JP6613583B2 - Wavelength conversion element, light source device and projector - Google Patents

Description

  The present invention relates to a wavelength conversion element, a light source device, a projector, and a method for manufacturing the wavelength conversion element.

2. Description of the Related Art Conventionally, there has been known an image display device that modulates illumination light emitted from a light source device to form an image according to image information, and enlarges and projects the image on a projection surface such as a screen (for example, Patent Documents). 1).
The image display device described in Patent Document 1 includes an illumination device, a polarization separation device, a spectroscopic device, a liquid crystal panel, a prism, and a projection optical device. The illumination device includes an excitation light source that emits excitation light and a phosphor. The phosphor converts part of the incident excitation light into fluorescence having a wavelength different from that of the excitation light. From the phosphor, fluorescence and another part of the excitation light are emitted as illumination light toward the same side as the side on which the excitation light is incident. The illumination light is separated into red, green and blue color lights by the spectroscopic device. Each separated color light is modulated by the corresponding liquid crystal panel. Each color light modulated by the liquid crystal panel is synthesized by the prism and projected from the projection optical device.

Japanese Patent Application Laid-Open No. 2012-4009

  In recent years, there has been an increasing demand for projectors with higher brightness. On the other hand, there has been a demand for a configuration that can efficiently extract fluorescence from a phosphor as illumination light.

  An object of the present invention is to solve at least a part of the problems described above, and an object of the present invention is to provide a wavelength conversion element that can efficiently extract fluorescence. Another object is to provide a light source device including the wavelength conversion element. Another object is to provide a projector including the light source device. Another object is to provide a method for manufacturing the wavelength conversion element.

  The wavelength conversion element according to the first aspect of the present invention includes a sintered body including a first metal oxide, and a phosphor layer including a bonding agent and a phosphor, and the phosphor layer includes the sintered body. It is formed on the body.

  According to the said 1st aspect, since the said sintered compact is comprised with the 1st metal oxide, the light reflection efficiency of a sintered compact is comparatively high. By using the sintered body as the substrate on which the phosphor layer is formed, light incident from the phosphor layer into the sintered body is efficiently reflected in a desired direction by the sintered body. Therefore, fluorescence can be efficiently extracted from the wavelength conversion element. Further, when such a wavelength conversion element is employed in a projector, the projector can form a high-luminance image.

In the first aspect, the first metal oxide is preferably aluminum oxide.
According to this structure, since the sintered compact is comprised with the aluminum oxide, the light reflection efficiency of a sintered compact can be made high compared with the case where the said sintered compact is comprised with another metal oxide.

In the first aspect, it is preferable that the sintered body includes a plurality of crystals made of the first metal oxide, and the particle size distribution of the plurality of crystals has a peak at 10 μm or less.
Here, when the crystal size increases and becomes close to a single crystal, the refractive index of the crystal is high, so that light incident on the sintered body is difficult to be emitted outside the sintered body. On the other hand, when the particle size distribution of the plurality of crystals has a peak at 10 μm or less, light incident on the sintered body is easily emitted outside the sintered body due to scattering inside the sintered body. Therefore, fluorescence can be efficiently extracted from the wavelength conversion element.

In the first aspect, it is preferable that the sintered body further includes a second metal oxide having a refractive index different from that of the first metal oxide.
According to this configuration, since the sintered bodies are made of metal oxides having different refractive indexes, the light reflection efficiency of the sintered bodies is high. By using the sintered body as the substrate on which the phosphor layer is formed, light incident from the phosphor layer into the sintered body is efficiently reflected in a desired direction by the sintered body. Therefore, fluorescence can be efficiently extracted from the wavelength conversion element.

In the first aspect, the second metal oxide is zirconium dioxide, and in the sintered body, the second metal compound is preferably 10% or less of the first metal oxide in a molar ratio. .
According to this configuration, since the sintered body is a sintered body containing aluminum oxide and zirconium dioxide, the strength of the phosphor layer is increased as compared with the case where the sintered body is composed only of aluminum oxide. be able to.
Here, when zirconium dioxide in the sintered body is 10% or less of the first metal compound by molar ratio, the light reflection efficiency of the sintered body is the case where the sintered body is composed only of the first metal compound. Increased compared to Specifically, when the zirconium dioxide in the sintered body is 10% or less of the first metal compound by molar ratio, the light incident on the sintered body from the phosphor layer is in the shallow part of the sintered body. The possibility of reflection increases. That is, it is possible to suppress the generation of light that does not reflect toward the side on which the excitation light is incident in the sintered body (for example, light that is emitted toward the side surface of the sintered body). Therefore, the fluorescence extraction efficiency from the wavelength conversion element to the side on which the excitation light is incident can be further increased.

In the first aspect, the sintered body preferably includes voids.
In addition, as said space | gap, the space | gap formed when sintering the precursor of a sintered compact can be illustrated.
Here, the light reflection efficiency of the sintered body including the voids is higher than the light reflection efficiency of the sintered body not including the voids. For this reason, according to this structure, fluorescence can be efficiently extracted from the wavelength conversion element.

In the first aspect, the total volume of the voids is preferably 0.5% or more and 10% or less with respect to the volume of the sintered body.
According to this configuration, since voids can continuously exist at the grain boundaries of the first metal oxide (for example, aluminum oxide), reflection and scattering of light increase, and the phosphor layer can be changed into the sintered body. Incidence of incident light is increased in the surface layer of the sintered body. Therefore, fluorescence can be efficiently extracted from the wavelength conversion element.

In the first aspect, the bonding agent is preferably made of an inorganic material.
In addition, as said inorganic material, the powder glass used as glass for sintering assistance (glass binder) can be illustrated.
According to this configuration, since the phosphor layer is composed of the inorganic material and the phosphor, the progress of the deterioration of the phosphor layer can be suppressed as compared with the case where a general organic material is used.
Moreover, after apply | coating the mixture containing fluorescent substance and an inorganic material on the said sintered compact, it can calcinate and can form a fluorescent substance layer on a sintered compact without using an adhesive agent. Specifically, after the inorganic material is dissolved and mixed with the phosphor during firing, the mixture is fixed onto the sintered body, whereby the phosphor layer is integrally formed on the sintered body. Therefore, the phosphor layer can be integrated with the sintered body without using an adhesive. Accordingly, the adhesive does not obstruct light incident on the sintered body from the phosphor layer as in the case where the phosphor is fixed to the sintered body by the adhesive. The emitted fluorescence is efficiently reflected. Furthermore, the process of forming the wavelength conversion element can be simplified.

In the said 1st aspect, it is preferable to have a reflection layer which is located in the opposite side to the said fluorescent substance layer of the said sintered compact, and reflects the light which passed the said sintered compact.
Here, if the sintered body is relatively thin, a part of the fluorescent light whose wavelength is converted by the phosphor layer may pass through the sintered body.
However, according to this configuration, even when a part of the fluorescent light passes through the sintered body, the reflection layer located on the opposite side of the sintered body from the sintered body causes the part of the fluorescent light to pass. It can reflect light. Thereby, compared with the case where there is no reflection layer, a sintered compact can be comprised thinly. Therefore, since the thickness of the interface in the thickness direction in the sintered body can be reduced, the spread of light emitted from the sintered body can be suppressed.
And since it becomes easy to condense the light inject | emitted from a wavelength conversion element, when the said wavelength conversion element is employ | adopted for a projector etc., the utilization efficiency of the light inject | emitted from a wavelength conversion element can be improved.

In the first aspect, it is preferable to further include a support substrate that supports the sintered body, and an adhesive layer provided between the support substrate and the sintered body.
According to this configuration, since the sintered body is fixed to the support substrate by the adhesive layer, the sintered body can be reliably held by the support substrate. Thereby, since the emission direction of the fluorescence is kept constant, the utilization efficiency of the fluorescence emitted from the wavelength conversion element can be increased.

In the first aspect, a support substrate that supports the sintered body, an adhesive layer provided between the support substrate and the sintered body, and provided between the support substrate and the adhesive layer, It is preferable to further include a reflective layer that reflects incident light.
According to this configuration, since the light that has passed through the sintered body can be reflected by the reflective layer positioned between the support substrate and the adhesive layer, fluorescence can be efficiently extracted from the wavelength conversion element.

A light source device according to a second aspect of the present invention includes the wavelength conversion element described above and a light source that emits excitation light that excites the phosphor layer.
Examples of the light source include a solid light source such as a laser that emits excitation light.
According to the said 2nd aspect, there can exist an effect similar to the wavelength conversion element which concerns on the said 1st aspect. Further, the light source device can convert the excitation light emitted from the light source into fluorescence and emit it. For example, when blue excitation light is emitted from a light source, the light source device can emit fluorescence including green and red color light using a wavelength conversion element.

A projector according to a third aspect of the present invention includes the light source device described above, a light modulation device that modulates light emitted from the light source device, and a projection optical device that projects image light from the light modulation device. It is characterized by providing.
According to the said 3rd aspect, there can exist an effect similar to the light source device which concerns on the said 2nd aspect. In addition, since the fluorescence extraction efficiency from the wavelength conversion element is high, the brightness of the projected image can be increased.

In the method for manufacturing a wavelength conversion element according to the fourth aspect of the present invention, a mixture containing a bonding agent and a phosphor is applied on a sintered body containing a metal oxide, and is lower than the sintering temperature of the sintered body. A step of firing the mixture at a temperature.
According to the fourth aspect, the phosphor layer can be easily formed on the sintered body. Further, since the phosphor layer is fired at a temperature lower than the sintering temperature of the sintered body, it is possible to suppress the deterioration of the sintered body when the phosphor layer is fired.
Further, since such a wavelength conversion element is a wavelength conversion element in which a sintered body and a phosphor layer are joined, it is not necessary to use an adhesive that fixes the sintered body and the phosphor layer. According to this, it can suppress that an adhesive agent degrades with the incident light and a fluorescent substance layer peels. Furthermore, since the adhesive agent which absorbs light is not provided, the light quantity of the emitted light from the wavelength conversion element containing reflected light can be raised.

FIG. 1 is a schematic diagram illustrating an outline of a projector according to a first embodiment of the invention. The schematic diagram which shows the outline of the illuminating device of the projector which concerns on the said 1st Embodiment. The top view of the fluorescent member in the illuminating device which concerns on the said 1st Embodiment. Sectional drawing of the fluorescent member in the illuminating device which concerns on the said 1st Embodiment. The schematic diagram which shows an example of the board | substrate (sintered body) of the wavelength conversion element which concerns on the said 1st Embodiment. The graph which shows the relationship between the crystal size of the board | substrate which concerns on the said 1st Embodiment, and light reflection efficiency. The graph which shows the relationship between the volume ratio of the space | gap which concerns on the said 1st Embodiment, and the light reflection efficiency of a board | substrate. The schematic diagram which shows an example of the board | substrate (sintered body) of the wavelength conversion element which concerns on 2nd Embodiment of this invention. The graph which shows the relationship between the ratio of the zirconium dioxide in the board | substrate which concerns on the said 2nd Embodiment, and light reflection efficiency. Sectional drawing of the fluorescent member in the projector which concerns on 3rd Embodiment of this invention.

[First Embodiment]
Hereinafter, a first embodiment of the present invention will be described based on the drawings.
[Schematic configuration of projector]
FIG. 1 is a schematic diagram illustrating a configuration of a projector 1 according to the present embodiment.
The projector 1 is a display device that modulates a light beam emitted from a light source provided therein to form an image according to image information, and enlarges and projects the image on a projection surface such as a screen SC1.
As shown in FIG. 1, the projector 1 is not shown in addition to the exterior housing 2 and the optical unit 3 housed in the exterior housing 2, but a control device that controls the projector 1, A cooling device that cools the target, and a power supply device that supplies power to the electronic components constituting the projector 1 are provided.

[Configuration of optical unit]
The optical unit 3 includes an illumination device 31, a color separation device 32, a collimating lens 33, a light modulation device 34, a color synthesis device 35, and a projection optical device 36.
The illumination device 31 emits illumination light WL. The configuration of the illumination device 31 will be described later.
The color separation device 32 separates the illumination light WL incident from the illumination device 31 into three color lights of red (R), green (G), and blue (B). The color separation device 32 includes dichroic mirrors 321, 322, total reflection mirrors 323, 324, 325, and relay lenses 326, 327.
The dichroic mirror 321 separates the illumination light WL from the illumination device 31 into red light LR and other color lights (green light LG and blue light LB). The dichroic mirror 321 transmits the red light LR and reflects other color lights (green light LG and blue light LB). The dichroic mirror 322 separates other color lights into green light LG and blue light LB. The dichroic mirror 322 reflects the green light LG and transmits the blue light LB.

The total reflection mirror 323 is disposed in the optical path of the red light LR, and reflects the red light LR transmitted through the dichroic mirror 321 toward the light modulation device 34 (34R). On the other hand, the total reflection mirrors 324 and 325 are disposed in the optical path of the blue light LB, and guide the blue light LB transmitted through the dichroic mirror 322 to the light modulation device 34 (34B). The green light LG is reflected by the dichroic mirror 322 toward the light modulation device 34 (34G).
The relay lenses 326 and 327 are disposed downstream of the dichroic mirror 322 in the optical path of the blue light LB. These relay lenses 326 and 327 have a function of compensating for the optical loss of the blue light LB due to the optical path length of the blue light LB being longer than the optical path lengths of the red light LR and the green light LG.

  The collimating lens 33 collimates light incident on a light modulation device 34 described later. The collimating lenses for red, green, and blue light are 33R, 33G, and 33B, respectively. In addition, the light modulation devices for red, green, and blue color lights are denoted as 34R, 34G, and 34B, respectively.

  The light modulation device 34 (34R, 34G, 34B) modulates the incident red, green, and blue color lights LR, LG, LB to form a color image corresponding to the image information. These light modulation devices 34 are constituted by a liquid crystal panel that modulates incident light. In addition, although illustration is abbreviate | omitted, the polarizing plate is arrange | positioned at the incident side and the emission side of the light modulation devices 34R, 34G, and 34B, respectively.

Image light from each of the light modulation devices 34R, 34G, and 34B is incident on the color synthesis device 35. The color synthesizer 35 synthesizes image lights corresponding to the color lights LR, LG, and LB, and emits the synthesized image light toward the projection optical device 36. In the present embodiment, the color composition device 35 is configured by a cross dichroic prism.
The projection optical device 36 projects the image light combined by the color combining device 35 onto a projection surface such as the screen SC1. With such a configuration, an enlarged image is projected on the screen SC1.

[Configuration of lighting device]
FIG. 2 is a schematic diagram illustrating a configuration of the illumination device 31 in the projector 1 according to the present embodiment.
The illumination device 31 emits the illumination light WL toward the color separation device 32 as described above. As shown in FIG. 2, the illumination device 31 includes a light source device 311, an afocal optical system 312, a homogenizer optical system 313, a polarization separation device 314, a phase difference plate 315, a pickup optical system 316, an integrator optical system 317, and a polarization conversion. An element 318, a superimposing lens 319, and a fluorescent member 4 are provided. The light source device 311 includes an array light source 311A and a collimator optical system 311B.

The array light source 311A of the light source device 311 corresponds to the light source of the present invention, and includes a plurality of semiconductor lasers 3111. Specifically, the array light source 311A is formed by arranging a plurality of semiconductor lasers 3111 in an array in a plane orthogonal to the illumination optical axis Ax1 of the light beam emitted from the array light source 311A. In addition, although mentioned later in detail, when the illumination optical axis of the light beam reflected by the fluorescent member 4 is Ax2, the illumination optical axis Ax1 and the illumination optical axis Ax2 are in the same plane and are orthogonal to each other. . On the illumination optical axis Ax1, an array light source 311A, a collimator optical system 311B, an afocal optical system 312, a homogenizer optical system 313, and a polarization separation device 314 are arranged in this order.
On the other hand, on the illumination optical axis Ax2, the fluorescent member 4 provided with the wavelength conversion element 41, the pickup optical system 316, the phase difference plate 315, the polarization separation device 314, the integrator optical system 317, and the polarization conversion element 318. And a superimposing lens 319 are arranged in this order.

The semiconductor laser 3111 constituting the array light source 311A emits excitation light (blue light BL) having a peak wavelength in a wavelength range of 440 to 480 nm, for example. The blue light BL emitted from the semiconductor laser 3111 is coherent linearly polarized light, and is emitted toward the polarization separation device 314 in parallel with the illumination optical axis Ax1.
Also, the array light source 311A matches the polarization direction of the blue light BL emitted from each semiconductor laser 3111 with the polarization direction of the polarization component (S polarization component) reflected by the polarization separation layer 3143 of the polarization separation device 314. Yes. Then, the blue light BL emitted from the array light source 311A enters the collimator optical system 311B.

The collimator optical system 311B converts the blue light BL emitted from the array light source 311A into parallel light. The collimator optical system 311B includes a plurality of collimator lenses 3112 arranged in an array corresponding to each semiconductor laser 3111, for example. The blue light BL converted into parallel light by passing through the collimator optical system 311B is incident on the afocal optical system 312.
The afocal optical system 312 adjusts the luminous flux diameter of the blue light BL incident from the collimator optical system 311B. The afocal optical system 312 includes a lens 3121 and a lens 3122. The blue light BL whose size is adjusted by passing through the afocal optical system 312 is incident on the homogenizer optical system 313.

  The homogenizer optical system 313 cooperates with a pickup optical system 316 described later to uniformize the illuminance distribution by the blue light BL in the illuminated area. The homogenizer optical system 313 includes a pair of multi-lens arrays 3131 and 3132. The blue light BL emitted from the homogenizer optical system 313 enters the polarization separation device 314.

  The polarization separation device 314 is a so-called prism-type polarization beam splitter (PBS), and allows one of p-polarized light and s-polarized light to pass therethrough and reflects the other polarized light. The polarization separation device 314 includes prisms 3141 and 3142 and a polarization separation layer 3143. Each of these prisms 3141 and 3142 is formed in a substantially triangular prism shape, has an inclined surface that makes an angle of 45 ° with respect to the illumination optical axis Ax1, and makes an angle of 45 ° with respect to the illumination optical axis Ax2. Yes.

The polarization separation layer 3143 is provided on the inclined surface, and has a polarization separation function for separating the blue light BL of the first wavelength band incident on the polarization separation layer 3143 into an S polarization component and a P polarization component. The polarization separation layer 3143 reflects the S-polarized component of the blue light BL and transmits the P-polarized component of the blue light BL. In addition, the polarization separation layer 3143 has a second wavelength band (green light GL and red light RL) different from the first wavelength band (the wavelength band of the blue light BL) among the light incident on the polarization separation layer 3143. The color separation function allows the light to pass through regardless of its polarization state. The polarization separation device 314 is not limited to the prism type, and a plate type polarization separation device may be used.
The blue light BL incident on the polarization separation layer 3143 is reflected toward the fluorescent member 4 as S-polarized excitation light BLs because the polarization direction thereof coincides with the S-polarized component.

The phase difference plate 315 is a ¼ wavelength plate disposed in the optical path between the polarization separation layer 3143 and the wavelength conversion element 41. The S-polarized excitation light BLs incident on the phase difference plate 315 is converted into circularly polarized excitation light BLc and then incident on the pickup optical system 316.
The pickup optical system 316 condenses the excitation light BLc toward the wavelength conversion element 41. The pickup optical system 316 includes a lens 3161 and a lens 3162. Specifically, the pickup optical system 316 collects a plurality of incident light beams (excitation light BLc) toward a wavelength conversion element 41 to be described later and superimposes them on the wavelength conversion element 41.

In the fluorescent member 4, a wavelength conversion element 41 that converts the wavelength of incident light is formed along a circumferential direction of the disk 42 on a disk 42 that can be rotated by a motor 43. The wavelength conversion element 41 emits red light and green light toward the side on which blue light (excitation light BLc) is incident.
Excitation light BLc from the pickup optical system 316 enters the wavelength conversion element 41. The wavelength conversion element 41 converts part of the excitation light BLc into fluorescent light YL including red light and green light. The fluorescent light YL has a peak wavelength in the wavelength range of 500 to 700 nm. The configuration of the wavelength conversion element 41 will be described later.
Then, the fluorescent light YL emitted from the wavelength conversion element 41 passes through the pickup optical system 316 and the phase difference plate 315 and enters the polarization separation device 314. The polarization separation device 314 combines the fluorescent light YL and the blue light (p-polarized blue light) passing through the polarization separation layer 3143 to generate white illumination light WL. The illumination light WL is emitted from the polarization beam splitter 314 and enters the integrator optical system 317.

  The integrator optical system 317 makes the illuminance distribution uniform in the illuminated area in cooperation with a superimposing lens 319 described later. The integrator optical system 317 includes a pair of lens arrays 3171 and 3172. The pair of lens arrays 3171 and 3172 includes a plurality of lenses arranged in an array. The illumination light WL emitted from the integrator optical system 317 enters the polarization conversion element 318.

The polarization conversion element 318 includes a polarization separation film and a phase difference plate, and converts the illumination light WL into linearly polarized light. The illumination light WL emitted from the polarization conversion element 318 enters the superimposing lens 319.
The superimposing lens 319 makes the illumination distribution in the illuminated area uniform by superimposing the illumination light WL in the illuminated area.

[Configuration of wavelength conversion element]
FIG. 3 is a plan view of the fluorescent member 4 of the illumination device 31 as viewed from the incident side of the excitation light BLc, and FIG. 4 is a cross-sectional view showing an A1-A1 cross section of the fluorescent member 4 shown in FIG. 3 and 4, the illustration of the motor 43 is omitted.
As described above, the wavelength conversion element 41 of the fluorescent member 4 converts part of the incident excitation light into fluorescence and emits it, and emits the other part without converting it into fluorescence. As shown in FIG. 3, the wavelength conversion element 41 is formed in a ring shape and is provided along the circumference of the disk 42.
The wavelength conversion element 41 includes a phosphor layer 411 and a substrate 412 as shown in FIG. Specifically, the wavelength conversion element 41 has a substrate 412 on which a phosphor layer 411 is formed. The substrate 412 is fixed to a metal disc 42 having a high thermal conductivity such as aluminum via an adhesive layer 413. The disk 42 is rotated by the motor 43, whereby the wavelength conversion element 41 that generates heat when the excitation light is incident is cooled. The disc 42 corresponds to the support substrate of the present invention, and the adhesive layer 413 corresponds to the adhesive layer of the present invention.

[Configuration of phosphor layer]
The phosphor layer 411 is formed on the substrate 412 by baking a mixture including a glass binder (bonding agent) that is an inorganic material and disposed on the substrate 412.
The phosphor is a YAG (Yttrium Aluminum Garnet) phosphor containing Ce ions. That is, the phosphor layer 411 is an inorganic phosphor layer, and the component ratio between the glass binder and the phosphor constituting the phosphor layer 411 is set to about 50% in this embodiment.

[Configuration of substrate (sintered body)]
FIG. 5 is a schematic diagram of a part of the substrate 412 of the wavelength conversion element 41.
The substrate 412 corresponds to the sintered body of the present invention, and reflects the light incident from the phosphor layer 411. This substrate 412 is a sintered body of aluminum oxide (Al ₂ O ₃ ). The substrate 412 includes a plurality of crystals made of aluminum oxide. The thickness of the substrate 412 in the direction along the incident direction of the excitation light BLc is set to about 1 mm. Aluminum oxide corresponds to the first metal oxide of the present invention. The substrate 412 in which each crystal axis is directed in a different direction can be manufactured mainly by a sintering process in which the sintering temperature and the sintering time are adjusted. In addition, a gap F is formed between the crystals C1 and C1.

Specifically, in this example, the size of the aluminum oxide crystal C1 was 2 to 5 μm. Between adjacent crystals, they are in close contact with each other, or there are voids F. The void F has a refractive index of 1, and the crystal C1 has a refractive index of 1.78. For this reason, the light is transmitted without being scattered in the inside of the crystal C1 or in the portion where the crystals C1 are in close contact with each other, and the light is scattered on the surfaces of the aluminum oxide and the void F. Accordingly, the size of the crystal C1 is small, and the thin voids F are present around it, so that the scattering characteristics are enhanced.
As described above, since the voids F are continuously present at the grain boundaries of the aluminum oxide having a thickness of several μm, reflection and scattering of light increase, and the fluorescent light YL incident from the phosphor layer 411 is reflected on the surface layer of the substrate 412. And is emitted toward the surface. Thereby, the fluorescent light YL incident on the substrate 412 from the phosphor layer 411 is repeatedly reflected in a small region on the substrate 412.

FIG. 6 is a graph showing the size and light reflection efficiency of the aluminum oxide crystal C1 constituting the substrate 412.
As shown in FIG. 6, a high light reflection efficiency can be obtained by appropriately setting the size of the aluminum oxide crystal C1.
When the size of the aluminum oxide crystal C1 is approximately 0.2 times or less of the wavelength of light, it is difficult to scatter at the interface between the crystal and the gap, so that the fluorescent light YL easily passes through the substrate 412 and the fluorescent light YL. The efficiency of taking out becomes worse.
When the crystal size is approximately 0.2 times or more of the wavelength of light, light scattering occurs effectively at the interface, so that the fluorescent light YL is easily reflected toward the phosphor layer 411 by the substrate 412. Therefore, sufficiently high extraction efficiency of the fluorescent light YL can be obtained.
However, when the size of the crystal C1 increases and becomes closer to a single crystal, the refractive index of the crystal C1 is high, so that the fluorescent light YL is emitted from the substrate 412 due to total reflection at the interface between the substrate 412 and the phosphor layer 411. It becomes difficult to enter the phosphor layer 411. Therefore, the extraction efficiency of the fluorescent light YL decreases. In addition, in a crystal that is sufficiently large with respect to the wavelength of light without reaching a single crystal, the interface between the crystal C1 and the gap F is large and the number thereof is reduced, so that the light reflection efficiency is reduced. In this way, high light reflection efficiency can be obtained by appropriately setting the size of the aluminum oxide crystal C1.
As the size of the aluminum oxide crystal C1 increases, the light straightness increases, and the scattering region widens. For this reason, since the overall light source size, that is, the apparent light emitting area becomes large, the amount of light that is not captured by the pickup optical system 316 increases. That is, the light use efficiency in the optical system is lowered.

Specifically, when the size of the crystal C1 is smaller than 0.1 μm and when the size of the crystal C1 is larger than 10 μm, the light reflection efficiency of the substrate 412 is less than 90% as shown in FIG.
On the other hand, when the size of the crystal C1 is 0.1 μm or more and 10 μm or less, the light reflection efficiency exceeds 90%. Further, when the size of the crystal C1 is 2 μm or more and 5 μm or less, higher light reflection efficiency is obtained, and when the size of the crystal C1 is 2.5 μm, the light reflection efficiency of the substrate 412 is the highest 95. %. Thus, in the substrate 412, the size of the aluminum oxide crystal C1 is preferably 0.1 μm or more and 10 μm or less. More preferably, they are 2 micrometers or more and 5 micrometers or less.

  Therefore, by setting the main crystal size from 0.1 μm to 10 μm, which is approximately 0.2 to 20 times the wavelength order, the maximum reflected light due to scattering can be obtained. That is, in the manufacturing process of the substrate 412 of the wavelength conversion element 41, aluminum oxide may be sintered so that the particle size distribution of the plurality of crystals C1 has a peak at 0.1 μm or more and 10 μm or less.

FIG. 7 is a graph showing the relationship between the volume ratio of the gap F and the light reflection efficiency.
In the substrate 412, when the volume ratio of the voids F is less than 0.5% or the volume ratio of the voids F exceeds 10%, the light reflection efficiency is remarkably lowered.
On the other hand, when the volume ratio is 0.5% or more and 10% or less, high light reflection efficiency is obtained. Further, when the volume ratio is 3% or more and 7% or less, higher light reflection efficiency can be obtained. Thus, in the substrate 412, the volume ratio of the voids F is preferably 0.5% or more and 10% or less, and more preferably 3% or more and 7% or less.

[Method of manufacturing wavelength conversion element]
The wavelength conversion element 41 described above is manufactured by the following manufacturing method, for example. First, the manufacturing process of the substrate 412 constituting the wavelength conversion element 41 will be described.
First, a binder, a plasticizer, an organic solvent, and the like are added to the Al ₂ O ₃ powder constituting the substrate 412 and then mixed by stirring to prepare a slurry for forming the substrate 412. This slurry is formed into a sheet shape to form a green sheet. Then, the green sheet is stamped into a predetermined shape by press working to form a plate-like green molded product (substrate precursor). This green molded product is sintered at a temperature of 1500 ° C. or more, for example, to form a substrate 412 that is a sintered body.

The phosphor layer 411 is formed on the substrate 412 formed by the above process. First, a mixture composed of a glass binder, a phosphor and an organic substance constituting the phosphor layer 411 is prepared. Then, the mixture is applied onto the substrate 412. Thereafter, the mixture is fired at a temperature exceeding the melting point of the glass. This temperature is lower than the temperature at which the substrate 412 that is the sintered body is sintered, and is 1000 ° C., for example.
As a result, the glass binder melts and the organic substance evaporates, so that an inorganic phosphor (phosphor layer 411) made of glass and phosphor is formed on the substrate 412.
That is, according to the above process, the wavelength conversion element 41 in which the phosphor layer 411 is formed on the substrate 412 by applying and baking a mixture containing a glass binder and a phosphor on the sintered body of aluminum oxide. Can be formed.
Note that since the substrate 412 is sintered at a temperature of 1500 ° C. or higher, even if the substrate 412 is heated to 1000 ° C. together with the mixture, the possibility that the substrate 412 is destroyed by heat is extremely low.

  In the present embodiment, since the substrate 412 is formed to be relatively thick and approximately 1 mm, the substrate 412 can reflect incident light with high efficiency. Therefore, the fluorescent light incident on the substrate 412 from the phosphor layer 411 is provided without providing a reflective layer such as a metal reflective film between the phosphor layer 411 and the substrate 412 or between the substrate 412 and the adhesive layer 413. A part of YL and the excitation light BLc is reflected by the substrate 412 toward the side on which the excitation light BLc is incident.

According to the projector 1 according to the first embodiment described above, the following effects can be obtained.
Since the substrate 412 is made of a metal oxide, the light reflection efficiency of the substrate 412 is relatively high. By using the above sintered body as the substrate 412 on which the phosphor layer 411 is formed, light that enters the substrate 412 from the phosphor layer 411 is efficiently reflected in a desired direction by the substrate 412. Therefore, the fluorescent light YL can be efficiently extracted from the wavelength conversion element. Note that light incident on the substrate 412 from the phosphor layer 411 includes fluorescent light YL and a part of the excitation light BLc that has not been converted into fluorescent light YL.
A projector employing such a wavelength conversion element 41 can form a high-luminance image.
Furthermore, since the substrate 412 is made of aluminum oxide, the light reflection efficiency of the substrate 412 can be increased as compared with the case where the substrate 412 is made of another metal oxide.

  According to this embodiment, since the particle size distribution of the plurality of crystals C1 has a peak at 10 μm or less, the fluorescent light YL can be efficiently extracted from the wavelength conversion element 41.

Here, the light reflection efficiency of the substrate 412 including the void F is higher than that of the substrate not including the void F. For this reason, according to this embodiment, since the substrate 412 includes the gap F, the fluorescent light YL can be efficiently extracted from the wavelength conversion element 41.
Further, if the total volume of the voids F of the substrate 412 is 0.5% or more and 10% or less with respect to the volume of the substrate 412, the voids F can continuously exist at the aluminum oxide grain boundaries. Light reflection and scattering increase, and the possibility that light incident on the substrate 412 from the phosphor layer 411 is reflected on the surface layer of the substrate 412 increases. Therefore, the fluorescent light YL can be efficiently extracted from the wavelength conversion element 41.

Since the phosphor layer 411 is composed of an inorganic material and a phosphor, the progress of deterioration of the phosphor layer can be suppressed as compared with the case of using a general organic material.
Further, the phosphor layer 411 can be formed on the substrate 412 without using an adhesive by applying a mixture containing the phosphor and the inorganic material onto the substrate 412 and then baking the mixture. Specifically, after the inorganic material is dissolved and mixed with the phosphor during firing, the mixture is fixed onto the substrate 412, whereby the phosphor layer is integrally formed on the substrate 412. Therefore, the phosphor layer can be integrated with the substrate 412 without using an adhesive. Accordingly, the adhesive does not block light incident on the substrate 412 from the phosphor layer 411 as in the case where the phosphor is fixed to the substrate 412 by the adhesive. The emitted fluorescence is efficiently reflected. Furthermore, the formation process of the wavelength conversion element 41 can be simplified.

The illuminating device 31 can convert the excitation light (blue light BL) emitted from the array light source 311A into fluorescent light YL and emit it. For example, when the phosphor layer 411 includes a YAG phosphor including Ce ions, the lighting device 31 can emit fluorescent light YL including green and red color lights.
Further, since the projector 1 can efficiently extract the fluorescent light YL from the wavelength conversion element 41, the brightness of the image projected from the projection optical device 36 can be increased.

The phosphor layer 411 can be easily formed on the substrate 412 by applying and baking a mixture containing the bonding agent and the phosphor on the substrate 412 containing aluminum oxide. Further, since the phosphor layer 411 is fired at a temperature lower than the sintering temperature of the substrate 412, it is possible to suppress deterioration of the substrate 412 when the phosphor layer 411 is fired.
Moreover, since such a wavelength conversion element 41 is a wavelength conversion element in which the substrate 412 and the phosphor layer 411 are directly bonded, it is not necessary to use an adhesive that fixes the substrate 412 and the phosphor layer 411. . According to this, the adhesive does not deteriorate due to incident light (for example, excitation light BLc), and the phosphor layer does not peel off. Furthermore, since no adhesive that absorbs light is provided, the amount of fluorescent light YL emitted from the wavelength conversion element 41 including reflected light can be increased.

[Second Embodiment]
Next, a second embodiment of the present invention will be described.
The projector according to the present embodiment has the same configuration as that of the projector 1, but the configuration of the substrate 412 that is a sintered body is different. In the following description, parts that are the same as or substantially the same as those already described are given the same reference numerals and description thereof is omitted.

[Configuration of substrate (sintered body)]
FIG. 8 is a schematic diagram of a part of the substrate employed in this embodiment, instead of the substrate 412 in the first embodiment. In the following description, the substrate 412 is different from the substrate 412 only in the components constituting the substrate, and therefore, the same reference numerals as those of the substrate 412 are used for description.
The substrate 412 is a sintered body of aluminum oxide and zirconium dioxide (ZrO ₂ ). The thickness of the substrate 412 is set to about 1 mm as in the first embodiment. Aluminum oxide and zirconium dioxide correspond to the first metal oxide and the second metal oxide of the present invention, respectively.
In such a substrate 412, a void F is formed as shown in FIG. 8 through a sintering process of aluminum oxide and zirconium dioxide.

Specifically, in the substrate 412, the size of the aluminum oxide crystal C1 is 2 to 5 μm, whereas the size of the zirconium dioxide crystal C2 is approximately 1 μm or less. In addition, the linear expansion coefficient of aluminum oxide is “7 × 10E-6”, whereas the linear expansion coefficient of zirconium dioxide is “1 × 10E-6”. Zirconium dioxide crystals are appropriately arranged. Therefore, the void F is formed between the aluminum oxide crystal C1 and the aluminum oxide crystal C1, or between the aluminum oxide crystal C1 and the zirconium dioxide crystal C2.
Aluminum oxide has a refractive index of 1.78, zirconium dioxide has a refractive index of 2.4, and air has a refractive index of 1. For this reason, since the voids F can continuously exist at the grain boundaries of aluminum oxide having a thickness of several μm, reflection and scattering of light by the substrate 412 increase. The possibility that the fluorescent light YL incident from the phosphor layer 411 is reflected on the surface layer of the substrate 412 increases. Thus, the fluorescent light YL incident on the substrate 412 from the phosphor layer 411 is reflected by the substrate 412.

FIG. 9 is a graph showing the relationship between the proportion of zirconium dioxide and the light reflection efficiency of the substrate 412.
In the substrate 412, when the ratio of zirconium dioxide to aluminum oxide in a molar ratio exceeds 12%, as shown in FIG. 9, the light reflection efficiency when the substrate 412 is composed of only aluminum oxide (in the case of 0%). Below 95%.
On the other hand, when the ratio is greater than 0% and equal to or less than 10%, it exceeds the light reflection efficiency when the substrate 412 is composed of only aluminum oxide. Further, when the ratio is 3% or more and less than 7%, higher light reflection efficiency is obtained, and when the ratio is 5%, the light reflection efficiency of the substrate 412 is the highest 98%.
Thus, in the substrate 412, the ratio of zirconium dioxide to aluminum oxide in terms of molar ratio is preferably 10% or less, and more preferably 3% or more and less than 7%.

According to the projector according to the second embodiment described above, the following effects can be obtained.
Since the substrate 412 is a sintered body containing aluminum oxide and zirconium dioxide, which are metal oxides having different refractive indexes, the light reflection efficiency of the substrate 412 is high. Since the phosphor layer 411 is formed on the substrate 412, the light incident on the substrate 412 from the phosphor layer 411 is efficiently reflected by the substrate 412 toward the side on which the excitation light BLs is incident. Therefore, the fluorescent light YL can be efficiently extracted from the wavelength conversion element 41. Note that light incident on the substrate 412 from the phosphor layer 411 includes fluorescent light YL and a part of the excitation light BLc that has not been converted into fluorescent light YL. A projector employing such a wavelength conversion element 41 can form a high-luminance image.

Since the substrate 412 is a sintered body containing aluminum oxide and zirconium dioxide, the strength of the phosphor layer 411 can be increased as compared with the case where the substrate 412 is composed only of aluminum oxide.
Here, when the zirconium dioxide in the substrate 412 is 10% or less of aluminum oxide in a molar ratio, the light reflection efficiency of the substrate 412 is higher than that in the case where the substrate 412 is composed of only aluminum oxide. Specifically, when zirconium dioxide in the substrate 412 is 10% or less of aluminum oxide in a molar ratio, the light incident on the substrate 412 from the phosphor layer 411 may be reflected in a shallow portion of the substrate 412. Is expensive. That is, generation of light that does not reflect toward the side on which the excitation light BLc is incident in the substrate 412 (for example, light emitted toward the side surface of the substrate 412) can be suppressed. Therefore, the fluorescent light YL can be efficiently extracted from the wavelength conversion element 41 toward the side on which the excitation light BLc is incident.

  The phosphor layer 411 can be easily formed on the substrate 412 by applying and baking a mixture containing a glass binder and a phosphor on the substrate 412 containing aluminum oxide and zirconium dioxide. Further, when the phosphor layer 411 is formed, the substrate 412 is sintered at a temperature (for example, 1000 ° C.) lower than the sintering temperature (for example, 1500 ° C.) of aluminum oxide and zirconium dioxide. It is possible to suppress deterioration when the body layer 411 is fired.

[Third Embodiment]
Next, a third embodiment of the present invention will be described.
The projector according to the present embodiment has the same configuration as that of the projector 1, but the configuration of the wavelength conversion element included in the fluorescent member of the illumination device 31 is different. In the following description, parts that are the same as or substantially the same as those already described are given the same reference numerals and description thereof is omitted.

FIG. 10 is a cross-sectional view showing the fluorescent member 4A according to the present embodiment. In FIG. 10, the motor 43 is not shown as in FIG.
The wavelength conversion element 41A of the fluorescent member 4A includes a phosphor layer 411, a substrate 412A, and a reflective layer 414. That is, the wavelength conversion element 41A is different from the wavelength conversion element 41 in that it includes a substrate 412A in which a phosphor layer 411 is formed on one surface and a reflection layer 414 is formed on the other surface. This wavelength conversion element 41 </ b> A is fixed to the disc 42 by the adhesive layer 413.

[Configuration of substrate (sintered body)]
The substrate 412A reflects the light incident from the phosphor layer 411 similarly to the substrate 412 described above. The substrate 412A is configured by a sintered body constituting the substrate 412 in the second embodiment, and the dimension (thickness) in the direction along the incident direction of the excitation light BLc is approximately 0.2 mm or more and 0.3 mm. It differs from the said board | substrate 412 which has a thickness of about 1 mm by the point set to less than.
Note that, since the substrate 412A is a sintered body containing zirconium dioxide as described above, the strength of the substrate 412A is approximately twice that of a substrate made of aluminum oxide alone. For this reason, even if the substrate 412A is thinned, the possibility that the substrate 412A is damaged is extremely small.

  Further, since the thickness of the substrate 412A is smaller than the thickness of the substrate 412, a component that passes through the substrate 412A toward the disc 42 is generated. In order to reflect the component, a reflective layer 414 made of silver (Ag) or the like is provided between the substrate 412A and the disc 42.

Here, when the substrate 412A is formed to be 0.2 mm, a part of the fluorescent light YL generated by the phosphor layer 411 passes through the substrate 412A. Reflected by the reflective layer 414. For this reason, the part of light passes through the substrate 412A twice.
Even in this case, the distance that the part of light passes through the substrate 412A is “0.2 mm × 2 times”, which is smaller than the distance that passes through the substrate 412 “1 mm × 2 times”. For this reason, the possibility that the fluorescent light YL repeats internal reflection within the substrate 412A is less than that of the substrate 412. That is, the substrate 412A of the present embodiment can make the light spread (internal reflection) within the substrate 412A approximately 1/5 as compared with the substrate 412, so that the wavelength conversion element 41A that emits the fluorescent light YL is a point. It is close to the light source. Therefore, the fluorescent light YL emitted from the wavelength conversion element 41A can be easily collected, and the utilization efficiency of the fluorescent light YL can be increased.

The projector according to the third embodiment described above has the following effects in addition to the same effects as the projector 1 according to each of the above embodiments.
Here, if the substrate 412A is relatively thin, part of the light incident on the substrate 412A from the phosphor layer 411 passes through the substrate 412A.
On the other hand, according to the present embodiment, even when part of the light incident from the phosphor layer 411 passes through the substrate 412A, the reflection located on the opposite side of the phosphor layer 411 with respect to the substrate 412A. The layer 414 can reflect some of the light. As a result, the substrate 412A can be made thinner than when the reflective layer 414 is not provided. Therefore, since the thickness of the interface in the thickness direction of the substrate 412A can be reduced, the spread of light emitted from the substrate 412A can be suppressed.
And since it becomes easy to condense the light inject | emitted from the wavelength conversion element 41, when the said wavelength conversion element 41 is employ | adopted for the projector 1, the utilization efficiency of the light utilized for image formation can be improved.

[Modification of Embodiment]
The present invention is not limited to the above-described embodiments, and modifications, improvements, and the like within the scope that can achieve the object of the present invention are included in the present invention.
In the first embodiment, the substrate 412 is made of aluminum oxide. However, the present invention is not limited to this. That is, the substrate 412 may be made of a metal oxide.
In the first embodiment, the particle size distribution of the aluminum oxide crystal C1 on the substrate 412 has a peak at 10 μm or less. However, the present invention is not limited to this. For example, when the peak of the particle size distribution of the crystal C1 is 30 μm or less, the light incident on the substrate 412 can be efficiently emitted.

  In the second to third embodiments, the substrates 412 and 412A are made of aluminum oxide and zirconium dioxide. However, the present invention is not limited to this. For example, as long as the substrates 412 and 412A are metal oxides having different refractive indexes, the substrates 412 and 412A may be made of other metal oxides.

  In each of the above embodiments, the substrates 412 and 412A include the void F, and the content of the void F is 0.5% or more and 10% or less. However, the present invention is not limited to this. For example, the substrates 412 and 412A may not include the gap F or may include 10% or more.

  In each of the above embodiments, the phosphor layer 411 is formed by sintering the phosphor and the glass binder. However, the present invention is not limited to this. For example, the phosphor layer 411 may be composed of a phosphor and an inorganic material different from the glass binder. Furthermore, the phosphor layer 411 may be composed of a phosphor and an organic material.

In each of the above embodiments, the wavelength conversion elements 41 and 41A are fixed to the disk 42 by the adhesive layer 413. However, the present invention is not limited to this. That is, the support substrate to which the wavelength conversion element 41 is fixed does not have to be the disk 42. For example, a rectangular shape in which a heat radiating plate or the like is provided on the surface opposite to the side on which the wavelength conversion element 41 is fixed. It may be fixed to the substrate. In this case, the motor 43 may not be provided.
In the above embodiments, the wavelength conversion element 41 is supported by the support substrate. However, the wavelength conversion element 41 is not necessarily supported by the support substrate. For example, if the heat dissipation of the wavelength conversion elements 41 and 41A is high, the support substrate is unnecessary.

  In the third embodiment, the reflective layer 414 is disposed between the substrate 412A and the adhesive layer 413. However, the present invention is not limited to this. For example, the reflective layer 414 may be disposed on the surface of the disc 42 opposite to the side on which the adhesive layer 413 is disposed. Even in this case, the same effect as the third embodiment can be obtained.

  In each of the embodiments described above, the transmission type light modulation device 34 (34R, 34G, 34B) is used as the light modulation device. However, the present invention is not limited to this. For example, instead of the transmission type light modulation device 34 (34R, 34G, 34B), a reflection type light modulation device may be used. In this case, color separation and color synthesis may be executed by the color synthesis device 35 without providing the color separation device 32.

In each of the above embodiments, the projector 1 includes the three light modulation devices 34 (34R, 34G, and 34B), but the present invention is not limited to this. That is, the present invention can also be applied to a projector using two or less or four or more light modulation devices.
Further, as the light modulation device, a light modulation device other than liquid crystal such as a digital micromirror device may be used.

  In each of the above embodiments, the example in which the illumination device 31 including the fluorescent member 4 is applied to the projector 1 has been shown. However, the present invention is not limited to this. For example, you may use the said illuminating device 31 for headlights, such as a lighting fixture and a motor vehicle.

DESCRIPTION OF SYMBOLS 1 ... Projector, 31 ... Illumination device, 31A ... Light source device (light source), 34 ... Light modulation device, 36 ... Projection optical device, 4, 4A ... Fluorescent member, 41, 41A ... Wavelength conversion element, 411 ... Phosphor layer, 412A 412A ... Substrate (sintered body) 413 Adhesive layer (adhesive layer) 414 Reflective layer 42 Disc (supporting substrate) F ... Void.

Claims (10)

A sintered body containing aluminum oxide and zirconium dioxide ;
A phosphor layer containing a bonding agent and a phosphor,
The phosphor layer is formed on the sintered body ,
In the sintered body, the zirconium dioxide, the wavelength converting element, characterized in der Rukoto than 4% of the aluminum oxide at a molar ratio. The wavelength conversion element according to claim 1 ,
The sintered body includes a plurality of crystals made of the aluminum oxide ,
The wavelength conversion element according to claim 1, wherein a particle size distribution of the plurality of crystals has a peak at 10 μm or less. In the wavelength conversion element according to claim 1 or 2 ,
The wavelength conversion element, wherein the sintered body includes voids. In the wavelength conversion element according to claim 3 ,
The total volume of the voids is 0.5% or more and 10% or less with respect to the volume of the sintered body. In the wavelength conversion element according to any one of claims 1 to 4 ,
The wavelength conversion element, wherein the bonding agent is made of an inorganic material. In the wavelength conversion element according to any one of claims 1 to 5 ,
A wavelength conversion element having a reflective layer that is located on a side opposite to the phosphor layer of the sintered body and reflects light that has passed through the sintered body. The wavelength conversion element according to claim 6 ,
A support substrate for supporting the sintered body;
A wavelength conversion element , further comprising: an adhesive layer provided between the support substrate and the reflective layer . In the wavelength conversion element according to any one of claims 1 to 5 ,
A support substrate for supporting the sintered body;
A wavelength conversion element, further comprising: an adhesive layer provided between the support substrate and the sintered body. The wavelength conversion element according to any one of claims 1 to 8 ,
And a light source that emits excitation light that excites the phosphor layer. The light source device according to claim 9 ;
A light modulation device that modulates light emitted from the light source device;
And a projection optical device that projects image light from the light modulation device.

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