WO2018016357A1

WO2018016357A1 - Wavelength conversion member and light-emitting device using same

Info

Publication number: WO2018016357A1
Application number: PCT/JP2017/025024
Authority: WO
Inventors: 忠仁古山
Original assignee: 日本電気硝子株式会社
Priority date: 2016-07-22
Filing date: 2017-07-07
Publication date: 2018-01-25
Also published as: CN107644932A; JP2018013670A; CN207320161U; TW201804171A

Abstract

Provided are a wavelength conversion member having a ceramic layer as a reflecting layer and excellent light emission intensity, and a light-emitting device which uses the same. A wavelength conversion member 10 characterized by being provided with a first porous ceramic layer 1 having a porosity of 20 vol% or greater, a phosphor layer 2 including a phosphor formed on the first porous ceramic layer, and a low-refractive-index layer 3 formed on the phosphor layer 2 and having a refractive index equal to or less than the refractive index of the phosphor.

Description

Wavelength converting member and light emitting device using the same

The present invention relates to a wavelength conversion member suitable as a fluorescent wheel for a projector and a light emitting device using the same.

Recently, in order to reduce the size of projectors, light emitting devices using light sources such as LEDs (Light Emitting Diodes) and phosphors have been proposed. For example, the wavelength of light from a light source is converted by a phosphor layer, and the obtained fluorescence is reflected to the incident side of the light source by a reflection layer provided adjacent to the wavelength conversion member and taken out to the outside. A wheel has been proposed (see, for example, Patent Document 1). The reflection type fluorescent wheel has an advantage that the fluorescent light extraction efficiency to the outside is high and the projector can easily have high brightness.

Patent Document 1 discloses a metal layer such as gold, silver, copper, and aluminum as a reflective layer. Since the metal layer has high thermal conductivity, the heat generated in the phosphor layer can be efficiently released to the outside, effectively suppressing the temperature quenching of the phosphor (a phenomenon in which the emission intensity decreases due to the temperature rise of the phosphor). There is an advantage that you can.

Japanese Patent Laid-Open No. 2015-1709

Since the metal layer has a relatively large coefficient of thermal expansion, the ratio of expansion and contraction when light is irradiated from the light source or when light irradiation is stopped is large. For this reason, the phosphor layer may be cracked or peeled off due to a difference in thermal expansion coefficient from the phosphor layer. Therefore, it is conceivable to use a ceramic layer having a relatively low thermal expansion coefficient and a relatively high thermal conductivity as the reflective layer. However, the ceramic layer is inferior in reflectivity, and sufficient emission intensity cannot be obtained. is there.

In view of the above, it is an object of the present invention to provide a wavelength conversion member having a ceramic layer as a reflection layer and having excellent emission intensity and a light emitting device using the same.

The wavelength conversion member of the present invention includes a first porous ceramic layer having a porosity of 20% by volume or more, a phosphor layer including a phosphor formed on the first porous ceramic layer, and a phosphor layer. And a low refractive index layer having a refractive index equal to or lower than the refractive index of the phosphor formed thereon.

In the wavelength conversion member of the present invention, the first porous ceramic layer functions as a reflective layer. Specifically, the fluorescence generated by irradiating the main surface of the phosphor layer (the main surface opposite to the first porous ceramic layer side) with excitation light is emitted from the first porous ceramic layer. Reflected and emitted to the outside from the same main surface as the excitation light incident surface in the phosphor layer. Here, the first porous ceramic layer exhibits a high light reflectivity by having a porosity of 20% by volume or more. Specifically, light is likely to be reflected at the interface between the pores and the ceramics present in the first porous ceramic layer due to the difference in refractive index between the two. In the present invention, since the ratio of pores in the first porous ceramic layer is as large as 20% by volume or more, and there are many interfaces that contribute to light reflection, the light reflectance of the entire first porous ceramic layer is large. Become. As a result, the fluorescence generated in the phosphor layer can be efficiently reflected by the first porous ceramic layer, and the emission intensity of the wavelength conversion member can be improved. The heat generated in the phosphor layer is dissipated through the first porous ceramic layer.

In the wavelength conversion member of the present invention, a low refractive index layer having a refractive index equal to or lower than the refractive index of the phosphor is formed on the phosphor layer. Thereby, the incident efficiency of the excitation light to the wavelength conversion member and the emission efficiency from the wavelength conversion member can be improved, and as a result, the emission intensity can be increased. In general, the phosphor layer has a configuration in which phosphor powder is dispersed in a matrix such as glass or resin. Here, since the refractive index of the phosphor powder is relatively high (for example, the refractive index nd of the YAG phosphor is about 1.8), the refractive index of the phosphor layer tends to be high. Therefore, when the low refractive index layer is not formed, the refractive index difference between the external air and the phosphor layer becomes large, and excitation light and fluorescence are easily reflected at the interface between the two.

In the wavelength conversion member of the present invention, it is preferable that the phosphor layer is bonded to the first porous ceramic layer through fusion or an inorganic bonding layer.

According to the above configuration, since the phosphor layer and the first porous ceramic layer can be joined without using a resin adhesive having low heat resistance, a wavelength conversion member having excellent heat resistance can be obtained. Can do. Specifically, since the resin adhesive deteriorates and blackens due to the irradiation heat of excitation light, the emission intensity tends to decrease with time, but such a problem hardly occurs according to the above configuration. In addition, since the resin adhesive has low thermal conductivity, when the phosphor layer and the first porous ceramic layer are bonded with the resin adhesive, the heat generated in the phosphor layer is on the first porous ceramic layer side. It is difficult to dissipate heat. On the other hand, if the phosphor layer is bonded to the first porous ceramic layer through fusion or an inorganic bonding layer, heat generated in the phosphor layer is efficiently dissipated to the first porous ceramic layer side. Easy to be.

In the wavelength conversion member of the present invention, the first porous ceramic layer is preferably made of at least one selected from aluminum oxide, magnesium oxide and zirconium oxide.

In the wavelength conversion member of the present invention, it is preferable that a heat dissipation layer is formed on the main surface of the first porous ceramic layer opposite to the main surface on which the phosphor layer is formed.

The heat generated in the phosphor layer is transferred to the first porous ceramic layer, but the first porous ceramic layer has a large number of pores and may have insufficient thermal conductivity. In such a case, if the above configuration is adopted, the heat generated in the phosphor layer and conducted to the first ceramic layer is easily released to the outside through the heat dissipation layer. Therefore, it is possible to further suppress the heat generation in the phosphor layer.

In the wavelength conversion member of the present invention, the heat dissipation layer is preferably a dense ceramic layer having a porosity of less than 20% by volume.

The dense ceramic layer is relatively excellent in thermal conductivity because the proportion of pores having heat insulation is as low as less than 20% by volume. Further, since the light transmitted without being reflected by the first porous ceramic layer can be reflected by the dense ceramic layer, the light reflectance can be improved as a whole of the wavelength conversion member.

In the wavelength conversion member of the present invention, the dense ceramic layer is preferably made of at least one selected from aluminum oxide, magnesium oxide and zirconium oxide.

In the wavelength conversion member of the present invention, a second porous ceramic layer having a porosity of 20% by volume or more is formed on the main surface of the heat dissipation layer opposite to the main surface on which the first porous ceramic layer is formed. It is preferable that

As will be described later, the first porous ceramic layer is produced, for example, by firing a green sheet as a raw material. Here, since the green sheet is easily contracted by firing, the laminated body including the first porous ceramic layer and the heat dissipation layer may be warped. In particular, when the thickness of each layer is small, warping is likely to occur. Therefore, by forming a second porous ceramic layer having a porosity of 20% by volume or more on the main surface of the heat dissipation layer opposite to the main surface on which the first porous ceramic layer is formed, the heat dissipation layer is formed. And the stress generated between the first ceramic layer and the stress generated between the heat dissipation layer and the second ceramic layer are balanced, and warpage during firing is less likely to occur.

In the wavelength conversion member of the present invention, it is preferable that the porosity, thickness and / or material of the first porous ceramic layer and the second porous ceramic layer are substantially the same. If it does in this way, the problem of the curvature in the baking process of the green sheet at the time of manufacture of the wavelength conversion member of the present invention can be controlled effectively. “Substantially the same” means that the porosity, thickness, and material are not so different as to affect the warpage in the firing process of the green sheet. Specifically, the porosity means that the difference is 5% or less. Moreover, about thickness, it means that the ratio of the difference of the thickness of each layer (The ratio of the difference of the thickness of each layer with respect to the layer with larger thickness among each layer) is 10% or less.

In the wavelength conversion member of the present invention, the phosphor layer is preferably formed by dispersing the phosphor in an inorganic binder. If it does in this way, it will become easy to improve the heat resistance of a fluorescent substance layer, and it will become difficult to produce malfunctions, such as breakage of a fluorescent substance layer by excitation light irradiation.

In the wavelength conversion member of the present invention, the low refractive index layer is preferably made of glass.

The wavelength conversion member of the present invention may have a wheel shape. In this case, it is suitable as a constituent member of the projector light source.

The light-emitting device of the present invention includes the above-described wavelength conversion member and a light source that irradiates the phosphor layer in the wavelength conversion member with excitation light.

The light emitting device of the present invention can be used as a projector light source.

According to the present invention, it is possible to provide a wavelength conversion member having a ceramic layer as a reflection layer and having excellent emission intensity and a light emitting device using the same.

(A) is a typical perspective view which shows the wavelength conversion member which concerns on the 1st Embodiment of this invention, (b) is a figure which shows a part of side cross section of the wavelength conversion member of (a). It is a figure which shows a part of side cross section of the wavelength conversion member which concerns on the 2nd Embodiment of this invention. It is a figure which shows a part of side cross section of the wavelength conversion member which concerns on the 3rd Embodiment of this invention. It is a figure which shows a part of side cross section of the wavelength conversion member which concerns on the 4th Embodiment of this invention. In an Example, it is a typical top view which shows the sample of the wavelength conversion member for performing characteristic evaluation.

Hereinafter, embodiments of the wavelength conversion member of the present invention will be described with reference to the drawings. However, the following embodiments are merely examples, and the present invention is not limited to the following embodiments. Moreover, in each drawing, the member which has the substantially the same function may be referred with the same code | symbol.

(1) Wavelength conversion member according to the first embodiment FIG. 1A is a schematic perspective view showing a wavelength conversion member according to the first embodiment of the present invention, and FIG. It is a figure which shows a part of side cross section of this wavelength conversion member.

The wavelength conversion member 10 includes a first porous ceramic layer 1, a phosphor layer 2 including a phosphor formed thereon, and a low refractive index layer 3 formed thereon. . The first porous ceramic layer 1, the phosphor layer 2, and the low refractive index layer 3 have wheel shapes that are substantially the same in outer diameter and are concentric. Excitation light is incident from the upper surface of the low refractive index layer 3 (surface opposite to the surface on which the phosphor layer 2 is formed), and is converted in wavelength by the phosphor contained in the phosphor layer 2 to emit fluorescence. The fluorescent light is reflected by the first porous ceramic layer 1 and is emitted to the outside from the upper surface of the low refractive index layer 3. Here, it is preferable that the first porous ceramic layer 1 has a higher thermal conductivity than the phosphor layer 2, which facilitates efficient release of heat generated in the phosphor layer 2 to the outside.

The porosity of the first porous ceramic layer 1 is 20% by volume or more, preferably 30% by volume or more, and particularly preferably 40% by volume or more. Since the first porous ceramic layer 1 has a porosity of 20% by volume or more, the first porous ceramic layer 1 exhibits a high light reflectance for the reasons described above. The upper limit of the porosity of the first porous ceramic layer 1 is preferably 80% by volume or less, 75% by volume or less, and particularly preferably 70% by volume or less. If the porosity of the first porous ceramic layer 1 is too high, the mechanical strength is lowered, or the heat conductivity is lowered to make it difficult to release the heat generated in the phosphor layer 2 to the outside.

The first porous ceramic layer 1 is made of aluminum oxide, magnesium oxide, zirconium oxide, titanium oxide, niobium oxide, zinc oxide, silicon oxide, yttrium oxide, aluminum nitride, boron nitride, silicon nitride, silicon carbide, or the like. Can be mentioned. These may be used alone or in combination of two or more. Among these, aluminum oxide, magnesium oxide, and zirconium oxide are preferable because they have high thermal conductivity and are inexpensive. In particular, aluminum oxide is preferable.

The thickness of the first porous ceramic layer 1 is preferably 0.05 to 2 mm, 0.1 to 1.5 mm, particularly preferably 0.2 to 1 mm. When the thickness of the 1st porous ceramic layer 1 is too small, mechanical strength will fall and it will become easy to break at the time of use. Moreover, it becomes difficult to obtain sufficient light reflectance. On the other hand, when the thickness of the 1st porous ceramic layer 1 is too large, there exists a tendency for the mass of the wavelength conversion member 10 and also the light emitting device using the same to become large. Further, when the wheel-shaped wavelength conversion member 10 is used as a light source for a projector, a load on a motor that rotates the wavelength conversion member 10 increases, or vibration due to rotation increases, which may cause damage.

Examples of the phosphor layer 2 include those in which a phosphor is dispersed in an inorganic binder. In this way, it becomes easy to match the thermal expansion coefficient with the first porous ceramic layer 1, and even when the temperature is increased by irradiation with excitation light, damage due to the difference in thermal expansion coefficient is unlikely to occur. Become. Glass etc. are mentioned as an inorganic binder.

As the glass used as the inorganic binder, borosilicate glass, phosphate glass and the like can be used. The softening point of the glass is preferably 250 to 1000 ° C, particularly 300 to 850 ° C. If the softening point of the glass is too low, the mechanical strength of the phosphor layer 2 is lowered, or it is easily melted by irradiation with excitation light. On the other hand, if the softening point of the glass is too high, the phosphor is deteriorated in the firing step during production, and the light emission intensity of the phosphor layer 2 is likely to be lowered.

The phosphor is not particularly limited as long as it emits fluorescence when incident excitation light is incident. Specific examples of the phosphor include, for example, an oxide phosphor, a nitride phosphor, an oxynitride phosphor, a chloride phosphor, an acid chloride phosphor, a sulfide phosphor, an oxysulfide phosphor, and a halide. Examples thereof include one or more selected from phosphors, chalcogenide phosphors, aluminate phosphors, halophosphate phosphors, and garnet compound phosphors. When blue light is used as excitation light, for example, phosphors that emit green light, yellow light, or red light as fluorescence may be mixed and used.

The average particle diameter (D ₅₀ ) of the phosphor is preferably 1 to 50 μm, particularly preferably 5 to 25 μm. If the average particle size of the phosphor is too small, the emission intensity tends to decrease. On the other hand, if the average particle diameter of the phosphor is too large, the emission color tends to be non-uniform.

The phosphor content in the phosphor layer 2 is preferably 5 to 80% by volume, 10 to 75% by volume, and particularly preferably 20 to 70% by volume. If the phosphor content is too small, the emission intensity tends to be insufficient. On the other hand, if the phosphor content is too large, the mechanical strength of the phosphor layer 2 tends to be insufficient.

The thickness of the phosphor layer 2 is preferably thinner as long as the excitation light is surely absorbed by the phosphor. This is because if the phosphor layer 2 is too thick, the scattering and absorption of light in the phosphor layer 2 becomes too large, and the emission efficiency of fluorescence may be lowered. Specifically, the thickness of the phosphor layer 2 is preferably 1 mm or less, 0.5 mm or less, particularly 0.3 mm or less. The lower limit of the thickness of the phosphor layer 2 is usually about 0.03 mm.

The low refractive index layer 3 is made of glass, for example. As the glass, borosilicate glass, phosphate glass, or the like can be used. The softening point of the glass is preferably 250 to 1000 ° C, particularly 300 to 850 ° C. If the softening point of the glass is too low, the mechanical strength of the low refractive index layer 3 is lowered or the glass is easily melted by irradiation with excitation light. On the other hand, if the softening point of the glass is too high, the phosphor is deteriorated in the firing step during production, and the light emission intensity of the phosphor layer 2 is likely to be lowered.

The refractive index (nd) of the low refractive index layer 3 is preferably 1.9 or less, 1.85 or less, 1.8 or less, 1.7 or less, particularly 1.6 or less. If the refractive index of the low refractive index layer 3 is too high, it is difficult to obtain the effect of improving the light emission intensity as described above. On the other hand, the lower limit of the refractive index of the low refractive index layer 3 is not particularly limited, but is practically 1.4 or more, and further 1.45 or more.

For example, the low refractive index layer 3 is fused to the phosphor layer 2. From the viewpoint of increasing the adhesion strength between the phosphor layer 2 and the low refractive index layer 3, the difference in thermal expansion coefficient (30 to 380 ° C.) between the phosphor layer 2 and the low refractive index layer 3 is 100 × 10 ⁻⁷ / ° C. or less. It is preferably 80 × 10 ⁻⁷ / ° C. or less, 60 × 10 ⁻⁷ / ° C. or less, and particularly preferably 40 × 10 ⁻⁷ / ° C. or less. Further, the difference between the softening point of the inorganic binder contained in the phosphor layer 2 and the softening point of the low refractive index layer 3 is preferably 200 ° C. or less, 150 ° C. or less, and particularly preferably 100 ° C. or less.

If the thickness of the low refractive index layer 3 is too large, excitation light or fluorescence tends to be absorbed, or scattering loss to the outside tends to increase. For this reason, the thickness of the low refractive index layer 3 is preferably 0.1 mm or less, 0.05 mm or less, 0.03 mm or less, and particularly 0.02 mm or less. The lower limit value of the thickness of the glass layer 20 is not particularly limited, but is practically 0.003 mm or more, and further 0.01 mm or more.

From the viewpoint of making it difficult for excitation light and fluorescence to be absorbed in the low refractive index layer 3, the total light transmittance of the low refractive index layer 3 is preferably 50% or more, 65% or more, particularly preferably 80% or more.

The phosphor layer 2 is preferably bonded to the first porous ceramic layer 1 via a fused or inorganic bonding layer. If it does in this way, the heat resistance of the wavelength conversion member 10 can be improved. Further, the heat generated in the phosphor layer 2 can be efficiently dissipated to the first porous ceramic layer 1 side.

As a method of fusing the phosphor layer 2 to the first porous ceramic layer 1, for example, the phosphor layer 2 is laminated on the main surface 1 a of the first porous ceramic layer 1, thermocompression bonded, and fired. A method is mentioned. For example, in the case of the phosphor layer 2 in which the phosphor is dispersed in the glass matrix, the first porous ceramic layer 1 and the glass matrix in the phosphor layer 2 are fused.

As a method of bonding the phosphor layer 2 to the first porous ceramic layer 1 with an inorganic bonding layer, a transparent inorganic material by a sol-gel method is applied on the main surface 1a of the porous ceramic layer 1, and the phosphor is coated thereon. A method in which the layer 2 is laminated and heated is exemplified. Examples of the transparent inorganic material by the sol-gel method include polysilazane. Polysilazane reacts with moisture in the air to generate ammonia and condense, thereby forming a SiO ₂ film. Thus, a bonding agent that forms an inorganic glass film at a relatively low temperature (room temperature to 200 ° C.) can be used as the transparent inorganic material. In addition, it is possible to use a bonding agent containing an alcohol-soluble organosilicon compound or other metal compound (organic or inorganic) and forming a SiO ₂ network similar to glass at a relatively low temperature in the presence of a catalyst. it can. In the bonding agent, when a metal alkoxide is used as the organometallic compound and an alcohol is used as the catalyst, hydrolysis and dehydration are promoted, and as a result, a SiO ₂ network is formed.

The wavelength conversion member 10 can be manufactured as follows.

A slurry containing ceramic powder as a raw material of the first porous ceramic layer 1 and an organic component such as a binder resin, a solvent, and a plasticizer is applied onto a resin film such as polyethylene terephthalate by a doctor blade method or the like, and heated. By drying, the 1st green sheet for porous ceramic layers 1 is produced. Here, the average particle diameter (D ₅₀ ) of the ceramic powder that is the raw material of the first porous ceramic layer 1 is preferably 0.1 to 10 μm. When the average particle diameter of the ceramic powder is too small, the porosity of the first porous ceramic layer 1 tends to be lowered. On the other hand, if the average particle size of the ceramic powder is too large, sintering becomes insufficient, and the mechanical strength of the first porous ceramic layer 1 tends to decrease. Next, the first green sheet for porous ceramic layer 1 is fired at about 1200 to 1500 ° C. In this way, the first porous ceramic layer 1 is obtained. Here, if the firing temperature is too low, sintering tends to be insufficient. On the other hand, if the firing temperature is too high, the porosity tends to decrease.

Also, a slurry containing glass powder as a glass matrix of the phosphor layer 2, phosphor and organic components such as a binder resin, a solvent, and a plasticizer is applied onto a resin film such as polyethylene terephthalate by a doctor blade method or the like. By heating and drying, a green sheet for the phosphor layer 2 is produced.

Furthermore, by applying a slurry containing glass powder to be the low refractive index layer 3 and organic components such as a binder resin, a solvent, and a plasticizer on a resin film such as polyethylene terephthalate by a doctor blade method or the like, and heating and drying. Then, a green sheet for the low refractive index layer 3 is prepared.

The porous ceramic layer 1, the phosphor layer 2, the green sheet for the phosphor layer 2, and the green sheet for the low refractive index layer 3 thus obtained are laminated and fired, whereby the porous ceramic layer 1, the phosphor layer 2, the low refractive index layer 3 The wavelength conversion member 10 formed by fusion bonding is obtained. Here, the firing temperature is preferably within the range of the softening temperature ± 100 ° C. of the glass powder in the phosphor layer 2 and the low refractive index layer 3, particularly within the range of the softening point ± 50 ° C. of the glass powder. If the firing temperature is too low, the porous ceramic layer 1 and the phosphor layer 2 or the phosphor layer 2 and the low refractive index layer 3 are difficult to fuse. Moreover, the sintering of the glass powder becomes insufficient, and the mechanical strength of the phosphor layer 2 and the low refractive index layer 3 tends to decrease. On the other hand, if the firing temperature is too high, the phosphor in the phosphor layer 2 may deteriorate and the emission intensity may decrease.

In the above method, the porous ceramic layer 1, the green sheet for the phosphor layer 2, and the green sheet for the low refractive index layer 3 are laminated and fired at the same time. However, the present invention is not limited to this. For example, the porous ceramic layer 1 and the green sheet for the phosphor layer 2 are first laminated and fired, and then the green sheet for the low refractive index layer 3 is laminated on the obtained phosphor layer 2 and further fired. Thus, the low refractive index layer 3 may be formed.

Alternatively, the porous ceramic layer 1, the phosphor layer 2, and the low refractive index layer 3 are fired separately for the porous ceramic layer 1 green sheet, the phosphor layer 2 green sheet, and the low refractive index layer 3 green sheet, respectively. Then, by bonding them using an inorganic bonding agent, the wavelength conversion member 10 in which the porous ceramic layer 1, the phosphor layer 2, and the low refractive index layer 3 are bonded by the inorganic bonding layer is obtained. You can also.

In addition to the above method, the phosphor layer 2 is formed on the porous ceramic layer 1 by applying the slurry for the phosphor layer 2 on the surface of the porous ceramic layer 1 and firing it. The low refractive index layer 3 may be formed by applying a slurry for the low refractive index layer 3 on the surface and further baking. As the slurry for the phosphor layer 2 and the slurry for the low refractive index layer 3 used here, those used for producing the green sheet for the phosphor layer 2 and the green sheet for the low refractive index layer 3 can be used.

In each of the above production methods, a degreasing step for removing organic substances may be performed before firing the green sheet or slurry. In addition, when the layers including the green sheet are stacked, the layers may be appropriately heat-pressed in order to enhance mutual adhesion.

(2) Wavelength conversion member according to the second embodiment FIG. 2 is a view showing a part of a side cross section of the wavelength conversion member according to the second embodiment of the present invention. In the wavelength conversion member 20 according to the present embodiment, the first heat dissipation layer 4 is provided on the main surface opposite to the main surface on which the phosphor layer 2 of the porous ceramic layer 1 is formed. Different from the wavelength conversion member 10 according to the embodiment. The heat dissipation layer 4 has a ring shape whose outer diameter is substantially the same and concentric with the first porous ceramic layer 1. Other configurations are the same as those of the wavelength conversion member 10 according to the first embodiment. By providing the heat dissipation layer 4 on the main surface of the porous ceramic layer 1, the heat generated in the phosphor layer 2 and conducted to the first porous ceramic layer 1 is transmitted to the outside through the heat dissipation layer 4 for the reasons described above. It becomes easy to be released. The thermal conductivity of the heat dissipation layer 4 is preferably 5 W / m · K or more, 10 W / m · K or more, and particularly preferably 20 W / m · K or more.

Examples of the heat dissipation layer 4 include a dense ceramic layer. The porosity of the dense ceramic layer is less than 20% by volume, preferably 15% by volume or less, and particularly preferably 10% by volume or less. If the porosity of the dense ceramic layer is too high, the thermal conductivity is lowered, and the heat dissipation tends to be lowered. On the other hand, the lower limit of the porosity of the dense ceramic layer is not particularly limited, but is actually 0.2% by volume or more.

Examples of the dense ceramic layer include those made of aluminum oxide, magnesium oxide, zirconium oxide, titanium oxide, niobium oxide, zinc oxide, yttrium oxide, aluminum nitride, boron nitride, silicon carbide and the like. These may be used alone or in combination of two or more. Among these, aluminum oxide, magnesium oxide, and zirconium oxide are preferable because they have high thermal conductivity and are inexpensive.

The heat dissipation layer 4 may be made of a metal such as sapphire, aluminum, silver, or copper other than the above.

The thickness of the heat dissipation layer 4 is preferably 0.2 to 2 mm, 0.3 to 1.5 mm, and particularly preferably 0.5 to 1 mm. When the thickness of the heat dissipation layer 4 is too small, it becomes difficult to obtain a sufficient heat dissipation effect. On the other hand, if the thickness of the heat dissipation layer 4 is too large, the wavelength conversion member 20 and the light emitting device using the same tend to increase in mass. Further, when the wheel-shaped wavelength conversion member 20 is used as a light source for a projector, a load on a motor that rotates the wavelength conversion member 20 increases, or vibration due to rotation increases, which may cause damage.

The wavelength conversion member 20 can be manufactured as follows.

The first green sheet for the porous ceramic layer 1 is produced in the same manner as in the wavelength conversion member 10.

Next, the heat dissipation layer 4 is prepared. When a dense ceramic layer is used as the heat dissipation layer 4, a green sheet for the dense ceramic layer is obtained in the same manner as the method for producing the green sheet for the porous ceramic layer 1 in the wavelength conversion member 10. A dense ceramic layer having a low porosity is obtained by sintering the green sheet for the dense ceramic layer at a relatively high temperature. Specifically, it is preferable that the dense ceramic layer green sheet is fired at about 1500 ° C. or higher, preferably 1600 ° C. or higher. Moreover, as the average particle size of the ceramic powder which is a raw material (D ₅₀₎ is small, easy to reduce the porosity of the dense ceramic layer.

Subsequently, the first porous ceramic layer 1 green sheet and the heat dissipation layer 4 are stacked and fired to obtain a laminate in which the first porous ceramic layer 1 and the heat dissipation layer 4 are joined.

In the same manner as in the wavelength conversion member 10, by bonding the phosphor layer 2 on the first porous ceramic layer 1 and further the low refractive index layer 3 on the phosphor layer 2 in the obtained laminate, The wavelength conversion member 20 is obtained.

Note that the heat-dissipating layer 4 may be bonded after the phosphor layer 2 and the low refractive index layer 3 are bonded to the first porous ceramic layer 1 first.

(3) Wavelength conversion member according to the third embodiment FIG. 3 is a view showing a part of a side cross section of the wavelength conversion member according to the third embodiment of the present invention. In the wavelength conversion member 30 according to the present embodiment, the heat dissipation layer 4 has substantially the same shape as the first porous ceramic layer 1 on the main surface opposite to the main surface on which the first porous ceramic layer 1 is formed. The second porous ceramic layer 1 'is provided. Other configurations are the same as those of the wavelength conversion member 20 according to the second embodiment. By setting it as such a structure, it becomes difficult to generate | occur | produce a curvature in the wavelength conversion member 30 at the time of a green sheet baking in a manufacturing process.

As for the porosity and thickness range of the second porous ceramic layer 1 ′ and specific examples of the material, the same materials as those of the first porous ceramic layer 1 can be selected. From the viewpoint of effectively suppressing the problem of warping of the wavelength conversion member 30 in the firing step during manufacturing, the porosity, thickness, and material of the first porous ceramic layer 1 and the second porous ceramic layer 1 ′ It is preferred that at least one is substantially the same, more preferably they are all substantially the same.

(4) Wavelength Conversion Member According to Fourth Embodiment FIG. 4A is a plan view of a wavelength conversion member 40 according to the fourth embodiment of the present invention, and FIG. 4B is A of FIG. -A 'sectional view. The wavelength conversion member 40 according to this embodiment is different from the wavelength conversion member 30 in that a notch C is provided in a part of the region where the phosphor layer 2 and the low refractive index layer 3 are formed. . The configuration of each layer is the same as that of the wavelength conversion member 30. In the cutout portion C, none of the first porous ceramic layer 1, the second porous ceramic layer 1 ′, the phosphor layer 2, the low refractive index layer 3 and the heat dissipation layer 4 is formed. A part of the outer periphery is completely missing, so that excitation light can be transmitted. Therefore, by using the wavelength conversion member 40, it is possible to obtain a light emitting device that can appropriately use both the case where the excitation light is converted in wavelength by the phosphor layer 2 and the fluorescence is extracted and the case where the excitation light is extracted as it is. .

(Light emitting device)
A light-emitting device of the present invention includes the above-described wavelength conversion member (any one of the wavelength conversion members 10 to 40) and a light source that irradiates the wavelength conversion member with excitation light. As the light source, an LED, an LD, or the like can be used. The excitation light emitted from the light source is wavelength-converted by the phosphor layer in the wavelength conversion member to emit fluorescence, and the fluorescence is reflected by the first porous ceramic layer, and the fluorescence is emitted from the same side as the excitation light irradiation side. Is done.

Hereinafter, the wavelength conversion member of the present invention will be described in detail with reference to examples. However, the present invention is not limited to the following examples.

Table 1 shows examples and comparative examples of the present invention.

Example 1
(Preparation of green sheet for porous ceramic layer)
To the Al ₂ O ₃ powder (average particle size (D ₅₀ ): 1 μm), polybutyl methacrylate as a binder, methyl ethyl ketone as a plasticizer, and butyl benzyl phthalate as a solvent are appropriately added, and the slurry is kneaded for 24 hours. Obtained. The obtained slurry was applied onto a polyethylene terephthalate (PET) film using a doctor blade method and dried to obtain a green sheet (thickness 0.32 mm) for a porous ceramic layer.

(Preparation of green sheet for phosphor layer)
In mol%, SiO ₂ : 58%, Al ₂ O ₃ : 6%, B ₂ O ₃ : 17%, Li ₂ O: 8%, Na ₂ O: 8%, K ₂ O: 3% The raw materials were mixed so that a film-like glass was obtained by a melt quenching method. The obtained film-like glass was pulverized using a ball mill to obtain a glass powder having an average particle diameter (D ₅₀ ) of 1 μm.

The obtained glass powder and a YAG (Y ₃ Al ₅ O ₁₂ ) phosphor powder (average particle diameter (D ₅₀ ): 15 μm) were mixed with 30 vol% glass powder, YAG (Y ₃ Al ₅ O ₁₂ ) phosphor. The powder was mixed to 70% by volume and mixed using a vibration mixer. A binder, a plasticizer, a solvent and the like were appropriately added to 50 g of the obtained mixed powder and kneaded for 24 hours to obtain a slurry. The obtained slurry was applied onto a PET film using a doctor blade method and dried to obtain a phosphor layer green sheet (thickness: 0.12 mm).

(Preparation of green sheet for low refractive index layer)
A binder, a plasticizer, a solvent, and the like were appropriately added to 50 g of the glass powder used for the production of the green sheet for the phosphor layer, and kneaded for 24 hours to obtain a slurry. The obtained slurry was applied onto a PET film using a doctor blade method and dried to obtain a green sheet (thickness 0.03 mm) for a low refractive index layer.

(Production of wavelength conversion member)
A porous ceramic layer green sheet and a dense ceramic layer (Al ₂ O ₃ sheet, product name HA-96-2 manufactured by MARUWA, Inc .; thickness 0.8 mm, thermal conductivity 23 W / m · K) are stacked as a heat dissipation layer And applying a pressure of 10 MPa at 100 ° C. for 5 minutes using a thermocompression bonding machine to make them adhere closely, followed by degreasing treatment at 600 ° C. for 8 hours in the atmosphere, and further firing at 1400 ° C. for 5 hours As a result, a ceramic layer laminate composed of two layers of a porous ceramic layer and a dense ceramic layer was produced.

In the ceramic layer laminate, the porosity of the porous ceramic layer and that of the dense ceramic layer were obtained by binarizing the cross-section reflected electron image and then calculating the area ratio of the pore portion. The light reflectance of the ceramic layer laminate was obtained from the average value of the reflected light intensity at each wavelength of 400 to 800 nm using UV-2500PC manufactured by Shimadzu Corporation.

Next, a green sheet for a phosphor layer is laminated on the porous ceramic layer of the ceramic layer laminate, and further a green sheet for a low refractive index layer is overlaid thereon, and using a thermocompression bonding machine at 100 ° C. for 5 minutes, 10 MPa After applying both pressures to each other, degreasing treatment was performed at 500 ° C. for 7 hours in the air, and baking was further performed at 700 ° C. for 1 hour to prepare a wavelength conversion member.

(Example 2)
A green sheet for porous ceramic layer (thickness 0.26 mm) was produced in the same manner as in Example 1. After four layers of porous ceramic layer green sheets are stacked and adhered by applying a pressure of 10 MPa at 100 ° C. for 5 minutes using a thermocompression bonding machine, degreasing treatment is performed at 600 ° C. for 8 hours in the atmosphere. The porous ceramic layer was obtained by baking at 1400 degreeC for 5 hours. The light reflectance of the porous ceramic layer was measured in the same manner as in Example 1. The results are shown in Table 1.

The green sheet for the phosphor layer obtained in Example 1 was further superimposed on the porous ceramic layer, and the green sheet for the low refractive index layer was further superimposed on the porous ceramic layer. After making it adhere by applying pressure, degreasing treatment was performed at 500 ° C. for 7 hours in the air, and further, baking was performed at 700 ° C. for 1 hour to prepare a wavelength conversion member.

(Comparative example)
On the dense ceramic layer (Al ₂ O ₃ sheet manufactured by MARUWA Co., Ltd., product name HA-96-2; thickness: 0.635 mm), the green sheet for the phosphor layer obtained in Example 1, and further on it The green sheets for the refractive index layer are overlaid and adhered by applying a pressure of 10 MPa at 100 ° C. for 5 minutes using a thermocompression bonding machine, and then degreased at 500 ° C. for 7 hours in the atmosphere. Furthermore, the wavelength conversion member was obtained by baking at 700 degreeC for 1 hour. The light reflectance of the dense ceramic layer was measured in the same manner as in Example 1. The results are shown in Table 1.

(Characteristic evaluation)
About each wavelength conversion member produced as mentioned above, the fluorescence peak intensity | strength and the surface temperature of the fluorescent substance layer were measured as follows. The results are shown in Table 1. In addition, the thing of the size shown in FIG. 5 (The thickness of each layer is as showing in Table 1) was used for the measurement.

The surface of the wavelength conversion member rotated at 8000 rpm (the surface on which the phosphor layer and the low refractive index layer were formed) was irradiated with laser light at an output of 30 W from a blue laser light source having a wavelength of 440 nm. The obtained fluorescence was received by a small spectroscope (USB-4000, manufactured by Ocean Optics) through an optical fiber, and an emission spectrum was obtained. The fluorescence peak intensity was read from the emission spectrum. Further, the surface temperature of the phosphor layer was measured using a thermography i5 manufactured by FLIR.

As apparent from Table 1, the wavelength conversion members of Examples 1 and 2 had a fluorescence peak intensity of 1279 (au) or higher, whereas the wavelength conversion member of the comparative example had a fluorescence peak intensity of 1112 ( a.u.) and inferior. In addition, when Example 1 and Example 2 are compared, when a laminated body of a porous ceramic layer and a dense ceramic layer is used as the light reflecting layer, it can be seen that the light reflectance is improved. Further, when a dense ceramic layer is laminated on the porous ceramic layer, the temperature of the phosphor layer is also lowered, which is considered to reduce the temperature quenching of the phosphor. Due to these two factors, the wavelength conversion member of Example 1 is considered to have a higher fluorescence peak intensity than the wavelength conversion member of Example 2.

DESCRIPTION OF SYMBOLS 1 1st porous ceramic layer 1 '2nd porous ceramic layer 2 Phosphor layer 3 Low refractive index layer 4

Heat dissipation layer

10, 20, 30, 40 Wavelength conversion member C Notch

Claims

A first porous ceramic layer having a porosity of 20% by volume or more;
A phosphor layer containing a phosphor formed on the first porous ceramic layer;
A low refractive index layer formed on the phosphor layer and having a refractive index equal to or lower than the refractive index of the phosphor;
A wavelength conversion member comprising:
2. The wavelength conversion member according to claim 1, wherein the phosphor layer is bonded to the first porous ceramic layer through a fusion or inorganic bonding layer.
The wavelength conversion member according to claim 1 or 2, wherein the first porous ceramic layer is made of at least one selected from aluminum oxide, magnesium oxide, and zirconium oxide.
The heat dissipation layer is formed on the main surface of the first porous ceramic layer opposite to the main surface on which the phosphor layer is formed. The wavelength conversion member as described.
The wavelength conversion member according to any one of claims 1 to 4, wherein the heat dissipation layer is a dense ceramic layer having a porosity of less than 20% by volume.
6. The wavelength conversion member according to claim 5, wherein the dense ceramic layer is made of at least one selected from aluminum oxide, magnesium oxide, and zirconium oxide.
A second porous ceramic layer having a porosity of 20% by volume or more is formed on the main surface of the heat dissipation layer opposite to the main surface on which the first porous ceramic layer is formed. The wavelength conversion member according to any one of claims 4 to 6.
The wavelength conversion member according to claim 7, wherein the porosity, thickness and / or material of the first porous ceramic layer and the second porous ceramic layer are substantially the same.
The wavelength conversion member according to any one of claims 1 to 8, wherein the phosphor layer is formed by dispersing the phosphor in an inorganic binder.
10. The wavelength conversion member according to claim 1, wherein the low refractive index layer is made of glass.
11. The wavelength conversion member according to claim 1, wherein the wavelength conversion member has a wheel shape.
The wavelength conversion member according to any one of claims 1 to 11,
A light source for irradiating the phosphor layer in the wavelength conversion member with excitation light;
A light-emitting device comprising:
The light emitting device according to claim 12, wherein the light emitting device is used as a projector light source.