Photosensitive resin composition for forming optical waveguides, optical waveguide, and method for manufacturing optical waveguides

Abstract

To provide a photosensitive resin composition for forming an optical waveguide which enables production of a cured product that is excellent in light transmittance, transparency and a high refractive index, and is also excellent in embedding property and patterning property, and an optical waveguide which has a core layer or a clad layer composed of the cured product.SOLUTION: A photosensitive resin composition for forming an optical waveguide contains a thermosetting resin, a thermoplastic resin, and an optical acid generator, where the optical acid generator contains an onium gallate salt having a triarylsulfonium cation and a gallate anion.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a photosensitive resin composition for forming optical waveguides, an optical waveguide, and a method for manufacturing an optical waveguide. [Background technology]

[0002] Optical communication technology has been developed that uses optical carriers to transfer data, and in recent years, optical waveguides have become widespread as a means of guiding these optical carriers from one point to another. An optical waveguide has a linear core and a cladding layer that surrounds it. The core layer is made of a material that is substantially transparent to the light of the optical carrier, and the cladding layer is made of a material with a lower refractive index than the core layer.

[0003] Various photosensitive resin compositions are used as materials for forming these cladding or core layers. For example, when forming patterns of cladding or core layers using these compositions, the desired cladding or core layer pattern is created by, for example, irradiating the material with ultraviolet (UV) light through a photomask.

[0004] Patent Document 1 discloses a photosensitive resin composition for forming optical waveguides, which contains an epoxy resin component containing a solid semi-aliphatic bifunctional epoxy resin and a photocationic polymerization initiator. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2018-100357 [Overview of the project] [Problems that the invention aims to solve]

[0006] However, the conventional technology described in Patent Document 1 has the problem that the resulting cladding layer and core layer have low light transmittance and are also less transparent due to coloring by heating or other processes. [Means for solving the problem]

[0007] The inventors of the present invention have found that the above problems can be solved by including a specific photoacid generator, and have completed the present invention. In other words, the present invention can be described as follows.

[0008] [1] Thermosetting resin and Thermoplastic resin and It contains a photoacid generator, A photosensitive resin composition for forming optical waveguides, wherein the photoacid generator comprises an onium gallate salt having a triarylsulfonium cation and a gallate anion. [2] The photosensitive resin composition for forming optical waveguides according to [1], wherein the triarylsulfonium cation comprises at least one compound represented by the following general formula (1). [ka] (In the above general formula (1), R 1 ~R 4 These independently represent alkyl groups, hydroxyl groups, alkoxy groups, alkylcarbonyl groups, arylcarbonyl groups, alkoxycarbonyl groups, aryloxycarbonyl groups, arylthiocarbonyl groups, acyloxy groups, arylthio groups, alkylthio groups, aryl groups, heterocyclic hydrocarbon groups, aryloxy groups, alkylsulfinyl groups, arylsulfinyl groups, alkylsulfonyl groups, arylsulfonyl groups, hydroxy(poly)alkyleneoxy groups, groups that condense with the benzene ring to form a condensed polycyclic hydrocarbon skeleton, substituted or unsubstituted silyl and amino groups, cyano groups, nitro groups, or halogen atoms, and a, b, c, and d are R 1 ~R 4 This represents the number of elements, where a is an integer from 1 to 5, c and d are integers from 0 to 5, and b is an integer from 0 to 4. [3] The gallate anion comprises a compound represented by the following general formula (5), in the photosensitive resin composition for forming optical waveguides according to [1] or [2]. [ka] (In the general formula (5), R 13 ~R 16 each independently represents a phenyl group or a perfluoroalkyl group which is substituted with a group selected from the group consisting of a perfluoroalkyl group, a perfluoroalkoxy group, a nitro group, a cyano group, an acyl group and a halogen atom, or is unsubstituted.) [4] The content of the photoacid generator is 0.3% by mass or more and 5.0% by mass or less based on the total solid content of the photosensitive resin composition for forming an optical waveguide, the photosensitive resin composition for forming an optical waveguide according to any one of [1] to [3]. [5] The thermosetting resin contains an epoxy resin, the photosensitive resin composition for forming an optical waveguide according to any one of [1] to [4]. [6] The epoxy resin contains a polyfunctional epoxy resin having three or more epoxy groups in the molecule, the photosensitive resin composition for forming an optical waveguide according to [5]. [7] The thermoplastic resin is a phenoxy resin, the photosensitive resin composition for forming an optical waveguide according to any one of [1] to [6]. [8] The weight average molecular weight of the phenoxy resin is 10,000 to 100,000, the photosensitive resin composition for forming an optical waveguide according to [7]. [9] Further contains a surfactant, the photosensitive resin composition for forming an optical waveguide according to any one of [1] to [8].

[10] Further contains an adhesion promoter, the photosensitive resin composition for forming an optical waveguide according to any one of [1] to [9].

[11] Further contains a solvent, the photosensitive resin composition for forming an optical waveguide according to any one of [1] to

[10] .

[12] The refractive index of the cured film with respect to light having a wavelength of 850 nm measured under the following conditions is 1.60 or more, the photosensitive resin composition for forming an optical waveguide according to any one of [1] to

[11] . (Condition) The refractive index with respect to light having a wavelength of 850 nm is measured for a cured film having a film thickness of 10 μm obtained by curing the photosensitive resin composition for forming an optical waveguide at 230 ° C. for 2 hours.

[13] A photosensitive resin composition for forming optical waveguides according to any one of [1] to

[12] , wherein the light transmittance of the cured film to light with a wavelength of 850 nm measured under the following conditions is 90%. (conditions) The transmittance of a 10 μm thick cured film obtained by curing the aforementioned photosensitive resin composition for forming optical waveguides at 230°C for 2 hours is measured for light with a wavelength of 850 nm.

[14] Substrate and A cladding layer formed on the substrate, A core layer for optical signal propagation having a predetermined shape is formed on the cladding layer, Equipped with, An optical waveguide in which the core layer or the cladding layer is made of a cured product of a photosensitive resin composition for forming an optical waveguide described in any of [1] to

[13] .

[15] A step of forming a cladding layer on a substrate made of a photosensitive resin composition for forming optical waveguides described in any of [1] to

[13] , The process involves applying a core-forming material onto the cladding layer, and then exposing and developing it to form a plurality of cores in a predetermined pattern. A step of forming a core layer consisting of the core portion and the cladding portion, by forming a cladding portion made of the photosensitive resin composition for forming optical waveguides between a plurality of core portions, A step of forming a cladding layer on the core layer, which is made of the photosensitive resin composition for forming optical waveguides, A method for manufacturing optical waveguides, including the optical waveguide.

[16] A step of forming a cladding layer on a substrate, consisting of a cladding layer forming material, The steps include applying a photosensitive resin composition for forming optical waveguides described in any of [1] to

[13] onto the cladding layer, and then exposing and developing it to form a plurality of core portions of a predetermined pattern, A step of forming a core layer consisting of the core portion and the cladding portion between a plurality of core portions, by forming a cladding portion made of the cladding layer forming material between the core portions, A step of forming a cladding layer made of the cladding layer forming material on the core layer, A method for manufacturing optical waveguides, including the optical waveguide. [Effects of the Invention]

[0009] According to the present invention, a photosensitive resin composition for forming optical waveguides can be provided that yields a cured product with excellent light transmittance, transparency, and high refractive index, and further exhibits excellent embedding and patterning properties. In other words, a photosensitive resin composition for forming optical waveguides with an excellent balance of these properties can be provided. Furthermore, an optical waveguide comprising a core layer or cladding layer made of the cured product can be provided. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic diagram showing the structure of the optical waveguide in this embodiment. [Modes for carrying out the invention]

[0011] Embodiments of the present invention will be described below with reference to the drawings. In all drawings, similar components are denoted by the same reference numerals, and descriptions are omitted where appropriate. Unless otherwise specified, "~" indicates a range from "greater than or equal to" to "less than or equal to".

[0012] The photosensitive resin composition for forming optical waveguides in this embodiment (hereinafter also simply referred to as "photosensitive resin composition") comprises a thermosetting resin, a thermoplastic resin, and a predetermined photoacid generator. The photosensitive resin composition for forming optical waveguides according to this embodiment yields a cured product with excellent light transmittance, transparency, and high refractive index, and further exhibits excellent embedding and patterning properties. In this embodiment, "embedding" specifically refers to applying a photosensitive resin composition to a substrate or layer having irregularities to cover those irregularities, and then flattening the outermost surface with a photosensitive resin film. Embedding can also be rephrased as flatness. The following describes each component contained in the photosensitive resin composition for forming optical waveguides.

[0013] [Thermosetting resin] Examples of thermosetting resins include triazine ring-containing resins such as epoxy resins, urea resins, and melamine resins; unsaturated polyester resins; maleimide resins such as bismaleimide compounds; polyurethane resins; diallyl phthalate resins; silicone resins; benzoxazine resins; polyimide resins; polyamideimide resins; cyanate ester resins such as benzocyclobutene resins, novolac-type cyanate resins, bisphenol A-type cyanate resins, bisphenol E-type cyanate resins, and tetramethylbisphenol F-type cyanate resins. These may be used individually or in combination of two or more types.

[0014] In this embodiment, the thermosetting resin preferably includes an epoxy resin. This improves the physical properties and processability of the core layer or cladding layer made from the cured product of the photosensitive resin composition.

[0015] As the epoxy resin, for example, an epoxy resin having two or more epoxy groups in one molecule can be used. Monomers, oligomers, and polymers in general can be used as epoxy resins, and their molecular weight and molecular structure are not particularly limited.

[0016] Examples of the epoxy resins include phenol novolac type epoxy resins, cresol novolac type epoxy resins, cresol naphthol type epoxy resins, biphenyl type epoxy resins, biphenyl aralkyl type epoxy resins, phenoxy resins, naphthalene skeleton type epoxy resins, bisphenol A type epoxy resins, bisphenol A diglycidyl ether type epoxy resins, bisphenol F type epoxy resins, bisphenol F diglycidyl ether type epoxy resins, bisphenol S diglycidyl ether type epoxy resins, glycidyl ether type epoxy resins, cresol novolac type epoxy resins, aromatic polyfunctional epoxy resins, aliphatic epoxy resins, aliphatic polyfunctional epoxy resins, alicyclic epoxy resins, and polyfunctional alicyclic epoxy resins. Epoxy resins may be used individually or in combination.

[0017] The epoxy resin may include a solid epoxy resin having two or more epoxy groups in its molecule. The solid epoxy resin may be one having two or more epoxy groups and being solid at 25°C (room temperature). This enhances the mechanical properties of the core layer or cladding layer made from the cured product of the photosensitive resin composition.

[0018] Furthermore, the epoxy resin may include polyfunctional epoxy resins with three or more functions in the molecule (i.e., polyfunctional epoxy resins having three or more epoxy groups in one molecule).

[0019] The polyfunctional epoxy resin with three or more functions preferably contains one or more epoxy resins selected from the group consisting of phenol novolac type epoxy resins, cresol novolac type epoxy resins, triphenylmethane type epoxy resins, dicyclopentadiene type epoxy resins, bisphenol A type epoxy resins, and tetramethylbisphenol F type epoxy resins, more preferably contains a novolac type epoxy resin, and even more preferably contains a cresol novolac type epoxy resin. This makes it possible to achieve an appropriate coefficient of thermal expansion while increasing the heat resistance of the cured product.

[0020] Furthermore, the epoxy resin may include a liquid epoxy resin having two or more epoxy groups in its molecule. This liquid epoxy resin can function as a film-forming agent and improve the brittleness of the cured product of the photosensitive resin composition.

[0021] As the liquid epoxy resin, an epoxy compound having two or more epoxy groups and being liquid at room temperature of 25°C can be used. The viscosity of this liquid epoxy resin at 25°C can be, for example, 1 mPa·s to 8000 mPa·s, preferably 5 mPa·s to 1500 mPa·s, and more preferably 10 mPa·s to 1400 mPa·s.

[0022] The liquid epoxy resin may include, for example, one or more selected from the group consisting of bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, alkyl diglycidyl ether, and alicyclic epoxy. These may be used individually or in combination of two or more. Among these, alkyl diglycidyl ether can be used from the viewpoint of reducing cracks after development.

[0023] The epoxy equivalent of the liquid epoxy resin is, for example, 100 g / eq to 200 g / eq, preferably 105 g / eq to 180 g / eq, and more preferably 110 g / eq to 170 g / eq. This improves the brittleness of the cured product.

[0024] When the liquid epoxy resin is included, the lower limit of the liquid epoxy resin content is, for example, 5% by mass or more, preferably 10% by mass or more, and more preferably 15% by mass or more, relative to the total nonvolatile components of the photosensitive resin composition. This improves the brittleness of the final cured product. On the other hand, the upper limit of the liquid epoxy resin content is, for example, 40% by mass or less, preferably 35% by mass or less, and more preferably 30% by mass or less, relative to the total nonvolatile components of the photosensitive resin composition. This allows for a balance in the properties of the cured product.

[0025] The lower limit of the epoxy resin content is, for example, 40% by mass or more, preferably 45% by mass or more, and more preferably 50% by mass or more, relative to the total nonvolatile components of the photosensitive resin composition. This improves the heat resistance and mechanical strength of the final cured product. On the other hand, the upper limit of the epoxy resin content is, for example, 90% by mass or less, preferably 85% by mass or less, and more preferably 80% by mass or less, relative to the total nonvolatile components of the photosensitive resin composition. This improves the patternability.

[0026] In this embodiment, the non-volatile components of the photosensitive resin composition refer to the remainder after removing volatile components such as water and solvents. The content relative to the total non-volatile components of the photosensitive resin composition refers to the content relative to the total non-volatile components of the photosensitive resin composition excluding the solvent, if a solvent is included.

[0027] [Thermoplastic resin] Examples of thermoplastic resins include phenoxy resins, polyvinyl acetal resins, acrylic resins, polyamide resins (e.g., nylon), thermoplastic urethane resins, polyolefin resins (e.g., polyethylene, polypropylene), polycarbonate, polyester resins (e.g., polyethylene terephthalate, polybutylene terephthalate), polyacetal, polyphenylene sulfide, polyether ether ketone, liquid crystal polymer, fluororesin (e.g., polytetrafluoroethylene, polyvinylidene fluoride), modified polyphenylene ether, polysulfone, polyethersulfone, polyarylate, polyamide-imide, polyether-imide, and thermoplastic polyimide. These may be used individually or in combination of two or more.

[0028] In this embodiment, it is preferable that the thermoplastic resin includes a phenoxy resin. This can improve the flexibility of the cured product of the photosensitive resin composition.

[0029] The weight-average molecular weight of the phenoxy resin is not particularly limited, but is preferably 10,000 to 100,000, and more preferably 20,000 to 80,000. By using such a relatively high molecular weight phenoxy resin, good flexibility and sufficient solubility in the solvent can be imparted to the cured product. In this embodiment, the weight-average molecular weight is measured, for example, as a polystyrene-converted value by gel permeation chromatography (GPC).

[0030] Furthermore, the phenoxy resin may have reactive groups such as epoxy groups at both ends of the molecular chain or within the molecular chain. The reactive groups in the phenoxy resin are capable of crosslinking with the epoxy groups in the epoxy resin. By using such a phenoxy resin, the solvent resistance and heat resistance of the cured product can be improved.

[0031] Furthermore, a phenoxy resin that is solid at 25°C is preferably used. Specifically, a phenoxy resin having a non-volatile content of 90% by mass or more is preferably used. By using such a phenoxy resin, the mechanical properties of the cured product can be improved.

[0032] Examples of the phenoxy resin include bisphenol A type phenoxy resin, bisphenol F type phenoxy resin, copolymer phenoxy resin of bisphenol A type and bisphenol F type, biphenyl type phenoxy resin, bisphenol S type phenoxy resin, copolymer phenoxy resin of biphenyl type phenoxy resin and bisphenol S type phenoxy resin, and one or more of these can be used. Among these, bisphenol A type phenoxy resin or copolymer phenoxy resin of bisphenol A type and bisphenol F type is preferred, and bisphenol A type phenoxy resin is more preferred.

[0033] The lower limit of the phenoxy resin content is, for example, 20 parts by mass or more, preferably 25 parts by mass or more, and more preferably 30 parts by mass or more, relative to the epoxy resin content. This can increase flexibility. On the other hand, the upper limit of the phenoxy resin content is, for example, 60 parts by mass or less, preferably 55 parts by mass or less, and more preferably 50 parts by mass or less. This increases the solubility of the phenoxy resin and enables the realization of a photosensitive resin composition with excellent coatability.

[0034] [Photoacid Generator] The photosensitive resin composition of this embodiment contains a photoacid generator. This improves processability during patterning, such as sensitivity and resolution.

[0035] The photosensitive resin composition of this embodiment is a chemically amplified photosensitive resin composition that utilizes the acid generated from a photoacid generator as a catalyst, and can be used as a negative-type photosensitive resin composition.

[0036] The aforementioned photoacid generator contains an onium gallate salt having a triarylsulfonium cation and a gallate anion. This improves both insulation reliability and patternability. The photosensitive resin composition of this embodiment includes a thermosetting resin and a thermoplastic resin, along with a photoacid generator containing an onium gallate salt having a triarylsulfonium cation and a gallate anion. As a result, a cured product with excellent light transmittance, transparency, and high refractive index can be obtained, and furthermore, a photosensitive resin composition for forming optical waveguides with excellent embedding (flatness) and patternability can be provided. In other words, a photosensitive resin composition for forming optical waveguides with an excellent balance of these properties can be provided. In other words, the present invention is a use invention that discovers an unknown attribute of a photosensitive resin composition containing a specific combination of components, which yields a cured product with excellent light transmittance, transparency, and high refractive index, as well as excellent embedding (flatness) and patterning properties, and that this attribute makes it suitable for optical waveguide formation. The aforementioned triarylsulfonium cation may include at least one compound represented by the following general formula (1).

[0037] [ka]

[0038] In the above general formula (1), R 1 ~R 4are, independently of each other, an alkyl group, a hydroxy group, an alkoxy group, an alkylcarbonyl group, an arylcarbonyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, an arylthiocarbonyl group, an acyloxy group, an arylthio group, an alkylthio group, an aryl group, a heterocyclic hydrocarbon group, an aryloxy group, an alkylsulfinyl group, an arylsulfinyl group, an alkylsulfonyl group, an arylsulfonyl group, a hydroxy(poly)alkyleneoxy group, a group that condenses with the benzene ring to which it is attached to form a condensed polycyclic hydrocarbon skeleton, a substituted or unsubstituted silyl group and an amino group, a cyano group, a nitro group or a halogen atom, and a, b, c, d are each R 1 ~R 4 represents the number of, a is an integer of 1 to 5, c and d are integers of 0 to 5, and b is an integer of 0 to 4. R 1 ~R 4 As the substituents of, in the general formula (1), R 1 ~R 4 are the same as those listed above.

[0039] In the general formula (1), R 1 ~R 4 As the alkyl group in, there are linear alkyl groups having 1 to 18 carbon atoms (methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-octyl, n-decyl, n-dodecyl, n-tetradecyl, n-hexadecyl, n-octadecyl, etc.), branched alkyl groups having 3 to 18 carbon atoms (isopropyl, isobutyl, sec-butyl, tert-butyl, isopentyl, neopentyl, tert-pentyl, isohexyl, isooctadecyl), and cycloalkyl groups having 3 to 18 carbon atoms (cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, 4-decylcyclohexyl, etc.).

[0040] In the general formula (1), R 1 ~R 4Examples of alkoxy groups in this context include linear alkoxy groups having 1 to 18 carbon atoms, or branched alkoxy groups having 3 to 18 carbon atoms (such as methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, sec-butoxy, tert-butoxy, hexyloxy, decyloxy, dodecyloxy, and octadecyloxy).

[0041] In general formula (1), R 1 ~R 4 Examples of aryl groups in this context include aryl groups having 6 to 10 carbon atoms (such as phenyl, tolyl, dimethylphenyl, and naphthyl).

[0042] In general formula (1), the condensed polycyclic hydrocarbon skeleton may consist of two or more rings, and may consist of six or fewer rings, preferably four or fewer rings, and more preferably three or fewer rings. The condensed polycyclic hydrocarbon skeleton may consist of cyclic hydrocarbons with different numbers of rings, such as five-membered rings or six-membered rings, formed by condensation. Examples of such condensed polycyclic hydrocarbon skeletons include the fluorene skeleton and derivatives of the fluorene skeleton. One or two of the above-mentioned substituents, such as alkyl groups, may be attached to the 9-position of the phenanthrene skeleton. The gallate anion may include a compound represented by the following general formula (5).

[0043] [ka]

[0044] In the above general formula (5), R 13 ~R 16 This independently represents a phenyl group or perfluoroalkyl group substituted with a group selected from the group consisting of perfluoroalkyl groups, perfluoroalkoxy groups, nitro groups, cyano groups, acyl groups, and halogen atoms, or an unsubstituted phenyl group or perfluoroalkyl group.

[0045] In the general formula (5) above, the number of carbon atoms in the perfluoroalkyl group is 1 to 8, preferably 1 to 4. Specific examples of perfluoroalkyl groups include linear perfluoroalkyl groups such as trifluoromethyl, pentafluoroethyl, heptafluoropropyl, nonafluorobutyl, perfluoropentyl, and perfluorooctyl; branched perfluoroalkyl groups such as heptafluoroisopropyl, nonafluoroisobutyl, nonafluoro-sec-butyl, and nonafluoro-tert-butyl; and perfluorocycloalkyl groups such as perfluorocyclopropyl, perfluorocyclobutyl, perfluorocyclopentyl, and perfluorocyclohexyl.

[0046] In the general formula (5) above, the number of carbon atoms in the perfluoroalkoxy group is 1 to 8, preferably 1 to 4. Specific examples of perfluoroalkoxy groups include linear perfluoroalkoxy groups such as trifluoromethoxy, pentafluoroethoxy, heptafluoropropoxy, nonafluorobutoxy, perfluoropentyloxy, and perfluorooctyloxy; and branched perfluoroalkoxy groups such as heptafluoroisopropoxy, nonafluoroisobutoxy, nonafluoro-sec-butoxy, and nonafluoro-tert-butoxy.

[0047] In the general formula (5) above, examples of halogen atoms include fluorine, chlorine, bromine, and iodine atoms.

[0048] In the above general formula (5), from the viewpoint of cationic polymerization performance, R 13 ~R 16 Preferably, the phenyl group is substituted with at least one selected from the group consisting of perfluoroalkyl groups and fluorine atoms.

[0049] Examples of the gallate anions mentioned above include (C6F5)4Ga-, ((CF3)2C6H3)4Ga-, (CF3C6H4)4Ga-, (C6F5)2GaF2-, C6F5GaF3-, and (C6H3F2)4Ga-. This enables high thermal dissociation.

[0050] The onium gallate salt undergoes thermal dissociation at the gallate anion (Ga-) upon heating. A specific example is that the onium gallate salt can be thermally dissociated by curing a resin film of a photosensitive resin composition through heating.

[0051] The onium gallate salt according to this embodiment exhibits relatively high thermal dissociation when a borate anion, sulfonate anion, phosphorus-based anion, or antimony-based anion is used as the counter anion.

[0052] In the manufacturing process using the photosensitive resin composition of this embodiment, the process compatibility of the photosensitive resin composition can be improved by setting the temperature of the heat treatment (e.g., curing treatment) after exposure to a temperature above the temperature at which thermal dissociation occurs.

[0053] The content of the photoacid generator is, for example, 0.3% to 5.0% by mass, preferably 0.5% to 4.5% by mass, and more preferably 1.0% to 4.0% by mass, relative to the total solid content of the photosensitive resin composition. Setting the content above the lower limit can improve patternability. On the other hand, setting it below the upper limit can improve insulation reliability. In this specification, "~" indicates that the upper and lower limits are included unless otherwise specified.

[0054] The onium gallate salt content may be, for example, 70% to 100% by mass, preferably 80% to 100% by mass, and more preferably 90% to 99% by mass, relative to the total amount of the photoacid generator. This can improve connection reliability and patternability.

[0055] The photosensitive resin composition of this embodiment may contain other photosensitive agents besides the photoacid generator. Examples of other photosensitive agents include onium salt compounds. More specifically, examples include iodonium salts such as diazonium salts and diaryliodonium salts, sulfonium salts such as triarylsulfonium salts, cationic photopolymerization initiators such as triarylpyryllium salts, benzylpyridinium thiocyanate, dialkylphenacylsulfonium salts, and dialkylhydroxyphenylphosphonium salts.

[0056] [Surfactants] The photosensitive resin composition of this embodiment may contain a surfactant. By including a surfactant, wettability during coating can be improved, and a uniform resin film and cured product can be obtained. Examples of surfactants include fluorine-based surfactants, silicone-based surfactants, alkyl-based surfactants, and acrylic-based surfactants.

[0057] The surfactant preferably contains at least one of a fluorine atom and a silicon atom. This contributes to obtaining a uniform resin film (improved coatability), improved developability, and improved adhesive strength. Such a surfactant is preferably a nonionic surfactant containing at least one of a fluorine atom and a silicon atom. Examples of commercially available surfactants that can be used include the "MegaFac" series from DIC Corporation: F-251, F-253, F-281, F-430, F-477, F-551, F-552, F-553, F-554, F-555, F-556, F-557, F-558, F-559, F-560, F-561, F-562, F-563, F-565, F-56 Examples include fluorine-containing oligomer surfactants such as F-569, F-570, F-572, F-574, F-575, F-576, R-40, R-40-LM, R-41, and R-94; fluorine-containing nonionic surfactants such as Futergent 250 and Futergent 251 manufactured by Neos Co., Ltd.; and silicone-based surfactants such as the SILFOAM® series (e.g., SD 100 TS, SD 670, SD 850, SD 860, SD 882) manufactured by Wacker Chemie.

[0058] The amount of the surfactant can be, for example, 0.001 to 1% by mass, preferably 0.005 to 0.5% by mass, based on the total amount of non-volatile components of the photosensitive resin composition.

[0059] [Adhesion enhancer] The photosensitive resin composition of this embodiment may contain an adhesion enhancer. This can further improve adhesion to inorganic materials.

[0060] The aforementioned adhesion aid is not particularly limited, but coupling agents such as amino group-containing coupling agents, epoxy group-containing coupling agents, acrylic group-containing coupling agents, mercapto group-containing coupling agents, vinyl group-containing coupling agents, vinyl group-containing coupling agents, ureido group-containing coupling agents, sulfide group-containing coupling agents, and acid anhydride-containing coupling agents can be used, with silane coupling agents being preferred. One type of silane coupling agent may be used alone, or two or more types may be used in combination. Among these, epoxysilane (i.e., a compound containing both an epoxy moiety and a group that generates a silanol group by hydrolysis in one molecule) is more preferred.

[0061] Examples of amino group-containing coupling agents include bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane, γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropylmethyldiethoxysilane, γ-aminopropylmethyldimethoxysilane, N-β(aminoethyl)γ-aminopropyltrimethoxysilane, N-β(aminoethyl)γ-aminopropyltriethoxysilane, N-β(aminoethyl)γ-aminopropylmethyldimethoxysilane, N-β(aminoethyl)γ-aminopropylmethyldiethoxysilane, and N-phenyl-γ-aminopropyltrimethoxysilane.

[0062] Examples of epoxy group-containing coupling agents include γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and γ-glycidylpropyltrimethoxysilane.

[0063] Examples of acrylic group-containing coupling agents or methacrylic group-containing coupling agents include γ-(methacryloxypropyl)trimethoxysilane, γ-(methacryloxypropyl)methyldimethoxysilane, and γ-(methacryloxypropyl)methyldiethoxysilane. Examples of mercapto group-containing coupling agents include 3-mercaptopropyltrimethoxysilane.

[0064] Examples of vinyl group-containing coupling agents include vinyltris(β-methoxyethoxy)silane, vinyltriethoxysilane, and vinyltrimethoxysilane. Examples of ureido group-containing coupling agents include 3-ureidopropyltriethoxysilane.

[0065] Examples of sulfide group-containing coupling agents include bis(3-(triethoxysilyl)propyl) disulfide and bis(3-(triethoxysilyl)propyl) tetrasulfide.

[0066] Examples of acid anhydride-containing coupling agents include 3-trimethoxysilylpropyl succinic anhydride, 3-triethoxysilylpropyl succinic anhydride, and 3-dimethylmethoxysilylpropyl succinic anhydride. While silane coupling agents are listed here, titanium coupling agents, zirconium coupling agents, etc., may also be used.

[0067] The content of the adhesion aid is preferably 0.3 to 5% by mass, more preferably 0.4 to 4%, and can be 0.5 to 3% by mass, based on the total amount of non-volatile components of the photosensitive resin composition.

[0068] [solvent] The photosensitive resin composition of this embodiment may contain a solvent. The solvent may be an organic solvent. The organic solvent is not particularly limited as long as it is capable of dissolving each component of the photosensitive resin composition and does not chemically react with each component.

[0069] Examples of organic solvents include acetone, methyl ethyl ketone, toluene, propylene glycol methyl ethyl ether, propylene glycol dimethyl ether, propylene glycol 1-monomethyl ether 2-acetate, diethylene glycol ethyl methyl ether, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, benzyl alcohol, propylene carbonate, ethylene glycol diacetate, propylene glycol diacetate, propylene glycol monomethyl ether acetate, dipropylene glycol methyl-n-propyl ether, butyl acetate, and γ-butyrolactone. These may be used individually or in combination.

[0070] The solvent is preferably used such that the total concentration of non-volatile components in the photosensitive resin composition is, for example, 30 to 75% by mass. This range allows for sufficient dissolution of each component and ensures good coatability. Furthermore, the viscosity of the photosensitive resin composition can be appropriately controlled by adjusting the content of the non-volatile components.

[0071] The viscosity of the varnish-like photosensitive resin composition at 25°C is, for example, 10 cP to 6000 cP, preferably 20 cP to 5000 cP, and more preferably 30 cP to 4000 cP. By keeping the viscosity within the above numerical range, the thickness of the coated film can be appropriately controlled. For example, a thickness of 1 μm to 100 μm, preferably 3 μm to 80 μm, and more preferably 5 μm to 50 μm can be achieved.

[0072] (Other additives) In addition to the components mentioned above, the photosensitive resin composition of this embodiment may contain other additives as needed. Examples of other additives include antioxidants, fillers such as silica, sensitizers, and film-forming agents.

[0073] <Photosensitive resin composition for optical waveguide formation> The photosensitive resin composition for forming optical waveguides according to this embodiment can be obtained by mixing the above-mentioned components.

[0074] The cured film obtained from the photosensitive resin composition for optical waveguide formation of this embodiment exhibits excellent light transmittance. For example, a cured film with a thickness of 10 μm, cured under nitrogen at 230°C for 2 hours, can have a light transmittance of 90% or more, preferably 95% or more, and more preferably 98% or more, for light with a wavelength of 850 nm. Therefore, the cured film obtained from the photosensitive resin composition for optical waveguide formation can be suitably used as a core layer or a cladding layer, particularly as a core layer.

[0075] The cured film obtained from the photosensitive resin composition for optical waveguide formation of this embodiment exhibits excellent refractive index. For example, a cured film with a thickness of 10 μm, cured under nitrogen at 230°C for 2 hours, can have a refractive index of 1.60 or higher, preferably 1.62 or higher, and more preferably 1.64 or higher, for light with a wavelength of 850 nm. Therefore, the cured film obtained from the photosensitive resin composition for optical waveguide formation can be suitably used as a core layer or cladding layer, particularly as a core layer.

[0076] The cured film obtained from the photosensitive resin composition for optical waveguide formation of this embodiment exhibits excellent heat resistance to coloration. For example, the cured film with a thickness of 10 μm can achieve a decrease in light transmittance for 850 nm light at a wavelength of 30% or less, preferably 15% or less, before and after storage at 230°C for 2 hours. Therefore, the cured film obtained from the photosensitive resin composition for optical waveguide formation exhibits excellent product reliability as a core layer or cladding layer.

[0077] <Optical waveguide> As shown in Figure 1, the optical waveguide 10 of this embodiment may have a laminated structure in which a lower cladding layer (undercladding layer) 130, a core layer 110 consisting of a patterned core portion 112 and a cladding portion 114 provided on the lower cladding layer 130, and an upper cladding layer (overcladding layer) 120 provided on the core layer 110 are laminated on the lower substrate 150. In this laminated structure, the upper substrate may be arranged on the upper surface side of the upper cladding layer 120.

[0078] In the optical waveguide of this embodiment, the lower cladding layer 130 and / or the upper cladding layer 120, or the core portion 112 can be formed from the aforementioned photosensitive resin composition, and the materials can be combined and used such that the refractive index of the cladding layers 120 and 130 is smaller than that of the core portion 112.

[0079] The method for manufacturing an optical waveguide in this embodiment includes, for example, the following steps. In the following example, the description will be based on an example in which the lower cladding layer 130 is formed using a photosensitive resin composition.

[0080] First, the photosensitive resin composition of this embodiment is dissolved in an organic solvent as needed to prepare a photosensitive varnish. Then, the photosensitive varnish is applied to the lower substrate 150.

[0081] Examples of the lower substrate 150 include silicon wafers, metal substrates, polymer films, and glass substrates. Examples of the metal substrate include stainless steel plates such as SUS. Specific examples of the polymer film include polyethylene terephthalate (PET) film, polyethylene naphthalate film, and polyimide film. The thickness is typically set within the range of 10 μm to 3 mm.

[0082] Examples of the aforementioned organic solvents include ethyl lactate, methyl ethyl ketone, cyclohexanone, 2-butanone, N,N-dimethylacetamide, diglyme, diethylene glycol methyl ethyl ether, propylene glycol methyl acetate, propylene glycol monomethyl ether, tetramethylfuran, and dimethoxyethane. These organic solvents are used individually or in combination of two or more to obtain a viscosity suitable for coating.

[0083] As for the coating method of the photosensitive varnish, for example, coating methods such as spin coater, coater, circular coater, and bar coater can be used, as well as screen printing, a method of forming a gap using spacers and injecting into it by capillary action, and a method of continuously coating in R-to-R using a coating machine such as a multi-coater. Furthermore, the optical waveguide can also be made into a film-like optical waveguide by peeling off the substrate.

[0084] After applying the photosensitive varnish, the organic solvent is removed by heating and drying. This forms an uncured photosensitive resin composition (coating film) on the lower substrate 150. Next, the coating film is cured by light irradiation to form the lower cladding layer 130.

[0085] Specifically, the aforementioned light irradiation includes ultraviolet (UV) irradiation. Examples of UV light sources include low-pressure mercury lamps, high-pressure mercury lamps, and ultra-high-pressure mercury lamps. The UV irradiation dose is typically 10 to 20,000 mJ / cm². 2 It is to that extent.

[0086] Furthermore, after exposure by light irradiation such as ultraviolet irradiation, a heat treatment can also be performed. The heat treatment conditions are typically 80 to 250°C for a period of 10 seconds to 2 hours.

[0087] Next, a core-forming material (photosensitive varnish) is applied to the lower cladding layer 130.

[0088] Examples of core-forming materials include various liquid epoxy resins such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, hydrogenated bisphenol A type epoxy resin, fluorinated epoxy resin, and epoxy-modified silicone resin, as well as various solid epoxy resins such as solid polyfunctional aliphatic epoxy resin. The formulation is designed to have a higher refractive index compared to the cladding layer-forming material. Furthermore, if necessary, the core-forming material may be prepared as a varnish and applied, and the aforementioned organic solvent may be used to obtain a viscosity suitable for coating, as well as various additives (antioxidants, adhesion promoters, leveling agents, UV absorbers) in an amount that does not degrade the function as an optical waveguide.

[0089] After applying the core-forming material (photosensitive varnish), an uncured core-forming material (coating film) is formed by heating and drying to remove the organic solvent. Next, a photomask with a predetermined pattern (optical waveguide pattern) is placed on the coating film, and light irradiation such as ultraviolet light is performed through the photomask, and further heat treatment is performed as necessary. After that, the unexposed portions of the uncured core-forming material (coating film) are dissolved and removed using a developer to form the core portion 112 with the predetermined pattern. Between the multiple core portions 112, a cladding portion 114 formed from the photosensitive resin composition of this embodiment is provided. The photosensitive resin composition of this embodiment is suitable for use in forming cladding layers because it has excellent embedding and patterning properties.

[0090] Furthermore, a photosensitive varnish, obtained by dissolving the photosensitive resin composition of this embodiment in the organic solvent, is applied to the core layer 110, followed by light irradiation such as ultraviolet irradiation, and further heat treatment as necessary to form the upper cladding layer 120. By following the above steps, the optical waveguide of this embodiment can be manufactured.

[0091] The cured film obtained from the photosensitive resin composition of this embodiment exhibits excellent heat resistance, suppressing yellowing due to heating, and possesses excellent transparency. Furthermore, it has excellent light transmittance at a wavelength of 850 nm, making it suitable for use as a material for forming optical waveguides. In addition, the photosensitive resin composition of this embodiment has good embedding and patterning properties, making it suitable for use as a cladding material.

[0092] Furthermore, the photosensitive resin composition of this embodiment can be used as the core forming material, and a photosensitive resin composition containing, for example, polyimide resin, alicyclic epoxy resin, cyclic olefin resin, acrylic resin, etc., can be used as the cladding layer forming material. The cured film obtained from the photosensitive resin composition of this embodiment exhibits excellent heat resistance, suppressing yellowing due to heating, and possesses excellent transparency. Furthermore, it has excellent light transmittance at a wavelength of 850 nm, making it suitable for use as a material for forming optical waveguides, particularly as a core material for optical waveguides. Moreover, the cured film obtained from the photosensitive resin composition of this embodiment has a high refractive index, making it even more suitable for use as a core material for optical waveguides.

[0093] When the optical waveguide obtained as described above is used in a product involving optical path conversion, such as a mixed optical-electrical (optical-electrical) substrate, the surface of the cladding layer in the optical waveguide on the substrate is subjected to a 45° mirror finish using a laser with a wavelength of 248 nm. Examples of known methods for processing the mirror include laser processing, dicing, and imprinting. The irradiation energy of the laser varies depending on the optical waveguide material and is set as appropriate.

[0094] The optical waveguide obtained in this way can be used, for example, as an optical waveguide for a mixed-signal flexible printed circuit board for optical and electrical transmission.

[0095] Although embodiments of the present invention have been described above, these are merely examples, and various other configurations can be adopted as long as they do not impair the effects of the present invention. [Examples]

[0096] The present invention will be described in more detail below with reference to examples, but the present invention is not limited thereto.

[0097] (Preparation of photosensitive resin composition for forming optical waveguides) The raw materials for each component, as formulated according to Table 1, were dissolved in propylene glycol monomethyl ether acetate (PGMEA) to obtain a mixed solution. The mixed solution was then filtered through a 0.2 μm polypropylene filter to obtain a varnish-like photosensitive resin composition with a viscosity of approximately 100 cP at 25°C. The viscosity of the photosensitive resin composition was measured using a cone-plate viscometer (TV-25, manufactured by Toki Sangyo Co., Ltd.) at a rotation speed of 100 rpm.

[0098] The details of the raw materials for each component in Table 1 are as follows. (Epoxy resin) • Epoxy resin 1: Cresol novolac type epoxy resin (EOCN-1020-55, manufactured by Nippon Kayaku Co., Ltd., solid at 25°C, n=3~6) [ka]

[0099] (Polyimide) In Comparative Example 3, the following polyimide resin was used.

[0100] 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane (hereinafter also referred to as BAFA), represented by the following formula

[0101] [ka]

[0102] 4,4'-diamino-2,2'-bis(trifluoromethyl)biphenyl (hereinafter also referred to as TFMB), represented by the following formula

[0103] [ka]

[0104] The following formula represents 4-[4-(1,3-dioxoisobenzofuran-5-ylcarbonyloxy)-2,3,5-trimethylphenyl]-2,3,6-trimethylphenyl 1,3-dioxoisobenzofuran-5-carboxylate (hereinafter also referred to as TMPBP-TME)

[0105] [ka]

[0106] [Synthesis Example 1] First, 37.62 g (102.7 mmol) of BAFA, 32.89 g (102.7 mmol) of TFMB, and 151.29 g (244.6 mmol) of TMPBP-TME were placed in a reaction vessel of appropriate size equipped with a stirrer and condenser. Then, 598.86 g of GBL was added to the reaction vessel. After aeration with nitrogen for 10 minutes, the temperature was raised to 60°C while stirring and the reaction was allowed to proceed for 1.5 hours. Subsequently, the reaction was further carried out at 180°C for 3 hours to polymerize bisaminophenol and acid anhydride, thereby preparing a polymerization solution. The obtained polymerization solution was diluted with acetone to prepare a diluent, and then the diluent was added dropwise to a water / methanol mixture of 1 / 3 to precipitate a white solid. The obtained white solid was collected and vacuum-dried at 120°C to obtain 205.55 g of polymer. GPC analysis of the polymer revealed a weight-average molecular weight (Mw) of 18200 and a polydispersity (weight-average molecular weight (Mw) / number-average molecular weight (Mn)) of 1.82. IR measurements of the polymer yielded values ​​of 1480, 1550, and 1670 cm⁻¹. -1 The peaks originating from the nearby amide group had disappeared, confirming that imidation was complete. Also, 1 ¹H-NMR measurements revealed peaks in the aromatic region (6.9 ppm to 8.9 ppm) with area ratios corresponding to the number of protons. Next, 197.16 g (182.6 mmol in terms of hydroxyl groups) of the obtained polyimide, 51.54 g (365.22 mmol) of 2-isocyanatoethyl acrylate (hereinafter also referred to as AOI, manufactured by Showa Denko Corporation), and 737.08 g of γ-butyllactone (GBL) were placed in a reaction vessel of appropriate size equipped with a stirrer and a condenser. The temperature was then raised to 120°C while stirring, and the reaction was carried out for 6 hours. The resulting reaction solution was diluted with acetone to prepare a diluent. This diluent was then added dropwise to a water / methanol mixture of 1 / 2 to precipitate a white solid. The obtained white solid was collected and vacuum-dried at 40°C to yield 183.99 g of polymer. GPC analysis of the polymer revealed a weight-average molecular weight (Mw) of 20,400 and a polydispersity (weight-average molecular weight (Mw) / number-average molecular weight (Mn)) of 1.80. 1 1H-NMR measurement results confirmed that crosslinking groups had been introduced into the polymer. The polymer with the introduced crosslinking groups contained the following repeating units in some parts. Furthermore, gas chromatography measurements revealed that the crosslinking group introduction rate was 60%.

[0107] (Phenoxy resin) • Phenoxy resin 1: Bisphenol A type phenoxy resin (jER1256, manufactured by Mitsubishi Chemical Corporation, Mw: approximately 50,000)

[0108] (Adhesion enhancer) • Coupling agent 1:3-Glycidoxypropyltrimethoxysilane (silane coupling agent, KBM-403, manufactured by Shin-Etsu Chemical Co., Ltd.) [ka]

[0109] (Surfactants) ·Surfactant 1: Oligomer containing fluorine-containing group and lipophilic group (R-41, manufactured by DIC)

[0110] (Photoacid generator) [Synthesis Example 1] Synthesis of lithium tetrakis(3,4,5-trifluorophenyl) gallate 360 parts super-dehydrated diethyl ether and 25.6 parts 1-bromo-3,4,5-trifluorobenzene were charged into a 125 mL four-necked flask that had been thoroughly dried under a nitrogen atmosphere, and the mixture was cooled to -78°C using a dry ice / acetone bath. 70 parts of 2.5 mol / L n-butyllithium hexane solution were added dropwise over 10 minutes, and the mixture was then stirred at -78°C for 30 minutes. 68 parts of diethyl ether solution containing 5 parts gallium(III) chloride were added dropwise over 10 minutes, and the mixture was stirred at -78°C for 3 hours. The reaction mixture was stirred while gradually returning to room temperature, and then stirred for a further 5 hours after returning to room temperature. The precipitated solid was filtered, and the reaction mixture was transferred to an evaporator. The solvent was removed by distillation to obtain a grayish-white product. The product was washed four times with 50 parts super-dehydrated hexane, and then vacuum-dried overnight to obtain lithium tetrakis(3,4,5-trifluorophenyl) gallate. The product is 19 Identified by 1F-NMR.

[0111] [Synthesis Example 2] Synthesis of Lithium Tetrakis(Pentafluorophenyl) Gallate Lithium tetrakis(pentafluorophenyl) gallate was obtained in the same manner as in Synthesis Example 1, except that 25.6 parts of 1-bromo-3,4,5-trifluorobenzene were replaced with 30 parts of bromopentafluorobenzene. The product was 19 Identified by 1F-NMR.

[0112] [Synthesis Example 3] Synthesis of Lithium Tetrakis[3,5-Bis(trifluoromethyl)phenyl] Gallate Lithium tetrakis[3,5-bis(trifluoromethyl)phenyl]gallate was obtained in the same manner as in Synthesis Example 1, except that 25.6 parts of 1-bromo-3,4,5-trifluorobenzene were replaced with 22.5 parts of 1-bromo-3,5-bis(trifluoromethyl)benzene. The product was 19 Identified by 1F-NMR.

[0113] [Synthesis Example 4] Synthesis of photoacid generator (A-1) 2.0 parts of a mixture containing 51% 4-[(2-methylphenyl)sulfinyl]biphenyl and 49% 4-[(2-methylphenyl)thio]biphenyl, 0.24 parts of 4-[(2-methylphenyl)thio]biphenyl, 1.2 parts of acetic anhydride, 0.72 parts of trifluoromethanesulfonic acid, and 6.5 parts of acetonitrile were homogeneously mixed and reacted at 60°C for 2 hours. The reaction solution was cooled to room temperature (approximately 25°C), added to 30 parts of deionized water, extracted with 30 parts of dichloromethane, and washed with water until the pH of the aqueous layer became neutral. The organic layer was transferred to a rotary evaporator, and the solvent was removed by distillation to obtain the product. 10 parts of ethyl acetate were added to this, and the mixture was dissolved in a 60°C water bath. Then, 30 parts of hexane were added and stirred, followed by standing in a refrigerator (approximately 5°C) for 30 minutes. The supernatant was removed, and this process was repeated twice to wash the product. This was then transferred to a rotary evaporator and the solvent was removed by distillation. The residue was dissolved in 27 parts of dichloromethane, and 2.8 parts of lithium tetrakis(3,4,5-trifluorophenyl) gallate synthesized in Synthesis Example 1 and 20 parts of deionized water were added. The mixture was stirred at room temperature for 1 hour. The aqueous layer was removed, and the organic layer was washed three times with 20 parts of deionized water. The organic layer was then transferred to a rotary evaporator and the solvent was removed by distillation to obtain A-1. The product was identified by 1H-NMR and 19F-NMR.

[0114] [ka]

[0115] [Synthesis Example 5] Synthesis of photoacid generator (A-2) A-2 was obtained in the same manner as in Synthesis Example 4, except that 2.8 parts of lithium tetrakis(3,4,5-trifluorophenyl)gallate were replaced with 3.5 parts of lithium tetrakis(pentafluorophenyl)gallate synthesized in Synthesis Example 2. The product was identified by 1H-NMR and 19F-NMR.

[0116] [ka]

[0117] [Synthesis Example 6] Synthesis of photoacid generator (A-3) A-3 was obtained in the same manner as in Synthesis Example 4, except that 2.8 parts of lithium tetrakis(3,4,5-trifluorophenyl)gallate were replaced with 4.3 parts of lithium tetrakis[3,5-bis(trifluoromethyl)phenyl]gallate synthesized in Synthesis Example 3. The product was identified by 1H-NMR and 19F-NMR.

[0118] [ka]

[0119] [Synthesis Example 7] Synthesis of photoacid generator (A-4) A-4 was obtained in the same manner as in Synthesis Example 4, except that 2.0 parts of a mixture containing 51% 4-[(2-methylphenyl)sulfinyl]biphenyl and 49% 4-[(2-methylphenyl)thio]biphenyl were replaced with 2.0 parts of a mixture containing 51% 4-[(2-methoxyphenyl)sulfinyl]biphenyl and 49% 4-[(2-methoxyphenyl)thio]biphenyl. The product was identified by 1H-NMR and 19F-NMR.

[0120] [ka]

[0121] [Synthesis Example 8] Synthesis of photoacid generator (A-5) A-5 was obtained in the same manner as in Synthesis Example 7, except that 2.8 parts of lithium tetrakis(3,4,5-trifluorophenyl)gallate were replaced with 3.5 parts of lithium tetrakis(pentafluorophenyl)gallate synthesized in Synthesis Example 2. The product was identified by 1H-NMR and 19F-NMR.

[0122] [ka]

[0123] [Synthesis Example 9] Synthesis of photoacid generator (A-6) A-6 was obtained in the same manner as in Synthesis Example 7, except that 2.8 parts of lithium tetrakis(3,4,5-trifluorophenyl)gallate were replaced with 4.3 parts of lithium tetrakis[3,5-bis(trifluoromethyl)phenyl]gallate synthesized in Synthesis Example 3. The product was identified by 1H-NMR and 19F-NMR.

[0124] [ka]

[0125] [Synthesis Example 10] Synthesis of photoacid generator (A-7) A-7 was obtained in the same manner as in Synthesis Example 4, except that 2.0 parts of a mixture containing 51% 4-[(2-methylphenyl)sulfinyl]biphenyl and 49% 4-[(2-methylphenyl)thio]biphenyl were replaced with 2.0 parts of a mixture containing 55% 4-[(phenyl)sulfinyl]biphenyl and 45% 4-(phenylthio)biphenyl. The product was identified by 1H-NMR and 19F-NMR.

[0126] [ka]

[0127] [Synthesis Example 11] Synthesis of photoacid generator (A-8) A-8 was obtained in the same manner as in Synthesis Example 10, except that 2.8 parts of lithium tetrakis(3,4,5-trifluorophenyl)gallate were replaced with 3.5 parts of lithium tetrakis(pentafluorophenyl)gallate synthesized in Synthesis Example 2. The product was identified by 1H-NMR and 19F-NMR.

[0128] [ka]

[0129] [Synthesis Example 12] Synthesis of photoacid generator (A-9) A-9 was obtained in the same manner as in Synthesis Example 10, except that 2.8 parts of lithium tetrakis(3,4,5-trifluorophenyl)gallate were replaced with 4.3 parts of lithium tetrakis[3,5-bis(trifluoromethyl)phenyl]gallate synthesized in Synthesis Example 3. The product was identified by 1H-NMR and 19F-NMR.

[0130] [ka]

[0131] [Synthesis Example 13] Synthesis of photoacid generator (B-1) 2.0 parts of a mixture containing 48% 2-(phenylsulfinyl)-fluorene and 52% 2-(phenylthio)-fluorene were homogeneously mixed with 3.1 parts of acetic anhydride and 1.6 parts of methanesulfonic acid, and reacted at 65°C for 3 hours. The reaction solution was cooled to room temperature (approximately 25°C), added to 5.0 parts of deionized water, extracted with 5.0 parts of dichloromethane, and washed with water until the pH of the aqueous layer became neutral. 15 parts of cyclohexane were added, stirred, and allowed to stand for 30 minutes before removing the supernatant. This process was repeated twice to wash the product. The residue was dissolved in 15.0 parts of dichloromethane, and 2.0 parts of lithium tetrakis(3,4,5-trifluorophenyl)gallate synthesized in Synthesis Example 1 and 10 parts of deionized water were added. The mixture was stirred at room temperature for 1 hour. The aqueous layer was removed, and the organic layer was washed three times with 10 parts of deionized water. The organic layer was then transferred to a rotary evaporator and the solvent was removed by distillation to obtain B-1. The products were identified by 1H-NMR and 19F-NMR.

[0132] [ka]

[0133] [Synthesis Example 14] Synthesis of photoacid generator (B-2) B-2 was obtained in the same manner as in Synthesis Example 13, except that 2.0 parts of lithium tetrakis(3,4,5-trifluorophenyl)gallate were replaced with 2.4 parts of lithium tetrakis(pentafluorophenyl)gallate synthesized in Synthesis Example 2. The product was identified by 1H-NMR and 19F-NMR.

[0134] [ka]

[0135] [Synthesis Example 15] Synthesis of photoacid generator (B-3) B-3 was obtained in the same manner as in Synthesis Example 13, except that 2.0 parts of lithium tetrakis(3,4,5-trifluorophenyl)gallate were replaced with 3.0 parts of lithium tetrakis[3,5-bis(trifluoromethyl)phenyl]gallate synthesized in Synthesis Example 3. The product was identified by 1H-NMR and 19F-NMR.

[0136] [ka]

[0137] [Synthesis Example 16] Synthesis of photoacid generator (B-4) B-4 was obtained in the same manner as in Synthesis Example 13, except that 2.0 parts of a mixture containing 48% 2-(phenylsulfinyl)-fluorene and 52% 2-(phenylthio)-fluorene was replaced with 2.0 parts of a mixture containing 48% 2-(phenylsulfinyl)-9,9-dimethylfluorene and 52% 2-(phenylthio)-9,9-dimethylfluorene. The product was identified by 1H-NMR and 19F-NMR.

[0138] [ka]

[0139] [Synthesis Example 17] Synthesis of photoacid generator (B-5) B-5 was obtained in the same manner as in Synthesis Example 16, except that 2.0 parts of lithium tetrakis(3,4,5-trifluorophenyl)gallate were replaced with 2.4 parts of lithium tetrakis(pentafluorophenyl)gallate synthesized in Synthesis Example 2. The product was identified by 1H-NMR and 19F-NMR.

[0140] [ka]

[0141] [Synthesis Example 18] Synthesis of photoacid generator (B-6) B-6 was obtained in the same manner as in Synthesis Example 16, except that 2.0 parts of lithium tetrakis(3,4,5-trifluorophenyl)gallate were replaced with 3.0 parts of lithium tetrakis[3,5-bis(trifluoromethyl)phenyl]gallate synthesized in Synthesis Example 3. The product was identified by 1H-NMR and 19F-NMR.

[0142] [ka]

[0143] [Synthesis Example 19] Synthesis of photoacid generator (B-7) B-7 was obtained in the same manner as in Synthesis Example 13, except that 2.0 parts of a mixture containing 48% 2-(phenylsulfinyl)-fluorene and 52% 2-(phenylthio)-fluorene was replaced with 2.0 parts of a mixture containing 48% 2-(phenylsulfinyl)-9,9-diethylfluorene and 52% 2-(phenylthio)-9,9-diethylfluorene. The product was identified by 1H-NMR and 19F-NMR.

[0144] [ka]

[0145] [Synthesis Example 20] Synthesis of photoacid generator (B-8) B-8 was obtained in the same manner as in Synthesis Example 19, except that 2.0 parts of lithium tetrakis(3,4,5-trifluorophenyl)gallate were replaced with 2.4 parts of lithium tetrakis(pentafluorophenyl)gallate synthesized in Synthesis Example 2. The product was identified by 1H-NMR and 19F-NMR.

[0146] [ka]

[0147] [Synthesis Example 21] Synthesis of photoacid generator (B-9) B-9 was obtained in the same manner as in Synthesis Example 19, except that 2.0 parts of lithium tetrakis(3,4,5-trifluorophenyl)gallate were replaced with 3.0 parts of lithium tetrakis[3,5-bis(trifluoromethyl)phenyl]gallate synthesized in Synthesis Example 3. The product was identified by 1H-NMR and 19F-NMR.

[0148] [ka]

[0149] • Photoacid generator (C-1): Triarylsulfonium borate salt (manufactured by Sunapro, CPI-310B) • Photoradical generator: Irugacure OXE01 (manufactured by BASF, oxime ester type photoradical generator)

[0150] The photosensitive resin compositions obtained in the examples or comparative examples were evaluated based on the following evaluation criteria.

[0151] [Heat-resistant coloration] The coloration of a 10 μm thick cured film obtained by curing a photosensitive resin composition at 230°C for 2 hours was evaluated according to the following criteria after heat treatment at 240°C for 15 minutes under atmospheric pressure. ◎: No coloring ×: Yellowing

[0152] [Refractive index] The refractive index of the cured film obtained as described above with respect to 850 nm light was measured using a spectroscopic ellipsometer MASS-104 (manufactured by FIBLAB, Inc.).

[0153] [Transmittance] The transmittance of the cured film obtained as described above for light with a wavelength of 850 nm was measured using a spectrophotometer V670 (manufactured by JASCO).

[0154] [Ease of embedding steps (evaluation of flatness)] A wafer with a cured film was obtained using the photosensitive resin composition of the example or comparative example by following the procedure below. (1) As a substrate, an 8-inch diameter silicon wafer was prepared, on which steps (convex portions) made of Cu, with a height of 3-4 μm and a width of 10 μm, were provided at a pitch of 20 μm. (2) The photosensitive resin composition was applied to the stepped surface of the substrate by spin coating to a thickness of 4 μm from the Si surface, and then dried in air at 100°C for 6 minutes. This formed a photosensitive resin film on the substrate. (3) The photosensitive resin film formed in (2) above is exposed to 800 mJ / cm using a manual exposure machine (HMW-201GX, manufactured by Oak Manufacturing Co., Ltd., using mixed light such as g-line, i-line, and h-line). 2 The entire image was exposed with the specified exposure level. (4) After exposure as described in (3), the photosensitive resin film was cured by heat treatment at 170°C for 120 minutes under a nitrogen atmosphere. The flatness of the cured film in which the step-filling properties of the photosensitive resin composition were obtained was evaluated according to the following criteria. ◎: The difference between the thickness of the hardened film on top of the Cu from the Si surface (hardened film + Cu thickness) and the thickness of the hardened film on top of the Si from the Si surface is 10% or less of the Cu thickness. ×: The difference between the thickness of the hardened film on top of the Cu from the Si surface (hardened film + Cu thickness) and the thickness of the hardened film on top of the Si from the Si surface is greater than 10% of the Cu thickness.

[0155] <Evaluation of patternability> The obtained photosensitive resin composition was coated onto an 8-inch silicon wafer using a spin coater. After coating, it was pre-baked in air on a hot plate at 120°C for 3 minutes to obtain a coating with a thickness of approximately 9.0 μm. This coating was irradiated with i-lines through a mask manufactured by Toppan Printing Co., Ltd. (which had a pattern of remaining and cutting out areas with a width of 1.0 to 100 μm). An i-line stepper (Nikon NSR-4425i) was used for the irradiation. After exposure, the wafer was placed on a hot plate and baked in air at 80°C for 5 minutes. Subsequently, the unexposed areas were dissolved and removed by spray developing using PGMEA as the developer for 30 seconds. Subsequently, the cross-section of a 100 μm wide via pattern on the obtained coating sample was observed using a benchtop SEM (Hitachi High-Technologies) to check for the occurrence of undercuts. The evaluation results are shown in Table 1. Criteria for evaluating patternability: ○: No undercut occurred ×: Undercut occurs

[0156] [Table 1]

[0157] [Table 2]

[0158] The results shown in Table 1 indicate that the cured film obtained from the photosensitive resin composition of this embodiment exhibits excellent heat resistance, suppressing yellowing due to heating, and possesses excellent transparency. Furthermore, its excellent light transmittance at a wavelength of 850 nm makes it suitable for use as a material for forming optical waveguides, particularly as a core material for optical waveguides. In addition, the high refractive index of the cured film obtained from the photosensitive resin composition of this embodiment suggests that it can be used even more suitably as a core material for optical waveguides. Moreover, the good embedding and patterning properties of the photosensitive resin composition of this embodiment suggest that it can also be suitably used as a cladding material. [Explanation of Symbols]

[0159] 10 Optical waveguide sheets 100 Optical waveguide film 101 Waveguide end face 110 core layers 112 Core section 114 Clad section 120 Upper cladding layer 130 Lower cladding layer 150 Lower base material layer

Claims

1. Thermosetting resin and Thermoplastic resin and It contains a photoacid generator, The thermosetting resin includes a polyfunctional epoxy resin having three or more epoxy groups in its molecule. The thermoplastic resin is a phenoxy resin. A photosensitive resin composition for forming optical waveguides, wherein the photoacid generator comprises an onium gallate salt having a triarylsulfonium cation represented by formula (1) and a gallate anion represented by general formula (5). 【Chemistry 1】 (In the general formula (1) above, R1 to R4 independently represent an alkyl group, a hydroxyl group, an alkoxy group, an alkylcarbonyl group, an arylcarbonyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, an arylthiocarbonyl group, an acyloxy group, an arylthio group, an alkylthio group, an aryl group, a heterocyclic hydrocarbon group, an aryloxy group, an alkylsulfinyl group, an arylsulfinyl group, an alkylsulfonyl group, an arylsulfonyl group, a hydroxy(poly)alkyleneoxy group, a group that condenses with the bonded benzene ring to form a condensed polycyclic hydrocarbon skeleton, a substituted or unsubstituted silyl group and amino group, a cyano group, a nitro group, or a halogen atom, and a, b, c, and d each represent the number of R1 to R4, where a is an integer from 1 to 5, c and d are integers from 0 to 5, and b is an integer from 0 to 4.) 【Chemistry 2】 (In the general formula (5) above, R 13 to R 16 independently represent a phenyl group or perfluoroalkyl group that is substituted with a group selected from the group consisting of a perfluoroalkyl group, a perfluoroalkoxy group, a nitro group, a cyano group, an acyl group, and a halogen atom, or an unsubstituted phenyl group or perfluoroalkyl group.)

2. The photosensitive resin composition for forming an optical waveguide according to claim 1, wherein the content of the photoacid generator is 0.3% by mass or more and 5.0% by mass or less with respect to the total solid content of the photosensitive resin composition for forming an optical waveguide.

3. The photosensitive resin composition for forming optical waveguides according to claim 1 or 2, wherein the weight-average molecular weight of the phenoxy resin is 10,000 to 100,000.

4. The photosensitive resin composition for forming optical waveguides according to claim 1 or 2, further comprising a surfactant.

5. The photosensitive resin composition for forming optical waveguides according to claim 1 or 2, further comprising an adhesion aid.

6. The photosensitive resin composition for forming optical waveguides according to claim 1 or 2, further comprising a solvent.

7. The photosensitive resin composition for forming optical waveguides according to claim 1 or 2, wherein the refractive index of the cured film for light with a wavelength of 850 nm, measured under the following conditions, is 1.60 or higher. (conditions) The refractive index of a cured film with a thickness of 10 μm obtained by curing the aforementioned photosensitive resin composition for forming optical waveguides at 230°C for 2 hours is measured for light with a wavelength of 850 nm.

8. The photosensitive resin composition for forming optical waveguides according to claim 1 or 2, wherein the light transmittance of the cured film to light with a wavelength of 850 nm, measured under the following conditions, is 90% or more. (conditions) The transmittance of a cured film with a thickness of 10 μm obtained by curing the aforementioned photosensitive resin composition for forming optical waveguides at 230°C for 2 hours is measured for light with a wavelength of 850 nm.

9. Substrate and A cladding layer formed on the substrate, A core layer including a core portion and a cladding portion having a predetermined shape for optical signal propagation, formed on the cladding layer, Equipped with, An optical waveguide wherein the core portion or the cladding layer is made of a cured product of the photosensitive resin composition for forming optical waveguides described in claim 1 or 2.

10. A step of forming a cladding layer on a substrate made of the photosensitive resin composition for forming optical waveguides according to claim 1 or 2, The process involves applying a core-forming material onto the cladding layer, and then exposing and developing it to form a plurality of cores in a predetermined pattern. A step of forming a core layer consisting of the core portion and the cladding portion, by forming a cladding portion made of the photosensitive resin composition for forming optical waveguides between a plurality of core portions, A step of forming a cladding layer on the core layer, which is made of the photosensitive resin composition for forming optical waveguides, A method for manufacturing optical waveguides, including the optical waveguide.

11. A step of forming a cladding layer on a substrate, consisting of a cladding layer forming material, The steps include applying the photosensitive resin composition for forming optical waveguides according to claim 1 or 2 onto the cladding layer, and then exposing and developing it to form a plurality of core portions of a predetermined pattern, A step of forming a core layer consisting of the core portion and the cladding portion, by forming a cladding portion made of the cladding layer forming material between a plurality of core portions, A step of forming a cladding layer made of the cladding layer forming material on the core layer, A method for manufacturing optical waveguides, including the optical waveguide.

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