Phosphor substrate and phosphor device

Abstract

A phosphor substrate (1) comprises only a phosphor portion (10) having a phosphor ceramic as a main component, and a plurality of pores (20) provided in the phosphor portion (10), wherein: the density of the phosphor substrate (1) is at least equal to 95% of the theoretical density of the phosphor ceramic; the plurality of pores (20) include a plurality of internal pores located inside the phosphor substrate (1); and the number of the plurality of internal pores per unit volume is 1.00×108 pores / mm3 or more and 1.00×1010 pores / mm3 or less.

Description

Phosphor substrate and phosphor device

[0001] The present invention relates to a phosphor substrate and a phosphor device.

[0002] Light source modules using solid-state light-emitting elements such as LEDs or semiconductor lasers as light sources are used in projectors, endoscopes, vehicle headlamps, lighting devices, liquid crystal display devices, etc. This type of light source module includes, for example, a light source and a phosphor device that emits fluorescence when excitation light emitted by the light source is incident thereon.

[0003] The phosphor device includes, for example, a substrate and a phosphor substrate provided on the substrate. For example, Patent Document 1 discloses a phosphor plate (phosphor substrate) including a fluorescent phase (phosphor portion), a light-transmitting phase that scatters light, and a plurality of voids (pores).

[0004] International Publication No. 2021 / 251252

[0005] Patent Document 1 discloses that in the cross section of a phosphor substrate, the area ratio of the phosphor portion is 60% and the area ratio of the light-transmitting phase is 40%. When the phosphor substrate has a light-transmitting phase, the proportion of the phosphor portion that converts excitation light into fluorescence is reduced. Therefore, it is difficult to increase the excitation light conversion efficiency of the phosphor substrate.

[0006] Therefore, for example, in the phosphor substrate disclosed in Patent Document 1, if the proportion of the translucent phase can be reduced and the proportion of the phosphor portion can be increased, it is possible to increase the excitation light conversion efficiency. However, in this case, the proportion of the translucent phase is reduced, making it impossible to scatter light, and it becomes difficult for the phosphor substrate to function as a light guide plate and extract the light outside the phosphor substrate. As a result, the amount of light emitted from the phosphor substrate is reduced, which means that the extraction efficiency is reduced and leads to a decrease in brightness.

[0007] The present invention has been made in view of the above problems, and has an object to provide a phosphor substrate or the like having high brightness.

[0008] In order to achieve the above object, one aspect of the phosphor substrate according to the present invention is a phosphor substrate comprising only a phosphor portion having a phosphor ceramic as a main component and a plurality of pores provided in the phosphor portion, wherein the density of the phosphor substrate is 95% or more of the theoretical density of the phosphor ceramic, the plurality of pores include a plurality of internal pores located inside the phosphor substrate, and the number of the plurality of internal pores per unit volume is 1.00×10 ８ pieces / mm ３ Above 1.00 x 10 １０ pieces / mm ３ The following is the result.

[0009] Moreover, one aspect of a phosphor device according to the present invention includes the above-described phosphor substrate and a support substrate that supports the phosphor substrate.

[0010] According to the present invention, it is possible to provide a phosphor substrate or the like having high brightness.

[0011] FIG. 1 is a diagram showing the configuration of a phosphor substrate according to an embodiment. FIG. 2 is a diagram showing an example of use of a phosphor substrate according to an embodiment. FIG. 3 is an enlarged cross-sectional view of region III in FIG. 1. FIG. 4 is a diagram showing an optical microscope photograph of a phosphor substrate according to an embodiment. FIG. 5 is a diagram showing a table showing the characteristics of a phosphor substrate according to Comparative Example 1, a phosphor substrate according to Example 3, a phosphor substrate according to Example 1, and a phosphor substrate according to Example 2. FIG. 6 is a diagram showing the relationship between the theoretical density ratio and the number of pores of a phosphor ceramic (YAG) depending on the pore diameter according to an embodiment. FIG. 7 is a cross-sectional view showing the configuration of a phosphor device according to Modification 1 of the embodiment.

[0012] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that each of the embodiments described below represents a specific example of the present invention. Therefore, the numerical values, shapes, materials, components, component arrangements and connection forms, steps, and step sequences shown in the following embodiments are merely examples and are not intended to limit the present invention. Therefore, among the components in the following embodiments, components not recited in independent claims will be described as optional components.

[0013] Furthermore, each figure is a schematic diagram and is not necessarily an exact illustration. Therefore, for example, the scales of the figures do not necessarily match. Furthermore, in each figure, substantially the same components are given the same reference numerals, and redundant explanations are omitted or simplified.

[0014] Furthermore, in this specification, terms indicating the relationship between elements, terms indicating the shape of elements such as circle or rectangle, and numerical ranges are not expressions that only express a strict meaning, but are expressions that also include a substantially equivalent range, for example, a difference of about a few percent.

[0015] Furthermore, in this specification, the terms "up" and "down" do not necessarily refer to the upward direction (vertically upward) and downward direction (vertically downward) in absolute spatial recognition.

[0016] Furthermore, in this specification, "A has B as a main component" means that the content of B contained in A is greater than 50%. In this case, the content of B may be 90% or more, 95% or more, 99% or more, or even 100%. Note that when the content of B contained in A is 100%, that is, when A consists only of B, A may contain unavoidable impurities that are mixed in during production. In other words, "100% content" means that the purity of B is so high that it can be considered to be substantially 100%.

[0017] (Embodiment) [Configuration] First, the configuration of a phosphor substrate 1 according to the embodiment will be described with reference to FIG.

[0018] Fig. 1 is a diagram showing the configuration of a phosphor substrate 1 according to this embodiment, in which Fig. 1(a) is a top view of the phosphor substrate 1, and Fig. 1(b) is a cross-sectional view of the phosphor substrate 1 taken along line bb in Fig. 1(a).

[0019] As shown in FIG. 1, the phosphor substrate 1 is a substrate that includes only a phosphor portion 10 and a plurality of pores 20 .

[0020] The phosphor section 10 is a member having phosphor ceramics as its main component. The phosphor section 10 is a member that emits fluorescence when light is incident on it. Specifically, the phosphor section 10 is excited by excitation light and emits fluorescence with a wavelength longer than that of the excitation light. As an example, the phosphor section 10 has yellow phosphor ceramics (yellow phosphor material) as its main component. In this case, the phosphor section 10 emits yellow fluorescence using light with a wavelength shorter than that of yellow light (e.g., ultraviolet light to blue light) as excitation light. In other words, the phosphor section 10 converts the wavelength of the excitation light to yellow light with a wavelength longer than that of the excitation light. Note that the emission wavelength of the phosphor section 10 is not limited to wavelengths in the visible light band, but may be a wavelength in the infrared light band. In this case, the phosphor section 10 includes phosphor ceramics that emit light with a wavelength in the infrared light band.

[0021] The phosphor section 10 according to this embodiment is a member made only of phosphor ceramics, with the phosphor ceramic content being 100%. As an example, the phosphor section 10 is a member made only of phosphor ceramics that is a sintered polycrystalline phosphor. In other words, the phosphor section 10 does not contain a binder or the like.

[0022] In this way, by making the phosphor section 10 only from phosphor ceramics, the heat resistance and thermal conductivity of the phosphor section 10 can be improved. Furthermore, in the case of a phosphor section made of phosphor particles and a binder such as silicone, the binder deteriorates and non-luminescent absorption increases. This results in a decrease in the excitation light conversion efficiency of this phosphor section, which converts excitation light into fluorescence. However, by making the phosphor section 10 only from phosphor ceramics, the excitation light conversion efficiency of the phosphor section 10 can be maintained over a long period of time.

[0023] Furthermore, examples of phosphor ceramics (phosphor materials) include YAG (yttrium aluminum garnet) ３ Al ５ O １２ ), LuAG (Lutetium Aluminum Garnet) Lu ３ Al ５ O１２ ), Lu ２ CaMg ２ Si ３ O １２ (Lutetium Calcium Magnesium Silicon Garnet) and TAG (Terbium Aluminum Garnet), Gd ３ Ga ５ O １２ , (Ga ０．６ Sc ０．４ ) ２ O ３ The dopant to be doped into the phosphor can be appropriately selected from Ce, Eu, Cr, etc. Furthermore, as the phosphor ceramic, two or more phosphor materials may be combined, for example, YAG and LuAG may be combined.

[0024] In this embodiment, the phosphor section 10 is a member made of only phosphor ceramics, which is sintered YAG. More specifically, the phosphor section 10 is made of Ce ３＋ The fluorescent lamp is made of only sintered YAG phosphor ceramics containing fluorescein, and emits yellow fluorescence.

[0025] The phosphor substrate 1 according to this embodiment has a first surface 1a and a second surface 1b located on the opposite side of the first surface 1a. The first surface 1a is the upper surface, and the second surface 1b is the lower surface. For example, the second surface 1b is a light incident surface onto which excitation light from a light source is incident, and the first surface 1a is a light exit surface from which fluorescent light is emitted.

[0026] The phosphor substrate 1 has a flat plate shape with a constant thickness, i.e., a flat rectangular parallelepiped shape. Since the phosphor substrate 1 has a flat plate shape, the phosphor portion 10 also has a flat plate shape. Note that the shape of the phosphor substrate 1 in this embodiment when viewed from above is square, but is not limited to this. The shape of the phosphor substrate 1 when viewed from above may also be circular, rectangular, or annular with a predetermined width.

[0027] The thickness of the flat-plate-shaped phosphor substrate 1 is on the order of microns, less than 200 μm. In this embodiment, the thickness of the phosphor substrate 1 is 100 μm or less. In order to lower the temperature of the phosphor substrate 1 and reduce distortion when irradiated with excitation light, the thickness of the phosphor substrate 1 should be 80 μm or less. On the other hand, considering the volume required for the excitation light incident on the phosphor substrate 1 to be absorbed by the phosphor ceramic and for the phosphor substrate 1 to emit light efficiently, the thickness of the phosphor substrate 1 should be 30 μm or more.

[0028] Here, the behavior of the phosphor substrate 1 when it is irradiated with excitation light will be described with reference to FIG.

[0029] Fig. 2 is a diagram showing an example of use of the phosphor substrate 1 according to this embodiment. Fig. 2 shows how light L1 from the light source 2 is incident on the phosphor substrate 1 and how output light L3 is emitted from the phosphor substrate 1.

[0030] 2 , light L1 emitted from a light source 2 is incident on the phosphor substrate 1. Specifically, light L1 emitted from the light source 2 is incident on the phosphor section 10 from the second surface 1b of the phosphor substrate 1. The light source 2 is, for example, a laser light source having a semiconductor laser that emits laser light as light L1. Therefore, the phosphor section 10 of the phosphor substrate 1 is irradiated with the laser light.

[0031] Light L1 emitted from the light source 2 is incident on the phosphor section 10 of the phosphor substrate 1 as excitation light. As a result, the phosphor section 10 is excited by the light L1 from the light source 2, and light L2 of a predetermined color is generated in the phosphor section 10. That is, a portion of the light L1 (excitation light) from the light source 2 is wavelength-converted in the phosphor section 10 to become light L2 (fluorescence) of a predetermined wavelength. Then, light L2, which is the fluorescence generated in the phosphor section 10, is mixed with another portion of the light L1 from the light source 2 that is light L1 from the light source 2 that has entered the phosphor section 10 and has not been wavelength-converted, and this mixed light is emitted from the phosphor section 10 as emitted light L3. In this embodiment, the emitted light L3 is emitted from the first surface 1a of the phosphor substrate 1. Therefore, the second surface 1b is a light incident surface, and the first surface 1a is a light exit surface.

[0032] Next, the plurality of pores 20 will be described.

[0033] The multiple pores 20 are voids (air bubbles) provided in the phosphor section 10. The multiple pores 20 are dispersed within the phosphor section 10. The multiple pores 20 are generated during the manufacturing process of the phosphor substrate 1. The size, shape, and number of the pores 20 vary depending on the manufacturing method of the phosphor substrate 1. The presence of the multiple pores 20 makes it possible to scatter both the excitation light incident on the phosphor substrate 1 and the generated fluorescence. Note that the sizes of the multiple pores 20 do not all need to be the same. The shape of the pores 20 is also irregular and is not limited to being spherical.

[0034] Furthermore, the plurality of pores 20 on the first surface 1a, which is an example of the surface of the phosphor substrate 1, will be described with reference to FIG.

[0035] Fig. 3 is an enlarged cross-sectional view of region III in Fig. 1. The pores 20 include a plurality of surface pores 21 located on the surface (first surface 1a in this example) of the phosphor substrate 1 and a plurality of internal pores 22 located inside the phosphor substrate 1. In this embodiment, the surface pores 21 and the internal pores 22 have the same degree of dispersion, number per unit volume, and size.

[0036] The surface pores 21 are voids (air bubbles) located within a distance D1 from the surface (first surface 1a). More specifically, when all of the voids are located within the distance D1 from the surface (first surface 1a), the voids are considered to be surface pores 21. Furthermore, a void exposed on the surface (e.g., first surface 1a) of the phosphor substrate 1 also falls under the category of surface pores 21. Note that the distance D1 is, for example, 0.3 μm or more and 5 μm or less, but is not limited thereto, and may be, for example, 0.5 μm or more and 4 μm or less, or 1 μm or more and 3 μm or less.

[0037] The internal pores 22 are voids (air bubbles) located in an area that is farther from the surface (first surface 1a) than the distance D1. More specifically, when at least a portion of one void is located in an area that is farther from the surface (first surface 1a) than the distance D1, the one void corresponds to an internal pore 22.

[0038] Furthermore, although the first surface 1a is used here as an example of the surface of the phosphor substrate 1, the same applies to the other surfaces (the other five surfaces in this embodiment in which the phosphor substrate 1 has a rectangular parallelepiped shape), and voids located within a distance D1 from the other surfaces correspond to surface pores 21.

[0039] Here, the density of the phosphor substrate 1 will be described. More specifically, the density of the phosphor substrate 1 is the mass density of the phosphor substrate 1. The density of the phosphor substrate 1 is 95% or more of the theoretical density of the phosphor ceramic that the phosphor portion 10 contains as a main component. Moreover, the density of the phosphor substrate 1 is less than 100% of the theoretical density of the phosphor ceramic.

[0040] The theoretical density is the density when the atoms of the phosphor ceramic, which is the main component of the phosphor portion 10, are ideally arranged in the phosphor substrate 1. In other words, the theoretical density is the density when it is assumed that there are no pores 20 in the phosphor substrate 1, and is a value calculated using the crystal structure. For example, if the density of the phosphor substrate 1 is 99% of the theoretical density of the phosphor ceramic, the remaining 1% corresponds to the pores 20. In other words, the higher the density of the phosphor substrate 1, the fewer the pores 20 there are.

[0041] In this embodiment, since a plurality of pores 20 exist inside the phosphor substrate 1, the density of the phosphor substrate 1 is less than 100% of the theoretical density, as described above.

[0042] The density of the phosphor substrate 1 is 95% or more and less than 100% of the theoretical density of the phosphor ceramic, and the theoretical density of the phosphor ceramic is 4.56 g / cm ３ Since YAG of 4.32 g / cm is used, the density of the phosphor substrate 1 is 4.32 g / cm ３ 4.56g / cm or more ３ It is more preferable that the density of the phosphor substrate 1 be 98% or more and less than 100% of the theoretical density of the phosphor ceramic.

[0043] In this embodiment, the phosphor substrate 1 is a substrate consisting only of a phosphor portion 10 having a phosphor ceramic as a main component and a plurality of pores 20. More specifically, the phosphor substrate 1 is a substrate consisting only of a phosphor portion 10 made only of a phosphor ceramic and a plurality of pores 20. In other words, the phosphor substrate 1 does not have a translucent phase as disclosed in Patent Document 1. For example, in a phosphor substrate having a translucent phase, the proportion of the phosphor portion 10 in the phosphor substrate is reduced by the amount of the translucent phase, making it difficult to increase the excitation light conversion efficiency for converting excitation light into fluorescence.

[0044] However, the phosphor substrate 1 according to this embodiment is composed only of the phosphor portion 10 and the plurality of pores 20, and its density is 95% or more of the theoretical density of phosphor ceramics, so that the proportion of the phosphor portion 10 in the phosphor substrate 1 is sufficiently high. Therefore, compared to a phosphor substrate having a translucent phase, the phosphor substrate 1 can convert excitation light sufficiently, increasing the total amount of fluorescence generated in the phosphor portion 10, and thus improving the excitation light conversion efficiency for converting excitation light into fluorescence.

[0045] The internal pores 22 will be described again.

[0046] Fig. 4 is a diagram showing an optical microscope photograph of the phosphor substrate 1 according to this embodiment. The diagram shown in Fig. 4 is a diagram of the phosphor substrate 1 observed with an optical microscope. The multiple voids shown in Fig. 4 are voids in the range of 5 µm in depth, and each represents an internal pore 22.

[0047] The number of the internal pores 22 per unit volume according to this embodiment is 1.00×10 ８ pieces / mm ３ Above 1.00 x 10 １０ pieces / mm ３ The number of the internal pores 22 per unit volume means the number density of the internal pores 22 .

[0048] As shown in Fig. 4, the internal pores 22 can be observed by an optical microscope. Thus, when observed from the top view, the number of the internal pores 22 per unit volume is 1.00 x 10 ８ pieces / mm ３Above 1.00 x 10 １０ pieces / mm ３ The number of the internal pores 22 per unit volume is 1.00×10 ９ pieces / mm ３ Above 1.00 x 10 １０ pieces / mm ３ It is better if it is less than 5.00 x 10 ９ pieces / mm ３ Above 1.00 x 10 １０ pieces / mm ３ It is even better if it is less than:

[0049] As described above, the pores 20 (internal pores 22) can scatter the excitation light and the fluorescence. If the number of internal pores 22 per unit volume of a phosphor substrate is small, the phosphor substrate functions as a light guide plate, trapping the generated fluorescence within the phosphor substrate and making it difficult to extract the generated fluorescence from the phosphor substrate.

[0050] In this embodiment, the number of the internal pores 22 per unit volume is 1.00×10 ８ pieces / mm ３ As described above, the number of pores 20 (internal pores 22) per unit volume is sufficiently high. Therefore, the excitation light and fluorescence can be scattered, and the generated fluorescence can be easily extracted to the outside of the phosphor substrate 1. As a result, the emitted light L3 emitted from the phosphor substrate 1 increases, and in other words, the brightness can be increased. In addition, the number of internal pores 22 per unit volume is 1.00×10 ９ pieces / mm ３ When the number of the internal pores 22 per unit volume is 5.00×10 or more, the brightness can be further increased. ９ pieces / mm ３ With this, the brightness can be further increased.

[0051] The number of the internal pores 22 per unit volume is 1.00×10 １０ pieces / mm ３ By setting the ratio of the phosphor portion 10 to the phosphor substrate 1 to be equal to or less than 1000 nm, the ratio of the phosphor portion 10 to the phosphor substrate 1 can be increased sufficiently, and therefore the excitation light can be converted sufficiently.

[0052] Next, the circularity of the internal pores 22 will be described.

[0053] The circularity of the internal pores 22 is C, the area of ​​the internal pores 22 is D, and the perimeter of the internal pores 22 is E. The circularity, C, is expressed by the following formula (1).

[0054] C = 4π × {D / (E ２ )} Formula (1)

[0055] D and E are values ​​calculated by image analysis of the optical microscope photograph shown in Fig. 4. C is a value between 0 and 1, and the closer C is to 1, the closer the internal pores 22 are to being perfectly circular.

[0056] Here, the number of the internal pores 22 is defined as A, and the number of the internal pores 22 having a circularity of 0.6 or more among the internal pores 22 is defined as B. In this case, A and B satisfy the formula (2).

[0057] B / A≧0.7 Formula (2)

[0058] That is, the ratio of the internal pores 22 having a circularity of 0.6 or more to the internal pores 22 is 70% or more. When formula (2) is satisfied, the number of the internal pores 22 can be sufficiently increased, and the number of the internal pores 22 per unit volume can be increased to 1.00×10 ８ pieces / mm ３ It can be more than that.

[0059] In this embodiment, the average size of the multiple internal pores 22 is 0.5 μm or more and 10 μm or less. Therefore, the average size of the multiple pores 20 is also 0.5 μm or more and 10 μm or less. The average size is, for example, an arithmetic mean, but other average values ​​may also be used. Note that the size of one internal pore 22 means, for example, the distance from one end to the other end of the internal pore 22 in the longitudinal direction as shown in an optical microscope photograph.

[0060] When the average size of the plurality of internal pores 22 is within the above range, the plurality of internal pores 22 can scatter the excitation light and fluorescence, and the generated fluorescence can be more easily extracted to the outside of the phosphor substrate 1, thereby increasing the brightness. In other words, a phosphor substrate 1 with high brightness can be realized.

[0061] The average size of the plurality of internal pores 22 is not limited to the above, but may be 200 nm or more and 3 μm or less, and is preferably in the range of 300 nm or more and 2 μm or less.

[0062] [Examples] Below, explanations will be given using four phosphor substrates, namely, phosphor substrates according to Comparative Example 1, Example 1, Example 2, and Example 3. For simplicity, the phosphor substrate according to Comparative Example 1 may be referred to as phosphor substrate 1A, the phosphor substrate according to Example 3 as phosphor substrate 1B, the phosphor substrate according to Example 1 as phosphor substrate 1C, and the phosphor substrate according to Example 2 as phosphor substrate 1D.

[0063] FIG. 5 is a table showing the characteristics of the phosphor substrate 1A according to Comparative Example 1, the phosphor substrate 1B according to Example 3, the phosphor substrate 1C according to Example 1, and the phosphor substrate 1D according to Example 2.

[0064] First, the four phosphor substrates 1A to 1D will be described.

[0065] Each of the four phosphor substrates is a substrate including a phosphor portion 10 and a plurality of pores 20. Phosphor substrate 1A according to Comparative Example 1 includes a phosphor portion 10, a plurality of pores 20, and a light-transmitting phase made of a plurality of alumina particles. Phosphor substrates 1B to 1D according to Examples 3, 1, and 2 are substrates made only of a phosphor portion 10 and a plurality of pores 20. Phosphor substrates 1B to 1D according to Examples 3, 1, and 2 are examples of the phosphor substrate 1 according to the present embodiment.

[0066] Each of the phosphor substrates 1B to 1D according to Example 3, Example 1, and Example 2 is manufactured by, for example, mixing and firing raw materials. For example, by changing the firing conditions for each of the phosphor substrates 1B to 1D, it is possible to manufacture phosphor substrates 1B to 1D each having different properties. Note that the phosphor substrate 1A according to Comparative Example 1 is manufactured by adding raw materials for the light-transmitting phase, mixing them, and firing them, in comparison with each of the phosphor substrates 1B to 1D.

[0067] In Figure 5, the characteristics of the four phosphor substrates 1A to 1D are shown, including the phosphor ratio, density of the phosphor substrate, number of internal pores 22 per unit volume, proportion of internal pores 22 with a circularity of 0.6 or more, diffuse reflectance, and brightness.

[0068] The phosphor ratio is a value indicating the ratio of the phosphor portion 10 to the phosphor portion 10 and the light-transmitting phase in each of the phosphor substrates 1A to 1D. For example, when the surface of each of the phosphor substrates 1A to 1D (for example, the surface corresponding to the first surface 1a) is observed, the ratio of the area occupied by the phosphor portion 10 to the total area of ​​the area occupied by the phosphor portion 10 and the area occupied by the light-transmitting phase corresponds to the phosphor ratio.

[0069] The density of the phosphor substrate is the density (mass density) of each of the phosphor substrates 1A to 1D, and is measured by, for example, the Archimedes method.

[0070] The number of internal pores 22 per unit volume means the number density of the internal pores 22, and is calculated by observing the surfaces of the phosphor substrates 1A to 1D, as shown in FIG.

[0071] The proportion of internal pores 22 with a circularity of 0.6 or more is the proportion of internal pores 22 with a circularity of 0.6 or more among the multiple internal pores 22, and is calculated by observing the surfaces of each of the phosphor substrates 1A to 1D and performing image analysis, as shown in Figure 4.

[0072] The diffuse reflectance indicates the degree of light scattering (diffusion) of each of the phosphor substrates 1A to 1D. A higher diffuse reflectance value indicates a higher degree of light scattering. Note that blue light was used to measure the diffuse reflectance here.

[0073] 5 shows that in the phosphor substrate 1A, the proportion of internal pores 22 with a circularity of 0.6 or more is 80% or more, and the diffuse reflectance is 5.0% or more and 8.0% or less. This is because variations in the numerical ranges occur due to variations in manufacturing.

[0074] Brightness represents the brightness per area of ​​light emitted in a certain direction from a light source with a wide spread. In this evaluation test, the intensity (brightness) of light in the reflected direction when 450 nm blue light was irradiated onto each of the mirror-finished 150 μm phosphor substrates 1A to 1D was measured using a luminance meter (TOPCON, SR-5000). The blue light was irradiated by a blue LD (laser diameter φ1 mm, output 0.05 W (with ND filter)). The brightness (intensity) of the light in the reflected direction was evaluated within a 1.5 mm square range from the center of each of the phosphor substrates 1A to 1D.

[0075] First, the phosphor substrate 1A according to Comparative Example 1 and the phosphor substrate 1C according to Example 1 will be compared.

[0076] The phosphor substrate 1A has a light-transmitting phase. Therefore, the phosphor ratio in the phosphor substrate 1A is 70%, and the density of the phosphor substrate 1A is 4.29 g / cm ３ The phosphor ceramic that is the main component of the phosphor portion 10 included in the phosphor substrate 1A is YAG, and the density of the phosphor substrate 1A is less than 95% of the theoretical density of YAG.

[0077] In the phosphor substrate 1A having a light-transmitting phase, the proportion of the phosphor portion 10 in the phosphor substrate 1A is reduced by the amount of the light-transmitting phase, making it difficult to increase the excitation light conversion efficiency for converting excitation light into fluorescence, and therefore making it difficult to increase the brightness. Therefore, the brightness of the phosphor substrate 1A is 1.173 mcd / m ２ , which is a low value.

[0078] On the other hand, like the phosphor substrate 1 according to the present embodiment, the phosphor substrate 1C is a substrate that does not have a light-transmitting phase and is composed only of a phosphor portion 10 (fluorescent phase) made of phosphor ceramics and a plurality of pores 20. Therefore, in the phosphor substrate 1C, the fluorescent phase is 100%, the phosphor ratio is 100%, and the density of the phosphor substrate 1C is 4.47 g / cm ３ The phosphor ceramic that is the main component of the phosphor portion 10 included in the phosphor substrate 1C is YAG, and the density of the phosphor substrate 1A is 95% or more of the theoretical density of YAG.

[0079] Thus, phosphor substrate 1C, which is an example of phosphor substrate 1 according to this embodiment, is composed only of phosphor portions 10 and a plurality of pores 20, and its density is 95% or more of the theoretical density of phosphor ceramics, so that the proportion of phosphor portions 10 in phosphor substrate 1C is sufficiently high. Therefore, phosphor substrate 1C can convert excitation light more satisfactorily than phosphor substrate 1A, which has a translucent phase. In other words, it can increase the excitation light conversion efficiency for converting excitation light into fluorescence, and therefore increase brightness. The brightness of phosphor substrate 1C is 1.688 mcd / m ２ and exhibits a higher value than the luminance of phosphor substrate 1A. Note that, like phosphor substrate 1C, phosphor substrate 1D according to Example 2 also consists only of phosphor portion 10 and a plurality of pores 20, and its density is 95% or more of the theoretical density of phosphor ceramics. Therefore, for the same reason as phosphor substrate 1C, phosphor substrate 1D also exhibits a higher value than the luminance of phosphor substrate 1A. Furthermore, phosphor substrate 1B according to Example 3 also exhibits a higher value than the luminance of phosphor substrate 1A, for the same reason as phosphor substrate 1C.

[0080] Next, the phosphor substrate 1B according to Example 3 and the phosphor substrate 1C according to Example 1 will be considered.

[0081] The phosphor substrate 1B and the phosphor substrate 1C have a plurality of internal pores 22 with a number per unit volume of 1.00×10 ８ pieces / mm ３ Above 1.00 x 10 １０ pieces / mm ３or less, the number of internal pores 22 per unit volume is sufficiently large to scatter the excitation light and fluorescence. In other words, the generated fluorescence can be easily extracted to the outside of the phosphor substrate 1B and the phosphor substrate 1C.

[0082] Furthermore, the phosphor substrate 1C has a higher number of internal pores 22 per unit volume and a higher proportion of internal pores 22 with a circularity of 0.6 or more than that of the phosphor substrate 1B.

[0083] A phosphor substrate 1C having a high number of internal pores 22 per unit volume and a high proportion of internal pores 22 with a circularity of 0.6 or greater is less able to function as a light guide plate than phosphor substrate 1B. This makes it more difficult for excitation light incident on phosphor substrate 1C to be guided, and also makes it more difficult for fluorescence to be guided throughout the entire phosphor substrate 1C, thereby improving extraction efficiency. In other words, phosphor substrate 1C can more effectively scatter excitation light and fluorescence, making it easier to extract the generated fluorescence from phosphor substrate 1C. As a result, the amount of output light L3 emitted from phosphor substrate 1C increases, thereby improving brightness.

[0084] For the above reasons, the luminance of the phosphor substrate 1C is 1.688 mcd / m ２ and the luminance of the phosphor substrate 1B (1.590 mcd / m ２ ) is higher than that of the phosphor substrate 1B. Like the phosphor substrate 1C, the phosphor substrate 1D according to Example 2 also has a sufficiently high number of internal pores 22 per unit volume and a sufficiently high proportion of internal pores 22 with a circularity of 0.6 or more. Therefore, for the same reason as the phosphor substrate 1C, the luminance of the phosphor substrate 1D is also higher than that of the phosphor substrate 1B.

[0085] The above comparison of the phosphor substrate 1A according to Comparative Example 1 with the phosphor substrates 1B to 1D according to Examples 3, 1, and 2 reveals the following. That is, in this embodiment, the phosphor substrate 1 is composed only of the phosphor portion 10 and a plurality of pores 20, and its density is 95% or more of the theoretical density of phosphor ceramics, so the proportion of the phosphor portion 10 in the phosphor substrate 1 is sufficiently high. Therefore, the phosphor substrate 1 can increase the excitation light conversion efficiency for converting excitation light into fluorescence. Furthermore, the number of the plurality of internal pores 22 per unit volume is 1.00×10 ８ pieces / mm ３ Above 1.00 x 10 １０ pieces / mm ３ or less, the number of the multiple internal pores 22 per unit volume is sufficiently large, allowing the excitation light and fluorescence to be scattered and the generated fluorescence to be easily extracted to the outside of the phosphor substrate 1. In this way, the phosphor substrate 1 has a high excitation light conversion efficiency for converting excitation light to fluorescence, and the generated fluorescence can be easily extracted to the outside of the phosphor substrate 1, thereby increasing the brightness.

[0086] Furthermore, the phosphor substrate 1C according to Example 1 and the phosphor substrate 1D according to Example 2 are compared. As shown in FIG. 5, the luminance of the phosphor substrate 1C (1.688 mcd / m ２ ) is the luminance of the phosphor substrate 1D (1.675 mcd / m ２ ) is higher than

[0087] In the phosphor substrate 1C, the density of the phosphor substrate 1C is 4.47 g / cm ３ The phosphor ceramic that is the main component of phosphor portion 10 included in phosphor substrate 1C is YAG, and the density of phosphor substrate 1C is approximately 98.2% of the theoretical density of YAG. In other words, the density of phosphor substrate 1C is 98% or more of the theoretical density of YAG.

[0088] In the phosphor substrate 1D, the density of the phosphor substrate 1D is 4.38 g / cm ３The phosphor ceramic that is the main component of the phosphor portion 10 included in the phosphor substrate 1D is YAG, and the density of the phosphor substrate 1D is approximately 96.2% of the theoretical density of YAG. In other words, the density of the phosphor substrate 1D is 95% or more, but less than 98%, of the theoretical density of YAG.

[0089] Thus, the density (mass density) of the phosphor substrate 1C according to Example 1 is higher than the density (mass density) of the phosphor substrate 1D according to Example 2. More specifically, the density of the phosphor substrate 1C is 98% or more of the theoretical density of phosphor ceramics (YAG). Therefore, the phosphor substrate 1C can convert excitation light more efficiently than the phosphor substrate 1D, which means that the excitation light conversion efficiency for converting excitation light into fluorescence can be increased. As a result, the luminance of the phosphor substrate 1C is higher than that of the phosphor substrate 1D.

[0090] The relationship between the number of multiple internal pores 22 per unit volume and the theoretical density ratio of the phosphor ceramic (YAG) will be described. FIG. 6 is a diagram showing the relationship between the theoretical density ratio of the phosphor ceramic (YAG) and the number of pores depending on the diameter of the pores according to this embodiment. The pores shown in FIG. 6 are an example of multiple internal pores 22. Here, calculations were performed using perfectly circular pores with a circularity of 1. The upper and lower limits of the number of pores per unit volume were calculated when the pore diameter (φ) was 200 nm or more and 3 μm or less. When the theoretical density ratio of the phosphor ceramic (YAG) was 0.95 or more and 0.995 or less, the number of pores per unit volume was 1.00×10 ６ pieces / mm ３ Above 1.00 x 10 １０ pieces / mm ３ As the pore diameter increases for the same theoretical density ratio of phosphor ceramics (YAG), the number of pores decreases, which reduces the probability of light diffusion (scattering) and makes light guided more likely. This reduces the extraction efficiency and brightness. Therefore, the number of pores per unit volume, i.e., the number of multiple internal pores 22 per unit volume, is 1.00 × 10 ８ pieces / mm ３ Above 1.00 x 10 １０ pieces / mm ３ The following is good:

[0091] The relationship between the number of internal pores 22 per unit volume and the diffuse reflectance will now be described.

[0092] The inventors have clarified through simulations that the higher the number of the internal pores 22 per unit volume, the higher the diffuse reflectance. Based on the results of this simulation, the number of the internal pores 22 per unit volume is set to 1.00×10 ８ pieces / mm ３ By setting the number of the internal pores 22 per unit volume within this range, the excitation light and fluorescence can be scattered in the phosphor substrate 1, and the generated fluorescence can be easily extracted to the outside of the phosphor substrate 1. In addition, it has become clear that it is preferable to set the number of the internal pores 22 per unit volume within this range. １０ pieces / mm ３ By setting the density (mass density) of the phosphor portions 10 in the phosphor substrate 1 to the value below, the density (mass density) of the phosphor portions 10 can be sufficiently increased, thereby increasing the excitation light conversion efficiency.

[0093] In this way, by controlling the number of multiple internal pores 22 per unit volume, it is possible to easily extract the generated fluorescence outside the phosphor substrate 1 while also increasing the excitation light conversion efficiency, thereby ultimately increasing the brightness.

[0094] [Modifications] Modifications of the embodiment will be described below, focusing on differences from the embodiment, and omitting or simplifying the description of commonalities.

[0095] FIG. 7 is a cross-sectional view showing the configuration of a phosphor device 100 according to the first modification of the embodiment.

[0096] The phosphor device 100 according to this modification is a device including the phosphor substrate 1 according to the embodiment and a support substrate 30 .

[0097] The phosphor substrate 1 is bonded to the support substrate 30. The phosphor substrate 1 is directly bonded to the support substrate 30. That is, the phosphor section 10 and the support substrate 30 are connected without an adhesive. The phosphor substrate 1 may be bonded to the support substrate 30 via an intermediary such as an Ag alloy such as AgPdCu (APC) or SnAgCu, an Au alloy such as Ag or AuSn, or a metal such as Au, Al, Pt, Rh, Pd, or Ti.

[0098] The support substrate 30 is a rigid substrate that supports the phosphor, and has higher rigidity than the phosphor substrate 1 .

[0099] Furthermore, the support substrate 30 not only has the function of supporting the phosphor substrate 1, but also has the function of dissipating heat generated by the phosphor substrate 1. In other words, the support substrate 30 also functions as a heat dissipation substrate. Therefore, the support substrate 30 is preferably made of a material with high thermal conductivity. Specifically, the thermal conductivity of the support substrate 30 is preferably higher than the thermal conductivity of the phosphor substrate 1. This allows the heat generated by the phosphor substrate 1 to be efficiently conducted to the support substrate 30.

[0100] A substrate having optical transparency, such as a glass substrate, may be used as the support substrate 30. More specifically, the support substrate 30 is optically transparent to the excitation light.

[0101] The support substrate 30 has a rectangular flat plate shape with a constant thickness. The shape of the support substrate 30 when viewed from above is rectangular, but is not limited to this. The shape of the support substrate 30 when viewed from above may be circular, for example.

[0102] The thickness of the support substrate 30 is thicker than the thickness of the phosphor substrate 1. In this modification, the thickness of the support substrate 30 is 400 μm or more. Specifically, the thickness of the support substrate 30 is five times or more the thickness of the phosphor substrate 1. The thickness of the support substrate 30 is preferably 1 mm or more.

[0103] Next, an example of use of phosphor device 100 according to this modification will be described. As shown in Fig. 7, light L1 from light source 2 is incident on phosphor device 100, and output light L3 is emitted from phosphor device 100. Note that light source 2 and phosphor device 100 constitute a light source module.

[0104] Light L1 emitted from light source 2 is incident as excitation light on phosphor section 10 of phosphor substrate 1. More specifically, light L1 emitted from light source 2 passes through optically transparent support substrate 30 and enters phosphor section 10. As a result, light L2 (fluorescence) of a predetermined wavelength is generated in phosphor section 10. Light L2 generated in phosphor section 10 is mixed with another portion of light L1 from light source 2 that has entered phosphor section 10 and is light L1 that has not been wavelength-converted, and this mixed light is emitted from phosphor section 10 (i.e., phosphor device 100) as emitted light L3.

[0105] For example, a case will be described in which the light source 2 is a laser light source that emits blue laser light, and the phosphor unit 10 is made of a yellow phosphor material made of YAG phosphor ceramics. In this case, when light L1, which is laser light emitted from the light source 2, is incident on the phosphor unit 10, the phosphor unit 10 is excited by absorbing a portion of the laser light (blue light), and yellow fluorescence is generated in the phosphor unit 10 as light L2. The yellow light L2 generated in the phosphor unit 10 and the blue light L1 that was not wavelength-converted in the phosphor unit 10 are mixed together to become white light, which is emitted from the first surface 1a of the phosphor unit 10. In other words, white light, a mixture of the yellow light L2 and the blue light L1, is emitted from the first surface 1a of the phosphor unit 10 as emitted light L3.

[0106] As described in the embodiment, the phosphor substrate 1 has high luminance. Since the phosphor device 100 according to this modification includes such a phosphor substrate 1, the phosphor device 100 also has high luminance.

[0107] [Effects, etc.] Invention 1 is a phosphor substrate 1, which comprises only a phosphor portion 10 having a phosphor ceramic as a main component and a plurality of pores 20 provided in the phosphor portion 10, the density of the phosphor substrate 1 being 95% or more of the theoretical density of the phosphor ceramic, the plurality of pores 20 having a plurality of internal pores 22 located on the surface of the phosphor substrate 1, and the number of the plurality of internal pores 22 per unit volume being 1.00×10 ８ pieces / mm ３ Above 1.00 x 10 １０ pieces / mm ３ The following is the result.

[0108] In such a phosphor substrate 1, the phosphor substrate 1 is composed only of the phosphor portion 10 and the plurality of pores 20, and the density is 95% or more of the theoretical density of phosphor ceramics, so that the proportion of the phosphor portion 10 in the phosphor substrate 1 is sufficiently high. Therefore, the phosphor substrate 1 can improve the excitation light conversion efficiency for converting excitation light into fluorescence. Furthermore, the number of the plurality of internal pores 22 per unit volume is 1.00×10 ８ pieces / mm ３ Above 1.00 x 10 １０ pieces / mm ３ or less, the number of the internal pores 22 per unit volume is sufficiently high, allowing the excitation light and fluorescence to be scattered and the generated fluorescence to be easily extracted to the outside of the phosphor substrate 1. In this way, the phosphor substrate 1 has a high excitation light conversion efficiency for converting excitation light to fluorescence, and the generated fluorescence can be easily extracted to the outside of the phosphor substrate 1, thereby increasing brightness. In other words, a phosphor substrate 1 with high brightness can be realized.

[0109] Invention 2 is a phosphor substrate 1 described in Invention 1, in which, when the number of the multiple internal pores 22 is A and the number of the multiple internal pores 22 having a circularity of 0.6 or more is B, A and B satisfy B / A≧0.7.

[0110] This allows the number of the internal pores 22 to be sufficiently increased, and the number of the internal pores 22 per unit volume can be increased to 1.00×10 ８ pieces / mm ３As a result, it becomes easy to scatter the excitation light and the fluorescence, and the generated fluorescence can be easily extracted to the outside of the phosphor substrate 1, which means that a phosphor substrate 1 with high brightness can be realized.

[0111] Invention 3 is the phosphor substrate 1 according to Invention 1 or 2, in which the phosphor ceramic is an yttrium aluminum garnet phosphor material.

[0112] This allows the phosphor substrate 1 to emit outgoing light L3 containing yellow light as fluorescence.

[0113] Invention 4 is the phosphor substrate 1 according to any one of Inventions 1 to 3, wherein the density of the phosphor substrate 1 is 98% or more of the theoretical density of the phosphor ceramic.

[0114] As a result, as shown by the phosphor substrate 1C according to Example 1, which is an example of the phosphor substrate 1, the proportion of the phosphor portions 10 in the phosphor substrate 1C is higher, and therefore the excitation light can be sufficiently converted. In other words, the phosphor substrate 1C can further increase the excitation light conversion efficiency for converting excitation light into fluorescence. As a result, a phosphor substrate 1 (phosphor substrate 1C) with high brightness can be realized.

[0115] Invention 5 is the phosphor substrate 1 according to any one of Inventions 1 to 4, wherein the average size of the plurality of internal pores 22 is 200 nm or more and 3 μm or less.

[0116] This allows the internal pores 22 to scatter the excitation light and fluorescence, and the generated fluorescence can be more easily extracted to the outside of the phosphor substrate 1, thereby increasing brightness. In other words, a phosphor substrate 1 with high brightness can be realized.

[0117] A sixth aspect of the present invention is a phosphor device 100 comprising the phosphor substrate 1 according to any one of the first to fifth aspects of the present invention and a support substrate 30 that supports the phosphor substrate 1 .

[0118] As described above, the phosphor substrate 1 has high brightness. Since the phosphor device 100 includes such a phosphor substrate 1, the phosphor device 100 also has high brightness.

[0119] (Others) Although the phosphor substrate and the like according to the present invention have been described based on the above-mentioned embodiment, the present invention is not limited to the above-mentioned embodiment and modifications.

[0120] Although the phosphor device 100 according to the modified example was a light-transmitting device, this is not limited thereto and may also be a light-reflecting device. In this case, a light-reflecting layer that reflects excitation light and fluorescence is provided between the phosphor substrate 1 and the support substrate 30. This light-reflecting layer may be, for example, a dielectric multilayer film or a metal film. In this case, the support substrate 30 may be an aluminum substrate (Al substrate), a copper substrate (Cu substrate), a molybdenum substrate (Mo substrate), a tungsten substrate (W substrate), a silicon substrate (Si substrate), a silicon carbide substrate (SiC substrate), an aluminum nitride substrate (AlN substrate), or the like.

[0121] In addition, the present invention also includes forms obtained by applying various modifications to each embodiment that a person skilled in the art would think of, and forms realized by arbitrarily combining the components and functions of each embodiment within the scope of the present invention.

[0122] 1, 1A, 1B, 1C, 1D Phosphor substrate 10 Phosphor portion 20 Pore 22 Internal pore 30 Support substrate 100 Phosphor device

Claims

1. A phosphor substrate comprising only a phosphor portion having a phosphor ceramic as a main component and a plurality of pores provided in the phosphor portion, wherein the density of the phosphor substrate is 95% or more of the theoretical density of the phosphor ceramic, the plurality of pores include a plurality of internal pores located inside the phosphor substrate, and the number of the plurality of internal pores per unit volume is 1.00 x 10 ８ pieces / mm ３ Above 1.00 x 10 １０ pieces / mm ３ Below is a phosphor substrate.

2. The phosphor substrate according to claim 1, wherein A and B satisfy the relationship B / A≧0.7, where A is the number of the plurality of internal pores and B is the number of the plurality of internal pores having a circularity of 0.6 or more.

3. The phosphor substrate according to claim 1, wherein the phosphor ceramic is an yttrium aluminum garnet phosphor material.

4. The phosphor substrate according to claim 1, wherein the density of the phosphor substrate is 98% or more of the theoretical density of the phosphor ceramic.

5. The phosphor substrate according to claim 1, wherein the average size of the plurality of internal pores is 200 nm or more and 3 μm or less.

6. A phosphor device comprising: the phosphor substrate according to any one of claims 1 to 5; and a support substrate that supports the phosphor substrate.

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