Resin composition for optical waveguide, dry film for optical waveguide, and optical waveguide

Abstract

Provided is a resin composition for an optical waveguide, comprising an epoxy resin (A), a (meth) acrylate resin (B), and a photopolymerization initiator (C). The (meth) acrylate resin (B) contains: a first (meth) acrylate compound (B-1) having a structural unit represented by formula (1) and a structural unit represented by formula (2); and a second (meth) acrylate compound (B-2) different from the first (meth) acrylate compound (B-1). The content of the first (meth) acrylate compound (B-1) is 5 mass% to 20 mass% with respect to the total amount of the epoxy resin (A) and the (meth) acrylate resin (B). The content of the second (meth) acrylate compound (B-2) is 30% by mass to 80% by mass with respect to the total amount of the epoxy resin (A) and the (meth) acrylate resin (B). (In formula (1) and formula (2), R1 to R3 each independently represent an alkyl group having 1 to 3 carbon atoms or a hydrogen atom, and R4 represents an acryloyl group or a methacryloyl group. ) (1) (2)

Description

Technical Field

[0001] The present disclosure relates to a resin composition for an optical waveguide, a dry film for an optical waveguide, and an optical waveguide. Background Art

[0002] In medium-distance communications, such as fiber-to-the-home (FTTH) and in-vehicle equipment, optical fiber cables are used as transmission media. However, in short-distance communications, there is a growing demand for high-density circuits with features such as narrow spacing, branching, crossover, and multilayer structures, which are difficult to achieve with optical fiber cables. Therefore, optical circuit boards including optical waveguides and optoelectronic composite boards including circuits that can meet all of these requirements have been proposed to meet these demands.

[0003] Examples of the optical waveguide include polymer optical waveguides using resin materials. In view of its compatibility with a wiring board including an electric circuit, the optical waveguide provided for the optoelectronic composite board is preferably a polymer optical waveguide.

[0004] The development step is one of the process steps for forming a polymer optical waveguide. Alkaline development using an alkaline aqueous solution as a developer is one of the development methods. As used herein, "alkaline development" refers to a method in which an uncured resin composition (which is not required for optical waveguide formation) is dissolved in an alkaline solution for development. According to this method, the resin composition used to form the optical waveguide must have excellent solubility in an alkaline aqueous solution (alkaline developability).

[0005] As described in Patent Document 1, examples of materials for such an optical waveguide include a resin composition for optical waveguide molding, which uses a resin containing a polymer having a carboxyl group (A), a (meth)acrylate (B), a photoradical polymerization initiator (C), and a phenolic antioxidant (D).

[0006] Reference List

[0007] Patent Literature

[0008] Patent Document 1: JP 5771978 B2 Summary of the Invention

[0009] The resin composition according to one aspect of the present disclosure is designed for optical waveguides. The resin composition contains an epoxy resin (A), a (meth)acrylate resin (B) and a photopolymerization initiator (C). The (meth)acrylate resin (B) comprises: a first (meth)acrylate compound (B-1) having a structural unit represented by the following formula (1) and a structural unit represented by the following formula (2); and a second (meth)acrylate compound (B-2) different from the first (meth)acrylate compound (B-1). Relative to the total mass of the epoxy resin (A) and the (meth)acrylate resin (B), the content of the first (meth)acrylate compound (B-1) is equal to or greater than 5% by mass and equal to or less than 20% by mass. Relative to the total mass of the epoxy resin (A) and the (meth)acrylate resin (B), the content of the second (meth)acrylate compound (B-2) is equal to or greater than 30% by mass and equal to or less than 60% by mass.

[0010] [Chemical Formula 1]

[0011] Formula (1)

[0012] Formula (2)

[0013] In formulae (1) and (2), R1 to R3 are each independently an alkyl group having 1 to 3 carbon atoms or a hydrogen atom, and R4 is an acryloyl group or a methacryloyl group.

[0014] A dry film according to another aspect of the present disclosure is designed for use in an optical waveguide and includes a resin layer containing the above-described resin composition for an optical waveguide or a semi-cured product of the resin composition for an optical waveguide.

[0015] An optical waveguide according to another aspect of the present disclosure includes a core and a cladding layer covering the core, wherein at least one of the core and the cladding layer contains a cured product of the optical waveguide resin composition.

[0016] The resin composition for an optical waveguide according to the present disclosure achieves both excellent alkali developability and low viscosity. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] [ Figure 1 ] Figure 1 is a cross-sectional view showing the configuration of a dry film for an optical waveguide according to an exemplary embodiment;

[0018] [ Figure 2A ] Figure 2A A method for manufacturing an optoelectronic composite panel including an optical waveguide according to an exemplary embodiment is shown;

[0019] [ Figure 2B ] Figure 2B A method for manufacturing an optoelectronic composite panel including an optical waveguide according to an exemplary embodiment is shown;

[0020] [ Figure 2C ] Figure 2C A method for manufacturing an optoelectronic composite panel including an optical waveguide according to an exemplary embodiment is shown;

[0021] [ Figure 2D ] Figure 2D A method for manufacturing an optoelectronic composite panel including an optical waveguide according to an exemplary embodiment is shown;

[0022] [ Figure 3A ] Figure 3A A method for manufacturing an optoelectronic composite panel including an optical waveguide according to an exemplary embodiment is shown;

[0023] [ Figure 3B ] Figure 3B A method for manufacturing an optoelectronic composite panel including an optical waveguide according to an exemplary embodiment is shown;

[0024] [ Figure 3C ] Figure 3C A method for manufacturing an optoelectronic composite panel including an optical waveguide according to an exemplary embodiment is shown; and

[0025] [ Figure 3D ] Figure 3D A method for manufacturing an optoelectronic composite panel including an optical waveguide according to an exemplary embodiment is shown. DETAILED DESCRIPTION

[0026] To improve the alkaline developability of the resin composition used, it is preferred to use a large amount of resin components with relatively low molecular weight. However, as the proportion of such resin components with low molecular weight increases, alkaline developability may improve, but when the resin components are processed into a dry film, for example, viscosity tends to increase. As viscosity increases, the dry film becomes sticky, resulting in reduced processability. To reduce viscosity, it is preferred to use a solid resin component with a relatively high molecular weight. Therefore, it is not easy to achieve both excellent alkaline developability and low viscosity.

[0027] The present disclosure provides a resin composition for an optical waveguide, a dry film for an optical waveguide, and an optical waveguide, all of which have excellent alkali developability and low viscosity.

[0028] 1. Resin composition for optical waveguide

[0029] The resin composition according to one aspect of the present disclosure is designed for use in optical waveguides. The resin composition contains an epoxy resin (A), a (meth)acrylate resin (B), and a photopolymerization initiator (C). The (meth)acrylate resin (B) includes: a first (meth)acrylate compound (B-1) having a structural unit represented by the following formula (1) and a structural unit represented by the following formula (2); and a second (meth)acrylate compound (B-2) different from the first (meth)acrylate compound (B-1).

[0030] [Chemical Formula 2]

[0031] Formula (1)

[0032] Formula (2)

[0033] The content of the first (meth)acrylate compound (B-1) is equal to or greater than 5% by mass and equal to or less than 20% by mass relative to the total mass of the epoxy resin (A) and the (meth)acrylate resin (B). The content of the second (meth)acrylate compound (B-2) is equal to or greater than 30% by mass and equal to or less than 60% by mass relative to the total mass of the epoxy resin (A) and the (meth)acrylate resin (B).

[0034] This optical waveguide resin composition has excellent alkali developability and low viscosity.

[0035] As used herein, "alkaline developability" means that the resin composition exhibits excellent solubility in alkaline developers generally used in alkaline development. In other words, excellent alkaline developability means that when forming an optical waveguide, unnecessary uncured portions can be easily removed using an alkaline developer.

[0036] Examples of developers include, but are not limited to, potassium hydroxide, sodium hydroxide, sodium carbonate, potassium carbonate, sodium phosphate, sodium silicate, ammonia, and amines. Any developing method can be used without limitation as long as the method can be used to remove uncured portions. Examples of developing methods include dipping, showering, spraying, and brushing.

[0037] As used herein, the term "low tack" means that when the resin composition is processed into a dry film for an optical waveguide, the surface of the dry film for an optical waveguide is not excessively tacky. Increasing tack can lead to problems. For example, when peeling off a protective film laminated on the resin layer 1 of the dry film for an optical waveguide, a portion of the resin layer 1 may adhere to the protective film, making the surface uneven and causing a loss of flatness.

[0038] <Epoxy Resin (A)>

[0039] Epoxy resin (A) contains an epoxy compound with light curing property and high transparency. Preferably, epoxy resin (A) contains at least one selected from the group consisting of solid bisphenol A epoxy compound (A-1), liquid bisphenol A epoxy compound (A-2) and polyfunctional aromatic epoxy compound (A-3) having three or more epoxy groups per molecule. Preferably, epoxy resin (A) contains solid bisphenol A epoxy compound (A-1), liquid bisphenol A epoxy compound (A-2) and polyfunctional aromatic epoxy compound (A-3) having three or more epoxy groups per molecule simultaneously.

[0040] The solid bisphenol A epoxy compound (A-1) is a bisphenol A epoxy compound that is solid at 25° C. and has one or two epoxy groups per molecule. Use of the solid bisphenol A epoxy compound (A-1) enables formation of an optical waveguide having transparency and a high glass transition temperature.

[0041] The lower limit of the epoxy equivalent of the solid epoxy bisphenol A epoxy compound (A-1) is not limited to any specific value, but is preferably equal to or greater than 400 g / eq, and more preferably equal to or greater than 670 g / eq. Its upper limit is preferably equal to or less than 1500 g / eq, and more preferably equal to or less than 1100 g / eq. If the epoxy equivalent is too small or too large, it will be difficult to form an optical waveguide. Specifically, if the epoxy equivalent is too small, it will be difficult to form a dry film. If the epoxy equivalent is too large, when forming the core 11 and the cladding layer 8 of the optical waveguide, the developability will be too significantly deteriorated and development cannot be performed as expected. For these reasons, setting the epoxy equivalent of the solid bisphenol A epoxy compound (A-1) to a value within this range enables the optical waveguide to be advantageously formed.

[0042] Examples of the solid bisphenol A epoxy compound (A-1) include 1001, 1002, 1003, 1055, 1004, 1004AF, 1003F, 1004F, 1005F, 1004FS, 1006FS, and 1007FS, all of which are manufactured by Mitsubishi Chemical Corporation. Furthermore, as the solid bisphenol A epoxy compound (A-1), any one of the compounds exemplified above may be used alone, or two or more selected from these compounds may be used in combination, either of which is appropriate.

[0043] The lower limit of the content of the solid bisphenol A epoxy compound (A-1) relative to the total mass of the epoxy resin (A) is preferably equal to or greater than 40% by mass, more preferably equal to or greater than 45% by mass. The upper limit of the content of the solid bisphenol A epoxy compound (A-1) relative to the total mass of the epoxy resin (A) is preferably equal to or less than 60% by mass, more preferably equal to or less than 55% by mass. If the content of the solid bisphenol A epoxy compound (A-1) is too little or too much, it will be difficult to form an optical waveguide. Specifically, if the content of the solid bisphenol A epoxy compound (A-1) is too little, the flexibility of the dry film made from the optical waveguide resin composition will decrease when forming an optical waveguide. On the other hand, if the content of the solid bisphenol A epoxy compound (A-1) is too much, its cured product will have too low a degree of heat resistance and will inevitably become brittle. In view of these considerations, as long as the content of the solid bisphenol A epoxy compound (A-1) is within the range defined above, a useful optical waveguide can be formed.

[0044] The liquid bisphenol A epoxy compound (A-2) is a bisphenol A epoxy compound that is liquid at 25° C. and has one or two epoxy groups in one molecule. The use of the liquid bisphenol A epoxy compound (A-2) enhances alkali developability.

[0045] The lower limit value of the viscosity of the liquid bisphenol A epoxy compound (A-2) at 25°C is not limited to any particular value. Specifically, the lower limit value is preferably equal to or greater than 100 mPa·s, and more preferably equal to or greater than 2000 mPa·s. The upper limit value is preferably equal to or less than 20,000 mPa·s, and more preferably equal to or less than 17,000 mPa·s.

[0046] Specific examples of the liquid bisphenol A epoxy compound (A-2) include 840, 840-S, 850, 850-S, and EXA-850CRP, all of which are produced by DIC Corporation.

[0047] As the liquid bisphenol A epoxy compound (A-2), any one of the compounds exemplified above may be used alone, or two or more compounds selected from these compounds may be used in combination, and either mode is appropriate.

[0048] The number average molecular weight of the liquid bisphenol A epoxy compound (A-2) is preferably smaller than the number average molecular weight of the second (meth)acrylate compound (B-2) described below, and more specifically, is preferably less than 3,000, more preferably equal to or less than 1,000, and even more preferably equal to or less than 500. The upper limit value of the number average molecular weight is not limited to any specific value, but is equal to or greater than 200.

[0049] Setting the number average molecular weight to a value within this range makes it easier to mix the liquid bisphenol A epoxy compound (A-2) and the second (meth)acrylate compound (B-2) together, thereby improving the alkali developability of the optical waveguide resin composition.

[0050] The lower limit of the content of the liquid bisphenol A epoxy compound (A-2) is preferably 15% by mass or more, more preferably 20% by mass or more, relative to the total mass of the epoxy resin (A). The upper limit of the content of the liquid bisphenol A epoxy compound (A-2) is preferably 35% by mass or less, more preferably 30% by mass or less, relative to the total mass of the epoxy resin (A). If the content of the liquid bisphenol A epoxy compound (A-1) is too low or too high, it may be difficult to form an optical waveguide.

[0051] The polyfunctional aromatic epoxy compound (A-3) is not limited to any specific compound as long as the polyfunctional aromatic epoxy compound (A-3) is an aromatic epoxy compound having three or more epoxy groups per molecule. Specific examples of the polyfunctional aromatic epoxy compound (A-3) include 2-[4-(2,3-epoxypropoxy)phenyl]-2-[4-[1,1-bis[4-([2,3-epoxypropoxy]phenyl)]ethyl]phenyl]propane. Examples of the polyfunctional aromatic epoxy compound (A-3) include VG3101 manufactured by Printec Co.

[0052] The lower limit of the content of the polyfunctional aromatic epoxy compound (A-3) is preferably 15% by mass or more, more preferably 20% by mass or more, relative to the total mass of the epoxy resin (A). The upper limit of the content of the polyfunctional aromatic epoxy compound (A-3) is preferably 35% by mass or less, more preferably 30% by mass or less, relative to the total mass of the epoxy resin (A). If the content of the polyfunctional aromatic epoxy compound (A-3) is too little or too much, the heat resistance and mechanical strength of the optical waveguide may be reduced.

[0053] Specifically, setting the content of the polyfunctional aromatic epoxy compound (A-3) to a value that is too small may cause the heat resistance of the resulting cured product to decrease. Setting the content of the polyfunctional aromatic epoxy compound (A-3) to a value that is too large may cause the cured product to become quite brittle. For these reasons, as long as the content of the polyfunctional aromatic epoxy compound (A-3) is within the range defined above, a suitable optical waveguide can be formed.

[0054] Optionally, other epoxy compounds may be used unless the advantages of this embodiment are compromised.

[0055] <(Meth)acrylate resin (B)>

[0056] The (meth)acrylate resin (B) contains a first (meth)acrylate compound (B-1) having a structural unit represented by the following formula (1) and a structural unit represented by the following formula (2), and a second (meth)acrylate compound (B-2) different from the first (meth)acrylate compound (B-1).

[0057] The content of the (meth)acrylate resin (B) is not limited to any specific value, but is preferably 35% by mass or more and 90% by mass or less, more preferably 45% by mass or more and 80% by mass or less, and even more preferably 55% by mass or more and 70% by mass or less, relative to the total mass of the epoxy resin (A) and the (meth)acrylate resin (B). Setting the content of the (meth)acrylate resin (B) to a value within this range enables favorable dry film formation and allows the composition to have excellent alkali developability.

[0058] [Chemical Formula 3]

[0059] Formula (1)

[0060] Formula (2)

[0061] The first (meth)acrylate compound (B-1) has a structural unit represented by formula (1) and a structural unit represented by formula (2).

[0062] In formula (1), R1 to R3 are each independently an alkyl group having 1 to 3 carbon atoms or a hydrogen atom. In formula (2), R4 represents an acryloyl group or a methacryloyl group.

[0063] The use of such a (meth)acrylate resin (B) enables, for example, reducing the viscosity when processing the resin composition into a dry film. Reducing the viscosity not only enables more efficient production of optical waveguides but also enables fine line processing.

[0064] Each of R1 to R3 is preferably an alkyl group having 1 to 3 carbon atoms, more preferably a methyl group. Use of such a substituent enables further reduction in viscosity.

[0065] Assuming that the average number of structural units represented by formula (1) contained in one molecule of the first (meth)acrylate compound (B-1) is m, and the average number of structural units represented by formula (2) contained in one molecule of the first (meth)acrylate compound (B-1) is n, the lower limit value of the m / n ratio is preferably equal to or greater than 1, more preferably equal to or greater than 1.2, even more preferably equal to or greater than 1.5, and most preferably equal to or greater than 1.9. The upper limit value of the m / n ratio is preferably equal to or less than 9, more preferably equal to or less than 7, and even more preferably equal to or less than 5. Use of such a first (meth)acrylate compound (B-1) enables further reduction in viscosity.

[0066] In formulas (1) and (2), R1 to R3 are each preferably an alkyl group having 1 to 3 carbon atoms, and more preferably a methyl group. In formula (2), R4 is preferably an acryloyl group. That is, the first (meth)acrylate compound (B-1) preferably contains a structural unit represented by the following formula (3) and a structural unit represented by the following formula (4). Use of such a (meth)acrylate compound (B-11) allows for reduced viscosity.

[0067] [Chemical Formula 4]

[0068] Formula (3)

[0069] Formula (4)

[0070] The number average molecular weight of the first (meth)acrylate compound (B-1) is not limited to any particular value, but its specific lower limit is preferably equal to or greater than 3,000, and more preferably equal to or greater than 4,000. Its upper limit is preferably equal to or less than 8,000, and more preferably equal to or less than 6,000. Setting the number average molecular weight of the first (meth)acrylate compound (B-1) to a value within this range allows for reduced viscosity.

[0071] The lower limit value of the content of the first (meth)acrylate compound (B-1) is preferably equal to or greater than 5% by mass, and more preferably equal to or greater than 7% by mass, relative to the total mass of the epoxy resin (A) and the (meth)acrylate resin (B). The upper limit value thereof is preferably equal to or less than 20% by mass, and more preferably equal to or less than 15% by mass. Setting the content of the first (meth)acrylate compound (B-1) to a value within this range allows for improved alkali developability and reduced tack.

[0072] As the first (meth)acrylate compound (B-1), only one type of compound may be used alone, or two or more types of compounds may be used in combination, whichever is appropriate.

[0073] The addition of the second (meth)acrylate compound (B-2) improves the developability during alkaline development. Furthermore, this allows the cured product of the optical waveguide resin composition to exhibit a high refractive index and a high glass transition temperature. Consequently, this enables the formation of a suitable optical waveguide.

[0074] The content of the second (meth)acrylate compound (B-2) is equal to or greater than 30% by mass and equal to or less than 80% by mass relative to the total mass of the epoxy resin (A) and the (meth)acrylate resin (B). The lower limit thereof is preferably equal to or greater than 35% by mass, and more preferably equal to or less than 45% by mass. The upper limit thereof is preferably equal to or less than 65% by mass, and more preferably equal to or less than 60% by mass. Setting the content of the second (meth)acrylate compound (B-2) to a value within this range enables improvement in alkali developability.

[0075] The second (meth)acrylate compound (B-2) is not limited to any particular compound unless the alkali developability is impaired, but preferably contains a urethane (meth)acrylate compound (B-21) or a bisphenol A (meth)acrylate compound (B-22) obtained by reacting an epoxy (meth)acrylate compound with a diisocyanate compound and a diol compound having a carboxyl group, and preferably contains both the urethane (meth)acrylate compound (B-21) and the bisphenol A (meth)acrylate compound (B-22). Furthermore, the epoxy (meth)acrylate compound more preferably has an average of two or more hydroxyl groups and ethylenically unsaturated groups per molecule.

[0076] The urethane (meth)acrylate compound (B-21) preferably has a larger number average molecular weight than the liquid bisphenol A epoxy compound (A-2). Specifically, the number average molecular weight of the urethane (meth)acrylate compound (B-21) is preferably equal to or greater than 3,000, more preferably equal to or greater than 5,000, and even more preferably equal to or greater than 8,000. In addition, the upper limit value thereof is preferably equal to or less than 30,000, more preferably equal to or less than 20,000, and even more preferably equal to or less than 15,000.

[0077] Setting the number average molecular weight of the urethane (meth)acrylate compound (B-21) to a value within this range enables favorable dry film formation, thereby enabling the resin composition to have excellent alkali developability. Furthermore, setting the number average molecular weight of the urethane (meth)acrylate compound (B-21) to a value greater than the number average molecular weight of the liquid bisphenol A epoxy compound (A-2) makes it easier to mix the liquid bisphenol A epoxy compound (A-2) and the second (meth)acrylate compound (B-2), thereby further improving alkali developability.

[0078] As one example of the above-mentioned urethane (meth)acrylate compound (B-21), a compound having a structural unit represented by the following formula (5) can be used:

[0079] [Chemical Formula 5]

[0080] Formula (5)

[0081] In this formula (5), R 21 to R 24 Independent of each other, R 21 is the residue of epoxy (meth)acrylate, R 22 is the residue of diisocyanate, R 23 is an alkyl group having 1 to 5 carbon atoms derived from the raw material diol, and R 24 is a hydrogen atom or a methyl group. As used herein, "residue" refers to the structure of a portion of each material component that remains when a functional group for binding is removed from the material component.

[0082] R in formula (5) 21 A skeleton having a phenyl group is preferred, and a bisphenol A skeleton is more preferred.

[0083] The use of a urethane (meth)acrylate compound (B-21) having such a structure allows for improved toughness and elasticity of the dry film formed thereby, thereby improving the formability of the dry film and the optical waveguide. Furthermore, this allows for increased glass transition temperature and also improved heat resistance.

[0084] Examples of the urethane (meth)acrylate compound (B-21) include UXE-3011, UXE-3012, and UXE-3024, all of which are produced by Nippon Kayaku Co. Ltd. As the urethane (meth)acrylate compound (B-21), any one of the compounds exemplified above may be used alone, or two or more compounds selected from these compounds may be used in combination, whichever is appropriate.

[0085] The content of the urethane (meth)acrylate compound (B-21) is equal to or greater than 20% by mass and equal to or less than 60% by mass relative to the total mass of the epoxy resin (A) and the (meth)acrylate resin (B). The lower limit thereof is preferably equal to or greater than 30% by mass. The upper limit thereof is preferably equal to or less than 50% by mass, and more preferably equal to or less than 40% by mass. Setting the content of the urethane (meth)acrylate compound (B-21) to a value within this range improves alkali developability.

[0086] The bisphenol A (meth)acrylate compound (B-22) is a bisphenol A (meth)acrylate compound having a total of one or two acryloyl groups and methacryloyl groups per molecule. Use of the bisphenol A (meth)acrylate compound (B-22) enables formation of an optical waveguide having high transparency.

[0087] The bisphenol A (meth)acrylate compound (B-22) preferably has one epoxy group per molecule. That is, the bisphenol A (meth)acrylate compound (B-22) preferably has one acryloyl group or methacryloyl group per molecule, and more preferably one acryloyl group. This allows the bisphenol A (meth)acrylate compound (B-22) to react with carboxyl groups and epoxy groups. Consequently, this allows not only an increase in the degree of curing of the optical waveguide resin composition but also an improvement in heat resistance.

[0088] The number average molecular weight of the bisphenol A (meth) acrylate compound (B-22) is preferably equal to or less than 2,000, and more preferably equal to or less than 1,000. Although not limited to any particular value, the number average molecular weight of the bisphenol A (meth) acrylate compound (B-22) is preferably equal to or greater than 200.

[0089] Examples of the bisphenol A (meth)acrylate compound (B-22) include EA-1010N, EA-1010LC, EA-1010NT2, and EA-1020LC3, all of which are produced by Shin-Nakamura Chemical Co., Ltd. In addition, as the bisphenol A (meth)acrylate compound (B-22), any one of the compounds exemplified above may be used alone, or two or more compounds selected from these compounds may be used in combination, whichever is appropriate.

[0090] The lower limit value of the content of the bisphenol A (meth)acrylate compound (B-22) is preferably equal to or greater than 5% by mass, and more preferably equal to or greater than 7% by mass, relative to the total mass of the epoxy resin (A) and the (meth)acrylate resin (B). The upper limit value is preferably equal to or less than 20% by mass, and more preferably equal to or less than 18% by mass. Setting the content of the bisphenol A (meth)acrylate compound (B-22) to a value within this range allows for improved heat resistance.

[0091] In addition, unless the advantages of the present embodiment are impaired, the (meth)acrylate resin (B) may be a (meth)acrylate compound different from the compounds illustrated above. For example, (meth)epoxyacrylate compounds and acrylate monomers used in general optical waveguide applications with alkaline developability can be used. In particular, it is preferred that the (meth)acrylate resin (B) contains an acrylate monomer, which is expected to be effectively used as a crosslinking agent. The acrylate monomer preferably has an average of two or more (meth)acryloyl groups per molecule, and more preferably has three or more (meth)acryloyl groups per molecule. Such a monomer crosslinking agent can improve the alkaline developability of the resin composition for optical waveguides and can increase the crosslinking density of the cured product.

[0092] The number average molecular weight of the monomeric cross-linking agent is preferably equal to or less than 1,000, and more preferably equal to or less than 500. The lower limit value thereof is not limited to any specific value, but is preferably equal to or greater than 100, for example.

[0093] Examples of the cross-linking agent having a (meth)acryloyl group include trimethylolpropane triacrylate.

[0094] <Photopolymerization Initiator (C)>

[0095] The photopolymerization initiator (C) is not limited to any specific compound as long as the photopolymerization initiator (C) is a compound having the ability to promote curing of the optical waveguide resin composition by irradiating the optical waveguide resin composition with light of a specific wavelength.

[0096] Specific examples of the photopolymerization initiator (C) include acylphosphine oxide compounds (C-1), oxime ester compounds having an oxime ester group, α-aminoacetophenone compounds, titanocene compounds, benzoin compounds, acetophenone compounds, anthraquinone compounds, thioxanthone compounds, ketal compounds, benzophenone compounds, tertiary amine compounds, and xanthone compounds. Preferably, the photopolymerization initiator (C) is the acylphosphine oxide compound (C-1).

[0097] Use of such a photopolymerization initiator (C) enables improvement in the curability of the optical waveguide resin composition.

[0098] Examples of the acylphosphine oxide compound (C-1) include bisacylphosphine oxide-based photopolymerization initiators and monoacylphosphine oxide-based photopolymerization initiators. Specific examples of the acylphosphine oxide compound (C-1) include bis-(2,6-dichlorobenzoyl)phenylphosphine oxide, bis-(2,6-dichlorobenzoyl)-2,5-dimethylphenylphosphine oxide, bis-(2,6-dichlorobenzoyl)-4-propylphenylphosphine oxide, bis-(2,6-dichlorobenzoyl)-1-naphthylphosphine oxide, bis-(2,6-dimethoxybenzoyl)phenylphosphine oxide, bis-(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, bis-(2,6-dimethoxybenzoyl)-2 ,5-dimethylphenylphosphine oxide, bis-(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, 2,6-dimethoxybenzoyldiphenylphosphine oxide, 2,6-dichlorobenzoyldiphenylphosphine oxide, methyl 2,4,6-trimethylbenzoylphenylphosphinate, 2-methylbenzoyldiphenylphosphine oxide, isopropyl pivaloylphenylphosphinate, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, ethyl 2,4,6-trimethylbenzoylphenylphosphinate and (2,6-dimethoxybenzoyl)-2,4,4-pentylphosphine oxide.

[0099] Commercially available acylphosphine oxide compounds such as Omnirad TPO, Omnirad TPO-L, LR8953X, and Omnirad 819, all of which are produced by IGM Resins, can be used.

[0100] The lower limit of the content of the photopolymerization initiator (C) is preferably equal to or greater than 0.1% by mass, and more preferably equal to or greater than 0.2% by mass, relative to the total mass of the epoxy resin (A) and the (meth)acrylate resin (B). The upper limit of the content of the photopolymerization initiator (C) is preferably equal to or less than 15% by mass, and more preferably equal to or less than 5% by mass, relative to the total mass of the epoxy resin (A) and the (meth)acrylate resin (B). Setting the content of the photopolymerization initiator (C) to a value within this range promotes curing of the optical waveguide resin composition and improves the chemical resistance of the cured product. This also reduces optical loss in the resulting optical waveguide.

[0101] Other photopolymerization initiators may be used as long as the advantages of this embodiment are not impaired. As the photopolymerization initiator (C), only one type may be used alone, or two or more types may be used in combination, whichever is appropriate.

[0102] In addition, the content may be adjusted by using a photopolymerization initiator (C) that exhibits high photosensitivity to the wavelength of radiation to be irradiated, as appropriate.

[0103] <Additives>

[0104] In addition to the components described above, the resin composition for optical waveguide may further contain other components as long as the advantages of the present embodiment are not impaired. Examples of other components include, but are not limited to, antioxidants, leveling agents, and solvents.

[0105] Examples of the phenolic antioxidant include AO-20, AO-30, AO-40, AO-50, AO-60, and AO-80, all manufactured by ADEKA Corporation, and SUMILIZER GA-80 manufactured by Sumitomo Chemical Co., Ltd.

[0106] Examples of the phosphite-based antioxidants include PEP-8, PEP-36, HP-10, 2112, 1178, and 1500, all produced by ADEKA Corporation, and JP-360 and JP-3CP, both produced by Johoku Chemical Co., Ltd.

[0107] Examples of the sulfur-based antioxidant include AO-412S and AO-503, both manufactured by ADEKA Corporation, and SUMILIZER TP-D manufactured by Sumitomo Chemical Co., Ltd.

[0108] As the antioxidant, any of the compounds described above may be used alone, or a combination of two or more selected from these compounds may be used; either method is suitable. However, it is preferred to use a phenolic antioxidant alone. Adding an antioxidant to the optical waveguide resin composition can advantageously form an optical waveguide having high heat resistance.

[0109] The antioxidant content is preferably greater than 0% by mass, more preferably equal to or greater than 0.2% by mass, and even more preferably equal to or greater than 0.3% by mass, relative to the total mass of the optical waveguide resin composition. The antioxidant content is preferably equal to or less than 5% by mass, more preferably equal to or less than 2% by mass, and even more preferably equal to or less than 1% by mass, relative to the total mass of the optical waveguide resin composition. If any antioxidant is added, if too little or too much antioxidant is added, the heat resistance of the cured product may not be sufficiently improved. Specifically, if too little antioxidant is added, even with the addition of the antioxidant, the intended effect may be difficult to achieve, and the heat resistance of the cured product may not be sufficiently improved. On the other hand, if too much antioxidant is added, the antioxidant may act as a plasticizer, thereby potentially causing a decrease in the heat resistance of the cured product. In view of these considerations, as long as the antioxidant content is within the above-defined range, a highly heat-resistant optical waveguide can be advantageously formed.

[0110] As the leveling agent, any of various dispersants commonly used as dispersants can be used. For example, PF-636 manufactured by OMNOVA Solutions can be used.

[0111] As can be seen from the above description, the resin composition for an optical waveguide according to the present embodiment can be effectively used to form a highly heat-resistant optical waveguide.

[0112] <Curing method>

[0113] Any method can be used to cure the optical waveguide resin composition without limitation, as long as the method enables photocuring. Specifically, for example, a method can be used in which the optical waveguide resin composition is irradiated with light having a wavelength of 365 nm and then heat-treated at 140° C. for 10 minutes. Note that the absorption wavelength and heat treatment conditions are not limited to any specific absorption wavelength and heat treatment conditions, as long as photocuring is enabled.

[0114] Alternatively, a method in which light having a wavelength of 365 nm is used at 1000 mJ / cm 2 A method of irradiating the optical waveguide resin composition with UV exposure and heat-treating it at 140° C. for 10 minutes. Note that the absorption wavelength and heat treatment conditions are not limited to any specific absorption wavelength and heat treatment conditions as long as photocuring can proceed.

[0115] Note that even by projection exposure using a photomask, photocuring of the optical waveguide resin composition according to this embodiment can be performed in the same manner, and a useful optical waveguide can be formed. Alternatively, photocuring can also be performed by using light outside the i-line range.

[0116] 2. Dry film for optical waveguide and optical waveguide

[0117] The resin composition for an optical waveguide according to the present embodiment can also be used as a material for a dry film for an optical waveguide used when forming an optical waveguide.

[0118] The dry film for optical waveguide according to the present embodiment (hereinafter referred to as "dry film for optical waveguide") is not limited to any specific dry film for optical waveguide, as long as the dry film includes the resin layer 1 containing the resin composition for optical waveguide or a semi-cured product of the resin composition for optical waveguide. Specifically, Figure 1 As shown, the dry film for an optical waveguide may include a film base material 2 on one surface of a resin layer 1 and a protective film 3 on the other surface of the resin layer 1. Note that the dry film for an optical waveguide only needs to include the resin layer 1 and may include not only the film base material 2 and the protective film 3 but also other layers. Note that the film base material 2 and the protective film 3 are not essential constituent elements. Figure 1 is a cross-sectional view showing the configuration of the dry film for an optical waveguide according to the present embodiment.

[0119] The resin layer 1 contains the optical waveguide resin composition or a semi-cured product thereof. The resin layer 1 is formed of the optical waveguide resin composition according to the present embodiment and thus has reduced viscosity, thereby improving workability.

[0120] The thickness of the resin layer 1 is preferably adjusted appropriately, but is preferably equal to or greater than 20 μm, and more preferably equal to or greater than 30 μm, for example. The thickness of the resin layer 1 is preferably equal to or less than 100 μm, and more preferably equal to or less than 80 μm. Setting the thickness of the resin layer 1 to a value within this range enables the cured product to have sufficient mechanical strength and enables the optical waveguide to be formed favorably.

[0121] The film substrate 2 is not limited to any specific film substrate. Examples of the film substrate 2 include polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polyolefins such as polyethylene and polypropylene; polycarbonates, polyamides, polyimides, polyamideimides, polyetherimides, polyether sulfides, polyethersulfones, polyetherketones, polyphenylene oxides, polyphenylene sulfides, polyarylates, polysulfones, and liquid crystal polymers. It is preferred to use any one selected from the group consisting of polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polypropylene, polycarbonates, polyamides, polyimides, polyamideimides, polyphenylene oxides, polyphenylene sulfides, polyarylates, and polysulfones, all of which have excellent flexibility and toughness.

[0122] The thickness of the film base material 2 is preferably adjusted appropriately, but is preferably, for example, equal to or greater than 3 μm and equal to or less than 250 μm. Setting the thickness of the film base material 2 to such a value enables the production of a dry film for an optical waveguide having excellent film strength and flexibility. This improves the processability of the dry film for an optical waveguide, making it possible to easily form a useful optical waveguide.

[0123] Furthermore, the surface of the film substrate 2 in contact with the resin layer 1 may be subjected to a release treatment using, for example, a fluorine-containing compound. The release treatment allows the resin layer 1 to be easily released from the film substrate 2 .

[0124] The protective film 3 is not limited to any particular protective film. Examples of the protective film 3 include polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; and polyolefins such as polyethylene and polypropylene. In particular, polyesters such as polyethylene terephthalate and polyolefins such as polyethylene and polypropylene are preferred because of their excellent flexibility and toughness.

[0125] The thickness of the protective film 3 is preferably adjusted appropriately, but is preferably, for example, equal to or greater than 10 μm and equal to or less than 250 μm. Setting the thickness of the protective film 3 to a value within this range enables the production of a dry film for an optical waveguide having excellent film strength and flexibility. This improves the processability of the dry film for an optical waveguide, allowing for easy formation of a useful optical waveguide. Furthermore, a peeling process can be performed in the same manner as for the film substrate 2.

[0126] For example, the method for forming a dry film for an optical waveguide may be, but is not limited to, the following method. First, for example, a solvent is added to the resin composition for an optical waveguide to convert the resin composition and the solvent into a varnish. The varnish is then applied to the film substrate 2. For example, a comma-type coater can be used to apply the varnish. The varnish is dried, thereby forming a resin layer 1 containing the resin composition for an optical waveguide on the film substrate 2. Then, a protective film 3 is further laminated on the resin layer 1. For example, a heat lamination method can be used as a method for laminating the protective film 3. The resin layer 1 contained in the dry film for an optical waveguide serves as a material for an optical waveguide. The dry film for an optical waveguide can be used to form the core or cladding layer of an optical waveguide, and either method is suitable.

[0127] Now refer to Figures 2A to 2D and Figures 3A to 3D The method for forming an optical waveguide according to the present embodiment will be described. In the following description, a method for manufacturing an optoelectronic composite board including an optical waveguide will be described. Note that, Figures 2A to 2D and Figures 3A to 3D A method for manufacturing a photovoltaic composite board including the optical waveguide according to the present embodiment is shown.

[0128] First, if Figure 2A As shown, a substrate 5 including a circuit 9 is provided. Next, as Figure 2B As shown in FIG. 1 , a cladding layer 8 (lower cladding layer 10) is formed on the surface of the substrate 5 on which the circuit 9 is provided. Any method can be used without limitation as a method for forming the lower cladding layer 10. For example, a method can be used in which a dry film for optical waveguide is stacked over the substrate 5 and the entire surface thereof is irradiated with light to cure the film.

[0129] Next, if Figure 2C As shown, a core portion 11 is formed on the lower cladding layer 10. Any method can be used as a method for forming the core portion 11 without limitation, as long as the optical waveguide resin composition according to this embodiment is used. For example, a method can be used in which a dry film for an optical waveguide containing the optical waveguide resin composition or a semi-cured product thereof is stacked on the lower cladding layer 10, cured by irradiating only selected areas with light, and then removing the uncured portion with an alkaline developer.

[0130] Next, the cladding layer 8 (upper cladding layer 13) is formed from a dry film for optical waveguide (see Figure 3D ). Specifically, Figure 2D As shown in FIG. 3 , the protective film 3 is peeled off from the optical waveguide dry film. Figure 3A As shown, the optical waveguide dry film is laminated on the assembly so that its resin layer 1 covers the lower cladding layer 10 and the core 11. Figure 3B As shown, the film base material 2 is peeled off from the optical waveguide dry film.

[0131] Next, if Figure 3C As shown, the resin layer 1 is irradiated with light having a wavelength of 365 nm emitted from the light source 12, thereby photocuring the optical waveguide resin composition. This converts the resin layer 1 into the upper cladding layer 13. Note that, as Figure 3D As shown, the through hole 15 can be formed in the following manner: Figure 3C As shown, the entire resin layer 1 except for the portion to be the through hole 15 is irradiated with light having a wavelength of 365 nm, and then the resin layer 1 is developed.

[0132] In this way, the optical waveguide dry film according to the present embodiment can be used to form an optical waveguide. That is, Figure 3D The optical waveguide shown in FIG includes a core 11, a lower cladding layer 10, and an upper cladding layer 13. The upper cladding layer 13 covers the core 11. The upper cladding layer 13 is a cured product of a resin composition for an optical waveguide.

[0133] Although the optical waveguide dry film is used to form the upper cladding layer 13, the lower cladding layer 10, and the core 11 in this embodiment, one or two selected from the group consisting of the upper cladding layer 13, the lower cladding layer 10, and the core 11 may be formed by using other dry films.

[0134] As can be seen from the foregoing description, the optical waveguide dry film according to this embodiment includes a resin layer 1 containing an optical waveguide resin composition. Furthermore, the optical waveguide according to this embodiment includes a core 11 and a cladding layer 8 covering the core 11. At least one of the core 11 and the cladding layer 8 contains a cured product of the optical waveguide resin composition.

[0135] 3. Aspects

[0136] As can be seen from the above description of the embodiments, the present disclosure has the following aspects. In the following description, only for the purpose of clarifying the corresponding relationship between the following aspects of the present disclosure and the above embodiments, reference numerals in parentheses are added to each constituent element.

[0137] The first aspect is a resin composition for an optical waveguide. The resin composition contains an epoxy resin (A), a (meth)acrylate resin (B), and a photopolymerization initiator (C). The (meth)acrylate resin (B) contains: a first (meth)acrylate compound (B-1) having a structural unit represented by the following formula (1) and a structural unit represented by the following formula (2); and a second (meth)acrylate compound (B-2) different from the first (meth)acrylate compound (B-1). Relative to the total mass of the epoxy resin (A) and the (meth)acrylate resin (B), the content of the first (meth)acrylate compound (B-1) is equal to or greater than 5% by mass and equal to or less than 20% by mass. Relative to the total mass of the epoxy resin (A) and the (meth)acrylate resin (B), the content of the second (meth)acrylate compound (B-2) is equal to or greater than 30% by mass and equal to or less than 80% by mass.

[0138] [Chemical Formula 6]

[0139] Formula (1)

[0140] Formula (2)

[0141] In formulae (1) and (2), R1 to R3 are each independently an alkyl group having 1 to 3 carbon atoms or a hydrogen atom, and R4 is an acryloyl group or a methacryloyl group.

[0142] This aspect enables the resin composition for an optical waveguide to simultaneously achieve excellent alkali developability and low viscosity.

[0143] The second aspect is a resin composition for an optical waveguide that can be implemented in combination with the first aspect. In the second aspect, the epoxy resin (A) contains at least one selected from the group consisting of a solid bisphenol A epoxy compound (A-1), a liquid bisphenol A epoxy compound (A-2), and a polyfunctional aromatic epoxy compound (A-3) having an average of three or more epoxy groups per molecule.

[0144] A third aspect is a resin composition for an optical waveguide that can be implemented in combination with the first or second aspect. In the third aspect, the (meth)acrylate resin (B) further comprises at least one selected from the group consisting of a polyurethane (meth)acrylate compound (B-21) and a bisphenol A (meth)acrylate compound (B-22).

[0145] The fourth aspect is a resin composition for an optical waveguide that can be implemented in combination with any one of the first to third aspects. In the fourth aspect, the first (meth)acrylate compound (B-1) comprises a (meth)acrylate compound (B-11) having a structural unit represented by the following formula (3) and a structural unit represented by the following formula (4):

[0146] [Chemical Formula 7]

[0147] Formula (3)

[0148] Formula (4)

[0149] This aspect allows for a further reduction in viscosity.

[0150] A fifth aspect is a resin composition for an optical waveguide that can be implemented in combination with any of the second to fourth aspects. In the fifth aspect, the content of the solid bisphenol A epoxy compound (A-1) is equal to or greater than 40% by mass and equal to or less than 60% by mass relative to the total mass of the epoxy resin (A).

[0151] A sixth aspect is a resin composition for an optical waveguide that can be implemented in combination with any of the second to fifth aspects. In the sixth aspect, the content of the liquid bisphenol A epoxy compound (A-2) is equal to or greater than 15% by mass and equal to or less than 30% by mass relative to the total mass of the epoxy resin (A).

[0152] A seventh aspect is a resin composition for an optical waveguide that can be implemented in combination with any one of aspects 2 to 6. In the seventh aspect, the content of the polyfunctional aromatic epoxy compound (A-3) is equal to or greater than 15% by mass and equal to or less than 30% by mass relative to the total mass of the epoxy resin (A).

[0153] The eighth aspect is a resin composition for an optical waveguide that can be implemented in combination with any one of the first to seventh aspects. In the eighth aspect, the photopolymerization initiator (C) contains an acylphosphine oxide compound (C1).

[0154] The ninth aspect is a dry film for an optical waveguide, comprising a resin layer (1) containing the optical waveguide resin composition according to any one of the first to eighth aspects or a semi-cured product thereof.

[0155] This aspect enables both excellent alkali developability and low viscosity to be achieved.

[0156] The tenth aspect is a dry film for optical waveguide that can be implemented in combination with the ninth aspect. In the eleventh aspect, the dry film further comprises at least one film selected from the group consisting of a film base material (2) and a protective film (3).

[0157] The eleventh aspect is an optical waveguide comprising a core (11) and a cladding layer (8; 10, 13) covering the core (11). At least one of the core (11) or the cladding layer (8; 10, 13) contains a cured product of the optical waveguide resin composition according to any one of the first to eighth aspects.

[0158] Example

[0159] Next, specific embodiments of the present disclosure will be described. Note that the embodiments described below are merely examples of the present disclosure and should not be construed as limiting.

[0160] [Epoxy resin (A)]

[0161] Solid bisphenol A epoxy compound (A-1), product name: JER-1006FS, produced by Mitsubishi Chemical Corporation, with an epoxy equivalent weight of 900 to 1100 g / eq;

[0162] Liquid bisphenol A epoxy compound (A-2), product name: 850-S, manufactured by DIC Corporation, with an epoxy equivalent weight of 183 to 193 g / eq; and

[0163] • Polyfunctional aromatic epoxy compound (A-3), product name: VG3101, manufactured by Printec Co., Ltd., epoxy equivalent of 205 to 215 g / eq.

[0164] [(Meth)acrylate resin (B)]

[0165] A first (meth)acrylate compound (B-1), product name: V-6850, manufactured by DIC Corporation;

[0166] Urethane (meth)acrylate compound (B-21), product name: UXE-3024, produced by Nippon Kayaku Co., Ltd.;

[0167] Bisphenol A (meth)acrylate compound (B-22), product name: EA-1010LC, manufactured by Shin-Nakamura Chemical Co., Ltd.; and

[0168] Other (meth)acrylate compounds, product name: PET-30, produced by DKS Co. Ltd.

[0169] [Photopolymerization initiator (C)]

[0170] Acylphosphine oxide compound (C-1), product name: Omnirad 819, produced by IGM Resins BV.

[0171] [additive]

[0172] Antioxidant, product name: AO-60, manufactured by ADEKA Corporation; and

[0173] Leveling agent: Product name: PF-636, produced by OMNOVA Solutions.

[0174] [Resin composition for optical waveguide]

[0175] Examples 1 and 2 and Comparative Examples 1 and 2 of optical waveguide resin compositions were prepared as follows. First, each material was weighed into a glass container to have any of the chemical compositions (parts by mass) shown in Table 1, and 2-butanone, toluene, and propylene glycol monomethyl ether acetate were added as a solvent at a ratio of 7:2:1. The mixture was then stirred under reflux at 80°C to obtain a uniform varnish-like composition in which all soluble solids were dissolved. The varnish-like composition thus obtained was filtered through a membrane filter made of polytetrafluoroethylene (PTFE) with a pore size of 1 μm. In this way, solid foreign matter contained therein was removed. The filtered varnish-like optical waveguide composition was then used.

[0176] [Dry film for optical waveguide]

[0177] Next, dry films were prepared using the optical waveguide resin compositions of Examples 1 and 2 and Comparative Examples 1 and 2. The varnish-like optical waveguide composition obtained as described above was applied to a PET film (product name: A4100, manufactured by Toyobo Co., Ltd.) serving as a film substrate using a multi-coater with a comma-shaped coating head (manufactured by Hirano Tecseed Co., Ltd.) so that the resin layer containing the optical waveguide resin composition would have a thickness of 50 μm, and then dried at 80°C for 30 minutes. In this way, a resin layer containing the optical waveguide resin composition having a thickness of 50 μm was formed on the PET film.

[0178] [Alkali Developability]

[0179] The dry film for optical waveguide prepared as described above was immersed in a sodium carbonate aqueous solution (concentration: 1%) for 10 minutes, and then the state of the dry film for optical waveguide was observed. The alkaline developability of the dry film was evaluated based on the following criteria:

[0180] Grade A: No residual resin layer on the film substrate; or

[0181] Rank B: Any resin layer remains on the film base material.

[0182] <stickiness>

[0183] The degree of tack on the surface of the dry film for optical waveguide thus prepared was evaluated. Tackiness was determined based on the tactile sensation felt by a tester placing their finger on the dry film using the following criteria:

[0184] Grade A: No fingerprints left on the surface; or

[0185] Grade B: Fingerprints are left on the surface.

[0186] [Table 1]

[0187]

[0188] List of Reference Numerals

[0189] 1 resin layer

[0190] 2. Film substrate

[0191] 3 protective film

[0192] 8 cladding layer

[0193] 11 core

Claims

1. A resin composition for an optical waveguide, comprising an epoxy resin (A), a (meth)acrylate resin (B) and a photopolymerization initiator (C). The (meth)acrylate resin (B) comprises: a first (meth)acrylate compound (B-1) having a structural unit represented by the following formula (1) and a structural unit represented by the following formula (2); and a second (meth)acrylate compound (B-2) different from the first (meth)acrylate compound (B-1), The content of the first (meth)acrylate compound (B-1) is equal to or greater than 5% by mass and equal to or less than 20% by mass relative to the total mass of the epoxy resin (A) and the (meth)acrylate resin (B), and The content of the second (meth)acrylate compound (B-2) is equal to or greater than 30% by mass and equal to or less than 80% by mass relative to the total mass of the epoxy resin (A) and the (meth)acrylate resin (B). [Chemical Formula 1] Formula (1) Formula (2) wherein in formulae (1) and (2), R1 to R3 are each independently an alkyl group having 1 to 3 carbon atoms or a hydrogen atom, and R4 is an acryloyl group or a methacryloyl group.

2. The resin composition according to claim 1, wherein The epoxy resin (A) contains at least one selected from the group consisting of a solid bisphenol A epoxy compound (A-1), a liquid bisphenol A epoxy compound (A-2), and a polyfunctional aromatic epoxy compound (A-3) having three or more epoxy groups per molecule.

3. The resin composition according to claim 1, wherein The (meth)acrylate resin (B) further includes at least one selected from the group consisting of a urethane (meth)acrylate compound (B-21) and a bisphenol A (meth)acrylate compound (B-22).

4. The resin composition according to claim 1, wherein The first (meth)acrylate compound (B-1) includes a (meth)acrylate compound (B-11) having a structural unit represented by the following formula (3) and a structural unit represented by the following formula (4): [Chemical Formula 4] Formula (3) Formula (4).

5. The resin composition according to claim 2, wherein The content of the solid bisphenol A epoxy compound (A-1) is equal to or greater than 40% by mass and equal to or less than 60% by mass relative to the total mass of the epoxy resin (A).

6. The resin composition according to claim 2, wherein The content of the liquid bisphenol A epoxy compound (A-2) is equal to or greater than 15% by mass and equal to or less than 30% by mass relative to the total mass of the epoxy resin (A).

7. The resin composition according to claim 2, wherein The content of the polyfunctional aromatic epoxy compound (A-3) is equal to or greater than 15% by mass and equal to or less than 30% by mass relative to the total mass of the epoxy resin (A).

8. The resin composition according to claim 1, wherein The photopolymerization initiator (C) contains an acylphosphine oxide compound (C-1). 9 . A dry film for an optical waveguide, comprising a resin layer comprising the resin composition according to claim 1 or a semi-cured product of the resin composition. 10 . The dry film according to claim 9 , further comprising at least one film selected from the group consisting of a film base material and a protective film.

11. An optical waveguide comprising a core and a cladding layer covering the core, At least one of the core or the cladding layer contains a cured product of the resin composition according to any one of claims 1 to 8 .

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