JP7626948B2 - Wavelength conversion member and method for producing same, light emitting device, and projector - Google Patents

Description

This disclosure relates to a wavelength conversion member and a manufacturing method thereof, a light emitting device, and a projector.

In image projection devices (projectors) that display color images by projecting light emitted from a light-emitting device onto a screen using a micromirror display element or the like, there is a demand for light-emitting devices with higher output. For example, Patent Document 1 proposes a light-emitting device equipped with a wavelength conversion element that has a higher conversion efficiency from excitation light to fluorescent light.

International Publication No. 2018/198949

One aspect of the present disclosure aims to provide a wavelength conversion member capable of forming a light emitting device with higher light emission efficiency, a manufacturing method thereof, a light emitting device, and a projector.

The first aspect is a wavelength conversion member comprising a substrate and a wavelength conversion layer disposed on the substrate and containing a binder and a phosphor. The wavelength conversion layer has a volume ratio of the phosphor to the binder of 0.75 to 1.45, and an average thickness of 55 μm to 146 μm.

The second aspect is a wavelength conversion member comprising a substrate and a wavelength conversion layer disposed on the substrate and containing a binder and a phosphor. In the wavelength conversion layer, in a cross section perpendicular to the surface on which the wavelength conversion layer is disposed on the substrate, the ratio of the sum of the particle cross-sectional areas of the phosphor particles to the cross-sectional area of the wavelength conversion layer is 56% or more and 70% or less, and the average thickness is 55 μm or more and 146 μm or less.

The third aspect is a light emitting device including the wavelength conversion member of the first or second aspect, a motor that rotates the wavelength conversion member, and a light source that irradiates the wavelength conversion member with light. The fourth aspect is a projector including the light emitting device of the third aspect, an image display system, and a projection optical system.

The fifth aspect is a method for producing a wavelength conversion member, comprising: applying a phosphor composition containing a binder, a solvent, and a phosphor, the boiling point of the solvent being 200°C or more and 300°C or less, the mass ratio of the solvent to the binder being 0.01 or more and 0.4 or less, and the mass ratio of the phosphor to the binder being 3.15 or more and 6.05 or less, to a substrate; and heat-treating the phosphor composition applied to the substrate to form a wavelength conversion layer.

According to one aspect of the present disclosure, it is possible to provide a wavelength conversion member capable of forming a light emitting device with higher light emission efficiency, a manufacturing method thereof, a light emitting device, and a projector.

FIG. 1 is a schematic diagram showing an example of the configuration of a light emitting device. FIG. 1 is a schematic diagram illustrating an example of the configuration of a projector. FIG. 1A is a schematic cross-sectional view showing an example of the configuration of a wavelength conversion member, FIG. 1B is a schematic perspective view showing an example of the configuration of a wavelength conversion member, and FIG. 1C is a schematic plan view showing an example of the configuration of a wavelength conversion member.

In this specification, the term "process" includes not only an independent process, but also a process that cannot be clearly distinguished from other processes, as long as the intended purpose of the process is achieved. In addition, the content of each component in the composition means the total amount of the multiple substances present in the composition, unless otherwise specified, when multiple substances corresponding to each component are present in the composition. Furthermore, the upper and lower limits of the numerical ranges described in this specification can be arbitrarily selected and combined from the numerical values exemplified as numerical ranges. In this specification, in the formulas representing the composition of phosphors or luminescent materials, multiple elements separated by commas (,) mean that at least one of these multiple elements is contained in the composition. In addition, in the formulas representing the composition of phosphors, the part before the colon (:) represents the host crystal, and the part after the colon (:) represents the activator element. In this specification, the relationship between color names and chromaticity coordinates, the relationship between the wavelength range of light and the color name of monochromatic light, etc., follow JIS Z8110. The half-width of a phosphor refers to the wavelength width (full width at half maximum; FWHM) of the emission spectrum of the phosphor where the emission intensity is 50% of the maximum emission intensity. Hereinafter, embodiments of the present invention will be described in detail. However, the embodiments shown below are examples of wavelength conversion members and their manufacturing methods, light-emitting devices, and projectors for embodying the technical ideas of the present invention, and the present invention is not limited to the wavelength conversion members and their manufacturing methods, light-emitting devices, and projectors shown below.

A wavelength conversion member according to a first aspect of the present invention includes a substrate and a wavelength conversion layer disposed on the substrate, the wavelength conversion layer including a binder and a phosphor. The volume ratio of the phosphor to the binder in the wavelength conversion layer is 0.75 to 1.45, and the average thickness is 55 μm to 146 μm.

The luminous efficiency of a light emitting device consisting of a light source, a wavelength conversion member, and an optical system including, for example, a lens and a reflector, is evaluated by the total efficiency, which is the product of the fluorescent efficiency in the wavelength conversion member and the light collection efficiency in the optical system. In other words, the total efficiency of a light emitting device means the luminous efficiency of the light emitting device as a whole. The fluorescent efficiency corresponds to the wavelength conversion efficiency of the wavelength conversion member, and is evaluated as the ratio of the intensity of the light emitted from the wavelength conversion layer to the intensity of the light incident from the light source. The light collection efficiency corresponds to the efficiency with which the light emitted from the wavelength conversion member is taken into the optical system, and is evaluated as the ratio of the intensity of the light output from the optical system to the intensity of the light emitted from the wavelength conversion layer.

A wavelength conversion member in which a wavelength conversion layer having a volume ratio of phosphor to binder contained in the wavelength conversion layer of 0.75 to 1.45 and an average thickness of 55 μm to 146 μm is disposed on a substrate can achieve higher fluorescence efficiency when combined with a light source to form a light emitting device. This can be considered, for example, as follows. Since the volume ratio of phosphor contained in the wavelength conversion layer is high, the fluorescence efficiency in the wavelength conversion layer is high, and the spread of light extracted from the wavelength conversion layer is suppressed, resulting in high light collection efficiency, and improving the total efficiency of the light emitting device. Furthermore, since the thickness of the wavelength conversion layer is within a specified range, the spread of light is suppressed and the light collection efficiency is high, the heat dissipation of the wavelength conversion layer is improved, and the rise in surface temperature is suppressed, resulting in high fluorescence efficiency. It is believed that the high fluorescence efficiency and light collection efficiency in this way improve the total efficiency of the light emitting device.

The wavelength conversion member of the second embodiment comprises a substrate and a wavelength conversion layer disposed on the substrate and containing a binder and a phosphor. In the cross section of the wavelength conversion layer perpendicular to the surface on which the wavelength conversion layer is disposed on the substrate, the ratio of the sum of the cross-sectional areas of the phosphor particles to the cross-sectional area of the wavelength conversion layer is 56% or more and 70% or less, and the average thickness is 55 μm or more and 146 μm or less.

A wavelength conversion member in which a wavelength conversion layer having an average thickness of 55 μm or more and 146 μm or less and a ratio of the total particle cross-sectional area of the phosphor to the cross-sectional area of the wavelength conversion layer in the cross section of the wavelength conversion layer is arranged on a substrate can achieve higher fluorescence efficiency when combined with a light source to form a light emitting device. This can be considered, for example, as follows. Since the volume ratio of the phosphor contained in the wavelength conversion layer is high, the fluorescence efficiency in the wavelength conversion layer is high, and the spread of the light extracted from the wavelength conversion layer is suppressed, resulting in high light collection efficiency, and the total efficiency of the light emitting device is improved. Furthermore, since the thickness of the wavelength conversion layer is within a predetermined range, the spread of light is suppressed and the light collection efficiency is high, the heat dissipation of the wavelength conversion layer is improved, and the rise in surface temperature is suppressed, resulting in high fluorescence efficiency. It is believed that the total efficiency of the light emitting device is improved by increasing the fluorescence efficiency and light collection efficiency in this way.

Here, the evaluation method of the fluorescence efficiency and the light collection efficiency will be described with reference to the drawings. FIG. 1 is a schematic diagram showing an example of a light emitting device. The light emitting device 200 includes a light source 210, a lens 222 that focuses the light from the light source 210 on a wavelength conversion member 250, and a dichroic mirror 224 that reflects the output light from the wavelength conversion member 250 and directs the direction of the output light toward the lens system 230. The wavelength conversion member 250 includes a disk-shaped substrate 252 and a wavelength conversion layer 254 containing a phosphor and a binder. The wavelength conversion layer 254 is arranged, for example, in an annular shape along the circumference of the substrate 252. The fluorescence efficiency of the light emitting device 200 is calculated by dividing the fluorescence output measured by the power meter at position B by the excitation output measured by the power meter at position A. The light collection efficiency is calculated by dividing the emission output measured by the power meter at position C by the fluorescence output measured by the power meter at position B. The total efficiency of the light emitting device 200 is calculated as the product of the fluorescence efficiency and the light collection efficiency, and corresponds to the value obtained by dividing the emission power by the excitation power. In addition, in evaluating the fluorescence efficiency, the surface temperature of the wavelength conversion layer 254 may be measured by infrared thermography to confirm that the rise in surface temperature is suppressed.

The wavelength conversion member includes a substrate and a wavelength conversion layer disposed on the substrate. An example of the configuration of the wavelength conversion member will now be described with reference to the drawings. FIG. 3(a) is a schematic cross-sectional view showing an example of the configuration of the wavelength conversion member, FIG. 3(b) is a schematic perspective view showing an example of the configuration of the wavelength conversion member, and FIG. 3(c) is a schematic plan view showing an example of the configuration of the wavelength conversion member. The wavelength conversion member 10 has a phosphor layer 14 formed on a substrate 12. In FIG. 3, the substrate 12 has a disk-like shape. The phosphor layer 14 is arranged in an annular shape along the circumference of the substrate 12. The wavelength conversion member 10 absorbs excitation light irradiated from a light source, generates converted light having a different wavelength from the excitation light, and emits the converted light. The wavelength conversion member 10 may, for example, absorb blue light from a light source, emit converted light having a different wavelength from the blue light converted by the phosphor layer 14, and reflect the blue light to emit a mixed color light of the converted light and the blue light, or may emit only the converted light. Wavelength conversion materials can convert the excitation light from a light source into light of various colors.

The substrate constituting the wavelength conversion member is not limited to a disk shape, and may have a shape such as a polygonal plate. The thickness of the substrate may be, for example, 0.1 mm or more and 1 mm or less, and preferably 0.4 mm or more or 0.6 mm or less.

The substrate may be a metal member containing a metal material such as aluminum, iron, copper, silver, nickel, or stainless steel. When the substrate is a metal member containing a metal material, the light incident on the wavelength conversion member can be wavelength converted by the wavelength conversion layer and reflected to the same side as the incident surface. Furthermore, the heat dissipation from the phosphor is improved, so the fluorescent efficiency of the wavelength conversion member can be increased.

The substrate may be a light-transmitting member that contains a light-transmitting material such as glass or aluminum oxide. By using a light-transmitting member as the substrate, the light incident on the wavelength conversion member can be wavelength-converted by the wavelength conversion layer and emitted to the opposite side of the incident surface. At least one of the main surface of the light-transmitting member on which the wavelength conversion layer is formed or the other main surface facing the main surface may be roughened in advance, for example, by etching or laser processing. This can suppress uneven light emission on the light-emitting surface of the wavelength conversion member.

At least a part of the surface of the substrate may be a reflective surface. The reflective surface may be formed at least in the region where the wavelength conversion layer is disposed. The reflective surface may be formed from a material containing at least one selected from the group consisting of silver and aluminum. The reflective surface of the substrate may be formed from the material of the substrate itself. That is, the substrate itself may be formed from a material containing at least one selected from the group consisting of silver and aluminum, and at least a part of the surface may be a reflective surface. Alternatively, the reflective surface may be formed by the surface of a reflective layer disposed on the substrate. Examples of materials for forming the reflective layer include silver, aluminum, alloys containing at least one selected from the group consisting of silver and aluminum, and resins containing metal oxides such as titanium oxide. The regular reflectance of the reflective surface may be, for example, 80% or more, and preferably 85% or more, or 90% or more. The upper limit of the regular reflectance may be, for example, 100% or less. When the regular reflectance of the reflective surface is 80% or more, there is a tendency that the amount of light extracted can be increased. The regular reflectance of the reflective surface of the substrate is measured using light with a wavelength of 450 nm.

The wavelength conversion layer disposed on the substrate may include a binder and a phosphor. The binder constituting the wavelength conversion layer may be an organic binder or an inorganic binder. The organic binder may include a cured resin, preferably a cured translucent resin. Examples of the resin include thermosetting resins such as epoxy resin, silicone resin, epoxy-modified silicone resin, and modified silicone resin. When the resin includes a silicone resin, the resin tends to have better heat resistance, light resistance, and the like. The silicone resin or modified silicone resin may include at least one selected from the group consisting of phenyl silicone resin, modified phenyl silicone resin, dialkyl silicone resin, and modified dialkyl silicone resin. Examples of the inorganic binder include glass, ceramics, and aluminum oxide.

The content of the binder in the wavelength conversion layer may be, for example, 10% by mass or more and 25% by mass or less, preferably 12% by mass or more or 14% by mass or more, and preferably less than 25% by mass, 23% by mass or less, or 20% by mass or less, relative to the total mass of the wavelength conversion layer.

The phosphor constituting the wavelength conversion layer may include, for example, at least one type of rare earth aluminate phosphor. The rare earth aluminate phosphor may have a composition including at least one first element selected from the group consisting of yttrium, lanthanum, lutetium, gadolinium, and terbium, at least one second element selected from the group consisting of aluminum, gallium, and scandium, and including at least aluminum, and cerium. The composition of the rare earth aluminate phosphor may have a molar content ratio of the first element, for example, when the total number of moles of the second element is 5 moles, of 2.5 or more and 3.5 or less, and preferably 2.8 or more and 3.2 or less. In addition, when the total number of moles of the second element is 5 moles, the molar content ratio of oxygen atoms may be, for example, 10 or more and 14 or less, and preferably 11 or more and 13 or less. In addition, the molar content ratio of aluminum to the total number of moles of the second element may be, for example, more than 0 and 1 or less, and preferably 0.4 or more and 1.0 or less. The second element in the composition of the rare earth aluminate phosphor may be partially substituted with at least one element selected from the group consisting of silicon and germanium. The rare earth aluminate phosphor may have a theoretical composition represented by, for example, the following formula (1).

(Y, Lu, Gd) ₃ (Ga, Al) ₅ O ₁₂ :Ce (1)

The rare earth aluminate phosphor may have a composition different from the theoretical composition as long as it has luminescence characteristics equivalent to those of the theoretical composition represented by formula (1). For example, the rare earth aluminate phosphor may have a composition represented by the following formula (1a).

(Y, Lu, Gd) _i (Ga, Al) ₅ O _j :Ce (1a)

In formula (1a), i and j may satisfy 2.5≦i≦3.5 and 10≦j≦14, and preferably satisfy 2.8≦i≦3.2 and 11≦j≦13.

The emission peak wavelength of the rare earth aluminate phosphor may be, for example, 450 nm or more and 580 nm or less, and preferably 490 nm or more, 500 nm or more, 520 nm or more, or 550 nm or more. The upper limit of the emission peak wavelength may be preferably 575 nm or less, 570 nm or less, or 560 nm or less. The half-width may be, for example, 80 nm or more and 150 nm or less, and preferably 90 nm or more, 100 nm or more, or 110 nm or more, and preferably 140 nm or less, 130 nm or less, or 125 nm or less.

The central particle size of the phosphor may be, for example, 15 μm or more and 40 μm or less, preferably 17 μm or more, 20 μm or more, 22 μm or more, or 24 μm or more, and preferably 35 μm or less, 33 μm or less, or 31 μm or less. When the central particle size of the phosphor is within the above range, a wavelength conversion member with higher fluorescence efficiency tends to be obtained. The central particle size of the phosphor means the volume average particle size (median diameter), and is the particle size corresponding to 50% of the volume cumulative frequency from the small diameter side in the volume cumulative particle size distribution. The volume average particle size is measured, for example, using a laser diffraction type particle size distribution measuring device.

The particle size distribution of the phosphor may be, for example, from the viewpoint of improving brightness, a single-peak particle size distribution, preferably a single-peak particle size distribution with a narrow distribution width. Specifically, in the volume-based particle size distribution, assuming that the particle size corresponding to 10% of the cumulative volume from the small diameter side _{is D10} and the particle size corresponding to 90% of the cumulative volume is _D90 , the ratio of _D90 to _D10 ( _D90 / _D10 ) may be, for example, 3.0 or less.

The density of the phosphor may be, for example, 4 g/cm3 or ^more and 7 g/cm3 ^or less, preferably 4.5 g/cm3 ^or more, and preferably 6.9 g/cm3 or ^less , 6 g/cm3 or ^less , or 5 g/cm3 or ^less .

The wavelength conversion layer may further contain other components in addition to the phosphor and binder. Examples of other components include fillers such as silica, barium titanate, titanium oxide, and aluminum oxide, light stabilizers, and colorants. When the wavelength conversion member contains other components, the content thereof can be appropriately selected depending on the purpose, etc. For example, when the other component contains a filler, the content thereof can be 0.01 parts by mass or more and 20 parts by mass or less per 100 parts by mass of the binder.

The mass ratio of phosphor to binder contained in the wavelength conversion layer may be, for example, 3.15 or more and 6.05 or less, preferably 3.5 or more, 3.8 or more, or 4 or more, and preferably 6 or less.

The volume ratio of the phosphor to the binder contained in the wavelength conversion layer may be, for example, 0.75 or more and 1.45 or less, preferably 0.8 or more, 0.84 or more, 0.88 or more, 0.94 or more, or 0.96 or more, and preferably 1.44 or less, 1.43 or less, 1.2 or less, or 1.0 or less. When the volume ratio of the phosphor to the binder is within the above range, the total efficiency of the light emitting device tends to be further improved. Here, the volume ratio of the phosphor to the binder contained in the wavelength conversion layer is calculated by dividing the area occupied by the phosphor by the area occupied by the resin in any cross section of the wavelength conversion layer. Here, the area occupied by the resin is calculated, for example, by subtracting the area occupied by the phosphor from the area of the wavelength conversion layer. In addition, any cross section of the wavelength conversion layer may be a cross section that intersects with the substrate on which the wavelength conversion layer is disposed.

The volume ratio of the phosphor to the binder contained in the wavelength conversion layer may be approximately calculated as the ratio of the volume of the phosphor to the volume of the binder contained in the phosphor composition forming the wavelength conversion layer. Here, the volume of the binder is calculated by dividing the mass of the binder contained in the phosphor composition by the density of the binder. Also, the volume of the phosphor is calculated by dividing the mass of the phosphor contained in the phosphor composition by the density of the phosphor.

In a cross section perpendicular to the surface on which the wavelength conversion layer is placed on the substrate, the ratio of the sum of the cross-sectional areas of the phosphor particles to the cross-sectional area of the wavelength conversion layer (hereinafter also referred to as the "cross-sectional ratio") may be, for example, 56% or more and 70% or less. The cross-sectional ratio may preferably be 58% or more, 60% or more, 61% or more, or 62% or more. The cross-sectional ratio may also be 68% or less, 66% or less, 65% or less, or 64% or less. When the cross-sectional ratio is within the above range, the luminous intensity of the output light tends to be further improved. Here, the sum of the cross-sectional areas of the phosphor particles is the sum of the cross-sectional areas of the individual phosphor particles observed in the cross section of the wavelength conversion layer.

The cross-sectional ratio is calculated, for example, as follows. In the cross section of the wavelength conversion layer perpendicular to the main surface of the substrate on which the wavelength conversion layer is disposed, a region having a predetermined horizontal width (for example, 640 μm) is arbitrarily selected. The vertical width of the wavelength conversion layer is measured by visually adjusting two parallel lines perpendicular to the thickness direction of the wavelength conversion layer so that each of the parallel lines coincides with the upper and lower surfaces of the wavelength conversion layer, and the vertical width of the wavelength conversion layer is measured as the distance between the two lines. The cross-sectional area of the wavelength conversion layer to be measured is calculated by multiplying the predetermined horizontal width of the wavelength conversion layer by the vertical width of the wavelength conversion layer.

The sum of the phosphor particle cross-sectional areas is calculated as the sum of the cross-sectional areas of each phosphor particle observed in the cross section of the wavelength conversion layer to be measured. The cross-sectional area of each phosphor particle in the cross section of the wavelength conversion layer is measured as the cross-sectional area of a particle identified as a phosphor particle in a reflected electron image obtained by observing the cross section of the wavelength conversion layer to be measured with a scanning electron microscope (SEM). The cross-sectional ratio is calculated by dividing the calculated sum of the phosphor particle cross-sectional areas by the cross-sectional area of the wavelength conversion layer.

The average thickness of the wavelength conversion layer may be, for example, 55 μm or more and 146 μm or less, preferably 60 μm or more or 75 μm or more, and preferably 145 μm or less, 140 μm or less, or 120 μm or less. When the average thickness of the wavelength conversion layer is within the above range, the total efficiency of the light emitting device tends to be improved. The thickness of the wavelength conversion layer is calculated by subtracting the arithmetic mean value of the thickness of the substrate from the arithmetic mean value of the total thickness of the wavelength conversion layer and the substrate. The arithmetic mean value of the total thickness of the wavelength conversion layer and the substrate and the arithmetic mean value of the thickness of the substrate are each calculated from measurements at any six points. The total thickness of the wavelength conversion layer and the substrate and the thickness of the substrate are measured, for example, by a contact thickness gauge.

The wavelength conversion layer may have a substantially uniform thickness. The coefficient of variation of the thickness of the wavelength conversion layer may be, for example, 0.4 or less, and preferably 0.3 or less. The lower limit of the coefficient of variation of the thickness of the wavelength conversion layer may be, for example, 0.09 or more. The coefficient of variation of the thickness of the wavelength conversion layer is calculated by dividing the standard deviation of the thickness of the wavelength conversion layer by the average thickness of the wavelength conversion layer.

In one embodiment, the wavelength conversion member may include a disk-shaped substrate having a reflective surface, and a wavelength conversion layer disposed in an annular shape on the reflective surface of the substrate along the circumference of the substrate.

2. Method for manufacturing wavelength conversion member The method for manufacturing a wavelength conversion member may include a step of applying a phosphor composition containing a binder, a solvent, and a phosphor onto a substrate, and a step of heat-treating the phosphor composition applied onto the substrate to form a wavelength conversion layer. The solvent constituting the phosphor composition may have a boiling point of 200° C. or more and 300° C. or less. The phosphor composition may have a mass ratio of the solvent to the binder of 0.01 or more and 0.4 or less, and a mass ratio of the phosphor to the binder of 3.15 or more and 6.05 or less.

By containing a specific content of a solvent exhibiting a specific boiling point in the phosphor composition forming the wavelength conversion layer, a wavelength conversion layer having a desired average thickness can be efficiently formed with good productivity, even when the phosphor content is high. The wavelength conversion layer formed has a high phosphor content and a predetermined average thickness, and therefore a light emitting device constructed using the wavelength conversion material can achieve good total efficiency.

The phosphor composition contains at least a binder, a solvent, and a phosphor. The binder contained in the phosphor composition may be an organic binder or an inorganic binder. The organic binder may contain, for example, a resin, preferably a translucent resin. Examples of the resin include thermosetting resins such as epoxy resin, silicone resin, epoxy-modified silicone resin, and modified silicone resin. When the resin contains a silicone resin, it tends to have better heat resistance, light resistance, and the like. The silicone resin or modified silicone resin may contain at least one selected from the group consisting of phenyl silicone resin, modified phenyl silicone resin, dialkyl silicone resin, and modified dialkyl silicone resin. Examples of the inorganic binder include glass, ceramics, and aluminum oxide.

The phosphor contained in the phosphor composition may include, for example, at least one type of rare earth aluminate phosphor. Details of the rare earth aluminate phosphor are as described above. The content of the phosphor in the phosphor composition may be, for example, 3.15 or more and 6.05 or less, preferably 3.5 or more, or 4 or more, and preferably 6 or less, as a mass ratio to the binder. When the content of the phosphor is within the above range, the total efficiency of the light emitting device tends to be higher.

The solvent contained in the phosphor composition may have a boiling point of, for example, 200°C or more and 300°C or less, preferably 210°C or more or 230°C or more, and preferably 280°C or less, 260°C or less, or 250°C or less. When the boiling point of the solvent is within the above range, the workability in the application process tends to be improved. From the viewpoint of the solubility of the binder, the solvent may contain, for example, an aliphatic hydrocarbon solvent, and may contain at least one selected from the group consisting of aliphatic hydrocarbon solvents having 12 to 16 carbon atoms. The solvent may preferably contain at least one selected from the group consisting of dodecane (boiling point 216°C), tridecane (boiling point 234°C), tetradecane (boiling point 254°C), pentadecane (boiling point 271°C), and hexadecane (boiling point 287°C).

The content of the solvent in the phosphor composition, expressed as a mass ratio of the solvent to the binder, may be, for example, 0.01 to 0.4, preferably 0.02 to 0.04, or 0.05 or more, and preferably 0.38 to 0.35, 0.3 to 0.2, or 0.1 to 0.1. The content of the solvent in the phosphor composition, expressed as a mass ratio of the solvent to the total mass of the binder and the phosphor, may be, for example, 0.002 to 0.06, preferably 0.01 to 0.05. If the content of the solvent is within the above range, the workability in the application process tends to be improved.

The phosphor composition can be prepared, for example, by mixing a binder, a solvent, and a phosphor. The phosphor composition may also be prepared by mixing a mixture of a binder and a solvent with a phosphor. The mixing method can be appropriately selected from commonly used mixing methods. Examples of the mixing method include a method using a vacuum degassing mixer, a stirrer, etc.

In the application step, the phosphor composition is applied to the substrate. Details of the substrate to which the phosphor composition is applied are as described above. The phosphor composition may be applied preferably onto the reflective surface of the substrate. Methods for applying the phosphor composition to the substrate include printing, coating, and adhesion of a phosphor composition sheet. The method for applying the phosphor composition to the substrate may preferably be a printing method.

The application of the phosphor composition by the printing method can be performed by screen printing, for example, by placing a screen plate at a desired position on the substrate and moving a squeegee over the placed screen plate to transmit the phosphor composition and form a phosphor composition layer of a predetermined thickness on the substrate. This allows the phosphor composition to be applied to the substrate with a substantially uniform thickness. In addition, the thickness of the phosphor composition layer formed can be adjusted by using a screen plate in which the line diameter, linearity, gauze thickness, aperture ratio, mesh number, etc. of the fibers constituting the screen are appropriately adjusted. The thickness of the phosphor composition layer formed on the substrate may be appropriately adjusted according to the thickness of the intended wavelength conversion layer. In addition, the amount of the phosphor composition applied may be an amount that allows the wavelength conversion layer to be formed to have the desired thickness. The average thickness of the wavelength conversion layer formed may be, for example, 55 μm or more and 146 μm or less, preferably 60 μm or more or 75 μm or more, and preferably 145 μm or less, 140 μm or less, or 120 μm or less.

In the heat treatment step, the phosphor composition applied to the substrate is heat-treated to form a wavelength conversion layer. The heat treatment step may include thermally curing the binder contained in the phosphor composition to form the wavelength conversion layer. The heat treatment temperature in the heat treatment step may be set appropriately according to the thermosetting characteristics of the binder. The heat treatment temperature may be, for example, a temperature lower than the boiling point of the solvent contained in the phosphor composition. This makes it possible to suppress the formation of voids and the like due to the evaporation of the solvent. The heat treatment temperature may be, for example, 50°C or higher and 180°C or lower, and preferably 100°C or higher or 150°C or lower. The heat treatment time may be, for example, 1 hour or higher and 10 hours or lower, and preferably 4 hours or higher or 8 hours or lower. The heat treatment atmosphere may be, for example, an air atmosphere.

In the heat treatment step, at least a portion of the solvent contained in the phosphor composition may be removed prior to thermal curing of the binder. The solvent can be removed by, for example, heating or reducing pressure on the phosphor composition. When the solvent is removed by heating, the temperature may be, for example, 50°C or higher and 180°C or lower, and preferably 100°C or higher or 150°C or lower. The time required for removing the solvent may be, for example, 1 hour or higher and 10 hours or lower, and preferably 4 hours or higher or 8 hours or lower.

Light-emitting device The light-emitting device comprises a wavelength conversion member of the first embodiment, a motor for rotating the wavelength conversion member, and a light source for irradiating the wavelength conversion member with light. The light-emitting device is configured to emit a mixed color light of light from the light source and light from the wavelength conversion member irradiated with light from the light source. By including a wavelength conversion member having a specific configuration, the light-emitting device can achieve good total efficiency. Details of the wavelength conversion member constituting the light-emitting device are as described above.

In the light emitting device, the wavelength conversion member is fixed to the rotating shaft of the motor and is arranged so as to be rotatable by the motor. Examples of the light source that irradiates the wavelength conversion member with light include a light emitting element. The light emitting element may be a semiconductor light emitting element, a light emitting diode, or a laser diode. The light source may be made up of one type of light emitting element alone or a combination of two or more types. Furthermore, the light emitting element that makes up the light source may be one or more than one.

The light source may have an emission peak wavelength within a wavelength range of, for example, 440 nm or more and 470 nm or less. The emission peak wavelength of the light source may preferably be within a wavelength range of, for example, 450 nm or more and 460 nm or less. The half-width of the light source may be, for example, 30 nm or less.

The output of the light source may be, for example, 0.5 W/mm2 ^{or more} , preferably 5 W/mm2 ^{or more} , or 10 W/mm2 or ^more , as the optical power density irradiated to the wavelength conversion member. The upper limit of the output of the light emitting element may be, for example, 1000 W/ ^mm2 or less, preferably 500 W/mm2 ^{or less} , or 150 W/mm2 or ^less .

The light-emitting device can be used to form, for example, a projector, which will be described later. By using a light-emitting device that exhibits good total efficiency, a high-output projector can be formed. The light-emitting device can be used not only as a light source device for a projector, but also as a light-emitting device provided in a light source for, for example, general lighting devices such as ceiling lights, special lighting devices such as spotlights, stadium lighting, and studio lighting, vehicle lighting devices such as headlamps, projection devices such as head-up displays, endoscope lights, imaging devices such as digital cameras, mobile phones, and smartphones, monitors for personal computers (PCs), notebook personal computers, televisions, personal digital assistants (PDXs), smartphones, tablet PCs, liquid crystal display devices such as mobile phones, and the like.

Projector The projector includes the above-mentioned light emitting device, an image display system, and a projection optical system. An example of the configuration of the projector will be described with reference to FIG. 2. FIG. 2 is a schematic configuration diagram of a projector 100. The projector 100 includes a light source 110, a wavelength conversion member 50, an image display system 120, and a projection optical system 130. In the projector 100, a mixture of light from the light source 110 and light obtained by wavelength-converting the light from the light source 110 by the wavelength conversion member 50 is irradiated onto the image display system 120. The image display system 120 converts the irradiated light into an image and projects it to the outside via the projection optical system 130.

The details of the light source 110 and the wavelength conversion member 50 constituting the projector 100 are as described above. The image display system 120 displays the image projected by the projector 100. The image display system 120 can be a liquid crystal panel, a digital mirror device (DMD), or the like. The projection optical system 130 projects to the outside an image obtained by converting the light emitted from the wavelength conversion member 50 by the image display system 120. The projection optical system 130 is composed of a plurality of lenses 131, and can perform zooming, focus adjustment, and the like. In addition to the above configuration, the projector 100 is composed of lenses 131, a dichroic mirror 132, and the like. In addition, depending on the design of the projector 100, a mirror, a dichroic mirror, a lens, a prism, and the like not shown in FIG. 2 may be further provided.

The present invention may include the following aspects.
[1] A wavelength conversion member comprising: a substrate; and a wavelength conversion layer disposed on the substrate and containing a binder and a phosphor, wherein the wavelength conversion layer has a volume ratio of the phosphor to the binder of 0.75 to 1.45 and an average thickness of 55 μm to 146 μm.

[2] A wavelength conversion member comprising a substrate and a wavelength conversion layer disposed on the substrate and containing a binder and a phosphor, in which in a cross section perpendicular to the surface on which the wavelength conversion layer is disposed on the substrate, the ratio of the sum of the particle cross-sectional areas of the phosphor particles to the cross-sectional area of the wavelength conversion layer is 56% or more and 70% or less, and the average thickness is 55 μm or more and 146 μm or less.

[3] The wavelength conversion member according to [1] or [2], wherein the phosphor includes at least one first element selected from the group consisting of yttrium, lanthanum, lutetium, gadolinium, and terbium, at least one element selected from the group consisting of aluminum, gallium, and scandium, and includes a rare earth aluminate phosphor having a composition including a second element including at least aluminum, and cerium.

[4] The wavelength conversion member according to any one of [1] to [3], wherein the phosphor has a median particle size of 15 μm or more and 40 μm or less.

[5] The wavelength conversion member according to any one of [1] to [4], wherein the substrate has a reflective surface made of a material containing at least one selected from the group consisting of silver and aluminum, and the wavelength conversion layer is disposed on the reflective surface.

[6] The wavelength conversion member according to any one of [1] to [5], wherein the binder contains a silicone resin.

[7] A light emitting device comprising a wavelength conversion member according to any one of [1] to [6], a motor for rotating the wavelength conversion member, and a light source for irradiating the wavelength conversion member with light.

[8] A projector comprising the light-emitting device described in [7], an image display system, and a projection optical system.

[9] A method for manufacturing a wavelength conversion member, comprising: applying a phosphor composition containing a binder, a solvent, and a phosphor, the boiling point of the solvent being 200°C or more and 300°C or less, the mass ratio of the solvent to the binder being 0.01 or more and 0.4 or less, and the mass ratio of the phosphor to the binder being 3.15 or more and 6.05 or less, to a substrate; and heat-treating the phosphor composition applied to the substrate to form a wavelength conversion layer.

[10] The method for producing a wavelength conversion member according to [9], wherein applying the phosphor composition onto the substrate includes screen printing the phosphor composition.

[11] The method for producing a wavelength conversion member according to [9] or [10], wherein the heat treatment of the phosphor composition includes a heat treatment at less than 200°C.

[12] The method for producing a wavelength conversion member according to any one of [9] to [11], wherein the phosphor includes at least one first element selected from the group consisting of yttrium, lanthanum, lutetium, gadolinium, and terbium, at least one element selected from the group consisting of aluminum, gallium, and scandium, and includes a rare earth aluminate phosphor having a composition including a second element including at least aluminum, and cerium.

[13] The method for producing a wavelength conversion member according to any one of [9] to [12], wherein the phosphor has a median particle size of 15 μm or more and 40 μm or less.

[14] The method for producing a wavelength conversion member according to any one of [9] to [13], wherein the solvent contains at least one selected from the group consisting of dodecane, tridecane, tetradecane, pentadecane, and hexadecane.

[15] The method for producing a wavelength conversion member according to any one of [9] to [14], wherein the substrate has a reflective surface made of a material containing at least one selected from the group consisting of silver and aluminum, and applying the phosphor composition onto the substrate includes applying the phosphor composition to the reflective surface.

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

Phosphors A rare earth aluminate phosphor having a theoretical composition represented by the following formula and a median particle size of 24 μm and a rare earth aluminate phosphor having a median particle size of 31 μm were prepared as phosphors.
Y ₃ Al ₅ O ₁₂ :Ce

The substrate was a disk-shaped substrate made of a metal containing aluminum, with a diameter of 33 mm and a thickness of 0.47 mm. The specular reflectance of the reflective surface of the substrate for light of 450 nm was 89%.

Example 1
5 parts by mass of dodecane was added to 100 parts by mass of dimethyl silicone resin, and mixed using a vacuum defoaming mixer. 400 parts by mass of rare earth aluminate phosphor with a central particle size of 24 μm was added thereto, and mixed using a vacuum defoaming mixer to obtain a phosphor composition. The obtained phosphor composition was applied to a substrate by screen printing to form a phosphor composition layer. Thereafter, the substrate was heat-treated in an oven at 60° C. for 4 hours, and then in an oven at 150° C. for 4 hours to form a wavelength conversion layer, and the wavelength conversion member of Example 1 was obtained.

Examples 2 to 16, Comparative Example 1 and Comparative Example 2
Each wavelength conversion member was obtained in the same manner as in Example 1, except that the median particle size and amount of phosphor added, and the type and amount of solvent added were changed as shown in Table 1.

For the wavelength conversion member obtained above, the volume ratio of phosphor to binder in the wavelength conversion layer and the average thickness of the phosphor layer were measured as follows. The results are shown in Table 1.

Measurement of volume ratio The density of the dimethyl silicone resin was set to 1.1 g/cm ³ , and the mass of the dimethyl silicone resin added to the phosphor composition was divided by the density to calculate the volume of the dimethyl silicone resin in the phosphor composition. The density of the rare earth aluminate phosphor was set to 4.6 g/cm ³ , and the mass of the rare earth aluminate phosphor added to the phosphor composition was divided by the density to calculate the volume of the rare earth aluminate phosphor in the phosphor composition. The volume ratio of the phosphor to the binder in the formed wavelength conversion layer was calculated by dividing the volume of the rare earth aluminate phosphor by the volume of the dimethyl silicone resin contained in the phosphor composition.

Measurement of average thickness The average thickness of the wavelength conversion layer was calculated by subtracting the arithmetic mean value of the thickness of the substrate alone measured at six points from the arithmetic mean value of the total thickness of the wavelength conversion layer and the substrate measured at six points. The total thickness of the wavelength conversion layer and the substrate and the thickness of the substrate alone were measured using a contact thickness gauge.

Relative total efficiency For the wavelength conversion member obtained above, the fluorescence efficiency and light collection efficiency in the light emitting device were calculated as follows, and the total efficiency was calculated as the product of the fluorescence efficiency and the light collection efficiency. The total efficiency in each light emitting device is shown in Table 1 as a relative total efficiency with the total efficiency of the light emitting device using the wavelength conversion member of Comparative Example 1 as the reference (100%).

To measure the total efficiency, a light emitting device as shown in Figure 1 was prepared. The wavelength conversion member was fixed to the rotating shaft of a motor and was made rotatable by the motor. The motor rotation speed was set to 7200 rpm, and the fluorescence efficiency and light collection efficiency were measured as follows.

Fluorescence efficiency Laser light from a laser diode having a wavelength of 450 nm was irradiated to the wavelength conversion member of each Example and Comparative Example at an intensity of 10 W through a dichroic mirror so that the diameter of the incident light was 0.25 ^mm2 . The radiant flux of the light emitted from the same surface as the surface into which the laser light was incident was separated by a dichroic mirror, and the intensity of the emitted light was measured using an integrating sphere. The fluorescence efficiency was calculated by dividing the intensity of the emitted light by the intensity of the incident light.

Light collection efficiency The wavelength conversion members of each Example and Comparative Example were irradiated with laser light from a laser diode having a wavelength of 455 nm. This irradiation was performed so that the diameter of the incident light was 0.6 mm on the upper surface of the wavelength conversion member into which the laser light was incident. Next, the outgoing light emitted from the same surface as the upper surface of the wavelength conversion member into which the laser light was incident was measured by the following method. First, the emission luminance of the light emitted from the wavelength conversion member of each Example and Comparative Example was measured with a color luminance meter, and the position showing the maximum luminance in the obtained emission spectrum was set as the center (measurement center), and the distance (mm) from the measurement center of two positions where the luminance in the emission spectrum was 1/100 (1%) of the maximum luminance was measured as an absolute value. Then, the sum of the distances (mm) from the measurement center to the two positions was calculated. This value is called the "1% width (mm)". The smaller the value of this 1% width, the narrower the area in which light is emitted, and the easier it is for light to enter the secondary optical system, resulting in a higher light collection efficiency. Comparing the obtained 1% width value with the light collection efficiency (=emission output x 100/fluorescence output) measured with a typical actual secondary optical system, it is found that the light collection efficiency can be approximated by the following formula, where the 1% width value is x. Using this formula, the light collection efficiency was calculated from the measured 1% width value.
Light collection efficiency = -0.0012x ² + 0.1243x + 58.783

As shown in Table 1, the volume ratio of the phosphor to the binder in the wavelength conversion layer is 0.75 to 1.45, and the average thickness of the wavelength conversion layer is 55 μm to 146 μm, so that the light emitting device according to the example has a higher total efficiency than the light emitting device according to the comparative example. Also, as shown in Table 1, by using a solvent with a boiling point of 200°C to 300°C, such as dodecane (boiling point 216°C), tridecane (boiling point 234°C), and hexadecane (boiling point 287°C), the mass ratio of the solvent to the binder is 0.01 to 0.4, and the mass ratio of the phosphor to the binder is 3.15 to 6.05, a wavelength conversion layer having a thickness of, for example, 55 μm to 146 μm is formed using a phosphor composition, and the total efficiency of the light emitting device obtained by the manufacturing method according to the example is higher than that of the light emitting device according to the comparative example.

For representative wavelength conversion members obtained above, the ratio of the sum of the phosphor particle cross-sectional areas to the cross-sectional area of the wavelength conversion layer (cross-sectional ratio) was evaluated as follows. The results are shown in Table 2.

Evaluation of the cross-sectional ratio Image analysis was performed using image analysis software (ImageJ) on the cross-sectional SEM image (width: 640 μm) of the wavelength conversion layer obtained using a scanning electron microscope (SEM), and binarization was performed on particles in which the cross-sectional outline of each phosphor could be confirmed in the cross-sectional SEM image. The cross-sectional area of each binarized phosphor particle was integrated to calculate the total cross-sectional area of the phosphor. The cross-sectional area of the wavelength conversion layer was calculated by visually adjusting the positions of two parallel lines perpendicular to the thickness direction of the wavelength conversion layer so that the wavelength conversion layer was sandwiched between them, and multiplying the vertical width of the wavelength conversion layer measured as the distance between the two parallel lines by the horizontal width of 640 μm. Next, the cross-sectional ratio (%) was calculated by dividing the total cross-sectional area of the phosphor by the cross-sectional area of the wavelength conversion layer.

The wavelength conversion member and light-emitting device including the same according to the present disclosure can be used as a light source device for a projector, an illumination device, an automobile display, a backlight source for a liquid crystal display, etc.

100 Projector; 110 Light source; 50 Wavelength conversion member; 130 Projection optical system; 200 Light emitting device

Claims (5)

applying a phosphor composition containing a binder, a solvent, and a phosphor, the solvent having a boiling point of 200° C. or more and 300° C. or less, a mass ratio of the solvent to the binder being 0.05 or more and 0.35 or less, and a mass ratio of the phosphor to the binder being 4 or more and 6 or less, onto a substrate;
and heat treating the phosphor composition applied on the substrate to form a wavelength conversion layer,
the phosphor includes a rare earth aluminate phosphor having a composition including at least one first element selected from the group consisting of yttrium, lanthanum, lutetium, gadolinium, and terbium, at least one second element selected from the group consisting of aluminum, gallium, and scandium, and including at least aluminum, and cerium;
The median particle size is 15 μm or more and 40 μm or less,
A method for producing a wavelength conversion member, wherein in a volume-based particle size distribution, the ratio (D ₉₀ /D ₁₀ ) of a particle size D ₉₀ corresponding to 90% cumulative volume from the small diameter side to a particle size D ₁₀ corresponding to 10% cumulative volume from the small diameter side is 3.0 or less. The method for producing a wavelength conversion member according to claim 1 , wherein applying the phosphor composition onto a substrate comprises screen-printing the phosphor composition. The method for producing a wavelength conversion member according to claim 1 , wherein the heat treatment of the phosphor composition includes a heat treatment at a temperature of less than 200° C. The method for producing a wavelength conversion member according to claim 1 , wherein the solvent contains at least one selected from the group consisting of dodecane, tridecane, tetradecane, pentadecane, and hexadecane. 2. The method for manufacturing a wavelength conversion member according to claim 1, wherein the substrate has a reflective surface made of a material containing at least one selected from the group consisting of silver and aluminum, and applying the phosphor composition onto the substrate includes applying the phosphor composition to the reflective surface.