JP7178074B2 - WAVELENGTH CONVERSION MEMBER, WAVELENGTH CONVERSION ELEMENT AND METHOD FOR MANUFACTURING WAVELENGTH CONVERSION MEMBER - Google Patents

Description

The present invention relates to a wavelength conversion member, a wavelength conversion element , and a method for manufacturing a wavelength conversion member .

Conventionally, as a wavelength conversion member that absorbs excitation light and emits light of different wavelengths, one made of a single crystal phosphor or a polycrystalline phosphor having a porosity of 0.5% or less is known (for example, Patent Document 1).

According to Patent Document 1, by using a single-crystal phosphor that does not contain pores or a polycrystalline phosphor that has a low porosity as a wavelength conversion member, wavelength conversion due to the presence of air-containing pores with low thermal conductivity It is said that the deterioration of the thermal conductivity of the member can be suppressed. In addition, since it does not contain pores or has a small porosity, backscattering of the irradiated excitation light is almost eliminated, and excitation is performed efficiently.

Japanese Patent No. 6164221

However, when there are no pores or when the porosity is small, there is little scattering in the wavelength conversion member, so the light spreads over a wide range and the area from which the light is emitted becomes large. In this case, since the light extracted from the wavelength conversion member cannot be efficiently collected by the lens and used, the coupling efficiency with the optical system is low.

An object of the present invention is to provide a wavelength conversion member having excellent coupling efficiency with an optical system, and a wavelength conversion element including a layer comprising the wavelength conversion member.

In one aspect of the present invention, in order to achieve the above objects, the following wavelength conversion members [1] to [ 5 ], wavelength conversion elements [ 6 ] to [ 9 ], and wavelength conversions [10] to [14] A method for manufacturing a member is provided.

[1] It consists of a sintered body of phosphor particle groups, and the area ratio of voids to the whole in an arbitrary cross section is in the range of 0.6% or more and 25% or less, and the phosphor particle groups , a wavelength conversion member, which is a particle group of a single-crystal phosphor .
[2] The phosphor has a composition formula (Y _{1-xyz Lu} x _Gd y _Cez ) 3 _+a Al _5-a O ₁₂ (0≦x≦0.9994, 0≦y≦0.0669, 0.0002≦z≦0.0067, −0.016≦a≦0.315).
[3] The wavelength conversion member according to [1] or [2] above, wherein the particle size (D50) of the particle group of the phosphor is in the range of 3 µm or more and 30 µm or less.
[4] The wavelength conversion member according to [3] above, wherein the particle size (D50) of the particle group of the phosphor is in the range of 3 µm or more and 15 µm or less.
[5] The wavelength conversion member according to any one of [1] to [4] above, wherein the area ratio is in the range of 1% or more and 15% or less.
[6] A wavelength conversion layer made of a sintered body of a phosphor particle group and having an area ratio of voids to the entirety of an arbitrary cut surface in the range of 0.6% or more and 25% or less, and the wavelength conversion layer and a pad metal formed on the opposite side of the wavelength conversion layer of the reflection film, wherein the particle group of the phosphor is a single crystal phosphor A wavelength conversion element, which is a group of particles.
[7] The phosphor has a composition formula (Y _1-xyz Lu _x Gd _y Ce _z ) _3+a Al _5-a O ₁₂ (0≦x≦0.9994, 0≦y≦0.0669, 0.0002≦z≦0.0067, −0.016≦a≦0.315).
[8] The wavelength conversion element according to [6] or [7] above, wherein the particle size (D50) of the particle group of the phosphor is in the range of 3 μm or more and 30 μm or less.
[9] Any one of the above [6] to [8], further comprising a flattening film formed between the wavelength conversion layer and the reflective film and having a flat surface in contact with the reflective film. A wavelength conversion element as described.
[10] A method of manufacturing the wavelength conversion member according to any one of [1] to [5] above, which comprises pulverizing and granulating an ingot of a single-crystal phosphor to obtain a phosphor particle group. a step of applying pressure to the phosphor particle group to solidify it; a step of sintering the solidified phosphor particle group to obtain a sintered body; and slicing the sintered body into a wafer a step of obtaining a sintered body in a shape, a step of annealing the wafer-shaped sintered body, and a step of polishing the annealed wafer-shaped sintered body. A method for manufacturing a conversion member.
[11] The method for producing a wavelength conversion member according to [10] above, wherein in the step of obtaining the phosphor particle group, the ingot is pulverized by heating and cooling, and then pulverized by a ball mill.
[12] The above [10] or [11], wherein in the step of obtaining the wafer-shaped sintered body, the wafer-shaped sintered body having a thickness in the range of 0.15 mm or more and 1.0 mm or less is obtained. 3. The method for manufacturing the wavelength conversion member according to 1.
[13] In the step of applying the annealing treatment, the annealing treatment is performed in an argon atmosphere at a temperature in the range of 1450° C. or more and 1600° C. or less for a time in the range of 5 hours or more and 5 hours or less. [10] The method for manufacturing the wavelength conversion member according to any one of [12].
[14] In the step of applying the polishing treatment, the polishing treatment is performed until the thickness of the wafer-shaped sintered body is within the range of 0.05 mm or more and 0.3 mm or less, above [10] to [13]. ] The manufacturing method of the wavelength conversion member of any one of 1 item|term.

ADVANTAGE OF THE INVENTION According to this invention, the wavelength conversion element containing the layer which consists of the wavelength conversion member excellent in the coupling efficiency with an optical system, and the wavelength conversion member can be provided.

FIGS. 1(a) and 1(b) are perspective views of the wavelength conversion member according to the first embodiment. FIGS. 2A and 2B are diagrams schematically showing optical paths of fluorescence emitted from a general wavelength conversion member made of phosphor and condensed on a lens. FIG. 3 is a SEM (Scanning Electron Microscope) observation image of a cut surface of an example of the wavelength conversion member according to the first embodiment. FIG. 4 is a flow chart showing an example of the manufacturing process of the wavelength conversion member 1 according to the embodiment. FIG. 5 is a cross-sectional view schematically showing pulling of a single crystal phosphor ingot by the CZ method. FIG. 6 is a vertical sectional view of the wavelength conversion element according to the second embodiment. 7(a) to 7(f) are vertical cross-sectional views showing the manufacturing process of the wavelength conversion element when a flattening film is formed on the reflecting film side surface of the wavelength conversion layer. FIG. 8 is a vertical sectional view of the wavelength conversion module according to the second embodiment.

[First embodiment]
(Structure of Wavelength Conversion Member)
FIGS. 1(a) and 1(b) are perspective views of a wavelength conversion member 1 according to the first embodiment. The wavelength conversion member 1 is made of a sintered body of phosphor particles and has a unique shape. In addition, the area ratio of the voids (pores) to the entirety of any cut surface of the wavelength conversion member 1 is in the range of 0.6% or more and 25% or less, preferably 1% or more and 15% or less. inside.

Although the shape of the wavelength conversion member 1 is not particularly limited, it is typically flat. In the example shown in FIGS. 1(a) and 1(b), the wavelength conversion member 1 has a flat plate shape with a circular planar shape.

FIG. 1(a) is a schematic diagram of a case where mixed light of a part of the excitation light and fluorescent light obtained by wavelength-converting the excitation light is extracted from the wavelength conversion member 1. FIG. For example, when the excitation light is blue light and the fluorescence is yellow light, white light can be extracted from the wavelength converting member 1 . FIG. 1(b) is a schematic diagram in which almost all excitation light is wavelength-converted and almost only fluorescence is extracted from the wavelength conversion member 1. FIG.

In the examples shown in FIGS. 1A and 1B, the wavelength conversion member 1 is used as a reflective wavelength conversion member that reflects the excitation light and extracts the light. It can also be used as a transmissive wavelength conversion member for taking out the .

FIGS. 2A and 2B are diagrams schematically showing optical paths of fluorescence emitted from a general wavelength conversion member 30 made of a phosphor and condensed on a lens 31. FIG. "P" in FIGS. 2A and 2B indicates the irradiation position of the excitation light.

As shown in FIG. 2A, the fluorescence emitted from the vicinity of the irradiation position P of the excitation light is condensed by the lens 31 as parallel light. On the other hand, as shown in FIG. 2B, fluorescence emitted from a position away from the irradiation position P of the excitation light is not collected as parallel light by the lens 31, and can be effectively used in the optical system. Can not.

Generally, in a wavelength conversion member made of a phosphor, as described above, when the wavelength conversion member does not contain pores or has a small porosity, the scattering in the wavelength conversion member is small. larger area. In this case, as shown in FIG. 2(b), the amount of light that cannot be used effectively in the optical system increases, and the coupling efficiency with the optical system decreases.

In addition, when extracting mixed light of a part of the excitation light that is reflected without being absorbed and fluorescence as white light or the like, if the area from which the fluorescence is emitted becomes large, the difference from the area from which the excitation light is emitted becomes large. , and there is a problem that color breakup occurs when the extracted light is irradiated to a distant place.

The wavelength conversion member 1 contains pores in an amount such that the area ratio of the voids (pores) to the entirety of the entire cut surface is 0.6% or more, thereby scattering light within the wavelength conversion member 1. . This suppresses the expansion of the area from which fluorescence is emitted, and increases the coupling efficiency with the optical system. In addition, the wavelength conversion member 1 contains pores in an amount such that the area ratio of the entire voids (pores) in an arbitrary cut surface is 1% or more. can further increase the coupling efficiency of

However, if the porosity is too high, the mechanical strength and thermal conductivity of the wavelength conversion member 1 may decrease to an impractical extent. The area ratio to the whole is 25% or less, preferably 15% or less.

FIG. 3 is a SEM (Scanning Electron Microscope) observation image of a cut surface of an example of the wavelength conversion member 1 . The wavelength conversion member 1 shown in FIG. 3 is a sintered body of single crystal phosphor having a composition represented by the composition formula (Y _0.998 Ce _0.002 ) ₃ Al ₅ O ₁₂ . The parts indicated by arrows are voids (pores), and the parts of the same color occupying the majority are phosphors. Thus, the area ratio of voids to the entirety of any cut surface of the wavelength conversion member 1 can be measured using SEM observation or the like.

Further, since the wavelength conversion member 1 is composed of phosphor particle groups, it has grain boundaries inside. Since grain boundaries scatter light like pores, they are important for improving the coupling efficiency of the wavelength conversion member 1 with the optical system.

Moreover, the wavelength conversion member 1 has excellent internal quantum efficiency. For example, the particulate phosphor constituting the wavelength conversion member 1 has a composition formula (Y _1-xyz Lu _x Gd _y Ce _z ) _3+a Al _5-a O ₁₂ (0≦x≦0.9994, 0 ≤ y ≤ 0.0669, 0.0002 ≤ z ≤ 0.0067, -0.016 ≤ a ≤ 0.315). The internal quantum efficiency is 0.95 or more when the peak wavelength is 450 nm, and the internal quantum efficiency is 0.90 or more when the temperature is 300° C. and the peak wavelength of the excitation light is 450 nm.

Further, when the particulate phosphor constituting the wavelength conversion member 1 is a single crystal having a composition represented by the composition formula (Y _0.998 Ce _0.002 ) ₃ Al ₅ O ₁₂ , the temperature is 25°C. , the internal quantum efficiency is 0.99 or more when the peak wavelength of the excitation light is 450 nm, and the internal quantum efficiency is 0.90 or more when the temperature is 300° C. and the peak wavelength of the excitation light is 450 nm.

Further, when the particulate phosphor constituting the wavelength conversion member 1 is a single crystal having a composition represented by the composition formula (Lu _0.998 Ce _0.002 ) ₃ Al ₅ O ₁₂ , the temperature is 25°C. , the internal quantum efficiency is 0.99 or more when the peak wavelength of the excitation light is 450 nm, and the internal quantum efficiency is 0.93 or more when the temperature is 300° C. and the peak wavelength of the excitation light is 450 nm.

According to Table A1.3 in Solid-State Lighting Research and Development: Multi Year Program Plan March 2011 (Updated May 2011) P.69, the internal quantum efficiency (Quantum Yield (25°C) across the visible spectrum) The figure for the year is 0.90, and it states that the target value for 2020 is 0.95. From this, it can be seen that the industry expects an improvement in quantum efficiency of about 0.01 in two years. It can be said that it is an excellent phosphor having a high quantum efficiency.

As described above, the wavelength conversion member 1 can maintain a high internal quantum efficiency even under a high temperature condition of 300°C. It can exhibit an excellent function as a wavelength conversion member used in a light emitting device having extremely high luminance per area.

Moreover, in order to improve heat dissipation, the thickness of the wavelength conversion member 1 is preferably 0.3 mm or less. As a specific example, the wavelength conversion member 1 made of a YAG-based single crystal phosphor is irradiated with a blue laser beam of 20 W or more with a spot diameter of 3.0 mm or less for use in high-brightness illumination such as a projector or a spotlight. In this case, considering the thermal conductivity of the wavelength conversion member 1, the thickness is preferably 0.3 mm or less. Further, when irradiating a wavelength conversion member 1 made of a YAG-based single crystal phosphor with a spot diameter of 0.300 mm or less with a blue laser beam of 2 W or more for use in vehicle headlights and flashlights, the wavelength conversion member Considering the thermal conductivity of 1, the thickness is preferably 0.3 mm or less. Moreover, in order to suppress cracking during processing, the thickness of the wavelength conversion member 1 is preferably 0.05 mm or more.

(Features of phosphor)
In general, single-crystal phosphors often show less decrease in fluorescence intensity with an increase in temperature than polycrystalline phosphors. preferable. That is, the wavelength conversion member 1 is preferably made of a sintered body of single-crystal phosphor particle groups.

For example, a YAG-based single-crystal phosphor exhibits less decrease in fluorescence intensity with an increase in temperature than a YAG-based polycrystalline phosphor. The small decrease in fluorescence intensity is due to the small decrease in internal quantum efficiency.

Moreover, although the phosphor constituting the wavelength conversion member 1 is not particularly limited, it is preferably a YAG-based phosphor that has excellent temperature characteristics. A YAG-based phosphor is a phosphor whose mother crystal is a Y ₃ Al ₅ O ₁₂ (YAG) crystal.

For example, as a phosphor constituting the wavelength conversion member 1, the composition formula (Y _1-xy-z Lu _x Gd _y Ce _z ) _3+a Al _5-a O ₁₂ (0≦x≦0.9994, 0≦y ≦0.0669, 0.0002≦z≦0.0067, −0.016≦a≦0.315), composition formula (Y _0.998 Ce _0.002 ) A YAG phosphor having a composition represented by ₃ Al ₅ O ₁₂ and a LuAG phosphor having a composition represented by a composition formula (Lu _0.998 Ce _0.002 ) ₃ Al ₅ O ₁₂ can be used. Here, Lu and Gd are components that substitute for Y and do not serve as luminescent centers. Ce is a component (activator) that substitutes Y and can serve as a luminescence center.

In addition, some atoms in the composition of the above phosphor may occupy different positions on the crystal structure. In addition, the value of O in the composition ratio in the above composition formula is described as 12, but in the above composition, the value of O in the composition ratio slightly deviated from 12 due to the presence of oxygen that is unavoidably mixed or missing. Also includes composition. In addition, the value of a in the composition formula is a value that inevitably changes during the manufacture of the phosphor, but changes within the numerical range of about -0.016 ≤ a ≤ 0.315 are have little effect on

The range of the numerical value of z in the above composition formula representing the concentration of Ce is 0.0002 ≤ z ≤ 0.0067 because when the numerical value of z is smaller than 0.0002, the Ce concentration is too low There is a problem that the absorption of excitation light becomes small and the external quantum efficiency becomes too small. This is because there is a high possibility that it will decrease. Moreover, if the numerical value of z is 0.0010 or more, wavelength conversion can be sufficiently performed even if the wavelength conversion member 1 is thin, so that cost reduction and heat dissipation can be improved.

When the phosphor constituting the wavelength conversion member 1 is a YAG-based phosphor, it preferably does not contain group 2 elements such as Ba and Sr and group 17 elements such as F and Br and has high purity. As a result, a phosphor with high brightness and long life can be realized.

When the phosphor constituting the wavelength conversion member 1 is a single crystal phosphor, for example, the CZ method (Czochralski Method), the EFG method (Edge Defined Film Fed Growth Method), the Bridgman method, and the FZ method (Floating Zone Method). can be obtained by a liquid phase growth method such as the Bernoulli method. A particle group of the single-crystal phosphor is obtained by pulverizing the ingot of the single-crystal phosphor obtained by the liquid phase growth method.

When the phosphor particle group constituting the wavelength conversion member 1 is a single-crystal phosphor particle group, the particle size (D50) is preferably in the range of 3 μm to 30 μm, more preferably 3 μm to 15 μm. It is more preferable to be within the following range. Here, D50 means the particle size at 50 vol % in the cumulative distribution.

When the particle size (D50) is 30 μm or less, sintering proceeds easily and the pores become smaller, so that the deterioration of the thermal conductivity of the wavelength conversion member 1 due to the pores can be suppressed. High-intensity excitation light can be applied if the thermal conductivity is high. Furthermore, when the particle size (D50) is 15 μm or less, the density of the wavelength conversion member 1 is further increased, and the thermal conductivity is improved. On the other hand, when the particle diameter (D50) is smaller than 3 μm, sintering proceeds easily, but the number of pores becomes too small, so that the scattering of light inside the wavelength conversion member 1 decreases, and the light distribution characteristic becomes Lambertian. away from Therefore, the coupling efficiency between the wavelength conversion member 1 and the optical system is lowered. Further, if the particle size is too small, there arises a problem that wavelength conversion efficiency and thermal conductivity are lowered.

YAG polycrystalline phosphors are synthesized by solid phase reaction of oxide powder raw materials such as Y ₂ O ₃ , Al ₂ O ₃ , and CeO ₂ . It is difficult to On the other hand, since the single-crystal YAG phosphor is produced by pulverizing an ingot of a single-crystal phosphor that has been melt-grown, it is possible to obtain a single-crystal YAG phosphor having a particle size of 100 μm or more.

Even if the wavelength conversion member 1 is composed of single-crystal phosphor particle groups, it does not contain a phosphor encapsulant or binder. Generally, the encapsulant and binder have lower thermal conductivity than the single-crystal phosphor, and the use of these lowers the heat dissipation of the wavelength conversion member.

[Manufacture of wavelength conversion member]
When manufacturing the wavelength conversion member 1 composed of a single-crystal phosphor particle group, pressure is applied to a single-crystal phosphor particle group obtained by pulverizing a single-crystal phosphor ingot to solidify and sinter. By doing so, a sintered body of particle groups of the single-crystal phosphor is obtained. The SPS (Spark Plasma Sintering) method or the CIP (Cold Isostatic Pressing) method can be used for solidifying and sintering the particle group of the single crystal phosphor.

Further, when manufacturing the wavelength conversion member 1 composed of a polycrystalline phosphor, the mixed raw material is subjected to a solid phase reaction using the SPS method or the CIP method, and then sintered to obtain a polycrystal having a predetermined shape. A sintered body of phosphor particles is obtained. For example, in order to produce a sintered body of a group of YAG-based single-crystal phosphor particles, powders of raw materials Y ₂ O ₃ , Lu ₂ O ₃ , Gd ₂ O ₃ , Al ₂ O ₃ , and CeO ₂ are used. The amounts are mixed according to the garnet composition, and solid-phase reacted.

To keep the ratio of voids in the wavelength conversion member 1 within the range of 0.6% to 25%, preferably within the range of 1% to 15%, with respect to the entire voids on any cut surface. Therefore, the ratio of voids is controlled by the particle size of the phosphor particles, the pressure in the sintering process, the firing temperature, the firing time, and the like, regardless of whether the phosphor is a single crystal or a polycrystal.

For example, the larger the particle size of the phosphor particles, the larger the voids, so the ratio of the voids increases. The particle size of the phosphor particles can be controlled, for example, by adjusting the processing time of the particle pulverization process using a planetary ball mill. Also, if the pressure in the sintering process is low, the voids remain without being crushed, so the proportion of the voids increases. Also, by increasing the firing temperature or lengthening the firing time in the sintering step, the firing progresses further, so that the voids become smaller and the ratio of the voids becomes smaller.

Below, the example of the manufacturing method of the more specific wavelength conversion member 1 is shown.

FIG. 4 is a flow chart showing an example of the manufacturing process of the wavelength conversion member 1 according to the embodiment. FIG. 4 shows, as an example, the flow of the manufacturing process of the wavelength conversion member 1 made of a sintered body of particle groups of a YAG-based single crystal phosphor.

First, a single crystal phosphor is grown to obtain an ingot (step S1). As starting materials, high-purity (99.99% or higher) Y ₂ O ₃ , Lu ₂ O ₃ , Gd ₂ O ₃ , CeO ₂ , and Al ₂ O ₃ powders are prepared and dry mixed to obtain a mixed powder. obtain. The raw material powders of Y, Lu, Gd, Ce, and Al are not limited to those described above. Moreover, when producing a single crystal phosphor that does not contain Lu or Gd, these raw material powders are not used.

FIG. 5 is a cross-sectional view schematically showing pulling of a single crystal phosphor ingot by the CZ method. The crystal growth apparatus 40 mainly includes an iridium crucible 41 , a ceramic cylindrical container 42 that houses the crucible 41 , and a high frequency coil 43 wound around the cylindrical container 42 .

The obtained mixed powder is placed in the crucible 41 , and high frequency energy of 30 kW is supplied to the crucible 41 by the high frequency coil 43 in a nitrogen atmosphere to generate an induced current and heat the crucible 41 . The mixed powder is thereby melted to obtain a melt 50 .

Next, after the tip of the seed crystal 51, which is a YAG-based single crystal phosphor, was brought into contact with the melt 50, it was pulled up at a pulling speed of 1 mm/h or less while rotating at a rotation speed of 10 rpm, and the pulling temperature was 1960° C. or higher. to grow a single crystal phosphor ingot 52 in the <111> direction. The single-crystal phosphor ingot 52 is grown in a nitrogen atmosphere under atmospheric pressure by introducing nitrogen into the cylindrical container 42 at a flow rate of 2 L/min.

Thus, for example, a single-crystal phosphor ingot 52 having a diameter of approximately 2.5 cm and a length of approximately 10 cm is obtained.

Next, the ingot of the single-crystal phosphor is pulverized into particles (step S2). First, a single-crystal phosphor ingot is rapidly heated and cooled to be coarsely pulverized to obtain a single-crystal phosphor particle group having a particle size of about 1 to 3 mm. Rapid heating can be carried out using a hydrogen/oxygen mixed gas burner. Rapid cooling can also be carried out by water cooling.

Subsequently, the particles are pulverized using a planetary ball mill and then dried. As a result, the particle size (D50) of the particle group can be in the range of 3 μm or more and 30 μm or less, more preferably in the range of 3 μm or more and 15 μm or less.

Next, pressure is applied to the single-crystal phosphor particles to solidify them (step S3). The solidification method is not particularly limited, and for example, the SPS method, the CIP method, etc. can be used. Further, solidification may be performed by sheet molding or slip casting. When using these methods, an organic binder is required to hold the particle groups on the wafer, but this organic binder can be removed during the process.

The magnitude of the pressure applied to the particle group during solidification is such that the particle group can be held in a solid state, and depends on the solidification method. For example, when using the CIP method, it is preferably 100 MPa or more.

Next, the solidified single-crystal phosphor particle group is sintered (step S4). By performing sintering, the mechanical strength of the solidified single-crystal phosphor particle group is improved, and the internal quantum efficiency is improved. The temperature and holding time of the heat treatment for sintering depend on the sintering method.

Also, sintering is performed under an argon atmosphere. When sintering is performed in an argon atmosphere, the increase in internal quantum efficiency is greater than when sintering is performed in air, an oxygen atmosphere, a nitrogen atmosphere, or a mixed gas atmosphere of 97.5% Ar and 2.5% hydrogen. It has been confirmed by the inventors of the present invention.

The temperature and holding time of the heat treatment for sintering depend on the type of single crystal phosphor and the sintering method. For example, when the single-crystal phosphor is a YAG-based single-crystal phosphor and is sintered in a kiln, the heat treatment temperature is preferably in the range of 1650° C. or higher and 1850° C. or lower. Moreover, the holding time after reaching the target temperature is preferably in the range of 1 hour or more and 10 hours or less.

If the heat treatment temperature is lower than 1650°C, sintering takes a long time and uneven sintering tends to occur. If it exceeds 1850°C, the phosphor may melt. If the holding time is shorter than 1 hour, the sintering may be insufficient, and if it is longer than 10 hours, sintering proceeds too much and grain growth progresses, resulting in a loss of grain size uniformity. .

When the SPS method is used for the solidification in step S3, the baking in step S4 is also continuously performed in the SPS apparatus. Specifically, for example, when the single-crystal phosphor is a YAG-based single-crystal phosphor, heat treatment is performed at 1530° C. to 1600° C. while applying a pressure of 30 MPa or more to the single-crystal phosphor particle group.

When the pressure is less than 30 MPa, sintering is difficult to proceed, and therefore pores increase. As a result, there arise problems such as a decrease in the thermal conductivity of the wavelength conversion member 1 and a blockage of excitation light from entering the wavelength conversion member 1 . If the heat treatment temperature is lower than 1530°C, the sintering takes a long time and uneven sintering tends to occur.

At this time, as the temperature rises, the density of the single-crystal phosphor particle group increases, and the piston that applies pressure to the single-crystal phosphor particle group is displaced. After the target temperature is reached and the displacement of the piston becomes almost zero, the temperature is maintained for a predetermined time. This holding time is preferably in the range of 30 seconds or more and 3 minutes or less. If it is shorter than 30 seconds, the sintering may be insufficient, and if it is longer than 3 minutes, the sintering proceeds too much and the homogeneity of grain size is lost.

In addition to the SPS method, there are other methods such as the HIP (Hot Iso-static Press) method, the VP (Vacuum Press) method, and the like as methods for performing heat treatment while applying pressure to the single crystal phosphor particle group. good too.

Next, the sintered body of the single-crystal phosphor particle group is sliced to obtain a wafer-shaped sintered body (step S5). Slicing can be performed using a multi-wire saw or the like.

If the thickness of the wafer-shaped sintered body is too thin, cracks may occur when slicing, resulting in a decrease in yield. From this point of view, the thickness of the wafer-shaped sintered body is preferably 0.15 mm or more. Also, if the thickness is too large, the number of sheets that can be cut out by slicing decreases, resulting in an increase in cost. From this point of view, the thickness of the wafer-shaped sintered body is preferably 1.0 mm or less.

Next, the sintered body of the wafer-shaped single-crystal phosphor particle group is subjected to an annealing treatment (step S6). By performing the annealing treatment, the internal quantum efficiency of the sintered body of the single-crystal phosphor particle group is improved.

If the temperature of the annealing treatment is too low or the annealing time is too short, the quantum efficiency of the sintered body of the single-crystal phosphor particle groups will not be sufficiently improved. Also, if the temperature of the annealing treatment is too high, the load on the apparatus will increase, and if the temperature is extremely high, the sintered body will melt. A longer annealing time is preferable from the viewpoint of increasing the quantum efficiency, but there is a problem that if the annealing time is too long, the cost increases. For this reason, the temperature of the annealing treatment is preferably in the range of 1450° C. or higher and 1600° C. or lower. Also, the annealing time is preferably 5 hours or longer. Further, if the annealing time exceeds 15 hours, there is almost no change in the amount of increase in the internal quantum efficiency of the sintered body of the single crystal phosphor particle group, and the longer the annealing time, the more the cost increases. , the annealing time is preferably 15 hours or less.

Also, the annealing treatment is performed in an argon atmosphere. When annealing is performed in an argon atmosphere, the increase in internal quantum efficiency is greater than when annealing is performed in air, an oxygen atmosphere, a nitrogen atmosphere, or a mixed gas atmosphere of 97.5% Ar and 2.5% hydrogen. It has been confirmed by the inventors of the present invention.

Next, the sintered body of the wafer-shaped single-crystal phosphor particle group is subjected to a polishing process (step S7). The polishing process is performed, for example, by a combination of grinding, diamond slurry polishing, CMP (Chemical Mechanical Polishing), and the like. The polishing process is performed until the target thickness of the wavelength conversion member 1 (preferably 0.05 mm or more and 0.3 mm or less) is obtained.

Through the above steps, a wafer-shaped wavelength conversion member 1 made of a sintered body of a YAG-based single-crystal phosphor particle group is obtained.

[Second embodiment]
(Structure of wavelength conversion element)
FIG. 6 is a vertical sectional view of the wavelength conversion element 10 according to the second embodiment. The wavelength conversion element 10 is formed on the wavelength conversion layer 11 made of the wavelength conversion member 1 according to the first embodiment, and on the opposite side of the wavelength conversion layer 11 to the light extraction side (hereinafter referred to as the back side). A reflective film 12, a protective film 13 formed on the back surface of the reflective film 12, a pad metal 14 formed on the back surface of the protective film 13, and a surface of the wavelength conversion layer 11 on the light extraction side. and an antireflection film 15 formed on the substrate.

The wavelength conversion layer 11 is made of the wavelength conversion member 1 . That is, the wavelength conversion layer 11 is made of a sintered body of phosphor particle groups, and the area ratio of voids to the entirety of any cut surface of the wavelength conversion layer 11 is in the range of 0.6% or more and 25% or less. , preferably in the range of 1% or more and 15% or less.

As with the wavelength conversion member 1, the thickness of the wavelength conversion layer 11 is also preferably in the range of 0.050 mm or more and 0.3 mm or less.

The reflective film 12 is, for example, a metal film made of a highly reflective metal such as silver, a silver alloy, or aluminum, a dielectric multilayer film, or a combination thereof. The dielectric multilayer film is a multilayer laminated film of a film with a high refractive index (n = 2.0 or more) and a film with a low refractive index (n = 1.5 or less). ₂ , ZrO ₂ , ZnO, etc. SiO ₂ , CaF ₂ , MgF ₂ and the like can be used as the material of the low refractive index film. The reflectance of the reflective film 12 is preferably 90 or higher with respect to the wavelength of light (for example, 450 to 700 nm) from the wavelength conversion layer 11 side.

The protective film 13 prevents the reflection film 12 from being mixed with solder or the pad metal 14 when the wavelength conversion element 10 is solder-mounted, thereby preventing the reflectance of the reflection film 12 from decreasing. For example, if the reflective film 12 is made of metal (such as silver, aluminum, or alloys thereof), the protective film 13 is necessary to protect the reflective film 12 . In particular, when silver is used for the reflective film 12, it is necessary to cover the reflective film 12 including the side surfaces with the protective film 13 in order to prevent the sulfurization phenomenon. The material of the protective film 13 is preferably a thermally stable oxide, nitride, refractory metal, or the like. Specifically, SiO ₂ , SiN, TiN, AlN, TiW, Pt, or the like can be used. can. If the reflective film 12 is made of a material such as a dielectric that is not easily corroded by solder or the pad metal 14, the wavelength conversion element 10 does not need to include the protective film 13. FIG.

The pad metal 14 has a structure with high wettability to solder. For example, it has a laminated film structure such as Ti/Ni/Au, Ti/Pt/Au from the reflective film 12 side (protective film 13 side).

The antireflection film 15 can suppress reflection of the excitation light on the surface when it enters the wavelength conversion element 10 . The antireflection film 15 is composed of a single layer film or a multilayer film of a dielectric film transparent to visible light. Instead of providing the anti-reflection film 15, unevenness may be provided on the surface of the wavelength conversion layer 11 on the light extraction side to suppress the reflection of the excitation light. Moreover, the anti-reflection film 15 may be further provided after providing unevenness on the light extraction side surface of the wavelength conversion layer 11 .

In order to accurately cover and effectively protect the reflective film 12 with the protective film 13, it is preferable to form the reflective film 12 and the protective film 13 on a flat surface. Further, when the reflective film 12 is made of a dielectric multilayer film, it is important that the refractive index and thickness of each layer are as designed in order to achieve a high reflectance. It is preferred to form membrane 12 . For these reasons, a flat film is provided on the reflecting film 12 side of the wavelength conversion layer 11 which has unevenness on the surface due to relatively high porosity, and the reflecting film 12 and the protective film 13 are formed thereon. is preferred.

7A to 7F are vertical cross-sectional views showing the manufacturing process of the wavelength conversion element 10 in the case of forming the flattening film 16 on the surface of the wavelength conversion layer 11 on the reflecting film 12 side. In addition, in FIGS. 7A to 7F, the pores are extremely enlarged in order to emphasize the unevenness of the surface of the wavelength conversion layer 11. FIG.

First, as shown in FIG. 7A, a flattening film 16 is formed on the back surface of the wavelength conversion layer 11 by CVD, sputtering, vapor deposition, SOG (Spin on Glass), or the like. The planarization film 16 is a film transparent to visible light, such as a SiO ₂ film, or a glass layer formed by a screen printing method, a coating method, or the like, and a baking process. At this stage, the planarizing film 16 is not yet planarized, and has unevenness corresponding to the unevenness of the surface of the wavelength conversion layer 11 .

Next, as shown in FIG. 7B, the planarizing film 16 is subjected to a planarizing process such as grinding, diamond slurry polishing, CMP, or the like to planarize it. As a result, the surface of the flattening film 16 in contact with the reflective film 12 becomes a flat surface.

In order to more reliably fill the holes in the surface of the wavelength conversion layer 11, the planarization film 16 is preferably formed relatively thick and then planarized. On the other hand, films that can be made relatively thick and that are transparent to visible light generally do not have high thermal conductivity. Therefore, in order to efficiently dissipate the heat generated in the wavelength conversion layer 11 to a heat sink connected to the pad metal 14, it is preferable to make the planarization film 16 as thin as possible by the planarization process within the range where the planarity can be maintained. In addition, since the planarizing film 16 is transparent and does not scatter, if the planarizing film 16 is too thick, the light spreads through the planarizing film 16, and the efficiency of coupling with the lens may decrease. be. For these reasons, the thickness of the planarizing film 16 is preferably 30 μm or less, more preferably 10 μm or less.

Next, as shown in FIG. 7C, the reflective film 12 is formed on the flattened flattening film 16 by sputtering, vapor deposition, or the like.

Next, as shown in FIG. 7D, a protective film 13 is formed to cover the surface and side surfaces of the reflective film 12 .

Next, as shown in FIG. 7E, a pad metal 14 is formed on the protective film 13 by sputtering, vapor deposition, or the like. Further, an antireflection film 15 may be formed on the light extraction side surface of the wavelength conversion layer 11 as necessary.

Next, as shown in FIG. 7F, the individual wavelength conversion elements 10 are singulated by blade dicing or the like.

FIG. 8 is a vertical sectional view of the wavelength conversion module 20 according to the second embodiment. The wavelength conversion module 20 is a module in which the wavelength conversion element 10 is fixed to the heat sink 21 by soldering, and the pad metal 14 of the wavelength conversion element 10 and the heat sink 21 are connected via the solder 22 . After solder mounting, the pad metal 14 may not be visible because the solder 22 and the pad metal 14 are mixed.

When the solder 22 is made of a metal material, the heat generated in the wavelength conversion layer 11 can be efficiently dissipated. Moreover, if the melting point of the solder 22 is too low, the wavelength conversion element 10 may be peeled off from the heat sink 21 when the temperature of the wavelength conversion layer 11 rises. Also, if the melting point of the solder 22 is too high, the heat generated during mounting of the wavelength conversion element 10 may deteriorate the reflective film 12 . For these reasons, SnAgCu (SAC), AuSn, AuGe, and AuSi are preferable materials for the solder 22 .

The heat sink 21 is preferably made of a material with high thermal conductivity such as Cu, CuW, CuMo, SiC, AlN, and diamond in order to efficiently lower the temperature of the wavelength conversion layer 11 . Furthermore, in order to prevent the wavelength conversion layer 11 from cracking, it is preferable that the heat sink 21 has a coefficient of linear expansion similar to that of the wavelength conversion layer 11 . For example, when the wavelength conversion layer 11 is made of a sintered body of a YAG-based phosphor particle group, CuW or CuMo, which has a coefficient of linear expansion similar to that of the wavelength conversion layer 11, is used among the materials having high thermal conductivity. It is preferable as a material for the heat sink 21 .

(Effect of Embodiment)
According to the said 1st Embodiment, the wavelength conversion member 1 excellent in coupling efficiency with an optical system can be provided. Further, according to the second embodiment, it is possible to provide the wavelength conversion element 10 and the wavelength conversion module 20 which include the wavelength conversion layer 11 made of the wavelength conversion member 1 and have excellent coupling efficiency with the optical system. can be done.

As Example 1, an example of a method of manufacturing a wavelength conversion member 1 made of a sintered body of a YAG-based single-crystal phosphor particle group using the SPS method will be described.

First, an ingot of a single crystal phosphor having a composition represented by the compositional formula (Y _0.998 Ce _0.002 ) ₃ Al ₅ O ₁₂ was grown by the CZ method (step S1).

Next, the single-crystal phosphor ingot was pulverized into particles (step S2). First, a single-crystal phosphor ingot was subjected to rapid heating using a hydrogen-oxygen mixed gas burner and rapid cooling by water cooling, and then coarsely pulverized to obtain a single-crystal phosphor particle group having a particle size of about 1 to 3 mm. . Subsequently, after milling the particles using a planetary ball mill for approximately 2 hours, the particles were dried at 80° C. for 1 day. As a result, a particle group of phosphor single crystals having a particle size (D50) of approximately 5 μm was obtained.

Here, balls made of aluminum oxide were used as the balls of the planetary ball mill. In fine pulverization using a planetary ball mill, the volume ratio of roughly pulverized single-crystal phosphor particles, balls, and ethanol was set to 1:1:1.

Next, solidification and sintering of the single-crystal phosphor particle groups were performed by the SPS method to obtain a sintered body (steps S3 and S4). First, a group of single-crystal phosphor particles was pre-pressed, and then placed in a carbon jig having an inner diameter of φ20 mm in an SPS apparatus. Next, after the inside of the SPS apparatus was evacuated, it was replaced with an argon atmosphere (1 atm). Next, a pressure of 80 MPa was applied to the particle group of the single-crystal phosphor in the carbon jig with a piston via a carbon punch. Next, while a pressure of 80 MPa was applied, an electric current was passed through the carbon punch and the carbon jig to heat the particle groups of the single crystal phosphor.

About 10 minutes after the start of heating, the temperature inside the carbon jig reached the target temperature of 1570°C. A hole having a diameter of 1 mm and a depth of 2 mm is formed in the side surface of the carbon jig, and the temperature inside the carbon jig can be measured using a pyrometer.

After the temperature inside the carbon jig reached the target temperature of 1570° C. and the displacement of the piston accompanying the rise in temperature became almost zero, this state was maintained for 3 minutes. After that, the pressurization was stopped and the temperature was lowered over 2 hours until reaching room temperature. As a result, a sintered body of a single-crystal phosphor particle group having a diameter of 20 mm and a height of 10 mm was obtained.

Next, using a multi-wire saw, the sintered body of the single-crystal phosphor particle group was sliced into wafers having a thickness of 0.5 mm (step S5).

Next, the wafer-shaped sintered body of single-crystal phosphor particle groups was subjected to an annealing treatment (step S6). First, a sintered body of wafer-shaped single crystal phosphor particle groups was placed in an annealing furnace, and after the inside of the annealing furnace was evacuated, the atmosphere was replaced with an argon atmosphere. Next, the temperature in the annealing furnace was raised to 1500° C. in about 4 hours, held at 1500° C. for 10 hours, and then lowered to room temperature in about 4 hours.

Next, the sintered body of the wafer-shaped single-crystal phosphor particle group was subjected to a polishing treatment by grinding and diamond slurry polishing (step S7). By this polishing treatment, the thickness of the sintered body of the wafer-shaped single-crystal phosphor particle group was reduced from 0.5 mm to 0.15 mm.

Through the above steps, a wafer-shaped wavelength conversion member made of a sintered compact of a single-crystal phosphor particle group having a composition represented by the composition formula (Y _0.998 Ce _0.002 ) ₃ Al ₅ O ₁₂ got 1.

As Example 2, an example of a method for manufacturing the wavelength conversion member 1 made of a sintered body of a YAG-based single crystal phosphor particle group using the CIP method will be described. The ingot growing process (step S1), crushing process (step S2), slicing process (step S5), annealing process (step S6), and polishing process (step S7) are the same as those in the first embodiment. Therefore, the description is omitted.

After the ingot growing step (step S1) and the pulverizing step (step S2), the particle groups of the single crystal phosphor were solidified by the CIP method (step S3). First, a group of single-crystal phosphor particles was pre-pressed, and then placed in a rubber jig having an inner diameter of φ20 mm in a CIP device. Next, the inside of the CIP apparatus was pressurized, and a pressure of 300 MPa was applied to the single-crystal phosphor particles at room temperature to solidify them.

Next, the solidified single-crystal phosphor particle group was sintered (step S5). First, the particle group of the solidified single-crystal phosphor is placed in a firing furnace, and the temperature in the firing furnace is raised to 1800° C. in about 8 hours under normal pressure while flowing argon gas into the firing furnace. , 1800° C. for 10 hours, and then cooled to room temperature in about 8 hours. As a result, a sintered body of a single-crystal phosphor particle group having a diameter of 17.5 mm and a height of 10 mm was obtained.

After that, through the slicing process (step S5), the annealing process (step S6), and the polishing process ₍ step _S7 ), the composition represented by the composition formula _{( Y0.998Ce0.002} ) _3Al5O12 is obtained. A wafer-shaped wavelength conversion member 1 made of a sintered body of a single-crystal phosphor particle group was obtained.

Although the embodiments and examples of the present invention have been described above, the present invention is not limited to the above-described embodiments and examples, and various modifications can be made without departing from the scope of the invention.

Moreover, the embodiments and examples described above do not limit the invention according to the scope of claims. Also, it should be noted that not all combinations of features described in the embodiments and examples are essential to the means for solving the problems of the invention.

DESCRIPTION OF SYMBOLS 1... Wavelength conversion member, 10... Wavelength conversion element, 20... Wavelength conversion module

Claims (14)

It consists of a sintered body of phosphor particle groups, and the area ratio of voids to the entirety of an arbitrary cut surface is in the range of 0.6% or more and 25% or less ,
The phosphor particle group is a single-crystal phosphor particle group,
Wavelength conversion member. The phosphor has a composition formula (Y _1-xyz Lu _x Gd _{y Cez} ) _3+a Al _5-a O ₁₂ (0≦x≦0.9994, 0≦y≦0.0669, 0.0002 ≤ z ≤ 0.0067, −0.016 ≤ a ≤ 0.315),
The wavelength conversion member according to claim 1. The particle size (D50) of the particle group of the phosphor is in the range of 3 μm or more and 30 μm or less.
The wavelength conversion member according to claim 1 or 2. The particle size (D50) of the particle group of the phosphor is in the range of 3 μm or more and 15 μm or less.
The wavelength conversion member according to claim 3. The area ratio is in the range of 1% or more and 15% or less,
The wavelength conversion member according to any one of claims 1 to 4. a wavelength conversion layer made of a sintered body of a phosphor particle group and having an area ratio of voids to the entirety of an arbitrary cut surface within a range of 0.6% or more and 25% or less;
a reflective film formed on the side opposite to the light extraction side of the wavelength conversion layer;
a pad metal formed on the opposite side of the reflective film from the wavelength conversion layer;
with
The phosphor particle group is a single-crystal phosphor particle group,
Wavelength conversion element. The phosphor has a composition formula (Y _1-xyz Lu _x Gd _{y Cez} ) _3+a Al _5-a O ₁₂ (0≦x≦0.9994, 0≦y≦0.0669, 0.0002 ≤ z ≤ 0.0067, −0.016 ≤ a ≤ 0.315),
The wavelength conversion element according to claim 6 . The particle size (D50) of the particle group of the phosphor is in the range of 3 μm or more and 30 μm or less.
The wavelength conversion element according to claim 6 or 7 . A flattening film formed between the wavelength conversion layer and the reflective film and having a flat surface in contact with the reflective film,
The wavelength conversion element according to any one of claims 6-8 . A method for manufacturing the wavelength conversion member according to any one of claims 1 to 5,
a step of pulverizing and granulating an ingot of a single crystal phosphor to obtain a particle group of the phosphor;
a step of applying pressure to the phosphor particles to solidify;
a step of sintering the solidified phosphor particle group to obtain a sintered body;
a step of slicing the sintered body to obtain a wafer-shaped sintered body;
a step of annealing the wafer-shaped sintered body;
a step of subjecting the wafer-shaped sintered body subjected to the annealing process to a polishing process;
including,
A method for manufacturing a wavelength conversion member. In the step of obtaining the phosphor particle group, the ingot is pulverized by heating and cooling, and then pulverized by a ball mill.
The manufacturing method of the wavelength conversion member according to claim 10. In the step of obtaining the wafer-shaped sintered body, the wafer-shaped sintered body having a thickness in the range of 0.15 mm or more and 1.0 mm or less is obtained.
The method for manufacturing the wavelength conversion member according to claim 10 or 11. In the step of applying the annealing treatment, the annealing treatment is performed in an argon atmosphere at a temperature in the range of 1450 ° C. or higher and 1600 ° C. or lower for a time in the range of 5 hours or more and 15 hours or less.
A method for manufacturing a wavelength conversion member according to any one of claims 10 to 12. In the step of performing the polishing process, the polishing process is performed until the thickness of the wafer-shaped sintered body is within the range of 0.05 mm or more and 0.3 mm or less.
A method for manufacturing a wavelength conversion member according to any one of claims 10 to 13.

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