Light-emitting element, manufacturing method for the same, manufacturing method for aluminum oxide precursor sol, and aluminum oxide precursor sol

Abstract

To improve the light extraction efficiency of a light-emitting element.SOLUTION: The light-emitting element includes a sapphire substrate and a light-emitting part formed on a first surface side of the sapphire substrate. Light emitted from the light-emitting part transmits through the sapphire substrate and is emitted from a second surface of the sapphire substrate that opposes the first surface. A plate-like crystal layer including plate-like crystals whose main component is aluminum oxide is formed on the second surface. On the surface of the plate-like crystal layer opposite to the side of the second surface, a concave-convex structure is provided.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a light-emitting element, a method for producing a light-emitting element, a method for producing a precursor sol of aluminum oxide, and a precursor sol of aluminum oxide. [Background technology]

[0002] In recent years, the development of light-emitting elements has progressed, for example, light-emitting elements that output ultraviolet light in a wavelength range with high sterilizing power in medical and food processing sites are being developed. This light-emitting element is formed, for example, by laminating an n-type semiconductor layer, a light-emitting layer, a p-type semiconductor layer, etc., in that order on the surface of a sapphire substrate. The ultraviolet light emitted from the light-emitting layer passes through the sapphire substrate and is emitted outside the light-emitting element from the back surface of the sapphire substrate.

[0003] However, because the sapphire substrate is a material with a high refractive index, the difference in refractive index on the back surface of the substrate, which serves as the light extraction surface, is large, and as a result, ultraviolet light is totally reflected by the back surface, which can significantly reduce the light extraction efficiency of the light emitted from the back surface of the sapphire substrate.

[0004] Therefore, Patent Document 1 discloses a configuration in which the surface of a sapphire substrate is made into a moth-eye surface to reduce reflection on the surface of the sapphire substrate. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2014 / 171467 Summary of the Invention [Problem to be solved by the invention]

[0006] In the embodiment of Patent Document 1, there is a concern that reflection at the light extraction surface cannot be sufficiently reduced.

[0007] Therefore, an object of the present invention is to improve the light extraction efficiency of a light-emitting device. [Means for solving the problem]

[0008] The means for solving the above problem is a light-emitting element comprising a sapphire substrate and a light-emitting portion formed on a first surface side of the sapphire substrate, wherein light emitted from the light-emitting portion passes through the sapphire substrate and is emitted from a second surface opposite to the first surface of the sapphire substrate, wherein a plate-like crystal layer including plate-like crystals mainly composed of aluminum oxide is formed on the second surface, and an uneven structure is provided on the surface of the plate-like crystal layer opposite to the second surface side. Effect of the Invention

[0009] It is possible to provide a light emitting device with improved light extraction efficiency. [Brief description of the drawings]

[0010] [Figure 1] FIG. 2 is a schematic diagram of a light-emitting element. [Diagram 2] 1 is a graph showing the correlation between film thickness and change in refractive index. [Diagram 3] FIG. 2 is an enlarged view of the area surrounded by circle 50 in FIG. 1. [Figure 4] 13 is a modified example of the light emitting element. [Diagram 5] 1A to 1C are diagrams illustrating a method for manufacturing a concave-convex structure. [Figure 6] FIG. 1 is a diagram illustrating a method for producing a precursor sol of aluminum oxide. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, the embodiment for carrying out the present invention will be described with reference to the drawings. However, the embodiment described below is one embodiment of the invention, and the present invention is not limited to this. Then, common configurations will be described with mutual reference to multiple drawings, and the description of configurations with common symbols will be omitted as appropriate. Items with the same name but different can be distinguished by adding "No. 0", such as the first item and the second item.

[0012] First Embodiment 1 is a schematic diagram of a light-emitting device 1 according to this embodiment. Here, a light-emitting device that emits light in the ultraviolet region will be described in detail, but the application is not limited to the ultraviolet region.

[0013] The light-emitting element 1 comprises a substrate 2 made of sapphire, a light-emitting section 3 provided on a front surface (first surface) 21 of the substrate 2, and a plate-like crystal layer 4 provided on a back surface (second surface) 22 of the substrate 2 opposite the light-emitting section 3.

[0014] The light-emitting element 1 in this embodiment is configured so that light emitted from the light-emitting section 3 passes through the substrate 2 and is emitted to the outside from the back surface 22 of the substrate 2. In this case, a plate crystal layer 4 may also be provided on the side surface (third surface) 23 of the substrate 2 in order to suppress reflection of light emitted from the side surface 23 of the substrate 2. The light-emitting element 1 is preferably provided in direct contact with the substrate 2, but another material or a space may be provided between the light-emitting element 1 and the substrate 2.

[0015] The light-emitting element 1 is a light-emitting element that emits light in the ultraviolet region with a wavelength of 200 nm or more and 350 nm or less. In particular, if the light-emitting element 1 is adjusted to emit light with a high intensity in the wavelength range of 260 nm or more and 280 nm or less, it can be used in medical treatment and food processing because it has a high sterilizing power.

[0016] The light emitting section 3 has a buffer layer 5 formed on the surface 21 of the substrate 2 made of sapphire, an n-clad layer 6 formed on the buffer layer 5, an n-electrode 7 and a light emitting layer 8 formed on the n-clad layer 6, and a p-electrode 10 formed on the light emitting layer 8. When a voltage is applied between the n-electrode 7 and the p-electrode 10, the light emitting layer 8 emits light.

[0017] The buffer layer 5 is formed on the surface 21 of the substrate 2 made of sapphire, and is made of GaN, AlN, AlGaN, or the like. The thickness of the buffer layer 5 is preferably 2.0 μm or more and 4.0 μm or less. By providing the buffer layer 5, the stress generated when a material with a different lattice constant is grown on the substrate 2 can be absorbed by the buffer layer 5, and a highly accurate light emitting element 1 with little deformation can be obtained.

[0018] The n-clad layer 6 is formed on the buffer layer 5 and is made of n-type AlGaN or the like. Germanium, selenium, tellurium, or the like may be used as n-type impurities. The thickness of the n-clad layer 6 is preferably 1.0 μm to 3.0 μm or less. An n-electrode 7 is formed on the n-clad layer 6.

[0019] The n-electrode 7 is an n-type semiconductor layer, and may be made of a known material.

[0020] The light emitting layer 8 is formed on the n-cladding layer 6, and is configured to have a band gap of 3.5 V or more in order to output deep ultraviolet light with a wavelength of 350 nm or less. The light emitting layer 8 is formed by alternately laminating barrier layers with large band gap energy and quantum well layers with small band gap energy. The thickness of each layer is preferably 20 nm or less.

[0021] The p-cladding layer 9 is formed on the light emitting layer 8, and is made of p-type AlGaN or the like. Magnesium, zinc, beryllium, or the like may be used as p-type impurities. The p-electrode 10 is formed on the p-cladding layer 9.

[0022] The plate crystal layer 4 is formed of plate crystals mainly composed of aluminum oxide, and is formed on the back surface 22 and side surface 23 of the substrate 2 made of sapphire. The plate crystals forming the plate crystal layer 4 are plate crystals that precipitate and grow on the surface layer of a film mainly composed of aluminum oxide when the surface layer of the film is subjected to peptization or the like by immersing the film in warm water. Here, the main component means the component with the highest content when multiple components are contained.

[0023] The p-electrode 10 is a p-type semiconductor layer, and may be made of a known material.

[0024] In order to increase the light extraction efficiency of the light-emitting element 1, it is effective to suppress Fresnel reflection that occurs when light emitted from the light-emitting section 3 passes through the substrate 2 and is emitted to the outside from the light extraction surfaces (rear surface 22 and side surface 23). The plate crystal layer 4 formed on the side surface 23 is preferably formed thinner than the plate crystal layer 4 formed on the rear surface 22. If the plate crystal layer 4 on the side surface 23 is too thick, there is a risk that the plate crystal layer 4 will peel off due to interference with surrounding objects.

[0025] In order to suppress reflection at the rear surface 22 and the side surface 23, the plate crystal layer 4 is preferably a layer whose refractive index increases continuously from the surface layer 42 side toward the substrate 2 side. For example, the refractive index changes as shown by the straight line (a), the curve (b), and the curve (c) in the graph of Fig. 2 are preferable. In particular, the refractive index change as shown by the straight line (a) or the curve (c) is more preferable.

[0026] The refractive index increases continuously from the surface layer 42 side toward the substrate 2 side, and thus the reflection reducing effect is greater than when layers with higher refractive indices are stacked in order from the surface layer 42 side. Furthermore, since the refractive index of the plate crystal layer 4 increases continuously from the surface layer 42 side toward the substrate 2 side, it is preferable that the surface have an uneven structure.

[0027] FIG. 3 is an enlarged view of the area surrounded by a circle 50 in FIG. 1. The plate crystal layer 4 has an uneven structure 45 on the surface layer 42 side. The pitch (distance between convex portions) P of the uneven structure 45 is preferably 50 nm or more and 350 nm or less, and more preferably 100 nm or more and 290 nm or less. By being in the above range, light in the ultraviolet region can be efficiently emitted to the outside of the light-emitting element 1. In addition, the height H1 of the uneven structure 45 is preferably 150 nm or more and 400 nm or less, and more preferably 200 nm or more and 300 nm or less. The pitch P of the uneven structure 45 is preferably smaller than the height H1 of the uneven structure 45. The shape of the uneven structure 45 is not particularly limited, and it is sufficient that it is configured to reduce the reflection of light incident from the substrate 2 side.

[0028] Furthermore, the plate crystal layer 4 has an intermediate layer 46 between the substrate 2 and the uneven structure 45. In order to suppress reflection at the interface with the substrate 2, it is desirable that the crystallinity of the intermediate layer 46 of the plate crystal layer 4 is higher than that of the uneven structure 45. When the crystallinity of aluminum oxide is high, the difference in refractive index with the substrate 2 made of sapphire, which is an aluminum oxide single crystal, is reduced, which is preferable in terms of suppressing reflection.

[0029] The crystallinity of aluminum oxide can be expressed by density, and the higher the density of aluminum oxide, the higher the crystallinity. 3 More than 3.82g / cm 3 It is preferable that the density is 3.20 g / cm or less. 3 More than 3.82g / cm 3 It is more preferable that the refractive index difference between the plate crystal layer 4 and the substrate 2 is reduced, which is preferable in terms of suppressing reflection.

[0030] The thickness H2 of the intermediate layer 46 is preferably 10 nm or more and 100 nm or less, and more preferably 20 nm or more and 60 nm or less. In addition, the thickness H2 of the intermediate layer 46 is preferably smaller than the height H1 of the concave-convex structure 45.

[0031] In this embodiment, in order to quantify the light extraction efficiency, the light transmittance of the base material 2 was determined. The light transmittance T in the present invention can be determined by the following formula (1). T = 100 - R1 - R2 - S1 (1)

[0032] Here, R1 is the reflectance of light incident from the buffer layer 5 to the substrate 2, R2 is the reflectance of light incident from the substrate 2 to the plate crystal layer 4, and S1 is the transmittance of the substrate 2. Note that S1 is a value that varies depending on the thickness of the substrate 2. In the present invention, the transmittance T is increased by reducing R2.

[0033] FIG. 4 shows a modified example of the light-emitting element 1 of this embodiment, and as shown in FIG. 4, a reflective layer 15 may be provided on the side surface 23 of the substrate 2. By providing the reflective layer 15 on the side surface 23, the path of the light emitted from the side surface 23 can be changed so that it is emitted from the back surface 22. This can improve the transmittance T. The reflective layer 15 can be formed of a metal film of aluminum, gold, copper, or the like using a plating method or a vapor deposition method. By using a mask, it is possible to avoid forming the film on places other than the side surface. The reflective layer 15 may be provided not only on the side surface 23, but also on the side of the light-emitting layer 8 opposite the substrate 2.

[0034] The light-emitting element 1 of this embodiment can be applied to semiconductor light-emitting elements such as light-emitting diodes and semiconductor lasers. As light-emitting diodes, they can be widely applied to elements that convert electrical signals into light, such as indoor lighting, automobile headlights, railway electronic bulletin boards, LCD TV backlights, and outdoor displays. They can also be applied to sterilization of refrigerators and air conditioners, 3D printers, medical equipment, and printing with inkjet printers. As semiconductor lasers, they can be applied to reading and recording on optical discs, optical communications such as PCs and mobile phones, measuring devices such as LiDAR (Light Detection and Ranging), and wood and metal processing.

[0035] Next, a description will be given of a manufacturing method of the light-emitting element 1. The light-emitting element 1 of this embodiment is manufactured by a step of forming a light-emitting portion 3 on a substrate 2 made of sapphire, a step of dividing the substrate 2 with a plurality of light-emitting portions 3 by dicing, and a step of forming a plate crystal layer 4 on the back surface side of the substrate 2 with the light-emitting portions 3.

[0036] The process of forming the light emitting section 3 involves stacking the buffer layer 5, n-clad layer 6, n-electrode 7, light emitting layer 8, p-clad layer 9, and p-electrode in order, and patterning each layer appropriately. The buffer layer 5, n-clad layer 6, light emitting layer 8, and p-clad layer 9 may be formed by metal organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), hydride vapor phase epitaxy (HVPE), or the like. The n-electrode 7 and p-electrode 10 may be formed by electron beam deposition, sputtering, or the like. After the light emitting section 3 is formed on the substrate 2 in this manner, the substrate 2 is divided into a plurality of substrates 2 with light emitting sections 3 by dicing.

[0037] A method for producing the uneven structure 45 will be described with reference to Fig. 5. Fig. 5(a) shows a state in which an aluminum oxide precursor sol 12 is supplied to a substrate 2. The plate crystal layer 4 is obtained by applying the aluminum oxide precursor sol 12 to the rear surface 22, and then drying or baking the aluminum oxide film formed thereon, and subjecting the film to a steam treatment or hot water immersion treatment to convert the surface layer into boehmite, thereby forming an uneven structure. The aluminum oxide precursor sol 12 is obtained by a production method described later, and is a liquid containing 2-ethylbutanol and 4-methyl-2-pentanol as solvents.

[0038] The aluminum oxide precursor sol 12 can be supplied by dropping the aluminum oxide precursor sol 12 from a thin tube or one or more fine holes. Other examples include a method in which the aluminum oxide precursor sol 12 is attached onto the substrate 2 through a slit, or a method in which the aluminum oxide precursor sol 12 is first attached to a plate and then transferred to the substrate 2. The aluminum oxide precursor sol 12 can be supplied to the substrate 2 by immersing the substrate 2 in the aluminum oxide precursor sol 12.

[0039] FIG. 5(b) shows a state in which the supplied aluminum oxide precursor sol 12 is spread on the substrate 2. Examples of methods for spreading the aluminum oxide precursor sol 12 on the substrate 2 include a spin coating method in which the substrate 2 is rotated to spread the dropped sol 12, and a blade coating method or roll coating method in which a blade or roll is moved on the substrate 2 to spread the dropped sol 12. It is also possible to spread the aluminum oxide precursor sol 12 while supplying it. Examples of the method include a slit coating method in which the aluminum oxide precursor sol 12 is supplied from a slit while the slit or substrate 2 is moved to spread the aluminum oxide precursor sol 12. In addition, a printing method in which the aluminum oxide precursor sol 12 once attached to a plate is transferred while the plate or substrate 11 is moved may also be used.

[0040] One example is a dip coating method in which the substrate 2 is once immersed in the aluminum oxide precursor sol 12 and then the substrate 2 is pulled up at a constant speed. When an optical member having a three-dimensionally complicated shape such as a concave surface is produced, it is difficult to bring the supply source of the aluminum oxide precursor sol 12 close, so a spin coating method is preferred.

[0041] FIG. 5(c) shows a state in which an aluminum oxide film 13 is formed by drying and / or baking the substrate 2. After coating the aluminum oxide precursor sol 12, the solvents contained in the sol, 2-ethylbutanol and 4-methyl-2-pentanol, are evaporated by drying or baking, forming an aluminum oxide film 13. Further heating causes a condensation reaction of unreacted alkoxide and hydroxyl groups to proceed. The heating temperature is preferably 140° C. or higher, which is necessary for volatilizing the solvent, and is preferably 200° C. or lower, taking into consideration the effects on the substrate and other peripheral members. Examples of heating methods include heating in a hot air circulating oven, a muffle furnace, an IH furnace, and heating with an IR lamp.

[0042] FIG. 5(d) shows a state in which a plate crystal layer 4 having an uneven structure 45 of aluminum oxide boehmite is formed on the substrate 2. The uneven structure 45 is formed by contacting the aluminum oxide film 13 obtained in the step of FIG. 5(c) with hot water at 60° C. or more and 100° C. or less. The layer having the uneven structure 45 formed is composed of crystals of aluminum oxide or hydroxide or hydrates thereof, and the main crystals are plate crystals of boehmite. Methods for contacting the aluminum oxide film 13 with hot water include a method of immersing the substrate 2 in hot water, and a method of contacting the aluminum oxide film 13 with running or misty hot water. Hereinafter, the crystals formed by contacting the aluminum oxide film 13 with hot water will be referred to as a plate crystal layer 4.

[0043] The pitch, height, and chemical composition of the microstructure of the uneven structure also change when the aluminum oxide (alumina) film is treated with steam or immersed in hot water. The higher the temperature of the steam or hot water, the faster the time it takes for the pitch, height, and chemical composition of the uneven structure to change to a certain point. If the temperature of the hot water is lowered, the treatment time can be extended to change them to the same state.

[0044] Next, a method for producing the precursor sol 12 of aluminum oxide will be described with reference to Fig. 6. The method for producing the precursor sol 12 of aluminum oxide includes the following steps (1) to (3). (1) A step of adding a β-diketone compound and an aluminum alkoxide or aluminum salt compound to a solvent and mixing them to prepare a solution containing an aluminum compound. (2) A step of adding water or water containing a catalyst to the solution obtained in the step (1) and mixing them to form a condensate of the aluminum alkoxide or aluminum salt compound and an organoaluminum compound 14 represented by the following general formula (1): (3) A step of heating the solution obtained in the step (2) to a temperature of 60° C. or higher and 150° C. or lower to obtain an aluminum oxide precursor sol 12.

[0045] 6(a) shows a state in which a solvent 104 is weighed into a container 103 having a lid 102 in an atmosphere of dry air or dry nitrogen with a low moisture content, or a dry inert gas 101 with a low moisture content. A mixture of 10.6 parts by weight or more and 15.0 parts by weight or less of 2-ethylbutanol and 2.2 parts by weight or more and 6.2 parts by weight or less of 4-methyl-2-pentanol is used as the solvent 104.

[0046] FIG. 6(b) shows a state in which aluminum alkoxide 105 is supplied into container 103 by dry air or dry nitrogen with a low moisture content, or dry inert gas 101 with a low moisture content, and separated into two liquid layers. Taking aluminum sec-butoxide as an example, since aluminum sec-butoxide has a larger specific gravity than the solvent 104, when aluminum sec-butoxide is slowly added to the solvent and allowed to stand, two liquid layers are separated. By adopting this state, aluminum sec-butoxide can be isolated from water contained in the air. When aluminum alkoxide 105 adheres to container 103 during weighing, grain growth occurs from the adhered portion, and the uniformity of the particles of the condensation product of the aluminum compound contained in aluminum oxide precursor sol 12 is lost.

[0047] 6(c) shows a process of dropwise mixing 3-methyl-2,4-pentanedione 106 into aluminum alkoxide solution 107. Aluminum alkoxide solution 107 is produced by stirring and mixing aluminum alkoxide 105 and solvent 104 in a two-liquid layer state with stirring blade 108 for 20 minutes to 60 minutes.

[0048] FIG. 6(d) shows a process in which a catalyst solution 109 obtained by mixing an acid catalyst in a solution containing a water-soluble solvent is added dropwise to an aluminum alkoxide solution 107 dissolved in 3-methyl-2,4-pentanedione 106 and a solvent 104, and then hydrolyzed to obtain a polycondensate of aluminum alkoxide 105.

[0049] FIG. 5(e) shows a process of obtaining an aluminum oxide precursor sol 12 by heating the sol made of the polycondensate at 100° C. or more and 120° C. or less for 90 minutes or more and 150 minutes or less.

[0050] In the method for producing the aluminum oxide precursor sol 12 of this embodiment, 10.6 parts by weight or more and 15.0 parts by weight or less of 2-ethylbutanol and 2.2 parts by weight or more and 6.2 parts by weight or less of 4-methyl-2-pentanol are mixed as a solvent in step (1). The content ratio of 4-methyl-2-pentanol in the reaction system is reduced, and in step (3), the stirring time is set to 20 minutes or more and 60 minutes or less so that 4-methyl-2-pentanol can be involved in the solvent exchange reaction to prevent 2-ethylbutanol from being consumed from the system due to solvent exchange with aluminum alkoxide.

[0051] However, if the stirring time of the aluminum alkoxide and the solvent is too long, gelation will proceed. This is thought to be due to the stronger interaction between the aluminum alkoxides after the solvent exchange. Therefore, even if the stirring time is long, it may cause abnormal particle growth.

[0052] The aluminum oxide precursor sol 12 contains particles containing a hydrolysate of an aluminum compound and / or a condensate thereof as a component, a solvent, and an organoaluminum compound represented by the following general formula (1).

[0053] [ka]

[0054] (In the formula, R1 and R2 represent an alkyl group having 1 to 6 carbon atoms, a perfluoroalkyl group, or an allyl group. R3 represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, a perfluoroalkyl group, an allyl group, or an aryl group. n is an integer of 1 to 3.)

[0055] In addition, the amount of solvent added, the amount of β-diketone compound added, the amount of water added or the amount of water added contained in the water containing the catalyst, or the temperature at which the solution is heated is adjusted so that the mass fractal dimension obtained by small-angle X-ray scattering measurement of the aluminum oxide precursor sol 12 is 1.02 or more and 1.12 or less. For example, the mass fractal dimension can be increased by increasing the amount of water added or the amount of water added contained in the water containing the catalyst. The mass fractal dimension can also be increased by increasing the temperature at which the solution is heated or by extending the heating time. It is preferable that the aluminum oxide precursor sol 12 contains 23.4 parts by weight or more and 52.5 parts by weight or less of 4-methyl-2-pentanol in the solvent.

[0056] In this embodiment, the particles containing the hydrolyzate and / or condensate of an aluminum compound in the aluminum oxide precursor sol 12 as a component have comb-shaped open spaces. This reduces the amount of hydrophobic organoaluminum compounds contained in the aluminum oxide film. The process of volatilization of the hydrophobic organoaluminum compounds in the film during drying and / or baking after applying the aluminum oxide precursor sol 12 onto a substrate is considered to involve not only volatilization through the pores between the remaining solvent particles, but also volatilization of the solvent molecules coordinated from the comb-shaped spaces of the particles. Therefore, the aluminum precursor sol 12 remains stable, and the density of the plate crystal layer 4 increases after immersion in warm water, suppressing light reflection, making it possible to fabricate a light-emitting device with good light extraction efficiency.

[0057] However, the size of the particles is on the nano-order, and secondary and tertiary particles are formed when the sol is dried, making it difficult to evaluate the particle shape by surface observation using an electron microscope or the like. Therefore, small angle X-ray scattering (SAXS) is used as a method for evaluating the state of particles containing hydrolyzates and / or condensates of aluminum compounds as components in the aluminum oxide precursor sol 12. The two-dimensional image obtained by the small angle X-ray scattering device was converted into a one-dimensional scattering profile with the q value (scattering vector) on the horizontal axis, and then the wave number and intensity were plotted logarithmically, and the mass fractal dimension was obtained as shape information from the slope.

[0058] In addition, shape analysis was used to obtain the shape from a double logarithmic plot, and the indirect Fourier transform (IFT) method was also used to estimate the size and shape by fitting the entire scattering profile.

[0059] In SAXS, monochromatic X-rays are irradiated onto a sample, and X-rays scattered from the sample at low angles are detected. i The incident X-ray is incident on a structure (distance between structures through which the X-ray passes) and the scattered X-ray has a wave number of k sThen the scattering vector q is given by the following equation (2). q=k i -k s =4πsinθ / λ (2)

[0060] Diffraction occurs when the scattered X-rays satisfy the following condition (3) (Bragg equation). nλ = 2d sinθ (3) n is an integer.

[0061] When the measurement angle θ is small, sinθ approaches 0, so d becomes large and large structures can be observed. In other words, this shows that it is possible to obtain structural information of particles at various scales depending on the measurement angle. The q value provides information on structural parameters from nanometers to submicrometers in real space.

[0062] The two-dimensional image obtained by the small-angle X-ray scattering device is converted into a one-dimensional scattering profile with the scattering intensity I on the vertical axis and the q value on the horizontal axis. g ≦1), the following relation (4) approximately holds: Ln(I(q))=A-1 / 3R g 2 q 2 (4)

[0063] If the vertical axis is the natural logarithm of the scattering intensity and the horizontal axis is q2 (Gunier plot), the particle size (radius of gyration Rg) can be calculated from the slope. In addition, the relationship between wave number and intensity is given by the following formula (5). I(q) ∝ q -D (5)

[0064] Therefore, by plotting the wave number and intensity on a log-log scale, shape information can be obtained from the slope of the plot. The slope D is called the mass fractal dimension, and takes values ​​from 0 to 3. A mass fractal dimension close to 1 indicates a rod shape, a mass fractal dimension close to 2 indicates a disk (plate) shape, and a mass fractal dimension close to 3 indicates a sphere shape. On the other hand, the surface fractal dimension D s Using this, we have the following relationship in equation (6). I(q) ∝ q -(6-Ds) (6)

[0065] D s A value of 2 indicates a smooth surface, and a value between 2 and 3 indicates an uneven surface. Furthermore, the size and shape can be estimated by fitting the entire scattering profile using the IFT method. The IFT method is a method for determining size and shape information from the small-angle scattering profile of a dilute system without assuming a model. ρ(r) is calculated by numerically solving the following equations (7) and (8).

[0066]

number

[0067] N is the number of particles per unit volume, and F(q) is the scattering function for a dilute system. ρ(r) is a function called the pair distance function (PDDF), which represents the distribution of electrons (electron density) at a distance from a certain atom (molecule, particle). Since the space occupied by electrons is the shape of the atom (molecule, particle), the shape of the scatterer can be estimated by calculating the PDDF.

[0068] The aluminum oxide precursor sol 12 of this embodiment contains as a main component a hydrolysate and / or a condensate of an aluminum compound obtained by contacting an aluminum compound with water in a solvent. When the aluminum compound is Al-X3 (X represents an alkoxyl group, an acyloxyl group, a halogen group, or a nitrate ion), the hydrolysate is a compound represented by Al-X2(OH), Al-X(OH)2, or Al-(OH)3. In the hydrolysate, the -OH groups react with each other or with the -X group and the -OH group to form an Al-O-Al bond with the elimination of H2O or XH. The resulting compound having one or more Al-O-Al bonds and a linear or branched structure is a condensate of the aluminum compound. It is preferable that the particles are amorphous.

[0069] The content of particles containing hydrolysates and / or condensates of aluminum compounds as components in the aluminum oxide precursor sol 12 is preferably 1% by weight to 7% by weight, and more preferably 2.5% by weight to 6% by weight, calculated as metal oxide. If the content is more than 7% by weight, the viscosity of the sol increases, and the film thickness is likely to be thick and non-uniform in one coating operation, and the desired light extraction performance may not be obtained. If the content is too low, less than 1% by weight, the film thickness in one coating operation becomes too thin, and coating and heating must be repeated multiple times, which increases the number of steps and the possibility of occurrence of defective appearance.

[0070] In addition, the average particle size of the particles containing the hydrolyzate of an aluminum compound and / or its condensate as a component is desirably 7.5 nm to 150 nm, preferably 7.5 nm to 35 nm, more preferably 7.5 nm to 25 nm. If the average particle size is less than 7.5 nm and the thickness of the aluminum oxide film exceeds 150 nm, the tensile stress generated during drying or baking after film formation becomes large, and cracks are likely to occur. If it exceeds 35 nm, the particles tend to aggregate during application, which is not preferable, and appearance defects tend to occur. If it exceeds 150 nm, it is not preferable, as it tends to gel.

[0071] Examples of aluminum compounds include aluminum ethoxide, aluminum isopropoxide, aluminum n-butoxide, aluminum sec-butoxide, aluminum tert-butoxide, aluminum acetylacetonate, and oligomers thereof, aluminum nitrate, aluminum chloride, aluminum acetate, aluminum phosphate, aluminum sulfate, aluminum hydroxide, etc. Among the above metal compounds, it is preferable to use metal alkoxides such as aluminum n-butoxide and aluminum sec-butoxide as raw materials.

[0072] Aluminum alkoxides are highly reactive to water, and are rapidly hydrolyzed by the addition of moisture in the air or water, causing the solution to become cloudy and precipitate to form. In addition, aluminum salt compounds are difficult to dissolve in organic solvents alone, and the solution is not very stable. To prevent this, stabilizers are added to stabilize the solution.

[0073] The stabilizer used is a β-diketone compound or a β-ketoester compound. In a solvent, the stabilizer becomes an enolate through keto-enol tautomerism. The enolate coordinates to an aluminum atom with the metal alkoxide undergoing alcohol elimination, generating an organometallic compound. The stabilizer coordinates to the oligomeric metal alkoxide, suppressing the rapid hydrolysis of the metal alkoxide. When the metal alkoxide is hydrolyzed and the particles grow, the liberated enolate further coordinates to the metal alkoxide to which the enolate is already coordinated.

[0074] In this way, the stabilizer forms a chelate together with the aluminum alkoxide. The organoaluminum compound generated in the aluminum oxide precursor sol 12 may aggregate depending on its chemical structure. It is presumed that the aggregation of the organoaluminum compound inhibits the formation of bonds between particles obtained by hydrolyzing the aluminum alkoxide in the optical film during the firing film formation. If the formation of bonds between particles is insufficient, the aluminum oxide protrusions are not formed sufficiently, and the anti-reflection performance deteriorates. In addition, since the organoaluminum compound may have a sublimation point of 150°C or higher, the organoaluminum compound cannot be completely removed from the aluminum oxide film by firing at a firing temperature lower than 200°C. In particular, since an ester exchange reaction occurs in β-ketoester compounds, organoaluminum compounds having a sublimation point of 150°C or higher are easily generated.

[0075] In addition, when a sol using at least aluminum-containing metal alkoxide and a stabilizer as raw materials is applied onto a sapphire substrate to form a film, the organoaluminum compound may aggregate during the film formation process, resulting in poor appearance such as unevenness in the film. Therefore, it is preferable to remove the organoaluminum compound precipitated by aggregation in the aluminum oxide precursor sol 12, or to decompose the organoaluminum compound so that as little as possible of the compound remains in the film even at low firing temperatures. This prevents the light extraction efficiency from deteriorating even at firing temperatures lower than 200°C.

[0076] Therefore, in the aluminum oxide precursor sol 12, a β-diketone compound having a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, a perfluoroalkyl group, an allyl group, or an aryl group at the α-position is used as a stabilizer. Furthermore, a β-diketone compound having an alkyl group having 1 to 6 carbon atoms, a perfluoroalkyl group, or an allyl group at the γ-position is used.

[0077] Specifically, the β-diketone compound is preferably a compound represented by the following general formula (2). General formula (2) R1COCHR3COR2 (In the formula, R1 and R2 represent an alkyl group having 1 to 6 carbon atoms, a perfluoroalkyl group, or an allyl group. R3 represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, a perfluoroalkyl group, an allyl group, or an aryl group.)

[0078] Specific examples of such β-diketone compounds are shown below. Examples of the β-diketone compounds include acetylacetone, 3-methyl-2,4-pentanedione, 3-ethyl-2,4-pentanedione, 3-butyl-2,4-pentanedione, 3-pentyl-2,4-pentanedione, 3-hexyl-2,4-pentanedione, 3-isopropyl-2,4-pentanedione, 3-isobutyl-2,4-pentanedione, 3-isopentyl-2,4-pentanedione, 3-isohexyl-2,4-pentanedione, 3-phenyl-2,4-pentanedione, 3-chloroacetylacetone, 2,6-dimethyl-3,5-heptanedione, and 2,6-dimethyl-3,5-heptanedione.

[0079] In particular, in order to suppress the aggregation of the organic aluminum compounds, it is preferable to use a β-diketone compound having a sterically bulky substituent. However, when a β-diketone compound having a sterically bulky substituent at the γ-position is used, the coordination of the β-diketone compound with the aluminum alkoxide is also inhibited, and the aluminum alkoxide cannot be kept stable. Therefore, by providing a substituent at the α-position, the aggregation of the organic aluminum compounds is suppressed. Since the α-position is located at the opposite pole to the ketone group, it does not sterically inhibit the coordination of the β-diketone compound with the aluminum alkoxide, and only suppresses the aggregation of the organic aluminum compounds themselves. However, it is thought that the aggregation suppression effect is reduced when the substituent itself, such as a long-chain alkyl group, has an interaction. Furthermore, an organic aluminum compound made of a β-diketone compound having an electron-donating functional group at the α-position is in a state where an electrophilic reaction is likely to occur at the α-carbon. Therefore, an organic aluminum compound made of a β-diketone compound having an electron-donating functional group at the α-position decomposes and becomes a compound with a lower boiling point, which is more preferable for removing the organic aluminum compound from the film during firing film formation.

[0080] The amount of the β-diketone compound added varies depending on the type of metal compound, but is preferably 0.3 to 2 moles per mole of aluminum alkoxide. In addition, the β-diketone compound is effective when mixed with the alkoxide for a certain period of time before adding water.

[0081] To induce hydrolysis, it is necessary to add an appropriate amount of water. The amount of water to be added varies depending on the solvent and concentration. The amount of water to be added, or the amount of water contained in water containing a catalyst, is generally 0.5 mol or more and less than 2 mol per mol of aluminum alkoxide. However, in order to coordinate solvent molecules to particles containing a hydrolyzate of an aluminum compound and / or its condensate as a component, it is preferable that the amount is 1.5 mol or more and less than 2 mol per mol of the aluminum compound, although it varies depending on the type of β-diketone compound to be added. Furthermore, it is more preferable that the amount is 1.65 mol or more and less than 2 mol.

[0082] A catalyst can be added to the water to accelerate part of the hydrolysis reaction. It is preferable to use an acid or base catalyst such as hydrochloric acid or phosphoric acid as the catalyst. It is preferable to use the catalyst at a concentration of 0.1 mol / L or less.

[0083] The shape of particles obtained by hydrolyzing aluminum alkoxide can be controlled by adding an acid or base catalyst. Furthermore, the stability of aluminum precursor sol 12 is further improved by including 0.001% by weight or more and less than 0.06% by weight of an acid or base in aluminum precursor sol 12. In order to coordinate solvent molecules to particles containing a hydrolysate and / or a condensate thereof as a component, the amount is preferably 0.02% by weight or more and less than 0.06% by weight.

[0084] The solvent may be any organic solvent in which raw materials such as aluminum compounds are uniformly dissolved and particles do not aggregate, etc. For example, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methylpropanol, 1-pentanol, 2-pentanol, cyclopentanol, 2-methylbutanol, 3-methylbutanol, 1-hexanol, 2-hexanol, 3-hexanol, 4-methyl-2-pentanol, 2-methyl-1-pentanol, 2-ethylbutanol, 2,4-dimethyl-3-pentanol, 3-ethylbutanol, 1-heptanol, etc. Monohydric alcohols such as 2-heptanol, 1-octanol, and 2-octanol; dihydric and higher alcohols such as ethylene glycol and triethylene glycol; ether alcohols such as methoxyethanol, ethoxyethanol, propoxyethanol, isopropoxyethanol, butoxyethanol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, and 1-propoxy-2-propanol; dimethoxyethane, diglyme, and tetrahydrofuran. ethers such as dioxane, diisopropyl ether, and cyclopentyl methyl ether; esters such as ethyl formate, ethyl acetate, n-butyl acetate, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, and propylene glycol monomethyl ether acetate; various aliphatic or alicyclic hydrocarbons such as n-hexane, n-octane, cyclohexane, cyclopentane, and cyclooctane; various aromatic hydrocarbons such as toluene, xylene, and ethylbenzene; various ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; various chlorinated hydrocarbons such as chloroform, methylene chloride, carbon tetrachloride, and tetrachloroethane; and aprotic polar solvents such as N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, and ethylene carbonate.

[0085] Among the above solvents, monohydric alcohols having 5 to 8 carbon atoms are preferred because they have high solubility in aluminum compounds and are less likely to absorb moisture. If hydrolysis of the aluminum compounds progresses due to moisture absorption by the solvent, it becomes difficult to control the particle size. In addition, moisture absorption during coating leads to particle aggregation and impairs the stability of optical properties. Furthermore, when a general low-boiling alcohol is used, the solvent volatilizes quickly and the above-mentioned stabilizer remains in the film, affecting the optical properties, but when a monohydric alcohol having 5 to 8 carbon atoms is used, the solvent volatilizes together with the stabilizer during drying and / or baking, so the stabilizer is less likely to remain. Among the above solvents, it is preferred to use 4-methyl-2-pentanol or the like as the solvent.

[0086] On the other hand, monohydric alcohols having 5 to 8 carbon atoms are highly hydrophobic, and it is difficult to uniformly mix them with water required for hydrolysis, making it difficult to maintain a constant particle size. Therefore, it is preferable to use a water-soluble solvent in combination with a monohydric alcohol having 5 to 8 carbon atoms.

[0087] The content of the solvent contained in the aluminum oxide precursor sol 12 of the present invention is desirably 50% by weight or more and 98% by weight or less, and preferably 60% by weight or more and 93% by weight or less.

[0088] When a mixture of solvents is used, the mixing ratio of the solvents is preferably, for example, 50% by weight to 90% by weight of a monohydric alcohol having 5 to 8 carbon atoms and 10% by weight to 50% by weight of a water-soluble solvent having a boiling point of 110° C. to 170° C. If the amount of the monohydric alcohol having 5 to 8 carbon atoms is too small, the film thickness becomes non-uniform during coating, resulting in poor appearance. If the amount of the monohydric alcohol having 5 to 8 carbon atoms is too large, the hydrophobicity of the solvent increases, and water does not disperse uniformly.

[0089] The water-soluble solvent referred to here refers to a solvent in which the solubility of water in the solvent at 23°C is 80% by weight or more. The water-soluble solvent has a boiling point of 110°C or more and 170°C or less. If a water-soluble solvent with a boiling point of less than 110°C is used, moisture absorption and whitening due to evaporation are likely to occur. If a water-soluble solvent with a boiling point of more than 170°C is used, it remains in the aluminum oxide film even after drying, causing variations in reflectance. It is preferable that the water-soluble solvent is a glycol ether.

[0090] When preparing the aluminum oxide precursor sol 12, the sol can be heated to promote the hydrolysis and condensation reaction of the aluminum alkoxide. The heating temperature varies depending on the boiling point of the solvent and the type of β-diketone compound, but is preferably 60°C to 150°C, and more preferably 75°C to 130°C. In particular, when the β-diketone compound is 3-methyl-2,4-pentanedione, the temperature is more preferably 75°C to 130°C. By heating in this manner, the particles grow and the particulate property is improved.

[0091] In the aluminum oxide precursor sol 12, a small amount of a metal compound consisting of at least one of compounds of Zr, Si, Ti, Zn, and Mg can be used together with the aluminum compound. As these metal compounds, metal alkoxides or metal salt compounds such as chlorides and nitrates can be used. It is particularly preferable to use metal alkoxides because by-products produced during the preparation of the sol have little effect on the film-forming properties during coating. The amount of the metal compound used is preferably 10 mol % or less with respect to 100 mol % of the aluminum compound.

[0092] Specific examples of zirconium alkoxides include zirconium tetramethoxide, zirconium tetraethoxide, zirconium tetra n-propoxide, zirconium tetraisopropoxide, zirconium tetra n-butoxide, and zirconium tetra t-butoxide.

[0093] As the silicon alkoxide, various types of silicon alkoxides represented by the general formula Si(OR)4 (R represents the same or different lower alkyl groups such as methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, etc.) can be used.

[0094] Examples of titanium alkoxides include tetramethoxytitanium, tetraethoxytitanium, tetra-n-propoxytitanium, tetraisopropoxytitanium, tetra-n-butoxytitanium, and tetraisobutoxytitanium.

[0095] Examples of the zinc compound include zinc acetate, zinc chloride, zinc nitrate, zinc stearate, zinc oleate, and zinc salicylate, with zinc acetate and zinc chloride being particularly preferred.

[0096] Examples of magnesium compounds include magnesium alkoxides such as dimethoxymagnesium, diethoxymagnesium, dipropoxymagnesium, and dibutoxymagnesium, magnesium acetylacetonate, and magnesium chloride. Among the above metal compounds, it is preferable to use metal alkoxides such as zirconium tetraisopropoxide, zirconium tetra n-butoxide, tetramethoxysilane, tetraethoxysilane, tetraisopropoxytitanium, tetra n-butoxytitanium, dipropoxymagnesium, and dibutoxymagnesium as raw materials.

[0097] <Example> The present invention will be specifically described below with reference to examples. However, the present invention is not limited to the examples. The aluminum oxide precursor sol 12 obtained in each example and comparative example was evaluated by the following method. The results are shown in Table 1.

[0098] (1) Preparation of aluminum oxide precursor F from aluminum oxide precursor sol A Aluminum sec-butoxide (ASBD, Kawaken Fine Chemicals) and β-diketone compound were added to the solvent and mixed and stirred until homogenized. 0.01M dilute hydrochloric acid was dissolved in a mixed solvent of the solvent and 1-ethoxy-2-propanol as catalytic water, and then slowly added to the aluminum sec-butoxide solution and stirred for a while. The final mixture ratio of the solvent and 1-ethoxy-2-propanol was adjusted to 7 / 3. The mixture was further stirred in a heated oil bath for 2 to 3 hours or more to prepare aluminum oxide precursor sols A to F. 2-Ethylbutanol and 4-methyl-2-pentanol were used as the solvent, either alone or in a mixture. The amounts of the β-diketone compound and each raw material used in the preparation and the heating temperature of the sol are shown in Table 1.

[0099] (2) Small-angle X-ray scattering (SAXS) measurement Small-angle X-ray scattering device (SAXess mc 2 The measurement was performed using an X-ray tube of 40 keV and 50 mA, a Cu target, a wavelength of 1.542 Å, a focal spot size of 0.4 mm × 12 mm, a camera length (distance between the sample and the detector) of 261 mm, and a q of 0.04 nm. -1 From 8 nm -1 Measurements were performed using an imaging plate detector, integrating the time for 15 minutes. The obtained two-dimensional image was converted into a one-dimensional scattering profile with the q value on the horizontal axis, and then desmearing correction was performed to remove smear caused by the slit. The particle size R g , surface fractal dimension D s , the mass fractal dimension D was calculated.

[0100] (3) Gas chromatography-mass spectrometry The organic components in the film were quantified using a gas chromatography mass spectrometer (TRACE GC ULTRA / DSQ; Thermofisher Scientific). The aluminum oxide precursor sol was applied to a Si substrate and dried at 140°C for 30 minutes. The resulting aluminum oxide film was sealed in a sample bottle, and the components in the aluminum oxide film were injected into the gas chromatography mass spectrometer using a headspace autosampler (COMBI PAL; CTC ANALYTICS) under the following conditions: incubation temperature 150°C, equilibration time 30 min, syringe temperature 150°C, injection volume 1 mL, and injection rate 1 mL / s.

[0101] The measurement conditions for gas chromatography mass spectrometry were as follows: injection port temperature 200°C, sample injection: splitless method, column: DB-WAX (Agilent Technologies) length 30 m, inner diameter 0.25 mm, film thickness 0.25 mm, carrier gas and flow rate helium: 1.0 mL / min, transfer line temperature 250°C, ionization method: electron ionization method, ionization voltage 70 eV, mass spectrometer: quadrupole type, measurement m / z range 20-650, ion source temperature 230°C. The column temperature was held at 40°C for 1 min, heated to 250°C at 5°C / min, and then held at 250°C for 1 min. The amount of components per film volume (g / cm) was calculated from the results of the component analysis, the area of ​​the Si substrate, and the film thickness of the aluminum oxide film. 3 The thickness of the aluminum oxide film was determined by measuring the thickness of a Si substrate coated with the aluminum oxide film using spectroscopic ellipsometry (JA Woollam EC-400) and simulating the thickness using the analysis software W-VASE. The aluminum oxide precursor sol and the amount of organic components used in the analysis are shown in Table 2.

[0102] (4) Particle size distribution measurement and evaluation Approximately 1 ml of the aluminum oxide precursor sol was placed in a glass cell and measured at 25° C. using a particle size distribution analyzer (Zetasizer Nano S, manufactured by Malvern Instruments). The refractive index was set to 1.5, the absorption to 0.01, and the solution viscosity was measured using a cone-plate type rotational viscometer (RE-105L, manufactured by Toki Sangyo Co., Ltd.) equipped with a standard rotor (1°34', R24) at 25° C. and 50 rpm. The viscosity was used for analysis.

[0103] (5) Transmittance measurement Measurements were made using a spectrophotometer U-4000 manufactured by Hitachi High-Tech Fielding Corp. After dicing a 2-inch diameter sapphire substrate into a size of approximately 10 mm x 10 mm without forming a light-emitting portion, films were formed on the back and side surfaces and the films were removed as described in the examples and comparative examples.

[0104] The transmittance measurements were performed at a starting wavelength of 800 nm, an ending wavelength of 200 nm, and a sampling interval of 1.00 nm. An uncoated sapphire substrate was used as a reference. The transmittance values ​​are listed in Table 1 as the average values ​​from 260 nm to 280 nm.

[0105] Example 1 In forming the light-emitting element 1 as shown in FIG. 1, a light-emitting portion 8 made of an AlGaN-based material was fabricated on a sapphire substrate having a diameter of 2 inches and a thickness of about 0.5 mm. Next, the substrate with the light-emitting portion was cut into squares for each element by dicing. Next, aluminum oxide precursor sol A was applied to the back side of the element by spin coating. At this time, aluminum oxide precursor sol A was dropped at the center of the coating surface of the substrate 2, that is, near the intersection of the diagonal lines of the square, and spreads over the coating surface as it rotates. However, since the substrate 2 is thin and its surface is roughened by dicing, the sol spreads to the sides by capillary action and a film is formed. After that, the substrate was baked for 30 minutes in a hot air circulating oven at 140° C. to coat it with an aluminum oxide film, and then immersed in warm water at 75° C. to form a plate crystal layer 4 on the back side of the substrate 2.

[0106] Example 2 The same operations as in Example 1 were performed, except that after applying the aluminum oxide precursor sol A by spin coating, the aluminum oxide precursor sol formed on the side surface was removed by contacting the side surface with a wiper moistened with a solvent in which the aluminum oxide precursor sol is highly soluble, such as alcohol, and wiping it up.

[0107] Example 3 After dicing the base material 2 with the light emitting portion 8, an aluminum mirror was deposited only on the side surface of the sapphire substrate to form a mirror surface. The same operations as in Example 1 were carried out.

[0108] (Examples 4 to 9) The same procedure as in Example 1 was carried out except that aluminum oxide precursor sols B to G were used.

[0109] The various evaluation results are summarized in Table 1.

[0110] [Table 1]

[0111] In Examples 1 to 9, good transmittance could be obtained by forming the plate crystal layer 4 on at least the back surface of the sapphire substrate.

[0112] The above-described embodiment can be modified as appropriate without departing from the technical concept.

[0113] For example, a plurality of embodiments may be combined, or part of at least one embodiment may be deleted or replaced.

[0114] In addition, new matters may be added to at least one embodiment. The disclosure of this specification includes not only what is explicitly described in this specification, but also all matters that can be understood from this specification and the drawings attached to this specification.

[0115] Furthermore, the disclosure of this specification includes the complement of each concept described in this specification. In other words, if this specification contains a statement that "A is greater than B," for example, even if the statement that "A is not greater than B" is omitted, this specification can be said to disclose that "A is not greater than B." This is because when a statement that "A is greater than B" is made, it is assumed that the case in which "A is not greater than B" is taken into consideration.

[0116] The disclosure of the present invention is given below.

[0117] (Configuration 1) A light-emitting device comprising: a sapphire substrate; and a light-emitting portion formed on a first surface side of the sapphire substrate, wherein light emitted from the light-emitting portion passes through the sapphire substrate and is emitted from a second surface opposite to the first surface of the sapphire substrate, wherein a plate-like crystal layer including plate-like crystals mainly composed of aluminum oxide is formed on the second surface, and an uneven structure is provided on a surface of the plate-like crystal layer opposite to the second surface.

[0118] (Configuration 2) 2. The light-emitting element according to configuration 1, wherein the plate crystal layer is formed on a third surface of the sapphire base material that intersects with the first surface and the second surface.

[0119] (Configuration 3) The light-emitting element according to configuration 1 or 2, characterized in that a third surface of the sapphire base intersecting the first surface and the second surface has a reflective layer that reflects light emitted from the light-emitting portion.

[0120] (Configuration 4) 4. The light-emitting element according to any one of configurations 1 to 3, further comprising a reflective layer on the first surface that reflects light reflected by the second surface.

[0121] (Configuration 5) 5. The light-emitting element according to any one of structures 1 to 4, wherein the pitch of the concave-convex structure is 50 nm or more and 350 nm or less.

[0122] (Configuration 6) 6. The light-emitting element according to any one of claims 1 to 5, wherein the height of the uneven structure is 150 nm or more and 400 nm or less.

[0123] (Configuration 7) 7. The light-emitting element according to any one of configurations 1 to 6, wherein the pitch of the concave-convex structure is smaller than the height of the concave-convex structure.

[0124] (Configuration 8) The light-emitting element according to any one of configurations 1 to 7, wherein the plate crystal layer has an intermediate layer mainly composed of aluminum oxide, and the intermediate layer is provided between the sapphire substrate and the uneven structure.

[0125] (Configuration 9) 9. The light-emitting device according to configuration 8, wherein the intermediate layer has a higher crystallinity of aluminum oxide than the uneven structure.

[0126] (Configuration 10) The density of the aluminum oxide in the intermediate layer is 2.70 g / cm 3 More than 3.82g / cm 3 A light-emitting device according to configuration 8, characterized in that:

[0127] (Configuration 11) 9. The light-emitting device according to configuration 8, wherein the thickness of the intermediate layer is smaller than the height of the concave-convex structure.

[0128] (Configuration 12) 12. The light-emitting element according to any one of configurations 1 to 11, wherein the aluminum oxide is boehmite.

[0129] (Configuration 13) The light-emitting element according to any one of configurations 1 to 12 is a semiconductor light-emitting element.

[0130] (Method 1) A method for manufacturing a light-emitting element, comprising the steps of: applying an aluminum oxide precursor sol to a second surface opposite to the first surface of a sapphire substrate; baking the aluminum oxide precursor sol to form an aluminum oxide film; and contacting the aluminum oxide film with hot water or water vapor at 60°C or higher and 100°C or lower to form a plate-like crystal layer having an uneven structure on the second surface.

[0131] (Method 2) The method for producing a light-emitting element according to method 1, further comprising the step of dividing the sapphire base material having a light-emitting portion formed thereon by dicing before the step of applying the aluminum oxide precursor sol.

[0132] (Method 3) 3. The method for producing a light-emitting element according to claim 1, further comprising the step of forming the plate crystal layer on a third surface of the sapphire substrate that intersects with the first surface and the second surface.

[0133] (Method 4) 4. The method for manufacturing a light-emitting element according to any one of Methods 1 to 3, further comprising the step of forming a reflective layer on a third surface of the sapphire base material that intersects with the first surface and the second surface.

[0134] (Sol 1) A precursor sol of aluminum oxide containing particles containing as components a hydrolysate of an aluminum compound and / or a condensate thereof, a solvent, and an organoaluminum compound represented by the following general formula (1), wherein the precursor sol of aluminum oxide has a mass fractal dimension of 1.02 or more and 1.12 or less as determined by small-angle X-ray scattering measurement:

[0135] [ka]

[0136] (In the formula, R1 and R2 represent an alkyl group having 1 to 6 carbon atoms, a perfluoroalkyl group, or an allyl group. R3 represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, a perfluoroalkyl group, an allyl group, or an aryl group. n is an integer of 1 to 3.)

[0137] (Sol manufacturing method 1) a step of adding water or water containing a catalyst to the solution and mixing the solution to form a condensate of the aluminum alkoxide or the aluminum salt compound and an organoaluminum compound represented by the following general formula (1); and a step of heating the solution containing the organoaluminum compound to 60° C. or higher and 150° C. or lower to obtain an aluminum oxide precursor sol, wherein the aluminum oxide precursor sol contains particles containing a hydrolysate of an aluminum compound and / or a condensate thereof as a component, a solvent, and the organoaluminum compound represented by the following general formula (1), and the amount of the solvent, the amount of the β-diketone compound, the amount of water or the water contained in the catalyst, or the temperature at which the solution is heated is adjusted so that the mass fractal dimension of the aluminum oxide precursor sol obtained by small-angle X-ray scattering measurement is 1.02 or higher and 1.12 or lower.

[0138] [ka]

[0139] (In the formula, R1 and R2 represent an alkyl group having 1 to 6 carbon atoms, a perfluoroalkyl group, or an allyl group. R3 represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, a perfluoroalkyl group, an allyl group, or an aryl group. n is an integer of 1 to 3.) [Explanation of symbols]

[0140] 1 Light emitting element 2. Sapphire substrate 3 Light emitting part 4 Plate-like crystal layer 21 Page 1 22 Side 2

Claims

1. A light emitting device comprising: a sapphire substrate; and a light emitting section formed on a first surface side of the sapphire substrate, wherein light emitted from the light emitting section is transmitted through the sapphire substrate and emitted from a second surface of the sapphire substrate opposite the first surface, a plate crystal layer including plate crystals mainly composed of aluminum oxide is formed on the second surface; The light-emitting device comprises a plate crystal layer having a surface opposite to the second surface, the plate crystal layer being provided with an uneven structure.

2. The light-emitting element according to claim 1 , wherein the plate crystal layer is formed on a third surface of the sapphire base material that intersects with the first surface and the second surface.

3. The light-emitting element according to claim 1 , further comprising a reflective layer on a third surface of the sapphire base intersecting with the first surface and the second surface, the reflective layer reflecting the light emitted from the light-emitting portion.

4. The light-emitting device according to claim 1 , further comprising a reflective layer on the first surface, the reflective layer reflecting the light reflected by the second surface.

5. The light-emitting element according to claim 1 , wherein the pitch of the concave-convex structure is 50 nm or more and 350 nm or less.

6. The light-emitting element according to claim 1 , wherein the height of the uneven structure is 150 nm or more and 400 nm or less.

7. The light-emitting device according to claim 1 , wherein the pitch of the uneven structure is smaller than the height of the uneven structure.

8. the plate crystal layer has an intermediate layer mainly composed of aluminum oxide, The light-emitting device according to claim 1 , wherein the intermediate layer is provided between the sapphire substrate and the uneven structure.

9. The light-emitting device according to claim 8 , wherein the intermediate layer has a higher crystallinity of aluminum oxide than the uneven structure.

10. The density of the aluminum oxide in the intermediate layer is 2.70 g / cm ３ 3.82g / cm or more ３ The light-emitting device according to claim 8, wherein:

11. The light-emitting device according to claim 8 , wherein the thickness of the intermediate layer is smaller than the height of the uneven structure.

12. The light emitting device according to claim 1 , wherein the aluminum oxide is boehmite.

13. 13. The light-emitting element according to claim 1, wherein the light-emitting element is a semiconductor light-emitting element.

14. A method for manufacturing a light-emitting device, comprising the steps of: applying an aluminum oxide precursor sol to a second surface of the sapphire substrate opposite to the first surface; forming an aluminum oxide film by calcining the aluminum oxide precursor sol; and contacting the aluminum oxide film with hot water or water vapor at 60° C. or more and 100° C. or less to form a plate-like crystal layer having an uneven structure on the second surface.

15. 15. The method for producing a light-emitting element according to claim 14, further comprising the step of dividing the sapphire base material having the light-emitting portion formed thereon by dicing before the step of applying the aluminum oxide precursor sol.

16. The method for manufacturing a light-emitting element according to claim 14, further comprising the step of forming the plate crystal layer on a third surface of the sapphire base material that intersects with the first surface and the second surface.

17. The method for manufacturing a light-emitting element according to claim 14, further comprising the step of forming a reflective layer on a third surface of the sapphire base material that intersects with the first surface and the second surface.

18. Particles containing a hydrolysate of an aluminum compound and / or a condensate thereof as a component; A solvent; An aluminum oxide precursor sol containing an organoaluminum compound represented by the following general formula (1): A precursor sol of aluminum oxide, characterized in that a mass fractal dimension of the precursor sol of aluminum oxide, as determined by small-angle X-ray scattering measurement, is 1.02 or more and 1.12 or less. 【Chemistry 1】 (In the formula, R １ , R ２ R represents an alkyl group having 1 to 6 carbon atoms, a perfluoroalkyl group, or an allyl group. ３ represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, a perfluoroalkyl group, an allyl group, or an aryl group; and n is an integer of 1 to 3.

19. A step of adding a β-diketone compound and an aluminum alkoxide or aluminum salt compound to a solvent and mixing them to prepare a solution containing an aluminum compound; a step of adding water or water containing a catalyst to the solution and mixing the solution to form a condensate of the aluminum alkoxide or the aluminum salt compound and an organoaluminum compound represented by the following general formula (1); a step of heating the solution containing the organoaluminum compound to a temperature of 60° C. or higher and 150° C. or lower to obtain a precursor sol of aluminum oxide; A method for producing an aluminum oxide precursor sol comprising the steps of: The aluminum oxide precursor sol comprises particles containing a hydrolysate of an aluminum compound and / or a condensate thereof as a component, A solvent; The organoaluminum compound is represented by the following general formula (1): a method for producing a precursor sol of aluminum oxide, comprising adjusting an amount of the solvent, an amount of the β-diketone compound, an amount of the water or an amount of water contained in water containing a catalyst, or a temperature at which the solution is heated, so that a mass fractal dimension of the precursor sol of aluminum oxide obtained by small-angle X-ray scattering measurement is 1.02 or more and 1.12 or less. 【Chemistry 2】 (In the formula, R １ , R ２ R represents an alkyl group having 1 to 6 carbon atoms, a perfluoroalkyl group, or an allyl group. ３ represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, a perfluoroalkyl group, an allyl group, or an aryl group; and n is an integer of 1 to 3.

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