JP2015143173A - Light-emitting device mounting ceramic substrate and light-emitting apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light-emitting device mounting ceramic substrate and a light-emitting apparatus having a high light reflectance in a near-ultraviolet light region.SOLUTION: The light-emitting device mounting ceramic substrate A comprises an alumina crystal particle 1-based ceramic sintered body including zirconia crystal particles 3. The alumina crystal particles 1 have nearly parallel opposite faces. The alumina crystal particles 1 including the zirconia crystal particles 3 exist 60% or more by number percentage in the ceramic sintered body. The zirconia crystal particles 3 are mixed crystals of monoclinic zirconia with at least one of tetragonal zirconia and cubic zirconia.

Description

  The present invention relates to a ceramic substrate for mounting a light emitting element and a light emitting device.

  In recent years, a light-emitting device in which a light-emitting element is mounted on a light-emitting element mounting substrate has been improved for high luminance and whitening, and is used as a backlight for a mobile phone, a large-sized liquid crystal television, and the like. Among them, it not only has high reflectivity compared to synthetic resins that have been used for conventional light-emitting element mounting substrates, but also has excellent heat resistance and durability, and does not deteriorate even when exposed to ultraviolet rays for a long time. For this reason, ceramic sintered bodies have attracted attention as light emitting element mounting substrates.

  For example, Patent Document 1 discloses a ceramic substrate for mounting a light emitting element, which is made of a ceramic sintered body mainly composed of alumina.

JP 2012-67008 A

  However, the ceramic substrate for mounting a light emitting element constituted by a ceramic sintered body mainly composed of alumina disclosed in Patent Document 1 has a problem that the reflectance of light in the near ultraviolet light region is low.

  Accordingly, an object of the present invention is to provide a ceramic substrate for mounting a light emitting element and a light emitting device having a high reflectance of light in the near ultraviolet light region.

  The ceramic substrate for mounting a light emitting element of the present invention is characterized by comprising a ceramic sintered body having alumina crystal particles mainly containing alumina crystal particles and containing zirconia crystal particles.

  The light-emitting device of the present invention is characterized in that a light-emitting element is provided on a substrate made of the above-described ceramic substrate for mounting a light-emitting element.

  ADVANTAGE OF THE INVENTION According to this invention, the ceramic base | substrate and light-emitting device for light emitting element mounting with the high reflectance of the light in a near ultraviolet light area | region can be obtained.

(A) is the cross-sectional schematic diagram which expanded partially the ceramic base | substrate for light emitting element mounting of this embodiment, (b) is the cross-sectional schematic diagram which expanded the conventional ceramic base | substrate for light emitting element mounting partially. is there. It is sectional drawing which shows typically one Embodiment of the light-emitting device of this invention, (a) is the light-emitting device whose ceramic base for light emitting element mounting is a flat substrate, (b) is a flat substrate. This is a light-emitting device having a surface made of a ceramic substrate for mounting light-emitting elements on the surface. Sample No. produced in the Examples 1 and sample no. It is the measurement result of the reflectance about 6 samples.

  FIG. 1A is a schematic cross-sectional view in which the light-emitting element mounting ceramic substrate of the present embodiment is partially enlarged, and FIG. 1B is a cross-sectional schematic diagram in which a conventional light-emitting element mounting ceramic substrate is partially expanded. FIG.

  The light emitting element mounting ceramic substrate A of the present embodiment is made of a ceramic sintered body mainly composed of alumina crystal particles 1 and includes alumina crystal particles 1 in which zirconia crystal particles 3 are encapsulated. According to the ceramic substrate A for mounting a light emitting element having such a configuration, the reflectance of light in the near ultraviolet region (wavelength: 360 to 400 nm) can be increased.

  Alumina usually has a trigonal corundum type crystal structure and a lattice constant of a = 0.47 to 0.48 nm and c = 0.128 to 0.132 nm. On the other hand, zirconia has three types of crystal structures depending on the temperature region, and is monoclinic, tetragonal, or cubic, but the lattice constant is, for example, a cubic = 0.500 to 0.520 nm.

  When the alumina crystal particles 1 and the zirconia crystal particles 3 having greatly different crystal structures and lattice constants are combined so that the zirconia crystal particles 3 are included in the alumina crystal particles 1, both crystal particles In addition to the influence of the difference in refractive index, a region in which the crystal lattice is deformed due to dislocations is formed in the alumina crystal particles 1 around the zirconia crystal particles 3. As a result, it is considered that the reflectance of light easily changes.

  Here, “mainly composed of the alumina crystal particles 1” means that the alumina content is 85% by mass or more as measured by Rietveld analysis. In this case, as long as the crystal structure of the alumina crystal particles 1 is maintained, other metal oxides (for example, Si, alkaline earth metal elements, rare earth elements, etc.) different from aluminum oxide may be dissolved.

The zirconia crystal particle 3 refers to a crystal particle mainly composed of zirconia (ZrO ₂ ), as long as it exhibits the above three crystal structures of monoclinic system, tetragonal system and cubic system. It also means that a component in which a component such as a stabilizing material is slightly dissolved is included. The ratio of the zirconia crystal particles 3 contained in the light emitting element mounting ceramic substrate A is preferably 1 to 10% by mass as measured by Rietveld analysis. In this case, the balance is approximately the content of the alumina crystal particles 1.

  FIG. 1B shows a schematic cross-sectional view in which a conventional ceramic substrate for mounting a light emitting device is partially enlarged. For mounting a light emitting device made of an alumina ceramic sintered body having no zirconia crystal particles 3. In the case of a ceramic substrate, the reflectance of light in the near ultraviolet region is low.

  Further, when the crystal structure is such that the zirconia crystal particles 3 are present at the grain boundaries of the alumina crystal particles 1, the zirconia crystal particles 3 are at the grain boundaries although there is a difference in refractive index between the crystal particles 1 and 3. Since the presence of the zirconia crystal particles 3 on the surface of the ceramic substrate A for mounting the light emitting element reflects the color of the zirconia crystal particles 3 deeply, the light reflectance in the near ultraviolet region is low. It becomes.

In the light emitting element mounting ceramic substrate A of the present embodiment, the alumina crystal particles 1 in which the number ratio of the alumina crystal particles 1 including the zirconia crystal particles 3 is recognized within the unit area in the cross section of the light emitting element mounting ceramic substrate A. When the total number is 100%, it is preferably 60% or more. As a result, the reflectance of light in the near ultraviolet region can be further increased. In this case, it is desirable that the zirconia crystal particles 3 are present at substantially the center of the alumina crystal particles 1.

  In the light emitting element mounting ceramic substrate A of the present embodiment, it is desirable that the alumina crystal particles 1 have opposing surfaces whose shapes are substantially parallel. Here, “substantially parallel” means that the opposed flat surfaces of the alumina crystal particles 1 are inclined within a range of 10 ° or less from the parallel state. The shape of the alumina crystal particle 1 is not round, but the shape when the alumina crystal particle 1 is viewed in cross section is elongated, so-called opposed surfaces are flat and the surfaces are almost parallel. is there. The alumina crystal particles 1 having such a shape have opposing flat surfaces, and the area of the light reflecting surface is increased. As a result, the reflectance of light in the near ultraviolet light region can be increased.

  In this case, the alumina crystal particles 1 desirably have a longest diameter of 10 to 40 μm and a shortest diameter of 5 to 10 μm in the cross section of the ceramic substrate A for mounting light emitting elements. At this time, the size (maximum diameter) of the zirconia crystal particles 3 is desirably 1 to 5 μm. The ratio D2 / D1 is preferably 0.09 to 0.19, where the average particle diameter of the alumina crystal particles 1 is D1 and the average particle diameter of the zirconia crystal particles 3 is D2. Here, the average particle diameters of the alumina crystal particles 1 and the zirconia crystal particles 3 are drawn in a circle including 20 to 30 alumina crystal particles 1 in the cross section of the ceramic substrate A for mounting a light emitting element, and within and around the circle. The selected crystal particles are selected, the contours of the alumina crystal particles 1 and the zirconia crystal particles 3 contained therein are image-processed, the area of the crystal particles is obtained, and the diameter when replaced with a circle having the same area Is obtained by calculating.

  In addition, the zirconia crystal particles 3 constituting the ceramic substrate A for mounting a light emitting element of the present embodiment are a two-phase mixed crystal of monoclinic zirconia and tetragonal zirconia, two phases of monoclinic zirconia and cubic zirconia. It is desirable that the mixed crystal be any one of three-phase mixed crystals of monoclinic zirconia, tetragonal zirconia, and cubic zirconia. The determination of what crystal system the zirconia crystal particles 3 have is obtained from the X-ray diffraction pattern of a sample obtained by pulverizing a ceramic sintered body.

  FIG. 2 is a cross-sectional view schematically showing an embodiment of the light-emitting device B of the present invention, where (a) is a light-emitting device in which the light-emitting element mounting ceramic substrate A is a flat substrate 8; Is a light emitting device in which a frame body 9 made of a ceramic substrate A for mounting light emitting elements is provided on the surface of a flat substrate 8.

  In the light emitting device B of the present embodiment, the conductor 5 is formed on the surface and / or inside of the substrate 8 made of the ceramic substrate A for mounting the light emitting element, and the light emitting element 7 is mounted on the surface of the conductor 5. . In the light emitting device B, as described above, since the substrate 8 includes the alumina crystal particles 1 including the zirconia crystal particles 3 in the ceramic sintered body mainly composed of the alumina crystal particles, the alumina crystal particles 1 And the difference in refractive index between the zirconia crystal particles 3 and the reflectance of light in the near ultraviolet region can be increased.

  As shown in FIG. 2B, when the light emitting device B is provided with a frame body 9 made of the same material as the substrate 8 made of the light emitting element mounting ceramic base A, the reflected light Can be condensed in a certain direction, and a light emitting device with higher emission intensity can be obtained. In this case, the same effect can be obtained even if at least one of the substrate made of the light emitting element mounting ceramic substrate A and the frame 9 is formed by the light emitting element mounting ceramic substrate A of the present embodiment.

Next, a manufacturing method of the light emitting element mounting ceramic substrate A of the present embodiment will be described. First, alumina powder and zirconia powder are prepared as raw material powders. The average particle diameter of the alumina powder is preferably 1 to 2 μm, and the average particle diameter of the zirconia powder is preferably 0.5 to 1 μm. Also, may be added sintering aids as needed, as a sintering aid, SiO _2, oxides of alkaline earth elements (Ca, Mg, Sr, Ba ) are preferred.

  Next, alumina powder and zirconia powder are mixed with an organic vehicle using a stirrer such as a ball mill to form a mixed powder, formed into a predetermined shape, and then fired at a temperature of 1500 to 1700 ° C. Thereby, the ceramic substrate A for mounting a light emitting element of the present embodiment can be obtained.

  This is because the alumina powder and zirconia powder having the above average particle size relationship are added in the range of 1 to 10 parts by mass of zirconia powder with respect to 100 parts by mass of alumina powder, and fired to promote the grain growth of alumina. This is because a ceramic sintered body having a crystal structure in which the zirconia crystal particles 3 are included in the alumina crystal particles 1 can be obtained by performing the above.

That is, the ceramic sintered body constituting the light emitting element mounting ceramic substrate A of the present embodiment is a combination of oxides of SiO ₂ and alkaline earth elements (Ca, Mg, Sr, Ba) as a sintering aid. A composition that forms a stable liquid phase is used. Thereby, even when baked at a high temperature, it is difficult to form a crystal phase generated from the sintering aid, so that the alumina powder as the main raw material is easily brought into contact with each other through the liquid phase. It is considered that the grain growth is promoted and the alumina crystal particles 1 including the zirconia crystal particles 3 are easily formed. In this case, it is preferable to adjust the composition of the sintering aid so that the composition of at least two elements (components) of the alkaline earth element is a composition close to equimolar. Further, by using such a sintering aid, the alumina crystal particles 1 have opposing surfaces whose shapes are substantially parallel.

  If the amount of the zirconia powder added is less than 1 part by mass, the grain growth of the alumina crystal particles 1 is suppressed, and the zirconia crystal particles 3 are in the substantially central region of the alumina crystal particles 1 (average grains from the periphery of the alumina crystal particles 1). It is difficult to be taken into a region where the thickness is about 10% of the diameter. When the amount of zirconia powder added is more than 10 parts by mass with respect to 100 parts by mass of alumina powder, it becomes difficult to form a dense molded body, although it depends on the amount of organic vehicle to be added. In addition, when forming a conductor on the surface or inside of the ceramic substrate A for mounting light emitting elements, the oxygen concentration in the firing atmosphere is changed according to the type of metal used as the conductor. For example, when tungsten (W) or molybdenum (Mo) is used as the conductor, a hydrogen-nitrogen mixed gas is used.

First, alumina powder having an average particle diameter of 1.6 μm (α alumina: purity 99.8 mass%), zirconia powder having an average particle diameter of 0.8 μm (purity 99.8 mass%), silicon oxide (SiO ₂ ), Calcium oxide (CaO) and magnesium oxide (MgO) were prepared. When the mixed powder of alumina powder and zirconia powder is 100 parts by mass, 4 parts by mass of silicon oxide (SiO ₂ ), 0.5 parts by mass of calcium oxide (CaO), and 0.5 parts by mass of magnesium oxide (MgO) Part of the mixture was added to prepare a mixed powder. The mixing ratio of alumina powder and zirconia powder is shown in Table 1. In addition, the ratio of the zirconia crystal particle contained in the ceramic substrate for mounting light emitting elements after firing almost coincided with the prepared composition.

  Next, an acrylic resin molding binder is added to the mixed powder, a slurry is prepared by a mill using high-purity alumina balls, and a ceramic green sheet having an average thickness of 200 μm is prepared by a doctor blade method. The green sheet was processed into a product shape using a mold.

Next, in order to sinter the molded product of this product shape, the temperature rising rate is about 150 ° C./h, the maximum temperature is 1570 to 1590 ° C., and the holding time at the maximum temperature is 2 hours in a pusher type tunnel furnace. Baking was performed under the conditions as described above, and a sample of a ceramic substrate for mounting a light-emitting element having a length, width, and thickness of 60 mm, 50 mm, and 0.4 mm, respectively, was produced. The obtained ceramic substrate for mounting light-emitting elements was a dense sintered body with a porosity of 1% or less as measured by Archimedes method.

  Next, with respect to the obtained sample of the ceramic substrate for mounting a light emitting element, the crystal structure, the average particle diameter of the crystal particles, and the reflectance were measured by the following method.

  The crystal structure of the ceramic substrate for mounting the light emitting element was evaluated using a scanning electron microscope equipped with an element analyzer after mirror polishing the surface of each sample to a depth of about 20 μm from the surface.

  The average particle size of the alumina crystal particles and the zirconia crystal particles is such that a circle containing about 20 alumina crystal particles or zirconia crystal particles is drawn in the cross section of the ceramic substrate for mounting the light emitting element, and the crystal particles are applied in and around the circle. Was selected, image processing was performed on the contour of each of the alumina crystal particles or zirconia crystal particles, the area of the crystal particles was determined, and the diameter when the circle was replaced with a circle having the same area was calculated.

  The sample size for reflectivity measurement was 30 mm, 30 mm, and 0.25 mm in length, width, and thickness, respectively. The reflectance of the produced reflectance measurement substrate was measured in the wavelength range of 360 to 500 nm using a spectrocolorimeter (CM-3700d manufactured by Konica Minolta). Table 1 lists the reflectivity at 360 nm, 380 nm, and 450 nm.

  Among the alumina crystal particles present in the ceramic sintered body, the number ratio of the alumina crystal particles 1 including the zirconia crystal particles is obtained by photographing a cross section of a piece obtained by cutting a ceramic substrate for mounting a light emitting element with a scanning electron microscope. It was determined by counting the number of crystal grains from the photograph of the obtained crystal structure. The unit area was a region where the total number of alumina crystal particles was 50.

  Further, the X-ray diffraction intensity of zirconia with respect to alumina (104 surface) was measured from the X-ray diffraction pattern of a sample obtained by pulverizing a part of the ceramic substrate for mounting light emitting elements, and the content ratio was determined for each zirconia crystal system. At this time, for tetragonal zirconia and cubic zirconia, the diffraction intensity was in a state where peaks overlapped. The diffraction intensity of each crystal zirconia with respect to the alumina (104) surface shown in Table 1 is a value when the alumina (104) surface is 1.

  As a comparative example, a sample (sample No. 2) prepared in the same manner using a sample (sample No. 1) to which zirconia powder was not added and a zirconia powder (average particle size 2 μm) whose average particle size is larger than that of alumina powder. Were made and evaluated. Sample No. In sample 2, it was confirmed that zirconia crystal particles were present at the grain boundaries of the alumina crystal particles.

As an example, FIG. 1 and sample no. The reflectance measurement results for the sample 6 were shown. As is clear from the results in Table 1, sample No. 3 to 8, the reflectance at a wavelength of 360 nm was 67% or more, and the reflectance at a wavelength of 380 nm was 72% or more. These samples had a crystal structure in which the zirconia crystal particles were included in the alumina crystal particles. Sample No. Nos. 3 to 8 were mixed crystals in which the zirconia crystal particles contained in the ceramic sintered body contained monoclinic zirconia and at least one of tetragonal zirconia and cubic zirconia.

  Among them, the sample No. 2 in which the number ratio of the alumina crystal particles including the zirconia crystal particles is 60% (30 out of 50) or more. In 6-8, the reflectance of light in wavelength 360nm was 70% or more.

  On the other hand, a sample (sample No. 1) to which zirconia powder was not added and a sample No. 1 having a crystal structure in which zirconia crystal particles exist at the grain boundaries of alumina crystal particles. In both cases, the reflectance at a wavelength of 380 nm or less was as low as 67%.

A ... Ceramic substrate for mounting light emitting element B ... Light emitting device 1 ... Alumina crystal particle 3 ... Zirconia crystal particle 5 ... Conductor 7 ...・ Light emitting element 8... Substrate 9.

Claims (5)

  A ceramic substrate for mounting a light emitting element, comprising a ceramic sintered body having alumina crystal particles mainly containing alumina crystal particles and containing zirconia crystal particles.   2. The ceramic substrate for mounting a light emitting element according to claim 1, wherein the alumina crystal particles have substantially parallel facing surfaces.   3. The ceramic substrate for mounting a light emitting element according to claim 1, wherein the alumina crystal particles enclosing the zirconia crystal particles are present in the ceramic sintered body in a number ratio of 60% or more. .   The ceramic for mounting a light emitting element according to any one of claims 1 to 3, wherein the zirconia crystal particles are a mixed crystal of monoclinic zirconia and at least one of tetragonal zirconia and cubic zirconia. Substrate.   A light emitting device comprising a light emitting element on a substrate made of the ceramic substrate for mounting a light emitting element according to claim 1.

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