JP6164221B2 - Fluorescent light source device - Google Patents

Description

  The present invention relates to a fluorescent light source device, and more particularly to a fluorescent light source device suitable as a light source for a projector, which includes a wavelength conversion member made of a phosphor excited by excitation light such as laser light.

Conventionally, as a green light source used in a projector device, a fluorescent light source device including a laser light source and a wavelength conversion member made of a phosphor excited by laser light from the laser light source is known (for example, a patent) Reference 1).
Specifically, in Patent Document 1, as shown in FIG. 8, as a green light source of a projector device, a laser light source 51 that emits laser light oscillating in a blue region, a fluorescent wheel 52, and the fluorescent wheel 52 are rotated. A fluorescent light source device including a wheel motor 53 is used. The fluorescent wheel 52 is formed by forming a wavelength conversion member made of a phosphor excited by the laser light on a base material that transmits the laser light from the laser light source 51.
In FIG. 8, 61 is a collimating lens, and 62 is a red light source composed of a red light emitting diode. Reference numerals 63A, 63B, 63C, 64A, 64B, and 64C denote condensing lenses. Reference numeral 65 denotes a dichroic lens that transmits light from a green light source and reflects light from a red light source. Reference numeral 66 denotes an incident lens for a light guide device. Reference numeral 67 denotes a reflection mirror, and reference numeral 68 denotes a light guide device.

Thus, in the fluorescent light source device having a rotating mechanism for rotating the fluorescent wheel 52, the wavelength conversion member is air-cooled by the rotation of the fluorescent wheel 52.
However, there is a problem that the configuration of the drive system of the fluorescent wheel 52 including the wheel motor 53 is complicated, and a long service life cannot be obtained for the wheel motor 53 due to deterioration of the constituent members. There is also a problem that the wavelength conversion member cannot be sufficiently cooled only by rotating the fluorescent wheel 52.

Thus, a fluorescent light source device having a configuration without a rotation mechanism has been proposed (for example, see Patent Document 2).
Specifically, in Patent Document 2, as shown in FIG. 9, a wavelength conversion member 71 made of a phosphor excited by laser light from a laser light source and a material having a thermal expansion coefficient different from that of the wavelength conversion member are used. A fluorescent light source device including a fluorescent light emitter having a substrate 72 and a thermal expansion absorption layer 73 made of barium sulfate formed between the wavelength conversion member 71 and the substrate 72 is disclosed.
In this fluorescent light source device, the substrate 72 is made of an aluminum nitride sintered body having high thermal conductivity, and the surface (the lower surface in FIG. 9) of the substrate 72 facing the laminated surface of the thermal expansion absorption layer 73 is made of metal. A heat dissipation plate 74 made of eutectic is joined. Further, a heat radiating fin 75 is fixed to the surface (the lower surface in FIG. 9) of the heat radiating plate 74 that faces the bonding surface with the substrate 72.

However, in the fluorescent light source device including the fluorescent light emitter having the thermal expansion absorption layer 73, the barium sulfate layer using glass as a binder has low thermal conductivity. Therefore, the heat generated by the laser beam irradiation on the wavelength conversion member 71 can be efficiently transferred to the heat dissipation plate 74 and the heat dissipation fin 75 via the substrate 72 and the substrate 72 to be radiated to the outside. Can not. Thereby, there exists a problem that the wavelength conversion member 71 will become high temperature.
Thus, when the wavelength conversion member 71 becomes high temperature, the phosphor constituting the wavelength conversion member 71 cannot be sufficiently excited by the laser light. In addition, the phosphor itself rises in temperature, causing a decrease in light flux due to temperature quenching, and various adverse effects such as a failure to obtain a sufficient fluorescent light flux occur.

JP 2011-13316 A JP 2011-198560 A

  The present invention has been made based on the circumstances as described above, and an object of the present invention is to provide a fluorescent light source device that can suppress the temperature rise of the wavelength conversion member due to irradiation of excitation light and can obtain high luminous efficiency. It is to provide.

The fluorescent light source device of the present invention is a fluorescent light source device including a wavelength conversion member made of a phosphor excited by excitation light,
The wavelength conversion member is bonded to the thermally conductive substrate via a bonding member made of solder on the surface opposite to the irradiated surface irradiated with the excitation light,
The wavelength conversion member has a thermal conductivity of 4.0 W / mK or more,
The phosphor constituting the wavelength conversion member is made of a polycrystalline material having a porosity of 0.5% or less,
The bonding member has a higher thermal conductivity than the wavelength conversion member, the area of the bonding member layer formed by the bonding member is larger than the area of the wavelength conversion member, and the heat conduction Smaller than the area of the conductive substrate.
In the fluorescent light source device of the present invention, the thermally conductive substrate is preferably made of a material having a difference in thermal expansion coefficient from that of the wavelength conversion member within ± 40% of the thermal expansion coefficient of the wavelength conversion member. .

  In the fluorescent light source device of the present invention, it is preferable that the thermally conductive substrate is made of a composite material of at least graphite and aluminum.

  In the fluorescent light source device of the present invention, it is preferable that the thermally conductive substrate is provided with a heat radiation fin.

In the fluorescent light source device of the present invention, the wavelength conversion member has a specific thermal conductivity, and the bonding member has a higher thermal conductivity than the wavelength conversion member. The heat generated in the member can be efficiently transmitted to the heat conductive substrate through the bonding member. In addition, since the heat conductive substrate is made of a material having a thermal expansion coefficient substantially equal to that of the wavelength conversion member, the heat cycle in which the heat of the wavelength conversion member is transferred to the heat conductive substrate through the bonding member is highly reliable. Is obtained. As a result, it is possible to prevent the thermal conversion substrate and the wavelength conversion member from peeling off and the wavelength conversion member from being cracked due to the thermal expansion of the wavelength conversion member and the thermal conductive substrate. .
Therefore, according to the fluorescent light source device of the present invention, heat generated in the wavelength conversion member can be efficiently transmitted to the heat conductive substrate through the bonding member and radiated to the outside. The temperature rise of the wavelength conversion member can be suppressed and high luminous efficiency can be obtained.

  In the fluorescent light source device of the present invention, since the phosphor constituting the wavelength conversion member is made of a single crystal material or a polycrystalline material having a porosity of 0.5% or less, the wavelength conversion member has a desired thermal conductivity. It can be of high thermal conductivity. Moreover, since the wavelength conversion member has no pores or almost no pores, the backscattering of the excitation light to be irradiated is almost eliminated and excitation is performed efficiently.

  In the fluorescent light source device of the present invention, the thermal conductive substrate is made of a composite material of at least graphite and aluminum, so that the thermal conductive substrate has a high thermal conductivity and a desired thermal expansion coefficient. Can do. In addition, since the composite material of graphite and aluminum has a specific gravity smaller than that of metal, it is possible to reduce the weight of the fluorescent light-emitting body in which the wavelength conversion member and the heat conductive substrate are bonded via the bonding member. .

In the fluorescent light source device of the present invention, since the heat conductive substrate is provided with heat radiating fins, a higher heat radiating effect is obtained by the heat conductive substrate due to the heat radiating effect of the heat radiating fins. Further, since it is not necessary to use a fin fixing joint member for fixing the heat radiation fin to the heat conductive substrate, it is not necessary to transfer heat to the heat radiation fin via the fin fixing joint member. Therefore, the temperature rise of the wavelength conversion member due to the irradiation of excitation light is further suppressed, so that the light emission efficiency can be further increased.
In addition, when the thermally conductive substrate is made of a composite material of at least graphite and aluminum, since the composite material has a low specific gravity, the weight of the thermally conductive substrate associated with the provision of heat radiation fins is suppressed. can do.

It is explanatory drawing which shows the outline | summary of an example of a structure of the fluorescence light source device of this invention. FIG. 2 is an explanatory perspective view illustrating an outline of a first embodiment of a configuration of a fluorescent light emitter in which a wavelength conversion member and a heat conductive substrate are bonded via a bonding member in the fluorescent light source device of FIG. 1. It is sectional drawing for description which shows the cross section of the fluorescent substance of FIG. It is explanatory drawing which shows the outline of an example of a structure of the light source unit in the strong excitation light source device used as a laser light source of the fluorescence light source device of FIG. It is a graph which shows the temperature quenching characteristic of the fluorescent substance which comprises the wavelength conversion member in the fluorescent substance of FIG. It is sectional drawing for description which shows the outline of 2nd Embodiment of the structure of the fluorescent light-emitting body with which the wavelength conversion member and the heat conductive board | substrate were joined via the joining member in the fluorescence light source device of this invention. It is sectional drawing for description which shows the outline of 3rd Embodiment of a structure of the fluorescent light-emitting body with which the wavelength conversion member and the heat conductive board | substrate were joined via the joining member in the fluorescence light source device of this invention. It is explanatory drawing which shows an example of a structure of the conventional fluorescence light source device. It is explanatory drawing which shows an example of a structure of the fluorescent light-emitting body which has a wavelength conversion member in the other example of a structure of the conventional fluorescence light source device.

Embodiments of the present invention will be described below.
FIG. 1 is an explanatory view showing an outline of an example of the configuration of the fluorescent light source device of the present invention, and FIG. 2 is a diagram illustrating a wavelength conversion member and a thermally conductive substrate in the fluorescent light source device of FIG. FIG. 3 is an explanatory perspective view showing an outline of the first embodiment of the configuration of the bonded fluorescent light emitter, and FIG. 3 is an explanatory cross sectional view showing a cross section of the fluorescent light emitter of FIG.
The fluorescent light source device 10 includes a laser light source 30 as an excitation light source and a fluorescent light emitter 20 having a wavelength conversion member 21 made of a fluorescent material excited by the laser light from the laser light source 30. In addition, the collimating lens 12 and the laser light that has been made substantially parallel by the collimating lens 12 are transmitted through the optical path from the light emitting port 30 </ b> A of the laser light source 30 to the fluorescent light emitter 20. The dichroic mirror 11 and the condensing lenses 13 and 14 for condensing the transmitted laser light are arranged in this order. The dichroic mirror 11 is arranged in a posture inclined at an angle of, for example, 45 ° with respect to the optical axis of the collimating lens 12.

As shown in FIGS. 2 and 3, the fluorescent light emitter 20 has a structure in which a rectangular plate-shaped wavelength conversion member 21 is bonded to a rectangular plate-shaped thermally conductive substrate 26 via a bonding member. belongs to. Between the heat conductive substrate 26 and the wavelength conversion member 21, a rectangular flat plate-shaped bonding member layer 29 made of a bonding member is formed.
The fluorescent light emitter 20 is disposed such that the surface of the wavelength conversion member 21 (the upper surface in FIG. 3) faces the light exit 30A of the laser light source 30, and the irradiated light is irradiated with excitation light by the surface. The surface is configured.

  The wavelength conversion member 21 is made of a phosphor having a thermal conductivity of 4.0 W / mK or more. When the thermal conductivity of the wavelength conversion member 21 is less than 4.0 W / mK, the heat generated by the irradiation of the excitation light in the wavelength conversion member cannot be efficiently transferred to the thermal conductive substrate 26, and the wavelength The conversion member becomes high temperature, and sufficient exchange for fluorescence (hereinafter referred to as “fluorescence conversion efficiency”) cannot be obtained.

The phosphor constituting the wavelength conversion member 21 is preferably made of a single crystal material or a polycrystalline material having a porosity of 0.5% or less.
By using a phosphor made of a single crystal material or a polycrystalline material having a porosity of 0.5% or less as the wavelength conversion member 21, the wavelength conversion member 21 has a high thermal conductivity having a desired thermal conductivity. be able to. The reason is that the single crystal material has no pores, and the polycrystalline material has few pores, so that the thermal conductivity is not greatly reduced due to the presence of air with low thermal conductivity in the pores. Because.
In addition, the wavelength conversion member 21 made of a single crystal material or a polycrystalline material has no pores or few pores, and there is almost no backscattering of the excitation light to be irradiated. So that the phosphor is efficiently excited.
Here, when a polycrystalline material having a porosity of more than 0.5% is used as the wavelength conversion member, a desired thermal conductivity cannot be obtained, as is apparent from an experimental example described later, that is, the thermal conductivity. Is less than 4.0 W / mK.

As a single crystal material, for example, a Czochralski method of growing a crystal (single crystal) by bringing a seed crystal into contact with a raw material that has been melted in a crucible and pulling it while rotating in a vertical direction ( Those obtained by the CZ method) are used.
Here, various materials and seed crystals can be used.

As a polycrystalline material, a raw material (a base material, a baking aid and an activator if necessary) is pulverized by using a pulverizer such as a ball mill to reduce the particle size to submicron or less. After the sintered body is formed by the slip casting method, the obtained fired body is subjected to hot isostatic pressing.
Here, various materials can be used as long as they can be sintered.

The single crystal material and polycrystalline material constituting the wavelength conversion member 21 are preferably those in which a rare earth compound is doped (activated) as an activator.
Examples of the rare earth compound include cerium (Ce), praseodymium (Pr), and samarium (Sm).
The doping amount of the rare earth compound is appropriately determined according to, for example, the type of the rare earth compound to be doped, and is, for example, about 0.5 mol%.

Specific examples of the phosphor constituting the wavelength conversion member 21 include a crystal material (YAG: Ce) in which cerium is doped into yttrium aluminum garnet (Y ₃ Al ₅ O ₁₂ ), yttrium aluminum garnet (Y ₃ Al ₅ O ₁₂ ) crystal material doped with praseodymium (YAG: Pr), yttrium aluminum garnet (Y ₃ Al ₅ O ₁₂ ) samarium doped crystal material (YAG: Sm), and lutetium Examples thereof include a crystal material (LuAG: Ce) in which cerium is doped in aluminum garnet (Lu ₃ Al ₅ O ₁₂ ).

The thickness of the wavelength conversion member 21 is preferably 30 to 200 μm, more preferably 50 to 150 μm.
When the thickness of the wavelength conversion member 21 is too small, the excitation light is transmitted, so that the wavelength conversion member 21 cannot sufficiently absorb the excitation light, and the conversion amount of fluorescence may be reduced. is there. On the other hand, when the thickness of the wavelength conversion member 21 is excessive, heat generated by the excitation light being irradiated by the thermal resistance of the wavelength conversion member 21 may accumulate in the wavelength conversion member 21 and become high temperature. is there.

Further, as shown in FIG. 3, the wavelength conversion member 21 has silicon dioxide (SiO 2) on the entire back surface (the lower surface in FIG. 3) from the viewpoint of bonding properties with the bonding member and the configuration of the fluorescent light source device 10. ₂ ) It is preferable that a metal film in which the reflective film layer 22, the protective film layers 23 and 24, and the solder wet film layer 25 are laminated is formed through a film (not shown).
In this metal film, the reflective film layer 22 is made of, for example, silver (Ag), the protective film layer 23 is made of, for example, titanium (Ti), and the protective film layer 24 is made of, for example, platinum (Pt). The layer 25 is made of, for example, gold (Au). Further, the reflective film layer 22, the protective film layers 23 and 24, and the solder wetting film layer 25 constituting the metal film can be formed by, for example, sputtering.
Here, even if a silicon dioxide film and a metal film are provided between the wavelength conversion member 21 and the heat conductive substrate 26, the thickness of the silicon dioxide film is as thin as 10 nm, so the thermal resistance is ignored. Further, since the metal film constituting each layer of the metal film is as thin as about several hundred nm and has a good thermal conductivity, heat transfer from the wavelength conversion member 21 to the heat conductive substrate 26 is possible. There will be no harmful effects.
In the example of this figure, the thickness of the silicon dioxide film is 10 nm. The thickness of each layer constituting the metal film is 110 nm for the reflective film layer 22, 100 nm for the protective film layer 23, 200 nm for the protective film layer 24, and 500 nm for the solder wetting film layer 25. Further, the surface of the wavelength conversion member 21 functions as an irradiated surface and also functions as a light emitting surface.

The thermally conductive substrate 26 has a high thermal conductivity, and a material whose difference in thermal expansion coefficient from the wavelength conversion member 21 is within ± 40% of the thermal expansion coefficient of the wavelength conversion member 21 (hereinafter referred to as “substrate”). "Material")). In this substrate material, the difference in thermal expansion coefficient from the wavelength conversion member 21 is preferably within ± 20% of the thermal expansion coefficient of the wavelength conversion member 21, and within ± 15% of the thermal expansion coefficient of the wavelength conversion member 21. More preferably.
That is, the coefficient of thermal expansion of the substrate material is required to be 0.6 C to 1.4 C [/ K], preferably 0 to 0.1 C, where C is the coefficient of thermal expansion of the wavelength conversion member 21. 8C to 1.2C [/ K], more preferably 0.85C to 1.15C [/ K].
When the thermal expansion coefficient of the material constituting the thermally conductive substrate 26 is too small and excessive, that is, when the difference between the thermal expansion coefficient of the material constituting the thermally conductive substrate 26 and the wavelength conversion member 21 is excessive. Due to thermal expansion, the thermally conductive substrate and the wavelength conversion member 21 may be peeled off or cracks may be generated in the wavelength conversion member 21.
Here, the thermal expansion coefficient of the wavelength conversion member 21 is 8.0 × 10 ⁻⁶ / K when YAG or LuAG is used as the phosphor constituting the wavelength conversion member 21.

Preferable specific examples of the substrate material include a composite material of graphite and aluminum (hereinafter also referred to as “graphite composite material”).
Here, the thermal expansion coefficient of the graphite composite is 7 × 10 ⁻⁶ to 8 × 10 ⁻⁶ / K, and the thermal conductivity is 168 to 425 W / mK.

The graphite composite material is obtained by a molten metal forging method.
Specifically, the graphite composite material is formed by immersing a graphite block in molten aluminum metal and forcing the molten aluminum metal into pores existing in the graphite block by applying high pressure to the molten aluminum metal. It can be produced by impregnating and then cooling. According to such a manufacturing method, the obtained specific graphite composite material can be made into a cast product having a dense shape and a small number of voids.

As the substrate material, for example, a composite material of silicon carbide and aluminum obtained by a melt forging method, a copper tungsten alloy, molybdenum, a diamond copper composite, an aluminum diamond composite, and the like can be used in addition to the graphite composite.
Here, the thermal expansion coefficient of the composite material of silicon carbide and aluminum is 6 × 10 ^{−6 to} 7 × 10 ⁻⁶ / K, and the thermal conductivity is 276 W / mK. The thermal expansion coefficient of the copper tungsten alloy is 6.4 × 10 ⁻⁶ / K, and the thermal conductivity is 167 W / mK. Molybdenum has a thermal expansion coefficient of 4.8 × 10 ⁻⁶ / K and a thermal conductivity of 138 W / mK. The thermal expansion coefficient of the diamond copper composite is 6 × 10 ⁻⁶ / K, and the thermal conductivity is 550 W / mK. The thermal expansion coefficient of the aluminum diamond composite is 7.5 × 10 ⁻⁶ / K, and the thermal conductivity is 500 W / mK.

As shown in FIG. 3, the heat conductive substrate 26 has a protective film layer 27 and a solder wetting film layer on the surface (upper surface in FIG. 3) of the base material 26A made of a substrate material, from the viewpoint of bonding properties with the bonding member. It is preferable that a metal film in which 28 is laminated in this order is formed.
In this metal film, the protective film layer 27 is made of, for example, a nickel-phosphorous plating film (Ni-P film) formed by an electroless plating method, and the solder wet film layer 28 is made of gold (for example, formed by a plating method). Au) film.
Here, even if the heat conductive substrate 26 is provided with a metal film, the metal constituting each layer of the metal film has a good heat conductivity. There is no adverse effect on heat transfer from the conversion member 21.
In the example of this figure, in the heat conductive substrate 26, the entire outer surface (front surface, back surface and side surface) of the base material 26A made of the substrate material is covered with a metal film made of the protective film layer 27 and the solder wet film layer 28. It will be. The thickness of each layer constituting the metal film is 2 μm for the protective film layer 27 and 0.1 μm for the solder wetting film layer 28.

The thickness of the base material 26A in the heat conductive substrate 26 is appropriately determined according to the thermal conductivity of the substrate material constituting the base material 26A from the viewpoint of exhaust heat.
Specifically, when the substrate material is a graphite composite material, the thickness of the base material 26A is preferably 1.0 to 2.0 μm.
Moreover, it is preferable that the area of the surface (upper surface in FIG. 3) in the heat conductive board | substrate 26 is larger than the area of the back surface in the wavelength conversion member 21 from viewpoints, such as exhaust heat property.

The bonding member has a higher thermal conductivity than the wavelength conversion member 21.
When the thermal conductivity of the bonding member is equal to or lower than the thermal conductivity of the wavelength conversion member 21, the heat generated by the excitation light irradiation in the wavelength conversion member 21 can be efficiently transmitted to the thermal conductive substrate 26. Therefore, the wavelength conversion member 21 becomes high temperature, and sufficient fluorescence exchange efficiency cannot be obtained.

As the joining member, flux-free solder is used.
Here, the thermal conductivity of the flux-free solder is 40 to 55 W / mK.

The wavelength conversion member 21 and the heat conductive substrate 26 are bonded by the bonding member using, for example, a reflow furnace, a flux-free solder sheet as a bonding member, and a wavelength on which a silicon dioxide film and a metal film are formed as necessary. It can be performed by a reflow method in which it is sandwiched between the conversion member 21 and the heat conductive substrate 26 and heated in an atmosphere of formic acid gas or hydrogen gas.
Thus, according to the joining method in which the reflow is performed by removing the surface oxide film of the flux-free solder sheet using the reducing power of formic acid or hydrogen, no voids are generated in the formed joining member layer 29, Good thermal conductivity is obtained.

The thickness of the joining member (flux-free solder sheet) used for joining the wavelength conversion member 21 and the heat conductive substrate 26 by the reflow method is, for example, 50 μm.
In addition, the formed bonding member layer 29 has a surface from the viewpoints of bondability between the wavelength conversion member 21 and the heat conductive substrate 26, exhaust heat by the bonding member layer 29, heat transfer to the heat conductive substrate 26, and the like. It is preferable that the area of the upper surface in FIG. 3 is larger than the area of the back surface of the wavelength conversion member 21 and the area of the back surface (lower surface in FIG. 3) is smaller than the area of the surface of the heat conductive substrate 26.

  As the laser light source 30 that irradiates the wavelength conversion member 21 with excitation light, for example, a laser light source unit 31 including a plurality of (14 in the example of FIG. 4) laser light emitting elements 32 as shown in FIG. A plurality of strong excitation light source devices (5 in this example) are used.

In the laser light source unit 31 of this strong excitation light source device, 14 laser light emitting elements 32 are arranged in two rows, and each of the seven laser light emitting elements 32 constituting each row is opposed to the light emitting surface. Are arranged to be. A collimating lens 33 is disposed in front of the light emitting surface of each of the 14 laser light emitting elements 32, and the laser light that has been made substantially parallel by each of the plurality of collimating lenses 33 is the same. A folding mirror 34 is provided to bend so as to proceed in the direction. Further, a condensing lens 35 for condensing the light reflected by each of the plurality of folding mirrors 34 and a light guide member 36 for allowing the laser light condensed by the condensing lens 35 to enter one end are provided. Yes. As the light guide member 36, for example, a quartz fiber having a diameter of 1.5 mm is used.
And the quartz fiber which comprises the light guide member 36 of the five laser light source units 31 is bundled, and by this, the laser light source 30 which consists of a strong excitation light source device by the other end of five bundled quartz fibers. A light exit 30A is configured.

In the fluorescent light source device 10 having such a configuration, the laser light emitted from the 14 laser light emitting elements 32 in each of the five laser light source units 31 constituting the laser light source 30 is substantially parallel by the collimating lens 33. After being converted to light, it is reflected toward the condenser lens 35 by the folding mirror 34. Then, the reflected light of the folding mirror 34 is collected by the condenser lens 35 and enters one end of the light guide member 36. In this way, the laser light incident on each of the light guide members 36 constituting the five light source units 31 is a light emission port formed by the other ends of these five light guide members 36 (quartz fibers). 30A is emitted as excitation light.
As shown in FIG. 1, the laser light emitted from the light emission port 30 </ b> A of the laser light source 30 is converted into substantially parallel light by the collimating lens 12, condensed by the condenser lenses 13 and 14, and fluorescent light emission. By irradiating the surface (irradiated surface) of the wavelength conversion member 21 constituting the body 20, it is converted into fluorescence.
Thus, the fluorescence emitted by irradiating the wavelength conversion member 21 with the laser light is emitted from the fluorescent light source device 10 and used as, for example, the light source light of the projector device.

In the fluorescent light source device 10, in the strong excitation light source device constituting the laser light source 30, for example, a laser beam having a wavelength of 445 nm is emitted at an output of 1.6 W as the laser light emitting element 32 constituting each of the plurality of laser light source units 31. When a thing is used, the excitation light of high energy density will be irradiated with respect to the wavelength conversion member 21. FIG. Specifically, the energy for exciting the phosphor constituting the wavelength conversion member 21 is about 100 W (excitation density is about 20 W / mm ² ).
Here, for example, since a general excitation density of a fluorescent light source device having a conventionally known fluorescent wheel having a configuration shown in FIG. 8 is 5 W / mm ² , the fluorescent light source device 10 includes a fluorescent wheel. The phosphor constituting the wavelength conversion member 21 is excited with light having an excitation density four times that of the fluorescent light source device.
On the other hand, under the condition that light having energy of about 100 W is irradiated as excitation light, the fluorescence conversion efficiency in the wavelength conversion member 21 is 50%, so about half of the excitation light energy becomes heat. Moreover, as shown in FIG. 5, the fluorescence conversion efficiency in the wavelength conversion member 21 decreases as the temperature of the wavelength conversion member 21 increases, and this temperature quenching causes a decrease in luminous flux.
FIG. 5 shows the relationship between the temperature of the phosphor constituting the wavelength conversion member 21 (wavelength conversion member temperature) and the relative value of the amount of fluorescent light flux.

Thus, in the fluorescent light source device 10, the wavelength conversion member 21 has a specific thermal conductivity of 4.0 W / mK or more, and the bonding member has a higher thermal conductivity than the wavelength conversion member 21. The heat generated in the wavelength conversion member 21 by being irradiated with the excitation light is efficiently transmitted to the heat conductive substrate 26 through the bonding member. Further, since the heat conductive substrate 26 is made of a substrate material having a thermal expansion coefficient substantially equal to that of the wavelength conversion member 21, the heat of the wavelength conversion member 21 is transmitted to the heat conductive substrate 26 through the bonding member. High reliability in thermal cycle.
As described above, since the fluorescent light emitter 20 has an excellent exhaust heat structure, it is possible to suppress an increase in the temperature of the wavelength conversion member 21 due to irradiation with excitation light. Therefore, the temperature of the wavelength conversion member 21 irradiated with the excitation light is set to a temperature at which the luminous flux decrease due to temperature quenching of the phosphor constituting the wavelength conversion member 21 is within 10%, specifically 200 ° C. or less. Since it can be preferably set to 150 ° C. or less, high luminous efficiency can be obtained.
Further, in the fluorescent light source device 10, the wavelength conversion member 21 and the heat conductive substrate 26 are thermally expanded to cause separation between the heat conductive substrate 26 and the wavelength conversion member 21, and the wavelength conversion member. No adverse effects such as the occurrence of cracks in 21 occur.

The present invention is not limited to the above embodiment, and various modifications can be made.
For example, in a fluorescent light emitter, a wavelength conversion member having a thermal conductivity of 4.0 W / mK or more is bonded to a thermally conductive substrate made of a substrate material via a bonding member having a higher thermal conductivity than the wavelength conversion member. What is necessary is just to have the structure formed by joining.
Specifically, for example, the heat conductive substrate may be provided with a heat radiating fin (see FIG. 7), or a metal film is provided only on the surface of a base material made of a substrate material. (See FIGS. 6 and 7).
In the case where the thermally conductive substrate is provided with heat radiating fins, a higher heat radiating effect is obtained by the heat conductive substrate due to the heat radiating effect of the heat radiating fins. Further, since it is not necessary to use a heat-fining bonding member such as grease to fix the heat-dissipating fin to the heat-conductive substrate, heat is transferred to the heat-dissipating fin via the heat-conductive bonding member. There is no need to do. Therefore, the temperature rise of the wavelength conversion member due to the irradiation of excitation light can be further suppressed, and the luminous efficiency can be further increased.
In addition, when the thermally conductive substrate is made of at least a graphite composite material, it is possible to suppress the weight of the thermally conductive substrate accompanying the provision of the heat radiation fins. This is because the graphite composite material has a smaller specific gravity than a metal such as copper, which is generally used as a constituent material of the heat radiation fin. Here, the specific gravity of the graphite composite material is about 1/4 of that of copper.

Moreover, the metal film may be formed in the wavelength conversion member in the whole outer surface other than the surface (surface to be irradiated) (refer FIG. 7).
When a metal film including a reflective film layer is formed on the side surface of the wavelength conversion member, the fluorescence obtained in the wavelength conversion member can be prevented from being emitted from the side surface. It can be used more efficiently.

As a specific example of another embodiment of the present invention, there is a fluorescent light source device including a fluorescent light emitter as shown in FIGS.
In these fluorescent light source devices according to FIGS. 6 and 7, similarly to the fluorescent light source device according to FIGS. 1 to 3, the temperature increase of the wavelength conversion member due to the irradiation of excitation light can be suppressed, and high luminous efficiency. Can be obtained.

Here, the fluorescent light-emitting body 41 of FIG. 6 has a configuration having a thermally conductive substrate 42 in which a metal film is provided only on the surface (upper surface in FIG. 6) of a base material 26A made of a substrate material. In addition, a metal film has the structure similar to the metal film provided in the heat conductive board | substrate 26 of the fluorescence light source device 10 which concerns on FIGS. 1-3, for example.
The fluorescent light source device having the fluorescent light emitter 41 of FIG. 6 uses a thermally conductive substrate 42 in which a metal film is provided only on the surface of the base material 26A made of a substrate material. Other than the above, the fluorescent light source device 10 according to FIGS.

7 has a configuration in which the heat conductive substrate 45 includes the heat radiation fins 46 on the back surface side (the lower surface side in FIG. 7). The heat conductive substrate 45 is a substrate in which a metal film is provided only on the surface (upper surface in FIG. 7) of a base material 45A made of a substrate material. In addition, a metal film has the structure similar to the metal film provided in the heat conductive board | substrate 26 of the fluorescence light source device 10 which concerns on FIGS. 1-3, for example. Further, a metal film is formed on the entire outer surface (back surface and side surface) other than the surface (irradiated surface) of the wavelength conversion member 21. In addition, a metal film has the structure similar to the metal film currently formed in the wavelength conversion member 21 of the fluorescence light source device 10 which concerns on FIGS. 1-3, for example.
In the fluorescent light source device having the fluorescent light emitter shown in FIG. 7, the fluorescent light emitter 44 uses the heat conductive substrate 45 having the heat dissipating fins 46 on the back surface side, and the surface of the wavelength conversion member 21 ( Except that a metal film is formed on the entire surface of the outer surface other than the surface to be irradiated), it has the same configuration as that of the fluorescent light source device according to FIG.

Moreover, the structure of the whole fluorescence light source device is not limited to what is shown in FIG. 1, A various structure is employable.
For example, in the fluorescent light source device 10 according to FIG. 1, the light of one laser light source (for example, a laser diode) is used, but there are a plurality of laser light sources, and a condensing lens is disposed in front of the wavelength conversion member, The form which irradiates a wavelength conversion member with condensed light may be sufficient. In addition, the excitation light is not limited to the light from the laser light source, and may be one that condenses the light of the LED as long as it can excite the wavelength conversion member, and further, from a lamp in which mercury, xenon, or the like is enclosed. May be light. When a light source having a width in the radiation wavelength such as a lamp or LED is used, the wavelength of the excitation light is a main radiation wavelength region emitted from the lamp or the like. However, the present invention is not limited to this.

  Hereinafter, experimental examples performed for confirming the effects of the present invention will be described.

[Experimental Example 1]
First, seven kinds of LuAG: Ce polycrystalline materials (thermal expansion coefficient 8.0 × 10 ⁻⁶ / K) having an outer diameter of 18 mm and a thickness of 100 μm and having the porosity shown in Table 1 were prepared. By cutting these seven kinds of polycrystalline materials with a dicing saw, a wavelength conversion member having a rectangular flat plate shape having a length of 3 mm, a width of 1.7 mm, and a thickness of 130 μm was obtained.
Then, using each of the obtained seven types of wavelength conversion members, seven types of fluorescent light emitters having the configurations of FIGS. 2 and 3 (hereinafter referred to as “experimental fluorescent light emitter (1)” to “experimental fluorescent light”). A light emitter (also referred to as “7”) was manufactured.
In the experimental fluorescent light emitter (1) to the experimental fluorescent light emitter (7), the heat conductive substrate has a rectangular flat plate shape of 25 mm long, 25 mm wide, and 1.6 mm thick, and graphite, aluminum, A composite material (coefficient of thermal expansion: 7.0 × 10 ⁻⁶ / K) was used. Further, a flux-free solder sheet (thermal conductivity 55 W / mK) having a length of 3.5 mm, a width of 2.2 mm, and a thickness of 50 μm was used as the joining member.

The produced experimental fluorescent light emitter (1) to experimental fluorescent light emitter (7) are used as fluorescent light emitters in the fluorescent light source device having the configuration shown in FIG. 1, and the experimental fluorescent light emitter (1) to the experimental fluorescent light emission are used. Each of the bodies (7) was irradiated with excitation light having an energy for exciting the phosphor of about 100 W (excitation density of about 20 W / mm ² ) from a laser light source under an environmental condition of a temperature of 25 ° C. Then, the temperature (surface temperature) of the heat conductive substrate is measured by a thermocouple, and the temperature of the wavelength conversion member is calculated based on the obtained measurement value and the thermal resistance of the wavelength conversion member constituting each fluorescent light emitter. did. The results are shown in Table 1 together with the thermal conductivity of the wavelength conversion member.
Here, a strong excitation light source device having the structure of FIG. 4 was used as the laser light source. In this strong excitation light source device, a laser light emitting element 32 that emits laser light having a wavelength of 445 nm at an output of 1.6 W is used, and a light guide member 36 that is made of a quartz fiber having a diameter of 1.5 mm. Using.

From the above results, as the porosity of the polycrystalline material constituting the wavelength conversion member increases, air having a low thermal conductivity (0.0241 W / mK) is present in the pores. It was revealed that the thermal conductivity was greatly reduced.
Moreover, it became clear that the temperature of the wavelength conversion member in the state irradiated with the excitation light can be set to 200 ° C. or less by setting the thermal conductivity of the wavelength conversion member to 4.0 W / mK or more. Moreover, in order to set the thermal conductivity of the wavelength conversion member to 4.0 W / mK or more, it is necessary to set the porosity of the crystal material (polycrystalline material) constituting the phosphor to 0.5% or less. It became clear.
That is, according to the fluorescent light emitter (1) to the fluorescent light emitter (4) according to the present invention, it was confirmed that the temperature increase of the wavelength conversion member due to the irradiation of the excitation light can be suppressed.

DESCRIPTION OF SYMBOLS 10 Fluorescence light source device 11 Dichroic mirror 12 Collimate lens 13, 14 Condensing lens 20 Fluorescent light-emitting body 21 Wavelength conversion member 22 Reflective film layer 23, 24 Protective film layer 25 Solder wet film layer 26 Thermally conductive substrate 26A Base material 27 Protection Film layer 28 Solder wetting film layer 29 Bonding member layer 30 Laser light source 30A Light exit port 31 Laser light source unit 32 Laser light emitting element 33 Collimator lens 34 Folding mirror 35 Condensing lens 36 Light guide member 41 Fluorescent light emitter 42 Thermally conductive substrate 44 Fluorescent light emitter 45 Thermally conductive substrate 45A Base material 46 Radiation fin 51 Laser light source 52 Fluorescent wheel 53 Wheel motor 61 Collimator lens 62 Red light source 63A, 63B, 63C, 64A, 64B, 64C Condensing lens 65 Dichroic lens 66 Light guide Incident lens 67 for apparatus Reflecting mirror 6 8 Light guide device 71 Wavelength conversion member 72 Substrate 73 Thermal expansion absorption layer 74 Heat dissipation plate 75 Heat sink for heat dissipation

Claims (4)

A fluorescent light source device including a wavelength conversion member made of a phosphor excited by excitation light,
The wavelength conversion member is bonded to the thermally conductive substrate via a bonding member made of solder on the surface opposite to the irradiated surface irradiated with the excitation light,
The wavelength conversion member has a thermal conductivity of 4.0 W / mK or more,
The phosphor constituting the wavelength conversion member is made of a polycrystalline material having a porosity of 0.5% or less,
The bonding member has a higher thermal conductivity than the wavelength conversion member, the area of the bonding member layer formed by the bonding member is larger than the area of the wavelength conversion member, and the heat conduction A fluorescent light source device characterized by being smaller than the area of the conductive substrate.   2. The fluorescence according to claim 1, wherein the thermally conductive substrate is made of a material having a difference in thermal expansion coefficient from the wavelength conversion member within ± 40% of the thermal expansion coefficient of the wavelength conversion member. Light source device. The fluorescent light source device according to claim 1 , wherein the thermally conductive substrate is made of at least a composite material of graphite and aluminum . The fluorescent light source device according to any one of claims 1 to 3, wherein the thermally conductive substrate is provided with a heat radiation fin .

Images