JP2021099415A - Wavelength conversion member and light-emitting device - Google Patents

Abstract

To provide a wavelength conversion member and a light-emitting device that can naturally obtain emission of a warm color with a small color temperature and can reduce the risks of temperature extinction.SOLUTION: A wavelength conversion member includes: a phosphor layer 120 having an incident surface for light and a back surface located on an opposite side to the side where the incident surface is located; and a reflection layer 110 arranged on the opposite side. The phosphor layer 120 includes: a phosphor particle 130; and a translucent ceramic 140 for combining the phosphor particles. The reflection layer 110 is made of a material based on copper, and the thickness of the phosphor layer 120 is in the range from 15 μm to 200 μm, both inclusive.SELECTED DRAWING: Figure 1

Description

The present invention relates to a wavelength conversion member and a light emitting device.

A light emitting device using a phosphor utilizes a phenomenon in which a phosphor layer of a wavelength conversion member emits light excited from a light source such as an LED (Light Emitting Diode) or LD (Laser Diode) as converted light having a different wavelength. doing. It is known that the phosphor layer is arranged by dispersing the phosphor particles in a resin typified by epoxy or silicone, but in recent years, LD has high energy efficiency and is easy to cope with miniaturization and high output. Is increasing in applications using as a light source.

Since the LD locally irradiates high-energy light, in the worst case, the conventional resin may be burnt and difficult to use. In addition, the irradiated portion of the phosphor layer becomes extremely hot, and the emission performance of the phosphor layer deteriorates due to temperature quenching due to the temperature rise. Therefore, an inorganic binder is used instead of the resin to improve the heat resistance of the phosphor layer. Further, as a base material for supporting the phosphor layer, aluminum or silver having excellent thermal conductivity is used.

Patent Document 1 discloses a reflective wavelength conversion member that reflects light from a light source and emits converted light. As a reflective base material that supports a phosphor layer, it has high light reflectance and heat dissipation. Excellent aluminum is used. Further, Patent Document 2 discloses a phosphor layer in which a large particle size yellow phosphor particle and a small particle size red phosphor particle are mixed so that the weight ratio thereof is 1.2 or more and 50 or less. It provides white light with good color rendition.

Further, Patent Document 3 describes a plurality of fluorescent particles 31, a plurality of hollow bodies 32 having a translucent member 32a as an outer shell and a hollow region 32b inside thereof, a plurality of fluorescent particles 31 and a plurality of hollows. A wavelength conversion member having a holding body 33 for holding the body 32 and a holding body 33 is disclosed.

WO2017 / 126441 Japanese Unexamined Patent Publication No. 2018-185367 Japanese Unexamined Patent Publication No. 2015-001709

Since Patent Document 1 uses aluminum as a base material that plays a role of reflecting light, it is necessary to suppress the reflection of light source light for the purpose of emitting warm colors, and it is necessary to suppress the reflection of light source light. It is necessary to increase the thickness. Further, Patent Document 2 is a mixture of two types of phosphor particles, but since it is a transmission type wavelength conversion member, it is necessary to suppress the transmission of light source light for the purpose of emitting warm colors. Therefore, it is necessary to increase the thickness of the phosphor layer or add a large amount of red phosphor. However, in such a configuration, there is a possibility that a problem of temperature quenching due to heat storage of the phosphor layer may occur.

Patent Document 3 exemplifies copper and copper alloy materials as an example of a base material of a reflective wavelength conversion member, but discloses that it is used as a reflecting plate in the same manner as a conventional aluminum base material or the like. The thickness of the phosphor layer in such a case is not taken into consideration because it is only intended to emit a warm color.

The present invention has been made in view of such circumstances, and provides a wavelength conversion member and a light emitting device capable of obtaining light emission of a warm color having a small color temperature and reducing the risk of temperature quenching. With the goal.

(1) In order to achieve the above object, the wavelength conversion member of the present invention is arranged on the back surface side and a phosphor layer having an incident surface on which light is incident and a back surface located on the opposite side of the incident surface. The fluorescent layer is formed of phosphor particles and translucent ceramics that bond the fluorescent particles to each other, and the reflective layer is formed of a material whose main component is copper. The thickness of the phosphor layer is 15 μm or more and 200 μm or less.

In this way, the reflective layer is made of a material containing copper as a main component. When the purpose is to emit light with a low color temperature, for example, when trying to obtain the desired color temperature by lowering the emission intensity of blue, which is the light source light, in the case of a reflective layer using aluminum, silver, etc., Since it is necessary to increase the thickness of the phosphor layer to suppress the intensity of the light source light, the risk of temperature extinction due to the heat storage of the phosphor layer increases. On the other hand, the material containing copper as a main component has a smaller reflectance of light in the short wavelength region (350 nm to 550 nm) than the reflectance of light in the long wavelength region (550 nm to 780 nm), and therefore emits light from the light source. Even if the intensity is increased, reflection in a relatively short wavelength region is suppressed, and it is possible to obtain light emission of a warm color having a small color temperature. In this way, when the purpose is to emit light with a low color temperature, it is not necessary to increase the film thickness of the phosphor layer to suppress the reflection of the light source light. Therefore, when a reflection layer using aluminum, silver, or the like is used. As compared with the above, the thickness of the phosphor layer can be reduced, and the heat storage of the phosphor layer can be suppressed, so that the risk of temperature quenching can be reduced.

(2) Further, in the wavelength conversion member of the present invention, the phosphor particles have a first phosphor particle having a fluorescence peak wavelength in the range of 420 nm or more and less than 620 nm, and a fluorescence peak wavelength in the range of 620 nm or more and 750 nm or less. The second phosphor particles include the second phosphor particles, and the second phosphor particles are characterized by having a volume ratio of 0.01 or more and 0.3 or less with respect to the first phosphor particles. For the purpose of making the appearance of an object closer to that of natural light, that is, obtaining light having excellent color rendering properties, for example, red phosphor particles may be mixed with the phosphor layer. When the second phosphor particles that emit red fluorescence are used to enhance the color rendering property, the color temperature is increased with a small amount of red phosphor particles as compared with the case where a reflective layer using aluminum, silver, etc. is used. It is possible to obtain a small light emission with high color rendering properties. This is because, as described above, it is not necessary to increase the film thickness of the phosphor layer, so that the amount of the red phosphor used can be suppressed. In addition, since the red phosphor is a material with higher heat generation than the phosphor on the short wavelength region side, heat storage in the phosphor layer can be suppressed by using a small amount, and the risk of temperature quenching can be reduced. it can.

(3) Further, in the wavelength conversion member of the present invention, the reflective layer is characterized in that the thermal conductivity is 250 W / m · K or more. As a result, heat dissipation can be ensured even in high-power applications, and the risk of temperature quenching due to heat storage in the phosphor layer can be reduced.

(4) Further, in the wavelength conversion member of the present invention, the surface roughness Ra of the reflective layer on the phosphor layer side is 7.0 μm or less. As a result, the film thickness of the phosphor layer formed on the reflective layer can be easily controlled, and the phosphor layer can be formed thin. In addition, the reflectance of the reflective layer with respect to the entire wavelength region can be increased.

(5) Further, in the wavelength conversion member of the present invention, the reflective layer has a concave recessed portion on the surface on the phosphor layer side, and the phosphor layer is formed in the recessed portion. There is. As a result, the area of the reflective layer in contact with the phosphor layer can be increased, and heat dissipation can be improved.

(6) Further, the light emitting device of the present invention is characterized by including a light emitting element that emits excitation light having a wavelength in a specific range and the wavelength conversion member according to any one of (1) to (5) above. There is. As a result, it is possible to obtain light emission of a warm color having a small color temperature. Further, when the purpose is to emit light with a small color temperature, the thickness of the phosphor layer can be reduced as compared with the case of using a reflective layer using aluminum, silver, etc., and the heat storage of the phosphor layer can be reduced. Since it can be suppressed, the risk of temperature quenching can be reduced.

According to the present invention, it is possible to obtain light emission of a warm color having a small color temperature. Further, when the purpose is to emit light with a small color temperature, the thickness of the phosphor layer can be reduced as compared with the case of using a reflective layer using aluminum, silver, etc., and the heat storage of the phosphor layer can be reduced. Since it can be suppressed, the risk of temperature quenching can be reduced.

It is a schematic diagram which shows an example of the wavelength conversion member of this invention. It is a schematic diagram which shows an example of the light emitting device of this invention. It is a graph which shows the reflectance for each wavelength of a metal. It is a schematic diagram which shows the modification of the wavelength conversion member of this invention. It is sectional drawing which shows the manufacturing process of the wavelength conversion member, each of (a), (b), (c). It is a table which shows various conditions and determination result of the wavelength conversion member of Example 1 and Comparative Example 1. It is a table which shows various conditions and determination result of the wavelength conversion member of Example 2 and Comparative Example 2.

Next, an embodiment of the present invention will be described with reference to the drawings. In order to facilitate understanding of the description, the same reference number is assigned to the same component in each drawing, and duplicate description is omitted. In the configuration diagram, the size of each component is conceptually represented, and does not necessarily represent the actual dimensional ratio.

[Structure of wavelength conversion member and light emitting device]
1 and 2 are schematic views showing an example of a wavelength conversion member 100 and a light emitting device 10. As shown in FIGS. 1 and 2, the light emitting device 10 includes a light emitting element 50 and a wavelength conversion member 100, and is generated by, for example, light source light reflected by the wavelength conversion member 100 and excitation by the light source light in the wavelength conversion member 100. The converted light is combined to emit the irradiation light. The irradiation light can be, for example, warm white light.

An LED (Light Emitting Diode) or an LD (Laser Diode) can be used as the light emitting element 50. The LED generates light source light having a wavelength in a specific range according to the design of the light emitting device 10. For example, LEDs generate blue light. Further, when LD is used, coherent light with little variation in wavelength and phase can be generated. The light emitting element 50 is not limited to these, and may be one that generates light other than visible light, but those that generate ultraviolet light, blue light, or green light are preferable, and those that generate blue light are particularly preferable. preferable.

The wavelength conversion member 100 includes a reflection layer 110 and a phosphor layer 120, and while reflecting the light source light by the reflection layer 110, excites the light source light to generate light having a different wavelength. The wavelength conversion member 100 is preferably formed in a plate shape. For example, it is possible to emit white light by generating fluorescence of green and red or yellow while reflecting blue light.

The reflective layer 110 is formed of a material whose main component is copper. The copper-based material is a material containing 70 wt% or more of copper. Further, from the viewpoint of heat dissipation, it is preferable that copper is contained in an amount of 80 wt% or more, more preferably 95 wt% or more, and further preferably 97 wt% or more. Examples of the material of the reflective layer 110 include pure copper (oxygen-free copper, tough pitch copper, phosphorylated copper, etc.), Cu-Zr-based copper alloy (zyroxide copper), Cu-Fe-based copper alloy, Cu-Mg-based copper alloy, and the like. Highly conductive copper alloys, highly conductive and highly heat-resistant copper alloys, high-strength and highly conductive heat-resistant copper alloys, tan copper, brass, bronze and the like can be used.

In this way, by using the reflective layer formed of the material whose main component is copper, the reflectance of light in the long wavelength region (550 nm to 780 nm) in the visible light region is compared with that of light in the short wavelength region (350 nm to 550 nm). ), Since the reflectance of the light is small, even if the emission intensity of the light source light (excitation light) is increased, the reflection in the relatively short wavelength region is suppressed, and the emission of warm colors with a small color temperature can be obtained. Can be done. FIG. 3 is a graph showing the reflectance of pure copper, aluminum, and silver for each wavelength in the visible light region. The reflectance of each metal in FIG. 3 was determined by relative total light reflectance measurement using an ultraviolet-visible spectrophotometer manufactured by JASCO Corporation. Although not shown in FIG. 3, copper alloys other than pure copper also tend to have a small reflectance of light in the short wavelength region as compared with the reflectance of light in the long wavelength region.

Further, for the purpose of emitting light having a small color temperature, for example, when a reflective layer is formed by using a material having a large reflectance of light in a long wavelength region and a large reflectance of light in a short wavelength region such as silver and aluminum. , It is necessary to increase the film thickness of the phosphor layer to suppress the reflection of the light source light. This is because, normally, the light source light uses light in a short wavelength region such as blue light, purple light, and ultraviolet light, but when the phosphor layer is thinned, a large amount of light source light is reflected and included in the converted light. That is, it becomes converted light containing a large amount of light in the short wavelength region, and inhibits light emission having a small color temperature. However, if the phosphor layer is made thicker, the risk of temperature quenching due to the heat storage of the phosphor layer increases.

On the other hand, since the reflection layer 110 of the present invention can relatively reduce the reflection of light in the short wavelength region, it is necessary to increase the film thickness of the phosphor layer 120 to suppress the reflection of the light source light. Absent. Therefore, the film thickness of the phosphor layer 120 can be reduced and the heat storage of the phosphor layer can be suppressed as compared with the case of using a reflective layer made of aluminum, silver, etc., thus reducing the risk of temperature quenching. it can.

Color temperature is defined as follows. That is, a blackbody is assumed as an ideal object. When this blackbody is heated, it emits light, and the wavelength / spectrum (color of light) of the emitted light is determined for each temperature of the blackbody, and when the temperature changes, the color of the light also changes. By associating the temperature of the blackbody with the color of the emitted light, the "temperature of the blackbody" is determined for a certain "color of light". Generally, this is called color temperature. The unit is Kelvin (K). White light emitted by receiving light from a light source is not always distributed on the radiation trajectory of a blackbody. Therefore, it is practically performed to display at the color temperature of blackbody radiation that appears to be the closest color to the light source. This is called the correlated color temperature. The color temperature in the present specification refers to this "correlated color temperature". The details of the correlated color temperature are specified in JIS Z 8725: 2015. In the present specification, the light emission of a warm color having a small color temperature means the light emission of a color having a color temperature of 2600 K or more and 5500 K or less at a correlated color temperature whose details are specified in JIS Z 8725: 2015.

The reflective layer 110 preferably has a thermal conductivity of 250 W / m · K or more at 20 ° C. As a result, heat dissipation can be ensured even in high-power applications, and the risk of temperature quenching due to heat storage of the phosphor layer 120 can be reduced. Among the materials whose main component is copper, for example, pure copper, zirconium copper, Cu-Fe copper alloy, Cu-Mg copper alloy, highly conductive copper alloy, highly conductive and highly heat resistant copper alloy, high strength and high conductive heat resistance. Since the sex copper alloy has high thermal conductivity, it can be suitably used for high output applications.

The surface roughness Ra of the reflective layer 110 on the phosphor layer 120 side is preferably 7.0 μm or less. As a result, the film thickness of the phosphor layer 120 formed on the reflective layer 110 can be easily controlled, and the phosphor layer 120 can be formed thin. In addition, the reflectance of the specular reflection (normal reflection) of the reflection layer with respect to the entire wavelength region can be increased. The surface roughness Ra is more preferably 6.3 μm or less, further preferably 1.6 μm or less, and particularly preferably 0.2 μm or less.

It is preferable that the reflective layer 110 has a concave recessed portion 115 on the surface on the phosphor layer 120 side, and the fluorescent substance layer 120 is formed in the recessed portion 115. As a result, the area of the reflective layer 110 in contact with the phosphor layer 120 can be increased, and heat dissipation can be improved. FIG. 4 is a schematic view showing a wavelength conversion member 100 in which a phosphor layer 120 is formed in a reflection layer 110 having a recessed portion 115.

The reflective layer 110 may be further provided with the base material 105 on the surface facing the surface on which the phosphor layer 120 is provided. As a result, when the mechanical strength is not sufficient with the reflective layer 110 and the phosphor layer 120 alone, the mechanical strength can be strengthened by the base material 105. At this time, the reflective layer 110 may be a thin film such as plating provided on the surface of the base material 105. The material of the base material 105 is not particularly limited, but can be formed of, for example, pure copper, a copper alloy, aluminum, iron, sapphire, glass, or the like. When the base material 105 is provided, the thermal conductivity of the base material is also preferably 250 W / m · K or more at 20 ° C.

The phosphor layer 120 is provided on the reflective layer 110, and is formed of the phosphor particles 130 and the translucent ceramics 140. The translucent ceramic 140 binds the phosphor particles 130 to each other and also bonds the reflective layer 110 and the phosphor particles 130. The thickness of the phosphor layer 120 is 15 μm or more and 200 μm or less. Further, the thickness of the phosphor layer 120 is preferably 20 μm or more and 80 μm or less. As a result, the film thickness of the phosphor layer 120 can be reduced as compared with the case where the reflective layer 110 using aluminum, silver, or the like is used for the purpose of light emission having a small color temperature. Since the heat storage of the layer 120 can be suppressed, the risk of temperature quenching can be reduced. Further, since the thickness of the phosphor layer 120 is thin, the heat generated in the phosphor layer 120 can be efficiently conducted to the reflective layer 110, and the temperature of the phosphor layer 120 can be prevented from rising. As a result, the fluorescence performance can be maintained even when irradiated with high-intensity light source light. That is, even when a high energy density laser is used as the light source, the phosphor particles 130 generate heat (heat storage) by forming the phosphor layer 120 as thin as possible within the range where a warm color design with a small color temperature is possible. Temperature quenching can be suppressed.

The thermal resistance, which indicates the difficulty of heat transfer, depends on the thermal resistance or thermal conductivity of the phosphor layer and the thickness when the area is constant, and the thicker the thermal resistance, the greater the thermal resistance. When the laser is irradiated, the smaller the thermal resistance, that is, the thinner the thickness, the easier it is for heat to be transferred and the less likely it is that heat storage occurs, and temperature quenching due to heat generation (heat storage) can be suppressed.

When the thickness of the phosphor layer is thinner than 15 μm, optical paths are generated in which the probability of the presence of phosphor particles is reduced in various optical paths in the phosphor layer, and uniform irradiation light is obtained in the plane of the phosphor layer. There is a risk that it will not be possible. Further, if it is thicker than 200 μm, there is a risk of temperature quenching due to heat storage of the phosphor layer, which may cause a problem especially in high output applications.

The phosphor layer 120 preferably has a porosity of 5 vol% or more and 50 vol% or less, and more preferably 20 vol% or more and 40 vol% or less. If it is less than 5 vol%, it becomes too dense and the risk of peeling of the phosphor layer 120 increases. On the other hand, when it is larger than 50 vol%, the excitation light escapes too much, so that the light emission becomes blue. In addition, the heat conduction of the phosphor layer 120 deteriorates, leading to temperature quenching.

The phosphor particles 130 include, for example, an yttrium aluminum garnet-based phosphor (YAG-based phosphor, YAG: Ce, also simply referred to as YAG) to which cerium (Ce) has been added, and a lutetium aluminum garnet-based phosphor (also referred to as YAG). LuAG-based phosphors, LuAG: Ce, also simply referred to as LuAG) can be used. Further, the red phosphor particles used as the second phosphor particles (described later) for enhancing the color playability include, for example, CASN and SCASN (CASN: Eu and SCASN: Eu, respectively) to which europium (Eu) is added. A nitride phosphor called (described) can be used.

In addition, the phosphor particles can be selected from the following materials according to the design of the color to be emitted. For example, _{a blue phosphor such as BaMgAl 10} O ₁₇ : Eu, ZnS: Ag, Cl, Eu, BaAl ₂ S ₄ : Eu or CaMgSi ₂ O ₆ : Eu, Zn ₂ SiO ₄ : Mn, (Y, Gd) BO ₃ : Tb, ZnS: Cu, Al, (M1) ₂ SiO ₄ : Eu, (M1) (M2) ₂ S: Eu, (M3) ₃ Al ₅ O ₁₂ : Ce, SiAlON: Eu, CaSiAlON: Eu, ( M1) Si ₂ O ₂ N: Eu or (Ba, Sr, Mg) ₂ SiO ₄ : Yellow or green phosphors such as Eu, Mn, (M1) ₃ SiO ₅ : Eu or (M1) S: Eu, etc. Yellow, orange or red phosphor, (Y, Gd) BO ₃ : Eu, Y ₂ O ₂ S: Eu, (M1) ₂ Si ₅ N ₈ : Eu, (M1) AlSiN ₃ : Eu or YPVO ₄ : Eu Red-based phosphors such as. In the above chemical formula, M1 contains at least one of the group consisting of Ba, Ca, Sr and Mg, M2 contains at least one of Ga and Al, and M3 contains Y, Gd and. At least one of the group consisting of Lu and Te is included. The above-mentioned phosphor particles are an example, and the phosphor particles used for the wavelength conversion member are not necessarily limited to the above.

The phosphor particle 130 includes a first phosphor particle 131 having a fluorescence peak wavelength in the range of 420 nm or more and less than 620 nm, and a second phosphor particle 132 having a fluorescence peak wavelength in the range of 620 nm or more and 750 nm or less. The two phosphor particles 132 preferably have a volume ratio of 0.01 or more and 0.3 or less with respect to the first phosphor particles 131.

As a result, when the second phosphor particles 132 that emit red fluorescence in order to enhance the color rendering property are used in addition to the first phosphor particles 131, the reflection layer 110 using aluminum, silver, or the like is used. With a small amount of red phosphor particles, it is possible to obtain light emission with a small color temperature and high color rendering properties. Further, the red phosphor is a material having high heat generation because the difference in energy between the light source light and the converted light is large as compared with the yellow phosphor and the green phosphor. However, in the present invention, the heat storage of the phosphor layer can be suppressed by reducing the usage fee of the red phosphor, so that the risk of temperature quenching can be reduced.

Even when two types of phosphor particles 130 are used in the phosphor layer 120, the above-mentioned phosphor particles are an example, and the first phosphor particles 131 and the second fluorescence used in the wavelength conversion member 100 are examples. The body particles 132 are not necessarily limited to the above. Further, the average particle size of the second phosphor particles 132 may be the same as or different from the average particle size of the first phosphor particles 131.

The phosphor particles 130 absorb the light source light (excitation light) and emit the converted light. For example, YAG: Ce absorbs light from a light source and emits yellow conversion light. Further, LuAG: Ce absorbs the light source light and emits the green conversion light. Further, the S-CASN absorbs the light source light and emits the red conversion light. For example, when the light source light is blue or purple, these phosphor particles can be combined alone or in combination to emit warm white synchrotron radiation with a small color temperature. can do.

The average particle size of the phosphor particles 130 is preferably 5 μm or more and 20 μm or less. Since it is 5 μm or more, the emission intensity of the converted light is increased, and thus the emission intensity of the wavelength conversion member 100 is increased. Further, since it is 20 μm or less, the temperature of each phosphor particle 130 can be kept low, and temperature quenching can be suppressed.

The translucent ceramic 140 is formed by hydrolyzing or oxidizing an inorganic binder, and is made of a translucent inorganic material. The translucent ceramic 140 is composed of, for example, silica (SiO ₂ ) and aluminum phosphate. Since the translucent ceramic 140 is made of an inorganic material, it does not deteriorate even when irradiated with high-energy light such as LD. Further, since the translucent ceramic 140 has translucency, it can be passed through without lowering the emission intensity of the light source light or the converted light.

The translucent substance is the emission of light that escapes from the opposite side when light is vertically incident on a target substance of 0.5 mm in the wavelength region of visible light (λ = 380 to 780 nm). A substance whose bundle has a characteristic of more than 80% of the incident light.

In the phosphor layer 120, the volume ratio of the phosphor particles 130 to the translucent ceramic 140 is preferably 2 or more and 10 or less, and more preferably 4 or more and 6 or less. When the volume ratio of the phosphor particles to the translucent ceramics is smaller than 2, the excitation light escapes too much and the light emission becomes blue. Further, when the volume ratio of the phosphor particles to the translucent ceramics is larger than 10, the translucent ceramics 140 adhering the reflective layer 100 and the phosphor particles 130 are insufficient, and the phosphor layer 120 may be peeled off. Increases.

The porosity and thickness of the phosphor layer of the wavelength conversion member, the average particle diameter of the phosphor particles, and the volume ratio of the phosphor particles to the translucent ceramics can be measured by analyzing SEM (scanning electron microscope) images. it can. The porosity of the phosphor layer in the analysis of the SEM image can be measured by, for example, as follows. First, the cross section of the phosphor layer in the direction perpendicular to the plane direction of the reflective layer is photographed by SEM at a magnification of 2000 times. Next, using the free software "ImageJ" developed by the National Institutes of Health (NIH), the phosphor layer portion was cut out into a rectangle from the photographed data, and the image was binarized. The image is binarized according to a certain threshold value such that the black part = voids, the white part = phosphor particles, and the binder (translucent ceramics) after solidification. Then, the porosity can be obtained by calculating the black part area ÷ (black part area + white part area) × 100. Since the voids have a random shape, the area porosity and the volume porosity can be considered to be equivalent. As the image used at this time, it is preferable to acquire cross-sectional images (for example, three or more) of a plurality of locations in the phosphor layer so as to have an average value of the entire phosphor layer.

Further, the thickness of the phosphor layer in the analysis of the SEM image can be measured by, for example, as follows. First, the cross section of the phosphor layer in the direction perpendicular to the plane direction of the reflective layer is photographed by SEM at a magnification of 2000 times. Next, the photographed image of the photographic data is binarized by a certain threshold value that enables the phosphor layer and the reflective layer to be distinguished by the binarized image using "ImageJ". Then, a range of the image recognized as the phosphor layer is defined from the image, a plurality of thicknesses in the vertical direction thereof are calculated at equal intervals, and the average value of the thickness of the phosphor layer can be obtained from the average value. As the image used at this time, it is preferable to acquire cross-sectional images (for example, three or more) of a plurality of locations in the phosphor layer so as to be an average value of the entire phosphor layer.

Further, the average particle size of the phosphor particles in the analysis of the SEM image can be measured by, for example, as follows. First, the cross section of the phosphor layer in the direction perpendicular to the plane direction of the reflective layer is photographed by SEM at a magnification of 2000 times. Next, using "ImageJ", the phosphor layer portion is cut out into a rectangle from the photographed data, and the image is binarized to obtain the phosphor particles in the phosphor layer and other portions (translucency). It is binarized by a certain threshold value that makes it possible to identify sex ceramics, voids, etc.). Then, the cross-sectional area of 100 or more particles recognized as phosphor particles can be calculated from the image, and the average particle diameter can be obtained from the cumulative distribution thereof. As the image used at this time, cross-sectional images (for example, three or more) of a plurality of locations in the phosphor layer are acquired so as to have an overall average particle size with respect to the particle size of the phosphor particles contained in the phosphor layer. It is preferable to do so. The average particle size of the phosphor particles obtained in this way is obtained by calculating and measuring a statistically sufficient number of cross-sectional images and the number of phosphor particles to obtain the phosphor particles specified at the time of manufacturing the wavelength conversion member. The difference from the average particle diameter as the median diameter (D50) becomes sufficiently small.

Further, the volume ratio of the phosphor particles to the translucent ceramics in the analysis of the SEM image can be calculated by, for example, as follows. First, the cross section of the phosphor layer in the direction perpendicular to the plane direction of the reflective layer is photographed by SEM at a magnification of 2000 times. Next, using "ImageJ", the phosphor layer portion is cut out into a rectangle from the photographed data, and the image is binarized with black part = void, white part = phosphor particle, and translucent ceramics. It is binarized by a certain threshold value. Also, the same image is binarized by another threshold that allows the phosphor particles and translucent ceramics to be distinguished. From these two types of binarized images, the area of the phosphor particles and the area of the translucent ceramics in the image are calculated. Then, by calculating (area of phosphor particles) ÷ (area of translucent ceramics), the volume ratio of phosphor particles to translucent ceramics can be obtained. Since the translucent ceramics have a random shape, it can be considered that the area ratio and the volume ratio are equivalent. As the image used at this time, it is preferable to acquire cross-sectional images (for example, three or more) of a plurality of locations in the phosphor layer so as to have an average value of the entire phosphor layer. It is also possible to calculate the volume ratio of the phosphor particles to the translucent ceramics by using the porosity and the cumulative distribution of the phosphor particles.

With such a wavelength conversion member and a light emitting device, it is possible to obtain light emission of a warm color having a small color temperature. Further, when the purpose is to emit light with a small color temperature, the thickness of the phosphor layer can be reduced as compared with the case of using a reflective layer using aluminum, silver, etc., and the heat storage of the phosphor layer can be reduced. Since it can be suppressed, the risk of temperature quenching can be reduced. The wavelength conversion member and the light emitting device of the present invention are suitably used in applications where high color rendering properties are required, especially in lighting. For example, it is used for lighting restaurants and the like, and can make food look delicious.

[Method of manufacturing wavelength conversion member]
5A, 5B, and 5C are cross-sectional views showing a manufacturing process of the wavelength conversion member of the present invention, respectively. First, prepare an inorganic binder, a solvent, and phosphor particles. The inorganic binder is preferably an organic silicate such as ethyl silicate. By using the organic silicate, the phosphor particles are dispersed in the entire printing paste, and a printing paste having an appropriate viscosity can be prepared. For example, when ethyl silicate is used as the inorganic binder, the mass of ethyl silicate is 70 wt% or more and 100 wt% or less, preferably 80 wt% or more and 90 wt% or less, based on the mass of water and the catalyst. In addition, the inorganic binder is prepared by reacting a raw material containing at least one of a group consisting of a silicon oxide precursor, a silicic acid compound, silica, and amorphous silica, which becomes silicon oxide by hydrolysis or oxidation, at room temperature. , It may be obtained by heat treatment at a temperature of 500 ° C. or lower. Examples of the silicon oxide precursor include those containing perhydropolysilazane, ethyl silicate, and methyl silicate as main components. As the solvent, a high boiling point solvent such as butanol, isophorone, α-terpineol, and glycerin can be used.

As the phosphor particles, for example, particles such as YAG and LuAG can be used. The type and amount of phosphor particles are adjusted according to the color temperature of the irradiation light to be obtained with respect to the light source light. At this time, two or more kinds of phosphor particles may be used. For example, when trying to obtain white light with respect to blue light, an appropriate amount of phosphor particles that emit green light and red light or yellow light when excited by blue light is selected. When the second phosphor particles are added to the first phosphor particles for the purpose of enhancing the color playability, the first phosphor particles having a fluorescence peak wavelength in the range of 420 nm or more and less than 620 nm has a fluorescence peak wavelength of 620 nm. Second phosphor particles having a fluorescence peak wavelength in the range of 750 nm or more are added after adjusting the volume ratio to 0.01 or more and 0.3 or less.

As shown in FIG. 5A, these inorganic binders, a solvent, and phosphor particles are mixed to prepare a paste (ink) 410. A ball mill or the like can be used for mixing. On the other hand, a reflective layer made of an inorganic material is prepared. The reflective layer uses a material whose main component is copper. The reflective layer is preferably plate-shaped. When the reflective layer is provided on the base material, the reflective layer is bonded to the base material at this point.

Next, as shown in FIG. 5B, the obtained paste 410 was heat-treated on the reflective layer 110 so as to have a thickness of a predetermined average film thickness in the range of 15 μm or more and 200 μm or less by using a screen printing method. Apply. Screen printing can be performed by pressing the paste 410 against the screen 520 stretched on the frame with the ink squeegee 510. In addition to the screen printing method, a spray method, a drawing method using a dispenser, and an inkjet method can be mentioned, but the screen printing method is preferable in order to stably form a thin phosphor layer.

Then, as shown in FIG. 5C, the printed paste 410 is dried and heat-treated in the furnace 600 to remove the solvent and the organic component of the inorganic binder to oxidize the main metal in the inorganic binder. (When the main metal is Si, it is _{converted to SiO 2} ), and at that time, the phosphor layer 120 and the reflective layer 110 are adhered to each other. Drying is preferably carried out at 100 ° C. or higher and 150 ° C. or lower for 20 minutes or longer and 60 minutes or shorter. The heat treatment temperature is preferably 150 ° C. or higher and 500 ° C. or lower, and the heat treatment time is preferably 0.5 hours or longer and 2.0 hours or lower. The rate of temperature rise is preferably 50 ° C./h or more and 200 ° C./h or less. Further, the heat treatment is preferably performed in an inert gas atmosphere.

In this way, the wavelength conversion member can be obtained. Then, the light emitting device can be manufactured by appropriately arranging the wavelength conversion member with respect to a light source such as an LED.

[Example]
(Method for preparing samples of Examples and Comparative Examples)
A reflective layer made of a flat plate having a length of 20 mm, a width of 20 mm, and a thickness of 2.0 mm made of pure copper and a reflective layer of the same size made of aluminum were prepared. Further, phosphor particles having an average particle size of 10 to 11 μm (YAG: Ce particles, LuAG: Ce particles, SCASN: Eu particles) were prepared. The average particle size was measured with a median diameter (D50) using HORIBA's Partica LA-960. The median diameter (D50) can be measured using a dry measurement or a wet measurement of a laser diffraction / scattering particle size distribution measuring device. These phosphor particles were weighed and mixed with α-terpineol (solvent) to prepare a dispersant, and mixed with ethyl silicate (inorganic binder) to prepare a printing paste.

Here, the printing paste for producing Example 1 and Comparative Example 1 was assumed to contain one kind of phosphor particles (YAG: Ce particles or LuAG: Ce particles). The printing paste for producing Example 2 and Comparative Example 2 includes first phosphor particles (YAG: Ce particles) having a fluorescence peak wavelength in the range of 420 nm or more and less than 620 nm, and 620 nm or more and 750 nm or less. Second phosphor particles (SCASSN: Eu particles) having a fluorescence peak wavelength were mixed so as to have a predetermined volume ratio. In addition, Examples 1-1 to 1-3 are collectively referred to as Example 1, and Comparative Examples 1-1 to 1-4 are collectively referred to as Comparative Example 1. Further, Examples 2-1 to 2-4 are collectively referred to as Example 2, and Comparative Example 2-1 and Comparative Example 2-2 are also referred to as Comparative Example 2.

Next, using a screen printing method, either of the printing pastes was applied to the above two types of reflective layers so as to have a thickness of 30 μm to 250 μm after firing. After coating, it was dried at 100 ° C. for 20 minutes and then sealed with an inorganic binder. Next, the temperature was raised to 350 ° C. at 150 ° C./h in an inert gas atmosphere using an electric furnace, and the samples were fired for 30 minutes to complete the samples of Examples and Comparative Examples.

To determine the film thickness (thickness) of the phosphor layer, take an SEM cross-sectional photograph of each sample at a magnification of 1000 times, draw 10 perpendicular lines at equal intervals with respect to the reflective layer, and draw 10 perpendicular lines from the top surface of the phosphor layer to the reflective layer. The distance to the top surface was measured, and the film thickness of the phosphor layer was calculated from the average length of the 10 lines.

(Sample evaluation method)
When each completed sample was laser-excited with 1000 mW of blue light, it was measured using a color illuminometer to see if the target color temperature was reached. The measured color temperature is the correlated color temperature specified in JIS Z 8725: 2015. A sample having a measured color temperature in the range of 2600 K or more and 5500 K or less was judged to have a pass color. In addition, the samples outside this range were judged to have failed the color.

Further, as an evaluation of heat dissipation (determination of temperature quenching), an emission intensity test was performed by excitation with a laser having an input of a maximum of 24 W. The excitation wavelength was 445 nm, and the irradiation diameter was adjusted to ^{0.3 mm 2 with a condenser lens.} At this time, the laser power was gradually increased, and if there was no decrease in light emission at 2 W, it was judged to be acceptable, and if there was a decrease in light emission, it was determined to be rejected as temperature quenching. FIG. 6 is a table showing various conditions of the samples of Example 1 and Comparative Example 1, the result (color tint) of whether or not the target color temperature was reached, and the result of whether or not temperature quenching occurred. Further, FIG. 7 is a table showing various conditions of the samples of Example 2 and Comparative Example 2, the result (color tint) of whether or not the target color temperature was reached, and the result of whether or not temperature quenching occurred. .. In both FIGS. 6 and 7, ◯ indicates a pass and × indicates a failure in terms of color and temperature quenching.

(Example 1 and Comparative Example 1)
The samples of Examples 1-1 to 1-3 and Comparative Example 1-4 are wavelength conversion members using a reflective layer of pure copper, and use YAG: Ce or LuAG: Ce particles as phosphor particles to obtain a target color. This is a sample prepared by changing the thickness of the phosphor layer at a temperature of 2600 K to 5500 K. Further, the samples of Comparative Examples 1-1 to 1-3 are wavelength conversion members using an aluminum reflective layer, and use YAG: Ce or LuAG: Ce particles as phosphor particles to set a target color temperature in Examples. This is a sample prepared by changing the thickness of the phosphor layer in the same range as in 1.

In Example 1-1, light emission with a thin film thickness and a warm color temperature was obtained. That is, by using the reflection layer made of pure copper, the reflection in the short wavelength region derived from the light source light is relatively suppressed, and even if the thickness of the phosphor layer is reduced, the color temperature is small and the color is warm. I was able to get light emission. Moreover, since the thickness of the phosphor layer was sufficiently thin, temperature quenching did not occur.

In Example 1-2, since the phosphor layer is thicker than in Example 1-1, more light source light is converted by the phosphor layer, and as a result, less light in the short wavelength region included in the irradiation light. , The color temperature became smaller, but it was within the target color temperature range. Further, although the thickness of the phosphor layer was 200 μm, temperature quenching did not occur with respect to the input of the above-mentioned light emitting element.

Comparative Examples 1-4 were produced in excess of the upper limit of the film thickness, and the color temperature could not be measured because the effect of copper as a reflective layer could not be obtained and temperature quenching occurred.

Example 1-3 is a sample prepared by changing the phosphor particles to LuAG: Ce under the same conditions as in Example 1-1. Even if the phosphor particles were changed to LuAG: Ce, the color temperature was within the target color temperature range. In addition, temperature quenching did not occur.

Comparative Example 1-1 aimed to obtain light emission within the target color temperature range by setting the thickness of the phosphor layer to 200 μm, but the combination of the thickness of the phosphor layer and the aluminum reflective layer generated heat. The color temperature could not be measured because the temperature could not be completely escaped and the temperature was extinguished with respect to the input of the light emitting element. In Comparative Example 1-2, temperature quenching could be prevented by setting the thickness of the phosphor layer to 30 μm, but light emission within the target color temperature range could not be obtained. It is considered that this is because the reflective layer is made of aluminum, so that light in the short wavelength region is also reflected well. Comparative Example 1-3 was produced under the same conditions as in Example 1-3 except that the reflective layer was made of aluminum, but the results were the same as those in Comparative Example 1-2.

(Example 2 and Comparative Example 2)
The samples of Examples 2-1 to 2-4 and Comparative Example 2-2 are wavelength conversion members using a reflective layer of pure copper, and the thickness of the phosphor layer is kept constant at 30 μm. This is a sample prepared by changing the volume ratio of red phosphor particles (SCASN: Eu particles) to Ce. The sample of Comparative Example 2-1 is a wavelength conversion member using an aluminum reflective layer, and the thickness of the phosphor layer is 30 μm, which is the same as that of Example 2, and the color temperature range is the same as that of Example 2-2. This is a sample prepared by determining the volume ratio of the red phosphor particles to YAG: Ce so as to be inside.

In Example 2, by setting the volume ratio of the red phosphor particles to YAG: Ce to 0.01 or more and 0.3 or less, irradiation light having a color temperature within the target color temperature range could be obtained. If the volume ratio of the red phosphor particles to YAG: Ce is smaller than 0.01, the effect of enhancing the color rendering property becomes weak. Further, when the volume ratio of the red phosphor particles to YAG: Ce is made larger than 0.3, the risk of temperature quenching due to the heat storage of the phosphor layer increases. Further, it is considered that the irradiation light becomes white light having a strong reddish tinge. Comparative Example 2-2 was produced at a volume ratio of red phosphor particles to YAG: Ce of 0.4, which exceeded the upper limit, and temperature quenching occurred because the amount of red phosphor added was too large. Moreover, the color temperature could not be measured.

When Comparative Example 2-1 was prepared so as to be within the same color temperature range as in Example 2-2, the volume ratio of the red phosphor particles to YAG: Ce was 0.1, and Example 2-2. The amount of red phosphor particles used increased as compared with the above. As a result, the color temperature could be measured in the initial stage of quenching, but it was different from Example 2-2 because heat storage in the phosphor layer was more likely to occur as compared with Example 2-2. , Temperature quenching occurred over time.

From the above results, it was found that the wavelength conversion member of the present invention can obtain light emission of a warm color having a small color temperature. Further, when the purpose is to emit light with a small color temperature, the thickness of the phosphor layer can be reduced as compared with the case of using a reflective layer using aluminum, silver, etc., and the heat storage of the phosphor layer can be reduced. It was found that the risk of temperature quenching can be reduced because it can be suppressed.

10 Light emitting device 50 Light emitting element 100 Wavelength conversion member 105 Base material 110 Reflective layer 115 Recessed portion 120 Fluorescent layer 130 Fluorescent particle 131 First phosphor particle 132 Second phosphor particle 140 Translucent ceramics 410 Paste 510 Ink squeegee 520 Screen 600 furnace

Claims (6)

It is a wavelength conversion member
A phosphor layer having an incident surface on which light is incident and a back surface located on the opposite side of the incident surface.
A reflective layer arranged on the back surface side is provided.
The phosphor layer is formed of phosphor particles and translucent ceramics that bond the fluorescent particles to each other.
The reflective layer is made of a material whose main component is copper.
A wavelength conversion member characterized in that the thickness of the phosphor layer is 15 μm or more and 200 μm or less. The phosphor particles include a first phosphor particle having a fluorescence peak wavelength in the range of 420 nm or more and less than 620 nm, and a second phosphor particle having a fluorescence peak wavelength in the range of 620 nm or more and 750 nm or less.
The wavelength conversion member according to claim 1, wherein the second phosphor particles have a volume ratio of 0.01 or more and 0.3 or less with respect to the first phosphor particles. The wavelength conversion member according to claim 1 or 2, wherein the reflective layer has a thermal conductivity of 250 W / m · K or more. The wavelength conversion member according to any one of claims 1 to 3, wherein the surface roughness Ra of the reflective layer on the phosphor layer side is 7.0 μm or less. The present invention according to any one of claims 1 to 4, wherein the reflective layer has a concave recessed portion on the surface on the phosphor layer side, and the phosphor layer is formed in the recessed portion. Wavelength conversion member. It is a light emitting device
A light emitting element that emits excitation light with a specific range of wavelengths,
A light emitting device comprising the wavelength conversion member according to any one of claims 1 to 5.

Images