Composite ceramic, phosphor element, laser lighting device, and method for producing composite ceramic

Abstract

A composite ceramic (1) comprises a sintered body including a nitride-based phosphor component (3) and Al2O3 as a main component of a matrix component (4), the composite ceramic (1) having a thickness of 220 μm or less and light absorptance of 21% or less with respect to incident light having a wavelength of 630 nm, wherein the matrix component (4) surrounding the nitride-based phosphor component (3) is sintered.

Description

Composite ceramics, phosphor element, laser lighting device, and method for manufacturing composite ceramics

[0001] The present disclosure relates to a composite ceramic, a phosphor element, a laser lighting device, and a method for manufacturing the composite ceramic.

[0002] Ceramic phosphors with excellent thermal conductivity are attracting attention as phosphors for laser lighting. ３ Al ５ O １２ ) and Al ２ O ３ Composite ceramic phosphors, which are made by mixing them with an inorganic matrix such as the above to form ceramics, have been commercialized in part due to their high efficiency and ease of production, and are used in automobile headlights and the like.

[0003] As with early LEDs, it is known that pseudo-white light produced by mixing blue laser light with a yellow phosphor (a phosphor with emission intensity in the yellow region) made of a garnet-based phosphor cannot produce phosphor ceramics for laser lighting with a low color temperature or good color rendering. It is also known that simply mixing a red phosphor (a phosphor with emission intensity in the red region) into a composite ceramic of a garnet-based phosphor and an inorganic matrix with the aim of lowering the color temperature or improving the color rendering does not produce a sufficiently efficient composite ceramic. To address these issues, the use of composite ceramic phosphors made of a nitride-based phosphor and an inorganic matrix has been investigated in recent years (see Patent Document 1).

[0004] WO2016 / 117623

[0005] The composite ceramic of nitride-based phosphors using fluoride as an inorganic matrix as described in Patent Document 1 has the problem that it does not have sufficient thermal conductivity and mechanical strength. ２ O ３ It is thought that composite ceramics using nitride-based phosphors and Al have high mechanical strength. ２ O ３Composite ceramics with silicon have the problem of low internal quantum efficiency.

[0006] One aspect of the present disclosure has been made in consideration of the above-described problems, and an object of the present disclosure is to provide a composite ceramic containing a red phosphor for laser illumination and having good internal quantum efficiency, a phosphor element and a laser illumination device each including the composite ceramic, and a method for manufacturing such a composite ceramic.

[0007] In order to solve the above problems, a composite ceramic according to one embodiment of the present disclosure is a composite ceramic comprising a nitride-based phosphor component and Al as a main component of a matrix component. ２ O ３ and a composite ceramic comprising a sintered body containing the above-mentioned matrix component, the matrix component having a thickness of 220 μm or less and an optical absorptivity of 21% or less for incident light having a wavelength of 630 nm, the matrix component being sintered to surround the nitride-based phosphor component.

[0008] In order to solve the above problems, a phosphor element according to one aspect of the present disclosure includes the composite ceramic according to one aspect of the present disclosure and a substrate that fixes the composite ceramic.

[0009] In order to solve the above problems, a laser illumination device according to an aspect of the present disclosure includes: a phosphor element according to an aspect of the present disclosure; a laser light source that irradiates excitation light onto the composite ceramic in the phosphor element; and a focusing member that focuses light output from the composite ceramic in the phosphor element.

[0010] In order to solve the above-described problems, a method for manufacturing a composite ceramic according to one embodiment of the present disclosure includes a mixing step of mixing a first raw material powder containing a nitride-based phosphor component and a matrix component; a first raw material powder containing step of containing the mixed first raw material powder in a molding die; a sintering step of sintering the first raw material powder contained in the molding die by a spark plasma sintering method or a hot press method; and a demolding step of removing the sintered body obtained in the sintering step from the molding die, wherein the thickness of the sintered body is 220 μm or less.

[0011] According to one aspect of the present disclosure, it is possible to provide a composite ceramic containing a red phosphor for laser illumination and having good internal quantum efficiency, a phosphor element and a laser illumination device including the composite ceramic, and a method for manufacturing such a composite ceramic.

[0012] FIG. 1 is a cross-sectional view showing the structure of a composite ceramic according to an embodiment of the present disclosure. FIG. 2 is a flowchart showing a method for manufacturing a composite ceramic according to an embodiment of the present disclosure. FIG. 3 is a flowchart showing an example of a method for manufacturing the phosphor element shown in FIG. 3. FIG. 4 is a cross-sectional view showing a laser illumination device according to an embodiment of the present disclosure. FIG. 5 is a graph showing the internal quantum efficiency of the composite ceramic obtained in Example 1 for each thickness. FIG. 6 is a diagram showing the optical absorption spectrum of a representative thickness of Example 1 with a solid line and the optical absorption spectrum of Comparative Example 1 with a dashed line. FIG. 7 is a diagram showing the optical absorption spectrum of Example 4. FIG. 8 is a diagram showing the laser excitation characteristics of a phosphor element using the composite ceramic of Example 4.

[0013] Embodiments of the present disclosure are described below. For ease of explanation, components having the same functions as those previously described will be denoted by the same reference numerals, and their descriptions will not be repeated. Hereinafter, the expression "A to B" for two numbers A and B means "greater than or equal to A and less than or equal to B," unless otherwise specified.

[0014] [Composite Ceramic 1] A composite ceramic according to one embodiment of the present disclosure is a ceramic comprising a nitride-based phosphor component and Al as a main component of a matrix component. ２ O ３ The composite ceramic has a thickness of 220 μm or less and an optical absorptivity of 21% or less for incident light with a wavelength of 630 nm, and in the composite ceramic, the matrix component is sintered to surround the nitride-based phosphor component.

[0015] The main component of the matrix is ​​Al ２ O ３As described in Patent Document 1, the use of alumina reduces the internal quantum efficiency of composite ceramics containing nitride-based phosphors. However, the cause of this has not been thoroughly investigated. That is, no investigation has been conducted into whether the nitride-based phosphors contained in the composite ceramics are degraded, or whether there are other causes for the reduction in internal quantum efficiency despite the absence of nitride-based phosphor degradation. After extensive research, the inventors discovered for the first time that there is little or no degradation of the nitride-based phosphors contained in composite ceramics, and that the composite ceramics have a high light absorption rate. They then discovered that the internal quantum efficiency can be dramatically improved by reducing the thickness of the composite ceramics, leading to the completion of the present invention.

[0016] Fig. 1 is a cross-sectional view showing an example of the structure of a composite ceramic 1 according to one embodiment of the present disclosure. The composite ceramic 1 is a ceramic composite formed of a sintered body containing a nitride-based phosphor component 3 and a matrix component 4. The composite ceramic 1 shown in Fig. 1 contains the nitride-based phosphor component 3 and the matrix component 4, and has a structure in which the matrix component 4 surrounds the nitride-based phosphor component 3 and is sintered. Note that Fig. 1 shows an example in which a garnet-based phosphor component 2 is further included.

[0017] As shown in Fig. 1, the composite ceramic 1 has a sea-island structure in which the nitride-based phosphor component 3 is mixed in the form of islands in the matrix component 4. In other words, the composite ceramic 1 has a structure in which the nitride-based phosphor component 3 is dispersed in the form of islands in the matrix component 4, which appears to be a relatively continuous sea. The matrix component 4 fills the spaces between the nitride-based phosphor components 3 dispersed in the form of islands. The nitride-based phosphor component 3 and the matrix component 4 are fixed to each other.

[0018] The composite ceramic 1 has at least two phases: a phosphor phase consisting of a nitride-based phosphor component 3 and a matrix phase consisting of a matrix component 4. Therefore, the composite ceramic 1 has a structure in which at least the two phases are mixed and adjacent phases are bonded together. Here, a structure in which at least the two phases are mixed and adjacent phases are bonded together refers to a structure in which the two phases are not dissolved in a solid but are separated into their respective phase regions in the solid, with adjacent phases being bonded together. This also includes cases in which sintering aids or impurities are present at grain boundaries. Alternatively, even if there is a slight altered phase or molten phase between particles, a composite ceramic can be considered as a material that basically has a solid two-phase structure.

[0019] Note that a solid solution in which at least adjacent phases among two or more phases form a solid solution with each other is excluded from the composite ceramic 1. Also excluded from the composite ceramic 1 are a bonded material in which two or more phases are simply bonded directly, and a composition in which at least the two phases are solidified with at least one of an inorganic glass and an organic binder.

[0020] The composite ceramic 1 may be a multi-wavelength luminescent ceramic composite made of a sintered body containing a matrix component and a nitride-based phosphor component 3 having two or more emission wavelengths. In this case, the composite ceramic 1 has a structure in which a plurality of nitride-based phosphor components having different emission wavelengths are mixed as different phases.

[0021] 1 , the composite ceramic 1 may further include a garnet-based phosphor component 2. That is, the composite ceramic 1 may have a structure in which a matrix component 4 surrounds and sinters the nitride-based phosphor component 3 and the garnet-based phosphor component 2. In this case, the composite ceramic 1 has a structure in which the nitride-based phosphor component 3 and the garnet-based phosphor component 2 are mixed as different phases.

[0022] (Nitride-Based Phosphor Component 3) In the present disclosure, the nitride-based phosphor component 3 refers to a phosphor containing nitrogen. Specific examples of the nitride-based phosphor component 3 include at least one phosphor selected from the group consisting of nitride-based phosphors and oxynitride-based phosphors.

[0023] The nitride-based phosphor component 3 is a red-based phosphor with excellent fluorescent properties that emits red-based fluorescence ranging from red to orange; for example, it emits red-based fluorescence when exposed to blue excitation light. Furthermore, the excitation light that does not contribute to excitation is scattered and transmitted. Therefore, the nitride-based phosphor component 3 outputs blue scattered light and red-based fluorescence. By including the nitride-based phosphor component 3 in the composite ceramic 1, a composite ceramic that emits incandescent-colored fluorescence can be obtained. Furthermore, by including the nitride-based phosphor component 3 in the composite ceramic 1, a composite ceramic 1 with even more excellent fluorescent properties can be obtained.

[0024] The nitride-based phosphor component 3 may be, for example, (La, Y) activated with at least one element of Eu and Ce. ３ Si ６ N １１ , La ３ Si ６ N １１、 CaAlSiN ３ , (Ca,Sr)AlSiN ３ , Sr ２ Si ５ N ８ , (Ba, Sr) ２ Si ５ N ８、 (Ba, Sr, Ca) ２ Si ５ N ８、 and (Ba, Sr) ２ (Si, Al) ５ N ８ Examples of suitable nitride-based phosphors include at least one nitride-based phosphor selected from the group consisting of: (1) In the following, for the sake of convenience, these nitride-based phosphors may be referred to as nitride-based phosphor (A). Eu and Ce are activators and are doped into the crystal.

[0025] As such, the nitride-based phosphor component 3 may be, for example, Eu:Sr ２ Si ５ N ８ , Eu:(Sr,Ba) ２ Si ５ N ８ , Eu: (Ca, Sr, Ba) ２ Si ５ N ８ , Ce:Sr ２ Si ５ N ８ , Ce:(Sr,Ba) ２ Si ５ N ８ , Ce:(Ca,Sr,Ba)Si ５ N ８ , (Eu,Ce):Sr ２ Si ５ N ８ , (Eu, Ce): (Sr, Ba) ２ Si ５ N ８ , (Eu, Ce): (Ca, Sr, Ba) ２ Si ５ N ８ Examples of nitride-based phosphors (A) include:

[0026] By including such alkaline earth silicon nitride as the nitride-based phosphor component 3 in the composite ceramic 1, it is possible to produce a composite ceramic 1 that emits stable reddish fluorescence.

[0027] In these nitride-based phosphors (A), at least one of Si and N in the composition formula may be substituted. When Si is substituted, Si is substituted with Al. When N is substituted, N is substituted with O.

[0028] Therefore, the nitride-based phosphor component 3 is Sr ２ Si ５ N ８ , (Sr, Ba) ２ Si ５ N ８ , or (Ca, Sr, Ba) ２ Si ５ N ８In the above, the phosphor may be a nitride phosphor in which a portion of Si is substituted with Al, or an oxynitride phosphor in which a portion of N is substituted with O. Also, the phosphor may be an oxynitride phosphor in which a portion of Si is substituted with Al and a portion of N is substituted with O. As an example, for example, (Sr, Ba) phosphor activated with at least one element of Eu and Ce. ２ (Si, Al) ５ N ８ , (Sr, Ba) ２ (Si, Al) ５ (N, O) ８ etc.

[0029] By including at least one of such nitride-based phosphors and oxynitride-based phosphors as the nitride-based phosphor component 3 in the composite ceramic 1, a more reliable composite ceramic 1 can be realized.

[0030] The nitride-based phosphor component 3 is, for example, CaAlSiN activated with at least one element of Eu and Ce. ３ and (Ca,Sr)AlSiN ３ For the sake of convenience, these nitride-based phosphors may be referred to as nitride-based phosphors (B) below. Eu and Ce are activators and are doped into the crystal. Thus, the nitride-based phosphor component 3 may be, for example, Eu:CaAlSiN ３ , Eu:(Ca,Sr)AlSiN ３ , Ce:CaAlSiN ３ , Ce:(Ca,Sr)AlSiN ３ , (Eu,Ce):CaAlSiN ３ , (Eu,Ce):(Ca,Sr)AlSiN ３ The nitride-based phosphor (B) may be any of the above.

[0031] Furthermore, as the nitride-based phosphor component 3, in addition to the nitride-based phosphor (A) and the nitride-based phosphor (B), for example, La activated with Ce can be used. ３ Si ６ N １１ , (La, Y) ３ Si ６N １１ etc. may also be used.

[0032] These nitride-based phosphors (A) and (B), as well as nitride-based phosphors other than these nitride-based phosphors (A) and (B), may be used separately or may be used in combination to the extent that they do not form a solid solution or react with each other.

[0033] (Garnet-based phosphor component 2) In the present disclosure, garnet-based phosphor component 2 refers to a phosphor whose crystal structure has a garnet structure. Garnet-based phosphor component 2 is a phosphor with a large refractive index and excellent fluorescent properties, and emits yellow-to-green yellowish fluorescence when exposed to blue excitation light, for example. Furthermore, the excitation light that does not contribute to excitation is scattered and transmitted. Therefore, garnet-based phosphor component 2 outputs blue scattered light and yellowish fluorescence. Garnet-based phosphor component 2 has excellent heat resistance, and can suppress deterioration even when irradiated with strong light from a high-power LD (laser diode) as excitation light, for example.

[0034] For example, a YAG (yttrium aluminum garnet) phosphor can be used as the garnet phosphor component 2. The YAG phosphor refers to a phosphor that can be attributed to the crystal structure of a YAG phosphor.

[0035] Examples of YAG-based phosphors include (Ce, Y) ３ Al ５ O １２ , (Ce, Lu) ３ Al ５ O １２ , (Ce, Lu, Y) ３ Al ５ O １２ , (Ce, Lu, Y) ３ (Al, Ga) ５ O １２The composite ceramic 1 can be easily realized to emit yellowish to greenish yellow fluorescence by including the YAG-based phosphor as the garnet-based phosphor component 2 in the composite ceramic 1. Furthermore, the composite ceramic 1 can be obtained to have more excellent fluorescent properties by including the YAG-based phosphor as the garnet-based phosphor component 2 in the composite ceramic 1.

[0036] In the present invention, the garnet-based phosphor component 2 is not necessarily required. For example, La ３ Si ６ N １１ , (La, Y) ３ Si ６ N １１ The composite ceramic 1 may include a single nitride-based phosphor such as the above and a matrix component 4 .

[0037] (Matrix component 4) Matrix component 4 is Al ２ O ３ The matrix component 4 may contain other matrix components such as MgO, but the matrix component 4 contains aluminum oxide (Al). ２ O ３ is the main component, and therefore has the highest content.

[0038] (Content of each component in composite ceramic 1) The content of the matrix component 4 in composite ceramic 1 is preferably in the range of 31 wt % or more and 90 wt % or less of all components in composite ceramic 1. The inventors have confirmed that by setting the matrix component to 90% or less, i.e., by setting the phosphor component to 10 wt % or more, even if the composite ceramic 1 has relatively large light absorption, the internal quantum efficiency does not decrease significantly. On the other hand, if the matrix component is too low, less than 31 wt %, sintering tends to become difficult. Note that when a sintering aid or scattering material is used, these are also counted as matrix components for convenience.

[0039] According to the studies of the present inventors, the pumping light power resistance can be further improved by increasing the content of the matrix component 4 in the composite ceramic 1. For these reasons, it is preferable that the content of the matrix component 4 in the composite ceramic 1 is set closer to the upper limit of the above range. For this reason, the content of the matrix component 4 in the composite ceramic 1 is more preferably 45 wt % or more, and even more preferably 60 wt % or more.

[0040] In the composite ceramic 1, the total content of the phosphor components including the nitride-based phosphor component 3 is preferably within a range of 10 wt % or more and 69 wt % or less of all the components in the composite ceramic 1. This makes it possible to provide a composite ceramic 1 for laser illumination that contains a red phosphor and that can be manufactured relatively easily.

[0041] In the composite ceramic 1, the content of each of the phosphor components including the nitride-based phosphor component 3 and the garnet-based phosphor component 2 is not particularly limited, and may be appropriately set so that the total content of the phosphor components falls within the above range. By appropriately adjusting each content depending on the type of phosphor component, a desired emission spectrum can be obtained.

[0042] For example, as described above, the garnet-based phosphor component 2 emits yellow or green fluorescence when exposed to blue excitation light. As described above, the nitride-based phosphor component 3 emits reddish fluorescence when exposed to blue excitation light. Furthermore, these phosphors scatter and transmit the excitation light that did not contribute to the excitation. Therefore, when irradiated with blue excitation light, the composite ceramic 1 containing the nitride-based phosphor component 3 and the garnet-based phosphor component 2 outputs reddish, low-color-temperature light that is a mixture of blue scattered light, yellowish fluorescence, and reddish fluorescence.

[0043] The content of the nitride-based phosphor component 3 in the composite ceramic 1 is preferably within a range of 2 wt % or more and 65 wt % or less of all components in the composite ceramic 1, more preferably within a range of 2 wt % or more and 59 wt % or less, and even more preferably within a range of 8 wt % or more and 59 wt % or less.

[0044] The content of the garnet-based phosphor component 2 in the composite ceramic 1 is preferably within a range of 2 wt % or more and 65 wt % or less of all components in the composite ceramic 1, more preferably within a range of 2 wt % or more and 59 wt % or less, and even more preferably within a range of 8 wt % or more and 59 wt % or less.

[0045] This makes it possible to obtain an emission spectrum with a low color temperature that also contains red to orange red fluorescence, which is particularly suitable for home lighting devices, lighting devices for projectors, automobile headlights, outdoor lighting, and particularly lighting devices for long-distance lighting.

[0046] (Particle size of each component in composite ceramic 1) The particle sizes of the garnet-based phosphor component 2 and the nitride-based phosphor component 3 contained in the composite ceramic 1 may be appropriately set depending on the type of the component so as to obtain a desired emission spectrum. Therefore, the particle sizes of the garnet-based phosphor component 2 and the nitride-based phosphor component 3 are not particularly limited.

[0047] However, the raw material powder used as the raw material of the garnet-based phosphor component 2 (in other words, the garnet-based phosphor component before sintering) preferably has a number-average particle size in the range of 3 μm or more and 50 μm or less. When the number-average particle size of the raw material powder of the garnet-based phosphor component 2 is within the above range, it is difficult to react with the matrix component 4 and the nitride-based phosphor component 3.

[0048] Similarly, the raw material powder (in other words, the garnet-based phosphor component before sintering) used as the raw material of the nitride-based phosphor component 3 preferably has a number-average particle size in the range of 3 μm to 50 μm. When the number-average particle size of the raw material powder of the nitride-based phosphor component 3 is within the above range, it is difficult to react with the matrix component 4 or the garnet-based phosphor component 2.

[0049] The number average particle size of these raw material powders may be a measurement value obtained by a scanning electron microscope (SEM), or, in the case where commercially available raw material powders are used as they are, the number average particle size may be the specification described on the delivery note or catalog.

[0050] Depending on the sintering method, these raw material powders may undergo grain growth during sintering. For this reason, the number-average particle size of the garnet-based phosphor component 2 contained per unit volume of the composite ceramic 1 is preferably, for example, in the range of 3 μm or more and 50 μm or less. Similarly, the number-average particle size of the nitride-based phosphor component 3 contained per unit volume of the composite ceramic 1 is preferably, for example, in the range of 3 μm or more and 50 μm or less. Note that, although these phosphor particles ideally have the size of primary particles, they may also have the size of secondary particles formed by the adhesion of several primary particles.

[0051] As described above, the matrix component 4 is sintered while surrounding the phosphor component. Therefore, it is preferable that the number average particle size of the raw material powder used as the raw material of the matrix component 4 (in other words, the matrix component before sintering) is smaller than the number average particle size of each raw material powder of the phosphor component. On the other hand, if the particle size of the raw material powder is too small, problems arise in terms of cost and hygroscopicity. Therefore, from the viewpoint of reactivity, the raw material powder used as the raw material of the matrix component 4 is preferably raw material powder having a number average particle size in the range of 0.01 μm or more and 1 μm or less.

[0052] The number average particle size of the matrix component 4 is preferably smaller than the number average particle size of the phosphor component. Like the raw material powder of the phosphor component, the raw material powder of the matrix component 4 may also undergo grain growth during sintering, depending on the sintering method. Therefore, the number average particle size of the matrix component 4 contained per unit volume of the composite ceramic 1 is preferably within the range of 0.01 μm or more and 10 μm or less. When the number average particle size of the matrix component 4 contained per unit volume of the composite ceramic 1 is within the above range, the sintering temperature can be further reduced, making it easier to produce composite ceramics containing red phosphors over a wider composition range.

[0053] Furthermore, by setting the number average particle size of the matrix component 4 within the above range, the matrix component 4 penetrates into the gaps between the phosphor components. This makes it possible to obtain a sintered body with a dense structure. In this way, by setting the number average particle size of the matrix component 4 within the above range, it is possible to obtain a composite ceramic 1 with a structure in which the matrix component 4 surrounds the phosphor component and is sintered, and adjacent phases are fixed together. Furthermore, by setting the number average particle sizes of the phosphor component and the matrix component 4 within the above ranges, it is possible to optimize the phase structure of the texture of the composite ceramic 1.

[0054] The number average particle diameters of the phosphor component and the matrix component 4 can be measured by SEM. The number average particle diameters of the other components described below can also be measured by SEM in the same manner.

[0055] In this disclosure, "particle size" refers to the particle size when the component to be measured is a perfect sphere. From the perspective of easy control of luminescence characteristics, it is desirable that the garnet-based phosphor component 2, the nitride-based phosphor component 3, the matrix component 4, and their raw material powders all have a perfect spherical shape. However, these garnet-based phosphor component 2, the nitride-based phosphor component 3, the matrix component 4, and their raw material powders do not necessarily have a perfect spherical shape. If these raw material powders are spherical particles, the phosphor component and the matrix component 4 contained in the composite ceramic 1 will also be roughly spherical. However, if these raw material powders are, for example, irregular, angular particles, the phosphor component and the matrix component 4 contained in the composite ceramic 1 will also be irregular, angular particles. Furthermore, depending on the sintering method, the raw material powders may grow and change shape during sintering. In this case, when the component to be measured is not a perfect sphere, "particle size" refers to the particle size when converted into a perfect sphere of the same volume.

[0056] (Sintering Aid) The composite ceramic 1 may further contain a sintering aid. When the raw material powder (first raw material powder) including the raw material powder used as the raw material of the phosphor component and the raw material powder used as the raw material of the matrix component 4 contains a sintering aid, the composite ceramic 1 also contains a sintering aid.

[0057] Examples of sintering aids used in the composite ceramic 1 include Si ３ N ４ , SiO ２ , CaO, MgO, ZnO, Y ２ O ３、 At least one selected from the group consisting of LiF, NaF, and KF can be used.

[0058] When the first raw material powder contains a sintering aid, the sintering temperature can be further lowered, making it easier to produce the composite ceramic 1. This also makes it possible to further reduce the risk of deteriorating the performance of the phosphor.

[0059] The content of the sintering aid in the first raw material powder and the composite ceramic 1 made from the first raw material powder is preferably in the range of 0.05 wt % or more and 10 wt % or less so as not to deteriorate the phosphor characteristics.

[0060] Furthermore, the number average particle size of the sintering aid contained per unit volume of the composite ceramic 1 is preferably in the range of 0.01 μm or more and 1 μm or less, since this easily exerts its effect as a sintering aid. As such, the sintering aid is extremely fine and present in trace amounts compared to the phosphor component and matrix component 4, and is therefore not shown in the drawings.

[0061] (Thickness of Composite Ceramic 1) The thickness of the composite ceramic 1 is 220 μm or less. According to the studies of the present inventors, the internal quantum efficiency of the composite ceramic 1 containing the nitride-based phosphor component 3 depends on the thickness of the composite ceramic 1. That is, the internal quantum efficiency of the composite ceramic 1 can be improved by reducing the thickness. Therefore, it is preferable that the composite ceramic 1 has a small thickness, for example, 220 μm or less, 180 μm or less, 150 μm or less, 120 μm or less, etc., but 100 μm or less is preferable, and 95 μm or less is more preferable.

[0062] The lower limit of the thickness of the composite ceramic 1 is preferably the smallest thickness possible within a range that allows production and maintains the strength required for applying the composite ceramic 1 to a phosphor element. For example, the composite ceramic 1 has a thickness of 5 μm or more, or 10 μm or more.

[0063] The internal quantum efficiency can be improved by setting the thickness of the composite ceramic 1 to 220 μm or less. The internal quantum efficiency of such a composite ceramic 1 is, for example, 70% or more, 80% or more, 85% or more, or 90% or more.

[0064] (Relative Density of Composite Ceramic 1) The relative density of the composite ceramic 1 is 85% or more. In this specification, the term "relative density" may refer to the ratio of the apparent density of the composite ceramic 1 to the theoretical density. For example, the relative density can be calculated by measuring the bulk density of the composite ceramic 1 and comparing it with the theoretical value.

[0065] By increasing the relative density of the composite ceramic 1 to 85% or more, the amount of pores present inside the composite ceramic 1 is reduced, thereby achieving high heat dissipation performance. The relative density of the composite ceramic 1 is preferably 90% or more, and more preferably 95% or more. The upper limit of the relative density of the composite ceramic 1 is not particularly limited, but is, for example, 99% or less or 98% or less.

[0066] (Internal Quantum Efficiency of Composite Ceramic 1) The internal quantum efficiency of composite ceramic 1 is preferably 70% or higher. In this specification, "internal quantum efficiency" refers to the ratio of the number of photons converted to fluorescence among the number of photons of absorbed excitation light. Unlike powder, composite ceramic 1 transmits light and uses the transmitted blue light as a light source. Therefore, the internal quantum efficiency can be measured by placing composite ceramic 1 at the center of an integrating sphere. A method for measuring internal quantum efficiency by placing a phosphor sample at the center of an integrating sphere is described in detail, for example, in Rev. Sci. Instrum. 85, 123115, 2014 (Reference 1). In the examples described below, the internal quantum efficiency was measured using a 120 mmφ integrating sphere unit (IFL-135) attached to a JASCO FP-8550 spectrofluorometer. The internal quantum efficiency was measured by placing composite ceramic 1 at the center of the integrating sphere. The measurement device was calibrated using Standard Phosphor Green (Lot No. NSG1301) manufactured by Sialon Corporation, and then the internal quantum efficiency was measured.

[0067] The thickness of the composite ceramic 1 is 220 μm or less, and therefore the internal quantum efficiency is high. The internal quantum efficiency of the composite ceramic 1 is more preferably 70% or more, even more preferably 80% or more, and particularly preferably 90% or more. The upper limit of the internal quantum efficiency of the composite ceramic 1 is not particularly limited, but is, for example, 99% or less or 98% or less. The internal quantum efficiency of the composite ceramic 1 refers to the internal quantum efficiency when irradiated with excitation light having a wavelength of 450 nm.

[0068] (Optical Absorption Spectrum of Composite Ceramic 1) The optical absorption spectrum of composite ceramic 1 can be measured, similarly to the internal quantum efficiency, by attaching a 120 mmφ integrating sphere unit (IFL-135) to a JASCO Corporation FP-8550 fluorescence spectrophotometer and measuring a synchronous spectrum with a synchronous wavelength difference of 0 nm. Because composite ceramic 1 has translucent, light-scattering properties, the optical absorption spectrum can be measured by placing composite ceramic 1 in the center of the integrating sphere, similarly to the internal quantum efficiency. In this case, the monochrome wavelength difference between the incident light side and the receiving light side is set to zero, and the optical absorption spectrum is measured. As a reference sample, the measured value when only a quartz glass cell for fixing composite ceramic 1 is set can be set as zero optical absorption.

[0069] (Carbon Content of Composite Ceramic 1) In Composite Ceramic 1, the carbon content in the sintered body is preferably 0.05 wt % or less. The sintered body of Composite Ceramic 1 is sintered by spark plasma sintering (SPS) or hot pressing, which will be described later. At this time, carbon from the manufacturing equipment or parts may be mixed into Composite Ceramic 1. According to the studies of the present inventors, a low carbon content in the sintered body has been confirmed to improve the internal quantum efficiency of Composite Ceramic 1 (compared to Comparative Example 2, which will be described later). The amount of carbon can be analyzed with high accuracy by oxygen flow combustion-infrared absorption spectroscopy.

[0070] Therefore, the internal quantum efficiency of the composite ceramic 1 can be improved by reducing the carbon content in the sintered body. In the composite ceramic 1, the carbon content in the sintered body is preferably close to 0 wt %, more preferably 0.05 wt % or less, and even more preferably 0.02 wt % or less.

[0071] (Excitation Light Power Tolerance of Composite Ceramic 1) The composite ceramic 1 according to one embodiment of the present disclosure has a pumping power tolerance of 0.5 kW / cm ２ The composite ceramic 1 according to one embodiment of the present disclosure has the above-mentioned resistance to excitation light power. As such, the composite ceramic 1 according to one embodiment of the present disclosure is a composite ceramic for low color temperatures that has high fluorescence power relative to excitation light power, can withstand laser excitation, and has high resistance to excitation light power. Therefore, according to one embodiment of the present disclosure, it is possible to realize a practical phosphor element for lasers that does not saturate fluorescence even at relatively high power.

[0072] The higher the pumping light power tolerance, the more the laser can withstand high-power laser excitation, so the upper limit is not particularly limited. However, based on the pumping light power tolerance (laser power tolerance) of laser light sources and various optical components that can be actually used, the upper limit of the pumping light power tolerance is set to 100 kW / cm. ２ Therefore, the excitation light power tolerance of the composite ceramic 1 according to one embodiment of the present disclosure is 0.5 kW / cm ２ More than 100kW / cm ２ It is desirable that the value is within the following range.

[0073] In this disclosure, the pumping light power tolerance is defined as a power tolerance of 1 cm ２ The excitation light power tolerance indicates the value at which the fluorescence power saturates relative to the excitation light power (specifically, the laser excitation light power) per unit time. The excitation light power tolerance can be measured using a phosphor evaluation device equipped with a laser light source, an integrating sphere, and a spectroscope.

[0074] (Modification of Composite Ceramic 1) Composite ceramic 1 may further contain a light-scattering component. As an example, the light-scattering component is a light scatterer having a refractive index that is 0.21 or more higher than that of matrix component 4. Examples of the light-scattering component include at least one selected from the group consisting of AlN, cBN, SiC, AlN-SiC solid solution, and diamond. These light-scattering components have particularly excellent light-scattering properties and can be suitably used as the light-scattering component.

[0075] The upper limit of the refractive index difference between the light scattering component and the matrix component 4 is not particularly limited. ２ O ３ The refractive index of SiC is 1.63, and when the above-exemplified light-scattering component is used as the light-scattering component, the refractive index of SiC, which has the highest refractive index, is about 2.72. Therefore, when the above-exemplified light-scattering component is used as the light-scattering component, the difference in refractive index between the light-scattering component and the matrix component 4 is a maximum of 1.1.

[0076] Furthermore, the number average particle size of the light-scattering component contained per unit volume of the composite ceramic 1 is preferably 0.25 μm or more and 40 μm or less, and more preferably 0.5 μm or more and 20 μm or less. This number average particle size of the light-scattering component may be measured by SEM or may be the specifications listed on the delivery note or catalog. When the number average particle size of the light-scattering component is within the above range, light scattering is maximized due to Mie scattering. When the number average particle size of the light-scattering component is within the above range, the maximum light scattering effect can be obtained.

[0077] The composite ceramic 1 may have a laminated structure including a second ceramic layer bonded to one of its main surfaces. The second ceramic layer may be made of Al ２ O ３ It is preferable that the composition consists of:

[0078] Conventionally, composite ceramics containing a red phosphor and suitable for high-power excitation that can withstand laser excitation have not been realized. Composite ceramics 1 is a composite ceramic containing a red phosphor that can be used for laser illumination using laser excitation. However, by further bonding a second ceramic layer, it is possible to suppress burning of the surface of composite ceramics 1 even when strongly excited by laser light.

[0079] The thickness of the second ceramic layer is not particularly limited, but it is desirable that the second ceramic layer be formed thinly, since it does not contain fluorescent components and does not contribute to fluorescent emission, and also from the standpoint of heat dissipation.

[0080] Furthermore, the composite ceramic 1 may have an uneven surface on one of its main surfaces. Such unevenness may be formed by a dicer or laser processing, or by roughening the main surface by polishing. By forming an uneven surface on one of the main surfaces of the composite ceramic 1, the fluorescence and excitation light generated inside can be scattered and extracted efficiently.

[0081] An AR coating film may also be provided on one main surface of the composite ceramic 1. This prevents the excitation light from being reflected from the surface to which the excitation light is irradiated when the composite ceramic 1 is used as a phosphor element for laser illumination. This reduces the loss of light when the excitation light is absorbed by the composite ceramic 1. Furthermore, it allows the fluorescence and scattered light generated in the phosphor of the composite ceramic 1 to be effectively extracted. This also has the effect of reducing color unevenness in the projected image output from the phosphor, which is caused by the specular reflection of the excitation light.

[0082] The material of the AR coating film is SiO ２ , TiO ２ , Si ３ N ４ These can be formed by a film forming method such as ion beam deposition or sputtering.

[0083] Hereinafter, the composite ceramic provided with the AR coating film in this manner may be referred to as an AR-coated composite ceramic. The AR-coated composite ceramic provided with the AR coating film in this manner is suitable for use in, for example, a phosphor element for laser illumination.

[0084] [Method for manufacturing composite ceramic] Next, a method for manufacturing a composite ceramic will be described. Fig. 2 is a flowchart showing an example of a method for manufacturing a composite ceramic according to one embodiment of the present disclosure. The method for manufacturing a composite ceramic according to one embodiment of the present disclosure includes at least the following steps S1 to S5.

[0085] As shown in Fig. 2, in the method for producing composite ceramics, first, a first raw material powder containing a nitride-based phosphor component and a matrix component is mixed (step S1, mixing step). Here, mixing the first raw material powder refers to mixing the components contained in the first raw material powder. At this time, the first raw material powder may contain the sintering aid. The first raw material powder can be mixed by either wet mixing or dry mixing. However, when nitride-based fine powder is used as part of the raw material, dry mixing is preferred to avoid a reaction between the nitride and moisture.

[0086] Next, the first raw material powder mixed in the mixing step is placed in a molding die (step S2, first raw material powder placing step).

[0087] Next, the first raw material powder contained in the mold is sintered (step S3, sintering step). At this time, the first raw material powder is sintered using SPS (spark plasma sintering) or hot pressing. The SPS and hot pressing are types of solid compression sintering methods, in which the first raw material powder contained in the mold is press-molded by applying pressure while being heated.

[0088] In the SPS method, a compact is sintered by pulse current heating while being pressed by mechanical pressure. In addition to the thermal and mechanical energy used in normal sintering, the SPS method can sinter a compact using a combination of sintering driving forces, including electromagnetic energy from pulse current, self-heating of the compact, and discharge plasma energy generated between the components.

[0089] As a result, the SPS method can sinter by raising the temperature to a high temperature in a short period of time while applying mechanical pressure, so even for the above-mentioned ternary, difficult-to-sinter compacts, it is possible to sinter them into sintered compacts in which the components contained in the compact are bonded uniformly at high density. Furthermore, because the SPS method has a short sintering time, it is possible to suppress the grain growth of each component.

[0090] In the hot pressing method, sintering is performed in a pressurized atmosphere, similar to the SPS method. The hot pressing method requires a longer sintering time than the SPS method. However, the hot pressing method is suitable for mass production.

[0091] The sintering temperature in the sintering step is preferably 1000° C. or higher and 2000° C. or lower. By setting the sintering temperature to 2000° C. or lower, the sintering temperature is not too high, and it is possible to suppress the generation of oxides and the formation of new compounds by the solid solution of the above components, and to avoid losing the properties of the above components including the nitride-based phosphor component.

[0092] Furthermore, by setting the sintering temperature to 1000°C or higher, the sintering temperature is not too low, and the primary particles of each component are likely to be bonded together. As a result, the components are likely to coexist without forming a solid solution, and adjacent phases are likely to be bonded together. This makes it easier to obtain a composite ceramic 1 that has sufficient processing strength as a bulk body and emits suitable warm white fluorescent light. The sintering time in the sintering step is not particularly limited and may be any time between 5 minutes and 20 hours, for example.

[0093] Next, the sintered body obtained in the sintering step is removed from the molding die (step S4, demolding step).

[0094] Then, the sintered body removed from the mold is subjected to a thinning step (step S5) of at least one of cutting and polishing so that the thickness is 220 μm or less. Note that a sintered body having a thickness of 220 μm or less can also be produced without cutting or polishing by using a thinner mold or adjusting the amount of first raw material powder contained in the mold. In this case, the thinning step does not need to be performed.

[0095] The method for cutting the sintered body is not particularly limited, and for example, the sintered body may be sliced ​​(cut) using a wire saw or the like. Furthermore, the method for polishing the sintered body is also not particularly limited. For example, the surface of the sintered body may be polished by rotating a polishing unit while a polishing liquid is being discharged from the discharge unit of a polishing device. This makes it possible to smooth the surface while reducing the thickness of the sintered body. Therefore, by polishing, a composite ceramic that is thin and has a smooth surface can be obtained.

[0096] The method for producing a composite ceramic may further include an annealing step of annealing the sintered body obtained in the thinning step in an ammonia atmosphere after the thinning step. The annealing step reduces the carbon content in the composite ceramic and further improves the internal quantum efficiency.

[0097] The annealing temperature is preferably, for example, 800° C. or higher and 1500° C. or lower. By annealing the sintered body at 800° C. or higher and 1500° C. or lower, it is possible to suitably prevent deformation of the composite ceramic during processing and to control defects in each phase. The annealing time is not particularly limited and may be any time, for example, 5 minutes or higher and 20 hours or lower.

[0098] [Phosphor Element 50] A phosphor element according to one embodiment of the present disclosure includes the composite ceramic 1 according to one embodiment of the present disclosure described above, and a substrate 51 that fixes the composite ceramic 1. Fig. 3 is a cross-sectional view showing an example of a phosphor element 50 according to one embodiment of the present disclosure. The phosphor element 50 shown in Fig. 3 includes the composite ceramic 1 provided with the AR coating film 41, the substrate 51, an adhesive layer 52, and a mirror 53.

[0099] The substrate 51 is a support member that supports the composite ceramic 1. The composite ceramic 1 is fixed on the substrate 51. The substrate 51 is not particularly limited as long as it can fix the composite ceramic 1. As an example, the substrate 51 may be made of a metal such as SUS, Al, Cu, Mo, Ag, or W, or an alloy thereof.

[0100] Furthermore, since Al, Cu, Mo, Ag, W, and the like have excellent thermal conductivity, it is possible to obtain a phosphor element 50 having excellent thermal conductivity. However, the substrate 51 is not limited to such a non-transparent substrate. The substrate 51 may be, for example, Al ２ O ３ The substrate may be a transparent substrate such as single crystal sapphire or polycrystalline alumina, as shown in FIG.

[0101] As shown in FIG. 3, the composite ceramic 1 is fixed to the substrate 51 so that the AR coating film 41 is positioned on the main surface opposite to the substrate 51 .

[0102] The mirror 53 is a reflector (mirror body) that reflects light transmitted through the composite ceramic 1. The mirror 53 is provided on the main surface of the composite ceramic 1 that faces the substrate 51. Hereinafter, the main surface of the composite ceramic 1 that faces the substrate 51 may be referred to as the "rear main surface," and the main surface opposite the substrate 51 may be referred to as the "front main surface."

[0103] The mirror 53 is provided on the back principal surface of the composite ceramic 1, and the AR coating film 41 is provided on the front principal surface of the composite ceramic 1. By providing the mirror 53 on the back principal surface of the composite ceramic 1 in this manner, when excitation light is irradiated onto the front principal surface of the composite ceramic 1, the light that has passed through the composite ceramic 1 can be reflected by the mirror 53. This improves the light utilization efficiency. The mirror 53 is not particularly limited as long as it can reflect the light that has passed through the composite ceramic 1, but for example, a silver-based mirror containing a specularly reflective material such as silver, aluminum, an aluminum alloy, or a silver alloy is preferably used.

[0104] The adhesive layer 52 is a layer that bonds the composite ceramic 1 provided with the mirror 53 to the substrate 51. The adhesive material used for the adhesive layer 52 is not particularly limited as long as it can bond the composite ceramic 1 provided with the mirror 53 to the substrate 51. Examples of the adhesive material include silver-based or silver alloy-based, and Sn- or Sn alloy-based inorganic adhesives.

[0105] 4 is a flowchart showing an example of a method for manufacturing the phosphor element 50 shown in FIG. As shown in FIG. 4, in the manufacturing method of the phosphor element 50, for example, the thinning step of step S5 includes a cutting step (step S11) for cutting the sintered body and a back main surface polishing step (step S12) for polishing the back main surface of the sintered body. Next, a mirror 53 is formed on the back main surface of the sintered body (step S13, mirror film forming step). This forms a mirror-attached composite ceramic in which the mirror 53 is bonded to one main surface of the composite ceramic 1.

[0106] On the other hand, a substrate 51 is prepared (step S21, substrate preparation step). Next, the substrate 51 and the mirror-attached composite ceramic obtained in step S13 are bonded together with an adhesive material that forms an adhesive layer 52 (step S14, bonding step). Next, the front principal surface of the sintered body is polished (step S15, front principal surface polishing step). After that, an AR coating film 41 is formed on the front principal surface of the sintered body (step S16, AR coating film formation step). This allows the phosphor element 50 shown in FIG. 3 to be manufactured.

[0107] 4, the front principal surface polishing step is performed after the bonding step, but the present disclosure is not limited to this. The front principal surface polishing step may be performed before the bonding step.

[0108] Furthermore, the phosphor element 50 according to one aspect of the present disclosure is not limited to the structure shown in Fig. 3. The phosphor element 50 may include, for example, a composite ceramic 1 and a substrate 51 to which the composite ceramic 1 is fixed.

[0109] [Laser Illumination Device 60] As described above, composite ceramics can be suitably used for phosphor elements for laser illumination (in other words, phosphor elements of a laser illumination device). A laser illumination device according to one aspect of the present disclosure includes a phosphor element, a laser light source that irradiates excitation light onto the composite ceramic in the phosphor element, and a light collecting member (first light collecting member) that collects light output from the composite ceramic in the phosphor element.

[0110] Fig. 5 is a cross-sectional view showing an example of a laser illuminator 60 according to one aspect of the present disclosure. The laser illuminator 60 shown in Fig. 5 includes, as an example of the phosphor element, the phosphor element 50 shown in Fig. 4. The laser illuminator 60 shown in Fig. 5 also includes a laser light source 61 as the laser light source, and a lens 63 as the first focusing member. The laser illuminator 60 shown in Fig. 5 also includes a lens 62 as a second focusing member that focuses the excitation light output from the laser light source 61.

[0111] The laser light source 61 irradiates the composite ceramic 1 in the phosphor element 50 with excitation light L1 as a first light via a lens 62. Specifically, the excitation light L1 output from the laser light source 61 is focused by the lens 62, and is irradiated from the lens 62 to the composite ceramic 1 in the phosphor element 50 as focused excitation light L1 (hereinafter referred to as "excitation light L1'").

[0112] The composite ceramic 1 absorbs at least a portion of the excitation light L1′ and outputs second light including light with a different wavelength from the excitation light L1′ (i.e., light with a different wavelength from the excitation light L1). For example, the garnet-based phosphor component 2 emits, for example, yellowish fluorescence Y in response to the blue light that is the excitation light L1, and the nitride-based phosphor component 3 emits redish fluorescence R in response to the blue light that is the excitation light L1. These phosphors also scatter the blue light that is the excitation light L1 and does not contribute to excitation, transmitting it as blue scattered light B. As a result, when the composite ceramic 1 in the phosphor element 50 is irradiated with blue excitation light L1, the phosphor element 50 outputs blue scattered light B, yellowish fluorescence Y, and reddish fluorescence R, as shown in FIG. 5 . These lights (second lights) output from the phosphor element 50 (specifically, the composite ceramic 1 of the phosphor element 50) are condensed by the lens 63. Then, these lights (i.e., blue scattered light B, yellowish fluorescent light Y, and reddish fluorescent light R) output from the phosphor element 50 are mixed together, and reddish incandescent light is output as beam L2 through lens 63.

[0113] The laser light source 61 is not particularly limited as long as it can emit excitation light L1, but an example thereof is a blue semiconductor LD (LD: laser diode) that emits blue light as the excitation light L1 as described above.

[0114] When the phosphor element 50 is equipped with a mirror 53 as described above, or when the substrate 51 is a non-transparent substrate that does not transmit the excitation light L1, the phosphor element 50 is arranged so that the composite ceramic 1 is located on the light emission side of the laser light source 61.

[0115] On the other hand, when the substrate 51 is a transmissive substrate and does not have a reflector such as a mirror 53 on the back main surface side of the composite ceramic 1, the excitation light L1 is irradiated from the surface of the substrate 51 opposite to the fixing surface of the composite ceramic 1. Note that even in this case, the second light is output from the front main surface side of the composite ceramic 1.

[0116] 5 illustrates an example in which both the first and second light collecting members are lenses, but these light collecting members may also be lenses or mirrors.

[0117] EXAMPLES The composite ceramic according to the present disclosure will be specifically described below with reference to examples and comparative examples, but the composite ceramic according to the present disclosure is not limited to these examples.

[0118] (Example 1 and Comparative Example 1) A nitride-based phosphor component, LYSN, was used in an amount of 30 wt %, and a matrix component, Al, was used in an amount of 30 wt %. ２ O ３ The raw material powders were dry-mixed to a concentration of 70 wt %. The raw material powders were then filled into a mold and sintered using the SPS method in a nitrogen atmosphere or a reduced-pressure nitrogen atmosphere at 1300 to 1400°C for 3 to 5 minutes, thereby producing the composite ceramic of Example 1. The produced composite ceramic was cut to thicknesses of 30 μm to 3 mm to create multiple samples, which were then surface-ground and the internal quantum efficiency of each sample was measured at an excitation wavelength of 450 nm. In the following measurements, the excitation wavelength was standardized to 450 nm. The internal quantum efficiency was measured using a 120 mmφ integrating sphere unit (IFL-135) attached to a JASCO FP-8550 spectrofluorometer calibrated with a standard phosphor, as described in the above embodiment.

[0119] The results are shown in Figure 6. As shown in Figure 6, the internal quantum efficiency of the composite ceramic of Example 1 improved as the thickness decreased, indicating thickness dependency of the internal quantum efficiency. In particular, when the thickness was thinner than 220 µm, the internal quantum efficiency was high, reaching 70% or more.

[0120] Next, optical absorption spectra were measured using composite ceramics of representative thicknesses. The optical absorption spectra were measured as described in the above embodiment. The results are shown in FIG. 7. As shown in FIG. 7, the 1.33 mm thick composite ceramic of Comparative Example 1 absorbed 45% of incident light with a wavelength of 630 nm. For the 0.22 mm thick composite ceramic, the absorption of incident light with a wavelength of 630 nm decreased to 21%, and for the 0.05 mm thick composite ceramic, the absorption of incident light with a wavelength of 630 nm decreased to 9%. This demonstrates that reducing the thickness of the composite ceramic reduces the optical absorption rate. This is the first time that we have found a good correlation between internal quantum efficiency and optical absorption rate at a wavelength of 630 nm. Therefore, from the results shown in FIG. 7, it is clear that LYSN-Al ２ O ３ In the LYSN-Al composite ceramics, the decrease in internal quantum efficiency is mainly caused by the absorption of light in the 630 nm band, and it can be said that reducing the thickness of the composite ceramics is a very effective countermeasure. ２ O ３ For the first time, composite ceramics with an internal quantum efficiency of 70% or more have been obtained in this system.

[0121] (Example 2) A composite ceramic of Example 2 having a thickness of 0.096 mm was produced in the same manner as Example 1, except that the amount of LYSN was increased to 40 wt %. When the internal quantum efficiency and light absorptance at 630 nm were measured in the same manner as Example 1, the internal quantum efficiency of the composite ceramic of Example 2 was 78%, and the light absorptance was 19%.

[0122] Example 3 A composite ceramic of Example 3 having a thickness of 0.047 mm was produced in the same manner as Example 1, except that the amount of LYSN was 20 wt % and the amount of CASN was 10 wt %. When the internal quantum efficiency and light absorptance at 630 nm were measured in the same manner as Example 1, the internal quantum efficiency of the composite ceramic of Example 3 was 72%, and the light absorptance was 12%.

[0123] Example 4 Composite ceramics of Example 4 with thicknesses of 0.053 mm and 0.093 mm were prepared in the same manner as Example 1, except that LYSN was replaced with 10 wt% YAG and 5 wt% CASN as the phosphor. At a thickness of 0.053 mm, the internal quantum efficiency was 71% and the light absorption rate was 10%. Examples 2 to 4 suggest that even with different compositions, there is a correlation between the internal quantum efficiency and the sample thickness and the light absorption rate at a wavelength of 630 nm.

[0124] A composite ceramic sample with the same composition as in Example 4 was used to fabricate a phosphor element as shown in Figure 3. The composite ceramic fabricated under the same conditions as in Example 4 was sliced ​​to a thickness of 0.4 mm using a diamond saw, and then ground and polished to produce a thin plate with a thickness of 50 µm. The use of alumina as the matrix component increased the mechanical strength, and even a 50 µm thin plate of composite ceramic could be handled without any problems.

[0125] Next, a 200 nm silver film was formed on the rear main surface of the composite ceramic using a sputtering method, forming a rear surface mirror 53. Furthermore, the composite ceramic was bonded to a substrate 51, which is a silver heat sink, via a silver-based adhesive layer 52. The silver-based adhesive used for the adhesive layer 52 is a thermosetting adhesive, but one that leaves no organic components after heating. In this example, the AR coating film 41 on the front main surface was omitted.

[0126] The phosphor element 50 thus fabricated was placed on a sample stage, and the fluorescence power versus excitation power was measured. A graph plotting the results is shown in Figure 9. Here, excitation was performed using a high-power semiconductor laser (optical fiber output type) of 450 nm. The laser light was focused to a beam diameter of 0.8 mm, and excitation was performed up to a laser excitation power of 17 W. In Figure 9, the vertical axis represents the fluorescence intensity. As shown in Figure 9, the phosphor element 50 exhibited a fluorescence intensity of 34 W / mm ２ (3.4 kW / cm ２ ) was obtained without a saturation point. This confirmed that Composite Ceramic 1 has optical power resistance at a practical level.

[0127] Example 5 A composite ceramic of Example 5 was produced by annealing a thin plate having the composition of Example 3 in an ammonia atmosphere. In the annealing treatment, the ammonia gas flow rate was 200 sccm, the annealing temperature was 900°C, and the annealing time was 3 hours. The thickness of the composite ceramic of Example 5 was 0.047 mm, which is the same as that of Example 3. However, the annealing treatment improved the internal quantum efficiency by 2% and reduced the light absorption rate at 630 nm by 1%.

[0128] (Comparative Example 2) As Comparative Example 2, a commercially available YAG-Al ２ O ３ The internal quantum efficiency and light absorptance of the composite ceramics of this system were measured in the same manner as in Example 1. The thickness of the composite ceramics of Comparative Example 2 was 0.2 mm. The internal quantum efficiency was 96% and the light absorptance was 3.6%.

[0129] Table 1 below summarizes the results of measuring the configuration and functions of each example and comparative example.

[0130] [Additional Note 1] The present disclosure can also be expressed as follows.

[0131] The composite ceramic according to the first aspect of the present disclosure comprises a nitride-based phosphor component and Al as a main component of a matrix component. ２ O ３ and a composite ceramic comprising a sintered body containing the nitride-based phosphor component, the composite ceramic having a thickness of 220 μm μm or less and an optical absorptivity of 21% or less for incident light with a wavelength of 630 nm, the matrix component being sintered to surround the nitride-based phosphor component.

[0132] The composite ceramic according to aspect 2 of the present disclosure may have a thickness of 100 μm or less in accordance with aspect 1.

[0133] A composite ceramic according to a third aspect of the present disclosure may be the composite ceramic of the first or second aspect, wherein the content of the matrix component is in the range of 31 wt % or more and 90 wt % or less of all components.

[0134] The composite ceramic according to Aspect 4 of the present disclosure may be any one of Aspects 1 to 3, and may have an internal quantum efficiency of 70% or more when irradiated with excitation light having a wavelength of 450 nm.

[0135] A composite ceramic according to Aspect 5 of the present disclosure is any one of Aspects 1 to 4, wherein the sintered body further includes a garnet-based phosphor component, and the matrix component is sintered to surround the nitride-based phosphor component and the garnet-based phosphor component.

[0136] A composite ceramic according to a sixth aspect of the present disclosure is any one of the first to fifth aspects, wherein the carbon content in the sintered body may be 0.05 wt % or less.

[0137] A composite ceramic according to a seventh aspect of the present disclosure is any one of the first to sixth aspects, wherein the nitride-based phosphor components are activated with at least one element of Eu and Ce, respectively, and the nitride-based phosphor components are activated with at least one element of Eu and Ce, respectively, and the nitride-based phosphor components are activated with at least one element of Eu and Ce, respectively. ３ Si ６ N １１ , La ３ Si ６ N １１、 CaAlSiN ３ , (Ca,Sr)AlSiN ３ , Sr ２ Si ５ N ８ , (Ba, Sr) ２ Si ５ N ８、 (Ba, Sr, Ca) ２ Si ５ N ８、 and (Ba, Sr) ２ (Si, Al) ５（ N, O) ８ It may contain at least one selected from the group consisting of:

[0138] According to an eighth aspect of the present disclosure, in the composite ceramic of the fourth aspect, the garnet-based phosphor component is (Ce, Y) ３ Al ５ O １２ , (Ce, Y, Gd) ３ Al)O １２ , (Ce, Lu) ３ Al５ O １２ , (Ce, Lu, Y) ３ Al ５ O １２ , (Ce, Lu, Y) ３ (Al, Ga) ５ O １２ It may contain at least one selected from the group consisting of:

[0139] A phosphor element according to a ninth aspect of the present disclosure includes the composite ceramic according to any one of the first to eighth aspects and a substrate for fixing the composite ceramic.

[0140] A laser illumination device according to aspect 10 of the present disclosure includes the phosphor element according to aspect 9, a laser light source that irradiates excitation light onto the composite ceramic in the phosphor element, and a focusing member that focuses the light output from the composite ceramic in the phosphor element.

[0141] A method for producing a composite ceramic according to an eleventh aspect of the present disclosure includes the steps of: ２ O ３ a first raw material powder containing step of containing the mixed first raw material powder in a molding die; a sintering step of sintering the first raw material powder contained in the molding die by a spark plasma sintering method or a hot press method; and a demolding step of removing the sintered body obtained in the sintering step from the molding die, wherein the thickness of the sintered body is 220 μm or less.

[0142] A method for producing a composite ceramic according to aspect 12 of the present disclosure may further include, in the method described in aspect 11, a thinning step of subjecting the sintered body to at least one of polishing and grinding so that the thickness is 220 μm μm or less.

[0143] A method for producing a composite ceramic according to aspect 13 of the present disclosure may be the same as that of aspect 12, further comprising an annealing step of annealing the sintered body obtained in the thinning step in an ammonia atmosphere.

[0144] [Additional Note 2] The present disclosure is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present disclosure.

[0145] REFERENCE SIGNS LIST 1 Composite ceramic 2 Garnet-based phosphor component 3 Nitride-based phosphor component 4 Matrix component 50 Phosphor element 51 Substrate 60 Laser illumination device 61 Laser light source 62, 63 Lens (light-collecting member)

Claims

1. Nitride phosphor component and Al as the main component of the matrix component ２ O ３ a composite ceramic comprising a sintered body including: a matrix component that surrounds the nitride-based phosphor component; and a sintered body that has a thickness of 220 μm or less and has an optical absorptivity of 21% or less for incident light having a wavelength of 630 nm.

2. The composite ceramic according to claim 1, having a thickness of 100 μm or less.

3. A composite ceramic according to claim 1 or 2, characterized in that the content of the matrix component is within the range of 31 wt % or more and 90 wt % or less of the total components.

4. The composite ceramic according to claim 1 or 2, which has an internal quantum efficiency of 70% or more when irradiated with excitation light having a wavelength of 450 nm.

5. The composite ceramic according to claim 1 or 2, wherein the sintered body further contains a garnet-based phosphor component, and the matrix component is sintered surrounding the nitride-based phosphor component and the garnet-based phosphor component.

6. The composite ceramic according to claim 1 or 2, wherein the carbon content in the sintered body is 0.05 wt % or less.

7. The nitride-based phosphor components are activated with at least one of Eu and Ce, (La, Y) ３ S ６ N １１ , La ３ S ６ N １１、 CaAlSiN ３ , (Ca,Sr)AlSiN ３ , Sr ２ S ５ N ８ , (Ba, Sr) ２ S ５ N ８、 (Ba, Sr, Ca) ２ S ５ N ８、 and (Ba, Sr) ２ (Si, Al) ５ N ８ The composite ceramic according to claim 1 or 2, comprising at least one selected from the group consisting of:

8. The garnet-based phosphor component is (Ce, Y) ３ A ５ O １２ , (Ce, Y, Gd) ３ Al)O １２ , (Ce, Lu) ３ A ５ O １２ , (Ce, Lu, Y) ３ A ５ O １２ , (Ce, Lu, Y) ３ (Al, Ga) ５ O １２ The composite ceramic according to claim 5, comprising at least one selected from the group consisting of:

9. A phosphor element comprising: the composite ceramic according to claim 1 or 2; and a substrate for fixing the composite ceramic.

10. A laser lighting device comprising: a phosphor element according to claim 9; a laser light source which irradiates excitation light onto the composite ceramic in the phosphor element; and a focusing member which focuses the light output from the composite ceramic in the phosphor element.

11. Nitride phosphor component and Al as the main component of the matrix component ２ O ３ a first raw material powder containing step of containing the mixed first raw material powder in a molding die; a sintering step of sintering the first raw material powder contained in the molding die by a spark plasma sintering method or a hot press method; and a demolding step of removing a sintered body obtained in the sintering step from the molding die, wherein the thickness of the sintered body is 220 μm or less.

12. The method for producing composite ceramics according to claim 11, further comprising a thinning step of subjecting the sintered body to at least one of cutting, polishing, and grinding so that the thickness is 220 μm or less.

13. The method for producing a composite ceramic according to claim 12, further comprising an annealing step of annealing the sintered body obtained in the thinning step in an ammonia-containing gas atmosphere.

Images