JP7727962B2 - Fluorescent light-emitting module and light-emitting device - Google Patents

Description

The present invention relates to a fluorescent light-emitting module and a light-emitting device using the same.

Fluorescence-emitting modules that receive excitation light and emit fluorescence are known. Such fluorescence-emitting modules are used in light-emitting devices such as projectors.

As an example of a fluorescence-emitting module, Patent Document 1 discloses a light source device that includes a light-emitting unit that emits excitation light, a fluorescence-generating unit that is excited by the excitation light and generates fluorescence, and a phosphor substrate made of a plate-shaped glass member that supports the fluorescence-generating unit and other components. In this fluorescence-emitting module, excitation light enters the phosphor substrate from the atmosphere. Furthermore, the excitation light that enters the phosphor substrate passes through the phosphor substrate and enters the fluorescence-generating unit, where fluorescence is generated.

JP 2012-9242 A

In the above-mentioned fluorescence-emitting module, due to the difference in refractive index between the atmosphere and the phosphor substrate, part of the excitation light incident on the phosphor substrate from the atmosphere is reflected toward the atmosphere. As a result, less excitation light enters the fluorescence generating unit than if part of the excitation light were not reflected, and therefore less fluorescence is generated in the fluorescence generating unit. Therefore, the above-mentioned fluorescence-emitting module has the problem of low light utilization efficiency.

In addition, in the above-mentioned fluorescence-emitting module, the fluorescence-generating portion on the phosphor substrate is composed of a phosphor material and a transparent resin. In the fluorescence-generating portion, the phosphor material generates the most heat when irradiated with excitation light. The heat generated in the phosphor material is thermally conducted and dissipated through the transparent resin. However, because the transparent resin has low thermal conductivity (i.e., high thermal resistance), it is difficult to efficiently dissipate the heat generated in the phosphor material. This heat causes a phenomenon in which the amount of generated fluorescence decreases (the so-called thermal quenching phenomenon), resulting in significant changes in the chromaticity of the light output from the above-mentioned fluorescence-emitting module. Furthermore, because the linear expansion coefficient of the transparent resin is significantly different from that of the fluorescence-generating portion and the phosphor substrate, the above-mentioned heat easily causes the fluorescence-generating portion to peel off from the phosphor substrate. This chromaticity change and peeling pose a problem of low reliability for the above-mentioned fluorescence-emitting module.

The object of the present invention is to provide a fluorescent light-emitting module and light-emitting device that has high light utilization efficiency and high reliability.

A fluorescence-emitting module according to one aspect of the present invention includes a phosphor substrate, which is a substrate made of a sintered phosphor containing a phosphor material, and a rotating unit that rotates the phosphor substrate around an axis extending in the thickness direction of the phosphor substrate.

Furthermore, a fluorescent light-emitting module according to one aspect of the present invention includes a phosphor substrate, which is a substrate made of a sintered phosphor containing a phosphor material and a high-thermal-conductivity material with a thermal conductivity of 100 W/m·K or more and 300 W/m·K or less.

Furthermore, a light-emitting device according to one aspect of the present invention includes the above-described fluorescent light-emitting module.

The present invention provides a fluorescent light-emitting module and light-emitting device that has high light utilization efficiency and high reliability.

FIG. 1 is a perspective view of a fluorescence light-emitting module according to a second embodiment. FIG. 2 is a cross-sectional view showing a cut surface of a part of the fluorescent light-emitting module taken along line II-II in FIG. FIG. 3 is a perspective view showing the appearance of the projector according to the first embodiment. FIG. 4A is a diagram showing a fluorescent light emitting module in the projector according to the first embodiment. FIG. 4B is a diagram showing the energy efficiency of transmitted light according to the first embodiment. FIG. 5A is a perspective view of a mold for manufacturing the phosphor substrate according to the first embodiment. FIG. 5B is a diagram showing the relationship between the Ce concentration of YAG:Ce and the thickness of the phosphor substrate according to the first embodiment. FIG. 5C shows the relationship between the Ce concentration of YAG:Ce and the temperature of the phosphor substrate according to the first embodiment. FIG. 5D shows the relationship between the spot size expansion ratio of the phosphor substrate according to the first embodiment. FIG. 6 is a cross-sectional view of a phosphor substrate according to another example 1 of the second embodiment. FIG. 7 is a cross-sectional view of a phosphor substrate according to another example 2 of the second embodiment. FIG. 8 is a perspective view of the fluorescence light-emitting module according to the first embodiment. FIG. 9 is a cross-sectional view showing a cut surface of a part of the fluorescent light-emitting module taken along line IX-IX in FIG. FIG. 10 is a schematic diagram showing the configuration of the projector according to the first embodiment. FIG. 11 is a perspective view of a fluorescence light-emitting module according to the third embodiment. FIG. 12 is a cross-sectional view showing a cut surface of a part of the fluorescent light-emitting module taken along line XII-XII in FIG. FIG. 13 is a perspective view of a fluorescence light-emitting module according to the fourth embodiment. FIG. 14 is a perspective view of a mold for manufacturing a phosphor substrate according to the fourth embodiment. FIG. 15 is a perspective view of a fluorescence light-emitting module according to the fifth embodiment. FIG. 16 is a cross-sectional view showing a cut surface of a part of the fluorescent light-emitting module taken along line XVI-XVI in FIG. FIG. 17 is a perspective view of a fluorescence light-emitting module according to the sixth embodiment.

The following describes in detail the fluorescent light-emitting module and other aspects of the present invention, using drawings.

The embodiments described below are all comprehensive or specific examples. The numerical values, shapes, materials, components, component placement and connection, manufacturing processes, and the order of manufacturing processes shown in the following embodiments are merely examples and are not intended to limit the scope of the present invention.

Furthermore, each figure is a schematic diagram and is not necessarily an exact illustration. Therefore, for example, the scales of the figures do not necessarily match. Furthermore, in each figure, substantially identical components are assigned the same reference numerals, and redundant explanations are omitted or simplified.

In this specification, terms indicating the relationship between elements, such as parallel or perpendicular, terms indicating the shape of elements, such as circular, and numerical ranges are not intended to be strictly defined, but rather to include a substantially equivalent range, for example, a difference of a few percent.

In addition, in this specification and drawings, the x-axis, y-axis, and z-axis refer to the three axes of a three-dimensional Cartesian coordinate system. In each embodiment, the direction parallel to the axis direction is referred to as the z-axis, and the two axes perpendicular to the z-axis are referred to as the x-axis and y-axis.

(Embodiment 1)
[Configuration of the fluorescence emission module]
First, the configuration of a fluorescence-emitting module 1c according to the present embodiment will be described with reference to the drawings. Fig. 8 is a perspective view of the fluorescence-emitting module 1c according to the present embodiment. Fig. 9 is a cross-sectional view showing a cut surface of part of the fluorescence-emitting module 1c taken along line IX-IX in Fig. 8.

As shown in Figures 8 and 9, the fluorescence-emitting module 1c is a module including a phosphor substrate 10c made of a sintered phosphor, an anti-reflection layer 30, a blue-transmitting dichroic multilayer film 40, a rotating unit 100, a fourth optical element 304, and two light-emitting units 200. For simplicity, only one light-emitting unit 200 is shown in Figure 8. This same designation may also be used in the following figures. The fluorescence-emitting module 1c may also include only one light-emitting unit 200. The fluorescence-emitting module 1c is used in light-emitting devices such as projectors and lighting devices. In this embodiment, a projector using the fluorescence-emitting module 1c will be used as an example. The phosphor substrate 10c is used as a light-transmitting phosphor wheel that receives excitation light L1 and emits transmitted light L2 containing fluorescence. The transmitted light L2 is used as projection light output by the projector.

The components of the fluorescence light-emitting module 1c are described below.

<Explanation of Light Emitting Part>
The light emitting unit 200 is a light source that emits excitation light L1. The excitation light L1 is light that excites the phosphor substrate 10c, which is a sintered phosphor. In other words, the excitation light L1 is light that excites the phosphor material contained in the sintered phosphor that constitutes the phosphor substrate 10c. Note that FIG. 9 shows a side view of the light emitting unit 200. The light emitting unit 200 is, for example, a semiconductor laser light source or an LED (Light Emitting Diode) light source, and is driven by a drive current to emit excitation light L1 of a predetermined color (wavelength).

In this embodiment, the light emitting unit 200 is a semiconductor laser light source. The semiconductor laser element included in the light emitting unit 200 is, for example, a GaN-based semiconductor laser element (laser chip) made of nitride semiconductor material. In this embodiment, the light emitting unit 200, which is a semiconductor laser light source, is a TO-CAN type light emitting device with an integrated collimating lens. The two light emitting units 200 may be multi-chip type lasers, as shown in Japanese Patent Application Laid-Open No. 2016-219779, or the collimating lens and TO-CAN may be separate entities.

As an example, the light emitting unit 200 emits laser light in the near-ultraviolet to blue range with a peak wavelength between 380 nm and 490 nm as excitation light L1. In this case, the peak wavelength of the excitation light L1 is, for example, 455 nm, and the excitation light L1 is blue light.

<Explanation of rotating parts>
The rotating unit 100 is a member that rotates the phosphor substrate 10c around an axis A1 extending in the thickness direction (z-axis direction) of the phosphor substrate 10c, and is, for example, a motor. More specifically, in this embodiment, the rotating unit 100 rotates the phosphor substrate 10c, the anti-reflection layer 30, and the blue-transmitting dichroic multilayer film 40 around the axis A1 in the direction of the arrow shown in FIG. 8. When the center of the circular phosphor substrate 10c in a planar view is defined as a center point C1, the axis A1 passes through the center point C1, i.e., penetrates the phosphor substrate 10c. Here, the planar view is taken as a view of the fluorescence-emitting module 1c from the positive direction of the z-axis. Note that the internal components of the rotating unit 100 are omitted from the illustration in FIG. 9.

Also, as shown in Figure 9, the phosphor substrate 10c is positioned so that it overlaps with the rotating part 100 in plan view.

<Fourth Optical Element>
The fourth optical element 304 is an optical member for controlling the optical path of the excitation light L1 output from the two light emitting units 200. As an example, the fourth optical element 304 is a lens for condensing the excitation light L1 . Note that Fig. 9 shows a side view of the fourth optical element 304.

<Explanation of phosphor substrate>
The phosphor substrate 10c is a substrate made of a sintered phosphor containing a phosphor material, and is a substrate having a circular shape as described above. That is, the phosphor substrate 10c is a disk shape having a flat surface. Specifically, here, the phosphor substrate 10c is a substrate made only of a sintered phosphor, and the sintered phosphor contains only the phosphor material as a main component.

Now, we will explain the sintered phosphor used in this embodiment.

A sintered phosphor is a fired body obtained by firing raw material powder of the phosphor material (for example, granules obtained by granulating raw material powder of the phosphor material), which is the main component, at a temperature lower than the melting point of the phosphor material. In addition, in the sintered phosphor, the raw material powders are bonded together during the firing process. Therefore, the sintered phosphor hardly requires a binder for bonding the granules together. More specifically, the sintered phosphor does not require any binder at all. As an example, the binder in the above Patent Document 1 is a transparent resin. Furthermore, known materials used as the binder include Al ₂ O ₃ material and glass material (i.e., SiO _d (0 < d ≦ 2)). Similarly, without being limited to a binder, the sintered phosphor hardly requires any materials (hereinafter referred to as other materials) other than the phosphor material contained in the sintered phosphor, and more specifically, does not require any other materials at all.

For example, when the total volume of the sintered phosphor is taken as 100 vol%, it is preferable that the volume of the phosphor material in the total volume of the sintered phosphor be 70 vol% or more. Furthermore, it is better that the volume of the phosphor material in the total volume of the sintered phosphor be 80 vol% or more, even better that it be 90 vol% or more, and even better that it be 95 vol% or more.

In other words, when the total volume of the sintered phosphor is taken as 100 vol%, it is preferable that the volume of other materials (e.g., binder) in the total volume of the sintered phosphor be less than 30 vol%. Furthermore, it is better that the volume of other materials (e.g., binder) in the total volume of the sintered phosphor be less than 20 vol%, even better that it be less than 10 vol%, and even better that it be less than 5 vol%.

When the vol% of other materials in the overall volume of the sintered phosphor is high (i.e., the volume ratio of other materials is high), phonon scattering occurs due to defects present at the interface between the phosphor material and other materials. As a result, the thermal conductivity of the sintered phosphor decreases. In particular, the decrease in thermal conductivity is significant when the volume of other materials is 30 vol% or more. In addition, non-radiative recombination at the interface also increases, resulting in a decrease in luminous efficiency. In other words, the lower the vol% of other materials in the overall volume of the sintered phosphor (i.e., the smaller the volume ratio of other materials), the better the thermal conductivity and luminous efficiency. For the above reasons, the sintered phosphor of the present invention has a volume of other materials of less than 30% of the overall volume of the sintered phosphor.

Here, the _phosphor material will be described. The phosphor material is, for example, a material composed of a crystalline phase having a garnet structure. The garnet structure is a crystalline structure expressed by the general formula _A3B2C3O12 . The element A is a rare earth element such as _Ca , Y, _La , Ce, Pr, Nd, Sm, Eu, Gd, Tb, or Lu. The element B is an element such as Mg, Al, Si, Ga, or Sc. The element C is an element such as Al, Si, or Ga. Such garnet structures include YAG (Yttrium Aluminum Garnet) _, LuAG (Lutetium Aluminum Garnet), _{Lu2CaMg2Si3O12} (Lutetium Calcium Magnesium Silicon Garnet), and _TAG (Terbium Aluminum Garnet) _. In this embodiment, the phosphor material is composed of _a crystalline phase _{expressed by} (Y1 _{-xCe x ) 3Al2Al3O12} (that is, (Y1 _{-xCe x} ) _{3Al5O12 )} (0.0001≦x< _0.1 ), that is, YAG:Ce.

In addition, when the phosphor material is composed of YAG:Ce, Al ₂ O ₃ may be used as a raw material. In this case, Al ₂ O ₃ may remain as an unreacted raw material in the sintered phosphor. However, the unreacted raw material Al ₂ O ₃ is different from the above-mentioned binder. In addition, when the total volume of the sintered phosphor is 100 vol%, the volume of the unreacted raw material Al ₂ O ₃ in the total volume of the sintered phosphor is 5 vol% or less.

The crystalline phase constituting the phosphor material may be a solid solution of multiple garnet crystalline phases with different chemical compositions. An example of such a solid solution is a solid solution (( ₁ -a)(Y1 _{-xCe x} ) _3Al2Al3O12.a ( _{Lu1 - yCey} ) _3Al2Al3O12 (0<a<1 ₎ ) of a garnet crystalline phase represented by ( _Y1 - _{xCe x} ) _3Al2Al3O12 ( _0.001 ≦x<0.1) and _a garnet crystalline _phase represented by ( _{Lu1 - yCey )3Al2Al3O12 (} 0.001≦y _{< 0.1} ). Further, examples of such solid solutions include _{a solid solution} (( _{1-b)(Y1-xCe x} ) _3Al2Al3O12.b (Lu1 _{-zCe z} ) _2CaMg2Si3O12 (0<b< ₁ ) ₎ of a garnet crystal phase represented by _{( Y1} -xCe x) _3Al2Al3O12 (0.001≦x<0.1) and _{a garnet crystal phase represented by (Lu1-zCe z ) 2CaMg2Si3O12 ( 0.0015 ≦ z <} 0.15). When _the phosphor material _is composed of a solid solution of multiple garnet crystal phases with different chemical compositions, the fluorescence spectrum of the fluorescence emitted by the phosphor material becomes broader, with an increase in green and red light components. Therefore, a projector that emits projection light with a wide color gamut can be provided.

Furthermore, the crystalline phase constituting the phosphor material may include a crystalline phase whose chemical composition is different from that of the crystalline phase represented by the above general formula _{A3B2C3O12 .} Such a crystalline phase may be (Y1 _{- xCe x} ) _{3Al2 + δAl3O12} ( _δ is _a positive number) which is Al-rich relative to the crystalline phase represented by (Y1 _{-xCe x ) 3Al2Al3O12} (0.001≦x<0.1). Further, such a crystalline phase may be (Y1 _- xCe _x ) _{3 + ζAl2Al3O12} (ζ _is a _positive number) _which is Y-rich relative to the crystalline phase represented by (Y1 _{-xCe x} ) _3Al2Al3O12 ( _0.001 ≦ _x < _0.1 ). These crystal phases have different chemical compositions from the crystal phase represented by the general formula A ₃ B ₂ C ₃ O ₁₂ , but maintain the garnet structure.

Furthermore, the crystalline phase that constitutes the phosphor material may contain a heterogeneous phase having a structure other than the garnet structure.

In this embodiment, the phosphor material made of YAG:Ce receives light incident on the phosphor substrate 10c from the negative z-axis direction as excitation light L1 and emits fluorescence. More specifically, light emitted from the light emitting unit 200 is irradiated onto the phosphor material as excitation light L1, causing the phosphor material to emit fluorescence as wavelength-converted light. In other words, the wavelength-converted light emitted from the phosphor material is light with a longer wavelength than the wavelength of excitation light L1.

In this embodiment, the wavelength-converted light emitted from the phosphor material includes fluorescent light, which is yellow light. The phosphor material, for example, absorbs light with a wavelength of 380 nm or more and 490 nm or less, and emits fluorescent light, which is yellow light, with a fluorescent peak wavelength in the wavelength range of 490 nm or more and 580 nm or less. By using YAG:Ce as the phosphor material, it is possible to easily emit fluorescent light with a fluorescent peak wavelength in the wavelength range of 490 nm or more and 580 nm or less.

As described above, a portion of the excitation light L1 incident on the phosphor material is wavelength-converted by the phosphor material and passes through the phosphor substrate 10c. The remaining portion of the excitation light L1 passes through the phosphor substrate 10c without being wavelength-converted by the phosphor material. The transmitted light L2 that passes through the phosphor substrate 10c contains fluorescence, which is wavelength-converted yellow light, and excitation light L1, which is wavelength-unconverted blue light. In other words, the transmitted light L2 is a combination of these two types of light, and is white light. For example, if the balance between fluorescence and excitation light L1 in the transmitted light L2 is disrupted, the chromaticity of the transmitted light L2 will change. More specifically, if fluorescence decreases, the proportion of excitation light L1 increases, and the proportion of blue light in the transmitted light L2 increases.

Also, as shown in Figure 8, in this embodiment, the excitation light L1 is irradiated at a position at a radius R from the center point C1 of the phosphor substrate 10c.

<Explanation of the coating layer>
<Blue-transmitting dichroic multilayer film>
The blue-transmission dichroic multilayer film 40 is located in the negative direction of the z-axis of the phosphor substrate 10c. The blue-transmission dichroic multilayer film 40 has a transmission-reflection characteristic of transmitting the excitation light L1 and reflecting the fluorescent light. In this embodiment, the blue-transmission dichroic multilayer film 40 has a transmission-reflection characteristic of transmitting blue light and reflecting yellow light.

Specifically, the blue-transmitting dichroic multilayer film 40 is composed of dichroic layers made of dielectric multilayer films, etc. By controlling the dielectric materials and/or the composition of the multilayer film that make up the dichroic layers, the blue-transmitting dichroic multilayer film 40 can have a predetermined reflectance for a predetermined wavelength and high transmission characteristics for blue wavelengths.

For example, if such a blue-transmission dichroic multilayer film 40 were not provided, some of the fluorescence generated in the phosphor material would be emitted from the phosphor substrate 10c in the negative direction of the z-axis and would not be usable as projection light for the projector. By providing the blue-transmission dichroic multilayer film 40, this portion of the light is reflected by the blue-transmission dichroic multilayer film 40 in the positive direction of the z-axis. This means that the entire fluorescence generated in the phosphor material in the phosphor substrate 10c is more likely to be directed in the positive direction of the z-axis. This improves the light utilization efficiency of the fluorescence-emitting module 1c. Furthermore, the blue-transmission dichroic multilayer film 40 also functions as an anti-reflection film for the excitation light L1 (blue light), making it possible to increase the amount of excitation light L1 incident on the phosphor substrate 10c compared to when the blue-transmission dichroic multilayer film 40 is not provided.

<Anti-reflection layer>
Furthermore, an anti-reflection layer 30 is located in the positive direction of the z-axis of the phosphor substrate 10c.

The anti-reflection layer 30 is a layer that prevents, or more specifically, suppresses, the reflection of transmitted light L2. In other words, the anti-reflection layer 30 is a layer that prevents transmitted light L2 traveling in the positive direction of the z axis from being reflected and traveling in the negative direction of the z axis.

The anti-reflection layer 30 reduces the reflectance of the transmitted light L2 emitted from the fluorescence light-emitting module 1c; in other words, it improves the transmittance of the transmitted light L2 and increases the amount of transmitted light L2 emitted from the fluorescence light-emitting module 1c. As a result, the amount of transmitted light L2 that can be used as projection light for a projector increases, for example. This increases the light utilization efficiency of the fluorescence light-emitting module 1c.

The antireflection layer 30 may be composed of, for example, a dielectric film or a fine uneven structure (so-called moth-eye structure) with a period smaller than the wavelength of light in the visible light region. When the antireflection layer 30 is composed of a dielectric film, the antireflection layer 30 can be easily manufactured by including an inorganic compound _{in the} antireflection layer 30. In this case, the antireflection layer 30 includes one or more inorganic compounds selected from SiO2, _TiO2 , _Al2O3 , ZnO, _{Nb2O5 ,} MgF, etc.

Furthermore, although Figures 8 and 9 show a configuration in which an anti-reflection layer 30 and a blue-transmission dichroic multilayer film 40 are provided, the fluorescence-emitting module 1c does not necessarily have to include an anti-reflection layer 30 and a blue-transmission dichroic multilayer film 40. In this case, the rotating part 100 and the phosphor substrate 10c are in contact with each other via an adhesive member.

The planar shapes of the anti-reflection layer 30 and the blue-transmission dichroic multilayer film 40 are, for example, the same as the phosphor substrate 10c, i.e., circular. Although not shown, the anti-reflection layer 30 and the blue-transmission dichroic multilayer film 40 may also be annular, arranged to overlap the position where the excitation light L1 is irradiated in planar view. In this case, the center of the annular shape overlaps with the center point C1 of the phosphor substrate 10c.

The anti-reflection layer 30 and the blue transmission dichroic multilayer film 40 are sufficiently thinner than the phosphor substrate 10c. For example, the thickness of each of the anti-reflection layer 30 and the blue transmission dichroic multilayer film 40 is, for example, 0.1 μm or more and 50 μm or less, but is not limited to this. Therefore, the anti-reflection layer 30 and the blue transmission dichroic multilayer film 40 are not components for supporting the phosphor substrate 10c.

<Effect of rotating part>
It is known that when the temperature of the phosphor substrate 10c increases due to irradiation with excitation light L1, a phenomenon occurs in which the emitted fluorescence decreases (so-called temperature quenching). For example, when temperature quenching occurs in the fluorescence-emitting module disclosed in Patent Document 1, the fluorescence emitted from the fluorescence generating unit decreases, resulting in problems such as a decrease in the light utilization efficiency of the fluorescence-emitting module.

Furthermore, the fluorescence-emitting module 1c according to this embodiment is equipped with a rotating section 100. This causes the phosphor substrate 10c and other components to rotate around axis A1, generating an airflow. This generated airflow cools the phosphor substrate 10c. In other words, the heat dissipation properties of the phosphor substrate 10c are improved. This prevents the temperature of the phosphor substrate 10c from increasing, thereby suppressing the decrease in fluorescence. This means that the light utilization efficiency of the fluorescence-emitting module 1c can be improved. Furthermore, because the decrease in fluorescence is suppressed, changes in the chromaticity of the transmitted light L2 can be suppressed. This results in a highly reliable fluorescence-emitting module 1c.

<Diameter of phosphor substrate>
The diameter of the disc-shaped phosphor substrate 10c is, for example, preferably 30 mm to 90 mm, more preferably 35 mm to 70 mm, and even more preferably 40 mm to 50 mm, but is not limited to these.

<Benefits of no substrate>
As described above, the fluorescence-emitting module 1c according to this embodiment does not include components for supporting the phosphor substrate 10c (such as the transparent phosphor substrate disclosed in Patent Document 1). In other words, the fluorescence-emitting module 1c according to this embodiment has a substrate-less structure. Therefore, unlike Patent Document 1, reflection of the excitation light L1 (i.e., optical loss of the excitation light L1) at the interface between the phosphor substrate and the atmosphere does not occur. Because there is no optical loss of the excitation light L1 at the interface, the excitation light L1 incident on the phosphor substrate 10c increases. As a result, the fluorescence generated by the phosphor material in the phosphor substrate 10c increases. In other words, the light utilization efficiency of the fluorescence-emitting module 1c can be improved. Furthermore, because the fluorescence-emitting module 1c does not include components for supporting the phosphor substrate 10c, the peeling of the fluorescence generating unit disclosed in Patent Document 1 does not occur. This results in a highly reliable fluorescence-emitting module 1c.

<Effect of blue-transmitting dichroic multilayer film>
Furthermore, by providing the blue-transmission dichroic multilayer film 40, it is possible to suppress Fresnel reflection of the excitation light L1, which is blue light, at the interface between the atmosphere and the phosphor substrate 10c, which would occur if the blue-transmission dichroic multilayer film 40 were not provided. In other words, the blue-transmission dichroic multilayer film 40 can suppress light loss due to reflection of the excitation light L1. By providing such a blue-transmission dichroic multilayer film 40, the excitation light L1 incident on the phosphor substrate 10c increases. As a result, the fluorescence generated by the phosphor material in the phosphor substrate 10c increases.

<Effects of sintered phosphor>
Further, the effect of the phosphor substrate 10c being made of a sintered phosphor will be described below.

For example, in Patent Document 1, the transparent resin corresponds to the binder. The refractive index of known binders containing this transparent resin is often different from the refractive index of phosphor materials such as YAG:Ce. For this reason, when phosphor materials such as YAG:Ce are combined with a binder, light scattering occurs. In this case, light loss occurs due to light scattering.

However, as described above, the sintered phosphor according to this embodiment requires almost no binder. Therefore, in a sintered phosphor, light loss due to light scattering and the like is unlikely to occur. In other words, by providing the fluorescent light-emitting module 1c with a phosphor substrate 10c made of a sintered phosphor, the light utilization efficiency of the fluorescent light-emitting module 1c can be improved.

<Adhesion>
The rotating part 100 and the phosphor substrate 10c are in contact with each other via an adhesive. The rotating part 100 is made of lightweight, highly thermally conductive aluminum, taking into consideration the load on the rotating part 100 itself (the motor) and its thermal conductivity. The outer diameter of the rotating part 100 is less than twice the radius R. Silicone resin is used as the adhesive to mitigate the difference in thermal expansion coefficients between the rotating part 100 and the phosphor substrate 10c. However, the rotating part 100 may be made of other materials, such as Cu or Fe, and the adhesive may be other epoxy resins or highly thermally conductive adhesives containing nano-Ag or nano-Cu.

<Diameter of phosphor substrate>
Here, the inventors have studied the relationship between the energy efficiency of the transmitted light L2 and the diameter of the phosphor substrate 10c, and the results of this study are shown in FIG.

Figure 4B is a diagram showing the energy efficiency of transmitted light L2 in this embodiment. This figure shows the results of an investigation into a phosphor substrate 10c with a diameter (indicated as φ in Figure 4B) of 5 mm or more and 90 mm or less.

The lower horizontal axis represents the energy of the excitation light L1. Here, the incident area of the excitation light L1 on the phosphor substrate 10c is 2 ^mm2 , so the upper horizontal axis represents the density of excitation energy (excitation density) in the incident area of the excitation light L1.

The vertical axis represents the energy efficiency of transmitted light L2. The vertical axis also represents the normalized value of the energy of transmitted light L2 for each data point representing the diameter of the phosphor substrate 10c, where the energy of transmitted light L2 when the energy of excitation light L1 is 0.5 W is set to 100%. For example, for data representing a phosphor substrate 10c with a diameter of 5 mm, the vertical axis represents the normalized value of the energy of transmitted light L2 emitted from a phosphor substrate 10c with a diameter of 5 mm when the energy of excitation light L1 is 0.5 W, where the energy of transmitted light L2 emitted from a phosphor substrate 10c with a diameter of 30 mm when the energy of excitation light L1 is 0.5 W is set to 100%. Similarly, for data representing a phosphor substrate 10c with a diameter of 30 mm, the vertical axis represents the normalized value of the energy of transmitted light L2 emitted from a phosphor substrate 10c with a diameter of 30 mm when the energy of excitation light L1 is 0.5 W.

The greater the energy of the excitation light L1, the more likely it is that the temperature of the phosphor substrate 10c will rise, and the more likely it is that thermal quenching will occur. When thermal quenching occurs, the energy of the transmitted light L2 will drop sharply. As shown in Figure 4B, for phosphor substrates 10c with a diameter of 5 mm or greater and 65 mm or less, there is a region where the energy of the transmitted light L2 drops sharply. For example, for a phosphor substrate 10c with a diameter of 30 mm, this region appears when the energy of the excitation light L1 increases from 70 W to 100 W.

Furthermore, Figure 4B shows that the larger the diameter of the phosphor substrate 10c, the more this region shifts toward higher energy excitation light L1. In other words, Figure 4B shows that the larger the diameter of the phosphor substrate 10c, the less likely thermal quenching occurs. This can be explained as follows.

Heat generated by irradiation with the excitation light L1 moves, for example, from the area irradiated with the excitation light L1 (for example, the position of radius R from the center point C1 described above) to the area not irradiated with the excitation light L1. The larger the diameter of the phosphor substrate 10c, the larger the area not irradiated with the excitation light L1. This area not irradiated with the excitation light L1 corresponds to the area to which heat moves from the area irradiated with the excitation light L1. Therefore, the larger the diameter of the phosphor substrate 10c, the easier it is for heat generated by irradiation with the excitation light L1 to move, making it less likely for the temperature of the phosphor substrate 10c to rise. As a result, thermal quenching is less likely to occur. In other words, the larger the diameter of the phosphor substrate 10c, the more efficiently transmitted light L2 can be obtained in areas where the energy of the excitation light L1 is high.

Furthermore, the inventors' studies have revealed that, for example, to achieve an output light of 15,000 lm from the light source module 600, the energy of the excitation light L1 must be approximately 100 W. The light source module 600 is an optical module comprising a fluorescent light-emitting module 1c and optical elements, as will be explained in detail in Figure 4A.

As mentioned above, the diameter of the phosphor substrate 10c is, for example, preferably 30 mm or more and 90 mm or less, more preferably 35 mm or more and 70 mm or less, and even more preferably 40 mm or more and 50 mm or less.

By having the diameter of the phosphor substrate 10c within the above range, when the energy of the excitation light L1 is 100 W, it is possible to obtain highly efficient transmitted light L2 (for example, 90% or more on the vertical axis of Figure 4B).

In other words, the diameter of the phosphor substrate 10c is set appropriately depending on the output light of the light source module 600. Note that if the diameter of the phosphor substrate 10c is large, the size of the light source module 600 will also increase. As a result, the size of light-emitting devices such as projectors 500 and lighting devices will also increase, reducing the commercial value of the light-emitting devices.

Therefore, for example, if the output light of the light source module 600 is the above-mentioned 15,000 lm, the diameter of the phosphor substrate 10c should be between 40 mm and 50 mm.

<Thickness of phosphor substrate>
The thickness of the phosphor substrate 10c (i.e., the length in the z-axis direction) is preferably 50 μm to 700 μm, more preferably 80 μm to 500 μm, and even more preferably 100 μm to 300 μm.

The thicker the phosphor substrate 10c, the higher the thermal conductivity of the phosphor substrate 10c, which means that the heat dissipation properties of the phosphor substrate 10c are improved.

On the other hand, the thicker the phosphor substrate 10c, the more easily the excitation light L1 is scattered by the phosphor substrate 10c. As a result, the light-emitting spot area of the transmitted light L2 on the phosphor substrate 10c increases when viewed in a plan view. As a result, in a projector, for example, optical elements such as lenses arranged on the optical path of the transmitted light L2 become larger, which causes problems such as the projector becoming larger in size.

Furthermore, the thicker the phosphor substrate 10c, the larger the volume of the phosphor substrate 10c. As a result, more phosphor material and high thermal conductivity material are required to manufacture one phosphor substrate 10c, which is also disadvantageous in terms of cost.

For these reasons, it is recommended that the thickness of the phosphor substrate 10c be within the above range.

[Study on Ce concentration]
As described above, the phosphor material according to this embodiment is YAG:Ce ((Y1 _{-xCe x} ) _3Al5O12 ) (0.0001 _{≦ x} <0.1). Here, the Ce concentration in YAG:Ce will be explained. The Ce concentration is the element ratio of Ce to the total of Y and Ce (i.e., Ce/(Y+Ce)(%)), and is expressed as x×100(%).

<Ce concentration and thickness>
First, the relationship between the Ce concentration and the thickness of the phosphor substrate 10c will be described.

The inventors conducted research to determine whether the output light (i.e., transmitted light L2) of the light source module 600 shown in Figure 4A would be white light, as an example. More specifically, they investigated the relationship between the Ce concentration of YAG:Ce and the thickness of the phosphor substrate 10c so that the chromaticity coordinates (x, y) of this output light would be (0.308 to 0.318, 0.324 to 0.334) in the CIE color system. The results of this research are shown in Figure 5B. The CIE color system is a color system established by the CIE (Commission Internationale de l'Eclairage).

Figure 5B shows the relationship between the Ce concentration in YAG:Ce and the thickness of the phosphor substrate 10c in this embodiment.

In Figure 5B, the vertical axis represents the thickness of the phosphor substrate 10c, and the horizontal axis represents the Ce concentration. Here, studies were conducted at Ce concentrations of 0.01%, 0.05%, 0.1%, 0.2%, and 0.3%.

Figure 5B shows three thicknesses of the phosphor substrate 10c for each Ce concentration. For each Ce concentration, when the thickness of the phosphor substrate 10c falls within the three ranges (more specifically, within the range from the thinnest to the thickest), the light output from the light source module 600 becomes white light (i.e., light with chromaticity coordinates within the above range). In other words, when the relationship between the Ce concentration of YAG:Ce and the thickness of the phosphor substrate 10c shown in Figure 5B is satisfied, the chromaticity coordinates of the light output from the light source module 600 fall within the above range.

Figure 5B shows that the lower the Ce concentration, the thicker the phosphor substrate 10c. In the YAG:Ce of this embodiment, Ce functions as the luminescence center, so the lower the Ce concentration, the less wavelength-converted light is generated. Therefore, in order for the chromaticity coordinates of the output light to fall within the above range, the lower the Ce concentration, the thicker the phosphor substrate 10c.

The thicker the phosphor substrate 10c, the less likely it is to break, for example. Therefore, the thicker the phosphor substrate 10c, the higher the reliability of the phosphor substrate 10c, and therefore of the fluorescence-emitting module 1c. For example, if the thickness of the phosphor substrate 10c is 100 μm or more, the reliability of the fluorescence-emitting module 1c can be sufficiently improved. For this reason, it is preferable that the Ce concentration be 0.1% or less.

Furthermore, a study conducted on the relationship between the Ce concentration and the temperature of the phosphor substrate 10c will be explained using Figure 5C. Note that in this study, as with the above, the relationship between the Ce concentration and the thickness of the phosphor substrate 10c shown in Figure 5B was satisfied so that the chromaticity coordinates of the output light from the light source module 600 fell within the above range.

<Ce concentration and temperature>
FIG. 5C shows the relationship between the Ce concentration of the YAG:Ce alloy and the temperature of the phosphor substrate 10c according to the present embodiment. More specifically, FIG. 5C shows the temperature of the phosphor substrate 10c when irradiated with excitation light L1 at each of the Ce concentrations shown in FIG. 5C. At this time, the phosphor substrate 10c and other components in the light source module 600 are rotated at 7,200 rpm. As described above, the relationship between the Ce concentration and the phosphor substrate 10c shown in FIG. 5B is also satisfied in FIG. 5C. In other words, the lower the Ce concentration, the thicker the phosphor substrate 10c.

As shown in Figure 5C, the lower the Ce concentration, the lower the temperature of the phosphor substrate 10c. Also, as shown in Figure 5B, the lower the Ce concentration, the thicker the phosphor substrate 10c, making it easier for heat generated by irradiation with excitation light L1 to transfer. Therefore, the lower the Ce concentration, the more effectively the temperature of the phosphor substrate 10c is prevented from rising. In other words, the lower the Ce concentration, the more effectively the temperature quenching phenomenon can be suppressed.

The inventors have also clarified that in order to sufficiently suppress the temperature quenching phenomenon, it is necessary to maintain the temperature of the phosphor substrate 10c at 150°C or less. Therefore, from the perspective of suppressing the temperature quenching phenomenon, it is preferable that the Ce concentration be 0.1% or less.

Furthermore, we will explain the study conducted on the relationship between Ce concentration and spot size expansion ratio. Note that in this study, as in the above, the relationship between Ce concentration and thickness of phosphor substrate 10c shown in Figure 5B was satisfied so that the chromaticity coordinates of the output light from light source module 600 were within the above range.

Figure 5D shows the relationship with the spot size expansion ratio of the phosphor substrate 10c according to this embodiment. The spot size expansion ratio indicates the ratio of the incident area of the phosphor substrate 10c onto which the excitation light L1 is incident to the exit area from which the transmitted light L2 is emitted. More specifically, the spot size expansion ratio is a value expressed as the exit area/incident area (%). The exit area has the same meaning as the light-emitting spot area described above.

<Ce concentration and spot size>
As shown in Fig. 5D, the higher the Ce concentration, the lower the spot size expansion ratio. Also, as shown in Fig. 5B, the higher the Ce concentration, the thinner the phosphor substrate 10c, and therefore the shorter the optical path between the excitation light L1 and the wavelength-converted light in the phosphor substrate 10c. This suppresses light scattering of the excitation light L1 and the wavelength-converted light in the phosphor substrate 10c. Therefore, the higher the Ce concentration, the more effectively the spot size expansion ratio can be suppressed.

As explained in [Projector Configuration], if the light emission spot area of transmitted light L2 is large, the first optical element 301 and second optical element 302 that focus transmitted light L2 will become large, and therefore the projector 500 will also become large. Conversely, by lowering the spot size expansion rate and reducing the light emission spot area of transmitted light L2, the projector 500 can be made more compact.

The inventors also clarified that, for example, in order to apply the fluorescent light-emitting module 1c to the projector 500, the spot size expansion ratio needs to be 250% or less. In other words, the Ce concentration should be 0.05% or more.

<Summary>
From the above, the inventors have found that the phosphor material is preferably YAG:Ce((Y _1-x Ce _x ) ₃ Al ₅ O ₁₂ ) (0.0005≦x<0.001)) with a Ce concentration of 0.05% or more and 0.1% or less.

This reduces the likelihood of damage to the phosphor substrate 10c, improving the reliability of the fluorescence-emitting module 1c. It also suppresses the thermal quenching phenomenon in the phosphor substrate 10c, resulting in a fluorescence-emitting module 1c with high light utilization efficiency. Furthermore, it also makes it possible to make the projector 500, an example of a light-emitting device, more compact.

The Ce concentration is preferably 0.06% or more and 0.09% or less, and even better 0.07% or more and 0.08% or less.

[Manufacturing method]
Here, a method for manufacturing the phosphor substrate 10c will be briefly described.

The phosphor material is composed of a crystalline phase represented by (Y _0.999 Ce _0.001 ) ₃ Al ₅ O _12. Furthermore, all of the phosphor materials are composed of a Ce ³⁺ activated phosphor.

To manufacture the phosphor substrate 10c, the following three types _of compound powders were used as raw materials: _Y2O3 , _Al2O3 , and _CeO2 . The purity and manufacturers of the raw materials were: _Y2O3 , _3N purity, from Nippon Yttrium Co., Ltd.; _Al2O3 , 3N purity, from Sumitomo Chemical Co., Ltd.; _{and CeO2 , 3N} purity, from Nippon Yttrium Co., Ltd.

As the raw materials, Y ₂ O ₃ , Al ₂ O ₃ , and CeO ₂ were weighed out so as to obtain a compound with a stoichiometric composition of (Y _0.999 Ce _0.001 ) ₃ Al ₅ O _12. Next, the weighed raw materials and alumina balls (diameter 10 mm) were placed in a plastic pot. The amount of alumina balls was such that they filled about one-third of the volume of the plastic pot. Thereafter, pure water was placed in the plastic pot, and the raw materials and pure water were mixed using a pot rotating device (BALL MILL ANZ-51S, manufactured by Nitto Chemical Co., Ltd.). This mixing was carried out for 12 hours. In this way, a slurry-like mixed raw material was obtained.

The mixed raw materials were granulated using a spray dryer. Polyvinyl alcohol was used as an adhesive (binder) during granulation.

The granulated mixed raw materials were pre-molded into a cylindrical shape using an electric hydraulic press (EMP-5, manufactured by Riken Seiki Co., Ltd.) and a cylindrical mold with a bottom. The molding pressure was 5 MPa.

Next, the pre-molded molded body was subjected to final molding using a cold isostatic pressing device. The pressure during final molding was 300 MPa. The molded body after final molding was then subjected to a heat treatment (binder removal treatment) to remove the adhesive (binder) used during granulation. The heat treatment temperature was 500°C, and the heat treatment time was 10 hours.

After the heat treatment, the molded body was fired in a tubular atmosphere furnace. The firing temperature was 1675°C. The firing time was 4 hours. The firing atmosphere was a mixed gas atmosphere of nitrogen and hydrogen.

After firing, the cylindrical fired product was sliced using a multi-wire saw. The sliced fired product was then polished to adjust the thickness of the fired product. This adjustment resulted in the fired product becoming the phosphor substrate 10c.

[Projector configuration]
Next, a projector 500 will be described. The fluorescence-emitting module 1c configured as described above is used in the projector 500 and lighting device (not shown) shown in Fig. 3. Fig. 3 is a perspective view showing the appearance of the projector 500 according to this embodiment. Fig. 10 is a schematic diagram showing the configuration of the projector 500 according to this embodiment. Fig. 4A is a schematic diagram showing the fluorescence-emitting module 1c in the projector 500 according to this embodiment. Note that, like Fig. 9, Fig. 4A shows a cross-sectional view of a portion of the fluorescence-emitting module 1c, two light-emitting units 200 in side view, and the internal components of the rotating unit 100 are omitted.

As shown in FIG. 10 , the projector 500 according to this embodiment includes a light source module 600. Similar to known projectors, the projector 500 also includes a homogenizing optical system 601, a display element unit 602, a light projecting unit 603, and a control circuit 604 that controls the display element unit 602. The homogenizing optical system 601 is composed of two multi-lens arrays (MLAs). The display element unit 602 is a substantially planar element that controls the transmitted light L2 that is output from the fluorescence emitting module 1c and passes through the homogenizing optical system 601 to output it as an image. In other words, the display element unit 602 generates light for the image. Specifically, the display element unit 602 is a transmissive liquid crystal panel. The display element unit 602 separates the transmitted light L2 into red light, green light, and blue light. The separated red light, green light, and blue light are then optically modulated by the corresponding display element units 602. As a result, an image is generated, and the red, green, and blue lights are wavelength-combined by a cross prism (not shown), which serves as an RGB combining unit. The light projecting unit 603 is a Tessar type. The transmitted light L2 output from the fluorescence light-emitting module 1c is controlled, in this order, by the homogenizing optical system 601, the display element unit 602, and the light projecting unit 603, to become projected light that is enlarged and projected onto, for example, a screen. The control circuit 604 controls the display element unit 602 and is realized, for example, by a microcomputer, but may also be realized by a processor. However, this configuration is not limited to this, and the homogenizing optical system 601 may also be a kaleidoscope-type structure such as a light pipe. Furthermore, projectors and light-emitting devices that do not require uniformity in the projected image may not have the homogenizing optical system 601. The display element unit 602 may be a DMD (Digital Micromirror Device) or LCOS (Liquid Crystal on Silicon). Furthermore, for example, the display element unit 602 may be a reflective liquid crystal panel or a DLP (Digital Light Processing) with a DMD. In time-division and monochrome projectors and light-emitting devices, the transmitted light L2 does not need to be separated into red, green, and blue light. The light-projecting unit 603 may be of another type, such as a Gaussian type.

Furthermore, the light source module 600 is an optical module including a fluorescent light-emitting module 1c, a first optical element 301, a second optical element 302, and a third optical element 303. In other words, the projector 500, which is an example of a light-emitting device, includes the fluorescent light-emitting module 1c.

The first optical element 301, the second optical element 302, and the third optical element 303 are optical components for controlling the optical path of the transmitted light L2 output from the fluorescence-emitting module 1c. As an example, each of the first optical element 301, the second optical element 302, and the third optical element 303 is a lens for focusing the transmitted light L2. As described above, the thicker the phosphor substrate 10c, the larger the emission spot area of the transmitted light L2 due to scattering. In this case, the first optical element 301, the second optical element 302, and the third optical element 303 become larger, and accordingly, the projector 500 also becomes larger. Therefore, it is necessary to control the emission spot area of the transmitted light L2, that is, to control the thickness of the phosphor substrate 10c.

As described above, the fourth optical element 304 focuses and controls the optical path of the excitation light L1 output from the two light emitting units 200.

Next, we will explain the behavior of light in Figure 4A.

Excitation light L1 emitted by the light emitting unit 200 enters the blue-transmitting dichroic multilayer film 40 via the fourth optical element 304. The excitation light L1 then enters the phosphor substrate 10c. A portion of the incident excitation light L1 is wavelength-converted by the phosphor material and passes through the phosphor substrate 10c as fluorescence. The other portion of the incident excitation light L1 passes through the phosphor substrate 10c without being wavelength-converted by the phosphor material. The transmitted light L2 that passes through the phosphor substrate 10c is a composite light containing yellow fluorescence and unwavelength-converted blue excitation light L1, and is white light. The transmitted light L2 enters the anti-reflection layer 30. The transmitted light L2 then exits the fluorescence-emitting module 1c (more specifically, the phosphor substrate 10c) with a substantially Lambertian light distribution.

Transmitted light L2 emitted from the fluorescence-emitting module 1c is collected and emitted by the first optical element 301, the second optical element 302, and the third optical element 303. Note that the first optical element 301, the second optical element 302, and the third optical element 303 do not have to collect the transmitted light L2 emitted from the fluorescence-emitting module 1c. For example, the first optical element 301, the second optical element 302, and the third optical element 303 may substantially collimate or weakly expand and radiate the emitted transmitted light L2. It is sufficient that the radiation angle of the transmitted light L2 emitted from the first optical element 301, the second optical element 302, and the third optical element 303 is a radiation angle that allows efficient light transmission in the projector 500 and lighting device in which the fluorescence-emitting module 1c is used.

Transmitted light L2 (i.e., output light from the light source module 600) emitted from the first optical element 301, second optical element 302, and third optical element 303 travels toward the homogenizing optical system 601. As described above, transmitted light L2 output from the light source module 600 is controlled in the order of the homogenizing optical system 601, display element unit 602, and light projecting unit 603, and becomes projected light that is enlarged and projected onto a screen. In other words, transmitted light L2 is light that is used as projection light output by the projector 500.

Furthermore, in this embodiment, a portion of the excitation light L1 is wavelength-converted by the phosphor material and passes through the phosphor substrate 10c. The other portion of the excitation light L1 passes through the phosphor substrate 10c without being wavelength-converted by the phosphor material. In this way, the transmitted light L2 that passes through the phosphor substrate 10c can be used, for example, as projection light. In other words, a fluorescence-emitting module 1c that can be used as a light-transmitting phosphor wheel is realized.

Furthermore, in this embodiment, the projector 500, which is an example of a light-emitting device, is equipped with a fluorescent light-emitting module 1c that has high light utilization efficiency. Therefore, the projector 500 has high light utilization efficiency.

<Placement>
As described above, the transmitted light L2 is emitted from the phosphor substrate 10c with a substantially Lambertian light distribution. In order to efficiently control the transmitted light L2 emitted from the phosphor substrate 10c with a substantially Lambertian light distribution, it is necessary to arrange the first optical element 301 close to the phosphor substrate 10c. On the other hand, since it is only necessary for the fourth optical element 304 to focus the excitation light L1 on the phosphor substrate 10c, the distance from the phosphor substrate 10c to the exit surface of the fourth optical element 304 can be made greater than the distance from the phosphor substrate 10c to the incident side surface of the first optical element 301. (For example, in this case, the spot size of the excitation light L1 on the phosphor substrate 10c is smaller than the spot size of the transmitted light L2.) Therefore, it is preferable to install the rotating unit 100 in the negative direction of the z-axis of the phosphor substrate 10c so that there is no interference between the rotating unit 100 and the optical elements (first optical element 301, second optical element 302, third optical element 303, and fourth optical element 304).

(Embodiment 2)
[Configuration of the fluorescence emission module]
Next, a fluorescence-emitting module 1 according to a second embodiment will be described with reference to Figures 1 and 2. Figure 1 is a perspective view of the fluorescence-emitting module 1 according to the present embodiment. Figure 2 is a cross-sectional view showing a cut surface of part of the fluorescence-emitting module 1 taken along line II-II in Figure 1.

The fluorescent light-emitting module 1 is a module comprising a phosphor substrate 10 made of sintered phosphor, an anti-reflection layer 30, a blue-transmitting dichroic multilayer film 40, a rotating section 100, and two light-emitting sections 200. For simplicity, only one light-emitting section 200 is shown in Figures 1 and 2.

In other words, in this embodiment, the phosphor substrate 10 is different from the phosphor substrate 10c according to embodiment 1 in that it is made of a sintered phosphor containing a phosphor material and a highly thermally conductive material.

<Explanation of phosphor substrate>
The phosphor substrate 10 is a substrate constituted by a sintered phosphor having a phosphor material and a high thermal conductivity material, and is a substrate having a circular shape as described above. That is, the phosphor substrate 10 is a disk shape having a flat surface. Specifically, here, the phosphor substrate 10 is a substrate constituted only by a sintered phosphor, and the sintered phosphor has only the phosphor material and the high thermal conductivity material as main components.

More specifically, as shown in FIG. 2, the phosphor substrate 10 is composed of a fluorescent structure 11 and multiple heat conduction structures 12. The fluorescent structure 11 is a structure composed of the fluorescent material contained in the sintered phosphor. The multiple heat conduction structures 12 are multiple structures composed of the highly thermally conductive material contained in the sintered phosphor.

Now, we will explain the sintered phosphor used in this embodiment.

A sintered phosphor is a fired body obtained by firing raw material powders of the above-mentioned main components, the phosphor material and the high thermal conductivity material (for example, granules formed by granulating the raw material powders of these materials), at a temperature lower than the melting point of these materials. In addition, in the sintered phosphor, the raw material powders are bonded together during the firing process. Therefore, the sintered phosphor hardly requires a binder for bonding the granules together. More specifically, the sintered phosphor does not require any binder at all. As an example, the binder in the above Patent Document 1 is a transparent resin. Furthermore, known materials used as the binder include Al ₂ O ₃ material and glass material (i.e., SiO _d (0 < d ≦ 2)). Similarly, the sintered phosphor is not limited to a binder, and hardly requires any materials (hereinafter referred to as other materials) other than the phosphor material and high thermal conductivity material contained in the sintered phosphor, and more specifically, does not require any other materials at all.

For example, when the total volume of the sintered phosphor is taken as 100 vol%, it is preferable that the total volume of the phosphor material and high thermal conductivity material in the total volume of the sintered phosphor be 70 vol% or more. Furthermore, it is better if the total volume of the phosphor material and high thermal conductivity material in the total volume of the sintered phosphor is 80 vol% or more, even better if it is 90 vol% or more, and even better if it is 95 vol% or more.

In other words, when the total volume of the sintered phosphor is taken as 100 vol%, it is preferable that the volume of other materials (e.g., binder) in the total volume of the sintered phosphor be less than 30 vol%. Furthermore, it is better that the volume of other materials (e.g., binder) in the total volume of the sintered phosphor be 20 vol% or less, even better that it be 10 vol% or less, and even better that it be 5 vol% or less.

<High thermal conductivity materials>
Next, the multiple heat conduction structures 12 made of a highly thermally conductive material will be described. The shape of the highly thermally conductive material, more specifically, the shape of each of the multiple heat conduction structures 12, is, for example, a particulate shape. The multiple heat conduction structures 12 made of a highly thermally conductive material are arranged on the phosphor substrate 10 so as to be surrounded by the fluorescent structure 11. Although not shown, the multiple heat conduction structures 12 may be arranged so that a portion of each of the multiple heat conduction structures 12 protrudes from the fluorescent structure 11. The fluorescent structure 11 serves as a base material for the multiple heat conduction structures 12. In other words, the multiple heat conduction structures 12 are embedded in the fluorescent structure 11. Some of the multiple heat conduction structures 12 are in contact with each other, i.e., in a so-called string-like state. The particle diameter of each of the multiple heat conduction structures 12, which is in a particulate shape, is, for example, 1 μm or more and 100 μm or less.

It is known that when the temperature of the phosphor substrate 10 increases due to irradiation with excitation light L1, a phenomenon occurs in which the amount of fluorescence generated decreases (known as thermal quenching). For example, when thermal quenching occurs in the fluorescence-emitting module disclosed in Patent Document 1, the amount of fluorescence emitted from the fluorescence generating unit decreases, resulting in problems such as a decrease in the light utilization efficiency of the fluorescence-emitting module.

However, in this embodiment, the sintered phosphor contains a highly thermally conductive material, which suppresses the decrease in fluorescence. Specifically, this is as follows:

A high-thermal-conductivity material is a material with a thermal conductivity of 100 W/m·K or more and 300 W/m·K or less, and has a higher thermal conductivity than phosphor materials such as YAG:Ce. Furthermore, the thermal conductivity of a high-thermal-conductivity material is preferably 130 W/m·K or more and 200 W/m·K or less, and even more preferably 145 W/m·K or more and 170 W/m·K or less. When the sintered phosphor constituting the phosphor substrate 10 contains a high-thermal-conductivity material, heat generated in the phosphor substrate 10 is easily transferred. In other words, the heat dissipation properties of the phosphor substrate 10 are improved. This suppresses the temperature rise of the phosphor substrate 10 due to irradiation with excitation light L1, thereby suppressing the decrease in fluorescence. In other words, a fluorescence-emitting module 1 with high light utilization efficiency is realized. Furthermore, because the decrease in fluorescence is suppressed, changes in the chromaticity of the transmitted light L2 can be suppressed. This results in a highly reliable fluorescence-emitting module 1.

Furthermore, if each of the multiple heat conduction structures 12 has a particle shape and the multiple heat conduction structures 12 are in contact with each other, the heat is more easily transmitted through the multiple heat conduction structures 12, thereby further improving the heat dissipation properties of the phosphor substrate 10.

<Types of high thermal conductive materials>
The high thermal conductivity material according to this embodiment is made of W, but as another example, it may be made of the following metal elements in terms of thermal conductivity, melting point, and linear expansion coefficient.

The high thermal conductivity material is, for example, a material containing at least one of Rh, Mo, W, SiC, and AlN. It is also preferable that the high thermal conductivity material be composed of one or more metal elements, alloys, or compounds selected from the above materials. The thermal conductivity of each element is 150 W/m·K for Rh, 135 W/m·K for Mo, 163 W/m·K for W, 200 W/m·K for SiC, and 150 W/m·K for AlN.

The thermal conductivity of these high thermal conductive materials is higher than the thermal conductivity of 11.2 W/m·K of the YAG:Ce that constitutes the phosphor material. Therefore, by including these high thermal conductive materials in the sintered phosphor, the heat dissipation properties of the phosphor substrate 10 can be improved.

Furthermore, the melting point of the high thermal conductivity material at atmospheric pressure is preferably 1700°C or higher and 3500°C or lower. For example, the melting points of the above metal elements and compounds at atmospheric pressure are 1963°C for Rh, 2623°C for Mo, 3422°C for W, 2730°C for SiC, and 2200°C for AlN. When manufacturing the phosphor substrate 10, it may be heated (fired) at a high temperature (e.g., 1650°C). Even in such cases, since the melting point of the high thermal conductivity material at atmospheric pressure is 1700°C or higher, melting of the high thermal conductivity material during the heat treatment is suppressed. Therefore, phosphor substrate 10 composed of a sintered phosphor containing a phosphor material and a high thermal conductivity material can be easily manufactured.

<Coefficient of thermal expansion>
The linear expansion coefficient of the high thermal conductivity material is preferably 1×10 ⁻⁷ /K or less. The linear expansion coefficient of the high thermal conductivity material is preferably 1×10 ⁻⁶ /K or more. In other words, the linear expansion coefficient of the high thermal conductivity material is close to the linear expansion coefficient of the phosphor material (the linear expansion coefficient of YAG:Ce is 8×10 ⁻⁶ /K). For example, the linear expansion coefficients of the above metal elements and compounds are 8.2×10 ⁻⁶ /K for Rh, 4.8×10 ⁻⁶ /K for Mo, 4.5×10 ⁻⁶ /K for W, 3.7×10 ⁻⁶ /K for SiC, and 4.0×10 ⁻⁶ /K for AlN.

When the linear expansion coefficient of the high thermal conductivity material is the above value, it becomes close to the linear expansion coefficient of the phosphor material. Therefore, even if the temperature of the phosphor substrate 10 increases due to irradiation with excitation light L1, peeling between the phosphor material and the high thermal conductivity material is suppressed. In other words, a highly reliable fluorescent light-emitting module 1 is realized.

<Summary>
In summary, when the high thermal conductivity material is any of Rh, Mo, W, SiC, and AlN, the thermal conductivity, linear expansion coefficient, and melting point of the high thermal conductivity material satisfy the above-mentioned values. This improves the heat dissipation of the phosphor substrate 10 and prevents peeling between the phosphor material and the high thermal conductivity material. This means that a highly reliable fluorescent light-emitting module 1 with high light utilization efficiency is achieved. Furthermore, since the high thermal conductivity material is prevented from melting during the manufacturing process of the phosphor substrate 10, the phosphor substrate 10 can be easily manufactured.

<Ratio of high thermal conductive materials>
The ratio of the phosphor material and the high thermal conductivity material in the phosphor substrate 10 is, for example, as follows: When the volume of the phosphor material is taken as 100, the volume of the high thermal conductivity material is preferably between 1 and several tens. The larger the volume of the high thermal conductivity material, the more the heat dissipation of the phosphor substrate 10 can be improved. When the volume of the high thermal conductivity material is within the above range, sufficient heat dissipation of the phosphor substrate 10 can be achieved.

<High thermal conductivity segmentation>
Furthermore, the phosphor substrate 10 according to this embodiment has a first region 21 and a second region 22. That is, the phosphor substrate 10 according to this embodiment is segmented into the first region 21 and the second region 22. More specifically, in a plan view, the phosphor substrate 10 has the first region 21 and a plurality of second regions 22. Note that in Fig. 1, the first region 21 is indicated by a dot, and in Fig. 2, the first region 21 is indicated by a dashed line, and the plurality of second regions 22 are rectangular regions surrounded by dashed double-dot lines.

The first region 21 and the multiple second regions 22 have different amounts of high thermal conductivity material. The multiple second regions 22 have a higher amount of high thermal conductivity material than the first region 21. In other words, the first region 21 only needs to have a lower amount of high thermal conductivity material than the multiple second regions 22, and the first region 21 in this embodiment does not contain high thermal conductivity material. However, the first region 21 may contain high thermal conductivity material. Furthermore, the excitation light L1 emitted by the light emitting unit 200 is incident on the first region 21.

When excitation light L1 is incident on a highly thermally conductive material (more specifically, multiple thermally conductive structures 12 made of highly thermally conductive material), the excitation light L1 is scattered or absorbed by the multiple thermally conductive structures 12, resulting in a decrease in the amount of fluorescence generated. Therefore, if the phosphor substrate 10 has a first region 21 and multiple second regions 22, when excitation light L1 is incident on the first region 21, which contains a smaller amount of highly thermally conductive material, the amount of fluorescence generated in the first region 21 increases. In other words, the light utilization efficiency of the fluorescence light-emitting module 1 can be further improved. It is preferable that the first region 21 does not contain a highly thermally conductive material. This increases the efficiency of wavelength conversion by the phosphor material.

As shown in FIG. 1, when the phosphor substrate 10 is viewed in a plan view, the first region 21 has an annular shape, and the center of the annular shape overlaps with the center point C1 of the phosphor substrate 10. The first region 21 is provided in a circular ring shape on a circumference that is equidistant from the center point C1 of the phosphor substrate 10. In other words, the first region 21 is provided in a band shape along the circumferential direction in a plan view.

Because the first region 21 has the above-described shape, the rotating unit 100 can more easily rotate the phosphor substrate 10 around the axis A1. In other words, it becomes easier to use the phosphor substrate 10 as a phosphor wheel.

Furthermore, when the phosphor substrate 10 is viewed in plan, the multiple second regions 22 are provided on the inside and outside of the annular shape of the first region 21. The second region 22 provided on the inside of the multiple second regions 22 will be referred to as the "inner second region 22," and the second region 22 provided on the outside of the multiple second regions 22 will be referred to as the "outer second region 22."

The inner second region 22 is disc-shaped, and the center of the disc overlaps with the center point C1 of the phosphor substrate 10. The inner second region 22 is in contact with the inner surface of the first region 21. The outer second region 22 is annular, like the first region 21, and the center of the annular shape overlaps with the center point C1 of the phosphor substrate 10. The outer second region 22 is in contact with the outer surface of the first region 21. In other words, the first region 21 is sandwiched between the inner second region 22 and the outer second region 22.

At this time, the heat generated in the first region 21 by irradiation with the excitation light L1 can be transferred to both of the two second regions 22 that sandwich the first region 21. In this case, the heat dissipation properties of the phosphor substrate 10 can be improved compared to, for example, a case in which the fluorescence-emitting module 1 has a second region 22 only on either the inside or outside of the first region 21. This makes it possible to suppress the rise in temperature of the phosphor substrate 10, thereby further suppressing the decrease in fluorescence.

Furthermore, as shown in Figures 1 and 2, the phosphor substrate 10 does not need to be supported by other components. In other words, the phosphor substrate 10 has rigid properties. Since the fluorescent structure 11 is a sintered phosphor and the thickness of the phosphor substrate 10 is within the above range, the phosphor substrate 10 has rigid properties. Furthermore, compared to the fluorescence generating section formed from a paint containing a phosphor and a transparent resin, as disclosed in Patent Document 1, the phosphor substrate 10 of this embodiment has much more rigid properties.

Furthermore, the fluorescence-emitting module 1 according to the present embodiment may be applied to the projector 500 in place of the fluorescence-emitting module 1c according to embodiment 1. In this case, too, the excitation light L1 is incident on the first region 21 of the phosphor substrate 10. In this way, by having the excitation light L1 incident on the first region 21, which has a lower content of highly thermally conductive material, the fluorescence can be increased, and the light utilization efficiency of the fluorescence-emitting module 1 can be further improved.

In this case, a portion of the incident excitation light L1 is wavelength-converted by the phosphor material contained in the first region 21 and passes through the phosphor substrate 10 as fluorescence. The other portion of the incident excitation light L1 passes through the phosphor substrate 10 without being wavelength-converted by the phosphor material contained in the first region 21. In this way, transmitted light L2 that passes through the phosphor substrate 10 can be used, for example, as projection light. In other words, a fluorescence-emitting module 1 that can be used as a light-transmitting phosphor wheel is realized.

<Effects of high thermal conductivity materials>
Furthermore, in the present embodiment, the sintered phosphor constituting the phosphor substrate 10 contains a highly thermally conductive material, thereby improving the heat dissipation of the phosphor substrate 10. This makes it possible to suppress an increase in the temperature of the phosphor substrate 10 due to irradiation with the excitation light L1, thereby suppressing a decrease in fluorescence and realizing a fluorescence light-emitting module 1 with higher light utilization efficiency.

In addition, since the sintered phosphor that makes up the phosphor substrate 10 is made of a highly thermally conductive material, the heat dissipation properties of the phosphor substrate 10 are improved and the temperature rise of the phosphor substrate 10 can be suppressed, making it possible to increase the energy of the excitation light L1 that can be input with a small-sized phosphor wheel. In other words, it becomes possible to emit a large luminous flux of light from a smaller size. As a specific example, the size of a phosphor wheel used in a projector that outputs 6000 lm of light was previously φ65 mm, but by including 60 vol% W as a highly thermally conductive material, it is possible to reduce the size to φ50 mm.

In summary, a highly reliable fluorescent light-emitting module 1 with high light utilization efficiency is realized.

[Manufacturing method]
Here, a method for manufacturing the phosphor substrate 10 will be briefly described.

The phosphor material is composed of a crystalline phase represented by (Y _0.999 Ce _0.001 ) ₃ Al ₅ O _12. Furthermore, all of the phosphor materials are composed of a Ce ³⁺ activated phosphor.

The following four types of compound powders were used as raw materials to manufacture the phosphor substrate 10. Specifically, the raw materials were Y ₂ O ₃ , Al ₂ O ₃ , CeO ₂ , and W. The purity and manufacturers of the respective materials were as follows: Y ₂ O ₃ , 3N purity, from Nippon Yttrium Co., Ltd.; Al ₂ O ₃ , 3N purity, from Sumitomo Chemical Co., Ltd.; CeO ₂ , 3N purity, from Nippon Yttrium Co., Ltd.; and W, 4N purity, from High Pure Chemical Research Institute Co., Ltd.

Here, two types of mixed raw materials are used. The two types of mixed raw materials are a first mixed raw material that does not contain W, and a second mixed raw material that contains W.

First, the first mixed raw material will be described. Y ₂ O ₃ , Al ₂ O ₃ , and CeO ₂ were weighed as the raw materials to obtain a compound with a stoichiometric composition of (Y _0.999 Ce _0.001 ) ₃ Al ₅ O _12. Next, the weighed raw materials and alumina balls (diameter 10 mm) were placed in a plastic pot. The amount of alumina balls was such that they filled about one-third of the volume of the plastic pot. Then, pure water was placed in the plastic pot, and the raw materials and pure water were mixed using a pot rotating device (BALL MILL ANZ-51S, manufactured by Nitto Chemical Co., Ltd.). This mixing was carried out for 12 hours. In this way, a slurry-like first mixed raw material was obtained.

The first mixed raw material was granulated using a spray dryer. During granulation, an acrylic binder was used as the adhesive (binder).

Next, the second mixed raw material will be described. _Y2O3 , _{Al2O3 ,} and _CeO2 were weighed as the raw materials to obtain a compound with a stoichiometric composition _{of Y3(Al0.999Cr0.001)5O12 . Furthermore , W was} weighed so that the volume of W was 10 when the volume of the phosphor material to be produced was 100. Next, the weighed _Y2O3 , _{Al2O3 , CeO2 ,} and W, along with alumina balls (diameter 10 mm), were placed in a plastic pot. The following procedure was followed in the same manner as for the first mixed raw material, and the second mixed raw material was granulated.

Next, we will explain the molding of the first mixed raw material and the second mixed raw material using Figure 5A.

Figure 5A is a perspective view of a mold 400 for manufacturing the phosphor substrate 10 according to this embodiment.

The granulated first and second mixed raw materials were pre-molded into a cylindrical shape using an electric hydraulic press (EMP-5, manufactured by Riken Seiki Co., Ltd.) and a cylindrical mold 400 with a bottom. The molding pressure was 5 MPa. At this time, the first mixed raw material, which did not contain W, was placed in the sixth area A4 of the mold 400, and the second mixed raw material, which contained W, was placed in the fifth area A3 and seventh area A5 of the mold 400.

As shown in FIG. 5A, a first partition 401 and a second partition 402 are provided inside the mold 400. The first partition 401 and the second partition 402 each have a bottomless cylindrical shape. The diameter of the first partition 401 is smaller than the diameter of the second partition 402, and the first partition 401 is positioned inside the second partition 402. The first partition 401 and the second partition 402 are made of a material (e.g., a resin material) that can be removed by heat treatment or the like.

The mold 400 is divided into three regions by a first partition 401 and a second partition 402. The three regions are a fifth region A3 having a cylindrical shape located at the center of the mold 400, a sixth region A4 having a bottomless cylindrical shape surrounding the fifth region A3, and a seventh region A5 having a bottomless cylindrical shape surrounding the sixth region A4. The fifth region A3 is surrounded by the first partition 401 and the bottom surface of the mold 400. The sixth region A4 is surrounded by the first partition 401, the second partition 402, and the bottom surface of the mold 400. The seventh region A5 is surrounded by the second partition 402 and the bottom and side surfaces of the mold 400.

Next, the pre-molded body was finally molded using a cold isostatic pressing device. The pressure during final molding was 300 MPa.

The molded body after heat treatment was fired in a tubular atmosphere furnace. The firing temperature was 1675°C. The firing time was 4 hours. The firing atmosphere was a mixed gas atmosphere of nitrogen and hydrogen. The adhesive used during granulation and the resin material used for the first partition 401 and second partition 402 were decomposed and removed during the temperature rise process, for example, at around 500°C.

After firing, the cylindrical fired product was sliced using a multi-wire saw. The sliced fired product was then polished to adjust the thickness of the fired product. This adjustment resulted in the fired product becoming the phosphor substrate 10.

Furthermore, the first mixed raw material in the sixth region A4 corresponds to the first region 21 of the phosphor substrate 10. The second mixed raw material in the fifth region A3 corresponds to the inner second region 22 of the phosphor substrate 10, and the second mixed raw material in the seventh region A5 corresponds to the outer second region 22 of the phosphor substrate 10.

The first partition 401 and second partition 402 may be made of a metal material. In this case, after the first mixed raw material is placed in the sixth area A4 and the second mixed raw material is placed in the fifth area A3 and the seventh area A5, the first partition 401 and second partition 402 are removed, for example, by being pulled upward. This allows the first mixed raw material to be held in the sixth area A4 and the second mixed raw material to be held in the fifth area A3 and the seventh area A5.

(Embodiment 3)
[Configuration of the fluorescence emission module]
Next, a fluorescence-emitting module 1d according to a third embodiment will be described with reference to Fig. 11 and Fig. 12. Fig. 11 is a perspective view of the fluorescence-emitting module 1d according to the present embodiment. Fig. 12 is a cross-sectional view showing a cut surface of part of the fluorescence-emitting module 1d taken along line XII-XII in Fig. 11.

The fluorescence-emitting module 1d is a module comprising a phosphor substrate 10d made of a sintered phosphor, an anti-reflection layer 30, a blue-transmitting dichroic multilayer film 40, a rotating unit (not shown), and two light-emitting units 200. For simplicity, only one light-emitting unit 200 is shown in Figures 11 and 12. The rotating unit according to this embodiment has the same configuration as the rotating unit 100 described above. Furthermore, in Figure 11, the axis A1 on the negative side of the z-axis from the blue-transmitting dichroic multilayer film 40 is not shown. The light-emitting unit 200 also emits excitation light L1, as described above.

The fluorescent light-emitting module 1d according to this embodiment differs mainly from the fluorescent light-emitting modules 1c and 1 according to embodiments 1 and 2 in that the phosphor substrate 10d is composed of a sintered phosphor containing a phosphor material and an oxide material that does not contain a luminescent center element.

The phosphor substrate 10d is a substrate composed of a sintered phosphor containing a phosphor material and an oxide material that does not contain a luminescent center element, and has a circular shape. In other words, the phosphor substrate 10d has a disk shape with a flat surface. The phosphor substrate 10d is a substrate composed only of a sintered phosphor, and the sintered phosphor contains only the phosphor material as its main component and an oxide material that does not contain a luminescent center element.

More specifically, as shown in FIG. 12, the phosphor substrate 10d is composed of a fluorescent structure 11d and an oxide structure 13d. Note that, as shown in FIG. 11, the phosphor substrate 10d is provided with a fluorescent structure 11d and two oxide structures 13d. In other words, the phosphor substrate 10d is composed of a fluorescent structure 11d and two oxide structures 13d, and the two oxide structures 13d have the same configuration. Each of the two oxide structures 13d is represented by an area surrounded by a dotted line in FIG. 11.

Fluorescent structure 11d is a structure composed of the phosphor material contained in the sintered phosphor. More specifically, fluorescent structure 11d is a structure composed only of the phosphor material contained in the sintered phosphor.

The oxide structure 13d is a structure composed of an oxide material that does not contain the luminescent center element of the sintered phosphor. More specifically, the oxide structure 13d is a structure composed only of an oxide material that does not contain the luminescent center element of the sintered phosphor. The oxide structure 13d is also an example of a first light-transmitting region of the phosphor substrate 10d. The first light-transmitting region is a region that is composed only of the oxide material that does not contain the luminescent center element, out of the phosphor material and the oxide material that does not contain the luminescent center element, and that transmits light that excites the phosphor material (excitation light L1).

As described above, the phosphor substrate 10d is a substrate having a circular shape. More specifically, the phosphor substrate 10d is a substrate whose circular shape is achieved by combining the phosphor structure 11d and two oxide structures 13d.

Here, the oxide structure 13d has an annular sector shape in a planar view of the phosphor substrate 10d. That is, the oxide structure 13d has a shape surrounded by two arcs and two straight lines. The term "annular sector" refers to a circular sector, a sector truncated sector, or a sector ring. Furthermore, the fluorescent structure 11d has a partially missing circular shape in a planar view of the phosphor substrate 10d. That is, by combining the oxide structure 13d with the portion of the fluorescent structure 11d, the phosphor substrate 10d becomes disk-shaped.

Here, as shown in Figure 11, the oxide structure 13d is arranged so that, in a plan view of the phosphor substrate 10d, the circumference of the circular phosphor substrate 10d overlaps with the outer arc of the two arcs representing the oxide structure 13d (i.e., the arc farther from the axis A1).

Now, we will explain the sintered phosphor used in this embodiment.

A sintered phosphor is a fired body obtained by firing raw material powders of the phosphor material, which is the main component, and an oxide material not containing a luminescent center element (for example, granules formed by granulating raw material powders of these materials) at a temperature lower than the melting point of these materials. In addition, in the sintered phosphor, the raw material powders are bonded together during the firing process. Therefore, the sintered phosphor hardly requires a binder for bonding the granules together. More specifically, the sintered phosphor does not require any binder at all. As an example, in the above Patent Document 1, the binder is a transparent resin. Furthermore, known materials used as the binder include Al ₂ O ₃ material and glass material (i.e., SiO _d (0 < d ≦ 2)). Similarly, without being limited to a binder, the sintered phosphor hardly requires any materials (hereinafter referred to as other materials) other than the phosphor material and the oxide material not containing a luminescent center element contained in the sintered phosphor, and more specifically, does not require any other materials at all.

For example, when the total volume of the sintered phosphor is taken as 100 vol%, it is preferable that the total volume of the phosphor material and the oxide material that does not contain a luminescent center element in the total volume of the sintered phosphor be 70 vol% or more. Furthermore, it is better that the total volume of the phosphor material and the oxide material that does not contain a luminescent center element in the total volume of the sintered phosphor be 80 vol% or more, even better that it be 90 vol% or more, and even better that it be 95 vol% or more.

In other words, when the total volume of the sintered phosphor is taken as 100 vol%, it is preferable that the volume of other materials (e.g., binder) in the total volume of the sintered phosphor be less than 30 vol%. Furthermore, it is better that the volume of other materials (e.g., binder) in the total volume of the sintered phosphor be 20 vol% or less, even better that it be 10 vol% or less, and even better that it be 5 vol% or less.

The fluorescent structure 11d, which is made of a fluorescent material, receives light incident on the fluorescent substrate 10d from the negative z-axis direction as excitation light L1 and emits fluorescence. More specifically, light emitted from the light emitting section 200 is irradiated as excitation light L1 onto the fluorescent material that makes up the fluorescent structure 11d, causing the fluorescent structure 11d to emit fluorescence as wavelength-converted light. In other words, the wavelength-converted light emitted from the fluorescent structure 11d is light with a longer wavelength than the wavelength of the excitation light L1.

The phosphor material in this embodiment is composed of YAG:Ce, as in embodiments 1 and 2, but may also be other phosphor materials as described above. In other words, the fluorescent structure 11d in this embodiment is composed of YAG:Ce.

In this embodiment, the wavelength-converted light emitted from the phosphor material (YAG:Ce) that constitutes the fluorescent structure 11d includes yellow fluorescent light. The phosphor material, for example, absorbs light with a wavelength of 380 nm or more and 490 nm or less, and emits yellow fluorescent light with a fluorescent peak wavelength in the wavelength range of 490 nm or more and 580 nm or less. By using YAG:Ce as the phosphor material, it is possible to easily emit fluorescent light with a fluorescent peak wavelength in the wavelength range of 490 nm or more and 580 nm or less.

In the above-described first and second embodiments, the transmitted light L2 contains fluorescent light, which is wavelength-converted yellow light, and excitation light L1, which is wavelength-unconverted blue light, and is a composite of these lights, resulting in white light.

However, in this embodiment, all of the excitation light L1 incident on the fluorescent structure 11d is wavelength-converted by the phosphor material and passes through the fluorescent structure 11d. Therefore, the transmitted light L3 that passes through the fluorescent structure 11d contains only wavelength-converted light. In other words, the transmitted light L3 is yellow light.

An example of an oxide material that does not contain a luminescent center element is aluminum oxide ( _Al2O3 ), which is a non-luminescent material obtained by removing the luminescent center element from the above-mentioned phosphor material. Note that _Al2O3 used as the _oxide material that does not contain a luminescent center element is different from the above-mentioned binder. Furthermore, the oxide material that does not contain a luminescent center element is _a material that has high transmittance in the wavelength region of the excitation light L1.

In this embodiment, the phosphor material is composed of YAG:Ce, and the luminescent center element is, for example, _Ce . Therefore, the non-luminescent material obtained by removing the luminescent center element from the phosphor material used in this embodiment is composed _{of Y3Al5O12} (i.e., YAG). As described above, the oxide structure 13d according to this embodiment is composed of _Y3Al5O12 ( _i.e. , _YAG ).

The oxide structure _13d made of _Y3Al5O12 transmits the excitation light L1, which is light incident on the phosphor substrate 10d from the negative direction of the z-axis. Unlike the fluorescent structure 11d, the oxide structure 13d does _not convert the wavelength of the excitation light L1. The transmittance of the oxide structure 13d in the wavelength region of the excitation light L1 is sufficient to be 50% or more, preferably 70% or more, even more preferably 80% or more, and even more preferably 90% or more. In other words, the wavelength region of the excitation light L1 does not change before and after passing through the oxide structure 13d, and here, the excitation light L1 is blue light.

Furthermore, the phosphor substrate 10d according to this embodiment has a third region 23 and a fourth region 24. In other words, the phosphor substrate 10d according to this embodiment is segmented into the third region 23 and the fourth region 24. More specifically, in a plan view, the phosphor substrate 10d has the third region 23 and multiple fourth regions 24. Note that in Figure 11, the third region 23 is indicated by a dot, and in Figure 12, the third region 23 is indicated by a dashed line, and the multiple fourth regions 24 are rectangular regions surrounded by dashed double-dot lines.

The third region 23 has the same shape as the first region 21 in embodiment 2, and the fourth region 24 has the same shape as the second region 22 in embodiment 2. However, as mentioned above, the phosphor substrate 10d does not contain a highly thermally conductive material.

As shown in FIG. 11, when the phosphor substrate 10d is viewed in a plan view, the third region 23 has an annular shape, and the center of the annular shape overlaps with the center point C1 of the phosphor substrate 10d. The third region 23 is provided in a circular ring shape on a circumference that is equidistant from the center point C1 of the phosphor substrate 10d. In other words, the third region 23 is provided in a band shape along the circumferential direction in a plan view. The excitation light L1 emitted by the light emitting unit 200 is incident on the third region 23. More specifically, as shown in FIG. 11, in this embodiment, the excitation light L1 is irradiated at a position of radius R from the center point C1 of the phosphor substrate 10d.

Furthermore, when the phosphor substrate 10d is viewed in a plan view, the third region 23 is provided with an oxide structure 13d (i.e., a first light-transmitting region). More specifically, when the phosphor substrate 10d is viewed in a plan view, the third region 23 is provided with a portion of the oxide structure 13d and a portion of the fluorescent structure 11d. Note that in Figure 11, among the dots indicating the third region 23, the third region 23 indicated by lighter dots has a portion of the oxide structure 13d provided therein, and the third region 23 indicated by darker dots has a portion of the fluorescent structure 11d provided therein.

Of the excitation light L1 incident on the third region 23, the excitation light L1 that enters the oxide structure 13d is transmitted through the oxide structure 13d. Furthermore, of the excitation light L1 incident on the third region 23, the excitation light L1 that enters the fluorescent structure 11d is wavelength converted by the fluorescent structure 11d and is emitted as transmitted light L3, which is wavelength-converted light.

Furthermore, when the phosphor substrate 10d is viewed in plan, the multiple fourth regions 24 are provided on the inside and outside of the annular shape of the third region 23. The fourth region 24 provided on the inside of the multiple fourth regions 24 will be referred to as the "inner fourth region 24," and the fourth region 24 provided on the outside of the multiple fourth regions 24 will be referred to as the "outer fourth region 24."

The inner fourth region 24 is disc-shaped, and the center of the disc overlaps with the center point C1 of the phosphor substrate 10d. The inner fourth region 24 is in contact with the inner surface of the third region 23. The outer fourth region 24 is annular, like the third region 23, and the center of the annular shape overlaps with the center point C1 of the phosphor substrate 10d. The outer fourth region 24 is in contact with the outer surface of the third region 23. In other words, the third region 23 is sandwiched between the inner fourth region 24 and the outer fourth region 24.

In this embodiment, the sintered phosphor further includes an oxide material that does not contain a luminescent center element. The phosphor substrate 10d is composed of only the oxide material of the phosphor material and oxide material, and has a first light-transmitting region that transmits light (excitation light L1) that excites the phosphor material.

As a result, when excitation light L1 is incident on the first light-transmitting region (i.e., oxide structure 13d) made of an oxide material that does not contain a luminescent center element, the excitation light L1 passes through the oxide structure 13d, and excitation light L1 is emitted from the phosphor substrate 10d. Similarly, when excitation light L1 is incident on fluorescent structure 11d made of a phosphor material, the excitation light L1 is wavelength-converted by fluorescent structure 11d, and transmitted light L3, which is wavelength-converted light, is emitted from the phosphor substrate 10d.

As a result, as the rotating portion rotates, the phosphor substrate 10d can emit excitation light L1 and wavelength-converted light in a time-division manner. In this embodiment, the phosphor substrate 10d can emit yellow light as excitation light L1 and blue light as wavelength-converted light in a time-division manner.

Furthermore, the fluorescence-emitting module 1d according to this embodiment may be applied to the projector 500 in place of the fluorescence-emitting module 1c according to embodiment 1. In this case, the projector 500 includes a DLP as the display element section 602, and can therefore be used as a 1-DLP (one-chip DLP) type projector.

In addition, in this embodiment, the oxide material is aluminum oxide or a non-luminescent material in which the luminescent center element has been removed from a phosphor material.

These materials have high light transmittance for excitation light L1 (i.e., light that excites the phosphor material). Therefore, the transmittance of excitation light L1 in the first light-transmitting region (oxide structure 13d) is high, and loss of excitation light L1 due to absorption is suppressed. This makes it possible to realize a fluorescence-emitting module 1d with high light utilization efficiency.

In addition, in this embodiment, when the phosphor substrate 10d is viewed in plan, the phosphor substrate 10d has a third region 23 having a circular ring shape, the center of which overlaps with the center (center point C1) of the phosphor substrate 10d, and a first light-transmitting region is provided in the third region 23. Furthermore, in this embodiment, the third region 23 also has a fluorescent structure 11d provided therein.

Because the third region 23 has the above-described shape, when excitation light L1 is incident on the third region 23, it becomes easier to use the phosphor substrate 10d, which can emit excitation light L1 and wavelength-converted light in a time-division manner, as a phosphor wheel.

In this embodiment, the fluorescence-emitting module 1d further includes a light-emitting section 200 that emits excitation light L1, which excites the phosphor material and enters the third region 23.

In this way, by the excitation light L1 being incident on the third region 23 where the fluorescent structure 11d and the oxide structure 13d are provided, the phosphor substrate 10d can more easily emit the excitation light L1 and the wavelength-converted light in a time-division manner.

In this embodiment, two oxide structures 13d are provided, but this is not limited to this. For example, one oxide structure 13d may be provided, or three or more oxide structures 13d may be provided.

In another example of this embodiment, when the phosphor material is composed of a phosphor material other than ( _{Y1 -xCe x )3Al5O12 (} 0.0001≦x<0.1), a non-luminescent material obtained by removing the luminescent center element from the phosphor material may be used. That is, for example, when the phosphor material is composed of (Lu1 _{-yCe y} ) _3Al2Al3O12 ( _0.001 ≦ _{y < 0.1} ), the non- _luminescent material obtained by removing the luminescent center element from the phosphor material may be composed of _Lu3Al5O12 .

[Manufacturing method]
Here, a method for manufacturing the phosphor substrate 10d will be briefly described.

The phosphor material is composed of a crystalline phase represented by (Y _0.999 Ce _0.001 ) ₃ Al ₅ O _12. Furthermore, all of the phosphor materials are composed of a Ce ³⁺ activated phosphor.

To manufacture the phosphor substrate 10d, the following three types _of compound powder were used as raw materials: _Y2O3 , _Al2O3 , and _CeO2 . The purity and manufacturers of the raw materials were: _Y2O3 , _3N purity, from Nippon Yttrium Co., Ltd.; _Al2O3 , 3N purity, from Sumitomo Chemical Co., Ltd.; _{and CeO2 , 3N} purity, from Nippon Yttrium Co., Ltd.

Here, two types of mixed raw materials are used. The two types of mixed raw materials are a first mixed raw material containing _CeO2 and a third mixed raw material not containing _CeO2 . Note that, since the first mixed raw material according to this embodiment is the same as the first mixed raw material according to the second embodiment, the steps up to the granulation of the first mixed raw material will be omitted.

First, the third mixed raw material will be described. _{Y2O3 and Al2O3} were weighed as the raw materials so as to obtain a compound _Y3Al5O12 having a stoichiometric composition. Next, _{the weighed Y2O3 and Al2O3 and alumina} balls (diameter 10 _{mm )} were placed in a plastic pot. The following procedure was followed in the same way as for the first mixed raw material _, and the third mixed raw material was granulated.

Next, we will explain how to mold the first mixed raw material and the third mixed raw material.

In the manufacturing method according to this embodiment, as in the second embodiment, a cylindrical mold with a partition on the inside is used. Here, the mold is divided into three regions by two partitions. The first mixed raw material is placed in one of the three regions, and the third mixed raw material is placed in the other two of the three regions. When the cylindrical bottom surface of the mold is viewed from above, the two regions in which the third mixed raw material is placed are each annular sector, and the shape of the one region in which the first mixed raw material is placed is a circle with two annular sectors removed. In other words, the two partitions are provided so that the first mixed raw material placed in one region corresponds to the fluorescent structure 11d, and the third mixed raw material placed in the other two regions corresponds to two oxide structures 13d.

Apart from the shape of the mold, the phosphor substrate 10d is manufactured by performing the same processes as in embodiments 1 and 2.

(Fourth embodiment)
[Configuration of the fluorescence emission module]
Next, a fluorescence light emitting module 1f according to a fourth embodiment will be described with reference to Fig. 13. Fig. 13 is a perspective view of the fluorescence light emitting module 1f according to the present embodiment.

The fluorescence-emitting module 1f is a module comprising a phosphor substrate 10f made of sintered phosphor, an anti-reflection layer 30, a blue-transmitting dichroic multilayer film 40, a rotating section (not shown), and two light-emitting sections 200. For simplicity, only one light-emitting section 200 is shown in Figure 13. The rotating section in this embodiment has the same configuration as the rotating section 100 described above. The light-emitting section 200 also emits excitation light L1, as described above.

The fluorescent light-emitting module 1f according to this embodiment differs from the fluorescent light-emitting module 1d according to embodiment 3 mainly in that the phosphor substrate 10f has a second light-transmitting region 14f instead of the first light-transmitting region (oxide structure 13d). In other words, the fluorescent sintered body according to this embodiment contains only phosphor material, and does not contain an oxide material that does not contain a luminescent center element.

The phosphor substrate 10f according to the present embodiment is a substrate made of a sintered phosphor having a phosphor material. The phosphor substrate 10f according to the present embodiment is a substrate having two second light transmitting regions 14f, a third region 23, and a fourth region 24. The phosphor substrate 10f according to the present embodiment is made of the phosphor structure 11d shown in the third embodiment.

The second light-transmitting region 14f is an opening in the phosphor substrate 10f. In other words, the second light-transmitting region 14f is composed of at least one of a through-hole that penetrates the phosphor substrate 10f in the thickness direction (z-axis direction) of the phosphor substrate 10f, and a cutout portion in the phosphor substrate 10f. Here, the second light-transmitting region 14f corresponds to the cutout portion. The second light-transmitting region 14f has the same shape as the oxide structure 13d (first light-transmitting region) shown in embodiment 3, but is not limited to this.

Here, we will explain the sintered phosphor used in this embodiment.

A sintered phosphor is a fired body in which raw material powder of the phosphor material (for example, granules formed by granulating raw material powder of the phosphor material), which is the main component described above, is fired at a temperature lower than the melting point of the phosphor material. In other words, the sintered phosphor of this embodiment is the same as the sintered phosphor of embodiment 1.

As described in embodiment 3, when excitation light L1 is incident on the fluorescent structure 11d, it emits wavelength-converted light (yellow light) with a wavelength longer than that of the excitation light L1 as transmitted light L3.

When excitation light L1 is incident on the second light-transmitting region 14f, it transmits the excitation light L1, which is blue light.

Furthermore, the phosphor substrate 10f according to this embodiment has segmented third regions 23 and fourth regions 24. More specifically, in plan view, the phosphor substrate 10f has the third region 23 and multiple fourth regions 24. Note that in Figure 13, the third regions 23 are indicated by dots.

The excitation light L1 emitted by the light emitting unit 200 is incident on the third region 23. More specifically, as shown in FIG. 13, in this embodiment, the excitation light L1 is irradiated at a position that is a radius R from the center point C1 of the phosphor substrate 10f.

Furthermore, when the phosphor substrate 10f is viewed in a plan view, the third region 23 is provided with a second light-transmitting region 14f. More specifically, when the phosphor substrate 10f is viewed in a plan view, the third region 23 is provided with a part of the second light-transmitting region 14f and a part of the fluorescent structure 11d. Note that in Figure 13, among the dots indicating the third region 23, the third region 23 indicated by lighter dots is provided with a part of the second light-transmitting region 14f, and the third region 23 indicated by darker dots is provided with a part of the fluorescent structure 11d.

In this embodiment, the phosphor substrate 10f has a second light-transmitting region 14f that transmits light (excitation light L1) that excites the phosphor material. The second light-transmitting region 14f is configured by at least one of a through-hole that penetrates the phosphor substrate 10f in the thickness direction of the phosphor substrate 10f and a notch formed by cutting out the phosphor substrate 10f.

As a result, when excitation light L1 enters the second light transmission region 14f, excitation light L1 is emitted from the phosphor substrate 10f. Similarly, when excitation light L1 enters the fluorescent structure 11d made of a fluorescent material, the excitation light L1 is wavelength-converted by the fluorescent structure 11d, and transmitted light L3, which is wavelength-converted light, is emitted from the phosphor substrate 10f.

As a result, as the rotating portion rotates, the phosphor substrate 10f can emit excitation light L1 and wavelength-converted light in a time-division manner. In this embodiment, the phosphor substrate 10f can emit yellow light as excitation light L1 and blue light as wavelength-converted light in a time-division manner.

Furthermore, the fluorescence-emitting module 1f according to this embodiment may be applied to the projector 500 in place of the fluorescence-emitting module 1c according to embodiment 1. In this case, the projector 500 includes a DLP as the display element section 602, and can therefore be used as a 1-DLP (one-chip DLP) type projector.

In this embodiment, when the phosphor substrate 10f is viewed in plan, the phosphor substrate 10f has a third region 23 having a circular ring shape, the center of which overlaps with the center of the phosphor substrate 10f (center point C1), and the third region 23 is provided with a second light-transmitting region 14f.

Furthermore, in this embodiment, a fluorescent structure 11d is also provided in the third region 23.

Because the third region 23 has the above-described shape, when excitation light L1 is incident on the third region 23, it becomes easier to use the phosphor substrate 10f, which can emit excitation light L1 and wavelength-converted light in a time-division manner, as a phosphor wheel.

In this embodiment, the fluorescence-emitting module 1f further includes a light-emitting section 200 that emits excitation light L1, which excites the phosphor material and enters the third region 23.

In this way, by the excitation light L1 being incident on the third region 23, which is provided with the fluorescent structure 11d and the second light-transmitting region 14f, the phosphor substrate 10f can more easily emit the excitation light L1 and wavelength-converted light in a time-division manner.

[Manufacturing method]
Here, a method for manufacturing the phosphor substrate 10f will be briefly described.

The phosphor material is composed of a crystalline phase represented by (Y _0.999 Ce _0.001 ) ₃ Al ₅ O _12. Furthermore, all of the phosphor materials are composed of a Ce ³⁺ activated phosphor.

To manufacture the phosphor substrate 10f, the first mixed raw material was granulated in the same manner as described above.

Next, we will explain the molding of the first mixed raw material using Figure 14.

Figure 14 is a perspective view of a mold 400f used to manufacture the phosphor substrate 10f according to this embodiment.

The mold 400f has an inner area A6 and two cutout areas A7.

The granulated first mixed raw material was pre-molded using an electric hydraulic press (EMP-5, manufactured by Riken Seiki Co., Ltd.) and a cylindrical mold 400 with a bottom. The first mixed raw material was placed in the inner region A6 of the mold 400f.

Next, the pre-molded body was finally molded using a cold isostatic pressing device.

After heat treatment, the molded body was fired using a tubular atmosphere furnace.

After firing, the cylindrical fired product was sliced using a multi-wire saw. The sliced fired product was then polished to adjust the thickness of the fired product. This adjustment resulted in the fired product becoming the phosphor substrate 10f.

The preliminary molding process, final molding process, firing process, slicing process, and polishing process are performed under the same conditions as in embodiment 1.

By using a mold 400f having two such cutout regions A7, a phosphor substrate 10f having two second light-transmitting regions 14f is manufactured.

Fifth Embodiment
Next, a fluorescence-emitting module 1g according to embodiment 5 will be described with reference to Figures 15 and 16. Figure 15 is a perspective view of fluorescence-emitting module 1g according to this embodiment. Figure 16 is a cross-sectional view showing a cut surface of part of fluorescence-emitting module 1g taken along line XVI-XVI in Figure 15.

The fluorescence-emitting module 1g is a module comprising a phosphor substrate 10g made of a sintered phosphor, an anti-reflection layer 30, a blue-transmitting dichroic multilayer film 40, a rotating unit (not shown), and two light-emitting units 200. For simplicity, only one light-emitting unit 200 is shown in Figures 15 and 16. The rotating unit according to this embodiment has the same configuration as the rotating unit 100 described above. Furthermore, in Figure 15, the axis A1 on the negative side of the z-axis from the blue-transmitting dichroic multilayer film 40 is not shown. The light-emitting unit 200 also emits excitation light L1, as described above.

Fluorescence-emitting module 1g according to the present embodiment differs from fluorescence-emitting modules 1c, 1d, and 1f according to embodiments 1, 2, 3, and 4 mainly in the following respect. Specifically, phosphor substrate 10g is composed of a sintered phosphor that includes a phosphor material, an oxide material that does not contain a luminescent center element, and a highly thermally conductive material.

The phosphor substrate 10g is a substrate composed of a sintered phosphor containing a phosphor material, an oxide material that does not contain a luminescent center element, and a highly thermally conductive material, and has a circular shape. In other words, the phosphor substrate 10g has a disk shape with a flat surface. The phosphor substrate 10g is a substrate composed only of a sintered phosphor, and the sintered phosphor contains only the phosphor material as its main component, an oxide material that does not contain a luminescent center element, and a highly thermally conductive material.

More specifically, as shown in FIG. 16, the phosphor substrate 10g is composed of a fluorescent structure 11g, an oxide structure 13g, and multiple heat conduction structures 12. As shown in FIGS. 15 and 16, the phosphor substrate 10g is provided with a fluorescent structure 11g, two oxide structures 13g, and multiple heat conduction structures 12. In other words, the phosphor substrate 10g is composed of a fluorescent structure 11g, two oxide structures 13g, and multiple heat conduction structures 12, and the two oxide structures 13g have the same configuration. The two oxide structures 13g are the areas surrounded by dotted lines in FIG. 15.

Fluorescent structure 11g is a structure composed of the phosphor material contained in the sintered phosphor. More specifically, fluorescent structure 11g is a structure composed only of the phosphor material contained in the sintered phosphor. Note that fluorescent structure 11g according to this embodiment has the same configuration as fluorescent structure 11d according to embodiment 3, except for its shape.

Oxide structure 13g is a structure composed of an oxide material that does not contain the luminescent center element of the sintered phosphor. More specifically, oxide structure 13g is a structure composed only of an oxide material that does not contain the luminescent center element of the sintered phosphor. Note that oxide structure 13g according to this embodiment has the same configuration as oxide structure 13d according to embodiment 3, except for the shape. In other words, oxide structure 13g is an example of a first light-transmitting region of phosphor substrate 10g.

As described above, the phosphor substrate 10g is a substrate having a circular shape. More specifically, the phosphor substrate 10g is a substrate that is circular in shape due to the combination of the phosphor structure 11g, two oxide structures 13g, and multiple heat conduction structures 12.

Here, the oxide structure 13g has an annular sector shape when viewed from above on the phosphor substrate 10g. In other words, the oxide structure 13g has a shape surrounded by two arcs and two straight lines.

Here, as shown in Figure 15, in a plan view of the phosphor substrate 10g, the two oxide structures 13g are arranged so that the outer arc (i.e., the arc farther from axis A1) of the two arcs representing the oxide structures 13g is closer to axis A1 than the circumference of the circular phosphor substrate 10g.

Furthermore, the combined shape of the fluorescent structure 11g and the multiple heat conduction structures 12 is a circle with two annular sector-shaped openings in a plan view of the phosphor substrate 10g. In other words, when the combined shape of the fluorescent structure 11g and the multiple heat conduction structures 12 is combined with the oxide structure 13g in these openings, the phosphor substrate 10g becomes disk-shaped.

Furthermore, the multiple heat conduction structures 12 are arranged on the phosphor substrate 10g so that they are surrounded by the fluorescent structure 11g. Although not shown, the multiple heat conduction structures 12 may be arranged so that a portion of the multiple heat conduction structures 12 protrudes from the fluorescent structure 11g. The fluorescent structure 11g serves as a base material for the multiple heat conduction structures 12. In other words, the multiple heat conduction structures 12 are embedded in the fluorescent structure 11g.

On the other hand, the multiple heat conduction structures 12 are not arranged in the oxide structure 13g on the phosphor substrate 10g. As shown in Figure 16, the multiple heat conduction structures 12 and the oxide structure 13g are not in contact with each other.

Now, we will explain the sintered phosphor used in this embodiment.

A sintered phosphor is a fired body obtained by firing raw material powders of the above-mentioned main components, namely, a phosphor material, an oxide material not containing a luminescent center element, and a high thermal conductivity material (for example, granules formed by granulating raw material powders of these materials) at a temperature lower than the melting point of these materials. In addition, in the sintered phosphor, the raw material powders are bonded together during the firing process. Therefore, the sintered phosphor hardly requires a binder for bonding the granules together. More specifically, the sintered phosphor does not require any binder at all. As an example, in the above Patent Document 1, the binder is a transparent resin. Furthermore, known materials used as the binder include Al ₂ O ₃ material and glass material (i.e., SiO _d (0 < d ≦ 2)). Similarly, without being limited to a binder, the sintered phosphor hardly requires any materials (hereinafter referred to as other materials) other than the phosphor material, oxide material not containing a luminescent center element, and high thermal conductivity material contained in the sintered phosphor, and more specifically, does not require any other materials at all.

For example, when the total volume of the sintered phosphor is taken as 100 vol%, it is preferable that the total volume of the phosphor material, oxide material not containing a luminescent center element, and high thermal conductivity material in the total volume of the sintered phosphor be 70 vol% or more. Furthermore, it is better that the total volume of the phosphor material, oxide material not containing a luminescent center element, and high thermal conductivity material in the total volume of the sintered phosphor be 80 vol% or more, even better that it be 90 vol% or more, and even better that it be 95 vol% or more.

In other words, when the total volume of the sintered phosphor is taken as 100 vol%, it is preferable that the volume of other materials (e.g., binder) in the total volume of the sintered phosphor be less than 30 vol%. Furthermore, it is better that the volume of other materials (e.g., binder) in the total volume of the sintered phosphor be 20 vol% or less, even better that it be 10 vol% or less, and even better that it be 5 vol% or less.

Furthermore, phosphor substrate 10g according to this embodiment has a first region 21 and a second region 22. That is, phosphor substrate 10g according to this embodiment is segmented into first region 21 and second region 22. More specifically, in a plan view, phosphor substrate 10g has first region 21 and a plurality of second regions 22. Note that in Fig. 15 , first region 21 is indicated by a dot, and in Fig. 16, first region 21 is indicated by a dashed line, and the plurality of second regions 22 are rectangular regions surrounded by dashed double-dot lines.

The first region 21 and the multiple second regions 22 have different amounts of high thermal conductivity material. The multiple second regions 22 have a higher amount of high thermal conductivity material than the first region 21. In other words, the first region 21 only needs to have a lower amount of high thermal conductivity material than the multiple second regions 22, and the first region 21 in this embodiment does not contain high thermal conductivity material. However, the first region 21 may contain high thermal conductivity material. Furthermore, the excitation light L1 emitted by the light emitting section 200 is incident on the first region 21. More specifically, as shown in FIG. 15, in this embodiment, the excitation light L1 is irradiated at a position that is a radius R from the center point C1 of the phosphor substrate 10g.

Furthermore, when the phosphor substrate 10g is viewed in a plan view, the first region 21 is provided with an oxide structure 13g (i.e., a first light-transmitting region). More specifically, when the phosphor substrate 10g is viewed in a plan view, the first region 21 is provided with a portion of the oxide structure 13g and a portion of the fluorescent structure 11g. Note that in Figure 15, among the dots indicating the first region 21, the first region 21 indicated by lighter dots has a portion of the oxide structure 13g provided therein, and the first region 21 indicated by darker dots has a portion of the fluorescent structure 11g provided therein.

Of the excitation light L1 incident on the first region 21, the excitation light L1 that enters the oxide structure 13g is transmitted through the oxide structure 13g. Furthermore, of the excitation light L1 incident on the first region 21, the excitation light L1 that enters the fluorescent structure 11g is wavelength converted by the fluorescent structure 11g and emitted as transmitted light L3, which is wavelength-converted light.

In this embodiment, the sintered phosphor further includes an oxide material that does not contain a luminescent center element. The phosphor substrate 10g is composed of only the oxide material of the phosphor material and oxide material, and has a first light-transmitting region that transmits light (excitation light L1) that excites the phosphor material. The first region 21 is provided with the first light-transmitting region.

As a result, when excitation light L1 is incident on the first light-transmitting region (i.e., oxide structure 13g) made of an oxide material that does not contain a luminescent center element, the excitation light L1 passes through the oxide structure 13g, and excitation light L1 is emitted from the phosphor substrate 10g. Similarly, when excitation light L1 is incident on fluorescent structure 11g made of a phosphor material, the excitation light L1 is wavelength-converted by fluorescent structure 11g, and transmitted light L3, which is wavelength-converted light, is emitted from the phosphor substrate 10g.

As a result, as the rotating portion rotates, the phosphor substrate 10g can emit excitation light L1 and wavelength-converted light in a time-division manner. In this embodiment, the phosphor substrate 10g can emit yellow light as excitation light L1 and blue light as wavelength-converted light in a time-division manner.

Furthermore, the fluorescence-emitting module 1g according to this embodiment may be applied to the projector 500 in place of the fluorescence-emitting module 1c according to embodiment 1. In this case, the projector 500 includes a DLP as the display element section 602, and can therefore be used as a 1-DLP (one-chip DLP) type projector.

In this embodiment, the oxide material is aluminum oxide or a non-luminescent material in which the luminescent center element has been removed from a phosphor material.

These materials have high light transmittance for excitation light L1 (i.e., light that excites the phosphor material). Therefore, the transmittance of excitation light L1 in the first light-transmitting region (oxide structure 13g) is high, and loss of excitation light L1 due to absorption is suppressed. This makes it possible to realize a fluorescent light-emitting module 1g with high light utilization efficiency.

(Embodiment 6)
Next, a fluorescence light emitting module 1h according to a sixth embodiment will be described with reference to Fig. 17. Fig. 17 is a perspective view of a fluorescence light emitting module 1h according to the present embodiment.

The fluorescence-emitting module 1h is a module comprising a phosphor substrate 10h made of a sintered phosphor, an anti-reflection layer 30, a blue-transmitting dichroic multilayer film 40, a rotating section (not shown), and two light-emitting sections 200. For simplicity, only one light-emitting section 200 is shown in Figure 17. The rotating section in this embodiment has the same configuration as the rotating section 100 described above. The light-emitting section 200 also emits excitation light L1, as described above.

The fluorescent light-emitting module 1h according to this embodiment differs from the fluorescent light-emitting module 1g according to embodiment 5 mainly in that the phosphor substrate 10h has a second light-transmitting region 14h instead of the first light-transmitting region (oxide structure 13g). In other words, the fluorescent sintered body according to this embodiment contains only a phosphor material and a high-thermal-conductivity material, and does not contain an oxide material that does not contain a luminescent center element.

In other words, the phosphor substrate 10h according to this embodiment is a substrate made of a sintered phosphor containing a phosphor material. Furthermore, the phosphor substrate 10h according to this embodiment is a substrate having two second light-transmitting regions 14h, a first region 21, and a second region 22. The sintered phosphor according to this embodiment is made of the fluorescent structure 11g shown in embodiment 5.

The second light-transmitting region 14h is an opening in the phosphor substrate 10h. That is, the second light-transmitting region 14h is composed of at least one of a through-hole that penetrates the phosphor substrate 10h in the thickness direction (z-axis direction) of the phosphor substrate 10h and a cutout portion cut out of the phosphor substrate 10h. Here, the second light-transmitting region 14h corresponds to the cutout portion. Note that the second light-transmitting region 14h in this embodiment has the same configuration as the second light-transmitting region 14f in embodiment 4, except for its shape. The second light-transmitting region 14h has the same shape as the oxide structure 13g (first light-transmitting region) shown in embodiment 5, but is not limited to this.

Here, we will explain the sintered phosphor used in this embodiment.

A sintered phosphor is a fired body obtained by firing raw material powders of the above-mentioned main components, the phosphor material and the high thermal conductivity material (for example, granules formed by granulating raw material powders of these materials), at a temperature lower than the melting points of these materials. In other words, the sintered phosphor of this embodiment is the same as the sintered phosphor of embodiment 2.

As described in embodiment 5, when excitation light L1 is incident on the fluorescent structure 11g, it emits wavelength-converted light (yellow light) with a wavelength longer than that of the excitation light L1 as transmitted light L3.

When excitation light L1 is incident on the second light-transmitting region 14h, it transmits the excitation light L1, which is blue light.

Furthermore, the phosphor substrate 10h according to this embodiment has segmented first regions 21 and second regions 22. More specifically, in plan view, the phosphor substrate 10h has a first region 21 and multiple second regions 22. Note that in Figure 17, the first regions 21 are indicated by dots.

The excitation light L1 emitted by the light emitting unit 200 is incident on the first region 21. More specifically, as shown in FIG. 17, in this embodiment, the excitation light L1 is irradiated at a position that is a radius R from the center point C1 of the phosphor substrate 10h.

Furthermore, when the phosphor substrate 10h is viewed in a plan view, the first region 21 is provided with a second light-transmitting region 14h. More specifically, when the phosphor substrate 10h is viewed in a plan view, the first region 21 is provided with a portion of the second light-transmitting region 14h and a portion of the fluorescent structure 11g. Note that in Figure 17, among the dots indicating the first region 21, the first region 21 indicated by lighter dots is provided with a portion of the second light-transmitting region 14h, and the first region 21 indicated by darker dots is provided with a portion of the fluorescent structure 11g.

The phosphor substrate 10h has a second light-transmitting region 14h that transmits light (excitation light L1) that excites the phosphor material. The second light-transmitting region 14h is composed of at least one of a through-hole that penetrates the phosphor substrate 10h in the thickness direction of the phosphor substrate 10h and a cutout portion where the phosphor substrate 10h is cut out. The second light-transmitting region 14h is provided in the first region 21.

As a result, when excitation light L1 enters the second light transmission region 14h, excitation light L1 is emitted from the phosphor substrate 10h. Similarly, when excitation light L1 enters the fluorescent structure 11g made of a fluorescent material, the excitation light L1 is wavelength-converted by the fluorescent structure 11g, and transmitted light L3, which is wavelength-converted light, is emitted from the phosphor substrate 10h.

Therefore, as the rotating part rotates, the phosphor substrate 10h can emit excitation light L1 and wavelength-converted light in a time-division manner. In this embodiment, the phosphor substrate 10h can emit yellow light as excitation light L1 and blue light as wavelength-converted light in a time-division manner.

Furthermore, the fluorescent light-emitting module 1h according to this embodiment may be applied to the projector 500 in place of the fluorescent light-emitting module 1c according to embodiment 1. In this case, the projector 500 includes a DLP as the display element section 602, and can therefore be used as a 1-DLP (one-chip DLP) type projector.

(Other embodiments)
While the fluorescence-emitting module and the like according to the present invention have been described above based on various embodiments, the present invention is not limited to these embodiments. As long as they do not deviate from the gist of the present invention, various modifications that would occur to those skilled in the art to the embodiments and other forms constructed by combining some of the components of the various embodiments are also included within the scope of the present invention.

The fluorescence-emitting modules 1 and 1c each include a phosphor substrate 10 and 10c, an anti-reflection layer 30, a blue-transmitting dichroic multilayer film 40, a rotating unit 100, and a light-emitting unit 200, but are not limited to this.

The fluorescence-emitting module 1c simply comprises a phosphor substrate 10c and a rotating unit 100. Unlike Patent Document 1, reflection of excitation light L1 generated at the interface between the phosphor substrate and the atmosphere does not occur. Therefore, the amount of excitation light L1 incident on the phosphor substrate 10c increases. As a result, the amount of fluorescence generated by the phosphor material in the phosphor substrate 10c increases. Furthermore, because the fluorescence-emitting module 1c does not include components for supporting the phosphor substrate 10c, the peeling of the fluorescence-generating unit disclosed in Patent Document 1 does not occur. Furthermore, rotation by the rotating unit 100 generates an airflow. This generated airflow suppresses the rise in temperature of the phosphor substrate 10c, thereby suppressing the decrease in fluorescence. In other words, the light utilization efficiency of the fluorescence-emitting module 1c can be improved. Furthermore, suppressing the decrease in fluorescence suppresses changes in the chromaticity of the transmitted light L2, and the aforementioned peeling does not occur. This results in a highly reliable fluorescence-emitting module 1c.

Similarly, the fluorescence-emitting module 1 may include a phosphor substrate 10, which is a substrate composed of a sintered phosphor containing a phosphor material and a highly thermally conductive material. Unlike Patent Document 1, reflection of the excitation light L1 generated at the interface between the phosphor substrate and the atmosphere does not occur. Therefore, the excitation light L1 incident on the phosphor substrate 10 increases. As a result, the fluorescence generated by the phosphor material in the phosphor substrate 10 increases. Furthermore, because the fluorescence-emitting module 1 does not include components for supporting the phosphor substrate 10, the peeling of the fluorescence-generating section disclosed in Patent Document 1 does not occur. Furthermore, since the sintered phosphor constituting the phosphor substrate 10 contains a highly thermally conductive material, the heat dissipation of the phosphor substrate 10 is improved. This suppresses the temperature rise of the phosphor substrate 10 due to irradiation with the excitation light L1, thereby suppressing the decrease in fluorescence. In other words, a fluorescence-emitting module 1 with high light utilization efficiency can be realized. Furthermore, suppressing the decrease in fluorescence suppresses the chromaticity change of the transmitted light L2, and the aforementioned peeling does not occur. Therefore, a highly reliable fluorescence-emitting module 1 is realized.

<Shape of heat conduction structure>
In the second embodiment, each of the heat conducting structures 12 has a particle shape, but may have a wire shape, a sheet shape, or a mesh shape. These other examples will now be described.

<Mesh shape>
Fig. 6 is a cross-sectional view of a phosphor substrate 10a according to Alternative Example 1 of Embodiment 2. Fig. 7 is a cross-sectional view of a phosphor substrate 10b according to Alternative Example 2 of Embodiment 2. Note that Figs. 6 and 7 correspond to the cross-sectional view of Fig. 2, and components such as the anti-reflection layer 30, the blue-transmitting dichroic multilayer film 40, the rotating unit 100, and the light emitting unit 200 are omitted from Figs. 6 and 7.

As shown in Figure 6, when each of the multiple heat conduction structures 12a has a wire shape, an example is, but is not limited to, a wire diameter of 1 μm to 50 μm and a length of 10 μm to 500 μm.

<Sheet shape>
7 shows an example in which each of the plurality of heat conducting structures 12b has a sheet shape. In this case, the fluorescent structure 11 and the plurality of heat conducting structures 12b are stacked. In the inner second region 22, the plurality of heat conducting structures 12b have a circular shape, and in the outer second region 22, the plurality of heat conducting structures 12b have an annular shape.

Also, although not shown, if each of the multiple heat conduction structures has a sheet shape, multiple through holes may be provided that penetrate the sheet shape in the thickness direction. In this case, each of the multiple heat conduction structures has a mesh shape. In other words, the multiple meshes in the mesh shape correspond to the multiple through holes.

By each of the multiple heat conduction structures 12 having these shapes, the heat dissipation properties of the phosphor substrates 10a and 10b can be further improved.

Furthermore, when each of the multiple heat conduction structures has a mesh shape, it is preferable that the first region 21 includes multiple heat conduction structures. In this case, it is preferable that the multiple heat conduction structures are provided across the first region 21 and multiple second regions 22. This makes it possible to increase the structural strength of the phosphor substrate 10b and suppress cracking of the phosphor substrate 10b.

However, as mentioned above, it is preferable that the first region 21 does not contain a high thermal conductivity material. This increases the efficiency of wavelength conversion by the phosphor material. Therefore, it is preferable that the first region 21 contains a lower amount of high thermal conductivity material than the multiple second regions 22.

As shown in FIG. 11, in a plan view of the phosphor substrate 10d, the oxide structure 13d is arranged so that the circumference of the circular phosphor substrate 10 overlaps with the outer arc of the two arcs representing the oxide structure 13d (i.e., the arc farther from the axis A1). However, this is not limited to this.

For example, oxide structure 13d may be provided in the same shape and at the same position as oxide structure 13g shown in Figure 15.

Furthermore, in embodiments 3 to 6, yellow light is emitted as the transmitted light L3, but this is not limited to this. For example, the phosphor material may be a combination of the yellow phosphor material YAG:Ce and a green phosphor material. In this case, the phosphor substrate can emit yellow light and green light as the excitation light L1, and blue light as the wavelength-converted light, in a time-division manner. Furthermore, for example, a red phosphor material may be used instead of the green phosphor material.

Furthermore, the above-described embodiments may be modified, substituted, added, or omitted in various ways within the scope of the claims or their equivalents.

1, 1c, 1d, 1f, 1g, 1h Fluorescence-emitting modules 10, 10a, 10b, 10c, 10d, 10f, 10g, 10h Phosphor substrates 14f, 14h Second light-transmitting region 21 First region 22 Second region 23 Third region 24 Fourth region 100 Rotating portion 200 Light-emitting portion C1 Center point L1 Excitation light L2, L3 Transmitted light R Radius

Claims (21)

A phosphor substrate which is a substrate constituted by a sintered phosphor having a phosphor material;
a rotating unit that rotates the phosphor substrate around an axis extending in a thickness direction of the phosphor substrate,
The sintered phosphor further includes a high thermal conductivity material having a thermal conductivity of 100 W/m K or more and 300 W/m K or less,
the high thermal conductivity material is composed of a metal element ,
the highly thermally conductive material is in the form of particles, wires, sheets, or meshes;
The high thermal conductivity material is surrounded by the phosphor material.
Fluorescence emission module. A phosphor substrate is a substrate constituted by a sintered phosphor having a phosphor material and a high thermal conductivity material having a thermal conductivity of 100 W/m K or more and 300 W/m K or less,
the high thermal conductivity material is composed of a metal element ,
the highly thermally conductive material is in the form of particles, wires, sheets, or meshes;
The high thermal conductivity material is surrounded by the phosphor material.
Fluorescence emission module. The high thermal conductivity material has a linear expansion coefficient of 1×10 ⁻⁷ /K or less.
3. The fluorescent light-emitting module according to claim 1 . 4. The fluorescent light-emitting module according to claim 1, wherein the highly thermally conductive material includes at least one of W, Mo, Rh, AlN, and SiC. The melting point of the high thermal conductivity material at normal pressure is 1700°C or higher.
The fluorescent light-emitting module according to any one of claims 1 to 4 . When the phosphor substrate is viewed from above ,
The phosphor substrate is
A first region;
a second region having a higher content of the high thermal conductivity material than the first region;
The fluorescent light-emitting module according to any one of claims 1 to 5 . When the phosphor substrate is viewed from above,
the first region has a circular ring shape;
The fluorescence light-emitting module according to claim 6 , wherein the center of the annular shape overlaps with the center of the phosphor substrate. The sintered phosphor further includes an oxide material that does not contain a luminescent center element,
the phosphor substrate has a first light-transmitting region that is made of only the oxide material of the phosphor material and the oxide material and transmits light that excites the phosphor material;
The fluorescence light-emitting module according to claim 7 , wherein the first region is provided with the first light-transmitting region. The fluorescent light-emitting module according to claim 8 , wherein the oxide material is aluminum oxide or a non-luminescent material obtained by removing the luminescent center element from the phosphor material. the phosphor substrate has a second light-transmitting region that transmits light that excites the phosphor material;
the second light transmitting region is configured by at least one of a through hole penetrating the phosphor substrate in a thickness direction of the phosphor substrate and a notch portion formed by cutting out the phosphor substrate,
The fluorescence light-emitting module according to claim 7 , wherein the first region is provided with the second light-transmitting region. 11. The fluorescence light-emitting module according to claim 7 , wherein the second region is provided on both the inside and outside of the annular shape when the phosphor substrate is viewed in plan. 12. The fluorescence emitting module according to claim 6 , further comprising a light emitting section that emits excitation light that excites the phosphor material and that is incident on the first region. a part of the incident excitation light is wavelength-converted by the phosphor material contained in the first region and passes through the phosphor substrate;
The fluorescence light-emitting module according to claim 12 , wherein the other part of the incident excitation light is transmitted through the phosphor substrate without being wavelength-converted by the phosphor material contained in the first region. The sintered phosphor further includes an oxide material that does not contain a luminescent center element,
The phosphor substrate is made of only the oxide material of the phosphor material and the oxide material, and has a first light-transmitting region that transmits light that excites the phosphor material.
The fluorescent light-emitting module according to claim 1 . The fluorescent light-emitting module according to claim 14 , wherein the oxide material is aluminum oxide or a non-luminescent material obtained by removing the luminescent center element from the phosphor material. When the phosphor substrate is viewed from above,
the phosphor substrate has a third region having an annular shape;
the center of the annular shape overlaps with the center of the phosphor substrate;
The fluorescence light-emitting module according to claim 14 or 15 , wherein the third region is provided with the first light-transmitting region. the phosphor substrate has a second light-transmitting region that transmits light that excites the phosphor material;
The second light-transmitting region is configured by at least one of a through-hole penetrating the phosphor substrate in a thickness direction of the phosphor substrate and a notch formed by cutting out the phosphor substrate.
The fluorescent light-emitting module according to claim 1 . When the phosphor substrate is viewed from above,
the phosphor substrate has a third region having an annular shape;
the center of the annular shape overlaps with the center of the phosphor substrate;
The fluorescence light-emitting module according to claim 17 , wherein the second light-transmitting region is provided in the third region. The fluorescence emitting module according to claim 16 or 18 , further comprising a light emitting section that emits excitation light that excites the phosphor material and that is incident on the third region. 20. The fluorescent light-emitting module according to claim 1 , wherein the phosphor material is (Y1 _{-xCe x} ) _3Al5O12 ( _{0.0005 ≦} x<0.001). A light emitting device comprising the fluorescent light emitting module according to any one of claims 1 to 20 .