Components for forming optical waveguide paths

Abstract

[Problem] To provide a composition that satisfies patterning properties, film-forming properties, and a high refractive index which are required for a composition for forming an optical waveguide by overcoming a trade-off therebetween. [Solution] A composition for forming an optical waveguide, comprising: a fluorene backbone-containing epoxy compound (A) represented by formula [1]; a monofunctional or bifunctional alicyclic epoxy compound (B); a monofunctional or bifunctional aromatic epoxy compound (C) different from the compound (A); and a photoacid generator (D). An optical waveguide comprising a cured product of the composition for forming an optical waveguide. (In formula [1], L1 and L2 each independently represent a naphthalenediyl group optionally having a substituent, and m and n each independently represent an integer of 0-10.)

Description

[Technical Field]

[0001] The present invention relates to a composition for forming optical waveguides, particularly an epoxy resin composition, and to an optical waveguide formed from the composition. [Background technology]

[0002] In a broad sense, an optical waveguide refers to a transmission path that uses light for communication. Currently, optical fibers made of quartz glass or plastic are already in practical use as transmission paths for transmitting light over long distances, and they are indispensable for achieving high-speed and high-precision transmission in communications.

[0003] Furthermore, transmission paths that transmit light within optical circuits and are formed on substrates using microfabrication technology are conventionally referred to as optical waveguides and research is progressing (hereinafter referred to as optical waveguides in this specification). In order to achieve even higher speed communication, the practical application of so-called optical interconnects is progressing, which convert electrical signals transmitted by metal wiring transmission paths, which have been used for transmission over relatively short distances such as within package substrates or between devices, directly from CPUs and LSIs into optical signals and transmit them as optical signals through optical waveguides from within the substrate.

[0004] In recent years, organic polymer optical waveguides formed from photosensitive materials using photolithography technology have been proposed, and the technology of completing wiring within a package substrate by using photolithography technology in all stages of formation, including the undercladding layer, the core phase which is the light guiding portion, and the topcladding layer which covers the core phase, is attracting attention. Photosensitive materials for forming optical waveguides require a desired high refractive index, as well as film-forming properties (such as film flatness), patternability, and stability that prevents the formation of precipitates or phase separation, in order to form fine optical waveguides on a substrate.

[0005] As a photosensitive material for forming optical waveguides, a photosensitive epoxy resin composition for forming optical waveguides has been proposed, which contains a polyfunctional epoxy resin having a bisphenol A type skeleton, a solid semi-aliphatic bifunctional epoxy resin, or other bifunctional epoxy resin as a resin component, and also contains a photocationic polymerization initiator (see, for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2020-20927 [Overview of the project] [Problems that the invention aims to solve]

[0007] As mentioned above, photosensitive materials for forming optical wave guides require patternability, film-forming properties, and high refractive index, but it is difficult to satisfy all of these simultaneously. For example, when polyfunctional resins or compounds are used to improve patternability, the molecular weight increases, significantly raising the viscosity of the material and potentially hindering film formation and film planarization. When using bifunctional or less functional resins or compounds, or low molecular weight compounds, to reduce the viscosity of the material in order to improve film formation, this can lead to a decrease in refractive index and a decline in patternability. When high refractive index is achieved by using high-density compounds, such as compounds containing aromatic rings, their rigidity and high density can worsen compatibility with other resins and compounds, potentially leading to precipitate formation and adversely affecting film formation. For example, while Patent Document 1 mentioned above evaluates patternability and also mentions increasing refractive index, it does not mention storage stability or film-forming properties due to the use of high molecular weight components, and it appears that it has not resolved all the conflicting relationships. Thus, improving patternability, improving film deposition, and increasing refractive index are, so to speak, in a trade-off relationship with one another, and there have been no reports to date of technologies proposed so far, such as those listed in the above-mentioned literature, that satisfy all of these requirements.

[0008] The present invention aims to resolve the conflicting relationship between patternability, film-forming ability, and high refractive index, which are required for compositions used to form optical waveguides, and to provide a composition that satisfies these performance requirements. [Means for solving the problem]

[0009] In order to solve the above problems, the present inventors conducted a sincere investigation and found that a composition comprising at least three epoxy compounds, including a difunctional fluorene epoxy compound containing a naphthalene ring, a difunctional or less alicyclic epoxy compound, and other difunctional or less aromatic epoxy compounds other than the fluorene epoxy compound, solves the above problems, leading to the present invention.

[0010] In other words, as a first aspect of the present invention, A fluorene skeleton-containing epoxy compound (A) represented by the following formula [1], Monofunctional or bifunctional alicyclic epoxy compound (B), A monofunctional or bifunctional aromatic epoxy compound (C) different from the aforementioned compound (A), This invention relates to a composition for forming optical waveguides, comprising a photoacid generator (D). [ka] (In formula [1], L 1 and L 2 Each of these independently represents a naphthalenediyl group which may have substituents, m and n each independently represent integers between 0 and 10. The second aspect relates to the optical waveguide forming composition according to the first aspect, wherein the alicyclic epoxy compound (B) is a liquid alicyclic epoxy compound. The third aspect relates to the optical waveguide forming composition according to the first or second aspect, wherein the aromatic epoxy compound (C) is a bifunctional aromatic epoxy compound. As a fourth aspect, there is provided a composition for forming an optical waveguide according to any one of the first to third aspects, wherein the alicyclic epoxy compound (B) is a bifunctional alicyclic epoxy compound, and the aromatic epoxy compound (C) is a bifunctional aromatic epoxy compound. As a fifth aspect, there is provided a composition for forming an optical waveguide according to any one of the first to fourth aspects, wherein the alicyclic epoxy compound (B) is a compound represented by the following formula [2]. [Chemical formula] (In formula [2], R 1 and R 2 each independently represents a linear or branched alkyl group having 1 to 6 carbon atoms which may have a hydrogen atom, an ester group or an ether group, or a cyclic alkyl group having 3 to 6 carbon atoms, or a combination of the linear or branched alkyl group and the cyclic alkyl group. At this time, the linear alkyl group having 2 or more carbon atoms, the branched alkyl group having 3 or more carbon atoms, or the cyclic alkyl group may form an epoxy ring together with adjacent carbon atoms. or R 1 and R 2 may be bonded to each other to form a ring having 4 to 6 carbon atoms, and at this time, an epoxy ring may be formed together with adjacent carbon atoms constituting the ring.) As a sixth aspect, there is provided a composition for forming an optical waveguide according to any one of the first to fifth aspects, wherein the aromatic epoxy compound (C) is an epoxy compound having a bisphenol A type skeleton or a bisphenol F type skeleton. As a seventh aspect, there is provided a composition for forming an optical waveguide according to any one of the first to sixth aspects, wherein the fluorene skeleton-containing epoxy compound (A) is a compound represented by formula [3]. [Chemical formula] The eighth aspect relates to an optical waveguide forming composition according to any one of the first to seventh aspects, wherein the alicyclic epoxy compound (B) is at least one compound represented by the following formulas [4], [5], [6]. [ka] The ninth aspect relates to a cured product which is a polymer of the optical waveguide forming composition described in any of the first to eighth aspects. The tenth aspect relates to an optical waveguide including a cured product of an optical waveguide forming composition described in any of the first to eighth aspects. As the eleventh viewpoint, the present invention includes a cladding layer made of a cured product of the optical waveguide forming composition described in any of the first to eighth viewpoints. Perspective 10 This relates to the optical waveguide described above. [Effects of the Invention]

[0011] The optical waveguide forming composition of the present invention can produce a cured product useful as an optical waveguide forming material, possessing a high refractive index of 1.54 or higher, good film formation properties without unevenness, phase separation, or aggregates, high patternability, and high storage stability. Furthermore, since the optical waveguide formation composition of the present invention has a viscosity that is easily handleable even in a solvent-free form, it can be provided as an optical waveguide formation material without the need for additional processes involving solvent addition, or concerns about health hazards or corrosion of surrounding equipment caused by solvents. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 shows a microscope photograph of the cured film after photolithography using the composition of Example 1, viewed from the edge direction. [Figure 2] Figure 2 shows a microscope photograph taken from the edge direction of the cured film after photolithography using the composition of Comparative Example 2. [Modes for carrying out the invention]

[0013] "Composition for Forming Optical Waveguide" The composition for forming an optical waveguide of the present invention contains a fluorene skeleton-containing epoxy compound (A), a monofunctional or bifunctional alicyclic epoxy compound (B), a monofunctional or bifunctional aromatic epoxy compound (C) different from the compound (A), and a photoacid generator (D). In this specification, the epoxy compounds of (A) to (C) above and other epoxy compounds described later are collectively referred to as "resin components", and "monofunctional or bifunctional" means containing one or two epoxy groups as functional groups.

[0014] [Fluorene Skeleton-Containing Epoxy Compound (A)] The fluorene skeleton-containing epoxy compound (A) used in the present invention is a compound represented by the following formula [1]. [Chemical Formula] In the above formula [1], L 1 and L 2 each independently represent a naphthalenediyl group which may have a substituent, and m and n each independently represent an integer of 0 to 10.

[0015] L 1 and L 2 Examples of the substituent of the naphthalenediyl group (on the naphthalene ring) in L and L 1 include alkyl groups having 1 to 6 carbon atoms such as methyl group, ethyl group, propyl group, isopropyl group, butyl group, and t-butyl group. 2 The number of substituents of the naphthalenediyl group in L and L 1 and L 2 is each independently 0 to 6, preferably 0 to 2, more preferably 0 or 1, and most preferably 0.

[0016] Fluorene skeleton-containing epoxy compounds (A) can preferably be compounds represented by the following formula [3]. [ka]

[0017] The above-mentioned fluorene skeleton-containing epoxy compound (A) can be a commercially available product. Examples include Ogusol® CG-500 and EG-280 (manufactured by Osaka Gas Chemical Co., Ltd.). Such epoxy compounds containing a fluorene skeleton having a naphthalene ring can be used individually or in combination of two or more. Furthermore, from the viewpoint of solubility of the resin component and refractive index, for example, the above-mentioned Ogusol® CG-500 can be used alone.

[0018] The fluorene skeleton-containing epoxy compound (A) is preferably included in a proportion of, for example, 5 to 50 parts by mass, and more preferably 10 to 40 parts by mass, relative to the total amount of epoxy compound (100 parts by mass). If the amount of fluorene skeleton-containing epoxy compound (A) is too small, it is difficult to obtain a sufficient refractive index, and conversely, if it is too large, deterioration of storage stability due to precipitation and a decrease in film-forming ability will occur.

[0019] [Monofunctional or bifunctional alicyclic epoxy compounds (B)] The monofunctional or bifunctional alicyclic epoxy compound (B) used in the present invention is not particularly limited as long as it is a compound having one or two alicyclic epoxy groups. In a preferred embodiment, the alicyclic epoxy compound (B) is in liquid form, and from the viewpoint of patternability (exposure sensitivity), a compound having two epoxy groups introduced into the alicyclic skeleton can be mentioned.

[0020] Examples of the alicyclic epoxy compound (B) mentioned above include the compound represented by the following formula [2]. [ka] In formula [2], R 1and R 2 Each of these independently represents a linear or branched alkyl group having 1 to 6 carbon atoms, which may have a hydrogen atom, an ester group, or an ether group, or a cyclic alkyl group having 3 to 6 carbon atoms, or a combination of the linear or branched alkyl group and the cyclic alkyl group, in which case the linear alkyl group having 2 or more carbon atoms, the branched alkyl group having 3 or more carbon atoms, or the cyclic alkyl group may form an epoxy ring together with adjacent carbon atoms, or R 1 and R 2 These atoms may bond to each other to form a ring with 4 to 6 carbon atoms, and in this case, they may bond together with adjacent carbon atoms constituting the ring to form an epoxy ring.

[0021] Examples of linear or branched alkyl groups having 1 to 6 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, n-pentyl group, 1-methylbutyl group, 2-methylbutyl group, 3-methylbutyl group, 1,1-dimethylpropyl group, 1,2-dimethylpropyl group, 2,2-dimethylpropyl group, 1-ethylpropyl group, n-hexyl group, 1-methylpentyl group, 2-methylpentyl group, 3-methylpentyl group, 4-methylpentyl group, 1,1-dimethylbutyl group, 1,2-dimethylbutyl group, 1,3-dimethylbutyl group, 2,2-dimethylbutyl group, 2,3-dimethylbutyl group, 3,3-dimethylbutyl group, 1-ethylbutyl group, 2-ethylbutyl group, 1,1,2-trimethylpropyl group, 1,2,2-trimethylpropyl group, 1-ethyl-1-methylpropyl group, and 1-ethyl-2-methylpropyl group. Examples of cyclic alkyl groups having 3 to 6 carbon atoms include cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl groups.

[0022] In a preferred embodiment, the alicyclic epoxy compound (B) can be a compound represented by the following formulas [4], [5], [6]. These compounds have low molecular weights and are liquid compounds, making them suitable not only from the viewpoint of patterning properties but also from the viewpoint of adjusting the viscosity of the composition. [ka]

[0023] The above-mentioned alicyclic epoxy compound (B) can be a commercially available product. As a difunctional alicyclic epoxy compound (B), for example, diepoxybicyclohexyl (e.g., Celoxide® 8000, 8010, manufactured by Daicel Corporation), 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexyl sa Examples include carboxylate (e.g., Celoxide® 2021P, manufactured by Daicel Corporation), epsilon-caprolactone-modified 3,4-epoxycyclohexylmethyl 3',4'-epoxycyclohexanecarboxylate (e.g., Celoxide® 2081, manufactured by Daicel Corporation), bis(3,4-epoxycyclohexylmethyl) adipate, and diepoxylated tetrahydroindene (e.g., Epocalic® THI-DE, manufactured by ENEOS Corporation). For example, as monofunctional alicyclic epoxy compounds, there are 3,4-epoxycyclohexylmethyl methacrylate (e.g., Cyclomer® M-100, manufactured by Daicel Corporation), 3,4-epoxycyclohexylmethyl methacrylate, and 1,2-epoxy-4-vinylcyclohexane (e.g., Celoxide® 2000, manufactured by Daicel Corporation). ), 1,2,8,9-diepoxylimonene (for example, Celoxide® 3000, manufactured by Daicel Corporation) can be used.

[0024] The alicyclic epoxy compound (B) is preferably included in an amount of, for example, 10 to 80 parts by mass, and more preferably 20 to 70 parts by mass, relative to the total amount of epoxy compound (100 parts by mass). If the amount of alicyclic epoxy compound (B) is too small, it is difficult to obtain sufficient patterning properties, and conversely, if it is too large, it becomes difficult to obtain a sufficient refractive index.

[0025] [Monofunctional or bifunctional aromatic epoxy compounds (C)] The present invention also includes a monofunctional or bifunctional aromatic epoxy compound (C) different from the epoxy compound (A). From the viewpoint of patternability (exposure sensitivity), the aromatic epoxy compound (C) may, in a preferred embodiment, be a compound having two epoxy groups. In particular, it is preferable that the epoxy compound has a bisphenol A type skeleton or a bisphenol F type skeleton.

[0026] A commercially available aromatic epoxy compound (C) can be used. Examples of the bifunctional aromatic epoxy compound (C) include jER® 806, a bisphenol F type epoxy compound manufactured by Mitsubishi Chemical Corporation, and jER® 828, a bisphenol A type epoxy compound also manufactured by Mitsubishi Chemical Corporation. Other examples of monofunctional aromatic epoxy compounds (C) include phenyl glycidyl ether (e.g., Denacol® EX-141, manufactured by Nagase ChemteX Corporation), phenol (EO) 5 glycidyl ether (e.g., Denacol® EX-145, manufactured by Nagase ChemteX Corporation), and p-tert-butylphenyl glycidyl ether (e.g., Denacol® EX-146, manufactured by Nagase ChemteX Corporation).

[0027] The aromatic epoxy compound (C) is preferably present in an amount of, for example, 5 to 60 parts by mass, and more preferably 10 to 50 parts by mass, relative to the total amount of epoxy compound (100 parts by mass). If the amount of aromatic epoxy compound (C) is too small, it becomes difficult to obtain a sufficient refractive index or a uniform film, while if it is too large, it becomes difficult to obtain sufficient patternability.

[0028] [Other epoxy compounds] The optical waveguide forming composition of the present invention may contain other epoxy compounds other than the epoxy compounds (A) to (C) above, as long as they do not impair the effects of the present invention. Examples include heterocyclic epoxy compounds such as triglycidyl isocyanurate and aliphatic epoxy compounds. Specific examples of the above-mentioned aliphatic epoxy compounds include monofunctional epoxy compounds such as glycidyl ethers of aliphatic alcohols and glycidyl esters of alkyl carboxylic acids, as well as polyglycidyl ethers of aliphatic polyhydric alcohols or their alkylene oxide adducts. Representative specific compounds include glycidyl ethers of monoalcohols such as allyl glycidyl ether, butyl glycidyl ether, 2-ethylhexyl glycidyl ether, and C12-13 mixed alcohol glycidyl ether; glycidyl ethers of polyhydric alcohols such as 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, triglycerin triglycidyl ether, trimethylolpropane triglycidyl ether, sorbitol tetraglycidyl ether, dipentaerythritol hexaglycidyl ether, polyethylene glycol diglycidyl ether, and polypropylene glycol diglycidyl ether; and polyglycidyl ethers of polyether polyols, which are alkylene oxide adducts of one or more aliphatic polyhydric alcohols such as propylene glycol, trimethylolpropane, and glycerin. These other epoxy compounds can be included, for example, in a proportion of 0 to 20 parts by mass relative to the total amount of epoxy compounds (100 parts by mass).

[0029] [Photoacid Generator (D)] The optical waveguide forming composition of the present invention contains a photoacid generator (D). Specific examples of photoacid generators (D) include onium salts such as iodonium salts, sulfonium salts, phosphonium salts, and selenium salts, metallocene complex compounds, iron arene complex compounds, disulfone compounds, sulfonic acid derivative compounds, triazine compounds, acetophenone derivative compounds, and diazomethane compounds.

[0030] Among the above onium salts, iodonium salts include, for example, diarylliodonium salts such as chlorides, bromides, mesylates, tosylates, trifluoromethanesulfonates, tetrafluoroborates, tetrakis(pentafluorophenyl)borates, hexafluorophosphates, hexafluoroarsenates, and hexafluoroantimonates, which are diarylliodonium salts such as diphenyliodonium, 4,4'-dichlorodiphenyliodonium, 4,4'-dimethoxydiphenyliodonium, 4,4'-di-tert-butyldiphenyliodonium, 4-methylphenyl(4-(2-methylpropyl)phenyl)iodonium, 3,3'-dinitrophenyliodonium, 4-(1-ethoxycarbonylethoxy)phenyl(2,4,6-trimethylphenyl)iodonium, and 4-methoxyphenyl(phenyl)iodonium.

[0031] Examples of the above sulfonium salts include triarylsulfonium chlorides, bromides, trifluoromethanesulfonates, tetrafluoroborates, hexafluorophosphates, hexafluoroarsenates, and hexafluoroantimonates, which are triarylsulfonium compounds such as triphenylsulfonium, diphenyl(4-tert-butylphenyl)sulfonium, tris(4-tert-butylphenyl)sulfonium, diphenyl(4-methoxyphenyl)sulfonium, tris(4-methylphenyl)sulfonium, tris(4-methoxyphenyl)sulfonium, tris(4-ethoxyphenyl)sulfonium, diphenyl(4-(phenylthio)phenyl)sulfonium, and tris(4-(phenylthio)phenyl)sulfonium.

[0032] Examples of the phosphonium salts mentioned above include arylphosphonium salts such as chlorides, bromides, tetrafluoroborates, hexafluorophosphates, and hexafluoroantimonates of triarylphosphoniums or tetraarylphosphoniums, such as tetraphenylphosphonium, ethyltriphenylphosphonium, tetra(p-methoxyphenyl)phosphonium, ethyltri(p-methoxyphenyl)phosphonium, and benzyltriphenylphosphonium.

[0033] Examples of the selenium salts mentioned above include triarylselenium salts such as triphenylselenium hexafluorophosphate.

[0034] Examples of the iron arene complex compounds mentioned above include bis(η5-cyclopentadienyl)(η6-isopropylbenzene)iron(II)hexafluorophosphate.

[0035] Among these, iodonium salts, sulfonium salts, etc., can be suitably used as photoacid generators. Commercially available products can be used, and examples include triarylsulfonium salts such as CPI-310FG and CPI-101A.

[0036] These photoacid generators (D) can be used individually or in combination of two or more. The photoacid generator (D) is usually preferably included in an amount of, for example, 0.1 to 10 parts by mass, and more preferably 0.2 to 5 parts by mass, per 100 parts by mass of the total mass of the epoxy compound (resin component). If the amount of photoacid generator (D) is less than 0.1 parts by mass, the photocuring reaction may not proceed sufficiently. If it exceeds 10 parts by mass, the degree of polymerization of the polymer will decrease, which may make it brittle and prone to cracking.

[0037] [Organic solvents] The optical waveguide forming composition of the present invention may also contain an organic solvent. When the prepared composition has low viscosity, there is no need to add organic solvents, and good film formation is possible. In this case, since it is solvent-free, it is also advantageous that there is no need for a process to volatilize the organic solvent by heat treatment or other means after film formation. Furthermore, by not including organic solvents, concerns such as health damage to workers due to inhalation during the volatilization of organic solvents, and corrosion of surrounding equipment, which may occur, are significantly reduced. Since the optical waveguide forming composition of the present invention is a relatively low viscosity composition, the inclusion of an organic solvent is not essential. However, even if an organic solvent is included, the above-mentioned effects of the present invention will not be lost, and it can be added in any proportion. The organic solvents that can be used in this invention are not particularly limited as long as they are organic solvents commonly used in the art. However, it is desirable to avoid using extremely polar or low polar solvents, such as water or hydrocarbon solvents like hexane, as this may cause precipitate formation or phase separation. Furthermore, caution is required as adding a large amount of organic solvent may prevent the formation of a sufficient film thickness during film formation.

[0038] [Other additives] The optical waveguide forming composition of the present invention may contain other additives commonly used in the art, to the extent that they do not impair the effects of the present invention. Examples of other additives include anti-reflective agents, ultraviolet absorbers, antioxidants, photostabilizers, sensitizers, surfactants, crosslinking agents, leveling agents, and silane coupling agents. When these other additives are used, they can usually be blended in a ratio of 10 parts by mass or less per 100 parts by mass of the total mass of the epoxy compound (resin component).

[0039] [Composition for forming optical waveguide] As described later, the optical waveguide forming composition of the present invention can be suitably used as a material for forming optical waveguides, and in particular suitably used as a material for forming the cladding layer of an optical waveguide. The method for preparing the optical waveguide-forming composition of this embodiment is not particularly limited. For example, the preparation method may involve further adding and mixing components (A), (B), (C), and (D), as well as other epoxy compounds and other additives as needed, to obtain a homogeneous solution, or using a conventional organic solvent in addition to these components. In the optical waveguide forming composition of the present invention, the proportions of each component can be, for example, when the total mass of epoxy compounds is 100 parts by mass, fluorene skeleton-containing epoxy compound (A) can be 10 to 40 parts by mass, alicyclic epoxy compound (B) can be 20 to 70 parts by mass, aromatic epoxy compound (C) can be 10 to 50 parts by mass, and other epoxy compounds can be 0 to 20 parts by mass. Alternatively, per 100 parts by mass of the total mass of the epoxy compounds (resin components), the proportions of photoacid generator (D) can be 0.2 to 5 parts by mass, and other additives can be 0 to 10 parts by mass. When using the above-mentioned organic solvent, the proportion of solids in the optical waveguide forming composition is not particularly limited as long as each component is uniformly dissolved in the organic solvent, but is, for example, 60% by mass or more, or 70% by mass or more. Preferably, the proportion of solids in the composition can be, for example, 75% by mass to 100% by mass. Here, solids refer to the total components of the optical waveguide forming composition excluding the organic solvent components.

[0040] Furthermore, it is preferable to use the optical waveguide forming composition after filtering it using a filter with a pore size of 0.05 to 5 μm or the like.

[0041] The optical waveguide forming composition of the present invention preferably has a viscosity that provides excellent workability in the formation of optical waveguides. For example, the viscosity of the above-mentioned optical waveguide forming composition can be 100 to 10,000 mPa·s at 25°C.

[0042] 《Optical waveguide》 The optical waveguide of the present invention includes a cured product of the above-mentioned optical waveguide forming composition, and preferably includes a cladding layer made of the cured product of the optical waveguide forming composition. For example, in one embodiment, the optical waveguide of the present invention is an optical waveguide comprising a core and a cladding layer having a lower refractive index than the core that surrounds the entire outer circumference thereof, wherein the cladding layer may be made of a cured product of the optical waveguide forming composition. The core only needs to be made of a material having a refractive index greater than that of the formed cladding layer. The optical waveguide of the present invention may be of any of the following types: graded index (GI) type, in which the refractive index of the core changes continuously with respect to the longitudinal direction; multistep index (MI) type, in which the refractive index of the core changes stepwise with respect to the longitudinal direction; or step index (SI) type, in which the refractive index changes discontinuously only at the interface between the core and the cladding. [Examples]

[0043] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0044] The compounds used in the examples and their abbreviations are as follows: [Fluorene skeleton-containing diepoxy compounds] CG-500: Ogusol (registered trademark) CG-500, manufactured by Osaka Gas Chemical Co., Ltd. PG-100: PG-100, Ogusol (registered trademark), manufactured by Osaka Gas Chemical Co., Ltd. [ka] [Bifunctional alicyclic epoxy compound] CEL-8010: Ceroxide (registered trademark) 8010, manufactured by Daicel Corporation. THI-DE: EPOCALIC (registered trademark) THI-DE, manufactured by ENEOS Corporation. CEL-2021P: Celoxide (registered trademark) 2021P (3',4'-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate), manufactured by Daicel Corporation. [ka] [Bifunctional aromatic epoxy compounds] jER806: jER (registered trademark) bisphenol F type epoxy resin, manufactured by Mitsubishi Chemical Corporation. jER828: jER (registered trademark) bisphenol A type epoxy resin, manufactured by Mitsubishi Chemical Corporation. [Difunctional and other epoxy compounds] YX-8000: Hydrogenated bisphenol A epoxy resin, manufactured by Mitsubishi Chemical Corporation. [ka] [Monofunctional alicyclic epoxy compound] M-100: Cyclomer (registered trademark) M-100 (3,4-epoxycyclohexylmethyl methacrylate), manufactured by Daicel Corporation. [Monofunctional aromatic epoxy compounds] EX-141: Denacol® EX-141 (phenylglycidyl ether), manufactured by Nagase ChemteX Corporation. [ka] [Polyfunctional alicyclic epoxy compounds] GT-401: Epolleed (registered trademark) GT-401 (butanetetracarboxylic acid tetra(3,4-epoxycyclohexylmethyl) modified ε-caprolactone), manufactured by Daicel Corporation. [Polyfunctional and other epoxy compounds] EHPE-3150: 1,2-epoxy-4-(2-oxyranyl)cyclohexane adduct of 2,2-bis(hydroxymethyl)-1-butanol, manufactured by Daicel Corporation. [ka] [Photoacid Generator] CPI-310FG: Triarylsulfonium salt type photoacid generator, manufactured by Sunapro Co., Ltd. [Organic solvents] PGMEA: Propylene glycol monomethyl ether acetate, manufactured by Showa Denko Corporation.

[0045] [Examples 1-5, Comparative Examples 1-7] In the quantities shown in Table 1, various epoxy compounds, and 100 parts by mass of the epoxy compounds, were placed in flasks along with a photoacid generator and, optionally, an organic solvent. The mixtures were stirred under heating at 110°C or below to completely dissolve the solid components. After cooling to room temperature, the mixtures were pressure-filtered in a cleanroom using a 3 μm diameter SUS filter to prepare the liquid compositions.

[0046] A 4-inch diameter circular silicon wafer substrate was cleaned with a UV / ozone irradiator. The composition was dropped onto the cleaned substrate and a film was deposited by spin coating to a thickness of 20 μm. The obtained film was subjected to photolithography to obtain a patterned cured film. Specifically, the prepared film was mask-exposed using a mask aligner, and only the light-irradiated areas were exposed. After exposure, it was baked at 60°C for 1 minute, and then developed with an organic solvent of PGMEA / IPA (2-propanol) (50 / 50 vol / vol%) for 3 minutes. Finally, a patterned cured film was obtained by post-baking at 100°C for 2 minutes.

[0047] For each composition, the film-forming properties during spin coating, the patternability of the cured film, the refractive index of the composition, and the storage stability of the composition were evaluated according to the following procedure.

[0048] [1. Film formability] The state of the film during spin coating (visual inspection) and after spin coating (visual inspection and microscopic inspection) was observed and evaluated according to the following evaluation criteria. The results are shown in Table 1. A: The overall appearance of the film is uniform, no phase separation is observed, and no bright spots originating from aggregates are detected. Cross-sectional observation with a microscope shows that the film thickness has a flatness of ±1 μm or less. B: Slight irregularities, phase separation, and bright spots are observed within the film. A slight gradient in film thickness is observed from the center to the edges. C: A uniform film cannot be formed, or aggregates are scattered throughout the film.

[0049] [2. Patterning ability] The cured film after photolithography was observed with a microscope from the edge direction, and the exposure sensitivity (patterning ability) was evaluated according to the following evaluation criteria. The results are shown in Table 1. Furthermore, microscopic observation photographs taken from the end face direction are shown in Figure 1 (Example 1) and Figure 2 (Comparative Example 2). A: Only the exposed areas hardened, while the unexposed areas were dissolved by organic development. B: The pattern is formed to some extent, but the unexposed areas are also slightly hardened, or the exposed areas are not hardened sufficiently, and the shape is not convex. C: The unexposed areas have hardened significantly, or the exposed areas have leached during development.

[0050] [3. Refractive index] The liquid refractive index of each composition at 589 nm was measured using an Abbe refractometer and evaluated according to the following evaluation criteria. The results are shown in Table 1. A: The refractive index is 1.54 or higher. C: The refractive index is less than 1.54.

[0051] [4.Storage stability] Each composition was stored at room temperature (23±3℃) for one month, and then its properties were observed visually and evaluated according to the following evaluation criteria. The results are shown in Table 1. A: No precipitates or phase separation were observed, and the solution remained clear and homogeneous. B: The liquid is slightly cloudy, or there is a precipitate at the bottom. C: Clear precipitates have formed and do not redissolve even with stirring.

[0052] [Table 1]

[0053] As shown in Table 1, each composition from Examples 1 to 5 exhibited excellent film-forming properties, good exposure sensitivity as shown in Figure 1, and also had a refractive index of 1.54 or higher, as well as excellent storage stability.

[0054] On the other hand, as shown in Table 1 and Figure 2, none of the compositions in Comparative Examples 1 to 7 were able to satisfy all performance requirements, including film-forming ability, exposure sensitivity, refractive index, and storage stability. In detail, in Comparative Example 7, which did not use epoxy compound (A) containing a fluorene skeleton, the refractive index decreased compared to the examples. Furthermore, even when epoxy compound containing a fluorene skeleton was used, in Comparative Example 1, which used an epoxy compound with a different structure from compound (A) according to the present invention, the refractive index improved, but the film-forming ability and storage stability were lacking. When the difunctional or monofunctional alicyclic epoxy compound (B) was not included (Comparative Example 2), the film-forming ability was poor and the exposure sensitivity was also inferior. Furthermore, when the composition did not contain a bifunctional or monofunctional aromatic epoxy compound (C) and instead contained a polyfunctional other epoxy compound (Comparative Example 5), the film-forming properties, exposure sensitivity, and storage stability were inferior. Adding the organic solvent of this composition (Comparative Example 6) slightly improved the film-forming properties, exposure sensitivity, and storage stability, but it did not reach the A rating equivalent to the Examples. Furthermore, even in the case where the compound did not contain a difunctional or monofunctional aromatic epoxy compound (C) but contained a monofunctional alicyclic epoxy compound (B), a polyfunctional alicyclic epoxy compound, and other polyfunctional epoxy compounds (Comparative Example 3), the film-forming ability, exposure sensitivity, and storage stability were inferior. Adding an organic solvent (Comparative Example 4) slightly improved the film-forming ability, exposure sensitivity, and storage stability, but this also did not reach the A rating equivalent to the Examples.

Claims

1. A fluorene skeleton-containing epoxy compound (A) represented by the following formula [1], Monofunctional or difunctional alicyclic epoxy compound (B), Aromatic epoxy compound (C) which contains both a monofunctional aromatic epoxy compound and a bifunctional aromatic epoxy compound, different from compound (A), It contains a photoacid generator (D), When the total mass of epoxy compounds is 100 parts by mass, the mixture contains 5 to 50 parts by mass of the fluorene skeleton-containing epoxy compound (A), 10 to 80 parts by mass of the alicyclic epoxy compound (B), and 5 to 60 parts by mass of the aromatic epoxy compound (C). A composition for forming optical waveguides, comprising 0.1 to 10 parts by mass of the photoacid generator (D) per 100 parts by mass of epoxy compounds. 【Chemistry 1】 (In formula [1], L １ and L ２ Each of these independently represents a naphthalenediyl group which may have substituents, m and n each independently represent integers between 0 and 10.

2. The optical waveguide forming composition according to claim 1, wherein the alicyclic epoxy compound (B) is a liquid alicyclic epoxy compound.

3. The alicyclic epoxy compound (B) is a bifunctional alicyclic epoxy compound. The optical waveguide formation composition according to claim 1 or claim 2.

4. The optical waveguide forming composition according to claim 1 or claim 2, wherein the alicyclic epoxy compound (B) is a compound represented by the following formula [2]. 【Chemistry 2】 (In formula [2], R １ and R ２ Each of these independently represents a linear or branched alkyl group having 1 to 6 carbon atoms, which may have a hydrogen atom, an ester group, or an ether group, or a cyclic alkyl group having 3 to 6 carbon atoms, or a combination of the linear or branched alkyl group and the cyclic alkyl group, in which case the linear alkyl group having 2 or more carbon atoms, the branched alkyl group having 3 or more carbon atoms, or the cyclic alkyl group may form an epoxy ring together with adjacent carbon atoms. or R １ and R ２ These atoms may bond to each other to form a ring with 4 to 6 carbon atoms, and in this case, they may combine with adjacent carbon atoms constituting the ring to form an epoxy ring.

5. The optical waveguide forming composition according to claim 1 or claim 2, wherein the bifunctional aromatic epoxy compound among the aromatic epoxy compounds (C) is an epoxy compound having a bisphenol A type skeleton or a bisphenol F type skeleton.

6. The optical waveguide forming composition according to claim 1 or claim 2, wherein the fluorene skeleton-containing epoxy compound (A) is a compound represented by formula [3]. 【Transformation 3】

7. The optical waveguide forming composition according to claim 1 or claim 2, wherein the alicyclic epoxy compound (B) is at least one compound represented by the following formulas [4], [5], and [6]. 【Chemistry 4】

8. A cured product which is a polymer of the optical waveguide forming composition according to claim 1 or claim 2.

9. An optical waveguide comprising a cured product of the optical waveguide forming composition according to claim 1 or claim 2.

10. The composition includes a cladding layer made of a cured product of the optical waveguide forming composition described in claim 1 or claim 2. The optical waveguide according to claim 9.

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