TWI845965B - Fluorescent ceramic components - Google Patents

Abstract

The present invention provides a wavelength conversion element, a projector and a fluorescent ceramic component with high light utilization efficiency. The wavelength conversion element 1 is used in the projector 100, receives excitation light L1, and emits reflected light L2 containing fluorescent light, and comprises: a substrate 10 having a light reflecting surface 13; and a fluorescent ceramic layer 20, which is located above the light reflecting surface 13 and contains a first crystalline phase having a garnet structure; the visible light reflectivity of the light reflecting surface 13 is greater than 95% and less than 100%; the density of the fluorescent ceramic layer 20 is greater than 97% and less than 100% of the theoretical density; and the film thickness of the fluorescent ceramic layer 20 is greater than 50 μm and less than 120 μm.

Description

Fluorescent ceramic components

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

In the past, a wavelength conversion element used in a projector was known.

For example, the wavelength conversion element disclosed in Patent Document 1 has a circular substrate in a top view and a fluorescent layer (fluorescent ceramic component) arranged along the circumferential direction of the substrate, which can be rotated by a motor connected to the center of the substrate. In Patent Document 1, this wavelength conversion element acts as a reflective fluorescent wheel of a projector, and the fluorescent light emitted by the fluorescent layer of the wavelength conversion element is used as the light (projection light) emitted by the projector.

[Learning Technology Literature]

[Patent Literature]

Patent document 1: Japanese Patent Publication No. 2019-66880

However, the above-mentioned known wavelength conversion elements, projectors and fluorescent ceramic components have problems such as low light utilization efficiency. Therefore, the present invention provides a wavelength conversion element, projector and fluorescent ceramic component with high light utilization efficiency.

A wavelength conversion element of one aspect of the present invention is used in a projector, receives excitation light, and emits reflected light including fluorescence, and comprises: a substrate having a light reflecting surface; and a fluorescent ceramic layer, located above the light reflecting surface, including a first crystal phase having a garnet structure; the visible light reflectivity of the light reflecting surface is greater than 95% and less than 100%; the density of the fluorescent ceramic layer is greater than 97% and less than 100% of the theoretical density; the film thickness of the fluorescent ceramic layer is greater than 50μm and less than 120μm.

In addition, a projector of one embodiment of the present invention comprises: an excitation light source that emits excitation light; and a wavelength conversion element that receives the excitation light and emits reflected light containing fluorescence.

In addition, a fluorescent ceramic component of one embodiment of the present invention is used in a projector, and includes a first crystal phase having a garnet structure and a second crystal phase having a structure other than a garnet structure; the density of the fluorescent ceramic component is greater than 97% and less than 100% of the theoretical density; the film thickness of the fluorescent ceramic component is greater than 50 μm and less than 300 μm.

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

1,1a,1x: Wavelength conversion element

10: Substrate

100: Projector

11: Substrate body

12: Light reflection layer

121: Light scattering particles

122: Adhesive

13: Light reflecting surface

2: Porous components

2a: Opening

20,20a,20b,20x: Fluorescent ceramic layer

3: Light source

30: Anti-reflection layer

4: Motor

5: Spectroscope

6: Display components

7: Projection optical components

8: Reflector

D,Dx: distance

L1: Excitation light

L12: Transmitted light

L2, L2x: reflected light

Figure 1 is a three-dimensional diagram of the wavelength conversion element in an implementation form.

FIG2 is a cross-sectional view showing the cross section of the wavelength conversion element along line II-II in FIG1.

FIG3 is a three-dimensional diagram showing the appearance of the projector in an implementation form.

FIG4 is a schematic diagram of the optical system of the projector in an implementation form.

FIG5A is a schematic diagram of a wavelength conversion element and a pore component of an implementation form.

FIG5B is a schematic diagram of a wavelength conversion element and a pore component of a comparative example of an implementation form.

FIG6 is a diagram showing the evaluation results of the wavelength conversion element of the embodiment and the comparative example of the implementation form.

FIG. 7 is a diagram showing the evaluation results of the wavelength conversion element of the embodiment of the implementation form.

Figure 8 is a three-dimensional diagram of the wavelength conversion element of variant example 1.

FIG9 is a cross-sectional view showing the cross-section of the wavelength conversion element along line IX-IX of FIG8.

Figure 10 (a) to (c) show the cross-sectional SEM images of the fluorescent ceramic layer of the embodiment of variant example 1.

FIG11 is a diagram showing the evaluation results of the wavelength conversion element of the embodiment of variant 1.

FIG. 12 is a three-dimensional diagram showing the fluorescent ceramic component of variation 2.

The following uses diagrams to explain in detail the wavelength conversion element and other aspects of the implementation form of the present invention.

In addition, the embodiments described below are all comprehensive or specific examples. The values, shapes, materials, components, configuration positions and connection forms of components, processes, and process sequences shown in the embodiments described below are all examples, and the main purpose is not to limit the present invention. In addition, the components of the embodiments described below that are not described in the independent claim items are described as arbitrary components.

In addition, each figure is a schematic diagram and is not a strict illustration. Therefore, for example, the scales in each figure do not necessarily have to be consistent. In addition, in each figure, the same symbols are given to substantially the same components, and repeated explanations are omitted or simplified.

In this specification, terms such as parallel or orthogonal that indicate the relationship between elements, terms such as circular or elliptical that indicate the shape of elements, and numerical ranges are not intended to be strictly defined, but are intended to include substantially equivalent ranges, such as those with differences of a few percent.

In addition, in this specification, "top view" refers to observing the wavelength conversion element in the direction perpendicular to the light reflecting surface of the substrate.

In addition, in this specification, the terms "above" and "below" of the wavelength conversion element do not refer to the absolute top (directly above the lead) and bottom (directly below the lead) in spatial cognition, but are terms defined by relative positional relationships based on the stacking order of the stacking structure. In addition, the terms "above" and "below" are applicable not only to the case where two components are arranged with a gap between them and there are other components between them, but also to the case where two components are arranged in close proximity to each other and the two components are in contact.

In addition, in this specification and drawings, the x-axis, y-axis, and z-axis represent the three axes of the three-dimensional orthogonal coordinate system. In each implementation form, the two axes parallel to the light reflection surface of the substrate are the x-axis and the y-axis, and the direction orthogonal to the light reflection surface is the z-axis direction. In addition, in each implementation form described below, there is a case where the positive direction of the z-axis is recorded as the top and the negative direction of the z-axis is recorded as the bottom.

(Implementation form)

[Structure of wavelength conversion element]

First, the structure of the wavelength conversion element 1 of this embodiment is explained using diagrams. FIG. 1 is a three-dimensional diagram of the wavelength conversion element 1 of this embodiment. FIG. 2 is a cross-sectional diagram showing the cross-section of the wavelength conversion element 1 along the II-II line of FIG. 1 .

As shown in FIG. 1 and FIG. 2 , the wavelength conversion element 1 is an element having a substrate 10 having a light reflecting surface 13, a fluorescent ceramic layer 20, and an anti-reflection layer 30.

In this embodiment, the wavelength conversion element 1 is a fluorescent wheel used in a projector to receive excitation light L1 and emit reflected light including fluorescence. The wavelength conversion element 1 has a disc shape, and a rotationally driven motor 4 is provided in the center of the wavelength conversion element 1 when viewed from above. Therefore, the wavelength conversion element 1 is rotationally driven in the direction of the arrow shown in Figure 1 with the motor 4 as the axis by the motor 4.

In addition, FIG. 1 shows a structure of a fluorescent wheel provided with a motor 4, but the wavelength conversion element 1 may not have a motor 4. In other words, the wavelength conversion element 1 may be a fixed element without being driven in rotation. With such a structure, the wavelength conversion element 1 becomes small, so a compact projector can be provided.

The fluorescent 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 fluorescent ceramic layer 20 is arranged in a ring shape on a circle with equal distances from the rotation center of the wavelength conversion element 1 (i.e., where the motor 4 is arranged). That is, the fluorescent ceramic layer 20 is arranged in a belt shape along the circumferential direction when viewed from above.

The fluorescent ceramic layer 20 includes a first crystalline phase having a garnet structure. More specifically, in the present embodiment, the fluorescent ceramic layer 20 is composed only of the first crystalline phase having a garnet structure. That is, the fluorescent ceramic layer 20 of the present embodiment does not contain a crystalline phase having a structure different from the garnet structure. The garnet structure is a crystalline structure represented by the general formula of A ₃ B ₂ C ₃ O _12. As element A, rare earth elements such as Ca, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb and Lu are used; as element B, elements such as Mg, Al, Si, Ga and Sc are used; as element C, elements such as Al, Si and Ga are used. Examples of such garnet structures include YAG (Yttrium Aluminum Garnet), LuAG (Lutetium Aluminum Garnet), Lu ₂ CaMg ₂ Si ₃ O ₁₂ (Lutetium Calcium Magnesium Silicon Garnet), and TAG (Terbium Aluminum Garnet). In the present embodiment, the fluorescent ceramic layer 20 is composed of a first crystalline phase represented by (Y _1-x Ce _x ) ₃ Al ₂ Al ₃ O ₁₂ (i.e., (Y _1-x Ce _x ) ₃ Al ₅ O ₁₂ )(0.001≦x<0.1), namely, YAG.

In addition, the first crystal phase constituting the fluorescent 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 (Y1 _{-xCex ) 3Al2Al3O12} (0.001≦x<0.1) _and a solid solution of a garnet crystal phase represented by (Lu1 _{-dCed ) 3Al2Al3O12} (0.001≦ _d <0.1) (( ₁ - _a )( _{Y1 - xCex} ) _3Al5O12‧a ( _{Lu1 - dCed ) 3Al2Al3O12} (0<a< ₁ )). In addition, as such solid solutions, there can be _{listed a garnet crystal} phase represented by ( _{Y1- xCex} ) _3Al2Al3O12 (0.001≦x<0.1) _and a solid solution of _a garnet crystal phase represented by (Lu1 _{-zCez ) 2CaMg2Si3O12} (0.0015≦z<0.15 _{) (} (1 _- b ₎ (Y1-xCex _{) 3Al2Al3O12‧b (} Lu1 _{-zCez ) 2CaMg2Si3O12 (} 0< _b <1)), etc. By forming the fluorescent ceramic layer 20 with a solid solution of multiple garnet crystal phases with different chemical compositions, the fluorescent spectrum of the fluorescent light emitted by the fluorescent ceramic layer 20 is made wider, and the green light component and the red light component are increased. Therefore, a projector that emits projection light with a wide color range can be provided.

In addition, the first crystalline phase constituting the fluorescent ceramic layer 20 may also include a crystalline phase having a chemical composition shifted relative to the crystalline phase represented by the above general formula A ₃ B ₂ C ₃ O _12. Examples of such crystalline phases include (Y _1-x Ce _x ) ₃ Al ₂ Al ₃ O ₁₂ (0.001≦x<0.1) which is Al-rich (Y 1-x Ce x ) ₃ Al _2+δ Al 3 O 12 (δ is a positive number) relative to the crystalline phase represented by (Y _1-x Ce _x ) 3 Al 2 Al ₃ O ₁₂ (0.001≦x<0.1). In addition, as such crystalline phases, there can be cited Y-rich (Y1 _{-xCex ) 3 + ζAl2Al3O12} (ζ is a positive number) relative to the crystalline phase represented by (Y1 _{-xCex ) 3Al2Al3O12} (0.001≦x< _0.1 ). Such crystalline phases, relative to the _{crystalline phase} represented by the general formula _{A3B2C3O12 ,} have a shifted chemical composition, but still maintain a garnet structure. By making _the fluorescent ceramic layer ₂₀ consist of a crystalline phase with a shifted chemical composition, regions with different refractive _indices are generated in the fluorescent ceramic layer 20, so that the excitation light L1 and the fluorescence are more dispersed, and the light-emitting area of the fluorescent ceramic layer 20 becomes smaller. Therefore, a wavelength conversion element 1 and a projector with smaller etendue and higher light utilization efficiency can be provided.

Furthermore, the fluorescent ceramic layer 20 may also include the first crystalline phase and different phases having structures other than the garnet structure. By constituting the fluorescent ceramic layer 20 with the first crystalline phase and different phases, regions with different refractive indices are generated in the fluorescent ceramic layer 20, so that the excitation light L1 and the fluorescence are more dispersed, and the luminous area of the fluorescent ceramic layer 20 becomes smaller. Therefore, a wavelength conversion element 1 and a projector with smaller light spread and higher light utilization efficiency can be provided.

The fluorescent ceramic layer 20 composed of YAG receives the light incident from the upper side of the wavelength conversion element 1 as the excitation light L1 and emits fluorescence. More specifically, the light emitted from the excitation light source described later is irradiated on the fluorescent ceramic layer 20 as the excitation light L1, so that the fluorescent ceramic layer 20 emits fluorescence as the wavelength conversion light. That is, the wavelength conversion light emitted from the fluorescent ceramic layer 20 is light having a longer wavelength than the wavelength of the excitation light L1.

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

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

The density of the fluorescent ceramic layer 20 is preferably 95% to 100% of the theoretical density, and more preferably 97% to 100% of the theoretical density. Here, the theoretical density is the density when the atoms in the layer are ideally arranged. In other words, the theoretical density is the density when there is no void in the fluorescent ceramic layer 20, and is a value calculated using the crystal structure. For example, when the density of the fluorescent ceramic layer 20 is 99%, the remaining 1% is equivalent to the void. That is, the higher the density of the fluorescent ceramic layer 20, the fewer the voids. If the density of the fluorescent ceramic layer 20 is within the above range, the total amount of fluorescence emitted by the fluorescent ceramic layer 20 increases, so a wavelength conversion element 1 and a projector with a larger amount of radiated light can be provided.

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

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

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

The anti-reflection layer 30 is a layer that prevents, or more specifically, suppresses, the reflection of the excitation light L1. The anti-reflection layer 30 reduces the reflectivity of the excitation light L1 in the wavelength conversion element 1, thereby increasing the amount of excitation light L1 reaching the fluorescent ceramic layer 20. As a result, the amount of excitation light L1 that can be absorbed by the fluorescent ceramic layer 20 also increases, so the amount of fluorescence emitted by the fluorescent ceramic layer 20 also increases. That is, by providing the anti-reflection layer 30, the amount of fluorescence emitted by the fluorescent ceramic layer 20 increases.

The anti-reflection layer 30 may be formed of, for example, a dielectric film or a fine concavo-convex structure with a period smaller than the wavelength of light in the visible light range (so-called moth-eye structure). 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 _SiO2 , _TiO2 , _Al2O3 , ZnO, _Nb2O5 , and MgF.

In addition, FIG. 1 and FIG. 2 show the configuration of an anti-reflection layer 30, but the wavelength conversion element 1 may not have an anti-reflection layer 30.

The substrate 10 is a disk-shaped plate and is a base material that supports the fluorescent ceramic layer 20 and the anti-reflection layer 30. The motor 4 is disposed in the center of the substrate 10 when viewed from above. As shown in FIG. 2 , the substrate 10 has a substrate body 11 and a light reflecting layer 12.

The substrate body 11 is preferably made of a material with high thermal conductivity. For example, the substrate body 11 is preferably made of a material with higher thermal conductivity than the fluorescent 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, etc. In addition, the substrate body 11 can also be made of a resin such as a PEN (polyethylene naphthalate) film or a PET (polyethylene terephthalate) film. Furthermore, when the substrate body 11 is a metal substrate, the substrate body 11 is made of 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 is lightweight, 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, less than 1.5 mm.

In addition, 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 fluorescent ceramic layer 20 is located. In this embodiment, the light reflecting surface 13 is composed of a surface included in the light reflecting layer 12.

The light reflecting surface 13 is a surface that reflects the fluorescence emitted by the fluorescent ceramic layer 20. In addition, the light reflecting surface 13 also reflects the excitation light L1 that is not converted into fluorescence in the fluorescent ceramic layer 20. The light reflecting surface 13 reflects the fluorescence and the excitation light L1 that is not converted into fluorescence upward. In this embodiment, the fluorescence and the excitation light L1 are light rays in the visible light range, so the higher the visible light reflectivity of the light reflecting surface 13, the less light loss. Specifically, the visible light reflectivity of the light reflecting surface 13 is preferably greater than 90% and less than 100%, and more preferably greater than 95% and less than 100%. If the visible light reflectivity of the light reflecting surface 13 is within the above range, the fluorescence and the excitation light L1 are reflected further upward, so the waveguide of the fluorescence and the excitation light L1 in the lateral direction (i.e., the direction parallel to the light reflecting surface 13) is suppressed, and the luminous area becomes smaller. Therefore, a wavelength conversion element 1 and a projector with a smaller light spread and higher light utilization efficiency can be provided. In addition, the reflectivity of the light in the wavelength range of 490nm to 780nm of the light reflecting surface 13 is preferably 90% to 100%, and more preferably 95% to 100%. If the reflectivity of the light in the wavelength range of 490nm to 780nm of the light reflecting surface 13 is within the above range, the fluorescence is reflected further upward, so the waveguide of the fluorescence in the lateral direction is suppressed, and the luminous area becomes smaller. Therefore, a wavelength conversion element 1 and a projector with smaller light spread and higher light utilization efficiency can be provided. In addition, in this embodiment, the visible light range is a wavelength range of 380nm to 780nm.

The light reflecting layer 12 can be made of any material as long as it can reflect the fluorescence and the excitation light L1 that is not converted into fluorescence upward. In the present embodiment, the light reflecting layer 12 is a composite layer composed of light scattering particles 121 and a binder 122 that disperses the light scattering particles 121. That is, the light reflecting layer 12 has light diffusion (light scattering) and reflects the fluorescence and the excitation light L1 that is not converted into fluorescence upward by light diffusion.

The light reflecting 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 can be inorganic compounds such as SiO2, TiO2, Al2O3 , ZnO , Nb2O5} , _ZrO2 , and _{CaCO3 ,} or resin materials such as styrene resins and acrylic resins. In addition, the binder 122 is preferably made of resin materials such as acrylic resins and silicone resins that are light-transmissive.

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

In addition, the light reflecting layer 12 may also be a metal layer composed of a metal having light reflectivity. For example, the metal is Ag, Al, or an alloy containing any of them. The light reflecting layer 12 is preferably formed by dry processing or wet processing of the metal. In such a case, the same effect as the case where the light reflecting layer 12 is composed of a composite layer containing light scattering particles 121 can also be expected.

In addition, a bonding layer may be provided between the light reflecting layer 12 and the fluorescent ceramic layer 20. By adopting such a structure, the light reflecting layer 12 and the fluorescent ceramic layer 20 can be more closely connected, so the heat generated in the fluorescent ceramic layer 20 can be more efficiently conducted to the substrate body 11 through the light reflecting layer 12. Therefore, a wavelength conversion element 1 with less thermal quenching of the fluorescent ceramic layer 20 and high efficiency can be provided. The bonding layer is preferably made of a transparent material such as a silicone resin or an epoxy resin. In addition, the thickness of the bonding layer is preferably greater than 1μm and less than 100μm, and more preferably greater than 1μm and less than 20μm.

In addition, FIG. 1 and FIG. 2 show the structure of providing a light reflecting layer 12, but the wavelength conversion element 1 may not have the light reflecting layer 12. In this case, the surface of the substrate body 11 becomes the light reflecting surface 13.

[Projector structure]

The wavelength conversion element 1 constructed as described above is used in the projector 100 shown in FIG. 3 and FIG. 4. FIG. 3 is a three-dimensional diagram showing the appearance of the projector 100 of this embodiment. FIG. 4 is a schematic diagram of the optical system of the projector 100 of this embodiment. The following uses FIG. 3 and FIG. 4 to explain the structure of the projector 100 of this embodiment.

As shown in FIG. 3 and FIG. 4 , the projector 100 of this embodiment has: a light source 3, a dichroic mirror 5, a wavelength conversion element 1, a display element 6, a projection optical component 7, and a reflective mirror 8.

The light source 3, for example, is a semiconductor laser light source or an LED (Light Emitting Diode) light source, which 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. In addition, the semiconductor laser element of the light source 3 is, for example, a GaN semiconductor laser element (laser chip) composed 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, light source 3 emits laser light in the range of near-ultraviolet to blue light with a peak wavelength of 380nm to 490nm. More specifically, light source 3 emits blue light with a peak wavelength of 445nm. Light source 3 of this embodiment is an example of an excitation light source. The laser light emitted by light source 3 reaches spectroscope 5.

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

That is, the spectroscope 5 has the characteristic of reflecting and transmitting the 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 passes through the spectroscope 5 without changing the direction; the other part of the laser light is reflected by the spectroscope 5, and the direction changes by 90°, and goes to the wavelength conversion element 1.

Here, another 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 the excitation light L1 and emits the reflected light L2 including the fluorescence. More specifically, the reflected light L2 includes the light converted and reflected by the fluorescent ceramic layer 20 and the light reflecting surface 13 respectively provided by the wavelength conversion element 1. More specifically, the reflected light L2 is the light including the yellow fluorescence generated by the fluorescent ceramic layer 20 and the blue light of the excitation light L1 which is not converted by the fluorescent ceramic layer 20. However, the proportion of fluorescence in the reflected light L2 is high, so the reflected light L2 is yellow light.

The laser light that passes through the dichroic mirror 5 without changing its direction reaches the reflector 8 as the transmitted light L12, and is reflected by the reflector 8 and goes to the other side of the dichroic mirror 5. Then, the transmitted light L12 is reflected by the other side of the dichroic mirror 5, and its direction is changed by 90°, and goes to the display element 6.

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

Thus, as shown in FIG4 , the optical axis of the reflected light L2 is consistent 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 compounded by these light rays is white light. That is, the light from the spectroscope 5 to the display element 6 is white light.

The mixed light of the reflected light L2 and the transmitted light L12, i.e., white light, goes to the display element 6. Here, if the reflected light L2 is a light with a large light spread, the size of the reflected light L2 irradiated to the display element 6 becomes larger compared to the size of the display element 6. Therefore, the ineffective (i.e., unusable) light components that are not irradiated to the display element 6 increase.

The display element 6 is a roughly planar element that controls the light (white light) passing through the opening 2a and outputs it as an image. In other words, the display element 6 generates light for the image. Specifically, the display element 6 is a DLP (Digital Light Processing) element having a DMD (Digital Micromirror Device). In addition, for example, the display element 6 can also be a reflective liquid crystal panel. In addition, between the display element 6 and the spectroscope 5, a compound eye lens, a polarization conversion element, and a mirror rod can also be provided.

The image light generated by the display element 6 is magnified and projected onto the screen through the projection optical component 7.

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

[Light behavior of wavelength conversion elements]

Here, the optical behavior of the wavelength conversion element 1 is explained 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 of the comparative example of the present embodiment. In addition, 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 explanation.

Here, the aperture member 2 is a member used to evaluate the size of the light etendue of the reflected light L2. The aperture member 2 is a light absorbing member, and is a member having an opening 2a provided in the center of the aperture member 2. If the proportion of the light component passing through the opening 2a of the aperture member 2 is relatively large, it can be said that the light etendue of the reflected light L2 is small.

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

The density of the fluorescent ceramic layers 20 and 20x is 4.41 g/cm ³ or more and 4.55 g/cm ³ or less, which is high. That is, there are few gaps in the fluorescent ceramic layers 20 and 20x and light scattering is not easy to occur, so light is easy to advance in the plane direction of the layer (that is, the x-axis direction or the y-axis direction), and so-called light guiding is easy to occur.

First, using Figure 5A, the wavelength conversion element 1 of this embodiment is explained.

If the thickness of the fluorescent ceramic layer 20 is very thin (50 μm or more and 120 μm or less) as in the present embodiment, the distance D in the plane direction of the layer (here, the x-axis direction) from the incidence of the excitation light L1 to the emission of the reflected light L2 can be further shortened. In other words, in the present embodiment, the luminous area (luminous spot diameter) of the fluorescent 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 fluorescent ceramic layer 20 can easily pass through the opening 2a of the aperture member 2. The light passing through the opening 2a can be used as light to be magnified and projected to 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 fluorescent ceramic layer 20 of the wavelength conversion element 1 is very thin, so the fluorescent light emitting area can be made very small. Therefore, more light passes through the opening 2a of the aperture member 2, so more light can be used as the projection light of the projector 100. That is, by the above-mentioned structure, a wavelength conversion element 1 with high light utilization efficiency is realized. Furthermore, by having such a wavelength conversion element 1, a projector 100 with high light utilization efficiency is realized.

Next, the wavelength conversion element 1x of the comparative example is explained using FIG. 5B .

If the thickness of the fluorescent ceramic layer 20x in the comparative example is very thick (200μm), the distance Dx in the plane direction of the layer from the incident excitation light L1 to the emission of the reflected light L2x becomes longer. In other words, in the comparative example, the luminous area (luminous spot diameter) of the fluorescent ceramic layer 20x becomes larger. Therefore, as shown in FIG5B, the reflected light L2x emitted from the fluorescent ceramic layer 20x by reflection on the light reflecting surface 13 is easily shielded by the aperture component 2. Therefore, the wavelength conversion element 1x in 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 forming the light reflecting layer 12 with a composite layer including light scattering particles 121, the visible light reflectivity of the light reflecting surface 13 can be further improved. In this way, the loss of light in the wavelength conversion element 1 can be further suppressed, thereby realizing a wavelength conversion element 1 with high light utilization efficiency.

[Implementation example]

Here, in the wavelength conversion element of Examples 1 to 3 and the comparative example of this embodiment, the manufacturing method and light utilization efficiency are explained.

First, the manufacturing method of the fluorescent ceramic layer is described.

The fluorescent ceramic layers of Examples 1 to 3 and the comparative example are all composed of the first crystalline phase represented by (Y _0.9953 Ce _0.0047 ) ₃ Al ₅ O _12. In addition, the fluorescent ceramic layers of Examples 1 to 3 and the comparative example are all composed of Ce ³⁺ activated fluorescent materials.

The fluorescent ceramic layers of Examples 1 to 3 and Comparative Examples use the following three raw materials as compound powders. Specifically, _Y2O3 (yttrium oxide, _purity 3N, YTTRIUM Co., Ltd., Japan), _Al2O3 (aluminum oxide, purity 3N, Sumitomo Chemical Co. _, Ltd.) and _CeO2 (cathode oxide, purity 3N, YTTRIUM Co., Ltd., Japan) are used.

First, weigh the above raw materials to make a compound of the stoichiometric composition (Y _0.9953 Ce _0.0047 ) ₃ Al ₅ O ₁₂ . Then, put the weighed raw materials and alumina balls (diameter 10 mm) into a plastic pot. The amount of alumina balls is about 1/3 of the volume of the plastic pot. Then, pour pure water into the plastic pot and use a pot rotating device (BALL MILL ANZ-51S, manufactured by NITTO CHEMICAL CO., LTD.) to mix the raw materials and pure water. This mixing is carried out for 12 hours. In this way, a slurry-like mixed raw material is obtained.

The slurry mixed raw material is dried in a dryer. Specifically, a Naflon (registered trademark) sheet is laid to cover the inner wall of a metal plate, and the mixed raw material flows onto the top of the Naflon (registered trademark) sheet. The metal plate, Naflon (registered trademark) sheet, and mixed raw material are dried in a dryer set at 150°C for 8 hours. Afterwards, the dried mixed raw material is recovered and granulated using a spray drying device. In addition, polyvinyl alcohol is used as an adhesive (binder) during granulation.

The mixed raw materials to be granulated are temporarily molded into a cylindrical shape using an electric hydraulic press (EMP-5 manufactured by Riken Seiki Co., Ltd.) and a cylindrical mold (outer diameter 58mm, inner diameter 38mm, height 130mm). The pressure during molding is set to 5MPa/ ^cm2 . Then, the temporarily molded body is formally molded using a cold isostatic press device. The pressure during formal molding is set to 300MPa. In addition, the molded body after formal molding is subjected to heat treatment (de-binder treatment) for the purpose of removing the adhesive (binder) used during granulation. The temperature of the heat treatment is set to 500℃. In addition, the time of the heat treatment is set to 10 hours.

The molded body after heat treatment is forged in a tubular gas environment furnace. The forging temperature is 1675℃. In addition, the forging time is 4 hours. The forging gas environment is a mixed gas environment of nitrogen and hydrogen. In addition, the outer diameter and inner diameter of the forged product after forging are 43mm and 29mm respectively.

Use a multi-wire saw to slice the cylindrical forged material after forging. The thickness of the sliced cylindrical forged material is about 700μm.

The forged product after slicing is ground by a grinding device to adjust the thickness of the forged product. By performing this adjustment, the forged product becomes a fluorescent ceramic layer. The thickness of the fluorescent ceramic layer is 53μm in Example 1, 75μm in Example 2, 106μm in Example 3, and 206μm in the comparative example.

In addition, the outer diameter and inner diameter of the fluorescent ceramic layer of Examples 1 to 3 and the comparative example are 43 mm and 29 mm, respectively. In addition, the fluorescent ceramic layer of Examples 1 to 3 and the comparative example is dark yellow.

Next, the evaluation of the fluorescent ceramic layer is explained.

First, the density of the fluorescent ceramic layer of Examples 1 to 3 and the comparative example was evaluated using the Archimedean method. The density of the fluorescent ceramic layer of Examples 1 to 3 and the comparative example was 4.49 g/cm ³ . In addition, the density of the fluorescent ceramic layer of Examples 1 to 3 and the comparative example was 98.7% of the theoretical density (4.55 g/cm ³ ) of Y ₃ Al ₅ O _12. In other words, the density of the fluorescent ceramic layer of Examples 1 to 3 and the comparative example was 97% or more and 100% or less of the theoretical density of Y ₃ Al ₅ O ₁₂ .

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

First, prepare an Al disc-shaped substrate body (diameter 50mm, thickness 0.5mm). Then, use a dispensing device to apply a light-reflecting layer containing a silicon-based resin dispersed with _TiO2 particles to the substrate body, making it circular (outer diameter 46mm, inner diameter 30mm). Here, the silicon-based resin contained in the light-reflecting layer also functions as an adhesive to bond the fluorescent ceramic layer to the substrate body.

Afterwards, the fluorescent ceramic layer is arranged so as to overlap with the light reflecting layer coated in a circular shape. Here, the thickness of the light reflecting layer is made to be about 50μm, and the fluorescent ceramic layer is fixed by a metal fixture. Afterwards, the light reflecting layer is hardened by heat treatment using a dryer. The temperature of the heat treatment at this time is 150°C. In addition, the visible light reflectivity of one side of the light reflecting layer, namely the light reflecting surface, is more than 95%.

In this way, the wavelength conversion element of Examples 1 to 3 and the comparative example having the fluorescent ceramic layer and substrate of Examples 1 to 3 and the comparative example respectively can be obtained.

Furthermore, the evaluation of wavelength conversion components is explained.

An evaluation device for wavelength conversion elements using a reflective laser excitation method is used to evaluate the wavelength conversion elements of Examples 1 to 3 and the comparative example. Specifically, in the evaluation device, the rotating wavelength conversion element is irradiated with excitation light (laser light), 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, this laser light is a Gaussian beam. In addition, the rotation speed of the wavelength conversion element is 7200rpm. A pore member is set in the evaluation device, and the pore 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 greater than 3 mm and less than 100 mm; the opening of the aperture member is a circular hole with an opening diameter of greater than 5 mm and less than 10 mm.

FIG6 is a graph showing the evaluation results of the wavelength conversion elements of Examples 1 to 3 and the comparative example of this embodiment. Specifically, FIG6 shows the relative value of the fluorescence energy (after passing through the opening), the relative value of the fluorescence energy (before passing through the opening) and the combination efficiency of the wavelength conversion elements of Examples 1 to 3 and the comparative example.

Here, the relative value of 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 by the wavelength conversion element of the comparative example after passing through the opening is assumed to be 100%.

In addition, the relative value of the 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 by the wavelength conversion element of the comparative example after passing through the opening is set to 100%.

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

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

As shown in FIG6 , the combination efficiency of the wavelength conversion elements of Example 1, Example 2, Example 3 and the comparative example is 85%, 86%, 84% and 81% respectively. That is, the combination efficiency of the examples is higher than that of the comparative example. The higher the combination efficiency, the more light passing through the opening in the generated fluorescence, that is, as shown in FIG5A and FIG5B , the smaller the luminous area of the fluorescence emitted by the wavelength conversion element. That is, the luminous area of the fluorescence emitted by the wavelength conversion element of Examples 1 to 3 is smaller than the luminous area of the fluorescence emitted by the wavelength conversion element of the comparative example, indicating that the wavelength conversion element of the example has a high light utilization efficiency.

In addition, as shown in FIG. 6 , it can be clearly seen that by making the thickness of the fluorescent ceramic layer of Examples 1 to 3 within the range of 50 μm to 120 μm, the bonding efficiency is very high compared to the comparative example. That is, by making the thickness of the fluorescent ceramic layer 20 of the present embodiment above within the range of 50 μm to 120 μm, a wavelength conversion element 1 with high light utilization efficiency is realized.

In addition, the relative values of the fluorescent energy (after passing through the opening) of the wavelength conversion elements of Example 1, Example 2, Example 3 and the comparative example are 103%, 106%, 105% and 100%, respectively. That is, the relative values of the fluorescent energy (after passing through the opening) in Examples 1 to 3 are higher than the relative values of the fluorescent energy (after passing through the opening) in the comparative example. Among Examples 1 to 3, the relative values of the fluorescent energy (after passing through the opening) of the wavelength conversion elements of Example 2 in which the thickness of the fluorescent ceramic layer is 76μm and Example 3 in which the thickness of the fluorescent ceramic layer is 106μm are higher.

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

Furthermore, the relative values of the fluorescence energy of the wavelength conversion elements of Example 1, Example 2, Example 3 and the comparative example (before passing through the opening) are 121%, 124%, 125% and 124%, respectively. The relative value of the fluorescence energy of the wavelength conversion element of Example 1, where the thickness of the fluorescent ceramic layer is the thinnest at 53μm (before passing through the opening), is lower than the relative values of the fluorescence energy of the wavelength conversion elements of Examples 2 and 3 and the comparative example (before passing through the opening). The inventor believes that the reason is that in the wavelength conversion element of Example 1, the fluorescent ceramic layer is thin, so that the fluorescent ceramic layer cannot fully absorb the laser light.

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

First, the manufacturing method of the fluorescent ceramic layer of the wavelength conversion element of Example 4 of this embodiment is described.

The fluorescent ceramic layers of Example 4 are all composed of the first crystalline phase represented by (Y _0.997 Ce _0.003 ) ₃ Al ₅ O _12. In addition, the fluorescent ceramic layers of Example 4 are all composed of Ce ³⁺ activated phosphors.

In Example 4, except that the raw materials are weighed to form a compound of a stoichiometric composition of (Y _0.997 Ce _0.003 ) ₃ Al ₅ O ₁₂ , the sintered product is obtained in the same order as in Examples 1 to 3. That is, the main difference between the fluorescent ceramic layers of Examples 1 to 3 and the fluorescent ceramic layer of Example 4 is the different composition ratio of Y to Ce.

The thickness of the fluorescent ceramic layer in Example 4 is 103μm.

In addition, the outer diameter and inner diameter of the fluorescent ceramic layer of Example 4 are 41 mm and 27 mm. In addition, the fluorescent ceramic layer of Example 4 is dark yellow.

Next, the evaluation of the fluorescent ceramic layer is explained.

First, the density of the fluorescent ceramic layer of Example 4 was evaluated using the Archimedean method. The density of the fluorescent ceramic layer of Example 4 was 4.48 g/cm ³ . In addition, the density of the fluorescent ceramic layer of Example 4 was 98.4% of the theoretical density (4.55 g/cm ³ ) of Y ₃ Al ₅ O _12. In other words, the density of the fluorescent ceramic layer of Example 4 was 97% or more and 100% or less of the theoretical density of Y ₃ Al ₅ O ₁₂ .

In addition, as described above, the fluorescent ceramic layer 20 of the present embodiment is composed of YAG having Ce ³⁺ and Ce ⁴⁺ , that is, the fluorescent ceramic layer 20 contains Ce ³⁺ and Ce ⁴⁺ . Then, the Ce ³⁺ abundance ratio and Ce ⁴⁺ abundance ratio of the fluorescent ceramic layer of Example 4 are evaluated using a hard X-ray XAFS device. Specifically, the XAFS spectrum of the fluorescent ceramic layer of Example 4 is obtained in the range of 5687eV~5777eV using a hard X-ray XAFS device. The obtained XAFS spectrum is subjected to a fitting analysis of a reference spectrum of Ce ³⁺ and a reference spectrum of Ce ⁴⁺ to evaluate the Ce ³⁺ abundance ratio and the Ce ⁴⁺ abundance ratio. In addition, in order to obtain the reference spectra of Ce ³⁺ and Ce ⁴⁺ , CeO ₂ and CeF ₃ were evaluated under the same conditions.

Table 1 is a table showing the Ce ³⁺ abundance ratio and Ce ⁴⁺ abundance ratio of the fluorescent ceramic layer of Example 4. As shown in Table 1, the Ce ³⁺ abundance ratio and Ce ⁴⁺ abundance ratio of the fluorescent ceramic layer of Example 4 are 78.3% and 21.7%, respectively. In the fluorescent ceramic layer of Example 4, Ce ³⁺ ×100%/(Ce ³⁺ +Ce ⁴⁺ )≧60% is satisfied, that is, the Ce ³⁺ abundance ratio is 60% or more.

[Table 1]

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

First, prepare a disc-shaped substrate body (diameter 50mm, thickness 0.5mm) coated with Ag on Al as a light-reflecting layer. Also, open a screw hole in the center of this substrate body. Then, set a fluorescent ceramic layer on this substrate body.

On the inner side of the fluorescent ceramic layer, a first plate member (outer diameter 26.5mm, thickness 100μm) of Al disk-shaped with a screw hole in the center is set. In addition, the fluorescent ceramic layer is a fluorescent ring; the first plate member is set on the inner side of the ring. Then, further, a second plate member (outer diameter 29mm, thickness 200μm) of Al disk-shaped with a screw hole in the center is set in a manner overlapping with the fluorescent 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 fluorescent ceramic layer is fixed to obtain a wavelength conversion element. That is, in the wavelength conversion element of Example 4, the fluorescent ceramic layer is sandwiched and fixed by the substrate body and the second plate component.

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

Furthermore, the evaluation of wavelength conversion components is explained.

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

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

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

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

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

As shown in FIG. 7 , the wavelength conversion element of Example 4 has a coupling efficiency of 85%. In addition, as mentioned above, the wavelength conversion element of the comparative example has a coupling efficiency of 81%. The wavelength conversion element of Example 4 with a higher coupling efficiency generates more light passing through the opening portion of the fluorescence and a smaller luminous area of the fluorescence. For example, as shown in FIG. 5A and FIG. 5B , in the wavelength conversion element of Example 4, more light passes through the opening portion 2a of the aperture member 2, so more light can be used as the projection light of the projector 100. That is, it means that the wavelength conversion element of Example 4 has a high light utilization efficiency.

Furthermore, the relative value of the fluorescence energy of the wavelength conversion element of Example 4 (after passing through the opening) and the relative value of the fluorescence energy (before passing through the opening) are 108% and 128%, respectively. Compared with the relative value of the fluorescence energy of the wavelength conversion element of Examples 1 to 3 (after passing through the opening) and the relative value of the fluorescence energy (before passing through the opening), this value is a higher value.

As described above, in the fluorescent ceramic layer of Example 4, the Ce ³⁺ existence ratio is more than 60%, and the Ce ⁴⁺ existence ratio is less than 40%. Therefore, the non-luminescent slowdown loss caused by Ce ⁴⁺ is reduced, so the fluorescent ceramic layer of Example 4 with a Ce ³⁺ existence ratio of more than 60% has a higher luminous efficiency. Therefore, the wavelength conversion element of Example 4 can improve the light utilization efficiency by having such a fluorescent ceramic layer. Furthermore, when a projector is equipped with such a wavelength conversion element 1, the light utilization efficiency of the projector can be improved. For example, a projector with low power consumption can be realized.

In addition, since the non-luminescent slowing loss caused by Ce ⁴⁺ is reduced, the heat generation of the fluorescent ceramic layer of Example 4 is reduced. Therefore, in a projector equipped with such a fluorescent ceramic layer, the maximum input energy of the excitation light L1 can be increased, that is, a high-output projector can be realized.

(Variant 1)

The fluorescent ceramic layer 20 of the embodiment is composed of only the first crystalline phase, but is not limited to this form. Here, a wavelength conversion element 1a having a fluorescent ceramic layer 20a including the first crystalline phase and the second crystalline phase is described.

[Structure of wavelength conversion element]

First, the structure of the wavelength conversion element 1a of this variant is explained using diagrams. FIG8 is a three-dimensional diagram of the wavelength conversion element 1a of this variant. FIG9 is a cross-sectional diagram showing the cross-section of the wavelength conversion element 1a along line IX-IX of FIG8 .

The wavelength conversion element 1a of this variant has the same structure as the wavelength conversion element 1 of the embodiment except that it has a fluorescent ceramic layer 20a. That is, as shown in Figures 8 and 9, the wavelength conversion element 1a has a substrate 10 having a light reflecting surface 13, a fluorescent ceramic layer 20a, and an anti-reflection layer 30.

In addition, in this variation, the wavelength conversion element 1a is also used in a projector to receive the excitation light L1 and emit a fluorescent wheel containing reflected light including fluorescence.

The fluorescent ceramic layer 20a includes a first crystalline phase and a second crystalline phase. More specifically, in this variation, the fluorescent ceramic layer 20a is composed of a first crystalline phase and a second crystalline phase.

The first crystalline 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 the structure of the first crystal phase. Therefore, the refractive index of the first crystal phase and the refractive index of the second crystal phase are different from each other.

When the fluorescent ceramic layer 20a is observed in cross section, when the area showing the image of the fluorescent ceramic layer 20a is 100%, the area showing the first crystalline phase is, for example, 10% to 99%. In addition, the area showing the first crystalline phase is not limited thereto, for example, it can be 75% to 98%, or 85% to 95%. That is, the fluorescent ceramic layer 20a of this variant mainly includes the first crystalline phase.

As an example, the second crystalline phase of this variant is a crystalline phase having a calcite structure, but it is not limited to this type and may also be a crystalline phase having a structure different from the garnet structure and the calcite structure.

The calcite structure is a crystal structure represented by the general formula of EFO _3. As the element E, rare earth elements such as Ca, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb and Lu are used; as the element F, elements such as Mg, Al, Si, Ga and Sc are used. As such garnet structures, YAP (Yttrium Aluminum Perovskite) and the like can be cited. In this modification, the second crystal phase is represented by (Y _1-y Ce _y )AlO ₃ (0≦y<0.1), that is, YAP.

In addition, the second crystalline phase can also be a solid solution of multiple calcium-titanium crystalline phases with different chemical compositions.

In addition, the second crystalline phase may include a crystalline phase having a chemical composition shifted relative to the crystalline phase represented by the above general formula EFO ₃ .

In addition, the fluorescent ceramic layer 20a of this variation is composed only of the first crystal phase and the second crystal phase, that is, it does not contain a crystal phase having a structure different from the garnet structure and the calcite 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 the material representing the second crystal phase in such a way 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. Thereby, as described above, the refractive index of the first crystal phase and the refractive index of the second crystal phase become different from each other. 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 more preferably 0.06 or more and 0.3 or less, and further preferably 0.07 or more and 0.15 or less.

Furthermore, for example, when the second crystal phase of the present modification example is a crystal phase having a structure different from _{the garnet} structure and _the calcite _{structure ,} suitable materials for representing the second crystal phase are _Al2O3 , _Y2O3 , _{Y4Al2O9 , Lu2O3 ,} and _Lu4Al2O9 .

The fluorescent ceramic layer 20a receives the light incident from the upper side of the wavelength conversion element 1a as the excitation light L1 and emits fluorescence. More specifically, the light emitted from the excitation light source described later is irradiated on the fluorescent ceramic layer 20a as the excitation light L1, so that the fluorescent ceramic layer 20a emits fluorescence as the wavelength conversion light. That is, the wavelength conversion light emitted from the fluorescent ceramic layer 20a is light having a longer wavelength than the wavelength of the excitation light L1.

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

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

The density of the fluorescent ceramic layer 20a is preferably 95% to 100% of the theoretical density, and more preferably 97% to 100% of the theoretical density. Here, the theoretical density is the density when the atoms in the layer are ideally arranged. In other words, the theoretical density is the density when there are no voids in the fluorescent ceramic layer 20a, and is a value calculated using the crystal structure. For example, when the density of the fluorescent ceramic layer 20a is 99%, the remaining 1% is equivalent to the voids. That is, the higher the density of the fluorescent ceramic layer 20a, the fewer the voids. If the density of the fluorescent ceramic layer 20a is within the above range, the total amount of fluorescence emitted by the fluorescent ceramic layer 20a increases, so a wavelength conversion element 1a and a projector with a larger amount of radiated light can be provided. In addition, the theoretical density is the theoretical density of the first crystal phase with garnet structure.

The density of the fluorescent ceramic layer 20a is preferably 4.32 g/cm ³ or more and 4.55 g/cm ³ or less, and more preferably 4.41 g/cm ³ or more and 4.55 g/cm ³ or less. As shown in this modification, when the fluorescent ceramic layer 20a is composed of YAG and YAP, if the density of the fluorescent ceramic layer 20a is within the above range, the density of the fluorescent ceramic layer 20a is 95% or more and 100% or more and 97% or more and 100% or less of the theoretical density, respectively. By making the density of the fluorescent ceramic layer 20a within the above range, the excitation light L1 absorbed by the fluorescent ceramic layer 20a can be efficiently converted into fluorescence. That is, a fluorescent ceramic layer 20a with high luminous efficiency is realized.

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

[Projector structure]

The wavelength conversion element 1a constructed as described above is used in a projector in the same manner as the wavelength conversion element 1 of the embodiment. That is, the wavelength conversion element 1a of this variant can be used instead of the wavelength conversion element 1 of the embodiment.

[Implementation example]

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

First, the manufacturing method of the fluorescent ceramic layer of the wavelength conversion element of Examples 5 and 6 is described.

The fluorescent ceramic layer of Example 5 is mainly composed of a crystalline phase represented by (Y _0.997 Ce _0.003 ) ₃ Al ₅ O ₁₂ (i.e., the first crystalline phase). In addition, as described above, the fluorescent ceramic layer of Example 5 also includes a second crystalline phase. The fluorescent ceramic layer of Example 6 is composed of a crystalline phase represented by (Y _0.997 Ce _0.003 ) ₃ Al ₅ O ₁₂ (i.e., the first crystalline phase). In addition, the fluorescent ceramic layers of Examples 5 and 6 are both composed of Ce ³⁺ activated phosphors.

The fluorescent ceramic layers of Examples 5 and 6 use the same raw materials as those used in Examples 1 to 3.

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

Then, in Example 5, a granulated mixed raw material is obtained by a method without using a spray drying device. Specifically, 100 g of the mixed raw material dried by a dryer is put into a mortar made of aluminum oxide. Then, a solution in which polyvinyl alcohol is dissolved in water at a ratio of 0.5 wt% is used as a polyvinyl alcohol solution, and 18 mL of this polyvinyl alcohol solution is further put into a mortar made of aluminum oxide. Then, the mixed raw material and the polyvinyl alcohol solution are mixed using a pestle. Then, the mixture of the mixed raw material and the polyvinyl alcohol solution is filtered using a sieve with 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 less than 512 μm is obtained. Then, the mixture is treated in a dryer set at 105°C for 30 minutes to remove moisture. In this way, the mixed raw material for granulation used in Example 5 is obtained. In addition, in Example 6, the mixed raw material is granulated in the same order as in Examples 1 to 3 to obtain a mixed raw material for granulation.

The fluorescent ceramic layers of Examples 5 and 6 are temporarily molded in the same way. Specifically, the mixed raw materials to be granulated are temporarily molded into a cylindrical shape using an electric hydraulic press (EMP-5, manufactured by Riken Seiki Co., Ltd.) and a cylindrical mold (outer diameter 66 mm, inner diameter 46 mm, height 130 mm). The pressure during molding is set to 5 MPa. Then, the temporarily molded body is formally molded using a cold isostatic pressurizing device. The pressure during formal molding is set to 300 MPa. In addition, the formally molded body is subjected to a heat treatment (de-binder treatment) for the purpose of removing the adhesive (binder) used during granulation. The temperature of the heat treatment is set to 500°C. In addition, the heat treatment time was set to 10 hours.

The molded body after heat treatment is forged in a tubular gas environment furnace. The forging temperature is 1675℃. In addition, the forging time is 4 hours. The forging gas environment is a mixed gas environment of nitrogen and hydrogen. In addition, the outer diameter and inner diameter of the forged product after forging are 49mm and 35mm respectively.

Use a multi-wire saw to slice the cylindrical forged material after forging. The thickness of the sliced cylindrical forged material is about 700μm.

In addition, in Examples 5 and 6, the sintered product is heated at a temperature above 1000°C.

The forged product after slicing is ground by a grinding device to adjust the thickness of the forged product. The thickness of the fluorescent ceramic layer is 118μm in Example 5 and 117μm in Example 6.

In addition, the outer diameter and inner diameter of the fluorescent ceramic layer of Examples 5 and 6 are both 49 mm and 35 mm. In addition, the fluorescent ceramic layer of Examples 5 and 6 is dark yellow.

Next, the evaluation of the fluorescent ceramic layer is explained.

First, the density of the fluorescent ceramic layer of Examples 5 and 6 was evaluated by the Archimedean method. The density of the fluorescent ceramic layer of Examples 5 and 6 was 4.48 g/cm ³ and 4.42 g/cm ³ , respectively. In addition, the density of the fluorescent ceramic layer of Examples 5 and 6 was 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 fluorescent ceramic layer 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, a scanning electron microscope (SEM) was used to evaluate the cross-sectional SEM image of the fluorescent ceramic layer of Example 5.

FIG10 shows a cross-sectional SEM image of the fluorescent ceramic layer of Example 5 of this variant. FIG10(a) shows a wide-range cross-sectional SEM image of the fluorescent ceramic layer of Example 5. In addition, the SEM image shown in FIG10(a) is equivalent to the image of the area surrounded by the dotted rectangle in the cross-sectional view shown in FIG9. FIG10(b) is an enlarged SEM image of the area surrounded by the one-point chain rectangle of FIG10(a). FIG10(c) is an enlarged SEM image of the area surrounded by the two-point chain rectangle of FIG10(a).

Here, the fluorescent ceramic layer of Example 5, that is, the fluorescent ceramic layer 20a of this variant, includes a single phase portion and a mixed phase portion different from the single phase portion. The single phase portion is shown in FIG10(b), and the mixed phase portion is shown in FIG10(c).

In this variation, in the SEM image of FIG10 , 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 calcite structure. In addition, in the SEM image of FIG10 , the darkest region corresponds to the void.

In the single phase portion, only the first crystal phase is provided among "the first crystal phase having a garnet structure and the second crystal phase having a structure different from the garnet structure (here, the calcite structure)". In addition, more specifically, here, in the single phase portion, only the first crystal phase is provided, and no other crystal phases having a structure different from the garnet structure and the calcite structure are provided.

In addition, the first crystal phase and the second crystal phase are mixed and arranged in the mixed phase portion. More specifically, only the first crystal phase and the second crystal phase are mixed and arranged in the mixed phase portion. In addition, the first crystal phase and the second crystal phase may be mixed and arranged in the mixed phase portion, and other crystal phases having a structure different from the garnet structure and the calcite structure may be further arranged.

The mixed phase part of Example 5 is a mixed configuration in which the first crystalline phase and the second crystalline phase are randomly intermixed, but it is not limited to this form. A mixed configuration in which the first crystalline phase and the second crystalline phase are periodically arranged is also possible.

In addition, the fluorescent ceramic layer of Example 5 includes multiple mixed phase parts. The areas surrounded by dotted lines in Figure 10(a) correspond to the mixed phase parts respectively.

The multiple mixed phases are surrounded by single phases. The shapes of the single phase and multiple mixed phases can also be described as islands. In this case, the single phase is equivalent to the sea, and the multiple mixed phases are equivalent to the island.

In addition, in the mixed phase part, it is appropriate to set more second crystalline phases than the first crystalline phase. For example, the ratio of the first crystalline phase to the second crystalline phase in the mixed phase part is as follows. When the fluorescent ceramic layer of Example 5 is observed in cross section (for example, Figure 10), when the area showing the image of the mixed phase part is 100%, the area showing the second crystalline phase is, for example, 10% to 99%. In addition, the area showing the second crystalline phase is not limited to this, for example, it can be 70% to 95%, or 80% to 90%. That is, in the mixed phase part of this variant, the second crystalline phase is mainly set.

In this way, the first crystal phase having a garnet structure and the second crystal phase having a calcite structure are mixed in the mixed phase. As described above, the refractive index of the first crystal phase is different from the refractive index of the second crystal phase. Therefore, the refractive index of the single phase portion of the first crystal phase is different from the refractive index of the mixed phase portion. In this variant, 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.

Furthermore, the size of the mixed phase portion is explained. In addition, the size of the mixed phase portion indicates the length of the long side direction of the mixed phase portion of the SEM image shown in FIG10. The size of the mixed phase portion is, for example, the length indicated by the double arrow in FIG10. 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.

Thus, the fluorescent ceramic layer (fluorescent ceramic layer 20a) of Example 5 includes the first crystalline phase and the second crystalline phase, and FIG. 10 shows that a single phase portion and a mixed phase portion are provided. On the other hand, the fluorescent ceramic layer of Example 6 is composed only of the first crystalline phase. Therefore, it is confirmed that the fluorescent ceramic layer of Example 6 does not have a mixed phase portion.

Next, the manufacturing method of the wavelength conversion element of Examples 5 and 6 is described.

First, prepare a disc-shaped substrate body (diameter 50mm, thickness 0.5mm) coated with Ag on Al as a light-reflecting layer. Also, open a screw hole in the center of this substrate body. Then, set a fluorescent ceramic layer on this substrate body.

On the inner side of the fluorescent ceramic layer, a third plate member (outer diameter 34.5 mm, thickness 100 μm) of Al with a screw hole in the center is set. In addition, the fluorescent ceramic layer is a fluorescent ring; the third plate member is set on the inner side of the ring. Then, a fourth plate member (outer diameter 39 mm, thickness 200 μm) of Al with a screw hole in the center is set in a manner overlapping with the fluorescent 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 fluorescent ceramic layer is fixed to obtain a wavelength conversion element. That is, in the wavelength conversion element of Examples 5 and 6, the fluorescent ceramic layer is sandwiched and fixed by the substrate body and the fourth plate component.

Furthermore, the evaluation of wavelength conversion components is explained.

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

FIG11 is a diagram showing the evaluation results of the wavelength conversion elements of Examples 5 and 6 of this variation. Specifically, FIG11 shows the relative value of the fluorescence energy (after passing through the opening), the relative value of the fluorescence energy (before passing through the opening), and the combination 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 by the wavelength conversion element of Example 6 after passing through the opening is 100%.

In addition, the relative value of the 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 by the wavelength conversion element of Example 6 after passing through the opening is set to 100%.

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

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

In addition, the wavelength conversion element of Example 5, which is equivalent to the wavelength conversion element 1a of this variant, has a combination efficiency of 87%. The wavelength conversion element of Example 6, which is equivalent to the wavelength conversion element 1 of the embodiment, has a combination efficiency of 82%.

As described above, the fluorescent ceramic layer (fluorescent ceramic layer 20a) of the wavelength conversion element of Example 5 is composed of a first crystalline phase and a second crystalline phase having different refractive indices.

Thus, regions with different refractive indices are generated in the fluorescent ceramic layer 20a, so the excitation light L1 and the fluorescence become easier to disperse. As a result, the light guide in the plane direction (i.e., the x-axis direction or the y-axis direction) of the implementation form shown in Figures 5A and 5B is suppressed, and the light-emitting area of the fluorescent ceramic layer 20a becomes smaller. Therefore, the combination 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 1a) of Example 5 with smaller light spread and higher light utilization efficiency is realized. When the projector is equipped with such a wavelength conversion element 1a, the light utilization efficiency of the projector can be further improved.

In addition, the fluorescent ceramic layer 20a includes a single phase portion and a mixed phase portion different from the single phase portion. In the single phase portion, only the first crystalline phase of the first crystalline phase and the second crystalline phase is provided; in the mixed phase portion, the first crystalline phase and the second crystalline phase are mixed and provided. The refractive index of these single phase portions and the refractive index of the mixed phase portion are different from each other.

Thus, regions with different refractive indices are generated in the fluorescent ceramic layer 20a, so the excitation light L1 and the fluorescence become easier to disperse. As a result, the luminous area of the fluorescent ceramic layer 20a becomes smaller. Therefore, a wavelength conversion element 1a with smaller light spread and higher light utilization efficiency can be realized.

In addition, when the size of the mixed phase is within the above range, the excitation light L1 and the fluorescence become easier to disperse.

In addition, the fluorescent ceramic layer 20a includes a plurality of mixed phase parts. Each of the plurality of mixed phase parts is surrounded by a single phase part.

As a result, the excitation light L1 and the fluorescence become easier to disperse. As a result, the light-emitting area of the fluorescent ceramic layer 20a becomes smaller. Therefore, a wavelength conversion element 1a with smaller light spread and higher light utilization efficiency is realized.

The above results show that the light guide suppression effect produced by the thin film thickness of the fluorescent ceramic layer 20a is not only used to improve the wavelength conversion element 1a's binding efficiency, but also the light guide suppression effect of the fluorescent ceramic layer 20a itself. In other words, it is shown that even if the film thickness of the fluorescent ceramic layer 20a is not controlled, the wavelength conversion element 1a's binding efficiency is still 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 greater than or equal to 0.05 and less than or equal to 0.5.

As a result, the excitation light L1 and the fluorescence become easier to disperse. As a result, the light-emitting area of the fluorescent ceramic layer 20a becomes smaller. Therefore, a wavelength conversion element 1a with smaller light spread and higher light utilization efficiency is realized.

In addition, the second crystalline phase is a crystalline 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.

(Variant 2)

Furthermore, the fluorescent ceramic layer 20b having a structure different from the fluorescent ceramic layers 20 and 20a is described.

Figure 12 is a three-dimensional diagram of the fluorescent ceramic component of this variant.

The fluorescent ceramic component of this variation is, for example, a fluorescent ceramic layer 20b having a layered shape.

The fluorescent ceramic layer 20b, like the fluorescent ceramic layers 20 and 20a shown in the embodiment and variation 1, is a component used in a projector.

The fluorescent ceramic layer 20b has the same structure as the fluorescent ceramic layer 20a of Modification 1 except for the following point. Specifically, the Ce ³⁺ abundance ratio is set to 60% or more.

That is, the fluorescent ceramic layer 20b includes a first crystalline phase having a garnet structure and a second crystalline phase having a structure other than the garnet structure. The first crystalline phase and the second crystalline phase have different refractive indices. In addition, in this variation, the first crystalline phase and the second crystalline phase are crystalline phases represented by YAG and YAP, respectively; the fluorescent ceramic layer 20b also mainly includes the first crystalline phase. In addition, the density of the fluorescent ceramic component (fluorescent ceramic layer 20b) 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. In addition, the film thickness of the fluorescent ceramic component (fluorescent ceramic layer 20b) is preferably not particularly limited, but in the case of setting restrictions, it is preferably 50μm or more and less than 500μm, and more preferably 50μm or more and less than 300μm. In addition, the film thickness is further preferably 50μm or more and less than 120μm.

The fluorescent ceramic component (fluorescent ceramic layer 20b) has the above-mentioned structure. Therefore, when the fluorescent ceramic layer 20b is used in a projector and irradiated with excitation light, regions with different refractive indices are generated in the fluorescent ceramic layer 20b, so the excitation light and the fluorescent light are more dispersed. As a result, the light guide in the plane direction of the layer shown in Figures 5A and 5B (that is, the x-axis direction or the y-axis direction) is suppressed, and the light-emitting area of the fluorescent ceramic layer 20b becomes smaller. Therefore, it becomes a fluorescent ceramic component with smaller light spread and higher light utilization efficiency. When the projector is equipped with such a fluorescent ceramic component (fluorescent ceramic layer 20b), the light utilization efficiency of the projector can be further improved.

Furthermore, the fluorescent ceramic layer 20b is composed of YAG and YAP having Ce ³⁺ and Ce ⁴⁺ , that is, the fluorescent ceramic layer 20b contains Ce ³⁺ and Ce ⁴⁺ . Here, in the fluorescent ceramic layer 20b, Ce ³⁺ ×100%/(Ce ³⁺ +Ce ⁴⁺ )≧60% is satisfied, that is, the Ce ³⁺ existence ratio is more than 60%.

The fluorescent ceramic layer 20b with a Ce ³⁺ existence ratio of 60% or more has a higher luminous efficiency because the non-luminescent slowdown loss caused by Ce ⁴⁺ is reduced. Furthermore, in a projector having such a fluorescent ceramic layer 20b, the light utilization efficiency can be improved. For example, a projector with low power consumption can be realized.

In addition, since the non-luminescent slowdown loss caused by Ce ⁴⁺ is reduced, the heat generation of the fluorescent ceramic layer 20b is reduced. Therefore, in a projector having such a fluorescent ceramic layer 20b, the maximum input energy of the excitation light can be increased, that is, a high-output projector can be realized.

(Other implementation forms)

The wavelength conversion element of the present invention is described above based on the embodiments and variants, but the present invention is not limited to these embodiments and variants. If it does not deviate from the main purpose of the present invention, the embodiments and variants are subjected to various modifications that can be thought of by people with ordinary knowledge in the relevant technical field, or other forms of combining and constructing some of the constituent elements of the embodiments and variants are all included in the scope of the present invention.

In addition, in the implementation form, the light source is a semiconductor laser light source, but it is not limited to this form and can also be an LED light source.

In addition, the above-mentioned implementation forms may be subject to various changes, substitutions, additions, omissions, etc. within the scope of the invention patent application or its equivalent scope.

1: Wavelength conversion element

10: Substrate

11: Substrate body

12: Light reflection layer

13: Light reflecting surface

20: Fluorescent ceramic layer

30: Anti-reflection layer

121: Light scattering particles

122: Adhesive

L1: Excitation light

Claims (6)

A fluorescent ceramic component is used in a projector, comprising: a first crystalline phase having a garnet structure; the density of the fluorescent ceramic component is greater than 97% and less than 100% of the theoretical density; the fluorescent ceramic component is composed only of the first crystalline phase, or only of the first crystalline phase and a second crystalline phase having a structure other than the garnet structure; the fluorescent ceramic component contains Ce ³⁺ and Ce ⁴⁺ ; and satisfies Ce ³⁺ ×100%/(Ce ³⁺ +Ce ⁴⁺ )≧60%. A fluorescent ceramic component as claimed in claim 1, 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 greater than 0.05 and less than 0.5. The fluorescent ceramic component of claim 1, wherein the fluorescent ceramic component is composed of the first crystalline phase represented by (Y _1-x Ce _x ) ₃ Al ₅ O ₁₂ (0.001≦x<0.1). The fluorescent ceramic component of claim 1, wherein the second crystalline phase is a crystalline phase represented by (Y _1-y Ce _y )AlO ₃ (0≦y<0.1). The fluorescent ceramic component of claim 1, wherein the density of the fluorescent ceramic component is greater than or equal to 4.41 g/cm ³ and less than or equal to 4.55 g/cm ³ . A fluorescent ceramic component as claimed in claim 1, wherein the film thickness of the fluorescent ceramic component is greater than 50 μm and less than 300 μm.

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