Wavelength conversion member, method for manufacturing the same, and light-emitting device

Abstract

To provide a wavelength conversion member excellent in uniformity of illumination characteristics and adhesion between a substrate and a phosphor layer, and also to provide a manufacturing method thereof, and a light-emitting device.SOLUTION: A wavelength conversion member 10 includes: a substrate 12; and a phosphor layer 14 disposed on the substrate 12 and composed of phosphor particles 16 and a light transmissive ceramic 18 binding between the phosphor particles with each other and between the substrate 12 and the phosphor particles 16. The phosphor layer 14 is characterized by not having a recess 22 of 50 μm long or longer than that, extending in a center direction from a circumference of the phosphor layer 14, in a visual field observing a top face of the phosphor layer 14 with a digital microscope of 100-fold magnification.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a wavelength conversion member, a method for manufacturing the same, 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 having a wavelength different from that of the light source by a phosphor layer. In recent years, applications using an LD as a light source, which is highly energy-efficient and easy to handle miniaturization and high output, have been increasing.

[0003] As such a wavelength conversion member, a structure in which a phosphor is dispersed in a resin typified by epoxy or silicone is often used. However, as the output of the light source increases, the resin burns and discolors, resulting in a deterioration of characteristics and a shortening of the lifespan. In response to such problems, a wavelength conversion member made only of inorganic materials using an inorganic binder instead of the resin has been devised, and the problem of heat resistance has been solved even when a high-energy light source is used (Patent Document 1).

[0004] On the other hand, when screen-printing a phosphor paste composition using a polymer solution as a binder liquid, bleeding may occur at the edge of the phosphor film, or the fluidity may decrease and a uniform-surface phosphor film may not be obtained. In response to such problems, a phosphor paste composition containing a low-viscosity polymer solution, a phosphor, and a thixotropy-imparting agent has been disclosed (Patent Document 2). Patent Document 2 describes that such a phosphor paste composition has less stringing during screen printing, good plate release, and the ink remaining on the plate can be easily removed, thus solving the printing property problems of the phosphor paste.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] The wavelength conversion member described in Patent Document 1 has been made more responsive to higher output light sources by using an inorganic binder as the binder constituting the phosphor layer. However, the structure and state of the produced phosphor layer are thought to differ depending on the manufacturing conditions of the phosphor ink printed on the surface of the substrate, which may affect luminescence characteristics such as brightness, color tone, and adhesion to the substrate. However, Patent Document 1 does not describe the manufacturing conditions of the phosphor ink.

[0007] Furthermore, the phosphor paste composition described in Patent Document 2 addresses the printing characteristics when a polymer solution is used as the binder liquid, and cannot be applied when an inorganic binder is used. In addition, many thixotropy-imparting agents contain organic substances, and including organic substances in the phosphor paste may worsen its heat resistance, making it difficult to accommodate higher output light sources.

[0008] This invention has been made in view of these circumstances, and aims to provide a wavelength conversion member, a method for manufacturing the same, and a light-emitting device that exhibit excellent uniformity of luminescence characteristics and adhesion between the substrate and the phosphor layer. [Means for solving the problem]

[0009] (1) In order to achieve the above objective, the wavelength conversion member of the present invention employs the following means. That is, the wavelength conversion member of an application example of the present invention is a wavelength conversion member comprising a substrate, a phosphor layer provided on the substrate and formed of phosphor particles and translucent ceramics that bond the phosphor particles to each other and to the substrate and to the phosphor particles, wherein the phosphor layer is characterized in that, in the field of view when the upper surface of the phosphor layer is observed with a 100x digital microscope, there are no recesses of 50 μm or more in length extending from the outer periphery of the phosphor layer toward the center.

[0010] In this way, the length of the recesses in the peripheral region of the phosphor layer where the phosphor layer is not unintentionally formed is sufficiently reduced, thereby reducing the leakage of light from the light source in the peripheral region.

[0011] (2) Furthermore, in the wavelength conversion member of the application example of (1) above, the phosphor layer is characterized in that, in the field of view, it has a concentric similar shape with the same center as the phosphor layer, and there is one or fewer pinholes in a region of 30% or less of the area of ​​the phosphor layer.

[0012] In this way, by reducing the number of pinholes in the central region of the phosphor layer, the occurrence of color unevenness can be reduced. Furthermore, the risk of the phosphor layer peeling off starting from the pinholes in the central region can be reduced.

[0013] (3) In addition, in the wavelength conversion member of the application example of (1) or (2) above, the phosphor layer is characterized in that it has a bleeding region in the outer peripheral region and the length in the direction from the outer peripheral to the center is 120 μm or less.

[0014] In this way, by sufficiently reducing the width of the blurred region in the outer peripheral area, a uniform structure is achieved throughout the phosphor layer, making it easier to obtain uniform luminescence characteristics. Furthermore, the risk of delamination of the phosphor layer starting from the blurred voids can be reduced. In addition, by allowing a slight blurring in the outer peripheral area, the occurrence of pinholes in the central area can be sufficiently reduced.

[0015] (4) The light-emitting device of the application example is a light-emitting device comprising a light-emitting element that emits light of a specific range of wavelengths and a wavelength conversion member of any of the application examples (1) to (3) above.

[0016] In this way, by using a wavelength conversion member that reduces recesses on the outer periphery of the phosphor layer, pinholes in the central region, or blurring in the outer region, the light emission characteristics of the light emission device are improved, and the risk of peeling of the phosphor layer can be reduced even when a high-power light-emitting element is used.

[0017] (5) Furthermore, a method for manufacturing a wavelength conversion member in an application example of the present invention is characterized by comprising the steps of: preparing a substrate; adjusting the viscosity of a phosphor ink, which is a mixture of phosphor particles and an inorganic binder, at 25°C to 35.0 dPa·s or more and 75.0 dPa·s or less; applying the phosphor ink to the surface of the substrate; and forming a phosphor layer by heat-treating the applied phosphor ink at a temperature of 500°C or less.

[0018] In this way, by adjusting the viscosity of the phosphor ink to a predetermined range, recesses on the outer periphery of the phosphor layer, pinholes in the central region, or bleeding in the outer periphery region are reduced, improving the luminescence characteristics and enabling the manufacture of a wavelength conversion member with excellent adhesion between the substrate and the phosphor layer. [Effects of the Invention]

[0019] The wavelength conversion member and light-emitting device of the present invention exhibit excellent uniformity of luminescence characteristics and adhesion between the substrate and the phosphor layer. Furthermore, the method for manufacturing the wavelength conversion member of the present invention can produce a wavelength conversion member with excellent uniformity of luminescence characteristics and adhesion between the substrate and the phosphor layer. [Brief explanation of the drawing]

[0020] [Figure 1] This is a schematic cross-sectional view showing an example of the cross-sectional structure of a wavelength conversion member according to an embodiment of the present invention. [Figure 2]This is an image obtained by photographing the field of view of the upper surface of a wavelength conversion member according to an embodiment of the present invention with a digital microscope at 100 times magnification. [Figure 3] This is an image obtained by photographing the field of view of the upper surface of a wavelength conversion member outside the scope of the present invention with a digital microscope at 100 times magnification, and a partial enlarged image thereof. [Figure 4] This is an image obtained by photographing the field of view of the upper surface of a wavelength conversion member according to an embodiment of the present invention with a digital microscope at 100 times magnification. [Figure 5] (a) and (b) are schematic views showing modified examples of the upper surface of the wavelength conversion member 10 according to the present embodiment. [Figure 6] This is an image obtained by photographing the field of view of the upper surface of a wavelength conversion member according to an embodiment of the present invention with a digital microscope at 100 times magnification. [Figure 7] (a) and (b) are conceptual views showing a part of an example of a light-emitting device according to an embodiment of the present invention. [Figure 8] This is a flowchart showing an example of a method for manufacturing a wavelength conversion member according to an embodiment of the present invention. [Figure 9] (a) to (e) are images obtained by photographing the field of view of the upper surface of the wavelength conversion member of the wavelength conversion member of the examples and comparative examples with a digital microscope at 100 times magnification. [Embodiments for Carrying Out the Invention]

[0021] 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 duplicate descriptions are omitted. In the configuration diagrams, the sizes of the respective components are conceptually represented and do not necessarily represent actual dimensional ratios.

[0022] [Configuration of Wavelength Conversion Member] Figure 1 is a schematic cross-sectional view showing an example of the cross-sectional structure of the wavelength conversion member 10 according to this embodiment. In the wavelength conversion member 10 according to this embodiment, a phosphor layer 14 is formed on a substrate 12. The wavelength conversion member 10 transmits or reflects incident light irradiated from a light source, and generates light of different wavelengths when excited by the incident light. For example, by transmitting or reflecting blue incident light, and emitting green, red, and yellow converted light converted by the phosphor layer 14, it is possible to convert light into various colors by combining the converted light and the incident light, or by using only the converted light.

[0023] The shape of the substrate 12 can be any shape that is applicable to the light-emitting device 40, and may be various shapes such as circular, rectangular, elliptical, or polygonal.

[0024] The material of the substrate 12 is appropriately selected according to the intended use. When used for applications that transmit excitation light from a light-emitting element, inorganic materials such as sapphire or glass can be used. It is particularly preferable to use sapphire, which has high thermal conductivity, as this suppresses the deterioration of the properties of the phosphor particles 16 due to temperature rise by suppressing heat accumulation in the phosphor layer 14. When used for applications that reflect excitation light from a light-emitting element, aluminum, iron, copper, or ceramics can be used. It is particularly preferable to use aluminum, which has high thermal conductivity and high reflectivity across the entire visible light spectrum, as this suppresses the deterioration of the properties of the phosphor particles 16 due to temperature rise by suppressing heat accumulation in the phosphor layer 14. In addition, a reflective layer may be formed on the main surface 13, which is the surface of the substrate 12 on the phosphor layer 14 side, by plating or vapor deposition of a light-reflecting material such as silver, or an enhanced reflective film such as TiO2 may be formed.

[0025] The phosphor layer 14 is provided as a film on the main surface 13 of the substrate 12 and is formed of phosphor particles 16 and translucent ceramics 18. The translucent ceramics 18 bond the phosphor particles 16 to each other and also bond the phosphor particles 16 to the substrate 12. As a result, when irradiated with high-energy-density light, heat can be efficiently dissipated because it is bonded to the substrate 12, which functions as a heat dissipation material, and temperature quenching of the phosphor can be suppressed. The thickness of the phosphor layer 14 is preferably 15 μm or more and 300 μm or less, and more preferably 50 μm or more and 200 μm or less. The phosphor particles 16 constituting the phosphor layer 14 may be one type or two or more types. The phosphor layer 14 may contain voids 20.

[0026] In the field of view observed with a 100x digital microscope on the upper surface of the phosphor layer 14, there are no recesses 22 extending from the outer periphery 30 toward the center of the phosphor layer 14 with a length of 50 μm or more. This reduces the leakage of light from the light source from the outer periphery region 34. Furthermore, it is possible to suppress delamination of the phosphor layer 14, particularly from the outer periphery 30, especially from the recesses 22, due to thermal stress generated by heat accumulation in the phosphor layer 14 due to high-energy light from the light source. In this specification, a recess 22 is defined as a portion of the outer periphery region 34 of the phosphor layer 14 where the phosphor layer 14 is not formed, extending from the outer periphery 30 toward the center. It is more preferable that the length of such recesses 22 extending from the outer periphery 30 toward the center of the phosphor layer 14 is 20 μm or less, and the width in the direction perpendicular to the length is 20 μm or less.

[0027] The outer periphery 30 of the phosphor layer 14 refers to the outer edge portion of the phosphor layer 14 in the field of view when observing the upper surface of the phosphor layer 14. Figure 2 is an image of the field of view taken when observing the upper surface of the wavelength conversion member 10 according to an embodiment of the present invention with a 100x digital microscope. As shown in Figure 2, for example, if the phosphor layer 14 is approximately circular, the outer periphery 30 of the phosphor layer 14 refers to a virtual circumference (virtual circle) that encompasses the entire phosphor layer 14.

[0028] The direction towards the center of the phosphor layer 14 refers to the direction from the outer circumference 30 of the phosphor layer 14 toward the center of the phosphor layer 14. For example, if the phosphor layer is approximately circular, it refers to the direction from a point on the outer circumference 30 toward the center of the circle.

[0029] Figure 3 shows an image of the field of view captured by observing the upper surface of a wavelength conversion member outside the scope of the present invention with a 100x digital microscope, and a magnified portion thereof. Figure 3 shows that the wavelength conversion member has recesses 22 with a length of 50 μm or more extending from the outer periphery 30 of the phosphor layer 14 toward the center. For example, the length of the recess 22 indicated by the arrow in the magnified portion is 100 μm. It can also be seen that there are many pinholes 24.

[0030] Preferably, the phosphor layer 14 has a concentric similar shape with the same center as the phosphor layer 14 in the field of view observed with a 100x digital microscope on its upper surface, and there is one or fewer pinholes 24 in a region of 30% or less of the area of ​​the phosphor layer 14. This reduces the occurrence of color unevenness. It also reduces the risk of peeling of the phosphor layer 14 starting from the pinholes 24 in the central region 32. In this specification, a pinhole 24 is an exposed void on the surface of the phosphor layer 14, and is a space surrounded by the phosphor layer 14 in a plan view. For example, the area of ​​the pinhole 24 is 500 μm². 2 As described above, the pinhole 24 has a depth of 15 μm or more from the upper surface of the phosphor layer 14.

[0031] In the field of view observed with a 100x digital microscope on the upper surface of the phosphor layer 14, the central region 32 of the phosphor layer 14 is defined as a concentrically similar shape with the same center as the phosphor layer 14, and having an area of ​​30% or less of the area of ​​the phosphor layer 14. The region between the outer edge of the central region 32 and the outer periphery 30 is defined as the outer periphery region 34 of the phosphor layer 14. Figure 4 is an image of the field of view taken with a 100x digital microscope on the upper surface of the wavelength conversion member 10 according to an embodiment of the present invention. As shown in Figure 4, for example, if the phosphor layer 14 is approximately circular, the central region 32 of the phosphor layer 14 is a concentrically similar shape within a circle. The outer periphery region 34 of the phosphor layer 14 is an annular region.

[0032] In the case of a wavelength conversion member 10 using a transmissive substrate 12, the pinhole 24 can be confirmed from an image taken from the field of view observed with a 100x digital microscope on the upper surface of the phosphor layer 14, with a black plate or black paper placed under the substrate 12. Image processing may be performed at this time. In the case of a wavelength conversion member 10 using a reflective substrate 12, the pinhole 24 can be confirmed by image processing of an image taken from the field of view observed with a 100x digital microscope on the upper surface of the phosphor layer 14. In either case, when confirming by image processing, a binarization threshold is determined so that voids exposed on the surface of the phosphor layer 14 that have a depth of 15 μm or more from the surface can be distinguished.

[0033] Unlike other parts, the pinholes 24 are areas with a low distribution of phosphor particles, resulting in uneven light emission characteristics and causing color unevenness. Furthermore, thermal stress generated by heat accumulation in the phosphor layer 14 due to high-energy light sources may cause delamination of the phosphor layer 14 starting from the pinholes 24. Therefore, it is preferable to suppress such pinholes 24. In particular, the central region 32 of the wavelength conversion member 10 is an area that is always used in the light-emitting device, so it is important to reduce the risk of color unevenness and delamination in the central region 32.

[0034] Figures 5(a) and 5(b) are schematic diagrams showing modified examples of the upper surface of the wavelength conversion member 10 according to this embodiment. Figure 5(a) shows the outer periphery 30, central region 32, and outer periphery region 34 of the phosphor layer 14 when the phosphor layer 14 is rectangular. When the phosphor layer 14 is rectangular, the direction toward the center of the phosphor layer 14 refers to the direction from a point on the outer periphery 30 toward each side perpendicular to the direction toward each side.

[0035] Figure 5(b) shows the outer periphery 30, central region 32, and outer peripheral region 34 of the phosphor layer 14 when the phosphor layer 14 is annular. As shown in Figure 5(b), when the phosphor layer 14 is annular, the outer periphery 30 and outer peripheral region 34 of the phosphor layer 14 are separated into inner and outer parts. In the case of such a band-shaped phosphor layer 14, it is preferable that the widths of the two outer peripheral regions 34 are equal. When the phosphor layer 14 is annular, the direction toward the center of the phosphor layer 14 refers to the direction toward the point at the shortest distance from a point on the outer periphery 30 to the center line of the phosphor layer 14.

[0036] The phosphor layer 14 has a blurred region 26 in its outer peripheral region 34, and the length in the direction from the outer peripheral 30 toward the center (width of the blurred region 26) is preferably 120 μm or less, and more preferably 80 μm or less. This results in a uniform structure throughout the phosphor layer 14, making it easier to obtain uniform luminescence characteristics. In addition, the risk of peeling of the phosphor layer 14 starting from the voids in the blurred region 26 can be reduced. If the length of the blurred region 26 in the direction from the outer peripheral 30 toward the center differs in different parts, the maximum value is used as the width of the blurred region 26.

[0037] Figure 6 is an image of the field of view captured by observing the upper surface of the wavelength conversion member 10 according to an embodiment of the present invention with a 100x digital microscope. As shown in Figure 6, for example, if the phosphor layer 14 is approximately circular, the blurring region 26 of the phosphor layer 14 becomes an annular region.

[0038] When the phosphor layer 14 has a bleeding region 26 in its outer peripheral region 34, it is preferable that the length in the direction from the outer peripheral region 30 toward the center is 50 μm or more. By adjusting the viscosity of the phosphor ink, etc., so that a bleeding region 26 of this magnitude is created, the occurrence of recesses 22 in the outer peripheral region 34 and pinholes 24 in the central region 32 can be sufficiently reduced. The bleeding region 26 is located in the outer peripheral region 34 of the phosphor layer 14 and is a region with more voids 20 than the central part of the phosphor layer 14. In this specification, the bleeding region 26 is a region located in the outer peripheral region 34 that includes a portion in which the film thickness is 70% or less of the average film thickness of the central region of the phosphor layer 14.

[0039] In the blurred region 26, the difference in the probability of the presence of phosphor particles 16 in the optical path becomes large, that is, the structure is not uniform, so it is preferable to make it as small as possible in order to obtain uniform luminescence characteristics. On the other hand, if too much focus is placed on making the blurred region 26 small, the number of recesses 22 extending from the outer periphery 30 towards the center and the number of pinholes 24 in the central region 32 will increase. In the outer periphery region 34, recesses 22 where phosphor particles 16 and translucent ceramics 18 do not exist are more undesirable than blurred region 26 where phosphor particles 16 and translucent ceramics 18 exist. Furthermore, since the central region 32 of the phosphor layer 14 is always used in the light-emitting device, reducing the risk of color unevenness and peeling in the central region 32 is more important than making the blurred region 26 small. Therefore, pinholes 24 in the central region 32 are more undesirable than blurred region 26 in the outer periphery region 34. The wavelength conversion member 10 of the present invention can sufficiently reduce the occurrence of recesses 22 in the outer peripheral region 34 and pinholes 24 in the central region 32 by allowing a slight blurring region 26 in the outer peripheral region 34.

[0040] It is preferable that the phosphor layer 14 does not have mesh marks. If there are mesh marks on the phosphor layer 14, cracks and pinholes 24 may occur due to localized changes in film thickness. Mesh marks refer to the grid-like pattern of a mesh remaining on the surface of the phosphor layer 14 when a high-viscosity phosphor ink is used during screen printing. Mesh marks can be confirmed by shining light on the phosphor layer 14.

[0041] The phosphor particles 16 can be, for example, yttrium-aluminum-garnet phosphors (YAG phosphors) and lutetium-aluminum-garnet phosphors (LAG phosphors). In addition, the phosphor particles 16 can be selected from the following materials depending on the design of the color to be emitted. For example, BaMgAl 10 O 17 Blue phosphors such as :Eu, ZnS:Ag,Cl, BaAl2S4:Eu or CaMgSi2O6:Eu, Zn2SiO4:Mn, (Y,Gd)BO3:Tb, ZnS:Cu,Al, (M1)2SiO4:Eu, (M1)(M2)2S:Eu, (M3)3Al5O 12 Examples of phosphors include yellow or green phosphors such as Ce, SiAlON:Eu, CaSiAlON:Eu, (M1)Si2O2N:Eu, or (Ba,Sr,Mg)2SiO4:Eu,Mn; yellow, orange, or red phosphors such as (M1)3SiO5:Eu or (M1)S:Eu; and red phosphors such as (Y,Gd)BO3:Eu,Y2O2S:Eu, (M1)2Si5N8:Eu, (M1)AlSiN3:Eu, or YPVO4:Eu. In the above chemical formulas, M1 includes at least one from the group consisting of Ba, Ca, Sr, and Mg; M2 includes at least one from Ga and Al; and M3 includes at least one from the group consisting of Y, Gd, Lu, and Te. The above phosphor particles 16 are just examples, and the phosphor particles 16 used in the wavelength conversion member 10 are not necessarily limited to those described above.

[0042] The average particle diameter of the phosphor particles 16 is preferably 5 μm or more and 50 μm or less, and more preferably 7 μm or more and 30 μm or less. When it is 5 μm or more, the emission intensity of the converted light increases, and consequently the emission intensity of the wavelength conversion member 10 increases. When it is 50 μm or less, the thickness of the phosphor layer 14 can be easily adjusted, and the risk of degranulation of the phosphor particles 16 can be reduced. In addition, the temperature of individual phosphor particles 16 can be kept low, and thermal quenching can be suppressed. In this specification, the average particle diameter is the median diameter (D50). The average particle diameter can be measured using dry or wet measurement with a laser diffraction / scattering particle size distribution analyzer.

[0043] Translucent ceramics 18 are formed by the hydrolysis or oxidation of an inorganic binder and are composed of translucent inorganic materials. Translucent ceramics 18 are composed of, for example, silica (SiO2) and aluminum phosphate. Furthermore, because translucent ceramics 18 are translucent, they can transmit light from a light source (incident light) or converted light. Since translucent ceramics 18 are made of inorganic materials, their heat resistance is improved, and deterioration is less likely to occur even when irradiated with high-energy light such as LDs.

[0044] Examples of inorganic binders that can be used include ethyl silicate and aqueous aluminum phosphate solutions.

[0045] Furthermore, a translucent material is defined as a material that, when light in the visible light wavelength range (λ=380~780nm) is incident perpendicularly on a 0.5mm thick object, has the characteristic that the radiant flux of light that exits from the opposite side exceeds 80% of the incident light.

[0046] [Configuration of the light-emitting device] Figures 7(a) and 7(b) are conceptual diagrams showing a part of an example of a light-emitting device according to an embodiment of the present invention. Figure 7(a) is a schematic diagram showing a transmissive light-emitting device of the present invention, and Figure 7(b) is a schematic diagram showing a reflective light-emitting device. The light-emitting device 40 comprises a light source 50 and a wavelength conversion member 10. The light source 50 is a light-emitting element that generates light source light of a specific range of wavelengths, and can be an LED or an LD, for example. The wavelength conversion member 10 can efficiently convert wavelengths even at high power, so it is preferable that the light source 50 is an LD.

[0047] [Manufacturing method for wavelength conversion components] An example of a method for manufacturing a wavelength conversion member will be described. Figure 8 is a flowchart showing an example of a method for manufacturing a wavelength conversion member according to an embodiment of the present invention. First, a base material 12 is prepared by processing raw materials and forming it into a predetermined shape (step S1).

[0048] Apart from the preparation of the substrate 12, a phosphor ink (phosphor paste) is prepared by mixing phosphor particles 16 with an inorganic binder (step S2). To prepare the phosphor ink, first, phosphor particles 16 having a predetermined average particle size are prepared. Depending on the design of the wavelength conversion member 10, various types of phosphor particles 16 can be used, and one type or two or more types may be used.

[0049] Next, the prepared phosphor particles 16 are weighed, dispersed in a solvent, and mixed with an inorganic binder to produce a phosphor ink for printing. At this time, the addition ratio of solvent and inorganic binder is adjusted to 15-45% in order to make the viscosity of the phosphor ink 35.0 dPa·s to 75.0 dPa·s. A ball mill or propeller agitator can be used for mixing. The mixing time is adjusted to 80-160 minutes. During mixing, in order to suppress viscosity variations due to temperature changes, the room temperature is adjusted to 20°C-25°C and the liquid temperature to 25°C-40°C. High-boiling point solvents such as α-terpineol, butanol, isophorone, and glycerin can be used as solvents.

[0050] Inorganic fine particles may be added to the phosphorescent ink to improve the hardness of the phosphor layer and to adjust its luminescence (light scattering) and other properties. Inorganic fine particles may also be added to adjust the viscosity of the phosphorescent ink.

[0051] If the viscosity of the phosphor ink is less than 35.0 dPa·s, bleeding is likely to occur at the edges (outer periphery) of the phosphor layer due to the flow of the phosphor ink. When bleeding occurs, there is a risk of deterioration in the distribution of phosphor particles and a decrease in luminescence properties due to localized thinning of the film thickness.

[0052] If the viscosity of the phosphor ink exceeds 75.0 dPs, and the application method is screen printing, mesh marks may remain on the phosphor layer, potentially causing cracking and peeling of the phosphor layer. Furthermore, poor fluidity of the phosphor ink increases the risk of voids (pinholes), resulting in uneven luminescence and color inconsistencies.

[0053] Next, a phosphorescent ink is applied to the surface of the substrate 12 prepared in the substrate preparation step (step S1) to form an ink layer (paste layer) (step S3). The phosphorescent ink can be applied using screen printing, spraying, dispensing, or inkjet methods. Screen printing is preferred because it allows for the stable formation of an ink layer with uniform thickness. The thickness of the ink layer is adjusted to a predetermined thickness after firing. It is preferable that the ink layer is formed along the shape of the substrate 12.

[0054] Then, the applied phosphor ink is heat-treated at a temperature of 150°C or higher to form a phosphor layer (Step S4). The heat treatment temperature is preferably 150°C to 500°C, and particularly preferably 300°C to 400°C. The heat treatment time is preferably set with a holding time of 20 minutes or more, and preferably 0.5 hours to 2.0 hours. The heating rate is preferably 2°C / min or higher, and more preferably 2°C / min to 10°C / min. A drying step may also be provided before the heat treatment. The drying temperature is preferably 100°C to 200°C (below the heat treatment temperature of the phosphor layer), and the drying time is more preferably 20 minutes to 60 minutes.

[0055] In this way, by adjusting the viscosity of the phosphor ink to a predetermined range and printing and heat-treating it on the substrate, defects such as depressions, pinholes, mesh marks, and bleeding areas can be suppressed, and wavelength conversion components with excellent distribution of phosphor particles and uniformity of film thickness can be manufactured. This improves the uniformity of the luminescence characteristics and the good adhesion between the substrate and the phosphor layer.

[0056] [Examples and Comparative Examples] (Fabrication of wavelength conversion components) (Example 1) A disc-shaped sapphire substrate with a diameter of φ50 mm and a thickness of t0.5 mm was prepared as the base material.

[0057] As a phosphor ink, a green phosphor (LAG-type phosphor) with an average particle size of 15 μm and a red phosphor (S-CASN-type phosphor) with an average particle size of 9 μm were weighed in a predetermined mass ratio. Ethyl silicate was weighed as an inorganic binder and α-terpineol as a solvent. The phosphor ink was prepared by mixing each of these components for 120 minutes using propeller stirring while maintaining the liquid temperature at 25°C to 40°C. At this time, the inorganic binder was added in a ratio such that the viscosity of the phosphor ink was 35 dPa·s.

[0058] The obtained phosphor ink was applied to a substrate by screen printing, and after drying the substrate at 100°C for 30 minutes, the wavelength conversion component was fabricated by heat treatment in an electric furnace in a non-oxidizing atmosphere at 150°C / h to 350°C for 20 minutes or more.

[0059] (Example 2) A wavelength conversion component was fabricated under the same conditions as in Example 1, except that the inorganic binder was added in a ratio such that the viscosity of the phosphor ink was 55 dPa·s.

[0060] (Example 3) A wavelength conversion component was fabricated under the same conditions as in Example 1, except that the inorganic binder was added in a ratio such that the viscosity of the phosphor ink was 75 dPa·s.

[0061] (Example 4) A wavelength conversion component was fabricated under the same conditions as in Example 1, except that the inorganic binder was added in a ratio such that the viscosity of the phosphor ink was 22 dPa·s.

[0062] (Example 5) A wavelength conversion component was fabricated under the same conditions as in Example 1, except that the inorganic binder was added in a ratio such that the viscosity of the phosphor ink was 4 dPa·s.

[0063] (Comparative Example 1) A wavelength conversion component was fabricated under the same conditions as in Example 1, except that the inorganic binder was added in a ratio such that the viscosity of the phosphor ink was 83 dPa·s.

[0064] (Comparative Example 2) A wavelength conversion component was fabricated under the same conditions as in Example 1, except that the inorganic binder was added in a ratio such that the viscosity of the phosphor ink was 108 dPa·s.

[0065] (Evaluation method) (A recess extending towards the center) Using a digital microscope (VHX-5000: Keyence Corporation), images of the top surface of the phosphor layer were taken at 100x magnification. A virtual circle (outer circumference) encompassing the entire phosphor layer was drawn, and the maximum distance of the concave section, which extends from the virtual circle toward the center of the phosphor layer, was identified.

[0066] (Number of pinholes) A black paper was placed under the substrate, and the image was examined using a digital microscope (VHX-5000: Keyence Corporation). For images of the top surface of the phosphor layer taken at 100x magnification, a threshold was set to distinguish voids exposed on the surface of the phosphor layer with a depth of 15 μm or more from the surface, and binarized image analysis was performed. For a virtual circle with radius r, a circle with radius 0.55r was drawn at the same center, and the area inside this circle was 500 μm². 2 The above-mentioned gaps were counted as the number of pinholes.

[0067] (Width of the bleeding area) A black sheet of paper was placed under the substrate, and the results were examined using a digital microscope (VHX-5000: Keyence Corporation). First, the average film thickness in the central region of the phosphor layer was determined. Next, for an image of the top view of the phosphor layer taken at 100x magnification, a threshold was set so that the portion where the thickness of the phosphor layer was 70% or less of the average film thickness in the central region was distinguished, and binarization image analysis was performed. Then, a circle was drawn that included all the portions where the thickness of the phosphor layer in the outer region was 70% or less of the average film thickness in the central region, and the difference from the outer edge was defined as the width of the blurred region.

[0068] (Viscosity of phosphorescent ink) The viscosity of the phosphor ink during manufacturing was measured using a viscometer (Visco Tester VT-04F). Measurements were taken while controlling the room temperature between 20°C and 25°C and the liquid temperature between 25°C and 40°C.

[0069] [Table 1]

[0070] Table 1 shows the viscosity and evaluation results of the phosphor inks used in the wavelength conversion members of the examples and comparative examples. Figures 9(a) to 9(e) are images of the top surface of the wavelength conversion members of the examples and comparative examples, respectively, taken with a 100x digital microscope. Figures 9(a) and 9(b) are images of the wavelength conversion members of Comparative Examples 2 and 1, respectively. Figures 9(c) to 9(e) are images of the wavelength conversion members of Examples 2, 4, and 5, respectively.

[0071] As shown in Table 1, the wavelength conversion members of Examples 1 to 5 had recesses extending towards the center controlled to a length of 50 μm or less, demonstrating that it is possible to manufacture wavelength conversion members with small recesses. In Examples 4 and 5, it was difficult to distinguish between individual recesses, but their lengths were all short. Although these are reference values, none of the recesses in Example 4 exceeded 20 μm, and none in Example 5 exceeded 40 μm.

[0072] The wavelength conversion members of Examples 1 to 3 were found to have a controlled length of recesses extending toward the center of 50 μm or less, one or fewer pinholes, and a width of the blurring region on the outer periphery of 120 μm or less, demonstrating the feasibility of manufacturing wavelength conversion members with excellent film uniformity.

[0073] On the other hand, in Examples 4 and 5, where the viscosity of the phosphor ink was relatively low, there were no long depressions, but bleeding occurred at the edges of the phosphor layer due to the flow of the phosphor ink, and the width of the bleeding area was wide. Pinholes were not observed in the central region of the phosphor layer.

[0074] Furthermore, in Comparative Examples 1 and 2, where the viscosity of the phosphor ink was higher, the poor fluidity of the phosphor ink resulted in the screen printing pattern (mesh) remaining as a trace on the phosphor layer throughout the entire phosphor layer. In addition, pinholes occurred not only in the central area but across the entire surface.

[0075] (Color unevenness confirmation test) A color uniformity check test was conducted for each wavelength conversion component. A blue LD with a wavelength of 450 nm was irradiated as a light source at an output of 0.5 W in the central and outer regions of the phosphor layer, and the chromaticity was measured at 4 points in both the central and outer regions (8 points in total) using a spectroradiometer. The ratio of the difference between the average values ​​of the central and outer regions to the overall average value (8 points) was then checked. In addition, the ratio of the difference between the maximum and minimum values ​​of the chromaticity in the central region to the overall average value (4 points) was checked. The same check was performed for the outer region.

[0076] In Examples 1-3, the difference in chromaticity between the central and peripheral regions was less than 5%. Furthermore, the difference in chromaticity between the central and peripheral regions themselves was also less than 5%. In other words, Examples 1-3 demonstrated uniform luminescence characteristics across the central, peripheral, and peripheral regions. In Examples 4 and 5, which had lower viscosity, the difference in chromaticity between the central and peripheral regions, and the difference in chromaticity within the peripheral region, was 5% or more, indicating uniform chromaticity. On the other hand, the difference in chromaticity within the central region was less than 5%. In other words, the central region demonstrated uniform luminescence characteristics. This is presumed to be due to the wide width of the blurred region of the phosphor layer, resulting in different light conversion characteristics due to the difference in porosity between the central and peripheral regions.

[0077] In comparative examples 1 and 2, which had high viscosity, the difference in chromaticity between the central and peripheral regions, the difference in chromaticity within the central region, and the difference in chromaticity within the peripheral region were all 5% or more. In other words, color unevenness was observed throughout. This is presumed to be because light from the light source escaped through depressions and pinholes in the phosphor layer, resulting in areas with a strong bluish tint.

[0078] In Examples 4 and 5, color unevenness occurred in the outer region of the phosphor layer, which is thought to be caused by bleeding regions. In Comparative Examples 1 and 2, color unevenness occurred, which is thought to be caused by pinholes or depressions. Since the central region of the wavelength conversion member is always used in the light-emitting device, it is considered important that no pinholes occur in the central region. Ideally, it would be best if neither pinholes nor bleeding regions occur, but it is thought that allowing a small amount of bleeding regions can sufficiently reduce the occurrence of pinholes in the central region of the phosphor layer.

[0079] Therefore, it was found that the wavelength conversion members of Examples 4 and 5 can be used in light-emitting devices that primarily utilize light passing through the phosphor layer in the central region, thereby suppressing the occurrence of color unevenness and other issues. On the other hand, it was found that the wavelength conversion members of Examples 4 and 5 are not suitable for use in light-emitting devices that utilize light passing through the phosphor layer in the region closer to the outer edge. Based on these findings, it was found that the viscosity of the phosphor ink during manufacturing is preferably between 35.0 dPa·s and 75.0 dPa·s.

[0080] Based on the above results, it has been confirmed that the wavelength conversion member of the present invention has small recesses extending from the outer periphery of the phosphor layer toward the center, and fewer pinholes in the central region. As a result, color unevenness due to excessive local excitation light emission can be suppressed, mesh marks on the surface of the phosphor layer can be eliminated, cracks and pinholes due to local changes in film thickness can be suppressed, adhesion between the substrate and the phosphor layer can be improved, and peel resistance can be improved.

[0081] Furthermore, the manufacturing method for the wavelength conversion member of the present invention, by setting the viscosity of the phosphor ink within an appropriate range, suppresses the recesses extending from the outer periphery of the phosphor layer toward the center and the bleeding in the outer region, and it has been confirmed that it is possible to manufacture a wavelength conversion member with fewer pinholes in the region near the center. In addition, the controllability of the film thickness is improved and it becomes easier to apply the film to the desired thickness, thus stabilizing the quality of the wavelength conversion member.

[0082] The present invention is not limited to the embodiments described above, and it goes without saying that it extends to various modifications and equivalents that fall within the spirit and scope of the present invention. Furthermore, the structure, shape, number, position, size, etc., of the components shown in each drawing are for illustrative purposes only and may be modified as appropriate. [Explanation of Symbols]

[0083] 10 Wavelength conversion member 12 Base material 13 Main surface 14 Phosphor layer 16 Phosphor particles 18 Translucent Ceramics 20 void 22 recess 24 pinholes 26. Area of ​​bleeding 30 Outer circumference 32 Central area 34 Outer area 40 Light-emitting devices 50 light source

Claims

1. A wavelength conversion member, Substrate and The substrate is provided with a phosphor layer formed of phosphor particles and translucent ceramics that bond the phosphor particles to each other and to the substrate and to the phosphor particles, The phosphor layer, in the field of view observed with a 100x digital microscope on its upper surface, does not have any recesses of 50 μm or more in length extending from the outer periphery of the phosphor layer toward the center. The wavelength conversion member is characterized in that the phosphor layer has a blurred region in its outer peripheral region, and the length in the direction from the outer peripheral region toward the center is 50 μm or more and 120 μm or less.

2. The wavelength conversion member according to claim 1, characterized in that the phosphor layer has a concentric similar shape with the same center as the phosphor layer in the field of view, and has one or fewer pinholes in a region of 30% or less of the area of ​​the phosphor layer.

3. A light-emitting device, A light-emitting element that emits light within a specific range of wavelengths, A light-emitting device comprising a wavelength conversion member according to claim 1 or claim 2.

4. A method for manufacturing a wavelength conversion member, The process of preparing the base material, A process for adjusting the viscosity of a phosphor ink, which is a mixture of phosphor particles and an inorganic binder, at 25°C to 35.0 dPa·s or more and 75.0 dPa·s or less, A step of applying the phosphor ink to the surface of the substrate such that the length of the bleeding region at the edge of the phosphor layer, in the direction from the outer periphery to the center, is 50 μm or more and 120 μm or less. A method for manufacturing a wavelength conversion member, characterized by comprising the step of forming the phosphor layer by heat-treating the coated phosphor ink at a temperature of 500°C or less.

Images