Optical fiber array, optical waveguide module, method for reducing refractive index of adhesive layer, and method for manufacturing optical fiber array

Abstract

Provided is an optical fiber array (1) comprising an adhesive layer (20) having a low refractive index and excellent transparency. An optical fiber array is provided with an optical fiber (10) and an adhesive layer (20), the optical fiber (10) is optically coupled to an optical waveguide element (30) through the adhesive layer (20), and the adhesive layer (20) has an Si element content of 10% or more in terms of content. The adhesive layer (20) preferably has a transmittance of 90% or more at a wavelength of 1310 nm. The refractive index of the adhesive layer (20) at a wavelength of 1310 nm is preferably 1.47 or less. Furthermore, the adhesive layer (20) is preferably a cured product containing (A) a siloxane compound having a reactive functional group and (B) a polymerization initiator.

Description

Technical Field

[0001] This invention relates to an optical fiber array, an optical waveguide module, a method for reducing the refractive index of an adhesive layer, and a method for manufacturing an optical fiber array. Background Technology

[0002] In recent years, the challenge has been the rapid increase in communication speeds and the need to cope with the surge in communication volume. One solution to this problem is silicon photonics, which combines optical communication technology with existing electrical communication technologies.

[0003] Silicon photonics is a technology that integrates optical waveguides, optical switches, optical modulators, optical receivers and other components on a silicon substrate. It is a technology that integrates optical devices and electronic circuits into optical integrated circuits to realize small, high-function optical devices.

[0004] Optical adhesives have long been required to possess optical properties such as low refractive index or high transparency. Common methods for reducing the refractive index include lowering the glass transition temperature of the resin composition or reducing the crosslinking density of the polymer. Additionally, methods using fluorine compounds are also known as methods for reducing the refractive index. However, fluorine compounds exhibit a very stable structure, making them difficult to decompose in the environment, raising concerns about environmental impact and gradually restricting their use.

[0005] For example, Patent Document 1 describes a low-refractive-index adhesive containing an acrylic matrix resin and porous hollow resin particles. In the technology of Patent Document 1, the focus is on the porous hollow resin particles from the viewpoints of adhesion and transparency.

[0006] Furthermore, Patent Document 2 describes the use of compounds containing aromatic rings and reactive silicon-containing groups in adhesive compositions for optical communication that exhibit excellent adhesion, moisture resistance, and low refractive index. However, if a large amount of resin material containing aromatic rings is used, the refractive index becomes high, thus only a refractive index exceeding 1.46, which is typically used as a raw material for optical fibers, can be obtained.

[0007] [Existing Technical Documents]

[0008] [Patent Literature]

[0009] Patent Document 1: Japanese Patent Application Publication No. 2011-037978

[0010] Patent Document 2: Japanese Patent Application Publication No. 2017-061599 Summary of the Invention

[0011] [The problem the invention aims to solve]

[0012] Under these circumstances, a fiber optic array using an adhesive with excellent optical properties is sought.

[0013] For example, the goal is to develop an optical fiber array that includes an adhesive layer with low refractive index and excellent transparency.

[0014] The present invention was made in view of the aforementioned issues, and its object is to provide an optical fiber array comprising an adhesive layer with low refractive index and excellent transparency, an optical waveguide module comprising the optical fiber array, a method for reducing the refractive index of the adhesive layer, and a method for manufacturing the optical fiber array.

[0015] [Technical means to solve the problem]

[0016] This invention relates to the following fiber arrays, optical waveguide modules, methods for reducing the refractive index of adhesive layers, and methods for manufacturing fiber arrays.

[0017] [1] An optical fiber array, comprising: Fiber optics, and Adhesive layer, The optical fiber is coupled to the optical waveguide element through the adhesive layer. The Si content of the adhesive layer is more than 10%.

[0018] [2] According to the fiber array described in [1], wherein the fiber array has: A substrate having grooves formed to accommodate the optical fibers; and The pressure plate is then fixed to the surface of the optical fiber. The optical fiber is bonded and fixed in the groove through the adhesive layer. The adhesive layer bonds the optical fiber to the optical waveguide element and bonds the substrate in which the optical fiber is housed in the groove to the pressure plate.

[0019] [3] According to the fiber array described in [2], wherein the substrate is a semiconductor substrate.

[0020] [4] According to the fiber array described in [3], one side of the semiconductor substrate has a ball grid array electrode.

[0021] [5] The fiber array according to any one of [1] to [4], wherein the adhesive layer has a transmittance of 90% or more at a wavelength of 1310 nm.

[0022] [6] The fiber array according to any one of [1] to [5], wherein the adhesive layer has a refractive index of 1.49 or less at a wavelength of 1310 nm.

[0023] [7] The fiber array according to any one of [1] to [6], wherein the adhesive layer comprises (A) a siloxane compound having reactive functional groups and (B) a curing agent of a polymerization initiator.

[0024] [8] According to the fiber array described in [7], wherein the (A) siloxane compound having a reactive functional group comprises (A1) a cyclic siloxane compound having a reactive functional group and (A2) a linear siloxane compound having a reactive functional group.

[0025] [9] The fiber array according to any one of [1] to [8], wherein the adhesive layer further comprises (C) an inorganic filler.

[0026]

[10] According to the fiber array described in [9], when the total amount of the components contained in the adhesive layer is set to 100 parts by weight, the content of the inorganic filler (C) is 0.1 parts by weight to 80 parts by weight.

[0027]

[11] According to the fiber array described in [9] or

[10] , wherein the average particle size of the inorganic filler (C) is 0.1 μm to 5.0 μm.

[0028]

[12] The fiber array according to any one of [1] to

[11] , wherein the adhesive layer comprises a cured material of (A) a siloxane compound having reactive functional groups, (B) a polymerization initiator and (C) an inorganic filler. The Si content in the adhesive layer derived from the siloxane compound with reactive functional groups of (A) is 5% or more.

[0029]

[13] An optical waveguide module comprising an optical fiber array as described in any one of [1] to

[12] .

[0030]

[14] A method for reducing the refractive index of an adhesive layer, wherein in an optical fiber array in which an optical fiber is optically coupled to an optical waveguide element through an adhesive layer, the Si content of the adhesive layer is set to 10% or more.

[0031]

[15] A method for manufacturing an optical fiber array, comprising manufacturing an optical fiber array in which optical fibers are optically coupled to optical waveguide elements through an adhesive layer, wherein in the method, The Si element content of the adhesive layer is set to be 10% or more.

[0032]

[16] According to the fiber array manufacturing method described in

[15] , the process of fixing the fiber in a groove formed in the optical waveguide element and the process of optically coupling the fiber to the optical waveguide element are performed simultaneously.

[0033] [The effects of the invention]

[0034] The present invention provides an optical fiber array comprising an adhesive layer with low refractive index and excellent transparency, an optical waveguide module comprising the optical fiber array, a method for reducing the refractive index of the adhesive layer, and a method for manufacturing the optical fiber array. Attached Figure Description

[0035] [ Figure 1 [This is an exploded 3D view of the optical waveguide module.]

[0036] [ Figure 2 [This is an enlarged view of the area near the connection.]

[0037] [ Figure 3 [ ] is a side view showing the state of the optical fiber fixed to the optical waveguide element.

[0038] [ Figure 4 ]yes Figure 3 AA cross-section view. Detailed Implementation

[0039] Hereinafter, embodiments of the present invention (hereinafter referred to as this embodiment) will be described.

[0040] This embodiment relates to an optical fiber array, an optical waveguide module, a method for reducing the refractive index of an adhesive layer, and a method for manufacturing an optical fiber array.

[0041] Furthermore, this invention is not limited to this embodiment. Additionally, the accompanying drawings are schematic diagrams, and this disclosure can be implemented with various modifications and alterations based on the knowledge of those skilled in the art. Furthermore, in this specification and the accompanying drawings, structural elements with the same symbol represent identical structural elements.

[0042] [definition]

[0043] In this application specification, ○ to △ (e.g., ○ parts by mass to △ parts by mass) means more than ○ and less than △ (more than ○ parts by mass and less than △ parts by mass).

[0044] In addition, in this application specification, the terms "comprising" or "containing" mean that the defined structural element is included, but do not exclude the existence of other structural elements.

[0045] [Fiber optic array]

[0046] like Figures 1-4As shown, the fiber array 1 of this embodiment includes an optical fiber 10 and an adhesive layer 20. Furthermore, the optical fiber 10 is covered by a cladding layer 11 and is shown in a configuration with an optical fiber 12. In the fiber array 1, the optical fiber 10 is optically coupled to the optical waveguide 32 of the optical waveguide element 30 via the adhesive layer 20.

[0047] like Figures 1-4 As shown, the fiber array 1 of this embodiment has a substrate 31 with a groove, namely a V-groove 33, formed to accommodate the optical fiber 10, and a pressure plate 40 that is then fixed to the surface of the optical fiber 10. The optical fiber 10 is then fixed in the V-groove 33 by an adhesive layer 20. Figure 3 , Figure 4 Furthermore, the adhesive layer 20 connects the optical fiber 10 to the optical waveguide element 30. Figure 3 And the substrate 31, in which the optical fiber 10 is housed in the V-groove 33, is connected to the pressure plate 40. Figure 4 ).

[0048] In addition, the substrate 31 may be made of glass, semiconductor, organic resin, etc., and preferably a semiconductor substrate.

[0049] Additionally, a ball grid array electrode (not shown) can be provided on one side of the substrate. By providing a ball grid array electrode on one side of the substrate, multiple electrical interfaces can be realized at high density, thus enabling miniaturization of silicon photonic devices. Furthermore, the ball grid array electrode is envisioned to be packaged and fixed to another substrate, etc., through a reflow process. Therefore, the adhesive layer in the fiber array of this embodiment is required to have heat resistance so as to withstand the temperature or time required for reflow heating.

[0050] In the fiber array 1 of this embodiment, the Si element content of the adhesive layer 20 is more than 10%, and the adhesive layer 20 has a low refractive index and excellent transparency.

[0051] Here, the Si element conversion content of adhesive layer 20 is the sum of the Si element conversion contents of each component contained in the adhesive composition forming adhesive layer 20.

[0052] The Si content of each component in the adhesive composition is calculated as the atomic weight / molecular weight of Si × the number of Si atoms in one molecule × 100 (%).

[0053] The adhesive layer 20 can be formed, for example, using the adhesive composition of this embodiment described later. There are no particular limitations on the adhesive composition of this embodiment that forms the adhesive layer 20 if the Si elemental content is 10% or more.

[0054] From the viewpoint of having a low refractive index and high transparency, the Si content of the adhesive layer 20 is 10% or more, preferably 12% or more, more preferably 15% or more, and even more preferably 20% or more, particularly preferably 30% or more or 35% or more.

[0055] The Si content of the adhesive layer 20 is preferably 10% to 50%, more preferably 15% to 45%, even more preferably 20% to 45%, and particularly preferably 30% to 40%.

[0056] [Optical Waveguide Module]

[0057] Alternatively, the fiber array 1 of this embodiment can be used to construct the optical waveguide module 50 (optical waveguide device). Figure 1 ).

[0058] The optical waveguide module 50 of this embodiment includes the optical fiber array 1.

[0059] Specifically, the optical waveguide module 50 of this embodiment includes an optical fiber array 1, an adhesive layer 20, and an optical waveguide element 30. The optical fiber array 1 is optically coupled to the optical waveguide 32 of the optical waveguide element 30 through the adhesive layer 20.

[0060] Furthermore, there are no particular limitations on the optical waveguide element 30 in the fiber array 1 and optical waveguide module 50 of this embodiment, if it is an element used in an optical integrated circuit.

[0061] The optical waveguide module 50 of this embodiment can be incorporated in the form of a silicon photonics device.

[0062] [Adhesive Composition]

[0063] The adhesive composition of the adhesive layer 20 included in the optical fiber array 1 forming this embodiment may include (A) a siloxane compound having reactive functional groups and (B) a polymerization initiator.

[0064] Specifically, the adhesive layer 20 may be formed from a cured adhesive composition comprising (A) a siloxane compound having reactive functional groups and (B) a polymerization initiator.

[0065] In the case described, from the viewpoint of having a low refractive index and high transparency, the Si element conversion content of the adhesive layer 20 derived from (A) a siloxane compound having a reactive functional group is preferably 5% or more.

[0066] Here, the Si element equivalent content of the siloxane compound with reactive functional group (A) in the adhesive layer 20 is the sum of the Si element equivalent content of the siloxane compound with reactive functional group (A) contained in the adhesive composition forming the adhesive layer 20.

[0067] The Si content of the adhesive layer 20 derived from (A) a siloxane compound having reactive functional groups is 5% or more, preferably 7% or more, more preferably 8% or more, and even more preferably 9% or more, particularly preferably 10% or more.

[0068] The Si content of the adhesive layer 20 derived from (A) a siloxane compound having reactive functional groups is preferably 5% to 40%, more preferably 7% to 30%, and even more preferably 8% to 20%, particularly preferably 9% to 20%.

[0069] (A) Siloxane compounds with reactive functional groups

[0070] The adhesive composition of this embodiment does not particularly limit the (A) siloxane compound having a reactive functional group, but preferably includes a cyclic siloxane compound having a reactive functional group (A1) or a linear siloxane compound having a reactive functional group (A2).

[0071] Hereinafter, siloxane compounds with reactive functional groups (A) will sometimes be referred to simply as "(A) siloxane compounds" or "(A) components".

[0072] (A1) Cyclic siloxane compounds with reactive functional groups

[0073] The adhesive composition of this embodiment may contain (A1) a cyclic siloxane compound having a reactive functional group (hereinafter also referred to as "(A1) component" or "(A1) cyclic siloxane compound") as (A) a siloxane compound having a reactive functional group.

[0074] (A1) If the component is a cyclic siloxane compound having more than one reactive functional group in one molecule, there is no particular limitation.

[0075] As a component (A1), it can be used alone or in combination with two or more.

[0076] The term "reactive functional group" refers to a functional group that can react with the functional groups of the compounds contained in the adhesive composition of this embodiment.

[0077] There are no particular limitations on reactive functional groups, but examples include: epoxy group, oxetyl group, glycidyl group, alkoxysilyl group, and vinyl ether group.

[0078] (A1) If the number of reactive functional groups in each molecule of the component is 1 or more, there is no particular limitation. From the viewpoint of optical properties or heat resistance, ease of obtaining raw materials or reactivity, it can be 2 or more, preferably 2 to 10, more preferably 2 to 6, and even more preferably 2 to 4, and particularly preferably 2 or 4.

[0079] Cyclic siloxane compounds are compounds that have a cyclic siloxane skeleton based on siloxane bonds (-Si-O-Si-).

[0080] The number of Si-O units forming the cyclic siloxane framework (equal to the number of silicon atoms forming the siloxane ring) is not particularly limited, but from the viewpoints of optical properties or heat resistance, ease of obtaining raw materials or reactivity, it is preferably 2 to 15, more preferably 3 to 10, and even more preferably 3 to 8, and particularly preferably 3 to 6.

[0081] (A1) The preferred component has a cationic polymerizable group as a reactive functional group that bonds to the cyclic siloxane backbone. A cationic polymerizable group refers to a functional group that undergoes chain polymerization in the presence of a cation.

[0082] The (A1) component has cationic polymerizable groups that are bonded to the cyclic siloxane backbone, which can reduce hardening shrinkage while maintaining heat resistance.

[0083] Examples of cationic polymerizable groups include: epoxy group, glycidyl group, oxetyl group, and vinyl ether group.

[0084] Furthermore, although there are no particular limitations, from the viewpoint of reducing the refractive index, the cationic polymerizable group is preferably a functional group that does not have an aromatic ring.

[0085] From the viewpoint of optical properties or heat resistance, ease of obtaining raw materials or storage stability of the composition, the cationic polymerizable group of component (A1) is preferably epoxy group.

[0086] The epoxy group is a group having an oxetine structure and is a substituent having a 3-membered ring (oxetine ring) containing two carbon atoms and one oxygen atom.

[0087] When the cationic polymerizable group is an epoxy group, the epoxy group can be either alicyclic or non-alicyclic.

[0088] From the viewpoint of achieving excellent transparency, the epoxy group is preferably an alicyclic epoxy group.

[0089] Alicyclic epoxy groups have an oxidized cycloalkene (cycloalkene oxide) structure as the alicyclic skeleton.

[0090] Oxidized cyclic olefins have an aliphatic ring and an epoxy group consisting of two adjacent carbon atoms and an oxygen atom constituting the aliphatic ring. Oxidized cyclic olefin structures can be obtained, for example, by epoxidizing cyclic olefins with oxidizing agents such as peroxides.

[0091] The alicyclic skeleton of the alicyclic epoxy group is not particularly limited, and examples include cyclopropane skeleton, cyclobutane skeleton, cyclopentane skeleton, cyclohexane skeleton, cycloheptane skeleton, cyclooctane skeleton, etc., with cyclohexane skeleton being preferred.

[0092] The non-alicyclic epoxy group is an epoxy group other than the alicyclic epoxy group. Examples of groups containing a non-alicyclic epoxy group include glycidyl group and glycidyloxypropyl group (preferably 3-glycidyloxypropyl group).

[0093] In component (A1), the epoxy group can be directly bonded to the cyclic siloxane skeleton, or it can be bonded to the cyclic siloxane skeleton via a linker group.

[0094] The linking group can be any divalent group, for example: alkylene groups (-(CH2)). n - (n is an integer greater than or equal to 0), ether bonds (-O-), and combinations thereof.

[0095] Furthermore, the epoxy groups are close to the cyclic siloxane backbone, which tends to produce a dense cured product when the adhesive composition is cured, resulting in excellent heat resistance (reflow resistance).

[0096] Therefore, when the epoxy group is bonded to the cyclic siloxane skeleton via a linker, the number of atoms present between the epoxy group and the cyclic siloxane skeleton is preferably 4 or less, more preferably 2 or less.

[0097] The weight average molecular weight of component (A1) is preferably 200 to 3,000, more preferably 300 to 2,000, and particularly preferably 400 to 1,000.

[0098] If the weight average molecular weight of component (A1) is within the range described, the viscosity of the adhesive composition becomes appropriate, and the balance between the optical properties or heat resistance of the cured product becomes good.

[0099] Furthermore, the weight-average molecular weight in this specification refers to the value calculated by gel permeation chromatography (GPC) using a calibration curve based on standard polystyrene.

[0100] The functional group equivalent (g / mol) of component (A1) is not particularly limited, but from the viewpoint of reactivity, it is preferably 50 to 1,000, more preferably 100 to 500, and particularly preferably 150 to 400.

[0101] Furthermore, the epoxy equivalent in this specification refers to the value measured according to Japanese Industrial Standards (JIS) K7236.

[0102] (A1) The content of component (A1) in the adhesive composition is not particularly limited. From the viewpoint of improving reflow resistance, when the total amount of the adhesive composition is set to 100 parts by mass, it is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, more preferably 2.0 parts by mass or more, and particularly preferably 5 parts by mass or more.

[0103] Furthermore, from the viewpoint of having a low refractive index and high transparency, when the total amount of the adhesive composition is set to 100 parts by mass, the content of component (A1) in the adhesive composition is preferably 95 parts by mass or less, more preferably 50 parts by mass or less, and even more preferably 30 parts by mass or less, and particularly preferably 15 parts by mass or less.

[0104] (A1) The preferred component is a liquid at 25°C, but it can also be a solid at room temperature.

[0105] From the viewpoint of the preparation of the adhesive composition and its dispensing properties, the viscosity of component (A1) at 25°C is preferably 10 mPa·s to 10,000 mPa·s, more preferably 20 mPa·s to 8,000 mPa·s, and particularly preferably 50 mPa·s to 5,000 mPa·s.

[0106] Furthermore, unless otherwise specified, the viscosity in this instruction manual is expressed using values ​​measured in accordance with Japanese Industrial Standard JIS K6833. Specifically, it can be determined by using a Type E viscometer at a rotation speed of 10 rpm.

[0107] As a component (A1), for example, a compound represented by the following general formula (1) can be used.

[0108] [Chemistry 1]

[0109] (where R) 1 Or R 2 The R group represents a glycidyl group, an epoxy group, or a hydrocarbon group with 1 to 6 carbon atoms, and n represents an integer from 3 to 10; multiple R groups may exist in the formula. 1 R 2 They can be the same or different; among them, there are multiple R. 1 Or R 2 (Among them, at least two are glycidyl groups or organic groups containing cyclohexyl epoxide)

[0110] Examples of compounds containing epoxy groups as component (A1) include: 2,4-bis[2-(3-{oxabicyclo[4.1.0]heptyl})ethyl]-2,4,6,6,8,8-hexamethyl-cyclotetrasiloxane, 4,8-bis[2-(3-{oxabicyclo[4.1.0]heptyl})ethyl]-2,2,4,6,6,8-hexamethyl-cyclotetrasiloxane, 2,4-bis[2-(3-{oxabicyclo[4.1.0]heptyl})ethyl]-6,8-dipropyl-2,4,6,8-tetramethyl-cyclotetrasiloxane, 4,8-bis[2-(3- [2,4,6,8-tetramethyl-cyclotetrasiloxane, 2,4,8-tris[2-(3-{oxabicyclo[4.1.0]heptyl})ethyl]-2,4,6,6,8-pentamethyl-cyclotetrasiloxane, 2,4,8-tris[2-(3-{oxabicyclo[4.1.0]heptyl})ethyl]-6-propyl-2,4,6,8-tetramethyl-cyclotetrasiloxane, 2,4,6,8-tetra[2-(3-{oxabicyclo[4.1.0]heptyl})ethyl]-2,4,6,8-tetramethyl-cyclotetrasiloxane.

[0111] There are no particular limitations on commercially available products when the (A1) component is a cyclic siloxane compound with an epoxy group. Examples include: KR-470 (functionality 4) or X-40-2670 (functionality 4) and X-40-2678 (functionality 2) (all manufactured by Shin-Etsu Chemical Co., Ltd.) as cyclic siloxane compounds with an alicyclic epoxy group; or X-40-2701 (functionality 4) (manufactured by Shin-Etsu Chemical Co., Ltd.), X-40-2728 (functionality 2) (manufactured by Shin-Etsu Chemical Co., Ltd.), and EP-3400L (functionality 4) (manufactured by ADEKA Co., Ltd.) as cyclic siloxane compounds with a non-alicyclic epoxy group, i.e., a glycidyl group.

[0112] (A1) The preferred components are these epoxy-modified cyclic siloxane compounds having two or four epoxy groups.

[0113] In addition, any one of these components (A1) may be used, or two or more may be used together.

[0114] (A1) The epoxy equivalent (g / mol) of the cyclic siloxane compound is not particularly limited, but from the viewpoint of reactivity, it is preferably 50 to 1000, more preferably 100 to 500, and even more preferably 150 to 400. Furthermore, in this specification, the epoxy equivalent can be determined according to JIS K7236.

[0115] (A1) The weight-average molecular weight of the cyclic siloxane compound is not particularly limited, but is preferably 200 to 3000, more preferably 300 to 2000, and even more preferably 400 to 1000. When the weight-average molecular weight of the (A1) cyclic siloxane compound is within the range described, the viscosity of the composition becomes suitable, and the workability is improved. Furthermore, in this specification, the weight-average molecular weight can be calculated by gel permeation chromatography (GPC) using a calibration curve based on standard polystyrene.

[0116] (A1) The cyclic siloxane compound is preferably a liquid at room temperature (25°C), but it can also be a solid. From an operational point of view, the viscosity of the (A1) cyclic siloxane compound at 25°C is preferably 10 mPa·s to 30000 mPa·s. Furthermore, in this specification, the viscosity can be measured according to Japanese Industrial Standard JIS K6833. Specifically, the viscosity can be determined by using an E-type viscometer at a rotation speed of 10 rpm. There are no particular limitations on the machine, rotor, or measurement range used in the measurement.

[0117] (A2) Straight-chain siloxane compounds with reactive functional groups

[0118] The adhesive composition of this embodiment may contain (A2) a linear siloxane compound having a reactive functional group (hereinafter also referred to as "(A2) component" or "(A2) linear siloxane compound") as (A) a siloxane compound having a reactive functional group.

[0119] (A2) If the component is a linear siloxane compound having more than one reactive functional group in one molecule, there is no particular limitation.

[0120] As a component (A2), it can be used alone or in combination with two or more.

[0121] The reactive functional groups of component (A2) are the same as those of component (A1) and are not particularly limited. Examples include epoxy, glycidyl, oxetyl, alkoxysilyl, vinyl ether, and alkoxy groups.

[0122] Furthermore, the reactive functional group of component (A2) is preferably a cationic polymerizable group. A cationic polymerizable group is a functional group that undergoes chain polymerization in the presence of a cation.

[0123] The (A2) component has cationic polymerizable groups that are bonded to the linear siloxane backbone, which can reduce hardening shrinkage while maintaining low refractive index.

[0124] Examples of cationic polymerizable groups include: epoxy group, glycidyl group, oxetyl group, and vinyl ether group.

[0125] Furthermore, although there are no particular limitations, from the viewpoint of reducing the refractive index, the cationic polymerizable group is preferably a functional group that does not have an aromatic ring.

[0126] (A2) The number of reactive functional groups in each molecule of the component is not particularly limited if it is 1 or more. From the viewpoint of optical properties or heat resistance, ease of obtaining raw materials or reactivity, it can be 2 or more, preferably 2 to 10, more preferably 2 to 6, and even more preferably 2 to 4, and particularly preferably 2.

[0127] Straight-chain siloxane compounds refer to compounds that have a straight-chain siloxane skeleton based on siloxane bonds (-Si-O-Si-).

[0128] The number of Si-O units forming a linear siloxane framework (equal to the number of silicon atoms forming the siloxane chain) is not particularly limited, but is preferably 2 to 50 from the viewpoints of optical properties or heat resistance, ease of obtaining raw materials or reactivity, more preferably 3 to 40, even more preferably 5 to 30, and particularly preferably 10 to 20.

[0129] From the viewpoint of optical properties, heat resistance, and adhesion, the cationic polymerizable group of component (A2) is preferably an epoxy group.

[0130] (A2) The preferred component is one or more epoxy groups within the molecule.

[0131] In the case of cationic polymerizability of epoxy groups, similar to component (A1), the epoxy group can be either alicyclic or non-alicyclic.

[0132] From the viewpoint of achieving excellent transparency, the epoxy group is preferably an alicyclic epoxy group.

[0133] In component (A2), the epoxy group can be directly bonded to the linear siloxane skeleton, or it can be bonded to the linear siloxane skeleton via a linker group.

[0134] The linking group can be any divalent group, for example: alkylene groups (-(CH2)). n - (n is an integer greater than or equal to 0), ether bonds (-O-), and combinations thereof.

[0135] Furthermore, the epoxy groups are close to the linear siloxane backbone, which tends to produce a dense cured product when the adhesive composition is cured, resulting in excellent heat resistance (reflow resistance).

[0136] Therefore, when the epoxy group is bonded to the linear siloxane skeleton via a linker, the number of atoms present between the epoxy group and the linear siloxane skeleton is preferably 4 or less, more preferably 2 or less.

[0137] The weight average molecular weight of component (A2) is preferably 200 to 10,000, more preferably 200 to 8,000, and particularly preferably 400 to 6,000.

[0138] If the weight average molecular weight of component (A2) is within the range described, the viscosity of the adhesive composition becomes appropriate, and the balance between the optical properties or heat resistance of the cured product becomes good.

[0139] The functional group content (g / mol) of component (A2) is not particularly limited, but from the viewpoint of reactivity, it is preferably 300 to 5,000, more preferably 350 to 3,000, even more preferably 400 to 2,700, and particularly preferably 400 to 1,500.

[0140] (A2) The content of the component in the adhesive composition is not particularly limited. From the viewpoint of having low refractive index and high transparency, when the total amount of the adhesive composition is set to 100 parts by mass, it is preferably 1 part by mass or more, more preferably 5 parts by mass or more, and even more preferably 10 parts by mass or more, and particularly preferably 20 parts by mass or more.

[0141] Furthermore, from the viewpoint of improving reflow resistance, when the total amount of the adhesive composition is set to 100 parts by mass, the content of component (A2) in the adhesive composition is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, and even more preferably 40 parts by mass or less, and particularly preferably 35 parts by mass or less.

[0142] (A2) The preferred component is a liquid at 25°C, but it can also be a solid at room temperature.

[0143] From the viewpoint of the preparation of the adhesive composition and its dispensing properties, the viscosity of component (A2) at 25°C is preferably 1 mPa·s to 500 mPa·s, more preferably 2 mPa·s to 300 mPa·s, and particularly preferably 5 mPa·s to 100 mPa·s.

[0144] As an example of (A2) component being a linear siloxane compound having an epoxy group, linear siloxane compounds having an epoxy group at the end can be cited, for example.

[0145] The term "linear siloxane compound with an epoxy group at the end" refers to a compound that has an alicyclic epoxy group or a non-alicyclic epoxy group at the end of the main chain formed by siloxane bonds.

[0146] (A2) The component only needs to have an epoxy group at at least one end of the main chain, preferably at all ends of the main chain (two ends of the main chain in the case of no branching).

[0147] (A2) In addition to the end of the main chain, the component may also have epoxy groups in the side chain, preferably only at the end of the main chain.

[0148] From the viewpoint of optical properties and adhesion, component (A2) is particularly preferred to have glycidyl ether structures at both ends.

[0149] As a component (A2), for example, a compound represented by the following general formula (2) may be used.

[0150] [Chemistry 2]

[0151] In general formula (2), R 4 ~R 7 and R 9 ~R 12 Each can be independently represented by a hydrocarbon group or an organic group containing a glycidyl group; R 3 and R 8 Each of these groups independently represents an organic group containing a glycidyl group; m represents -[Si(R 5 (R) 11 The )O]- represents the number of moles of siloxane units in one molecule, and is a number from 0 to 3000; n represents -[Si(R 6 (R) 10 The molar number of siloxane units in one molecule represented by [O] is a number ranging from 0 to 3000.

[0152] (A2) Examples of linear siloxane compounds having alicyclic or non-alicyclic epoxy group at the end are not particularly limited, such as modified silicone oil.

[0153] There are no particular limitations on commercially available modified silicone oils. Examples include: X-22-169B and X-22-169AS, which are modified silicone oils with alicyclic epoxy groups at both ends; X-22-163, KF-105, X-22-163A, X-22-163B, and X-22-163C, which are modified silicone oils with epoxy groups at both ends; X-22-2046 and KF-102, which are modified silicone oils with alicyclic epoxy groups in the side chain; X-22-343, KF-101, KF-1001, and X-22-2000, which are modified silicone oils with epoxy groups in the side chain; and X-22-9002, which is a modified silicone oil with epoxy groups at both ends and in the side chain (all manufactured by Shin-Etsu Chemical Co., Ltd.).

[0154] (A2) The preferred component is modified silicone oil.

[0155] In addition, (A2) may use any one of these, or two or more of them together.

[0156] (A2) The epoxy equivalent (g / mol) of the linear siloxane compound is not particularly limited, but from the viewpoint of reactivity, it is preferably 100 to 4000, more preferably 120 to 2000, and even more preferably 150 to 1000.

[0157] (A2) The weight average molecular weight of the linear siloxane compound is not particularly limited, but is preferably 200 to 10,000, more preferably 200 to 8,000, and even more preferably 400 to 6,000. When the weight average molecular weight of the linear siloxane compound (A2) is within the range described, the viscosity of the composition becomes suitable and the workability is improved.

[0158] (A2) The linear siloxane compound is preferably a liquid at room temperature (25°C), but it may also be a solid. From an operational point of view, the viscosity of the (A2) linear siloxane compound at 25°C is preferably 1 mPa·s to 500 mPa·s, more preferably 2 mPa·s to 300 mPa·s, and even more preferably 5 mPa·s to 100 mPa·s.

[0159] The mixing ratio of component (A1) and component (A2)

[0160] In the adhesive composition, the (A) siloxane compound, the (A1) cyclic siloxane compound with reactive functional groups helps to reduce the refractive index and improve heat resistance.

[0161] In addition, (A2) linear siloxane compounds with reactive functional groups help to reduce the crosslinking density of the hardened material, thereby reducing the refractive index and improving transparency.

[0162] Therefore, (A) siloxane compounds contain both (A1) and (A2) components.

[0163] At this time, in the siloxane compound (A), the ratio (mass ratio) of component (A1) to component (A2) is 100:0 to 0:100, and can be 90:10 to 10:90, 85:15 to 5:95, 75:25 to 15:85, 70:25 to 25:75, 65:35 to 35:65, 60:40 to 30:70, 55:45 to 25:75, or 50:50 to 20:80.

[0164] Furthermore, when the total amount of the adhesive composition is set to 100 parts by mass, the content of component (A) in the adhesive composition of this embodiment is preferably 5 to 99 parts by mass, more preferably 10 to 70 parts by mass, further preferably 20 to 60 parts by mass, and particularly preferably 30 to 50 parts by mass. By setting the content of component (A) within the aforementioned range, the refractive index can be reduced and the adhesion improved.

[0165] (B) Polymerization initiator

[0166] The adhesive composition of this embodiment contains (B) a polymerization initiator (hereinafter also referred to as "(B) component").

[0167] (B) is not particularly limited if it can initiate the polymerization reaction of (A).

[0168] In this embodiment, component (B) can be made by using an appropriate compound based on the type of reactive functional groups possessed by component (A).

[0169] As component (B), it can be used alone or in combination with two or more.

[0170] As component (B) of this embodiment, a photopolymerization initiator is preferably used.

[0171] There are no particular limitations on whether a photopolymerization initiator is a compound such as an acid, base, or free radical that produces (A1) component and (A2) by irradiating an active energy line.

[0172] Here, active energy lines include all light in a broad sense, such as alpha rays, beta rays, electromagnetic waves such as gamma rays and X-rays, electron beams (EB), ultraviolet light of about 100 nm to 400 nm, and visible light of about 400 nm to 800 nm, with ultraviolet light being the preferred type.

[0173] When the reactive functional group of component (A) is a cationic polymerizable group, a photoacid generator is preferably used as a photopolymerization initiator.

[0174] Photoacid generators are compounds that produce acids by irradiation with active energy lines.

[0175] Cationic polymerization occurs between the cationic polymerizable groups of component (A) through the catalytic effect of the acid generated from the photoacid generator.

[0176] There are no particular limitations on photoacid generators. Examples include: onium salts, halogenated compounds, diazomethane compounds, sulfone compounds, sulfonic acid compounds, and other compounds that produce acids through radiation.

[0177] From the viewpoint of having a low refractive index and high transparency, onionium salts are preferred as photoacid generators. Onionium salts are salt compounds of onionium ions and anions. Onionium salts undergo photoreactions to release Lewis acids or Brinzyl acids (protic acids).

[0178] There is no particular limitation on the onium salt, but it is preferably selected from at least one onium salt selected from the group consisting of onium borate salt and onium gallate salt.

[0179] In this case, the onium salt is preferably composed of at least one cation selected from the group consisting of monium and matte.

[0180] There are no particular limitations on gallic acid onium salts, and onium salts represented by the following general formula (3) can be used.

[0181] [Chemistry 3]

[0182] In equation (3), R 13 ~R 16 R represents an alkyl, aryl, or heterocyclic group having 1 to 18 carbon atoms, respectively. 13 ~R 16 At least one of them is an aryl group, and the number of carbons in the aryl group (excluding the number of carbons in the substituents) is 6 to 14. The aryl group may have substituents. E represents elements in groups 15-17 (as designated by the International Union of Pure and Applied Chemistry, IUPAC) with a valence n. n is an integer from 1 to 3. R 17 As an organic group bonded to E, R 17 The number of R is n+1, and there are (n+1) R 17 They can be the same or different from each other, and there are two or more R's. 17 They can form ring structures containing element E directly or via -O-, -S-, -SO-, -SO2-, -NH-, -CO-, -COO-, -CONH-, alkylene, or phenylene. Gallic onium salts may contain an anion having a tetraphenyl gallate skeleton, wherein the hydrogen atom of the phenyl group of the tetraphenyl gallate skeleton may be substituted with at least one halogen atom selected from the group consisting of fluorine, chlorine, bromine and iodine atoms.

[0183] The anion with a tetraphenylgallate skeleton can be tetra(pentafluorophenyl)gallate.

[0184] Gallic acid onium salts can be synthesized, for example, based on the method described in Japanese Patent Application Publication No. 2017-048325.

[0185] Examples of gallic acid onium salts include tetra(pentafluorophenyl)gallic acid 4-isopropyl-4'-methyldiphenyl sulfonium, tetra(pentafluorophenyl)gallic acid-triarylsulfonium, tetra(pentafluorophenyl)gallic acid diphenyl[4-(phenylthio)phenyl]sulfonium, and tetra(pentafluorophenyl)gallic acid 4-isopropylphenyl(p-tolyl)sulfonium, but are not limited to these compounds.

[0186] There are no particular limitations on the borate salts, and the onion salts represented by the following general formula (4) can be used.

[0187] [Chemistry 4]

[0188] In general formula (4), R 18 ~R 21 Each is independently an alkyl group having 1 to 18 carbon atoms or Ar, wherein at least one is Ar, and Ar is an aryl group having 6 to 14 carbon atoms (excluding the carbon number of the following substituents), and a portion of the hydrogen atoms in the aryl group may be derived from an alkyl group having 1 to 8 carbon atoms, an alkyl group having 1 to 8 carbon atoms substituted with halogen atoms, an alkenyl group having 2 to 18 carbon atoms, an alkynyl group having 2 to 18 carbon atoms, an aryl group having 6 to 14 carbon atoms, a nitro group, a hydroxyl group, a cyano group, or -OR. 23 The alkoxy or aryloxy group represented by R 24 CO- represents the acyl group, R 25 COO- represents the acyloxy group, -SR 26 The alkylthio or arylthio group, -NR 27 R 28 The substitution of amino or halogen atoms is represented. R 23 ~R 26 It is an alkyl group having 1 to 8 carbon atoms or an aryl group having 6 to 14 carbon atoms. R 27 and R 28 It consists of hydrogen atoms, alkyl groups having 1 to 8 carbon atoms, or aryl groups having 6 to 14 carbon atoms; E represents elements in groups 15 to 17 (IUPAC notation) with an atomic valence n. n is an integer from 1 to 3. R 22 As an organic group bonded to E, R 22 The number of R is n+1, and there are (n+1) R 22 They can be the same or different from each other, and there are two or more R's. 22They can form ring structures containing element E directly or via -O-, -S-, -SO-, -SO2-, -NH-, -CO-, -COO-, -CONH-, alkylene, or phenylene. Onium borate salts may contain anion having a tetraphenylborate skeleton, wherein the hydrogen atom of the phenyl group in the tetraphenylborate skeleton may be substituted with at least one halogen atom selected from the group consisting of fluorine, chlorine, bromine and iodine atoms.

[0189] The anion with a tetraphenylborate skeleton can be tetra(pentafluorophenyl)borate.

[0190] Onium borate salts can be synthesized, for example, based on the method described in Japanese Patent Application Publication No. 2014-205624.

[0191] Specific examples of onium borate salts include tetra(pentafluorophenyl)boronic acid 4-isopropyl-4'-methyldiphenyl sulfonium tetra(pentafluorophenyl)boronic acid-triarylsulfonium tetra(pentafluorophenyl)boronic acid diphenyl[4-(phenylthio)phenyl]sulfonium tetra(pentafluorophenyl)boronic acid 4-isopropylphenyl(p-tolyl)sulfonium tetra(pentafluorophenyl)boronic acid, but are not limited to these compounds.

[0192] (B) The content of component (B) in the adhesive composition is not particularly limited. From the viewpoint of polymerizability or the viewpoint of making the cured material low in refractive index and high transparency, it is 0.05 to 20.0 parts by mass relative to 100 parts by mass of the siloxane compound having reactive functional groups in (A), preferably 0.1 to 15 parts by mass, more preferably 0.3 to 10 parts by mass, and even more preferably 0.5 to 5 parts by mass.

[0193] Furthermore, the content of component (B) can be appropriately designed based on various factors such as the type or properties of the polymeric compound, the type and amount of irradiation of the active energy line (in the case of using an active energy line), heating temperature, curing time, humidity, and thickness of the adhesive composition, and is not limited to the range described above.

[0194] [Any other ingredients]

[0195] The adhesive composition of this embodiment may, as needed, contain any component other than component (A) and component (B), such as those described below, without prejudice to the spirit of this embodiment.

[0196] (C) Inorganic fillers

[0197] The adhesive composition of this embodiment may contain (C) inorganic filler (hereinafter also referred to as "(C) component") as any component.

[0198] (C) If the component is a granular body formed from inorganic materials, there are no particular limitations.

[0199] As inorganic materials, silicon dioxide, talc, aluminum oxide, aluminum nitride, calcium carbonate, aluminum silicate, magnesium silicate, magnesium carbonate, barium sulfate, barium carbonate, calcium sulfate, aluminum hydroxide, calcium silicate, potassium titanate, titanium oxide, zinc oxide, silicon carbide, silicon nitride, boron nitride, etc. can be used.

[0200] (C) Components may be used alone or in combination with two or more.

[0201] As for component (C), from the viewpoint of refractive index, it is preferable to use silicon dioxide particles.

[0202] In addition, silicon dioxide is preferably amorphous silicon dioxide.

[0203] Regarding component (C), from the perspective of preventing aggregation, its surface can be treated with coupling agents such as silane coupling agents.

[0204] (C) The shape of the component is not particularly limited and can be any of the following: spherical, flake-like, needle-like, or amorphous.

[0205] In adhesive compositions using flake-like or needle-like inorganic fillers as optical adhesives, light may sometimes scatter if the orientation of the inorganic fillers is disordered. Therefore, from the viewpoint of refractive index or transmittance, silica particles are preferably spherical, with a sphericity of 0.8 or higher, and more preferably approximately spherical with a sphericity of 0.9 or higher.

[0206] (C) The average particle size of the component is preferably 5.0 μm or less, more preferably 3.0 μm or less, even more preferably 1.0 μm or less, and particularly preferably 0.5 μm or less.

[0207] In this specification, the term "average particle size" unless otherwise specified refers to the median particle size (D50) of the volume standard determined by laser diffraction scattering method in accordance with International Standardization Organization (ISO) 13320 (2020).

[0208] Transmittance can be improved by setting the average particle size of component (C) below the upper limit.

[0209] (C) There is no particular limitation on the lower limit of the average particle size of the component, but from the viewpoint of the viscosity of the adhesive composition, it is preferably 0.1 μm or more, and more preferably 0.2 μm or more.

[0210] (C) The average particle size of the component is preferably 0.1 μm to 5.0 μm, more preferably 0.2 μm to 2.0 μm.

[0211] Inorganic fillers with different average particle sizes can be used in combination. For example, inorganic fillers with an average particle size of 0.1 μm or more but less than 0.5 μm can be used in combination with inorganic fillers with an average particle size of 0.5 μm to 5.0 μm.

[0212] Furthermore, when using silica as an inorganic filler, its manufacturing method is not particularly limited. Examples include: spherical silica powder obtained by reacting metallic silicon with oxygen; spherical silica powder obtained by melting pulverized silica; and silica fillers obtained by sol-gel method, sedimentation method, or aqueous solution wet method. Among these, from the viewpoint of optical properties, silica particles obtained by the sol-gel method, i.e., sol-gel silica particles, are particularly preferred as they have high sphericity and a relatively sharp particle size distribution.

[0213] When the total amount of the adhesive composition is set to 100 parts by mass, the content of component (C) in the adhesive composition of this embodiment is preferably 0.1 parts by mass to 80 parts by mass, more preferably 5 parts by mass to 70 parts by mass, and even more preferably 10 parts by mass to 60 parts by mass.

[0214] By setting the content of component (C) within the range described above, reflow resistance is improved and the refractive index is reduced.

[0215] Furthermore, in order to ensure that the Si elemental conversion content of the adhesive layer 20 is 10% or more, it is preferable to include silica particles as the (C) inorganic filler. By including silica particles, the Si elemental conversion content of the adhesive layer 20 can be increased and the refractive index of the adhesive layer can be reduced. When the total amount of the adhesive composition is set to 100 parts by mass, the content of silica particles is preferably 0.1 parts by mass to 80 parts by mass, more preferably 5 parts by mass to 70 parts by mass, and even more preferably 10 parts by mass to 60 parts by mass.

[0216] (D) Oxycyclic butane compounds

[0217] The adhesive composition of this embodiment may contain (D)oxetane compounds (hereinafter also referred to as "(D) components") as any component.

[0218] (D) If the component is a compound containing an oxobutane ring, there are no special restrictions.

[0219] By including component (D) in the adhesive composition, the initial adhesion can be improved. Preferably, it does not contain compounds such as oxobutane compounds having aromatic rings, which may increase the refractive index of the adhesive composition.

[0220] (D) There is no particular limitation on the mixing ratio of the components. When the total amount of the adhesive composition is set to 100 parts by mass, it is preferably 1 to 5 parts by mass.

[0221] Examples of oxetane compounds include 3,3'-(oxybis(methylene)bis(3-ethyloxetane), 3-ethyl-3-hydroxymethyloxetane, 3-(methyl)allyloxymethyl-3-ethyloxetane, (3-ethyl-3-oxetane-butylmethoxy)methylbenzene, 4-fluoro-[1-(3-ethyl-3-oxetane-butylmethoxy)methyl]benzene, [1-(3-ethyl-3-oxetane-butylmethoxy)ethyl]phenyl ether, isobutoxymethyl (3-ethyl-3-oxetane-butylmethyl) ether, 2-ethylhexyl (3-ethyl-3-oxetane-butylmethyl) ether, ethyl diethylene glycol (3-ethyl-3-oxetane-butylmethyl) ether, tetrahydrofurfuryl (3-ethyl-3-oxetane-butylmethyl) ether, and tetrabromophenyl (3-ethyl-3-oxetane-butylmethyl) The ethers include, but are not limited to, 2-tetrabromophenoxyethyl (3-ethyl-3-oxetane butylmethyl) ether, pentachlorophenyl (3-ethyl-3-oxetane butylmethyl) ether, pentabromophenyl (3-ethyl-3-oxetane butylmethyl) ether, ethylene glycol bis(3-ethyl-3-oxetane butylmethyl) ether, triethylene glycol bis(3-ethyl-3-oxetane butylmethyl) ether, tetraethylene glycol bis(3-ethyl-3-oxetane butylmethyl) ether, trimethylolpropane tri(3-ethyl-3-oxetane butylmethyl) ether, pentaerythritol tri(3-ethyl-3-oxetane butylmethyl) ether, pentaerythritol tetra(3-ethyl-3-oxetane butylmethyl) ether, dipentaerythritol tetra(3-ethyl-3-oxetane butylmethyl) ether, and di-trimethylolpropane tetra(3-ethyl-3-oxetane butylmethyl) ether.

[0222] Commercially available products as oxetane compounds include, for example: OXT-212, OX-221, OXT-213, OXT-101 (manufactured by Dong-A Synthetic Co., Ltd.).

[0223] (E) Other additives

[0224] The adhesive composition of this embodiment may also contain other additives, such as coupling agents, stabilizers, ion traps, leveling agents, antioxidants, defoamers, viscosity modifiers, solvents, etc., as needed, without prejudice to the spirit of this embodiment.

[0225] The content of each additive can be appropriately selected.

[0226] There is no particular limitation on the method for manufacturing the adhesive composition of this embodiment. For example, the adhesive composition of this embodiment can be obtained by simultaneously or separately introducing component (A), component (B), and, if necessary, component (C), component (D), and other additives (E) into a suitable mixer, heating them as needed to melt them, and simultaneously stirring and mixing them to form a homogeneous composition.

[0227] The mixer is not particularly limited and can include a pulverizer, Henschel mixer, three-roll mill, ball mill, planetary mixer, and bead mill, among others, which include a stirring device and a heating device. Additionally, these devices can be used in combination.

[0228] The adhesive composition thus obtained has both photocurable and thermocurable properties.

[0229] [Viscosity of the adhesive composition]

[0230] The viscosity of the adhesive composition in this embodiment is not particularly limited, but can be adjusted appropriately according to the application.

[0231] For example, as long as the components are selected and the mixing ratio is appropriately adjusted so that the viscosity of the adhesive composition at 25°C is in the range of 0.01 Pa·s to 1,000 Pa·s.

[0232] Unless otherwise specified, the viscosity in this instruction manual is expressed using values ​​measured in accordance with Japanese Industrial Standard JIS K6833. Specifically, it can be determined by measuring with a Type E viscometer at a rotation speed of 10 rpm.

[0233] From the viewpoint of achieving good injectability, the viscosity of the adhesive composition at 25°C can be 0.05 Pa·s to 200 Pa·s, preferably 0.1 Pa·s to 100 Pa·s, more preferably 0.1 Pa·s to 50 Pa·s, and even more preferably 0.1 Pa·s to 20 Pa·s.

[0234] If the viscosity of the adhesive composition is too low, it will fail to maintain its shape and flow during application. If the viscosity of the adhesive composition is too high, it will result in poor injectability or unevenness during application.

[0235] In addition, the thixotropic index (TI) value of the adhesive composition is preferably 0.5 to 3.0.

[0236] In this specification, TI is the ratio of viscosity at 5 rpm to viscosity at 50 rpm, measured using an E-type viscometer at 25°C, and is calculated by dividing the viscosity at 5 rpm by the viscosity at 50 rpm.

[0237] The Thixotropic viscosity (TI) value is an indicator of the dependence of viscosity on shear rate (the rotational speed of a viscometer) and represents thixotropy. For example, the TI value of a Newtonian fluid like water, whose viscosity does not change even when the shear rate changes, is 1. When the TI value is less than 1, lower shear force indicates lower viscosity compared to higher shear force; conversely, when the TI value is greater than 1, lower shear force indicates higher viscosity compared to higher shear force. A higher TI value indicates greater thixotropy.

[0238] If the TI value is 0.5 to 3.0, the workability of the adhesive composition becomes good when injected. The adhesive composition can have thixotropy close to that of a Newtonian fluid with a TI value of 0.8 to 1.2, or it can have thixotropy of a non-Newtonian fluid with a thixotropic index greater than 1.2.

[0239] [Curing of the adhesive composition]

[0240] The adhesive composition of this embodiment can be easily cured by irradiation with the active energy line, preferably light with a wavelength of 10 nm to 600 nm, more preferably ultraviolet light with a wavelength of 100 nm to 500 nm, further preferably ultraviolet light with a wavelength of 250 nm to 450 nm, and particularly preferably ultraviolet light with a wavelength of 300 nm to 400 nm, thereby producing a cured product.

[0241] When the adhesive composition of this embodiment is cured by ultraviolet irradiation, the amount of ultraviolet irradiation (cumulative light intensity) used is preferably 500 mJ / cm. 2 ~30,000 mJ / cm 2 There are no particular limitations on the devices used for irradiating ultraviolet light; for example, previously known devices can be cited.

[0242] [Refractive index, transmittance, and reflow resistance of the hardened material]

[0243] The adhesive composition of this embodiment has a Si content of 10% or more and exhibits excellent optical properties when cured, thus it can be used as the adhesive layer 20 included in the optical fiber array 1 of this embodiment.

[0244] In this case, if the adhesive composition contains (A1) a cyclic siloxane compound with reactive functional groups and (A2) a linear siloxane compound with reactive functional groups as (A) siloxane compound, the optical properties or heat resistance of the cured material will be better.

[0245] Specifically, the adhesive composition of this embodiment has a low refractive index, high transparency, and good reflow resistance in its cured form.

[0246] The refractive index of the hardened material and adhesive layer 20 in this embodiment at a wavelength of 1310 nm and / or 589 nm and at 25°C can be 1.49 or less, preferably 1.48 or less, more preferably 1.47 or less, and even more preferably 1.46 or less or 1.45 or less.

[0247] The refractive index of the hardened material and adhesive layer 20 at a wavelength of 1310 nm and / or 589 nm and at 25°C can be 1.40 or more but less than 1.49, preferably 1.41 or more but less than 1.49, more preferably 1.42 to 1.48, and even more preferably 1.43 to 1.47.

[0248] Unless otherwise specified, the refractive index in this specification is expressed using the value determined in accordance with the JIS K7142:2014A method.

[0249] The hardened material of this embodiment has a transmittance of 80% or more at a thickness of 100 μm, a wavelength of 1310 nm and / or 589 nm, and a temperature of 25°C, preferably 85% or more, more preferably 90% or more, and even more preferably 92% or more.

[0250] The transmittance of the hardened material at a thickness of 100 μm, a wavelength of 1310 nm and / or 589 nm, and a temperature of 25°C can be in the range of 80% to 99%, preferably 85% to 95%, more preferably 87% to 95%, and even more preferably 90% to 95%.

[0251] The adhesive layer 20 included in the fiber array 1 of this embodiment has a transmittance of 75% or more at a wavelength of 1310 nm and / or 589 nm and a temperature of 25°C, preferably 80% or more, more preferably 85% or more, and even more preferably 90% or more.

[0252] The transmittance of the adhesive layer 20 included in the fiber array 1 of this embodiment at a wavelength of 1310 nm and / or 589 nm and at 25°C can be in the range of 75% to 99%, preferably 80% to 95%, more preferably 85% to 95%, and even more preferably 90% to 95%.

[0253] Unless otherwise specified, the transmittance in this specification is expressed using the value measured in accordance with JIS K7105.

[0254] The cured adhesive composition of this embodiment and the adhesive layer 20 exhibit excellent heat resistance, with particularly excellent reflow resistance.

[0255] In this specification, reflow resistance refers to the property of withstanding thermal shock at a maximum temperature of 260°C for 1 minute. That is, the cured adhesive composition and adhesive layer 20 of this embodiment have the following properties: when encapsulating electronic components, the changes in physical properties are small before and after the reflow process (maximum temperature of about 260°C) for soldering.

[0256] For example, the adhesive composition of this embodiment has the property that the change in adhesion strength is small before and after the reflow process when the cured material is formed.

[0257] The reflow resistance of the cured adhesive composition can be evaluated by assessing the rate of reduction in adhesive strength.

[0258] Regarding the adhesion strength of the hardened material, there are no particular limitations if the same method is used before and after the reflow process; for example, a bare film shear test can be performed to determine it.

[0259] The method for determining the shear strength of bare wafers is as follows.

[0260] (1) Apply the adhesive composition (sample) onto a glass substrate.

[0261] (2) The Si chip is placed on the coated sample to make a test piece.

[0262] (3) The test piece is hardened by ultraviolet (UV) irradiation from the glass substrate side.

[0263] (4) After the sample has been light-cured, the shear strength of the bare sheet should be determined quickly using an adhesive strength tester. The value should be set as the adhesive strength before reflow.

[0264] (5) Next, the test piece was subjected to a heat treatment for 6 minutes. For the heat treatment, the temperature was increased from room temperature, and each of the following six stages—170°C, 160°C, 160°C, 260°C, 255°C, and cooling—was performed for 1 minute, constituting one group. This heat treatment was repeated for 3 groups. After the heat treatment, the shear strength of the bare sheet was quickly measured in the same manner as before reflow. This value was taken as the adhesion strength after reflow.

[0265] (6) Calculate the rate of decrease in adhesion strength before and after the reflow process according to the following formula (1).

[0266] [Formula 1]

[0267] The heat treatment described in (5) is a heat treatment that mimics the reflow process performed in the packaging process. The sample before heat treatment is referred to as "before reflow process", and the sample after heat treatment is referred to as "after reflow process".

[0268] Furthermore, the smaller the absolute value of the rate of decrease in adhesion strength before and after the reflow process as expressed in Equation (1), the smaller the change caused by heat treatment, and therefore it is preferred.

[0269] Regarding the cured adhesive composition and adhesive layer 20 of this embodiment, the absolute value of the rate of decrease in adhesive strength before and after the reflow process as expressed in formula (1) can be 74% or less, preferably 65% ​​or less, more preferably 55% or less, and even more preferably 50% or less, particularly preferably 40% or less. Furthermore, there is no particular limitation on the lower limit of the absolute value of the rate of decrease in adhesive strength, for example, it can be 0% or more.

[0270] [Manufacturing methods for fiber optic arrays]

[0271] The fiber array 1 of this embodiment is manufactured by a method of manufacturing a fiber array 1 in which the optical fiber 10 is optically coupled to the optical waveguide element 30 through the adhesive layer 20, wherein the Si element content of the adhesive layer 20 is set to 10% or more.

[0272] At this time, the steps of fixing the optical fiber 10 in the groove (V-groove 33) formed in the optical waveguide element 30 and coupling the optical fiber 10 to the optical waveguide 32 of the optical waveguide element 30 can be performed independently. Alternatively, in the manufacturing method of the fiber array 1 in this embodiment, the steps of fixing the optical fiber 10 in the groove (V-groove 33) formed in the optical waveguide element 30 and coupling the optical fiber 10 to the optical waveguide 32 of the optical waveguide element 30 can be performed simultaneously.

[0273] The following describes a method for fixing the optical fiber 10 to the optical waveguide element 30. Furthermore, this fixing method is merely an example, and this disclosure can be implemented in various modified and improved forms based on the knowledge of those skilled in the art.

[0274] First, the optical fiber 10 is inserted into the V-groove 33, so that the end of the optical fiber 10 abuts against the side of the optical waveguide 32. Here, proper alignment is performed to reduce losses at the connection between the optical fiber 10 and the optical waveguide 32.

[0275] Next, the pressure plate 40 is positioned on the optical fiber 10. Then, the adhesive composition is dropped into the V-groove 33. Alternatively, the pressure plate 40 can be integrally formed with the substrate 31.

[0276] The adhesive composition dropped into the V-groove 33 permeates into the gap between the optical fiber 10 and the V-groove 33 through capillary action, and also permeates along the abutment of the optical fiber 10 and the pressure plate 40, as well as into the gap between the optical fiber 10 and the optical waveguide 32. Therefore, the adhesive composition needs to be injectable in order to permeate both the gap between the optical fiber 10 and the V-groove 33 and the gap between the optical fiber 10 and the optical waveguide 32, and the viscosity or TI value of the adhesive composition needs to be set to an appropriate value.

[0277] Next, the adhesive composition is cured by irradiating it with ultraviolet light, thereby bonding the optical fiber 10 to the optical waveguide 32, the optical fiber 10 to the V-groove 33, and the optical fiber 10 to the pressure plate 40. Alternatively, a heat-based curing step can be added after the ultraviolet-based curing step.

[0278] That is, the adhesive layer 20 in this embodiment can also serve the following functions: to couple the optical fiber 10 to the optical waveguide 32 of the optical waveguide element 30, to fix the optical fiber 10 in the groove, i.e., the V-groove 33, formed in the optical waveguide element 30, and to fix the optical fiber 10 to the pressure plate 40.

[0279] That is, the adhesive layer 20 of this embodiment can be used for both optical path coupling and V-groove fixing.

[0280] In addition, the adhesive layer 20 may not necessarily perform these bonding simultaneously. It can also be used as an adhesive layer for optical path coupling of optical fiber 10 and optical waveguide 32 of optical waveguide element 30, or as an adhesive layer for fixing optical fiber 10 to V-groove 33 formed in the groove of optical waveguide element 30.

[0281] [Uses of Adhesive Compositions]

[0282] The adhesive composition of this embodiment has excellent optical properties or heat resistance, and is therefore not limited to optical adhesives for bonding optical components, but can be used for a variety of applications.

[0283] For example, the adhesive composition of this embodiment can be used as an adhesive or sealant or a raw material for fixing, joining or protecting optical components, electronic components or semiconductor components.

[0284] Optical components that are based on the adhesive composition of this embodiment may include, but are not limited to, optical fibers, fiber arrays, optical waveguide elements, lenses, filters, diffraction gratings, and active optical elements.

[0285] Furthermore, the adhesive composition of this embodiment has excellent optical properties or heat resistance, and is therefore particularly preferred for use as an optical adhesive for silicon photonics.

[0286] The adhesive composition of this embodiment can be used to fix the optical fiber 10 in the groove (V groove 33) formed in the optical waveguide element 30, or to couple the optical fiber 10 to the optical waveguide 32 of the optical waveguide element 30.

[0287] In addition, it is preferable to use the adhesive composition of this embodiment to simultaneously fix the optical fiber 10 in the groove, i.e., the V-groove 33, formed in the optical waveguide element 30 and to couple the optical fiber 10 to the optical waveguide 32 of the optical waveguide element 30.

[0288] For example, the adhesive composition of this embodiment can be used in methods for fixing optical fibers in grooves formed in optical waveguide elements, and in methods for optically coupling optical fibers to optical waveguide elements.

[0289] In addition, the adhesive composition of this embodiment can also be used to simultaneously perform a method of fixing an optical fiber in a groove formed in an optical waveguide element and optically coupling the optical fiber to the optical waveguide element.

[0290] [method]

[0291] As shown in the embodiments described later, the adhesive composition of this embodiment has a Si content of 10% or more, resulting in excellent optical properties or heat resistance when the cured material is formed.

[0292] Therefore, this embodiment provides a method for reducing the refractive index of the adhesive layer 20, wherein in the fiber array 1 in which the optical fiber 10 is optically coupled to the optical waveguide element 30 through the adhesive layer 20, the Si content of the adhesive layer 20 is set to 10% or more.

[0293] Furthermore, as shown in the embodiments described later, in the adhesive composition of this embodiment, the optical properties or heat resistance of the cured material are excellent when both (A) are cyclic siloxane compounds containing (A1) having reactive functional groups and (A2) having reactive functional groups as (A) siloxane compounds.

[0294] Therefore, this embodiment provides a method for reducing the refractive index of the adhesive layer 20 (a cured version of the adhesive composition), which includes a step of combining (A1) a cyclic siloxane compound having reactive functional groups, (A2) a linear siloxane compound having reactive functional groups and (B) a polymerization initiator in an optical fiber array 1 in which the optical fiber 10 is optically coupled to the optical waveguide element 30 through the adhesive layer 20.

[0295] In addition, this embodiment provides a method for suppressing the reduction in adhesion strength of the adhesive layer 20 (a hardened version of the adhesive composition) caused by heating, which includes a step of combining (A1) a cyclic siloxane compound having reactive functional groups, (A2) a linear siloxane compound having reactive functional groups and (B) a polymerization initiator in an optical fiber array 1 in which the optical fiber 10 is optically coupled to the optical waveguide element 30 through the adhesive layer 20.

[0296] [Example]

[0297] The present invention will now be described in more detail through examples and comparative examples, but the present invention is not limited to these examples. Furthermore, in the following examples, unless otherwise specified, parts and % represent parts by mass and percentage by mass.

[0298] [Examples 1-20, Comparative Example 1]

[0299] Adhesive compositions were prepared by mixing the specified amounts of each component using a three-roll mill according to the formulations shown in Tables 1 to 4. In Tables 1 to 3, the amount of each component is expressed in parts by mass (in g). The components used in the examples and comparative examples are as follows.

[0300] • (A1) Cyclic siloxane compounds ((A1) components)

[0301] (A1-1) KR-470 (manufactured by Shin-Etsu Chemical Co., Ltd., alicyclic epoxy group, epoxy functional group 4, viscosity at 25°C 3 Pa·s, epoxy equivalent 200 g / mol) represented by the following formula

[0302] [Chemistry 5]

[0303] (A1-2) A cyclic dimethylsiloxane compound in which n is 4 and has four 3-glycidoxypropyl groups in the molecule (product name: EP-3400L, manufactured by ADEKA, non-alicyclic epoxy group, epoxy functional group number 4, viscosity at 25°C 100 Pa·s, epoxy equivalent 174 g / mol)

[0304] (A1-3) X-40-2678 (manufactured by Shin-Etsu Chemical Co., Ltd., alicyclic epoxy group, epoxy functional group number 2, viscosity at 25°C 120 Pa·s, epoxy equivalent 290 g / mol) is represented by the following formula.

[0305] [Chemistry 6]

[0306] (A1-4) X-40-2728 (manufactured by Shin-Etsu Chemical Co., Ltd., non-alicyclic epoxy group, epoxy functional group number 2, viscosity at 25°C 26 mPa·s, epoxy equivalent 280 g / mol) represented by the following formula (R is alkyl)

[0307] [Chemistry 7]

[0308] • (A2) Straight-chain siloxane compounds ((A2) component)

[0309] (A2-1) The modified silicone oil with alicyclic epoxy groups at both ends represented by the following formula (product name: X-22-169AS, manufactured by Shin-Etsu Chemical Co., Ltd., alicyclic epoxy group, number average molecular weight 1,000, viscosity at 25°C 25 Pa·s, epoxy equivalent 500 g / mol).

[0310] [Chemistry 8]

[0311] (A2-2) The following formula (m=0, R) a =Methyl, R b = Organic groups with epoxy groups) refers to modified silicone oil with epoxy groups (glycidyl ether structure) at both ends (product name: KF-105, manufactured by Shin-Etsu Chemical Co., Ltd., non-alicyclic epoxy group, number average molecular weight 980, viscosity at 25°C 15 Pa·s, epoxy equivalent 490 g / mol).

[0312] [Chemistry 9]

[0313] • (B) Polymerization initiator ((B) component)

[0314] (B-1) 4-Isopropyl-4'-methyldiphenylboronic acid as a boronic acid salt

[0315] (B-2) Tetra(pentafluorophenyl)gallic acid 4-isopropyl-4'-methyldiphenyl monazine as an onium salt of gallic acid

[0316] • (C) Inorganic particles ((C) components)

[0317] (C-1) Spherical silica particles (Product name: KE-S30HG, manufactured by Japan Catalyst Co., Ltd., D50 is 0.3 μm, spherical sol-gel silica particles)

[0318] • (D) Oxybutane compounds ((D) components)

[0319] (D-1) 3,3'-(oxybis(methylene)bis(3-ethyloxetane) (Product name: OXT-221, manufactured by Toa Synthetic Co., Ltd.)

[0320] (X) Epoxy compounds

[0321] (X-1) Alicyclic epoxy (Product name: 2021P, manufactured by Daicel Chemical Industries)

[0322] [Evaluation of characteristics]

[0323] In the examples and comparative examples, the viscosity of the adhesive composition and the properties of the cured product obtained by hardening the adhesive composition (adhesion strength, strength reduction rate before and after reflow, refractive index, transmittance) were measured in the following manner.

[0324] (Viscosity of the adhesive composition)

[0325] Using an E-type viscometer (model: TVE-22H, rotor name: 1°34'×R24) manufactured by Toki Sangyo Co., Ltd. (set to the appropriate measurement range (H, R or U)), the viscosity of the adhesive composition was measured within 1 hour after its preparation at 25°C and a rotor speed of 10 rpm. The value was read 1 minute after the start of the measurement.

[0326] (Curing of the adhesive composition)

[0327] The hardening conditions were set as follows: a UV irradiation machine using a metal halide lamp as the lamp source, with a peak wavelength of 365 nm and a heat output of 30,000 mJ / cm². 2 After irradiating with UV light, the accumulated light intensity is dried at 120°C for 60 minutes using a dryer.

[0328] (Refractive index)

[0329] The refractive index of a 100 μm thick cured film made from the adhesive composition was measured at 589 nm using an Abbe refractometer (manufactured by Atago Corporation, NAR-2T). Additionally, the refractive index of a cured adhesive composition formed on a glass substrate was measured at 1310 nm using a spectroscopic ellipsometry (manufactured by Semilab Corporation, SE-2000).

[0330] (Transmission rate)

[0331] The transmittance of a 100 μm thick cured material made from the adhesive composition was determined using a UV-Vis spectrophotometer (V-670, manufactured by Nippon Spectrophotometer Co., Ltd.) at measurement wavelengths of 589 nm and 1310 nm.

[0332] (Reflow resistance)

[0333] The adhesive strength of the cured adhesive composition was determined by shear testing of the bare sheet.

[0334] The method for determining the shear strength of bare wafers is as follows.

[0335] (1) The prepared adhesive composition (sample) is coated onto a glass substrate in the form of an adhesive. The coating size is set to 1.5 mm in length × 1.5 mm in width × 0.5 mm in thickness.

[0336] (2) Place 2 mm 2 The Si chip is placed on the coated sample to make a test piece.

[0337] (3) The test piece is hardened by UV irradiation from the glass substrate side under the hardening conditions.

[0338] (4) After the sample has been light-cured, the shear strength of the bare sheet should be determined quickly using a universal adhesive strength tester (Dage, Series 4000). The value should be set as the adhesive strength before reflow.

[0339] (5) Next, the test piece was subjected to a heat treatment for 6 minutes. For the heat treatment, the temperature was increased from room temperature, and each of the following six stages—170°C, 160°C, 160°C, 260°C, 255°C, and cooling—was performed for 1 minute, constituting one group. This heat treatment was repeated for 3 groups. After the heat treatment, the shear strength of the bare sheet was quickly measured in the same manner as before reflow. This value was taken as the adhesion strength after reflow.

[0340] (6) Calculate the rate of decrease in adhesion strength before and after the reflow process according to the following formula (1).

[0341] [Formula 2]

[0342] (Si elemental content conversion)

[0343] The converted Si content of each component is shown in Table 5.

[0344] The Si concentration is calculated using the atomic weight / molecular weight of Si.

[0345] The Si content of each component in the adhesive composition is calculated using the atomic weight / molecular weight of Si × the number of Si atoms in one molecule × 100 (%). Furthermore, the atomic weight of Si is set to 28.09.

[0346] Tables 1 to 4 show the results obtained by calculating the Si element equivalent content derived from the (A) siloxane compound with reactive functional groups contained in the adhesive composition, and the Si element equivalent content of the adhesive composition as a whole.

[0347] [Table 1]

[0348] [Table 2]

[0349] [Table 3]

[0350] [Table 4]

[0351] [Table 5]

[0352] [result]

[0353] According to Tables 1 to 4, when the Si content of the adhesive composition is 10% or more, the hardened material (adhesive layer) has a low refractive index, high transmittance, and excellent optical properties.

[0354] Specifically, it can be seen that in Examples 1 to 20, the refractive index at wavelengths of 1310 nm and 589 nm and at 25°C is less than 1.49, which is a low refractive index, and the transmittance is as high as 75% or more, thus exhibiting excellent transparency.

[0355] In addition, it is known that the adhesive compositions of Examples 1 to 20 have low viscosity and therefore excellent injectability.

[0356] That is, it can be seen that by using the adhesive compositions of Examples 1 to 20 to form an adhesive layer, an optical fiber array 1 including an adhesive layer 20 with low refractive index and excellent transparency can be realized.

[0357] Based on the comparison of Examples 1 and 2, it can be seen that regardless of the type of component (A) (structure of the siloxane compound, type of functional group or number of functional groups), the refractive index is low and the transparency is excellent.

[0358] A comparison of Examples 3 to 5 and Examples 4 to 6 shows that if (D)oxobutane compounds are included, the adhesion strength before reflux is higher.

[0359] A comparison of Examples 6 to 9 shows that the refractive index and reflow resistance can be adjusted by changing the mixing ratio of the (A1) cyclic siloxane compound and the (A2) linear siloxane compound. Increasing the proportion of the (A1) cyclic siloxane compound improves the reflow resistance, while increasing the proportion of the (A2) linear siloxane compound decreases the refractive index.

[0360] Based on the comparison of Examples 6, 10 to 12, it can be seen that regardless of the type (type or number of functional groups) of the (A1) cyclic siloxane compound, the refractive index is low and the transparency is excellent.

[0361] Furthermore, a comparison of Examples 6 and 10 shows that when the functional group of the (A1) cyclic siloxane compound is an alicyclic epoxy group, it exhibits superior reflow resistance compared to the case of non-alicyclic epoxy groups.

[0362] Furthermore, a comparison of Examples 6 and 11 shows that when the number of functional groups in the (A1) cyclic siloxane compound is large, the reflux resistance is excellent.

[0363] A comparison of Examples 6 and 13 shows that regardless of the type (functional group) of the (A2) linear siloxane compound, the refractive index is low and the transparency is excellent.

[0364] Furthermore, a comparison of Examples 6 and 13 shows that when the functional group of the (A2) linear siloxane compound is an alicyclic epoxy group, it exhibits superior reflow resistance compared to the case of non-alicyclic epoxy groups.

[0365] A comparison of Examples 14 and 15 shows that regardless of the content of inorganic filler (C), the refractive index is low and the transparency is excellent.

[0366] A comparison of Examples 16 and 17 shows that regardless of the type of polymerization initiator (B), the refractive index is low and the transparency is excellent.

[0367] As can be seen from Examples 18 to 20, even without the (C) inorganic filler, the refractive index is low and the transparency is excellent.

[0368] Comparative Example 1 is an example that does not contain component (A) but contains epoxy compound (X), and has a high refractive index because the Si element content of the adhesive composition is less than 10%.

[0369] [Industry availability]

[0370] The fiber array of the present invention includes an adhesive layer with low refractive index and excellent transparency, making it particularly effective for use in silicon photonics technology. Furthermore, the resin composition of the present invention does not contain fluorine compounds and can be made with a low refractive index, thus making it effective as an optical adhesive from an environmental point of view.

[0371] Explanation of icon numbers

[0372] 1: Fiber optic array

[0373] 10: Fiber optic

[0374] 11: Covering layer

[0375] 12: With fiber optic cable

[0376] 20: Adhesive layer

[0377] 30: Optical waveguide components

[0378] 31: Substrate

[0379] 32: Optical waveguide

[0380] 33: V-groove (groove section)

[0381] 40: Pressure plate

[0382] 50: Optical waveguide module (optical waveguide device)

Claims

1. A fiber optic array, comprising: Fiber optics, and Adhesive layer, The optical fiber is coupled to the optical waveguide element through the adhesive layer. The Si content of the adhesive layer is more than 10%.

2. The fiber optic array according to claim 1, wherein, The fiber array has: A substrate having grooves formed to accommodate the optical fibers; and The pressure plate is then fixed to the surface of the optical fiber. The optical fiber is bonded and fixed in the groove through the adhesive layer. The adhesive layer bonds the optical fiber to the optical waveguide element and bonds the substrate in which the optical fiber is housed in the groove to the pressure plate.

3. The fiber optic array according to claim 2, wherein, The substrate is a semiconductor substrate.

4. The fiber optic array according to claim 3, wherein, The semiconductor substrate has a ball grid array electrode on one side.

5. The fiber optic array according to any one of claims 1 to 4, wherein, The adhesive layer has a transmittance of over 90% at a wavelength of 1310 nm.

6. The fiber optic array according to any one of claims 1 to 5, wherein, The adhesive layer has a refractive index of less than 1.49 at a wavelength of 1310 nm.

7. The fiber optic array according to any one of claims 1 to 6, wherein, The adhesive layer comprises (A) a hardened compound of a siloxane compound having reactive functional groups and (B) a polymerization initiator.

8. The fiber optic array according to claim 7, wherein, The (A) siloxane compound having a reactive functional group comprises (A1) a cyclic siloxane compound having a reactive functional group and (A2) a linear siloxane compound having a reactive functional group.

9. The fiber optic array according to any one of claims 1 to 8, wherein, The adhesive layer also contains (C) an inorganic filler.

10. The fiber optic array according to claim 9, wherein, When the total amount of the components contained in the adhesive layer is set to 100 parts by weight, the content of the inorganic filler (C) is 0.1 parts by weight to 80 parts by weight.

11. The fiber optic array according to claim 9 or 10, wherein, The average particle size of the inorganic filler (C) is 0.1 μm to 5.0 μm.

12. The fiber optic array according to any one of claims 1 to 11, wherein, The adhesive layer comprises a hardened material consisting of (A) a siloxane compound with reactive functional groups, (B) a polymerization initiator, and (C) an inorganic filler. The Si content in the adhesive layer derived from the siloxane compound with reactive functional groups of (A) is 5% or more.

13. An optical waveguide module comprising an optical fiber array according to any one of claims 1 to 12.

14. A method for reducing the refractive index of an adhesive layer, wherein in an optical fiber array in which an optical fiber is optically coupled to an optical waveguide element through the adhesive layer, the Si content of the adhesive layer is set to 10% or more.

15. A method for manufacturing an optical fiber array, comprising manufacturing an optical fiber array in which optical fibers are optically coupled to optical waveguide elements through an adhesive layer, wherein in the method, The Si element content of the adhesive layer is set to be 10% or more.

16. The method for manufacturing an optical fiber array according to claim 15, wherein, Simultaneously, the process of fixing the optical fiber in the groove formed in the optical waveguide element and the process of optically coupling the optical fiber to the optical waveguide element are performed.

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