Epoxy resin composition, epoxy resin composition for optical waveguide, epoxy resin composition for interlayer insulation, resin-coated film, and liquid material

Abstract

Epoxy resin compositions each comprising an epoxy resin (A), one or more ester compounds (B), and a photopolymerization initiator (C), wherein the ester compounds (B) include at least one compound selected from among active ester compounds (B1) having a vinyl group and an aromatic ring and acid anhydride compounds (B2) having a vinyl group.

Description

Epoxy resin composition, epoxy resin composition for optical waveguide, epoxy resin composition for interlayer insulation, resin-coated film and liquid material

[0001] The present invention relates to an epoxy resin composition, and to an epoxy resin composition for optical waveguides, an epoxy resin composition for interlayer insulation, a resin-attached film, and a liquid material containing the same.

[0002] Optical fiber has traditionally been the mainstream transmission medium in the fields of FTTH (Fiber to the Home) and long-distance and medium-distance communications in the automotive field. In recent years, high-speed optical transmission over short distances of less than 1 meter has become necessary. In this area, optical waveguide-type optical wiring boards are suitable because they offer high-density wiring (narrow pitch, branching, crossing, multilayering, etc.), surface mountability, integration with electrical substrates, and small-diameter bending capabilities that are not possible with optical fiber.

[0003] An optical waveguide is obtained by forming a clad and a core using two types of ultraviolet (UV)-curable optical waveguide resin compositions with high transparency and different refractive indices. Generally, such optical waveguide resin compositions contain a resin, such as an epoxy resin, an acrylic resin, or a silicone resin, and a curing agent (see, for example, Patent Documents 1 and 2). Of these resins, epoxy resins are preferred from the viewpoints of heat resistance and optical signal transmission. When epoxy resins are used as optical waveguide materials, photoacid generators (cationic photopolymerization initiators) capable of initiating the ring-opening polymerization reaction of epoxy groups by light such as ultraviolet light are preferably used as polymerization initiators.

[0004] On the other hand, Patent Document 3 describes a resin composition containing (A) an epoxy resin, (B) an active ester compound having a carbon-carbon unsaturated bond, and (C) a resin having an unsaturated hydrocarbon group, wherein the content of component (A) is 10 to 50 mass% when the resin component is taken as 100 mass%, the content of component (C) is 3 to 30 mass% when the resin component is taken as 100 mass%, and component (B) is an active ester compound having a styryl group. Patent Document 3 also describes that such a resin composition can form an insulating layer with a low dielectric loss tangent.

[0005] International Publication No. 2020 / 203366 Japanese Patent Application Laid-Open No. 2020-166107 Japanese Patent No. 6776749

[0006] An object of the present invention is to provide an epoxy resin composition that has good photocurability, heat resistance after curing, and photopatterning properties, and that can suppress optical loss in the 1310 nm wavelength band.

[0007] The present inventors have conducted extensive research to solve the above problems and have arrived at the present invention.

[0008] An epoxy resin composition according to a first aspect of the present invention comprises an epoxy resin (A), an ester compound (B), and a photopolymerization initiator (C), wherein the ester compound (B) comprises one or more selected from an active ester compound (B1) having a vinyl group and an aromatic ring and an acid anhydride compound (B2) having a vinyl group.

[0009] An epoxy resin composition for an optical waveguide according to a second aspect of the present invention includes the epoxy resin composition according to the first aspect.

[0010] An epoxy resin composition for interlayer insulation according to a third aspect of the present invention includes the epoxy resin composition according to the first aspect.

[0011] A resin-coated film according to a fourth aspect of the present invention has a resin layer containing the epoxy resin composition according to the first aspect or a semi-cured product of the epoxy resin composition, and a support film.

[0012] A liquid material according to a fifth aspect of the present invention includes the epoxy resin composition according to the first aspect.

[0013] It would be desirable if an epoxy resin composition used as a material for optical waveguides could be used not only for cladding layers and core layers, but also for various layers in electrical substrates. For example, it would be desirable if an epoxy resin composition for optical waveguides with excellent transparency could also have interlayer insulating properties and be used as an epoxy resin composition for interlayer insulation. However, conventional methods for curing epoxy resin compositions for optical waveguides, in which epoxy groups in an epoxy resin undergo ring-opening polymerization with each other using a photoacid generator (cationic photopolymerization initiator), tend to generate hydroxyl groups during the ring-opening polymerization reaction of the epoxy groups. Resin compositions that generate hydroxyl groups after photocuring are not suitable as materials for insulating applications.

[0014] Furthermore, it is difficult to directly use known epoxy resin compositions for interlayer insulation as materials for optical waveguides. For example, the aforementioned Patent Document 3 discloses that a cured product of the resin composition can form a suitable insulating layer, but the resin composition is unsuitable as a material for optical waveguides. Specifically, the active ester compound component of the resin composition described in Patent Document 3 has a styryl group. Therefore, it is expected that the reactivity to light (photocurability) is low and that it is difficult to form a fine core layer pattern during exposure.

[0015] Therefore, it would be advantageous to develop a new epoxy resin composition that has the physical properties required for use in optical waveguides and is expected to be less likely to generate hydroxyl groups during the photopolymerization reaction.

[0016] Therefore, as a result of intensive studies by the present inventors, it has been found that a new epoxy resin composition can be obtained which is expected to have suitable physical properties for optical waveguide applications (photocurability, heat resistance, optical patterning properties, and optical loss suppression properties) and is unlikely to generate hydroxyl groups during the photopolymerization reaction, by including a resin composition which contains an epoxy resin, one or more compounds selected from an active ester compound having a vinyl group and an aromatic ring, and an acid anhydride compound having a vinyl group, and a photopolymerization initiator.

[0017] As described above, the present invention can provide an epoxy resin composition that has good photocurability, heat resistance after curing, and photopatterning properties, and that can suppress optical loss in the 1310 nm wavelength band.

[0018] In this specification, the term "epoxy resin" also includes the meaning of "epoxy compound," that is, it encompasses both epoxy resins as polymers and epoxy resin monomers capable of forming epoxy resins.

[0019] In this specification, "ester compound" means a compound having a "-COO-" structure that can react with an epoxy group of an epoxy resin to undergo ring-opening polymerization. In other words, "ester compound" includes not only ester compounds having an ester bond but also acid anhydride compounds having an acid anhydride group.

[0020] As used herein, the term "active ester compound" refers to a compound that contains at least one ester bond in its structure and has an aliphatic chain, an aliphatic ring, or an aromatic ring bonded to both sides of the ester bond.

[0021] In this specification, the term "hydrocarbon skeleton" refers to a skeleton having mainly cyclic and / or chain saturated hydrocarbons and / or unsaturated hydrocarbons. ２ "-" may be substituted with a general divalent group such as -COO-, -OCO-, or -O-. In this specification, "hydrocarbon group" mainly means a group having cyclic and / or chain saturated hydrocarbons and / or unsaturated hydrocarbons. In addition, "-CH ２ The "-" may be substituted with a general divalent group such as -COO-, -OCO-, or -O-, or may be substituted with "-CH" contained in a hydrocarbon group. ３ " may be substituted with common end groups such as -COOH, -OH, -CN, etc.

[0022] As used herein, "having good photocurability" means that a dry film produced from the epoxy resin composition is cured satisfactorily without leaving any tacky feel or the like. As used herein, "having good heat resistance after curing" means that a cured product of the epoxy resin composition does not significantly discolor after prolonged heating. As used herein, "having good photopatterning properties" means that a core of an appropriate width can be formed after exposure of the dry film.

[0023] Hereinafter, embodiments of the present invention will be described in detail. Note that the scope of the present invention is not limited to the embodiments described here, and various modifications can be made without departing from the spirit of the present invention.

[0024] 1. Epoxy Resin Composition The epoxy resin composition according to this embodiment (hereinafter also simply referred to as the "resin composition") mainly contains an epoxy resin (A), an ester compound (B), and a photopolymerization initiator (C). The ester compound (B) includes one or more selected from an active ester compound (B1) having a vinyl group and an aromatic ring, and an acid anhydride compound (B2) having a vinyl group.

[0025] The components contained in the resin composition will be described in detail below.

[0026] [Epoxy Resin (A)] The type of epoxy resin (A) contained in the resin composition is not particularly limited as long as it does not impair the effects of photocurability, heat resistance, optical patterning ability, and suppression of optical loss according to the present embodiment. Specifically, the epoxy resin (A) includes one or more epoxy resins that are generally used mainly for optical waveguide applications.

[0027] The epoxy resin (A) may be a liquid epoxy resin or a solid epoxy resin. In this specification, with respect to an epoxy resin, "liquid" means that it is liquid at room temperature, and "solid" means that it is solid at room temperature.

[0028] (Partially Esterified Epoxy Resin (A1)) The epoxy resin (A) preferably contains a partially esterified epoxy resin (A1). In this specification, the term "partially esterified epoxy resin" refers to a partially modified esterified epoxy resin obtained by reacting some of the epoxy groups of an epoxy resin with (meth)acrylic acid to partially esterify it. The (meth)acrylation rate of the partially esterified epoxy resin (A1) is not particularly limited, but is preferably, for example, 25% to 75%, more preferably 40% to 60%, and particularly preferably 50%.

[0029] When the epoxy resin (A) contains the partially esterified epoxy resin (A1), the epoxy resin (A) may further contain an epoxy resin other than the partially esterified epoxy resin (A1) described below. Alternatively, the epoxy resin (A) may contain only the partially esterified epoxy resin (A1) or only an epoxy resin other than the partially esterified epoxy resin (A1) described below.

[0030] When the epoxy resin (A) contains a partially esterified epoxy resin (A1), the radical polymerization reaction of the epoxy resin proceeds favorably at the double bond moiety of the partially esterified epoxy resin (A1), and therefore, an epoxy resin composition having excellent photopatterning properties can be finally obtained.

[0031] Specifically, the partially esterified epoxy resin (A1) is preferably a compound having a structure represented by the following formula (1-A1):

[0032]

[0033] (In formula (1-A1), R １（Ａ１） and R ２（Ａ１） are each independently a hydrogen atom or a methyl group, and R ３（Ａ１） is a hydrocarbon skeleton having 13 to 27 carbon atoms.

[0034] In the above formula (1-A1), R ３（Ａ１） is preferably a hydrocarbon skeleton having 13 to 24 carbon atoms, and more preferably a hydrocarbon skeleton having 13 to 15 carbon atoms.

[0035] When the epoxy resin (A) contains a compound having a structure represented by the above formula (1-A1), the photoradical polymerization reaction of the epoxy resin proceeds more favorably at the (meth)acrylic group moiety in the above formula (1-A1), thereby ultimately ensuring the production of an epoxy resin composition with excellent photopatterning properties.

[0036] Furthermore, the compound having the structure represented by the above formula (1-A1) is a compound derived from a bisphenol-type epoxy resin (i.e., in the above formula (1-A1), R ３（Ａ１） is a bisphenol-type hydrocarbon skeleton).

[0037] The compound derived from such a bisphenol type epoxy resin is more preferably a compound derived from one or more epoxy resins selected from the group consisting of bisphenol A type epoxy resin, bisphenol AP type epoxy resin, bisphenol AF type epoxy resin, bisphenol B type epoxy resin, bisphenol BP type epoxy resin, bisphenol C type epoxy resin, bisphenol E type epoxy resin, bisphenol F type epoxy resin, bisphenol G type epoxy resin, bisphenol M type epoxy resin, bisphenol S type epoxy resin, bisphenol P type epoxy resin, bisphenol PH type epoxy resin, bisphenol TMC type epoxy resin, and bisphenol Z type epoxy resin.

[0038] Among these, the compound derived from the bisphenol epoxy resin is more preferably a compound derived from one or more of a bisphenol A epoxy resin and a bisphenol F epoxy resin. These bisphenol epoxy resins (preferably one or more of a bisphenol A epoxy resin and a bisphenol F epoxy resin) may be any epoxy resin known to those skilled in the art and generally used primarily for optical waveguide applications. When the partially esterified epoxy resin (A1) is a modified compound derived from these epoxy resins, an epoxy resin composition with better photopatterning properties can be reliably obtained.

[0039] Such a partially esterified epoxy resin (A1) may be synthesized by a known method, or a commercially available product may be used. Examples of commercially available partially esterified epoxy resins (A1) include "3000AD-E5" and "3000MD-E5" manufactured by Kyoeisha Chemical Co., Ltd., "BFEA-50", "BEEM-50", and "BAEM-50" manufactured by KSM Corporation, "EBECRYL 3605" manufactured by Daicel Allnex Corporation, "EA-1010N" manufactured by Shin-Nakamura Chemical Co., Ltd., and "LUXYDIR" manufactured by DIC Corporation.

[0040] These partially esterified epoxy resins (A1) may be used singly or in combination of two or more. The epoxy equivalent of these partially esterified epoxy resins (A1) is not particularly limited, but is preferably, for example, about 180 g / eq to 1250 g / eq.

[0041] The content of the partially esterified epoxy resin (A1) is preferably 50 parts by mass or more relative to 100 parts by mass of the epoxy resin (A). When the content of the partially esterified epoxy resin (A1) is 50 parts by mass or more relative to 100 parts by mass of the epoxy resin (A), an epoxy resin composition having excellent photopatterning properties can be reliably obtained.

[0042] The content of the partially esterified epoxy resin (A1) per 100 parts by mass of the epoxy resin (A) is more preferably 55 parts by mass or more, even more preferably at least a value selected from the group consisting of 60 parts by mass, 70 parts by mass, 80 parts by mass, and 90 parts by mass, and particularly preferably 100 parts by mass. By increasing the content of the partially esterified epoxy resin (A1) per 100 parts by mass of the epoxy resin (A) and decreasing the content of the other epoxy resins described below, the photopatterning effect can be further enhanced.

[0043] (Other Epoxy Resins) The other epoxy resins are not particularly limited as long as they do not impair the effects of photocurability, heat resistance, optical patterning properties, and suppression of optical loss according to this embodiment. Specifically, any epoxy resin other than the aforementioned partially esterified epoxy resin (A1) known to those skilled in the art and generally used primarily for optical waveguide applications may be used. The other epoxy resins may be either liquid epoxy resins or solid epoxy resins.

[0044] Examples of other epoxy resins include bisphenol A type epoxy resins, hydrogenated bisphenol A type epoxy resins, polyfunctional epoxy resins, bisphenol F type epoxy resins, alicyclic epoxy resins, bisphenol E type epoxy resins, brominated epoxy resins, fluorine-containing epoxy resins, aromatic epoxy resins, novolac type epoxy resins, biphenyl skeleton type epoxy resins, and aliphatic epoxy resins.

[0045] Among these other epoxy resins, bisphenol A epoxy resins are preferred because of their high transparency and ease of UV curing. Bisphenol A epoxy resins may be synthesized by known methods, or commercially available products may be used. For example, commercially available solid bisphenol A epoxy resins include "1001," "1002," "1003," "1055," "1004," "1004AF," "1003F," "1004F," "1005F," "1004FS," "1006FS," and "1007FS" manufactured by Mitsubishi Chemical Group Corporation. Furthermore, commercially available liquid bisphenol A epoxy resins include "Epiclon (registered trademark) 850S" manufactured by DIC Corporation and "JER (registered trademark) 825" manufactured by Mitsubishi Chemical Corporation.

[0046] The hydrogenated bisphenol A epoxy resin may be synthesized by a known method, or a commercially available product may be used. For example, commercially available hydrogenated bisphenol A epoxy resins include "YS8040" and "YX8034" manufactured by Mitsubishi Chemical Group Corporation.

[0047] Examples of polyfunctional epoxy resins include 2-[4-(2,3-epoxypropoxy)phenyl]-2-[4-[1,1-bis[4-([2,3-epoxypropoxy]phenyl)]ethyl]phenyl]propane, cresol novolac epoxy resins, and the like. Polyfunctional epoxy resins may be synthesized by known methods, or commercially available products may be used. For example, commercially available polyfunctional epoxy resins include "VG3101M80" manufactured by Printec Co., Ltd. and "EPPN-502" manufactured by Nippon Kayaku Co., Ltd. Commercially available polyfunctional (alicyclic) epoxy resins include "EHPE3150" manufactured by Daicel Corporation.

[0048] The fluorine-containing epoxy resin may be synthesized by a known method, or a commercially available product may be used. For example, a commercially available fluorine-containing epoxy resin product is "YX7760" manufactured by Mitsubishi Chemical Group Corporation.

[0049] The epoxy equivalent of these other epoxy resins is not particularly limited, but is preferably, for example, about 170 g / eq to 1200 g / eq.

[0050] These other epoxy resins may be used singly or in combination of two or more.

[0051] The content of these other epoxy resins is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, even more preferably 20 parts by mass or less, and particularly preferably 10 parts by mass or less, relative to 100 parts by mass of the epoxy resin (A).

[0052] The content of the epoxy resin (A) relative to the total resin components of the epoxy resin (A) and the ester compound (B) is preferably adjusted so that the equivalent ratio of the total of the ester groups and acid anhydride groups of the ester compound (B) described below to the epoxy groups of the epoxy resin (A) is 0.1 or more and 3 or less, from the viewpoint of the reaction mechanism between the epoxy groups and the ester bond and / or the acid anhydride group.

[0053] The equivalent ratio of the total of the ester groups and acid anhydride groups in the ester compound (B) to the epoxy groups in the epoxy resin (A) is more preferably adjusted to 0.2 or more and 2.5 or less, and even more preferably adjusted to 0.25 or more and 2 or less.

[0054] [Ester Compound (B)] In the resin composition according to the present embodiment, the ester compound (B) contains one or more selected from an active ester compound (B1) having a vinyl group and an aromatic ring and an acid anhydride compound (B2) having a vinyl group. Details of these compounds are described below.

[0055] (Active Ester Compound (B1)) When the resin composition contains an active ester compound (B1) having a vinyl group and an aromatic ring as the ester compound (B), both a radical polymerization reaction at the vinyl group portion of the active ester compound (B1) and a ring-opening polymerization reaction between the ester bond of the active ester compound (B1) and the epoxy group of the epoxy resin (A) proceed favorably. As a result, an epoxy resin composition having good photocurability, heat resistance, photopatterning properties, and optical loss suppression properties can be obtained. In addition, since the epoxy group of the epoxy resin (A) undergoes ring-opening polymerization with the ester bond, it is expected that hydroxyl groups will be less likely to be generated after the photopolymerization reaction.

[0056] Specifically, the active ester compound (B1) preferably includes one or more compounds having structures represented by the following formulas (1-B1) and (2-B1).

[0057]

[0058] (In formula (1-B1), R １（Ｂ１） is hydrogen or a methyl group, and R ２（Ｂ１） is a hydrocarbon skeleton having 1 to 15 carbon atoms, and R ３（Ｂ１） is a hydrocarbon group having 1 to 40 carbon atoms, and one of the five bonds of the benzene ring indicated by * in (1a) is R indicated by * in (1b). ３（Ｂ１） and the remaining bond is bonded to a hydrogen atom or a hydrocarbon group having 1 to 2 carbon atoms.)

[0059]

[0060] (In formula (2-B1), R ４（Ｂ１） is hydrogen or a methyl group, and R ５（Ｂ１） is a hydrocarbon skeleton having 1 to 15 carbon atoms, and R ６（Ｂ１） is a hydrocarbon group having 1 to 40 carbon atoms, and one of the five bonds of the benzene ring indicated by * in (2a) is bonded to the bond of oxygen indicated by * in (2b), and the remaining bond is bonded to hydrogen or a hydrocarbon group having 1 to 2 carbon atoms.

[0061] When the active ester compound (B1) contains one or more compounds having the structures represented by the above formulas (1-B1) and (2-B1), both the radical polymerization reaction at the (meth)acrylic group moiety and the ring-opening polymerization reaction between the ester bond adjacent to the benzene ring and the epoxy group of the epoxy resin (A) proceed favorably and reliably. Therefore, an epoxy resin composition having excellent photocurability, heat resistance, photopatterning properties, and optical loss suppression properties can be reliably obtained. Furthermore, as mentioned above, it is expected that hydroxyl groups will be less likely to be generated after the photopolymerization reaction.

[0062] In the above formula (1-B1), R ２（Ｂ１） is preferably a hydrocarbon skeleton having 1 to 10 carbon atoms, more preferably a hydrocarbon skeleton having 1 to 6 carbon atoms. ３（Ｂ１） is preferably a hydrocarbon group having 1 to 25 carbon atoms. ５（Ｂ１） is preferably a hydrocarbon skeleton having 1 to 10 carbon atoms, more preferably a hydrocarbon skeleton having 1 to 5 carbon atoms. ６（Ｂ１） is preferably a hydrocarbon group having 1 to 25 carbon atoms.

[0063] Such an active ester compound (B1) may be synthesized by any method known to those skilled in the art, or a commercially available reagent may be used. For example, an active ester compound (B1) having the structural formula represented by the above formula (1-B1) includes 2-methyl-1,4-phenylene bis[4-[[[4-(acryloyloxy)butoxy]carbonyl]oxy]benzoate.

[0064] Furthermore, for example, an active ester compound (B1) having the structural formula represented by the above formula (2-B1) includes dienestrol diacetate.

[0065] Other examples of the activated ester compound (B1) having the structural formula represented by formula (2-B1) above include eugenol acetate represented by formula (2-B1-a) below, 2-vinylphenyl acetate represented by formula (2-B1-b) below, 4-cyanophenyl 4-(3-butenyloxy)benzoate represented by formula (2-B1-c) below, and 4-methoxyphenyl 4-(3-butenyloxy)benzoate represented by formula (2-B1-d) below.

[0066]

[0067] These active ester compounds (B1) may be used singly or in combination of two or more. The ester equivalent of the active ester compound (B1) is not particularly limited, but may be, for example, 150 g / eq to 380 g / eq.

[0068] (Acid Anhydride Compound (B2)) When the resin composition contains an acid anhydride compound (B2) having a vinyl group as the ester compound (B), both the radical polymerization reaction at the vinyl group portion of the acid anhydride compound (B2) and the ring-opening polymerization reaction between the acid anhydride group of the acid anhydride compound (B2) and the epoxy group of the epoxy resin (A) proceed favorably. Therefore, an epoxy resin composition having excellent photocurability, heat resistance, photopatterning properties, and optical loss suppression properties can be obtained. Furthermore, since the epoxy group of the epoxy resin (A) undergoes ring-opening polymerization with the acid anhydride group, it is expected that hydroxyl groups will be less likely to be generated after the photopolymerization reaction.

[0069] Specifically, the acid anhydride compound (B2) preferably contains one or more compounds having a structure represented by the following formula (3-B2):

[0070]

[0071] (In formula (3-B2), R １（Ｂ２） is hydrogen or a methyl group, and R ２（Ｂ２） is a hydrocarbon skeleton having 1 to 15 carbon atoms, and one of the bonds of the carbon atom indicated by * in (3b) is R ２（Ｂ２） and the other bond is bonded to a hydrogen atom or a hydrocarbon group having 1 to 2 carbon atoms.)

[0072] When the acid anhydride compound (B2) contains a compound having the structure represented by the above formula (3-B2), both the radical polymerization reaction at the (meth)acrylic group moiety and the ring-opening polymerization reaction between the acid anhydride group and the epoxy group of the epoxy resin (A) proceed favorably and reliably. Therefore, an epoxy resin composition having excellent photocurability, heat resistance, photopatterning properties, and optical loss suppression properties can be reliably obtained. Furthermore, as described above, it is expected that hydroxyl groups will be less likely to be generated after the photopolymerization reaction.

[0073] In the above formula (3-B2), R ２（Ｂ２） is preferably a hydrocarbon skeleton having 1 to 25 carbon atoms, more preferably a hydrocarbon skeleton having 1 to 12 carbon atoms.

[0074] Such an acid anhydride compound (B2) may be synthesized by any method known to those skilled in the art, or a commercially available reagent may be used. For example, an example of a compound having a structure represented by the above formula (3-B2) is allylsuccinic anhydride.

[0075] Other examples of the acid anhydride compound (B2) include "EPICLON B 4500" manufactured by DIC Corporation. These acid anhydride compounds (B2) may be used alone or in combination of two or more. The acid anhydride group equivalent of the acid anhydride compound (B2) is not particularly limited, but may be, for example, 100 g / eq to 200 g / eq.

[0076] As the ester compound (B), the ester compound (B1) and the acid anhydride compound (B2) may be used in combination.

[0077] As described above, from the viewpoint of the reaction mechanism between the ester bond and / or acid anhydride group and the epoxy group, the content of the ester compound (B1) and / or acid anhydride compound (B2) relative to the total resin components is preferably adjusted so that the equivalent ratio of the total of the ester groups and acid anhydride groups in the ester compound (B) to the epoxy groups in the epoxy resin (A) is from 0.1 to 3. The more preferable range is also as described above.

[0078] [Photopolymerization initiator (C)] The resin composition contains a photopolymerization initiator (C). The photopolymerization initiator (C) is not particularly limited as long as it is a polymerization initiator that generates active species such as radicals, anions, and cations upon irradiation with light such as ultraviolet light and promotes photocuring of the resin composition containing the epoxy resin (A) and the ester compound (B).

[0079] The photopolymerization initiator (C) preferably contains a radical photopolymerization initiator (C1). When the photopolymerization initiator (C) contains the radical photopolymerization initiator (C1), the radical polymerization reaction of the vinyl group moiety in the ester compound (B) (and the optionally contained partially esterified epoxy resin (A1)) can be favorably and reliably promoted. As a result, an epoxy resin composition having good photocurability, heat resistance, photopatterning properties, and optical loss suppression properties can be more reliably obtained.

[0080] Examples of the radical photopolymerization initiator (C1) include aromatic ketones, acylphosphine oxide compounds, aromatic onium salt compounds, organic peroxides, thio compounds (thioxanthone compounds, thiophenyl group-containing compounds, etc.), hexaarylbiimidazole compounds, oxime ester compounds, borate compounds, azinium compounds, metallocene compounds, other active ester compounds, compounds having a carbon-halogen bond, and alkylamine compounds. Commercially available products can also be used as the radical photopolymerization initiator (C1). Examples of commercially available radical photopolymerization initiators (C1) include the "OXE" series (e.g., "OXE01," "OXE02," "OXE03," and "OXE04" manufactured by BASF Japan Ltd.), the "omnirad" series and "Omnipol" series manufactured by IGM Corporation, and the "ADEKA COOLS NCI" series manufactured by ADEKA Corporation.

[0081] The photopolymerization initiator (C) may contain a cationic photopolymerization initiator (C2) (photoacid generator) as long as the effects of photocurability, heat resistance, photopatterning properties, and light loss suppression properties according to this embodiment are not impaired. Examples of the cationic photopolymerization initiator (C2) include antimony-based polymerization initiators, phosphorus-based polymerization initiators, special phosphorus-based polymerization initiators, and borate-based polymerization initiators. Furthermore, commercially available products can be used as the cationic photopolymerization initiator (C2). Examples of commercially available cationic photopolymerization initiators (C2) include the "WPI" series manufactured by Fujifilm Photo Pure Chemical Industries, Ltd., "CPI-310FG" and "CPI-101A" manufactured by San-Apro Co., Ltd., and "SP-170" manufactured by ADEKA Corporation.

[0082] These photopolymerization initiators (C) may be used singly or in combination of two or more.

[0083] The total content of the photopolymerization initiator (C) is not particularly limited, but is preferably 0.5 parts by mass or more and 15 parts by mass or less, more preferably 1 part by mass or more and 10 parts by mass or less, and even more preferably 1 part by mass or more and 5 parts by mass or less, relative to 100 parts by mass of the epoxy resin (A).

[0084] [Other Polymerization Initiators] The resin composition may contain a polymerization initiator other than the photopolymerization initiator. Specifically, the resin composition preferably contains a thermal polymerization initiator (D) that generates an active species such as an anion or a cation upon heating and promotes curing of the resin composition containing the epoxy resin (A) and the ester compound (B).

[0085] For example, the resin composition preferably contains an anionic polymerization initiator (D1), which is an example of the thermal polymerization initiator (D). By including the anionic polymerization initiator (D1) in the resin composition, the ring-opening polymerization reaction between the ester bond and / or acid anhydride group and the epoxy group of the epoxy resin (A) can be favorably and reliably promoted. Therefore, an epoxy resin composition having excellent photocurability, heat resistance, photopatterning properties, and optical loss suppression properties can be more reliably obtained. In addition, it is expected that hydroxyl groups will be less likely to be generated after the photopolymerization reaction.

[0086] Examples of the anionic polymerization initiator (D1) include organic phosphines such as triphenylphosphine, tertiary amines such as 1,8-diazabicyclo(5,4,0)undecene-7, and imidazoles such as 2-methylimidazole.

[0087] In particular, the anionic polymerization initiator (D1) is preferably used in combination with the above-mentioned radical photopolymerization initiator (C1). By using these polymerization initiators in combination, both the radical polymerization reaction of the vinyl group moiety and the ring-opening polymerization reaction of the ester bond and / or acid anhydride group with the epoxy group can be favorably and reliably promoted.

[0088] The total content of the anionic polymerization initiator (D1) is not particularly limited, but is preferably from 0.1 to 3 mass%, more preferably from 0.5 to 2 mass%, and even more preferably from 0.8 to 1.5 mass%, relative to 100 parts by mass of the epoxy resin (A).

[0089] [Other Additives] In addition to the components described above, the resin composition may further contain other additives as long as the effects of the photocurability, heat resistance, photopatternability, and optical loss suppression properties according to this embodiment are not impaired. Examples of other additives include antioxidants, leveling agents, coupling agents (silane coupling agents), flame retardants, and inorganic fillers.

[0090] In particular, from the viewpoint of improving heat resistance, it is preferable that the resin composition further contains an antioxidant. The antioxidant is not particularly limited, and phenol-based antioxidants, phosphite-based antioxidants, sulfur-based antioxidants, etc. can be used. Among these, the antioxidant is preferably a phenol-based antioxidant.

[0091] Commercially available phenolic antioxidants can be used, such as "AO-20," "AO-30," "AO-40," "AO-50," "AO-60," and "AO-80" manufactured by Adeka Corporation, and "SUMILIZER GA-80" manufactured by Sumitomo Chemical Co., Ltd.

[0092] The content of the antioxidant (C) is not particularly limited, but is preferably 0 parts by mass or more and 5 parts by mass or less, and more preferably 0 parts by mass or more and 3 parts by mass or less, relative to 100 parts by mass of the epoxy resin (A).

[0093] As described above, the resin composition according to this embodiment has good photocurability, heat resistance after curing, and photopatterning properties, and can suppress optical loss in the 1310 nm wavelength band. Furthermore, in the resin composition according to this embodiment, the ester bond of the active ester compound (B1) and / or the acid anhydride group of the acid anhydride compound (B2) undergo ring-opening polymerization with the epoxy group of the epoxy resin (A). Therefore, it is expected that hydroxyl groups will be less likely to be generated after the photopolymerization reaction. Therefore, as described below, the resin composition according to this embodiment is expected to be suitable not only for optical waveguide applications, but also for interlayer insulation applications.

[0094] 2. Epoxy Resin Composition for Optical Waveguides The epoxy resin composition for optical waveguides according to this embodiment includes the epoxy resin composition according to the above-described embodiment, which has favorable effects in terms of photocurability, heat resistance, optical patterning properties, and optical loss suppression properties. Therefore, the epoxy resin composition for optical waveguides according to this embodiment can be suitably used as a material for films and the like used in producing optical waveguides. However, the epoxy resin composition for optical waveguides according to this embodiment does not necessarily have to be used after a film has been formed in the production of an optical waveguide.

[0095] The epoxy resin composition for optical waveguides according to this embodiment or a film that can be produced using the same may be used to produce either the core layer or the cladding layer of an optical waveguide. However, optical patterning ability is a characteristic that is primarily required when forming a core layer in a fine pattern. Furthermore, optical loss in the 1310 nm wavelength band occurs primarily in the core. Therefore, when the epoxy resin composition for optical waveguides according to this embodiment or a film that can be produced using the same is used for the core, it can more effectively exhibit the effects of good optical patterning ability and suppression of optical loss in the 1310 nm wavelength band.

[0096] In the optical waveguide finally manufactured by this method, the core layer has good optical patterning properties and can suppress optical loss in the 1310 nm wavelength band, thereby realizing excellent optical communication. Therefore, a substrate on which such an optical waveguide is formed is preferably used as an optical transmission printed wiring board, and is preferably used for, for example, a mobile phone, a personal digital assistant, etc.

[0097] 3. Epoxy Resin Composition for Interlayer Insulation The epoxy resin composition for interlayer insulation according to this embodiment includes the epoxy resin composition according to the above-described embodiment, which is unlikely to generate hydroxyl groups after a photopolymerization reaction and is expected to be used as an insulating material. It is expected that the epoxy resin composition for interlayer insulation can be suitably used, for example, as a material for a layer to be laminated on a clad layer in order to insulate an optical waveguide formed from a core layer and a clad layer.

[0098] The epoxy resin composition for interlayer insulation preferably further contains a filler from the viewpoint of reducing the thermal expansion coefficient of the cured product of the resin composition. The filler material is not particularly limited, but examples thereof include silica, alumina, glass, cordierite, silicone oxide, barium sulfate, barium carbonate, talc, clay, mica powder, zinc oxide, etc. Of these, from the viewpoints of insulating properties and industrial availability, the filler material preferably contains silica.

[0099] When an epoxy resin composition for interlayer insulation contains a filler, the filler is generally contained in the form of particles. The average particle size of the filler particles is not particularly limited, but from the viewpoint of obtaining an interlayer insulation layer with low surface roughness, it is preferably 5 μm or less, and more preferably 2 μm or less. Furthermore, from the viewpoint of suppressing an increase in the viscosity of the varnish when made into a resin varnish and preventing a decrease in handleability, the average particle size of the filler particles is preferably 0.01 μm or more, and more preferably 0.05 μm or more.

[0100] When the epoxy resin composition for interlayer insulation contains a filler, the content of the filler is preferably 20 parts by mass or more and 300 parts by mass or less, and more preferably 50 parts by mass or more and 200 parts by mass or less, per 100 parts by mass of the epoxy resin (A).

[0101] 4. Resin-Coated Film The resin-coated film according to this embodiment has a support film and a resin layer containing the epoxy resin composition according to the above-described embodiment or a semi-cured product of the epoxy resin composition. The resin layer is preferably a resin layer containing the epoxy resin composition for optical waveguides according to the above-described embodiment or a semi-cured product of the epoxy resin composition for optical waveguides, or a resin layer containing the epoxy resin composition for interlayer insulation according to the above-described embodiment or a semi-cured product of the epoxy resin composition for interlayer insulation.

[0102] In this specification, the term "semi-cured product" refers to a resin composition that has been prepared by applying a liquid material containing a varnish-like epoxy resin composition as described below, and then optionally heating, drying, and irradiating with light, such as ultraviolet light, at an appropriate temperature and time, so that the resin has partially cured and is in a state where it can be further cured. Furthermore, in this specification, the term "uncured product" refers to a resin composition that has been optionally heated and dried at an appropriate temperature and time, so that the resin has not yet cured.

[0103] In this specification, the term "cured product" refers to a resin layer that does not melt even when heated due to the curing reaction of an uncured or semi-cured resin layer that has progressed due to irradiation with light such as ultraviolet light, causing the resin to crosslink. The core layer and / or clad layer of the optical waveguide include a cured product of the resin layer.

[0104] The resin-containing film according to this embodiment may have, for example, a support film on at least one surface of the resin layer. Furthermore, the resin-containing film may have a protective film laminated on the other surface of the resin layer. Furthermore, the resin-containing film may have other layers in addition to the resin layer, the support film, and an optional protective film.

[0105] The support film is not particularly limited, but examples thereof include polyethylene terephthalate (PET) film, biaxially oriented polypropylene film, polyethylene naphthalate film, polyimide film, etc. Among these, PET film is preferable. The protective film is not particularly limited, but examples thereof include polypropylene film, etc.

[0106] The method for producing the resin-coated film is not particularly limited, but examples thereof include the following method. First, a varnish-like liquid material containing the epoxy resin composition according to the above-described embodiment is prepared by adding a solvent or the like as needed. Next, the prepared liquid material is applied to a support film. This application can be performed using a comma coater or the like. The applied liquid material is then heated and dried at an appropriate temperature and time, and if necessary, irradiated with light, such as ultraviolet light, to form a resin layer containing an uncured or semi-cured epoxy resin composition on the support film, thereby obtaining a resin-coated film. Furthermore, a protective film may be laminated on this resin layer. Examples of methods for laminating the protective film include thermal lamination.

[0107] In this specification, a film formed on the support film or the like and containing a resin layer containing an uncured product of the epoxy resin composition or a semi-cured product of the epoxy resin composition is also referred to as a dry film.

[0108] The resin-coated film according to this embodiment is suitable for use as a material for an optical waveguide. Specifically, the resin-coated film is suitable for use in producing a core layer or clad layer, preferably a core layer, of an optical waveguide. Furthermore, the resin-coated film can also be used as a material for a layer for insulating an optical waveguide.

[0109] 5. Liquid Material The liquid material according to this embodiment includes the epoxy resin composition according to the above-described embodiment. The liquid material is preferably a liquid material for an optical waveguide. Furthermore, the epoxy resin composition is preferably the epoxy resin composition for an optical waveguide according to the above-described embodiment or the epoxy resin composition for interlayer insulation according to the above-described embodiment.

[0110] Specifically, as described above, the liquid material is a varnish-like epoxy resin composition according to the embodiment described above, containing, as necessary, a solvent, etc. The solvent is not particularly limited as long as it is an arbitrary epoxy resin solvent known to those skilled in the art, and examples thereof include methyl ethyl ketone, toluene, xylene, gamma butyrolactone, acetone, methyl isobutyl ketone, cyclohexanone, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, ethyl acetate, butyl acetate, ethyl lactate, N,N-dimethylformamide, dimethylacetamide, dimethyl sulfoxide, and N-methyl-2-pyrrolidone.

[0111] The liquid material according to this embodiment can be used directly in the production of a core layer or clad layer, preferably a core layer, of an optical waveguide without going through a film formation process, and can also be used directly as a material for a layer for insulating an optical waveguide.

[0112] As described above, this specification discloses various aspects of the technology, the main aspects of which are summarized below.

[0113] The epoxy resin composition according to a first aspect of the present invention contains an epoxy resin (A), an ester compound (B), and a photopolymerization initiator (C), wherein the ester compound (B) includes one or more selected from an active ester compound (B1) having a vinyl group and an aromatic ring and an acid anhydride compound (B2) having a vinyl group.

[0114] An epoxy resin composition according to a second aspect of the present invention is the epoxy resin composition according to the first aspect, wherein the active ester compound (B1) includes one or more compounds having structures represented by the following formulas (1-B1) and (2-B1):

[0115]

[0116] (In formula (1-B1), R １（Ｂ１） is hydrogen or a methyl group, and R ２（Ｂ１） is a hydrocarbon skeleton having 1 to 15 carbon atoms, and R ３（Ｂ１）is a hydrocarbon group having 1 to 40 carbon atoms, and one of the five bonds of the benzene ring indicated by * in (1a) is R indicated by * in (1b). ３（Ｂ１） and the remaining bond is bonded to a hydrogen atom or a hydrocarbon group having 1 to 2 carbon atoms.)

[0117]

[0118] (In formula (2-B1), R ４（Ｂ１） is hydrogen or a methyl group, and R ５（Ｂ１） is a hydrocarbon skeleton having 1 to 15 carbon atoms, and R ６（Ｂ１） is a hydrocarbon group having 1 to 40 carbon atoms, and one of the five bonds of the benzene ring indicated by * in (2a) is bonded to the bond of oxygen indicated by * in (2b), and the remaining bond is bonded to hydrogen or a hydrocarbon group having 1 to 2 carbon atoms.

[0119] An epoxy resin composition according to a third aspect of the present invention is the epoxy resin composition according to the first or second aspect, wherein the acid anhydride compound (B2) includes one or more compounds having a structure represented by the following formula (3-B2):

[0120]

[0121] (In formula (3-B2), R １（Ｂ２） is hydrogen or a methyl group, and R ２（Ｂ２） is a hydrocarbon skeleton having 1 to 15 carbon atoms, and one of the bonds of the carbon atom indicated by * in (3b) is R ２（Ｂ２） and the other bond is bonded to a hydrogen atom or a hydrocarbon group having 1 to 2 carbon atoms.)

[0122] An epoxy resin composition according to a fourth aspect of the present invention is the epoxy resin composition according to any one of the first to third aspects, wherein the epoxy resin (A) comprises a partially esterified epoxy resin (A1).

[0123] An epoxy resin composition according to a fifth aspect of the present invention is the epoxy resin composition according to the fourth aspect, wherein the content of the partially esterified epoxy resin (A1) is 50 parts by mass or more relative to 100 parts by mass of the epoxy resin (A).

[0124] An epoxy resin composition related to a sixth aspect of the present invention is the epoxy resin composition according to the fourth or fifth aspect, wherein the partially esterified epoxy resin (A1) is a compound having a structure represented by the following formula (1-A1):

[0125]

[0126] (In formula (1-A1), R １（Ａ１） and R ２（Ａ１） are each independently a hydrogen atom or a methyl group, and R ３（Ａ１） is a hydrocarbon skeleton having 13 to 27 carbon atoms.

[0127] An epoxy resin composition according to a seventh aspect of the present invention is the epoxy resin composition according to any one of the first to sixth aspects, wherein the photopolymerization initiator (C) includes a radical photopolymerization initiator (C1).

[0128] An epoxy resin composition according to an eighth aspect of the present invention is the epoxy resin composition according to any one of the first to seventh aspects, further comprising an anionic polymerization initiator (D1).

[0129] An epoxy resin composition for optical waveguides according to a ninth aspect of the present invention comprises the epoxy resin composition according to any one of the first to eighth aspects.

[0130] An epoxy resin composition for interlayer insulation according to a tenth aspect of the present invention comprises the epoxy resin composition of any one of the first to eighth aspects.

[0131] A resin-coated film according to an eleventh aspect of the present invention has a resin layer containing the epoxy resin composition of any one of the first to eighth aspects or a semi-cured product of the epoxy resin composition, a resin layer containing the epoxy resin composition for optical waveguides of the ninth aspect or a semi-cured product of the epoxy resin composition for optical waveguides, or a resin layer containing the epoxy resin composition for interlayer insulation of the tenth aspect or a semi-cured product of the epoxy resin composition for interlayer insulation, and a support film.

[0132] A liquid material according to a twelfth aspect of the present invention comprises the epoxy resin composition according to any one of the first to eighth aspects, the epoxy resin composition for optical waveguides according to the ninth aspect, or the epoxy resin composition for interlayer insulation according to the tenth aspect.

[0133] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples in any way.

[0134] In this example, various epoxy resin compositions were prepared by varying the content ratio of various epoxy resins (A), including a partially esterified epoxy resin (A1), and an ester compound (B). The prepared epoxy resin compositions were then evaluated for photocurability, optical loss in the 1310 nm wavelength band, and heat resistance and photopatternability of the cured products.

[0135] First, the raw materials used in preparing the epoxy resin compositions of the present examples are summarized below.

[0136] <Epoxy Resin (A)> [Partially Esterified Epoxy Resin (A1)] "3000AD-E5": bisphenol A type epoxy resin (acrylate ratio 50%, liquid epoxy resin), manufactured by Kyoeisha Chemical Co., Ltd. (epoxy equivalent 390 g / eq) "3000MD-E5": bisphenol A type epoxy resin (methacrylate ratio 50%, liquid epoxy resin), manufactured by Kyoeisha Chemical Co., Ltd. (epoxy equivalent 420 g / eq) "BFEA-50": bisphenol F type epoxy resin (acrylate ratio 50%, liquid epoxy resin), manufactured by KSM Corporation (epoxy equivalent 360 g / eq) [Other Epoxy Resins] "YS8040": hydrogenated bisphenol A type epoxy resin (solid epoxy resin), manufactured by Mitsubishi Chemical Corporation (epoxy equivalent 1000 g / eq) "1006FS": bisphenol A type epoxy resin (solid epoxy resin), manufactured by Mitsubishi Chemical Corporation (epoxy equivalent 1000 g / eq) "EHPE3150": multifunctional (alicyclic) bisphenol A type epoxy resin (solid epoxy resin), manufactured by Daicel Chemical Industries, Ltd. (epoxy equivalent 180 g / eq) "YX7760": fluorine-containing bisphenol A type epoxy resin (solid epoxy resin), manufactured by Mitsubishi Chemical Corporation (epoxy equivalent 224 g / eq) "VG3101M80": bisphenol A type trifunctional epoxy resin (solid epoxy resin), manufactured by Printec Co., Ltd. (epoxy equivalent 210 g / eq) <Ester Compound (B)> [Activated Ester Compound (B1)] "2-methyl-1,4-phenylene bis[4-[[[4-(acryloyloxy)butoxy]carbonyl]oxy]benzoate": reagent, manufactured by Tokyo Chemical Industry Co., Ltd. (ester equivalent: 336 g / eq) "Dienestrol diacetate": reagent, manufactured by Tokyo Chemical Industry Co., Ltd. (ester equivalent: 175 g / eq) [Acid anhydride compound (B2)] "Allylsuccinic anhydride": reagent, manufactured by Tokyo Chemical Industry Co., Ltd. (acid anhydride equivalent: 140 g / eq) <Photopolymerization initiator (C)> "OXE02": radical photopolymerization initiator, manufactured by BASF Japan Ltd. "CPI310FG": cationic photopolymerization initiator, manufactured by San-Apro Co., Ltd. <Thermal polymerization initiator (D)> "DMAP" (N,N-dimethylaminopyridine): an anionic polymerization initiator, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. <Antioxidants> "AO-60": a phenolic antioxidant, manufactured by ADEKA Corporation,

[0137] "2-methyl-1,4-phenylene bis[4-[[[4-(acryloyloxy)butoxy]carbonyl]oxy]benzoate" is an active ester compound (B1) having a structural formula represented by the following formula (1-B1-1).

[0138] "Dienestrol diacetate" is an active ester compound (B1) having the structural formula represented by the following formula (2-B1-1).

[0139] "Allylsuccinic anhydride" is an acid anhydride compound (B2) having the structural formula represented by the following formula (3-B2-1).

[0140] Next, the methods for preparing the epoxy resin compositions (resin varnishes) and the methods for producing the dry films used in each evaluation in each Example and Comparative Example are described below. Furthermore, the methods for evaluating photocurability, measuring and evaluating optical loss, measuring and evaluating heat resistance of the cured products, and measuring and evaluating photopatterning properties are also described below.

[0141] <Method of Preparing Epoxy Resin Composition (Resin Varnish)> In each Example and Comparative Example, the components were blended according to the formulation (parts by mass) shown in Tables 1 to 3 below, and the mixed solvent of MEK and toluene was adjusted to 55 parts by mass per 100 parts by mass of the total epoxy resin. The blend and mixed solvent were then mixed while heating at 50°C to 60°C. Next, the mixture was filtered through a membrane filter with a pore size of 1.0 μm and then degassed, thereby preparing the epoxy resin compositions (resin varnishes) of Examples 1 to 17 and Comparative Examples 1 to 6.

[0142] <Method for manufacturing dry film> The epoxy resin composition (resin varnish) of each example and comparative example was applied to a PET film (product number A4100) manufactured by Toyobo Co., Ltd. using a multi-coater with a comma coater head manufactured by Hirano Tecseed Co., Ltd. The PET film was then dried at 130°C for 10 minutes to a predetermined thickness, and a release film, OPP-MA420 manufactured by Oji Specialty Paper Co., Ltd., was thermally laminated onto it. In this way, a dry film of the desired thickness was finally obtained for use in subsequent evaluation tests.

[0143] <Method for Evaluating Photocurability> The photocurability of the epoxy resin composition was evaluated by the following method. Specifically, the dry films of each of the Examples and Comparative Examples prepared as described above were subjected to a 10 mW / cm irradiance using an electrodeless H bulb manufactured by Heraeus K.K. ２ at an illuminance of 2000 mJ / cm ２ The film was cured by irradiating it with ultraviolet light. The surface of the cured film was then touched with a finger. Photocurability was evaluated according to the following criteria. The evaluation results are summarized in Tables 1 to 3 below. Evaluation criteria: A: No tacky feel on the surface of the film after curing B: No part of the film adheres to the finger, but the film surface feels tacky C: Part of the film adheres to the finger, and the film surface feels tacky

[0144] <Method for measuring and evaluating optical loss in the 1310 nm wavelength band> (Production of waveguide samples) For measuring and evaluating optical loss in the 1310 nm wavelength band, first, the 7 μm-thick dry films of each Example and Comparative Example produced as described above were used as core dry films to produce waveguide samples. Note that, as shown in Table 3 below, the epoxy resin compositions (resin varnishes) of Comparative Examples 2 and 3 had poor photocurability and could not be used to form dry films, so optical loss was not measured.

[0145] The cladding dry films for each of the Examples and Comparative Examples of the waveguide samples were manufactured by the following method. The base epoxy resin (A) was 100 parts by mass of the epoxy resin (A) having the same composition as the core composition of each of the Examples and Comparative Examples to be evaluated, and 10 parts by mass of "YX8040" was further added per 100 parts by mass of the epoxy resin (A), for a total of 110 parts by mass of the epoxy resin (A). The cladding composition other than the epoxy resin (A) was the same as the core composition of each of the Examples and Comparative Examples to be evaluated, as shown in Tables 1 to 3 below. That is, the blending amounts of the ester compound (B), photopolymerization initiator (C), thermal polymerization initiator (D), and antioxidant in the cladding composition were determined as the amounts (parts by mass) relative to 100 parts by mass of the epoxy resin (A) in the original core composition or the amounts (phr) relative to the resin components in the original core composition, as shown in Tables 1 to 3 below. The cladding composition blend containing 110 parts by weight of epoxy resin (A) prepared in this manner was dissolved in a mixed solvent of 50 parts by weight of MEK and toluene per 110 parts by weight of epoxy resin (A). The mixture was then filtered through a polytetrafluoroethylene (PTFE) membrane filter with a pore size of 1.0 μm and degassed to prepare a resin varnish. The prepared resin varnish was applied to a PET film (product number A4100) manufactured by Toyobo Co., Ltd. using a multi-coater with a comma coater head manufactured by Hirano Tecseed Co., Ltd. The film was then dried to obtain a 20 μm-thick dry film for cladding.

[0146] Next, the obtained dry film for cladding was laminated onto a substrate using a vacuum laminator "V-130" under conditions of 65°C and 0.3 MPa. After that, it was exposed to 2 J / cm irradiated with an ultra-high pressure mercury lamp. ２ After irradiation, the release film of the clad dry film was peeled off, and the clad dry film was heat-treated at 160° C. for 30 minutes to harden the clad dry film and form an underclad.

[0147] The core dry film in each example and comparative example was then laminated onto the surface of the underclad using a vacuum laminator "V-130" under the same method and conditions as described above. After peeling off the release film from the core dry film, the film was heat-treated at 150°C for 15 minutes, exposed to a light intensity of 2 J / cm2 from an ultra-high pressure mercury lamp with a mask placed on it, and then further heat-treated at 160°C for 30 minutes. The unexposed portions of the dry film were then dissolved and removed by development using a water-based flux cleaner (Arakawa Chemical Industries, Ltd., "Pine Alpha ST-100SX") adjusted to 55°C as the developer. After dissolution and removal, the core portion was finish-washed with water, air-blown, and dried at 120°C for 15 minutes to form a core.

[0148] Furthermore, a dry film for cladding was laminated onto the formed core using a vacuum laminator "V-130" under conditions of 80°C and 0.3 MPa. After peeling off the release film from the laminated dry film for cladding, the core was heat-treated at 140°C for 20 minutes and then irradiated with 2 J / cm using an ultra-high pressure mercury lamp. ２ The clad dry film was irradiated with ultraviolet light at a light intensity of 1000 nm. Thereafter, the laminated film was further heat-treated at 160° C. for 30 minutes to harden the clad dry film and form an overclad, thereby obtaining a waveguide sample for evaluation.

[0149] (Measurement and Evaluation of Optical Loss in the 1310 nm Wavelength Band) Using the waveguide samples manufactured as described above, optical loss in the 1310 nm wavelength band was measured using the following method. Light from a 1310 nm LED light source was passed through an optical fiber with a core diameter of 9 μm and an NA of 0.12 and incident on the end of the manufactured waveguide sample via matching oil (silicone oil). Furthermore, an optical fiber with a core diameter of 50 μm and an NA of 0.21 was passed through the same matching oil, and the other end of the waveguide sample was connected to a power meter to measure the power (P1) when an optical circuit was inserted. In addition, the power (P0) was measured by butting two similar optical fibers together without an optical circuit. From the measured value, the optical loss (dB / cm) at a wavelength of 1310 nm was calculated using the formula -10 log (P1 / Po). The calculation results of optical loss (dB / cm) at a wavelength of 1310 nm for each example and comparative example are summarized in Tables 1 to 3 below. When the optical loss was 0.6 dB / cm or less, the optical loss was evaluated as being well suppressed, and when the optical loss was more than 0.6 dB / cm, the optical loss was evaluated as being large.

[0150] <Method for measuring and evaluating heat resistance of cured products> The heat resistance of the cured products was measured by the following method. First, the dry films of each of the Examples and Comparative Examples, each having a thickness of 20 μm, were irradiated with 2 J / cm 2 of an ultra-high pressure mercury lamp. ２ The dry film was irradiated with ultraviolet light at a light intensity of 1000 uV. After irradiation, the release film was peeled off, and the film was heat-treated at 160°C for 30 minutes to obtain a cured film. Thereafter, the YI value of the cured epoxy resin composition before heating was measured as the initial YI value using a spectrophotometer ("CM5", manufactured by Konica Minolta, Inc.) in accordance with ASTM E313. As shown in the measurement results in Tables 1 to 3 below, the initial YI value of Example 14 was 0.3, while the initial YI values ​​of the other Examples and Comparative Examples were all the same, 0.2.

[0151] The cured products of each Example and Comparative Example were then heated at 150°C for 100 hours using a thermostatic oven (Perfect Oven PHH402, manufactured by Espec Corporation). After heating, the YI value of the cured products of each Example and Comparative Example was measured using the same method as before heating. If the YI value of the cured product after heating was less than 0.8, the heat resistance of the cured product of the epoxy resin composition was evaluated as good. On the other hand, if the YI value of the cured product after heating was 0.8 or higher, the heat resistance of the cured product of the epoxy resin composition was evaluated as poor. The measurement results are summarized in Tables 1 to 3 below.

[0152] <Method for measuring and evaluating photo-patterning property> The photo-patterning property of the epoxy resin composition was measured and evaluated by the following method. Specifically, the 7 μm-thick core dry film of each of the Examples and Comparative Examples produced as described above was laminated onto the underclad using a vacuum laminator "V-130" under the same conditions as above. After peeling off the release film from the dry film, a mask for forming a 7 μm-wide core was placed on top, and the film was exposed to 2 J / cm irradiated with an ultra-high pressure mercury lamp. ２ The dry film was exposed to a light intensity of 1000 kJ / cm² and further heat-treated at 150°C for 15 minutes. The unexposed portions of the dry film were then developed using a water-based flux cleaner (Pine Alpha ST-100SX, manufactured by Arakawa Chemical Industries, Ltd.) adjusted to 55°C as the developer, thereby dissolving and removing the unexposed portions. After dissolving and removing the unexposed portions, the core portion was given a final wash with water, air-blown, and dried at 120°C for 15 minutes to form a core. The shape of the formed core, specifically its core width, was then measured using a confocal microscope (manufactured by Lasertec Corporation), and the photopatternability was evaluated based on the measured values. The core width measurement was the average value obtained by measuring five random locations. The evaluation criteria for photopatternability are shown below. The core width measurements and evaluation results are summarized in Tables 1 to 3 below. Evaluation criteria: A: The measured core width is within the range of 6.0 μm or more and 8.0 μm or less. B: The measured core width is within the range of 5.5 μm or more and less than 6.0 μm, or more than 8.0 μm and 8.5 μm or less. C: The measured core width is within the range of less than 5.5 μm or more than 8.5 μm.

[0153] The evaluation and measurement results for each of the above examples and comparative examples, along with the blended compositions, are summarized in the following Tables 1 to 3. In the following Tables 1 to 3, "-" indicates that the composition was not blended or that no measurement was made.

[0154]

[0155]

[0156]

[0157] <Discussion> As shown in Tables 1 and 2 above, the epoxy resin compositions of Examples 1 to 17 contain an epoxy resin (A), any one of dienestrol diacetate (active ester compound (B1)), 2-methyl-1,4-phenylene bis[4-[[[4-(acryloyloxy)butoxy]carbonyl]oxy]benzoic acid] (active ester compound (B1)), and allylsuccinic anhydride (acid anhydride compound (B2)), and a photopolymerization initiator (C). All of these epoxy resin compositions were evaluated as being good.

[0158] This is believed to be due to the favorable progress of the photo-ring-opening polymerization reaction between the ester bond of the active ester compound (B1) or the acid anhydride group of the acid anhydride compound (B2) and the epoxy group of the epoxy resin (A). Furthermore, it is believed that such photo-ring-opening polymerization reaction resulted in almost no generation of hydroxyl groups after the photopolymerization reaction. As a result, the epoxy resin composition exhibited favorable photocurability and effectively suppressed optical loss. Furthermore, the cured product exhibited favorable heat resistance without discoloration after heating. Furthermore, it is believed that the favorable progress of the radical polymerization reaction due to the vinyl group of the active ester compound (B1) or the acid anhydride compound (B2) also resulted in favorable photo-patterning properties.

[0159] In particular, the epoxy resin compositions of Examples 1 to 17 also contain a partially esterified epoxy resin (A1) as the epoxy resin (A). Therefore, it is presumed that the radical polymerization reaction also proceeded favorably at the double bond moiety of the partially esterified epoxy resin (A1), resulting in better photopatterning properties.

[0160] On the other hand, the epoxy resin composition of Comparative Example 1, which contained only the partially esterified epoxy resin (A1) "3000AD-E5" as a resin component, exhibited high optical loss, poor heat resistance of the cured product, and slightly inferior photopatterning properties. This is thought to be because the radical polymerization reaction of the double bonds in the partially esterified epoxy resin (A1) proceeded, but the ring-opening polymerization reaction of the epoxy groups did not proceed because the resin composition did not contain the ester compound (B). As a result, it is assumed that a large number of epoxy groups ultimately remained in the cured product. Furthermore, since the radical polymerization reaction proceeded only through the double bonds contained in the partially esterified epoxy resin (A1) itself, it is assumed that the photopatterning properties were also slightly inferior.

[0161] The epoxy resin composition of Comparative Example 2, which contained only another epoxy resin, "1006FS," as a resin component, was unable to form a dry film. This is thought to be because the resin composition did not contain a cationic photopolymerization initiator that favorably promotes the ring-opening polymerization reaction of the epoxy groups in "1006FS."

[0162] The resin composition of Comparative Example 3, which contained only dienestrol diacetate (active ester compound (B1)) as a resin component, also failed to form a dry film. This is thought to be because the resin component did not contain an epoxy resin, and the polymerization reaction did not proceed smoothly.

[0163] The epoxy resin composition of Comparative Example 4, which contained the partially esterified epoxy resin (A1) "3000AD-E5" and another epoxy resin "YS8040" as resin components, exhibited slightly inferior photocurability, significant optical loss, and the cured product had poor heat resistance and photopatternability. This is believed to be because the resin composition did not contain the ester compound (B), and the ring-opening polymerization reaction of the epoxy groups in the partially esterified epoxy resin (A1) and the other epoxy resins did not proceed satisfactorily. As a result, it is believed that many epoxy groups ultimately remained in the cured product. Furthermore, because the content of "3000AD-E5" (partially esterified epoxy resin (A1)) was lower than the content of "YS8040" (the other epoxy resin), the radical polymerization reaction of the double bonds hardly proceeded, resulting in poor photopatternability.

[0164] The epoxy resin composition of Comparative Example 5 differs from the epoxy resin composition of Comparative Example 1 in that the photopolymerization reaction of "3000AD-E5" was induced using a cationic photopolymerization initiator (C2) instead of a radical photopolymerization initiator (C1). The epoxy resin composition of Comparative Example 5 exhibited greater optical loss and a cured product with poorer heat resistance than the results of Comparative Example 1. This is thought to be because the polymerization of the partially esterified epoxy resin (A1) using the cationic photopolymerization initiator (C2) caused the epoxy groups of the partially esterified epoxy resin (A1) to undergo ring-opening polymerization with each other, ultimately resulting in the generation of hydroxyl groups.

[0165] The epoxy resin composition of Comparative Example 6 differs from the epoxy resin composition of Comparative Example 2 in that the photopolymerization reaction of "1006FS" was induced using a cationic photopolymerization initiator (C2) instead of a radical photopolymerization initiator (C1). With the epoxy resin composition of Comparative Example 6, a dry film could be formed, but the optical loss was large and the heat resistance of the cured product was poor. This is thought to be because the epoxy groups in the epoxy resin (A) underwent ring-opening polymerization with each other when the epoxy resin (A) was polymerized using the cationic photopolymerization initiator (C2), resulting in the generation of hydroxyl groups.

[0166] This application is based on Japanese Patent Application No. 2023-219707 filed on December 26, 2023, the contents of which are incorporated herein by reference.

[0167] The embodiments and examples disclosed herein should be understood to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0168] According to the present invention, it is possible to provide an epoxy resin composition that has good photocurability, heat resistance after curing, and optical patterning properties, and that can suppress optical loss in the 1310 nm wavelength band. Furthermore, it is expected that the epoxy resin composition can be suitably used not only as a material for optical waveguides for forming core layers and cladding layers, but also as a material for insulating the optical waveguides.

Claims

1. An epoxy resin composition containing an epoxy resin (A), an ester compound (B), and a photopolymerization initiator (C), wherein the ester compound (B) contains one or more selected from an active ester compound (B1) having a vinyl group and an aromatic ring and an acid anhydride compound (B2) having a vinyl group.

2. The epoxy resin composition according to claim 1, wherein the active ester compound (B1) contains one or more of the compounds having the structures represented by the following formula (1-B1) and formula (2-B1). (In formula (1-B1), R １（Ｂ１） is hydrogen or a methyl group, R ２（Ｂ１） is a hydrocarbon skeleton having 1 to 15 carbon atoms, R ３（Ｂ１） is a hydrocarbon group having 1 to 40 carbon atoms, and among the five bonds of the benzene ring indicated by * in (1a), any one of the bonds is bonded to the bond of R3(B1) indicated by * in (1b), and the remaining bonds are bonded to hydrogen or a hydrocarbon group having 1 to 2 carbon atoms.) (In formula (2-B1), R ４（Ｂ１） is hydrogen or a methyl group, R ５（Ｂ１） is a hydrocarbon skeleton having 1 to 15 carbon atoms, R ６（Ｂ１） is a hydrocarbon group having 1 to 40 carbon atoms, and among the five bonds of the benzene ring indicated by * in (2a), any one of the bonds is bonded to the bond of oxygen indicated by * in (2b), and the remaining bonds are bonded to hydrogen or a hydrocarbon group having 1 to 2 carbon atoms.) 3. The epoxy resin composition according to claim 1, wherein the acid anhydride compound (B2) contains one or more compounds having a structure represented by the following formula (3-B2). (In formula (3-B2), R １（Ｂ２） is hydrogen or a methyl group, and R ２（Ｂ２） is a hydrocarbon skeleton having 1 to 15 carbon atoms, and among the bonds of the carbon indicated by * in (3b), one of the bonds is the bond of R ２（Ｂ２） indicated by * in (3a), and the other bond is bonded to hydrogen or a hydrocarbon group having 1 to 2 carbon atoms.) 4. The epoxy resin composition according to claim 1, wherein the epoxy resin (A) contains a partially esterified epoxy resin (A1).

5. The epoxy resin composition according to claim 4, wherein the content of the partially esterified epoxy resin (A1) is 50 parts by mass or more with respect to 100 parts by mass of the epoxy resin (A).

6. The epoxy resin composition according to claim 4, wherein the partially esterified epoxy resin (A1) is a compound having a structure represented by the following formula (1-A1). (In formula (1-A1), R １（Ａ１） and R ２（Ａ１） are each independently hydrogen or a methyl group, and R ３（Ａ１） is a hydrocarbon skeleton having 13 to 27 carbon atoms.) 7. The epoxy resin composition according to claim 1, wherein the photopolymerization initiator (C) contains a radical photopolymerization initiator (C1).

8. The epoxy resin composition according to claim 1, further containing an anionic polymerization initiator (D1).

9. An epoxy resin composition for an optical waveguide, containing the epoxy resin composition according to any one of claims 1 to 8.

10. An epoxy resin composition for interlayer insulation, containing the epoxy resin composition according to any one of claims 1 to 8.

11. A film with a resin, having a resin layer containing the epoxy resin composition according to any one of claims 1 to 8 or a semi-cured product of the epoxy resin composition, and a support film.

12. A liquid material containing the epoxy resin composition according to any one of claims 1 to 8.

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