Wavelength conversion member, and light-emitting device

Abstract

To provide a wavelength conversion member and a light-emitting device, with which color unevenness is suppressed so that uniform emission light can be obtained.SOLUTION: A wavelength conversion member 10 comprises: a substrate 12; and a phosphor layer 14 which is provided on one main surface of the substrate 12, and which is formed of phosphor particles 16, and translucent ceramics 18 for bonding the phosphor particles 16 to each other and for bonding the substrate 12 and the phosphor particles 16. In a prescribed region 32 including the center 30 of a surface that is irradiated with a laser beam, of the phosphor layer, when measuring the chromaticity Cx per unit region 34 of emission light obtained when the prescribed region 32 is irradiated with a laser beam of a wavelength 450 nm (±10 nm), by using an imaging color luminance meter, an area ratio of the unit region 34 where a value of the chromaticity Cx exceeds a range of ±2% from a center value of the chromaticity Cx, is less than 3% relative to the prescribed region 32.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a wavelength conversion member and a light emitting device.

Background Art

[0002] There is known a light emitting device using a wavelength conversion member that emits light irradiated from a light source such as an LED (Light Emitting Diode) or an LD (Laser Diode) as conversion light of a different wavelength by a phosphor layer. In recent years, applications using an LD as a light source, which has high energy efficiency and is easy to handle miniaturization and high output, have been increasing.

[0003] Conventionally, a phosphor layer is known to be formed by dispersing phosphor particles in a resin typified by epoxy or silicone. However, due to the high output of recent light emitting elements, there is concern about performance degradation due to alteration and deterioration of the resin caused by heat generation. To solve such heat resistance problems, it has become possible to cope with the high output of the light source by using an inorganic binder as a binder, including particulate phosphor and a binder. (Patent Documents 1 and 2)

[0004] In order to obtain predetermined light emission characteristics, the size of the phosphor particles constituting the phosphor layer is adjusted. It is known that a relatively large particle diameter of about several tens of μm has excellent light emission characteristics, but it is also necessary that color unevenness does not occur in addition to the light emission characteristics. Patent Document 3 describes adjusting the median diameter d50 or the maximum particle diameter dmax for the purpose of manufacturing a light emitting device with little color deviation including a green phosphor.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0006] As in Patent Document 3, in order to suppress color unevenness (color deviation), the particle diameter of phosphor particles has been adjusted, but there is still room for improvement.

[0007] The present invention has been made in view of such circumstances, and an object thereof is to provide a wavelength conversion member and a light emitting device in which color unevenness is suppressed and uniform emitted light can be obtained.

MEANS FOR SOLVING THE PROBLEMS

[0008] (1) In order to achieve the above object, the wavelength conversion member of the present invention takes the following means. That is, the wavelength conversion member of the application example of the present invention is a wavelength conversion member, which includes a base material, phosphor particles provided on one main surface of the base material, and a translucent ceramic that binds the phosphor particles to each other and the base material and the phosphor particles, and a phosphor layer formed thereby. In a predetermined region including the center of the surface of the phosphor layer irradiated with laser light, when the chromaticity Cx per unit region of the emitted light obtained when the predetermined region is irradiated with laser light having a wavelength of 450 nm (± 10 nm) is measured by an imaging color luminance meter, the area ratio of the unit region where the value of the chromaticity Cx exceeds the range of ± 2% from the central value of the chromaticity Cx to the predetermined region is less than 3%.

[0009] By setting the area ratio of the unit region where the value of the chromaticity Cx exceeds the range of ± 2% from the central value of the chromaticity Cx to less than 3% in this way, color unevenness of the wavelength conversion member is suppressed and uniform emitted light can be obtained.

[0010] (2) Further, in the wavelength conversion member of the application example of (1) above, the difference obtained by subtracting the minimum particle diameter from the maximum particle diameter of the phosphor particles is 18 μm or less.

[0011] In this way, by setting the difference obtained by subtracting the minimum particle diameter from the maximum particle diameter of the phosphor particles to 18 μm or less, the difference in the light emission efficiency of each phosphor particle can be reduced, and color unevenness of the wavelength conversion member can be suppressed.

[0012] (3) Further, in the wavelength conversion member of the application example of (1) or (2) above, the thickness of the phosphor layer is characterized in that it is 1.5 times or more the average particle diameter of the phosphor particles.

[0013] In this way, by setting the thickness of the phosphor layer to 1.5 times or more the average particle diameter of the phosphor particles, the optical path where no phosphor particles exist in the optical path from the base material to the surface of the phosphor layer can be reduced, and the leakage of the light source light can be prevented. As a result, color unevenness of the wavelength conversion member can be suppressed.

[0014] (4) Further, in the wavelength conversion member of any one of the application examples of (1) to (3) above, the average particle diameter of the phosphor particles is characterized in that it is 6 μm or more and 25 μm or less.

[0015] In this way, by setting the average particle diameter of the phosphor particles to 6 μm or more and 25 μm or less, the light emission efficiency of each phosphor particle can be increased, and while suppressing color unevenness of the wavelength conversion member, the illuminance can be increased.

[0016] (5) Further, the light emitting device of the application example of the present invention is a light emitting device, and is characterized by including a light emitting element that emits light of a specific range of wavelengths and a wavelength conversion member of any one of the application examples of (1) to (4) above.

[0017] The wavelength conversion member of the present invention can be used as a light emitting device that can suppress color unevenness and can cope with the high output of a light emitting element such as an LD.

Effect of the Invention

[0018] According to the wavelength conversion member of the present invention, color unevenness is suppressed, and uniform emitted light can be obtained.

Brief Description of the Drawings

[0019]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0020] Next, embodiments of the present invention will be described with reference to the drawings. For ease of understanding of the description, the same reference numerals are assigned to the same components in each drawing, and overlapping descriptions are omitted. In the configuration diagrams, the sizes of the respective components are conceptually represented and do not necessarily represent actual dimensional ratios.

[0021] [Configuration of Wavelength Conversion Member] Figs. 1(a) and (b) are a cross-sectional view and a plan view schematically showing a wavelength conversion member according to an embodiment of the present invention, respectively. Fig. 2 is a schematic view showing an enlarged cross-section of a phosphor layer portion of the wavelength conversion member. The wavelength conversion member 10 according to the embodiment of the present invention has a phosphor layer 14 formed on a substrate 12. The wavelength conversion member 10 transmits or reflects incident light irradiated from a light source, and generates light having a different wavelength by being excited by the incident light. For example, while transmitting or reflecting incident light of blue light, it emits converted light such as green, red, or yellow converted by the phosphor layer 14, and combines the converted light and the incident light, or uses only the converted light to convert it into emitted light of various colors.

[0022] The shape of the substrate 12 may be any shape applicable to the light emitting device 100, and may be various shapes such as circular, rectangular, elliptical, polygonal, and the like.

[0023] The material of the substrate 12 is appropriately selected according to the intended use. When used for the purpose of reflecting excitation light from a light source, aluminum, iron, copper, etc. or ceramics can be used. In particular, it is preferable to use aluminum which has a high thermal conductivity and a high reflectivity in the entire visible light region. Further, a reflective layer may be formed by providing a material that reflects light such as silver on the main surface 13 which is the surface of the substrate 12 on the phosphor layer 14 side by plating, vapor deposition, or the like, or an anti-reflection film such as TiO 2 etc. may be formed. When used for the purpose of transmitting excitation light from a light source, inorganic materials such as sapphire and glass can be used. It is particularly preferable to use sapphire which has a high thermal conductivity. By using a material having a high thermal conductivity for the substrate 12, the heat storage of the phosphor layer 14 can be suppressed, and the deterioration of the characteristics of the phosphor particles 16 due to a temperature rise can be suppressed.

[0024] The phosphor layer 14 is provided as a film on the main surface 13 of the base material 12 and is formed of phosphor particles 16 and translucent ceramics 18. The translucent ceramics 18 binds the phosphor particles 16 to each other and binds the phosphor particles 16 and the base material 12. Thereby, since it is joined to the base material 12 that functions as a heat radiating material against irradiation with light of high energy density, heat can be efficiently radiated, and temperature quenching of the phosphor can be suppressed. The phosphor layer 14 may contain a filler 20 or voids.

[0025] In a predetermined region 32 including the center (center 30 of the phosphor layer) of the surface of the phosphor layer 14 irradiated with the laser light, when the chromaticity Cx per unit region 34 of the emitted light obtained when the predetermined region 32 is irradiated with laser light having a wavelength of 450 nm (±10 nm) is measured with an imaging color luminance meter, the area ratio of the unit region 34 in which the value of the chromaticity Cx exceeds the range of ±2% from the central value of the chromaticity Cx with respect to the predetermined region 32 is less than 3%.

[0026] In this way, by setting the area ratio of the unit region 34 in which the value of the chromaticity Cx exceeds the range of ±2% from the central value of the chromaticity Cx with respect to the predetermined region 32 to less than 3%, color unevenness of the wavelength conversion member 10 is suppressed, and uniform emitted light can be obtained.

[0027] Chromaticity is what represents, using numerical values, the hue, chroma, and colorfulness of the properties of a color, excluding lightness. In this specification, it is represented using the chromaticity Cx corresponding to the value of the x-axis represented by the xy chromaticity diagram of the CIE-XYZ color system established by the International Commission on Illumination (CIE). In the xy chromaticity diagram, as the value of the x-axis increases, the ratio of "redness" increases, and as the value decreases, the ratio of "blueness" increases. As the value of the y-axis increases, the ratio of "greenness" increases, and as the value decreases, the ratio of "blueness" increases. Also, the point where Cx = Cy = 1 / 3 (= approximately 0.33) is called the white point.

[0028] The value of chromaticity Cx can be measured as follows. On the upper surface of a predetermined region 32 including the center of the surface of the phosphor layer 14 irradiated with the laser light, the chromaticity Cx for each unit region 34 of the emitted light obtained when irradiating the laser light with a wavelength of 450 nm (±10 nm) is measured by an imaging color luminance meter. Next, the central value of the chromaticity Cx for each unit region 34 is obtained. Then, the area ratio (%) of the predetermined region 32 of the unit region 34 whose chromaticity Cx value exceeds the range of ±2% from the central value of the chromaticity Cx is obtained.

[0029] The central value of the chromaticity Cx is the average value of the chromaticity Cx values for each unit region 34 measured as described above. Further, the area ratio (%) of the predetermined region 32 of the unit region 34 whose chromaticity Cx value exceeds the range of ±2% from the central value of the chromaticity Cx is the ratio, expressed as a percentage, of the total area of the unit regions 34 whose chromaticity Cx value of the unit region 34 exceeds the range of ±2% from the central value of the chromaticity Cx to the area of the predetermined region 32.

[0030] The predetermined region 32 including the center 30 of the phosphor layer is preferably a 4 mm × 4 mm square region centered on the center 30 of the phosphor layer. When the center 30 of the phosphor layer cannot be accurately determined, a region such as a 4 mm × 4 mm square region may be set near the center 30 of the phosphor layer and used as the predetermined region 32 including the center 30 of the phosphor layer. Since the area of the phosphor layer 14 is small, if it is difficult to set a 4 mm × 4 mm square region near the center 30 of the phosphor layer, a smaller region may be used as the predetermined region 32 including the center 30 of the phosphor layer.

[0031] In the field of view observed with a 100-fold digital microscope on the upper surface of the phosphor layer 14, the outer edge portion of the phosphor layer 14 is defined as the outer periphery 40 of the phosphor layer 14. For example, when the phosphor layer 14 is substantially rectangular, the outer periphery 40 of the phosphor layer 14 is a virtual rectangle that encloses the entire phosphor layer 14. Also, for example, when the phosphor layer 14 is substantially circular, the outer periphery 40 of the phosphor layer 14 is a virtual circumference that encloses the entire phosphor layer 14.

[0032] In the field of view observed with a digital microscope with a magnification of 100 times on the upper surface of the phosphor layer 14, a region having the same center as the center 30 of the phosphor layer and being concentrically similar to the outer periphery 40 and having an area of 49% of the area of the phosphor layer 14 is defined as the central region 42 of the phosphor layer 14. As shown in Fig. 1(b), for example, when the phosphor layer 14 is substantially rectangular, the central region 42 of the phosphor layer 14 has the same center as the center 30 of the phosphor layer and is inside a rectangle having a length similar to the outer periphery 40 and 70% of the length. Further, for example, when the phosphor layer 14 is substantially circular, the central region 42 of the phosphor layer 14 has the same center as the center 30 of the phosphor layer and is inside a circle having a radius of 70%. A predetermined region 32 including the center 30 of the phosphor layer is preferably set inside the central region 42 of the phosphor layer 14.

[0033] Fig. 3 is a schematic diagram showing an example of the predetermined region 32 and the unit region 34. The imaging color luminance meter can use the predetermined region 32 as a unit region 34 displayed with pixels of a predetermined size and measure the chromaticity for each of the unit regions 34. The unit regions 34 preferably have equal areas. Further, the unit regions 34 are preferably congruent squares. The size of the unit region 34 varies depending on the settings and performance of the imaging color luminance meter, but can be, for example, a square region of 160 μm × 160 μm. The unit region 34 may also be a region corresponding to one or more pixels of the imaging color luminance meter.

[0034] In the example of the predetermined region 32 and the unit region 34 in FIG. 3, the unit region 34 marked with a "+" indicates a unit region 34 where the value of the chromaticity Cx exceeds the range of +2% from the central value of the chromaticity Cx. Also, the unit region 34 marked with a "-" indicates a unit region 34 where the value of the chromaticity Cx exceeds the range of -2% from the central value of the chromaticity Cx. In the example of FIG. 3, there are 625 unit regions 34 with equal areas (25×25), and a total of 8 unit regions 34 exceed the range of ±2% of the value of the chromaticity Cx from the central value of the chromaticity Cx. Therefore, the area ratio of the unit regions 34 that exceed the range of ±2% of the value of the chromaticity Cx from the central value of the chromaticity Cx to the predetermined region 32 can be calculated as 8 / 625·100 = 1.28%. In the example of FIG. 3, only the unit regions 34 that exceed the range of ±2% of the value of the chromaticity Cx from the central value of the chromaticity Cx are marked with "+" and "-", but numerical values or colors can be displayed for all the unit regions 34 to indicate the unit regions 34 that exceed the range of ±2% of the value of the chromaticity Cx from the central value of the chromaticity Cx.

[0035] The thickness of the phosphor layer 14 is preferably 1.5 times or more the average particle diameter of the phosphor particles 16. Thereby, it is possible to reduce the optical path where no phosphor particles exist in the optical path from the base material to the surface of the phosphor layer, and prevent the leakage of the light source light (for example, blue light). As a result, color unevenness of the wavelength conversion member can be suppressed. Also, the thickness of the phosphor layer 14 is preferably 10 μm or more and 300 μm or less, and more preferably 25 μm or more and 200 μm or less.

[0036] The difference obtained by subtracting the minimum particle diameter from the maximum particle diameter of the phosphor particles 16 is preferably 18 μm or less. Thereby, it is possible to reduce the difference in the light emission efficiency of each phosphor particle 16 and suppress the color unevenness of the wavelength conversion member 10.

[0037] The average particle diameter of the phosphor particles 16 is preferably 6 μm or more and 25 μm or less, more preferably 9 μm or more and 21 μm or less. Thereby, the luminous efficiency of each phosphor particle 16 can be increased, and while suppressing color unevenness of the wavelength conversion member 10, the illuminance can be increased. Further, when it is 25 μm or less, adjustment of the thickness of the phosphor layer 14 becomes easy, and the risk of the phosphor particles 16 being detached can be reduced. Also, the temperature of each phosphor particle 16 can be kept low, and temperature quenching can be suppressed. In the present specification, the average particle diameter means the median diameter (D50). During manufacturing, the difference obtained by subtracting the minimum particle diameter from the average particle diameter and the maximum particle diameter can be measured or calculated using dry measurement or wet measurement of a laser diffraction / scattering type particle size distribution measuring device.

[0038] The difference obtained by subtracting the minimum particle diameter from the average particle diameter and the maximum particle diameter of the phosphor particles 16 in the phosphor layer 14 of the wavelength conversion member 10 can also be measured or calculated by analyzing an SEM (scanning electron microscope) image.

[0039] The average particle diameter of the phosphor particles 16 in the analysis of the SEM image can be measured, for example, as follows. First, the upper surface of a predetermined region 32 of the phosphor layer 14 is photographed with an SEM at a magnification of 1000 times. Next, using image analysis software, an image of an appropriate size is cut out in a rectangle from the photographed photo data. The cut-out image is binarized with a certain threshold value such that the phosphor particles 16 in the phosphor layer 14 and other portions (the translucent ceramics 18, the filler 20, voids, etc.) can be discriminated. Next, the areas of, for example, 100 or more particles recognized as phosphor particles 16 are calculated from the image. The phosphor particles 16 that are cut off at the image edge are not included. Then, the calculated areas are converted into equivalent circle diameters, and the average particle diameter of the phosphor particles 16 can be obtained from the cumulative distribution.

[0040] Note that, for the image used at this time, it is preferable to randomly acquire a plurality of images (for example, five or more images) at a plurality of locations in a predetermined region 32 of the phosphor layer 14 so that the average particle diameter of the phosphor particles 16 included in the predetermined region 32 of the phosphor layer 14 is the overall average particle diameter. The average particle diameter of the phosphor particles 16 obtained in this way is such that the difference from the average particle diameter as the median diameter (D50) of the phosphor particles 16 defined during the manufacture of the wavelength conversion member 10 becomes sufficiently small by statistically calculating and measuring a sufficient number of the number of images and the number of phosphor particles 16.

[0041] The difference obtained by subtracting the minimum particle diameter from the maximum particle diameter of the phosphor particles 16 in the analysis of the SEM image can be measured, for example, as follows. First, in the same manner as for obtaining the average particle diameter, the upper surface of a predetermined region 32 of the phosphor layer 14 is photographed with an SEM at a magnification of 1000 times, cut out, and binarized to calculate the areas of, for example, 100 or more particles recognized as phosphor particles 16 from the image. Next, the calculated areas are converted into equivalent circle diameters, and the maximum particle diameter and the minimum particle diameter of the image are obtained. Then, using the average value of the maximum particle diameters of the plurality of images and the average value of the minimum particle diameters of the plurality of images, the difference obtained by subtracting the minimum particle diameter from the maximum particle diameter can be obtained. The difference between the maximum particle diameter and the minimum particle diameter of the phosphor particles 16 can also be obtained using image analysis software. As the image analysis software, for example, the free software "ImageJ" developed by the National Institutes of Health (NIH) of the United States can be used.

[0042] As the phosphor particles 16, for example, yttrium aluminum garnet-based phosphors (YAG-based phosphors) and lutetium aluminum garnet-based phosphors (LAG-based phosphors) can be used. In addition, the phosphor particles 16 can be selected from the following materials according to the design of the color to be emitted. For example, BaMgAl 10 O 17 :Eu, ZnS:Ag,Cl, BaAl 2 S 4 :Eu or CaMgSi 2 O 6 :Eu and other blue phosphors, Zn2 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 : Eu, Mn and other yellow or green phosphors, (M1) 3 SiO 5 : Eu or (M1)S:Eu and other yellow, orange or red phosphors, (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 and other red phosphors can be mentioned. 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 at least one of the group consisting of Y, Gd, Lu and Te. The phosphor particles 16 constituting the phosphor layer 14 can be applied even if they are a mixture of two or more types, but it is preferably one type. Note that the above phosphor particles 16 are an example, and the phosphor particles 16 used in the wavelength conversion member 10 are not necessarily limited to the above.

[0043] The translucent ceramic 18 is formed by hydrolysis or oxidation of an inorganic binder and is composed of an inorganic material having translucency. The translucent ceramic 18 is, for example, silica (SiO 2) It is composed of aluminum phosphate. Also, since the translucent ceramic 18 has translucency, it can transmit the light source light (incident light) and the converted light. Since the translucent ceramic 18 is made of an inorganic material, its heat resistance is improved, and it is less likely to deteriorate even when used for irradiating high-energy light such as an LD.

[0044] As the inorganic binder, for example, ethyl silicate, aluminum phosphate aqueous solution, etc. can be used.

[0045] Note that a substance having translucency refers to a substance having the property that when light is perpendicularly incident in the visible light wavelength region (λ = 380 to 780 nm) on a target substance of 0.5 mm, the radiant flux of the light passing through from the opposite side exceeds 80% of the incident light.

[0046] [Configuration of the light-emitting device] FIGS. 4(a) and (b) are conceptual diagrams each showing a part of an example of a light-emitting device according to an embodiment of the present invention. FIG. 4(a) represents a transmissive light-emitting device of the present invention, and FIG. 4(b) represents a reflective light-emitting device. The light-emitting device 100 includes a light source 50 and a wavelength conversion member 10. The light source 50 is a light-emitting element that generates light source light having a specific range of wavelengths, and for example, an LED, an LD, etc. can be used. Since the wavelength conversion member 10 of the present invention can efficiently perform wavelength conversion even at high power, the light source 50 is preferably an LD.

[0047] [Manufacturing method of the wavelength conversion member] An example of the manufacturing method of the wavelength conversion member will be described. FIG. 5 is a flowchart showing an example of the manufacturing method of the wavelength conversion member according to an embodiment of the present invention. First, a raw material is processed to prepare a base material 12 formed into a predetermined shape (step S1).

[0048] Separate from the preparation of the base material 12, phosphor particles 16 and an inorganic binder are mixed to prepare a phosphor ink (phosphor paste) (step S2). To prepare the phosphor ink, first, phosphor particles 16 having a predetermined average particle diameter and a difference between the maximum particle diameter and the minimum particle diameter are prepared. When the difference between the maximum particle diameter and the minimum particle diameter is large, it is necessary to remove coarse particles and fine particles with respect to the average particle diameter. Depending on the design of the wavelength conversion member 10, various phosphor particles 16 can be used.

[0049] Next, the prepared phosphor particles 16 are weighed, dispersed in a solvent, and mixed with an inorganic binder to prepare a phosphor ink for printing. The addition ratios of the solvent and the inorganic binder can be adjusted to, for example, 15 to 45%. For mixing, a ball mill, propeller stirring, or the like can be used. The mixing time can be adjusted to, for example, 80 to 160 minutes. As the solvent, high boiling point solvents such as α-terpineol, butanol, isophorone, and glycerin can be used.

[0050] A filler (inorganic fine particles) 20 may be added to the phosphor ink for the purpose of improving the hardness of the phosphor layer and adjusting the light emission property (light scattering property) and the like. Further, the inorganic fine particles can also be added for the purpose of adjusting the viscosity of the phosphor ink.

[0051] Next, the phosphor ink is applied to the surface of the base material 12 prepared in the base material preparation step (step S1) to form an ink layer (paste layer) (step S3). As the method of applying the phosphor ink, a screen printing method, a spray method, a drawing method using a dispenser, or an inkjet method can be used. The screen printing method is preferable because an ink layer with a uniform thickness can be stably formed. Further, the thickness of the ink layer is adjusted so as to have a predetermined thickness after firing. The ink layer is preferably formed along the shape of the base material 12.

[0052] Then, the phosphor layer is formed by heat-treating the applied phosphor ink at a temperature of 150°C or higher (Step S4). The heat treatment temperature is preferably 150°C or higher and 500°C or lower, more preferably 300°C or higher and 400°C or lower. The heat treatment time preferably provides a holding time of 20 minutes or longer, and is preferably 0.5 hour or longer and 2.0 hours or shorter. Also, the heating rate is preferably 2°C / min or higher and 10°C / min or lower. Further, a drying step may be provided before the heat treatment. The drying temperature is preferably 100°C or higher and 200°C or lower (less than the heat treatment temperature of the phosphor layer), and the drying time is more preferably 20 minutes or longer and 60 minutes or shorter.

[0053] By doing so, color unevenness is suppressed, and a wavelength conversion member capable of obtaining uniform emitted light can be manufactured.

[0054] [Examples and Comparative Examples] (Fabrication of Wavelength Conversion Member) (Example 1) A rectangular plate-shaped aluminum substrate with dimensions of 35 mm × 15 mm and a thickness t of 0.5 mm was prepared as the substrate.

[0055] Separately, as the phosphor ink, a yellow phosphor (YAG-based phosphor) with an average particle diameter of 9 μm and a difference between the maximum particle diameter and the minimum particle diameter of 11 μm was weighed, ethyl silicate was used as the inorganic binder, and α-terpineol was used as the solvent. While controlling the liquid temperature to 25°C to 40°C, the phosphor ink was prepared by mixing them with a propeller stirrer for 80 minutes.

[0056] The obtained phosphor ink was applied onto the substrate by screen printing so that the film thickness after heat treatment would be 30 μm. After drying the applied substrate at 100°C for 20 minutes, the temperature was raised to 150°C at 2°C / min in a non-oxidizing atmosphere using an electric furnace, and heat treatment was performed for 30 minutes or longer to fabricate a wavelength conversion member.

[0057] (Example 2) A wavelength conversion member of Example 2 was fabricated under the same conditions as in Example 1, except that a yellow phosphor with a difference between the maximum particle diameter and the minimum particle diameter of 6 μm was used.

[0058] (Example 3) A wavelength conversion member of Example 3 was fabricated under the same conditions as in Example 1, except that a yellow phosphor with a difference between the maximum particle diameter and the minimum particle diameter of 18 μm was used.

[0059] (Example 4) A wavelength conversion member of Example 4 was fabricated under the same conditions as in Example 1, except that a yellow phosphor with a difference between the maximum particle diameter and the minimum particle diameter of 12 μm was used and it was applied so that the film thickness after heat treatment became 50 μm.

[0060] (Example 5) A wavelength conversion member of Example 5 was fabricated under the same conditions as in Example 4, except that a yellow phosphor with a difference between the maximum particle diameter and the minimum particle diameter of 11 μm was used.

[0061] (Example 6) A wavelength conversion member of Example 6 was fabricated under the same conditions as in Example 1, except that a yellow phosphor with an average particle diameter of 11 μm and a difference between the maximum particle diameter and the minimum particle diameter of 10 μm was used.

[0062] (Example 7) A wavelength conversion member of Example 7 was fabricated under the same conditions as in Example 1, except that a yellow phosphor with an average particle diameter of 25 μm and a difference between the maximum particle diameter and the minimum particle diameter of 12 μm was used and it was applied so that the film thickness after heat treatment became 40 μm. (Example 8) A wavelength conversion member of Example 8 was fabricated under the same conditions as in Example 7, except that a yellow phosphor with a difference between the maximum particle diameter and the minimum particle diameter of 11 μm was used and it was applied so that the film thickness after heat treatment became 60 μm.

[0063] (Comparative Example 1) A wavelength conversion member of Comparative Example 1 was fabricated under the same conditions as in Example 1, except that a yellow phosphor with an average particle diameter of 11 μm and a difference between the maximum particle diameter and the minimum particle diameter of 25 μm was used.

[0064] (Comparative Example 2) A wavelength conversion member of Comparative Example 2 was produced under the same conditions as in Example 1, except that a yellow phosphor having an average particle diameter of 11 μm and a difference between the maximum particle diameter and the minimum particle diameter of 25 μm was used, and the coating was applied so that the film thickness after heat treatment was 12 μm.

[0065] (Evaluation Method) (Average Particle Diameter of Phosphor Particles) For the wavelength conversion members of the examples and comparative examples, the upper surface of a predetermined region including the center of the surface irradiated with the laser light of the phosphor layer was photographed at a magnification of 1000 times using SEM. For the image, the average particle diameter of the phosphor particles was determined using image analysis software. The predetermined region including the center of the phosphor layer was a 4 mm × 4 mm square region centered on the center of the phosphor layer.

[0066] (Difference between the Maximum Particle Diameter and the Minimum Particle Diameter of Phosphor Particles) Using the above image, the difference between the average value of the maximum particle diameter and the average value of the minimum particle diameter of the phosphor particles was determined, and this was taken as the difference between the maximum particle diameter and the minimum particle diameter of the phosphor particles.

[0067] (Measurement of the Thickness of the Phosphor Layer) The thickness of the substrate was measured with a high-precision contact digital sensor. Then, the thickness including the phosphor layer was measured, and the thickness of the phosphor layer was calculated from the difference.

[0068] (Measurement of Chromaticity Cx per Unit Area) A predetermined region including the center of the phosphor layer of the wavelength conversion members of the examples and comparative examples was irradiated with a laser beam having a wavelength of 450 nm to cause luminescence. Next, the chromaticity Cx per unit area was measured with an imaging color luminance meter. Next, the central value of the chromaticity Cx was determined. Then, the area ratio of the predetermined region of the unit region where the value of the chromaticity Cx exceeded the range of ±2% from the central value of the chromaticity Cx was determined in percentage (%). The unit region was a 160 μm × 160 μm region obtained by dividing each side of the predetermined region including the center of the phosphor layer into 25 parts.

[0069] (Measurement of Illuminance) FIG. 6 is a conceptual diagram showing a reflection type evaluation system for a light emission intensity (illuminance) test on a wavelength conversion member. The wavelength conversion members of the examples and comparative examples were irradiated with a laser beam having a wavelength of 450 nm to emit light, and the illuminance was measured with a spectral irradiance meter.

[0070] The table in FIG. 7 is a table showing the evaluation results of the wavelength conversion members of the examples and comparative examples. As shown in FIG. 7, for the wavelength conversion members of the examples and comparative examples, the same values as the design values at the time of manufacture were measured for the average particle diameter D50 and the value obtained by subtracting the minimum particle diameter from the maximum particle diameter. On the other hand, there were some cases where the thickness of the phosphor layer had a slight difference from the design value at the time of manufacture.

[0071] For the wavelength conversion members of Examples 1 to 8, with respect to the chromaticity Cx per unit area, the area ratio with respect to a predetermined area of a unit area where the value of the chromaticity Cx exceeds the range of ±2% from the central value of the chromaticity Cx was less than 3% in all cases, indicating that color unevenness was suppressed.

[0072] On the other hand, for the wavelength conversion members of Comparative Examples 1 and 2, with respect to the chromaticity Cx per unit area, the area ratio with respect to a predetermined area of a unit area where the value of the chromaticity Cx exceeds the range of ±2% from the central value of the chromaticity Cx exceeded 3% in all cases, indicating that color unevenness was not suppressed.

[0073] From the results of Comparative Example 1, it was found that when the difference obtained by subtracting the minimum particle diameter from the maximum particle diameter of the phosphor particles was too large, color unevenness could not be suppressed. Thus, it was found that the difference obtained by subtracting the minimum particle diameter from the maximum particle diameter of the phosphor particles is preferably 18 μm or less.

[0074] From the results of Comparative Example 2, it was found that when the thickness of the phosphor layer was about the same as the average particle diameter of the phosphor particles, color unevenness could not be suppressed. Thus, it was found that the thickness of the phosphor layer is preferably 1.5 times or more the average particle diameter of the phosphor particles. Note that Comparative Example 2 is an example in which the difference obtained by subtracting the minimum particle diameter from the maximum particle diameter of the phosphor particles also exceeds 18 μm.

[0075] For Examples 1 to 5 using phosphor particles with an average particle diameter of 9 μm, Examples 7 and 8 using phosphor particles with an average particle diameter of 25 μm had higher illuminance. From this, it was found that if the average particle diameter is 25 μm or less, the illuminance can be increased while suppressing color unevenness.

[0076] From the above results, it was confirmed that the wavelength conversion member of the present invention suppresses color unevenness and can obtain uniform emitted light.

[0077] The present invention is not limited to the above embodiments, and it goes without saying that the present invention extends to various modifications and equivalents included in the spirit and scope of the present invention. Also, the structure, shape, number, position, size, etc. of the components shown in each drawing are for convenience of explanation and can be changed as appropriate.

Explanation of Reference Numerals

[0078] 10 Wavelength conversion member 12 Substrate 13 Main surface 14 Phosphor layer 16 Phosphor particles 18 Translucent ceramics 20 Filler 30 Center of the phosphor layer 32 Predetermined region 34 Unit region 40 Outer periphery 42 Central region 50 Light source 100 Light-emitting device

Claims

1. A wavelength conversion member, comprising: a substrate; a phosphor layer provided on one main surface of the substrate and formed of phosphor particles, a translucent ceramic that binds the phosphor particles to each other and the substrate to the phosphor particles; and in a predetermined region including the center of the surface of the phosphor layer irradiated with laser light, when the chromaticity Cx per unit area of the emitted light obtained when irradiating the predetermined region with laser light having a wavelength of 450 nm (±10 nm) is measured by an imaging color luminance meter, the area ratio of the unit region in which the value of the chromaticity Cx exceeds the range of ±2% from the central value of the chromaticity Cx with respect to the predetermined region is less than 3%. The wavelength conversion member is characterized by this.

2. The wavelength conversion member according to claim 1, wherein the difference obtained by subtracting the minimum particle diameter from the maximum particle diameter of the phosphor particles is 18 μm or less.

3. The wavelength conversion member according to claim 1, wherein the thickness of the phosphor layer is 1.5 times or more the average particle diameter of the phosphor particles.

4. The wavelength conversion member according to claim 1, wherein the average particle diameter of the phosphor particles is 6 μm or more and 25 μm or less.

5. A light emitting device, comprising: a light emitting element that emits light having a specific wavelength range; and the wavelength conversion member according to any one of claims 1 to 4. The light emitting device is characterized by this.

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