Wavelength conversion element, light source device, and projector

Abstract

Provided are a wavelength conversion element, a light source device, and a projector, which can improve light utilization efficiency. The wavelength conversion element (20) includes: a wavelength conversion layer (22) having a recess (22d) on a surface, which converts blue excitation light B into yellow fluorescent light Y; a first matching layer (23) provided on a light incident surface (22a) in the surface of the wavelength conversion layer (22); and a first flat layer (24) provided on a surface opposite to the surface of the first matching layer (23) facing the wavelength conversion layer (22), and entering the recess (22d) of the light incident surface (22a), and the light refractive index of the first matching layer (23) is between the light refractive index of the wavelength conversion layer (22) and the light refractive index of the first flat layer (24).

Description

Technical Field

[0001] This invention relates to wavelength conversion elements, light source devices, and projectors. Background Technology

[0002] Conventionally, as shown in Patent Document 1, optical converters using ceramic light-converting materials with voids are known. In such optical converters, if voids are exposed on the surface of the ceramic light-converting material, the surface flatness is lost, and therefore reflective layers and the like that should be formed on the surface cannot be formed flatly, resulting in a decrease in light utilization efficiency. Therefore, in the optical converter described in Patent Document 1, a filling material layer composed of materials such as SiO2 is deposited on the surface of the ceramic light-converting material to fill the voids, thereby flattening the surface of the ceramic light-converting material.

[0003] Patent Document 1: Japanese Patent Publication No. 2018-512617 Summary of the Invention

[0004] However, as described in Patent Document 1, when a filler material layer is provided on the surface of the ceramic light conversion material, interfacial reflection caused by the difference in refractive index between the filler material layer and the ceramic light conversion material occurs, resulting in light loss. Therefore, there is a limit to the improvement of light utilization efficiency.

[0005] The wavelength conversion element comprises: a wavelength conversion layer having a recess on its surface to convert first light of a first wavelength into second light of a second wavelength different from the first wavelength; a first layer disposed on a first surface of the wavelength conversion layer; and a first planarization layer disposed on a surface of the first layer opposite to the surface of the wavelength conversion layer and extending into the recess, wherein the optical refractive index of the first layer is between the optical refractive index of the wavelength conversion layer and the optical refractive index of the first planarization layer.

[0006] The light source device includes: the wavelength conversion element described above; and a light-emitting element that emits the first light toward the first surface of the wavelength conversion layer.

[0007] The projector includes: the aforementioned light source device; a light modulation device that modulates light from the light source device in accordance with image information to form image light; and a projection optics device that projects the image light. Attached Figure Description

[0008] Figure 1 This is a diagram showing a schematic structure of the projector according to this embodiment.

[0009] Figure 2 This is a diagram showing the general structure of the light source device.

[0010] Figure 3This is a cross-sectional view showing the main structural components of the wavelength conversion element.

[0011] Figure 4 This is a graph showing the reflectance of the color separation layer to fluorescence.

[0012] Figure 5 This is a graph showing the reflectivity of the dichroic layer to the excitation light.

[0013] Label Explanation

[0014] 1: Projector; 2: Light source device; 3: Color separation optical system; 4R, 4G, 4B: Light modulation device; 5: Synthesizing optical system; 6: Projection optical device; 7a: First dichroic mirror; 7b: Second dichroic mirror; 8a: First total internal reflection mirror; 8b: Second total internal reflection mirror; 8c: Third total internal reflection mirror; 9a: First relay lens; 9b: Second relay lens; 9R, 9G, 9B: Field lens; 10: Excitation light source unit; 10a: Semiconductor laser; 10b 11: Collimating lens; 11: Telephoto optical system; 11a: Convex lens; 11b: Concave lens; 12: Beam equalizer optical system; 12a: First multi-lens array; 12b: Second multi-lens array; 13: Condensing optical system; 13a: First lens; 13b: Second lens; 20: Wavelength conversion element; 21: Heat dissipation substrate; 21a: Through hole; 22: Wavelength conversion layer; 22a: Light incident surface; 22b: Light exiting surface; 22c: Vent; 22d: Recess 23: First mating layer; 23a: Light incident surface; 23b: Light exiting surface; 23c: Opening; 24: First planarization layer; 24a: Light incident surface; 24b: Light exiting surface; 25: Color separation layer; 25a: Light incident surface; 25b: Light exiting surface; 26: Joining component; 27: Second mating layer; 27a: Light incident surface; 27b: Light exiting surface; 27c: Opening; 28: Second planarization layer; 28a: Light incident surface; 28b: Light exiting surface; 29: Anti-reflection layer 29a: Light incident surface; 29b: Light exit surface; 30: Pickup optical system; 31: First collimating lens; 32: Second collimating lens; 80: Uniform illumination optical system; 81: First lens array; 81a: First lens; 82: Second lens array; 82a: Second lens; 83: Polarization conversion element; 84: Overlapping lens; 100ax: Illumination optical axis; B: Excitation light; B1: Blue light; SCR: Screen; WL: Illumination light; Y: Fluorescence. Detailed Implementation

[0015] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0016] Furthermore, in the accompanying drawings used in the following description, the parts that are considered features are sometimes enlarged for ease of understanding, and the size ratios of the constituent elements may not be the same as in reality.

[0017] Figure 1 This is a diagram showing a schematic structure of the projector 1 according to this embodiment. Figure 2 This is a diagram showing the general structure of the light source device 2.

[0018] like Figure 1 As shown, the projector 1 of this embodiment is a projection-type image display device that displays images on a screen SCR. The projector 1 includes a light source device 2, a color separation optical system 3, light modulation devices 4R, 4G, and 4B, a combining optical system 5, and a projection optical device 6.

[0019] The light source device 2 emits white illumination light WL toward the color separation optical system 3.

[0020] The color separation optical system 3 separates the illumination light WL emitted from the light source device 2 into red light LR, green light LG, and blue light LB. The color separation optical system 3 includes a first dichroic mirror 7a and a second dichroic mirror 7b, a first total reflection mirror 8a, a second total reflection mirror 8b and a third total reflection mirror 8c, as well as a first relay lens 9a and a second relay lens 9b.

[0021] The first dichroic mirror 7a separates the illumination light WL from the light source device 2 into red light LR and other light including green light LG and blue light LB. The first dichroic mirror 7a allows red light LR to pass through and reflects the other light (green light LG and blue light LB). On the other hand, the second dichroic mirror 7b reflects green light LG and allows blue light LB to pass through, thereby separating the other light (green light LG and blue light LB) into green light LG and blue light LB.

[0022] The first total internal reflection mirror 8a is positioned in the optical path of the red light LR, reflecting the red light LR that has passed through the first dichroic mirror 7a toward the optical modulation device 4R. On the other hand, the second total internal reflection mirror 8b and the third total internal reflection mirror 8c are positioned in the optical path of the blue light LB, guiding the blue light LB that has passed through the second dichroic mirror 7b to the optical modulation device 4B. The green light LG is reflected from the second dichroic mirror 7b toward the optical modulation device 4G.

[0023] The first relay lens 9a is disposed on the light-incident side of the second total internal reflection mirror 8b in the optical path of the blue light LB. The second relay lens 9b is disposed on the light-outcrowding side of the second total internal reflection mirror 8b in the optical path of the blue light LB. The first relay lens 9a and the second relay lens 9b have the function of compensating for the light loss of the blue light LB caused by the fact that the optical path length of the blue light LB is longer than that of the red light LR and the green light LG.

[0024] Optical modulation devices 4R, 4G, and 4B form image light by modulating light from light source device 2 according to image information. Specifically, optical modulation device 4R modulates red light LR according to image information to form image light corresponding to red light LR. Optical modulation device 4G modulates green light LG according to image information to form image light corresponding to green light LG. Optical modulation device 4B modulates blue light LB according to image information to form image light corresponding to blue light LB.

[0025] The optical modulation devices 4R, 4G, and 4B, for example, use transmissive liquid crystal panels. Additionally, polarizers (not shown) are disposed on the incident and emission sides of the liquid crystal panel.

[0026] In addition, field lenses 9R, 9G, and 9B are respectively arranged on the incident side of the optical modulation devices 4R, 4G, and 4B. The field lenses 9R, 9G, and 9B parallelize the red light LR, green light LG, and blue light LB incident on the optical modulation devices 4R, 4G, and 4B, respectively.

[0027] Image light from the light modulation devices 4R, 4G, and 4B is incident on the combining optical system 5. The combining optical system 5 combines the image light corresponding to the red light LR, green light LG, and blue light LB, and emits the combined image light toward the projection optical device 6. The combining optical system 5 uses, for example, a cross-shaped dichroic prism.

[0028] The projection optics 6, consisting of a projection lens group, projects the image light synthesized by the synthesis optics system 5 toward the SCR screen. This results in a magnified image being displayed on the SCR screen.

[0029] Next, the structure of the light source device 2 will be explained.

[0030] like Figure 2 As shown, the light source device 2 includes an excitation light source assembly 10, a telephoto optical system 11, a beam equalizer optical system 12, a focusing optical system 13, a wavelength conversion element 20, a pickup optical system 30, and a uniform illumination optical system 80.

[0031] The excitation light source assembly 10 includes a plurality of semiconductor lasers 10a that emit blue excitation light B composed of laser light and a plurality of collimating lenses 10b. The peak wavelength of the emission intensity of the excitation light B is, for example, 450 nm. The plurality of semiconductor lasers 10a are arranged in an array in a plane perpendicular to the illumination optical axis 100ax. Furthermore, as semiconductor lasers 10a, lasers emitting blue light with wavelengths other than 450 nm, such as 455 nm or 460 nm, can also be used. The semiconductor lasers 10a correspond to light-emitting elements. Additionally, the excitation light B corresponds to the first light, and the wavelength of the excitation light B corresponds to the first wavelength.

[0032] Collimating lenses 10b are arranged in an array in a plane perpendicular to the illumination optical axis 100ax, corresponding to each semiconductor laser 10a. Collimating lenses 10b convert the excitation light B emitted from the corresponding semiconductor laser 10a into parallel light.

[0033] The telephoto optical system 11 includes, for example, a convex lens 11a and a concave lens 11b. The telephoto optical system 11 reduces the beam diameter of the excitation light B, which is composed of a parallel beam emitted from the excitation light source unit 10.

[0034] The beam equalizer optical system 12 includes, for example, a first multi-lens array 12a and a second multi-lens array 12b. The beam equalizer optical system 12 causes the intensity distribution of the excitation light B to be such that, in the wavelength conversion layer 22 (see below)... Figure 3 The beam equalizer optical system 12, together with the focusing optical system 13, causes multiple small beams emitted from multiple lenses of the first multilens array 12a and the second multilens array 12b to overlap on the wavelength conversion element 20. This results in a uniform intensity distribution of the excitation light B illuminating the wavelength conversion element 20.

[0035] The focusing optical system 13 includes, for example, a first lens 13a and a second lens 13b. In this embodiment, the first lens 13a and the second lens 13b are each composed of a convex lens. The focusing optical system 13 is arranged in the optical path from the beam equalizer optical system 12 to the wavelength conversion element 20, so that the excitation light B is focused and incident on the wavelength conversion element 20.

[0036] Wavelength conversion element 20 converts a portion of the incident blue excitation light B into fluorescent Y (see reference). Figure 3 It emits a white illumination light WL containing blue light B1, which is another part of the excitation light B, and fluorescent Y. The structure of the wavelength conversion element 20 will be described later.

[0037] The pickup optical system 30 includes, for example, a first collimating lens 31 and a second collimating lens 32. The pickup optical system 30 is a parallelizing optical system that substantially parallelizes the light emitted from the wavelength conversion element 20. The first collimating lens 31 and the second collimating lens 32 are each composed of a convex lens.

[0038] The parallelized light from the pickup optical system 30 is incident on the uniform illumination optical system 80. The uniform illumination optical system 80 includes a first lens array 81, a second lens array 82, a polarization conversion element 83, and an overlapping lens 84.

[0039] The first lens array 81 has a plurality of first lenses 81a for splitting the illumination light WL from the wavelength conversion element 20 into a plurality of partial beams. The plurality of first lenses 81a are arranged in a matrix in a plane perpendicular to the illumination optical axis 100ax.

[0040] The second lens array 82 has a plurality of second lenses 82a corresponding to the plurality of first lenses 81a of the first lens array 81. The plurality of second lenses 82a are arranged in a matrix in a plane perpendicular to the illumination optical axis 100ax.

[0041] The second lens array 82, together with the overlapping lens 84, causes the images of each first lens 81a of the first lens array 81 to be imaged near the image forming areas of the optical modulation device 4R, the optical modulation device 4G, and the optical modulation device 4B, respectively.

[0042] The polarization conversion element 83 converts the light emitted from the second lens array 82 into linearly polarized light. The polarization conversion element 83 includes, for example, a polarization separation film and a phase difference plate (not shown).

[0043] The overlapping lens 84 focuses the light beams emitted from the polarization conversion element 83 and overlaps them near the image forming areas of the optical modulation devices 4R, 4G, and 4B, respectively.

[0044] Next, the structure of the wavelength conversion element 20 will be described.

[0045] Figure 3 This is a cross-sectional view showing the main structural components of the wavelength conversion element 20. Additionally, Figure 3 Equivalent to using inclusion Figure 2 The plane containing the illumination optical axis 100ax is the cross-section of the wavelength conversion element 20 after being cut.

[0046] like Figure 3 As shown, the wavelength conversion element 20 includes a heat dissipation substrate 21, a wavelength conversion layer 22, a first matching layer 23, a first planarization layer 24, a dichroic layer 25, a bonding member 26, a second matching layer 27, a second planarization layer 28, and an anti-reflection layer 29. The wavelength conversion element 20 of this embodiment is a fixed-type phosphor that prevents the incident position of the excitation light B relative to the wavelength conversion layer 22 from changing over time.

[0047] The heat dissipation substrate 21 is made of a metal material with excellent heat dissipation properties, such as aluminum or copper. The heat dissipation substrate 21 is a support member for the wavelength conversion layer 22. The wavelength conversion layer 22 is supported on the heat dissipation substrate 21 via a bonding member 26. Although not shown, the heat dissipation substrate 21 may also have a heat dissipation component to improve heat dissipation efficiency. The heat dissipation component is, for example, a heat sink with a structure having multiple fins. In this embodiment, the heat dissipation substrate 21 is made of a non-transparent component.

[0048] Excitation light B enters the wavelength conversion layer 22 through the through hole 21a formed in the heat dissipation substrate 21. That is, the heat dissipation substrate 21 is a component that supports the wavelength conversion layer 22 at a region different from the incident region where excitation light B enters, dissipates heat generated in the wavelength conversion layer 22 to the outside, and supports the wavelength conversion layer 22 at portions other than the through hole 21a.

[0049] The wavelength conversion layer 22 has a light incident surface 22a on which excitation light B emitted from the excitation light source assembly 10 is incident, and a light exit surface 22b opposite to the light incident surface 22a. As Figure 3 illustrated, in the present embodiment, the wavelength conversion layer 22 has a plurality of air holes 22c disposed inside thereof. The wavelength conversion layer 22 has light scattering properties by means of the plurality of air holes 22c.

[0050] A part of the plurality of air holes 22c are exposed to the surface of the wavelength conversion layer 22. Therefore, on the light incident surface 22a and the light exit surface 22b, which are surfaces of the wavelength conversion layer 22, concave portions 22d are formed by the air holes 22c. That is, the wavelength conversion layer 22 has the concave portions 22d on its surface.

[0051] The wavelength conversion layer 22 is a transmission-type wavelength conversion layer that converts excitation light B incident from the light incident surface 22a into fluorescence Y, and emits the converted fluorescence Y from the light exit surface 22b. The wavelength of the fluorescence Y is different from that of the excitation light B. Specifically, the fluorescence Y is yellow light having a peak wavelength in a wavelength range of 500 to 700 nm. In addition, the fluorescence Y corresponds to second light, and the wavelength of the fluorescence Y corresponds to a second wavelength. Furthermore, the light incident surface 22a of the wavelength conversion layer 22 corresponds to a first surface, and the light exit surface 22b of the wavelength conversion layer 22 corresponds to a second surface.

[0052] In the present embodiment, the wavelength conversion layer 22 is a ceramic phosphor formed by firing phosphor particles. As the phosphor particles constituting the wavelength conversion layer 22, a cerium ion-containing yttrium aluminum garnet (YAG) based phosphor is used. That is, the wavelength conversion layer 22 of the present embodiment is composed of a YAG-based phosphor. The optical refractive index of the wavelength conversion layer 22 in the present embodiment is 1.83.

[0053] Taking YAG:Ce as an example, as the phosphor particles, it is possible to use particles containing a material obtained by mixing raw material powders containing constituent elements such as yttrium oxide (Y₂O₃), aluminum oxide (Al₂O₃) and cerium oxide (CeO₂) and subjecting the mixture to a solid-state reaction, Y-Al-O amorphous particles obtained by a wet method such as a co-precipitation method or a sol-gel method, or YAG particles obtained by a gas phase method such as a spray drying method, a flame thermal decomposition method or a thermal plasma method.

[0054] Furthermore, the phosphor particles can be formed from one material or particles formed from two or more materials. As the wavelength conversion layer 22, it is preferable to use a wavelength conversion layer in which phosphor particles are dispersed in an inorganic binder such as alumina, or a wavelength conversion layer formed by firing a glass binder (an inorganic material) and phosphor particles. Alternatively, the wavelength conversion layer 22 can be formed by firing the phosphor particles without using a binder.

[0055] In this embodiment, the wavelength conversion layer 22 converts the wavelength of a portion of the blue excitation light B emitted from the excitation light source assembly 10 to generate yellow fluorescence Y. Then, white illumination light WL is emitted, which is a combination of the generated fluorescence Y and another portion of the excitation light B, namely the blue light B1 that has not undergone wavelength conversion but has passed through the wavelength conversion layer 22.

[0056] Here, the white balance of the illumination light WL emitted from the wavelength conversion layer 22 is determined by the BY ratio, which is the ratio of the amount of blue light B1 to the amount of fluorescent light Y. In the projector 1, the conditions used to obtain a practical white balance for the illumination light WL are, for example, a BY ratio of 50%, that is, 50% blue light B1 and 50% fluorescent light Y. The BY ratio is determined at least based on the content of phosphor particles in the wavelength conversion layer 22.

[0057] It is known that the BY ratio is affected by the thickness of the wavelength conversion layer 22. For example, if the thickness of the wavelength conversion layer 22 with a certain YAG ratio is relatively thin, the amount of blue light B1 transmitted through the wavelength conversion layer 22 can be increased. However, when the thickness of the wavelength conversion layer 22 is less than 40 μm, it is difficult to manufacture the wavelength conversion layer 22. Therefore, from a manufacturing point of view, the lower limit of the thickness of the wavelength conversion layer 22 is preferably 40 μm.

[0058] Furthermore, if the thickness of the wavelength conversion layer 22 with a certain YAG ratio is relatively increased, the amount of blue light B1 transmitted through the wavelength conversion layer 22 will decrease. Moreover, if the thickness of the wavelength conversion layer 22 exceeds 300 μm, reabsorption of fluorescent Y occurs within the wavelength conversion layer 22, thus reducing the amount of fluorescent Y emitted from the light emitting surface 22b. Therefore, from the viewpoint of the light utilization efficiency of fluorescent Y, the upper limit of the thickness of the wavelength conversion layer 22 is preferably 300 μm.

[0059] Based on the above viewpoints, the thickness of the wavelength conversion layer 22 in this embodiment is set to be 40 μm or more and 300 μm or less.

[0060] like Figure 3As shown, the first matching layer 23 is disposed on the light incident surface 22a of the wavelength conversion layer 22. In other words, the first matching layer 23 is disposed between the wavelength conversion layer 22 and the first planarization layer 24, which will be described later. The first matching layer 23 has a light incident surface 23a from the first planarization layer 24 and a light emitting surface 23b from which light is emitted to the wavelength conversion layer 22. The first matching layer 23 is equivalent to the first layer.

[0061] In this embodiment, the first matching layer 23 is a single layer composed of aluminum oxide (Al2O3) with a refractive index of 1.64. The first matching layer 23 is formed, for example, by vapor deposition or sputtering. Furthermore, the material of the first matching layer 23 is not limited to Al2O3. For example, it can be a composite material containing yttrium fluoride (YF3), zinc oxide (ZnO2), titanium monoxide (TiO), etc. Additionally, the first matching layer 23 is not limited to a single layer. For example, it can be a multilayer film configured to combine layers with high and low refractive indices to suppress the reflection of excitation light B.

[0062] Additionally, in the first matching layer 23, at a position opposite to the recess 22d formed on the surface of the wavelength conversion layer 22, the first matching layer 23 is sometimes not formed to cover the recess 22d, thereby creating an opening 23c.

[0063] The first planarization layer 24 is disposed on the light incident surface 23a of the first matching layer 23, that is, on the side opposite to the surface of the first matching layer 23 that faces the wavelength conversion layer 22. In other words, the first planarization layer 24 is disposed between the first matching layer 23 and the dichroic layer 25, which will be described later. The first planarization layer 24 has a light incident surface 24a from which light is incident from the dichroic layer 25 and a light emitting surface 24b from which light is emitted to the first matching layer 23.

[0064] The first planarization layer 24 is formed as a recess 22d that enters the light incident surface 22a of the wavelength conversion layer 22 through the opening 23c of the first matching layer 23, and the light incident surface 24a is substantially planarized. That is, even if a portion of the first matching layer 23 produces an opening 23c caused by the recess 22d of the wavelength conversion layer 22, the light incident surface 24a of the first planarization layer 24 is formed to be substantially flat.

[0065] The first planarization layer 24 is made of a transparent inorganic material, such as silicon dioxide (SiO2). In this embodiment, the first planarization layer 24 is formed by calcining a polysilazane solution. The refractive index of the SiO2 in the first planarization layer 24 is 1.43. The first planarization layer 24 has a different refractive index than the wavelength conversion layer 22. Furthermore, the material of the first planarization layer 24 is not limited to SiO2. For example, it can also be a composite material containing silicon oxynitride (SiON), yttrium fluoride (YF3), silicon nitride (SiNx), etc.

[0066] The first planarization layer 24 also functions as a stress-relieving layer to mitigate stress caused by heat generated in the wavelength conversion layer 22. In this embodiment, the first planarization layer 24 is set to a thickness of less than half the thickness of the wavelength conversion layer 22. By setting such a thickness, the aforementioned stress-relieving function can be effectively performed.

[0067] The dichroic layer 25 is disposed on the light incident surface 24a of the first planarization layer 24, that is, on the side opposite to the surface of the first planarization layer 24 that faces the first mating layer 23. The dichroic layer 25 has a light incident surface 25a for the excitation light B to be incident on and a light emitting surface 25b for emitting light to the first planarization layer 24. In this embodiment, the light emitted from the excitation light source unit 10 is configured to directly incident on the dichroic layer 25. However, if other components such as a transparent substrate are provided in the light incident area to allow light to pass through, the light can also be configured to be incident on the dichroic layer 25 via other components. The dichroic layer 25 is equivalent to a reflective layer.

[0068] The dichroic layer 25 is formed to be substantially flat by being disposed on the substantially flat light incident surface 24a of the first planarization layer 24. The dichroic layer 25 has the property of allowing excitation light B to pass through and reflecting fluorescence Y. The dichroic layer 25 reflects fluorescence Y generated in the wavelength conversion layer 22 and emitted from the light incident surface 22a toward the first matching layer 23, thereby improving the light utilization efficiency of fluorescence Y.

[0069] Here, consider the case where the flatness of the light incident surface 22a is low. In this case, it is difficult to achieve good topographical composition of the color layer 25. If the color layer 25 cannot be well topographically composed relative to the light incident surface 22a, it cannot achieve ideal reflectivity, or the fluorescence Y cannot be reflected toward the light incident surface 22a, resulting in reduced light utilization efficiency of the fluorescence Y.

[0070] In contrast, in the wavelength conversion element 20 of this embodiment, the recess 22d is sealed by the first planarization layer 24, forming a first planarization layer 24 with a substantially planarized surface. Here, a substantially planarized surface refers to a flatness that allows for good topography of the color separation layer 25 through methods such as vapor deposition, and an unevenness that allows for the formation of the color separation layer 25.

[0071] The wavelength conversion element 20 of this embodiment has a uniform dichroic layer 25 formed on the first planarization layer 24. That is, the wavelength conversion element 20 of this embodiment has a uniform dichroic layer 25 formed over the entire area of ​​the light incident surface 24a.

[0072] like Figure 3As shown, the second matching layer 27 is disposed on the light emitting surface 22b of the wavelength conversion layer 22, that is, the surface of the wavelength conversion layer 22 opposite to the light incident surface 22a. In other words, the second matching layer 27 is disposed between the wavelength conversion layer 22 and the second planarization layer 28, which will be described later. The second matching layer 27 has a light incident surface 27a from the wavelength conversion layer 22 and a light emitting surface 27b from which light is emitted into the second planarization layer 28. The second matching layer 27 is equivalent to a second layer.

[0073] In this embodiment, the second matching layer 27, like the first matching layer 23, is a single layer composed of Al2O3. Furthermore, the material of the second matching layer 27 is not limited to Al2O3. For example, it can be a composite material containing YF3, ZnO2, TiO, etc. Additionally, the second matching layer 27 is not limited to a single layer. For example, it can be a multilayer film configured to combine layers with high and low refractive indices to suppress the reflection of excitation light B. Furthermore, in this embodiment, the first matching layer 23 and the second matching layer 27 use the same material, but it can also be a structure using different materials.

[0074] Similar to the first matching layer 23, in the second matching layer 27, at a position opposite to the recess 22d formed on the surface of the wavelength conversion layer 22, sometimes the second matching layer 27 is not formed to cover the recess 22d, and an opening 27c is created.

[0075] The second planarization layer 28 is disposed on the light emitting surface 27b of the second matching layer 27, that is, on the side of the second matching layer 27 opposite to the surface of the wavelength conversion layer 22. In other words, the second planarization layer 28 is disposed between the second matching layer 27 and the antireflection layer 29 described later. The second planarization layer 28 has a light incident surface 28a from which light is incident from the second matching layer 27 and a light emitting surface 28b from which light is emitted to the antireflection layer 29.

[0076] The second planarization layer 28 is formed as a recess 22d that enters the light emitting surface 22b of the wavelength conversion layer 22 through the opening 27c of the second matching layer 27, and the light emitting surface 28b is substantially planarized. That is, even if a portion of the second matching layer 27 produces an opening 27c caused by the recess 22d of the wavelength conversion layer 22, the light emitting surface 28b of the second planarization layer 28 is formed to be substantially planar.

[0077] As the material for the second planarization layer 28, the same transparent inorganic material, such as SiO2, is used as the material for the first planarization layer 24. The material of the second planarization layer 28 is not limited to SiO2. For example, it can also be a composite material containing SiON, YF3, SiNx, etc. Furthermore, in this embodiment, the first planarization layer 24 and the second planarization layer 28 are made of the same material, but it is also possible to use different materials.

[0078] The second planarization layer 28 also functions as a stress-relieving layer to mitigate stress caused by heat generated in the wavelength conversion layer 22. In this embodiment, the second planarization layer 28 is set to a thickness of less than half the thickness of the wavelength conversion layer 22. By setting such a thickness, the aforementioned stress-relieving function can be effectively performed.

[0079] An antireflective layer 29 is disposed on the light-emitting surface 28b of the second planarization layer 28, that is, on the side opposite to the surface of the second planarization layer 28 that faces the second mating layer 27. The antireflective layer 29 has a light-incident surface 29a from which light is incident from the second planarization layer 28 and a light-emitting surface 29b from which light is emitted outward. The light-emitting surface 28b of the second planarization layer 28 is substantially flat, therefore the antireflective layer 29 is also formed to be substantially flat. In addition, this embodiment employs a structure in which the heat dissipation substrate 21 is bonded to the light-incident surface 25a of the dichroic layer 25 via the bonding member 26, but the wavelength conversion layer 22 can also be supported by bonding the heat dissipation substrate 21 to the light-emitting surface 29b of the antireflective layer 29.

[0080] The antireflection layer 29 has the property of allowing the excitation light B and fluorescence Y emitted from the wavelength conversion layer 22 to pass through. By providing such an antireflection layer 29, it is possible to prevent the illumination light WL emitted from the light emitting surface 22b of the wavelength conversion layer 22 from being reflected towards the wavelength conversion layer 22 when it is emitted to the outside. As a result, the illumination light WL generated by the wavelength conversion layer 22 can be efficiently extracted from the wavelength conversion layer 22.

[0081] Thus, the anti-reflective layer 29 is a layer that suppresses light reflection at the interface between the second planarization layer 28 and air. The anti-reflective layer 29 can be constructed by alternately stacking layers with low refractive index, such as SiO2, and layers with high refractive index, such as tantalum pentoxide (Ta2O5).

[0082] The following is a detailed explanation of the first matching layer 23 and the second matching layer 27.

[0083] As described above, in this embodiment, a first matching layer 23 is provided between the wavelength conversion layer 22 and the first planarization layer 24. Furthermore, the optical refractive index of the first matching layer 23 is 1.64, which is between the optical refractive index of the wavelength conversion layer 22 (1.83) and the optical refractive index of the first planarization layer 24 (1.43).

[0084] Here, we consider the case where no first matching layer 23 is disposed between the first planarization layer 24 and the wavelength conversion layer 22. In this case, since the first planarization layer 24 and the wavelength conversion layer 22 have different refractive indices, interface reflection caused by the refractive index difference occurs. Therefore, a portion of the light emitted from the first planarization layer 24 toward the wavelength conversion layer 22 is reflected toward the first planarization layer 24 side, resulting in light loss and reduced light utilization efficiency.

[0085] In contrast, in the wavelength conversion element 20 of this embodiment, a first matching layer 23 is provided between the wavelength conversion layer 22 and the first planarization layer 24. This first matching layer 23 has an optical refractive index between the optical refractive index of the first planarization layer 24 and the optical refractive index of the wavelength conversion layer. Therefore, the difference in optical refractive index between the wavelength conversion layer 22 and the first matching layer 23, and the difference in optical refractive index between the first matching layer 23 and the first planarization layer 24, are both smaller than the difference in optical refractive index between the wavelength conversion layer 22 and the first planarization layer 24. This suppresses interface reflection generated within the wavelength conversion element 20. Furthermore, it suppresses light loss caused by interface reflection, thereby improving light utilization efficiency.

[0086] Here, when the light refractive index of the first matching layer 23 is n, the light refractive index of the wavelength conversion layer 22 is n1, and the light refractive index of the first planarization layer 24 is n2, ideally n satisfies the following relationship (1).

[0087] [Mathematical Expression 1]

[0088]

[0089] By having a refractive index that satisfies equation (1), the first matching layer 23 can suppress the reflection of light generated between the wavelength conversion layer 22 and the first planarization layer 24. In practice, n preferably satisfies the relationship of equation (2), and more preferably satisfies the relationship of equation (3).

[0090] [Mathematical Expression 2]

[0091]

[0092] [Mathematical Expression 3]

[0093]

[0094] In this embodiment, since n1 = 1.83, n2 = 1.43, and n = 1.64, equations (2) and (3) are valid. In other words, the material of the first matching layer 23 is selected in a manner that makes equation (2) or equation (3) valid.

[0095] In addition, when the optical refractive index of the first matching layer 23 is set to n, the wavelength of the excitation light B is λ, and the film thickness of the first matching layer 23 is d, the ideal optical distance (n·d) satisfies the following equation (4).

[0096] n·d=λ / 4…(4)

[0097] That is, the ideal film thickness of the first matching layer 23 can be calculated using Equation (4). Here, the measured value of the film thickness is preferably within ±20% of the ideal value calculated by Equation (4), and more preferably within ±10%.

[0098] When equation (4) is satisfied, the phase of the reflected light generated at the interface between the first planarization layer 24 and the first matching layer 23 is opposite to the phase of the reflected light generated at the interface between the first matching layer 23 and the wavelength conversion layer 22. Moreover, due to their interference, the reflection between the wavelength conversion layer 22 and the first planarization layer 24 is further suppressed. Furthermore, when the first matching layer 23 is composed of multiple films, the optical distance between each layer is specified by λ / 4, λ / 2, etc., so that the reflected wave becomes smaller at the interface of each layer.

[0099] Furthermore, as described above, the structure of the second matching layer 27 is the same as that of the first matching layer 23. Specifically, the refractive index of the second matching layer 27, disposed between the wavelength conversion layer 22 and the second planarization layer 28, is 1.64, which is between the refractive index of the wavelength conversion layer 22 (1.83) and the refractive index of the second planarization layer 28 (1.43). Therefore, the difference in refractive index between the wavelength conversion layer 22 and the second matching layer 27, and the difference in refractive index between the second matching layer 27 and the second planarization layer 28, are both smaller than the difference in refractive index between the wavelength conversion layer 22 and the second planarization layer 28. As a result, interface reflection generated within the wavelength conversion element 20 can be suppressed. Moreover, light loss caused by interface reflection can be suppressed, and light utilization efficiency can be improved.

[0100] Here, when the refractive index of the second matching layer 27 is set to n, the refractive index of the wavelength conversion layer 22 is n1, and the refractive index of the second planarization layer 28 is n2, ideally, n satisfies the relationship in equation (1) above. However, in reality, it is preferable to satisfy the relationship in equation (2) above, and more preferably to satisfy the relationship in equation (3) above. In this embodiment, since n1 = 1.83, n2 = 1.43, and n = 1.64, both equations (2) and (3) are valid. In other words, the material of the second matching layer 27 is selected in a way that makes equation (2) or equation (3) valid.

[0101] Furthermore, when the refractive index of the second matching layer 27 is set to n, the wavelength of the excitation light B is λ, and the film thickness of the second matching layer 27 is d, ideally the optical distance (n·d) satisfies the above equation (4). That is, the ideal film thickness of the second matching layer 27 can be calculated using equation (4). Here, the measured value of the film thickness is preferably within ±20% of the ideal value calculated by equation (4), and more preferably within ±10%.

[0102] Figure 4This is a line graph showing the average reflectance of the dichroic layer 25 near the wavelength region of fluorescence Y. In this graph, the horizontal axis represents the wavelength of light incident on the dichroic layer 25, and the vertical axis represents the average reflectance of the dichroic layer 25. The average reflectance is the average of the reflectances that vary depending on the position within the dichroic layer 25. In this graph, as a comparative example, the average reflectance is shown when the dichroic layer 25 is formed without forming the first planarization layer 24 on the light incident surface 22a of the wavelength conversion layer 22.

[0103] like Figure 4 As shown, in the dichroic layer 25 of this embodiment, i.e., the dichroic layer 25 formed on the first planarization layer 24, the average reflectance of fluorescence Y is higher than that of the comparative example. Therefore, fluorescence Y emitted from the light incident surface 22a side of the wavelength conversion layer 22 is efficiently reflected by the dichroic layer 25 in its original emission direction, and the light utilization efficiency is improved.

[0104] Figure 5 This is a line graph showing the average reflectance of the dichroic layer 25 near the wavelength region of the excitation light B. In this graph, the horizontal axis represents the wavelength of light incident on the dichroic layer 25, and the vertical axis represents the average reflectance of the dichroic layer 25. In this graph, the average reflectance is shown overlaid for each 10 nm variation in the thickness of the first planarization layer 24 within the range of 410 nm to 490 nm.

[0105] like Figure 5 As shown, in this embodiment, regardless of the thickness of the first planarization layer 24, the average reflectance of the dichroic layer 25 to the excitation light B is 4% or less in the wavelength range of 445 nm to 490 nm. Specifically, in the wavelength range of 450 nm to 485 nm, the average reflectance is 2% or less. Furthermore, in this embodiment, the difference between the maximum and minimum reflectance of the dichroic layer 25 to the excitation light B is 2% or less. Therefore, even if manufacturing errors occur due to the thickness of the first planarization layer 24, the reflection of the incident excitation light B can be suppressed, improving light utilization efficiency. Moreover, the maximum and minimum reflectance are the maximum and minimum values ​​of the reflectance that deviate based on the position within the dichroic layer 25, respectively.

[0106] As explained above, the wavelength conversion element 20, the light source device 2, and the projector 1 according to this embodiment can achieve the following effects.

[0107] According to the wavelength conversion element 20 of this embodiment, a first matching layer 23 having an optical refractive index between the wavelength conversion layer 22 and the first planarization layer 24 is disposed between the wavelength conversion layer 22 and the first planarization layer 24. Therefore, the difference in optical refractive index between the wavelength conversion layer 22 and the first matching layer 23, and the difference in optical refractive index between the first matching layer 23 and the first planarization layer 24, are both smaller than the difference in optical refractive index between the wavelength conversion layer 22 and the first planarization layer 24. This suppresses light loss caused by interface reflection generated within the wavelength conversion element 20, thereby improving light utilization efficiency.

[0108] Furthermore, according to the wavelength conversion element 20 of this embodiment, since the dichroic layer 25 reflects the fluorescence Y emitted from the light incident surface 22a side of the wavelength conversion layer 22, the emission of fluorescence Y from the light incident surface 22a side to the outside is suppressed, and the light utilization efficiency of fluorescence Y is improved.

[0109] Furthermore, according to the wavelength conversion element 20 of this embodiment, by making the first matching layer 23 have a light refractive index that satisfies formula (2) or formula (3), the reflection of light generated between the wavelength conversion layer 22 and the first planarization layer 24 can be further suppressed.

[0110] Furthermore, according to the wavelength conversion element 20 of this embodiment, since the film thickness of the first matching layer 23 satisfies equation (4), the phase of the reflected light generated at the interface between the first planarization layer 24 and the first matching layer 23 is opposite to the phase of the reflected light generated at the interface between the first matching layer 23 and the wavelength conversion layer 22. Therefore, through their interference, the reflection between the wavelength conversion layer 22 and the first planarization layer 24 is further suppressed.

[0111] Furthermore, according to the wavelength conversion element 20 of this embodiment, the average reflectance of the dichroic layer 25 to the excitation light B is 4% or less, and the difference between the maximum and minimum reflectance of the dichroic layer 25 to the excitation light B is 2% or less. That is, the reflectance to the excitation light B is suppressed to a small extent, and the deviation of the reflectance of the dichroic layer 25 to the excitation light B caused by deviations in the film thickness of the first planarization layer 24 is suppressed, thereby improving the light utilization efficiency.

[0112] Furthermore, according to the wavelength conversion element 20 of this embodiment, when the wavelength conversion layer 22 is a YAG-based phosphor and the first planarization layer 24 is SiO2, the first matching layer 23 is Al2O3 with a light refractive index between the light refractive index of the wavelength conversion layer 22 and the light refractive index of the first planarization layer 24, thus enabling the realization of a wavelength conversion element 20 with high light utilization efficiency.

[0113] Furthermore, according to the wavelength conversion element 20 of this embodiment, a second matching layer 27 having a refractive index between the wavelength conversion layer 22 and the second planarization layer 28 is disposed between the wavelength conversion layer 22 and the second planarization layer 28. Therefore, the difference in refractive index between the wavelength conversion layer 22 and the second matching layer 27, and the difference in refractive index between the second matching layer 27 and the second planarization layer 28, are both smaller than the difference in refractive index between the wavelength conversion layer 22 and the second planarization layer 28. This suppresses light loss caused by interface reflection generated within the wavelength conversion element 20, thereby improving light utilization efficiency.

[0114] Furthermore, according to the wavelength conversion element 20 of this embodiment, the reflection of light between air and the second planarization layer 28 is suppressed by the anti-reflection layer 29, thereby improving the light utilization efficiency.

[0115] Furthermore, according to the light source device 2 of this embodiment, since it is equipped with the wavelength conversion element 20 described above and the semiconductor laser 10a that emits excitation light B toward the light incident surface 22a of the wavelength conversion layer 22, the light utilization efficiency of the light source device 2 is improved.

[0116] Furthermore, according to this embodiment, the projector 1 has improved light utilization efficiency because it includes the light source device 2, the light modulation devices 4R, 4G, 4B that modulate the light from the light source device 2 in accordance with the image information to form image light, and the projection optical device 6 that projects image light.

[0117] This invention is not limited to the above-described embodiments, and appropriate modifications can be made without departing from the spirit of the invention.

[0118] For example, the specific descriptions of the shape, quantity, configuration, material, manufacturing method, etc. of each component of the wavelength conversion element 20, the light source device 2, and the projector 1 are not limited to the above embodiments and can be appropriately modified.

[0119] Furthermore, while the above embodiment illustrates an example of mounting the light source device 2 on a projector 1 using a liquid crystal panel, it is not limited to this. For example, it can also be mounted on a projector using a digital micromirror device as a light modulation device.

[0120] Alternatively, the light source device 2 can also be a structure with a rotating phosphor wheel that is rotated by a motor.

[0121] Furthermore, while the above embodiment illustrates an example of mounting the light source device 2 on the projector 1, it is not limited to this. The light source device 2 can also be applied to lighting fixtures, automotive headlights, etc.

[0122] [Summary of this disclosure]

[0123] The following is a summary published in this note.

[0124] (Postscript 1)

[0125] A wavelength conversion element is characterized by comprising: a wavelength conversion layer having a recess on its surface for converting first light of a first wavelength into second light of a second wavelength different from the first wavelength; a first layer disposed on a first surface of the wavelength conversion layer; and a first planarization layer disposed on a surface of the first layer opposite to the surface of the wavelength conversion layer and extending into the recess on the first surface, wherein the optical refractive index of the first layer is between the optical refractive index of the wavelength conversion layer and the optical refractive index of the first planarization layer.

[0126] According to the structure in Appendix 1, a first layer with a refractive index between the wavelength conversion layer and the first planarization layer is disposed between the wavelength conversion layer and the first planarization layer. Therefore, the difference in refractive index between the wavelength conversion layer and the first layer, and the difference in refractive index between the first layer and the first planarization layer, are both smaller than the difference in refractive index between the wavelength conversion layer and the first planarization layer. This suppresses light loss caused by interface reflection generated within the wavelength conversion element, thereby improving light utilization efficiency.

[0127] (Postscript 2)

[0128] According to Appendix 1, the wavelength conversion element is characterized in that it further comprises a reflective layer disposed on the side opposite to the surface of the first planar layer that is opposite to the surface of the first layer, so that the first light passes through and the second light emitted from the wavelength conversion layer is reflected.

[0129] According to the structure in Appendix 2, since the reflective layer reflects the second light emitted from the first side of the wavelength conversion layer, it suppresses the second light from the first side to the outside, thus improving the light utilization efficiency of the second light.

[0130] (Note 3)

[0131] According to Appendix 1 or 2, the wavelength conversion element is characterized in that, when the optical refractive index of the first layer is n, the optical refractive index of the wavelength conversion layer is n1, and the optical refractive index of the first planarization layer is n2, the following is satisfied:

[0132]

[0133] According to the structure in Appendix 3, by having a light refractive index that satisfies the above formula in the first layer, it is possible to further suppress the reflection of light generated between the wavelength conversion layer and the first planarization layer.

[0134] (Note 4)

[0135] The wavelength conversion element according to any one of Appendix 1 to Appendix 3 is characterized in that, when the optical refractive index of the first layer is n, the first wavelength is λ, and the film thickness of the first layer is d, it satisfies: n·d=λ / 4.

[0136] According to the structure in Appendix 4, by satisfying the above equation, the phase of the reflected light generated at the interface between the first planarization layer and the first layer is opposite to the phase of the reflected light generated at the interface between the first layer and the wavelength conversion layer. Therefore, through their interference, the reflection between the wavelength conversion layer and the first planarization layer is further suppressed.

[0137] (Note 5)

[0138] According to Appendix 2, the wavelength conversion element is characterized in that the average reflectivity of the reflective layer to the first light is less than 4%, and the difference between the maximum and minimum reflectivity of the reflective layer to the first light is less than 2%.

[0139] According to the structure in Appendix 5, the reflectivity of the first light is suppressed to a smaller extent, and the deviation of the reflectivity of the first light caused by the deviation of the film thickness of the first planarization layer is suppressed, thereby improving the light utilization efficiency.

[0140] (Note 6)

[0141] The wavelength conversion element according to any one of Appendices 1-5 is characterized in that the wavelength conversion layer is composed of a yttrium aluminum garnet (YAG) phosphor, the first layer is a monolayer composed of Al2O3, and the first planarization layer is SiO2.

[0142] According to the structure in Appendix 6, when the wavelength conversion layer is a YAG-type phosphor and the first planarization layer is SiO2, since the first layer uses Al2O3 with a light refractive index between the light refractive index of the wavelength conversion layer and the light refractive index of the first planarization layer, a wavelength conversion element with high light utilization efficiency can be realized.

[0143] (Note 7)

[0144] The wavelength conversion element according to any one of Appendices 1 to 6 is characterized in that it comprises: a second layer disposed on a second surface of the wavelength conversion layer opposite to the first surface; and a second planarization layer disposed on a surface of the second layer opposite to the surface of the wavelength conversion layer and extending into the recess of the second surface, wherein the optical refractive index of the second layer is between the optical refractive index of the wavelength conversion layer and the optical refractive index of the second planarization layer.

[0145] According to the structure in Appendix 7, a second layer with a refractive index between the wavelength conversion layer and the second planarization layer is disposed between the wavelength conversion layer and the second planarization layer. Therefore, the difference in refractive index between the wavelength conversion layer and the second layer, and the difference in refractive index between the second layer and the second planarization layer, are both smaller than the difference in refractive index between the wavelength conversion layer and the second planarization layer. This suppresses light loss caused by interface reflection generated within the wavelength conversion element, thereby improving light utilization efficiency.

[0146] (Note 8)

[0147] The wavelength conversion element according to Appendix 7 is characterized in that it further comprises an anti-reflection layer disposed on the side opposite to the surface of the second planar layer that is opposite to the second layer, allowing the first light and the second light to pass through.

[0148] According to the structure in Appendix 8, the reflection of light between the air and the second planarization layer is suppressed by the anti-reflective layer, thus improving the light utilization efficiency.

[0149] (Postscript 9)

[0150] A light source device, characterized in that it comprises: a wavelength conversion element as described in any one of Appendix 1 to Appendix 8; and a light-emitting element that emits the first light toward the first surface of the wavelength conversion layer.

[0151] According to the structure in Appendix 9, a light source device with high light utilization efficiency can be realized.

[0152] (Postscript 10)

[0153] A projector, characterized in that it comprises: a light source device as described in Appendix 9; a light modulation device that modulates light from the light source device in accordance with image information to form image light; and a projection optics device that projects the image light.

[0154] According to the structure in Appendix 10, a projector with high light utilization efficiency can be realized.

Claims

1. A wavelength conversion element, characterized in that, The wavelength conversion element includes: A wavelength conversion layer having recesses on its surface converts a first wavelength of light into a second wavelength of light that is different from the first wavelength. The first layer is disposed on a first surface of the wavelength conversion layer; as well as A first planarization layer is disposed on the side of the first layer opposite to the side facing the wavelength conversion layer, and extends into the recess of the first surface. The refractive index of the first layer is between that of the wavelength conversion layer and the refractive index of the first planarization layer. When the refractive index of the first layer is n, the refractive index of the wavelength conversion layer is n1, and the refractive index of the first planarization layer is n2, the following conditions are met: 。 2. The wavelength conversion element according to claim 1, characterized in that, The wavelength conversion element further includes a reflective layer disposed on the side opposite to the face of the first planar layer, allowing the first light to pass through and reflecting the second light emitted from the wavelength conversion layer.

3. The wavelength conversion element according to claim 1, characterized in that, When the refractive index of the first layer is n, the first wavelength is λ, and the thickness of the first layer is d, the following conditions are met: 。 4. The wavelength conversion element according to claim 2, characterized in that, The average reflectivity of the reflective layer to the first light is less than 4%, and the difference between the maximum and minimum reflectivity of the reflective layer to the first light is less than 2%.

5. The wavelength conversion element according to any one of claims 1 to 4, characterized in that, The wavelength conversion layer is composed of yttrium aluminum garnet (YAG) based phosphors. The first layer is a single layer composed of Al2O3. The first planarization layer is SiO2.

6. The wavelength conversion element according to any one of claims 1 to 4, characterized in that, The wavelength conversion element includes: A second layer, disposed on a second surface of the wavelength conversion layer opposite to the first surface; and A second planarization layer is disposed on the side of the second layer opposite to the side opposite to the wavelength conversion layer, and extends into the recess of the second surface. The optical refractive index of the second layer is between that of the wavelength conversion layer and the second planarization layer.

7. The wavelength conversion element according to claim 6, characterized in that, The wavelength conversion element also includes an anti-reflection layer disposed on the side opposite to the surface of the second planar layer, allowing the first light and the second light to pass through.

8. A light source device, characterized in that, The light source device includes: The wavelength conversion element as claimed in claim 1; and A light-emitting element that emits the first light toward the first surface of the wavelength conversion layer.

9. A projector, characterized in that, The projector has the following features: The light source device according to claim 8; An optical modulation device that modulates light from the light source device in accordance with image information to form image light; and A projection optical device that projects the image light.

Images