Light-emitting device

Abstract

This light emitting device comprises an ultraviolet light-emitting element, a resin adhesive layer, and an optical member in the stated order. The ultraviolet light-emitting element has an adhesive surface in contact with the resin adhesive layer, and the optical member has an adhesive surface in contact with the resin adhesive layer. The light-emitting device has a joint region which is rectangular and in which the optical member and the ultraviolet light-emitting element overlap when viewed from the optical axis direction of the optical member. When viewed from the optical axis direction of the optical member, the adhesive surface of the ultraviolet light-emitting element forms a concave curve, and the adhesive surface of the optical member forms a convex curve in a first cross section along one diagonal of the joint region. The absolute value |Ha-Hb| of the difference between the height difference Ha (Ha > 0) of the concave curve in the joint region and the height difference Hb (Hb > 0) of the convex curve in the joint region is 0 or more and less than Ha.

Description

Light-emitting device

[0001] The present disclosure relates to a light emitting device.

[0002] Patent Document 1 discloses a light emitting device including, in this order, an ultraviolet light emitting element, a bonding member, and a lens body. The ultraviolet light emitting element has an emission surface that emits ultraviolet light. The lens body has an incident surface that faces the emission surface of the ultraviolet light emitting element. The incident surface of the lens body is formed in a convex shape toward the emission surface of the ultraviolet light emitting element to eliminate any air bubbles remaining in the bonding member.

[0003] Japanese Patent Application Publication No. 2023-173280

[0004] The light emitting device includes an ultraviolet light emitting element, a resin adhesive layer, and an optical member in this order. The ultraviolet light emitting element has an adhesive surface in contact with the resin adhesive layer. The optical member has an adhesive surface in contact with the resin adhesive layer. The resin adhesive layer adheres the adhesive surface of the ultraviolet light emitting element to the adhesive surface of the optical member so that the adhesive surface faces the adhesive surface of the optical member.

[0005] When viewed from the optical axis direction of the optical member, the ultraviolet light emitting element is disposed inside the periphery of the optical member, and the ultraviolet light emitting element is smaller than the optical member. When viewed from the optical axis direction of the optical member, the bonding area where the optical member and the ultraviolet light emitting element overlap has the same rectangular shape as the bonding surface of the ultraviolet light emitting element. The rectangle includes a square.

[0006] The inventors of the present application have discovered that before bonding the ultraviolet light emitting element to the optical component, the bonding surface of the ultraviolet light emitting element may have a concave curved surface. The concave curved surface is thought to be formed by residual stress. The concave curved surface may be a double curved surface (e.g., a bowl-shaped curved surface) or a single curved surface (e.g., a cylindrical curved surface).

[0007] Whether the concave curved surface is a double curved surface or a single curved surface, the adhesive surface forms a concave curve in a first cross section along one diagonal line of the bonding region as viewed from the optical axis direction of the optical member. Note that when the concave curved surface is a single curved surface, the adhesive surface forms a straight line in a second cross section along another diagonal line of the bonding region as viewed from the optical axis direction of the optical member.

[0008] When the adhesive surface of the ultraviolet light emitting element is a concave curved surface and the adhesive surface of the optical element is a flat surface, the gap between the ultraviolet light emitting element and the optical element at the first cut surface varies greatly, which can result in a loss of adhesion of the resin adhesive layer.

[0009] One aspect of the present disclosure provides a technique for improving the adhesion between an ultraviolet light emitting element and an optical component when the adhesive surface of the ultraviolet light emitting element is a concave curved surface.

[0010] A light-emitting device according to one aspect of the present disclosure includes, in this order, an ultraviolet light-emitting element, a resin adhesive layer, and an optical member. The ultraviolet light-emitting element has an adhesive surface in contact with the resin adhesive layer, and the optical member has an adhesive surface in contact with the resin adhesive layer. The light-emitting device has a rectangular bonding region where the optical member and the ultraviolet light-emitting element overlap when viewed from the optical axis direction of the optical member. In a first cross-section along one diagonal line of the bonding region when viewed from the optical axis direction of the optical member, the bonding surface of the ultraviolet light-emitting element forms a concave curve, and the bonding surface of the optical member forms a convex curve. The absolute value |Ha - Hb| of the difference between the height difference Ha (Ha > 0) of the concave curve in the bonding region and the height difference Hb (Hb > 0) of the convex curve in the bonding region is equal to or greater than 0 and less than Ha.

[0011] According to one aspect of the present disclosure, when the adhesive surface of the ultraviolet light emitting element is a concave curved surface, the adhesiveness between the ultraviolet light emitting element and the optical member can be improved.

[0012] Fig. 1 is a cross-sectional view showing a light-emitting device according to one embodiment. Fig. 2 is a plan view showing an example of a rectangular bonding region where an optical member and an ultraviolet light-emitting element overlap, as viewed from the optical axis direction of the optical member. Fig. 3 is a cross-sectional view showing an example of a first cut surface taken along line III-III in Fig. 2. Fig. 4 is a cross-sectional view showing the first cut surface according to a first modified example. Fig. 5 is a cross-sectional view showing the first cut surface according to a second modified example.

[0013] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In each drawing, the same or corresponding components are denoted by the same reference numerals, and their description may be omitted. In the specification, the symbol "to" indicating a range of values ​​means that the values ​​before and after it are included as the lower and upper limits. The range of values ​​includes the range rounded up or down.

[0014] A light emitting device 1 according to one embodiment will be described with reference to Fig. 1. The light emitting device 1 includes, in this order, an ultraviolet light emitting element 2, a resin adhesive layer 3, and an optical member 4. The ultraviolet light emitting element 2 has an adhesive surface 21 in contact with the resin adhesive layer 3. The optical member 4 has an adhesive surface 41 in contact with the resin adhesive layer 3.

[0015] The ultraviolet light emitted by the ultraviolet light-emitting element 2 passes through the resin adhesive layer 3 and the optical member 4 in this order. The peak emission wavelength of the ultraviolet light-emitting element 2 is preferably 210 nm to 320 nm, and more preferably 260 nm to 290 nm. The "peak emission wavelength" is the wavelength at which the output value is highest in the spectral distribution of the emitted light.

[0016] The radiant flux of the ultraviolet light-emitting element 2 is, for example, more than 20 mW, preferably 35 mW or more, and more preferably 40 mW or more. From the viewpoint of the heat dissipation property of the ultraviolet light-emitting element 2, the radiant flux of the ultraviolet light-emitting element 2 may be 120 mW or less. The radiant flux is the radiant energy emitted per unit time. The radiant flux is measured in accordance with CIE 127:2007.

[0017] The ultraviolet light emitting element 2 has, for example, a substrate 22 and a semiconductor layer 23. The ultraviolet light emitting element 2 has, for example, a flip-chip structure. When the ultraviolet light emitting element 2 has a flip-chip structure, ultraviolet light generated in the semiconductor layer 23 is emitted through the substrate 22. The substrate 22 is a transparent substrate that transmits ultraviolet light.

[0018] The substrate 22 is made of, for example, a sapphire substrate or an aluminum nitride substrate. An aluminum nitride substrate is a substrate made of a single crystal of aluminum nitride. A sapphire substrate or an aluminum nitride substrate is a transparent substrate that transmits ultraviolet light. The thickness of the substrate 22 is, for example, 0.05 mm to 2 mm.

[0019] The semiconductor layer 23 is provided on the opposite side of the substrate 22 from the optical member 4. The semiconductor layer 23 emits light when a voltage is applied to it. An electrode for applying a voltage to the semiconductor layer 23 is not shown, but is formed on the opposite side of the substrate 22 from the semiconductor layer 23 so as not to block ultraviolet light traveling from the semiconductor layer 23 to the substrate 22. This prevents a decrease in light extraction efficiency.

[0020] The ultraviolet light emitting element 2 may be bonded to a mounting substrate (not shown) via solder bumps (not shown). The mounting substrate is a ceramic substrate made of, for example, aluminum nitride sintered body, aluminum oxide sintered body, or LTCC (Low Temperature Co-fired Ceramics) on which electrodes are formed.

[0021] The resin adhesive layer 3 adheres the adhesive surface 21 of the ultraviolet light-emitting element 2 to the adhesive surface 41 of the optical member 4 so that they face each other. The material of the resin adhesive layer 3 is not particularly limited as long as it transmits ultraviolet light emitted by the ultraviolet light-emitting element 2, but from the viewpoint of light resistance, it is preferably a fluororesin or a silicone resin.

[0022] The adhesive surface 41 of the optical member 4 may be larger than the adhesive surface 21 of the ultraviolet light-emitting element 2. In this case, it is preferable to form the resin adhesive layer 3 over the entire adhesive surface 41 of the optical member 4, and then overlay the resin adhesive layer 3 and the ultraviolet light-emitting element 2. The resin adhesive layer 3 only needs to cover at least the entire adhesive surface 21 of the ultraviolet light-emitting element 2. The resin adhesive layer 3 may also be formed over the entire adhesive surface 21 of the ultraviolet light-emitting element 2, and then overlay the resin adhesive layer 3 and the optical member 4.

[0023] The method for forming the resin adhesive layer 3 is not particularly limited, and examples thereof include spin coating, spray coating, bar coating, gravure coating, screen printing, inkjet coating, etc. Alternatively, a method can be used in which the resin adhesive layer 3 formed on a support member such as a release film is transferred to the adhesive surface 21 of the ultraviolet light-emitting element 2 or the adhesive surface 41 of the optical member 4.

[0024] To improve the adhesive strength of the resin adhesive layer 3, at least one (preferably both) of the two adhesive surfaces 21, 41 may be cleaned. The cleaner is not particularly limited, but examples include hydrocarbon solvents such as ethanol and acetone, fluorine-based solvents such as AS-300 (manufactured by AGC Inc.), and aqueous cleaners such as alkaline detergents. Furthermore, at least one (preferably both) of the two adhesive surfaces 21, 41 may be subjected to a surface activation treatment. Examples of the surface activation treatment include UV ozone treatment, atmospheric pressure plasma treatment, excimer UV treatment, and corona treatment.

[0025] The step of bonding the optical member 4 and the ultraviolet light emitting element 2 using the resin adhesive layer 3 may be performed under atmospheric pressure or in a vacuum. Furthermore, the bonding step may be performed while heating the optical member 4 and the ultraviolet light emitting element 2.

[0026] After the bonding step, a heat treatment or an autoclave treatment (heating and pressurizing treatment) can be performed. After the bonding step, an aging treatment can be performed on the resin adhesive layer 3 by emitting light from the ultraviolet light emitting element 2. The heat treatment, autoclave treatment, and aging treatment described above can be performed in an atmospheric pressure atmosphere or an inert gas atmosphere.

[0027] The shear storage modulus G' of the resin adhesive layer 3 is preferably 0.1 GPa to 10 GPa. G' is measured in accordance with JIS K7244-10:2005. If G' is 0.1 GPa or more, the adhesive strength of the resin adhesive layer 3 is good. G' is more preferably 0.5 GPa or more. On the other hand, if G' is 10 GPa or less, the resin adhesive layer 3 is likely to deform so as to absorb variations in the distance D between the ultraviolet light-emitting element 2 and the optical member 4. Furthermore, if G' is 10 GPa or less, thermal distortion can be reduced and the occurrence of cracks can be suppressed. G' is more preferably 5 GPa or less.

[0028] The optical member 4 suppresses total reflection of ultraviolet rays and improves the efficiency of extracting ultraviolet rays. The optical member 4 is, for example, a lens. The optical member 4 may be a spherical lens or an aspherical lens. Although not shown, the optical member 4 may have a flange that protrudes radially outward from the periphery of the convex curved surface 42, which will be described later.

[0029] The optical member 4 has an adhesive surface 41 and a convex curved surface 42 facing away from the adhesive surface 41. Ultraviolet light emitted by the ultraviolet light-emitting element 2 enters the adhesive surface 41 and exits from the convex curved surface 42. The convex curved surface 42 is a dome-shaped curved surface whose center protrudes further than the periphery.

[0030] The optical member 4 is a lens in this embodiment, but may be a cover glass.

[0031] Although not shown, the convex curved surface 42 of the optical member 4 may have irregularities that prevent reflection of ultraviolet light generated by the ultraviolet light-emitting element 2. The irregularities of the convex curved surface 42 have, for example, a moth-eye structure, and prevent ultraviolet light traveling from the inside of the optical member 4 to the outside from being reflected back into the optical member 4, thereby improving the efficiency of extracting ultraviolet light.

[0032] Although not shown, the light emitting device 1 may be provided with an anti-reflection film on the convex curved surface 42 of the optical member 4. The anti-reflection film prevents ultraviolet light traveling from the inside of the optical member 4 to the outside from being reflected back into the optical member 4, thereby improving the efficiency of extracting ultraviolet light. A general anti-reflection film is used as the anti-reflection film.

[0033] Although not shown, the convex curved surface 42 of the optical member 4 may have irregularities that scatter the ultraviolet light generated by the ultraviolet light-emitting element 2. The irregularities of the convex curved surface 42 scatter the ultraviolet light emitted from the convex curved surface 42, thereby emitting the ultraviolet light over a wider range.

[0034] The material of the optical member 4 is not particularly limited as long as it transmits ultraviolet light emitted by the ultraviolet light-emitting element 2, and is, for example, oxide glass. Oxide glass can be processed by various processing methods such as thermoforming or grinding and polishing, and a processing method suitable for the shape of the optical member 4 can be selected. Examples of oxide glass include soda-lime glass, alkali-free glass, chemically strengthened glass, and lanthanum borate glass. In order to reduce the loss of ultraviolet light by the optical member 4, a material with low ultraviolet absorption is suitable as the material of the optical member 4, and the material of the optical member 4 is preferably quartz, quartz glass, or sapphire.

[0035] An example of a rectangular bonding area A where the optical member 4 and the ultraviolet light emitting element 2 overlap, as viewed from the optical axis direction of the optical member 4, will be described with reference to Fig. 2. As shown in Fig. 2, as viewed from the optical axis direction of the optical member 4, the ultraviolet light emitting element 2 is disposed inside the periphery of the optical member 4, and the ultraviolet light emitting element 2 is smaller than the optical member 4. As viewed from the optical axis direction of the optical member 4, the bonding area A has the same rectangular shape as the adhesive surface 21 of the ultraviolet light emitting element 2. The rectangle includes a square.

[0036] The inventors of the present application have found that before the ultraviolet light emitting element 2 and the optical member 4 are bonded together, the bonding surface 21 of the ultraviolet light emitting element 2 may have a concave curved surface. The concave curved surface is thought to be formed by residual stress. The concave curved surface may be a double curved surface (for example, a bowl-shaped curved surface) or a single curved surface (for example, a cylindrical curved surface).

[0037] Whether the concave curved surface is a double curved surface or a single curved surface, the adhesive surface 21 forms a concave curve in a first cut surface along one diagonal line of the bonding region A as viewed from the optical axis direction of the optical member 4. When the concave curved surface is a single curved surface, the adhesive surface 21 forms a straight line in a second cut surface along another diagonal line of the bonding region A as viewed from the optical axis direction of the optical member 4.

[0038] Therefore, the inventors of the present application investigated reducing the variation in the gap between the ultraviolet light emitting element 2 and the optical element 4 by processing the adhesive surface 41 of the optical element 4 into a convex curved surface before bonding the ultraviolet light emitting element 2 and the optical element 4. As a result, they found that processing the adhesive surface 41 of the optical element 4 into a convex curved surface can improve the adhesiveness of the resin adhesive layer 3. The processing of the convex curved surface is not particularly limited, and may be, for example, polishing.

[0039] When the concave curved surface of the ultraviolet light-emitting element 2 is a double curved surface (for example, a bowl-shaped curved surface), it is preferable that the convex curved surface of the optical element 4 is a double curved surface (for example, a dome-shaped curved surface). Furthermore, when the concave curved surface of the ultraviolet light-emitting element 2 is a single curved surface (for example, a cylindrical curved surface), it is preferable that the convex curved surface of the optical element 4 is a single curved surface (for example, a cylindrical curved surface). It is preferable that the two adhesive surfaces 21, 41 have shapes that are inverted from each other.

[0040] 3 to 5 show examples of the first cut surface. Fig. 3 shows the case where Hb is the same as Ha, Fig. 4 shows the case where Hb is smaller than Ha, and Fig. 5 shows the case where Hb is larger than Ha. As shown in Figs. 3 to 5, on the first cut surface, the bonding surface 21 of the ultraviolet light-emitting element 2 forms a concave curve, and the bonding surface 41 of the optical member 4 forms a convex curve. The absolute value |Ha - Hb| of the difference between the height difference Ha (Ha > 0) of the concave curve in the bonding region A and the height difference Hb (Hb > 0) of the convex curve in the bonding region A is equal to or greater than 0 and less than Ha.

[0041] Ha is the maximum displacement from the straight line connecting both ends of the concave curve in the bonding area A. Similarly, Hb is the maximum displacement from the straight line connecting both ends of the convex curve in the bonding area A. |Ha-Hb| represents the variation in the distance D between the ultraviolet light-emitting element 2 and the optical member 4, that is, the difference between the maximum and minimum values ​​of the distance D. Incidentally, if the bonding surface 21 of the ultraviolet light-emitting element 2 is a concave curved surface and the bonding surface 41 of the optical member 4 is a flat surface, Hb is zero, and therefore |Ha-Hb| is Ha.

[0042] According to this embodiment, the adhesive surface 41 of the optical member 4 is processed into a convex curved surface, so that |Ha - Hb| can be made less than Ha, and the variation in the distance D can be reduced compared to when the adhesive surface 41 of the optical member 4 is flat. The smaller the variation in the distance D, the smaller the deformation amount of the resin adhesive layer 3 required to absorb that variation. Therefore, the adhesiveness of the resin adhesive layer 3 can be improved. The smaller |Ha - Hb| is, the better. It is most preferable that |Ha - Hb| is zero.

[0043] However, from the standpoint of yield, it is difficult to process |Ha - Hb| to completely zero. If there is a difference between Ha and Hb, it is preferable that Hb is smaller than Ha. As shown in FIG. 4, when Hb is smaller than Ha, the distance D is smallest at both ends of the bonding area A and is largest at the center of the bonding area A. This distribution of distance D does not change even if the apex of the convex curve and the apex of the concave curve are shifted left or right in FIG. 4. Therefore, even if the apex of the convex curve and the apex of the concave curve are shifted left or right in FIG. 4, the variation in distance D remains |Ha - Hb|.

[0044] On the other hand, when Hb is larger than Ha as shown in FIG. 5 , the distance D is basically largest at both ends of the joint area A and smallest at the center of the joint area A. This distribution of the distance D changes when the apex of the convex curve and the apex of the concave curve are shifted left or right in FIG. 5 . For example, the distance D becomes larger at the left end of the joint area A in FIG. 5 as the apex of the convex curve is shifted rightward in FIG. 5 . Therefore, when the apex of the convex curve and the apex of the concave curve are shifted left or right in FIG. 5 , the variation in the distance D may exceed |Ha - Hb|.

[0045] From the viewpoint of relaxing the alignment accuracy requirements between the vertices of the convex curve and the concave curve, it is preferable that Hb be smaller than Ha. If yield is not taken into consideration, it is preferable that Hb be equal to Ha. Therefore, it is preferable that Hb be equal to or smaller than Ha.

[0046] Ha is determined by factors such as residual stress during the manufacture of the ultraviolet light-emitting element 2. The greater the residual stress, the greater Ha. Ha is preferably 300 nm or more, more preferably 400 nm or more, and even more preferably 500 nm or more. Ha is preferably 10 μm or less, and more preferably 1 μm or less.

[0047] Hb is adjusted according to Ha. Hb is preferably 50 nm or more, more preferably 100 nm or more, even more preferably 200 nm or more, even more preferably 300 nm or more, even more preferably 400 nm or more, and even more preferably 500 nm or more. Hb is preferably 10 μm or less, more preferably 1 μm or less.

[0048] The smaller |Ha - Hb| is, the smaller the variation in the distance D is, and the smaller the deformation amount of the resin adhesive layer 3 required to absorb that variation is. Therefore, it is possible to improve the adhesiveness of the resin adhesive layer 3. |Ha - Hb| is preferably less than 300 nm, more preferably 200 nm or less, and even more preferably 100 nm or less.

[0049] In addition, when the concave curved surface of the ultraviolet light-emitting element 2 is a double curved surface (for example, a bowl-shaped curved surface) and the convex curved surface of the optical member 4 is a double curved surface (for example, a dome-shaped curved surface), it is preferable that |Ha-Hb| is less than Ha on each of the first cut surface and the second cut surface, and it is more preferable that Ha and Hb are each within the above-mentioned numerical range.

[0050] Furthermore, when the concave curved surface of the ultraviolet light-emitting element 2 is a single curved surface (for example, a cylindrical curved surface) and the convex curved surface of the optical member 4 is a single curved surface (for example, a cylindrical curved surface), it is sufficient that |Ha - Hb| is less than Ha on the first cross section. On the second cross section, the concave curved surface of the ultraviolet light-emitting element 2 and the convex curved surface of the optical member 4 each form a straight line.

[0051] Ha and Hb are measured by cutting the light emitting device 1 after the ultraviolet light emitting element 2 and the optical member 4 are bonded to form the light emitting device 1. Since it is not possible to form both the first cut surface and the second cut surface at the same time, Ha and Hb can be measured only on the first cut surface. Note that it is also possible to measure Ha and Hb on the first cut surface, then bond the first cut surfaces together to form the second cut surface, and measure Ha and Hb on the second cut surface.

[0052] A bowl-shaped curved surface or a dome-shaped curved surface has a rotationally symmetric shape. Therefore, it is estimated that Ha and Hb on the second cross section are similar to Ha and Hb on the first cross section. Furthermore, for a cylindrical curved surface, the variation in the distance D on the second cross section is small, so there is no need to examine the second cross section.

[0053] The maximum thickness of the resin adhesive layer 3 in the bonding region A is preferably 4 μm or less. If the maximum thickness is 4 μm or less, it is possible to reduce stress that occurs when the resin adhesive layer 3 is deteriorated by ultraviolet rays emitted by the ultraviolet light emitting element 2, thereby suppressing the occurrence of cracks in the resin adhesive layer 3. The maximum thickness is more preferably 3 μm or less.

[0054] According to this embodiment, the adhesive surface 41 of the optical member 4 is processed into a convex curved surface, which reduces variations in the distance D compared to when the adhesive surface 41 of the optical member 4 is flat. Therefore, even if the maximum thickness of the resin adhesive layer 3 in the bonding region A is 4 μm or less, the optical member 4 and the ultraviolet light emitting element 2 can be firmly bonded together.

[0055] The minimum thickness of the resin adhesive layer 3 in the bonding region A should be larger than |Ha-Hb|, and is preferably 1 μm or more.

[0056] This application claims priority based on Japanese Patent Application No. 2024-028158 filed with the Japan Patent Office on February 28, 2024, the entire contents of which are incorporated herein by reference.

[0057] Although the light-emitting device according to the present disclosure has been described above, the present disclosure is not limited to the above-described embodiments, etc. Various changes, modifications, substitutions, additions, deletions, and combinations are possible within the scope of the claims. Naturally, these also fall within the technical scope of the present disclosure.

[0058] REFERENCE SIGNS LIST 1 Light emitting device 2 Ultraviolet light emitting element 21 Adhesion surface 3 Resin adhesive layer 4 Optical member 41 Adhesion surface

Claims

1. A light emitting device comprising, in this order, an ultraviolet light emitting element, a resin adhesive layer, and an optical member, wherein the ultraviolet light emitting element has an adhesive surface in contact with the resin adhesive layer, and the optical member has an adhesive surface in contact with the resin adhesive layer; the light emitting device has a rectangular bonding region where the optical member and the ultraviolet light emitting element overlap when viewed from the optical axis direction of the optical member; in a first cross section along one diagonal line of the bonding region when viewed from the optical axis direction of the optical member, the bonding surface of the ultraviolet light emitting element forms a concave curve, and the bonding surface of the optical member forms a convex curve; and the absolute value |Ha - Hb| of the difference between the height difference Ha (Ha > 0) of the concave curve in the bonding region and the height difference Hb (Hb > 0) of the convex curve in the bonding region is 0 or more and less than Ha.

2. The light emitting device according to claim 1, wherein Ha is 300 nm or more.

3. The light-emitting device according to claim 1 or 2, wherein |Ha-Hb| is less than 300 nm.

4. The light-emitting device according to claim 1 or 2, wherein Hb is equal to or less than Ha.

5. The light emitting device according to claim 1 or 2, wherein the maximum thickness of said resin adhesive layer in said bonding region is 4 μm or less.

6. The light emitting device according to claim 1 or 2, wherein the resin adhesive layer contains a fluororesin or a silicone resin.

7. The light emitting device according to claim 1 or 2, wherein the resin adhesive layer has a shear storage modulus of 0.1 GPa to 10 GPa.

8. The light emitting device according to claim 1 or 2, wherein the ultraviolet light emitting element has an emission peak wavelength of 210 nm to 320 nm.

9. The light emitting device according to claim 1 or 2, wherein the optical member is a lens.

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