JP7708100B2 - Resin composition, optical element, and ultraviolet emitting device - Google Patents

Description

The present invention relates to a resin composition, an optical element, and an ultraviolet light-emitting device.

From the perspective of environmental conservation, etc., semiconductor light-emitting elements such as ultraviolet LED elements (light-emitting diode elements) have been attracting attention as a light source for ultraviolet light-emitting devices, replacing conventional mercury lamps. These ultraviolet LED elements are used for a variety of purposes depending on the emission wavelength. For example, they can be used in the curing process of ultraviolet curable resins, in the treatment of skin diseases, and in the sterilization of viruses and pathogens.

However, UV LED elements have low light extraction efficiency, since only a portion of the light generated in the active layer of the LED element can be extracted and used outside the UV LED element, which has hindered their widespread use. To improve light extraction efficiency, UV LED elements with flip-chip and vertical structures have been considered, but the light extraction efficiency remains low at around a few percent, and further improvements in light utilization efficiency are required.

In response to this, Patent Document 1 discloses a technique in which a photonic crystal having an uneven structure is formed by etching on the light emitting surface of an LED element, and a part of the totally reflected light is extracted to the outside of the LED.
Furthermore, techniques for providing an optical member on an LED element have also been considered, and Patent Document 2 discloses a technique for using a hemispherical lens made of sapphire, Patent Document 3 discloses a spinel sintered body, and Patent Document 4 discloses a fluororesin as the optical member.

Regarding the study of materials for bonding semiconductor light-emitting elements such as ultraviolet LED elements to optical components, Patent Document 5 discloses a technology that uses a translucent resin as a material for bonding the light-emitting element to the covering member. Patent Document 6 discloses a technology that uses a thermoplastic resin or a curable resin as a material for forming the adhesive member.

Japanese Patent No. 6349036 Japanese Patent No. 6230038 International Publication No. 2018/066636 International Publication No. 2017/208535 Japanese Patent Application Publication No. 2018-67630 International Publication No. 2016/190207

In this way, techniques for improving the light extraction efficiency by combining a semiconductor light emitting element with an optical member have been studied and proposed from various angles.
However, little research has been done on materials for bonding the semiconductor light emitting element and the optical member.
The inventors' investigations revealed that, for example, when resins such as those disclosed in Patent Documents 5 and 6 are used as adhesive materials, the light extraction efficiency is low due to the low refractive index of the resin. This is believed to be because a large amount of light is reflected at the interface between the semiconductor light emitting element and the resin, and the light is not emitted to the outside of the semiconductor light emitting element.

Therefore, the present invention aims to provide a resin composition that has a high refractive index and excellent light extraction efficiency when used in an ultraviolet light-emitting device. It also aims to provide an optical element having a resin composition layer of such a resin composition, and an ultraviolet light-emitting device having the optical element.

As a result of intensive research, the inventors discovered that the above problems could be solved by a resin composition in which specific metal oxide nanoparticles are dispersed in a resin, and thus completed the present invention.

That is, the present invention and one aspect thereof relate to the following [1] to [23].
[1] A resin composition in which metal oxide nanoparticles are dispersed in a resin,
The resin composition used in an ultraviolet light emitting device has a refractive index n _d (C) of the resin composition and a refractive index n _d (R) of the resin for d-line (wavelength 587.6 nm) that satisfy the relationship n _d (C) - _{n d} (R) ≧ 0.03.
[2] The resin composition according to [1], wherein the band gap of the metal oxide nanoparticles is 4.8 eV or more.
[3] _The resin _composition according to [ _{1 ]} or _[ 2], wherein the metal oxide nanoparticles include at least one type of nanoparticles selected from the group consisting of _Gd2O3 , _HfO2 , _La2O3 , _Y2O3 , _Yb2O3 , _ZrO2 , _Al2O3 , and _SiO2 .
[4] The resin composition according to any one of [1] to [3], wherein the metal oxide nanoparticles have an average primary particle size of 2 to 80 nm.
[5] The resin composition according to any one of [1] to [4], wherein the content of the metal oxide nanoparticles is 15% by mass or more and 70% by mass or less.
[6] The resin composition according to any one of the above [1] to [5], wherein the resin composition has a refractive index n _d (C) of 1.39 or more.
[7] The resin composition according to any one of [1] to [6] above, wherein the average transmittance in a wavelength range of 260 to 400 nm is 70% or more.
[8] The resin composition according to any one of [1] to [7], wherein the resin is at least one of a fluororesin and a silicone resin.
[9] The ultraviolet light emitting device comprises a semiconductor light emitting element having a peak wavelength λ(D) in a wavelength range of 250 to 400 nm and an optical member;
The resin composition according to any one of [1] to [8], which is used for bonding a light emission surface of the semiconductor light emitting element and the optical member.
[10] An optical element comprising a resin composition layer and an optical member that transmits ultraviolet light,
The resin composition layer is made of a resin composition in which metal oxide nanoparticles are dispersed in a resin,
a refractive index n _d (C)′ of the resin composition layer and a refractive index n _d (R) of the resin with respect to d line (wavelength 587.6 nm) satisfy the relationship n _d (C)′-n _d (R)≧0.03;
An optical element for use in an ultraviolet light emitting device, comprising the optical member having the resin composition layer formed on at least a partial region of the surface thereof.
[11] The optical element according to [10], wherein the refractive index n _d (O) of the optical member and the refractive index n _d (C)' of the resin composition layer for the d line (wavelength 587.6 nm) satisfy the relationship Δn _d = |n _d (O) -n _d (C)'|≦0.35.
[12] The optical element according to [10] or [11], wherein the optical member is made of quartz, sapphire, or spinel.
[13] The optical member is made of inorganic glass,
The optical element according to the above [10] or [11], wherein the inorganic glass is a highly ultraviolet-transmitting glass having a maximum absorption coefficient αmax of 0.2 mm ⁻¹ or less in a wavelength range of 260 to 400 nm.
[14] The optical element according to any one of [10] to [13], wherein the ultraviolet light emitting device comprises a semiconductor light emitting element having a peak wavelength λ(D) in a wavelength range of 250 to 400 nm.
[15] The optical element according to [14], wherein the resin composition layer is used for bonding a light emission surface of the semiconductor light emitting element and the optical member.
[16] An ultraviolet light emitting device having a substrate, a semiconductor light emitting element provided on the substrate, and an optical element provided on the semiconductor light emitting element,
the optical element comprises a resin composition layer and an optical member that transmits ultraviolet light,
The resin composition layer is made of a resin composition in which metal oxide nanoparticles are dispersed in a resin,
a refractive index n _d (C)′ of the resin composition layer and a refractive index n _d (R) of the resin with respect to d line (wavelength 587.6 nm) satisfy the relationship n _d (C)′-n _d (R)≧0.03;
the resin composition layer is formed on at least a partial region of the surface of the optical member,
an ultraviolet light emitting device, the optical element being provided on a light emission surface of the semiconductor light emitting element via the resin composition layer;
[17] The ultraviolet light emitting device according to [16], wherein the peak wavelength λ(D) of light emitted by the semiconductor light emitting element is in the wavelength range of 250 to 400 nm.
[18] The ultraviolet light emitting device according to [17] above, wherein the resin composition layer has a refractive index n _o (C)′ of 1.4 or more at the peak wavelength λ(D).
[19] The ultraviolet light emitting device according to [17] or [18], wherein the refractive index n _o (O) of the optical member and the refractive index n _o (C)' of the resin composition layer at the peak wavelength λ(D) satisfy the relationship Δn _o = |n _o (O) -n _o (C)'|≦0.42.
[20] The adhesive strength between the light emission surface of the semiconductor light emitting element and the optical member by the resin composition layer is 5 N/ ^mm2 or more in shear strength. The ultraviolet light emitting device according to any one of [16] to [19].
[21] The ultraviolet light emitting device according to any one of [16] to [20] above, wherein the semiconductor light emitting element has a flip chip structure or a vertical structure.
[22] The ultraviolet light emitting device according to any one of [16] to [21] above, wherein the resin composition layer covers at least a part of a side surface of the semiconductor light emitting element.
[23] The ultraviolet light emitting device according to any one of [16] to [22], wherein a part of the optical member is in contact with the substrate or is bonded to the substrate.

According to the present invention, a resin composition with a high refractive index can be provided by dispersing metal oxide nanoparticles in a resin. By using this in an ultraviolet light-emitting device having a semiconductor light-emitting element, the reflection of light at the interface between the semiconductor light-emitting element and the resin composition can be suppressed, and more light can be emitted outside the semiconductor light-emitting element, thereby improving the output of the ultraviolet light-emitting device.

FIG. 1 is a schematic cross-sectional view of an optical element according to this embodiment. FIG. 2 is a schematic cross-sectional view of the ultraviolet light emitting device according to this embodiment. FIG. 3 is a schematic cross-sectional view showing a modified example of the ultraviolet light emitting device according to the present embodiment. FIG. 4 is a schematic cross-sectional view showing a modified example of the ultraviolet light emitting device according to the present embodiment. FIG. 5 is a schematic cross-sectional view showing a modified example of the ultraviolet light emitting device according to the present embodiment. FIG. 6 is a schematic cross-sectional view showing a modified example of the ultraviolet light emitting device according to this embodiment. FIG. 7 is a schematic cross-sectional view showing a modified example of the ultraviolet light emitting device according to this embodiment. FIG. 8 is a schematic cross-sectional view showing a modified example of the ultraviolet light emitting device according to this embodiment. FIG. 9 is a schematic cross-sectional view showing a modified example of the ultraviolet light emitting device according to this embodiment. FIG. 10 is a schematic cross-sectional view showing a modified example of the ultraviolet light emitting device according to this embodiment. FIG. 11 is a schematic cross-sectional view showing a modified example of the ultraviolet light emitting device according to this embodiment. FIG. 12 is a schematic cross-sectional view showing a modified example of the ultraviolet light emitting device according to this embodiment. FIG. 13 is a schematic cross-sectional view showing a modified example of the ultraviolet light emitting device according to this embodiment. FIG. 14 is a schematic cross-sectional view showing a modified example of the ultraviolet light emitting device according to this embodiment. FIG. 15 is a schematic cross-sectional view showing a modified example of the ultraviolet light emitting device according to this embodiment. FIG. 16 is a schematic cross-sectional view showing a modified example of the ultraviolet light emitting device according to this embodiment.

The present invention will be described in detail below, but the present invention is not limited to the following embodiments, and can be modified as desired without departing from the gist of the present invention. In addition, the use of "to" to indicate a range of values means that the values before and after the range are included as the lower and upper limits.

[Resin composition]
The resin composition according to the present embodiment contains a resin and metal oxide nanoparticles, and the metal oxide nanoparticles are dispersed in the resin. The dispersion of the metal oxide nanoparticles allows the refractive index of the resin composition to be higher than that of the resin. The refractive index has wavelength dispersion and is expressed by the following Cauchy dispersion formula.
n(λ)=A+(B/λ ² )+(C/λ ⁴ )
In the formula, λ represents the wavelength of light, and n(λ) represents the refractive index for light of wavelength λ. A, B, and C are constants that are experimentally determined.
In addition, when the resin composition is used for an ultraviolet light emitting device, the refractive index in the ultraviolet wavelength region is important, but for convenience, the refractive index at the d line (wavelength 587.6 nm) is used in this specification. By increasing the refractive index at the d line, the refractive index in the ultraviolet wavelength region can also be increased.

The resin composition satisfies the relationship n _d (C)-n d (R)≧0.03, where n d (C) is the refractive index of the resin composition and _{n d} (R) is the refractive index of the resin relative to the _d -line (wavelength 587.6 nm), and is used in ultraviolet light-emitting devices. Note that the refractive index relative to the d-line may hereinafter be simply referred to as the d-line refractive index.

By forming an organic-inorganic composite material in which metal oxide nanoparticles are dispersed in a resin, the d-line refractive index n _d (C) of the resin composition can be increased. The higher the d-line refractive index n _{d (C) of the resin composition, the higher the refractive index in the ultraviolet wavelength range, and the higher the output of the ultraviolet light emitting device. The improvement in the d-line refractive index n d (} C) of the resin composition by forming it into an organic-inorganic composite material can be expressed as the difference with the d-line refractive index n _d (R) of the resin. That is, the difference in the d-line refractive index expressed by n _d (C) - _{n d} (R) is 0.03 or more, preferably 0.05 or more, and more preferably 0.1 or more. The upper limit of the difference in the d-line refractive index is not particularly limited, but is usually 1 or less.

By increasing the d-line refractive index n _d (C) of the resin composition, total reflection and Fresnel reflection at the interface between the light-emitting surface of the semiconductor light-emitting element and the resin composition, and at the interface between the optical member and the resin composition can be suppressed, thereby suppressing the decrease in light extraction efficiency. As a result, the output of the ultraviolet light-emitting device can be improved. Therefore, the d-line refractive index n _d (C) of the resin composition is preferably 1.39 or more, preferably 1.4 or more, and more preferably 1.45 or more. The upper limit of the d-line refractive index n _d (C) is not particularly limited, but is usually 1.6 or less from the viewpoint of the balance between the adhesiveness of the optical element and the optical member and the improvement of the output of the ultraviolet light-emitting device. The d-line refractive index n _d (C) of the resin composition can be adjusted by increasing or decreasing the amount of metal oxide nanoparticles.

The average transmittance (average transmittance) of the resin composition in the wavelength range of 260 to 400 nm is preferably 70% or more, more preferably 75% or more, from the viewpoint of achieving high output of the ultraviolet light emitting device. The higher the average transmittance, the better, but it is usually 100% or less.
In this specification, the transmittance of light of each wavelength is a value measured using a visible-ultraviolet spectrophotometer. That is, the transmittance is not an internal transmittance but an external transmittance including the surface reflectance of the interface, and is the external transmittance converted into a thickness of 10 μm.

The resin composition is used in ultraviolet light emitting devices, and is preferably used in ultraviolet light emitting devices including a semiconductor light emitting element having a peak wavelength λ(D) in the wavelength range of 250 to 400 nm. Since the light extraction efficiency is lower in semiconductor light emitting elements that emit ultraviolet light with short wavelengths, the resin composition is preferably used in ultraviolet light emitting devices including a semiconductor light emitting element having a peak wavelength in the wavelength range of more preferably 250 to 370 nm, even more preferably 250 to 330 nm, and particularly preferably 250 to 290 nm.
In addition, it is preferably used between an optical member and a semiconductor light emitting element in an ultraviolet light emitting device, and more preferably used for adhesion. Adhesion does not necessarily require strong adhesive strength to be achieved only by the resin composition, and it is also possible to achieve both high light extraction efficiency and adhesive strength by using another adhesive at a place other than the optical path, for example, at the interface between the substrate of the ultraviolet light emitting device and the optical member. Details of the ultraviolet light emitting device will be described later.

When two members, i.e., adherends, are bonded together using a resin composition, the resin composition is softened by heating to a temperature equal to or higher than its softening point, and then brought into contact with the two adherends to be bonded. The resin composition is then cooled and hardened, so that the two adherends are bonded together via the resin composition layer.
Furthermore, when a thermosetting resin, a photocurable resin, or the like is used, the resin composition is applied to the adhesive surface of at least one of the adherends, the adherends are bonded together, and then the resin composition is cured by exposure to heat or light, so that the two adherends are bonded together via a resin composition layer.

The preferred adherends are optical components and semiconductor light-emitting elements in an ultraviolet light-emitting device, but this does not exclude the use of the resin composition according to this embodiment for bonding other components. In the case of other components, components that require optical transparency are preferred, and examples of such components include bonding between glass fibers, bonding between lenses, bonding between prisms, and bonding between optical filters.

(Metal Oxide Nanoparticles)
The band gap of the metal oxide nanoparticles is preferably 4.8 eV or more so that they do not have absorption on the longer wavelength side than 260 nm in order to increase the transmittance of deep ultraviolet light. The larger the band gap, the more suitable it can be used for a light emitting device with a shorter wavelength, so the band gap is more preferably 4.9 eV or more, and even more preferably 5.0 eV or more. The upper limit of the band gap is not particularly limited, but is usually 10 eV or less. The band gap of each metal oxide is the value described in "ACS nano, 2012, 6, 5, 4349".

Examples of metal oxide nanoparticles with a band gap of 4.8 eV or more include _Gd2O3 (5.28 eV), _HfO2 (5.41 eV), _La2O3 (5.77 eV), _Y2O3 (5.85 _{eV), Yb2O3 ( 5.1} eV), _{ZrO2 (} 5.04 _eV ), _Al2O3 (8.3 eV), _{and SiO2} (9.1 eV).
It is preferable that the nanoparticles contain at least one type of nanoparticle selected from the above group. From the viewpoint of increasing hardness and refractive index, nanoparticles of a composite oxide composed of two or more types of nanoparticles may be used.

The metal oxide nanoparticles preferably contain ZrO ₂ or Al ₂ O ₃ from the viewpoint of availability, and more preferably contain ZrO ₂ since the metal oxide nanoparticles alone have a high refractive index of 2.1.

Metal oxide nanoparticles may be either manufactured or commercially available. When manufactured, they can be obtained by known methods such as a hydrothermal method, a supercritical method, or a gas phase method.
Commercially available ZrO ₂ products include, for example, ZSL-10A, ZSL-10T, ZSL-20N (all manufactured by Daiichi Kigenso), Nanouse (registered trademark) ZR-40BL, Nanouse (registered trademark) ZR-30BS, Nanouse (registered trademark) ZR-30AL (all manufactured by Nissan Chemical Industries, Ltd.), Zirconeo-Cw series (manufactured by ITEC Co., Ltd.), and SZR series (manufactured by Sakai Chemical Industries, Ltd.).
Commercially available products of Al ₂ O ₃ include, for example, Aluminasol AS-520-A (manufactured by Nissan Chemical Industries, Ltd.), Baylar (registered trademark) Al series such as Al-L7, Al-ML15, and Al-C2 (manufactured by Taki Chemical Industries, Ltd.), and CATALOID series (manufactured by JGC Catalysts and Chemicals Co., Ltd.).

The average primary particle size of the metal oxide nanoparticles is preferably 2 nm or more, and more preferably 5 nm or more, because the surface area per volume becomes relatively small, the amounts of the silane coupling agent and carboxylic acid used, which will be described later, can be reduced, and the dispersibility in the resin is improved.
On the other hand, the average primary particle size of the metal oxide nanoparticles is preferably 80 nm or less, and more preferably 50 nm or less, because light scattering is less likely to occur and the optical properties are excellent, particularly the visible light transmittance is increased.
The average primary particle size of the metal oxide nanoparticles can be determined by observation with a transmission electron microscope.

In some cases, metal oxide nanoparticles are dispersed in the resin in a state where some of them are secondary aggregated, rather than primary particles. In this case, the average secondary particle diameter of the metal oxide nanoparticles is preferably 10 nm or more, more preferably 30 nm or more. This is because, like the average primary particle diameter, the surface area per volume is relatively small, the amount of silane coupling agent and carboxylic acid used, which will be described later, is reduced, and the dispersibility in the resin is good. In addition, in order to prevent light from being scattered and the light extraction efficiency from decreasing, the average secondary particle diameter is preferably 120 nm or less, more preferably 100 nm or less.
The average secondary particle size of the metal oxide nanoparticles can be measured by dynamic light scattering.

The shape of the metal oxide nanoparticles is preferably close to spherical from the viewpoint of reducing the specific surface area per volume in order to reduce the amount of silane coupling agent or carboxylic acid used.
In the case of plate-like metal oxide nanoparticles, the particles preferably have a major axis of 15 nm or more.
When the metal oxide nanoparticles have a shape other than spherical, it is preferable that their volume is equal to or greater than the volume of a sphere having an average primary particle size of 2 nm, and it is more preferable that their volume is equal to or greater than the volume of a sphere having an average primary particle size of 5 nm.

The content of the metal oxide nanoparticles in the resin composition is preferably 15% by mass or more, more preferably 20% by mass or more, from the viewpoint of increasing the d-line refractive index of the resin composition. Also, from the viewpoint of preventing the resin composition from undergoing cohesive failure and increasing the adhesion between the optical element and the optical member, the content is preferably 70% by mass or less, more preferably 60% by mass or less.
The content of metal oxide nanoparticles in the resin composition can be determined by thermogravimetric analysis. The resin composition is kept at, for example, 400° C. for a certain period of time, and the weight loss is measured to determine the content of metal oxide nanoparticles. That is, the weight loss is the resin content, and the weight of the remainder is the metal oxide nanoparticle content.

(resin)
The resin constituting the resin composition is not particularly limited as long as it is a resin that is usually used as a resin interposed between a light-emitting element and an optical member in a light-emitting device. On the other hand, in an ultraviolet light-emitting device, a light-emitting element that emits light with a shorter wavelength such as ultraviolet light or deep ultraviolet light is used, so the energy of the emitted light is large. Therefore, from the viewpoint of preventing deterioration of the resin due to photodecomposition caused by the light emitted by the light-emitting element, the resin is preferably a resin with high light resistance to ultraviolet light, more preferably at least one of a fluororesin and a silicone-based resin, and even more preferably an amorphous fluororesin or silicone resin.
The resin may be used alone or in combination of two or more kinds.

Examples of amorphous fluororesins that can be used include CYTOP (product name, CYTOP is a registered trademark) manufactured by AGC and Teflon (registered trademark) AF manufactured by Mitsui Chemours Fluoroproducts. These amorphous fluororesins are transparent and have no absorption even in the deep ultraviolet region. This reduces the loss of light emitted from the light-emitting element and improves the light extraction efficiency.

When using, for example, Cytop (trade name) as the amorphous fluororesin, the functional group at the polymer end may be A type having a COOH group, M type having CONH-Si(OR) _n groups, S type having a _CF3 group, etc. The type is appropriately selected from the viewpoints of adhesion between the light-emitting element and the optical member and dispersibility of the metal oxide nanoparticles.

The glass transition temperature of the amorphous fluororesin is preferably 80°C or higher, more preferably 100°C or higher, from the viewpoint of preventing deformation of the resin due to heat generation from the light-emitting element. Also, from the viewpoint of preventing the temperature from becoming too high when bonding the light-emitting element and the optical component, which would cause the resin to decompose, the glass transition temperature is preferably 260°C or lower, more preferably 250°C or lower.

Silicone resins are those in which the main bond structure is a siloxane bond in which silicon and oxygen are alternately bonded, to which an organic functional group is bonded. Examples of organic functional groups are preferably functional groups that have no absorption in the deep ultraviolet region, such as alkyl groups, vinyl groups, (meth)acryloxy groups, and epoxy groups. In the alkyl group, some or all of the hydrogen atoms may be substituted with halogen atoms such as fluorine atoms and chlorine atoms. In this specification, the (meth)acryloxy group is used as a general term that includes at least one of an acryloxy group and a methacryloxy group.

The main skeleton structure may be a straight chain structure represented by (--R ¹ R ² SiO--), but silsesquioxane represented by (--R ³ SiO _1.5 -) is particularly preferred, in which R ¹ to R ³ represent organic functional groups.
Silsesquioxanes, which have a structure in which one organic functional group and three oxygen atoms are bonded to a silicon atom, have fewer organic functional groups than straight-chain structures, and therefore have particularly excellent light resistance and heat resistance. Although random structures, ladder structures, and cage structures are known as silsesquioxane skeletons, they can be used without particular limitations in one embodiment of the present invention. Examples of silsesquioxane resins include the SR series, SP series, and SO series manufactured by Konishi Chemical Co., Ltd.

(Other ingredients)
In addition to the resin and metal oxide nanoparticles, the resin composition may contain other components, such as silane coupling agents, carboxylic acids, amines, and amides.
Among them, silane coupling agents and carboxylic acids are preferred because they are suitable for use in compounding resins and metal oxide nanoparticles when obtaining a resin composition. Compounding can be performed by a known method using a silane coupling agent or a carboxylic acid. For example, the method described in Japanese Patent No. 6028733 or Japanese Patent Publication No. 2013-177259 can be used as a compounding method using a silane coupling agent. For example, the method described in Japanese Patent No. 5375617 can be used as a compounding method using a carboxylic acid.

The silane coupling agent may be an organosilicon compound having both a hydrophobic organic functional group that contributes to reaction or interaction with organic substances and a hydrolyzable group (alkoxy group) in one molecule, and any known silane coupling agent can be used as appropriate.
For example, a silane coupling agent represented by the following formula is preferred.
R ¹ _a Si(OR ² ) _b
In the formula, ^R1 represents an organic functional group, ^OR2 represents an alkoxy group having 1 or 2 carbon atoms, a and b each independently represent an integer of 1 or more, and the sum (a+b) is 4. When a is 2 or more, the multiple ^R1s may be the same or different. When b is 2 or more, the multiple ^OR2s may be the same or different.

In the above formula, ^OR2 is preferably a methoxy group or an ethoxy group. b is preferably 3.
The organic functional group represented by ^R1 can be a hydrophobic organic functional group known in silane coupling agents, but is preferably a functional group that does not absorb in the deep ultraviolet region. Examples of such organic functional groups include alkyl groups, vinyl groups, (meth)acryloxy groups, and epoxy groups. In addition, the alkyl groups may have some or all of the hydrogen atoms substituted with halogen atoms such as fluorine atoms and chlorine atoms.

Examples of the silane coupling agent represented by the above formula include 3,3,3-trifluoropropyltrimethoxysilane, n-octadecyltrimethoxysilane, triethoxy-1H,1H,2H,2H-tridecafluoro-n-octylsilane, vinyltrimethoxysilane, n-propyltrimethoxysilane, n-dodecyltrimethoxysilane, n-decyltrimethoxysilane, n-octyltrimethoxysilane, heptadecatrifluorodecyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-acryloxypropyltrimethoxysilane, and γ-glycidoxypropyltriethoxysilane.
Among these, from the viewpoint of affinity when an amorphous fluororesin is used as the resin, silane coupling agents containing fluorine atoms are preferred, and 3,3,3-trifluoropropyltrimethoxysilane and triethoxy-1H,1H,2H,2H-tridecafluoro-n-octylsilane are more preferred.

As a component derived from a silane coupling agent, it is preferable to include at least one of a hydrolyzate of a silane coupling agent and a hydrolysis condensate of a silane coupling agent, and it may also include a silane coupling agent that has not undergone a hydrolysis reaction.

The carboxylic acid may be any molecule having one or more carboxyl groups in one molecule. This promotes binding or adsorption to metal oxide nanoparticles, allowing the metal oxide nanoparticles to be more uniformly dispersed in the resin.

The stronger the acidity of the carboxyl group, the more preferable, and the acid dissociation constant represented by pKa is preferably 4 or less, more preferably 3 or less, and even more preferably 2 or less. Examples of carboxylic acids with low pKa include organic acids in which one or more hydrogen atoms bonded to the carbon atom at the α-position of an alkyl group bonded to a carboxyl group are substituted with a halogen atom.
Among the carboxylic acids substituted with halogen atoms, those substituted with fluorine atoms having high electronegativity and those with many substitutions are preferred because they have low pKa. Specific examples include perfluoropentanoic acid, perfluorohexanoic acid, and tridecafluoroheptanoic acid. Among them, tridecafluoroheptanoic acid is preferred from the viewpoint of compatibility when an amorphous fluororesin is used as the resin.

[Optical elements]
As shown in FIG. 1, an optical element 10 according to this embodiment includes an optical member 1 that transmits ultraviolet light and a resin composition layer 2, and is used in an ultraviolet light emitting device.

(Resin composition layer)
The resin composition layer 2 is made of a resin composition, and the resin composition is one described in the above [Resin composition]. That is, the refractive index of the resin composition is increased by dispersing metal oxide nanoparticles in the resin, and a resin composition is used in which the difference between the d-line refractive index of the resin composition and the d-line refractive index of the resin is 0.03 or more. The preferred embodiment of the resin composition is also the same as the preferred embodiment described in the above [Resin composition].

The resin composition layer 2 is provided on the surface of the optical member 1, i.e., on at least one of the light incident surface and the light exit surface. It is sufficient that the resin composition layer 2 is formed on at least a partial region of such a surface.
For example, the resin composition layer 2 may be provided on the entire area (whole surface) on the surface of the optical member 1 as shown in Fig. 2, or may be provided on a partial area on the surface of the optical member 1 in accordance with the size of the semiconductor light-emitting element 3 that is the other adherend as shown in Fig. 3. Furthermore, as shown in Fig. 4, Fig. 10, etc., the resin composition layer 2 may be formed not only on the bonding surface between the optical member 1 and the semiconductor light-emitting element 3 but also on the side surface of the semiconductor light-emitting element 3. Furthermore, as shown in Fig. 4, Fig. 7, etc., the semiconductor light-emitting element 3 may be sealed with the resin composition layer 2 while being bonded to the optical member 1.
As shown in FIG. 8, FIG. 12, and the like, a separate adhesive layer 5 may be used together with the resin composition layer 2 to achieve both high light extraction efficiency and adhesive strength.

The preferred d-line refractive index n _d (C)' of the resin composition layer is the same as the preferred d-line refractive index n _d (C) of the resin composition. That is, the d-line refractive index n _d (C)' of the resin composition layer is preferably 1.39 or more, and is preferably 1.4 or more, preferably 1.45 or more, in order to increase the light extraction efficiency of the semiconductor light-emitting element and increase the output of the ultraviolet light-emitting device. In addition, the upper limit of the d-line refractive index n _d (C)' is not particularly limited, but is usually 1.6 or less from the viewpoint of the balance between the adhesion between the optical element and the optical member and the improvement in the output of the ultraviolet light-emitting device. The d-line refractive index n _d (C)' of the resin composition can be adjusted by increasing or decreasing the amount of metal oxide nanoparticles.
Since the resin composition layer is composed of a resin composition, the d-line refractive index n _d (C)′ of the resin composition layer and the d-line refractive index n _d (C) of the resin composition have the same value.

From the viewpoint of adhesion, the thickness of the resin composition layer is preferably 1 μm or more, more preferably 3 μm or more, and even more preferably 5 μm or more. From the viewpoint of suppressing light loss in the resin composition layer, the thickness is preferably 100 μm or less, more preferably 50 μm or less, and even more preferably 30 μm or less.

(Optical components)
The optical member 1 has a light incident surface and a light exit surface, and is provided with an optically functional surface in at least a partial area of at least one of the light incident surface and the light exit surface. The light incident surface is a surface onto which light emitted from, for example, a semiconductor light emitting element is incident, and the light exit surface is a surface from which the incident light passes through the optical member and is exited to irradiate the outside.

Optically functional surfaces include surfaces that refract, diffract, or scatter light, highly reflective surfaces such as mirrors, low-reflective surfaces with enhanced transparency, and various filters with wavelength selectivity. The entire light entrance surface or light exit surface of an optical component may have this function, or only a partial area of the surface may have this function.

As long as the optical member can exhibit the above-mentioned functions, various conventionally known optical members can be used. The shape is not particularly limited, and examples thereof include a plate, a lens, a lens array, a diffraction grating, a diffractive optical element, and a grating cells array. In addition, a metal or a dielectric may be formed on the surface in a single layer or multiple layers.
In particular, a spherical, semispherical or aspherical convex lens shape is preferred, with a semispherical shape being more preferred.

When the optical member is bonded to a light emitting element such as a semiconductor light emitting element, the light emission surface of the light emitting element is formed of a high refractive index material, so that the light extraction efficiency can be significantly improved by forming the optical member from a high refractive index material. Therefore, the d-line refractive index n _d (O) of the optical member is preferably 1.45 or more, more preferably 1.5 or more, even more preferably 1.6 or more, even more preferably 1.65 or more, and particularly preferably 1.7 or more.

The absolute value of the difference in d-line refractive index between the optical member and the resin composition layer, Δn _d =|n _d (O)-n _d (C)'|, is preferably 0.35 or less, more preferably 0.30 or less, and even more preferably 0.28 or less, from the viewpoint of preventing reflection at the interface between the optical member and the resin composition layer. The lower limit of Δn _d is not particularly limited.

The light emitted by the light-emitting element passes through an optical member processed into the shape of a lens, etc., and is emitted outside the ultraviolet light-emitting device. Therefore, by using a material that is highly transparent to the light emitted by the light-emitting element as the material for forming the optical member, the loss of light can be reduced and the light extraction efficiency can be improved.
The distance that light travels within an optical member is usually about 0.5 to 5 mm, and the absorption coefficient k(O) at the emission wavelength of the light emitting element of the optical member is preferably 0.2 mm ⁻¹ or less, more preferably 0.15 mm ⁻¹ or less, even more preferably 0.1 mm ⁻¹ or less, and particularly preferably 0.07 mm ⁻¹ or less.

The optical element is preferably used in an ultraviolet light emitting device including a semiconductor light emitting element, and the semiconductor light emitting element preferably has a peak wavelength λ (D) in the wavelength range of 250 to 400 nm. In a semiconductor light emitting element that emits ultraviolet light with a short wavelength, the light extraction efficiency is lower, so it is more preferably used in an ultraviolet light emitting device having a peak wavelength in the wavelength range of 250 to 370 nm, even more preferably 250 to 330 nm, and particularly preferably 250 to 290 nm. The peak wavelength λ (D) is more preferably in the wavelength range of 260 to 285 nm for sterilization purposes, more preferably in the wavelength range of 290 to 330 nm for medical purposes, and more preferably in the wavelength range of 340 to 380 nm for resin curing purposes.

By placing the optical element so that the resin composition layer is in close contact with the light emission surface of the semiconductor light emitting element, the light extraction efficiency of the semiconductor light emitting element can be increased. When the optical element is used in an ultraviolet light emitting device that includes a semiconductor light emitting element, it is preferable to provide a resin composition layer at least on the light incidence surface of the optical element.

The absolute value of the difference between the refractive index n _o (O) of the optical member and the refractive index n _o (C)' of the resin composition layer at the peak wavelength λ(D) of the semiconductor light emitting element, Δn _o =|n _o (O)-n _o (C)'|, is preferably 0.42 or less, more preferably 0.40 or less, even more preferably 0.35 or less, and particularly preferably 0.30 or less, from the viewpoint of preventing reflection at the interface between the optical member and the resin composition layer. In addition, the lower limit of Δn _o is not particularly limited.

It is preferable that the optical component has a high glass transition temperature Tg(O) so that the shape of the optical component does not change even when it is heated during the production process, such as the bonding process of the light-emitting element and the optical component. Tg(O) is preferably 350°C or higher, more preferably 400°C or higher, and even more preferably 500°C or higher.

The material constituting the optical member is not particularly limited, and examples of the material that can be used include inorganic glass, quartz (Tg: 1060°C, Tc: 1210°C, n _d : 1.46), crystalline sapphire (n _d (ordinary light): 1.77, melting point: 2053°C), spinel, and transparent ceramic materials such as aluminum oxynitride.

If the material is highly durable, does not deteriorate even when exposed for long periods to high-output light emitted by semiconductor light-emitting elements, especially light with short wavelengths such as ultraviolet light, and has excellent heat resistance, the product life of the optical component can be extended. From this perspective, it is preferable to use inorganic materials for optical components, specifically inorganic glass, quartz, sapphire, and spinel.

Furthermore, inorganic glass can be easily processed into various shapes, and is particularly suitable for use in terms of reducing manufacturing costs and mass production.
In order to suppress the loss of light while it is passing through the optical component, the inorganic glass is more preferably a highly ultraviolet-transmitting glass having a maximum absorption coefficient αmax of 0.2 mm ^-1 or less in the wavelength range of 260 to 400 nm, and the maximum absorption coefficient αmax in such wavelength range is even more preferably 0.15 mm ^-1 or less, even more preferably 0.1 mm ^-1 or less, and particularly preferably 0.07 mm ^-1 or less. The smaller the maximum absorption coefficient αmax, the more preferable.

When inorganic glass is used as an optical component, examples include borosilicate glass, silicate glass, phosphate glass, and fluorophosphate glass.

Borosilicate glass is glass containing _SiO2 and _B2O3 as main components, as _{well as Al2O3 , alkaline} earth metal oxides (MgO, CaO, SrO, BaO), alkali metal oxides ( _Li2O , _Na2O , _K2O ), and other metal oxides.
Silicate glass is _glass containing _SiO2 as a main component, as _well as _B2O3 , _Al2O3 , alkaline earth metal oxides (MgO, CaO, SrO, BaO), alkali metal oxides ( _Li2O , _Na2O , _K2O ), and other metal oxides.
Phosphate glass is glass containing P ₂ O ₅ as a main component, as well as Al ₂ O ₃ , alkaline earth metal oxides (MgO, CaO, SrO, BaO), alkali metal oxides (Li ₂ O, Na ₂ O, K ₂ O), and other metal oxides.
Fluorophosphate glass is a glass containing P ₂ O ₅ as a main component, as well as Al, alkaline earth metals (Mg, Ca, Sr, Ba), alkali metals (Li, Na, K), fluorides of other metals, and oxides of other metals.
In this specification, the main component of glass refers to a network-forming oxide that forms the skeleton of the glass among the components that make up the glass.

It is preferable that the optical component has a high glass transition temperature Tg so that the shape of the optical component does not change even when it is heated during the production process, such as the bonding process of the semiconductor light emitting element and the optical component. Tg is preferably 350°C or higher, more preferably 400°C or higher, and even more preferably 500°C or higher. There is no particular limit to the upper limit of Tg, but it is usually 1000°C or lower.

For such glasses, if the content of iron is high, the ultraviolet transmittance decreases, so it is preferable that the glass constituting the optical member has a reduced content of iron. Here, the iron component is present in the glass as a valence of Fe3 ⁺ or Fe2 ⁺ , and the total iron oxide content obtained by converting the iron component contained in the _glass into _Fe2O3 is represented as _T - _Fe2O3 .
The T-Fe ₂ O ₃ content in the glass is preferably 10 ppm by mass or less, more preferably 5 ppm by mass or less, even more preferably 2.5 ppm by mass or less, even more preferably 2 ppm by mass or less, and particularly preferably 1 ppm by mass or less, and the lower the content the better. The above iron component is introduced into the glass mainly as an impurity contained in the glass raw materials, excluding iron contamination from the melting process.

In particular, when the semiconductor light-emitting element emits ultraviolet light in the wavelength range of 250 nm to 400 nm, the content of T-Fe ₂ O ₃ in the inorganic glass having high transmittance in the ultraviolet range is preferably 5 ppm by mass or less, more preferably 2 ppm by mass or less, even more preferably 1.5 ppm by mass or less, even more preferably 1 ppm by mass or less, particularly preferably less than 0.9 ppm by mass, and the lower the content, the more preferable.

In addition, it is also preferable that the optical members are made of quartz, sapphire, or spinel in order to increase durability and reduce the absorption coefficient in the ultraviolet region. Quartz is a high-purity _SiO2 glass with a d-line refractive index of 1.46 and a refractive index of about 1.5 at 275 nm. Sapphire is a single crystal of α-alumina (α _{- Al2O3} ) with a d-line refractive index of 1.77 and a refractive index of about 1.83 _{at 275} nm. Spinel is a crystal of _MgO.Al2O3 ( _MgAl2O4 ).

The optical member may have an anti-reflection film formed on its surface. For example, a single layer or multi-layer film of a dielectric material such as _SiO2 , _MgF2 , _Al2O3 , _HfO2 , _ZrO2 , _{or Ta2O5} may be used. By forming the anti-reflection film, Fresnel reflection on the surface of the optical member is reduced, and _the light extraction efficiency can be further improved.

[Ultraviolet light emitting device]
2, an ultraviolet light emitting device 20 according to this embodiment has a substrate 4, a semiconductor light emitting element 3 provided on the substrate 4, and an optical element 10 provided on the semiconductor light emitting element 3. The optical element 10 has a resin composition layer 2 formed on at least a partial region of the surface of an optical member 1, and the optical element 10 is provided on the light emission surface of the semiconductor light emitting element 3 via the resin composition layer 2.
By providing the semiconductor light-emitting element 3 and the optical member 1 with the resin composition layer 2 interposed therebetween, no space, i.e., no air layer, is present between the semiconductor light-emitting element 3 and the optical member 1. This prevents total reflection occurring at the interface between the light-emitting surface and air, thereby achieving high light extraction efficiency.

The optical element in the ultraviolet light emitting device can be the same as that described in the above [Optical element]. That is, the resin composition layer constituting the optical element uses a resin composition characterized by a high refractive index, in which metal oxide nanoparticles are dispersed in the resin and the difference between the d-line refractive index of the resin composition and the d-line refractive index of the resin is 0.03 or more. The preferred embodiment of the resin composition is the same as the preferred embodiment described in the above [Resin composition].
As the optical members constituting the optical element, those described above in (Optical members) can be used, and the preferred embodiments are also the same.

The semiconductor light-emitting element in the ultraviolet light-emitting device may be one that is commonly used, but it is preferable that it has a peak wavelength λ (D) in the wavelength range of 250 to 400 nm. In a semiconductor light-emitting element that emits ultraviolet light with a short wavelength, the light extraction efficiency is lower, so it is more preferable that it is used in an ultraviolet light-emitting device that has a peak wavelength in the wavelength range of 250 to 370 nm, even more preferably 250 to 330 nm, and particularly preferably 250 to 290 nm. As mentioned above, the more preferable wavelength range of the peak wavelength λ (D) varies depending on the application. Specifically, for sterilization applications, it is more preferable that the peak wavelength λ (D) is in the wavelength range of 260 to 285 nm. For medical applications, it is more preferable that the peak wavelength λ (D) is in the wavelength range of 290 to 330 nm. For resin curing applications, it is more preferable that the peak wavelength λ (D) is in the wavelength range of 340 to 380 nm.

In the ultraviolet light emitting device, the light emitting surface of the semiconductor light emitting element and the optical member are closely attached via the resin composition layer. When the semiconductor light emitting element and the optical member are bonded only by the resin composition layer without using a separate adhesive layer, the adhesive strength between the light emitting surface of the semiconductor light emitting element and the optical member by the resin composition layer is preferably 5 N/mm2 or ^more in shear strength, more preferably 7 N/ ^mm2 or more, and even more preferably 10 N/mm2 or ^more . The upper limit of the shear strength is not particularly limited, but is usually 20 N/ ^mm2 or less.
The shear strength is a value measured in accordance with MIL STD 883, and can be measured using a bond tester DAGE 4000plus manufactured by Nordson Co. The shear strength can be adjusted, for example, by the number of organic functional groups contained in the adhesive layer, for example, the resin composition layer.

Semiconductor light-emitting elements can be of either a vertical structure in which a semiconductor layer is formed on an LED substrate, with electrodes provided on the rear surface of the LED substrate and on the surface of the semiconductor layer, or a flip-chip structure in which both a p-electrode and an n-electrode are provided on the surface of the semiconductor layer. The light-emitting surface of a semiconductor light-emitting element is often an AlGaN-based semiconductor layer or a transparent electrode in the vertical structure, and sapphire or aluminum nitride in the flip-chip structure.

As described above, the ultraviolet light-emitting device 20 according to this embodiment has a substrate 4, a semiconductor light-emitting element 3 provided on the substrate 4, and an optical element 10 provided on the semiconductor light-emitting element 3. In the ultraviolet light-emitting device 20 of FIG. 2, a resin composition layer 2 is formed on the entire surface of the optical member 1, and the entire surface of the light-emitting surface of the semiconductor light-emitting element 3 is bonded to the optical member 1 via the resin composition layer 2. With this configuration, when forming the resin composition layer 2, it is sufficient to coat the resin composition on the entire bonding surface of the optical member 1, making it easy to form the resin composition layer 2.

For such a configuration, Figures 3 to 16 are shown as modified examples of the ultraviolet light-emitting device 20, but the configuration of the ultraviolet light-emitting device according to this embodiment is not limited to these.

3, the ultraviolet light-emitting device 20 has a resin composition layer 2 formed on a partial region of the surface of the optical component 1, and the entire light-emitting surface of the semiconductor light-emitting element 3 is bonded to the optical component 1 via the resin composition layer 2. With this configuration, when forming the resin composition layer 2, it is sufficient to coat the entire bonding surface of the semiconductor light-emitting element 3 with the resin composition, making it easy to form the resin composition layer 2.

In the ultraviolet light-emitting device 20 of Figure 4, a resin composition layer 2 is formed on a partial region of the surface of an optical component 1, and the resin composition layer 2 is provided and sealed not only on the entire light emission surface of a semiconductor light-emitting element 3 but also on the entire region of the side surface.
5, the resin composition layer 2 is formed on the entire surface area of the optical member 1, and the resin composition layer 2 is provided and sealed not only on the entire light emission surface of the semiconductor light emitting element 3 but also on the entire side area. The resin composition layer 2 is provided between the substrate 4 and the optical member 1 with no gap therebetween.
By sealing the semiconductor light-emitting element 3 with the resin composition layer 2, the intrusion of substances from the outside that accelerate the deterioration of the semiconductor light-emitting element 3, such as moisture in the air, can be prevented, and as a result, deterioration in the performance of the semiconductor light-emitting element 3 can be suppressed.

6, the outer periphery of the optical member 1 is stretched to contact the substrate 4. The entire light emitting surface of the semiconductor light emitting element 3 is bonded to the optical member 1 via the resin composition layer 2.
7, the outer periphery of the optical member 1 is stretched to contact the substrate 4. The semiconductor light emitting element 3 is sealed with the resin composition layer 2 and bonded to the optical member 1 via the resin composition layer 2.
By having a part of the optical member 1 in contact with or bonded to the substrate 4, the optical member 1 is less likely to fall off the semiconductor light emitting device 3. The optical member 1 and the substrate 4 may be in contact with the substrate 4 by extending the outer periphery of the optical member 1 as shown in Fig. 6 and Fig. 7, or may be in contact with each other on other surfaces. As shown in Fig. 8, the optical member 1 may be in contact with the substrate 4 via an adhesive layer 5 or the like.

In the ultraviolet light emitting device 20 of Fig. 8, the optical element 10 is bonded to the substrate 4 via the adhesive layer 5. The adhesive layer 5 may be made of one material, or may be composed of a plurality of adhesives or members. The optical element 10 is provided on the semiconductor light emitting element 3 via the resin composition layer 2. Since the optical element 10 is bonded to the substrate 4 via the adhesive layer 5, the optical element 10 is unlikely to fall off even if the resin composition layer 2 is made of a material with no adhesive properties.
The adhesive layer 5 may be made of a conventionally known adhesive, for example, an inorganic adhesive such as metal solder or low-melting glass. When the adhesive layer 5 is provided at a position where it is not strongly exposed to the light emitted from the semiconductor light-emitting element 3, it may be made of an organic adhesive such as a silicone adhesive. Ceramics materials and glass may also be used.

In the ultraviolet light emitting device 20 of Fig. 9, the peripheral portion of the optical member 1 is stretched and fixed to the substrate 4 via an adhesive layer 5. Instead of stretching the peripheral portion of the optical member 1, another member may be adhered to the peripheral portion of the optical member 1 to form a similar shape. On the other hand, the semiconductor light emitting element 3 is sealed with the resin composition layer 2 and is in close contact with the optical member 1 via the resin composition layer 2. Since the adhesive layer 5 increases the adhesive strength, the resin composition layer 2 can also be designed to prioritize improvement of light extraction efficiency over adhesiveness.
10, a recess is provided on a part of the surface of a substrate, and the peripheral portion of an optical member 1 is extended toward the recess and fixed to a substrate 4 via an adhesive layer 5. Instead of extending the peripheral portion of the optical member 1, a similar shape may be obtained by adhering another member to the peripheral portion of the optical member 1. The entire light emission surface of the semiconductor light emitting element 3 is in close contact with the optical member 1 via a resin composition layer 2.
By stretching the peripheral portion of the optical member 1 and fixing it to the substrate 4 via the adhesive layer 5, the adhesion between the optical member 1 and the semiconductor light-emitting element 3 is strengthened and the intrusion of moisture and the like from the outside is prevented, thereby suppressing deterioration in the performance of the semiconductor light-emitting element 3. In addition, the amount of light emitted by the semiconductor light-emitting element 3 that hits the adhesive layer 5 can be suppressed.
The adhesive layer 5 may be made of a conventionally known adhesive, for example, an inorganic adhesive such as metal solder, low melting point glass, etc. When the adhesive layer 5 is provided at a position where it is not strongly exposed to the light emitted from the semiconductor light emitting element 3, it may be made of an organic adhesive such as a silicone-based adhesive.

11, a resin composition layer 2 is formed on a partial region of the surface of an optical member 1, and the resin composition layer 2 covers not only the entire light emission surface of a semiconductor light emitting element 3 but also at least a portion of the side surface. In addition, the outer periphery of the optical member 1 is stretched to cover a portion of the side surface of the semiconductor light emitting element 3 together with the resin composition layer 2. Instead of stretching the outer periphery of the optical member 1, a similar shape may be obtained by adhering another member to the outer periphery of the optical member 1.
4, the resin composition layer 2 may cover the entire side surface of the semiconductor light emitting element 3. By covering at least a portion of the side surface of the semiconductor light emitting element 3, high light extraction efficiency can be obtained for light emitted from the side surface.

12, the outer periphery of the substrate 4 is stretched and fixed to the optical member 1 via an adhesive layer 5. Instead of stretching the outer periphery of the substrate 4, a similar shape may be obtained by adhering another member to the outer periphery of the substrate 4. On the other hand, the entire light emission surface of the semiconductor light emitting element 3 is in close contact with the optical member 1 via a resin composition layer 2.
13, the outer periphery of the optical member 1 is stretched and fixed to the substrate 4 via the adhesive layer 5. Instead of stretching the outer periphery of the optical member 1, another member may be bonded to the outer periphery of the optical member 1 to form a similar shape. Meanwhile, the inside of the portion of the substrate 4 that contacts the optical member 1 is raised to provide a convex portion, so that the substrate 4 is also fixed to the side surface of the adhesive layer 5. The entire light emission surface of the semiconductor light emitting element 3 is in close contact with the optical member 1 via the resin composition layer 2.
14, the outer periphery of the substrate 4 is extended to form a stepped shape, and an adhesive layer 5 is provided on the stepped portion to fix the outer periphery and a partial region of the spherical surface of the optical member 1. The entire light emission surface of the semiconductor light emitting element 3 is in close contact with the optical member 1 via the resin composition layer 2.
The effect of the adhesive layer 5 is the same as that of the adhesive layer 5 in Fig. 8 etc. Also, by bonding on multiple surfaces as in Fig. 13 and Fig. 14 instead of bonding on only one surface, stronger bonding can be achieved.

15, the ultraviolet light-emitting device 20 has a substrate 4 in the shape of a container provided with side walls, and is covered with a cover 6. A resin composition layer 2 is formed on the entire surface of an optical member 1, and the entire light-emitting surface of a semiconductor light-emitting element 3 is bonded to the optical member 1 via the resin composition layer 2.
16, the cover 6 is in the form of a lid having side walls and is provided on a substrate 4. A resin composition layer 2 is formed on a partial region of the surface of an optical member 1, and the entire light emission surface of a semiconductor light emitting element 3 is bonded to the optical member 1 via the resin composition layer 2.
The cover 6 may be made of any material that transmits the light emitted from the semiconductor light emitting element 3, and is preferably made of a material that is highly transmissive at the wavelength of the emitted light. Examples of such materials include quartz and inorganic glass.
The cover 6 and the substrate 4 can be bonded with metal solder, an inorganic adhesive, an organic adhesive, or the like, which prevents the intrusion of moisture and the like from the outside world and suppresses deterioration of the performance of the semiconductor light emitting element 3 .
16, when the cover 6 is box-shaped, the substrate 4 may be flat, which reduces costs. Furthermore, since the side surface is formed by the cover 6, the light emitted in the side direction from the semiconductor light-emitting element 3 can also be extracted to the outside, thereby further improving the extraction efficiency.

The ultraviolet light emitting device is prepared by attaching the semiconductor light emitting element 3 to the substrate 4 by a known method such as die bonding, and processing and molding the optical element 1 separately. Next, a resin composition that will become the resin composition layer 2 is prepared. The resin composition is applied to the adhesive surface of the optical element 1 by a known method such as spin coating, dip coating, potting, etc. to form the resin composition layer 2, and the optical element 10 is prepared. At this time, depending on the resin composition, heating may be performed to remove the solvent. The optical element 10 is placed so that the resin composition layer 2 is in contact with the light emission surface of the semiconductor light emitting element 3, and is heated to a temperature at which the resin composition softens, for example, 100°C to 270°C. A load can also be applied to the optical element 10 so that the softened resin composition layer 2 fills the gap between the optical element 1 and the semiconductor light emitting element 3. Next, the resin composition layer 2 is cooled and hardened to bring the optical element 1 and the semiconductor light emitting element 3 into close contact with each other, and the ultraviolet light emitting device 20 is obtained. The ultraviolet light emitting device 20 can also be made in the order of first providing the optical element 10 on the semiconductor light emitting element 3 and then attaching it to the substrate 4.
Furthermore, when a thermosetting resin, a photocurable resin, or the like is used as the resin composition, the resin composition is applied to at least one of the adhesive surfaces of the optical member 1 and the semiconductor light-emitting element 3, and after they are bonded together, they are cured by irradiating them with heat or light, so that the optical member 1 and the semiconductor light-emitting element 3 are closely adhered to each other by the resin composition layer 2, thereby obtaining the ultraviolet light-emitting device 20. The ultraviolet light-emitting device 20 can also be produced by first providing the optical element 10 on the semiconductor light-emitting element 3 and then attaching it to the substrate 4.

The present invention is explained in detail below with reference to examples, but the present invention is not limited to these.

[Example 1-1: Resin composition 1]
2 g of amorphous fluororesin (CYTOP CTL-109AE, manufactured by AGC, solid content concentration 9 wt%) was weighed into a 20 mL vial and diluted with 1 mL of fluorosolvent (CYTOP CT-SOLV100E, manufactured by AGC). Then, 100 mg of tridecafluoroheptanoic acid was added and stirred until homogenous. The obtained fluororesin solution was transparent.
In a separate vial, 0.75 mL of ZrO2 _{nanoparticles} (ZSL-20N, Daiichi Kigenso Co., Ltd., solid content concentration 20 wt%, average secondary particle diameter 60-105 nm, band gap 5.04 eV) was weighed and diluted with 3 mL of pure water. The resulting liquid that became the aqueous layer containing the metal oxide nanoparticles was slightly cloudy.
The aqueous layer containing the metal oxide nanoparticles was gently added to the fluororesin solution, and the mixture was stirred and then degassed using a planetary centrifugal mixer (Thinky Mixer ARE-310). After this operation, the _ZrO2 nanoparticles contained in the aqueous layer were transferred to the fluororesin solution, and the upper aqueous layer became transparent, while the lower layer became a slightly cloudy fluororesin solution.
By removing the upper layer, a resin composition solution in which _ZrO2 nanoparticles were dispersed in a fluororesin solution was obtained. This resin composition solution was dried at 50°C for 5 minutes and then at 100°C for 30 minutes to obtain resin composition 1.

[Example 1-2: Resin composition 2]
A resin composition 2 in which _ZrO2 nanoparticles were dispersed in a fluororesin was obtained in the same manner as in Example 1, except that the amount of tridecafluoroheptanoic acid was 40 mg and the amount of _ZrO2 nanoparticles was 0.2 mL.

[Example 1-3: Resin composition 3]
Resin composition 3 in which _ZrO2 nanoparticles were dispersed in a fluororesin was obtained in the same manner as in Example 1, except that the amount of tridecafluoroheptanoic acid was 300 mg and the amount of _ZrO2 nanoparticles was 2.2 mL.

[Example 1-4: Resin composition 4]
An amorphous fluororesin (CYTOP CTX-809SP2, manufactured by AGC, solid content concentration 9% by weight) was used as it was to prepare resin composition 4.

[Example 1-5: Resin composition 5]
An amorphous fluororesin (CYTOP CTL-109AE, manufactured by AGC, solid content concentration 9% by weight) was used as it was to prepare resin composition 5.

[Example 1-6: Resin composition 6]
0.75 g of amorphous silicone resin (silsesquioxane, SR-13H, solid content concentration 94.4 wt%) was weighed into a 20 mL vial. Next, 1.1 g of ZrO2 _{nanoparticles} (SZR-KM, manufactured by Sakai Chemical Industry Co., Ltd., zirconia concentration 30.5 wt%, dispersant concentration 3.1 wt%, particle size distribution D50 obtained by dynamic light scattering method is 7 nm, band gap 5.04 eV) was added. This solution was stirred using a rotation-revolution mixer (Awatori Rentaro ARE-310, manufactured by Thinky Co., Ltd.) to obtain a resin composition solution in which _ZrO2 nanoparticles were dispersed in silicone resin. This resin composition solution was dried at 50 ° C for 5 minutes and then at 100 ° C for 30 minutes to obtain resin composition 6.

[Example 1-7: Resin composition 7]
Resin composition 7 in which _ZrO2 nanoparticles were dispersed in silicone resin was obtained in the same manner as in Example 1-6, except that 0.5 g of amorphous silicone resin was weighed out and 1.6 g of _ZrO2 nanoparticles were added.

[Example 1-8: Resin composition 8]
An amorphous silicone resin (SR-13H, solid content concentration 94.4% by weight) was used as it was to prepare resin composition 8.

The resin compositions of Examples 1-1 to 1-3, 1-6, and 1-7 are working examples, and the resin compositions of Examples 1-4, 1-5, and 1-8 are comparative examples in which metal oxide nanoparticles are not dispersed. The compositions are summarized in the table below. Note that the dispersant in Table 2 is a dispersant that was originally contained in the _ZrO2 nanoparticles used, and was not added separately.

[evaluation]
(Refractive index measurement)
The resin composition solution was dropped onto quartz glass and coated with a bar coater having a gap of 150 μm. It was then dried at 50° C. for 5 minutes and then at 100° C. for 30 minutes to form a resin composition layer with a thickness of 6 μm, which was used as a sample for measuring the refractive index.
The refractive index of the sample was measured using a prism coupler (Model 2010, manufactured by Metricon). The measurement temperature was 30° C., and the wavelengths were 452 nm, 532 nm, and 632 nm. From the refractive indices at these three wavelengths, the refractive index for light of a specific wavelength was calculated using Cauchy's dispersion formula expressed by the following formula.
n(λ)=A+(B/λ ² )+(C/λ ⁴ )
In the formula, λ represents the wavelength of light, and n(λ) represents the refractive index for light of wavelength λ. A, B, and C are constants that are experimentally determined.
Table 3 shows the measured refractive indexes at wavelengths of 452 nm, 532 nm, and 632 nm, as well as the refractive indexes at wavelengths of 265 nm, 275 nm, 285 nm, and 587.6 nm (d-line) calculated using Cauchy's dispersion formula.
The resin compositions of Examples 1-4 and 1-5 are composed only of resin, and the resin is the same as the resin in the resin compositions of Examples 1-1 to 1-3. Therefore, the d-line refractive index n _d (R) of the resin in the resin compositions of Examples 1-1 to 1-3 is the same as the d-line refractive index n _d (C) = 1.34 of the resin compositions of Examples 1-4 and 1-5. Similarly, the resin composition of Example 1-8 is composed only of resin, and the resin is the same as the resin in the resin compositions of Examples 1-6 and 1-7. Therefore, the d-line refractive index n _d (R) of the resin in the resin compositions of Examples 1-6 and 1-7 is the same as the d-line refractive index n _d (C) = 1.42 of the resin composition of Example 1-8.

(Average transmittance)
The resin composition solution was dropped onto quartz glass and coated with a bar coater having a gap of 150 μm. The glass was then dried at 50° C. for 5 minutes and then at 100° C. for 30 minutes to form a resin composition layer having a thickness of 6 μm, which was used as a measurement sample for transmittance measurement.
The external transmittance was measured in the wavelength range of 260 to 400 nm using a spectrophotometer (Ocean Insight, model: HR2000) and the average value was calculated. The results are shown in Table 3.

[Examples 3-1 to 3-20: Optical elements]
As optical members, the raw materials such as nitrates, sulfates, hydroxides, oxides, and boric acid were weighed and thoroughly mixed so as to obtain the compositions of Examples 2-1 to 2-4 listed in Table 4, and then the mixture was poured into a platinum crucible and heated and melted for 1.5 to 3 hours at a temperature range of 1150°C to 1350°C. This molten glass was dripped from a pipe attached to a glass melting furnace and cooled and solidified to obtain rough glass balls in a rough spherical shape. Next, the surface of the rough glass balls was polished to produce polished glass balls. In addition to the above method, polished glass balls can also be obtained by machining the glass plate obtained by molding and solidifying it into a plate shape with a blade or the like, and by reheating and deforming it to produce a glass block, and then polishing the surface with a ball polishing machine.
The obtained glass grinding ball was sliced and polished into a hemispherical shape to produce a hemispherical lens (optical component). Note that the blanks in the composition in Table 4 mean that the content of the corresponding component was below the detection limit.

The resin composition solution prepared in the same manner as above was applied by potting using a micropipette to the flat surface of the obtained optical member, which was a hemispherical lens, and dried at 50° C. for 5 minutes and then at 100° C. for 30 minutes to form a resin composition layer. The thickness of the resin composition layer was 10 μm.
The resin composition layer of the resin composition of Example 1-1 was formed on the flat surface of the hemispherical lens made of the glass of Example 2-1 to Example 2-4 to obtain the optical elements of Examples 3-1 to 3-4. The resin composition of Example 1-2 and the glass of Examples 2-1 to 2-4 were used to obtain the optical elements of Examples 3-5 to 3-8 in a similar manner. The resin composition of Example 1-3 and the glass of Examples 2-1 to 2-4 were used to obtain the optical elements of Examples 3-9 to 3-12 in a similar manner. The resin composition of Example 1-6 and the glass of Examples 2-1 to 2-4 were used to obtain the optical elements of Examples 3-13 to 3-16 in a similar manner. The resin composition of Example 1-7 and the glass of Examples 2-1 to 2-4 were used to obtain the optical elements of Examples 3-17 to 3-20 in a similar manner. All of Examples 3-1 to 3-20 are examples.

[evaluation]
(Refractive index measurement)
The refractive index of the optical member was measured using a precision refractometer (Shimadzu Corporation, model: KPR-200, KPR-2000) by using a glass block prepared by the same method as above and processed into a rectangular parallelepiped shape with a side of 5 mm or more and a thickness of 5 mm or more. Table 4 shows the measured value at 587.6 nm (d line) and the refractive index at wavelengths of 265 nm, 275 nm, and 285 nm calculated by Cauchy's dispersion formula.
For the optical element, the refractive index n _d (O) of the optical member and the refractive index n _d (C)' of the resin composition layer, and the absolute value of the difference therebetween, Δn _d = |n _d (O) - n _d (C)'|, for the d line (wavelength 587.6 nm) are shown in Tables 5 and 6. The refractive index n _d (C)' of the resin composition layer is the same as the refractive index n _d (C) of the resin composition.

(Absorption Coefficient)
The absorption coefficient of the optical member was calculated by measuring the external transmittance of samples made by polishing both sides of a glass block to a thickness of 10 mm, 5 mm, and 1 mm using a spectrophotometer (Hitachi High-Technologies Corporation, model: U-4100) and calculating the absorption coefficient. The external transmittance and the absorption coefficient are related by the following formula. T is the external transmittance, α is the absorption coefficient, d is the thickness of the sample, and r is the one-sided reflectance.
lnT=-α×d+ln(1-r) ²
Table 4 shows the absorption coefficient at each wavelength and the maximum value αmax of the absorption coefficient in the wavelength range of 260 to 400 nm.

(Fe content)
The total iron oxide content (T-Fe ₂ O ₃ ) of the optical member was measured by ICP mass spectrometry according to the following procedure. A mixed acid of hydrofluoric acid and sulfuric acid was added to a crushed glass block, and the mixture was heated to decompose. After decomposition, hydrochloric acid was added to a certain amount, and the Fe concentration was measured by ICP mass spectrometry. The concentration was calculated using a calibration curve made using a standard solution. The T-Fe ₂ O ₃ in the glass was calculated from this measured concentration and the amount of glass decomposed. The ICP mass spectrometer used was an Agilent 8800 manufactured by Agilent Technologies. The results are shown in Table 4.

(Glass Transition Temperature)
The glass transition temperature Tg of the optical member was measured by machining a glass block into a cylindrical sample with a diameter of 5 mm and a length of 20 mm, using a thermomechanical analyzer (manufactured by Rigaku Corporation, model: Thermo Plus TMA8310) at a heating rate of 5° C./min. The results are shown in Table 4.

[Examples 4-1 to 4-17: Ultraviolet light emitting devices]
A semiconductor light-emitting element having a peak wavelength λ(D) of 275 nm, a flip-chip structure, and a mirror-finished light-emitting surface of a sapphire substrate was provided on a metal-wired aluminum nitride substrate. An optical element was prepared by forming a resin composition layer of each of the resin compositions of Examples 1-1 to 1-8 on the flat surface of a hemispherical optical member made of Example 2-4 or quartz, and the optical element was arranged so that the resin composition layer was in contact with the light-emitting surface of the semiconductor light-emitting element. Thereafter, the optical element was placed on a hot plate and heated at 260° C. for 10 minutes, and then cooled, thereby providing the optical element on the semiconductor light-emitting element via the resin composition layer, and an ultraviolet light-emitting device was obtained. Note that the optical element can also be provided in the same process in the case of a semiconductor light-emitting element having an aluminum nitride substrate as a light-emitting surface.

The effect of improving the light extraction efficiency obtained by the ultraviolet light emitting device described above was verified by calculating the output of the emitted light emitted from the semiconductor light emitting element to the outside of the light emitting element through optical simulation.
In the optical simulation, the output of the emitted light emitted outside the light emitting element is calculated by the ray tracing method. The calculation model of the semiconductor light emitting element used in the calculation is shown in Table 7, and the resin composition layer and the optical member used in each study example are shown in Tables 8 and 9.
The semiconductor light emitting element is composed of a contact layer, a light emitting layer, and a sapphire substrate in that order from the substrate side. The contact layer is made of p-GaN, which is a perfect absorber of ultraviolet light, and the light emitting layer is made of an AlGaN-based semiconductor material with a refractive index of about 2.5.

The light generated in the light emitting layer passes through the sapphire substrate and is emitted from the light emitting surface on the upper side of the sapphire substrate to the outside of the semiconductor light emitting element. The output of the emitted light is counted by counting the light emitted above the light emitting surface of the semiconductor light emitting element. Here, Example 4-1 is an ultraviolet light emitting device of a semiconductor light emitting element that does not have an optical element, and is a comparative example that does not use an optical element. Examples 4-5, 4-6, 4-10, and 4-11 are comparative examples in which Example 1-4 or Example 1-5, which is a resin in which metal oxide nanoparticles are not dispersed, is used in the resin composition layer of the optical element. Examples 4-16 and 4-17 are comparative examples in which Example 1-8, which is a resin in which metal oxide nanoparticles are not dispersed, is used in the resin composition layer of the optical element.

For the output of emitted light of the ultraviolet light-emitting device in each of the study examples shown in Tables 8 and 9, the ratio to the output of emitted light of Example 4-1 is defined as the Enhancement Factor. In other words, the Enhancement Factor is a value that indicates how many times the light output of the ultraviolet light-emitting device is increased by attaching an optical element to the semiconductor light-emitting element. Tables 8 and 9 show the results of an optical simulation using a semiconductor light-emitting element with a peak wavelength λ(D) = 275 nm.

The Enhancement Factors of Examples 4-2 to 4-17 all exceed 1.0, and it is understood that the light extraction efficiency can be improved by providing an optical element on a semiconductor light emitting element. Furthermore, the Enhancement Factors of Examples 4-2 to 4-4 are larger than those of Examples 4-5 and 4-6. This shows that the light extraction efficiency can be further improved by using a resin composition having a higher refractive index than the resin by dispersing metal oxide nanoparticles in the resin composition layer of the optical element. Similarly, the Enhancement Factors of Examples 4-7 to 4-9 are larger than those of Examples 4-10 and 4-11, and it is understood that the light extraction efficiency can be further improved by using an optical element having a resin composition layer with a higher refractive index. In addition, the Enhancement Factors of Examples 4-12 and 4-13 are larger than that of Example 4-16, and the Enhancement Factors of Examples 4-14 and 4-15 are larger than that of Example 4-17. It can be seen that the light extraction efficiency can be further improved by using an optical element having a resin composition layer with an increased refractive index.

These results show that by attaching an optical element to a semiconductor light-emitting element via a resin composition layer in which metal oxide nanoparticles are dispersed in resin to increase the refractive index, the light extraction efficiency can be improved compared to conventional methods.

Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention. This application is based on a Japanese patent application (Patent Application No. 2020-094666) filed on May 29, 2020, the contents of which are incorporated herein by reference.

Reference Signs List 1 Optical member 2 Resin composition layer 3 Semiconductor light emitting element 4 Substrate 5 Adhesive layer 6 Cover 10 Optical element 20 Ultraviolet light emitting device

Claims (17)

An optical element comprising a resin composition layer and an optical member that transmits ultraviolet light,
The resin composition layer is made of a resin composition in which metal oxide nanoparticles are dispersed in a resin,
a refractive index n _d (C) of the resin composition and a refractive index n _d (R) of the resin with respect to d line (wavelength 587.6 nm) satisfy the relationship n _d (C) - _{n d} (R) ≧ 0.03;
the resin is at least one of an amorphous fluororesin and a silicone resin whose main skeleton structure is silsesquioxane;
The optical member is used in an ultraviolet light emitting device having the resin composition layer formed on at least a partial region of a surface thereof,
the optical member is made of inorganic glass,
The adhesive strength between the optical member and the adherend due to the resin composition layer is 5 N/mm2 ^or more and 20 N/mm2 or ^less in terms of shear strength ,
The inorganic glass is an optical element that is a highly ultraviolet-transmitting glass having a maximum absorption coefficient αmax of 0.2 mm ⁻¹ or less in the wavelength region of 260 to 400 nm. The optical element according to claim 1 , wherein the band gap of the metal oxide nanoparticles is 4.8 eV or more. _3. The optical _element according to claim ₁ , _wherein the metal oxide nanoparticles comprise at least one type of nanoparticles selected from _the group consisting of _Gd2O3 , _HfO2 , _La2O3 , _Y2O3 , _Yb2O3 , _ZrO2 , _Al2O3 , and _SiO2 . 4. The optical element according to claim 1, wherein the metal oxide nanoparticles have an average primary particle size of 2 to 80 nm. 5. The optical element according to claim 1, wherein the content of the metal oxide nanoparticles is 15% by mass or more and 70% by mass or less. 6. The optical element according to claim 1, wherein the resin composition has a refractive index n _d (C) of 1.39 or more. 7. The optical element according to claim 1, wherein the average transmittance of the resin composition in a wavelength range of 260 to 400 nm is 70% or more. The optical element according to any one of claims 1 to 7, wherein the refractive index n _d (O) of the optical member and the refractive index n _d (C)' of the resin composition layer for d line (wavelength 587.6 nm) satisfy the relationship Δn _d = | n _d (O) -n _d (C)'| ≦ 0.35. The optical element according to any one of claims 1 to 8 , wherein the ultraviolet light emitting device comprises a semiconductor light emitting element having a peak wavelength λ(D) in the wavelength range of 250 to 400 nm. The optical element according to claim 9 , wherein the resin composition layer is used as the adherend to bring the light emission surface of the semiconductor light emitting element into close contact with the optical member. An ultraviolet light emitting device having a substrate, a semiconductor light emitting element provided on the substrate, and an optical element provided on the semiconductor light emitting element,
the optical element comprises a resin composition layer and an optical member that transmits ultraviolet light,
the optical member is made of inorganic glass,
the resin composition layer has a shear strength of adhesion between the light emission surface of the semiconductor light emitting element and the optical member of 5 N/mm2 ^or more and 20 N/mm2 ^or less;
The inorganic glass is a highly ultraviolet-transmitting glass having a maximum absorption coefficient αmax of 0.2 mm ⁻¹ or less in a wavelength range of 260 to 400 nm,
The resin composition layer is made of a resin composition in which metal oxide nanoparticles are dispersed in a resin,
a refractive index n _d (C)′ of the resin composition layer and a refractive index n _d (R) of the resin with respect to d line (wavelength 587.6 nm) satisfy the relationship n _d (C)′-n _d (R)≧0.03;
the resin is at least one of an amorphous fluororesin and a silicone resin whose main skeleton structure is silsesquioxane;
the resin composition layer is formed on at least a partial region of the surface of the optical member,
an ultraviolet light emitting device, the optical element being provided on a light emission surface of the semiconductor light emitting element via the resin composition layer; 12. The ultraviolet light emitting device according to claim 11 , wherein the peak wavelength λ(D) of the light emitted by the semiconductor light emitting element is in the wavelength range of 250 to 400 nm. 13. The ultraviolet light emitting device according to claim 12 , wherein the refractive index n _o (C)' of the resin composition layer at the peak wavelength λ(D) is 1.4 or more. The ultraviolet light emitting device according to claim 12 or 13, wherein the refractive index n _o (O) of the optical member and the refractive index n _o (C)' of the resin composition layer at the peak wavelength λ(D) satisfy the relationship Δn _o = |n _o (O) -n _o (C)'|≦ 0.42 . 15. The ultraviolet light emitting device according to claim 11 , wherein the semiconductor light emitting element has a flip chip structure or a vertical structure. The ultraviolet light emitting device according to any one of claims 11 to 15 , wherein the resin composition layer covers at least a part of a side surface of the semiconductor light emitting element. 17. The ultraviolet light emitting device according to claim 11, wherein a part of the optical member is in contact with the substrate or is bonded to the substrate.