Resin composition

Abstract

The present invention provides: a resin composition with which it is possible to manufacture an optical waveguide having a small optical transmission loss without performing a development step during the formation of a core layer of the optical waveguide; a resin sheet which contains the resin composition; an optical waveguide which comprises a cured product of the resin composition; a method for manufacturing the optical waveguide; and an opto-electric hybrid substrate which is provided with the optical waveguide. Disclosed is a resin composition which contains (A) an epoxy resin, (B) a compound that has a (meth)acryloyl group, and (C) a photoradical generator. The resin composition satisfies the relationship of n(A) < n(B), where n(A) is the refractive index of a cured product of the component (A) at the wavelength of 1,310 nm (in cases where the resin composition contains two or more types of components (A), it is the weighted average value of the refractive indexes of respective cured products of the components (A) based on the mass ratio), and n(B) is the refractive index of a cured product of the component (B) at the wavelength of 1,310 nm (in cases where the resin composition contains two or more types of components (B), it is the weighted average value of the refractive indexes of respective cured products of the components (B) based on the mass ratio).

Description

resin composition

[0001] The present invention relates to a resin composition, and further to a resin sheet, an optical waveguide, a method for manufacturing an optical waveguide, and an optical-electrical hybrid board.

[0002] Technological advances such as 5G communications, autonomous driving, IoT, artificial intelligence, and big data are driving demands for ultra-high-speed and high-capacity communications. Semiconductor packages, which underpin these advances, have traditionally supported high-speed communications by passing high-frequency currents through them. However, in recent years, issues such as noise generation, communication loss, and heat generation due to high-speed communications have become apparent. To address these issues, active efforts have been made in recent years to implement optical circuits on electrical wiring boards to achieve energy-saving, low-latency, and high-speed communications (Patent Documents 1 and 2).

[0003] JP 2007-500365 A JP 2010-90328 A

[0004] Research into the introduction of silicon photonics is being actively conducted, particularly in data centers where high-speed transmission is required. Silicon photonics is highly compatible with conventional LSI manufacturing processes. Therefore, it is expected that the use of silicon photonics will enable the formation of nanometer-sized thin-wire waveguides at low cost, based on the technology cultivated in electronic circuit integration technology.

[0005] For example, silicon photonics is expected to enable the formation of optical integrated circuits on chips using thin-wire waveguides. When manufacturing an optoelectronic hybrid substrate equipped with such a chip, an optical waveguide is required on the optoelectronic hybrid substrate in order to extract signal light from the thin-wire waveguide within the chip to the outside of the chip and connect it to the wiring between chips. Generally, forming the core layer of the optical waveguide includes a development process. However, optical waveguides that include a development process for forming the core layer can have high optical transmission loss. Specifically, optical waveguides that include a development process for forming the core layer can have high optical transmission loss because: (1) the development process generates unevenness on the surface of the core layer, which scatters light; and (2) the development process increases the exposed surface of the core layer, which makes it easier for foreign matter to adhere to such exposed surface, resulting in light scattering by the foreign matter.

[0006] The present invention has been made in view of the above, and aims to provide a resin composition that can produce an optical waveguide with low optical transmission loss without performing a development step in forming the core layer of the optical waveguide; a resin sheet containing the resin composition; an optical waveguide that includes a cured product of the resin composition; a method for producing the optical waveguide; and an optical-electrical hybrid board that includes the optical waveguide.

[0007] The present inventors have conducted extensive research to solve the above-mentioned problems. As a result, the present inventors have discovered a resin composition comprising (A) an epoxy resin, (B) a compound having a (meth)acryloyl group, and (C) a photoradical generator, in which the refractive index of a cured product of the component (A) at a wavelength of 1310 nm (when the resin composition contains two or more types of the component (A)), is n （Ａ） The refractive index of the cured product of the (B) component (when the resin composition contains two or more (B) components, the weighted average value of the refractive indexes of the cured products of the (B) components based on the mass ratio) is n （Ｂ） In this case, n （Ａ） <n （Ｂ） The inventors have found that the above-mentioned problems can be solved by using a resin composition that satisfies the following relationship, and have completed the present invention.

[0008] <1> A resin composition comprising (A) an epoxy resin, (B) a compound having a (meth)acryloyl group, and (C) a photoradical generator, wherein the refractive index of a cured product of the component (A) at a wavelength of 1,310 nm (when the resin composition contains two or more types of component (A)), is n （Ａ） The refractive index of the cured product of the (B) component (when the resin composition contains two or more (B) components, the weighted average value of the refractive indexes of the cured products of the (B) components based on the mass ratio) is n （Ｂ） In this case, n （Ａ） <n （Ｂ）<2> The resin composition according to <1>, wherein the component (A) contains an epoxy resin having one or more skeletons selected from the group consisting of an alicyclic skeleton and a siloxane skeleton. <3> The refractive index n of a cured product of the component (A) at a wavelength of 1,310 nm satisfies the relationship: （Ａ） and the refractive index n of the cured product of component (B). （Ｂ－１） The difference in refractive index of the cured product is n （Ｂ） -n （Ａ） The resin composition according to <1> or <2>, wherein the content of the component (A) in the non-volatile components in the resin composition is M （Ａ） (mass%), and the content of component (B) is M （Ｂ） (mass%), the mass ratio M （Ｂ） / M （Ａ） is 0.01 or more and 5 or less. <5> The resin composition according to any one of <1> to <4>, wherein the molecular weight of the component (B) (weight average molecular weight (Mw) when the molecular weight has a distribution) is 3,000 or less. <6> The resin composition according to any one of <1> to <5>, wherein the component (B) contains one or more compounds selected from the group consisting of (B-1) a compound having a molecular weight (weight average molecular weight (Mw) when the molecular weight has a distribution) of 300 or less, and (B-2) a compound having a viscosity of 1,000 mPa s or less at 25°C. <7> The resin composition according to any one of <1> to <6>, wherein the component (B) contains (B-3) a compound having two or more (meth)acryloyl groups. <8> The resin composition further contains (D) a compound having a carboxyl group and an ethylenically unsaturated bond, and the refractive index of a cured product of the component (D) at a wavelength of 1,310 nm (when the resin composition contains two or more types of component (D)), is a weighted average of the refractive indexes of the cured products of the respective components (D) based on the mass ratio) is n （Ｄ） In this case, n （Ｄ） ≦n （Ｂ）The resin composition according to any one of <1> to <7>, which satisfies the following relationship. <9> The resin composition according to any one of <1> to <8>, further comprising (E) a thermal curing accelerator. <10> The resin composition according to any one of <1> to <9>, which is used for producing an optical waveguide capable of transmitting light having a wavelength of 1,300 nm to 1,320 nm. <11> A resin sheet comprising a support and a resin composition layer formed on the support, wherein the resin composition layer comprises the resin composition according to any one of <1> to <10>. <12> An optical waveguide comprising a core layer and a clad layer, wherein the core layer and the clad layer each comprise a cured product of the resin composition according to any one of <1> to <10>. <13> The optical waveguide according to <12>, which is capable of transmitting light having a wavelength of 1,300 nm to 1,320 nm. <14> The optical waveguide according to <13>, characterized in that the content (B)core of the cured product of the (B) component in the core layer is greater than the content (B)clad of the cured product of the (B) component in the clad layer. <15> An optical-electrical hybrid board comprising the optical waveguide according to any one of <12> to <14>. <16> A method for producing an optical waveguide, comprising, in this order: forming a first resin composition layer; curing the first resin composition layer; forming a second resin composition layer on the first resin composition layer; exposing a portion of the second resin composition layer; forming a third resin composition layer on the second resin composition layer; and curing another portion of the second resin composition layer and the third resin composition layer, wherein the first resin composition layer, the second resin composition layer, and the third resin composition layer each contain the resin composition according to any one of <1> to <10>. <17> The manufacturing method according to <16>, wherein in the step of subjecting a part of the second resin composition layer to an exposure treatment, an exposed part of the second resin composition layer forms a core layer of an optical waveguide, and a non-exposed part of the second resin composition layer forms a clad layer of the optical waveguide.<18> The manufacturing method according to <16> or <17>, wherein, in the step of subjecting a part of the second resin composition layer to an exposure treatment, a content (B)exposed of components derived from the component (B) in an exposed part is larger than a content (B)unexposed of components derived from the component (B) in a non-exposed part.

[0009] According to the present invention, it is possible to provide a resin composition that can produce an optical waveguide with low optical transmission loss without performing a development step in forming the core layer of the optical waveguide; a resin sheet containing the resin composition; an optical waveguide that includes a cured product of the resin composition; a method for producing the optical waveguide; and an opto-electrical hybrid board that includes the optical waveguide.

[0010] FIG. 1 is a perspective view schematically illustrating an optical waveguide manufactured by a manufacturing method of the present invention. FIG. 2 is a schematic cross-sectional view illustrating step (1) of a method for manufacturing an optical waveguide according to an embodiment of the present invention. FIG. 3 is a schematic cross-sectional view illustrating step (2-1) of a method for manufacturing an optical waveguide according to an embodiment of the present invention. FIG. 4 is a schematic cross-sectional view illustrating step (2-2) of a method for manufacturing an optical waveguide according to an embodiment of the present invention. FIG. 5 is a schematic cross-sectional view illustrating step (3) of a method for manufacturing an optical waveguide according to an embodiment of the present invention. FIG. 6 is a schematic cross-sectional view illustrating a portion of step (4) of a method for manufacturing an optical waveguide according to an embodiment of the present invention. FIG. 7 is a schematic cross-sectional view illustrating a portion of step (4) of a method for manufacturing an optical waveguide according to an embodiment of the present invention. FIG. 8 is a schematic cross-sectional view illustrating step (5) of a method for manufacturing an optical waveguide according to an embodiment of the present invention. FIG. 9 is a schematic cross-sectional view illustrating step (6-1) of a method for manufacturing an optical waveguide according to an embodiment of the present invention. FIG. 10 is a schematic cross-sectional view illustrating step (6-2) of a method for manufacturing an optical waveguide according to an embodiment of the present invention. FIG. 11 is a schematic cross-sectional view for explaining step (6) of the method for manufacturing an optical waveguide according to one embodiment of the present invention.

[0011] The present invention will be described in detail below with reference to embodiments and examples. However, the present invention is not limited to the following embodiments and examples, and can be implemented with any modifications within the scope of the claims of the present invention and their equivalents.

[0012] [Explanation of Terms] In this specification, the term "(meth)acryloyl group" includes an acryloyl group, a methacryloyl group, and a combination thereof. The term "(meth)acrylate compound" refers to a compound having a (meth)acryloyl group, and includes an acrylate compound, a methacrylate compound, and a combination thereof. However, (meth)acrylate compounds do not include (meth)acrylic acid. The term "(meth)acrylic acid" includes acrylic acid, methacrylic acid, and a combination thereof.

[0013] As used herein, the term "aromatic group" refers to a group obtained by removing one or more hydrogen atoms from an aromatic compound. Specifically, an n-valent aromatic group refers to a group obtained by removing n hydrogen atoms from an aromatic compound. Here, the aromatic compound may be a heteroatom-free aromatic compound composed only of carbon atoms and hydrogen atoms, or a heteroatom-containing aromatic compound composed of carbon atoms, hydrogen atoms, and heteroatoms. As used herein, the term "aromatic compound" refers to a compound containing an aromatic ring. Furthermore, as used herein, the term "aromatic ring" refers to a ring that conforms to the Hückel rule, in which the number of electrons contained in the π-electron system on the ring is 4p + 2 (p is an integer of 1 or greater), and includes monocyclic aromatic rings and fused polycyclic aromatic rings in which two or more monocyclic aromatic rings are fused together. The aromatic ring may be an aromatic carbocycle having only carbon atoms as ring-constituting atoms, or an aromatic heterocycle having, in addition to carbon atoms, heteroatoms such as oxygen, nitrogen, or sulfur atoms as ring-constituting atoms. In this specification, unless otherwise specified, the number of carbon atoms in the aromatic ring is preferably 3 or more, more preferably 4 or more or 5 or more, and even more preferably 6 or more, and the upper limit is preferably 24 or less, more preferably 18 or less or 14 or less, and even more preferably 10 or less. The number of carbon atoms does not include the number of carbon atoms of substituents.

[0014] In this specification, the term "non-volatile components" in relation to the resin composition refers to components constituting the resin composition other than the (G) organic solvent, which will be described later.

[0015] [Resin Composition] The resin composition of the present invention comprises (A) an epoxy resin, (B) a compound having a (meth)acryloyl group, and (C) a photoradical generator. The resin composition of the present invention also has a refractive index of a cured product of the component (A) at a wavelength of 1310 nm that is n （Ａ） The refractive index of the cured product of component (B) is n （Ｂ） In this case, n （Ａ） <n （Ｂ） Hereinafter, the component (B) may be referred to as the "high refractive index component (B)."

[0016] As mentioned above, conventional techniques generally include a development step when forming a core layer of an optical waveguide. However, optical waveguides that include a development step in the formation of the core layer sometimes suffer from increased optical transmission loss. In contrast, the resin composition of the present invention, which contains a combination of the above-mentioned components (A) to (C), can be subjected to an exposure treatment to create a refractive index difference between the exposed and unexposed regions, thereby forming a core layer without the need for a development step. Specifically, by subjecting the resin composition to a selective exposure treatment, the exposed regions exhibit a higher refractive index than the unexposed regions, making it possible to use the exposed regions as the core layer and the unexposed regions as the cladding layer. The reason why the exposed regions exhibit a higher refractive index than the unexposed regions in the resin composition of the present invention is presumed to be as follows: That is, during the exposure treatment, the curing reaction by radical polymerization progresses in the exposed regions, consuming the (B) high-refractive-index component (monomer), and reducing its content (concentration). As a result, a difference (gradient) in the concentration of the (B) high refractive index component occurs between the exposed and non-exposed areas, and this concentration difference serves as a driving force for the diffusion of the (B) high refractive index component present in the non-exposed areas into the exposed areas (hereinafter, this phenomenon is also referred to as "monomer diffusion"). Thus, in the exposed areas, in addition to the cured product of the (B) high refractive index component, the (B) high refractive index component (monomer) that has diffused from the surrounding non-exposed areas is present, resulting in a relatively higher refractive index compared to the surrounding non-exposed areas. Furthermore, in the non-exposed areas, the high refractive index component (B) moves to the exposed areas due to monomer diffusion, resulting in a relatively lower refractive index compared to the exposed areas. In particular, since the curing reaction by radical polymerization has a higher reaction rate than the curing reaction by cationic polymerization, a difference in the concentration of the (B) high refractive index component between the exposed and non-exposed areas is likely to occur, and a difference in refractive index between the exposed and non-exposed areas is likely to occur. In this way, the resin composition of the present invention, which can form the core layer of an optical waveguide using monomer diffusion and a curing reaction by radical polymerization, makes it possible to form the core layer without the need for a development step, and significantly contributes to the production of optical waveguides with low optical transmission loss.

[0017] As described below, the resin composition of the present invention may further contain (D) a compound having a carboxyl group and an ethylenically unsaturated bond (hereinafter, sometimes referred to as "component (D)"). When such component (D) is contained, the curing reaction of the resin composition progresses in the exposed area, and the component (D) is also consumed. Therefore, a difference in the concentration of component (D) occurs between the exposed area and the non-exposed area, but the component (D) has a larger molecular weight than the high refractive index component (monomer) (B), and is therefore less likely to diffuse into the exposed area than the high refractive index component (B). In this way, it is believed that diffusion into the exposed area due to the exposure treatment occurs selectively and specifically in the high refractive index component (B).

[0018] The resin composition of the present invention may further contain, as optional components, (D) a compound having a carboxyl group and an ethylenically unsaturated bond, (E) a heat curing accelerator, (F) other additives, and (I) a solvent. Each component contained in the resin composition of the present invention will be described in detail below.

[0019] <(A) Epoxy Resin> The resin composition of the present invention contains (A) an epoxy resin as component (A). The epoxy resin refers to a curable resin having an epoxy group. The (A) epoxy resin may be used alone or in combination of two or more types.

[0020] Examples of epoxy resins include bisphenol-type epoxy resins, dicyclopentadiene-type epoxy resins, trisphenol-type epoxy resins, naphthol novolac-type epoxy resins, phenol novolac-type epoxy resins, tert-butyl-catechol-type epoxy resins, naphthalene-type epoxy resins, naphthol-type epoxy resins, anthracene-type epoxy resins, glycidylamine-type epoxy resins, glycidyl ester-type epoxy resins, cresol novolac-type epoxy resins, biphenyl-type epoxy resins, linear aliphatic epoxy resins, epoxy resins having a butadiene structure, alicyclic epoxy resins, heterocyclic epoxy resins, spiro ring-containing epoxy resins, siloxane skeleton-containing epoxy resins, cyclohexane-type epoxy resins, cyclohexanedimethanol-type epoxy resins, naphthylene ether-type epoxy resins, trimethylol-type epoxy resins, and tetraphenylethane-type epoxy resins. Bisphenol-type epoxy resins refer to epoxy resins having a bisphenol structure, such as bisphenol A-type epoxy resins, bisphenol F-type epoxy resins, bisphenol S-type epoxy resins, and bisphenol AF-type epoxy resins. Biphenyl-type epoxy resin refers to an epoxy resin having a biphenyl structure, where the biphenyl structure may have a substituent such as an alkyl group, an alkoxy group, an aryl group, etc. Therefore, bixylenol-type epoxy resins and biphenylaralkyl-type epoxy resins are also included in biphenyl-type epoxy resins.

[0021] The component (A) preferably contains an epoxy resin having one or more skeletons selected from the group consisting of an alicyclic skeleton and a siloxane skeleton.

[0022] In the present invention, the term "alicyclic skeleton" refers to a non-aromatic ring. The alicyclic skeleton may have a substituent at a substitutable position. The alicyclic skeleton may be a saturated ring consisting of only single bonds, or a non-aromatic unsaturated ring having either a double bond or a triple bond, and among these, the alicyclic skeleton is preferably a saturated ring consisting of only single bonds. The saturated ring may be a saturated carbocyclic ring having carbon atoms as ring-constituting atoms, or a saturated heterocyclic ring having heteroatoms such as oxygen atoms, nitrogen atoms, and sulfur atoms as ring-constituting atoms in addition to carbon atoms.

[0023] The saturated ring is preferably a saturated ring having 3 to 18 carbon atoms, more preferably a saturated ring having 5 to 16 carbon atoms. Examples of the saturated ring include monocyclic saturated carbocyclic rings such as monocycloalkane rings such as a cyclobutane ring, a cyclopentane ring, a cyclohexane ring, a cycloheptane ring, a cyclooctane ring, a cyclononane ring, a cyclodecane ring, a cycloundecane ring, and a cyclododecane ring; bicyclic saturated carbocyclic rings such as a bicyclo[2.2.1]heptane ring (norbornane ring), a bicyclo[4.4.0]decane ring (decalin ring), a bicyclo[5.3.0]decane ring, a bicyclo[4.3.0]nonane ring (hydrindane ring), a bicyclo[3.2.1]octane ring, a bicyclo[5.4.0]undecane ring, a bicyclo[3.3.0]octane ring, and a bicyclo[3.3.1]nonane ring; ２，６ ] decane ring (tetrahydrodicyclopentadiene ring), tricyclo[3.3.1.1 ３，７ ] decane ring (adamantane ring), tricyclo[6.2.1.0 ２，７ ]undecane ring and other saturated tricyclic carbocyclic rings; tetracyclo[6.2.1.1 ３，６ .0 ２，７ tetracyclic saturated carbocyclic rings such as a dodecane ring; pentacyclo[9.2.1.1 ４，７ .0 ２，１ 0.0 ３，８ ] pentadecane ring, pentacyclo[6.5.1.1 ３，６ .0 ２，７ .0 ９，１３ saturated carbocyclic rings such as a five-ring saturated carbocyclic ring such as a pentadecane ring (tetrahydrotricyclopentadiene ring); saturated monocyclic heterocyclic rings such as a pyrrolidine ring, a pyrazolidine ring, an imidazolidine ring, a tetrahydrofuran ring, a 1,3-dioxolane ring, a piperidine ring, a piperazine ring, a tetrahydropyran ring, a 1,3-dioxane ring, a 1,4-dioxane ring, a thiane ring, a 1,3-dithiane ring, a 1,4-dithiane ring, a morpholine ring, a thiomorpholine ring, an oxazolidine ring; saturated bicyclic heterocyclic rings such as a 7-oxabicyclo[4.1.0]heptane ring (1,2-epoxycyclohexane ring), a 1-azabicyclo[2.2.2]octane (quinuclidine ring), a decahydroquinoline ring, a decahydroisoquinoline ring; saturated bicyclic heterocyclic rings such as a 1-azatricyclo[3.3.1.1３，７ ]decane (1-azaadamantane ring), 2-azatricyclo[3.3.1.1 ３，７ ] decane (2-azaadamantane ring) and other saturated heterocyclic rings such as tricyclic saturated heterocyclic rings.

[0024] In component (A), the alicyclic skeleton is preferably a saturated carbocyclic ring, more preferably a monocyclic saturated carbocyclic ring, and even more preferably a cyclohexane ring.

[0025] When component (A) has an alicyclic skeleton, the epoxy group may be bonded directly to the alicyclic skeleton, or may be bonded via a linker structure having 1 to 100 skeletal atoms selected from the group consisting of carbon atoms, oxygen atoms, sulfur atoms, and nitrogen atoms. Component (A) may also have an epoxy group in which oxygen atoms are attached to two carbon atoms that constitute the alicyclic skeleton (alicyclic epoxy group).

[0026] When component (A) has two or more alicyclic skeletons in one molecule, the alicyclic skeletons may be the same or different.

[0027] In the present invention, the term "siloxane skeleton" refers to a skeleton having a siloxane (Si-O-Si) bond, and may be a cyclic siloxane skeleton or a chain siloxane skeleton. The siloxane skeleton may have a substituent at a substitutable position.

[0028] The number of silicon atoms forming siloxane bonds in the siloxane skeleton is not particularly limited, but is preferably 3 or more in one molecule of an epoxy resin having a siloxane skeleton, and the upper limit is not particularly limited, but may be, for example, 20 or less, 15 or less, 10 or less, 8 or less, 6 or less, etc. Examples of siloxane skeletons include linear siloxane skeletons such as a substituted or unsubstituted trisiloxane skeleton, a substituted or unsubstituted tetrasiloxane skeleton, and a substituted or unsubstituted pentasiloxane skeleton; and cyclic siloxane skeletons such as a substituted or unsubstituted cyclotetrasiloxane skeleton, a substituted or unsubstituted cyclopentasiloxane skeleton, and a substituted or unsubstituted cyclohexasiloxane skeleton.

[0029] When component (A) has a siloxane skeleton, the epoxy group may be bonded directly to the siloxane skeleton, or may be bonded via a linker structure having 1 to 100 skeleton atoms selected from the group consisting of carbon atoms, oxygen atoms, sulfur atoms, and nitrogen atoms.

[0030] When component (A) has two or more siloxane skeletons in one molecule, the siloxane skeletons may be the same or different.

[0031] As described above, component (A) preferably contains an epoxy resin having one or more skeletons selected from the group consisting of an alicyclic skeleton and a siloxane skeleton. Of these two skeletons, the component (A) may contain an epoxy resin having only an alicyclic skeleton, an epoxy resin having only a siloxane skeleton, or an epoxy resin having both an alicyclic skeleton and a siloxane skeleton. Furthermore, the substituents that the alicyclic skeleton or siloxane skeleton may have are not particularly limited as long as they do not impair the effects of the present invention, and examples include alkyl groups, alkoxy groups, aryl groups, aryloxy groups, and halogen atoms. The alkyl groups used as substituents may be linear or branched, and the number of carbon atoms in the alkyl groups is preferably 1 to 12, more preferably 1 to 6, and even more preferably 1 to 3. The alkoxy groups used as substituents may be linear or branched, and the number of carbon atoms in the alkoxy groups is preferably 1 to 12, more preferably 1 to 6. The aryl group used as a substituent is a group in which one hydrogen atom on the aromatic ring has been removed from an aromatic hydrocarbon, and the number of carbon atoms therein is preferably 6 to 14, more preferably 6 to 10. The number of carbon atoms in the aryloxy group used as a substituent is preferably 6 to 14, more preferably 6 to 10. Examples of halogen atoms used as a substituent include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0032] Component (A) preferably has two or more epoxy groups per molecule. When the total amount of component (A) is taken as 100% by mass, the proportion of epoxy resins having two or more epoxy groups per molecule is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, and is usually 100% by mass or less.

[0033] Epoxy resins include those that are liquid at a temperature of 20°C (hereinafter referred to as "liquid epoxy resins") and those that are solid at a temperature of 20°C (hereinafter referred to as "solid epoxy resins").

[0034] The liquid epoxy resin is preferably a liquid epoxy resin having two or more epoxy groups in one molecule.

[0035] Preferred liquid epoxy resins include bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol AF type epoxy resins, naphthalene type epoxy resins, glycidyl ester type epoxy resins, glycidyl amine type epoxy resins, phenol novolac type epoxy resins, alicyclic epoxy resins such as alicyclic epoxy resins having an ester skeleton, cyclohexane type epoxy resins, cyclohexane dimethanol type epoxy resins, and epoxy resins having a butadiene structure.

[0036] Specific examples of liquid epoxy resins include "HP-4032", "HP-4032-D", and "HP-4032-SS" (naphthalene type epoxy resins) manufactured by DIC Corporation; "828US", "828EL", "828", "825", and "Epicoat 828EL" (bisphenol A type epoxy resins) manufactured by Mitsubishi Chemical Corporation; "807" and "1750" (bisphenol F type epoxy resins) manufactured by Mitsubishi Chemical Corporation; "152" (phenol novolac type epoxy resin) manufactured by Mitsubishi Chemical Corporation; and "630" and "630LSD" manufactured by Mitsubishi Chemical Corporation. "," "604" (glycidylamine type epoxy resin); "ED-523T" (glycirol type epoxy resin) manufactured by ADEKA Corporation; "EP-3950L" and "EP-3980S" (glycidylamine type epoxy resin) manufactured by ADEKA Corporation; "EP-4088S" (dicyclopentadiene type epoxy resin) manufactured by ADEKA Corporation; "ZX1059" (mixture of bisphenol A type epoxy resin and bisphenol F type epoxy resin) manufactured by Nippon Steel Chemical & Material Co., Ltd.; "EX-252" and "EX-721" (glycidylamine type epoxy resin) manufactured by Nagase ChemteX Corporation. glycidyl ester type epoxy resin); "EHPE3150CE" manufactured by Daicel Corporation, "THI-DE" manufactured by ENEOS Corporation, "Shofree CDMDG" manufactured by Resonac Corporation, "LDO" manufactured by SYMRISE (alicyclic epoxy resin); "Celloxide 2021P", "Celloxide 2081P", "Celloxide 2000", "Celloxide 8000" manufactured by Daicel Corporation (alicyclic epoxy resin having an ester skeleton); "PB-3600" manufactured by Daicel Corporation, "JP-100", "JP-200" manufactured by Nippon Soda Co., Ltd. (alicyclic epoxy resin having a butadiene structure) Examples of epoxy resins include those having a siloxane skeleton, such as "ZX1658" and "ZX1658GS" manufactured by Nippon Steel Chemical & Material Co., Ltd. (liquid 1,4-glycidylcyclohexane type epoxy resins); "YX8000" and "YX8034" manufactured by Mitsubishi Chemical Corporation (hydrogenated bisphenol A type epoxy resins); "YL9028", "YL9029", and "YL9113" manufactured by Mitsubishi Chemical Corporation (epoxy resins having a siloxane skeleton); and "KR-470", "X-40-2678", and "X-40-2669" manufactured by Shin-Etsu Silicones Co., Ltd. (epoxy resins having a siloxane skeleton).

[0037] As the solid epoxy resin, a solid epoxy resin having three or more epoxy groups in one molecule is preferred, and an aromatic solid epoxy resin having three or more epoxy groups in one molecule is more preferred.

[0038] Preferred solid epoxy resins include bixylenol-type epoxy resins, naphthalene-type epoxy resins, naphthalene-type tetrafunctional epoxy resins, cresol novolac-type epoxy resins, dicyclopentadiene-type epoxy resins, trisphenol-type epoxy resins, naphthol-type epoxy resins, biphenyl-type epoxy resins, naphthylene ether-type epoxy resins, anthracene-type epoxy resins, bisphenol A-type epoxy resins, bisphenol AF-type epoxy resins, and tetraphenylethane-type epoxy resins.

[0039] Specific examples of solid epoxy resins include "HP4032H" (naphthalene type epoxy resin) manufactured by DIC Corporation; "HP-4700" and "HP-4710" (naphthalene type tetrafunctional epoxy resins) manufactured by DIC Corporation; "N-690" (cresol novolac type epoxy resin) manufactured by DIC Corporation; "N-695" (cresol novolac type epoxy resin) manufactured by DIC Corporation; "HP-7200", "HP-7200HH", "HP-7200H", and "HP-7200L" (dicyclopentadiene type epoxy resins) manufactured by DIC Corporation; and "EXA-73" manufactured by DIC Corporation. 11", "EXA-7311-G3", "EXA-7311-G4", "EXA-7311-G4S", "HP6000" (naphthylene ether type epoxy resin); "EPPN-502H" (trisphenol type epoxy resin) manufactured by Nippon Kayaku Co., Ltd.; "NC7000L" (naphthol novolac type epoxy resin) manufactured by Nippon Kayaku Co., Ltd.; "NC3000H", "NC3000", "NC3000L", "NC3000FH", "NC3100" (biphenyl type epoxy resin) manufactured by Nippon Kayaku Co., Ltd.; "ESN475V" manufactured by Nippon Steel Chemical & Material Co., Ltd. "," ESN4100V" (naphthalene-type epoxy resin); "ESN485" (naphthol-type epoxy resin) manufactured by Nippon Steel Chemical & Material Co., Ltd.; "ESN375" (dihydroxynaphthalene-type epoxy resin) manufactured by Nippon Steel Chemical & Material Co., Ltd.; "YX4000H", "YX4000", "YX4000HK", "YL7890" (bixylenol-type epoxy resin) manufactured by Mitsubishi Chemical Corporation; "YL6121" (biphenyl-type epoxy resin) manufactured by Mitsubishi Chemical Corporation; "YX8800" (anthracene-type epoxy resin) manufactured by Mitsubishi Chemical Corporation; "YX7700" (phenol aralkyl type epoxy resin) manufactured by Hishi Chemical Co., Ltd.; "PG-100" and "CG-500" manufactured by Osaka Gas Chemicals Co., Ltd.; "YX7760" (bisphenol AF type epoxy resin) manufactured by Mitsubishi Chemical Corporation; "YL7800" (fluorene type epoxy resin) manufactured by Mitsubishi Chemical Corporation; "1010" (bisphenol A type epoxy resin) manufactured by Mitsubishi Chemical Corporation; "1031S" (tetraphenylethane type epoxy resin) manufactured by Mitsubishi Chemical Corporation; "WHR991S" (phenolphthalimidine type epoxy resin) manufactured by Nippon Kayaku Co., Ltd.;Examples include "EHPE3150" manufactured by Daicel Corporation, "DE-102" and "DE-103" manufactured by ENEOS Corporation, and "DCPD-DE" (alicyclic epoxy resin) manufactured by Japan Material Technology Co., Ltd.

[0040] The resin composition may contain only a liquid epoxy resin as the epoxy resin, only a solid epoxy resin, or a combination of a liquid epoxy resin and a solid epoxy resin. When a liquid epoxy resin and a solid epoxy resin are used in combination, the ratio by mass between them (liquid epoxy resin:solid epoxy resin) is preferably 1:0.01 to 1:50, more preferably 1:0.05 to 1:20, and even more preferably 1:0.1 to 1:10.

[0041] The epoxy equivalent of the epoxy resin is preferably 50 g / eq. to 5,000 g / eq., more preferably 50 g / eq. to 3,000 g / eq., even more preferably 80 g / eq. to 2,000 g / eq., and even more preferably 110 g / eq. to 1,000 g / eq. The epoxy equivalent is the mass of an epoxy resin containing one equivalent of epoxy groups. This epoxy equivalent can be measured in accordance with JIS K7236.

[0042] The weight average molecular weight (Mw) of the epoxy resin is preferably 100 to 5,000, more preferably 250 to 3,000, and even more preferably 400 to 1,500. The weight average molecular weight (Mw) of the epoxy resin can be measured by gel permeation chromatography (GPC) as a polystyrene-equivalent value.

[0043] The content of component (A) in the resin composition is preferably 20% by mass or more, more preferably 40% by mass or more, even more preferably 60% by mass or more or 70% by mass or more, relative to 100% by mass of the total of components (A), (B), and (C), and is preferably 93% by mass or less, more preferably 85% by mass or less, even more preferably 80% by mass or less or 75% by mass or less.

[0044] When the resin composition contains components other than the components (A) to (C), the content of the component (A) in the resin composition is preferably 20% by mass or more, more preferably 30% by mass or more, even more preferably 40% by mass or more or 45% by mass or more, relative to 100% by mass of the non-volatile components in the resin composition, and is preferably 90% by mass or less, more preferably 80% by mass or less, even more preferably 75% by mass or less.

[0045] <(B) High Refractive Index Component (Compound Having a (Meth)acryloyl Group)> The resin composition of the present invention contains a (B) high refractive index component as the (B) component. Unless otherwise specified, the (B) high refractive index component does not include components that fall under the above-mentioned (A) component. The (B) high refractive index component is a compound having a (meth)acryloyl group. One type of (B) high refractive index component may be used alone, or two or more types may be used in combination.

[0046] As described above, the resin composition of the present invention has a refractive index of n （Ａ） The refractive index of the cured product of component (B) is n （Ｂ） In this case, n （Ａ） <n （Ｂ） The refractive index of the cured product of each of the components (A), (B), etc. can be measured by the method described in <Test Example 1: Measurement of refractive index of cured product> below.

[0047] Regarding the measurement of the refractive index of the cured product of each component, in detail, (1): When the object to be measured for refractive index is a cured product of a photocurable resin (for example, (B) a high refractive index component, (D) a compound having a carboxyl group and an ethylenically unsaturated bond, etc.), the refractive index of the cured product at a wavelength of 1310 nm can be measured by the methods described in (1-1) to (1-5) below. (1-1): 0.2 mass% of a photopolymerization initiator is added to 100 mass% of the photocurable resin to obtain a photocurable resin mixture. (1-2): The photocurable resin mixture (and, if necessary, a resin varnish prepared by dissolving the photocurable resin mixture in an organic solvent) is applied to the flat surface of a member having a flat surface, such as a silicon wafer, to obtain a resin layer with a thickness of 10 μm. (1-3): The formed resin layer is subjected to irradiation with light at a wavelength of 365 nm and an illuminance of 35 mW / cm. ２ and exposure dose 2 J / cm ２ (1-4): The exposed resin layer is subjected to a heat treatment at 190°C for 90 minutes in an atmospheric atmosphere to cure the resin layer. (1-5): The cured resin layer obtained is measured at a wavelength of 1310 nm, at room temperature (23°C), and under atmospheric pressure (1 atm). When various conditions such as the type and amount of photopolymerization initiator, (if necessary, the amount of organic solvent used in preparing the resin varnish), the wavelength and exposure dose of light in the exposure treatment, and the heating temperature and heating time in the heat treatment after exposure are changed, the coefficient of variation of the refractive index due to such condition changes is 0.5% or less.

[0048] The photopolymerization initiator used in the above step (1-1) can be appropriately selected depending on the type of the photocurable resin. For example, when the photocurable resin is a resin that cures by photoradical polymerization, a photoradical generator can be used as the photopolymerization initiator. As the photoradical generator, for example, the components described in the section <(C) Photoradical Generator> below can be used. Furthermore, for example, when the photocurable resin is a resin that cures by photocationic polymerization, a photoacid generator can be used as the photopolymerization initiator.

[0049] Regarding the measurement of the refractive index of the cured product of each component, more specifically, (2): When the refractive index to be measured is a cured product of a thermosetting resin (e.g., epoxy resin (A)), the refractive index of the cured product at a wavelength of 1310 nm can be measured using the methods described below in (2-1) to (2-4). (2-1): 0.2 mass% of a heat curing accelerator is added to 100 mass% of the thermosetting resin to obtain a thermosetting resin mixture. (2-2): The thermosetting resin mixture (and, if necessary, a resin varnish prepared by dissolving the thermosetting resin mixture in an organic solvent) is applied to the flat surface of a member having a flat surface, such as a silicon wafer, to obtain a resin layer with a thickness of 10 μm. (2-3): The formed resin layer is subjected to a heat treatment at 190°C for 90 minutes in an atmospheric atmosphere to cure the resin layer. (2-4): The cured product of the obtained resin layer is measured at a wavelength of 1310 nm, at room temperature (23°C), and under atmospheric pressure (1 atm). In addition, when various conditions such as the type and amount of the heat curing accelerator, (if necessary, the amount of the organic solvent used in preparing the resin varnish), and the heating temperature and heating time in the heat treatment are changed, the coefficient of variation of the refractive index due to such condition changes is 0.5% or less.

[0050] The heat curing accelerator used in the step (2-1) can be appropriately selected depending on the type of the thermosetting resin. For example, the components described in the section <(E) Heat Curing Accelerator> below can be used as the heat curing accelerator.

[0051] When the resin composition contains two or more types of (A) component, the refractive index of the cured product of the (A) component is the weighted average of the refractive indexes of the cured products of the respective (A) components based on the mass ratio. When the resin composition contains two or more types of (B) component, the refractive index of the cured product of the (B) component is the weighted average of the refractive indexes of the cured products of the respective (B) components based on the mass ratio.

[0052] As the component (B), for example, a (meth)acrylate compound having one or more (preferably two or more) (meth)acryloyl groups in one molecule can be used.

[0053] Examples of the (meth)acrylate compound include hydroxyalkyl acrylates such as 2-hydroxyethyl acrylate and 2-hydroxybutyl acrylate; mono- or diacrylates of glycols such as ethylene glycol, methoxytetraethylene glycol, polyethylene glycol and propylene glycol; acrylamides such as N,N-dimethylacrylamide and N-methylolacrylamide; aminoalkyl acrylates such as N,N-dimethylaminoethyl acrylate; polyhydric alcohols such as trimethylolpropane, pentaerythritol and dipentaerythritol, or polyhydric acrylates of adducts of such polyhydric alcohols with ethylene oxide, propylene oxide or ε-caprolactone; acrylates of phenols such as phenyl acrylate and phenoxyethyl acrylate, or ethylene oxide or propylene oxide adducts of such phenols; epoxy acrylates derived from glycidyl ethers such as trimethylolpropane triglycidyl ether; modified epoxy acrylates; melamine acrylates; and / or methacrylates corresponding to the above acrylates. Of these, polyvalent acrylates or polyvalent methacrylates are preferred, and examples of trivalent or higher acrylates or methacrylates include trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, trimethylolpropane EO-adduct tri(meth)acrylate, glycerin PO-adduct tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, oligomer of 1,4-butanediol (meth)acrylate, oligomer of 1,6-hexanediol (meth)acrylate, oligomer of trimethylolpropane (meth)acrylate, oligomer of pentaerythritol (meth)acrylate, tetramethylolmethane tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and (meth)acrylic acid ester of N,N,N',N'-tetrakis(β-hydroxyethyl)ethyldiamine.Furthermore, examples of the trivalent or higher acrylates or methacrylates include phosphate triester (meth)acrylates such as tri(2-(meth)acryloyloxyethyl)phosphate, tri(2-(meth)acryloyloxypropyl)phosphate, tri(3-(meth)acryloyloxypropyl)phosphate, tri(3-(meth)acryloyl-2-hydroxyloxypropyl)phosphate, di(3-(meth)acryloyl-2-hydroxyloxypropyl)(2-(meth)acryloyloxyethyl)phosphate, and (3-(meth)acryloyl-2-hydroxyloxypropyl)di(2-(meth)acryloyloxyethyl)phosphate. In the above explanation, the term "EO added" means that ethylene oxide has been added. In the above explanation, the term "PO added" means that propylene oxide has been added.

[0054] The component (B) is not particularly limited as long as it has a (meth)acryloyl group, but it is preferable that it further has an aromatic group. The aromatic group is as described above. When the component (B) has an aromatic group, the number of aromatic groups per molecule of the component (B) may be one or two or more. When the component (B) has two or more aromatic groups, the aromatic groups may be the same or different.

[0055] Commercially available products can be used for component (B), including, for example, "EA-0200," "EA-F5710," and "EA-300" manufactured by Osaka Gas Chemicals Co., Ltd., "1-NMA" and "DABP" manufactured by JFE Chemical Corporation, "M-305," "M-211B," and "M-208" manufactured by Toagosei Co., Ltd., "EBECRYL600" manufactured by Daicel-Allnex Corporation, and "A-BPML" manufactured by Shin-Nakamura Chemical Co., Ltd.

[0056] The molecular weight of component (B) (weight average molecular weight (Mw) when the molecular weight has a distribution) is preferably 3,000 or less, more preferably 2,000 or less, and even more preferably 1,000 or less. The lower limit of the molecular weight of component (B) is not particularly limited, but may be, for example, 100 or more, 150 or more, etc. The molecular weight of component (B) can be measured as a polystyrene-equivalent value by gel permeation chromatography (GPC).

[0057] The (meth)acrylic equivalent of component (B) is preferably at least 80, more preferably at least 100, and even more preferably at least 150, and is preferably at most 3,000, more preferably at most 2,000, and even more preferably at most 1,000. The (meth)acrylic equivalent of component (B) represents the mass (molecular weight) of component (B) per equivalent of (meth)acryloyl groups.

[0058] The content of component (B) in the resin composition is preferably 5% by mass or more, more preferably 15% by mass or more, even more preferably 20% by mass or more or 23% by mass or more, relative to 100% by mass of the total of components (A), (B), and (C), and is preferably 75% by mass or less, more preferably 50% by mass or less, even more preferably 30% by mass or less or 25% by mass or less.

[0059] When the resin composition contains components other than the components (A) to (C), the content of the component (B) in the resin composition is preferably 3% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more, relative to 100% by mass of the non-volatile components in the resin composition, and is preferably 65% ​​by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less or 25% by mass or less.

[0060] In a preferred embodiment, the (B) high refractive index component includes one or more compounds selected from the group consisting of (B-1) a compound having a molecular weight (weight average molecular weight (Mw) when the molecular weight has a molecular weight distribution) of 300 or less (hereinafter, sometimes referred to as "(B-1) component"), and (B-2) a compound having a viscosity of 1,000 mPa·s or less at 25°C (hereinafter, sometimes referred to as "(B-2) component"). When the (B) high refractive index component includes one or more compounds selected from the group consisting of the (B-1) component and the (B-2) component, the (B) high refractive index component can move easily in the resin composition, thereby further promoting monomer diffusion. In particular, it is more preferable that the (B) high refractive index component include both the (B-1) component and the (B-2) component. When the (B) high refractive index component contains both the (B-1) component and the (B-2) component, the (B) high refractive index component may contain a component that is both the (B-1) component and the (B-2) component as a single component. Also, when the (B) high refractive index component contains both the (B-1) component and the (B-2) component, the (B) high refractive index component may contain the (B-1) component and the (B-2) component as mutually different components.

[0061] The lower limit of the molecular weight of the component (B-1) is not particularly limited, but can be, for example, at least 100 or at least 150. The molecular weight of the component (B-1) can be measured as a polystyrene-equivalent value by gel permeation chromatography (GPC).

[0062] The viscosity of component (B-2) is preferably 900 mPa s or less, more preferably 800 mPa s or less, 700 mPa s or less, 500 mPa s or less, 300 mPa s or less, 150 mPa s or less, or 100 mPa s or less at 25° C. There are no particular restrictions on the lower limit of the viscosity of component (B-2), but it can be, for example, 1 mPa s or more, 10 mPa s or more, or the like at 25° C.

[0063] In another preferred embodiment, the (B) high refractive index component includes (B-3) a compound having two or more (meth)acryloyl groups (hereinafter, may be referred to as "component (B-3).") When the (B) high refractive index component includes component (B-3), the reaction rate of the curing reaction by radical polymerization becomes higher, and therefore, a difference in concentration of the (B) high refractive index component between exposed and unexposed portions of the resin composition becomes more likely to occur, and a difference in refractive index between exposed and unexposed portions of the resin composition becomes more likely to occur.

[0064] The number of (meth)acryloyl groups contained in component (B-3) is not particularly limited as long as it is at least 2, but is preferably at least 3 or at least 4. The number of (meth)acryloyl groups contained in component (B-3) is not particularly limited, but may be, for example, 10 or less, 8 or less, etc.

[0065] In a more preferred embodiment, the high refractive index component (B) includes one or more compounds selected from the group consisting of the component (B-1) and the component (B-2), and the component (B-3). In such an embodiment, the high refractive index component (B) may include, as a single component, the component (B-1), a component that is the component (B-2) and the component (B-3), a component that is the component (B-1) and the component (B-3), or a component that is the component (B-2) and the component (B-3). In addition, in such an embodiment, the high refractive index component (B) may include, as mutually different components, one or more compounds selected from the group consisting of the component (B-1) and the component (B-2), and the component (B-3).

[0066] When the resin composition of the present invention further contains (D) a compound having a carboxyl group and an ethylenically unsaturated bond, as described below, it is important that the molecular weight Mw1 of the (B) component (when the resin composition contains two or more (B) components, the weighted average molecular weight of each (B) component based on the mass ratio) is smaller than the weight average molecular weight Mw2 of the (D) component, and the Mw1 / Mw2 ratio is preferably 0.5 or less, more preferably 0.3 or less, and even more preferably 0.1 or less, 0.08 or less, 0.06 or less, or 0.05 or less. The lower limit of the Mw1 / Mw2 ratio is not particularly limited and can be, for example, 0.001 or more, 0.002 or more, etc.

[0067] Refractive index n of the cured product of component (A) （Ａ） and the refractive index n of the cured product of component (B). （Ｂ） The difference in refractive index of the cured product is n （Ｂ） -n （Ａ） is preferably 0.03 or more, more preferably 0.05 or more, and even more preferably 0.08 or more. （Ｂ） -n （Ａ） When the refractive index difference n of the cured product is equal to or greater than the lower limit, the difference in refractive index between the exposed and unexposed areas is more likely to occur, thereby making it possible to further reduce the optical transmission loss of the optical waveguide. （Ｂ） -n （Ａ） The upper limit of is not particularly limited and may be, for example, 0.6 or less, 0.5 or less, 0.4 or less, 0.3 or less, etc. The refractive index of the cured product of each component can be measured using the method described below in <Test Example 1: Measurement of refractive index of cured product>.

[0068] The content of component (A) in the nonvolatile components of the resin composition is M （Ａ） (mass%), and the content of component (B) is M （Ｂ） (mass%), the mass ratio M （Ｂ） / M （Ａ） is preferably 0.01 or more, more preferably 0.04 or more, even more preferably 0.06 or more, and is preferably 5 or less, more preferably 4 or less, even more preferably 3.5 or less.

[0069] <(C) Photoradical Generator> The resin composition of the present invention contains a (C) photoradical generator as the component (C). Unless otherwise specified, the (C) photoradical generator does not include those corresponding to the above-mentioned components (A) and (B). As the (C) photoradical generator, a compound capable of generating radicals upon exposure to actinic rays can be used. The (C) photoradical generator may be used alone or in combination of two or more types.

[0070] Examples of the photoradical generator include an oxime ester-based photopolymerization initiator, an α-aminoketone-based photopolymerization initiator, a phosphine oxide-based photopolymerization initiator, an α-hydroxyketone-based photopolymerization initiator, a benzoin-based photopolymerization initiator, a benzyl ketal-based photopolymerization initiator, and an acylphosphine-based photopolymerization initiator.

[0071] Examples of the oxime ester photopolymerization initiator include 2-(benzoyloxyimino)-1-[4-(phenylthio)phenyl]octan-1-one (OXE01), [1-[9-ethyl-6-(2-methylbenzoyl)carbazol-3-yl]ethylideneamino]acetate (OXE02), ethanone, 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-, 1-(O-acetyloxime), and the like.

[0072] Examples of the α-aminoketone photopolymerization initiator include 2-methyl-1-phenyl-2-morpholinopropan-1-one, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, 2-methyl-1-(4-hexylphenyl)-2-morpholinopropan-1-one, 2-ethyl-2-(dimethylamino)-1-(4-morpholinophenyl)butan-1-one, 2-benzyl-2-(dimethylamino)-1-(4-morpholinophenyl)butan-1-one, 2-(dimethylamino)-2-(4-methylphenylmethyl)-1-(4-morpholinophenyl)butan-1-one, 2-methyl-1-(9,9-dibutylfluoren-2-yl)-2-morpholinopropan-1-one, and compounds having a structure represented by the following formula (C3-1):

[0073]

[0074] (In formula (C3-1), R Ｘ is a group represented by the following formula (C3-2); and d represents an integer of 1 to 10.

[0075]

[0076] (In formula (C3-2), * represents a bond.)

[0077] Examples of the phosphine oxide photopolymerization initiator include bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, (2,4,6-trimethylbenzoyl)diphenylphosphine oxide, and polyoxyethylene glycerin ether tris[phenyl(2,4,6-trimethylbenzoyl)phosphinate] (Polymeric TPO-L).

[0078] Examples of the phosphine oxide photopolymerization initiator include bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, (2,4,6-trimethylbenzoyl)diphenylphosphine oxide, and polyoxyethylene glycerin ether tris[phenyl(2,4,6-trimethylbenzoyl)phosphinate] (Polymeric TPO-L).

[0079] Examples of the α-hydroxyketone photopolymerization initiator include 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropanone, 1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methylpropanone, and 2-hydroxy-1-{4-[4-(2-hydroxy-2-methylpropionyl)benzyl]phenyl}-2-methylpropan-1-one.

[0080] Examples of benzoin-based photopolymerization initiators include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, etc. Examples of benzil ketal-based photopolymerization initiators include 2,2-dimethoxy-2-phenylacetophenone, etc.

[0081] Examples of the acylphosphine photopolymerization initiator include bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide and compounds having a structure represented by the following formula (C4-1):

[0082]

[0083] (In formula (C4-1), R Ｙis a group represented by the following formula (C4-2); a, b, and c each independently represent an integer of 1 to 10.

[0084]

[0085] (In formula (C4-2), * represents a bond.)

[0086] Commercially available photopolymerization initiators can be used, including, for example, "Irgacure-OXE01," "Irgacure-OXE02," "Irgacure-OXE04," and "Irgacure TPO" manufactured by BASF; "Omnirad 907," "Omnirad 369," "Omnirad 379," "Omnirad 379EG," "Omnirad 819," "Omnirad TPO," "Omnipol 910," "Omnipol TP," and "Omnipol 9210" manufactured by IGM; and "N-1919" manufactured by ADEKA Corporation.

[0087] The content of component (C) in the resin composition is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 0.7% by mass or more, relative to 100% by mass of the total of components (A), (B), and (C), and is preferably 10% by mass or less, more preferably 7% by mass or less, and even more preferably 4% by mass or less or 3.5% by mass or less.

[0088] When the resin composition contains components other than the components (A) to (C), the content of the component (C) in the resin composition is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, even more preferably 0.5% by mass or more, relative to 100% by mass of the non-volatile components in the resin composition, and is preferably 5% by mass or less, more preferably 3.5% by mass or less, even more preferably 2.5% by mass or less.

[0089] <(D) Compound Having a Carboxyl Group and an Ethylenically Unsaturated Bond> The resin composition of the present invention may contain (D) a compound having a carboxyl group and an ethylenically unsaturated bond as an optional component. The (D) compound having a carboxyl group and an ethylenically unsaturated bond as component (D) does not include components (A) to (C) described above, unless otherwise specified. When the resin composition contains component (D), the resin composition is soluble in an alkaline developer (e.g., a 1% by mass aqueous sodium carbonate solution) and can be developed in an alkaline environment. The (D) compound having a carboxyl group and an ethylenically unsaturated bond may be used alone or in combination of two or more.

[0090] The term "ethylenically unsaturated bond" refers to a non-aromatic carbon-carbon unsaturated bond, such as a non-aromatic carbon-carbon double bond or carbon-carbon triple bond. Hereinafter, a group having an ethylenically unsaturated bond may be referred to as an "ethylenically unsaturated group." The ethylenically unsaturated group is usually a monovalent group, and examples thereof include a vinyl group, an allyl group, a propargyl group, a butenyl group, an ethynyl group, a phenylethynyl group, a maleimide group, a nadimide group, and a (meth)acryloyl group. From the viewpoint of reactivity in photoradical polymerization, a (meth)acryloyl group is preferred.

[0091] The number of ethylenically unsaturated groups per molecule of component (D) may be 1 or 2 or more. Furthermore, when component (D) contains two or more ethylenically unsaturated groups per molecule, those ethylenically unsaturated groups may be the same or different.

[0092] In an embodiment in which the resin composition contains component (D), the refractive index of a cured product of component (D) at a wavelength of 1310 nm is n （Ｄ） In this case, n （Ｄ） ≦n （Ｂ） It is preferable that the following relationship is satisfied. The refractive index of the cured product of the component (D) can be the refractive index measured by the method described in <Test Example 1: Measurement of refractive index of cured product> described below. When the resin composition contains two or more types of component (D), the refractive index of the cured product of the component (D) is the weighted average of the refractive indexes of the cured products of each component (D) based on the mass proportion.

[0093] Refractive index n of the cured product of component (B) （Ｂ） and the refractive index n of the cured product of component (D). （Ｄ） The difference in refractive index of the cured product is n （Ｂ） -n （Ｄ） is preferably 0.01 or more, more preferably 0.03 or more, and is preferably 0.25 or less, more preferably 0.2 or less, and even more preferably 0.15 or less.

[0094] In one embodiment, component (D) includes an unsaturated modified (meth)acrylic resin.

[0095] The unsaturated modified (meth)acrylic resin can be produced by reacting a resin having structural units obtained by polymerizing (meth)acrylic acid with an ethylenically unsaturated group-containing epoxy compound to introduce an ethylenically unsaturated group.

[0096] Examples of ethylenically unsaturated group-containing epoxy compounds used in the production of unsaturated modified (meth)acrylic resins include glycidyl methacrylate, 4-hydroxybutyl (meth)acrylate glycidyl ether, and 3,4-epoxycyclohexylmethyl (meth)acrylate. Furthermore, it is also possible to react an acid anhydride with the hydroxy group generated during the introduction of the unsaturated group. Examples of acid anhydrides include maleic anhydride, succinic anhydride, itaconic anhydride, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, trimellitic anhydride, pyromellitic anhydride, and benzophenonetetracarboxylic dianhydride. These may be used alone or in combination of two or more.

[0097] Such unsaturated modified (meth)acrylic resins can be synthesized by known methods, but commercially available products may also be used, such as "Cyclomer P(ACA)Z-250," "Cyclomer P(ACA)Z-251," "Cyclomer P(ACA)Z-254F," "Cyclomer P(ACA)Z-300," and "Cyclomer P(ACA)Z-320," manufactured by Daicel Allnex Co., Ltd.

[0098] In another embodiment, the component (D) includes an acid-modified epoxy (meth)acrylate resin.

[0099] The acid-modified epoxy (meth)acrylate resin can be produced by acid-modifying an epoxy (meth)acrylate resin by a known method.

[0100] Epoxy (meth)acrylate resins can be produced, for example, by reacting an epoxy resin with (meth)acrylic acid. The epoxy resin used to produce the epoxy (meth)acrylate resin preferably does not have an aromatic group. Examples of epoxy resins that do not have an aromatic group include linear aliphatic epoxy resins, epoxy resins having a butadiene structure, alicyclic epoxy resins, cyclohexane-type epoxy resins, and cyclohexanedimethanol-type epoxy resins.

[0101] The acid modification of the epoxy (meth)acrylate resin can be carried out by reacting an acid anhydride with the hydroxyl group of the epoxy (meth)acrylate resin. The acid anhydride used for the acid modification is as described above in relation to the unsaturated modified (meth)acrylic resin.

[0102] From the viewpoint of improving the alkaline developability of the resin composition, the acid value of component (D) is preferably 0.1 mgKOH / g or more, more preferably 0.5 mgKOH / g or more, even more preferably 1 mgKOH / g or more, 10 mgKOH / g or more, still more preferably 20 mgKOH / g or more, 30 mgKOH / g or more, 40 mgKOH / g or more, or 50 mgKOH / g or more. The upper limit of the acid value of component (D) is preferably 200 mgKOH / g or less, more preferably 150 mgKOH / g or less, even more preferably 120 mgKOH / g or less, or 100 mgKOH / g or less.

[0103] The weight average molecular weight (Mw) of component (D) is preferably more than 10,000, more preferably 15,000 or more, even more preferably 16,000 or more, 18,000 or more, or 20,000 or more. The upper limit of the weight average molecular weight (Mw) of component (D) is preferably 100,000 or less, more preferably 80,000 or less, even more preferably 60,000 or less, or 50,000 or less. The weight average molecular weight (Mw) of component (D) can be measured as a polystyrene-equivalent value by gel permeation chromatography (GPC).

[0104] When the resin composition contains (D) a compound having a carboxyl group and an ethylenically unsaturated bond, the content of the component (D) in the resin composition is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 13% by mass or more, relative to 100% by mass of the non-volatile components in the resin composition, and is preferably 60% by mass or less, more preferably 50% by mass or less, and even more preferably 40% by mass or less or 38% by mass or less.

[0105] <(E) Heat Curing Accelerator> The resin composition of the present invention may contain a (E) heat curing accelerator as an optional component. Unless otherwise specified, the (E) heat curing accelerator as component (E) does not include those corresponding to the above-mentioned components (A) to (D). The (E) heat curing accelerator functions, for example, as a catalyst or thermal radical generator, thereby accelerating the curing reaction of the resin (A) such as the epoxy resin, thereby accelerating the thermal curing of the resin composition. When the resin composition contains component (E), one type of (E) heat curing accelerator may be used alone, or two or more types may be used in combination.

[0106] Examples of the (E) thermal curing accelerator include phosphorus-based curing accelerators, urea-based curing accelerators, guanidine-based curing accelerators, imidazole-based curing accelerators, metal-based curing accelerators, and amine-based curing accelerators. Furthermore, a thermal radical generator may be used as the (E) thermal curing accelerator.

[0107] Examples of the phosphorus-based curing accelerator include aliphatic phosphonium salts such as tetrabutylphosphonium bromide, tetrabutylphosphonium chloride, tetrabutylphosphonium acetate, tetrabutylphosphonium decanoate, tetrabutylphosphonium laurate, bis(tetrabutylphosphonium)pyromellitate, tetrabutylphosphonium hydrogenhexahydrophthalate, tetrabutylphosphonium 2,6-bis[(2-hydroxy-5-methylphenyl)methyl]-4-methylphenolate, and di-tert-butyldimethylphosphonium tetraphenylborate; methyltriphenylphosphonium bromide, ethyltriphenylphosphonium bromide, propyltriphenylphosphonium bromide, butyltriphenylphosphonium bromide, benzyltriphenylphosphonium chloride, tetraphenylphosphonium bromide, p-tolyltriphenylphosphonium tetra-p-tolylborate, and tetraphenylphosphonium bromide. aromatic phosphonium salts such as tetraphenylborate, tetraphenylphosphonium tetra-p-tolylborate, triphenylethylphosphonium tetraphenylborate, tris(3-methylphenyl)ethylphosphonium tetraphenylborate, tris(2-methoxyphenyl)ethylphosphonium tetraphenylborate, (4-methylphenyl)triphenylphosphonium thiocyanate, tetraphenylphosphonium thiocyanate, and butyltriphenylphosphonium thiocyanate; aromatic phosphine-borane complexes such as triphenylphosphine-triphenylborane; aromatic phosphine-quinone addition products such as triphenylphosphine-p-benzoquinone addition products; aliphatic phosphines such as tributylphosphine, tri-tert-butylphosphine, trioctylphosphine, di-tert-butyl(2-butenyl)phosphine, di-tert-butyl(3-methyl-2-butenyl)phosphine, and tricyclohexylphosphine;Dibutylphenylphosphine, di-tert-butylphenylphosphine, methyldiphenylphosphine, ethyldiphenylphosphine, butyldiphenylphosphine, diphenylcyclohexylphosphine, triphenylphosphine, tri-o-tolylphosphine, tri-m-tolylphosphine, tri-p-tolylphosphine, tris(4-ethylphenyl)phosphine, tris(4-propylphenyl)phosphine, tris(4-isopropylphenyl)phosphine, tris(4-butylphenyl)phosphine, tris(4-tert-butylphenyl)phosphine, tris(2,4-dimethylphenyl)phosphine, tris(2,5-dimethylphenyl)phosphine, tris(2,6-dimethylphenyl)phosphine aromatic phosphines such as phenylphosphine, tris(3,5-dimethylphenyl)phosphine, tris(2,4,6-trimethylphenyl)phosphine, tris(2,6-dimethyl-4-ethoxyphenyl)phosphine, tris(2-methoxyphenyl)phosphine, tris(4-methoxyphenyl)phosphine, tris(4-ethoxyphenyl)phosphine, tris(4-tert-butoxyphenyl)phosphine, diphenyl-2-pyridylphosphine, 1,2-bis(diphenylphosphino)ethane, 1,3-bis(diphenylphosphino)propane, 1,4-bis(diphenylphosphino)butane, 1,2-bis(diphenylphosphino)acetylene, and 2,2′-bis(diphenylphosphino)diphenyl ether;

[0108] Examples of the urea-based curing accelerator include 1,1-dimethylurea; aliphatic dimethylureas such as 1,1,3-trimethylurea, 3-ethyl-1,1-dimethylurea, 3-cyclohexyl-1,1-dimethylurea, and 3-cyclooctyl-1,1-dimethylurea; 3-phenyl-1,1-dimethylurea, 3-(4-chlorophenyl)-1,1-dimethylurea, 3-(3,4-dichlorophenyl)-1,1-dimethylurea, 3-(3-chloro-4-methylphenyl)-1,1-dimethylurea, 3-(2-methylphenyl)-1,1-dimethylurea, 3-(4-methylphenyl)-1,1-dimethylurea, and 3-(3,4-dimethylphenyl)-1,1-dimethylurea. aromatic dimethylureas such as N,N-(1,4-phenylene)bis(N',N'-dimethylurea), N,N-(4-methyl-1,3-phenylene)bis(N',N'-dimethylurea) [toluene bisdimethylurea], and the like.

[0109] Examples of guanidine curing accelerators include dicyandiamide, 1-methylguanidine, 1-ethylguanidine, 1-cyclohexylguanidine, 1-phenylguanidine, 1-(o-tolyl)guanidine, dimethylguanidine, diphenylguanidine, trimethylguanidine, tetramethylguanidine, pentamethylguanidine, 1,5,7-triazabicyclo[4.4.0]dec-5-ene, 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene, 1-methylbiguanide, 1-ethylbiguanide, 1-n-butylbiguanide, 1-n-octadecylbiguanide, 1,1-dimethylbiguanide, 1,1-diethylbiguanide, 1-cyclohexylbiguanide, 1-allylbiguanide, 1-phenylbiguanide, and 1-(o-tolyl)biguanide.

[0110] Examples of the imidazole curing accelerator include 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, and 1-benzyl-2-methylimidazole. Phenylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazolium trimellitate, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2,4-diamino-6-[2'-methylimidazolyl -(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-undecylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanuric acid adduct, 2-phenylimidazole isocyanuric acid adduct imidazole compounds such as 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazole, 1-dodecyl-2-methyl-3-benzylimidazolium chloride, 2-methylimidazoline, and 2-phenylimidazoline, as well as adducts of imidazole compounds with epoxy resins. Commercially available imidazole curing accelerators include, for example, "1B2PZ", "2E4MZ", "2MZA-PW", "2MZ-OK", "2MA-OK", "2MA-OK-PW", "2PHZ", "2PHZ-PW", "Cl1Z", "Cl1Z-CN", "Cl1Z-CNS", and "C11Z-A" manufactured by Shikoku Chemicals Corporation; and "P200-H50" manufactured by Mitsubishi Chemical Corporation.

[0111] Examples of metal-based curing accelerators include organometallic complexes or organometallic salts of metals such as cobalt, copper, zinc, iron, nickel, manganese, and tin. Specific examples of organometallic complexes include organic cobalt complexes such as cobalt(II) acetylacetonate and cobalt(III) acetylacetonate, organic copper complexes such as copper(II) acetylacetonate, organic zinc complexes such as zinc(II) acetylacetonate, organic iron complexes such as iron(III) acetylacetonate, organic nickel complexes such as nickel(II) acetylacetonate, and organic manganese complexes such as manganese(II) acetylacetonate. Examples of organometallic salts include zinc octoate, tin octoate, zinc naphthenate, cobalt naphthenate, tin stearate, and zinc stearate.

[0112] Examples of the amine curing accelerator include trialkylamines such as triethylamine and tributylamine, 4-dimethylaminopyridine, benzyldimethylamine, 2,4,6-tris(dimethylaminomethyl)phenol, 1,8-diazabicyclo(5,4,0)-undecene, etc. Commercially available amine curing accelerators may be used, such as "MY-25" manufactured by Ajinomoto Fine-Techno Co., Inc.

[0113] Examples of the thermal radical generator include peroxide-based radical polymerization initiators and azo-based radical polymerization initiators.

[0114] Examples of the peroxide radical polymerization initiator include hydroperoxide compounds such as 1,1,3,3-tetramethylbutyl hydroperoxide; dialkyl peroxide compounds such as tert-butylcumyl peroxide, di-tert-butyl peroxide, di-tert-hexyl peroxide, di-tert-amyl peroxide, dicumyl peroxide, 1,4-bis(1-tert-butylperoxy-1-methylethyl)benzene, and 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane; and diacid compounds such as dilauroyl peroxide, didecanoyl peroxide, dicyclohexyl peroxydicarbonate, and bis(4-tert-butylcyclohexyl)peroxydicarbonate. peroxide compounds; and peroxyester compounds such as tert-butyl peroxyacetate, tert-butyl peroxybenzoate, tert-butylperoxyisopropyl monocarbonate, tert-butylperoxy-2-ethylhexanoate, tert-butylperoxyneodecanoate, tert-hexylperoxyisopropyl monocarbonate, tert-butyl peroxylaurate, (1,1-dimethylpropyl) 2-ethylperhexanoate, tert-butyl 2-ethylperhexanoate, tert-butyl 3,5,5-trimethylperhexanoate, tert-butylperoxy-2-ethylhexyl monocarbonate, and tert-butylperoxymaleic acid.

[0115] Examples of the azo radical polymerization initiator include azonitrile compounds such as 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), 1,1'-azobis(cyclohexane-1-carbonitrile), 1-[(1-cyano-1-methylethyl)azo]formamide, and 2-phenylazo-4-methoxy-2,4-dimethyl-valeronitrile; 2,2'-azobis[2-methyl-N-[1,1-bis(hydroxymethyl)-2-hydroxyethyl]propionamide], 2,2'-azobis[2-methyl-N-[1,1-bis(hydroxymethyl)-2-hydroxyethyl]propionamide], and 2,2'-azobis[2-methyl-N-[1,1-bis(hydroxymethyl)-2-hydroxyethyl]propionamide]. azoamide compounds such as 2,2'-azobis[2-methyl-N-[2-(1-hydroxybutyl)]-propionamide], 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)-propionamide], 2,2'-azobis(2-methylpropionamide) dihydrate, 2,2'-azobis[N-(2-propenyl)-2-methylpropionamide], 2,2'-azobis(N-butyl-2-methylpropionamide), and 2,2'-azobis(N-cyclohexyl-2-methylpropionamide); alkyl azo compounds such as 2,2'-azobis(2,4,4-trimethylpentane) and 2,2'-azobis(2-methylpropane); and the like.

[0116] Examples of commercially available thermal radical generators include "Perbutyl C," "Perbutyl A," "Perbutyl P," "Perbutyl L," "Perbutyl O," "Perbutyl ND," "Perbutyl Z," "Perbutyl I," "Percumyl P," "Percumyl D," "Perhexyl D," "Perhexyl A," "Perhexyl I," "Perhexyl Z," "Perhexyl ND," "Perhexyl O," and "Perhexyl PV," all manufactured by NOF Corporation; and "Luperox DTA" manufactured by Arkema Yoshitomi Co., Ltd.

[0117] When the resin composition contains a heat curing accelerator (E), the content of the component (E) in the resin composition is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, even more preferably 0.09% by mass or more, relative to 100% by mass of the non-volatile components in the resin composition, and is preferably 5% by mass or less, more preferably 3% by mass or less, even more preferably 1% by mass or less.

[0118] <(F) Other Additives> The resin composition of the present invention may further contain (F) other additives as an optional component. The (F) other additives as component (F) do not include those corresponding to the above-mentioned components (A) to (E). Examples of (F) other additives include thermosetting resins other than epoxy resins (e.g., active ester resins, phenolic resins, naphthol resins, carbodiimide resins, acid anhydride resins, cyanate ester resins, and amine resins); sensitizers; adhesion aids; surfactants such as fluorine-based surfactants, nonionic surfactants, cationic surfactants, anionic surfactants, and silicone-based surfactants; thermoplastic resins; colorants such as phthalocyanine blue, phthalocyanine green, iodine green, diazo yellow, crystal violet, titanium oxide, carbon black, and naphthalene black; hydroquinone, phenothiazine, methylhydroquinone, halogenated hydroxybenzoates, and the like. Examples of the (F) other additives include polymerization inhibitors such as hydroquinone monomethyl ether, catechol, and pyrogallol; thickeners such as bentone and montmorillonite; silicone-based, fluorine-based, and vinyl resin-based antifoaming agents; flame retardants such as phosphorus-based flame retardants (e.g., phosphate ester compounds, phosphazene compounds, phosphinic acid compounds, and red phosphorus), nitrogen-based flame retardants (e.g., melamine sulfate), halogen-based flame retardants, and inorganic flame retardants (e.g., antimony trioxide); ultraviolet absorbers such as benzotriazole-based ultraviolet absorbers; and stabilizers such as borate-based stabilizers, titanate-based stabilizers, aluminate-based stabilizers, zirconate-based stabilizers, isocyanate-based stabilizers, carboxylic acid-based stabilizers, and carboxylic anhydride-based stabilizers. One type of (F) other additive may be used alone, or two or more types may be used in combination.

[0119] <(G) Organic Solvent> The resin composition of the present invention may further contain an organic solvent (G) as an optional volatile component in combination with the non-volatile components such as the above-described components (A) to (F). Examples of the organic solvent include ketone-based solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; ester-based solvents such as methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, isoamyl acetate, methyl propionate, ethyl propionate, and γ-butyrolactone; ether-based solvents such as tetrahydropyran, tetrahydrofuran, 1,4-dioxane, diethyl ether, diisopropyl ether, dibutyl ether, diphenyl ether, and anisole; alcohol-based solvents such as methanol, ethanol, propanol, butanol, and ethylene glycol; 2-ethoxyethyl acetate, propylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, ethyl diglycol acetate, γ-butyrolactone, and methyl methoxypropionate. Examples of the organic solvent (G) include ether ester solvents such as ethyl acetate; ester alcohol solvents such as methyl lactate, ethyl lactate, and methyl 2-hydroxyisobutyrate; ether alcohol solvents such as 2-methoxypropanol, 2-methoxyethanol, 2-ethoxyethanol, propylene glycol monomethyl ether, and diethylene glycol monobutyl ether (butyl carbitol); amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methyl-2-pyrrolidone; sulfoxide solvents such as dimethyl sulfoxide; nitrile solvents such as acetonitrile and propionitrile; aliphatic hydrocarbon solvents such as hexane, cyclopentane, cyclohexane, and methylcyclohexane; and aromatic hydrocarbon solvents such as benzene, toluene, xylene, ethylbenzene, and trimethylbenzene. The organic solvent (G) may be used singly or in combination of two or more.

[0120] The content of the (G) organic solvent in the resin composition may be, for example, 60% by mass or less, 40% by mass or less, 30% by mass or less, 20% by mass or less, 15% by mass or less, or 10% by mass or less, relative to 100% by mass of all components of the resin composition. The content of the (G) organic solvent in the resin composition may also be 0% by mass.

[0121] [Method for Producing Resin Composition] The resin composition can be produced, for example, by mixing components that can be contained in the resin composition. Therefore, the resin composition can be produced by a production method including a step of mixing (A) an epoxy resin, (B) a high refractive index component, and (C) a photoradical generator. This production method may also include a step of mixing optional components such as components (D) to (G). Furthermore, if necessary, the components may be kneaded or stirred using a kneading device such as a three-roll mill, ball mill, bead mill, or sand mill, or a stirring device such as a super mixer or planetary mixer. Components (A) to (G) may be mixed in part or all at the same time, or they may be mixed sequentially.

[0122] [Characteristics of Resin Composition] The resin composition of the present invention contains a combination of the components (A), (B), and (C) (and, as necessary, the components (D), (E), (F), and (G)), and therefore can produce an optical waveguide with low optical transmission loss without performing a development step in forming the core layer of the optical waveguide.

[0123] The resin composition of the present invention allows the manufacture of an optical waveguide without a development step during the formation of the core layer of the optical waveguide. For example, when a portion of the resin composition is exposed to light during the formation of the core layer of the optical waveguide, a curing reaction of the resin composition (consumption of the high refractive index component (B)) progresses in the exposed portion, resulting in a decrease in the content of the high refractive index component (B). This creates a concentration gradient of the high refractive index component (B) between the exposed and non-exposed portions, and to eliminate this concentration gradient, the high refractive index component (B) present in the non-exposed portion diffuses into the exposed portion (monomer diffusion). Therefore, when the resin composition of the present invention is selectively exposed to light, the refractive index becomes relatively high in the exposed portion and relatively low in the non-exposed portion. As a result, as the curing of the resin composition progresses in the exposed portion, a refractive index difference occurs between the exposed and non-exposed portions, forming a core layer (high refractive index portion) and a clad layer (low refractive index portion) covering the core layer.

[0124] The resin composition of the present invention can produce an optical waveguide having low optical transmission loss. For example, when the optical transmission loss of the optical waveguide is measured according to the method described in the section <Test Example 3: Measurement of Optical Transmission Loss> below, the optical transmission loss value is preferably less than 1 dB / cm, more preferably less than 0.5 dB / cm.

[0125] As described above, when the resin composition of the present invention is exposed to light, a curing reaction proceeds in the exposed areas. In such cured areas (cured areas), bonds are formed due to the curing reaction, reducing the solubility in the developer. Therefore, when the resin composition of the present invention is subjected to an exposure treatment, exposed areas with relatively low solubility in the developer and unexposed areas with relatively high solubility in the developer are formed. Therefore, the resin composition of the present invention functions as a negative-type photosensitive resin composition. When the resin composition of the present invention is used to form a cladding layer of an optical waveguide, a development step can be added during the formation of the cladding layer to form trenches or holes in the optical waveguide.

[0126] The resin composition of the present invention can be characterized by excellent resolution (ability to form a thin-wire waveguide). For example, as described in the section <Test Example 2: Evaluation Test of Resolution (Ability to Form a Thin-Wire Waveguide)> below, when an attempt was made to form a line layer having a thickness of 50 μm and an L / S (line / space) of 50 μm / 50 μm using the resin composition of the present invention, such a line could be formed. Furthermore, when the resin composition of the present invention contains (D) a compound having a carboxyl group and an unsaturated bond, the resin composition is soluble in an alkaline developer (e.g., a 1% by mass aqueous sodium carbonate solution) and can be developed in an alkaline solution.

[0127] [Uses of Resin Composition] The resin composition of the present invention can be used as a resin composition for producing an optical waveguide. The resin composition of the present invention is preferably used to form an optical waveguide capable of transmitting light with a wavelength of 1300 nm to 1320 nm, and is also preferably used to form a single-mode optical waveguide. In a more preferred embodiment, the resin composition of the present invention can be used to form a single-mode optical waveguide for light with a wavelength of 1310 nm.

[0128] [Resin Sheet] The resin composition of the present invention can be used as it is, or may be used in the form of a resin sheet.

[0129] In one embodiment, the resin sheet includes a support and a layer of a resin composition (hereinafter simply referred to as a "resin composition layer") provided on the support, and is characterized in that the resin composition layer is formed from the resin composition of the present invention.

[0130] The thickness of the resin composition layer varies depending on the application, and may be appropriately determined depending on the application. For example, from the viewpoint of thinning, the thickness of the resin composition layer is preferably 100 μm or less, 80 μm or less, 60 μm or less, 50 μm or less, 40 μm or less, or 30 μm or less. The lower limit of the thickness of the resin composition layer is not particularly limited, but may be, for example, 1 μm or more, 5 μm or more, etc.

[0131] Examples of the support include a thermoplastic resin film, a metal foil, and a release paper, and a thermoplastic resin film and a metal foil are preferred. Therefore, in a preferred embodiment, the support is a thermoplastic resin film or a metal foil.

[0132] When a thermoplastic resin film is used as the support, examples of the thermoplastic resin include polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), acrylics such as polycarbonate (PC) and polymethyl methacrylate (PMMA), cyclic polyolefins, triacetyl cellulose (TAC), polyether sulfide (PES), polyether ketone, polyimide, etc. Among these, polyethylene terephthalate and polyethylene naphthalate are preferred, and inexpensive polyethylene terephthalate is particularly preferred.

[0133] When a metal foil is used as the support, examples of the metal foil include copper foil and aluminum foil, with copper foil being preferred. The copper foil may be a foil made of a single metal, such as copper, or a foil made of an alloy of copper and another metal (e.g., tin, chromium, silver, magnesium, nickel, zirconium, silicon, titanium, etc.).

[0134] The surface of the support to be bonded to the resin composition layer may be subjected to a matte treatment, a corona treatment, or an antistatic treatment. Alternatively, the support may be a support with a release layer, which has a release layer on the surface to be bonded to the resin composition layer. Examples of the release agent used in the release layer of the support with a release layer include one or more release agents selected from the group consisting of alkyd resins, polyolefin resins, urethane resins, and silicone resins. Commercially available release agents include alkyd resin-based release agents such as "SK-1," "AL-5," and "AL-7" manufactured by Lintec Corporation. Commercially available release layer-containing supports include PET films having a release layer primarily composed of an alkyd resin-based release agent, such as "SK-1," "AL-5," and "AL-7" manufactured by Lintec Corporation; "Lumirror T60" manufactured by Toray Industries, Inc.; "Purex" manufactured by Teijin Limited; and "Uni-Peel" manufactured by Unitika Ltd.

[0135] The thickness of the support is not particularly limited, but is preferably in the range of 5 μm to 75 μm, and more preferably in the range of 10 μm to 60 μm. When a support with a release layer is used, it is preferable that the thickness of the entire support with a release layer is in the above range.

[0136] When a metal foil is used as the support, a metal foil with a support substrate may be used, which is a thin metal foil with a peelable support substrate attached thereto. In one embodiment, the metal foil with a support substrate includes a support substrate, a release layer provided on the support substrate, and a metal foil provided on the release layer. When a metal foil with a support substrate is used as the support, the resin composition layer is provided on the metal foil.

[0137] In the metal foil with a supporting substrate, the material of the supporting substrate is not particularly limited, and examples thereof include copper foil, aluminum foil, stainless steel foil, titanium foil, copper alloy foil, etc. When copper foil is used as the supporting substrate, it may be electrolytic copper foil or rolled copper foil. Furthermore, the release layer is not particularly limited as long as it can release the metal foil from the supporting substrate, and examples thereof include an alloy layer of an element selected from the group consisting of Cr, Ni, Co, Fe, Mo, Ti, W, and P; an organic coating; and the like.

[0138] In the metal foil with a supporting substrate, the material of the metal foil is preferably, for example, copper foil or copper alloy foil.

[0139] In the metal foil with a supporting substrate, the thickness of the supporting substrate is not particularly limited, but is preferably in the range of 10 μm to 150 μm, more preferably in the range of 10 μm to 100 μm. The thickness of the metal foil may be, for example, in the range of 0.1 μm to 10 μm.

[0140] In one embodiment, the resin sheet may further include an optional layer as needed. Examples of such optional layers include a protective film provided on the surface of the resin composition layer that is not bonded to the support (i.e., the surface opposite the support). The thickness of the protective film is not particularly limited, but is, for example, 1 μm to 40 μm. By laminating the protective film, adhesion of dust and the like to the surface of the resin composition layer and scratches can be suppressed.

[0141] The resin sheet can be produced, for example, by preparing a resin varnish by dissolving the resin composition in an organic solvent or by applying the resin varnish to a support using a die coater or the like, and then drying the varnish to form a resin composition layer.

[0142] The organic solvent may be the same as the organic solvent described as a component of the resin composition. The organic solvent may be used alone or in combination of two or more.

[0143] Drying may be carried out by known methods such as heating or hot air blowing. Drying conditions are not particularly limited, but drying is carried out so that the content of organic solvent in the resin composition layer becomes 10% by mass or less, preferably 5% by mass or less. Although this varies depending on the boiling point of the organic solvent in the resin composition or resin varnish, for example, when a resin composition or resin varnish containing 30% by mass to 60% by mass of organic solvent is used, the resin composition layer can be formed by drying at 50°C to 150°C for 3 to 10 minutes.

[0144] The resin sheet can be stored in a rolled state. There may be cases where the resin sheet is not used immediately after production. In such cases, it is preferable to store the resin sheet in a frozen and / or refrigerated state after production so as not to impair its properties. Among these, it is more preferable to store the resin sheet in a frozen state after production. The temperature conditions for storing the resin sheet in a frozen or refrigerated state are, for example, 8°C or lower, preferably 0°C or lower, and more preferably -18°C or lower. The lower limit of such a temperature is not particularly limited and can be, for example, -40°C or higher. When the resin sheet is stored in a frozen or refrigerated state, it is desirable to thaw and adjust the temperature by leaving the resin sheet in a usage environment (temperature 15°C to 28°C, relative humidity 40% RH to 60% RH), and use the resin sheet after the resin composition layer contained in the resin sheet has reached the same temperature as the usage environment, but this is not limited thereto. When the resin sheet has a protective film, it can be used by peeling off the protective film.

[0145] [Optical Waveguide and Manufacturing Method Thereof] An optical waveguide can be manufactured using the resin composition (and resin sheet) described above. The present invention also provides such an optical waveguide. Hereinafter, embodiments of the optical waveguide will be described with reference to the drawings.

[0146] Fig. 1 is a perspective view schematically showing an optical waveguide 10 according to one embodiment of the present invention. As shown in Fig. 1, the optical waveguide 10 includes a core layer 100 and a clad layer 200. The core layer 100 and the clad layer 200 contain a cured product of the resin composition of the present invention, and preferably contain only a cured product of the resin composition of the present invention.

[0147] The core layer 100 is provided in the cladding layer 200. Thus, the core layer 100 is covered by the cladding layer 200. In one example, the entire peripheral surface of the core layer 100 is covered by the cladding layer 200. The core layer 100 and the cladding layer 200 are in direct contact with each other without any other layer therebetween, and therefore an interface 100I can be formed between the core layer 100 and the cladding layer 200. Because the core layer 100 has a higher refractive index than the cladding layer 200, light (not shown) can be transmitted within the core layer 100 from one end (incident end) 100A of the core layer 100 to the other end (exit end) 100B.

[0148] Various wavelengths of light can be selected that can be transmitted by the optical waveguide 10. For example, preferred wavelength ranges of the transmitted light can be 840 nm to 860 nm (e.g., 850 nm), 1300 nm to 1320 nm (e.g., 1310 nm), 1540 nm to 1560 nm (e.g., 1550 nm), etc. Among these, the wavelength range of light transmitted through the optical transmission line 10 is preferably 1300 nm to 1320 nm.

[0149] The optical waveguide 10 may be a single-mode optical waveguide or a multi-mode optical waveguide, but is preferably a single-mode optical waveguide. In particular, the optical waveguide 10 is preferably a single-mode optical waveguide for light in the preferred wavelength range described above. For example, the optical waveguide 10 is preferably a single-mode optical waveguide for light with a wavelength of 1310 nm.

[0150] It is desirable to set the width L of the core layer 100 appropriately within a range that allows light transmission. A specific range of the width L of the core layer 100 is preferably 0.5 μm or more, more preferably 1 μm or more, and even more preferably 2 μm or more, and is preferably 30 μm or less, more preferably 20 μm or less, and even more preferably 10 μm or less or 5 μm or less. The width L of the core layer 100 corresponds to the line width (line) of the core layer 100 when viewed in the thickness direction.

[0151] It is desirable to set the spacing S of the core layers 100 appropriately within a range that allows light transmission. A specific range of the spacing S of the core layers 100 is preferably 50 μm or more, more preferably 70 μm or more, and even more preferably 100 μm or more, and is preferably 1000 μm or less, more preferably 700 μm or less, and even more preferably 500 μm or less. The spacing S of the core layers 100 corresponds to the spacing (space) between the core layers as viewed in the thickness direction.

[0152] It is desirable to set the thickness T of the core layer 100 appropriately within a range that allows light transmission. A specific range of the thickness T of the core layer 100 is preferably 0.5 μm or more, more preferably 1 μm or more, and even more preferably 2 μm or more, and is preferably 50 μm or less, more preferably 30 μm or less, and even more preferably 20 μm or less or 10 μm or less.

[0153] The thickness of the cladding layer 200 is greater than the thickness T of the core layer 100. The specific thickness of the cladding layer 200 is preferably 5 μm or more, more preferably 7 μm or more, and even more preferably 10 μm or more, and is preferably 100 μm or less, more preferably 60 μm or less, and even more preferably 40 μm or less or 30 μm or less.

[0154] In an optical waveguide manufactured using the above-described resin composition (and resin sheet), the core layer 100 contains a relatively large amount of the cured product of the high refractive index component (B) as a result of the migration of the high refractive index component (monomer) due to monomer diffusion. In contrast, the clad layer 200 contains a relatively small amount of the cured product of the high refractive index component (B). Therefore, the content of the cured product of the (B) component in the core layer 100, (B)core, is greater than the content of the cured product of the (B) component in the clad layer, (B)clad.

[0155] The optical waveguide 10 may include any element other than the core layer 100 and the cladding layer 200, as needed. Examples of the optional elements include a protective layer (not shown) that protects the core layer 100 and the cladding layer 200, a wiring layer (not shown) such as a plating layer, a trench or hole (not shown) for forming the wiring layer, and a substrate 300. In the optical waveguide 10 that includes the substrate 300, the cladding layer 200 is usually provided on the substrate 300, and the core layer 100 is provided within the cladding layer 200.

[0156] The substrate 300 may be a hard substrate such as a glass substrate, metal substrate, ceramic substrate, wafer, or circuit board. Examples of the wafer include semiconductor wafers such as silicon wafers, gallium arsenide (GaAs) wafers, indium phosphide (InP) wafers, gallium phosphide (GaP) wafers, gallium nitride (GaN) wafers, gallium telluride (GaTe) wafers, zinc selenium (ZnSe) wafers, and silicon carbide (SiC) wafers, or pseudo wafers. Examples of the pseudo wafer include a plate-shaped member comprising a molding resin and electronic components embedded in the molding resin. Examples of the circuit board include a glass epoxy substrate, a metal substrate, a polyester substrate, a polyimide substrate, a BT resin substrate, and a thermosetting polyphenylene ether substrate. Here, the term "circuit board" refers to a substrate having a patterned conductor layer (circuit) formed on one or both sides of the above-mentioned substrate. Furthermore, the substrate 300 may be a film formed of a plastic material such as polyethylene terephthalate, polyimide, polyester, etc. Furthermore, a flexible circuit board may be employed as the substrate 300.

[0157] The optical waveguide 10 can be manufactured using the resin composition of the present invention. For example, the optical waveguide 10 can be manufactured by a method comprising, in this order: (1) a step of forming a first resin composition layer; (2) a step of curing the first resin composition layer; (3) a step of forming a second resin composition layer on the first resin composition layer; (4) a step of exposing a portion of the second resin composition layer; (5) a step of forming a third resin composition layer on the second resin composition layer; and (6) a step of curing another portion of the second resin composition layer and the third resin composition layer. The first resin composition layer, the second resin composition layer, and the third resin composition layer each contain the resin composition of the present invention, and preferably contain only the resin composition of the present invention. If necessary, the method may further include a step (7) of forming a conductor layer as a wiring layer after step (6) is completed.

[0158] <Step (1)> A method for producing an optical waveguide according to one embodiment of the present invention includes a step (1) of forming a first resin composition layer containing the resin composition of the present invention.

[0159] 2 is a schematic cross-sectional view illustrating step (1) of a method for producing an optical waveguide according to an embodiment of the present invention. In this embodiment, as shown in FIG. 2, an example in which a first resin composition layer 210 is formed on a substrate 300 is described.

[0160] There are no particular limitations on the method for forming the first resin composition layer 210. For example, the first resin composition layer 210 may be formed by applying a resin composition onto the substrate 300. From the viewpoint of smooth application, a varnish-like resin composition containing a solvent may be prepared, and the varnish-like resin composition may be applied.

[0161] Examples of coating methods include gravure coating, microgravure coating, reverse coating, kiss reverse coating, die coating, slot die coating, lip coating, comma coating, blade coating, roll coating, knife coating, curtain coating, chamber gravure coating, slot orifice coating, spin coating, slit coating, spray coating, dip coating, hot melt coating, bar coating, applicator coating, air knife coating, curtain flow coating, offset printing, brush coating, and screen printing.

[0162] The resin composition may be applied in one application or in multiple applications. Also, different application methods may be combined. To avoid contamination, the application is preferably performed in an environment where foreign matter is unlikely to be generated, such as a clean room.

[0163] After application of the resin composition, the first resin composition layer 210 may be dried, if necessary. Drying can be performed using a drying device such as a hot air oven or a far-infrared oven. It is preferable to set the drying conditions appropriately depending on the composition of the resin composition. Specifically, the drying temperature is preferably 50°C or higher, more preferably 70°C or higher, and even more preferably 80°C or higher, and preferably 150°C or lower, more preferably 130°C or lower, and even more preferably 120°C or lower. The drying time is preferably 30 seconds or higher, more preferably 60 seconds or higher, and even more preferably 120 seconds or higher, and preferably 60 minutes or lower, more preferably 20 minutes or lower, and even more preferably 5 minutes or lower.

[0164] The first resin composition layer 210 may be formed using, for example, the resin sheet described above. Specifically, the first resin composition layer 210 can be formed on the substrate 300 by laminating the resin composition layer of the resin sheet on the substrate 300. The lamination is performed, for example, by pressing the resin composition layer of the resin sheet onto the substrate 300 while heating it. This lamination is preferably performed under reduced pressure by a vacuum lamination method. Furthermore, prior to lamination, a preheat treatment may be performed to heat the resin sheet and the substrate, as necessary.

[0165] The lamination conditions are, for example, a pressure bonding temperature (lamination temperature) of 70°C to 140°C and a pressure bonding pressure of 1 kgf / cm ２ ~11 kgf / cm ２ (9.8 x 10 ４ N / m ２ ~107.9 x 10 ４ N / m ２ The lamination can be carried out under the conditions of a pressure of 20 mmHg (26.7 hPa) or less, and a pressure bonding time of 5 to 300 seconds. The lamination is preferably carried out under reduced pressure with an air pressure of 20 mmHg (26.7 hPa) or less. The lamination may be carried out in a batch system or continuously using a roll.

[0166] The vacuum lamination method can be carried out using a commercially available vacuum laminator, such as a vacuum applicator manufactured by Nikko Materials Co., Ltd., a vacuum pressure laminator manufactured by Meiki Seisakusho Co., Ltd., a roll dry coater manufactured by Hitachi Industries, Ltd., or a vacuum laminator manufactured by Hitachi AIC Corporation.

[0167] When the first resin composition layer 210 is formed using a resin sheet provided with a support, the support is usually peeled off at an appropriate time before the step (3).

[0168] <Step (2)> The method for producing an optical waveguide according to one embodiment of the present invention includes, after step (1), step (2) of curing the first resin composition layer. This step (2) may involve, for example, heat treating the first resin composition layer 210. The conditions for the heat treatment may be selected depending on the composition of the resin composition, and may be preferably in the range of 150°C to 250°C for 20 minutes to 180 minutes, and more preferably in the range of 160°C to 230°C for 30 minutes to 120 minutes. The heat treatment may be performed in air or in an inert gas atmosphere such as nitrogen. Of these, an inert gas atmosphere such as nitrogen is preferred as the heat treatment atmosphere.

[0169] The first resin composition layer 210 may be cured by an exposure treatment. As the light used in the exposure treatment, it is preferable to use an appropriate actinic ray according to the composition of the resin composition of the present invention. The wavelength of the actinic ray is, for example, 190 nm to 1000 nm, preferably 240 nm to 550 nm, but light rays of other wavelengths may also be used. Specific examples of actinic light sources include ultraviolet light, visible light, electron beams, X-rays, etc., with ultraviolet light being preferred. The exposure dose range is preferably 10 mJ / cm. ２ More preferably, 50 mJ / cm ２ More preferably, 200 mJ / cm ２ or more, preferably 10,000 mJ / cm ２ or less, more preferably 8,000 mJ / cm ２ More preferably, 4,000 mJ / cm or less ２ Below, 3,000mJ / cm ２ Below, 2,000mJ / cm２ or less or 1,000 mJ / cm ２ The first resin composition layer 210 may be cured by a combination of exposure treatment and heat treatment.

[0170] When the first resin composition layer 210 is formed using a resin sheet having a support, in step (2), a support (not shown) may be present on the first resin composition layer 210. When a support is present on the first resin composition layer 210, exposure may be performed through the support, or exposure may be performed after peeling off the support.

[0171] As described above, the optical waveguide according to one embodiment of the present invention may have a trench or a hole from the viewpoint of ensuring a wiring layer in an opto-electric hybrid board. When the optical waveguide has a trench or a hole, the trench or the hole can be formed by performing a combination of a selective exposure process and a development process in forming the cladding layer.

[0172] <Step (2-1)> When the optical waveguide has a trench or a hole, the step (2) includes a step (2-1) of subjecting a part of the first resin composition layer 210 to an exposure treatment.

[0173] 3 is a schematic cross-sectional view illustrating step (2-1) of the method for manufacturing an optical waveguide according to one embodiment of the present invention. In step (2-1), a latent image is formed in the first resin composition layer 210 by selective exposure treatment. Specifically, in the exposure treatment, light P is selectively irradiated onto specific portions of the first resin composition layer 210. After the exposure treatment, the first resin composition layer 210 is provided with exposed portions 211 that have been irradiated with light and unexposed portions 212 that have not been irradiated with light. Because the resin composition of the present invention functions as a negative photosensitive resin composition, a latent image corresponding to portions other than trenches or holes is formed.

[0174] From the viewpoint of performing selective exposure, the exposure treatment in step (2-1) is usually performed using a mask 400. Specifically, in this exposure treatment, light P is irradiated onto the first resin composition layer 210 through a first mask 400 having a light-transmitting portion 401 and a light-shielding portion 402. The light P passes through the light-transmitting portion 401 and enters the exposed portion 211, but cannot pass through the light-shielding portion 402 and therefore cannot enter the non-exposed portion 212. Therefore, the first resin composition layer 210 can be provided with an exposed portion 211 corresponding to the light-transmitting portion 401 and a non-exposed portion 212 corresponding to the light-shielding portion 402. The first mask 400 may be brought into close contact with the first resin composition layer 210 as shown in FIG. 3 (contact exposure method), or exposure may be performed using parallel light without being in close contact (non-contact exposure method).

[0175] Generally, the light-transmitting portion 401 of the first mask 400 is formed to have a planar shape corresponding to the cladding layer of the optical waveguide. Therefore, the light-shielding portion 402 of the first mask 400 is formed to have a planar shape corresponding to the trench or hole of the optical waveguide. Unless otherwise specified, the "planar shape" refers to the shape seen from the thickness direction.

[0176] The light P used in the exposure treatment in step (2-1) can be actinic rays in the same range as that used in the exposure treatment of the first resin composition layer 210 in step (2). The range of exposure dose in step (2-1) is the same as that of the first resin composition layer 210 in step (2).

[0177] When step (2) includes step (2-1), the width (line width when viewed from the thickness direction) of the light-transmitting portion 401 of the first mask 400 is usually larger than the width L of the core layer 100, from the viewpoint of creating a sufficient refractive index difference between the core layer 100 and the cladding layer 200.

[0178] Since the resin composition of the present invention functions as a negative photosensitive resin composition, the solubility in a developer is reduced in the exposed portion 211. On the other hand, the solubility in a developer is high in the non-exposed portion 212. Utilizing this difference in solubility between the exposed portion 211 and the non-exposed portion 212, the subsequent development process in step (2-2) is carried out.

[0179] When step (2) includes step (2-1), step (2) may further include step (X1) of preheating the first resin composition layer after step (2-1) and before step (2-2) in order to cure the first resin composition layer. Step (X1) can quickly reduce the solubility of the exposed portion 111 in a developer. Heating in step (X1) may be performed using a hot plate or an oven. The heating temperature may be, for example, 40°C or higher and 110°C or lower. The heating time may be, for example, 30 seconds or higher and 60 minutes or lower.

[0180] <Step (2-2)> When the step (2) includes the step (2-1), the step (2) further includes a step (2-2) of subjecting the first resin composition layer to a development treatment.

[0181] 4 is a schematic cross-sectional view illustrating step (2-2) of the method for manufacturing an optical waveguide according to one embodiment of the present invention. The development process in step (2-2) allows the latent image formed in step (2-1) to be developed. Since the resin composition of the present invention functions as a negative photosensitive resin composition, as shown in FIG. 4, the development process does not remove the exposed portion 211, but removes the non-exposed portion 212 (see FIG. 3). The exposed portion 211 of the first resin composition layer 210 remaining after development may have the same planar shape as the light-transmitting portion 401 of the first mask 400 used in step (2-1).

[0182] The development method is usually a wet development method in which the first resin composition layer 210 is brought into contact with a developer. As the developer, a safe, stable developer with good operability, such as an alkaline solution, an aqueous developer, or an organic solvent, is used. Furthermore, as the development method, a known method such as spraying, swing immersion, brushing, or scraping may be appropriately adopted.

[0183] Examples of alkaline aqueous solutions used as the developer include aqueous solutions of alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, and potassium hydroxide; carbonates or bicarbonates such as sodium carbonate and sodium bicarbonate; alkali metal phosphates such as sodium phosphate and potassium phosphate; and alkali metal pyrophosphates such as sodium pyrophosphate and potassium pyrophosphate; and aqueous solutions of organic bases that do not contain metal ions, such as tetraalkylammonium hydroxide. An aqueous solution of tetramethylammonium hydroxide (TMAH) is preferred because it does not contain metal ions and does not affect the semiconductor chip.

[0184] Examples of organic solvents used as developers include acetone, ethyl acetate, propylene glycol monomethyl ether acetate, alkoxyethanols having an alkoxy group having 1 to 4 carbon atoms, ethyl alcohol, isopropyl alcohol, butyl alcohol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, cyclopentanone, and cyclohexanone.

[0185] The concentration of such organic solvents is preferably 2% by mass to 100% by mass, and more preferably 2% by mass to 90% by mass, based on the total amount of the developer. The temperature of such organic solvents can be adjusted according to the developability. These organic solvents can be used alone or in combination of two or more. Examples of organic solvent-based developers that can be used alone include propylene glycol monomethyl ether acetate, 1,1,1-trichloroethane, N-methylpyrrolidone, N,N-dimethylformamide, cyclohexanone, cyclopentanone, methyl isobutyl ketone, and γ-butyrolactone.

[0186] The developer may contain additives such as surfactants and antifoaming agents, if necessary, to improve the developing action.

[0187] The development time is preferably 10 seconds to 5 minutes. The temperature of the developer during development is not particularly limited, but is preferably 20° C. or higher and 50° C. or lower, more preferably 40° C. or lower.

[0188] After development using the developer, the first resin composition layer 210 may be further rinsed. The rinsing is preferably performed with a solvent different from the developer. The rinsing time is preferably 5 seconds to 1 minute.

[0189] When forming trenches or holes, two or more development methods may be used in combination as needed. Development methods include dipping, bathing, spraying, high-pressure spraying, brushing, slapping, etc., with the high-pressure spraying method being preferred for improving resolution. When using the spraying method, the spray pressure is preferably 0.05 MPa to 0.3 MPa.

[0190] After development using a developer, a desmear treatment may be carried out to remove unexposed areas that cannot be completely removed by development. The desmear treatment may be carried out according to various methods known to those skilled in the art and used in the manufacture of printed wiring boards.

[0191] By curing the first resin composition layer 210 in step (2), a cured first resin composition layer 220 is obtained on the substrate 300, as shown in Fig. 4. This cured first resin composition layer 220 forms a part of the cladding layer 200, and hereinafter may be referred to as the "first cladding layer" 220.

[0192] <Step (3)> The method for producing an optical waveguide according to one embodiment of the present invention includes, after step (2), step (3) of forming a second resin composition layer containing the resin composition of the present invention on the first resin composition layer.

[0193] 5 is a schematic cross-sectional view illustrating step (3) of the method for producing an optical waveguide according to one embodiment of the present invention. In step (3), as shown in FIG. 5, a second resin composition layer 110 containing the resin composition of the present invention is formed on a first clad layer 220 as a cured first resin composition layer.

[0194] There are no particular limitations on the method for forming the second resin composition layer 110. For example, the second resin composition layer 110 may be formed by applying the resin composition of the present invention onto the first clad layer 220. From the viewpoint of smooth application, a varnish-like resin composition may be applied. The application of the resin composition in step (3) may be performed in the same manner as the application of the resin composition in step (1). Furthermore, after application of the resin composition, the second resin composition layer 110 may be dried, if necessary. The second resin composition layer 110 may be dried using the same method and conditions as those for drying the first resin composition layer 210.

[0195] The second resin composition layer 110 may be formed using, for example, the resin sheet described above. Specifically, the second resin composition layer 110 can be formed on the first clad layer 220 by laminating a resin composition layer of the resin sheet on the first clad layer 211. The lamination of the resin sheet in step (3) can be performed in the same manner as the lamination of the resin sheet in step (1). The support of the resin sheet is peeled off at an appropriate time before step (5).

[0196] <Step (4)> The method for producing an optical waveguide according to one embodiment of the present invention includes, after step (3), step (4) of subjecting a part of the second resin composition layer to an exposure treatment.

[0197] FIG. 6 is a schematic cross-sectional view illustrating a portion of step (4) of the method for manufacturing an optical waveguide according to one embodiment of the present invention. In step (4), as shown in FIG. 5, a core layer is formed in the second resin composition layer 110 by selective exposure. Specifically, in the exposure process, light P is selectively irradiated to specific portions of the second resin composition layer 110. After the exposure process, the second resin composition layer 110 is provided with an exposed portion 111 irradiated with light and a non-exposed portion 112 not irradiated with light. In this exposure process, the content of the (B) high refractive index component decreases in the exposed portion 111 as the curing reaction of the resin composition progresses. As a result, a concentration gradient of the (B) high refractive index component is generated between the exposed portion 111 and the non-exposed portion 112. To eliminate this concentration gradient, the (B) high refractive index component present in the non-exposed portion 112 diffuses into the exposed portion 111 (monomer diffusion). Therefore, the refractive index becomes relatively high in the exposed portion 111, and relatively low in the non-exposed portion 112. As a result, as the curing of the resin composition in the exposed portion 111 progresses, a difference in refractive index occurs between the exposed portion 111 and the non-exposed portion 112, and the core layer 100 is formed.

[0198] From the viewpoint of performing selective exposure, the exposure treatment in step (4) is usually performed using a mask 410. Specifically, in this exposure treatment, light P is irradiated onto the second resin composition layer 110 through a second mask 410 having a light-transmitting portion 411 and a light-shielding portion 412. The light P passes through the light-transmitting portion 411 and enters the exposed portion 111, but cannot pass through the light-shielding portion 412 and therefore cannot enter the non-exposed portion 112. Therefore, the second resin composition layer 110 can be provided with an exposed portion 111 corresponding to the light-transmitting portion 411 and a non-exposed portion 112 corresponding to the light-shielding portion 412. The second mask 410 may be in close contact with the second resin composition layer 110 as shown in FIG. 6, or exposure may be performed using parallel light without being in close contact.

[0199] The light-transmitting portion 411 of the second mask 410 is formed to have a planar shape corresponding to the core layer of the optical waveguide. Therefore, the light-shielding portion 412 of the second mask 410 is formed to have a planar shape corresponding to the portion of the optical waveguide where the core layer is not present. The light-transmitting portion 411 having a planar shape corresponding to the core layer may be referred to as a "mask pattern" hereinafter.

[0200] The light P used in the exposure treatment in step (4) may be actinic rays in the same range as that used in the exposure treatment of the first resin composition layer 210 in step (2). The exposure dose in step (4) may be the same as that used in the exposure treatment of the first resin composition layer 210 in step (2).

[0201] When the second resin composition layer 110 is formed using a resin sheet having a support, in step (4), a support (not shown) may be present on the second resin composition layer 110. When a support is present on the second resin composition layer 110, exposure may be performed through the support, or exposure may be performed after peeling off the support.

[0202] The method for manufacturing an optical waveguide according to one embodiment of the present invention may further include a step of subjecting the second resin composition layer 110 to a heat treatment after step (4) and before step (5) in order to harden the second resin composition layer 110. Such a heat treatment can further increase the refractive index difference between the exposed portion 111 and the non-exposed portion 112. Furthermore, such a heat treatment can produce an optical waveguide with excellent mechanical strength. The heat treatment conditions can be the same as those for the heat treatment of the first resin composition layer 210 in step (2).

[0203] In a method for manufacturing an optical waveguide according to one embodiment of the present invention, as a result of the migration of the high refractive index component (B) (monomer) due to monomer diffusion, the exposed portion 111 contains a relatively large amount of components derived from the component (B) (including a cured product of the component (B) and the component (B) before curing). In contrast, the non-exposed portion 112 contains a relatively small amount of components derived from the component (B) (including the component (B) before curing). Therefore, the content (B) of components derived from the component (B) in the exposed portion 111, "exposed," is greater than the content (B) of components derived from the component (B) in the non-exposed portion 112, "unexposed."

[0204] 7 is a schematic cross-sectional view illustrating a portion of step (4) of the method for producing an optical waveguide according to one embodiment of the present invention. By curing a portion (exposed portion 111) of the second resin composition layer 110 in step (4), a core layer 100 is formed as a cured second resin composition layer on the first cladding layer 220, as shown in FIG. 7 . The non-exposed portion 112 of the second resin composition layer is cured to form a portion of the cladding layer in the subsequent step (6). Therefore, in the method for producing an optical waveguide according to one embodiment of the present invention, the exposed portion 111 of the second resin composition layer forms the core layer 100 of the optical waveguide, and the non-exposed portion 112 of the second resin composition layer forms the cladding layer 200 of the optical waveguide.

[0205] <Step (5)> The method for producing an optical waveguide according to one embodiment of the present invention includes, after step (4), step (5) of forming a third resin composition layer on the core layer (and the unexposed portion of the second resin composition layer).

[0206] 8 is a schematic cross-sectional view illustrating step (5) of the method for producing an optical waveguide according to one embodiment of the present invention. In step (5), as shown in FIG. 8, a third resin composition layer 230 is formed on the core layer 100 (and the non-exposed portion 112 of the second resin composition layer).

[0207] There are no particular limitations on the method for forming the third resin composition layer 230. For example, the third resin composition layer 230 may be formed by applying the resin composition of the present invention onto the core layer 100 (and the non-exposed portion 112 of the second resin composition layer). From the viewpoint of smooth application, a varnish-like resin composition may be applied. The application of the resin composition in step (5) may be performed in the same manner as the application of the resin composition in step (1). Furthermore, after application of the resin composition, the third resin composition layer 230 may be dried, if necessary. The third resin composition layer 230 may be dried using the same method and conditions as those for drying the first resin composition layer 210.

[0208] The third resin composition layer 230 may be formed, for example, using the resin sheet described above. Specifically, the third resin composition layer 230 can be formed on the core layer 100 (and the non-exposed portion 112 of the second resin composition layer) by laminating the resin composition layer of the resin sheet on the core layer 100 (and the non-exposed portion 112 of the second resin composition layer). The lamination of the resin sheet in step (5) can be performed in the same manner as the lamination of the resin sheet in step (1). Furthermore, the support of the resin sheet may be peeled off in any step.

[0209] <Step (6)> The method for producing an optical waveguide according to one embodiment of the present invention includes, after step (5), step (6) of curing the third resin composition layer 230. The curing of the third resin composition layer 230 in step (6) can usually be performed by the same method as the curing of the first resin composition layer 210.

[0210] <Step (6-1)> When the optical waveguide has a trench or a hole, the step (6) includes a step (6-1) of selectively exposing the third resin composition layer to light.

[0211] 9 is a schematic cross-sectional view illustrating step (6-1) of a method for manufacturing an optical waveguide according to one embodiment of the present invention. In this embodiment, the latent image formed in step (6-1) has the same planar shape as the latent image formed in step (2-1), but this is not limited to this. Therefore, the location of the latent image formed in the third resin composition layer 230 in step (6-1) is arbitrary, as long as the core layer 100 and the cladding layer 200 can be formed in step (6).

[0212] In step (6-1), a latent image is formed in the third resin composition layer 230 by selective exposure treatment. Specifically, light P is selectively irradiated onto specific portions of the third resin composition layer 230. After the exposure treatment, the third resin composition layer 230 is provided with exposed portions 231 that have been irradiated with light and unexposed portions 232 that have not been irradiated with light. Because the resin composition of the present invention functions as a negative photosensitive resin composition, a latent image corresponding to portions other than the trenches or holes is formed.

[0213] From the viewpoint of performing selective exposure, the exposure treatment in step (6-1) is usually performed using a mask 420. Specifically, in this exposure treatment, light P is irradiated onto the third resin composition layer 230 through a third mask 420 including a light-transmitting portion 421 and a light-shielding portion 422. The light P passes through the light-transmitting portion 421 and enters the exposed portion 231, but cannot pass through the light-shielding portion 422 and therefore cannot enter the non-exposed portion 232. Therefore, the third resin composition layer 230 can be provided with an exposed portion 231 corresponding to the light-transmitting portion 421 and a non-exposed portion 232 corresponding to the light-shielding portion 422. The third mask 420 may be in close contact with the third resin composition layer 230 as shown in FIG. 9, or exposure may be performed using parallel light without being in close contact.

[0214] In general, the light-transmitting portion 421 of the third mask 420 is formed to have a planar shape corresponding to the cladding layer of the optical waveguide, and the light-shielding portion 422 of the third mask 420 is formed to have a planar shape corresponding to the trench or hole of the optical waveguide.

[0215] The light P used in the exposure treatment in step (6-1) can be actinic rays in the same range as that used in the exposure treatment of the first resin composition layer 210 in step (2). The range of exposure dose in step (6-1) is the same as that used in the exposure treatment of the first resin composition layer 210 in step (2).

[0216] When step (6) includes step (6-1), the width (line width when viewed from the thickness direction) of the light-transmitting portion 421 of the third mask 420 is typically larger than the width L of the core layer 100, from the viewpoint of creating a sufficient refractive index difference between the core layer 100 and the cladding layer 200.

[0217] Since the resin composition of the present invention functions as a negative photosensitive resin composition, the solubility in a developer is reduced in the exposed portion 231. On the other hand, the solubility in a developer is high in the non-exposed portion 232. Utilizing this difference in solubility between the exposed portion 231 and the non-exposed portion 232, the subsequent development process in step (6-2) is carried out.

[0218] When step (6) includes step (6-1), step (6) may include step (X2) of preheating the third resin composition layer after step (6-1) and before step (6-2) in order to cure the third resin composition layer. Step (X2) can quickly reduce the solubility of the exposed portion 231 in the developer. The preheating in step (X2) can be performed using the same method and conditions as those used for preheating in step (X1), which step (2) may include.

[0219] <Step (6-2)> When step (6) includes step (6-1), step (6) further includes step (6-2) of subjecting the third resin composition layer to a development treatment. The development of the third resin composition layer 230 in step (6-2) can usually be performed in the same manner as the development of the first resin composition layer 210 in step (2-2).

[0220] 10 is a schematic cross-sectional view illustrating step (6-2) of the method for manufacturing an optical waveguide according to one embodiment of the present invention. The development process in step (6-2) allows the latent image formed in step (6-1) to be developed. Since the resin composition of the present invention functions as a negative-type photosensitive resin composition, as shown in FIG. 10 , the development process does not remove the exposed portion 231, but removes the non-exposed portion 232 (see FIG. 9 ). The exposed portion 231 of the third resin composition layer remaining after development may have the same planar shape as the light-transmitting portion 421 of the mask 420 used in step (6-1).

[0221] The development process in step (6-2) forms trenches or holes 500 in the optical waveguide. In this embodiment, the latent image formed in step (6-1) and the latent image formed in step (2-1) have the same planar shape, so trenches or holes 500 having a constant width in the thickness direction are formed (see FIG. 10 ), but this is not limited to this. Therefore, the shape of the trenches or holes 500 that the optical waveguide can have is arbitrary.

[0222] FIG. 11 is a schematic cross-sectional view illustrating step (6) of the method for manufacturing an optical waveguide according to one embodiment of the present invention. By curing the third resin composition layer 230 in step (6), a cured third resin composition layer 240 is formed on the core layer 100, as shown in FIG. 11 . Furthermore, in step (6), a portion of the non-exposed portion 112 of the second resin composition layer formed in step (4) is also cured. In this embodiment, the non-exposed portion 112 of the cured second resin composition layer is also included in the cured third resin composition layer 240. This cured third resin composition layer 240 forms a portion of the cladding layer 200 and may be referred to as the "second cladding layer" 240 hereinafter. The cladding layer 200 is then formed from this second cladding layer 240 and the first cladding layer 220. Therefore, an optical waveguide 10 can be obtained, which includes the cladding layer 200 including the first cladding layer 220 and the second cladding layer 240, and the core layer 100 provided within this cladding layer 200.

[0223] <Step (7)> ​​The method for manufacturing an optical waveguide according to one embodiment of the present invention may further include, after step (6), step (7) of forming a conductor layer as a wiring layer. The conductor layer may be formed in any location; for example, the conductor layer may be formed inside the trench or hole 500, or may be formed on the second cladding layer 240, for example. The conductor layer is preferably formed by plating. Furthermore, before forming the conductor layer by plating, the location where the conductor layer is to be formed may be subjected to a roughening treatment.

[0224] The procedure and conditions for the roughening treatment are not particularly limited. For example, the area where the conductor layer is to be formed can be roughened by performing a swelling treatment with a swelling liquid, a roughening treatment with an oxidizing agent, and a neutralization treatment with a neutralizing liquid in this order.

[0225] Examples of swelling solutions used in the roughening treatment include alkaline solutions and surfactant solutions, with alkaline solutions being preferred. Examples of alkaline solutions include sodium hydroxide solutions and potassium hydroxide solutions. Examples of commercially available swelling solutions include "Swelling Dip Securigance P" and "Swelling Dip Securigance SBU" manufactured by Atotech Japan. The swelling treatment using a swelling solution is not particularly limited, but can be carried out by, for example, immersing the area where the conductor layer is to be formed in a swelling solution at 30°C to 90°C for 1 to 20 minutes. From the viewpoint of suppressing swelling of the resin in the area where the conductor layer is to be formed to an appropriate level, it is preferable to immerse the area where the conductor layer is to be formed in a swelling solution at 40°C to 80°C for 5 to 15 minutes.

[0226] An example of an oxidizing agent used in the roughening treatment is an alkaline permanganate solution prepared by dissolving potassium permanganate or sodium permanganate in an aqueous solution of sodium hydroxide. The roughening treatment using an oxidizing agent such as an alkaline permanganate solution is preferably carried out by immersing the area where the conductor layer is to be formed in the oxidizing agent solution heated to 60°C to 100°C for 10 minutes to 30 minutes. The concentration of permanganate in the alkaline permanganate solution is preferably 5% by mass to 10% by mass. Commercially available oxidizing agents include alkaline permanganate solutions such as "Concentrate Compact CP" and "Dosing Solution Securigance P" manufactured by Atotech Japan.

[0227] The neutralizing solution used in the roughening treatment is preferably an acidic aqueous solution, and a commercially available product such as "Reduction Solution Securigant P" manufactured by Atotech Japan, Inc. Treatment with a neutralizing solution can be carried out by immersing the surface that has been roughened with an oxidizing agent in a neutralizing solution at 30°C to 80°C for 5 to 30 minutes. From the standpoint of workability, etc., a method in which the object that has been roughened with an oxidizing agent is immersed in a neutralizing solution at 40°C to 70°C for 5 to 20 minutes is preferred.

[0228] After the roughening treatment is completed, a conductor layer is formed on the roughened area. Specifically, a semi-additive method is preferable from the viewpoint of ease of production, since the surface of the roughened area can be plated by a method such as a semi-additive method or a full-additive method to form a conductor layer having a desired shape. An example of forming a conductor layer by a semi-additive method is shown below.

[0229] A plating seed layer is formed by electroless plating on the roughened area. A second mask pattern is then formed on the formed plating seed layer, exposing a portion of the plating seed layer in accordance with the desired shape. A metal layer is then formed on the exposed plating seed layer by electrolytic plating, and the second mask pattern is then removed. The unnecessary plating seed layer is then removed by etching or the like, forming a conductor layer having a desired wiring pattern.

[0230] The method for manufacturing the optical waveguide 10 may further include any optional steps in combination with the steps described above. For example, the method for manufacturing the optical waveguide 10 may further include a step of forming a protective layer (not shown). Furthermore, the method for manufacturing the optical waveguide 10 may further include a step of dicing the manufactured optical waveguide 10.

[0231] The above-described steps may be repeated in the method for manufacturing the optical waveguide 10. For example, steps (1) to (6) (including step (7) as necessary) may be repeated to manufacture an optical waveguide having a multilayer structure in which core layers and clad layers are alternately provided on the substrate 300 in the thickness direction.

[0232] [Opto-electrical Hybrid Board and Manufacturing Method Thereof] An opto-electrical hybrid board according to one embodiment of the present invention includes the optical waveguide described above. Typically, the opto-electrical hybrid board includes an optical waveguide and an electric circuit board. The electric circuit board may include electronic components and wiring connected to the electronic components. Examples of the electronic components include passive components such as capacitors, inductors, and resistors; and active components such as semiconductor chips. The optical waveguide and the wiring of the electric circuit board may be connected via an opto-electrical conversion element. The opto-electrical conversion element may include a combination of a light-emitting element (e.g., a surface-emitting light-emitting diode) capable of converting electricity to light and a light-receiving element (e.g., a photodiode) capable of converting light to electricity. Furthermore, the opto-electrical hybrid board may include an optical element such as a mirror for adjusting the optical path.

[0233] A preferred example of an opto-electrical hybrid substrate is one that includes a chip in which an optical integrated circuit is formed on a silicon wafer. This chip is expected to be put to practical use in the near future using silicon photonics, and is expected to be mounted, for example, in a semiconductor package. An opto-electrical hybrid substrate that includes this chip includes, for example, an electric circuit board, a chip mounted on the electric circuit board, and an optical waveguide. The optical waveguide can be used to connect the wiring of the electric circuit board to the chip or to connect multiple chips together.

[0234] Chips manufactured using silicon photonics generally use light with wavelengths of 1310 nm and 1550 nm, with 1310 nm being the most common (Sho Yoshida, Daisuke Suganuma, Takaaki Ishigure, "Fabrication of Single-Mode Polymer Waveguides Using the Mosquito Method and Low Loss," 28th Spring Conference of the Japan Institute of Electronics Packaging, 2014). Therefore, it is preferable that the optical waveguide be capable of transmitting light with wavelengths of 1310 nm and 1550 nm or close thereto, and it is preferable that it be capable of transmitting light with wavelengths of, for example, 1300 nm to 1320 nm. The optical waveguides according to the above-described embodiments are capable of transmitting light with these wavelengths.

[0235] Generally, between single mode and multimode, single mode can achieve faster transmission. Therefore, from the viewpoint of high-speed transmission, single mode optical waveguides are preferable as optical waveguides applied to optical-electrical hybrid circuits. In single mode optical waveguides, it is preferable that the width of the core layer is small. For example, it is preferable to form a core layer with a width of 10 μm or less, or 5 μm or less. Furthermore, optical waveguides having such a narrow core layer are preferable from the viewpoint of increasing the degree of freedom in package design when the optical waveguide is applied to a semiconductor package. According to the optical waveguides of the above-described embodiments, it is possible to reduce the width of the core layer as described above.

[0236] On the other hand, when connecting multiple opto-electrical hybrid boards, the boards may be connected via optical fibers. For example, multiple opto-electrical hybrid boards may be installed in a rack and connected to each other via optical fibers. Multimode optical fibers are the mainstream for connecting boards in this way. Therefore, from the perspective of enabling connection with optical fibers, a multimode optical waveguide may be used as the optical waveguide provided in the opto-electrical hybrid board.

[0237] From the viewpoint of enhancing versatility, it is desirable that the optical waveguide be applicable to both single-mode and multi-mode. Furthermore, it is desirable to reduce the minimum width of the core layer of such optical waveguides to increase the degree of freedom in the line width of the core layer. According to the optical waveguides of the above-described embodiments, by using the core resin composition of the present invention for the core, a fine core can be formed, thereby reducing the minimum width of the core layer. Furthermore, according to the optical waveguides of the above-described embodiments, both single-mode and multi-mode optical waveguides can be obtained. Therefore, the optical waveguides of the above-described embodiments can be applied in a wide range of applications. Furthermore, because the optical waveguides of the above-described embodiments are applicable in such a wide range of applications and can suppress optical transmission loss, they are suitable for application to opto-electrical hybrid boards.

[0238] Since the opto-electric hybrid board includes the optical waveguide described above, the manufacturing method of the opto-electric hybrid board includes the same method as the manufacturing method of the optical waveguide.

[0239] [Semiconductor Device] A semiconductor device according to one embodiment of the present invention includes the above-described opto-electric hybrid substrate. Examples of such semiconductor devices include various semiconductor devices used in electrical products (e.g., computers, mobile phones, smartphones, tablet devices, wearable devices, digital cameras, medical equipment, and televisions) and vehicles (e.g., motorcycles, automobiles, trains, ships, and aircraft).

[0240] The present invention will be specifically described below with reference to examples. However, the present invention is not limited to these examples. In the following description, "parts" and "%" representing amounts mean "parts by mass" and "% by mass", respectively, unless otherwise specified. Furthermore, the temperature and pressure conditions were room temperature (23°C) and atmospheric pressure (1 atm), unless otherwise specified.

[0241] Examples 1 to 21 and Comparative Examples 1 to 6: Preparation of Resin Compositions Each component was weighed and mixed in the amount (parts by mass of non-volatile components) shown in Tables 1 to 3 below, and 10 parts by mass of PGMEA (propylene glycol monomethyl ether acetate) was further added and uniformly dispersed using a high-speed rotary mixer to obtain a varnish-like resin composition. Details of each component shown in Tables 1 to 3 below are as follows.

[0242] (A) Epoxy Resins "YX8000": hydrogenated bisphenol A type epoxy resin (liquid epoxy resin having an alicyclic skeleton), manufactured by Mitsubishi Chemical Corporation, epoxy equivalent: approximately 205 g / eq., viscosity (25°C): 18.5 mPa·s "EHPE3150": epoxy resin having a structure represented by the following formula (A1) (solid epoxy resin having an alicyclic skeleton), manufactured by Daicel Corporation, epoxy equivalent: approximately 177 g / eq.

[0243]

[0244] (In formula (A1), n ​​represents an integer of 1 to 30.)

[0245] "YL9028": Epoxy resin having a siloxane skeleton, manufactured by Mitsubishi Chemical Corporation, epoxy equivalent weight: approximately 243 g / eq., viscosity (25°C): 170 mPa·s "KR-470": Epoxy resin having a siloxane skeleton, manufactured by Shin-Etsu Chemical Co., Ltd., epoxy equivalent weight: 200 g / eq., viscosity (25°C): 3,000 mPa·s

[0246] (B) Compounds Having a (Meth)acryloyl Group "M-305": a mixture of pentaerythritol triacrylate and pentaerythritol tetraacrylate (pentaerythritol triacrylate content: 55% to 63%), manufactured by Toagosei Co., Ltd., weight-average molecular weight: 298, viscosity (25°C) 180 mPa·s to 800 mPa·s "A-BPML": biphenyl methyl acrylate, manufactured by Shin-Nakamura Chemical Co., Ltd., molecular weight: 238, viscosity (25°C) 30 mPa·s "M-211B": bisphenol A-type epoxy acrylate, manufactured by Toagosei Co., Ltd., weight-average molecular weight: 512, viscosity (25°C) 950 mPa·s to 1,350 mPa·s "DABP": a compound having a structure represented by the following formula (B1), 4,4'-bisacryloxymethylbiphenyl, manufactured by JFE Chemical Corporation, molecular weight 322, solid compound

[0247]

[0248] "M-208": bisphenol F type epoxy acrylate, manufactured by Toagosei Co., Ltd., weight average molecular weight 485, viscosity (25°C) 500 to 700 mPa·s "EA-0200": acrylate having a fluorene skeleton, manufactured by Osaka Gas Chemicals Co., Ltd., molecular weight 547, viscosity (25°C) greater than 100,000 mPa·s "EBECRYL 600": bisphenol A type epoxy acrylate, manufactured by Daicel Allnex Corporation, weight average molecular weight 485, viscosity (60°C) 3,000 mPa·s

[0249] (C) Photoradical Generator "Omnirad 379EG": a compound having a structure represented by the following formula (C1), manufactured by IGM

[0250]

[0251] "Irgacure OXE-02": a compound having a structure represented by the following formula (C2), manufactured by BASF

[0252]

[0253] "Omnipol 910": a compound having a structure represented by the following formula (C3-1), manufactured by IGM

[0254]

[0255] (In formula (C3-1), R Ｘ is a group represented by the following formula (C3-2); and d represents an integer of 1 to 10.

[0256]

[0257] (In formula (C3-2), * represents a bond.)

[0258] (D) Compound having a carboxyl group and an ethylenically unsaturated bond "(ACA)Z250": an acrylic oligomer having a carboxyl group, manufactured by Daicel-Allnex Corporation, a DPM (dipropylene glycol monomethyl ether) solution containing 45% by mass of non-volatile components, weight average molecular weight (Mw) 22,000, acid value 69 mgKOH / g, viscosity (25°C) 15,250 mPa·s "(ACA)Z254F": an acrylic oligomer having a carboxyl group, manufactured by Daicel-Allnex Corporation, a DPM (dipropylene glycol monomethyl ether) solution containing 55% by mass of non-volatile components, weight average molecular weight (Mw) 21,000, acid value 70 mgKOH / g, viscosity (25°C) 20,000 mPa·s "RA-4101": acrylic oligomer having a carboxyl group, manufactured by Negami Chemical Industrial Co., Ltd., a mixed solution of PGMEA (propylene glycol monomethyl ether acetate) and PGME (propylene glycol monomethyl ether) with a non-volatile component of 25% by mass, weight average molecular weight (Mw) of 40,000, acid value of 60 mgKOH / g, viscosity (25°C) of 1,000 mPa s

[0259] (E) Thermal curing accelerators: "Lupelox DTA": di-t-amyl peroxide, manufactured by Arkema Yoshitomi Co., Ltd.; "1B2PZ": 2-phenyl-1-benzyl-1H-imidazole, manufactured by Shikoku Chemicals Corporation.

[0260] Test Example 1: Measurement of refractive index of cured product Each of components (A), (B), and (D) was applied to a silicon wafer to form a 10 μm-thick resin layer. Specifically, for components (B) and (D), 100 parts of each component was mixed with 1 part of a PGMEA (propylene glycol monomethyl ether acetate) solution containing 20% ​​by mass of non-volatile components of a photopolymerization initiator ("Omnirad 379EG" manufactured by IMG) and the resulting mixture was applied to the silicon wafer. For component (A), 100 parts of the component was mixed with 1 part of an MEK (methyl ethyl ketone) solution containing 20% ​​by mass of non-volatile components of a heat curing accelerator ("1B2PZ" manufactured by Shikoku Chemicals Corporation) and the resulting mixture was applied to the silicon wafer. The formed resin layers of components (B) and (D) were exposed to light using a projection exposure apparatus ("UX-2240" manufactured by Ushio Inc.) at a wavelength of 365 nm and an illuminance of 35 mW / cm. ２ and exposure dose 2 J / cm ２ The resin layer of component (A) and the resin layers of components (B) and (D) after exposure were placed in a clean oven, heated from room temperature to 190°C, and after reaching 190°C, heat treatment was carried out for 90 minutes in an air atmosphere to cure the resin layers, thereby obtaining cured products of each component. The refractive index n (measurement wavelength: 1310 nm) of the obtained cured products of each component was measured at room temperature and atmospheric pressure using a 2010M type prism coupler (manufactured by Metricon) with a 1310 nm laser beam. In addition, the refractive index difference n （Ｂ） -n （Ａ） When the resin composition contains two or more types of component (A), the refractive index n of the cured product of component (A) is calculated. （Ａ） is the weighted average of the refractive indexes of the cured products of the components (A) based on the mass ratio. （Ｂ） -n （Ａ） When the resin composition contains two or more types of component (B), the refractive index n of the cured product of component (B) is calculated. （Ｂ） was the weighted average of the refractive indexes of the cured products of the components (B) based on their mass proportions.

[0261] Test Example 2: Evaluation test of resolution (nano-wire waveguide formability) The varnish-like resin compositions obtained in the examples and comparative examples were applied to a silicon wafer by spin coating so that the thickness of the resin composition layer after drying would be 50 μm. After application of the resin composition, the wafer was dried at 90° C. for 3 minutes to form a resin composition layer. The resin composition layer was exposed to light using a projection exposure apparatus ("UX-2240" manufactured by Ushio Inc.) at a wavelength of 365 nm and an illuminance of 35 mW / cm. ２ and exposure dose 2 J / cm ２ For the exposure, a quartz glass mask was used to draw a plurality of straight lines with a length of 5 cm and an L / S (line / space) of 50 μm / 50 μm.

[0262] The entire surface of the exposed resin composition layer was spray-developed for 1 minute using a developer at a spray pressure of 0.2 MPa. In the examples and comparative examples other than Example 1, a 1% by mass aqueous solution of sodium carbonate at 30°C was used as the developer. In Example 1, since alkaline development was not possible, PGMEA (propylene glycol monomethyl ether acetate) was used as the developer. After spray development, the resin composition layer was exposed to light using a projection exposure apparatus ("UX-2240" manufactured by Ushio Inc.) at a wavelength of 365 nm and an illuminance of 35 mW / cm. ２ and exposure dose 2 J / cm ２ The coated film was then subjected to ultraviolet exposure at 190° C. for 1 hour in an air atmosphere, to obtain an evaluation sample A formed of a cured product of the resin composition.

[0263] Evaluation sample A was observed under a scanning electron microscope (SEM) (magnification: 2000 times). From the observation results, the resolution was evaluated according to the following evaluation criteria. The line width refers to the width of the line layer.

[0264] [Evaluation criteria for resolution (narrow-wire waveguide formability)] "◯": Lines having a line width of 50 μm at a thickness of 50 μm were formed, and alkaline development was possible. "Δ": Lines having a line width of 50 μm at a thickness of 50 μm were formed, but alkaline development was not possible. "×": Lines having a line width of 50 μm at a thickness of 50 μm were not formed.

[0265] <Test Example 3: Measurement of optical transmission loss> (1-1) Formation of first clad layer The varnish-like resin compositions obtained in the Examples and Comparative Examples were applied to a silicon wafer by spin coating so that the thickness of the resin composition layer after drying would be 10 μm. After application of the resin composition, the layer was dried at 90° C. for 3 minutes to form a resin composition layer I. The resin composition layer I was exposed to a projection exposure apparatus ("UX-2240" manufactured by Ushio Inc.) at a wavelength of 365 nm and an illuminance of 35 mW / cm. ２ and exposure dose 2 J / cm ２ After the ultraviolet exposure, the substrate was placed in a clean oven and heated from room temperature to 190°C. After the temperature reached 190°C, the substrate was subjected to a heat treatment for 90 minutes in an air atmosphere to cure the resin composition layer I, thereby forming a first clad layer.

[0266] (1-2) Formation of Core Layer The varnish-like resin compositions obtained in the Examples and Comparative Examples were applied onto the first clad layer by spin coating so that the thickness of the resin composition layer after drying would be 5 μm. After application of the resin composition, it was dried at 90° C. for 3 minutes to form a resin composition layer II. The resin composition layer II was exposed to light using a projection exposure apparatus ("UX-2240" manufactured by Ushio Inc.) at a wavelength of 365 nm and an illuminance of 35 mW / cm. ２ and exposure dose 2 J / cm ２ The resin composition was exposed to ultraviolet light for 100 seconds. The exposure was performed using a quartz glass mask that depicted multiple straight lines with a length of 5 cm and an L / S (line / space) of 5 μm / 100 μm. In the L / S of this quartz glass mask, the lines corresponded to the width of the core layer, and the spaces corresponded to the spacing between the core layers. In the exposed portions of the resin composition layer II, a core layer was formed by photocuring the resin composition. Through the above operations, an intermediate laminate B1 was obtained, which comprised a silicon wafer / first cladding layer / core layer and a resin composition layer (non-exposed portion) in this order. It was confirmed that, through such operations, clear core patterns (mask pattern; multiple straight lines with a length of 5 cm and an L / S (line / space) of 5 μm / 100 μm) could be formed in Examples 1 to 21.

[0267] (1-3) Formation of Second Clad Layer The varnish-like resin compositions obtained in the Examples and Comparative Examples were applied by spin coating onto the core layer and the resin composition layer (non-exposed area) of the intermediate laminate B1 so that the thickness of the resin composition layer after drying would be 10 μm. After application of the resin composition, the layer was dried at 90° C. for 3 minutes to form a resin composition layer III. After forming the resin composition layer III, a projection exposure apparatus ("UX-2240" manufactured by Ushio Inc.) was used to expose the layer to light at a wavelength of 365 nm and an illuminance of 35 mW / cm. ２ and exposure dose 2 J / cm ２ The sample was then exposed to ultraviolet light. After the exposure, the sample was placed in a clean oven and heated from room temperature to 190°C. After reaching 190°C, a 90-minute heat treatment was performed in an air atmosphere to cure the resin composition layer III and form a second clad layer. Through the above operations, a sample laminate B2 was obtained, which included a silicon wafer, a first clad layer, a core layer, and a second clad layer in this order. In this sample laminate B2, the combination of the first clad layer and the second clad layer constituted the clad layer. Thus, an optical waveguide was obtained, which included the clad layer and a core layer within the clad layer.

[0268] (2) Preparation of Test Substrate From the sample laminate B2 produced by the above operation, the portion where the core layer was formed, i.e., the core layer on which a 5 cm linear pattern was drawn and the surrounding cladding layer, was cut out to obtain a test substrate B3 equipped with an optical transmission path. The cutting conditions were as follows: Dicing device: DAD3221 (manufactured by Disco Corporation) Blade: ZH14-SD4000-VI-50 Spindle rotation speed: 30 K / min Cutting speed: 5 mm / sec Blade height: 0.060 mm Dicing tape: T-80W (manufactured by Denka Company, 80 umt)

[0269] (3-1) Measurement of Optical Transmission Loss of Calibration Optical System As described below, the transmission loss of an optical system configured by excluding the test substrate B3 and the light-collecting module from the optical system for measuring the transmission loss of the test substrate B3 was measured. That is, a calibration optical system was obtained by connecting a light source (1310 nm light source, THORLABS's "LPSC-1310-FC") and a light receiver (Keysight's optical power meter "N7742") via an optical fiber (input fiber) on a vibration-isolating table covered with a blackout curtain. The light source was made to emit light, and the intensity of the light entering the receiver was measured with the receiver, thereby measuring the loss of this calibration optical system.

[0270] (3-2) Measurement of Optical Transmission Loss Test substrate B3 was placed on a vibration-isolating table covered with a blackout curtain. A focusing module (numerical aperture 0.18) was connected to one end (input end) of the optical waveguide of test substrate B3, and a light source (1310 nm light source, THORLABS's "LPSC-1310-FC") was connected to the focusing module via an optical fiber (input fiber). Another focusing module (numerical aperture 0.18) was connected to the other end (output end) of the optical waveguide of test substrate B3, and a light receiver (Keysight's optical power meter "N7742") was connected to the focusing module via an optical fiber (output fiber). Through these operations, an optical system was obtained in which light emitted from the light source passed through the optical fiber (input fiber), focusing module, optical waveguide, focusing module, and optical fiber (output fiber) in this order before entering the light receiver. Hereinafter, this optical system may be referred to as the "sample optical system." The light source was turned on and the intensity of the light that entered the receiver was measured by the receiver to measure the loss of the sample optical system.

[0271] The loss of the optical waveguide included in the test substrate B3 was determined by subtracting the loss of the calibration optical system from the loss of the sample optical system.

[0272] (3-3) Measurement of Optical Transmission Loss (dB / cm) of Optical Waveguide After completing the loss measurement for the 5 cm-long optical waveguide, the optical waveguide was cut to 4 cm and the same measurement was performed. Then, the optical waveguide was cut to 3 cm and the measurement was repeated, and measured values ​​were calculated for each of the 5 cm-long optical waveguide, the 4 cm-long optical waveguide, and the 3 cm-long optical waveguide. The measurement results were then plotted on a coordinate system with the optical waveguide length on the horizontal axis and the optical waveguide loss on the vertical axis to obtain the coordinates of three points representing the measurement results. An approximation line for these three points was calculated using the least squares method, and the slope of the approximation line was determined as the loss per unit distance of the optical waveguide (optical transmission loss). Using the calculated values, the optical transmission loss was evaluated according to the following evaluation criteria.

[0273] [Evaluation criteria for optical transmission loss] "◎": Optical transmission loss value is less than 0.3 dB / cm "◯": Optical transmission loss value is 0.3 dB / cm or more and less than 0.5 dB / cm "△": Optical transmission loss value is 0.5 dB / cm or more and less than 1 dB / cm "×": Optical transmission loss value is 1 dB / cm or more

[0274]

[0275]

[0276]

[0277] 10 Optical waveguide 100 Core layer 100A Incident side end of core layer 100B Emission side end of core layer 100I Interface between core layer and clad layer 110 Second resin composition layer 111 Exposed portion of second resin composition layer 112 Non-exposed portion of second resin composition layer 200 Clad layer 210 First resin composition layer 211 Exposed portion of first resin composition layer 212 Non-exposed portion of first resin composition layer 220 First clad layer (cured first resin composition layer) 230 Third resin composition layer 231 Exposed portion of third resin composition layer 232 Non-exposed portion of third resin composition layer 240 Second clad layer (including cured third resin composition layer) 300 Substrate 400 First mask 401 Light-transmitting portion of first mask 402 Light-shielding portion of first mask 410 Second mask 411: Light-transmitting portion of second mask 412: Light-shielding portion of second mask 420: Third mask 421: Light-transmitting portion of third mask 422: Light-shielding portion of third mask 500: Trench or hole P: Light (active light)

Claims

1. A resin composition comprising (A) an epoxy resin, (B) a compound having a (meth)acryloyl group, and (C) a photoradical generator, wherein the refractive index of a cured product of the (A) component at a wavelength of 1310 nm (when the resin composition contains two or more (A) components, the weighted average of the refractive indexes of the cured products of each (A) component based on the mass ratio) is n （Ａ） The refractive index of the cured product of the (B) component (when the resin composition contains two or more (B) components, the weighted average value of the refractive indexes of the cured products of the (B) components based on the mass ratio) is n （Ｂ） In this case, n （Ａ） <n （Ｂ） A resin composition that satisfies the relationship:

2. The resin composition according to claim 1, wherein component (A) comprises an epoxy resin having one or more skeletons selected from the group consisting of an alicyclic skeleton and a siloxane skeleton.

3. Refractive index n of the cured product of component (A) at a wavelength of 1,310 nm （Ａ） and the refractive index n of the cured product of component (B). （Ｂ） The difference in refractive index of the cured product is n （Ｂ） -n （Ａ） The resin composition according to claim 1, wherein is 0.03 or more.

4. The content of component (A) in the nonvolatile components of the resin composition is M （Ａ） (mass%), and the content of component (B) is M （Ｂ） (mass%), the mass ratio M （Ｂ） / M （Ａ） The resin composition according to claim 1, wherein is 0.01 or more and 5 or less.

5. The resin composition according to claim 1, wherein the molecular weight of component (B) (weight average molecular weight (Mw) when it has a molecular weight distribution) is 3,000 or less.

6. The resin composition according to claim 1, wherein component (B) contains one or more compounds selected from the group consisting of (B-1) compounds having a molecular weight (weight average molecular weight (Mw) if the molecular weight has a distribution) of 300 or less, and (B-2) compounds having a viscosity of 1,000 mPa·s or less at 25°C.

7. The resin composition according to claim 1, wherein component (B) includes (B-3) a compound having two or more (meth)acryloyl groups.

8. The resin composition further contains (D) a compound having a carboxyl group and an ethylenically unsaturated bond, and the refractive index of the cured product of the (D) component at a wavelength of 1310 nm (when the resin composition contains two or more (D) components, the weighted average of the refractive indexes of the cured products of each (D) component based on the mass ratio) is n （Ｄ） In this case, n （Ｄ） ≦n （Ｂ） The resin composition according to claim 1, which satisfies the following relationship:

9. The resin composition according to claim 1, further comprising (E) a thermal curing accelerator.

10. The resin composition according to claim 1, which is used for producing an optical waveguide capable of transmitting light having a wavelength of 1300 nm to 1320 nm.

11. A resin sheet comprising a support and a resin composition layer formed on the support, wherein the resin composition layer contains the resin composition according to any one of claims 1 to 10.

12. An optical waveguide comprising a core layer and a clad layer, wherein the core layer and the clad layer each comprise a cured product of the resin composition according to any one of claims 1 to 10.

13. The optical waveguide according to claim 12, capable of transmitting light with a wavelength of 1300 nm to 1320 nm.

14. The optical waveguide according to claim 12, wherein the content of the cured product of component (B) in the core layer, (B)core, is greater than the content of the cured product of component (B) in the clad layer, (B)clad.

15. An optical / electrical hybrid board comprising the optical waveguide according to claim 12.

16. A method for manufacturing an optical waveguide, comprising the steps of: forming a first resin composition layer; curing the first resin composition layer; forming a second resin composition layer on the first resin composition layer; exposing a portion of the second resin composition layer; forming a third resin composition layer on the second resin composition layer; and curing another portion of the second resin composition layer and the third resin composition layer, in this order, wherein the first resin composition layer, the second resin composition layer, and the third resin composition layer each comprise the resin composition according to any one of claims 1 to 10.

17. The manufacturing method according to claim 16, characterized in that in the step of subjecting a portion of the second resin composition layer to an exposure treatment, the exposed portion of the second resin composition layer forms a core layer of the optical waveguide, and the non-exposed portion of the second resin composition layer forms a clad layer of the optical waveguide.

18. The manufacturing method described in claim 16, characterized in that in the step of subjecting a portion of the second resin composition layer to an exposure treatment, the content (B)exposed of components derived from component (B) in the exposed portion is greater than the content (B)unexposed of components derived from component (B) in the unexposed portion.

Images