JP2018053227A - Phosphor, wavelength conversion element, light source device and projector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a phosphor that can be excellent in both thermal conductivity and light scattering properties and provide a wavelength conversion element, a light source device and a projector including the phosphor.SOLUTION: A phosphor has a sintered body of a ceramic material. The sintered body has as a main phase 2 Ce:YAlO, and as an auxiliary phase 3, a ceramic material differing in refractive index from the main phase 2. The sintered body has a crystal grain boundary and a pore 4 in the crystal grain boundary.SELECTED DRAWING: Figure 1

Description

The present invention relates to a phosphor, a wavelength conversion element, a light source device, and a projector.

Patent Document 1 describes a light source device that uses fluorescence emitted from a phosphor as illumination light. The phosphor includes a binder made of an organic material and phosphor particles dispersed in the binder. However, since the heat resistance of the organic material is lower than that of the inorganic material, the binder deteriorates due to heat when irradiated with high-intensity laser light as excitation light.

Patent Document 2 discloses an inorganic phosphor that does not contain an organic material. The inorganic phosphor is formed by sintering a plurality of phosphor particles.

JP 2009-277516 A Special table 2013-518172 gazette

However, since the phosphor of Patent Document 2 has a plurality of pores, the thermal conductivity of the phosphor is lower than the thermal conductivity of the phosphor particles. For this reason, when high-intensity laser light is irradiated as excitation light, heat is stored, and the luminous efficiency of the phosphor particles decreases. Furthermore, the more the pores of a phosphor, the easier it is to break. There is a possibility that the phosphor breaks due to thermal stress. For example, when high intensity excitation light is irradiated, a large thermal stress is generated due to an in-plane temperature difference. Also,
In order to use the phosphor as a point light source, when the excitation light is focused and irradiated in a narrow region, the phosphor becomes high temperature at the excitation light irradiation position, and a large thermal stress is generated.

When a phosphor having a plurality of pores is processed into a phosphor layer having a certain thickness by polishing, for example, it is inevitable that the pores are exposed on the surface of the phosphor layer. Therefore, “indentations” due to pores exist on the surface of the phosphor layer. In the light source device described in Patent Document 1, an optical functional layer such as a dielectric multilayer film may be provided on the surface of the phosphor layer in order to improve the light utilization efficiency. However, when the optical functional layer is formed on the phosphor layer of Patent Document 2 having a depression on the surface, it is difficult to form the optical functional layer in the intended state at the depression, It is difficult to form an optical functional layer.

On the other hand, the pores have a function of scattering fluorescence emitted inside the phosphor. The light scattering function inside the phosphor is necessary for increasing the efficiency of extracting the fluorescence emitted inside the phosphor and using the fluorescence efficiently. If the pores are reduced, the number of scattering sources in the phosphor is reduced, so that not only the fluorescence utilization efficiency is lowered, but also the emission area of the fluorescence is enlarged, and the fluorescence utilization efficiency by the subsequent optical system is lowered.

  It is also desired to improve the quantum yield of the phosphor.

An object of the present invention is to provide a phosphor in which at least one of the above problems is solved. Another object of the present invention is to provide a wavelength conversion element, a light source device, and a projector having the phosphor as described above.

A first aspect of the present invention is a phosphor comprising a sintered body of a ceramic material, wherein the sintered body is Ce: Y ₃ Al ₅ O ₁₂ as a main phase, and the main phase is refracted as a sub phase. Ceramic materials having different rates, and the sintered body has a crystal grain boundary and provides a phosphor having pores in the crystal grain boundary.
In the phosphor according to the first aspect, the subphase preferably functions as a light scattering source. Specifically, the boundary between the main phase and the subphase functions as a light scattering source. Therefore, in the sintered body according to the first aspect, the amount of pores can be reduced as compared with the sintered body not including the subphase. That is, the thermal conductivity can be increased. Therefore, it is possible to achieve both thermal conductivity and light scattering characteristics.

In the first aspect, the subphase contains Ce: YAlO ₃ , CeO ₂ , Y ₂ O ₃ as the first crystal grains.
Or Ce: Y ₂ O ₃ .
According to this configuration, the quantum yield of the phosphor is higher than when the phosphor does not contain a subphase. In addition, the subphase preferably functions as a scattering source.

In the first aspect, the subphase further includes second crystal grains different from the first crystal grains,
The second crystal grains may include Ce: YAlO ₃ , CeO ₂ , Y ₂ O ₃ , or Ce: Y ₂ O ₃ .
According to this configuration, the subphase preferably functions as a scattering source.

In the first aspect, the subphase contains Ce: YAlO ₃ , CeO ₂ , or Ce: Y ₂ O ₃ , and the atomic concentration [Y] (at%) of yttrium in the sintered body is the following requirement ( i) and (ii) may be satisfied.
(I) 0.6 <[Y]
(Ii) 0.6 <[Re] / [Al] ≦ 0.652
However, [Re] is the sum of the atomic concentration of yttrium and the atomic concentration of cerium, and [A
l] is the atomic concentration of aluminum.
According to this configuration, the subphase can be reliably formed in the sintered body. Furthermore, since the phosphor can be sufficiently densified and the amount of pores can be reduced, it is possible to obtain a high-quality phosphor with an excellent balance between the amount of the main phase that emits fluorescence and the subphase that functions as a scattering source. Can do.

In the first aspect, the main phase may surround the subphase.
According to this configuration, the main phase and the subphase are present as different crystal grains, and the respective functions can be suitably exhibited.

In the first aspect, the pores may be scaly.
If the pores are scale-like, the surface area is larger than that of spherical pores of the same volume, so that the light traveling inside the phosphor is likely to hit the pores and more easily scatter.

In the first aspect, the crystal grains constituting the main phase and the crystal grains constituting the subphase may be granular.
According to this configuration, the phosphor can be easily manufactured.

1st aspect WHEREIN: 90 volume% or more and less than 100 volume% may be sufficient as the ratio of the volume of the said main phase with respect to the total volume of the said main phase and the said subphase.
According to this structure, it is excellent in the balance of the quantity of the main phase which emits fluorescence, and the subphase which functions as a scattering source, and it can be set as a high quality fluorescent substance.

According to a second aspect of the present invention, there is provided a wavelength conversion element having a phosphor layer using the phosphor as a forming material.
According to this configuration, since the wavelength conversion element includes the above-described phosphor, it is not easily damaged by heat and has a desired light scattering characteristic.

According to a third aspect of the present invention, there is provided a light source device including the wavelength conversion element described above and a light source that irradiates the phosphor layer included in the wavelength conversion element with excitation light.
According to this configuration, since the light source device includes the above-described phosphor, it is not easily damaged by heat.

A fourth aspect of the present invention includes the light source device, a light modulation device that modulates light from the light source device according to image information to form image light, and a projection optical system that projects the image light. Provide a projector.
According to this configuration, since the projector includes the above-described phosphor, it is not easily damaged by heat.

A fifth aspect of the present invention provides a wavelength conversion element having a phosphor layer and an optical functional layer provided on the surface of the phosphor layer. The phosphor layer includes a ceramic fluorescent material as a first crystallite,
The first crystallite is made of a sintered body including a ceramic material having a different refractive index as the second crystallite. The sintered body has crystal grain boundaries and pores in the crystal grain boundaries.
In the wavelength conversion element according to the fifth aspect, the second crystallite preferably functions as a scattering source.
Specifically, the boundary between the first crystallite and the second crystallite functions as a light scattering source. Therefore, in the sintered body according to the fifth aspect, the amount of pores can be reduced as compared with the sintered body not including the second crystallite. That is, it is possible to reduce the amount of the depression formed by exposing the pores to the surface of the phosphor layer. Therefore, defects are hardly generated in the optical functional layer formed on the surface of the phosphor layer.

In the fifth aspect, the first crystallite includes Ce: Y ₃ Al ₅ O ₁₂ , and the second crystallite includes Ce: YAlO ₃ , CeO ₂ , Y ₂ O ₃ , Ce: Y ₂ O ₃ or YAlO ₃ may also be included.
According to this configuration, the quantum yield of the phosphor is higher than when the phosphor does not contain a subphase. The second crystallite preferably functions as a scattering source.

In the fifth aspect, the optical functional layer may be an antireflection film.
According to this configuration, a wavelength conversion element having an antireflection film having few defects and a high antireflection function on the surface can be provided.

In the fifth aspect, the optical functional layer may be a dichroic film.
According to this configuration, it is possible to provide a wavelength conversion element having a dichroic film having few defects and a high wavelength selection function on the surface. Therefore, the fluorescence generated by the phosphor layer is emitted in a desired direction.

In the fifth aspect, the optical functional layer may be a reflective film.
According to this configuration, it is possible to provide a wavelength conversion element having a reflective film with few defects and a high reflection function on the surface. Therefore, the fluorescence generated by the phosphor layer is emitted in a desired direction.

In the fifth aspect, the phosphor layer further includes a ceramic material different from the second crystallite as a third crystallite, and a refractive index of the third crystallite is different from a refractive index of the first crystallite. It may be.
According to this configuration, the third crystallite also preferably functions as a scattering source.

According to a sixth aspect of the present invention, there is provided a light source device comprising: the above-described wavelength conversion element; and a light source that irradiates the phosphor layer included in the wavelength conversion element with excitation light.
Since the light source device having this configuration includes the wavelength conversion element as described above, it can emit high-luminance light.

According to a seventh aspect of the present invention, there is provided the above light source device, a light modulation device that modulates light from the light source device according to image information to form image light, and a projection optical system that projects the image light. A projector is provided.
Since the projector having this configuration includes the above-described light source device, it can project a high-luminance image.

According to an eighth aspect of the present invention, there is provided a light source that emits excitation light, a wavelength conversion element that includes a phosphor layer that emits fluorescence when excited by the excitation light, and the excitation between the light source and the wavelength conversion element. A condensing optical system disposed on the optical path of the light and condensing the excitation light toward the phosphor layer, wherein the phosphor layer includes a ceramic fluorescent material as a first crystallite, and a second Provided is a light source device comprising a sintered body including a crystallite having a refractive index different from that of the first crystallite.
In the light source device according to the eighth aspect, the second crystallite preferably functions as a scattering source. Specifically, the boundary between the first crystallite and the second crystallite functions as a light scattering source. Therefore, in the sintered body according to the eighth aspect, the amount of pores can be reduced as compared with the sintered body not including the second crystallite. That is, the thermal conductivity can be increased. Therefore, the temperature rise of the phosphor layer is reduced and the phosphor layer is not easily damaged.

In the eighth aspect, the first crystallite may include Ce: Y ₃ Al ₅ O ₁₂ , and the second crystallite may include YAlO ₃ .
In the sintered body containing YAlO ₃ (hereinafter referred to as YAP), the crystallite diameters of the first crystallite and the second crystallite tend to be smaller when the sintered body is produced than when no YAP is contained. It is in. The sintered body has high bending strength when the crystallite diameter of the crystallite constituting the sintered body is small. Therefore, according to the above configuration, damage due to thermal stress is unlikely to occur.

According to a ninth aspect of the present invention, there is provided the above light source device, a light modulation device that modulates light from the light source device according to image information to form image light, and a projection optical system that projects the image light. A projector is provided.
Since the projector having this configuration includes the light source device described above, it has high reliability.

It is a SEM photograph which shows an example of the fluorescent substance of 1st Embodiment. It is a schematic diagram which shows the mode of light emission when the conventional fluorescent substance is irradiated with excitation light. It is a schematic diagram which shows the mode of light emission when the excitation light is irradiated to the fluorescent substance of 1st Embodiment. 1 is a schematic diagram showing a projector 1000 according to a first embodiment. It is a schematic diagram which shows the wavelength conversion element which concerns on 1st Embodiment. It is A1-A1 sectional drawing of the wavelength conversion element shown to FIG. 4A. It is a schematic diagram which shows the mode of the bleeding in the inorganic fluorescent substance which does not contain a subphase or a pore. It is a schematic diagram which shows the mode of the bleeding in the fluorescent substance of 1st Embodiment. It is an example of the light emission profile for demonstrating a blur. It is a graph which shows typically the relation between the amount of bleed and the amount of fluorescence emitted from a wavelength conversion element. It is a graph which shows the relationship between the amount of bleeding and the magnitude | size of a liquid crystal light modulation apparatus. It is a graph which shows the relationship between the amount of bleeding and the average crystal grain diameter of a crystal grain. It is a graph which shows the relationship between the amount of bleeding and the mass (Si content) of a sintering aid. It is a schematic diagram explaining a projector 1006 of a modification of the first embodiment. It is a schematic diagram which shows the wavelength conversion element which concerns on the modification of 1st Embodiment. It is A2-A2 sectional drawing of the wavelength conversion element shown to FIG. 12A. It is a schematic diagram which shows the light source device 1500 of 1st Embodiment. It is a schematic diagram which shows the projector which concerns on 2nd Embodiment. It is a schematic diagram which shows the wavelength conversion element which concerns on 2nd Embodiment. It is XVb-XVb arrow sectional drawing of the wavelength conversion element shown to FIG. 15A. It is a figure which shows the wavelength conversion element which has a fluorescent substance layer which does not contain a 2nd crystallite. It is a figure which shows the mode of the wavelength conversion element of 2nd Embodiment. It is a schematic diagram explaining the projector of the modification of 2nd Embodiment. It is a schematic diagram which shows the wavelength conversion element which concerns on the modification of 2nd Embodiment. It is XIXb-XIXb arrow sectional drawing of the wavelength conversion element shown to FIG. 19A.

[First Embodiment]
Hereinafter, the phosphor, the wavelength conversion element, the light source device, and the projector according to the present embodiment will be described with reference to the drawings. In all the drawings below, the dimensions and ratios of the constituent elements are appropriately changed in order to make the drawings easy to see.

FIG. 1 is an SEM photograph showing an example of the phosphor of the present embodiment, and a reflected electron image (BSE image).
It is. The phosphor 1 of the present embodiment is made of a ceramic material sintered body.
The phosphor 1 includes Ce: Y ₃ Al ₅ O ₁₂ (hereinafter referred to as “Ce: YAG”) as the main phase 2, and includes two types of ceramic materials as the subphase 3. Two types of ceramic materials are Ce: YAlO ₃ (hereinafter referred to as “Ce: YAP”) and Ce: Y ₂ O ₃ .
Further, the phosphor 1 includes a plurality of pores 4.
In FIG. 1, a crystal grain made of Ce: Y ₂ O ₃ is indicated by a symbol YO. In the BSE image, C
Since it is not easy to distinguish e: YAG and Ce: YAP, in FIG.
: The crystal grain consisting of YAG and the crystal grain consisting of Ce: YAP are indicated by the symbol GP, respectively.
The phosphor 1 has a crystal grain boundary and has pores 4 in the crystal grain boundary.

Ce: YAP corresponds to the first crystal grains recited in the claims, and Ce: Y ₂ O ₃ corresponds to the second crystal grains recited in the claims. The material for forming the second crystal grains is different from the material for forming the first crystal grains. Hereinafter, in this specification, crystal grains constituting the main phase 2 are referred to as crystal grains 2a, and crystal grains constituting the subphase 3 are referred to as crystal grains 3a.

Ce: YAG is a yellow phosphor that emits yellow fluorescence when irradiated with excitation light.
The main phase 2 is formed by sintering a plurality of crystal grains 2a made of Ce: YAG.

The subphase 3 is made of a material different from that of the main phase 2. In this embodiment, the formation material of the subphase 3 is Ce: YAP and Ce: Y ₂ O ₃ , but is not limited thereto. The forming material is, for example, A
It may be l ₂ O ₃ , CeO ₂ , Y ₂ O ₃ , YAP. Al ₂ O ₃ , CeO ₂ , and Y ₂ O ₃ are starting materials used when synthesizing Ce: YAG as described later. The subphase 3 may be made of one type of forming material, or may be made of a plurality of forming materials as in the present embodiment. Note that at least one of the main phase 2, the first crystal grains, and the second crystal grains may contain a metal impurity contained in the starting material.

The refractive index of the above-described materials, Ce: YAG (1.83), Al 2 O 3 (1.76), Ce
: YAP (1.93), CeO ₂ (2.2), Y ₂ O ₃ (1.87), Ce: Y ₂ O ₃ (1.
87-2.2), YAP (1.93). The refractive index of Ce: Y ₂ O ₃ varies depending on the Ce content. The refractive index of Ce: YAP and the refractive index of Ce: Y ₂ O ₃ are the main phase 2 (Ce: Y
Since the refractive index is different from that of AG), the subphase 3 preferably functions as a scattering source.

In addition, since the thermal conductivity of these substances constituting the subphase 3 is equivalent to Ce: YAG, even if the phosphor 1 has the subphase 3, the thermal conductivity of the phosphor 1 is greatly reduced. There is no.

The crystal grains 2a and the crystal grains 3a are preferably granular. With such a configuration, the phosphor can be easily manufactured. Here, in this embodiment, “granular” means that the ratio of the short side to the long side is 0.3 or more when the shape of the crystal grain in the SEM photograph is approximated by a rectangle. The average crystal grain size of the crystal grains 2a is preferably 0.8 μm or more and 1.2 μm or less.

Regarding the crystal grain 3a, when the thickness of the phosphor 1 is 200 μm, it is 0.5 μm or more and 20
It is good that it is μm or less. When the crystal grain 3a is made of Ce: YAP, the average grain size of the crystal grain 3a is preferably 0.8 μm or more and 1.2 μm or less. Further, the crystal grain 3a is Ce.
When composed of O ₂ or Ce: Y ₂ O ₃ , the average crystal grain size of the crystal grains 3a is preferably 0.33 μm or more and 0.5 μm or less.

The crystal grains 2a may be in the form of a film. When the shape of the crystal grain 2a is a film,
Since the surface area of the crystal grain 2a becomes large and it becomes easy to scatter light as will be described later, it is preferable. For the same reason, the crystal grains 3a may be in the form of a film.

Here, in this embodiment, the average crystal grain size of the crystal grains 2a and 3a is obtained as follows.

First, the phosphor 1 is broken, and an SEM BSE image is taken of the broken surface. At that time, imaging is performed at a magnification such that approximately 50 crystal grains are included in one field of view.

Next, based on the obtained SEM photograph, image processing for distinguishing each crystal grain along the crystal grain boundary is performed.

Next, the area of each crystal grain is obtained from the SEM photograph after image processing, and the equivalent circle diameter, which is the diameter of a circle having an area equal to the area obtained for each crystal grain, is calculated. The average crystal grain size is obtained by arithmetically averaging the obtained equivalent circle diameter.

The pores 4 are preferably scaly. Here, in the present embodiment, “scale-like” means that when the pore shape in the SEM photograph is approximated by a rectangle, the ratio of the short side to the long side is 0.3.
Refers to the smaller one. However, the pore 4 may have a ratio of the short side to the long side of 0.3 or more.

As will be described later, the pores 4 have a function of scattering the light traveling inside the phosphor 1 by reflecting or refracting it. Therefore, if the pores 4 are scaly, since the surface area is larger than the spherical pores of the same volume, the light traveling inside the phosphor 1 easily hits the pores 4.
It becomes easier to scatter. The “light traveling inside the phosphor 1” includes both excitation light incident on the phosphor 1 and fluorescence emitted from the phosphor 1.

When the phosphor 1 includes the pores 4, the thermal conductivity is low as compared with the case where the phosphor 1 does not include the pores 4. On the other hand, the pores 4 have a function of scattering light traveling inside the phosphor 1. Therefore, the pore volume ρ is preferably set according to the physical properties required for the phosphor 1, that is, thermal conductivity and light scattering characteristics. The pore volume ρ will be described later.

In order to reduce the influence of the heat storage of the phosphor 1, the thermal conductivity is 9 W / m ·
It is preferable that it is k or more. In order to achieve such thermal conductivity, the pore volume ρ is 0.
It is preferably 01% or more and less than 5%.

In the phosphor 1, the volume of the main phase 2 is larger than the volume of the subphase 3. As shown in FIG. 1, the main phase 2 surrounds the subphase 3. That is, the subphase 3 exists in the crystal grain boundary of the main phase 2. The main phase 2 and the subphase 3 exist as different crystal grains, and each function can be suitably exhibited.

Using X-ray diffraction, Ce: YAG, Ce: YAP and Ce: Y ₂ contained in the phosphor 1
Each ratio of O ₃ was measured. As a result, Ce: YAG was 91.8% by volume, and Ce: YAP was 5%.
. 7% by volume and Ce: Y ₂ O ₃ were 2.5% by volume.

In the phosphor 1, the ratio of the volume of the main phase 2 to the total volume of the main phase 2 and the subphase 3 is 9
It is preferably 0% by volume or more and less than 100% by volume. With such a volume ratio, the amount of the main phase 2 that emits fluorescence and the amount of the subphase 3 that functions as a scattering source is excellent in balance, and a high-quality phosphor can be obtained.

Further, in the sintered body constituting the phosphor 1, the atomic concentration of yttrium in the sintered body (at
%) Preferably satisfies the following requirements (i) and (ii). In the following requirements (i) and (ii), [Y] indicates the atomic concentration of yttrium. [Re] represents the sum of the atomic concentration of yttrium and the atomic concentration of cerium. [Al] indicates the atomic concentration of aluminum. In addition, each atomic concentration shows the density | concentration with respect to the whole quantity of the metal atom in a sintered compact.
(I) 0.6 <[Y]
(Ii) 0.6 <[Re] / [Al] ≦ 0.652

[Y] calculated from the stoichiometry of YAG (Y _{3 Al 5} O ₁₂ ), which is the base crystal of Ce: YAG
The value of is 0.6. Therefore, the condition (i) indicates that the phosphor 1 contains an excess of yttrium atoms than the amount calculated from the stoichiometry. Yttrium atoms contained in excess of the stoichiometric amount constitute subphase 3. That is, by satisfying the condition (i), the subphase 3 can be reliably formed in the phosphor 1.

The lower limit in the condition (ii) will be described. When the value of [Re] / [Al] is 0.6 or less, Al ₂ O ₃ is basically generated as a subphase. As will be described in detail later, the quantum yield of the phosphor containing Al ₂ O ₃ as the subphase is lower than the quantum yield of the phosphor not containing the subphase. Therefore, the value of [Re] / [Al] is preferably larger than 0.6.

Although the upper limit in the condition (ii) will be described in detail later, [Re] / [Al] ≦ 0.
By setting it to 652, it is possible to prevent the sintering temperature of the sintered body from exceeding the heat resistance temperature of a general sintering furnace. Therefore, the obtained phosphor can be sufficiently densified, the amount of pores can be reduced, and the amount of the main phase that emits fluorescence and the subphase that functions as a scattering source is excellent in balance, and a high-quality phosphor is obtained. be able to.

In this specification, “amount of pores” refers to the ratio of the total volume of a plurality of pores to the volume of the phosphor. The pore volume ρ can be obtained as follows.

The volume of the phosphor is V ₀ and the total volume of the plurality of pores contained in the phosphor is V ₂ . Porosity ρ
Is given by equation (1).
ρ = V ₂ / V ₀ (1)

If the mass of the phosphor is W, the phosphor density ρ ₁ is given by equation (2).
ρ ₁ = W / V ₀ (2)
The phosphor volume V ₀ and the phosphor mass W can be measured.

Here, the composition of the main phase, the composition of the subphase, and the volume ratio of the main phase to the subphase are determined using X-ray crystal diffraction. Using the results obtained by X-ray crystal diffraction and the theoretical density of the main phase and the theoretical density of the subphase, the theoretical density ρ ₂ of the phosphor itself is obtained.

The theoretical density ρ ₂ can be expressed by Equation (3) using V ₀ , V ₂ , and W. Moreover, Formula (3)
Therefore, the volume V ₂ is expressed as the following formula (4).
ρ ₂ = W / (V ₀ −V ₂ ) (3)
V ₂ = V ₀ −W / ρ ₂ (4)

From the above formulas (1), (2), and (4), the pore volume ρ can be expressed by the formula (5). That is, the pore volume ρ can be obtained from the equation (5) using the measured density ρ ₁ and the theoretical density ρ ₂ .
ρ = 1−ρ ₁ / ρ ₂ (5)

The phosphor 1 having the above configuration exhibits the following light emission behavior. FIG. 2A is a schematic diagram showing a state of light emission when the conventional phosphor 1X not including the subphase 3 is irradiated with excitation light.
These are the schematic diagrams which show the mode of light emission when the fluorescent substance 1 of this embodiment is irradiated with excitation light. It is assumed that both the phosphor 1X and the phosphor 1 have Ce: YAG as the main phase 2.

In the phosphor 1X shown in FIG. 2A, for example, when the excitation light B, which is blue laser light, is irradiated, the main phase 2 of the phosphor 1X absorbs a part of the excitation light B, and the yellow fluorescence YL is isotropically emitted. Eject.
The fluorescence YL is refracted and reflected by the plurality of pores 4 existing inside the phosphor 1X, proceeds while changing the traveling direction (while being scattered), and is emitted to the outside of the phosphor 1.

Further, the remaining part of the excitation light B that has not been absorbed by the main phase 2 passes through the phosphor 1X. At that time, similarly to the fluorescence YL, the light passes through the phosphor 1X while being scattered by being refracted and reflected by the plurality of pores 4. Thereby, white light in which excitation light B and fluorescence YL are mixed is emitted from phosphor 1X.

However, in the phosphor 1X, in order to sufficiently scatter the excitation light B and the fluorescence YL, a large number of pores 4 are used.
Therefore, when compared with the thermal conductivity of Ce: YAG constituting the main phase 2, the phosphor 1
The thermal conductivity of X as a whole is low. For this reason, when high-intensity laser light is irradiated as the excitation light B, the phosphor 1X stores heat and may be damaged by heat. For example, the luminous efficiency of the phosphor 1X is lowered.

On the other hand, the phosphor 1 shown in FIG. 2B includes subphases 3 (a plurality of crystal grains 3a) having a refractive index different from that of the main phase 2. The subphase 3 can scatter the excitation light B and the fluorescence YL by refraction or reflection. Therefore, in the phosphor 1, the ability to scatter the excitation light B and the fluorescence YL is equivalent to that of the phosphor 1X, but the amount of pores ρ can be reduced.

That is, since the subphase 3 suitably functions as a scattering source, the amount of pores ρ can be reduced,
The thermal conductivity can be increased as compared with the phosphor 1X. Therefore, the phosphor 1 that can achieve both thermal conductivity and optical properties can be obtained.

The inventors made phosphor A not containing subphase 3, phosphor B and phosphor C containing subphase 3, and measured their quantum yield. The main phases 2 of phosphor A, phosphor B, and phosphor C were all Ce: YAG. The subphase 3 of the phosphor B was Ce: YAP and Ce: Y ₂ O _3, and the subphase 3 of the phosphor C was Al ₂ O ₃ . In phosphor B, the value of [Re] / [Al] is 0.
. 63, and the volume ratio of Ce: YAG, Ce: YAP, and Ce: Y ₂ O ₃ was 90: 9: 1. In phosphor C, the value of [Re] / [Al] is 0.58, and Ce: YAG and Al ₂
The volume ratio of O ₃ was 92: 8. The quantum yield of phosphor A was 91.7%, the quantum yield of phosphor B was 94.2%, and the quantum yield of phosphor C was 75.6%.

Thus, it was found that Ce: YAP and Ce: Y ₂ O ₃ improve the quantum yield. It was also found that the quantum yield was improved when the phosphor contained only one of Ce: YAP and Ce: Y ₂ O _{3 as a} subphase. Furthermore, it was found that CeO ₂ and Y ₂ O ₃ also improve the quantum yield. Therefore, the subphase 3 preferably includes crystal grains 3a containing Ce: YAP, Ce: Y ₂ O ₃ , CeO ₂ , or Y ₂ O ₃ .

[Phosphor production method]
The phosphor as described above can be manufactured as follows.
First, a raw material powder composed of Y ₂ O ₃ powder, Al ₂ O ₃ powder, and CeO ₂ powder is mixed with ethanol. The obtained slurry is agitated while pulverizing the raw material powder with a ball mill.

At this time, a sintering aid containing Si atoms may be added to the raw material powder. As a sintering aid, S
Examples thereof include iO ₂ , CaO, and MgO. Further, a substance that exhibits the same effect as SiO ₂ , CaO, or MgO during firing, for example, TEOS (Tetraethyl orthosilicate) may be added as a sintering aid. For example, the sintering aid is 10 after sintering with respect to the mass of the raw material powder.
Add to remain at 0 ppm. In addition, when adding a substance that exhibits the same effect as SiO ₂ , CaO or MgO as a sintering aid, such as TEOS, when the sintering aid is converted into an equivalent substance after sintering, Equivalent material is, for example, 1 after sintering relative to the mass of the raw powder
Add to remain at 00 ppm.

Next, ethanol is removed from the obtained slurry, and the raw material powder is dried. The coarse particles are removed by sieving the dried raw material powder. As a result, the particle diameter is several tens of nm.
To obtain a raw material powder composed of secondary particles having a particle diameter of several μm to several hundred μm containing primary particles of Y ₂ O ₃ , Al ₂ O ₃ and CeO ₂ of several hundred nm. Thereafter, an appropriate amount of Y ₂ O ₃ powder having a particle size of several μ to several tens μm is added to the raw material powder.

Next, it is pressed into a desired shape, molded and fired. Relatively large Y in the firing process
Since up to the inside of the ₂ O ₃ powder does not reach the aluminum, after a relatively large Y ₂ O ₃ powder is calcined, Y ₂ O ₃ or Ce,: a first crystal grains consisting of Y ₂ O _3.

  Here, the upper limit value of the condition (ii) will be described.

The heat resistance temperature (usable temperature) of a general sintering furnace having a heating element of molybdenum disilicide is approximately 1700 ° C. On the other hand, when the blending amount of the Y ₂ O ₃ powder is increased in the raw material powder, an excessive amount of Y ₂ O ₃ behaves as an impurity in the sintered body, and the sintering temperature of the entire system tends to increase. For this reason, if [Re] / [Al] exceeds 0.652, the sintering temperature of the sintered body theoretically exceeds the heat resistance temperature of a general sintering furnace, so that it cannot be sufficiently sintered. Then
In the obtained sintered body, densification is insufficient and the amount of pores ρ increases, so that a good phosphor cannot be obtained.

It is desirable to sinter in a general sintering furnace under an oxygen atmosphere. Alternatively, after sintering in a neutral atmosphere such as nitrogen or a reducing atmosphere such as hydrogen, annealing may be performed at 1000 ° C. to 1400 ° C. in an oxygen atmosphere. The sintering temperature may be, for example, 1500 ° C. or higher and 1750 ° C. or lower. Further, a hot press sintering method or a hot isostatic pressing sintering method may be used.

On the other hand, when the blending amount of the Y ₂ O ₃ powder is increased within a range that satisfies the condition (ii), the raw material powder can be suitably sintered to obtain a desired sintered body.
As described above, the phosphor of the present embodiment is obtained.

According to the phosphor configured as described above, it is possible to provide a phosphor capable of achieving both thermal conductivity and light scattering characteristics.

FIG. 3 is a schematic diagram showing a projector 1000 according to the present embodiment. FIG. 4A is a schematic diagram illustrating a wavelength conversion element included in the projector 1000. 4B is an A1-A1 cross-sectional view of the wavelength conversion element shown in FIG. 4A.

As shown in FIG. 3, the projector 1000 according to the present embodiment includes a light source device 100, a color separation light guide optical system 200, a liquid crystal light modulation device 400R, a liquid crystal light modulation device 400G, a liquid crystal light modulation device 400B, a cross dichroic prism 500, and A projection optical system 600 is provided.

The light source device 100 includes a light source 10, a condensing optical system 20, a wavelength conversion element 30, a motor 50, a collimating optical system 60, a first lens array 120, a second lens array 130, a polarization conversion element 140, and a superimposing lens 150.

The light source 10 is blue light composed of laser light as excitation light (emission intensity peak: about 445 n).
m). The light source 10 may consist of one laser light source or may consist of many laser light sources. A laser light source that emits blue light having a wavelength other than 445 nm (for example, 460 nm) can also be used.

The condensing optical system 20 includes a first lens 22 and a second lens 24. The condensing optical system 20 is
It arrange | positions in the optical path from the light source 10 to the wavelength conversion element 30, and injects into the fluorescent substance layer 42 (after-mentioned) in the state which condensed blue light substantially. The first lens 22 and the second lens 24 are convex lenses.

As shown in FIGS. 3 and 4A, the wavelength conversion element 30 includes a substrate 40 that is circular in plan view, and a phosphor layer 42 that is provided along the circumferential direction of the substrate 40 on one surface of the substrate 40. Yes. The wavelength conversion element 30 can be rotated by a motor 50 connected to the center of the substrate 40. The wavelength conversion element 30 emits red light and green light toward the side opposite to the side on which blue light is incident.

The substrate 40 is made of a material that transmits blue light. As a material of the substrate 40, for example, quartz glass, crystal, sapphire, optical glass, transparent resin, or the like can be used.

Blue light from the light source 10 enters the phosphor layer 42 from the substrate 40 side. As shown in FIG. 4B, a dichroic film 44 that transmits blue light and reflects red light and green light is provided between the phosphor layer 42 and the substrate 40.

The phosphor layer 42 is excited by blue light having a wavelength of about 445 nm. The phosphor layer 42 is
Part of the blue light from the light source 10 is converted into light containing yellow light, and the remaining part of the blue light is passed through without conversion. The phosphor in the present embodiment described above is used as the phosphor layer 42.

The collimating optical system 60 includes a first lens 62 and a second lens 64, and the wavelength conversion element 3.
The light from 0 is approximately collimated. The first lens 62 and the second lens 64 are convex lenses.

The first lens array 120 has a plurality of first small lenses 122 for dividing the light from the collimating optical system 60 into a plurality of partial light beams. The plurality of first small lenses 122 are light source optical axes 1.
They are arranged in a matrix in a plane orthogonal to 00ax.

The second lens array 130 has a plurality of second small lenses 132 corresponding to the plurality of first small lenses 122 of the first lens array 120. The second lens array 130 includes the superimposing lens 15.
0, the image of each first small lens 122 of the first lens array 120 is converted into the liquid crystal light modulation device 40.
The image is formed in the vicinity of the image forming area of 0R, the liquid crystal light modulator 400G, and the liquid crystal light modulator 400B. The plurality of second small lenses 132 are arranged in a matrix in a plane orthogonal to the light source optical axis 100ax.

The polarization conversion element 140 converts each partial light beam divided by the first lens array 120 into linearly polarized light.

The polarization conversion element 140 transmits one linear polarization component of the polarization component included in the light from the wavelength conversion element 30 as it is, and reflects the other linear polarization component in a direction perpendicular to the light source optical axis 100ax. A reflection layer that reflects the other linearly polarized light component reflected by the polarization separating layer in a direction parallel to the light source optical axis 100ax, and the other linearly polarized light component reflected by the reflective layer is converted into one linearly polarized light component. And a phase difference plate.

The superimposing lens 150 condenses the partial light beams from the polarization conversion element 140 and superimposes them in the vicinity of the image forming regions of the liquid crystal light modulation device 400R, the liquid crystal light modulation device 400G, and the liquid crystal light modulation device 400B. The first lens array 120, the second lens array 130, and the superimposing lens 150 are:
An integrator optical system that makes the in-plane light intensity distribution of the light from the wavelength conversion element 30 uniform is configured.

The color separation light guide optical system 200 includes a dichroic mirror 210 and a dichroic mirror 22.
0, reflection mirror 230, reflection mirror 240, reflection mirror 250 and relay lens 260,
A relay lens 270 is provided. The color separation light guide optical system 200 separates the light from the light source device 100 into red light, green light, and blue light, and the liquid crystal light modulation device 400R to which the red light, green light, and blue light respectively correspond, and the liquid crystal light modulation. The light is guided to the device 400G and the liquid crystal light modulation device 400B.
A condensing lens 300R, a condensing lens 300G, and a condensing lens 300B are disposed between the color separation light guide optical system 200 and the liquid crystal light modulation device 400R, the liquid crystal light modulation device 400G, and the liquid crystal light modulation device 400B, respectively. ing.

The dichroic mirror 210 is a dichroic mirror that transmits a red light component and reflects a green light component and a blue light component.

The dichroic mirror 220 is a dichroic mirror that reflects a green light component and transmits a blue light component.

The red light that has passed through the dichroic mirror 210 is reflected by the reflecting mirror 230, passes through the condenser lens 300R, and enters the image forming area of the liquid crystal light modulation device 400R for red light.

The green light reflected by the dichroic mirror 210 is further reflected by the dichroic mirror 220, passes through the condenser lens 300G, and enters the image forming area of the liquid crystal light modulation device 400G for green light.

The blue light that has passed through the dichroic mirror 220 passes through the relay lens 260, the incident-side reflecting mirror 240, the relay lens 270, the exit-side reflecting mirror 250, and the condensing lens 300B to form an image of the liquid crystal light modulation device 400B for blue light. Incident into the area.

The liquid crystal light modulation device 400R, the liquid crystal light modulation device 400G, and the liquid crystal light modulation device 400B modulate incident color light according to image information to form a color image. Although not shown, between the condenser lens 300R, the condenser lens 300G, and the condenser lens 300B and the liquid crystal light modulation device 400R, the liquid crystal light modulation device 400G, and the liquid crystal light modulation device 400B, incident side polarization is respectively provided. A plate is disposed, and an exit-side polarizing plate is disposed between the liquid crystal light modulation device 400R, the liquid crystal light modulation device 400G, the liquid crystal light modulation device 400B, and the cross dichroic prism 500, respectively.

The cross dichroic prism 500 includes the liquid crystal light modulation device 400R and the liquid crystal light modulation device 4.
00G and the image lights emitted from the liquid crystal light modulation device 400B are combined to form a color image.

The color image emitted from the cross dichroic prism 500 is output from the projection optical system 600.
Is enlarged and projected to form an image on the screen SCR.

In order to efficiently capture the fluorescence emitted from the phosphor layer 42 by the collimating optical system 60, it is desirable that the area of the region where the fluorescence is emitted from the phosphor layer 42 is small.

However, in the inorganic phosphor, “smearing” occurs in which the fluorescence is emitted while spreading in the plane direction from the position where the excitation light is incident, by the following mechanism. Therefore, the area of the region where the fluorescence is emitted tends to increase.

FIG. 5A is a schematic diagram showing a state of bleeding in phosphor 1Y which is an inorganic phosphor composed of only main phase 2 which is Ce: YAG and does not contain subphases or pores. FIG. 5B is a schematic diagram showing a state of bleeding in the phosphor 1 of the present embodiment.
As shown in FIG. 5A, in the phosphor 1Y, a part of the fluorescence traveling inside the phosphor 1Y is totally reflected on the surface of the phosphor 1Y and propagates in the in-plane direction. Fluorescence totally reflected inside the phosphor 1Y is indicated by symbols Y1 and Y2 in the figure.

Since the phosphor 1Y is composed only of the main phase 2, even if a crystal grain boundary exists, the fluorescence YL is not easily refracted or reflected inside the phosphor 1Y. Therefore, the fluorescence is inside the phosphor 1Y,
After traveling to a position away from the position where the excitation light B is incident in the in-plane direction, the light is emitted to the outside of the phosphor 1Y. As a result, “smudge” is observed.

On the other hand, as shown in FIG. 5B, in the phosphor 1 of the present embodiment, the fluorescent light is refracted or reflected by the subphase 3 or the pores 4, so that the traveling direction of the fluorescence is easily changed. Then, when there is no subphase 3 or pores 4, the fluorescence YL emitted at an angle that causes total reflection on the surface of the phosphor 1 also changes the traveling direction, so that the approach angle is different from the total reflection condition. The light enters the surface of the phosphor 1 and is easily emitted from the phosphor 1 to the outside. As a result, in the phosphor 1, the internal fluorescence is more easily emitted to the outside of the phosphor than in the phosphor 1Y, and “blotting” is reduced.

When the phosphor 1 of this embodiment is used for the wavelength conversion element 30, parameters such as the amount of crystal grains 3a, the amount of pores ρ, and the shape have a correlation with the amount of “smear” as will be described in detail later. Therefore, it is preferable to appropriately design the phosphor 1 and adjust the bleeding.

In the present embodiment, the “bleed amount” is defined as follows. Diameter on phosphor 0
. A 4 mm region is uniformly irradiated with excitation light, and an emission profile of fluorescence emitted from the phosphor is measured. The relationship between the distance from the center of the region irradiated with the excitation light and the emission intensity is shown as an emission profile in FIG. The vertical axis represents the light intensity, and the horizontal axis represents the distance from the center. In the light emission profile, twice the distance L at which the light intensity is 20% of the maximum value is defined as the amount of bleeding (unit: mm).

FIG. 7 is a graph schematically showing the relationship between the amount of bleeding and the total amount of fluorescence emitted from the wavelength conversion element, with the horizontal axis indicating the amount of bleeding and the vertical axis indicating the total amount of fluorescence. A large amount of bleeding corresponds to a small amount of pores ρ, and a small amount of pores ρ corresponds to a high sintering temperature. When the sintering temperature is high and the amount of pores ρ is small, the amount of excitation light that is not absorbed and backscattered decreases, and the amount of fluorescence increases. Therefore, the relationship between the amount of bleeding and the total amount of fluorescence tends to be as shown in FIG. There is a correlation that as the amount of blur increases, the fluorescence increases.

Therefore, if we focus only on reducing the amount of blurring, the amount of light as a projector light source will be insufficient, or the amount of fluorescence for mixing white light with blue excitation light will be reduced, and the color balance will be disrupted. Another problem can arise.

In a projector such as the projector 1000 of this embodiment, a liquid crystal light modulation device having a diagonal size of about 0.4 inch to 1.2 inch is used. According to the results of the study by the inventors shown in FIG. 8, the amount of bleeding is about 0.7 mm for a 0.4 inch diagonal liquid crystal light modulator, and for the 1.2 inch diagonal liquid crystal light modulator. It has been found that a bleed amount of about 1.1 mm is desirable.

The amount of bleeding is controlled as follows.
FIG. 9 is a graph showing the relationship between the amount of bleeding and the average crystal grain size of crystal grains, where the horizontal axis represents the amount of blur (mm) and the vertical axis represents the average crystal grain size (μm) of the crystal grains. In FIG. 9, a mixed crystal grain means a mixture of Ce: YAP crystal grains and Ce: YAG crystal grains.

As the average crystal grain size increases, the amount of blurring tends to increase because the number of interfaces where light is refracted or reflected decreases. The crystal grain size can be adjusted by controlling the sintering time and the sintering temperature.

From FIG. 9, the average crystal grain size of the mixed crystal grains is preferably 0.8 μm or more and 1.2 μm or less, and the average crystal grain size of Y ₂ O ₃ is preferably 0.33 μm or more and 0.50 μm or less. I understand that.

FIG. 10 is a graph showing the relationship between the amount of bleeding and the Si content when a Si-based sintering aid is used during sintering, where the horizontal axis represents the amount of bleeding (mm) and the vertical axis represents the phosphor. Si content (ppm) is shown. If the Si content is high, that is, if a large amount of sintering aid is used during sintering, the sintering is likely to proceed, and as a result of the reduction of pores, the amount of bleeding tends to increase.
FIG. 10 shows that the Si content is preferably 200 ppm or less.

Considering the relationship between the amount of bleeding and the amount of pores ρ, when the amount of pores ρ decreases, the number of interfaces where light is refracted or reflected decreases, and the amount of bleeding tends to increase. The amount of pores ρ can be adjusted by controlling the sintering time and the sintering temperature.

As described above, by appropriately controlling each parameter related to the amount of bleeding, the wavelength conversion element 30 having the phosphor layer 42 with an appropriate amount of bleeding can be obtained. Further, in the projector 1000 including the light source device 100 having such a wavelength conversion element 30, the use efficiency of the fluorescence emitted from the phosphor layer 42 is high, so that a bright image can be projected.

According to the phosphor configured as described above, it is possible to provide a phosphor capable of achieving both thermal conductivity and light scattering characteristics.

Further, since the wavelength conversion element having the above-described configuration has the above-described phosphor, it is not easily damaged by heat, has a desired light scattering characteristic, and has high reliability. The light source device and projector provided with the above-described wavelength conversion element have high reliability.

Although the projector 1000 has been described in the present embodiment, the configuration of the projector is not limited to this.

FIG. 11 is a schematic diagram illustrating a projector 1006 according to a modification, and corresponds to FIG. In the following description, the same reference numerals are given to members common to the projector 1000, and the description is omitted. The projector 1006 includes a light source device 106 and a second light source device 702 instead of the light source device 100 in the projector 1000. The light source device 106 includes a wavelength conversion element 34, a collimating optical system 70, a dichroic mirror 80, and a collimating condensing optical system 90.

The light source 10 is disposed so that the optical axis is orthogonal to the light source optical axis 106ax.
The collimating optical system 70 includes a first lens 72 and a second lens 74, and makes the light from the light source 10 substantially parallel. The first lens 72 and the second lens 74 are convex lenses.

The dichroic mirror 80 is disposed in the optical path from the collimating optical system 70 to the collimating condensing optical system 90 so as to intersect with each of the optical axis of the light source 10 and the light source optical axis 106ax at an angle of 45 °. The dichroic mirror 80 reflects blue light and transmits red light and green light.

The collimator condensing optical system 90 has a function of causing the blue light from the dichroic mirror 80 to be incident on the phosphor layer 42 in a substantially condensed state, and a function of substantially collimating the fluorescence emitted from the phosphor layer 42. . The collimator condensing optical system 90 includes a first lens 92 and a second lens 94. The first lens 92 and the second lens 94 are convex lenses.

FIG. 12A is a schematic diagram illustrating a wavelength conversion element included in the projector 1006. FIG.
2B is an A2-A2 cross-sectional view of the wavelength conversion element shown in FIG. 12A. As shown in FIG. 12A, the wavelength conversion element 34 has a phosphor layer 42 provided along the circumferential direction of the substrate 40 on one surface of the substrate 40. In the light source device 106, the blue light from the light source 10 enters the phosphor layer 42 from the side opposite to the substrate 40. As shown in FIG. 12B, a reflective film 45 that reflects visible light is provided between the phosphor layer 42 and the substrate 40. Therefore, fluorescence is emitted toward the side on which the blue light is incident.

It is not necessary to use a disk made of a material that transmits excitation light as the substrate 40, and a disk made of an opaque material such as metal may be used.

The second light source device 702 includes a second light source device 710, a condensing optical system 760, a scattering plate 732, and a collimating optical system 770.

The condensing optical system 760 includes a first lens 762 and a second lens 764. Condensing optical system 7
60 condenses blue light from the second light source device 710 near the scattering plate 732. First lens 7
62 and the 2nd lens 764 consist of convex lenses.

The scattering plate 732 scatters the blue light from the second light source device 710 and converts it into blue light having a light distribution similar to fluorescence emitted from the wavelength conversion element 34. As the scattering plate 732, for example, a microlens array can be used.

The collimating optical system 770 includes a first lens 772 and a second lens 774, and the scattering plate 7.
The light from 32 is made substantially parallel. The first lens 772 and the second lens 774 are convex lenses.

The dichroic mirror 80 combines the blue light from the second light source device 702 with the yellow light from the wavelength conversion element 34 to generate white light.

Also in the wavelength conversion element 34 as described above, by using the phosphor 1 of the present embodiment, the wavelength conversion element 34 which is not easily damaged by heat and has desired light scattering characteristics can be obtained. In addition, a highly reliable light source device and projector can be provided.

FIG. 13 is a schematic diagram illustrating another example of the light source device. The light source device 1500 includes a substrate 1501.
And a light emission surface 1502a of the excitation light source 1502.
And a phosphor layer 1503 provided on the side.

As the excitation light source 1502, various types of light sources that emit blue excitation light can be used.
The phosphor layer 1503 uses the phosphor of this embodiment described above as a forming material.

In the light source device 1500 having such a configuration, by using the phosphor 1 of the present embodiment, the highly reliable light source device 150 that is not easily damaged by heat and has desired light scattering characteristics.
It can be set to zero.

[Second Embodiment]
Hereinafter, the wavelength conversion element, the light source device, and the projector according to the second embodiment will be described with reference to FIGS.

FIG. 14 is a schematic diagram of a projector 1000M according to the present embodiment. The projector 1000M is different from the projector 1000 according to the first embodiment in that the projector 1000M includes the light source device 100M instead of the light source device 100 described above. The light source device 100M is different from the light source device 100 in that it includes a wavelength conversion element 30M in place of the wavelength conversion element 30 described above. Since other configurations are the same as those of the projector 1000, the same elements as those in FIG. 3 are denoted by the same reference numerals, and detailed description thereof is omitted.

The light source device 100M includes a light source 10, a condensing optical system 20, a wavelength conversion element 30M, and a motor 50.
, A collimating optical system 60, a first lens array 120, a second lens array 130, a polarization conversion element 140, and a superimposing lens 150.

The condensing optical system 20 is disposed in the optical path from the light source 10 to the wavelength conversion element 30M.
The blue light is incident on the phosphor layer 42M in a substantially condensed state. The phosphor layer 42M will be described later.

  The collimating optical system 60 makes the light from the wavelength conversion element 30M substantially parallel.

15A is a schematic diagram of the wavelength conversion element 30M, and FIG. 15B is a line segment XVb− in FIG. 15A.
It is arrow sectional drawing in XVb.

As illustrated in FIG. 15A, the wavelength conversion element 30M includes a substrate 40 that is circular in plan view, and a wavelength conversion unit 41AM that is provided along the circumferential direction of the substrate 40 on one surface of the substrate 40. As illustrated in FIG. 15B, the wavelength conversion unit 41AM includes a phosphor layer 42M, a dichroic film 44 provided on the first surface 42aM of the phosphor layer 42M, and a second surface 42 of the phosphor layer 42M.
and an antireflection film 47 provided on bM. The phosphor layer 42 </ b> M is provided along the circumferential direction of the substrate 40 on one surface of the substrate 40. The wavelength conversion element 30M can be rotated by a motor 50 connected to the center of the substrate 40. The wavelength conversion element 30M emits red light and green light toward the side opposite to the side on which the blue light is incident. Each of the dichroic film 44 and the antireflection film 47 corresponds to the optical functional layer described in the claims.

The phosphor layer 42M is excited by blue light having a wavelength of about 445 nm that is emitted from the light source 10 and incident on the phosphor layer 42M from the substrate 40 side. The phosphor layer 42M converts part of the blue light from the light source 10 into light containing yellow light, and passes the remaining part of the blue light without conversion.

The phosphor layer 42M includes a plurality of first crystallites 421 made of a ceramic fluorescent material and a plurality of second crystallites 422 made of a ceramic material having a refractive index different from that of the first crystallite 421.
And a sintered body obtained by sintering. The first crystallite 421 corresponds to a main phase, and the second crystallite 422 corresponds to a subphase (first crystal grain). The phosphor layer 42M is obtained by subjecting the above-described sintered body to processing such as cutting and polishing. In FIG. 15B, for simplicity, one first crystallite 4
21 is indicated by a two-dot chain line, and the other first crystallites 421 are shown as forming a continuous and integral layer.

Various materials can be used for the first crystallite 421 as long as it is a ceramic fluorescent material. In the phosphor layer 42M of the present embodiment, Ce: Y ₃ Al ₅ O is used as the first crystallite 421.
₁₂ (hereinafter referred to as Ce: YAG) was used.

Various materials can be used for the second crystallite 422 as long as it is a ceramic material having a refractive index different from that of the first crystallite 421. In the phosphor layer 42M of the present embodiment, the second
YAP was used as the crystallite 422. For example, Al ₂ O ₃ , Ce: Y ₂ O ₃ instead of YAP
Ce: YAP, CeO ₂ or Y ₂ O ₃ can also be used. Al ₂ O ₃ , CeO ₂ and Y ₂ O ₃ are starting materials used in the synthesis of Ce: YAG. YAP is also Ce:
It is a byproduct generated when YAG is synthesized. As mentioned above, Ce: YAP and Ce: Y
2O3 improves the quantum yield of the phosphor.

The phosphor layer 42M may include a third crystallite having a refractive index different from that of the first crystallite 421 and made of a ceramic material different from that of the second crystallite 422. The third crystallite corresponds to the second crystal grain. As the third crystallite, for example, YAP, Al ₂ O ₃ , Ce:
Y ₂ O ₃ , Ce: YAlO ₃ , CeO ₂ or Y ₂ O ₃ can be used. Note that at least one of the first crystallite 421, the second crystallite 422, and the third crystallite may contain a metal impurity contained in a starting material or the like.

The sintered body has crystal grain boundaries and has pores 4 in the crystal grain boundaries. The pores 4 are generated at the crystal grain boundaries during the production of the sintered body. When the sintered body is processed to form the phosphor layer 42M, the pores 4 existing inside the sintered body are exposed on the surface of the phosphor layer 42M. for that reason,
On the surface of the phosphor layer 42M, there is a recess 42x caused by the pores 4.

If the sintered body includes many pores 4, there are many indentations 42x on the surface of the phosphor layer 42M.
Therefore, in order to form the optical functional layer on the surface of the phosphor layer 42M in a good state, it is preferable that the pore volume ρ is small. Further, since the thermal conductivity of the phosphor layer 42M is higher when the amount of pores ρ is smaller, the phosphor layer 42M is less likely to be damaged by thermal stress. On the other hand, as mentioned above,
The pores 4 have a function of scattering the light traveling inside the phosphor layer 42M. Therefore, the pore volume ρ is preferably set in consideration of physical properties required for the phosphor layer 42M, that is, thermal conductivity and light scattering characteristics.

In order to reduce the influence of the heat storage of the phosphor layer 42M, the thermal conductivity of the phosphor layer 42M is 2
It is preferably 9 W / m · k or more at 5 ° C. In order to achieve such thermal conductivity, the pore volume ρ is preferably 0.01% or more and less than 5%.

The second crystallite 422 is present at the crystal grain boundary of the first crystallite 421. In the phosphor layer 42M, the volume of the first crystallite 421 is larger than the volume of the second crystallite 422.

The phosphor layer 42M can be manufactured as follows. First, a sintered body including the first crystallite 421, the second crystallite 422, and the pores 4 is created using the method for manufacturing the phosphor 1 according to the first embodiment. Next, the obtained sintered body is subjected to processing such as cutting and polishing to obtain a phosphor layer 42M having a desired thickness.

The dichroic film 44 is a dielectric multilayer film provided between the phosphor layer 42M and the substrate 40. The dichroic film 44 is formed on the first surface 42aM of the phosphor layer 42M by a vapor phase method after processing the sintered body to obtain the phosphor layer 42M. At that time, a defective portion 44x in which the dichroic film 44 is not formed in a desired state is formed at a position where the dichroic film 44 overlaps the recess 42x of the phosphor layer 42M.

The antireflection film 47 is a dielectric multilayer film provided on the second surface 42bM of the phosphor layer 42M. The antireflection film 47 is formed on the second surface 42bM of the phosphor layer 42M by a vapor phase method after processing the sintered body to obtain the phosphor layer 42M. At that time, in the antireflection film 47, the phosphor layer 42M
A defective portion 47x in which the antireflection film 47 is not formed in a desired state is formed at a position overlapping with the recess 42x.

The wavelength conversion element 30M exhibits the following light emission behavior. FIG. 16 is a schematic diagram illustrating a state of light emission when the wavelength conversion element 30XM having the phosphor layer 420M not including the second crystallite 422 is irradiated with the excitation light B as a comparative example. FIG. 17 shows the wavelength conversion element 30M of this embodiment.
It is a schematic diagram which shows the mode of light emission when the excitation light B is irradiated.

When the wavelength conversion element 30XM shown in FIG. 16 is irradiated with the excitation light B via the condensing optical system 20,
The excitation light B passes through the dichroic film 44 and enters the phosphor layer 420M. Phosphor layer 4
In 20M, the first crystallite 421 absorbs part of the excitation light B and emits yellow fluorescence YL isotropically. The fluorescence YL travels inside the phosphor layer 420M while being scattered by the pores 4 existing inside the phosphor layer 420M, and is emitted to the outside of the phosphor layer 420M.

The remaining part of the excitation light B that has not been absorbed by the first crystallite 421 is the phosphor layer 420.
M is transmitted. At that time, the phosphor layer 420 is scattered by the pores 4 in the same manner as the fluorescence YL.
M is transmitted. Thereby, white light in which excitation light B and fluorescence YL are mixed is emitted from phosphor layer 420M.

The phosphor layer 420M includes a large number of pores 4 in order to sufficiently scatter the excitation light B and the fluorescence YL. Therefore, a large number of recesses 42x are formed on the surface of the phosphor layer 420M. In FIG. 16, the three indentations 42x of the first surface 420aM and the three indentations 42x of the second surface 420bM are combined to show that a total of six indentations 42x are formed.

Therefore, the dichroic film 44 provided in contact with the first surface 420aM of the phosphor layer 420M has many defect portions 44x, and the antireflection film 47 provided in contact with the second surface 420bM has many defects. It has a portion 47x. Therefore, it was difficult for each film to exert desired physical properties.

Furthermore, since the phosphor layer 420M includes a large number of pores 4, the thermal conductivity of the phosphor layer 420M as a whole is lower than that of Ce: YAG constituting the first crystallite 421. Therefore, the phosphor layer 420M easily stores heat when irradiated with high-intensity excitation light B, and is easily damaged by thermal stress.

In contrast, in the wavelength conversion element 30M illustrated in FIG. 17, the phosphor layer 42M includes a plurality of second crystallites 422 having a refractive index different from that of the first crystallites 421. The second crystallite 422 scatters the excitation light B and the fluorescence YL by refraction or reflection. That is, the second crystallite 422 preferably functions as a scattering source. Therefore, in the phosphor layer 42M, the ability to scatter the excitation light B and the fluorescence YL is equal to the scattering ability in the phosphor layer 420M, but the pore volume ρ is set to the phosphor layer 42.
It can be made smaller than the pore volume ρ at 0M. As a result, not only is the amount of the recess 42x reduced, but the thermal conductivity of the phosphor layer 42M is increased.

In FIG. 17, one recess 42x on the first surface 42aM and two recesses 42x on the second surface 42bM are combined to show that a total of three recesses 42x are formed. As a result, in the dichroic film 44 provided in contact with the first surface 42aM of the phosphor layer 42M and the antireflection film 47 provided in contact with the second surface 42bM, the defect portion 44x, The amount (number) of 47x is small, and the physical properties of each film are improved. That is, the physical properties of each film are close to the ideal physical properties (design values).

The wavelength conversion element 30M includes an optical functional layer having good characteristics on the surface. Specifically, since the amount (number) of defective portions 44x of the dichroic film 44 is small, the fluorescence YL generated by the phosphor layer 42M is reflected by the dichroic film 44 with higher efficiency than the comparative example, and the substrate 40 Can be emitted from the phosphor layer 42M in the opposite direction. Furthermore, since the amount (number) of the defective portions 47x of the antireflection film 47 is small, the fluorescence YL has a higher efficiency than the comparative example and the second surface 42b.
M can be ejected to the outside. Thus, the fluorescence YL generated in the phosphor layer 42M
Can be taken out in a desired direction with high efficiency.

Further, since the thermal conductivity of the phosphor layer 42M is higher than that of the comparative example, it is difficult to store heat even if the small area is irradiated with the high intensity excitation light B, and damage due to thermal stress is unlikely to occur.

In the sintered body containing YAP as the second crystallite 422, the crystallite diameters of the first crystallite 421 and the second crystallite 422 are smaller when the sintered body is manufactured than when the YAP is not included. Tend to be. The sintered body has high bending strength when the crystallite diameter of the crystallite constituting the sintered body is small. Therefore, the phosphor layer 42M containing YAP is not easily damaged by thermal stress.

Since the light source device 100M according to the present embodiment includes the wavelength conversion element 30M, the light source device 100M can emit high-luminance light and is not easily damaged by heat.

Since the projector 1000M according to the present embodiment includes the light source device 100M, it can project a high-luminance image and is not easily damaged by heat.

Although the projector 1000M has been described in the present embodiment, the configuration of the projector is not limited to this.

FIG. 18 is a schematic diagram illustrating a projector 1006M according to a modification. The projector 1006M is different from the projector 1006 shown in FIG. 11 in that the projector 1006M includes a light source device 106M instead of the light source device 106 of the first embodiment. The light source device 106M is different from the light source device 106 in that it includes a wavelength conversion element 34M instead of the wavelength conversion element 34 described above. Since the other configuration is the same as that of the projector 1006, the same elements as those in FIG. 11 are denoted by the same reference numerals, and detailed description thereof is omitted.

The collimator condensing optical system 90 has a function of causing the blue light from the dichroic mirror 80 to be substantially collected and incident on the phosphor layer 42M, and a function of substantially collimating the fluorescence emitted from the phosphor layer 42M. .

In the light source device 106M, the blue light from the light source 10 enters the phosphor layer 42M from the side opposite to the substrate 40.

FIG. 19A is a schematic diagram of a wavelength conversion element 34M included in the projector 1006M.
FIG. 19B is a cross-sectional view taken along line XIXb-XIXb in FIG. 19A.

As shown in FIGS. 19A and 19B, the wavelength conversion element 34M includes a substrate 40, a phosphor layer 42M provided in a ring shape on the substrate 40, and a reflection provided between the substrate 40 and the phosphor layer 42M. A film (optical function layer) 45 and an antireflection film (optical function layer) 47 provided on the second surface 42bM of the phosphor layer 42M are provided. The phosphor layer 42M, the reflection film 45, and the antireflection film 47 constitute a wavelength conversion unit 41BM. The wavelength conversion unit 41BM emits fluorescence toward the side on which the blue light is incident.

As the substrate 40, a disk made of an opaque material having a high thermal conductivity such as metal may be used.

The dichroic mirror 80 converts the blue light from the second light source device 702 into the wavelength conversion element 34M.
To produce white light.

Similarly to the wavelength conversion element 30M, the wavelength conversion element 34M includes an optical function layer having good characteristics on the surface. Specifically, since the amount (number) of the defect portions 45x of the reflective film 45 is small, the fluorescence YL generated by the phosphor layer 42M is reflected by the reflective film 45 with high efficiency and fluorescent in the direction opposite to the substrate 40. It can be ejected from the body layer 42M. Further, since the amount (number) of the defective portions 47x of the antireflection film 47 is small, the excitation light B and the fluorescence YL can be efficiently used as in the wavelength conversion element 30M. In addition, since the thermal conductivity of the phosphor layer 42M is higher than that of the comparative example, damage due to thermal stress hardly occurs.

In each of the above embodiments, the laser light source is used as the excitation light source, but a light emitting diode may be used.
In each of the above embodiments, the phosphor layer is provided on a rotatable substrate, but the present invention is not limited to this. A phosphor layer may be provided on the fixed substrate.
In each of the above embodiments, a liquid crystal light modulation device is used as the light modulation device, but the present invention is not limited to this. A digital micromirror device may be used as the light modulation device.

The preferred embodiment of the present invention has been described above with reference to the accompanying drawings.
The present invention is not limited to such examples. Various shapes, combinations, and the like of the constituent members shown in the above-described examples are examples, and various modifications can be made based on design requirements and the like without departing from the gist of the present invention.

In each of the above embodiments, an example in which the light source device according to the present invention is mounted on a projector is shown.
It is not limited to this. The light source device according to the present invention can also be applied to lighting fixtures, automobile headlights, and the like.

1, 1X, 1Y ... phosphor, 2 ... main phase, 2a, 3a ... crystal grains, 3 ... subphase, 4 ... pores, 10
... Light source, 20 ... Condensing optical system, 30, 34, 30M, 34M ... Wavelength conversion element, 40, 150
DESCRIPTION OF SYMBOLS 1 ... Board | substrate, 42, 42M, 42N, 1503 ... Phosphor layer, 42aM ... 1st surface, 42bM
... 2nd surface, 44 ... Dichroic film (optical functional layer), 45 ... Reflective film (optical functional layer), 4
7: Antireflection film (optical functional layer), 90 ... Collimated condensing optical system (condensing optical system), 100,
106, 1500 ... light source device, 421 ... first crystallite, 422 ... second crystallite, 600 ... projection optical system, 1000,1006 ... projector, 1502 ... excitation light source (light source), B ... excitation light, YL, Y1 , Y2 ... fluorescence.

In the first aspect, the subphase contains Ce: YAlO ₃ , CeO ₂ , or Ce: Y ₂ O ₃ , and the atomic concentration [Y] (at%) of yttrium in the sintered body is the following requirement ( i) and (ii) may be satisfied.
(I) 0.6 <[Y] / [Al]
(Ii) 0.6 <[Re] / [Al] ≦ 0.652
However, [Re] is the sum of the atomic concentration of yttrium and the atomic concentration of cerium, and [Al] is the atomic concentration of aluminum.
According to this configuration, the subphase can be reliably formed in the sintered body. Furthermore, since the phosphor can be sufficiently densified and the amount of pores can be reduced, it is possible to obtain a high-quality phosphor with an excellent balance between the amount of the main phase that emits fluorescence and the subphase that functions as a scattering source. Can do.

In the sintered body constituting the phosphor 1, the atomic concentration (at%) of yttrium in the sintered body preferably satisfies the following requirements (i) and (ii). In the following requirements (i) and (ii), [Y] indicates the atomic concentration of yttrium. [Re] represents the sum of the atomic concentration of yttrium and the atomic concentration of cerium. [Al] indicates the atomic concentration of aluminum. In addition, each atomic concentration shows the density | concentration with respect to the whole quantity of the metal atom in a sintered compact.
(I) 0.6 <[Y] / [Al]
(Ii) 0.6 <[Re] / [Al] ≦ 0.652

The value of [Y] / [Al] calculated from the stoichiometry of YAG (Y ₃ Al ₅ O ₁₂ ), which is the base crystal of Ce: YAG, is 0.6. Therefore, the condition (i) indicates that the phosphor 1 contains an excess of yttrium atoms than the amount calculated from the stoichiometry. Yttrium atoms contained in excess of the stoichiometric amount constitute subphase 3. That is, by satisfying the condition (i), the subphase 3 can be reliably formed in the phosphor 1.

Claims (22)

A phosphor made of a sintered body of a ceramic material,
The sintered body includes Ce: Y ₃ Al ₅ O ₁₂ as a main phase, and a ceramic material having a refractive index different from that of the main phase as a subphase,
The sintered body has a crystal grain boundary and a phosphor having pores in the crystal grain boundary. The subphase includes Ce: YAlO ₃ , CeO ₂ , Y ₂ O ₃ , or Ce: Y ₂ as the first crystal grains.
The phosphor according to claim 1 containing O ₃ . The subphase further includes second crystal grains different from the first crystal grains, and includes Ce: YAlO ₃ , CeO ₂ , Y ₂ O ₃ , or Ce: Y ₂ O ₃ as the second crystal grains. Item 3. The phosphor according to Item 2. The subphase includes Ce: YAlO ₃ , CeO ₂ , or Ce: Y ₂ O ₃ ,
The atomic concentration [Y] (at%) of yttrium in the sintered body is the following requirements (i) and (
The phosphor according to claim 2 or 3, which satisfies ii).
(I) 0.6 <[Y]
(Ii) 0.6 <[Re] / [Al] ≦ 0.652
(However, [Re] is the sum of the atomic concentration of yttrium and the atomic concentration of cerium, and [Al
] Is the atomic concentration of aluminum. ) The phosphor according to claim 1, wherein the main phase surrounds the subphase.   The phosphor according to any one of claims 1 to 5, wherein the pores are scale-like. The phosphor according to any one of claims 1 to 6, wherein crystal grains constituting the main phase and crystal grains constituting the subphase are granular. The phosphor according to any one of claims 1 to 7, wherein a ratio of a volume of the main phase to a total volume of the main phase and the sub phase is 90% by volume or more and less than 100% by volume. The wavelength conversion element which has a fluorescent substance layer which uses the fluorescent substance of any one of Claim 1 to 8 as a forming material. The wavelength conversion element according to claim 9,
A light source that irradiates the phosphor layer of the wavelength conversion element with excitation light. The light source device according to claim 10;
A light modulation device that modulates light from the light source device according to image information to form image light; and
A projection optical system that projects the image light. A wavelength conversion element having a phosphor layer and an optical functional layer provided on the surface of the phosphor layer,
The phosphor layer includes a ceramic fluorescent material as a first crystallite and the first as a second crystallite.
The crystallite is made of a sintered body including a ceramic material having a different refractive index,
The sintered body has a crystal grain boundary and a wavelength conversion element having pores in the crystal grain boundary. The first crystallite includes Ce: Y ₃ Al ₅ O ₁₂ ,
The second crystallite is Ce: YAlO ₃ , CeO ₂ , Y ₂ O ₃ , Ce: Y ₂ O ₃ or YAlO _3.
The wavelength conversion element of Claim 12 containing.   The wavelength conversion element according to claim 12, wherein the optical functional layer is an antireflection film. The wavelength conversion element according to claim 12, wherein the optical function layer is a dichroic film.   The wavelength conversion element according to claim 12 or 13, wherein the optical functional layer is a reflective film. The phosphor layer further includes a ceramic material different from the second crystallite as a third crystallite,
The wavelength conversion element according to any one of claims 12 to 16, wherein a refractive index of the third crystallite is different from a refractive index of the first crystallite. The wavelength conversion element according to any one of claims 12 to 17,
A light source that irradiates the phosphor layer of the wavelength conversion element with excitation light. The light source device according to claim 18;
A light modulation device that modulates light from the light source device according to image information to form image light; and
A projection optical system that projects the image light. A light source that emits excitation light;
A wavelength conversion element having a phosphor layer that is excited by the excitation light and emits fluorescence; and
A condensing optical system disposed on the optical path of the excitation light between the light source and the wavelength conversion element, and condensing the excitation light toward the phosphor layer;
The phosphor layer includes a ceramic fluorescent material as a first crystallite and the first as a second crystallite.
A light source device comprising a sintered body including a crystallite and a ceramic material having a different refractive index. The first crystallite includes Ce: Y ₃ Al ₅ O ₁₂ ,
The light source device according to claim 20, wherein the second crystallite includes YAlO ₃ . A light source device according to claim 20 or 21,
A light modulation device that modulates light from the light source device according to image information to form image light; and
A projection optical system that projects the image light.

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