orthogonal to the light reflecting surface is the z-axis direction. In addition, in each embodiment described below, the positive z-axis direction is described as upward, and the negative z-axis direction is described as downward.

(implementation form) [Configuration of wavelength conversion element] First, the configuration of the wavelength conversion element 1 of the present embodiment will be described with reference to the drawings. FIG. 1 is a perspective view of the wavelength conversion element 1 of the present embodiment. FIG. 2 is a cross-sectional view showing a cross-section of the wavelength conversion element 1 along the line II-II of FIG. 1 .

As shown in FIGS. 1 and 2 , the wavelength conversion element 1 includes a substrate 10 having a light reflecting surface 13 , a phosphor ceramic layer 20 , and an antireflection layer 30 .

In the present embodiment, the wavelength conversion element 1 is used in a projector, and is a fluorescent wheel that receives excitation light L1 and emits reflected light including fluorescent light. The wavelength conversion element 1 has a disk shape, and a motor 4 that is rotationally driven is provided at the center of the wavelength conversion element 1 in plan view. Therefore, the wavelength conversion element 1 is rotationally driven by the motor 4 in the direction of the arrow shown in FIG. 1 using the motor 4 as a shaft.

In addition, although FIG. 1 shows the structure of the fluorescent wheel provided with the motor 4, the wavelength conversion element 1 may not have the motor 4. That is, the wavelength conversion element 1 may be a fixed element without being driven to rotate. With such a configuration, the wavelength conversion element 1 can be reduced in size, so that a compact projector can be provided.

The phosphor ceramic layer 20 is a layer located above the light reflecting surface 13 of the substrate 10 . In this embodiment, the wavelength conversion element 1 is a fluorescent wheel, so the fluorescent ceramic layer 20 is a fluorescent ring. The phosphor ceramic layer 20 is provided annularly on the circumference at an equal distance from the rotation center portion of the wavelength conversion element 1 (ie, where the motor 4 is provided). That is, the phosphor ceramic layer 20 is provided in a band shape along the circumferential direction in plan view.

The phosphor ceramic layer 20 includes a first crystal phase having a garnet structure. More specifically, in the present embodiment, the phosphor ceramic layer 20 is composed of only the first crystal phase having a garnet structure. That is, the phosphor ceramic layer 20 of the present embodiment does not contain a crystal phase having a structure different from the garnet structure. The garnet structure is a crystal structure represented by the general formula of A ₃ B ₂ C ₃ O ₁₂ . For element A, use rare earth elements such as Ca, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, and Lu; for element B, use elements such as Mg, Al, Si, Ga, and Sc; C, the application of elements such as Al, Si and Ga. Examples of such garnet structures include YAG (Yttrium Aluminum Garnet), LuAG (Lutetium Aluminum Garnet), Lu ₂ CaMg ₂ Si ₃ O ₁₂ (Lutetium Aluminum Garnet) (Lutetium Calcium Magnesium Silicon Garnet) and TAG (Terbium Aluminum Garnet), etc. In this embodiment, the phosphor ceramic layer 20 is made of (Y _{1 - x} Ce _x ) ₃ Al ₂ Al ₃ O ₁₂ (that is, (Y _{1 - x} Ce _x ) ₃ Al ₅ O ₁₂ ) (0.001≦x <0.1), the first crystal phase is composed of YAG.

In addition, 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. Examples of such solid solutions include a garnet crystal phase represented by (Y _{1 - x} Ce _x ) ₃ Al ₂ Al ₃ O ₁₂ (0.001≦x<0.1) and a garnet crystal phase represented by (Lu _{1 - d} Ce _d ) ₃ Al ₂ Solid solution of garnet crystal phase represented by Al ₃ O ₁₂ (0.001≦d<0.1) ((1-a)(Y _{1 - x} Ce _x ) ₃ Al ₅ O ₁₂ ·a (Lu _{1 - d} Ce _d ) ₃ Al ₂ Al ₃ O ₁₂ (0<a<1)). In addition, as these solid solutions, a garnet crystal phase represented by (Y _{1 - x} Ce _x ) ₃ Al ₂ Al ₃ O ₁₂ (0.001≦x<0.1) and a garnet crystal phase represented by (Lu _{1 - z} Ce _z ) can be mentioned. ₂ Solid solution of garnet crystal phase represented by CaMg ₂ Si ₃ O ₁₂ (0.0015≦z<0.15) ((1-b)(Y _{1 - x} C _x ) ₃ Al ₂ Al ₃ O ₁₂ ·b (Lu _{1 - z} Ce _z ) ₂ CaMg ₂ Si ₃ O ₁₂ (0<b<1)) and the like. By forming the phosphor ceramic layer 20 with a solid solution of a plurality of garnet crystal phases with different chemical compositions, the fluorescence spectrum of the fluorescence emitted by the phosphor ceramic layer 20 is broadened and the green color is increased. light component and red light component. Therefore, a projector that emits projected light with a wide color gamut can be provided.

In addition, the first crystal phase constituting the phosphor ceramic layer 20 may include a crystal phase whose chemical composition is shifted from the crystal phase represented by the general formula A ₃ B ₂ C ₃ O ₁₂ described above. Examples of such crystal phases include (Y _{1 -x Ce x ) 3 that is rich in Al with respect to the crystal phase represented by (Y 1 -x Ce x ) 3 Al 2 Al 3} O ₁₂ (0.001≦x<0.1 _{) .} Al _{2 + δ} Al ₃ O ₁₂ (δ is a positive number). In addition, as these crystal phases, (Y _{1 -x Ce x ) rich in Y relative to the crystal phase represented by (Y 1 -x Ce x ) 3 Al 2} Al ₃ O ₁₂ (0.001≦ _x <0.1) can be mentioned _. ) _{3 + ζ} Al ₂ Al ₃ O ₁₂ (ζ is a positive number), etc. These crystal phases maintain a garnet structure even though the chemical composition is shifted relative to the crystal phase represented by the general formula A ₃ B ₂ C ₃ O ₁₂ . By making the phosphor ceramic layer 20 composed of crystal phases whose chemical composition is shifted, regions with different refractive indices are generated in the phosphor ceramic layer 20, so the excitation light L1 and the fluorescence are more dispersed, and the phosphor ceramic The light emitting area of the layer 20 becomes smaller. Therefore, the wavelength conversion element 1 and the projector with smaller etendue and higher light utilization efficiency can be provided.

Furthermore, the phosphor ceramic layer 20 may include the first crystal phase and a different phase having a structure other than the garnet structure. By forming the phosphor ceramic layer 20 with the first crystal phase and the different phases, regions with different refractive indices are generated in the phosphor ceramic layer 20, so that the excitation light L1 and the fluorescent light are more dispersed, and the phosphor ceramic layer 20 is formed. The light emitting area of the ceramic layer 20 becomes smaller. Therefore, the wavelength conversion element 1 and the projector with smaller etendue and higher light utilization efficiency can be provided.

The phosphor ceramic layer 20 made of YAG receives light incident from above the wavelength conversion element 1 as excitation light L1 and emits fluorescent light. More specifically, the phosphor ceramic layer 20 is irradiated with light emitted from an excitation light source described later as excitation light L1 , thereby emitting fluorescence from the phosphor ceramic layer 20 as wavelength-converted light. That is, the wavelength-converted light emitted from the phosphor ceramic layer 20 is light having a wavelength longer than that of the excitation light L1.

In the present embodiment, the wavelength-converted light emitted from the phosphor ceramic layer 20 includes fluorescent light of yellow-based light. The phosphor ceramic layer 20 absorbs, for example, light having a wavelength of 380 nm to 490 nm and emits fluorescent light having a fluorescence peak wavelength in a range of 490 nm to 580 nm. By forming the phosphor ceramic layer 20 with YAG, the phosphor ceramic layer 20 that emits fluorescence having a fluorescence peak wavelength in the range of wavelengths from 490 nm to 580 nm can be easily realized.

The x-coordinate of the chromaticity diagram of the wavelength-converted light emitted from the phosphor ceramic layer 20 is preferably 0.415 or less, more preferably 0.410 or less, and further preferably 0.408 or less. If the x-coordinate of the chromaticity diagram of the wavelength-converted light emitted from the phosphor ceramic layer 20 is the above-mentioned value, the thermal quenching of the phosphor ceramic layer 20 becomes small, so that a phosphor with high luminous efficiency can be realized. Light body ceramic layer 20 .

The density of the phosphor ceramic layer 20 is preferably not less than 95% and not more than 100% of the theoretical density, more preferably not less than 97% and not more than 100% of the theoretical density. Here, the theoretical density is the density when atoms in the layer are ideally arranged. In other words, the theoretical density is assumed to be the density when there is no void in the phosphor ceramic layer 20 , and is a value calculated from the crystal structure. For example, when the density of the phosphor ceramic layer 20 is 99%, the remaining 1% corresponds to voids. That is, the higher the density of the phosphor ceramic layer 20, the fewer the voids. If the density of the phosphor ceramic layer 20 is within the above range, the total amount of fluorescent light emitted by the phosphor ceramic layer 20 increases, so that the wavelength conversion element 1 and the projector with a larger amount of emitted light can be provided.

In addition, the density of the phosphor ceramic layer 20 is preferably 4.32 g/cm ³ or more and 4.55 g/cm ³ or less, more preferably 4.41 g/cm ³ or more and 4.55 g/cm ³ or less. As shown in the present embodiment, when the phosphor ceramic layer 20 is formed of YAG, if the density of the phosphor ceramic layer 20 is within the above-mentioned range, the density of the phosphor ceramic layer 20 is 95% or more of the theoretical density and 100%. % below and above 97% and below 100%. By making the density of the phosphor ceramic layer 20 within the above-mentioned range, the excitation light L1 absorbed by the phosphor ceramic layer 20 can be efficiently converted into fluorescent light. That is, the phosphor ceramic layer 20 with high luminous efficiency is realized.

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

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

The anti-reflection layer 30 is a layer that prevents, more specifically, suppresses reflection of the excitation light L1. The anti-reflection layer 30 reduces the reflectance of the excitation light L1 in the wavelength conversion element 1 and increases the amount of the excitation light L1 reaching the phosphor ceramic layer 20 . As a result, the amount of excitation light L1 that the phosphor ceramic layer 20 can absorb also increases, so the amount of fluorescent light emitted from the phosphor ceramic layer 20 also increases. That is, by providing the anti-reflection layer 30, the amount of fluorescent light emitted from the phosphor ceramic layer 20 is increased.

The anti-reflection layer 30 may be constituted by, for example, a dielectric film, a fine concavo-convex structure (so-called moth-eye structure) having a period smaller than the wavelength of light in the visible light range, or the like. When the anti-reflection layer 30 is formed of a dielectric film, the anti-reflection layer 30 preferably contains an inorganic compound. In this case, the anti-reflection layer 30 contains one or more inorganic compounds selected from SiO ₂ , TiO ₂ , Al ₂ O ₃ , ZnO, Nb ₂ O ₅ , and MgF.

1 and 2 , the configuration in which the anti-reflection layer 30 is provided is shown, but the wavelength conversion element 1 may not include the anti-reflection layer 30 .

The substrate 10 is a disc-shaped plate, and is a substrate supporting the phosphor ceramic layer 20 and the antireflection layer 30 . The motor 4 is disposed in the center of the substrate 10 in a plan view. As shown in FIG. 2 , the substrate 10 includes a substrate body 11 and a light reflection 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 higher thermal conductivity than the phosphor ceramic layer 20 , but is not limited to this form. The substrate body 11 is, for example, a glass substrate, a quartz substrate, a GaN substrate, a sapphire substrate, a Si substrate, a metal substrate, or the like. In addition, the substrate main body 11 may be formed of resin such as a PEN (polyethylene terephthalate) film or a PET (polyethylene terephthalate) film. Furthermore, when the substrate body 11 is a metal substrate, the substrate body 11 is made of metal materials such as Al, Fe, and Ti.

In this embodiment, the substrate body 11 is a metal substrate made of Al. Al has high thermal conductivity and light weight, so it can 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.

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

The light reflecting surface 13 is a surface reflecting the fluorescent light emitted from the phosphor ceramic layer 20 . In addition, the light reflecting surface 13 also reflects the excitation light L1 that has not been converted into fluorescent light in the phosphor ceramic layer 20 . The light reflecting surface 13 reflects the fluorescent light and the excitation light L1 that has not been converted into fluorescent light upward. In the present embodiment, since the fluorescent light and the excitation light L1 are light in the visible light range, the higher the visible light reflectance of the light reflecting surface 13 is, the less the loss of light is. Specifically, the visible light reflectance of the light reflecting surface 13 is preferably 90% or more and 100% or less, and more preferably 95% or more and 100% or less. If the visible light reflectance of the light reflecting surface 13 is in the above range, the fluorescent light and the excitation light L1 are reflected upward, so that the fluorescent light and the excitation light L1 are guided in the lateral direction (ie, the direction parallel to the light reflecting surface 13 ). Being suppressed, the light emitting area becomes smaller. Therefore, the wavelength conversion element 1 and the projector with smaller etendue and higher light utilization efficiency can be provided. In addition, the reflectance of light in the wavelength range of 490 nm to 780 nm of the light reflecting surface 13 is preferably 90% or more and 100% or less, more preferably 95% or more and 100% or less. If the reflectance of light in the wavelength range from 490 nm to 780 nm of the light reflecting surface 13 is in the above range, the fluorescent light is reflected further upward, so that the guided wave of the fluorescent light in the lateral direction is suppressed, and the light emitting area becomes smaller. Therefore, the wavelength conversion element 1 and the projector with smaller etendue and higher light utilization efficiency can be provided. In addition, in this embodiment, the visible light range is a wavelength range of 380 nm or more and 780 nm or less.

The light reflection layer 12 may be formed of any material as long as it can reflect the fluorescent light and the excitation light L1 that has not been converted into fluorescent light upward. In the present embodiment, the light reflection layer 12 is a composite layer composed of the light scattering particles 121 and the binder 122 in which the light scattering particles 121 are dispersed. That is, the light reflection layer 12 has a light diffusing property (light scattering property), and reflects the fluorescent light and the excitation light L1 that is not converted into the fluorescent light upward by the light diffusing.

The light reflection layer 12 diffuses light by 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 inorganic compounds or resin materials. 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 styrene-based resins and acrylics Resin and other resin materials. In addition, the adhesive 122 is preferably composed of resin materials such as acrylic resin and silicone resin having light transmittance.

By providing the light reflection layer 12 , the visible light reflectance of the light reflection surface 13 can be improved. Furthermore, by forming the light reflection layer 12 with a composite layer including the light scattering particles 121 , the visible light reflectance of the light reflection surface 13 can be further improved. That is, the loss of light in the wavelength conversion element 1 can be more suppressed.

In addition, the light reflection layer 12 may be a metal layer made of a metal having light reflection properties. For example, the metal is Ag, Al, or an alloy containing any of these. The light reflection layer 12 is preferably formed by dry processing or wet processing of the metal. In these cases, the same effects as in the case where the light reflection layer 12 is constituted by a composite layer including the light scattering particles 121 can be expected.

In addition, a bonding layer may also be provided between the light reflection layer 12 and the phosphor ceramic layer 20 . With such a configuration, the light reflection layer 12 and the phosphor ceramic layer 20 can be brought into closer contact, so that the heat generated in the phosphor ceramic layer 20 can be transferred to the substrate more efficiently through the light reflection layer 12 The body 11 conducts. Therefore, the wavelength conversion element 1 with less thermal quenching of the phosphor ceramic layer 20 and high efficiency can be provided. The bonding layer is preferably made of a transparent material such as silicone resin or epoxy resin. In addition, the thickness of the bonding layer is preferably 1 μm or more and less than 100 μm, and more preferably 1 μm or more and less than 20 μm.

1 and 2 , the configuration in which the light reflection layer 12 is provided is shown, but the wavelength conversion element 1 may not include the light reflection layer 12 . In this case, the surface of the substrate body 11 becomes the light reflecting surface 13 .

[Configuration of the projector] The wavelength conversion element 1 configured as described above is used in the projector 100 shown in FIGS. 3 and 4 . FIG. 3 is a perspective view showing the appearance of the projector 100 of the present embodiment. FIG. 4 is a schematic diagram of the optical system of the projector 100 of the present embodiment. Hereinafter, the configuration of the projector 100 according to the present embodiment will be described with reference to FIGS. 3 and 4 .

As shown in FIGS. 3 and 4 , the projector 100 of the present embodiment includes a light source 3 , a dichroic mirror 5 , a wavelength conversion element 1 , a display element 6 , a projection optical member 7 , and a reflection 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 driving 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 range from near-ultraviolet to blue light having a wavelength of 380 nm or more and 490 nm or less. More specifically, the light source 3 emits blue light having a peak wavelength of 445 nm. The light source 3 of the present embodiment is an example of an excitation light source. The laser light emitted by the light source 3 reaches the beam splitter 5 .

The beam splitter 5 is arranged at an angle of 45 degrees with respect to the optical axis of the light source 3 . The beam splitter 5 of the present embodiment is a beam splitter that transmits a part of blue light and reflects the other part, and transmits yellow fluorescent light.

That is, the beam splitter 5 has the characteristics of reflecting and transmitting light in the wavelength range of the laser light emitted from the light source 3 . Therefore, a part of the laser light emitted from the light source 3 is transmitted through the beam splitter 5 without changing the direction of travel; the other part of the laser light is reflected by the beam splitter 5 , and the direction of travel is changed by 90° to the wavelength conversion element 1 .

Here, the other part of the laser light emitted from the light source 3 reaches the wavelength conversion element 1 as the excitation light L1 . The wavelength conversion element 1 receives excitation light L1 and emits reflected light L2 including fluorescent light. More specifically, the reflected light L2 includes light wavelength-converted and reflected by the phosphor ceramic layer 20 and the light reflecting surface 13 included in the wavelength conversion element 1 , respectively. More specifically, the reflected light L2 is light including excitation light L1 including yellow-based fluorescent light generated by the phosphor ceramic layer 20 and blue light of fluorescent light that is not converted by the phosphor ceramic layer 20 . However, in the reflected light L2, the ratio of fluorescent light is high, so the reflected light L2 is yellow light.

The laser light that has passed through the beam splitter 5 without changing its advancing direction reaches the reflector 8 as transmitted light L12 , is specularly reflected by the reflector 8 , and travels to the other side of the beam splitter 5 . Then, the transmitted light L12 is reflected by the other surface of the dichroic mirror 5 , and the traveling direction is changed by 90° to travel to the display element 6 .

Further, the reflected light L2 reaches the beam splitter 5 . At this time, the beam splitter 5 is arranged at an angle of 45 degrees with respect to the optical axis of the reflected light L2, and also transmits yellow fluorescent light. Therefore, the traveling direction of the reflected light L2 reaching the beam splitter 5 does not change.

Thereby, as shown in FIG. 4 , the optical axis of the reflected light L2 coincides with the optical axis of the transmitted light L12 and is directed 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 combined with these light rays is white light. That is, the light ray going from the beam splitter 5 to the display element 6 is white light.

The mixed light of the reflected light L2 and the transmitted light L12 , that is, white light, travels to the display element 6 . Here, if the reflected light L2 is light with a large etendue, the size of the reflected light L2 irradiated to the display element 6 becomes larger than the size of the display element 6 . Therefore, there are many light components that are not irradiated to the display element 6 and that are not used (that is, cannot be used).

The display element 6 is a substantially flat element that controls the light (white light) passing through the opening 2a and outputs it as a picture. In other words, the display element 6 generates light for images. The display element 6 is, specifically, a DLP (Digital Light Processing, digital light processing) element having a DMD (Digital Micromirror Device, digital micromirror element). In addition, for example, the display element 6 may be a reflective liquid crystal panel or the like. In addition, between the display element 6 and the beam splitter 5, a fly-eye lens, a polarization conversion element, a mirror rod, and the like may be provided.

The light for images generated by the display element 6 is projected by the projection optical member 7 to be enlarged and projected onto the screen.

The projector 100 uses only the light irradiated on the display element 6 as projection light. That is, the smaller the etendue of the reflected light L2 is, the more light can be used as the projection light of the projector 100 .

[Light behavior of wavelength conversion element] Here, the optical behavior of the wavelength conversion element 1 will be described using this embodiment and a comparative example.

FIG. 5A is a schematic diagram of the wavelength conversion element 1 and the aperture member 2 of the present embodiment. FIG. 5B is a schematic diagram of the wavelength conversion element 1x and the aperture member 2 in the comparative example of the present embodiment. In addition, here, for convenience, the aperture member 2, the wavelength conversion elements 1 and 1x, the excitation light L1, and the reflected light L2 are used for description.

Here, the aperture member 2 is a member for evaluating the magnitude of the etendue of the reflected light L2. The aperture member 2 is a light absorbing member, and is a member provided with an opening portion 2 a in the central portion of the aperture member 2 . When the ratio of the light component passing through the opening 2a of the aperture member 2 is relatively large, it can be said that the etendue of the reflected light L2 is small.

The wavelength conversion element 1x of the comparative example is the same as the wavelength conversion element 1 of the present embodiment except that the thickness of the phosphor ceramic layer 20x is thicker (for example, 200 μm) than that of the phosphor ceramic layer 20 of the present embodiment. composition.

The density of the phosphor ceramic layers 20 and 20x is 4.41 g/cm ³ or more and 4.55 g/cm ³ or less, and the density is high. That is, in the phosphor ceramic layers 20 and 20x, there are few voids and light scattering is unlikely to occur. Therefore, light tends to travel in the plane direction of the layers (ie, the x-axis direction or the y-axis direction), and so-called light guiding is likely to occur.

First, the wavelength conversion element 1 of the present embodiment will be described with reference to FIG. 5A .

If the thickness is very thin (50 μm or more and 120 μm or less) like the phosphor ceramic layer 20 of the present embodiment, the plane direction (here, the x-axis direction) of the layer from the incident of the excitation light L1 to the output of the reflected light L2 can be achieved. ), the distance D is even shorter. In other words, in the present embodiment, the fluorescent light-emitting area (light-emitting spot diameter) of the phosphor ceramic layer 20 is very small. Therefore, as shown in FIG. 5A , the reflected light L2 reflected by the light reflecting surface 13 and emitted from the phosphor ceramic layer 20 easily passes through the opening 2 a of the aperture member 2 . The light passing through the opening 2a can be used as the light to be enlarged and projected onto the screen via the display element 6 and the projection optical member 7 as described above.

That is, in this embodiment, the thickness of the phosphor ceramic layer 20 included in the wavelength conversion element 1 is very thin, so that the luminescent area of the fluorescent light can be made very small. Therefore, since there are many light rays passing through the openings 2 a of the aperture member 2 , many light rays can be used as the projection light of the projector 100 . That is, with the above configuration, the wavelength conversion element 1 with high light utilization efficiency is realized. Furthermore, by including these wavelength conversion elements 1, the projector 100 with high light utilization efficiency is realized.

Next, the wavelength conversion element 1x of the comparative example will be described with reference to FIG. 5B.

When the thickness is very thick (200 μm) like the phosphor ceramic layer 20x of the comparative example, the distance Dx in the plane direction of the layer from which the excitation light L1 is incident and the reflected light L2x is emitted becomes longer. In other words, in the comparative example, the light-emitting area (light-emitting spot diameter) of the fluorescent light of the phosphor ceramic layer 20x is increased. Therefore, as shown in FIG. 5B , the reflected light L2 x emitted from the phosphor ceramic layer 20 x by the reflection by the light reflecting surface 13 is easily shielded by the aperture member 2 . Therefore, the wavelength conversion element 1x of the comparative example has low light utilization efficiency.

In addition, as described above, in this embodiment, by providing the light reflecting layer 12 and further comprising the light reflecting layer 12 with a composite layer including the light scattering particles 121 , the visible light reflectance of the light reflecting surface 13 can be further improved. Thereby, the loss of light in the wavelength conversion element 1 can be further suppressed, so that the wavelength conversion element 1 with high light utilization efficiency can be realized.

[Example] Here, in the wavelength conversion elements of Examples 1 to 3 and the comparative example of the present embodiment, the manufacturing method and the light utilization efficiency will be described.

First, the manufacturing method of the phosphor ceramic layer will be described.

The phosphor ceramic layers of Examples 1 to 3 and Comparative Example are all composed of a first crystal phase represented by (Y _0.9953 Ce _0.0047 ) ₃ Al ₅ O ₁₂ . In addition, the phosphor ceramic layers of Examples 1 to 3 and the comparative example are all composed of Ce ^{3 +} activated phosphor.

The phosphor ceramic layers of Examples 1 to 3 and Comparative Examples used the following three kinds of raw materials as compound powders. Specifically, Y ₂ O ₃ (yttrium oxide, purity 3N, Japan YTTRIUM Co., Ltd.), Al ₂ O ₃ (alumina, 3N purity, Sumitomo Chemical Co., Ltd.), and CeO ₂ (cerium oxide, 3N purity, Japan YTTRIUM Co., Ltd.) were used. Co., Ltd.).

First, the above-mentioned raw materials are weighed so as to be a compound of stoichiometric composition (Y _0.9953 Ce _0.0047 ) ₃ Al ₅ O ₁₂ . Then, the weighed raw materials and alumina balls (10 mm in diameter) were put into a plastic pot. The amount of alumina balls is about 1/3 of the volume of the plastic pot. Then, pure water was put into the plastic pot, and the raw material 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 materials were dried with a dryer. Specifically, the Naflon (registered trademark) sheet was laid so as to cover the inner wall of the metal disk, and the mixed raw material was made to flow over the Naflon (registered trademark) sheet. The metal pan, the Naflon (registered trademark) sheet, and the mixed raw material were treated with a dryer set to 150° C. for 8 hours and dried. Then, the mixed raw material after drying is recovered, and the mixed raw material is granulated by a spray drying apparatus. In addition, at the time of granulation, polyvinyl alcohol was used as a binder (binder).

The granulated mixed raw material is temporarily formed into a cylindrical shape using an electric hydraulic press (manufactured by Riken Seiki Co., Ltd., EMP-5) and a cylindrical mold (outer diameter 58mm, inner diameter 38mm, height 130mm). . The pressure during molding was 5 MPa/cm ² . Then, using a cold equalizing and pressing device, the once-molded molded body is fully molded. The pressure at the time of main molding was 300 MPa. In addition, the molded body after the main molding is subjected to heat treatment (binder removal treatment) for the purpose of removing the binder (binder) used in the granulation. The temperature of the heat treatment was set to 500°C. In addition, the time for the heat treatment was set to 10 hours.

The formed body after heat treatment is calcined in a tubular gas atmosphere furnace. The calcination temperature was set to 1675°C. In addition, the calcination time was made 4 hours. The calcining gas atmosphere is a mixed gas atmosphere of nitrogen and hydrogen. In addition, the outer diameter and inner diameter of the calcined product after calcination were 43 mm and 29 mm, respectively.

Using a multi-wire saw, the calcined cylindrical calcined material was sliced. The thickness of the cylindrical calcined product cut into pieces was about 700 μm.

The calcined material after slicing is ground by a grinding device, and the thickness of the calcined material is adjusted. By performing this adjustment, the calcined product becomes 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 Comparative Example.

In addition, the outer diameter and inner diameter of the phosphor ceramic layers of Examples 1 to 3 and the comparative example were 43 mm and 29 mm, respectively. In addition, the phosphor ceramic layers of Examples 1 to 3 and the comparative example were dark yellow.

Next, the evaluation of the phosphor ceramic layer will be described.

First, the density of the phosphor ceramic layers of Examples 1 to 3 and Comparative Example was evaluated by the Archimedes method. The densities of the phosphor ceramic layers of Examples 1 to 3 and Comparative Example were all 4.49 g/cm ³ . In addition, the densities of the phosphor ceramic layers of Examples 1 to 3 and the comparative example were all 98.7% of the theoretical density (4.55 g/cm ³ ) of Y ₃ Al ₅ O ₁₂ . That is, the densities of the phosphor ceramic layers of Examples 1 to 3 and the comparative example are all 97% or more and 100% or less of the theoretical density of Y ₃ Al ₅ O ₁₂ .

Next, a method of manufacturing the wavelength conversion element will be described.

First, an Al disk-shaped substrate body (50 mm in diameter, 0.5 mm in thickness) was prepared. Next, using a dispensing apparatus, a light reflection layer containing a silicone-based resin dispersed with TiO ₂ particles was coated on the substrate body to make it circular (outer diameter 46 mm, inner diameter 30 mm). Here, the silicon-oxygen resin contained in the light reflection layer also functions as an adhesive for bonding the phosphor ceramic layer to the substrate body.

After that, the phosphor ceramic layer was arranged so as to overlap with the light reflection layer coated in a circular shape. Here, the thickness of the light reflection layer was set to about 50 μm, and the phosphor ceramic layer was fixed with a metal jig. Then, the light reflection layer is hardened by performing heat processing with a dryer. The temperature of the heat treatment at this time was 150°C. In addition, the visible light reflectance of the light reflection surface, which is one surface included in the light reflection layer, is 95% or more.

In this way, the wavelength conversion elements of Examples 1 to 3 and Comparative Examples each including the phosphor ceramic layers and substrates of Examples 1 to 3 and Comparative Examples described above were obtained.

Further, evaluation of the wavelength conversion element will be described.

The wavelength conversion elements of Examples 1 to 3 and the comparative example were evaluated by an evaluation device for wavelength conversion elements of a reflection type laser excitation method. Specifically, in this evaluation apparatus, excitation light (laser light) is irradiated to the rotating wavelength conversion element, and the fluorescence energy of the fluorescence emitted from the wavelength conversion element is evaluated by a power meter. The wavelength, output and irradiation spot diameter (1/e ² ) of the laser light are 455nm, 70W and 1.2mm, respectively. In addition, the laser light is a Gaussian beam. In addition, the rotational speed of the wavelength conversion element was 7200 rpm. An aperture member is provided in the evaluation device, and the aperture member shields a part of the fluorescence emitted from the wavelength conversion element. In this case, for example, the distance between the wavelength conversion element 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.

FIG. 6 is a graph showing the evaluation results of the wavelength conversion elements of Examples 1 to 3 and Comparative Example of the present embodiment. Specifically, FIG. 6 shows the relative value of fluorescence energy (after passing through the opening), the relative value of fluorescence energy (before passing through the opening), and the binding efficiency of the wavelength conversion elements of Examples 1 to 3 and Comparative Example.

Here, the relative value of the fluorescence energy (after passing through the opening) is the relative value of the fluorescence energy of the fluorescence emitted by each wavelength conversion element after passing through the opening of the aperture member. In addition, the fluorescence energy of the fluorescence emitted from the wavelength conversion element of the comparative example after passing through the opening was set to 100%.

In addition, the relative value of fluorescence energy (before passing through the opening) is the relative value of the fluorescence energy of the fluorescence emitted by each wavelength conversion element before passing through the opening of the aperture member. In addition, the fluorescence energy of the fluorescence emitted from the wavelength conversion element of the comparative example after passing through the opening was set to 100%.

In addition, the binding efficiency is the ratio of the relative value of fluorescence energy (after passing through the opening) to the relative value of fluorescence energy (before passing through the opening). That is, the binding efficiency is a value obtained by dividing the relative value of fluorescence energy (after passing through the opening) by the relative value of fluorescence energy (before passing through the opening).

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

As shown in FIG. 6 , the combining efficiencies of the wavelength conversion elements of Example 1, Example 2, Example 3 and Comparative Example are 85%, 86%, 84% and 81%, respectively. That is, the combining efficiency of the examples is higher than that of the comparative example. The higher the binding efficiency, the more light passing through the openings in the generated fluorescent light, that is, the smaller the light emitting area of the fluorescent light emitted by the wavelength conversion element, as shown in FIGS. 5A and 5B . That is, the light emitting area of the fluorescent light emitted by the wavelength conversion element of Examples 1 to 3 is smaller than that of the fluorescent light emitted by the wavelength conversion element of the comparative example, indicating that the wavelength conversion element of the embodiment has high light utilization efficiency.

In addition, as shown in FIG. 6 , by setting the thickness of the phosphor ceramic layers of Examples 1 to 3 in the range of 50 μm or more and 120 μm or less, the bonding efficiency is very high compared to the comparative example. That is, by making the thickness of the phosphor ceramic layer 20 of the present embodiment described above in the range of 50 μm or more and 120 μm or less, the wavelength conversion element 1 with high light utilization efficiency is realized.

In addition, the relative values of fluorescence energy (after passing through the opening) of the wavelength conversion elements of Example 1, Example 2, Example 3, and Comparative Example were 103%, 106%, 105%, and 100%, respectively. That is, in Examples 1 to 3, the relative value of fluorescence energy (after passing through the opening) was higher than that of the comparative example (after passing through the opening). On the other hand, among Examples 1 to 3, the relative values of fluorescence energy (through the openings) of the wavelength conversion element of Example 2 in which the thickness of the phosphor ceramic layer was 76 μm and the wavelength conversion element of Example 3 in which the thickness of the phosphor ceramic layer was 106 μm later) higher.

In addition, as shown in FIG. 6 , it can be clearly seen that by setting the thickness of the phosphor ceramic layers of Examples 2 and 3 in the range of 70 μm or more and 120 μm or less, compared with the comparative example, a very high fluorescence energy relative value (after passing through the opening). That is, by making the thickness of the phosphor ceramic layer 20 of the present embodiment described above in the range of 70 μm or more and 120 μm or less, the wavelength conversion element 1 with higher light utilization efficiency is realized.

Further, the relative values of fluorescence energy (before passing through the opening) of the wavelength conversion elements of Example 1, Example 2, Example 3 and Comparative Example were 121%, 124%, 125% and 124%, respectively. The relative value of the fluorescence energy of the wavelength conversion element of Example 1 (before passing through the opening) with the thinnest phosphor ceramic layer of 53 μm is compared with the fluorescence energy of the wavelength conversion element of Examples 2 and 3 and the comparative example. The value (before passing through the opening) is lower. The inventor believes that the reason is that in the wavelength conversion element of Example 1, the thickness of the phosphor ceramic layer is thin, so that the phosphor ceramic layer cannot sufficiently absorb the laser light.

Here, further, in the wavelength conversion element of Example 4 of the present embodiment, the manufacturing method and the light utilization efficiency will be described.

First, the manufacturing method of the phosphor ceramic layer with which the wavelength conversion element of Example 4 of this embodiment is equipped is described.

The phosphor ceramic layers of Example 4 are all composed of the first crystal phase represented by (Y _0.997 Ce _0.003 ) ₃ Al ₅ O ₁₂ . In addition, the phosphor ceramic layers of Example 4 are all composed of Ce ^{3 +} activated phosphor.

In Example 4, a calcined product was obtained in the same procedure as in Examples 1 to 3, except that the raw materials were weighed so as to be a compound having a stoichiometric composition (Y _0.997 Ce _0.003 ) ₃ Al ₅ O ₁₂ . That is, the main point of difference between the phosphor ceramic layers of Examples 1 to 3 and the phosphor ceramic layer of Example 4 is the point in which the composition ratio of Y and Ce is different.

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

In addition, the outer diameter and inner diameter of the phosphor ceramic layer of Example 4 were 41 mm and 27 mm. In addition, the phosphor ceramic layer of Example 4 was dark yellow.

Next, the evaluation of the phosphor ceramic layer will be described.

First, the density of the phosphor ceramic layer of Example 4 was evaluated by the Archimedes method. The density of the phosphor ceramic layer of Example 4 was 4.48 g/cm ³ . In addition, the density of the phosphor ceramic layer of Example 4 is all 98.4% of the theoretical density (4.55 g/cm ³ ) of Y ₃ Al ₅ O ₁₂ . That is, the density of the phosphor ceramic layer of Example 4 is 97% or more and 100% or less of the theoretical density of Y ₃ Al ₅ O ₁₂ .

In addition, as described above, the phosphor ceramic layer 20 of the present embodiment is composed of YAG having Ce ^{3 +} and Ce ^{4 +} , that is, the phosphor ceramic layer 20 includes Ce ^{3 +} and Ce ^{4 +} . Next, the Ce ^{3 +} existence ratio and the Ce ^{4 +} existence ratio of the phosphor ceramic layer of Example 4 were evaluated using a hard X-ray XAFS apparatus. Specifically, using a hard X-ray XAFS apparatus, the XAFS spectrum of the phosphor ceramic layer of Example 4 was acquired in the range of 5687 eV to 5777 eV. The obtained XAFS spectrum was subjected to fitting analysis of the reference spectrum of Ce ^{3 +} and the reference spectrum of Ce ^{4 +} , thereby evaluating the Ce ^{3 +} existence ratio and the Ce ^{4 +} existence ratio. In addition, 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 is a table showing the Ce ^{3 +} existence ratio and the Ce ^{4 +} existence ratio of the phosphor ceramic layer of Example 4. As shown in Table 1, the Ce ^{3 +} existence ratio and the Ce ^{4 +} existence ratio of the phosphor ceramic layer of Example 4 were 78.3% and 21.7%, respectively. In the phosphor ceramic layer of Example 4, Ce ^{3 +} ×100%/(Ce ^{3 +} +Ce ^{4 +} )≧60%, that is, the Ce ^{3 +} existence ratio is 60% or more. [Table 1]

Next, the manufacturing method of the wavelength conversion element of Example 4 is described.

First, as a light reflection layer, an Ag-coated Al disk-shaped substrate body (50 mm in diameter, 0.5 mm in thickness) was prepared. In addition, a screw hole is opened in the center portion of the base body. Next, on the substrate body, a phosphor ceramic layer is provided.

Inside the phosphor ceramic layer, an Al disc-shaped first plate member (outer diameter 26.5 mm, thickness 100 μm) having a screw hole in the center was provided. In addition, the phosphor ceramic layer is a phosphor ring, and the first plate member is provided on the inner side of the ring. Then, a disk-shaped second plate member (outer diameter 29 mm, thickness 200 μm) of Al having a screw hole in the center was provided 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 and fixed. In this way, the phosphor ceramic layer is fixed to obtain a wavelength conversion element. That is, in the wavelength conversion element of Example 4, the phosphor ceramic layer is sandwiched and fixed by the substrate body and the second plate member.

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

Further, evaluation of the wavelength conversion element will be described.

The wavelength conversion element of Example 4 was evaluated by the same method as Examples 1-3.

FIG. 7 is a graph showing the evaluation results of the wavelength conversion element of Example 4 of the present embodiment. Specifically, FIG. 7 shows the relative value of fluorescence energy (after passing through the opening), the relative value of fluorescence energy (before passing through the opening), and the binding efficiency of the wavelength conversion element of Example 4. In addition, FIG. 7 also shows the relative value of fluorescence energy (after passing through the opening), the relative value of fluorescence energy (before passing through the opening), and the binding efficiency of the wavelength conversion elements of Examples 1 to 3 and the comparative example for comparison. .

Here, the relative value of the fluorescence energy (after passing through the opening) is the relative value of the fluorescence energy of the fluorescence emitted from the wavelength conversion element after passing through the opening of the aperture member. In addition, the fluorescence energy of the fluorescence emitted from the wavelength conversion element of the comparative example after passing through the opening was set to 100%.

In addition, the relative value of fluorescence energy (before passing through the opening) is the relative value of the fluorescence energy of the fluorescence emitted from the wavelength conversion element before passing through the opening of the aperture member. In addition, the fluorescence energy of the fluorescence emitted from the wavelength conversion element of the comparative example after passing through the opening was set to 100%.

In addition, the binding efficiency is the ratio of the relative value of fluorescence energy (after passing through the opening) to the relative value of fluorescence energy (before passing through the opening). That is, the binding efficiency is a value obtained by dividing the relative value of fluorescence energy (after passing through the opening) by the relative value of fluorescence energy (before passing through the opening).

As shown in FIG. 7 , the combining efficiency of the wavelength conversion element of Example 4 was 85%. In addition, as described above, the binding efficiency of the wavelength conversion element of the comparative example was 81%. Combined with the wavelength conversion element of the fourth embodiment with higher efficiency, the generated fluorescence has more light passing through the opening, and the fluorescent light-emitting area is smaller. For example, as shown in FIGS. 5A and 5B , in the wavelength conversion element of the fourth embodiment, more light passes through the opening 2 a of the aperture member 2 , so that more light can be used as the projection light of the projector 100 . That is, it shows that the wavelength conversion element of Example 4 has high light utilization efficiency.

Further, the relative value of fluorescence energy (after passing through the opening) and the relative value of fluorescence energy (before passing through the opening) of the wavelength conversion element of Example 4 were 108% and 128%, respectively. This value is higher than the relative value of fluorescence energy (after passing through the opening) and the relative value of fluorescence energy (before passing through the opening) of the wavelength conversion elements of Examples 1 to 3.

As described above, in the phosphor ceramic layer of Example 4, the Ce ^{3 +} existence ratio was 60% or more, and the Ce ^{4 +} existence ratio was as small as less than 40%. Therefore, the non-luminescence relaxation loss due to Ce ^{4 +} is reduced, so that the phosphor ceramic layer of Example 4 in which the Ce ^{3 +} existence ratio is 60% or more has a higher luminous efficiency. Therefore, the wavelength conversion element of Example 4 can improve the light utilization efficiency by having these phosphor ceramic layers. Furthermore, when the projector is provided with these wavelength conversion elements 1, the light utilization efficiency of the projector can be improved. For example, a projector with low power consumption can be realized.

In addition, the heat generation of the phosphor ceramic layer of Example 4 is reduced because the non-luminescence relaxation loss due to Ce ^{4 +} is reduced. Therefore, in a projector provided with these phosphor ceramic layers, the maximum input energy of the excitation light L1 can be increased, that is, a projector with high output can be realized.

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

[Configuration of wavelength conversion element] First, the structure of the wavelength conversion element 1a of this modification is demonstrated using drawings. FIG. 8 is a perspective view of the wavelength conversion element 1a of this modification. FIG. 9 is a cross-sectional view showing a cross-section of the wavelength conversion element 1 a on line IX-IX of FIG. 8 .

The wavelength conversion element 1a of the present modification has the same configuration as the wavelength conversion element 1 of the embodiment except for the point that the phosphor ceramic layer 20a is provided. That is, as shown in FIGS. 8 and 9 , the wavelength conversion element 1 a includes the substrate 10 having the light reflecting surface 13 , the phosphor ceramic layer 20 a , and the antireflection layer 30 .

In addition, in this modification, the wavelength conversion element 1a is also used in a projector, and is a fluorescent wheel that receives the excitation light L1 and emits reflected light including fluorescent light.

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

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

In addition, the second crystal phase is a crystal phase having a structure different from the garnet structure. That is, the second crystal phase has a structure different from that 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 showing the image of the phosphor ceramic layer 20a is 100%. In addition, the area which shows a 1st crystal phase is not limited to this, For example, 75% or more and 98% or less may be sufficient as it, and 85% or more and 95% or less may be sufficient as it. That is, the phosphor ceramic layer 20a of this modification mainly includes the first crystal phase.

As an example, the second crystal phase in this modification is a crystal phase having a perovskite structure, but is not limited to this type, 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 of EFO ₃ . For element E, rare earth elements such as Ca, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, and Lu are used; for element F, elements such as Mg, Al, Si, Ga, and Sc are used. As such a garnet structure, YAP (Yttrium Aluminum Perovskite) etc. are mentioned. In this modification, the second crystal phase is represented by (Y _{1 - y} Ce _y )AlO ₃ (0≦y<0.1), that is, represented by YAP.

In addition, the second crystal phase may be a solid solution of a plurality of perovskite crystal phases having different chemical compositions.

In addition, the second crystal phase may include a crystal phase whose chemical composition is shifted from the crystal phase represented by the general formula EFO ₃ described above.

In addition, the phosphor ceramic layer 20a of this modification is composed of only the first crystal phase and the second crystal phase, that is, does not contain a crystal phase having a structure different from the garnet structure and the perovskite structure.

In this modification, the material representing the second crystal phase is YAP as an example, but is not limited to this material. In addition, it is preferable to select so 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. Indicates the material of the second crystal phase. Thereby, 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. 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 more preferably 0.06 or more and 0.3 or less, and further preferably 0.07 or more and 0.15 or less.

In addition, for example, when the second crystal phase of this modification is a crystal phase having a structure different from the garnet structure and the perovskite structure, the material representing the second crystal phase is preferably Al ₂ O ₃ and Y ₂ O ₃ , Y ₄ Al ₂ O ₉ , Lu ₂ O ₃ and Lu ₄ Al ₂ O ₉ and the like.

The phosphor ceramic layer 20a receives light incident from above the wavelength conversion element 1a as excitation light L1, and emits fluorescent light. More specifically, the phosphor ceramic layer 20a is irradiated with light emitted from an excitation light source described later as excitation light L1, whereby fluorescence is emitted from the phosphor ceramic layer 20a as wavelength-converted light. That is, the wavelength-converted light emitted from the phosphor ceramic layer 20a is light having a wavelength longer than that of the excitation light L1.

In this modification, the wavelength-converted light emitted from the phosphor ceramic layer 20a includes fluorescent light of yellow-based light. The phosphor ceramic layer 20a, for example, absorbs light having a wavelength of 380 nm to 490 nm, and emits fluorescence having a fluorescence peak wavelength in a range of 490 nm to 580 nm. By constituting the phosphor ceramic layer 20a with YAG and YAP, the phosphor ceramic layer 20a that emits fluorescence having a fluorescence peak wavelength in the range of wavelengths from 490 nm to 580 nm can be easily realized.

The x-coordinate of the chromaticity diagram of the wavelength-converted light emitted from the phosphor ceramic layer 20a is preferably 0.415 or less, more preferably 0.410 or less, and further preferably 0.408 or less. If the x-coordinate of the chromaticity diagram of the wavelength-converted light emitted from the phosphor ceramic layer 20a is the above-mentioned value, the thermal quenching of the phosphor ceramic layer 20a is reduced, so that a phosphor ceramic layer with high luminous efficiency can be realized. 20a.

The density of the phosphor ceramic layer 20a is preferably not less than 95% and not more than 100% of the theoretical density, and more preferably not less than 97% and not more than 100% of the theoretical density. Here, the theoretical density is the density when atoms in the layer are ideally arranged. In other words, the theoretical density is assumed to be the density when there is no void in the phosphor ceramic layer 20a, and is a value calculated from the crystal structure. For example, when the density of the phosphor ceramic layer 20a is 99%, the remaining 1% corresponds to voids. That is, the higher the density of the phosphor ceramic layer 20a, the smaller the voids. If the density of the phosphor ceramic layer 20a is within the above range, the total amount of fluorescent light emitted by the phosphor ceramic layer 20a increases, so that a wavelength conversion element 1a and a projector with a larger amount of emitted light can be provided. In addition, the theoretical density is the theoretical density of the first crystal phase having a garnet structure.

The density of the phosphor ceramic layer 20a is preferably 4.32 g/cm ³ or more and 4.55 g/cm ³ or less, 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 formed of YAG and YAP, if the density of the phosphor ceramic layer 20a falls within the above-mentioned range, the density of the phosphor ceramic layer 20a becomes 95% of the theoretical density, respectively. Above 100% and below 97% below 100%. By making the density of the phosphor ceramic layer 20a into the above-mentioned range, the excitation light L1 absorbed by the phosphor ceramic layer 20a can be efficiently converted into fluorescent light. That is, the phosphor ceramic layer 20a with high luminous efficiency is realized.

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

[Configuration of the projector] The wavelength conversion element 1a configured as described above is used in a projector similarly to the wavelength conversion element 1 of the embodiment. That is, the wavelength conversion element 1a of this modification may be used instead of the wavelength conversion element 1 of the embodiment.

[Example] Here, in the wavelength conversion elements of Examples 5 and 6, the manufacturing method and the light utilization efficiency will be described. In addition, the wavelength conversion element of Example 5 has the same structure as the wavelength conversion element 1a of this modification, and the wavelength conversion element of Example 6 has the same structure as the wavelength conversion element 1 of embodiment.

First, the manufacturing method of the phosphor ceramic layer with which the wavelength conversion element of Example 5 and 6 is equipped is described.

The phosphor ceramic layer of Example 5 is mainly composed of a crystal phase represented by (Y _0.997 Ce _0.003 ) ₃ Al ₅ O ₁₂ (ie, the first crystal phase). In addition, as described above, the phosphor ceramic layer of Example 5 also includes the second crystal phase. The phosphor ceramic layer of Example 6 is composed of a crystal phase represented by (Y _0.997 Ce _0.003 ) ₃ Al ₅ O ₁₂ (ie, the first crystal phase). In addition, the phosphor ceramic layers of Examples 5 and 6 are all composed of Ce ^{3 +} activated phosphor.

For the phosphor ceramic layers of Examples 5 and 6, the same raw materials as those used in Examples 1 to 3 were used.

First, the above-mentioned raw materials are weighed so as to be a compound of stoichiometric composition (Y _0.997 Ce _0.003 ) ₃ Al ₅ O ₁₂ . Then, the above-mentioned raw materials were mixed in the same procedure as in Examples 1 to 3 to obtain a slurry-like mixed raw material.

Then, in Example 5, a mixed raw material for granulation was obtained by a method without using a spray drying apparatus. Specifically, 100 g of the mixed raw material dried by a dryer was put into a mortar made of alumina. Then, a solution obtained by dissolving polyvinyl alcohol in water at a ratio of 0.5 wt % was used as a polyvinyl alcohol solution, and 18 mL of this polyvinyl alcohol solution was further put into a mortar made of alumina. Then, the mixed raw material and the polyvinyl alcohol solution were mixed with a pestle. Then, the mixture of the mixed raw material and the polyvinyl alcohol solution was filtered through a mesh having an opening of 512 μm. As a result, a mixture of the mixed raw material and the polyvinyl alcohol solution having a particle size of about 512 μm or less was obtained. Thereafter, the mixture was treated with a dryer set at 105° C. for 30 minutes to remove moisture. In this way, the granulated mixed raw material used in Example 5 was obtained. In addition, in Example 6, the mixed raw material was granulated in the same procedure as in Examples 1 to 3 to obtain a granulated mixed raw material.

The phosphor ceramic layers of Examples 5 and 6 were temporarily formed by the same method. Specifically, the mixed raw material to be granulated is temporarily molded using an electric hydraulic press (manufactured by Riken Seiki Co., Ltd., EMP-5) and a cylindrical mold (outer diameter 66mm, inner diameter 46mm, height 130mm). It is cylindrical. The pressure at the time of molding was 5 MPa. Then, using a cold equalizing and pressing device, the once-molded molded body is fully molded. The pressure at the time of main molding was 300 MPa. In addition, the molded body after the main molding is subjected to heat treatment (binder removal treatment) for the purpose of removing the binder (binder) used in the granulation. The temperature of the heat treatment was set to 500°C. In addition, the time for the heat treatment was set to 10 hours.

The formed body after heat treatment is calcined in a tubular gas atmosphere furnace. The calcination temperature was set to 1675°C. In addition, the calcination time was made 4 hours. The calcining gas atmosphere is a mixed gas atmosphere of nitrogen and hydrogen. In addition, the outer diameter and inner diameter of the calcined product after calcination were 49 mm and 35 mm, respectively.

Using a multi-wire saw, the calcined cylindrical calcined material was sliced. The thickness of the cylindrical calcined product cut into pieces was about 700 μm.

In addition, in Examples 5 and 6, the calcined product after calcination was heat-treated at a temperature of 1000° C. or higher.

The calcined material after slicing is ground by a grinding device, and the thickness of the calcined material is adjusted. The thickness of the phosphor ceramic layer was 118 μm in Example 5 and 117 μm in Example 6.

In addition, the outer diameter and inner diameter of the phosphor ceramic layers of Examples 5 and 6 were both 49 mm and 35 mm. In addition, the phosphor ceramic layers of Examples 5 and 6 were dark yellow.

Next, the evaluation of the phosphor ceramic layer will be described.

First, the density of the phosphor ceramic layers of Examples 5 and 6 was evaluated by the Archimedes method. The densities of the phosphor ceramic layers of Examples 5 and 6 were 4.48 g/cm ³ and 4.42 g/cm ³ , respectively. In addition, the densities of the phosphor ceramic layers of Examples 5 and 6 were 98.4% and 97.1% of the theoretical density (4.55 g/cm 3 ) of Y ₃ Al ₅ O ₁₂ , respectively. That is, the density of the phosphor ceramic layers of Examples 5 and 6 was 97% or more and 100% or less of the theoretical density of Y ₃ Al ₅ O ₁₂ .

Then, the cross-sectional SEM image of the phosphor ceramic layer of Example 5 was evaluated using a scanning electron microscope (SEM).

FIG. 10 is an SEM image showing a cross section of the phosphor ceramic layer of Example 5 of the present modification. FIG. 10( a ) is an SEM image showing a broad cross section of the phosphor ceramic layer of Example 5. FIG. In addition, the SEM image shown in FIG. 10( a ) corresponds to the image of the area enclosed by the dotted rectangle in the cross-sectional view shown in FIG. 9 . Fig. 10(b) is an enlarged SEM image of the area enclosed by the rectangle of a dotted chain line in Fig. 10(a). Fig. 10(c) is an enlarged SEM image of the area enclosed by the rectangle of the two-dot chain line in Fig. 10(a).

Here, the phosphor ceramic layer of Example 5, that is, the phosphor ceramic layer 20a of this modification, includes a single-phase portion and a mixed-phase portion distinguished from the single-phase portion. A single-phase portion is shown in FIG. 10( b ), and a mixed-phase portion is shown in FIG. 10( c ).

In this modification, in the SEM image of FIG. 10 , the darker region corresponds to the first crystal phase having a garnet structure, and the lighter region corresponds to the second crystal phase having a perovskite structure. Furthermore, in the SEM image of Figure 10, the darkest region corresponds to a void.

In the single-phase portion, only a first crystal phase having a garnet structure and a second crystal phase having a structure different from the garnet structure (here, a perovskite structure) are provided. In addition, more specifically, here, in the single-phase portion, only the first crystal phase is provided, and other crystals having structures different from the garnet structure and the perovskite structure are not provided.

In addition, in the mixed phase portion, both the first crystal phase and the second crystal phase are provided in a mixed manner. More specifically, in the mixed phase portion, only both the first crystal phase and the second crystal phase are provided in a mixed manner. In addition, in the mixed phase portion, both the first crystal phase and the second crystal phase may be mixed, and another crystal phase having a structure different from the garnet structure and the perovskite structure may be further provided.

The mixed phase portion of Example 5 is provided in a structure in which both the first crystal phase and the second crystal phase are randomly intermixed, but is not limited to this form, and both the first crystal phase and the second crystal phase are periodically Configurable hybrid setups that are configured randomly are also possible.

In addition, the phosphor ceramic layer of Example 5 includes a plurality of mixed-phase portions. The regions enclosed by the dotted lines in FIG. 10( a ) correspond to the mixed-phase portions, respectively.

Surroundings of the complex mixed-phase parts are respectively surrounded by single-phase parts. The shape of the single-phase portion and the plural mixed-phase portion can also be said to be in the shape of a sea island. In this case, the single-phase part corresponds to the sea, and the plural mixed-phase part corresponds to the island.

In addition, in the mixed phase portion, it is preferable to provide more second crystal phases than the first crystal phases. 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 of Example 5 is observed in cross-section (for example, Fig. 10 ), when the total area of the image showing the mixed phase portion is 100%, the area showing the second crystal phase is, for example, 10% or more. Below 99%. The area showing the second crystal phase is not limited to this, and may be, for example, 70% or more and 95% or less, or 80% or more and 90% or less. That is, in the mixed phase part of this modification, the 2nd crystal phase is mainly provided.

In this way, in the mixed phase portion, both the first crystal phase having a garnet structure and the second crystal phase having a perovskite structure are provided in a mixed manner. 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 modification, 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 that of the mixed-phase portion.

Further, the size of the mixed phase portion will be described. In addition, the size of the mixed phase portion represents the length in the longitudinal direction of the mixed phase portion of the SEM image shown in FIG. 10 . The size of the mixed phase portion is, for example, the length indicated by the double arrow in FIG. 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 further preferably 2 μm or more and less than 100 μm.

In this way, the phosphor ceramic layer (phosphor ceramic layer 20 a ) of Example 5 includes the first crystal phase and the second crystal phase, and the single-phase portion and the mixed-phase portion are provided as shown in FIG. 10 . On the other hand, the phosphor ceramic layer of Example 6 was composed of only the first crystal phase. Therefore, it was confirmed that the phosphor ceramic layer of Example 6 was not provided with a mixed phase portion.

Next, the manufacturing methods of the wavelength conversion elements of Examples 5 and 6 will be described.

First, as a light reflection layer, an Ag-coated Al disk-shaped substrate body (50 mm in diameter, 0.5 mm in thickness) was prepared. In addition, a screw hole is opened in the center portion of the base body. Next, on the substrate body, a phosphor ceramic layer is provided.

On the inner side of the phosphor ceramic layer, a third plate member (outer diameter 34.5 mm, thickness 100 μm) of Al disk shape having a screw hole opened in the center was provided. In addition, the phosphor ceramic layer is a phosphor ring, and the third plate member is provided on the inner side of the ring. Then, a fourth plate member (outer diameter 39 mm, thickness 200 μm) of Al disc-shaped with a screw hole opened in the center was provided 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 and fixed. In this way, the phosphor ceramic layer is fixed to obtain a wavelength conversion element. That is, in the wavelength conversion elements of Examples 5 and 6, the phosphor ceramic layer is sandwiched and fixed by the substrate body and the fourth plate member.

Further, evaluation of the wavelength conversion element will be described.

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

FIG. 11 is a graph showing the evaluation results of the wavelength conversion elements of Examples 5 and 6 of the present modification. Specifically, FIG. 11 shows the relative value of fluorescence energy (after passing through the opening), the relative value of fluorescence energy (before passing through the opening), and the binding efficiency of the wavelength conversion elements of Examples 5 and 6.

Here, the relative value of the fluorescence energy (after passing through the opening) is the relative value of the fluorescence energy of the fluorescence emitted by each wavelength conversion element after passing through the opening of the aperture member. In addition, the fluorescence energy of the fluorescence emitted from the wavelength conversion element of Example 6 after passing through the opening was set to 100%.

In addition, the relative value of fluorescence energy (before passing through the opening) is the relative value of the fluorescence energy of the fluorescence emitted by each wavelength conversion element before passing through the opening of the aperture member. In addition, the fluorescence energy of the fluorescence emitted from the wavelength conversion element of Example 6 after passing through the opening was set to 100%.

In addition, the binding efficiency is the ratio of the relative value of fluorescence energy (after passing through the opening) to the relative value of fluorescence energy (before passing through the opening). That is, the binding efficiency is a value obtained by dividing the relative value of fluorescence energy (after passing through the opening) by the relative value of fluorescence energy (before passing through the opening).

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

In addition, the coupling efficiency of the wavelength conversion element of Example 5, which is equivalent to the wavelength conversion element 1a of the present modification, was 87%. The binding efficiency of the wavelength conversion element of Example 6, which is equivalent to the wavelength conversion element 1 of the embodiment, was 82%.

As described above, the phosphor ceramic layer (phosphor ceramic layer 20 a ) included in the wavelength conversion element of Example 5 is composed of the first crystal phase and the second crystal phase having different refractive indices from each other.

As a result, regions with different refractive indices are generated in the phosphor ceramic layer 20a, so that the excitation light L1 and the fluorescent light are easily dispersed. As a result, the light guide in the plane direction (that is, the x-axis direction or the y-axis direction) of the layers shown in FIGS. 5A and 5B in the embodiment is suppressed, and the light-emitting area of the phosphor ceramic layer 20a becomes smaller. . Therefore, the coupling efficiency of the wavelength conversion element of Example 5 becomes higher than that of the wavelength conversion element of Example 6. That is, the wavelength conversion element (wavelength conversion element 1 a ) of Example 5 with smaller etendue and higher light utilization efficiency is realized. When the projector is provided with these wavelength conversion elements 1a, the light utilization efficiency of the projector can be further improved.

In addition, the phosphor ceramic layer 20a includes a single-phase portion and a mixed-phase portion distinguished from the single-phase portion. In the single-phase portion, only the first crystal phase among the first crystal phase and the second crystal phase is provided; in the mixed-phase portion, both the first crystal phase and the second crystal phase are provided in a mixed manner. The refractive index of the single-phase portion and the refractive index of the mixed-phase portion are different from each other.

As a result, regions with different refractive indices are generated in the phosphor ceramic layer 20a, so that the excitation light L1 and the fluorescent light are more easily dispersed. As a result, the light-emitting area of the phosphor ceramic layer 20a becomes smaller. Therefore, the wavelength conversion element 1a with smaller etendue and higher light utilization efficiency can be realized.

In addition, when the size of the mixed-phase portion is within the above-mentioned range, the excitation light L1 and the fluorescent light are more easily dispersed.

In addition, the phosphor ceramic layer 20a includes a plurality of mixed-phase portions. The periphery of each of the plural mixed-phase parts is surrounded by the single-phase part.

Thereby, the excitation light L1 and the fluorescent light are more easily dispersed. As a result, the light-emitting area of the phosphor ceramic layer 20a becomes smaller. Therefore, the wavelength conversion element 1a with smaller etendue and higher light utilization efficiency is realized.

The above results show that not only the light guide suppressing effect produced by the thin film thickness of the phosphor ceramic layer 20a, but also the light guide suppressing effect of the phosphor ceramic layer 20a itself, improves the bonding efficiency of the wavelength conversion element 1a. That is, it was shown that even if the film thickness of the phosphor ceramic layer 20a is not controlled, the bonding efficiency of the wavelength conversion element 1a is improved.

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.

Thereby, the excitation light L1 and the fluorescent light are more easily dispersed. As a result, the light-emitting area of the phosphor ceramic layer 20a becomes smaller. Therefore, the wavelength conversion element 1a with smaller etendue and higher light utilization efficiency is realized.

In addition, the second crystal phase is a crystal phase represented by (Y _{1 - y} Ce _y )AlO ₃ (0≦y<0.1).

This makes it easy to make 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 configuration of the phosphor ceramic layer 20b different from that of the phosphor ceramic layers 20 and 20a will be described.

FIG. 12 is a perspective view of the phosphor ceramic member of this modification.

As an example, the phosphor ceramic member of the present modification is a phosphor ceramic layer 20b having a layered shape.

Like the phosphor ceramic layers 20 and 20a shown in the embodiment and modification 1, the phosphor ceramic layer 20b is a member used in a projector.

The phosphor ceramic layer 20b has the same configuration as the phosphor ceramic layer 20a of Modification 1 except for the following point. Specifically, in this regard, the Ce ^{3 +} existence ratio is set to 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 from each other. In addition, in this modification, the first crystal phase and the second crystal phase are crystal phases represented by YAG and YAP, respectively; the phosphor ceramic layer 20b also mainly includes the first crystal phase. In addition, the density of the phosphor ceramic member (phosphor ceramic layer 20b) is preferably 95% or more and 100% or less of the theoretical density, more preferably 97% or more and 100% or less of the theoretical density. In addition, the film thickness of the phosphor ceramic member (phosphor ceramic layer 20b) is preferably not particularly limited, but when a limit is set, it is preferably 50 μm or more and less than 500 μm, more preferably 50 μm or more and less than 300 μm. In addition, the film thickness is more preferably 50 μm or more and less than 120 μm.

The phosphor ceramic member (phosphor ceramic layer 20 b ) has the above-described configuration. Therefore, when the phosphor ceramic layer 20b is used in a projector and irradiated with excitation light, regions with different refractive indices are generated in the phosphor ceramic layer 20b, so that the excitation light and the fluorescent light are more dispersed. As a result, the light guide in the plane direction of the layer (that is, the x-axis direction or the y-axis direction) shown in FIGS. 5A and 5B in the embodiment is suppressed, and the light-emitting area of the phosphor ceramic layer 20b becomes smaller. . Therefore, it becomes a phosphor ceramic member with smaller etendue and higher light utilization efficiency. When the projector is provided with these phosphor ceramic members (the phosphor ceramic layer 20 b ), the light utilization efficiency of the projector can be further improved.

Further, the phosphor ceramic layer 20b is composed of YAG and YAP having Ce ^{3 +} and Ce ^{4 +} , that is, the phosphor ceramic layer 20b includes Ce ^{3 +} and Ce ^{4 +} . Here, in the phosphor ceramic layer 20b, Ce ^{3 +} ×100%/(Ce ^{3 +} +Ce ^{4 +} )≧60%, that is, the Ce ^{3 +} existence ratio is 60% or more.

In the phosphor ceramic layer 20b in which the Ce ^{3 +} existence ratio is 60% or more, the non-luminescence relaxation loss due to Ce ^{4 +} is reduced, so that the luminous efficiency becomes high. Furthermore, in the projector provided with these phosphor ceramic layers 20b, the light utilization efficiency can be improved. For example, a projector with low power consumption can be realized.

In addition, since the non-emission relaxation loss due to Ce ^{4 +} is reduced, the heat generation of the phosphor ceramic layer 20b is reduced. Therefore, in a projector provided with these phosphor ceramic layers 20b, the maximum input energy of excitation light can be increased, that is, a projector with high output can be realized.

(Other Embodiments) As mentioned above, although the wavelength conversion element etc. of this invention were demonstrated based on embodiment and modification, this invention is not limited to these embodiment and modification. Unless deviating from the gist of the present invention, the embodiment and the modification may be constructed by various modifications that are conceivable by those skilled in the art, or by combining some of the constituent elements of the embodiment and the modification Other forms are included in the scope of the present invention.

In addition, in embodiment, although the light source is a semiconductor laser light source, it is not limited to this form, An LED light source may be sufficient as it.

In addition, various changes, substitutions, additions, omissions, and the like can be made in the above-described embodiments within the scope of the claims of the invention or their equivalents.

1, 1a, 1x: wavelength conversion element 10: Substrate 100: Projector 11: Substrate body 12: Light reflection layer 121: Light Scattering Particles 122: Binder 13: light reflecting surface 2: Pore member 2a: Opening 20, 20a, 20b, 20x: phosphor ceramic layer 3: Light source 30: Anti-reflection layer 4: Motor 5: Beamsplitter 6: Display components 7: Projection optics 8: Reflector D, Dx: distance L1: Excitation light L12: transmitted light L2, L2x: Reflected light

FIG. 1 is a perspective view of a wavelength conversion element according to an embodiment. FIG. 2 is a cross-sectional view showing a cross-section of the wavelength conversion element along the line II-II of FIG. 1 . FIG. 3 is a perspective view showing the appearance of the projector according to the embodiment. FIG. 4 is a schematic diagram of the optical system of the projector according to the embodiment. FIG. 5A is a schematic diagram of the wavelength conversion element and the aperture member of the embodiment. 5B is a schematic diagram of the wavelength conversion element and the aperture member in the comparative example of the embodiment. FIG. 6 is a graph showing the evaluation results of the wavelength conversion elements of Examples and Comparative Examples of the embodiment. FIG. 7 is a graph showing the evaluation result of the wavelength conversion element of the example of the embodiment. FIG. 8 is a perspective view of the wavelength conversion element of Modification 1. FIG. FIG. 9 is a cross-sectional view showing a cross-section of the wavelength conversion element on line IX-IX of FIG. 8 . FIGS. 10( a ) to ( c ) are SEM images showing the cross section of the phosphor ceramic layer of the Example of Modification 1. FIG. FIG. 11 is a graph showing the evaluation results of the wavelength conversion element of the Example of Modification 1. FIG. FIG. 12 is a perspective view showing a phosphor ceramic member of Modification 2. FIG.

1: wavelength conversion element

10: Substrate

11: Substrate body

12: Light reflection layer

13: light reflecting surface

20: phosphor ceramic layer

30: Anti-reflection layer

121: Light Scattering Particles

122: Binder

L1: Excitation light

Claims (16)

A wavelength conversion element, used in a projector, receives excitation light and emits reflected light including fluorescent light, comprising: a substrate having a light reflecting surface; and a phosphor ceramic layer, located above the light-reflecting surface, comprising a first crystal phase having a garnet structure; The visible light reflectance of the light reflecting surface is more than 95% and less than 100%; The density of the phosphor ceramic layer is more than 97% and less than 100% of the theoretical density; The film thickness of the phosphor ceramic layer is 50 μm or more and less than 120 μm. The wavelength conversion element of claim 1, wherein, The film thickness of the phosphor ceramic layer is 70 μm or more and less than 120 μm. The wavelength conversion element of claim 1, wherein, It further comprises an anti-reflection layer, which is located above the phosphor ceramic layer to prevent the reflection of the excitation light. The wavelength conversion element of claim 1, wherein, The substrate includes a substrate body and a light reflection layer; The light reflection surface is formed by a surface included in the light reflection layer. The wavelength conversion element of claim 4, wherein, The light-reflecting layer contains light-scattering particles. The wavelength conversion element of claim 4, wherein, The light reflection layer contains Ag. The wavelength conversion element of claim 1, wherein the phosphor ceramic layer is composed of the first crystal phase represented by (Y _{1 - x} Ce _x ) ₃ Al ₅ O ₁₂ (0.001≦x<0.1). The wavelength conversion element according to claim 1, wherein the density of the phosphor ceramic layer is 4.41 g/cm ³ or more and 4.55 g/cm ³ or less. The wavelength conversion element of claim 1, wherein, The phosphor ceramic layer further includes a second crystal phase having a structure different from the garnet structure. The wavelength conversion element of claim 9, wherein, The phosphor ceramic layer includes a single-phase portion and a mixed-phase portion different from the single-phase portion; In the single-phase portion, only the first crystal phase among the first crystal phase and the second crystal phase is provided; In the mixed phase portion, both the first crystal phase and the second crystal phase are provided in a mixed manner. The wavelength conversion element of claim 10, wherein, The phosphor ceramic layer includes a plurality of the mixed-phase portions; The periphery of each of the plurality of mixed-phase parts is surrounded by the single-phase part. The wavelength conversion element of claim 9, wherein, 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. The wavelength conversion element according to claim 9, wherein the second crystal phase is a crystal phase represented by (Y _{1 - y} C _y )AlO ₃ (0≦y<0.1). The wavelength conversion element according to any one of claims 1 to 13, wherein the phosphor ceramic layer contains Ce ^{3 +} and Ce ^{4 +} ; and Ce ^{3 +} ×100%/(Ce ^{3 +} +Ce ^{4 +} )≧ 60%. A projector comprising: an excitation light source that emits excitation light; and The wavelength conversion element according to any one of claims 1 to 14 receives the excitation light and emits reflected light including fluorescence. A phosphor ceramic component used in a projector, comprising: a first crystalline phase having a garnet structure; and The second crystal phase has a structure other than the garnet structure; The density of the phosphor ceramic component is more than 97% and less than 100% of the theoretical density; The film thickness of the phosphor ceramic member is 50 μm or more and less than 300 μm.

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