Resin composition for optical waveguide, and dry film, optical waveguide, and semiconductor package substrate using same

Abstract

One aspect of the present invention pertains to a resin composition for an optical waveguide, the resin composition comprising epoxy compounds (A) and cationic curing catalysts (B). The epoxy compounds (A) include an epoxy group-containing polyorganosiloxane compound (a1). The percentage content of the polyorganosiloxane compound (a1) is 40 mass% or more with respect to 100 mass% of the epoxy compounds (A). The cationic curing catalysts (B) include a curing catalyst (b1) having an anionic species from which a conjugate acid having a strength that is equal to or more than the strength of HSbF6 is obtained, and a curing catalyst (b2) having an anionic species from which a conjugate acid having a strength that is less than the strength of HSbF6 is obtained.

Description

Resin composition for optical waveguide, and dry film, optical waveguide, and semiconductor package substrate using the same

[0001] The present invention relates to a resin composition for an optical waveguide, and to a dry film, an optical waveguide, and a semiconductor package substrate using 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] It is known that an optical waveguide is formed by forming a cladding layer, a core layer, etc. using a highly transparent resin material, exposing the cladding layer to ultraviolet (UV) radiation or the like, developing the cladding layer, and then curing the resin. It has also been reported that a resin composition containing an epoxy compound and a curing agent, which have excellent light resistance, etc., is used as the resin material for such an optical waveguide (Patent Document 1).

[0004] However, in recent years, there has been a demand for optical waveguide materials with even higher performance. Specifically, optical waveguide materials are being required to have lower optical loss and excellent light resistance, light resistance and developability, film handling properties, patterning properties, curing properties, etc. In response to this demand, a curable resin composition containing an epoxy group-containing polyorganosiloxane compound and a hydrogenated epoxy resin has been reported as a material with excellent light resistance, etc. (Patent Document 2).

[0005] The resin composition described in Patent Document 2 has excellent photocurability and light resistance, but is not a composition for optical waveguides. The epoxy group-containing polyorganosiloxane compound contained in the resin composition does not have UV curability by itself, and the hydrogenated epoxy resin contained in the resin composition contains a large amount of aliphatic moieties. Therefore, when used for optical waveguides, there is a problem that optical loss at a wavelength of 1310 nm becomes large.

[0006] Therefore, the main object of the present invention is to improve the above problems and to provide a resin composition for optical waveguides that has low optical loss and is excellent in light resistance, developability, film handling properties, patterning properties, and curing properties, as well as a dry film and an optical waveguide using the same.

[0007] JP 2017-134319 A JP 2022-100721 ​​A

[0008] As a result of extensive research into solving the above problems, the present inventors have found that the above problems can be solved by the following configuration.

[0009] That is, a resin composition for an optical waveguide according to one aspect of the present invention contains an epoxy compound (A) and a cationic curing catalyst (B), the epoxy compound (A) contains an epoxy group-containing polyorganosiloxane compound (a1), the content of the polyorganosiloxane compound (a1) is 40 mass% or more relative to 100 mass% of the epoxy compound (A), and the cationic curing catalyst (B) is a polyorganosiloxane having a conjugate acid strength of HSbF ６ and a curing catalyst (b1) having an anion species having a strength of at least HSbF ６ and a curing catalyst (b2) having an anion species having a strength lower than that of the curing catalyst (b1).

[0010] FIG. 1 is a schematic cross-sectional view illustrating one embodiment of a method for forming an optical waveguide using the resin composition of this embodiment.

[0011] Hereinafter, embodiments for carrying out the present invention will be specifically described, but the present invention is not limited to these.

[0012] [Resin Composition for Optical Waveguide] The resin composition for optical waveguide of this embodiment (hereinafter sometimes simply referred to as resin composition) contains an epoxy compound (A) and a cationic curing catalyst (B). The epoxy compound (A) contains an epoxy group-containing polyorganosiloxane compound (a1). The content of the polyorganosiloxane compound (a1) is 40 mass% or more relative to 100 mass% of the epoxy compound (A). The cationic curing catalyst (B) is a polyorganosiloxane having a conjugate acid strength of HSbF ６and a curing catalyst (b1) having an anion species having a strength of at least HSbF ６ and a curing catalyst (b2) having an anion species having a strength lower than that of the curing catalyst (b1).

[0013] With this configuration, the resin composition of this embodiment can suppress optical loss (particularly optical loss at a wavelength of 1310 nm) in the cured product. Furthermore, it is also excellent in light resistance, patterning properties, developability, film handling properties, and curing properties, making it extremely useful for industrial applications. That is, according to the present invention, it is possible to provide a resin composition for optical waveguides that has low optical loss and is excellent in light resistance, developability, film handling properties, patterning properties, and curing properties, as well as a dry film and an optical waveguide using the same. Furthermore, it is possible to provide a semiconductor package substrate including the optical waveguide.

[0014] The resin composition of this embodiment is for optical waveguides and can be used for both clad layers and core layers. However, since optical loss at a wavelength of 1310 nm occurs in the core, the resin composition of this embodiment is more effective when used for the core layer.

[0015] (Epoxy Compound (A)) The epoxy compound (A) of this embodiment contains an epoxy group-containing polyorganosiloxane compound (a1). Furthermore, the epoxy compound (A) may contain an epoxy compound (a2) other than the polyorganosiloxane compound (a1). Each epoxy compound will be described below.

[0016] Epoxy group-containing polyorganosiloxane compound (a1) of the present embodiment is a compound having siloxane bond as the main chain and containing epoxy group.By using such an epoxy group-containing compound having siloxane bond, it is possible to obtain a resin composition having excellent light resistance, patterning property, developability, film handling property, etc.

[0017] More specifically, examples of the epoxy group-containing polyorganosiloxane compound (a1) of this embodiment include compounds represented by the following formula (1):

[0018] In formula (1), R １ ~R ５ are each independently a hydrogen atom, a monovalent organic group having 1 to 20 carbon atoms which may have a substituent, a group represented by the following formula (2), or a group represented by the following formula (3):

[0019] R １ ~R ５ may be the same or different groups, but R １ ~R ５ At least one of the above is a group represented by the following formula (2) or (3).

[0020] In formula (2), R ７ is a divalent organic group having 1 to 20 carbon atoms which may have a substituent.

[0021] In formula (3), R ８ is a divalent organic group having 1 to 20 carbon atoms which may have a substituent.

[0022] Also, R ６ is a monovalent organic group having 1 to 7 carbon atoms, and a to d are integers satisfying a+b+c=1 and 0≦d<4.

[0023] In this embodiment, examples of the "monovalent organic group having 1 to 20 carbon atoms which may have a substituent" include a linear alkyl group having 1 to 20 carbon atoms, a branched alkyl group having 1 to 20 carbon atoms, an alkyl group having 1 to 20 carbon atoms which has a cyclic structure, an aromatic hydrocarbon group having 1 to 20 carbon atoms, and a heterocyclic group having 1 to 20 carbon atoms. More specific examples include alkyl groups such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a sec-butyl group, a tert-butyl group, an octyl group, and a cyclohexyl group; aromatic functional groups such as a phenyl group, a naphthyl group, a carbazole group, and a phenethyl group; and ether groups such as a furanyl group and a polyethylene glycol group.

[0024] In a preferred embodiment, R １ ~R ５ is a hydrogen atom, a methyl group, a phenyl group, or the like.

[0025] In the present embodiment, examples of the "monovalent organic group having 1 to 7 carbon atoms" include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a cyclohexyl group, and a phenyl group. ６ Among these, is preferably a methyl group or a phenyl group.

[0026] In this embodiment, examples of the "divalent organic group having 1 to 20 carbon atoms" include a methylene group, an ethylene group, a propylene group, an isopropylene group, and a butylene group. ７ Among these, R is preferably a methylene group. ８ Among these, is preferably a methylene group.

[0027] The epoxy equivalent of the epoxy group-containing polyorganosiloxane compound (a1) is not particularly limited, but is usually preferably 100 g / equivalent or more and 5000 g / equivalent or less. Having the epoxy equivalent within the above range has the advantage of being able to form a uniform cured film and improve crosslink density. A more preferred lower limit of the epoxy equivalent is 150 g / equivalent or more, more preferably 200 g / equivalent or more. A more preferred upper limit is 2000 g / equivalent or less, and more preferably 1000 g / equivalent or less. In this specification, "epoxy equivalent" is defined as "the mass of an epoxy resin (in the present invention, an epoxy group-containing polyorganosiloxane) containing 1 equivalent of epoxy groups" and can be measured in accordance with JIS K7236.

[0028] The weight average molecular weight (Mw) of the epoxy group-containing polyorganosiloxane (a1) of this embodiment is not particularly limited, but is preferably 300 or more and 10,000 or less. Having the weight average molecular weight (Mw) within this range has the advantage of excellent handleability. A more preferred lower limit of the weight average molecular weight is 500 or more, more preferably 700 or more. A more preferred upper limit is 7,500 or less, more preferably 5,000 or less.

[0029] The number average molecular weight (Mn) of the epoxy group-containing polyorganosiloxane (a1) of the present invention is not particularly limited, but is preferably 150 or more and 9000 or less. Having the number average molecular weight (Mn) within the above range has the advantage of excellent handleability. A more preferred lower limit of the number average molecular weight is 250 or more, and even more preferably 600 or more. Furthermore, a more preferred upper limit is 6500 or less, and particularly preferably 4000 or less.

[0030] The weight average molecular weight (Mw) of the epoxy group-containing polyorganosiloxane can be measured by gel permeation chromatography (GPC).

[0031] These epoxy group-containing polyorganosiloxanes (a1) may be used alone or in combination of two or more.

[0032] In addition, the epoxy group-containing polyorganosiloxane (a1) used in this embodiment is preferably solid at room temperature. That is, it is preferable to use a polyorganosiloxane (a1) having a melting point of 50 ° C. or higher. This is thought to improve the film performance when made into a film.

[0033] The epoxy group-containing polyorganosiloxane (a1) of the present invention is not particularly limited as long as it is a polyorganosiloxane containing epoxy group, but it is preferable that it has a cyclic siloxane structure in the polyorganosiloxane skeleton.It is thought that the epoxy group-containing polyorganosiloxane (a1) has a cyclic siloxane structure, which has the advantage of improving the impact resistance of the cured product.

[0034] The content of the epoxy group-containing polyorganosiloxane (a1) in the resin composition of this embodiment is 40% by mass or more relative to 100% by mass of the epoxy compound (A). If the content is less than 40% by mass, the suppression of light loss may be insufficient or the heat resistance may be reduced. A more preferred range of the content is 80% by mass or more. There is no particular limitation on the upper limit of the content of the epoxy group-containing polyorganosiloxane (a1), and it may be 100% by mass. However, from the viewpoint of the curability of the resin composition, the film performance (tackiness) when made into a film, etc., it is preferably 100% by mass or less, more preferably 95% by mass or less.

[0035] Epoxy Compound (a2) Other Than Polyorganosiloxane Compound (a1) The resin composition of this embodiment may contain, as the epoxy compound (A), an epoxy compound (a2) other than the epoxy group-containing polyorganosiloxane (a1). Examples of such epoxy compound (a2) include bisphenol A epoxy compounds, hydrogenated bisphenol A epoxy compounds, bisphenol AF epoxy compounds, polyfunctional epoxy compounds, alicyclic epoxy compounds, novolac epoxy compounds, and aliphatic epoxy compounds.

[0036] Among these, the use of an epoxy compound that is solid at room temperature (i.e., an epoxy compound having a melting point of about 50° C. or higher) as the epoxy compound (a2) has the advantage of improving the film performance when made into a film. In addition, the use of an alicyclic epoxy compound or a polyfunctional epoxy compound has the advantage of improving the curability.

[0037] The epoxy compound (a2) is preferably an epoxy compound having a weight-average molecular weight of 1,000 or more. This has the advantage of improving the film performance when made into a film. The upper limit of the weight-average molecular weight is not particularly limited, but from the viewpoint of compatibility with the polyorganosiloxane compound, it is preferably 4,000 or less.

[0038] The bisphenol A epoxy compound used in this embodiment may be a solid bisphenol A epoxy compound or a liquid bisphenol A epoxy compound. The bisphenol A epoxy compound may be prepared by a known method, but commercially available products can also be used. For example, solid bisphenol A epoxy compounds include 1001, 1002, 1003, 1055, 1004, 1004AF, 1003F, 1004F, 1005F, 1004FS, 1006FS, and 1007FS manufactured by Mitsubishi Chemical Corporation. Liquid bisphenol A epoxy compounds include "Epiclon 850S" manufactured by DIC Corporation and "JER (registered trademark) 825" manufactured by Mitsubishi Chemical Corporation.

[0039] The hydrogenated bisphenol A epoxy compound used in this embodiment may be prepared by a known method, or a commercially available product such as "JER (registered trademark) YX8040" manufactured by Mitsubishi Chemical Corporation or "JER (registered trademark) YX8034" manufactured by Mitsubishi Chemical Corporation may be used.

[0040] The bisphenol AF epoxy compound used in this embodiment is a fluorine-containing epoxy subclass, and may be prepared by a known method, but commercially available products such as "YX7760" manufactured by Mitsubishi Chemical Corporation may also be used.

[0041] The polyfunctional epoxy compound used in this embodiment is not particularly limited, but examples thereof include aromatic epoxy compounds having two or more epoxy groups. The polyfunctional epoxy compound may be prepared by a known method, but commercially available products can also be used. Examples of commercially available products that can be used include "VG3101" manufactured by Printec Co., Ltd.

[0042] The alicyclic epoxy compound used in this embodiment is not particularly limited, but commercially available products can be used, such as "EHPE-3150" manufactured by Daicel Chemical Industries, Ltd.

[0043] The epoxy compound (a2) as described above may be used alone or in combination of two or more.

[0044] The content of the epoxy compound (a2) in the resin composition of this embodiment is preferably 5% by mass or more and 60% by mass or less, more preferably 5% by mass or more and 20% by mass or less, based on 100% by mass of the epoxy compound (A).

[0045] (Cationic Curing Catalyst (B)) The resin composition of the present embodiment contains a cationic curing catalyst (B). The cationic curing catalyst (B) is a cationic curing catalyst having a conjugate acid strength of HSbF ６ and a curing catalyst (b1) having an anion species having a strength of at least HSbF ６ The resin composition of the present embodiment contains a curing catalyst (b2) having an anion species with a strength lower than that of the cationic curing catalyst (B). By containing such a cationic curing catalyst (B), the resin composition of the present embodiment has sufficient curability (uniform UV curing is possible) and patterning ability.

[0046] The curing catalyst (b1) is particularly suitable for curing a polymer having a conjugate acid strength of HSbF ６ The curing catalyst (b2) preferably contains an ionic photoacid generator having an anion species with a strength of at least HSbF. ６ and preferably contains an ionic photoacid generator having an anion species with a strength lower than that of HPF ６ It is more preferred that the photosensitive resin composition contains an ionic photoacid generator having an anion species with a strength of not more than 1.0.

[0047] The curing catalyst (b1) is, for example, (Rf) ｎ PF ６－ｎ － an ionic photoacid generator (Rx) having ｎ BX ４－ｎ － and (Rx) ｎ GaX ４－ｎ － The curing catalyst (b2) contains at least one ionic photoacid generator selected from the group consisting of ionic photoacid generators having the formula: ６ －an ionic photoacid generator having BF ４ － an ionic photoacid generator having the formula (Rf)SO ３ － and ionic photoacid generators having a sulfite ion.

[0048] In addition, (Rf) ｎ PF ６－ｎ － and (Rf)SO ３ － In the formula (Rf), Rf is a perfluoroalkyl group. ｎ PF ６－ｎ － In the formula, n is any number from 1 to 5. (Rf) ｎ PF ６－ｎ － In the formula (Rf), the number of carbon atoms in Rf is, for example, 1 or more and 3 or less, and when there are multiple Rfs, the Rfs may be the same or different from each other. ３ － The number of carbon atoms in Rf is, for example, 1 or more and 8 or less.

[0049] (Rx) ｎ BX ４－ｎ － and (Rx) ｎ GaX ４－ｎ － In each of the above, Rx is a phenyl group in which some of the hydrogen atoms are substituted with halogen atoms or electron-withdrawing substituents. The halogen atoms are fluorine atoms, chlorine atoms, bromine atoms, etc. The electron-withdrawing substituents are, for example, trifluoromethyl groups, nitro groups, cyano groups, etc. (Rx) ｎ BX ４－ｎ － and (Rx) ｎ GaX ４－ｎ － In each of the above formulas, X is a halogen atom, and preferably a fluorine atom. (Rx) ｎ BX ４－ｎ － and (Rx) ｎ GaX ４－ｎ －In each of the formulas, n is any number from 1 to 4. When there are a plurality of Rx, Rx may be the same or different. Rx can be, for example, C ６ F ５ , (CF ３ ) ２ C ６ H ３ , C.F. ３ C ６ H ４ , or C ６ H ３ F ２ etc. (Rx) ｎ BX ４－ｎ － For example, (C ６ F ５ ) ４ B － , ((CF ３ ) ２ C ６ H ３ ) ４ B － , (CF ３ C ６ H ４ ) ４ B － , (C ６ F ５ ) ２ BF ２ － , C ６ F ５ BF ３ － Or (C ６ H ３ F ２ ) ４ B － etc.

[0050] The cationic species in the ionic photoacid generator contained in the curing catalyst (b1) and the cationic species in the ionic photoacid generator contained in the curing catalyst (b2) are not particularly limited, and examples thereof include at least one selected from the group consisting of various aromatic oniums, more specifically, various aromatic diazoniums, aromatic haloniums, aromatic sulfoniums, and the like.

[0051] The content of the curing catalyst (B) is preferably 1% by mass or more and 4% by mass or less relative to 100% by mass of the epoxy compound (A). It is believed that such a content can more reliably achieve the effects (curability, patternability) described above. A more preferred range of the content is 1% by mass or more and 2% by mass or less.

[0052] In addition, the content ratio of the curing catalyst (b1) to the curing catalyst (b2) in the curing catalyst (B) is preferably 0.25 to 2 parts by mass of the curing catalyst (b2) per 1 part by mass of the curing catalyst (b1), which is believed to more reliably achieve the effects (curability, patternability) described above.

[0053] (Other Components) In addition to the above, the resin composition of the present embodiment may also contain additives such as antioxidants, leveling agents, coupling agents (silane coupling agents), flame retardants, and inorganic fillers.

[0054] In order to further improve heat resistance, the resin composition of this embodiment preferably 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, phenol-based antioxidants are preferred.

[0055] The specific phenolic antioxidant is not particularly limited, and commercially available products 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.

[0056] The content of the antioxidant is preferably 5% by mass or less relative to the total amount of the epoxy compounds. Furthermore, since the antioxidant may not be contained, the content is preferably 0% by mass or more. That is, the content of the antioxidant is preferably 0% by mass or more and 5% by mass or less relative to the total amount of the epoxy compounds.

[0057] The resin composition according to the present embodiment as described above is excellent in light resistance, patterning properties, developability, and curability, and also has excellent film performance (film handleability) when made into a film. In addition, the cured product has small optical loss, making it extremely useful as a material for optical waveguides.

[0058] [Dry Film for Optical Waveguide] The resin composition for an optical waveguide can be used as a material for a dry film used in producing an optical waveguide.

[0059] The dry film for optical waveguides according to another embodiment of the present invention is not particularly limited as long as it includes a layer made of the resin composition. Specifically, the dry film for optical waveguides includes a layer made of a semi-cured or cured product of the resin composition (hereinafter also simply referred to as a resin composition layer). The dry film of this embodiment may also include a substrate film laminated on at least one side of the resin composition layer. Furthermore, a protective film may be laminated on the other side of the resin composition layer.

[0060] The dry film for optical waveguide of this embodiment only needs to have the resin composition layer, and may have other layers in addition to the film substrate and protective film, and the film substrate and protective film are not required.

[0061] The film substrate 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 preferably used.

[0062] The protective film is not particularly limited, but examples thereof include polypropylene films.

[0063] The method for producing the dry film for optical waveguides of this embodiment is not particularly limited, and examples thereof include the following methods. First, a solvent or the like is added to the resin composition for optical waveguides described above to form a varnish, and the varnish is applied to a film substrate. This application can be performed using a comma coater or the like. Then, the varnish is dried to form a resin composition layer on the film substrate. Furthermore, a protective film is laminated on this resin composition layer. Examples of the lamination method include a thermal lamination method.

[0064] The resin composition layer in this dry film for optical waveguides is used as a material for optical waveguides. The dry film for optical waveguides may be used when producing a core or a clad of an optical waveguide, but is preferably used for the core because it can further suppress light loss at a wavelength of 1310 nm. The dry film of this embodiment has excellent light resistance, curing properties, and developability, and is also easy to handle.

[0065] Furthermore, the resin composition for an optical waveguide according to this embodiment does not necessarily have to be used as a dry film, and may be used, for example, in the form of a varnish. This composition for an optical waveguide may be used in producing a core of an optical waveguide, or in producing a clad, similar to a dry film for an optical waveguide. Thus, when an optical waveguide is produced using the resin composition for an optical waveguide and the dry film for an optical waveguide, end face deformation and the like are unlikely to occur even when subjected to heat treatment, and an optical waveguide with high connection reliability can be obtained.

[0066] The present invention also encompasses an optical waveguide formed from the above-described resin composition for an optical waveguide and the above-described dry film for an optical waveguide. That is, the optical waveguide of this embodiment is an optical waveguide comprising a core layer and a clad layer having a refractive index lower than that of the core layer, and is characterized in that the clad layer and / or the core layer are formed from the above-described resin composition for an optical waveguide or dry film. In a preferred embodiment, the core layer is formed from the above-described resin composition for an optical waveguide or dry film. The optical waveguide of this embodiment is highly useful for industrial applications because it is less susceptible to end face deformation even at high temperatures and has high connection reliability.

[0067] An embodiment of forming an optical waveguide on a substrate using the dry film of this embodiment will be described below with reference to Fig. 1. The reference numerals in the figure represent the following: 1 clad dry film, 2 core dry film, 3 clad, 3a underclad, 3b overclad, and 4 core.

[0068] In forming the optical waveguide of this embodiment, a clad dry film and a core dry film are used to form the core and clad, respectively. Note that in the following embodiments, the above-mentioned optical waveguide dry film is used as the core dry film.

[0069] 1(a), a cladding dry film 1 is laminated onto the surface of a substrate 10 on which an electric circuit 11 is formed, and then the cladding dry film 1 is cured by irradiation with light such as ultraviolet light or by heating. The cladding dry film 1 may be the same as the optical waveguide dry film described above, but it is preferable to use a dry film with a lower refractive index than the core dry film 2.

[0070] The substrate 10 may be, for example, a flexible printed wiring board having an electrical circuit formed on one side of a transparent base material such as a polyimide film, or a printed wiring board such as a glass epoxy board. By this process, an undercladding 3a is formed and laminated on the surface of the substrate 10, as shown in FIG. 1(b).

[0071] 1(c), a core dry film 2 is laminated on the surface of the undercladding 3a, and then a mask having slits of the core pattern is placed over it, and photocurable light such as ultraviolet light is irradiated through the slits to expose the core pattern to the core dry film 2. The exposure method may be a selective exposure method using a mask, or a direct writing method in which a laser beam is scanned and irradiated along the pattern shape.

[0072] Next, after the exposure, the core dry film 2 is developed using a developer such as an aqueous flux cleaner to remove the resin from the unexposed and uncured portions of the core dry film 2. As a result, a core 4 having a predetermined core pattern is formed on the surface of the underclad 3a, as shown in FIG.

[0073] Next, as shown in Fig. 1(e), a clad dry film 1 is laminated to cover the underclad 3a and the core 4. Then, the clad dry film 1 is cured by light irradiation or heating to form an overclad 3b as shown in Fig. 1(f). In this way, an optical waveguide A is formed on the surface of the substrate 10, with the core 4 embedded in the clad 3 consisting of the underclad 3a and the overclad 3b.

[0074] The optical waveguide A thus obtained has the above-described configuration, and is therefore excellent in light resistance and suppresses optical loss (particularly optical loss at a wavelength of 1310 nm). Therefore, the substrate 10 on which such an optical waveguide A is formed is preferably used as an optical transmission printed wiring board, and is preferably used for applications such as CPO (Co-Packed Optics) and optical transceivers.

[0075] Furthermore, the present invention also includes a semiconductor package substrate including the optical waveguide described above.

[0076] As described above, this specification discloses various aspects of the technology, the main aspects of which are summarized below.

[0077] The resin composition for optical waveguide according to the first aspect of the present invention contains an epoxy compound (A) and a cationic curing catalyst (B), wherein the epoxy compound (A) contains an epoxy group-containing polyorganosiloxane compound (a1), and the content of the polyorganosiloxane compound (a1) is 40 mass% or more relative to 100 mass% of the epoxy compound (A), and the cationic curing catalyst (B) is a polyorganosiloxane having a conjugate acid strength of HSbF ６ and a curing catalyst (b1) having an anion species having a strength of at least HSbF ６ and a curing catalyst (b2) having an anion species having a strength lower than that of the curing catalyst (b1).

[0078] The resin composition for optical waveguides according to a second aspect of the present invention is the resin composition for optical waveguides according to the first aspect, in which the polyorganosiloxane compound (a1) has a structure represented by the following formula (1): [In formula (1), R １ ~R ５ are each independently a hydrogen atom, a monovalent organic group having 1 to 20 carbon atoms which may have a substituent, a group represented by the following formula (2), or a group represented by the following formula (3); R １ ~R ５ At least one of R is a group represented by the following formula (2) or (3): ６ is a monovalent organic group having 1 to 7 carbon atoms; a to d are integers satisfying a+b+c=1 and 0≦d<4. (In formula (2), R ７ is a divalent organic group having 1 to 20 carbon atoms which may have a substituent. (In formula (3), R ８ represents a divalent organic group having 1 to 20 carbon atoms which may have a substituent.

[0079] A resin composition for optical waveguides according to a third aspect of the present invention is the resin composition for optical waveguides according to the first or second aspect, in which the content of the curing catalyst (B) is 1% by mass or more and 4% by mass or less relative to 100% by mass of the epoxy compound (A).

[0080] A resin composition for optical waveguides according to a fourth aspect of the present invention is the resin composition for optical waveguides according to any one of the first to third aspects, in which the content ratio of the hard curing catalyst (b1) to the curing catalyst (b2) is 0.25 parts by mass or more and 2 parts by mass or less of the curing catalyst (b2) per part by mass of the curing catalyst (b1).

[0081] A resin composition for optical waveguides according to a fifth aspect of the present invention is the resin composition for optical waveguides according to any one of the first to fourth aspects, in which the epoxy compound (A) further contains an epoxy compound (a2) different from the polyorganosiloxane compound (a1).

[0082] A dry film according to a sixth aspect of the present invention is formed using the resin composition for an optical waveguide according to any one of the first to fifth aspects.

[0083] An optical waveguide according to a seventh aspect of the present invention is formed using the resin composition for an optical waveguide according to any one of the first to fifth aspects.

[0084] A semiconductor package substrate according to an eighth aspect of the present invention includes the optical waveguide of the seventh aspect.

[0085] The present invention will be described in more detail below with reference to examples, although the present invention is not limited to the following examples.

[0086] <Epoxy Compound (a1)> First, epoxy group-containing polyorganosiloxanes 1 to 3 were synthesized, and the epoxy equivalent, molecular weight, and ２９ Si-NMR was measured by the following methods.

[0087] (Epoxy Equivalent Weight) The epoxy equivalent weight was measured based on JIS K 7236.

[0088] (Number average molecular weight (Mn) and weight average molecular weight (Mw)) The weight average molecular weight and number average molecular weight were measured by gel permeation chromatography (GPC). The apparatus and measurement conditions used for the GPC measurement are as follows. Apparatus: GPC Model: HLC-8220GPC (manufactured by Tosoh Corporation) Column: KF-G, KF-401HQ, KF-402HQ, KF-402.5HQ (manufactured by Showa Denko K.K.) Detector: UV-8420 (manufactured by Tosoh Corporation), 254 nm Eluent: THF (0.3 mL / min, 40°C) Sample: 10% tetrahydrofuran solution (10 μm injection) Calibration curve: Standard polystyrene (manufactured by Tosoh Corporation)

[0089] ( ２９ Si-NMR measurement method) Measurement was carried out using the following apparatus, measurement conditions, and sample preparation method. Apparatus: JNM-ECS400 manufactured by JEOL Ltd., TUNABLE (10), Si-free, AT10 probe Measurement conditions: Relaxation delay / 15 seconds, number of scans / 1024, measurement mode / non-gated decoupled pulse method (NNE), spin / none, measurement temperature / 25°C Sample preparation: Tris(2,4-pentanedionato)chromium (which may be used alone or in combination of two or more) was added to deuterated chloroform to give a concentration of 0.5 wt %. ２９ A solvent for Si-NMR measurement was obtained. 1.5 g of the epoxy group-containing polyorganosiloxane to be measured was weighed out and ２９ The solution was dissolved in 2.5 ml of a solvent for Si-NMR measurement and placed in a 10 mm diameter Teflon (registered trademark) NMR sample tube.

[0090] <Synthesis Examples> First, the raw materials, catalysts, and solvents used in each Synthesis Example are as follows: Hexamethyldisiloxane (manufactured by NuSil Technology, product name: S-7205) 1,1,3,3-tetramethyldisiloxane (manufactured by NuSil Technology) Methyl silicate MS51 (manufactured by Mitsubishi Chemical Corporation) 1,2-epoxy-4-vinylcyclohexane (manufactured by Daicel Corporation) 1-allyl-2,3-epoxypropane (manufactured by Osaka Soda Co., Ltd.) 1,2-epoxy-4-vinylcyclohexane (manufactured by Daicel Corporation) Tetrahydrofuran (manufactured by Kishida Chemical Co., Ltd.) Toluene (manufactured by Godo Co., Ltd.) Methanol (manufactured by Kishida Chemical Co., Ltd.) Heptane (manufactured by Kishida Chemical Co., Ltd.) 1N hydrochloric acid (manufactured by Kishida Chemical Co., Ltd.) Platinum(0)-[1,3-bis(cyclohexyl)imidazol-2-ylidene][1,3-divinyl-1,1,3,3-tetramethyldisiloxane] complex (manufactured by Umicore Japan, product name: Umicore HS432) Activated carbon (manufactured by Osaka Gas Chemicals Co., Ltd., Purified Shirasagi)

[0091] <Synthesis Example 1: Epoxy Group-Containing Polyorganosiloxane 1> (Synthesis of Epoxy Group-Containing Polyorganosiloxane 1) As raw materials, 744 parts by weight of 1,1,3,3-tetramethyldisiloxane, 599 parts by weight of hexamethyldisiloxane, 500 parts by weight of methyl silicate MS51, 1148 parts by weight of tetrahydrofuran as a solvent, a mixture of 140 parts by weight of 1N hydrochloric acid and 140 parts by weight of methanol as a catalyst and water was used, and hydrolysis and condensation were carried out at 30 ° C. 500 parts by weight of heptane was added, and the hydrochloric acid was removed by washing with demineralized water. After that, the mixture was heated at 76 to 120 ° C. and a reduced pressure of 10 to 20 torr for 13 hours, and 804 parts by weight of polyorganosiloxane precursor 1 was obtained.

[0092] 560 parts by weight of the polyorganosiloxane precursor 1 obtained above was dissolved in 531 parts by weight of heptane, and then 10.5 parts by weight of platinum (0)-[1,3-bis(cyclohexyl)imidazol-2-ylidene][1,3-divinyl-1,1,3,3-tetramethyldisiloxane] complex was added and stirred. After heating to 70 ° C, 503 parts by weight of 1,2-epoxy-4-vinylcyclohexane was added dropwise over 5 hours. Furthermore, 840 parts by weight of activated carbon was added, and the process of stirring for 2 hours and then filtering was repeated three times. The mixture was heated at 70 ° C and a reduced pressure of 40 torr for 10 hours, and 791 parts by weight of epoxy group-containing polyorganosiloxane 1 was obtained.

[0093] (Evaluation results of epoxy group-containing polyorganosiloxane 1) The number average molecular weight of the obtained epoxy group-containing polyorganosiloxane 1 was 1300, the weight average molecular weight was 2500, the epoxy equivalent was 325 g / equivalent, and the M unit, D unit, T unit, and Q unit relative to the total silicon were 65 mol% (a = 0.65), 2 mol% (b = 0.02), 0 mol% (c = 0), and 33 mol% (d = 0.33), respectively. This epoxy group-containing polyorganosiloxane 1 has a cyclic siloxane structure represented by the formula (3) (wherein, R ８ is a methyl group), and the polyorganosiloxane has a branched structure in the polysiloxane skeleton.

[0094] <Synthesis Example 2: Epoxy Group-Containing Polyorganosiloxane 2> (Synthesis of Epoxy Group-Containing Polyorganosiloxane 2) As raw materials, 744 parts by weight of 1,1,3,3-tetramethyldisiloxane, 599 parts by weight of hexamethyldisiloxane, 500 parts by weight of methyl silicate MS51, 1148 parts by weight of tetrahydrofuran as a solvent, a mixture of 140 parts by weight of 1N hydrochloric acid and 140 parts by weight of methanol as a catalyst and water was used, and hydrolysis and condensation were carried out at 30 ° C. 500 parts by weight of heptane was added, and the hydrochloric acid was removed by washing with demineralized water. After that, the mixture was heated at 76 to 120 ° C. and a reduced pressure of 10 to 20 torr for 13 hours, and 804 parts by weight of polyorganosiloxane precursor 2 was obtained.

[0095] 560 parts by weight of the polyorganosiloxane precursor 2 obtained above was dissolved in 531 parts by weight of heptane, and then 10.5 parts by weight of platinum (0)-[1,3-bis(cyclohexyl)imidazol-2-ylidene][1,3-divinyl-1,1,3,3-tetramethyldisiloxane] complex was added and stirred. After heating to 70 ° C, 503 parts by weight of 1-allyl-2,3-epoxypropane was added dropwise over 5 hours. 840 parts by weight of activated carbon was added, stirred for 2 hours, and then filtered. This process was repeated three times, and the mixture was heated at 70 ° C and a reduced pressure of 40 torr for 10 hours to obtain 791 parts by weight of epoxy group-containing polyorganosiloxane 2.

[0096] (Evaluation results of epoxy group-containing polyorganosiloxane 2) The obtained epoxy group-containing polyorganosiloxane 2 had a number average molecular weight of 1300, a weight average molecular weight of 2500, and an epoxy equivalent of 325 g / equivalent. The proportions of M units, D units, T units, and Q units relative to the total silicon were 65 mol% (a = 0.65), 2 mol% (b = 0.02), 0 mol% (c = 0), and 33 mol% (d = 0.33), respectively.

[0097] This epoxy group-containing polyorganosiloxane 2 is a polyorganosiloxane that has a glycidyl epoxy group represented by the following formula (4) as a cyclic siloxane structure and contains a branched structure in the polysiloxane skeleton.

[0098] <Synthesis Example 3: Epoxy Group-Containing Polyorganosiloxane 3> (Synthesis of Epoxy Group-Containing Polyorganosiloxane 3) As raw materials, 744 parts by weight of 1,1,3,3-tetramethyldisiloxane, 599 parts by weight of hexamethyldisiloxane, 500 parts by weight of methyl silicate MS51, 1148 parts by weight of tetrahydrofuran as a solvent, a mixture of 140 parts by weight of 1N hydrochloric acid and 140 parts by weight of methanol as a catalyst and water was used, and hydrolysis and condensation were carried out at 30 ° C. 500 parts by weight of heptane was added, and the hydrochloric acid was removed by washing with demineralized water. After that, the mixture was heated at 76 to 120 ° C. and a reduced pressure of 10 to 20 torr for 13 hours, and 804 parts by weight of polyorganosiloxane precursor 3 was obtained.

[0099] 560 parts by weight of the polyorganosiloxane precursor 3 obtained above was dissolved in 531 parts by weight of heptane, and then 10.5 parts by weight of platinum (0)-[1,3-bis(cyclohexyl)imidazol-2-ylidene][1,3-divinyl-1,1,3,3-tetramethyldisiloxane] complex was added and stirred. After heating to 70 ° C., 251 parts by weight of 1,2-epoxy-4-vinylcyclohexane (manufactured by Daicel Corporation) and 251 parts by weight of 1-allyl-2,3-epoxypropane were added dropwise over 5 hours. Furthermore, 840 parts by weight of activated carbon was added, stirred for 2 hours, and the process of filtering was repeated three times, followed by heating for 10 hours at 70 ° C. under a reduced pressure of 40 torr to obtain 791 parts by weight of epoxy group-containing polyorganosiloxane 3.

[0100] (Evaluation results of epoxy group-containing polyorganosiloxane 3) The obtained epoxy group-containing polyorganosiloxane 3 had a number average molecular weight of 1300, a weight average molecular weight of 2500, and an epoxy equivalent of 325 g / equivalent. The proportions of M units, D units, T units, and Q units relative to the total silicon were 65 mol% (a = 0.65), 2 mol% (b = 0.02), 0 mol% (c = 0), and 33 mol% (d = 0.33), respectively.

[0101] The epoxy group-containing polyorganosiloxane 3 has a cyclic siloxane structure comprising a glycidyl epoxy group represented by the formula (4) and a cyclic siloxane structure represented by the formula (3) (wherein R ８ is a methyl group) and has a branched structure in the polysiloxane skeleton.

[0102] Next, the raw materials other than the epoxy group-containing polyorganosiloxane used in preparing the resin composition in this example are listed below.

[0103] <Epoxy Compounds (a2)> "JER (registered trademark) YX8040": hydrogenated bisphenol A epoxy compound, manufactured by Mitsubishi Chemical Corporation; "Epikote 1006": bisphenol A epoxy compound, manufactured by Mitsubishi Chemical Corporation; "EHPE-3150": alicyclic epoxy compound, manufactured by Daicel Chemical Industries, Ltd.; "YX7760": bisphenol AF epoxy resin (manufactured by Mitsubishi Chemical Corporation); "VG3101": multifunctional epoxy compound, manufactured by Printec Co., Ltd. (3 epoxy groups)

[0104] <Curing catalyst (B)> (Curing catalyst (b1)) "CPI-310B": manufactured by San-Apro Co., Ltd., a triarylsulfonium salt type photoacid generator, anion species B (C ６ F ５ ) ４ － "CPI-210S": Triarylsulfonium salt type photoacid generator manufactured by San-Apro Co., Ltd., anion species (Rf) ｎ PF ６－ｎ － (Curing catalyst (b2)) "CPI-110P": manufactured by San-Apro Co., Ltd., a triarylsulfonium salt type photoacid generator, an anion species PF ６ － "IRGACURE 250": BASF, diaryliodonium salt type photoacid generator, anion species PF ６ －

[0105] <Antioxidants> "AO-60": phenolic antioxidant, manufactured by ADEKA Corporation

[0106] (Examples 1 to 13 and Comparative Examples 1 to 9) <Preparation of Resin Compositions for Optical Waveguides> Components were blended according to the blending compositions (parts by mass) shown in Tables 1 and 2 below, and the mixed solvent of MEK and toluene was adjusted to 55 parts by mass per 100 parts by mass of the resin, and mixed while heating to 50 to 80° C. Next, the mixture was filtered through a membrane filter with a pore size of 0.5 μm and then degassed to prepare resin varnishes of the resin compositions for optical waveguides of Examples 1 to 13 and Comparative Examples 1 to 9.

[0107] <Formation of Dry Film> The resin composition varnish for optical waveguides of each of the Examples and Comparative Examples 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, and dried to a predetermined thickness, followed by thermal lamination with a release film, OPP-MA420 manufactured by Oji Specialty Paper Co., Ltd., to obtain a dry film for use with a resin layer thickness of 7 μm.

[0108] <Evaluation method>

[0109] (Light resistance) For light resistance, instead of the above-mentioned resin varnish, a curable resin composition was prepared by blending a total of 2 parts by mass (solid content) of the curing catalyst (B) with 100 parts by mass of the epoxy resin component of each of the Examples and Comparative Examples and thoroughly mixing them. The curable resin composition of each of the Examples and Comparative Examples was applied to a thickness of 50 μm on a 2 mm thick glass plate using a film applicator, and then measured at 700 mW / cm using an electrodeless H bulb manufactured by Heraeus K.K. ２ at an illuminance of 2000 mJ / cm ２ A coating film was prepared by UV irradiation, and the coating film was subjected to a light resistance test under the following conditions: Apparatus: Metaling Weather Meter MV3000 manufactured by Suga Test Instruments Co., Ltd. Irradiance: 0.4 kW / m ２ Black panel temperature: 63°C Humidity: 50% Test time: 72 hours

[0110] Then, the YI value (ASTM E313) after the light resistance test was measured, and since the smaller the YI value, the better the light resistance, the evaluation was performed according to the following criteria: 1 or less: Excellent, More than 1, 2 or less: Good, More than 2: Fail

[0111] (Curability) The dry films of each Example and Comparative Example were irradiated with ultraviolet light to evaluate their curability. After UV curing, the surface of each film was touched with a finger to check for the presence or absence of tackiness according to the following criteria: A: No tackiness felt B: No adhesion to finger, but tackiness felt C: Tackiness felt, and part of the film adhered to the finger

[0112] (Developability) The dry films of the Examples and Comparative Examples were laminated onto a silicon wafer, a step tablet was placed on it, and an ultra-high pressure mercury lamp equivalent to 2000 mJ was used for irradiation. The wafer was then heated at 150°C for 30 minutes, and developed using a water-based flux cleaner ("Pine Alpha ST-100SX" manufactured by Arakawa Chemical Industries, Ltd.). After development, it was observed how many numbers on the step tablet could be developed. The larger this value, the better the developability.

[0113] The step tablet used was Stouffer Transmission Step Wedge PART #T2115.

[0114] (Film Performance) The resin composition varnish for optical waveguides of each Example and Comparative Example was applied to a PET film and dried at 130°C for 10 minutes to obtain a film (resin layer thickness: 7 µm). The following evaluations were made on the film: 1. Whether resin cracks occurred at the fold when bent at 90 degrees. 2. Whether cracks or powder fall-off occurred at the edge when the film was cut with a cutter.

[0115] Then, cases where neither 1 nor 2 occurred were judged as A, cases where either 1 or 2 occurred were judged as B, and cases where both 1 and 2 occurred were judged as C.

[0116] (Optical Loss) First, optical waveguides were formed using the dry films of each Example and Comparative Example. For the optical waveguides of Examples 1 to 13 and Comparative Examples 1 to 9, the dry films of Examples 1 to 13 and Comparative Examples 1 to 9 were used as core dry films, and dry films having a refractive index smaller than that of the optical waveguides of Examples 1 to 13 and Comparative Examples 1 to 9 were prepared and used for the clad layers.

[0117] The dry cladding film was laminated onto a substrate that had been subjected to oxygen plasma treatment at 65°C and 0.3 MPa using a vacuum laminator "V-130." Then, the substrate was exposed to 2 J / cm irradiated with an ultra-high pressure mercury lamp. ２The cladding curable film was irradiated with ultraviolet light under the conditions of (a) and (b), and then the release film was peeled off and heat-treated at 140° C. for 30 minutes to form an undercladding in which the cladding dry film was cured.

[0118] Next, a core dry film was used and laminated onto the surface of the underclad using a vacuum laminator "V-130" under the same conditions as above. After peeling off the release film, the film was heat-treated at 100°C for 15 minutes, and a 7 μm wide mask was placed on top and exposed to 2 J / cm irradiated with an ultra-high pressure mercury lamp. ２ and then heat-treated at 140° C. for 13 minutes. Next, a development process was carried out using a water-based flux cleaner ("Pine Alpha ST-100SX" manufactured by Arakawa Chemical Industries, Ltd.) adjusted to 55° C. as a developer to dissolve and remove the unexposed portions of the dry film. After a finish cleaning with water and air blowing, the film was dried at 120° C. for 15 minutes to form a core, and an optical waveguide for evaluation testing was obtained.

[0119] Furthermore, a dry film for cladding was laminated thereon using a vacuum laminator "V-130" under conditions of 80°C and 0.3 MPa. After peeling off the release film, the laminate was heat treated at 140°C for 20 minutes, and then irradiated with an ultra-high pressure mercury lamp at 2 J / cm. ２ The cladding curable film was irradiated with ultraviolet light under the conditions of (a) and (b) and then heat-treated at 140° C. for 30 minutes to form an overclad in which the cladding dry film was cured, thereby obtaining an optical waveguide for evaluation testing.

[0120] Thereafter, the optical waveguide sample was cut into a size of 50 mm x 50 mm using a DAC552 manufactured by Disco Corporation at 0.3 mm / sec so that the core was exposed.

[0121] Using the optical waveguide sample manufactured as described above, optical loss at a wavelength of 1310 nm 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 silicone oil was introduced into the end of the manufactured optical waveguide sample via matching oil (refractive index 1.505). 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 side of the optical waveguide sample was connected to a power meter, and the power (P1) when an optical circuit was inserted was measured. In addition, the power (P0) measured by butting two similar optical fibers together without an optical circuit was also measured. From the measured value, the optical loss (1310 nm) was calculated using the formula -10 log (P1 / Po).

[0122] (Patterning ability) As described above, a core was formed using a 7 μm-wide mask, and then the shape of the core was observed with a confocal microscope (manufactured by Lasertec Corp.) If the core width after curing was ±2 μm or less, it was judged as pass, and if it exceeded ±2 μm, it was judged as fail.

[0123] The results are shown in Tables 1 and 2.

[0124]

[0125]

[0126] <Evaluation and Discussion> From the results in Tables 1 and 2, the resin compositions for optical waveguides of the present invention used in the examples were excellent in light resistance, developability, and curability. Furthermore, it was confirmed that the performance of films produced using these resin compositions for optical waveguides of the present invention was also good, with small optical loss and excellent patterning properties.

[0127] On the other hand, in the comparative examples using resin compositions that do not satisfy the provisions of the present invention, the results were inferior to those of the examples in at least one of the evaluation tests. Specifically, in Comparative Example 1, in which the curing catalyst (b2) was not used, the patterning properties were poor, and in Comparative Example 2, in which the curing catalyst (b1) was not used, sufficient light resistance, curability, developability, and film performance could not be obtained. In addition, in Comparative Examples 3 to 8, in which the content of the polyorganosiloxane compound (a1) was low, and in Comparative Example 9, in which the polyorganosiloxane compound (a1) was not used, the light resistance and film performance were poor, and the light loss was also large.

[0128] This application is based on Japanese Patent Application No. 2023-196035, filed on November 17, 2023, the contents of which are incorporated herein by reference.

[0129] In order to express the present invention, the present invention has been properly and sufficiently described above through embodiments with reference to specific examples, drawings, etc., but it should be recognized that those skilled in the art can easily make changes and / or improvements to the above-described embodiments. Therefore, unless changes or improvements made by those skilled in the art deviate from the scope of the claims set forth in the claims, such changes or improvements are construed as being encompassed within the scope of the claims.

[0130] The present invention has wide industrial applicability in technical fields related to optical waveguides and various optical devices.

Claims

1. Contains an epoxy compound (A) and a cationic curing catalyst (B), wherein the epoxy compound (A) contains an epoxy group-containing polyorganosiloxane compound (a1), and the content of the polyorganosiloxane compound (a1) is 40 mass% or more relative to 100 mass% of the epoxy compound (A), and the cationic curing catalyst (B) has a conjugate acid strength of HSbF ６ and a curing catalyst (b1) having an anion species having a strength of at least HSbF ６ and a curing catalyst (b2) having an anion species having a strength lower than that of the curing catalyst (b1).

2. The resin composition for optical waveguides according to claim 1, wherein the polyorganosiloxane compound (a1) has a structure represented by the following formula (1): [In formula (1), R １ ~R ５ are each independently a hydrogen atom, a monovalent organic group having 1 to 20 carbon atoms which may have a substituent, a group represented by the following formula (2), or a group represented by the following formula (3); R １ ~R ５ At least one of R is a group represented by the following formula (2) or (3): ６ is a monovalent organic group having 1 to 7 carbon atoms; a to d are integers satisfying a+b+c=1 and 0≦d<4. (In formula (2), R ７ is a divalent organic group having 1 to 20 carbon atoms which may have a substituent. (In formula (3), R ８ represents a divalent organic group having 1 to 20 carbon atoms which may have a substituent.

3. The resin composition for optical waveguides according to claim 1, wherein the content of the curing catalyst (B) is 1% by mass or more and 4% by mass or less based on 100% by mass of the epoxy compound (A).

4. The resin composition for optical waveguides according to claim 1, wherein the content ratio of the curing catalyst (b1) to the curing catalyst (b2) is 0.25 parts by mass or more and 2 parts by mass or less of the curing catalyst (b2) per 1 part by mass of the curing catalyst (b1).

5. The resin composition for optical waveguides according to claim 1, wherein the epoxy compound (A) further contains an epoxy compound (a2) different from the polyorganosiloxane compound (a1).

6. A dry film formed using the resin composition for optical waveguides according to any one of claims 1 to 5.

7. An optical waveguide formed using the resin composition for an optical waveguide according to any one of claims 1 to 5.

8. A semiconductor package substrate comprising the optical waveguide according to claim 7.

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