Wavelength conversion device, method for manufacturing wavelength conversion device, light source device, and projector

Abstract

To provide a wavelength conversion device that can improve the bonding strength of a wavelength conversion layer at low cost, a method for manufacturing a wavelength conversion device, a light source device, and a projector.SOLUTION: A wavelength conversion device of the present invention comprises: a wavelength conversion layer that converts first light incident thereon into second light having a wavelength range different from the first light; a substrate that is connected to the wavelength conversion layer in a thermally conductive manner; and a bonding layer that bonds the wavelength conversion layer and the substrate to each other. The bonding layer has a first metal layer and a second metal layer. The first metal layer is arranged toward the substrate with respect to the second metal layer between the substrate and the wavelength conversion layer. The second metal layer is arranged between the first metal layer and the wavelength conversion layer. The substrate does not have a plating layer on a surface and is joined to the first metal layer.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a wavelength converter, a method for manufacturing a wavelength converter, a light source device, and a projector. [Background technology]

[0002] Recently, there has been a lighting device that includes a light source that emits laser light and a wavelength conversion element that emits fluorescence upon incidence of the laser light, thereby generating fluorescence as illumination light. In this lighting device, the wavelength conversion element includes a phosphor layer, a substrate that supports the phosphor layer, and a bonding layer that bonds the phosphor layer to the substrate. For example, copper, which has excellent heat dissipation properties, is used as the material for the substrate, and nano-silver paste is sometimes used as the bonding layer.

[0003] Patent Document 1 below discloses a bonding technique for bonding semiconductor components to a copper substrate using nanosilver paste. It is known that such a bonding technique can improve bonding strength by, for example, suppressing the formation of an oxide film on the copper substrate by sintering in a nitrogen atmosphere, or by subjecting the copper substrate to a nickel-gold plating treatment. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-077780 Summary of the Invention [Problem to be solved by the invention]

[0005] However, nickel-gold plating has the drawback of being expensive, and even when the sintering process is carried out in a nitrogen atmosphere, it is difficult to achieve a completely oxygen-free environment, which can lead to oxidation of the copper substrate surface and a decrease in bonding strength. [Means for solving the problem]

[0006] In order to solve the above problem, one embodiment of a wavelength conversion device of the present invention comprises a wavelength conversion layer that converts incident first light into second light having a wavelength band different from that of the first light, a substrate that is thermally connected to the wavelength conversion layer, and a bonding layer that bonds the wavelength conversion layer to the substrate, wherein the bonding layer has a first metal layer and a second metal layer, the first metal layer is disposed between the substrate and the wavelength conversion layer and on the substrate side with respect to the second metal layer, the second metal layer is disposed between the first metal layer and the wavelength conversion layer, and the substrate does not have a plating layer on its surface and is bonded to the first metal layer.

[0007] Furthermore, one embodiment of the present invention provides a method for manufacturing a wavelength conversion device having a wavelength conversion layer, a substrate thermally connected to the wavelength conversion layer, and a bonding layer bonding the wavelength conversion layer to the substrate, the method comprising: a first step of placing a first metal material on the substrate; a second step of high-frequency heating the substrate to sinter the first metal material and form a first metal layer on the substrate; a third step of placing a second metal material on the first metal layer; a fourth step of placing the wavelength conversion layer on the second metal material; and a fifth step of drying the second metal material to form a second metal layer and bonding it to the first metal layer to generate the bonding layer.

[0008] A light source device according to one aspect of the present invention includes the wavelength conversion device according to the above aspect, and a light source that emits the first light to the wavelength conversion device.

[0009] Furthermore, a projector according to one aspect of the present invention comprises a light source device according to the above aspect, an optical modulation device that modulates the light emitted from the light source device in accordance with image information, and a projection optical device that projects the light modulated by the optical modulation device. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram showing a schematic configuration of a projector according to an embodiment. [Figure 2] FIG. 1 is a diagram illustrating a schematic configuration of a lighting device. [Figure 3] FIG. 2 is a cross-sectional view showing a configuration of a main part of a wavelength conversion device. [Figure 4A] 3A to 3C are diagrams each showing a part of a manufacturing process of a wavelength converter. [Figure 4B] 3A to 3C are diagrams each showing a part of a manufacturing process of a wavelength converter. [Figure 4C] 1A to 1C are diagrams each showing a part of a manufacturing process of a wavelength converter. [Figure 4D] 3A to 3C are diagrams each showing a part of a manufacturing process of a wavelength converter. [Figure 4E] 1A to 1C are diagrams each showing a part of a manufacturing process of a wavelength converter. [Figure 4F] 3A to 3C are diagrams each showing a part of a manufacturing process of a wavelength converter. [Figure 5A] 10A to 10C are diagrams illustrating a part of a process according to a modified example. [Figure 5B] 10A to 10C are diagrams illustrating a part of a process according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, the drawings used in the following explanation may show characteristic parts enlarged for convenience in order to make the features easier to understand, and the dimensional ratios of each component may not necessarily be the same as in reality.

[0012] First, an example of a projector according to this embodiment will be described. FIG. 1 is a diagram showing a schematic configuration of a projector according to this embodiment. 1, the projector 1 of this embodiment is a projection-type image display device that displays a color image on a screen SCR. The projector 1 includes an illumination device 2, a color separation optical system 3, a light modulation device 4R, a light modulation device 4G, a light modulation device 4B, a combining optical system 5, and a projection optical system 6.

[0013] The color separation optical system 3 separates the illumination light WL incident from the illumination device 2 into red light LR, green light LG, and blue light LB. The color separation optical system 3 mainly includes a first dichroic mirror 7a, a second dichroic mirror 7b, a first reflecting mirror 8a, a second reflecting mirror 8b, and a third reflecting mirror 8c, and a first relay lens 9a and a second relay lens 9b.

[0014] The first dichroic mirror 7a separates the illumination light WL into red light LR and other light, green light LG and blue light LB. The first dichroic mirror 7a transmits the separated red light LR and reflects the other light, green light LG and blue light LB. On the other hand, the second dichroic mirror 7b reflects the green light LG and transmits the blue light LB, thereby separating the other light into green light LG and blue light LB.

[0015] The first reflecting mirror 8a is disposed in the optical path of the red light LR and reflects 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 reflecting mirror 8b and the third reflecting mirror 8c are disposed in the optical path of the blue light LB and guide the blue light LB that has passed through the second dichroic mirror 7b toward the optical modulation device 4B. The green light LG is reflected from the second dichroic mirror 7b toward the optical modulation device 4G.

[0016] The first relay lens 9a and the second relay lens 9b are disposed after the second dichroic mirror 7b in the optical path of the blue light LB.

[0017] The light modulation device 4R modulates the red light LR according to image information to form image light corresponding to the red light LR. The light modulation device 4G modulates the green light LG according to image information to form image light corresponding to the green light LG. The light modulation device 4B modulates the blue light LB according to image information to form image light corresponding to the blue light LB.

[0018] For example, a transmissive liquid crystal panel is used for the light modulation device 4R, the light modulation device 4G, and the light modulation device 4B. Furthermore, a polarizing plate (not shown) is disposed on each of the incident side and the exit side of the liquid crystal panel.

[0019] Furthermore, field lenses 10R, 10G, and 10B are arranged on the incident sides of optical modulation device 4R, optical modulation device 4G, and optical modulation device 4B, respectively. Field lenses 10R, 10G, and 10B collimate the red light LR, green light LG, and blue light LB incident on optical modulation device 4R, optical modulation device 4G, and optical modulation device 4B, respectively.

[0020] The image light from the light modulation device 4R, the light modulation device 4G, and the light modulation device 4B is incident on the combining optical system 5. The combining optical system 5 combines the image light corresponding to the red light LR, the green light LG, and the blue light LB, respectively, and emits this combined image light toward the projection optical system 6. The combining optical system 5 uses, for example, a cross dichroic prism.

[0021] The projection optical system 6 is made up of a group of projection lenses, and projects the image light combined by the combining optical system 5 onto the screen SCR in an enlarged form, thereby displaying an enlarged color image on the screen SCR.

[0022] (Lighting equipment) Next, an illumination device 2 according to this embodiment will be described. Fig. 2 is a diagram showing a schematic configuration of the illumination device 2. As shown in Fig. 2, the illumination device 2 includes a light source device 2A, an integrator optical system 31, a polarization conversion element 32, and a superimposing lens 33a. In this embodiment, the integrator optical system 31 and the superimposing lens 33a form a superimposing optical system 33.

[0023] The light source device 2A includes an array light source 21A, a collimator optical system 22, an afocal optical system 23, a first retardation plate 28a, a polarization separation element 25, a first focusing optical system 26, a wavelength conversion device 40, a second retardation plate 28b, a second focusing optical system 29, and a diffuse reflection element 30.

[0024] The array light source 21A, collimator optical system 22, afocal optical system 23, first retardation plate 28a, polarization separation element 25, second retardation plate 28b, second focusing optical system 29, and diffuse reflector 30 are sequentially arranged on an optical axis ax1. Meanwhile, the wavelength conversion device 40, first focusing optical system 26, polarization separation element 25, integrator optical system 31, polarization conversion element 32, and superimposing lens 33a are sequentially arranged on an illumination optical axis ax2. The optical axis ax1 and the illumination optical axis ax2 are in the same plane and are perpendicular to each other.

[0025] The array light source 21A includes a plurality of semiconductor lasers 211 as solid-state light sources. The plurality of semiconductor lasers 211 are arranged in an array in a plane perpendicular to the optical axis ax1. The semiconductor lasers 211 emit, for example, a blue light beam BL (e.g., laser light having a peak wavelength of 460 nm). The array light source 21A emits a ray bundle consisting of the plurality of light beams BL. In this embodiment, the array light source 21A corresponds to the "light source" in the claims.

[0026] The light beams BL emitted from the array light source 21A are incident on the collimator optical system 22. The collimator optical system 22 converts the light beams BL emitted from the array light source 21A into parallel light. The collimator optical system 22 is composed of, for example, a plurality of collimator lenses 22a arranged in an array. The plurality of collimator lenses 22a are arranged corresponding to the plurality of semiconductor lasers 211.

[0027] The light beam BL that has passed through the collimator optical system 22 enters the afocal optical system 23 . The afocal optical system 23 adjusts the beam diameter of the light beam BL. The afocal optical system 23 is composed of, for example, a convex lens 23a and a concave lens 23b.

[0028] The light ray BL that has passed through the afocal optical system 23 is incident on the first retardation plate 28a. The first retardation plate 28a is, for example, a rotatable half-wave plate. The light ray BL emitted from the semiconductor laser 211 is linearly polarized light. By appropriately setting the rotation angle of the first retardation plate 28a, the light ray BL that passes through the first retardation plate 28a can be made to contain a predetermined ratio of S-polarized component and P-polarized component relative to the polarization separation element 25. By rotating the first retardation plate 28a, the ratio of the S-polarized component and the P-polarized component can be changed.

[0029] The light beam BL, which contains an S-polarized component and a P-polarized component generated by passing through the first retardation plate 28a, enters the polarization separation element 25. The polarization separation element 25 is formed, for example, by a polarization beam splitter having wavelength selectivity. The polarization separation element 25 also forms an angle of 45° with respect to the optical axis ax1 and the illumination optical axis ax2.

[0030] The polarization separation element 25 has a polarization separation function of separating the light ray BL into a light ray BLs having an S-polarized component and a light ray BLp having a P-polarized component relative to the polarization separation element 25. Specifically, the polarization separation element 25 reflects the light ray BLs having an S-polarized component and transmits the light ray BLp having a P-polarized component.

[0031] The polarization separation element 25 also has a color separation function of transmitting the fluorescence YL, which has a different wavelength band from that of the light BL, regardless of its polarization state.

[0032] The S-polarized light beam BLs emitted from the polarization separation element 25 is incident on the first focusing optical system 26. The first focusing optical system 26 focuses the light beam BLs toward the wavelength conversion device 40.

[0033] In this embodiment, the first focusing optical system 26 is composed of, for example, a first lens 26a and a second lens 26b. The light beam BLs emitted from the first focusing optical system 26 is incident on the wavelength conversion device 40 in a focused state.

[0034] The fluorescence YL generated by the wavelength converter 40 is collimated by the first light-collecting optical system 26 and then enters the polarization separation element 25. The fluorescence YL is transmitted through the polarization separation element 25.

[0035] On the other hand, P-polarized light ray BLp emerging from polarization separation element 25 is incident on second retardation plate 28b. Second retardation plate 28b is composed of a quarter-wave plate arranged in the optical path between polarization separation element 25 and diffuse reflection element 30. Therefore, P-polarized light ray BLp emerging from polarization separation element 25 is converted by second retardation plate 28b into, for example, right-handed circularly polarized blue light BLc1, and then enters second focusing optical system 29. The second light-collecting optical system 29 is composed of, for example, convex lenses 29a and 29b, and causes the blue light BLc1 to be incident on the diffuse reflecting element 30 in a condensed state.

[0036] The diffuse reflecting element 30 is disposed on the opposite side of the polarization separating element 25 from the phosphor layer 42, and diffusely reflects the blue light BLc1 emitted from the second focusing optical system 29 toward the polarization separating element 25. It is preferable to use a diffuse reflecting element 30 that can Lambertian-reflect the blue light BLc1 without disturbing the polarization state.

[0037] Hereinafter, the light diffusely reflected by the diffuse reflecting element 30 will be referred to as blue light BLc2. According to this embodiment, blue light BLc2 with a substantially uniform illuminance distribution is obtained by diffusively reflecting blue light BLc1. For example, right-handed circularly polarized blue light BLc1 is reflected as left-handed circularly polarized blue light BLc2.

[0038] The blue light BLc2 is converted into parallel light by the second focusing optical system 29 and then enters the second retardation plate 28b again.

[0039] The left-handed circularly polarized blue light BLc2 is converted by the second retardation plate 28b into S-polarized blue light BLs1. The S-polarized blue light BLs1 is reflected by the polarization separation element 25 towards the integrator optical system 31.

[0040] As a result, the blue light BLs1 generates illumination light WL together with the fluorescence YL that has passed through the polarization separation element 25. That is, the blue light BLs1 and fluorescence YL are emitted in the same direction from the polarization separation element 25, and white illumination light WL is generated as a mixture of the blue light BLs1 and the fluorescence (yellow light) YL. In this way, the light source device 2A generates white illumination light WL.

[0041] The illumination light WL is emitted toward the integrator optical system 31. The integrator optical system 31 is composed of, for example, a lens array 31a and a lens array 31b. The lens arrays 31a and 31b are each composed of a plurality of small lenses arranged in an array.

[0042] The illumination light WL transmitted through the integrator optical system 31 is incident on the polarization conversion element 32. The polarization conversion element 32 is composed of a polarization separation film and a retardation plate. The polarization conversion element 32 converts the illumination light WL containing unpolarized fluorescence YL into linearly polarized light.

[0043] The illumination light WL that has passed through the polarization conversion element 32 is incident on the superimposing lens 33a. The superimposing lens 33a cooperates with the integrator optical system 31 to homogenize the illuminance distribution of the illumination light WL in the illuminated area. In this way, the illumination device 2 emits the illumination light WL.

[0044] (Wavelength conversion device) 3 is a cross-sectional view showing the configuration of the main part of the wavelength converter 40. Hereinafter, the light beam BLs emitted from the first light-collecting optical system 26 and incident on the phosphor layer 42 will be referred to as excitation light BLs. As shown in FIG. 3 , the wavelength conversion device 40 includes a substrate 41, a phosphor layer 42, and a bonding layer 50. The wavelength conversion device 40 of this embodiment has a fixed configuration in which the substrate 41 does not rotate. The substrate 41 has a first surface 41a facing the first focusing optical system 26 and a second surface 41b opposite to the first surface 41a. The bonding layer 50 bonds the substrate 41 and the phosphor layer 42. The wavelength conversion device 40 of this embodiment further includes a reflective member 43 provided between the bonding layer 50 and the phosphor layer 42. In this embodiment, the phosphor layer 42 is an example of the "wavelength conversion layer" of the present invention.

[0045] Substrate 41 is connected to phosphor layer 42 in a manner that allows thermal conductivity. It is preferable to use a material with high thermal conductivity and excellent heat dissipation properties as the material for substrate 41, and in this embodiment, substrate 41 is formed using copper. Note that by providing a heat dissipation member made of a heat sink on second surface 41b of substrate 41, the heat dissipation properties of substrate 41 may be further improved and thermal deterioration of phosphor layer 42 may be suppressed.

[0046] In this embodiment, the phosphor layer 42 is a ceramic phosphor formed by firing phosphor particles. The phosphor particles constituting the phosphor layer 42 are made of YAG (Yttrium Aluminum Garnet) phosphor containing Ce ions.

[0047] The phosphor particles may be made of one material, or a mixture of particles formed using two or more materials may be used. A phosphor layer in which phosphor particles are dispersed in an inorganic binder such as alumina, or a phosphor layer formed by firing a glass binder, which is an inorganic material, and phosphor particles may be suitably used as the phosphor layer 42. Alternatively, the phosphor layer may be formed by firing phosphor particles without using a binder.

[0048] The phosphor layer 42 is bonded onto a first surface 41a of the substrate 41 via a bonding layer 50, which will be described later. The phosphor layer 42 has a front surface 42a that receives excitation light BLs and emits fluorescence YL obtained by wavelength-converting the excitation light BLs, and a back surface 42b opposite the front surface 42a, i.e., a back surface 42b on which a reflecting member 43 and the substrate 41 are provided. That is, in this embodiment, the substrate 41 is disposed on the side opposite the front surface 42a on which the excitation light BLs of the phosphor layer 42 is incident. The reflecting member 43 reflects light incident from the phosphor layer 42 toward the first focusing optical system 26. In this embodiment, the excitation light BLs is an example of the "first light" of the present invention, and the fluorescence YL is an example of the "second light having a wavelength band different from that of the first light" of the present invention.

[0049] The phosphor layer 42 has light scattering properties due to a plurality of pores formed therein. Some of the pores are formed on the rear surface 42b of the phosphor layer 42, causing unevenness on the rear surface 42b of the phosphor layer 42 due to the pores. The phosphor layer 42 of this embodiment includes a planarizing film (not shown) that planarizes the rear surface 42b. The planarizing film is made of, for example, SiO2, an inorganic material having light transmissivity, and flattens the rear surface 42b by penetrating into the unevenness on the rear surface 42b.

[0050] The reflecting member 43 of this embodiment is configured by laminating a total reflecting layer made of a multilayer film and a reflecting layer made of a metal material such as Ag that has high reflectance. The reflecting member 43 is formed by sequentially depositing the multilayer film and the reflecting layer on the rear surface 42b of the phosphor layer 42 by vapor deposition, sputtering, or the like.

[0051] In the present embodiment, by making the surface of the phosphor layer 42 substantially flat by the planarizing film as described above, the reflective member 43 can be uniformly formed on the back surface 42b of the phosphor layer 42. This improves the adhesion between the phosphor layer 42 and the reflective member 43, and the bonding layer 50 can favorably bond the substrate and the phosphor layer 42 via the reflective member 43.

[0052] In this way, the reflecting member 43 reflects a portion of the fluorescence YL generated in the phosphor layer 42 and heading toward the substrate 41 toward the surface 42a, thereby enabling the fluorescence YL to be efficiently extracted to the outside of the phosphor layer 42.

[0053] The bonding layer 50 has a first metal layer 51 and a second metal layer 52. The first metal layer 51 is disposed between the substrate 41 and the phosphor layer 42 and on the substrate 41 side of the second metal layer 52. In other words, the first metal layer 51 is a metal layer facing the substrate 41. The second metal layer 52 is a metal layer disposed between the first metal layer 51 and the phosphor layer 42. The first metal layer 51 and the second metal layer 52 are sintered under different heating conditions as described below, and therefore have different sintering densities. Therefore, the first metal layer 51 and the second metal layer 52 are not integrated with each other, but are composed of two metal layers with different boundaries.

[0054] The bonding layer 50 has a size sufficient to cover the entire back surface 42b of the phosphor layer 42. In the present embodiment, in a planar view, the outer periphery of the bonding layer 50 is located outside the outer periphery of the phosphor layer 42. Therefore, in a planar view, the phosphor layer 42 is placed on the bonding layer 50.

[0055] The first metal layer 51 is bonded to the first surface 41a of the substrate 41. In the present embodiment, no plating layer is provided on the first surface 41a of the substrate 41, and the first surface 41a of the substrate 41 and the first metal layer 51 are directly bonded together. A method for bonding the first metal layer 51 to the substrate 41 will be described later.

[0056] The first metal layer 51 is covered with the second metal layer 52. The second metal layer 52 covers the first metal layer 51 except for the surface that is bonded to the substrate 41. The second metal layer 52 is in contact with the back surface 42b of the phosphor layer 42.

[0057] The first metal layer 51 is formed by sintering a first metal material containing metal particles made of at least Ag. The second metal layer 52 is formed by sintering a second metal material containing metal particles made of at least Ag. In this embodiment, nanosilver paste is used as the first metal material and the second metal material. Note that the first metal material and the second metal material may contain metal particles other than Ag, such as metal particles of Au or Cu.

[0058] It is known that the thermal conductivity and adhesive strength of the first or second metal material change depending on the content of metal particles. For example, it is known that the greater the content of metal particles, the higher the thermal conductivity of the metal material, but the lower the adhesive strength as a bonding layer.

[0059] In contrast, in the bonding layer 50 of this embodiment, the content of metal fine particles of the first metal material constituting the first metal layer 51 is greater than the content of metal fine particles of the second metal material constituting the second metal layer 52. With this configuration, the thermal conductivity of the first metal layer 51 can be made greater than that of the second metal layer 52, and the adhesive strength of the second metal layer 52 to the phosphor layer 42 can be made greater than the adhesive strength of the first metal layer 51 to the phosphor layer 42. According to the bonding layer 50 of the present embodiment, heat generated in the phosphor layer 42 during the production of the fluorescence YL is efficiently transferred to the substrate 41 via the first metal layer 51, thereby efficiently dissipating the heat from the phosphor layer 42. Furthermore, the phosphor layer 42 is well bonded to the substrate 41 by the second metal layer 52, which can prevent problems such as peeling or breakage of the phosphor layer 42 due to thermal stress.

[0060] Next, a method for manufacturing the wavelength converter 40 of this embodiment will be described. The manufacturing method of the wavelength conversion device 40 of this embodiment includes a first step of placing a first metal material on a substrate 41, a second step of sintering the first metal material by high-frequency heating the substrate 41 to form a first metal layer 51 on the substrate 41, a third step of placing a second metal material on the first metal layer 51, a fourth step of placing a phosphor layer 42 on the second metal material, and a fifth step of bonding the second metal layer 52 formed by drying the second metal material to the first metal layer 51 to generate a bonding layer 50. The method for manufacturing the wavelength converter 40 of this embodiment further includes a preparation step of reducing the surface of the base material that constitutes the substrate 41 as a pre-step before the first step.

[0061] Each step will be described below. Note that Figures 4A to 4E are views showing parts of the manufacturing process of the wavelength converter 40.

[0062] 4A, in the preparation step, for example, a base material 41A made of pure copper is immersed for 1 minute in a solution P of dilute sulfuric acid, which is prepared by diluting 5 ml of sulfuric acid with 100 ml of pure water. This reduces the surface of the base material 41A, and the preparation step of the substrate 41 in which the oxide film is removed from the surface is completed.

[0063] 4B, in the first step, nanosilver paste is placed on the substrate 41 as the first metal material 151. In the case of this embodiment, the nanosilver paste is applied onto the first surface 41a of the substrate 41 by, for example, screen printing.

[0064] 4C, in the second step, an alternating current is passed through a coil K disposed around the substrate 41, thereby high-frequency heating the substrate 41. At this time, heat is generated on the surface of the substrate 41 by eddy currents caused by electromagnetic induction. As a result, the first metal material 151 disposed on the first surface 41a can be heated.

[0065] As a condition for high frequency heating, it is desirable to use a high frequency band of, for example, 10 KHz or more. By using such a high frequency band, it is possible to efficiently generate heat only on the surface of the substrate 41, and to efficiently heat the nano silver paste.

[0066] The second process includes a first heating step in which the substrate 41 is heated to 50°C to 100°C, and a second heating step in which the substrate 41 is heated to 200°C to 300°C. In this embodiment, in the first heating step, an alternating current is passed through the coil K for 10 minutes at 80° C. to heat the substrate 41. The first heating step makes it possible to volatilize the solvent in the nanosilver paste. In addition, as a second heating step, an alternating current is passed through the coil K for 120 minutes at 200°C to 300°C to heat the substrate 41. In the second heating step, the first metal material 151 made of nanosilver paste is sintered to form a first metal layer 51 on the substrate 41. The temperature and heating time of the high-frequency heating described above are merely examples and are not limited to the above values.

[0067] High-frequency heating does not easily raise the temperature of the atmosphere surrounding the substrate 41 because the substrate 41 itself generates heat. As a result, the air around the substrate 41 is heated and activated, making it difficult for an oxide film to form on the surface of the substrate 41. Therefore, according to the second step using high-frequency heating, it is possible to make it difficult for an oxide film to form on the first surface 41a of the substrate 41, and therefore it is possible to suppress a decrease in bonding strength due to the formation of an oxide film at the interface between the first metal layer 51 and the substrate 41. Therefore, it is possible to sufficiently increase the bonding strength between the substrate 41 and the first metal layer 51.

[0068] Conventionally, when bonding nanosilver paste to a substrate made of pure copper, nickel-gold plating is required to prevent the formation of an oxide film on the surface of the substrate, which increases costs. Alternatively, the sintering process may be performed in a nitrogen atmosphere to prevent the formation of an oxide film on the surface of the substrate, but maintaining a complete vacuum atmosphere is difficult, making it difficult to completely prevent the formation of an oxide film. In contrast, according to the manufacturing method of the wavelength conversion device 40 of this embodiment, the first surface 41a of the substrate 41 and the first metal layer 51 can be directly bonded without an oxide film therebetween, without providing a plating layer on the substrate 41 and without using special equipment such as a nitrogen atmosphere, thereby enabling good bonding between the bonding layer and the substrate 41 while reducing costs.

[0069] 4D, in the third step, nanosilver paste is placed on the first metal layer 51 as the second metal material 152. As described above, the content of metal particles in the first metal material 151 is greater than the content of metal particles in the second metal material 152. That is, in the case of this embodiment, for example, a dispenser D is used to apply nanosilver paste with a reduced content of silver particles as the second metal material 152 onto the first metal layer 51.

[0070] 4E, in the fourth step, the phosphor layer 42 is placed on the second metal material 152. In the case of this embodiment, for example, the phosphor layer 42 held by the mounter M is placed on the second metal material 152 while being pressed against it. As a result, the second metal material 152 pressed by the phosphor layer 42 wets and spreads on the first metal layer 51, thereby covering the surface of the first metal layer 51.

[0071] Next, in the fifth step, as shown in FIG. 4F , the second metal layer 52 formed by drying the second metal material 152 is bonded to the first metal layer 51 to form the bonding layer 50. In this embodiment, the second metal material 152 is dried using a dryer T. Because the film thickness of the second metal material 152 is thinner than that of the first metal layer 51, the drying time can be shorter than when the entire bonding layer is dried in the dryer T. In this embodiment, the temperature inside the dryer T is set to 200°C, and the second metal material 152 is dried for two hours. During the drying process using the dryer T, an oxide film is formed on the surface of the substrate 41 except for the bonding interface between the first metal layer 51 and the substrate 41. However, this oxide film does not affect the bonding strength of the bonding layer 50 and is therefore not a problem.

[0072] In this embodiment, the first metal layer 51 and the second metal layer 52 are both made of nanosilver paste, which provides excellent adhesion between the first metal layer 51 and the second metal layer 52. Therefore, the bonding layer 50 can stably bond the phosphor layer 42 bonded to the first metal layer 51 to the substrate 41 bonded to the second metal layer 52. The first metal layer 51 and the second metal layer 52 are sintered under different heating conditions, resulting in different sintering densities. Therefore, the first metal layer 51 and the second metal layer 52 are not integrated with each other, but are composed of two metal layers with different boundaries.

[0073] Here, as a comparative example, consider the case where second metal material 152 is dried using high-frequency heating, similar to first metal material 151. When second metal material 152 is rapidly heated by high-frequency heating, bumping occurs, in which gas contained in the solvent of the nanosilver paste is expelled to the outside, which may cause poor bonding at the interface between second metal material 152 and phosphor layer 42 arranged on second metal material 152.

[0074] In contrast, in the present embodiment, a heating process using a dryer T is adopted for the second metal material 152 that comes into contact with the phosphor layer 42 instead of high-frequency heating, so that the phosphor layer 42 and the second metal material 152 can be bonded well.

[0075] Although the above-mentioned boiling also occurs in the first heating step of the second process, the gas is discharged from the outer surface of the first metal material 151 opposite the substrate 41, and therefore the effect of the gas generated by the boiling on the bonding surfaces of the first metal material 151 and the substrate 41 is very small. In this manner, the wavelength converter 40 of this embodiment shown in FIG. 3 can be manufactured.

[0076] As described above, the content of silver particles in the first metal material 151 is greater than the content of silver particles in the second metal material 152, so the thermal conductivity of the first metal layer 51 can be made greater than the thermal conductivity of the second metal layer 52. In addition, the adhesive strength of the second metal layer 52 to the phosphor layer 42 can be made greater than the adhesive strength of the first metal layer 51 to the phosphor layer 42.

[0077] As described above, the wavelength conversion device 40 of this embodiment includes a phosphor layer 42 that converts incident excitation light BLs into fluorescence YL, a substrate 41 that is thermally connected to the phosphor layer 42, and a bonding layer 50 that bonds the phosphor layer 42 to the substrate 41. The bonding layer 50 has a first metal layer 51 and a second metal layer 52. The first metal layer 51 is disposed between the substrate 41 and the phosphor layer 42 and on the substrate 41 side with respect to the second metal layer 52, and the second metal layer 52 is disposed between the first metal layer 51 and the phosphor layer 42. The substrate 41 does not have a plating layer on its surface and is bonded to the first metal layer 51.

[0078] According to the wavelength conversion device 40 of this embodiment, a bonding layer 50 is provided which has a first metal layer 51 directly bonded to the substrate 41 without using a plating layer and a second metal layer 52 which bonds the first metal layer 51 and the phosphor layer 42 together, thereby enabling good bonding between the phosphor layer 42 and the substrate 41 while reducing costs.

[0079] In the bonding layer 50 of this embodiment, the first metal layer 51 is covered with the second metal layer 52. This increases the contact area between the second metal layer 52 and the first metal layer 51, thereby improving the bonding reliability between them.

[0080] Furthermore, according to the manufacturing method of the wavelength converter 40 of this embodiment, the first metal layer 51 that bonds to the substrate 41 and the second metal layer 52 that bonds the first metal layer 51 and the phosphor layer 42 can be formed by an optimal heating method. By sintering the first metal layer 51 using high-frequency heating, it is possible to directly bond the first surface 41a of the substrate 41 to the first metal layer 51 without providing a plating layer on the substrate 41 and without an oxide film therebetween, thereby achieving good bonding between the phosphor layer 42 and the substrate 41 while reducing costs. Furthermore, special equipment such as a nitrogen atmosphere is not required to suppress the formation of an oxide film. By sintering the second metal layer 52 using a conventional drying process rather than high-frequency heating, it is possible to prevent poor bonding of the phosphor layer 42 due to bumping, and therefore the phosphor layer 42 can be well bonded to the first metal layer 51 via the second metal layer 52. Therefore, it is possible to manufacture a wavelength conversion device 40 in which the bonding strength of the phosphor layer 42 to the substrate 41 can be improved at low cost.

[0081] Furthermore, the light source device 2A equipped with this wavelength conversion device 40 can realize a highly reliable light source device that generates bright fluorescence YL by suppressing peeling of the phosphor layer 42 and increasing the cooling efficiency of the phosphor layer 42. Furthermore, according to the projector 1 of this embodiment, since the projector 1 is provided with the light source device 2A, the projector 1 can form a high-brightness image.

[0082] The technical scope of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, the case where the base material 41A is immersed in a solution made of dilute sulfuric acid has been taken as an example of a preparation step in the method for manufacturing the wavelength converter 40, but the preparation step is not limited to reducing the surface of the base material 41A.

[0083] 5A and 5B are diagrams showing some of the steps according to the modified example. As shown in Fig. 5A, a hydrogen plasma treatment PZ is performed on the surface of a base material 41A made of pure copper, thereby removing an oxide film from the surface of the base material 41A, and the preparation step for a substrate 141 shown in Fig. 5B is completed.

[0084] 5B has an uneven portion 141a consisting of a plurality of recesses or protrusions on its surface. Therefore, by heating the first metal material 151 arranged on the first surface 41a, the first metal layer 51 is bonded to the uneven portion 141a of the substrate 141. According to this configuration, the first metal layer 51 penetrates into the gaps of the uneven portion 141a, creating an anchor effect, thereby further improving the bonding reliability between the bonding layer 50 including the first metal layer 51 and the substrate 41.

[0085] In addition, the specific descriptions of the shape, number, arrangement, materials, etc. of each component of the wavelength conversion device, light source device, and projector are not limited to the above embodiments and can be modified as appropriate. The present invention may be applied to a projector that uses a digital micromirror device as a light modulation device. Furthermore, the projector of the present invention does not need to have multiple light modulation devices, and may be a single-panel projector that has only one light modulation device.

[0086] Summary of this disclosure A summary of this disclosure is provided below.

[0087] (Appendix 1) a wavelength conversion layer that converts incident first light into second light having a wavelength band different from that of the first light; a substrate thermally connected to the wavelength conversion layer; a bonding layer that bonds the wavelength conversion layer to the substrate, the bonding layer includes a first metal layer and a second metal layer; the first metal layer is disposed between the substrate and the wavelength conversion layer on the substrate side with respect to the second metal layer; the second metal layer is disposed between the first metal layer and the wavelength conversion layer; the substrate does not have a plating layer on its surface and is bonded to the first metal layer; Wavelength conversion device.

[0088] A wavelength conversion device of this configuration is provided with a bonding layer having a first metal layer directly bonded to the substrate without using a plating layer and a second metal layer bonding the first metal layer and the phosphor layer, thereby enabling good bonding between the wavelength conversion layer and the substrate while reducing costs.

[0089] (Appendix 2) The first metal layer is covered with the second metal layer. 2. A wavelength conversion device according to claim 1.

[0090] According to this configuration, the contact area between the second metal layer and the first metal layer increases, thereby improving the reliability of the joint therebetween.

[0091] (Appendix 3) the surface of the substrate has an uneven portion; the first metal layer is bonded to the uneven portion of the substrate; 3. A wavelength conversion device according to claim 1 or 2.

[0092] According to this configuration, the first metal layer penetrates into the gaps between the concave and convex portions, thereby generating an anchor effect, and therefore the bonding reliability between the bonding layer including the first metal layer and the substrate can be further improved.

[0093] (Appendix 4) the thermal conductivity of the first metal layer is greater than the thermal conductivity of the second metal layer; an adhesive strength of the second metal layer to the wavelength conversion layer that is greater than an adhesive strength of the first metal layer to the wavelength conversion layer; 4. A wavelength conversion device according to claim 1.

[0094] This configuration allows the heat of the wavelength conversion layer to be efficiently transferred to the substrate via the first metal layer, thereby efficiently dissipating the heat from the wavelength conversion layer. In addition, the wavelength conversion layer is well bonded to the substrate by the second metal layer, which prevents problems such as peeling or damage to the wavelength conversion layer due to thermal stress.

[0095] (Appendix 5) A method for manufacturing a wavelength conversion device having a wavelength conversion layer, a substrate thermally connected to the wavelength conversion layer, and a bonding layer bonding the wavelength conversion layer to the substrate, comprising: a first step of disposing a first metal material on the substrate; a second step of sintering the first metal material by high frequency heating the substrate to form a first metal layer on the substrate; a third step of disposing a second metallic material on the first metallic layer; a fourth step of disposing the wavelength conversion layer on the second metallic material; and a fifth step of bonding a second metal layer formed by drying the second metal material to the first metal layer to form the bonding layer. A method for manufacturing a wavelength conversion device.

[0096] This configuration allows the first metal layer, which bonds to the substrate, and the second metal layer, which bonds to the first metal layer and the phosphor layer, to be formed using an optimal heating method. By sintering the first metal layer using high-frequency heating, the substrate and the first metal layer can be directly bonded without providing a plating layer on the substrate and without an intervening oxide film, thereby achieving good bonding between the wavelength conversion layer and the substrate while reducing costs. Furthermore, special equipment, such as a nitrogen atmosphere, is not required to suppress the formation of an oxide film. Furthermore, since the second metal layer is sintered using a conventional drying process rather than high-frequency heating, the occurrence of bonding defects due to bumping can be suppressed, and the wavelength conversion layer can be well bonded to the first metal layer via the second metal layer. Therefore, a wavelength conversion device can be manufactured that can improve the bonding strength of the wavelength conversion layer to the substrate at low cost.

[0097] (Appendix 6) The method further includes a preparation step of reducing the surface of a base material constituting the substrate as a pre-step of the first step. A method for manufacturing the wavelength converter described in Supplementary Note 5.

[0098] According to this configuration, it is possible to prepare a substrate from which an oxide film formed on the surface has been removed.

[0099] (Appendix 7) the first metallic material includes metallic fine particles made of at least Ag, the second metal material includes metal fine particles made of at least Ag; A method for manufacturing a wavelength converter according to claim 5 or 6.

[0100] According to this configuration, the bonding layer having the first metal layer and the second metal layer can be manufactured by sintering the first metal material and the second metal material.

[0101] (Appendix 8) The content of the metal fine particles in the first metal material is greater than the content of the metal fine particles in the second metal material. 8. A method for manufacturing a wavelength converter according to claim 7.

[0102] With this configuration, the thermal conductivity of the first metal layer can be made greater than that of the second metal layer, and the adhesive strength of the second metal layer can be made greater than that of the first metal layer.

[0103] (Appendix 9) The second process includes a first heating step of heating the substrate at 50°C to 100°C, and a second heating step of heating the substrate at 200°C to 300°C. A method for manufacturing a wavelength converter according to any one of Supplementary Note 5 to Supplementary Note 8.

[0104] According to this configuration, the solvent in the first metal material is volatilized in the first heating step, and the first metal material is sintered in the second heating step, thereby forming a first metal layer on the substrate.

[0105] (Appendix 10) A wavelength conversion device according to any one of Supplementary Note 1 to Supplementary Note 4; a light source that emits the first light to the wavelength conversion device, Light source device.

[0106] According to this configuration, it is possible to realize a highly reliable light source device that generates bright light by suppressing peeling of the wavelength conversion layer and increasing the cooling efficiency of the wavelength conversion layer.

[0107] (Appendix 11) a light source device according to claim 10; a light modulation device that modulates the light emitted from the light source device in accordance with image information; a projection optical device that projects the light modulated by the light modulation device, projector.

[0108] According to this configuration, since the projector includes the light source device, it can form a high-brightness image. [Explanation of symbols]

[0109] 1...projector, 2A...light source device, 4B, 4G, 4R...light modulation device, 40...wavelength conversion device, 41, 141...substrate, 41A...base material, 42a...surface, 50, 55...bonding layer, 51...first metal layer, 52...second metal layer, 141a...uneven portion, 151...first metal material, 152...second metal material.

Claims

1. a wavelength conversion layer that converts incident first light into second light having a wavelength band different from that of the first light; a substrate thermally connected to the wavelength conversion layer; a bonding layer that bonds the wavelength conversion layer to the substrate, the bonding layer includes a first metal layer and a second metal layer; the first metal layer is disposed between the substrate and the wavelength conversion layer on the substrate side with respect to the second metal layer; the second metal layer is disposed between the first metal layer and the wavelength conversion layer; the substrate does not have a plating layer on its surface and is bonded to the first metal layer; Wavelength conversion device.

2. The first metal layer is covered with the second metal layer.

2. The wavelength conversion device according to claim 1.

3. the surface of the substrate has an uneven portion; the first metal layer is bonded to the uneven portion of the substrate; 3. The wavelength conversion device according to claim 1 or 2.

4. the thermal conductivity of the first metal layer is greater than the thermal conductivity of the second metal layer; an adhesive strength of the second metal layer to the wavelength conversion layer that is greater than an adhesive strength of the first metal layer to the wavelength conversion layer; 3. The wavelength conversion device according to claim 1 or 2.

5. A method for manufacturing a wavelength conversion device having a wavelength conversion layer, a substrate thermally connected to the wavelength conversion layer, and a bonding layer bonding the wavelength conversion layer to the substrate, comprising: a first step of disposing a first metal material on the substrate; a second step of sintering the first metal material by high frequency heating the substrate to form a first metal layer on the substrate; a third step of disposing a second metallic material on the first metallic layer; a fourth step of disposing the wavelength conversion layer on the second metallic material; and a fifth step of bonding a second metal layer formed by drying the second metal material to the first metal layer to generate the bonding layer. A method for manufacturing a wavelength conversion device.

6. The method further includes a preparation step of reducing a surface of a base material constituting the substrate as a pre-step of the first step. The method for manufacturing a wavelength converter according to claim 5 .

7. the first metallic material includes metallic fine particles made of at least Ag, the second metal material includes metal fine particles made of at least Ag; The method for manufacturing a wavelength converter according to claim 5 .

8. The content of the metal fine particles in the first metal material is greater than the content of the metal fine particles in the second metal material. The method for manufacturing a wavelength converter according to claim 7 .

9. the second process includes a first heating step of heating the substrate to 50°C to 100°C, and a second heating step of heating the substrate to 200°C to 300°C; A method for manufacturing a wavelength converter according to any one of claims 5 to 8.

10. The wavelength conversion device according to claim 1 or 2, a light source that emits the first light to the wavelength conversion device, Light source device.

11. The light source device according to claim 10; a light modulation device that modulates the light emitted from the light source device in accordance with image information; a projection optical device that projects the light modulated by the light modulation device, projector.

Images