Resin composition, cured product, and optical fiber array

Abstract

Provided is a resin composition for an adhesive, the composition having a low refractive index and a low weight reduction rate after a reflow step is performed.　The resin composition for an adhesive comprises: (A) a siloxane compound that has a reactive functional group; and (B) a polymerization initiator. The (B) polymerization initiator contains at least one onium salt selected from the group consisting of onium borate salts and onium gallate salts. The onium salt preferably contains at least one cation selected from the group consisting of iodonium and sulfonium.

Description

Resin composition, cured product, and optical fiber array

[0001] The present invention relates to a resin composition, a cured product, and an optical fiber array.

[0002] In recent years, the increasing speed of information and communications has led to the need to deal with the rapid increase in communication volume. One solution to these problems is silicon photonics, which combines conventional electrical communication technology with optical communication technology.

[0003] Silicon photonics is a technology that integrates elements such as optical waveguides, optical switches, optical modulators, and photodetectors on a silicon substrate, and by integrating optical devices and electronic circuits into optical integrated circuits, it is possible to realize small, highly functional optical devices.

[0004] Conventionally, optical adhesives have been required to have optical properties such as low refractive index and high transparency. Generally, methods for lowering the refractive index include methods for lowering the glass transition temperature of a resin composition and methods for lowering the crosslinking density of a polymer. Another known method for lowering the refractive index is the use of fluorine compounds. However, fluorine compounds have a very stable structure and are difficult to decompose in the environment, raising environmental concerns, and their use is being restricted.

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

[0006] Furthermore, Patent Document 2 describes the use of a compound having an aromatic ring and a reactive silicon-containing group in an adhesive composition for optical communications that has excellent adhesion, moisture resistance, and a low refractive index. However, the use of a large amount of a resin material having an aromatic ring increases the refractive index, and the refractive index obtained is only higher than the refractive index of 1.46 of quartz glass, which is a common raw material for optical fibers.

[0007] JP 2011-037978 A JP 2017-061599 A

[0008] In a situation where resin compositions are used in a wide variety of applications, such as for adhesives, there has been a demand for resin compositions with excellent optical properties and heat resistance. For example, there has been a demand for resin compositions for adhesives that have a low refractive index and a small weight loss rate after a reflow process. The present invention has been made in view of the above problems, and an object of the present invention is to provide a resin composition for adhesives that has a low refractive index and a small weight loss rate after a reflow process, and a cured product thereof. Another object of the present invention is to provide an optical fiber array using a resin composition for adhesives that has a low refractive index and a small weight loss rate after a reflow process.

[0009] The present invention relates to the following resin compositions for adhesives, cured products, and optical fiber arrays: [1] A resin composition for adhesives, comprising: (A) a siloxane compound having a reactive functional group; and (B) a polymerization initiator, wherein the polymerization initiator (B) comprises at least one onium salt selected from the group consisting of onium borate salts and onium gallate salts. [2] The resin composition according to [1] above, wherein the onium salt comprises at least one cation selected from the group consisting of iodonium and sulfonium. [3] The resin composition according to [1] or [2] above, wherein the onium gallate salt is an onium salt represented by the following general formula (1): [In general formula (1), R １ ~R ４ each independently represents an alkyl group having 1 to 18 carbon atoms, an aryl group, or a group having a heterocycle, and R １ ~R ４ at least one of is an aryl group, the number of carbon atoms in the aryl group (excluding the number of carbon atoms in the substituent) is 6 to 14, and the aryl group may have a substituent; E represents an element of Group 15 to 17 (IUPAC notation) with a valence of n, and n is an integer of 1 to 3; R ５ is an organic group bonded to E, and R ５ The number of R is n+1, and (n+1) R ５ may be the same or different, and two or more R ５ are directly connected to each other or -O-, -S-, -SO-, -SO ２A ring structure containing the element E may be formed via -, -NH-, -CO-, -COO-, -CONH-, an alkylene group, or a phenylene group.] [4] The resin composition according to [1] or [2] above, wherein the onium borate salt is an onium salt represented by the following general formula (2): [In general formula (2), R ６ ~R ９ are each independently an alkyl group having 1 to 18 carbon atoms or Ar, provided that at least one is Ar, and Ar is an aryl group having 6 to 14 carbon atoms (not including the carbon atoms of the following substituents), and some of the hydrogen atoms in the aryl group are replaced with an alkyl group having 1 to 18 carbon atoms, an alkyl group having 1 to 8 carbon atoms substituted with a halogen atom, 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 １１ an alkoxy group or an aryloxy group represented by R １２ an acyl group represented by CO-, R １３ an acyloxy group represented by COO-; １４ an alkylthio group or an arylthio group represented by the formula: １５ R １６ or a halogen atom, １１ ~R １４ is an alkyl group having 1 to 8 carbon atoms or an aryl group having 6 to 14 carbon atoms, R １５ and R １６ is a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or an aryl group having 6 to 14 carbon atoms; E represents an element of Group 15 to 17 (IUPAC notation) with a valence of n, n is an integer of 1 to 3, and R １０ is an organic group bonded to E, and R １０ The number of R is n+1, and (n+1) R １０ may be the same or different, and two or more R １０ are directly connected to each other or -O-, -S-, -SO-, -SO ２A ring structure containing the element E may be formed via -, -NH-, -CO-, -COO-, -CONH-, an alkylene group, or a phenylene group.] [5] The resin composition according to any one of [1] to [4] above, wherein the content of the (B) polymerization initiator is 0.3 to 20.0 parts by mass per 100 parts by mass of the (A) siloxane compound having a reactive functional group. [6] The resin composition according to any one of [1] to [5] above, wherein the (A) siloxane compound having a reactive functional group includes (A1) a cyclic siloxane compound having a reactive functional group and (A2) a linear siloxane compound having a reactive functional group. [7] The resin composition according to any one of [1] to [6] above, further including (C) an inorganic filler. [8] The resin composition according to any one of [1] to [7] above, further including (D) an oxetane. [9] A cured product of the resin composition according to any one of [1] to [8] above.

[10] The cured product according to [9] above, which has a refractive index of 1.47 or less at a wavelength of 1310 nm.

[11] The cured product according to [9] or

[10] above, which has a thickness of 100 μm and a transmittance of 85% or more at a wavelength of 1310 nm.

[12] The cured product according to any one of [9] to

[11] above, which has an absolute value of the weight loss rate before and after heating at 260°C, represented by the following formula (1), of 16% or less.

[13] The resin composition according to any one of [1] to [8] above, which is used for fixing an optical fiber in a groove formed in an optical waveguide element.

[14] The resin composition according to any one of [1] to [8] above, which is used for optically coupling an optical fiber to an optical waveguide element.

[15] The resin composition according to any one of [1] to [8] above, which is used for simultaneously fixing an optical fiber in a groove formed in an optical waveguide element and optically coupling the optical fiber to the optical waveguide element.

[16] An optical fiber array comprising: the resin composition according to any one of [1] to

[15] above, an optical fiber, and an optical waveguide element, wherein the optical fiber is optically coupled to the optical waveguide element by means of the resin composition.

[0010] According to the present invention, it is possible to provide a resin composition for adhesives having a low refractive index and a small weight loss rate after a reflow process, a cured product of the resin composition, and an optical fiber array using the resin composition for adhesives having a low refractive index and a small weight loss rate after a reflow process.

[0011] 3 is an exploded perspective view of the optical waveguide module, an enlarged view of the vicinity of the connection portion, a side view showing a state in which an optical fiber is fixed to an optical waveguide element, and a cross-sectional view taken along the line AA in FIG.

[0012] An embodiment of the present invention (hereinafter, the present embodiment) will be described below. The present embodiment relates to a resin composition for adhesives, a cured product of the resin composition, and an optical fiber array. Note that the present invention is not limited to the present embodiment. Also, the drawings are schematic, and the present disclosure can be implemented in various forms with various modifications and improvements based on the knowledge of those skilled in the art. Note that components with the same reference numerals in this specification and drawings indicate the same components.

[0013] [Definitions] In this specification, ○ to △ (for example, ○ parts by mass to △ parts by mass) means ○ or more and △ or less (○ parts by mass or more and △ parts by mass or less). In addition, in this specification, the terms "comprise" or "comprises" mean that the specified component is included, but do not exclude the presence of other components.

[0014] [Resin Composition] The resin composition of the present embodiment comprises (A) a siloxane compound having a reactive functional group and (B) a polymerization initiator, wherein the polymerization initiator (B) comprises at least one onium salt selected from the group consisting of onium borate salts and onium gallate salts, and is for use as an adhesive.

[0015] (A) Siloxane Compound Having a Reactive Functional Group The siloxane compound having a reactive functional group (A) contained in the resin composition of this embodiment is not particularly limited, but preferably contains (A1) a cyclic siloxane compound having a reactive functional group or (A2) a linear siloxane compound having a reactive functional group. Hereinafter, the siloxane compound having a reactive functional group (A) may be simply referred to as "(A) siloxane compound" or "(A) component."

[0016] (A1) Cyclic siloxane compound having a reactive functional group The resin 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"). The (A1) component is not particularly limited as long as it is a cyclic siloxane compound having one or more reactive functional groups per molecule. As the (A1) component, one type may be used alone, or two or more types may be used in combination.

[0017] The reactive functional group refers to a functional group that can react with a functional group possessed by a compound contained in the resin composition of the present embodiment. The reactive functional group is not particularly limited, but examples thereof include an epoxy group, an oxetanyl group, a glycidyl group, an alkoxysilyl group, and a vinyl ether group.

[0018] There are no particular limitations on the number of reactive functional groups per molecule in the component (A1), as long as it is one or more. From the standpoints of optical properties, heat resistance, availability of raw materials, reactivity, and the like, it is desirable for the number to be two or more, and the number is preferably 2 to 10, more preferably 2 to 6, even more preferably 2 to 4, and particularly preferably 2 or 4.

[0019] The cyclic siloxane compound refers to a compound having a cyclic siloxane skeleton based on siloxane bonds (—Si—O—Si—). The number of Si—O units forming the cyclic siloxane skeleton (equal to the number of silicon atoms forming the siloxane ring) is not particularly limited, but from the viewpoints of optical properties, heat resistance, availability of raw materials, reactivity, etc., it is preferably 2 to 15, more preferably 3 to 10, even more preferably 3 to 8, and particularly preferably 3 to 6.

[0020] It is preferable that the component (A1) has a cationically polymerizable group as the reactive functional group bonded to the cyclic siloxane skeleton. The cationically polymerizable group refers to a functional group that undergoes chain polymerization in the presence of cations. By having the component (A1) have a cationically polymerizable group bonded to the cyclic siloxane skeleton, it is possible to provide heat resistance while reducing cure shrinkage. Examples of the cationically polymerizable group include an epoxy group, a glycidyl group, an oxetanyl group, and a vinyl ether group. Although not particularly limited, from the viewpoint of reducing the refractive index, it is preferable that the cationically polymerizable group is a functional group that does not have an aromatic ring.

[0021] From the viewpoints of optical properties, heat resistance, availability of raw materials, and storage stability of the composition, it is preferable that the cationically polymerizable group of component (A1) is an epoxy group. The epoxy group is a group having an oxirane structure, and is a substituent having a three-membered ring (oxirane ring) consisting of two carbon atoms and one oxygen atom. When the cationically polymerizable group is an epoxy group, the epoxy group may be an alicyclic epoxy group or a non-alicyclic epoxy group. From the viewpoint of achieving excellent transparency, it is preferable that the epoxy group be an alicyclic epoxy group.

[0022] The alicyclic epoxy group has a cycloalkene oxide structure as an alicyclic skeleton. The cycloalkene oxide structure is a structure having an aliphatic ring and an epoxy group that constitutes the aliphatic ring and is composed of two adjacent carbon atoms and oxygen atoms. The cycloalkene oxide structure can be obtained, for example, by epoxidizing a cycloalkene with an oxidizing agent such as a peroxide. The alicyclic skeleton of the alicyclic epoxy group is not particularly limited, but examples include a cyclopropane skeleton, a cyclobutane skeleton, a cyclopentane skeleton, a cyclohexane skeleton, a cycloheptane skeleton, and a cyclooctane skeleton, and preferably a cyclohexane skeleton.

[0023] The non-alicyclic epoxy group is an epoxy group other than the above-mentioned alicyclic epoxy groups. Examples of groups containing a non-alicyclic epoxy group include a glycidyl group and a glycidoxypropyl group (preferably a 3-glycidoxypropyl group).

[0024] In the component (A1), the epoxy group may be bonded directly to the cyclic siloxane skeleton, or may be bonded via a linking group. The linking group may be any divalent group, such as an alkylene group (-(CH ２ ) ｎ Examples of such bonds include - (n is an integer of 0 or more), ether bonds (-O-), and combinations thereof. Although the epoxy group and the cyclic siloxane skeleton are close to each other, a dense cured product tends to be obtained when the resin composition is cured, and the cured product has excellent heat resistance (reflow resistance). Therefore, when the epoxy group is bonded to the cyclic siloxane skeleton via a linking group, the number of atoms between the epoxy group and the cyclic siloxane skeleton is preferably 4 or less, and more preferably 2 or less.

[0025] 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. When the weight-average molecular weight of component (A1) is within the above range, the viscosity of the resin composition becomes appropriate, and the optical properties and heat resistance of the cured product are well balanced. Note that the weight-average molecular weight in this specification refers to a value calculated by gel permeation chromatography (GPC) using a calibration curve based on standard polystyrene.

[0026] There are no particular limitations on the functional group equivalent weight (g / mol) of component (A1), but from the standpoint of reactivity, it is preferably 50 to 1,000, more preferably 100 to 500, and particularly preferably 150 to 400. In this specification, the epoxy equivalent weight refers to a value measured in accordance with JIS K7236.

[0027] The content of component (A1) in the resin composition is not particularly limited, but from the viewpoint of improving reflow resistance, it is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, even more preferably 2.0 parts by mass or more, and particularly preferably 5 parts by mass or more, when the total amount of the resin composition is 100 parts by mass. Also, from the viewpoint of achieving a low refractive index and high transparency, the content of component (A1) in the resin composition is preferably 95 parts by mass or less, more preferably 50 parts by mass or less, even more preferably 30 parts by mass or less, and particularly preferably 15 parts by mass or less, when the total amount of the resin composition is 100 parts by mass.

[0028] Component (A1) is preferably a liquid at 25°C, but may be a solid at room temperature. From the viewpoint of preparation and dispensability of the resin composition, component (A1) preferably has a viscosity at 25°C of 10 to 10,000 mPa·s, more preferably 20 to 8,000 mPa·s, and particularly preferably 50 to 5,000 mPa·s. In this specification, viscosity is expressed as a value measured in accordance with Japanese Industrial Standard JIS K6833, unless otherwise specified. Specifically, it can be determined by measuring using an E-type viscometer at a rotation speed of 10 rpm.

[0029] As the component (A1), for example, a compound represented by the following general formula (3) can be used.

[0030] [In general formula (3), R １７ or R １８ represents a glycidyl group, an epoxy group, or a hydrocarbon group having 1 to 6 carbon atoms, and n represents an integer of 3 to 10. １７ , R １８ may be the same or different. １７ or R １８ At least two of them are organic groups containing a glycidyl group or an epoxycyclohexylethyl group.

[0031] Examples of compounds in which the component (A1) is a cyclic siloxane compound having an epoxy group include 2,4-di[2-(3-{oxabicyclo[4.1.0]heptyl})ethyl]-2,4,6,6,8,8-hexamethyl-cyclotetrasiloxane, 4,8-di[2-(3-{oxabicyclo[4.1.0]heptyl})ethyl]-2,2,4,6,6,8-hexamethyl-cyclotetrasiloxane, 2,4-di[2-(3-{oxabicyclo[4.1.0]heptyl})ethyl]-6,8-dipropyl-2,4,6,8-tetramethyl-cyclotetrasiloxane, 4,8-di[2-(3-{oxabicyclo[ 4.1.0]heptyl})ethyl]-2,6-dipropyl-2,4,6,8-tetramethyl-cyclotetrasiloxane, 2,4,8-tri[2-(3-{oxabicyclo[4.1.0]heptyl})ethyl]-2,4,6,6,8-pentamethyl-cyclotetrasiloxane, 2,4,8-tri[2-(3-{oxabicyclo[4.1.0]heptyl})ethyl]-6-propyl-2,4,6,8-tetramethyl-cyclotetrasiloxane, and 2,4,6,8-tetra[2-(3-{oxabicyclo[4.1.0]heptyl})ethyl]-2,4,6,8-tetramethyl-cyclotetrasiloxane.

[0032] When component (A1) is a cyclic siloxane compound having an epoxy group, commercially available products include, but are not limited to, cyclic siloxane compounds having an alicyclic epoxy group such as KR-470 (functionality 4), X-40-2670 (functionality 4), and X-40-2678 (functionality 2) (all manufactured by Shin-Etsu Chemical Co., Ltd.), and cyclic siloxane compounds having a glycidyl group, which is a non-alicyclic epoxy group such as 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 Corporation). It is preferable that component (A1) be one of these epoxy-modified cyclic siloxane compounds having two or four epoxy groups. Component (A1) may be any one of these compounds, or two or more of these compounds may be used in combination.

[0033] The epoxy equivalent (g / mol) of the (A1) cyclic siloxane compound is not particularly limited, but from the viewpoint of reactivity, it is preferably 50 to 1,000, more preferably 100 to 500, and even more preferably 150 to 400. In this specification, the epoxy equivalent can be measured in accordance with JIS K7236.

[0034] The weight-average molecular weight of the (A1) cyclic siloxane compound is not particularly limited, but is preferably 200 to 3,000, more preferably 300 to 2,000, and even more preferably 400 to 1,000. When the weight-average molecular weight of the (A1) cyclic siloxane compound is within the above range, the viscosity of the composition becomes appropriate and workability is improved. Note that, in this specification, the weight-average molecular weight can be calculated by gel permeation chromatography (GPC) using a calibration curve based on standard polystyrene.

[0035] The (A1) cyclic siloxane compound is preferably a liquid at room temperature (25°C), but may also be a solid. From the viewpoint of workability, the viscosity of the (A1) cyclic siloxane compound at 25°C is preferably 10 to 30,000 mPa·s. In this specification, viscosity can be measured in accordance with Japanese Industrial Standard JIS K6833. Specifically, viscosity can be determined by measuring using an E-type viscometer at a rotation speed of 10 rpm. The measurement is not particularly limited by the equipment, rotor, or measurement range used.

[0036] (A2) Linear siloxane compound having a reactive functional group The resin 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"). The (A2) component is not particularly limited as long as it is a linear siloxane compound having one or more reactive functional groups per molecule. As the (A2) component, one type may be used alone, or two or more types may be used in combination.

[0037] The reactive functional group of component (A2) is the same as that of component (A1) and is not particularly limited, but examples thereof include epoxy groups, glycidyl groups, oxetanyl groups, alkoxysilyl groups, vinyl ether groups, and alkoxyl groups. Furthermore, it is preferable that component (A2) has a cationically polymerizable group as the reactive functional group. A cationically polymerizable group refers to a functional group that undergoes chain polymerization in the presence of cations. By including a cationically polymerizable group bonded to a linear siloxane skeleton in component (A2), it is possible to achieve low refractive index while also reducing cure shrinkage. Examples of cationically polymerizable groups include epoxy groups, glycidyl groups, oxetanyl groups, and vinyl ether groups. Although not particularly limited, from the perspective of lowering the refractive index, it is preferable that the cationically polymerizable group is a functional group that does not have an aromatic ring.

[0038] There are no particular limitations on the number of reactive functional groups per molecule of the component (A2), so long as it is one or more. From the standpoints of optical properties, heat resistance, ease of raw material availability, reactivity, and the like, it is preferable for the number to be two or more, and the number is preferably 2 to 10, more preferably 2 to 6, even more preferably 2 to 4, and particularly preferably 2.

[0039] The linear siloxane compound refers to a compound having a linear siloxane skeleton based on siloxane bonds (—Si—O—Si—). The number of Si—O units forming the linear siloxane skeleton (equal to the number of silicon atoms forming the siloxane chain) is not particularly limited, but is preferably 2 to 50, more preferably 3 to 40, even more preferably 5 to 30, and particularly preferably 10 to 20, from the viewpoints of optical properties, heat resistance, availability of raw materials, reactivity, etc.

[0040] From the viewpoints of optical properties, heat resistance, and adhesiveness, it is preferable that the cationically polymerizable group of component (A2) is an epoxy group. It is preferable that component (A2) has one or more epoxy groups in the molecule. When the cationically polymerizable group is an epoxy group, the epoxy group may be an alicyclic epoxy group or a non-alicyclic epoxy group, as with component (A1). From the viewpoint of achieving excellent transparency, it is preferable that the epoxy group is an alicyclic epoxy group.

[0041] In the component (A2), the epoxy group may be bonded directly to the linear siloxane skeleton, or may be bonded via a linking group. The linking group may be any divalent group, such as an alkylene group (-(CH ２ ) ｎ Examples of such bonds include - (n is an integer of 0 or more), ether bonds (-O-), and combinations thereof. Although the epoxy group and the linear siloxane skeleton are close to each other, a dense cured product tends to be obtained when the resin composition is cured, and the cured product has excellent heat resistance (reflow resistance). Therefore, when the epoxy group is bonded to the linear siloxane skeleton via a linking group, the number of atoms between the epoxy group and the linear siloxane skeleton is preferably 4 or less, and more preferably 2 or less.

[0042] 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. When the weight-average molecular weight of component (A2) is within this range, the viscosity of the resin composition becomes appropriate, and the cured product has a good balance of optical properties and heat resistance.

[0043] There are no particular limitations on the amount of functional groups (g / mol) in the component (A2), but from the standpoint 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.

[0044] The content of component (A2) in the resin composition is not particularly limited, but from the viewpoint of achieving a low refractive index and high transparency, it is preferably 1 part by mass or more, more preferably 5 parts by mass or more, even more preferably 10 parts by mass or more, and particularly preferably 20 parts by mass or more, when the total amount of the resin composition is 100 parts by mass. Also, from the viewpoint of improving reflow resistance, the content of component (A2) in the resin composition is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, even more preferably 40 parts by mass or less, and particularly preferably 35 parts by mass or less, when the total amount of the resin composition is 100 parts by mass.

[0045] The component (A2) is preferably a liquid at 25° C., but may be a solid at room temperature. From the viewpoint of preparation and dispensability of the resin composition, the component (A2) preferably has a viscosity at 25° C. of 1 to 500 mPa s, more preferably 2 to 300 mPa s, and particularly preferably 5 to 100 mPa s.

[0046] Examples of when component (A2) is a linear siloxane compound having an epoxy group include a linear siloxane compound having an epoxy group at its terminal. A linear siloxane compound having an epoxy group at its terminal means a compound having an alicyclic epoxy group or a non-alicyclic epoxy group at the terminal of a main chain formed by siloxane bonds. While component (A2) may have an epoxy group at at least one terminal of the main chain, it is preferable that it has an epoxy group at all terminals of the main chain (or at both terminals of the main chain if the main chain is not branched). Component (A2) may have epoxy groups on side chains in addition to the terminals of the main chain, but it is preferable that it has epoxy groups only at the terminals of the main chain. From the viewpoints of optical properties and adhesiveness, it is particularly preferable that component (A2) has a glycidyl ether structure at both terminals.

[0047] As the component (A2), for example, a compound represented by the following general formula (4) can be used.

[0048] [In general formula (4), R ２０ ~R ２３ and R ２５ ~R ２８ R each independently represents an organic group containing a hydrocarbon group or a glycidyl group. １９ and R ２４ each independently represents an organic group containing a glycidyl group; m represents -[Si(R ２１ ) (R ２７ n represents the number of moles of siloxane units represented by —[Si(R )O]— in one molecule, and is a number from 0 to 3000. ２２ ) (R ２６ )O]— in one molecule, and is a number from 0 to 3000.

[0049] When the component (A2) is a linear siloxane compound having an alicyclic epoxy group or a non-alicyclic epoxy group at its terminal, examples of the compound include, but are not limited to, modified silicone oil. Commercially available modified silicone oils include, but are not limited to, modified silicone oils having alicyclic epoxy groups at both ends such as X-22-169B and X-22-169AS, modified silicone oils having epoxy groups at both ends such as X-22-163, KF-105, X-22-163A, X-22-163B, and X-22-163C, modified silicone oils having alicyclic epoxy groups in the side chain such as X-22-2046 and KF-102, modified silicone oils having epoxy groups in the side chain such as X-22-343, KF-101, KF-1001, and X-22-2000, modified silicone oils having epoxy groups in the side chain, and X-22-9002, modified silicone oil having epoxy groups at both ends and in the side chain (all manufactured by Shin-Etsu Chemical Co., Ltd.). It is preferred that component (A2) is a modified silicone oil. The component (A2) may be any one of these, or two or more of them may be used in combination.

[0050] The epoxy equivalent (g / mol) of the linear siloxane compound (A2) is not particularly limited, but from the viewpoint of reactivity, it is preferably 100 to 4,000, more preferably 120 to 2,000, and even more preferably 150 to 1,000.

[0051] The weight-average molecular weight of the linear siloxane compound (A2) is not particularly limited, but is, for example, 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 above range, the viscosity of the composition becomes appropriate, and workability is improved.

[0052] The linear siloxane compound (A2) is preferably a liquid at room temperature (25°C), but may also be a solid. From the viewpoint of workability, the viscosity of the linear siloxane compound (A2) at 25°C is preferably 1 to 500 mPa·s, more preferably 2 to 300 mPa·s, and even more preferably 5 to 100 mPa·s.

[0053] Blending ratio of component (A1) and component (A2) Among the siloxane compounds (A) contained in the resin composition, the cyclic siloxane compound (A1) having a reactive functional group contributes to lowering the refractive index and improving heat resistance. Furthermore, the linear siloxane compound (A2) having a reactive functional group contributes to lowering the refractive index and improving transparency by reducing the crosslink density of the cured product. Therefore, the siloxane compound (A) contains both component (A1) and component (A2). In this case, the ratio (mass ratio) of the siloxane compound (A), component (A1) to component (A2) is preferably 100:0 to 0:100, 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.

[0054] The content of component (A) in the resin composition of this embodiment is preferably 5 to 99 parts by mass, more preferably 10 to 70 parts by mass, even more preferably 20 to 60 parts by mass, and particularly preferably 30 to 50 parts by mass, when the total amount of the resin composition is 100 parts by mass. By setting the content of component (A) within the above range, it is possible to lower the refractive index and improve adhesion.

[0055] (B) Polymerization Initiator The resin composition of this embodiment contains (B) a polymerization initiator (hereinafter also referred to as "component (B)"), and the polymerization initiator (B) contains at least one onium salt selected from the group consisting of onium borate salts and onium gallate salts. As component (B), one type may be used alone, or two or more types may be used in combination.

[0056] The component (B) of this embodiment is a photopolymerization initiator. When the reactive functional group possessed by the component (A) is a cationically polymerizable group, it is preferable to use a photoacid generator as the photopolymerization initiator. The photoacid generator is a compound that generates an acid upon irradiation with active energy rays. The catalytic effect of the acid generated from the photoacid generator causes cationic polymerization to proceed between the cationically polymerizable groups possessed by the component (A). In other words, the component (B) is a compound that generates an acid that cures the components (A1) and (A2) upon irradiation with active energy rays. Here, active energy rays include all light in the broad sense, such as radiation such as α-rays and β-rays, electromagnetic waves such as γ-rays and X-rays, electron beams (EB), ultraviolet rays of about 100 to 400 nm, and visible light of about 400 to 800 nm, with ultraviolet rays being preferred.

[0057] In this embodiment, an onium salt is used as the component (B) from the viewpoint of achieving a low refractive index and excellent heat resistance. The onium salt is a salt compound of an onium ion and an anion. The onium salt undergoes a photoreaction to release a Lewis acid or a Bronsted acid (protonic acid).

[0058] From the viewpoint of achieving a low refractive index and excellent heat resistance, the onium salt preferably contains at least one onium salt selected from the group consisting of onium borates and onium gallates, and in this case, the onium salt preferably contains at least one cation selected from the group consisting of iodonium and sulfonium.

[0059] The onium gallate salt is not particularly limited, but an onium salt represented by the following general formula (1) can be used.

[0060] [In general formula (1), R １ ~R ４ each independently represents an alkyl group having 1 to 18 carbon atoms, an aryl group, or a group having a heterocycle, and R １ ~R ４at least one of is an aryl group, the number of carbon atoms in the aryl group (excluding the number of carbon atoms in the substituent) is 6 to 14, and the aryl group may have a substituent; E represents an element of Group 15 to 17 (IUPAC notation) with a valence of n, and n is an integer of 1 to 3; R ５ is an organic group bonded to E, and R ５ The number of R is n+1, and (n+1) R ５ may be the same or different, and two or more R ５ are directly connected to each other or -O-, -S-, -SO-, -SO ２ A ring structure containing the element E may be formed via -, -NH-, -CO-, -COO-, -CONH-, an alkylene group, or a phenylene group.]

[0061] The onium gallate salt is not particularly limited as long as it has a cation containing a gallium atom. The onium gallate salt may also contain an anion having a tetraphenyl gallate skeleton, and the hydrogen atoms of the phenyl groups in the tetraphenyl gallate skeleton may be substituted with at least one halogen atom selected from the group consisting of fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms. The anion having a tetraphenyl gallate skeleton may be tetrakis(pentafluorophenyl)gallate. The onium gallate salt can be synthesized, for example, according to the method described in JP-A-2017-048325.

[0062] Examples of onium gallate salts include 4-isopropyl-4'-methyldiphenyliodonium tetrakis(pentafluorophenyl)gallate, triarylsulfonium tetrakis(pentafluorophenyl)gallate, diphenyl[4-(phenylthio)phenyl]sulfonium tetrakis(pentafluorophenyl)gallate, and 4-isopropylphenyl(p-tolyl)iodonium tetrakis(pentafluorophenyl)gallate, but are not limited to these compounds.

[0063] The onium borate salt is not particularly limited, but an onium salt represented by the following general formula (2) can be used.

[0064] [In general formula (2), R ６ ~R ９ are each independently an alkyl group having 1 to 18 carbon atoms or Ar, provided that at least one is Ar, and Ar is an aryl group having 6 to 14 carbon atoms (not including the carbon atoms of the following substituents), and some of the hydrogen atoms in the aryl group are replaced with an alkyl group having 1 to 18 carbon atoms, an alkyl group having 1 to 8 carbon atoms substituted with a halogen atom, 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 １１ an alkoxy group or an aryloxy group represented by R １２ an acyl group represented by CO-, R １３ an acyloxy group represented by COO-; １４ an alkylthio group or an arylthio group represented by the formula: １５ R １６ or a halogen atom, １１ ~R １４ is an alkyl group having 1 to 8 carbon atoms or an aryl group having 6 to 14 carbon atoms, R １５ and R １６ is a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or an aryl group having 6 to 14 carbon atoms; E represents an element of Group 15 to 17 (IUPAC notation) with a valence of n, n is an integer of 1 to 3, and R １０ is an organic group bonded to E, and R １０ The number of R is n+1, and (n+1) R １０ may be the same or different, and two or more R １０ are directly connected to each other or -O-, -S-, -SO-, -SO ２ A ring structure containing the element E may be formed via -, -NH-, -CO-, -COO-, -CONH-, an alkylene group, or a phenylene group.]

[0065] The onium borate salt is not particularly limited as long as it has a cation containing a boron atom. The onium borate salt may also contain an anion having a tetraphenylborate skeleton, in which the hydrogen atoms of the phenyl groups in the tetraphenylborate skeleton may be substituted with at least one halogen atom selected from the group consisting of fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms. The anion having the tetraphenylborate skeleton is preferably tetrakis(pentafluorophenyl)borate. The onium borate salt can be synthesized, for example, according to the method described in JP-A-2014-205624.

[0066] Specific examples of the onium borate salt include 4-isopropyl-4'-methyldiphenyliodonium tetrakis(pentafluorophenyl)borate, triarylsulfonium tetrakis(pentafluorophenyl)borate, triphenylsulfonium tetrakis(pentafluorophenyl)borate, triphenylsulfonium tetraphenylborate, 4-t-butylphenyl-diphenylsulfonium tetrakis(pentafluorophenyl)borate, 4-t-butylphenyl-diphenylsulfonium tetraphenylborate, diphenyl[4-(phenylthio)phenyl]sulfonium tetrakis(pentafluorophenyl)borate, diphenyl[4-(phenylthio)phenyl]sulfonium tetraphenylborate, [4-(4-biphenylylthio)phenyl]-4-biphenylylphenylsulfonium tetrakis(pentafluorophenyl)borate, [4-(4-biphenylylthio)phenyl]-4-biphenylylphenylsulfonium tetraphenylborate, (2-methyl)phenyl[4-(4-biphenylylthio)phenyl]4-biphenylylsulfonium sulfonium tetrakis(pentafluorophenyl)borate, (2-methyl)phenyl[4-(4-biphenylylthio)phenyl]4-biphenylylsulfonium tetraphenylborate, [4-(4-biphenylylthio)-3-methylphenyl]4-biphenylylphenylsulfonium tetrakis(pentafluorophenyl)borate, [4-(4-biphenylylthio)-3-methylphenyl]4-biphenylylphenylsulfonium tetraphenylborate, (2-methyl)phenyl[4-(4-biphenylylthio)-3-methylphenyl]

[0033] 4-biphenylylsulfonium tetrakis(pentafluorophenyl)borate, (2-methyl)phenyl[4-(4-biphenylylthio)-3-methylphenyl]4-biphenylylsulfonium tetraphenylborate, (2-methoxy)phenyl[4-(4-biphenylylthio)-3-methoxyphenyl]4-biphenylylsulfonium tetrakis(pentafluorophenyl)borate, (2-methoxy)phenyl[4-(4-biphenylylthio)-3-methoxyphenyl]4-biphenylylsulfonium tetraphenylborate,(2-ethoxy)phenyl[4-(4-biphenylylthio)-3-ethoxyphenyl]4-biphenylylsulfonium tetrakis(pentafluorophenyl)borate, (2-ethoxy)phenyl[4-(4-biphenylylthio)-3-ethoxyphenyl]4-biphenylylsulfonium tetraphenylborate, (2-butoxy)phenyl[4-(4-biphenylylthio)-3-butoxyphenyl]4-biphenylylsulfonium tetrakis(pentafluorophenyl)borate, (2-butoxy)phenyl[4-(4-biphenylylthio)-3 -butoxyphenyl]4-biphenylylsulfonium tetraphenylborate, tris[4-(4-acetylphenylsulfanyl)phenyl]sulfonium tetrakis(pentafluorophenyl)borate, tris[4-(4-acetylphenylsulfanyl)phenyl]sulfonium methanesulfonate, tris[4-(4-acetylphenylsulfanyl)phenyl]sulfonium butanesulfonate, tris[4-(4-acetylphenylsulfanyl)phenyl]sulfonium octanesulfonate, tris[4-(4-acetylphenyl sulfanyl)phenyl]sulfonium tetraphenylborate, tris[4-(4-acetylphenylsulfanyl)phenyl]sulfonium p-toluenesulfonate, tris[4-(4-acetylphenylsulfanyl)phenyl]sulfonium 10-camphorsulfonate, tris[4-(4-acetyl-3-methylphenylthio)phenyl]sulfonium trifluoromethanesulfonate, tris[4-(4-acetyl-3-methylphenylthio)phenyl]sulfonium nonafluorobutanesulfonate, tris[4-(4-acetyl tris[4-(4-acetyl-3-methylphenylthio)phenyl]sulfonium heptadecafluorooctanesulfonate, tris[4-(4-acetyl-3-methylphenylthio)phenyl]sulfonium tetrakis(pentafluorophenyl)borate, tris[4-(4-acetyl-3-methylphenylthio)phenyl]sulfonium methanesulfonate, tris[4-(4-acetyl-3-methylphenylthio)phenyl]sulfonium butanesulfonate, tris[4-(4-acetyl-3-methylphenylthio)phenyl]sulfonium octanesulfonate,Tris[4-(4-acetyl-3-methylphenylthio)phenyl]sulfonium tetraphenylborate, tris[4-(4-acetyl-3-methylphenylthio)phenyl]sulfonium p-toluenesulfonate, tris[4-(4-acetyl-3-methylphenylthio)phenyl]sulfonium 10-camphorsulfonate, tris[4-(4-acetyl-3-ethylphenylthio)phenyl]sulfonium trifluoromethanesulfonate, tris[4-(4-acetyl-3-ethylphenylthio)phenyl]sulfonium )phenyl]sulfonium nonafluorobutanesulfonate, tris[4-(4-acetyl-3-ethylphenylthio)phenyl]sulfonium heptadecafluorooctanesulfonate, tris[4-(4-acetyl-3-ethylphenylthio)phenyl]sulfonium tetrakis(pentafluorophenyl)borate, tris[4-(4-acetyl-3-ethylphenylthio)phenyl]sulfonium methanesulfonate, tris[4-(4-acetyl-3-ethylphenylthio)phenyl]sulfonium butanesulfonate, tris[4-(4-acetyl-3-ethylphenylthio)phenyl]sulfonium octanesulfonate, tris[4-(4-acetyl-3-ethylphenylthio)phenyl]sulfonium tetraphenylborate, tris[4-(4-acetyl-3-ethylphenylthio)phenyl]sulfonium p-toluenesulfonate, tris[4-(4-acetyl-3-ethylphenylthio)phenyl]sulfonium 10-camphorsulfonate, tris[4-(4-acetyl-3-butylphenylthio)phenyl]sulfonium trifluoromethanesulfonate, tris[4-(4-acetyl-3-butylphenylthio)phenyl]sulfonium nonafluorobutanesulfonate, tris[4-(4-acetyl-3-butylphenylthio)phenyl]sulfonium heptadecafluorooctanesulfonate and tris[4-(4-acetyl-3-butylphenylthio)phenyl]sulfonium tetrakis(pentafluorophenyl)borate, but are not limited to these compounds. ,

[0067] The content of component (B) in the resin composition is not particularly limited, but from the viewpoint of polymerizability and achieving a low refractive index and excellent heat resistance of the cured product, it is preferably 0.05 to 30 parts by mass, preferably 0.1 to 20 parts by mass, more preferably 0.2 to 10 parts by mass, and even more preferably 0.3 to 5 parts by mass, per 100 parts by mass of the siloxane compound (A) having a reactive functional group. Note that a smaller amount of component (B) is preferable from the viewpoint of reducing the weight loss rate after the reflow process. When component (A) is a siloxane compound having a reactive functional group, a large amount of component (B) may generate excessive acid, which may accelerate decomposition of the siloxane compound during reflow. Note that the content of component (B) may be appropriately determined taking into consideration various factors, such as the type and properties of the polymerizable compound, the type and dose of active energy rays (if active energy rays are used), the heating temperature, the curing time, the humidity, and the thickness of the resin composition, and is not limited to the above range.

[0068] [Other Optional Components] The resin composition of this embodiment may contain optional components other than the above-described component (A) and component (B), such as the components described below, as necessary, within the scope of this embodiment.

[0069] (C) Inorganic Filler The resin composition of this embodiment may contain (C) an inorganic filler (hereinafter also referred to as "component (C)") as an optional component. The component (C) is not particularly limited as long as it is a granular material formed from an inorganic material. Examples of inorganic materials that can be used include silica, talc, alumina, aluminum nitride, calcium carbonate, aluminum silicate, magnesium silicate, magnesium carbonate, barium sulfate, barium carbonate, lime sulfate, aluminum hydroxide, calcium silicate, potassium titanate, titanium oxide, zinc oxide, silicon carbide, silicon nitride, and boron nitride.

[0070] The component (C) may be used alone or in combination of two or more. From the viewpoint of refractive index, silica particles are preferably used as the component (C). Furthermore, amorphous silica is preferred. The component (C) may be surface-treated with a coupling agent such as a silane coupling agent to prevent aggregation. The shape of the component (C) is not particularly limited and may be spherical, scaly, needle-like, irregular, or the like. However, when a scaly or needle-like inorganic filler is used as a resin composition for an optical adhesive, light may be scattered if the orientation of the inorganic filler is disordered. Therefore, from the viewpoint of refractive index and transmittance, the silica particles are preferably spherical, with a sphericity of 0.8 or more, and more preferably a substantially spherical shape with a sphericity of 0.9 or more.

[0071] The average particle size of component (C) 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. In this specification, unless otherwise specified, average particle size refers to the volume-based median diameter (D50) measured by a laser diffraction scattering method in accordance with ISO-13320 (2020). By setting the average particle size of component (C) to the upper limit or less, transmittance can be increased. While there is no particular restriction on the lower limit of the average particle size of component (C), from the viewpoint of the viscosity of the resin composition, it is preferably 0.1 μm or more, and more preferably 0.2 μm or more. The average particle size of component (C) is preferably 0.1 μm to 5.0 μm, more preferably 0.2 μm to 2.0 μm. Inorganic fillers with different average particle sizes may be used in combination. For example, an inorganic filler with an average particle size of 0.1 μm or more and less than 0.5 μm may be used in combination with an inorganic filler with an average particle size of 0.5 μm to 5.0 μm.

[0072] In addition, when silica is used as an inorganic filler, its manufacturing method is not particularly limited.For example, spherical silica powder obtained by reacting metal silicon with oxygen, spherical silica powder obtained by melting pulverized silica, silica filler obtained by the sol-gel method, precipitation method, aqueous solution wet method can be exemplified.Among these, from the viewpoint of optical properties, silica particles obtained by the sol-gel method, that is, sol-gel silica particles, which have high sphericity and a relatively sharp particle size distribution, are particularly preferred.

[0073] The content of component (C) in the resin composition of this embodiment is preferably 0.1 to 80 parts by mass, more preferably 5 to 70 parts by mass, and even more preferably 10 to 60 parts by mass, when the total amount of the resin composition is 100 parts by mass. By setting the content of component (C) within the above range, it is possible to improve reflow resistance and lower the refractive index.

[0074] (D) Oxetane Compound The resin composition of this embodiment may contain an oxetane compound (D) (hereinafter also referred to as "component (D)") as an optional component. The component (D) is not particularly limited as long as it is a compound containing an oxetane ring. When the resin composition contains component (D), initial adhesion can be improved. However, it is preferable not to contain compounds that may increase the refractive index of the resin composition, such as oxetane compounds having aromatic rings. The blending ratio of component (D) is not particularly limited, but it is preferably 1 to 5 parts by mass when the total amount of the resin composition is 100 parts by mass.

[0075] Examples of the oxetane compound include 3,3'-(oxybismethylene)bis(3-ethyloxetane), 3-ethyl-3-hydroxymethyloxetane, 3-(meth)allyloxymethyl-3-ethyloxetane, (3-ethyl-3-oxetanylmethoxy)methylbenzene, 4-fluoro-[1-(3-ethyl-3-oxetanylmethoxy)methyl]benzene, [1-(3-ethyl-3-oxetanylmethoxy)ethyl]phenyl ether, and isobutyl ether. 2-ethylhexyl (3-ethyl-3-oxetanylmethyl) ether, ethyl diethylene glycol (3-ethyl-3-oxetanylmethyl) ether, tetrahydrofurfuryl (3-ethyl-3-oxetanylmethyl) ether, tetrabromophenyl (3-ethyl-3-oxetanylmethyl) ether, 2-tetrabromophenoxyethyl (3-ethyl-3-oxetanylmethyl) ) ether, pentachlorophenyl (3-ethyl-3-oxetanylmethyl) ether, pentabromophenyl (3-ethyl-3-oxetanylmethyl) ether, ethylene glycose bis(3-ethyl-3-oxetanylmethyl) ether, triethylene glycol bis(3-ethyl-3-oxetanylmethyl) ether, tetraethylene glycol bis(3-ethyl-3-oxetanylmethyl) ether, trimethylolpropane tris(3-ethyl-3-oxetanylmethyl) ether, pentaerythritol tris(3-ethyl-3-oxetanylmethyl) ether, pentaerythritol tetrakis(3-ethyl-3-oxetanylmethyl) ether, dipentaerythritol tetrakis(3-ethyl-3-oxetanylmethyl) ether, ditrimethylolpropane tetrakis(3-ethyl-3-oxetanylmethyl) ether, and the like, but are not limited thereto.

[0076] Commercially available oxetane compounds include, for example, OXT-212, OX-221, OXT-213, and OXT-101 (manufactured by Toagosei Co., Ltd.).

[0077] (E) Other Additives If desired, the resin composition of the present embodiment may further contain other additives, such as a coupling agent, a stabilizer, an ion trapping agent, a leveling agent, an antioxidant, an antifoaming agent, a viscosity modifier, a solvent, etc., within the scope of the present embodiment. The content of each additive can be appropriately selected.

[0078] The method for producing the resin composition of this embodiment is not particularly limited. For example, the resin composition of this embodiment can be obtained by simultaneously or separately introducing component (A), component (B), and, if necessary, component (C), component (D), and component (E) and other additives into an appropriate mixer, and stirring and mixing them while melting them by heating if necessary to form a homogeneous composition. The mixer is not particularly limited, but examples include a Raikai mixer, a Henschel mixer, a three-roll mill, a ball mill, a planetary mixer, and a bead mill equipped with a stirring device and a heating device. These devices may also be used in appropriate combination. The resin composition obtained in this manner is photocurable and thermosetting.

[0079] [Viscosity of Resin Composition] The viscosity of the resin composition of this embodiment is not particularly limited and may be adjusted appropriately depending on the application. For example, the components may be selected and their blending ratios adjusted appropriately so that the viscosity of the resin composition at 25°C is in the range of 0.01 to 1,000 Pa·s. In this specification, unless otherwise specified, viscosity is expressed as a value measured in accordance with Japanese Industrial Standard JIS K6833. Specifically, it can be determined by measuring using an E-type viscometer at a rotation speed of 10 rpm. From the viewpoint of improving injectability, the viscosity of the resin composition at 25°C is preferably 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. If the viscosity of the resin composition is too low, it may not maintain its shape when applied and may flow. If the viscosity of the resin composition is too high, the injectability may be poor or unevenness may occur when the resin composition is applied.

[0080] In addition, the thixotropic index value (TI (Thixotropic Index) value) of the resin composition is preferably 0.5 to 3.0. In this specification, the TI value is the ratio of the viscosity at 5 rpm and 50 rpm measured at 25°C using an E-type viscometer, and is calculated as the viscosity at 5 rpm / the viscosity at 50 rpm. The TI value measures the dependency of viscosity on shear rate (the rotation speed of the viscometer) and is an index representing thixotropy. A Newtonian fluid such as water, whose viscosity does not change even when the shear rate changes, has a TI value of 1. A TI value smaller than 1 indicates that a smaller shear force results in a smaller viscosity than a larger shear force, and a TI value greater than 1 indicates that a smaller shear force results in a larger viscosity than a larger shear force. The larger the TI value, the more thixotropic the resin composition. A TI value of 0.5 to 3.0 improves workability when injecting the resin composition. The resin composition may have thixotropy close to that of a Newtonian fluid with a TI value of 0.8 to 1.2, or may have thixotropy of a non-Newtonian fluid with a thixotropy index of more than 1.2.

[0081] [Cured Product of Resin Composition] The resin composition of this embodiment can be easily cured into a cured product by irradiating it with the above-mentioned active energy rays, preferably light having a wavelength of 10 nm to 600 nm, more preferably ultraviolet light having a wavelength of 100 nm to 500 nm, even more preferably ultraviolet light having a wavelength of 250 nm to 450 nm, and particularly preferably ultraviolet light having a wavelength of 300 nm to 400 nm. When the resin composition of this embodiment is cured by ultraviolet irradiation, the irradiation amount (cumulative light amount) of the ultraviolet light used is 500 to 30,000 mJ / cm. ２ The device used for irradiating ultraviolet light is not particularly limited, and examples thereof include conventionally known devices.

[0082] [Refractive Index, Transmittance, Reflow Resistance, and Weight Loss Rate Before and After Heating of Cured Product] (Refractive Index of Cured Product) The resin composition of this embodiment contains (A) a siloxane compound having a reactive functional group and (B) a polymerization initiator, and the (B) polymerization initiator contains at least one onium salt selected from the group consisting of onium borate salts and onium gallate salts, resulting in excellent optical properties and heat resistance when cured. Specifically, the cured product of the resin composition of this embodiment has a low refractive index, high transparency, and a small weight loss rate after the reflow process. In this case, if the resin composition contains both (A1) a cyclic siloxane compound having a reactive functional group and (A2) a linear siloxane compound having a reactive functional group as the (A) siloxane compound, the cured product will have even better optical properties and heat resistance.

[0083] The cured product of this embodiment may have a refractive index of 1.49 or less at a wavelength of 1310 nm and / or 589 nm at 25°C, preferably 1.48 or less, more preferably 1.47 or less, even more preferably 1.46 or less, or 1.45 or less. The refractive index of the cured product of this embodiment may have a refractive index of 1.40 or more but less than 1.49 at a wavelength of 1310 nm and / or 589 nm at 25°C, 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. Unless otherwise specified, the refractive index herein is expressed as a value measured in accordance with JIS K7142:2014 Method A.

[0084] (Transmittance of Cured Product) The cured product of this embodiment has a transmittance of 80% or more, preferably 85% or more, more preferably 90% or more, and even more preferably 92% or more at 25°C for a thickness of 100 μm and a wavelength of 1310 nm and / or 589 nm. The transmittance of the cured product of this embodiment has a thickness of 100 μm and a wavelength of 1310 nm and / or 589 nm for a thickness of 100 μm and a wavelength of 80 to 99%, preferably 85 to 95%, more preferably 87 to 95%, and even more preferably 90 to 95%.

[0085] (Reflow Resistance of Cured Product) The cured product of the resin composition of this embodiment has excellent heat resistance, particularly excellent reflow resistance, and exhibits a small weight loss rate after the reflow process. In this specification, reflow resistance refers to the ability to withstand thermal shock at a maximum temperature of 260°C for 1 minute. In other words, the cured product of the resin composition of this embodiment has the property of showing little change in physical properties before and after the reflow process (maximum temperature of approximately 260°C) in which electronic components are soldered when mounted. For example, the resin composition of this embodiment has the property of showing little change in adhesive strength before and after the reflow process when cured.

[0086] The reflow resistance of a cured resin composition can be evaluated by the rate of decrease in evaluated adhesive strength. The adhesive strength of the cured product can be measured by any method, as long as it is the same before and after the reflow process. For example, it can be measured by die shear measurement. The die shear strength is measured as follows: (1) A resin composition (sample) is applied to a glass substrate. (2) A Si chip is placed on the applied sample to prepare a test piece. (3) The test piece is irradiated with UV light from the glass substrate side to cure the sample. (4) After the sample is photocured, the die shear strength is immediately measured using a bond tester. This value is taken as the adhesive strength before reflow. (5) Next, the test piece is subjected to a 6-minute heat treatment. The heat treatment involves raising the temperature from room temperature to 170°C, 160°C, 160°C, 260°C, 255°C, and cooling, with each step consisting of 6 steps of 1 minute each. This heat treatment is repeated three times. After the heat treatment, the die shear strength is immediately measured in the same manner as before reflow. This value is the adhesive strength after reflow. (6) The rate of decrease in adhesive strength before and after the reflow process is calculated using the following formula (2). The heat treatment in (5) above simulates the reflow process carried out in the mounting process. The sample before the heat treatment is labeled "before the reflow process," and the sample after the heat treatment is labeled "after the reflow process."

[0087] The smaller the absolute value of the rate of decrease in adhesive strength before and after the reflow process represented by formula (2), the smaller the fluctuation due to heat treatment, and therefore the more preferable. The cured product of the resin composition of this embodiment preferably has an absolute value of the rate of decrease in adhesive strength before and after the reflow process represented by formula (2) of 74% or less, preferably 65% ​​or less, more preferably 55% or less, even more preferably 50% or less, and particularly preferably 40% or less. There is no particular restriction on the lower limit of the absolute value of the rate of decrease in adhesive strength, but it is, for example, 0% or more.

[0088] (Weight loss rate of cured product before and after heating) Furthermore, the cured product of the resin composition of this embodiment has a small weight loss rate before and after heating. Specifically, the absolute value of the weight loss rate of the cured product of the resin composition of this embodiment before and after heating at 260°C, as expressed by the following formula (1), is 16% or less. The method for evaluating the weight loss rate of the cured resin composition is not particularly limited as long as it is the same before and after heating, but it can be measured, for example, by the following method. (1) The resin composition (sample) is applied to a glass substrate. (2) A Si chip is placed on the applied sample to prepare a test piece. (3) The test piece is irradiated with UV light from the glass substrate side to cure the sample. (4) After the sample is photocured, its weight is measured. This value is the weight before heating. (5) Next, the sample is subjected to a heat treatment. The heat treatment involves raising the temperature from room temperature to 260°C, holding it for 6 minutes, and then cooling. After the heat treatment, the weight is promptly measured in the same manner as before heating. This value is the weight after heating. (6) The rate of decrease in adhesive strength before and after heating is calculated using the above formula (1).

[0089] The smaller the weight loss rate before and after heating represented by formula (1), the smaller the fluctuation due to heat treatment, and therefore the more preferable. The cured product of the resin composition of this embodiment preferably has an absolute value of the weight loss rate before and after heating represented by formula (2) of 16% or less, preferably 15% or less, more preferably 13% or less, even more preferably 10% or less, and particularly preferably 5% or less. The lower limit of the absolute value of the weight loss rate is not particularly limited, but is, for example, 0% or more. The resin composition of this embodiment can further reduce the weight loss rate after the reflow process by combining (A) a siloxane compound having a reactive functional group and (B) a polymerization initiator selected from the group consisting of onium borate salts and onium gallate salts.

[0090] [Uses of Resin Composition] The resin composition of this embodiment has excellent optical properties and heat resistance, and therefore can be used for a variety of applications, including but not limited to optical adhesives for bonding optical components. For example, the resin composition of this embodiment can be used as an adhesive or sealant for fixing, bonding, or protecting optical components, electronic components, and semiconductor components, or as a raw material thereof. Examples of optical components that can be used with the resin composition of this embodiment include, but are not limited to, optical fibers, fiber arrays, optical waveguide elements, lenses, filters, diffraction gratings, and optically active elements. Furthermore, the resin composition of this embodiment has excellent optical properties and heat resistance, and therefore can be suitably used, particularly as an optical adhesive for silicon photonics.

[0091] As described below, the resin composition of this embodiment can be used to fix the optical fiber 10 in a groove (V-groove 33) formed in the optical waveguide element 30, or to optically couple the optical fiber 10 to the optical waveguide 32 of the optical waveguide element 30. It is also preferable to use the resin composition of this embodiment to simultaneously fix the optical fiber 10 in the V-groove 33, which is a groove formed in the optical waveguide element 30, and optically couple the optical fiber 10 to the optical waveguide 32 of the optical waveguide element 30.

[0092] For example, the resin composition of the present embodiment may be used in a method for fixing an optical fiber to a groove formed in an optical waveguide element, or a method for optically coupling an optical fiber to an optical waveguide element. The resin composition of the present embodiment may also be used in a method for simultaneously fixing an optical fiber to a groove formed in an optical waveguide element and optically coupling the optical fiber to an optical waveguide element.

[0093] [Optical Fiber Array] The resin composition of this embodiment is preferably used for bonding optical fibers and optical waveguide elements. Specifically, it is preferable to construct an optical fiber array 1 using the resin composition of this embodiment. As shown in FIGS. 1 to 4 , the optical fiber array 1 of this embodiment includes optical fibers 10 and an adhesive layer 20. The optical fibers 10 are covered with a coating 11 and are shown in the form of ribbon fibers 12. In the optical fiber array 1, the optical fibers 10 are optically coupled to the optical waveguides 32 of the optical waveguide element 30 by the adhesive layer 20.

[0094] 1 to 4, the optical fiber array 1 of this embodiment includes a substrate 31 having a V-groove 33 formed therein for accommodating the optical fibers 10, and a presser plate 40 adhesively fixed to the surface of the optical fibers 10, and the optical fibers 10 are adhesively fixed to the V-groove 33 by an adhesive layer 20 (FIGS. 3 and 4). The adhesive layer 20 bonds the optical fibers 10 to the optical waveguide element 30 (FIG. 3), and also bonds the substrate 31 with the optical fibers 10 accommodated in the V-groove 33 to the presser plate 40 (FIG. 4).

[0095] The substrate 31 may be made of, for example, glass, a semiconductor, an organic resin, or the like, with a semiconductor substrate being preferred. The substrate may also have a ball grid array electrode (not shown) on one surface. Providing a ball grid array electrode on one surface of the substrate allows for a high density of multiple electrical interfaces, thereby enabling the miniaturization of silicon photonics devices. The ball grid array electrode is positioned with the expectation that it will be mounted and fixed to another substrate or the like by a reflow process. Therefore, the adhesive layer in the optical fiber array of this embodiment is required to be heat resistant so as to withstand the temperatures and time required during reflow heating.

[0096] The adhesive layer 20 may be formed using the resin composition of this embodiment. That is, the optical fiber array 1 of this embodiment includes an optical fiber 10 and an adhesive layer 20, where the optical fiber 10 is optically path-coupled to the optical waveguide element 30 via the adhesive layer 20, and the adhesive layer 20 may include (A) a siloxane compound having a reactive functional group and (B) a polymerization initiator, where the polymerization initiator (B) includes at least one onium salt selected from the group consisting of onium borate salts and onium gallate salts. In other words, the optical fiber array 1 of this embodiment includes a resin composition including (A) a siloxane compound having a reactive functional group and (B) a polymerization initiator, where the polymerization initiator (B) includes at least one onium salt selected from the group consisting of onium borate salts and onium gallate salts, the optical fiber 10, and the optical waveguide element 30, where the optical fiber 10 is optically path-coupled to the optical waveguide element 30 via the resin composition.

[0097] In this case, the optical fiber array 1 has a substrate 31 in which a V-groove 33 for accommodating the optical fiber 10 is formed, and a pressure plate 40 adhesively fixed to the surface of the optical fiber 10, and the optical fiber 10 is adhesively fixed to the V-groove 33 by an adhesive layer 20, which bonds the optical fiber 10 to the optical waveguide element 30 and also bonds the substrate 31 with the optical fiber 10 accommodated in the V-groove 33 to the pressure plate 40.

[0098] [Optical Waveguide Module] An optical waveguide module 50 (optical waveguide device) may be constructed using the optical fiber array 1 of this embodiment ( FIG. 1 ). The optical waveguide module 50 of this embodiment includes the optical fiber array 1 described above. Specifically, the optical waveguide module 50 of this embodiment includes the optical fiber array 1, an adhesive layer 20, and an optical waveguide element 30, and the optical fiber array 1 is optically coupled to the optical waveguide 32 of the optical waveguide element 30 via the adhesive layer 20. The adhesive layer 20 may be formed using the resin composition of this embodiment. Note that the optical fiber array 1 and the optical waveguide element 30 in the optical waveguide module 50 of this embodiment are not particularly limited as long as they are used in optical integrated circuits. The optical waveguide module 50 of this embodiment may be incorporated as a silicon photonics device.

[0099] [Method for Manufacturing Optical Fiber Array] The method for manufacturing the optical fiber array 1 of this embodiment is a method for manufacturing an optical fiber array 1 in which optical fibers 10 are optically coupled to an optical waveguide element 30 via an adhesive layer 20, the adhesive layer 20 being formed of a cured product of a resin composition containing (A) a siloxane compound having a reactive functional group and (B) a polymerization initiator, the polymerization initiator (B) containing at least one onium salt selected from the group consisting of onium borate salts and onium gallate salts. In this case, the step of fixing the optical fibers 10 in the V-grooves 33 formed in the optical waveguide element 30 and the step of optically coupling the optical fibers 10 to the optical waveguides 32 of the optical waveguide element 30 may be performed separately. Alternatively, in the method for manufacturing the optical fiber array 1 of this embodiment, the step of fixing the optical fibers 10 in the V-grooves 33 formed in the optical waveguide element 30 and the step of optically coupling the optical fibers 10 to the optical waveguides 32 of the optical waveguide element 30 may be performed simultaneously.

[0100] A method for fixing the optical fiber 10 to the optical waveguide element 30 will be described below. Note that this fixing method is merely exemplary, and the present disclosure can be embodied in various forms with various modifications and improvements based on the knowledge of those skilled in the art. First, the optical fiber 10 is fitted into the V-groove 33, and the end of the optical fiber 10 is brought into contact with the side surface on the optical waveguide 32 side. Here, accurate alignment is performed to reduce loss at the connection point between the optical fiber 10 and the optical waveguide 32. Next, the presser plate 40 is placed on the optical fiber 10. Thereafter, a resin composition is dripped into the V-groove 33. Note that the presser plate 40 may be formed integrally with the substrate 31.

[0101] The resin composition dropped into the V-groove 33 permeates, by capillary action, into the gap between the optical fiber 10 and the V-groove 33, along the contact portion between the optical fiber 10 and the presser plate 40, and also into the gap between the optical fiber 10 and the optical waveguide 32. Therefore, in order to enable the resin composition 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, the resin composition needs to be injectable, and the viscosity and TI value of the resin composition need to be set to appropriate values.

[0102] Next, the resin composition is irradiated with ultraviolet light to harden it, 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 presser plate 40. A thermal curing process may be added after the ultraviolet curing process. That is, the adhesive layer 20 in this embodiment can also serve to optically couple the optical fiber 10 to the optical waveguide 32 of the optical waveguide element 30, fix the optical fiber 10 to the V-groove 33, which is a groove portion formed in the optical waveguide element 30, and fix the optical fiber 10 to the presser plate 40. That is, the adhesive layer 20 in this embodiment can simultaneously perform the bonding for optical path coupling and the bonding for V-groove fixation. It is not necessary for the adhesive layer 20 to perform these bonding functions simultaneously. The adhesive layer 20 may be used as an adhesive layer for optically coupling the optical fiber 10 to the optical waveguide 32 of the optical waveguide element 30, or as an adhesive layer for V-groove fixation for fixing the optical fiber 10 to the V-groove 33, which is a groove portion formed in the optical waveguide element 30.

[0103] [Method] As shown in the examples described below, the resin composition of this embodiment combines (A) a siloxane compound having a reactive functional group with (B) a polymerization initiator containing at least one onium salt selected from the group consisting of onium borate salts and onium gallate salts, resulting in excellent optical properties and heat resistance when cured. Therefore, this embodiment provides a method for reducing the refractive index of a cured product of a resin composition (adhesive composition) for adhesives, which includes a step of combining (A) a siloxane compound having a reactive functional group with (B) a polymerization initiator containing at least one onium salt selected from the group consisting of onium borate salts and onium gallate salts. Furthermore, this embodiment provides a method for improving the heat resistance of a cured product of a resin composition (adhesive composition) for adhesives before and after a reflow process, which includes a step of combining (A) a siloxane compound having a reactive functional group with (B) a polymerization initiator containing at least one onium salt selected from the group consisting of onium borate salts and onium gallate salts.

[0104] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples. In the following examples, parts and % represent parts by mass and % by mass unless otherwise specified.

[0105] Synthesis Example 1 Synthesis of Lithium Tetrakis(pentafluorophenyl)gallate 500 mL of ultra-dehydrated diethyl ether and 30 g (121.46 mmol) of pentafluorobromobenzene were placed in a 125 mL four-neck flask thoroughly dried under a nitrogen atmosphere, and the flask was cooled to -78°C using a dry ice / acetone bath. Next, 47.4 mL of a 2.5 mol / L n-butyllithium hexane solution was added dropwise to the flask over 10 minutes and stirred at -78°C for 30 minutes. 49.3 mL of a 0.6 mol / L gallium(III) chloride diethyl ether solution was added dropwise over 10 minutes, and the reaction was carried out with stirring at -78°C for 3 hours. The reaction solution was gradually returned to room temperature while stirring, and then stirred at room temperature for 5 hours. The reaction solution was filtered to remove precipitate, and then concentrated under reduced pressure to obtain a grayish-white product. The product was washed four times with 30 mL of ultra-dehydrated hexane and then dried overnight under vacuum to obtain lithium tetrakis(pentafluorophenyl)gallate.

[0106] Synthesis Example 2: 25 mL of dichloromethane, 1.69 g (5 mmol) of 4-isopropylphenyl(p-tolyl)iodonium chloride, and 4.4 g (6 mmol) of lithium tetrakis(pentafluorophenyl)gallate were added to a 50 mL recovery flask and stirred at room temperature for 2 hours. The reaction solution was filtered to remove the precipitate, and then concentrated under reduced pressure to obtain 4-isopropylphenyl(p-tolyl)iodonium tetrakis(pentafluorophenyl)gallate (B-2).

[0107] Synthesis Example 3 1.6 g (8 mmol) of diphenyl sulfoxide, 1.5 g (8 mmol) of diphenyl sulfide, 2.5 g (24 mmol) of acetic anhydride, 1.5 g (10 mmol) of trifluoromethanesulfonic acid, and 13 g of acetonitrile were uniformly mixed and reacted at 40°C for 6 hours. The reaction solution was cooled to room temperature, poured into 60 g of distilled water, extracted with 60 g of dichloromethane, and washed with water until the pH of the aqueous layer became neutral. The dichloromethane layer was concentrated under reduced pressure to obtain a brown liquid product. 20 g of ethyl acetate was added to the product and dissolved in a 60°C water bath, 60 g of hexane was added, and the mixture was stirred. After cooling to 5°C and allowing to stand for 30 minutes, the supernatant was removed. This procedure was repeated twice to wash the product. The solution containing the washed product was concentrated under reduced pressure to obtain diphenyl[4-(phenylthio)phenyl]sulfonium triflate. This triflate was dissolved in 50 g of dichloromethane and mixed with 66 g of an aqueous solution containing an equimolar amount of lithium tetrakis(pentafluorophenyl)gallate, and the reaction was carried out at room temperature for 3 hours. The dichloromethane layer of the reaction solution was washed twice with water and then concentrated under reduced pressure to obtain diphenyl[4-(phenylthio)phenyl]sulfonium tetrakis(pentafluorophenyl)gallate (B-3).

[0108] [Examples 1 to 14, Comparative Examples 1 and 2] Resin compositions were prepared by mixing predetermined amounts of each component using a three-roll mill according to the formulations shown in Tables 1 to 3. In Tables 1 to 3, the amount of each component is expressed in parts by mass (unit: g). The components used in the examples and comparative examples are as follows.

[0109] (A1) Cyclic siloxane compound (component (A1)) (A1-1) KR-470 (manufactured by Shin-Etsu Chemical Co., Ltd., alicyclic epoxy group, epoxy functional group number 4, viscosity at 25°C 3 Pa s, epoxy equivalent 200 g / mol) represented by the following formula: (A1-2) 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 an alkyl group): (A1-3) X-40-2678 represented by the following formula (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)

[0110] (A2) Linear siloxane compound (component (A2)) (A2-1) Modified silicone oil having 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): (A2-2) The following formula (m=0, R ａ = methyl group, R ｂ = organic group having an epoxy group) 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)

[0111] (B) Polymerization initiator (component (B)) (B-1) As an onium borate salt, 4-isopropyl-4'-methyldiphenyliodonium tetrakis(pentafluorophenyl)borate (product name: PI2074, manufactured by Elkem) (B-2) Onium gallate salt of Synthesis Example 2 (B-3) Onium gallate salt of Synthesis Example 3 (B') Polymerization initiator (for comparative example, not an onium salt) (B-X) Bis[4-n-alkyl(C10-13)phenyl]iodonium hexafluorophosphate

[0112] (C) Inorganic particles (component (C)) (C-1) Spherical silica particles (product name: KE-S30HG, manufactured by Nippon Shokubai Co., Ltd., D50 is 0.3 μm, spherical sol-gel silica particles)

[0113] (D) Oxetane Compound (Component (D)) (D-1) 3,3'-(oxybismethylene)bis(3-ethyloxetane) (product name: OXT-221, manufactured by Toagosei Co., Ltd.)

[0114] (X) Epoxy Compound (X-1) Alicyclic Epoxy (Product Name: 2021P, manufactured by Daicel Chemical Industries, Ltd.)

[0115] [Evaluation of Properties] In the examples and comparative examples, the viscosity of the resin composition and the properties of the cured product obtained by curing the resin composition (refractive index, transmittance, adhesive strength, rate of strength reduction before and after reflow, yellowing after reflow, and rate of weight reduction) were measured as follows.

[0116] (Viscosity of Resin Composition) Using an E-type viscometer manufactured by Toki Sangyo Co., Ltd. (model number: TVE-22H, rotor name: 1°34' x R24) (set to an appropriate measurement range (H, R or U)), the viscosity of the resin composition was measured within 1 hour from its preparation at 25°C with a rotor rotation speed of 10 rpm, and the value was read 1 minute after the start of measurement.

[0117] (Curing of Resin Composition) The curing conditions were a peak wavelength of 365 nm and 30,000 mJ / cm using a UV irradiator with a metal halide lamp light source. ２ After UV irradiation with an integrated light amount of 10 ...

[0118] (Refractive Index) The refractive index at 589 nm of a 100 μm thick cured film prepared from the resin composition was measured using an Abbe refractometer (NAR-2T, manufactured by Atago Co., Ltd.). In addition, the refractive index at 1310 nm of a cured product of the resin composition formed into a film on a glass substrate was measured using a spectroscopic ellipsometer (SE-2000, manufactured by Semilab).

[0119] (Transmittance) The transmittance of a 100 μm thick cured product prepared from the resin composition was measured using an ultraviolet-visible spectrophotometer (V-670, manufactured by JASCO Corporation) at measurement wavelengths of 589 nm and 1310 nm.

[0120] (Reflow Resistance) The adhesive strength of the cured resin composition was measured by die shear measurement. The die shear strength was measured as follows: (1) The prepared resin composition (sample) was applied as an adhesive onto a glass substrate. The application size was 1.5 mm length x 1.5 mm width x 0.5 mm thickness. (2) A 2 mm thick adhesive was applied to the applied sample. ２A Si chip of 1000 mm was placed on the test piece to prepare a test specimen. (3) The test piece was irradiated with UV light from the glass substrate side under the above-mentioned curing conditions to cure the sample. (4) After the sample was photocured, the die shear strength was immediately measured using a universal bond tester (Dage, Series 4000). This value was used as the adhesive strength before reflow. (5) Next, the test piece was subjected to a 6-minute heat treatment. The heat treatment consisted of raising the temperature from room temperature to 170°C, 160°C, 160°C, 260°C, 255°C, and cooling, with each set consisting of six steps of 1 minute each. This heat treatment was repeated three times. After the heat treatment, the die shear strength was immediately measured in the same manner as before reflow. This value was used as the adhesive strength after reflow. (6) The rate of decrease in adhesive strength before and after the reflow process was calculated using the following formula (2):

[0121] (Weight Loss Rate) The weight loss rate of the cured resin composition before and after heating was measured by the following method. (1) The resin composition (sample) was applied onto a glass substrate. The application size was 1.5 mm length x 1.5 mm width x 0.5 mm thickness. (2) A 2 mm thick film was applied onto the applied sample. ２ A Si chip of 1000 nm was placed on the test piece to prepare a test piece. (3) The test piece was irradiated with UV light from the glass substrate side to harden the sample. (4) After the sample was light-hardened, its weight was measured. This value was taken as the weight before heating. (5) Next, the test piece was subjected to a heat treatment. The heat treatment involved raising the temperature from room temperature to 260°C, holding it for 6 minutes, and then cooling. After the heat treatment, the weight was promptly measured in the same manner as before heating. This value was taken as the weight after heating. (6) The weight loss rate before and after heating was calculated using the following formula (1).

[0122] (Yellowing after Reflow) The transmittance of a 100 μm thick cured product after reflow was measured using an ultraviolet-visible spectrophotometer (V-670, manufactured by JASCO Corporation) at measurement wavelengths of 589 nm and 1310 nm.

[0123]

[0124]

[0125]

[0126] [Results] As can be seen from Tables 1 to 3, resin compositions comprising (A) a siloxane compound having a reactive functional group and (B) a polymerization initiator, wherein the polymerization initiator comprises at least one onium salt selected from the group consisting of onium borate salts and onium gallate salts, had a low refractive index, suppressed weight loss even at high temperatures, and exhibited excellent heat resistance. Specifically, the cured products of the resin compositions of Examples 1 to 14 had low refractive indices at 25°C at wavelengths of 1310 nm and 589 nm, and excellent heat resistance, with absolute values ​​of weight loss rates before and after heating at 260°C of 16% or less. Furthermore, the resin compositions of Examples 1 to 14 were found to have excellent injectability due to their low viscosity. Furthermore, the cured products of the resin compositions of Examples 1 to 14 were found to have excellent transparency due to their high transmittance.

[0127] A comparison of Examples 1 to 3 shows that the refractive index and heat resistance can be adjusted by adjusting the blending ratio of the (A1) cyclic siloxane compound and the (A2) linear siloxane compound. Increasing the ratio of the (A1) cyclic siloxane compound improves heat resistance, while increasing the ratio of the (A2) linear siloxane compound decreases the refractive index. A comparison of Examples 1 to 3 with Examples 4 to 6 shows that the inclusion of the (D) oxetane compound increases the adhesive strength before reflow.

[0128] Comparison of Examples 6, 7 to 9, and 13 shows that the refractive index is low and the heat resistance is excellent, regardless of the type of cyclic siloxane compound (A1) (type and number of functional groups).

[0129] A comparison of Examples 7 to 10 shows that the refractive index is low and the heat resistance is excellent regardless of the type of (B) polymerization initiator. A comparison of Examples 7 to 10 shows that when the (B) polymerization initiator is an onium gallate salt, the heat resistance is superior to that of an onium borate salt. A comparison of Examples 4 to 6 shows that a lower content of (B) polymerization initiator relative to the (A) siloxane compound having a reactive functional group results in better heat resistance.

[0130] The resin compositions of Examples 1 to 14 had a transmittance of 63% or more at 1310 nm after reflow, and yellowing was suppressed.

[0131] From Example 13, it can be seen that even when the inorganic filler (C) is not contained, the refractive index is low and the heat resistance is excellent.

[0132] In Comparative Example 1, the polymerization initiator (B) was not an onium salt, but the absolute value of the weight loss rate before and after heating at 260°C was 18.6%, indicating poor heat resistance. Comparative Example 2 did not contain the siloxane compound (A) having a reactive functional group, but the refractive index was high. Furthermore, when comparing Comparative Example 2 with Example 8, Example 8, which used a siloxane compound having a reactive functional group as component (A), had a smaller weight loss rate than Comparative Example 2, which used an alicyclic epoxy. In other words, it can be seen that the weight loss rate after the reflow process can be further reduced by combining the siloxane compound (A) having a reactive functional group and the polymerization initiator (B).

[0133] The resin composition of the present invention has a low refractive index, a small weight loss rate after a reflow process, and good heat resistance, making it useful as an adhesive, and is particularly useful as an adhesive for optical components. Furthermore, the resin composition of the present invention can achieve a low refractive index without containing a fluorine compound, making it useful as an optical adhesive from an environmental perspective.

[0134] REFERENCE SIGNS LIST 1 Optical fiber array 10 Optical fiber 11 Coating 12 Ribbon fiber 20 Adhesive layer 30 Optical waveguide element 31 Substrate 32 Optical waveguide 33 V-groove (groove portion) 40 Pressing plate 50 Optical waveguide module (optical waveguide device)

Claims

1. A resin composition for use as an adhesive, comprising: (A) a siloxane compound having a reactive functional group; and (B) a polymerization initiator, wherein the polymerization initiator (B) contains at least one onium salt selected from the group consisting of onium borate salts and onium gallate salts.

2. The resin composition according to claim 1, wherein the onium salt contains at least one cation selected from the group consisting of iodonium and sulfonium.

3. The resin composition according to claim 1 or 2, wherein the onium gallate salt is an onium salt represented by the following general formula (1): [In general formula (1), R １ ~R ４ each independently represents an alkyl group having 1 to 18 carbon atoms, an aryl group, or a group having a heterocycle; R １ ~R ４ at least one of is an aryl group, the number of carbon atoms in the aryl group (excluding the number of carbon atoms in the substituent) is 6 to 14, and the aryl group may have a substituent; E represents an element of Group 15 to 17 (IUPAC notation) with a valence of n, n is an integer of 1 to 3; R ５ is an organic group bonded to E, R ５ The number of R is n+1, and (n+1) R ５ may be the same or different, and two or more R ５ are mutually directly or -O-, -S-, -SO-, -SO ２ A ring structure containing the element E may be formed via -, -NH-, -CO-, -COO-, -CONH-, an alkylene group or a phenylene group.] 4. The resin composition according to claim 1 or 2, wherein the onium borate salt is an onium salt represented by the following general formula (2): [In general formula (2), R ６ ~R ９ are each independently an alkyl group having 1 to 18 carbon atoms or Ar, provided that at least one of them is Ar, and Ar is an aryl group having 6 to 14 carbon atoms (not including the carbon number of the following substituents), and some of the hydrogen atoms in the aryl group are selected from an alkyl group having 1 to 18 carbon atoms, an alkyl group having 1 to 8 carbon atoms substituted with a halogen atom, 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 １１ an alkoxy group or an aryloxy group represented by the formula: １２ an acyl group represented by CO-; １３ an acyloxy group represented by COO-; １４ an alkylthio group or an arylthio group represented by the formula: １５ R １６ or a halogen atom; １１ ~R １４ is an alkyl group having 1 to 8 carbon atoms or an aryl group having 6 to 14 carbon atoms, R １５ and R １６ is a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or an aryl group having 6 to 14 carbon atoms; E represents an element of Group 15 to Group 17 (IUPAC notation) with a valence of n, n is an integer of 1 to 3, R １０ is an organic group bonded to E, R １０ The number of R is n+1, and (n+1) R １０ may be the same or different, and two or more R １０ are mutually directly or -O-, -S-, -SO-, -SO ２ A ring structure containing the element E may be formed via -, -NH-, -CO-, -COO-, -CONH-, an alkylene group or a phenylene group.] 5. A resin composition described in any one of claims 1 to 4, wherein the content of the (B) polymerization initiator is 0.3 to 20.0 parts by mass per 100 parts by mass of the (A) siloxane compound having a reactive functional group.

6. The resin composition according to any one of claims 1 to 5, 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.

7. The resin composition according to any one of claims 1 to 6, further comprising (C) an inorganic filler.

8. The resin composition according to any one of claims 1 to 7, further comprising (D) an oxetane.

9. A cured product of the resin composition according to any one of claims 1 to 8.

10. The cured product according to claim 9, having a refractive index of 1.47 or less at a wavelength of 1,310 nm.

11. The cured product according to claim 9 or 10, wherein the cured product has a thickness of 100 μm and a transmittance of 85% or more at a wavelength of 1,310 nm.

12. The cured product according to any one of claims 9 to 11, in which the absolute value of the weight loss rate before and after heating at 260°C, as represented by the following formula (1), is 16% or less.

13. The resin composition according to any one of claims 1 to 8, which is used for fixing an optical fiber in a groove formed in an optical waveguide element.

14. The resin composition according to any one of claims 1 to 8, which is used for optically coupling an optical fiber to an optical waveguide element.

15. A resin composition according to any one of claims 1 to 8, which is used to simultaneously fix an optical fiber to a groove formed in an optical waveguide element and optically couple the optical fiber to the optical waveguide element.

16. An optical fiber array comprising: a resin composition according to any one of claims 1 to 15; an optical fiber; and an optical waveguide element, wherein the optical fiber is optically coupled to the optical waveguide element via the resin composition.

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