JP2019066880A - Phosphor, wavelength conversion element, light source device and projector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a phosphor capable of achieving both thermal conductivity and light scattering characteristics. In addition, a wavelength conversion element, a light source device, and a projector having the above-mentioned phosphor are provided. SOLUTION: The phosphor is made of a sintered body of a ceramic material, and the sintered body contains Ce: Y3Al5O12 as the main phase 2 and a ceramic material having a refractive index different from that of the main phase 2 as the sub-phase 3. Including. The sintered body has a crystal grain boundary and has pores 4 at the crystal grain boundary. [Selection diagram] Fig. 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 comprises 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 is deteriorated by heat when irradiated with laser light of high intensity as excitation light.

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

JP, 2009-277516, A Japanese Patent Application Publication No. 2013-518172

  However, since the phosphor of Patent Document 2 has a plurality of pores, the thermal conductivity of the phosphor is lower than that of the phosphor particles. Therefore, when high intensity laser light is irradiated as excitation light, heat is stored, and the luminous efficiency of the phosphor particles is reduced. Furthermore, since the phosphor is more easily broken as the number of pores is increased. Thermal stress may cause the phosphor to break. For example, when high intensity excitation light is irradiated, a large thermal stress is generated due to the in-plane temperature difference. Further, if the excitation light is focused in a narrow area and irradiated in order to use the phosphor as a point light source, the phosphor becomes high temperature at the irradiation position of the excitation light and a large thermal stress is generated.

  When a phosphor having a plurality of pores is processed into a phosphor layer of a certain thickness, for example, by polishing, it is inevitable that the pores are exposed on the surface of the phosphor layer. Therefore, on the surface of the phosphor layer, there are "dents" due to the pores. 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 utilization efficiency of light. However, in the case of forming an optical functional layer on the phosphor layer of Patent Document 2 having depressions on the surface, it is difficult to form the optical functional layer in the intended state at the portion of the depression, and It is difficult to form an optical functional layer.

  On the other hand, the pores have a function of scattering the fluorescence emitted inside the phosphor. The light scattering function inside the phosphor is necessary to enhance the efficiency of taking out the fluorescence emitted inside the phosphor to efficiently utilize the fluorescence. When the pores are reduced, the scattering source in the fluorescent body is reduced, so that not only the utilization efficiency of the fluorescence is reduced, but also the emission region of the fluorescence is expanded, and the utilization efficiency of the fluorescence by the optical system in the latter stage is reduced.

  In addition, it is desired to improve the quantum yield of phosphors.

  An object of the present invention is to provide a phosphor in which at least one of the above-mentioned 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 above-described phosphor.

A first aspect of the present invention is a phosphor comprising a sintered body of a ceramic material, wherein the sintered body is refracted with Ce: Y ₃ Al ₅ O ₁₂ as a main phase and the main phase as a sub phase. And a ceramic material having different rates, wherein the sintered body has grain boundaries and provides a phosphor having pores at the grain boundaries.
In the phosphor according to the first aspect, the auxiliary phase suitably 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 smaller than in the sintered body not containing the sub phase. That is, the thermal conductivity can be increased. Therefore, it is possible to make thermal conductivity and light scattering characteristics compatible.

In the first aspect, the subphase may include Ce: YAlO ₃ , CeO ₂ , Y ₂ O ₃ , or Ce: Y ₂ O ₃ as the first crystal grain.
According to this configuration, the quantum yield of the phosphor is higher than in the case where the phosphor does not contain a secondary phase. Also, the secondary phase preferably functions as a scattering source.

In the first aspect, the subphase further includes a second crystal grain different from the first crystal grain, and Ce: YAlO ₃ , CeO ₂ , Y ₂ O ₃ , or Ce: Y ₂ as the second crystal grain. O ₃ may be included.
According to this configuration, the secondary phase suitably functions as a scattering source.

In the first embodiment, 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 satisfies 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 [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 of the amounts of the main phase emitting fluorescence and the subphase functioning as a scattering source. Can.

In the first aspect, the main phase may surround the sub phase.
According to this configuration, the main phase and the sub phase exist as different crystal grains, and each function can be suitably exhibited.

In the first aspect, the pores may be scaly.
When the pores are scaly, the surface area is larger than spherical pores of the same volume, and thus the light traveling inside the phosphor is likely to strike the pores and scatter more easily.

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.

In the first aspect, the ratio of the volume of the main phase to the total volume of the main phase and the subphase may be 90% by volume or more and less than 100% by volume.
According to this configuration, it is possible to obtain a high quality phosphor with an excellent balance of the amounts of the main phase that emits fluorescence and the subphase that functions as a scattering source.

A second aspect of the present invention provides a wavelength conversion element having a phosphor layer using the above-described phosphor as a forming material.
According to this configuration, since the wavelength conversion element includes the above-described phosphor, it is unlikely to be damaged by heat and has the desired light scattering characteristics.

A third aspect of the present invention provides a light source device including the above-described wavelength conversion element, and a light source for irradiating excitation light onto the phosphor layer of the wavelength conversion element.
According to this configuration, since the light source device includes the above-described phosphor, it is unlikely to be 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 unlikely to be 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 is made of a sintered body including a ceramic fluorescent material as a first crystallite and a ceramic material having a refractive index different from that of the first crystallite as a second crystallite. The sintered body has grain boundaries and pores in the 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 smaller than in the sintered body not including the second crystallite. That is, the amount of depressions formed by exposing the pores to the surface of the phosphor layer can be reduced. Therefore, it is hard to produce a defect in the optical function layer formed in the surface of a fluorescent substance layer.

In a fifth aspect, the first crystallite comprises Ce: Y ₃ Al ₅ O ₁₂ and the second crystallite comprises Ce: YAlO ₃ , CeO ₂ , Y ₂ O ₃ , Ce: Y ₂ O ₃ or YAlO ₃ may include a.
According to this configuration, the quantum yield of the phosphor is higher than in the case where the phosphor does not contain a secondary phase. In addition, the second crystallite preferably functions as a scattering source.

In the fifth aspect, the optical function layer may be an antireflective film.
According to this configuration, it is possible to provide a wavelength conversion element provided with an antireflective film having few defects and a high antireflective function on the surface.

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

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

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

A sixth aspect of the present invention provides a light source device including the above-described wavelength conversion element, and a light source for emitting excitation light to the phosphor layer of the wavelength conversion element.
Since the light source device of this configuration has the wavelength conversion element as described above, it can emit high-intensity light.

According to a seventh aspect of the present invention, there is provided a light source device as described above, a light modulation device for modulating light from the light source device according to image information to form image light, and a projection optical system for projecting the image light. To provide a projector having the
Since the projector of this configuration includes the above-described light source device, it is possible to project a high brightness image.

According to an eighth aspect of the present invention, there is provided a light source for emitting excitation light, a wavelength conversion element having a phosphor layer excited by the excitation light to emit fluorescence, the excitation between the light source and the wavelength conversion element A focusing optical system disposed on a light path of light and focusing the excitation light toward the phosphor layer, the phosphor layer comprising a ceramic fluorescent material as a first crystal element, There is provided a light source device comprising a sintered body containing, as a crystallite, a refractive index different from that of the first crystallite.
In the light source device according to the eighth aspect, the second crystallite suitably 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 smaller than in 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 less likely to be broken.

In an eighth aspect, the first crystallite may include Ce: Y ₃ Al ₅ O ₁₂ , and the second crystallite may include YAlO ₃ .
In a sintered body containing YAlO ₃ (hereinafter, YAP), the crystallite diameters of the first crystallite and the second crystallite tend to be smaller when producing the sintered body as compared to the case where YAP is not contained. It is in. The sintered body has high bending strength if the crystallite diameter of the crystallites constituting the sintered body is small. Therefore, according to the said structure, the failure | damage by a thermal stress does not occur easily.

According to a ninth aspect of the present invention, there is provided a light source device as described above, a light modulation device for modulating light from the light source device according to image information to form image light, and a projection optical system for projecting the image light. To provide a projector having the
The projector of this configuration is highly reliable because it includes the above-described light source device.

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 excitation light is irradiated to the fluorescent substance of 1st Embodiment. FIG. 1 is a schematic view 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 an A1-A1 sectional view of a wavelength conversion element shown in Drawing 4A. It is a schematic diagram which shows the mode of the bleeding in the inorganic fluorescent substance which does not contain a subphase and 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 bleeding. It is a graph which shows typically the relationship between the amount of bleeding and the quantity of fluorescence emitted from a wavelength conversion element. 5 is a graph showing the relationship between the amount of bleeding and the size of the liquid crystal light modulation device. It is a graph which shows the relationship between the amount of bleeding and the average grain size 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 auxiliary agent. It is a schematic diagram explaining the projector 1006 of the modification of 1st 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 concerning 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 converter 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 directional cross-sectional view 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 addition, in all the following drawings, in order to make a drawing intelligible, the dimension, the ratio, etc. of each component are suitably varied.

FIG. 1 is a SEM photograph showing an example of the phosphor of the present embodiment, which is a backscattered electron image (BSE image). The phosphor 1 of the present embodiment is made of a sintered body of a ceramic material.
The phosphor 1 contains Ce: Y ₃ Al ₅ O ₁₂ (hereinafter referred to as “Ce: YAG”) as the main phase 2 and contains two types of ceramic materials as the sub phase ₃ . Two types of ceramic materials are Ce: YAlO ₃ (hereinafter referred to as “Ce: YAP”) and Ce: Y ₂ O ₃ . Furthermore, the phosphor 1 includes a plurality of pores 4.
In Figure 1, Ce: shows a Y ₂ O ₃ consisting of crystal grains in the code YO. In the BSE image, it is not easy to distinguish between Ce: YAG and Ce: YAP. Therefore, in FIG. 1, crystal grains made of Ce: YAG and crystal grains made of Ce: YAP are indicated by the symbol GP. .
The phosphor 1 has crystal grain boundaries and also has pores 4 at the crystal grain boundaries.

Ce: YAP corresponds to the first crystal grain described in the claims, and Ce: Y ₂ O ₃ corresponds to the second crystal grain described in the claims. The forming material of the second crystal grain is different from the forming material of the first crystal grain. Hereinafter, in the present specification, crystal grains constituting the main phase 2 are referred to as crystal grains 2 a, and crystal grains constituting the sub phase 3 are referred to as crystal grains 3 a.

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

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

The refractive index of each material described above is 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), a YAP (1.93). The refractive index of Ce: Y ₂ O ₃ varies depending on the content of Ce. Since the refractive index of Ce: YAP and the refractive index of Ce: Y ₂ O ₃ are different from the refractive index of main phase 2 (Ce: YAG), subphase 3 preferably functions as a scattering source.

  The thermal conductivity of these substances constituting the sub phase 3 is equivalent to that of Ce: YAG, so that even if the phosphor 1 has the sub phase 3, the thermal conductivity of the phosphor 1 is greatly reduced. There is no.

  The crystal grains 2 a and the crystal grains 3 a are preferably granular. With such a configuration, manufacture of the phosphor is easy. Here, in the present embodiment, “granular” refers to one in which 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.

About the crystal grain 3a, when the thickness of the fluorescent substance 1 is 200 micrometers, it is good that they are 0.5 micrometer or more and 20 micrometers or less. When the crystal grain 3a consists of Ce: YAP, it is preferable that the average crystal grain size of the crystal grain 3a is 0.8 micrometer or more and 1.2 micrometers or less. When the crystal grains 3a are composed of CeO 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 shape, the surface area of the crystal grain 2a is increased, which is preferable because light is easily scattered as described later. For the same reason, the crystal grains 3a may be in the form of a film.

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

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

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

  Next, the area of each crystal grain is determined 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 determined for each crystal grain, is calculated. The average grain size is determined by arithmetically averaging the obtained equivalent circle diameters.

  The pores 4 are preferably scaly. Here, in the present embodiment, “scale-like” means that the ratio of the short side to the long side is smaller than 0.3 when the shape of the pore in the SEM photograph is approximated by a rectangle. However, the pores 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 light reflected and refracted inside the fluorescent substance 1. Therefore, when the pores 4 are scaly, the surface area is larger than spherical pores of the same volume, and thus the light traveling inside the phosphor 1 is likely to strike the pores 4 and scatter more easily. The “light traveling inside the fluorescent substance 1” includes both the excitation light incident on the fluorescent substance 1 and the fluorescence emitted from the fluorescent substance 1.

  When the phosphor 1 includes the pores 4, the thermal conductivity is lower than when 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 amount ρ may be set according to the physical properties required for the phosphor 1, that is, the thermal conductivity and the light scattering characteristic. The pore amount ρ will be described later.

  In order to reduce the influence of heat storage of the phosphor 1, the thermal conductivity is preferably 9 W / m · k or more at 25 ° C. In order to realize such thermal conductivity, the pore amount ρ is preferably 0.01% 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 periphery of the sub phase 3. That is, subphase 3 is present at the grain boundaries of main phase 2. The main phase 2 and the sub phase 3 exist as mutually different crystal grains, and can exhibit their respective functions suitably.

Each ratio of Ce: YAG, Ce: YAP and Ce: Y ₂ O ₃ contained in phosphor 1 was measured using X-ray diffraction. As a result, Ce: YAG was 91.8% by volume, Ce: YAP was 5.7% by volume, and Ce: Y ₂ O ₃ was 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 preferably 90% by volume or more and less than 100% by volume. With such a volume ratio, it is possible to obtain a high quality phosphor with an excellent balance of the amounts of the main phase 2 emitting fluorescence and the sub phase 3 functioning as a scattering source.

Moreover, in the sintered body which comprises the fluorescent substance 1, it is preferable that the atomic concentration (at%) of the yttrium in a sintered body satisfy | fills the following requirements (i) and (ii). In the following requirements (i) and (ii), [Y] indicates the atomic concentration of yttrium. [Re] indicates 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

The value of [Y] calculated from the stoichiometry of YAG (Y _{3 Al 5} O ₁₂ ), which is a parent crystal of Ce: YAG, is 0.6. Therefore, condition (i) indicates that phosphor 1 contains an excess of yttrium atoms than the amount calculated from the stoichiometry. The yttrium atom contained in excess over the stoichiometry constitutes subphase 3. That is, by satisfying the condition (i), the sub phase 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 _secondary phase is lower than the quantum yield of the phosphor containing no _secondary phase. Therefore, it is preferable that the value of [Re] / [Al] is larger than 0.6.

  The upper limit of the condition (ii) will be described in detail later, but by setting [Re] / [Al] ≦ 0.652, the sintering temperature of the sintered body exceeds the heat resistance temperature of a general sintering furnace. It can be avoided. Therefore, the resulting phosphor can be sufficiently densified to reduce the amount of pores, and the balance between the amount of the main phase emitting fluorescence and the subphase functioning as a scattering source is excellent, and a high quality phosphor is obtained. be able to.

  In the present specification, "the amount of pores" refers to the ratio of the total volume of the plurality of pores to the volume of the phosphor. The pore amount ρ can be determined 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 . The pore amount ρ is given by equation (1).
ρ = V ₂ / V ₀ (1)

Also, assuming that the mass of the phosphor is W, the density _{1 1 of the} phosphor is given by equation (2).
ρ ₁ = W / V ₀ (2)
Incidentally, it is possible to measure the mass W of the phosphor volume V ₀ and phosphor.

Here, using X-ray crystal diffraction, the composition of the main phase, the composition of the subphase, and the volume ratio of the main phase to the subphase are determined. The theoretical density _{2 2} of the phosphor itself is determined using the result obtained by X-ray crystal diffraction and the theoretical density of the main phase and the theoretical density of the auxiliary phase.

The theoretical density _{2 2} can be expressed by equation (3) using V ₀ , V ₂ and W. Further, from equation (3), the volume V ₂ is expressed by the following equation (4).
_{2 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 amount ρ can be expressed by the formula (5). That is, using the actual density _{1 1} and the theoretical density _{2 2} , the pore amount ρ can be obtained from the equation (5).
ρ = 1−ρ ₁ / ρ ₂ (5)

  The phosphor 1 having the above-described configuration exhibits the following light emission behavior. FIG. 2A is a schematic view showing a state of light emission when the conventional phosphor 1X which does not contain the sub phase 3 is irradiated with excitation light, and FIG. 2B is a case where the phosphor 1 of the present embodiment is irradiated with excitation light. It is a schematic diagram which shows the mode of light emission. 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 a 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 Eject.
The fluorescence YL is refracted or reflected by the plurality of pores 4 present inside the phosphor 1X, travels while changing the traveling direction (scattering), and is emitted to the outside of the phosphor 1X.

  Further, the remaining part of the excitation light B which is not absorbed by the main phase 2 passes through the phosphor 1X. At that time, the fluorescent substance 1X is transmitted while being scattered by being refracted or reflected by the plurality of pores 4 in the same manner as the fluorescence YL. Thus, white light in which the excitation light B and the fluorescence YL are mixed is emitted from the phosphor 1X.

  However, in the phosphor 1X, a large number of pores 4 are formed in order to cause the excitation light B and the fluorescence YL to be sufficiently scattered. Therefore, compared with the thermal conductivity of Ce: YAG constituting the main phase 2, the phosphor The thermal conductivity of the entire 1X is low. Therefore, when a high-intensity laser beam is irradiated as the excitation light B, the phosphor 1X is thermally stored and may be damaged by heat. For example, the luminous efficiency of the phosphor 1X is reduced.

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

  That is, since the subphase 3 suitably functions as a scattering source, the pore amount ρ can be reduced, and the thermal conductivity can be increased more than the phosphor 1X. Therefore, it is possible to make the phosphor 1 compatible with the thermal conductivity and the optical property.

The inventors prepared phosphor A containing no subphase 3 and phosphor B and C containing subphase 3 and measured their quantum yields. The main phases 2 of phosphor A, phosphor B and phosphor C were all Ce: YAG. The _secondary phase 3 of phosphor B was Ce: YAP and Ce: Y ₂ O _3, and the _secondary phase ₃ of phosphor C was Al ₂ O ₃ . In the phosphor B, the value of [Re] / [Al] was 0.63, and the volume ratio of Ce: YAG, Ce: YAP, and Ce: Y ₂ O ₃ was 90: 9: 1. In the phosphor C, the value of [Re] / [Al] is 0.58, and the volume ratio of Ce: YAG to Al ₂ O ₃ is 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. Also, it was found that the quantum yield is improved also when the phosphor contains only one of Ce: YAP and Ce: Y ₂ O ₃ as the secondary phase. Furthermore, it was found that CeO ₂ and Y ₂ O ₃ also improve the quantum yield. Therefore, it subphase 3 _{Ce: YAP, Ce: Y 2} O 3, preferably includes crystal grains 3a comprising CeO ₂ or Y ₂ O _3,.

[Method of manufacturing phosphor]
The phosphor as described above can be manufactured as follows.
First, raw material powder consisting of Y ₂ O ₃ powder, Al ₂ O ₃ powder and CeO ₂ powder is mixed with ethanol. While grinding the raw material powder with a ball mill, the obtained slurry is stirred.

At this time, a sintering aid containing Si atoms may be added to the raw material powder. As the sintering aid, SiO ₂ , CaO and MgO can be exemplified. Further, SiO _2, materials that exhibit the same effect as CaO or MgO, for example TEOS (Tetraethyl orthosilicate) may be added as a sintering aid during sintering. The sintering aid is added, for example, so that 100 ppm remains after sintering with respect to the mass of the raw material powder. When a substance that exhibits the same effect as SiO ₂ , CaO, or MgO at the time of sintering, such as TEOS, is added as a sintering aid, when the sintering aid is converted to an equivalent substance after sintering, An equivalent substance is added, for example, so that 100 ppm remains after sintering with respect to the mass of the raw material powder.

Next, ethanol is removed from the obtained slurry to dry the raw material powder. The coarse particles are removed by sieving the dried raw material powder. Thereby, a raw material powder comprising secondary particles having a particle diameter of several μm to several hundreds of μm containing primary particles of Y ₂ O ₃ , Al ₂ O ₃ and CeO ₂ having a particle diameter of several tens of nm to several hundreds of nm Is obtained. Thereafter, an appropriate amount of relatively large Y ₂ O ₃ powder having a particle diameter of several μm to several tens μm is added to the raw material powder.

Then, it is pressed into a desired shape, shaped and fired. In the firing process, since a relatively large Y ₂ O ₃ to the inside of the powder it does not reach the aluminum, a relatively large Y ₂ O ₃ after the powder is sintered, Y ₂ O ₃ or Ce,: made of Y ₂ O ₃ first It becomes 1 crystal grain.

  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 about 1700 ° C. On the other hand, when the compounding amount of the Y ₂ O ₃ powder in the raw material powder is increased, the excessive amount of Y ₂ O ₃ acts as an impurity in the sintered body, and the sintering temperature of the entire system tends to increase. Therefore, when [Re] / [Al] exceeds 0.652, theoretically, the sintering temperature of the sintered body exceeds the heat resistance temperature of a general sintering furnace, and sufficient sintering can not be performed. Then, in the obtained sintered body, the densification is insufficient and the amount of pores 増 加 increases, so that a good phosphor can not be obtained.

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

On the other hand, the conditions in the case of increasing the amount of Y ₂ O ₃ powder in a range satisfying (ii) the raw material powder preferably by sintering, it is possible to obtain a desired sintered body.
As described above, the phosphor of the present embodiment is obtained.

  According to the phosphor having the above-described configuration, it is possible to provide a phosphor capable of achieving both the thermal conductivity and the light scattering property.

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

  As shown in FIG. 3, the projector 1000 according to this 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 focusing 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 a laser light source that emits blue light (peak of emission intensity: about 445 nm) made of laser light as excitation light. The light source 10 may consist of one laser light source, or may consist of multiple laser light sources. In addition, a laser light source that emits blue light of 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 disposed in the optical path from the light source 10 to the wavelength conversion element 30, and causes the blue light to be incident on the phosphor layer 42 (described later) in a substantially condensed state. 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 having a circular shape in plan view, and a phosphor layer 42 provided on one surface of the substrate 40 along the circumferential direction of the substrate 40. There is. The wavelength conversion element 30 is rotatable 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 the 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, quartz, 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 converts part of the blue light from the light source 10 into light including yellow light, and passes the remaining part of the blue light without conversion. As the phosphor layer 42, the phosphor in the above-described embodiment is used.

  The collimating optical system 60 includes a first lens 62 and a second lens 64, and substantially collimates the light from the wavelength conversion element 30. 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 arranged in a matrix in a plane orthogonal to the light source optical axis 100ax.

  The second lens array 130 includes 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, together with the superimposing lens 150, images of the respective first small lenses 122 of the first lens array 120 in the vicinity of the image forming area of the liquid crystal light modulation device 400R, the liquid crystal light modulation device 400G, and the liquid crystal light modulation device 400B. To form an image. 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 flux divided by the first lens array 120 into linearly polarized light.

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

  The superimposing lens 150 condenses the partial light fluxes from the polarization conversion element 140 to superimpose them in the vicinity of the image forming area 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 constitute an integrator optical system that makes the in-plane light intensity distribution of the light from the wavelength conversion element 30 uniform.

The color separation light guide optical system 200 includes a dichroic mirror 210, a dichroic mirror 220, a reflection mirror 230, a reflection mirror 240, a reflection mirror 250, a relay lens 260, and a relay lens 270. 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 corresponding to red light, green light and blue light, liquid crystal light modulation The light is guided to the device 400G and the liquid crystal light modulation device 400B.
A condenser lens 300R, a condenser lens 300G, and a condenser lens 300B are disposed between the color separation light guide optical system 200, the liquid crystal light modulator 400R, the liquid crystal light modulator 400G, and the liquid crystal light modulator 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 the green light component and transmits the blue light component.

  The red light having passed through the dichroic mirror 210 is reflected by the reflection mirror 230, passes through the condenser lens 300R, and is incident on 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 is incident on the image forming area of the liquid crystal light modulator 400G for green light.

  The blue light having passed through the dichroic mirror 220 passes through the relay lens 260, the reflection mirror 240 on the incident side, the relay lens 270, the reflection mirror 250 on the emission side, and the condenser lens 300B to form an image of the liquid crystal light modulator 400B for blue light. It is incident on 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 the incident color light according to the image information to form a color image. Although not shown in the figure, incident side polarization is provided between the condensing lens 300R, the condensing lens 300G, the condensing 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. A plate is disposed, and an exit side polarization plate is disposed between the liquid crystal light modulation device 400R, the liquid crystal light modulation device 400G, and the liquid crystal light modulation device 400B and the cross dichroic prism 500, respectively.

  The cross dichroic prism 500 combines the image lights emitted from the liquid crystal light modulation device 400R, the liquid crystal light modulation device 400G, and the liquid crystal light modulation device 400B to form a color image.

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

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

  However, in the inorganic phosphor, “bleeding” is emitted by the fluorescence from the position where the excitation light is incident while being spread in the surface direction by the following mechanism. Therefore, the area of the region from which the fluorescence is emitted tends to be large.

FIG. 5A is a schematic view showing a state of bleeding in a fluorescent substance 1Y which is an inorganic fluorescent substance which is composed only of the main phase 2 which is Ce: YAG and does not contain a sub phase or pores. FIG. 5B is a schematic view showing the 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. The fluorescence totally reflected inside the phosphor 1Y is indicated by symbols Y1 and Y2 in the figure.

  Since the phosphor 1Y is composed of only the main phase 2, the fluorescence YL is not easily refracted or reflected inside the phosphor 1Y even if there are crystal grain boundaries. Therefore, the fluorescence travels from inside the phosphor 1Y to a position separated in the in-plane direction from the position where the excitation light B is incident, and then is emitted to the outside of the phosphor 1Y, and as a result, "blurring" is observed .

  On the other hand, as shown in FIG. 5B, in the phosphor 1 of the present embodiment, the fluorescence is refracted or reflected by the subphase 3 or the pores 4 so that the traveling direction of the fluorescence is easily changed. Then, in the absence of the subphase 3 and the pores 4, the fluorescence YL emitted at an angle at which the light is totally reflected on the surface of the phosphor 1 also changes its traveling direction, thereby having an approach angle different from the total reflection condition. The light is incident on the surface of the phosphor 1 and is easily emitted from the phosphor 1 to the outside. As a result, in the phosphor 1, internal fluorescence is more easily emitted to the outside of the phosphor than in the phosphor 1 Y, and “blur” is reduced.

  When the phosphor 1 of the present embodiment is used for the wavelength conversion element 30, parameters such as the amount of crystal grains 3a, the amount of pores お よ び and the shape correlate with the amount of “blur” as described in detail later. Therefore, it is good to design the fluorescent substance 1 appropriately and to adjust the bleeding.

  In the present embodiment, the “blurring amount” is defined as follows. Excitation light is uniformly irradiated to the area | region of diameter 0.4mm on fluorescent substance, and the emission profile of the fluorescence inject | emitted from fluorescent substance is measured. The relationship between the distance from the center of the region irradiated with the excitation light and the emission intensity is shown in FIG. 6 as an emission profile. The ordinate represents the light intensity, and the abscissa 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, where the horizontal axis represents the amount of bleeding and the vertical axis represents the total amount of fluorescence. A large amount of bleeding corresponds to a small amount of pores ρ, and a small amount of pores 対 応 corresponds to a high sintering temperature. When the sintering temperature is high and the pore amount 少 な い is small, the amount of excitation light which is not absorbed and backscatters decreases, and the amount of fluorescence increases, so 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 bleeding increases, the fluorescence increases.

  Therefore, when focusing only on reducing the amount of bleeding, the amount of light as a light source of the projector is insufficient, or the amount of fluorescence for mixing with blue excitation light to make white light decreases, and color balance is broken. Another problem may arise.

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

The amount of such 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, in which the horizontal axis represents the amount of bleeding (mm) and the vertical axis represents the average crystal grain size (μm) of crystal grains. In FIG. 9, mixed crystal grains mean a mixture of crystal grains of Ce: YAP and crystal grains of Ce: YAG.

  As the average grain size increases, the amount of bleeding tends to increase because the interface at which light is refracted or reflected decreases. The 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 using a Si-based sintering aid at the time of sintering, in which the horizontal axis is the amount of bleeding (mm) and the vertical axis is the phosphor. The Si content (ppm) is shown. If the Si content is high, that is, if a large amount of a sintering aid is used at the time of sintering, sintering tends to proceed, and as a result of the reduction of pores, the amount of bleeding tends to increase.
From FIG. 10, it is understood that the Si content is preferably 200 ppm or less.

  Further, considering the relationship between the amount of bleeding and the amount of pores 、, when the amount of pores 減少 decreases, the interface at which light is refracted or reflected decreases, so the amount of bleeding tends to increase. The pore amount ρ can be adjusted by controlling the sintering time and the sintering temperature.

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

  According to the phosphor having the above-described configuration, it is possible to provide a phosphor capable of achieving both the thermal conductivity and the light scattering property.

  In addition, since the wavelength conversion element having the above-described configuration includes the above-described phosphor, it is difficult to be damaged by heat, has desired light scattering characteristics, and has high reliability. A light source device and a projector provided with the above 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 view for explaining a projector 1006 according to a modification, and corresponds to FIG. In the following description, members common to those of the projector 1000 are denoted by the same reference numerals, and the description thereof 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 focusing optical system 90.

The light source 10 is disposed such that the optical axis is orthogonal to the light source optical axis 106 ax.
The collimating optical system 70 includes a first lens 72 and a second lens 74 to substantially collimate the light from the light source 10. 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 the optical axis of the light source 10 and each of the light source optical axis 106 ax at an angle of 45 °. The dichroic mirror 80 reflects blue light and transmits red light and green light.

  The collimating and condensing optical system 90 has a function of causing the blue light from the dichroic mirror 80 to be substantially condensed and to be incident on the phosphor layer 42, and a function of approximately collimating the fluorescence emitted from the phosphor layer 42. . The collimating and focusing 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 view showing a wavelength conversion element which the projector 1006 has. FIG. 12B 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 on one surface of the substrate 40 along the circumferential direction of the substrate 40. In the light source device 106, 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 for reflecting visible light is provided between the phosphor layer 42 and the substrate 40. Therefore, fluorescence is emitted toward the side where blue light is incident.

  It is not necessary to use a disc made of a material that transmits excitation light as the substrate 40, and a disc 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 focusing optical system 760, a scattering plate 732 and a collimating optical system 770.

  The focusing optical system 760 includes a first lens 762 and a second lens 764. The condensing optical system 760 condenses the blue light from the second light source device 710 in the vicinity of the scattering plate 732. The first lens 762 and the second lens 764 are convex lenses.

  The scattering plate 732 scatters the blue light from the second light source device 710 into blue light having a light distribution similar to the 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 to substantially collimate the light from the scattering plate 732. The first lens 772 and the second lens 774 are made of 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, it is possible to obtain the wavelength conversion element 34 that is not easily damaged by heat and has desired light scattering characteristics. In addition, a highly reliable light source device and a projector can be provided.

  FIG. 13 is a schematic view showing another example of the light source device. The light source device 1500 includes an excitation light source (light source) 1502 provided on the substrate 1501 and a phosphor layer 1503 provided on the light emission surface 1502 a side of the excitation light source 1502.

As the excitation light source 1502, various ones can be adopted as long as they emit blue excitation light.
The phosphor layer 1503 uses the phosphor of the above-described embodiment as a forming material.

  In the light source device 1500 having such a configuration, by using the phosphor 1 of the present embodiment, it is possible to obtain a highly reliable light source device 1500 which is not easily damaged by heat and has desired light scattering characteristics. .

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. 14 to 19.

  FIG. 14 is a schematic view 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 light source device 100M is provided instead of the light source device 100 described above. The light source device 100M is different from the light source device 100 in that the light source device 100M includes a wavelength conversion element 30M instead of the wavelength conversion element 30 described above. The other configuration is the same as the configuration of the projector 1000, so the same elements as those in FIG. 3 are denoted with the same reference numerals, and the detailed description will be omitted.

  The light source device 100M includes a light source 10, a focusing optical system 20, a wavelength conversion element 30M, 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, and causes the blue light to be incident on the phosphor layer 42M in a substantially condensed state. The phosphor layer 42M will be described later.

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

  15A is a schematic view of the wavelength conversion element 30M, and FIG. 15B is a cross-sectional view taken along line XVb-XVb in FIG. 15A.

  As illustrated in FIG. 15A, the wavelength conversion element 30M includes a substrate 40 having a circular shape in plan view, and a wavelength conversion unit 41AM provided along the circumferential direction of the substrate 40 on one surface of the substrate 40. As shown in FIG. 15B, the wavelength conversion unit 41AM is provided on the phosphor layer 42M, the dichroic film 44 provided on the first surface 42aM of the phosphor layer 42M, and the second surface 42bM of the phosphor layer 42M. And the anti-reflection film 47. 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 is rotatable 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. The dichroic film 44 and the anti-reflection film 47 both correspond to the optical functional layer described in the claims.

  The phosphor layer 42M is emitted from the light source 10 and is excited by blue light having a wavelength of about 445 nm which is 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 including yellow light, and passes the remaining part of the blue light without conversion.

  The phosphor layer 42M is formed by sintering 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 crystallites 421. It consists of a sintered compact obtained. The first crystallite 421 corresponds to the main phase, and the second crystallite 422 corresponds to the subphase (first crystal grain). The phosphor layer 42M is obtained by subjecting the above-described sintered body to processing such as cutting or polishing. In FIG. 15B, for the sake of simplicity, one first crystallite 421 is shown by a two-dot chain line, and the other first crystallite 421 is shown as forming a continuous 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 ₁₂ (hereinafter, referred to as Ce: YAG) is used as the first crystallite 421.

As the second crystallite 422, various materials can be used 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, YAP is used as the second crystallite 422. For example, Al ₂ O ₃ , Ce: Y ₂ O ₃ , Ce: YAP, CeO ₂ or Y ₂ O ₃ can be used instead of YAP. Al ₂ O ₃ , CeO ₂ and Y ₂ O ₃ are starting materials used in synthesizing Ce: YAG. In addition, YAP is a by-product generated when synthesizing Ce: YAG. As described above, Ce: YAP and Ce: Y2O3 improve the quantum yield of phosphors.

The phosphor layer 42M may have a third crystallite made of a ceramic material different from the second crystallite 422 while having a refractive index different from that of the first crystallite 421. The third crystallite corresponds to a 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 the metal impurity contained in the starting material or the like.

  The sintered body has grain boundaries and also has pores 4 at the grain boundaries. The pores 4 are generated at grain boundaries when the sintered body is formed. 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. Therefore, on the surface of the phosphor layer 42M, the depression 42x resulting from the pores 4 is present.

  When the sintered body contains a large number of pores 4, the number of depressions 42x on the surface of the phosphor layer 42M is also large. Therefore, in order to form the optical function layer on the surface of the phosphor layer 42M in a good state, it is preferable that the pore amount 少 な い be small. In addition, since the thermal conductivity of the phosphor layer 42M is high when the pore amount 少 な い is small, breakage of the phosphor layer 42M due to thermal stress hardly occurs. On the other hand, as described above, the pores 4 have a function of scattering light traveling inside the phosphor layer 42M. Therefore, the pore amount ρ may be set in consideration of the physical properties required for the phosphor layer 42M, that is, the thermal conductivity and the light scattering characteristics.

  In order to reduce the influence of heat storage of the phosphor layer 42M, the thermal conductivity of the phosphor layer 42M is preferably 9 W / m · k or more at 25 ° C. In order to realize such thermal conductivity, the pore amount ρ is preferably 0.01% or more and less than 5%.

  The second crystallite 422 is present at the 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.

  This phosphor layer 42M can be manufactured as follows. First, using the method of manufacturing the phosphor 1 according to the first embodiment, a sintered body including the first crystallite 421, the second crystallite 422, and the pores 4 is created. Next, the obtained sintered body is subjected to processing such as cutting or 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 this time, at the position where the dichroic film 44 overlaps the recess 42 x of the phosphor layer 42 M, a defect portion 44 x in which the dichroic film 44 is not formed in a desired state is formed.

  The anti-reflection film 47 is a dielectric multilayer film provided on the second surface 42bM of the phosphor layer 42M. The anti-reflection 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, a defect portion 47x in which the antireflective film 47 is not formed in a desired state is formed at a position overlapping the recess 42x of the phosphor layer 42M in the antireflective film 47.

  The wavelength conversion element 30M exhibits the following light emission behavior. FIG. 16 is a schematic view showing a state of light emission when the excitation light B is irradiated to the wavelength conversion element 30XM having the phosphor layer 420M not including the second crystallite 422 as a comparative example. FIG. 17 is a schematic view showing a state of light emission when the wavelength conversion element 30M of this embodiment is irradiated with the excitation light B. As shown in FIG.

  When the excitation light B is irradiated to the wavelength conversion element 30XM shown in FIG. 16 through the focusing optical system 20, the excitation light B passes through the dichroic film 44 and is incident on the phosphor layer 420M. In the phosphor layer 420M, the first crystallite 421 absorbs a part of the excitation light B, and emits yellow fluorescence YL isotropically. The fluorescence YL travels the inside of the phosphor layer 420M while being scattered by the pores 4 present 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 is not absorbed by the first crystallite 421 passes through the phosphor layer 420M. At this time, the light is transmitted by the phosphor layer 420M while being scattered by the pores 4 in the same manner as the fluorescence YL. Accordingly, white light in which the excitation light B and the fluorescence YL are mixed is emitted from the 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 recesses 42x of the first surface 420aM and the three recesses 42x of the second surface 420bM are combined to indicate that a total of six recesses 42x are formed.

  Therefore, the dichroic film 44 provided in contact with the first surface 420aM of the phosphor layer 420M has many defects 44x, and the anti-reflection film 47 provided in contact with the second surface 420bM has many defects. It has a part 47x. Therefore, it was difficult for each film to exhibit desired physical properties.

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

  On the other hand, in the wavelength conversion element 30M shown in FIG. 17, a plurality of second crystallites 422 having a refractive index different from that of the first crystallite 421 are included in the phosphor layer 42M. The second crystallite 422 scatters the excitation light B or 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 pore amount ρ may be smaller than the pore amount ρ in the phosphor layer 420M while making the ability to scatter the excitation light B and the fluorescence YL equal to the scattering ability in the phosphor layer 420M. it can. As a result, not only the amount of the recess 42x is reduced but also the thermal conductivity of the phosphor layer 42M is increased.

  In FIG. 17, one recess 42x of the first surface 42aM and two recesses 42x of the second surface 42bM are combined to indicate 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 is provided with an optical functional layer having good characteristics on the surface. Specifically, since the amount (number) of the defective portion 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 that of the comparative example. Can be emitted from the phosphor layer 42M in the opposite direction. Furthermore, since the amount (number) of the defect portions 47x of the anti-reflection film 47 is small, the fluorescence YL can be emitted from the second surface 42bM to the outside with higher efficiency than that of the comparative example. In this manner, the fluorescence YL generated in the phosphor layer 42M can be extracted with high efficiency in a desired direction.

  Further, since the thermal conductivity of the phosphor layer 42M is higher than that of the comparative example, even if the small area is irradiated with the high intensity excitation light B, it is difficult to store heat and breakage due to thermal stress does not occur easily.

  In a sintered body containing YAP as the second crystallite 422, the crystallite diameter of the first crystallite 421 and the second crystallite 422 is smaller when producing the sintered body as compared to the case where YAP is not contained. Tend to The sintered body has high bending strength if the crystallite diameter of the crystallites constituting the sintered body is small. Therefore, in the phosphor layer 42M containing YAP, breakage due to thermal stress hardly occurs.

  Since the light source device 100M according to the present embodiment includes the wavelength conversion element 30M, it can emit light with high brightness 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 brightness 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 view illustrating a projector 1006M according to a modification. The projector 1006M is different from the projector 1006 illustrated in FIG. 11 in that the projector 1006M includes a light source device 106M instead of the light source device 106 according to the first embodiment. The light source device 106M is different from the light source device 106 in that the light source device 106M includes a wavelength conversion element 34M instead of the wavelength conversion element 34 described above. The other configuration is the same as the configuration of the projector 1006, so the same elements as those in FIG.

  The collimating and condensing optical system 90 has a function of causing the blue light from the dichroic mirror 80 to be substantially condensed in a state of being substantially condensed, and a function of approximately collimating the fluorescence emitted from the phosphor layer 42M. .

  In the light source device 106M, 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 view of the wavelength conversion element 34M of the projector 1006M, and FIG. 19B is a cross-sectional view taken along line XIXb-XIXb of FIG. 19A.

  As shown in FIGS. 19A and 19B, the wavelength conversion element 34M includes the substrate 40, the phosphor layer 42M provided in a ring shape on the substrate 40, and the 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 included. The phosphor layer 42M, the reflection film 45, and the anti-reflection film 47 constitute a wavelength conversion unit 41BM. The wavelength conversion unit 41BM emits fluorescence toward the blue light incident side.

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

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

  Like the wavelength conversion element 30M, the wavelength conversion element 34M also has an optical functional layer with good characteristics on the surface. Specifically, since the amount (number) of the defective portions 45x of the reflective film 45 is small, the fluorescence YL generated in the phosphor layer 42M is reflected by the reflective film 45 with high efficiency, and the fluorescence in the direction opposite to the substrate 40 It can be ejected from the body layer 42M. Further, since the amount (number) of the defect portions 47x of the anti-reflection 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, breakage due to thermal stress hardly occurs.

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

  Although the preferred embodiments according to the present invention have been described above with reference to the accompanying drawings, the present invention is not limited to such embodiments. The shapes, combinations, and the like of the constituent members shown in the above-described example are merely examples, and various changes can be made based on design requirements and the like without departing from the spirit of the present invention.

  Although the example which mounted the light source device by this invention in the projector was shown in said each embodiment, it is not restricted to this. The light source device according to the present invention can also be applied to a lighting fixture, a headlight of a car, and the like.

  1, 1X, 1Y: phosphor, 2: main phase, 2a, 3a: crystal grain, 3: secondary phase, 4: pore, 10: light source, 20: focusing optical system, 30, 34, 30M, 34M: wavelength Conversion element, 40, 1501 ... substrate, 42, 42M, 42N, 1503 ... phosphor layer, 42aM ... first surface, 42bM ... second surface, 44 ... dichroic film (optical function layer), 45 ... reflection film ( Optical functional layer) 47 Antireflection film (optical functional layer) 90 Collimated condensing optical system (condensing optical system) 100 106 106 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.

As the second crystallite 422, various materials can be used 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, YAP is used as the second crystallite 422. For example, Al ₂ O ₃ , Ce: Y ₂ O ₃ , Ce: YAP, CeO ₂ or Y ₂ O ₃ can be used instead of YAP. Al ₂ O ₃ , CeO ₂ and Y ₂ O ₃ are starting materials used in synthesizing Ce: YAG. In addition, YAP is a by-product generated when synthesizing Ce: YAG. As described above, Ce: YAP and Ce: Y ₂ O ₃ improve the quantum yield of phosphors.

Claims (22)

A phosphor made of a sintered body of a ceramic material,
The sintered body contains 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 sub phase,
The phosphor having a grain boundary and having pores in the grain boundary. The phosphor according to claim 1, wherein the subphase contains Ce: YAlO ₃ , CeO ₂ , Y ₂ O ₃ , or Ce: Y ₂ O ₃ as first crystal grains. The subphase further includes a second crystal grain different from the first crystal grain, and the second crystal grain includes Ce: YAlO ₃ , CeO ₂ , Y ₂ O ₃ , or Ce: Y ₂ O ₃ as the second crystal grain. The phosphor according to item 2. The subphase includes Ce: YAlO ₃ , CeO ₂ , or Ce: Y ₂ O ₃ .
The phosphor according to claim 2 or 3, wherein the atomic concentration [Y] (at%) of yttrium in the sintered body satisfies the following requirements (i) and (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 any one of claims 1 to 4, wherein the main phase surrounds the periphery of the sub phase.   The phosphor according to any one of claims 1 to 5, wherein the pores are scaly.   The phosphor according to any one of claims 1 to 6, wherein the crystal grains constituting the main phase and the crystal grains constituting the sub phase are granular.   The phosphor according to any one of claims 1 to 7, wherein the ratio of the volume of the main phase to the total volume of the main phase and the subphase is 90% by volume or more and less than 100% by volume.   A wavelength conversion element having a phosphor layer comprising the phosphor according to any one of claims 1 to 8 as a forming material. A wavelength conversion element according to claim 9;
A light source for emitting excitation light to the phosphor layer of the wavelength conversion element. A 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 for projecting the image light. A wavelength conversion element comprising a phosphor layer and an optical functional layer provided on the surface of the phosphor layer,
The phosphor layer is made of a sintered body including a ceramic fluorescent material as a first crystallite and a ceramic material having a refractive index different from that of the first crystallite as a second crystallite,
The wavelength conversion element, wherein the sintered body has grain boundaries and pores in the grain boundaries. The first crystallite comprises Ce: Y ₃ Al ₅ O ₁₂ ,
The wavelength conversion element according to claim 12, wherein the second crystallite contains Ce: YAlO ₃ , CeO ₂ , Y ₂ O ₃ , Ce: Y ₂ O ₃ or YAlO ₃ .   The wavelength conversion element according to claim 12, wherein the optical function layer is an antireflective 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, wherein the optical function 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. A wavelength conversion element according to any one of claims 12 to 17.
A light source for emitting excitation light to the phosphor layer of the wavelength conversion element. A 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 for projecting the image light. A light source for emitting excitation light;
A wavelength conversion element having a phosphor layer which is excited by the excitation light to emit fluorescence;
And a focusing optical system disposed on the optical path of the excitation light between the light source and the wavelength conversion element, for condensing the excitation light toward the phosphor layer;
The phosphor layer is a light source device comprising a sintered body including a ceramic fluorescent material as a first crystallite and a ceramic material having a refractive index different from that of the first crystallite as a second crystallite. The first crystallite comprises Ce: Y ₃ Al ₅ O ₁₂ ,
It said second crystallites, the light source device of claim 20 including the 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 for projecting the image light.

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