WO2021039730A1 - Optical element, glass, and luminescence device - Google Patents

Abstract

The present invention pertains to an optical element provided with an optical member and an adhesive layer, the optical member having a light incident surface, a light emission surface, and an optical functional surface on at least one among the light incident surface and the light emission surface, wherein the adhesive layer is provided on the surface of at least one among the light incident surface and the light emission surface of the optical member, and the adhesive layer is made of organic glass and has an average external transmittance of at least 30% when the thickness thereof is 1 mm and the wavelength of light is 260-285 nm.

Description

Optical elements, glass and light emitting devices

The present invention relates to an optical element, glass and a light emitting device.

As a light source in an ultraviolet light emitting device, an ultraviolet LED (light emitting diode) is attracting attention instead of a conventional mercury lamp from the viewpoint of environmental protection and the like. This ultraviolet LED is used in various applications depending on the emission wavelength. For example, it can be used in a curing process of an ultraviolet curable resin, treatment of skin diseases, sterilization of viruses and pathogens, and the like.

However, the ultraviolet LED has a low efficiency of extracting the light emitted by the ultraviolet LED element, which hinders its widespread use. Although LED elements such as flip-chip structures and vertical structures are being studied in order to improve the light extraction efficiency, the light extraction efficiency is still low at around 8%, and further improvement in light utilization efficiency is required. There is.

On the other hand, Patent Document 1 discloses a technique in which a photonic crystal having a concavo-convex structure is formed on the light emitting surface of an LED element by etching processing, and a part of the totally reflected light is taken out of the LED.
Further, a technique of providing an optical member on the LED element is also being studied. As the optical member, a sapphire hemispherical lens is used in Patent Document 2, a spinel sintered body is used in Patent Document 3, and a fluororesin is used in Patent Document 4. The techniques used for each are disclosed.

As a study on a material for adhering an LED element and an optical member, Patent Document 5 discloses a technique of using a translucent resin as a member for adhering a light emitting element and a covering member. Further, Patent Document 6 discloses a technique of using a thermoplastic resin or a curable resin as a material for forming an adhesive member.

Japanese Patent No. 6349036 Japanese Patent No. 6230038 International Publication No. 2018/0663636 International Publication No. 2017/208535 Japanese Patent Application Laid-Open No. 2018-67630 International Publication No. 2016/190207 Japanese Patent Application Laid-Open No. 2018-35046

As described above, techniques for improving the light extraction efficiency by combining the LED element with the optical member have been studied and proposed from various angles.
However, not many studies have been made on the material for adhering the LED element and the optical member. When a resin as disclosed in Patent Documents 5 and 6 is used as an adhesive material, the resin may be deteriorated by the light emitted from the LED element, and the transmittance may be lowered or damaged. The deterioration is remarkable when the ultraviolet LED element is used.

Further, although it is not an adhesive material, Patent Document 7 discloses a technique of using fluorine-containing glass as a sealing material for sealing a light source. However, when the fluorine-containing glass is used as an adhesive material, it is considered difficult to improve the light extraction efficiency because fluorine is a component that greatly lowers the refractive index.

In view of the above circumstances, the present invention focuses on a material for adhering an LED element and an optical member, and among ultraviolet rays, has excellent transparency to short wavelength ultraviolet rays (UV-C) having a wavelength of about 260 to 285 nm, and UV-. An object of the present invention is to provide an optical element having an adhesive layer that is not easily deteriorated by C irradiation. Another object of the present invention is to provide a glass used for adhering members and a light emitting device having the glass as an adhesive layer.

As a result of diligent studies by the present inventors, it was found that the above problems can be solved by using glass having specific characteristics as the adhesive layer, and the present invention has been completed.

That is, the present invention relates to the following [1] to [15].
[1] An optical element including an optical member and an adhesive layer, wherein the optical member has a light incident surface and a light emitting surface, and an optical function is provided on at least one of the light incident surface and the light emitting surface. The adhesive layer is provided on the surface of at least one of the light incident surface and the light emitting surface of the optical member, and the adhesive layer is made of inorganic glass and has a wavelength of 1 mm in thickness. An optical element having an average value of external transmittance of 30% or more at 260 to 285 nm.
[2] The absolute value Δnd of the difference between the refractive index nd (O) of the optical member and the refractive index nd (A) of the adhesive layer with respect to the d-line (wavelength 587.6 nm) is Δnd = | nd (O). The optical element according to the above [1], wherein −nd (A) | ≦ 0.35.
[3] The absolute value ΔTc of the difference between the bending point Tc (O) of the optical member and the bending point Tc (A) of the adhesive layer is ΔTc = | Tc (O) −Tc (A) | ≧ 300 (° C.). The optical element according to the above [1] or [2].
[4] The optical element according to any one of [1] to [3], wherein the yield point Tc (A) of the adhesive layer is Tc (A) ≤400 (° C.).
[5] The inorganic glass constituting the adhesive layer has a difference in average transmittance of 10% or less at wavelengths of 260 to 285 nm before and after the ultraviolet irradiation test under the following conditions, as described in [1] to [4]. The optical element according to any one.
Ultraviolet irradiation test: Both main surfaces of the glass plate obtained by molding the inorganic glass into a plate shape are mirror-optically polished to a thickness of 1 mm. One of the polished surfaces of the glass plate is arranged so as to face a position 20 cm from a 400 W high-pressure mercury lamp that emits ultraviolet rays having a wavelength of 220 to 400 nm, and the high-pressure mercury lamp is irradiated with ultraviolet rays for 100 hours.
[6] The optical element according to any one of [1] to [5], wherein the adhesive layer has a thickness of 0.01 to 0.2 mm.
[7] The optical element according to any one of [1] to [6], wherein the optical member is a lens, a lens array, a diffraction grating, a diffraction optical element, or a grating cell array.
[8] A glass used for adhering members, the average value of external transmittance at a wavelength of 260 to 285 nm at a thickness of 1 mm is 30% or more, and the yield point Tc (A) is Tc (A) ≦. Glass at 400 (° C).
[9] The absolute value Δnd of the difference between the refractive index nd (O) of the member to be bonded and the refractive index nd (A) of the glass with respect to the d-line (wavelength 587.6 nm) is Δnd = | nd (O). The glass according to the above [8], wherein −nd (A) | ≦ 0.35.
[10] The glass according to the above [8] or [9], wherein the refractive index nd (A) is nd (A) ≥ 1.50.
_{[11] The content of P 2} O ₅ , ZnO and Li ₂ O in terms of mol% based on oxide is 65% or more in total, and Nb ₂ O ₅ , TiO ₂ , CeO ₂ , V ₂ O ₅ and Bi. ₂ The glass according to any one of [8] to [10] above, wherein the total of O ₃ and WO _{3 is less than 0.1%.}
[12] The glass according to any one of [8] to [11] above, wherein the content in molar% of the oxide standard _{is less than 0.01% of Fe 2} O _3.
[13] The glass according to any one of [8] to [12] above, wherein the transmittance at a wavelength of 265 nm after an ultraviolet irradiation test under the following conditions is 30% or more.
Ultraviolet irradiation test: Both main surfaces of a glass plate obtained by molding glass into a plate shape are mirror-optically polished to a thickness of 1 mm. One of the polished surfaces of the glass plate is arranged so as to face a position 20 cm from a 400 W high-pressure mercury lamp that emits ultraviolet rays having a wavelength of 220 to 400 nm, and the high-pressure mercury lamp is irradiated with ultraviolet rays for 100 hours.
[14] The content of oxide-based mol% is P ₂ O ₅ 30 to 60%, ZnO 10 to 60%, Li ₂ O 1 to 30%, SiO ₂₀ to 6%, Al ₂ O _{3 0 ~ 6%, Na 2 O} 0 ~ 20%, K 2 O 0 ~ 15%, BaO 0 ~ 10%, CaO 0 ~ 10%, Ta 2 O 5 0 ~ 3%, SnO 0 ~ 3%, La 2 The glass according to any one of the above [8] to [13], which is O ₃₀ to 5%, Gd ₂ O ₃₀ to 5%, and Y ₂ O _{30 to 5%.}
[15] An optical member made of a substrate, an LED element provided on the substrate, and an inorganic glass provided on the LED element that allows light emitted from the LED element to be transmitted and irradiated to the outside. A light emitting device having an adhesive layer provided between the LED element and the optical member, wherein the adhesive layer is made of the glass according to any one of [8] to [14].

According to the present invention, by using a specific inorganic glass as the adhesive layer, an optical element having excellent transparency to short wavelength ultraviolet rays (UV-C) having a wavelength of about 260 to 285 nm and less deterioration due to UV-C irradiation can be obtained. Can be provided. Further, the optical element according to the present invention can be used at a relatively high temperature as compared with the case where a resin is used as the adhesive layer.
Further, the glass used for adhering the members according to the present invention has excellent transparency to short wavelength ultraviolet rays (UV-C) having a wavelength of about 260 to 285 nm, and the member (adhesion) is made of glass. , The difference in refractive index from the member is small. Therefore, when used for bonding LED elements and optical members such as lenses, glass fibers, and lenses, the loss of light due to reflection and absorption is small, and the light extraction efficiency and transmittance are reduced. The decrease can be prevented.

FIG. 1 is a schematic cross-sectional view showing an example of an optical element. FIG. 2 is a schematic cross-sectional view showing an example of an optical device.

Hereinafter, the present invention will be described in detail, but the present invention is not limited to the following embodiments, and can be arbitrarily modified and carried out without departing from the gist of the present invention. Further, "-" indicating a numerical range is used to mean that the numerical values described before and after the numerical range are included as the lower limit value and the upper limit value.
Unless otherwise specified, the content (content) of each component in glass is expressed in mol% based on oxides.
In the present specification, the mass-based ratio (percentage, parts, etc.) is the same as the weight-based ratio (percentage, parts, etc.).

[Optical element]
As shown in FIG. 1, the optical element 10 according to the present embodiment includes an optical member 1 and an adhesive layer 2.
The optical member 1 has a light incident surface and a light emitting surface, and has an optical functional surface on at least one of the light incident surface and the light emitting surface. The optical functional surface may be provided in at least a part of a light incident surface or a light emitting surface.
The adhesive layer 2 is provided on the surface of at least one of the light incident surface and the light emitting surface of the optical member 1. Further, the adhesive layer 2 is made of inorganic glass, and the average value of the external transmittance at a wavelength of 260 to 285 nm at a thickness of 1 mm is 30% or more.

The mode of the adhesive layer is not limited as long as the adhesive layer is provided on at least one surface of the light incident surface and the light emitting surface of the optical member. For example, the adhesive layer may be provided in the entire region (entire surface) on the surface, or may be provided in a partial region on the surface of the optical member according to the size of the LED element or the like to be the other adherend. It may be. Further, the adhesive layer may be formed not only on the adhesive surface between the optical member and the other adherend but also on the side surface of the other adherend. Further, the other adherend may be adhered to the optical member while being sealed with the adhesive layer.

The light transmittance of each wavelength in the present specification is a value measured by using a visible ultraviolet spectrophotometer. That is, the transmittance is not the internal transmittance but the external transmittance including the surface reflectance of the interface, and is the external transmittance converted to a thickness of 1 mm.

{Inorganic glass}
The adhesive layer made of inorganic glass (hereinafter, may be simply referred to as “glass”) is provided on at least one surface of the light incident surface and the light emitting surface of the optical member. As described above, the adhesive layer does not have to be provided on the entire surface of the light incident surface or the light emitting surface, and may be provided in at least a part of the region.
When two members (adhesions) to be bonded to each other are bonded to each other by glass, the glass is softened by heating to a temperature equal to or higher than the softening point, and is brought into contact with the two adherends to be bonded. Then, by cooling and curing, the two adherends are adhered to each other via the adhesive layer. The two adherends are, for example, an optical member and the other adherend in the optical element according to the present embodiment.
Further, the adhesive layer can be formed by preparing the material of the adhesive layer as a frit paste, applying it to the adhesive surface by a known coating method, and then heating it to decalcify and defoam.
Further, the adhesive layer can also be formed by preparing the material of the adhesive layer as a green sheet, placing a small piece of the green sheet on the adhesive surface and heating it to decalcify and defoam.
Furthermore, the material of the adhesive layer is prepared as a glass sheet by machining such as slicing and polishing, and small pieces cut to the size required for adhesion are heated while being in contact with the adhesive surface and fused to form the adhesive layer. Can be formed.

For example, when the LED element and the optical member are adhered to each other, the light emitted from the LED element passes through the glass which is the adhesive layer and is introduced into the inside of the optical member.
At this time, even if the light emitted from the LED element is short wavelength ultraviolet light (UV-C) having a wavelength of about 260 to 285 nm, the optical element according to the present embodiment is compared with the case where a resin is used as the adhesive layer. As a result, deterioration due to long-term exposure to UV-C is suppressed, so that the product life can be extended.

Although the glass functions as an adhesive layer for an optical element that adheres an LED element or the like to an optical member, it can also be used for bonding other members. The member in this case is not particularly limited, but it is preferably a member that requires light transmission. That is, in addition to the adhesion between the optical member and the LED element, it can also be preferably used for adhesion between glass fibers, adhesion between lenses, adhesion between prisms, adhesion between optical filters, and the like.

Glass has low absorption of short-wavelength ultraviolet rays (UV-C) having a wavelength of about 260 to 285 nm, and has high UV-C transparency. That is, the average value of the external transmittance at a wavelength of 260 to 285 nm at a thickness of 1 mm is 30% or more, preferably 40% or more, and more preferably 55% or more. The higher the external transmittance, the more preferable, but 90% or less is practical.
The transmittance for UV-C can be adjusted mainly by the amount of UV-C absorbing component contained in the glass. Examples of the UV-C absorbing component include Nb ₂ O ₅ , TiO ₂ , CeO ₂ , V ₂ O ₅ , Bi ₂ O ₃ , WO ₃ , Fe ₂ O ₃ and SnO.

It is preferable that the UV-C transmittance of glass is high. As an example of the case where glass is molded into a plate shape to form a glass plate, the transmittance at a wavelength of 265 nm at a thickness of 1 mm is preferably 30% or more, more preferably 40% or more, still more preferably 50% or more. The higher the transmittance, the more preferable, but 85% or less is practical.

When glass is used as an adhesive layer, if the glass deteriorates due to low UV-C resistance, the glass may be discolored. Furthermore, the glass may not function as an adhesive layer if it is cracked due to deterioration. Therefore, the transmittance of the glass at a wavelength of 265 nm after the ultraviolet irradiation test under the following conditions is preferably 30% or more, more preferably 40% or more, still more preferably 50% or more. Further, the higher the transmittance, the more preferable, but 85% or less is practical.
Discoloration of glass occurs when the UV-C absorbing component becomes a coloring component and causes the glass to develop color. Therefore, as described above, the UV-C resistance can be improved by adjusting the type and amount of the UV-C absorbing component.
Ultraviolet irradiation test: Both main surfaces of a glass plate obtained by molding glass into a plate shape are mirror-optically polished to a thickness of 1 mm. One of the polished surfaces of the glass plate is arranged so as to face a position 20 cm from a 400 W high-pressure mercury lamp that emits ultraviolet rays having a wavelength of 220 to 400 nm, and the high-pressure mercury lamp is irradiated with ultraviolet rays for 100 hours.

Further, the difference in the average transmittance of the glass at a wavelength of 260 to 285 nm before and after the ultraviolet irradiation test under the same conditions as described above is preferably 10% or less, more preferably 8% or less, still more preferably 5% or less.
Specifically, the difference in the average transmittance means that the average transmittance of the glass at a wavelength of 260 to 285 nm before the ultraviolet irradiation test is T0 (%), and the glass at a wavelength of 260 to 285 nm after the ultraviolet irradiation test. It is a value represented by | T0-T1 | (%) when the average transmittance of is T1 (%). It can be determined that the smaller the difference, the higher the UV-C resistance. The "average transmittance (T0) of glass at a wavelength of 260 to 285 nm before the ultraviolet irradiation test" is synonymous with the "average value of the external transmittance of glass at a wavelength of 260 to 285 nm at a thickness of 1 mm". ..

It is preferable that the difference between the refractive index of glass and the refractive index of the member (adhesion) to be adhered such as an optical member is small. This suppresses total reflection and Frenel reflection at the interface between the adherend and the glass when glass is used for bonding the LED element to an optical member such as a lens, glass fibers to each other, or lenses to each other. This is to prevent a decrease in transmittance.

When the refractive index for the d-line (wavelength 587.6 nm) is expressed as nd, the absolute value Δnd of the difference between the refractive index nd (O) of the adherend and the refractive index nd (A) of the glass with respect to the d-line is It is represented by Δnd = | nd (O) -nd (A) |. The value of Δnd is preferably 0.35 or less, more preferably 0.30 or less, and even more preferably 0.25 or less. Specifically, for example, in the optical element according to the present embodiment, the absolute value Δnd of the difference between the refractive index nd (O) of the optical member and the refractive index of glass, that is, the refractive index nd (A) of the adhesive layer is described above. It is preferably in the range.

As described above, the refractive index of the glass is preferably a value that makes the difference from the refractive index of the adherend small, so that the refractive index of the glass itself differs depending on the refractive index of the adherend. For example, when used for adhering an optical member made of glass, the refractive index nd (A) with respect to the d-line of glass is preferably 1.50 or more, more preferably 1.52 or more, still more preferably 1.53 or more. More preferably .54 or higher. The upper limit is not particularly limited, but 1.70 or less is practical.

When adhering an adherend with glass, if the temperature at which the glass softens (softening point) is high, heat treatment at a high temperature is required. If the heat treatment temperature at that time is too high, the adherend may be deteriorated depending on the heat resistance of the adherend. Therefore, it is preferable that the softening point of the glass is low.

The softening point of glass does not always match the glass transition temperature Tg and the yield point Tc, but they have a correlation. Therefore, by lowering the glass transition temperature Tg and the yield point Tc of the glass, the softening point is lowered as a result, and deterioration of the adherend can be prevented. The softening point, glass transition temperature, and yield point of the glass in the present specification are the same as the softening point, glass transition temperature, and yield point of the adhesive layer in the optical element of the present embodiment.
The yield point Tc (A) of the glass is preferably 400 ° C. or lower, more preferably 380 ° C. or lower, and even more preferably 350 ° C. or lower. The lower limit is not particularly limited, but 250 ° C. or higher is practical.

When one of the adherends is an optical member, the yield point Tc (O) of the optical member is preferably higher than the yield point Tc (A) of the glass. Further, the absolute value ΔTc of the difference between the bending point Tc (A) of the glass and the bending point Tc (O) of the optical member is represented by ΔTc = | Tc (O) -Tc (A) |. The value of ΔTc is preferably 300 ° C. or higher, more preferably 320 ° C. or higher, and even more preferably 350 ° C. or higher. The upper limit is not particularly limited, but 500 ° C. or lower is practical.
When a single crystal such as sapphire is used as the optical member, the yield point of the optical member cannot be defined. In this case, the absolute value of the difference between the melting point Tm (O) of the optical member and the bending point Tc (A) of the glass is preferably 300 ° C. or higher, more preferably 350 ° C. or higher, still more preferably 400 ° C. or higher.

The glass transition temperature Tg (A) of the glass is preferably 380 ° C. or lower, more preferably 350 ° C. or lower, and even more preferably 320 ° C. or lower. The lower limit is not particularly limited, but 230 ° C. or higher is practical.

The thickness of the adhesive layer made of glass is preferably 0.01 mm or more, more preferably 0.05 mm or more, from the viewpoint of adhesiveness to the adherend. Further, the thickness of the adhesive layer is preferably 0.2 mm or less, more preferably 0.15 mm or less, and particularly preferably 0.1 mm or less from the viewpoint of suppressing the loss of light in the adhesive layer.

As the composition system of the glass constituting the adhesive layer as described above, phosphate glass, borate glass and the like can be preferably used.
The specific glass composition will be described below. The% indicating the content of each component is an oxide-based molar% display unless otherwise specified.

P ₂ O ₅ is an essential component (glass-forming oxide) that forms glass. The content of P ₂ O ₅ is preferably 30% or more, more preferably 35% or more. On the other hand, if it is excessively contained, the weather resistance may be deteriorated and the reliability of the adhesive layer may be deteriorated. Therefore, the content thereof is preferably 60% or less, more preferably 55% or less, still more preferably 50% or less. 45% or less is even more preferable.

ZnO is a component that can improve the meltability of glass and lower the glass transition temperature and softening temperature. The ZnO content is preferably 10% or more, more preferably 15% or more. On the other hand, if it is excessively contained, the glass becomes unstable and may be devitrified. Therefore, the ZnO content is preferably 60% or less, more preferably 50% or less, further preferably 45% or less, and 40% or less. Even more preferable.

Li ₂ O is a component that can improve the meltability of glass and lower the glass transition temperature and softening temperature. The content of Li ₂ O is preferably 1% or more, more preferably 3% or more, further preferably 5% or more, still more preferably 7% or more. On the other hand, if it is contained in an excessive amount, the glass may become unstable or devitrified. Therefore, _{the content of Li 2} O is preferably 30% or less, more preferably 28% or less.

The _{total content of P 2} O ₅ , Zn _{O and Li 2} O is preferably 65% or more, more preferably 70% or more. On the other hand, the upper limit of the total content is 100%, and the glass may be composed of only these three components without containing other components.

SiO ₂ is an _{optional component that can form a glass skeleton together with P 2} O ₅ to increase the stability of the glass, increase the devitrification resistance, and prevent the phase separation of the glass, and may not be contained (0%). ). On the other hand, if it is excessively contained, the glass transition point and the yield point may increase. Therefore, the content thereof is preferably 6% or less, more preferably 3% or less.

Al ₂ O ₃ is an optional component that can enhance weather resistance and may not be contained (0%). On the other hand, if it is contained in excess, the melting temperature of the glass may increase. Therefore, the content thereof is preferably 6% or less, more preferably 3% or less.

Na ₂ O is an optional component capable of lowering the melting temperature of the glass and lowering the glass transition temperature and the softening temperature, and may not be contained (0%). On the other hand, if it is contained in an excessive amount, the glass may become unstable. Therefore, the content thereof is preferably 20% or less, more preferably 15% or less.

K ₂ O is an optional component capable of lowering the melting temperature of the glass and lowering the glass transition temperature and the softening temperature, and may not be contained (0%). On the other hand, if it is contained in an excessive amount, the liquidus temperature may increase. Therefore, the content thereof is preferably 15% or less, more preferably 10% or less.

BaO is an optional component that can lower the melting temperature of the glass and improve the stability of the glass, and may not be contained (0%). On the other hand, if it is contained in an excessive amount, the glass may become unstable or the liquidus temperature may rise. Therefore, the content thereof is preferably 10% or less, more preferably 5% or less.

CaO is an optional component that can lower the melting temperature of the glass and improve the stability of the glass, and may not be contained (0%). On the other hand, if it is contained in an excessive amount, the liquidus temperature may rise, so the content thereof is preferably 10% or less, more preferably 5% or less.
In addition, MgO and SrO can be added in the range of 0 to 5% from the same viewpoint as CaO.

Ta ₂ O ₅ is an optional component that raises the refractive index of glass and may not be contained (0%). On the other hand, since it is a component that lowers the transmittance in the deep ultraviolet region, its content is preferably 3% or less, more preferably 1% or less.

SnO is an optional component that can improve the transmittance by using only an amount suitable as a reducing agent, and may not be contained (0%). On the other hand, since it is a component that absorbs light in the ultraviolet region, its content is preferably 3% or less, more preferably 1% or less.

La ₂ O ₃ is an optional component capable of maintaining a high ultraviolet transmittance while increasing the refractive index, and may not be contained (0%). On the other hand, since the liquidus temperature may rise or devitrify, the content thereof is preferably 5% or less, more preferably 3% or less.

Gd ₂ O ₃ is an optional component capable of maintaining a high ultraviolet transmittance while increasing the refractive index, and may not be contained (0%). On the other hand, since it is a component that lowers the transmittance in the near-ultraviolet region, its content is preferably 5% or less, more preferably 3% or less.

Y ₂ O ₃ is an optional component that can maintain a high ultraviolet transmittance while increasing the refractive index, and can lower the liquidus temperature and improve the devitrification resistance by coexisting with _{La 2} O _3. It does not have to be (0%). On the other hand, since the melting temperature, molding temperature, and liquid phase temperature may rise or devitrify, the content thereof is preferably 5% or less, more preferably 3% or less.

Nb ₂ O ₅ , TiO ₂ , CeO ₂ , V ₂ O ₅ , Bi ₂ O ₃ , WO ₃ and Fe ₂ O ₃ show absorption in the ultraviolet region, especially UV-C light, like the SnO. It is an ingredient. Therefore, although these are all optional components, their content is preferably small and may not be contained (0%).
Among them, Fe ₂ O ₃ is inevitably mixed as an impurity from the raw material, and in particular, trivalent iron (Fe ³⁺ ) shows strong absorption to light in the ultraviolet region, so its content is 0.01%. It is preferably less than, more preferably less than 0.005%. Since divalent iron (Fe ²⁺ ) has absorption in the infrared region, it is also effective to shift the valence of iron ions to divalent by setting the melting atmosphere to the reducing side. Examples of this method include adding a reducing agent to the raw material and making the molten atmosphere non-oxidizing.

The total content of Nb ₂ O ₅ , TiO ₂ , CeO ₂ , V ₂ O ₅ , Bi ₂ O ₃ and WO ₃ is preferably less than 0.1%, more preferably 0.05% or less.
In addition to the above, CuO, MnO ₂ , NiO, CoO and Cr ₂ O ₃ may also be contained, but it is preferable that these are not contained other than the unavoidable impurities mixed from the raw materials and the like, that is, they are not intentionally contained. ..
Further, F is an optional component that can improve the weather resistance of the glass and may not be contained (0%). On the other hand, since it is a component that lowers the refractive index of glass, its content is preferably 10% by mass or less, and more preferably 8% by mass or less.

The details of the inorganic glass constituting the adhesive layer in the optical element have been described above, but the inorganic glass can be used not only as the adhesive layer but also for adhering other members.

That is, the glass according to the present embodiment used for adhering the members has an average value of external transmittance of 30% or more at a wavelength of 260 to 285 nm at a thickness of 1 mm, and a yield point Tc (A) of 400 ° C. or less. is there.
A preferred embodiment of such glass is the same as the preferred embodiment of the inorganic glass described as the adhesive layer. Further, the member that is an adherend is not limited to the optical member, but the absolute value Δnd = | nd (O) of the difference between the refractive index nd (O) of the member and the refractive index nd (A) of the glass with respect to the d-line. The value represented by −nd (A) | is preferably 0.35 or less, more preferably 0.30 or less, and even more preferably 0.25 or less.

The member (adhesion) to be adhered using glass is not particularly limited, but it is preferably a member that requires light transmission. For example, the glass according to the present embodiment can be preferably used for bonding an optical member and an LED element, bonding glass fibers to each other, bonding lenses to each other, bonding prisms to each other, bonding optical filters to each other, and the like.

{Optical member}
The optical member has a light incident surface and a light emitting surface, and includes an optical functional surface in at least a part of at least one of the light incident surface and the light emitting surface.
The light incident surface is, for example, a surface on which light emitted from an LED element is incident, and the light emitting surface is a surface through which the incident light is transmitted through the optical member and emits light to irradiate the outside. It is the surface to be done.

Optical functional surfaces include those that refract, diffract, and scatter light by the surface, high-reflection surfaces such as mirrors, low-reflection surfaces with enhanced transparency, and various filters with wavelength selectivity. Therefore, the entire surface of the light incident surface or the light emitting surface of the optical member may have the function, or a part of the surface may have the function.

As the optical member, various conventionally known optical members can be used as long as the above functions can be exhibited. The shape is not particularly limited, and examples thereof include a lens, a lens array, a diffraction grating, a diffraction optical element, and a grating cell array. In addition, a metal or a dielectric film formed on the surface thereof in a single layer or in multiple layers can be mentioned.
In particular, the optical member preferably has a spherical or aspherical convex lens shape as shown in FIG.

When the optical member is bonded to a light emitting element (for example, an LED element), the light emitting surface of the light emitting element is made of a high refractive index material. Therefore, by making the optical member high refractive index glass, the light extraction efficiency Can be greatly improved. Therefore, the refractive index nd (O) of the optical member with respect to the d-line (587.6 nm) is preferably nd (O) ≧ 1.5. More preferably, nd (O) ≧ 1.6, further preferably nd (O) ≧ 1.65, and particularly preferably nd (O) ≧ 1.7.

The light emitted by the light emitting element passes through an optical member processed into a shape such as a lens and is emitted to the outside of the light emitting device. Therefore, by making the material forming the optical member highly transparent at the emission wavelength emitted by the light emitting element, it is possible to suppress the loss of light and further improve the light extraction efficiency. The distance through which light passes in the optical member is about 0.5 mm to 5 mm, and the absorption coefficient k (O) at the emission wavelength of the light emitting element of the optical member is k (O) ≤ 0.2 (mm ^-1 ). It is preferable, more preferably k (O) ≦ 0.15 (mm ^-1 ), and even more preferably k (O) ≦ 0.1 (mm ^-1 ).

It is preferable that the optical member has a high glass transition temperature Tg (O) so that the shape of the optical member is not deformed even when the optical member is heated in a production process such as a bonding process between the light emitting element and the optical member. Tg (O) ≧ 350 ° C. is preferable, Tg (O) ≧ 400 ° C. is more preferable, and Tg (O) ≧ 500 ° C. is particularly preferable.

The material constituting the optical member is not particularly limited, and is inorganic glass, quartz glass (Tg: 1060 ° C., Tc: 1210 ° C., nd: 1.46), crystalline sapphire (nd (normal light): 1.77, Melting point: 2053 ° C.), spinel, and resin can be used. Above all, an optical member made of inorganic glass is preferable because the difference in refractive index from the adhesive layer made of inorganic glass can be reduced.

Inorganic glass can be easily processed into various shapes, and is suitable from the viewpoint of reduction of manufacturing cost and mass production. Furthermore, compared to the case of resin, inorganic glass has no risk of deterioration even when exposed to high-power light emitted by LED elements or short-wavelength light such as ultraviolet rays for a long time, and has excellent heat resistance. Therefore, it is expected that the life of the optical element will be extended.

When inorganic glass is used as the optical member, examples of the inorganic glass include borosilicate glass, silicate glass, phosphoric acid glass, and fluorinated glass.

The borosilicate glass contains SiO ₂ and B ₂ O ₃ as main components, Al ₂ O ₃ , alkaline earth metal oxides (MgO, CaO, SrO, BaO), and alkali metal oxides (Li ₂ O, Na _{2). O,} K 2 _O), and other glass containing metal oxides.
The phosphoric acid glass contains P ₂ O ₅ as a main component, Al ₂ O ₃ , alkaline earth metal oxides (MgO, CaO, SrO, BaO), and alkali metal oxides (Li ₂ O, Na ₂ O, K). ₂ O), glass containing other metal oxides and the like can be mentioned.

The optical member can also have an antireflection film formed on its surface. As the antireflection film, for example, a monolayer film or a multilayer film of a dielectric such as _{SiO 2} , MgF ₂ , Al ₂ O ₃ , HfO ₂ , ZrO ₂ , Ta ₂ O _{5 is used.} By forming the antireflection film, Fresnel reflection on the surface of the optical member is reduced, so that the light extraction efficiency can be further improved.

[Optical device]
As shown in FIG. 2, the optical device 20 according to the present embodiment is provided on the substrate 4, the LED element 3 provided on the substrate 4, and the LED element 3, and emits light from the LED element 3. It has an optical member 1 made of inorganic glass that allows light to be transmitted and irradiated to the outside, and an adhesive layer 2 provided between the LED element 3 and the optical member 1. As the adhesive layer 2, the same glass as described in {Inorganic glass} in the above [optical element] can be used.

The light emitting device is prepared by forming the LED element 3 on the substrate 4 by a known method and separately molding the optical member 1. Next, the inorganic glass to be the adhesive layer 2 is produced. The inorganic glass is softened by heating it to a temperature equal to or higher than the softening point, and the softened inorganic glass is brought into contact with the adhesive surface of the optical member 1 or the LED element 3 to be adhered before being cured. Then, by cooling and curing, the optical member 1 and the LED element 3 are adhered by the adhesive layer 2, and the light emitting device 20 can be obtained.

In forming the adhesive layer 2 made of inorganic glass, the material of the adhesive layer 2 is prepared as a frit paste, applied to the adhesive surface by a known coating method such as screen printing, and then heated to decalcify and defoam. It can be carried out.
Further, the adhesive layer 2 can also be formed by preparing the material of the adhesive layer 2 as a green sheet, placing a small piece of the green sheet on the adhesive surface and heating it to decalcify and defoam.
Further, the adhesive layer can also be formed by preparing the material of the adhesive layer 2 as a plate material, forming a sheet by redraw molding, placing the sheet small pieces on the adhesive surface, heating and fusing them.
Further, the material of the adhesive layer 2 is prepared as a glass sheet by machining such as slicing or polishing, and small pieces cut to a size required for adhesion are heated while being in contact with the adhesive surface and fused. Can be formed.

The present invention will be specifically described with reference to Examples below, but the present invention is not limited thereto.

[Adhesive layer (inorganic glass): Test Examples 1-1 to 1-30]
Raw materials such as carbonates, nitrates, sulfates, hydroxides, oxides, boric acid, and phosphoric acid, which correspond to each other, so as to obtain glasses having the compositions shown in Tables 1 and 2 (indicated by mol% based on oxides). After weighing and thoroughly mixing, the mixture was placed in a platinum pit and heated in a temperature range of 1150 ° C. to 1200 ° C. for 1.5 hours to 3 hours to melt. The molten glass was poured into a preheated mold, cooled, formed into a plate, held at a temperature near the glass transition temperature for 4 hours, and then slowly cooled to room temperature at a cooling rate of −60 ° C./h.
In the table, Test Examples 1-1 to 1-27 are inorganic glasses according to Examples, and Test Examples 1-28 to 1-30 are inorganic glasses according to Comparative Examples. In addition, blanks in the table indicate that the component is not substantially contained. In addition, here, "substantially not contained" means that it is below the level of impurities contained in raw materials and the like, that is, it is not intentionally contained.

The physical characteristics of the obtained inorganic glass were measured by the following methods. The results are shown in Tables 3 and 4. In Table 4, "-" in Test Examples 1-28 and 2-28 was judged to be unsuitable for use as an adhesive layer because the inorganic glass obtained in Test Example 1-28 became cloudy. It means that each physical property is not measured. Further, "ND" in Test Examples 1-23 to 1-25 means that the measurement has not been performed.

(Refractive index: nd (A))
The refractive index nd (A) of the adhesive layer with respect to the d-line (wavelength 587.56 nm) was measured using a precision refractive index meter (manufactured by Shimadzu Corporation, model: KPR-200, KPR-2000).
As a sample, a rectangular parallelepiped shape having a side of 5 mm or more and a thickness of 5 mm or more was used, and the sample obtained by slowly cooling at a temperature lowering rate of −60 ° C./h was measured.

(Average coefficient of thermal expansion: α (50-350 ° C))
The average coefficient of thermal expansion at 50 to 350 ° C. was measured using a thermomechanical analyzer (manufactured by Rigaku Co., Ltd., trade name: TMA8310) under the condition of a heating rate of 10 ° C./min.
However, for Test Examples 1-17 to 1-20, 22, 25, 26, the average coefficient of thermal expansion at 50 to 300 ° C., and for Test Examples 1-21, 23, 24, 29, the average coefficient of thermal expansion at 50 to 250 ° C. The coefficient of expansion was measured respectively.

(Glass transition temperature: Tg, yield point: Tc)
From the thermal expansion curve obtained when measuring the average coefficient of thermal expansion, the bending point of expansion (the temperature corresponding to the viscosity of 12.3 dPa · s) is set to the glass transition temperature Tg (° C.), and the expansion apparently stops and contracts. The temperature at which the temperature changes to is determined as the yield point Tc (° C.).

(Transmittance)
For the transmittance, the external transmittance was measured using a spectrophotometer (manufactured by JASCO Corporation, model: V-570).
Before and after the ultraviolet irradiation test under the following conditions, the transmittance at a wavelength of 265 nm and the average transmittance at a wavelength of 260 to 285 nm were measured. The value of the average transmittance at a wavelength of 260 to 285 nm before the ultraviolet irradiation test is the average value of the external transmittance at a wavelength of 260 to 285 nm at a thickness of 1 mm.
Ultraviolet irradiation test: Both main surfaces of a glass plate obtained by molding the inorganic glass constituting the adhesive layer into a plate shape are mirror-optically polished to a thickness of 1 mm. One of the polished surfaces of the glass plate is placed so as to face a position 20 cm from a 400 W high-pressure mercury lamp (manufactured by Harrison Toshiba Lighting Co., Ltd., type: H400-P) that emits ultraviolet rays having a wavelength of 220 to 400 nm, and the high pressure is provided. Irradiate ultraviolet rays from a mercury lamp for 100 hours.
In Tables 3 and 4, "transmittance (265 nm)" means the transmittance at a wavelength of 265 nm before the ultraviolet irradiation test. The “transmittance after UV irradiation” means the transmittance at a wavelength of 265 nm after the ultraviolet irradiation test. The "average transmittance (260 to 285 nm)" means the average transmittance at a wavelength of 260 to 285 nm before the ultraviolet irradiation test. The "average transmittance after UV irradiation" means the average transmittance at a wavelength of 260 to 285 nm after the ultraviolet irradiation test.

[Optical element: Test Examples 2-1 to 2-30]
_{As an optical member, SiO 2} 5.8%, B ₂ O ₃ 66.6%, La ₂ O ₃ 19.3%, Y ₂ O ₃ 8.3% are displayed in mol% based on oxides. , Corresponding raw materials such as nitrates, sulfates, hydroxides, oxides, boric acid, etc. are weighed, mixed well, and then put into a platinum pit, and placed in a temperature range of 1150 ° C to 1350 ° C for 1.5 hours. It was heated for 3 hours and melted. The molten glass was poured into a preheated mold, cooled, formed into a plate, held at a temperature near the glass transition temperature for 4 hours, and then slowly cooled to room temperature at a cooling rate of −60 ° C./h.

The refractive index nd (O), the yield point Tc (O), and the glass transition point Tg (O) of the optical member obtained above with respect to the d-line were measured by the same method as that of the inorganic glass. The O) was 1.74, the yield point Tc (O) was 720 ° C, and the glass transition point Tg (O) was 685 ° C. Of these, the refractive index and yield point are the refractive index nd (A) and yield point Tc (A) of each inorganic glass obtained in Test Examples 1-1 to 1-30 (excluding Test Example 1-28). The difference between the above was taken, and Δnd and ΔTc were calculated. The results are shown in Tables 3 and 4.

As an optical member, a glass melt having the composition shown above was dropped from a pipe attached to a glass melting furnace and cooled and solidified to obtain a coarse sphere-shaped glass coarse ball. Next, the surface of the rough glass ball was polished to prepare a glass polishing ball. In addition, a glass block can be made by machining with a blade or the like from a glass plate obtained by molding and solidifying it into a plate shape, and by reheating and deforming it, and polishing the surface with a ball polishing machine is also possible. Can be obtained. A hemispherical lens (optical member) was produced by processing the obtained glass polishing ball into a hemispherical shape by slicing or polishing.
Each glass to be the adhesive layer obtained in Test Examples 1-1 to 1-30 is thinly polished on the optical member, and on a hemispherical lens, the temperature is 20 ° C. to 100 ° C. higher than the yield point Tc for 5 minutes to 15 minutes. Each optical element was obtained by heating for a minute and adhering. The formation of the adhesive layer is not limited to the above method, and a frit paste-like material may be applied or a green sheet-like material may be formed on a hemispherical lens and produced by the same heat treatment. Test Examples 2-1 to 2-27 are Examples, and Test Examples 2-28 to 2-30 are Comparative Examples.

[Adhesive layer (inorganic glass): Test Examples 3-1 to 3-8]
The raw materials shown in Table 5 were weighed, mixed sufficiently, and then put into a platinum crucible and heated and melted in a temperature range of 1150 ° C. to 1200 ° C. for 1.5 hours to 3 hours. The molten glass was poured into a preheated mold, cooled, formed into a plate, held at a temperature near the glass transition temperature for 4 hours, and then slowly cooled to room temperature at a cooling rate of −60 ° C./h.
In the table, the content of raw materials is basically expressed in mol% based on oxides, but only alkali metals are expressed in mol% based on fluoride. Test Examples 3-1 to 3-8 are the inorganic glasses according to the examples. In addition, blanks in the table indicate that the component is not substantially contained. Further, F (fluorine) in the table is the content of F (indicated by mass%) in the inorganic glass analyzed by fluorescent X-ray analysis.

The physical characteristics of the obtained inorganic glass were measured by the method described above. However, the average coefficient of thermal expansion α was measured in the temperature range shown in Table 6. The results are shown in Table 6. In addition, "ND" in Test Examples 3-1 to 3-8 means that the measurement has not been performed.

[Optical element: Test Examples 4-1 to 4-8]
As the optical member, the same optical member as that used in Test Examples 2-1 to 2-30 was prepared. The difference between the optical member and the refractive index nd (A) and the yield point Tc (A) of each of the inorganic glasses obtained in Test Examples 3-1 to 3-8 was taken to calculate Δnd and ΔTc, respectively. The results are shown in Table 6.

From the results in Tables 1 to 6, inorganic glass having excellent transparency to short wavelength ultraviolet rays (UV-C) having a wavelength of 260 to 285 nm and UV-C resistance was obtained. Since such inorganic glass has a lower yield point Tc than conventional glass, it can be suitably used for bonding members. In addition, since the difference in refractive index between the optical member, which is an adherend, is small, reflection or absorption occurs when the LED element is used for bonding an optical member such as a lens, glass fibers, or lenses. It was suggested that the loss of light due to this is small, and it is possible to prevent a decrease in light extraction efficiency and transmittance.

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 invention. This application is based on a Japanese patent application filed on August 30, 2019 (Japanese Patent Application No. 2019-158703), the contents of which are incorporated herein by reference.

1 Optical member 2 Adhesive layer 3 LED element 4 Substrate 10 Optical element 20 Light emitting device

Claims (15)

1. An optical element having an optical member and an adhesive layer.
   The optical member has a light incident surface and a light emitting surface, and has an optical functional surface on at least one of the light incident surface and the light emitting surface.
   The adhesive layer is provided on at least one surface of the light incident surface and the light emitting surface of the optical member.
   The adhesive layer is an optical element made of inorganic glass and having an average value of external transmittance of 30% or more at a wavelength of 260 to 285 nm at a thickness of 1 mm.
2. The absolute value Δnd of the difference between the refractive index nd (O) of the optical member and the refractive index nd (A) of the adhesive layer with respect to the d-line (wavelength 587.6 nm) is Δnd = | nd (O) -nd ( A) The optical element according to claim 1, wherein | ≤ 0.35.
3. The absolute value ΔTc of the difference between the yield point Tc (O) of the optical member and the yield point Tc (A) of the adhesive layer is ΔTc = | Tc (O) −Tc (A) | ≧ 300 (° C.). , The optical element according to claim 1 or 2.
4. The optical element according to any one of claims 1 to 3, wherein the yield point Tc (A) of the adhesive layer is Tc (A) ≤400 (° C.).
5. The inorganic glass constituting the adhesive layer has a difference in average transmittance of 10% or less at a wavelength of 260 to 285 nm before and after an ultraviolet irradiation test under the following conditions, according to any one of claims 1 to 4. Optical element.
   Ultraviolet irradiation test: Both main surfaces of the glass plate obtained by molding the inorganic glass into a plate shape are mirror-optically polished to a thickness of 1 mm. One of the polished surfaces of the glass plate is arranged so as to face a position 20 cm from a 400 W high-pressure mercury lamp that emits ultraviolet rays having a wavelength of 220 to 400 nm, and the high-pressure mercury lamp is irradiated with ultraviolet rays for 100 hours.
6. The optical element according to any one of claims 1 to 5, wherein the thickness of the adhesive layer is 0.01 to 0.2 mm.
7. The optical element according to any one of claims 1 to 6, wherein the optical member is a lens, a lens array, a diffraction grating, a diffraction optical element, or a grating cell array.
8. Glass used for bonding members
   The average value of the external transmittance at a wavelength of 260 to 285 nm at a thickness of 1 mm is 30% or more.
   A glass having a yield point Tc (A) of Tc (A) ≤ 400 (° C.).
9. The absolute value Δnd of the difference between the refractive index nd (O) of the member to be bonded and the refractive index nd (A) of the glass with respect to the d-line (wavelength 587.6 nm) is Δnd = | nd (O) -nd ( A) The glass according to claim 8, wherein | ≤ 0.35.
10. The glass according to claim 8 or 9, wherein the refractive index nd (A) is nd (A) ≥ 1.50.
11. The content in molar% of the oxide standard is
    The total of P ₂ O ₅ , ZnO and Li ₂ O is 65% or more, and the total of Nb ₂ O ₅ , TiO ₂ , CeO ₂ , V ₂ O ₅ , Bi ₂ O ₃ and WO ₃ is less than 0.1%. The glass according to any one of claims 8 to 10.
12. The content in molar% of the oxide standard is
    Fe ₂ O ₃ less than 0.01%,
    The glass according to any one of claims 8 to 11.
13. The glass according to any one of claims 8 to 12, which has a transmittance of 30% or more at a wavelength of 265 nm after an ultraviolet irradiation test under the following conditions.
    Ultraviolet irradiation test: Both main surfaces of a glass plate obtained by molding glass into a plate shape are mirror-optically polished to a thickness of 1 mm. One of the polished surfaces of the glass plate is arranged so as to face a position 20 cm from a 400 W high-pressure mercury lamp that emits ultraviolet rays having a wavelength of 220 to 400 nm, and the high-pressure mercury lamp is irradiated with ultraviolet rays for 100 hours.
14. The content in molar% of the oxide standard is
    P ₂ O ₅ 30-60%,
    ZnO 10-60%,
    Li ₂ O 1-30%,
    SiO ₂ 0 ~ 6%,
    _{Al 2 O 3 0 ~ 6%} ,
    Na ₂ O 0 to 20%,
    K ₂ O 0 to 15%,
    BaO 0-10%,
    CaO 0-10%,
    _{Ta 2 O 5 0 ~ 3%} ,
    SnO 0-3%,
    _{La 2 O 3 0 ~ 5%} ,
    Gd ₂ O ₃₀ to 5% and Y ₂ O ₃₀ to 5%,
    The glass according to any one of claims 8 to 13.
15. With the board
    The LED element provided on the substrate and
    An optical member provided on the LED element and made of inorganic glass that allows light emitted from the LED element to be transmitted and irradiated to the outside.
    An adhesive layer provided between the LED element and the optical member,
    Have,
    A light emitting device in which the adhesive layer is made of the glass according to any one of claims 8 to 14.

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