Method for producing epoxy-modified compound for optical waveguides

Abstract

This method for producing an epoxy-modified compound for optical waveguides comprises performing a synthesis reaction using an acid anhydride and an epoxy resin having reactive hydroxyl groups such that the equivalent ratio of reactive groups in the acid anhydride with respect to the reactive hydroxyl groups is 0.04-2.0.

Description

Method for producing epoxy-modified compound for optical waveguide

[0001] The present invention relates to a method for producing an epoxy-modified compound for an optical waveguide.

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

[0003] An optical waveguide is obtained by forming a clad and a core using two types of ultraviolet (UV)-curable optical waveguide resin compositions with high transparency and different refractive indices. Generally, such optical waveguide resin compositions contain a resin, such as an epoxy resin, an acrylic resin, or a silicone resin, and a curing agent (see, for example, Patent Documents 1 and 2). Of these resins, epoxy resins are preferred from the viewpoints of heat resistance and optical signal transmission. Patent Documents 1 and 2 also list many types of epoxy resins. Furthermore, of these epoxy resins, bisphenol A-type epoxy resins have traditionally been more preferred from the viewpoints of their ability to form highly transparent optical waveguide resin compositions and facilitate UV curing.

[0004] International Publication No. 2020 / 203366 Japanese Patent Application Laid-Open No. 2020-166107

[0005] An object of the present invention is to provide a method for producing an epoxy-modified compound for optical waveguides that can suppress optical loss in the 1310 nm wavelength band, has high storage stability, and exhibits good developability.

[0006] The present inventors have conducted extensive research to solve the above problems and have arrived at the present invention. That is, the present invention includes the following preferred embodiments.

[0007] A method for producing an epoxy-modified compound for optical waveguides according to an aspect of the present invention includes carrying out a synthesis reaction using an epoxy resin having a reactive hydroxyl group and an acid anhydride such that the equivalent ratio of the reactive hydroxyl group to the reactive group of the acid anhydride is 0.04 or more and 2.0 or less.

[0008] Epoxy resins, particularly bisphenol A epoxy resins, which have been widely used, contain aromatic and aliphatic skeletons containing many reactive hydroxyl groups, CH groups, and epoxy groups. When an optical waveguide is formed using such epoxy resins containing many reactive hydroxyl groups, optical loss in the 1310 nm wavelength band increases. The loss can exceed 0.40 dB / cm.

[0009] If the optical loss in the 1310 nm wavelength band is large, the length of the waveguide cannot be increased, which poses a problem of limiting the range of application in technologies that use light in the 1310 nm wavelength band, such as silicon photonics.

[0010] As a result of the research conducted by the present inventors, it was found that when an epoxy-modified compound obtained by reacting an epoxy resin having a reactive hydroxyl group with an acid anhydride is used as a material for an optical waveguide, optical loss in the 1310 nm wavelength band can be suppressed. However, it was also found that the compounding ratio of the epoxy resin to the acid anhydride affects the stability and developability of the resin varnish.

[0011] Therefore, as a result of further intensive studies by the present inventors, it has been found that by carrying out a synthesis reaction using an epoxy resin and an acid anhydride such that the equivalent ratio of the reactive groups of the acid anhydride to the reactive hydroxyl groups of the epoxy resin is 0.04 or more and 2.0 or less, it is possible to suppress light loss in the 1310 nm wavelength band, and to obtain a material for optical waveguides (specifically, an epoxy-modified compound for optical waveguides) that has high storage stability and good developability.

[0012] As described above, the present invention can provide a method for producing an epoxy-modified compound for optical waveguides that can suppress optical loss in the 1310 nm wavelength band, has high storage stability, and exhibits good developability.

[0013] In this specification, the term "epoxy resin" or "epoxy compound" is intended to encompass not only epoxy resin as a polymer, but also monomers capable of forming epoxy resin.

[0014] In this specification, the term "reactive hydroxyl group (of an epoxy resin)" refers to a reactive alcoholic hydroxyl group contained in the repeating skeleton of an epoxy resin.

[0015] Hereinafter, embodiments of the present invention will be described in detail. Note that the scope of the present invention is not limited to the embodiments described here, and various modifications can be made without departing from the spirit of the present invention.

[0016] First, the raw materials used in the method for producing the epoxy-modified compound for optical waveguide according to this embodiment will be described in detail below.

[0017] (Epoxy Resin) The epoxy resin is not particularly limited as long as it has a reactive hydroxyl group and is known to those skilled in the art to be used in preparing a resin composition for an optical waveguide. Specifically, the epoxy resin may be a liquid epoxy resin or a solid epoxy resin.

[0018] In this specification, with respect to epoxy resins, "liquid" means that the resin is in a liquid state at room temperature, and "solid" means that the resin is in a solid state at room temperature.

[0019] Examples of liquid epoxy resins include bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol E type epoxy resins, brominated epoxy resins, alicyclic epoxy resins, aliphatic epoxy resins, etc. Examples of solid epoxy resins include bisphenol A type epoxy resins, hydrogenated bisphenol A type epoxy resins, bisphenol F type epoxy resins, brominated epoxy resins, fluorinated epoxy resins, aromatic epoxy resins, novolac type epoxy resins, biphenyl skeleton type epoxy resins, alicyclic epoxy resins, etc.

[0020] In this embodiment, the epoxy resin preferably contains a bisphenol A epoxy resin, from the viewpoints of forming a resin composition for an optical waveguide with high transparency and facilitating UV curing. Furthermore, from the viewpoints of more reliably achieving the effects of suppressing optical loss and providing good storage stability and developability, the epoxy resin preferably contains a liquid bisphenol A epoxy resin, and more preferably consists of only a liquid bisphenol A epoxy resin.

[0021] The epoxy equivalent of the epoxy resin is not particularly limited, but is preferably about 170 g / eq to 1200 g / eq.

[0022] Such epoxy resins may be synthesized by known methods, or commercially available products may be used. For example, when a liquid bisphenol A type epoxy resin is used as the epoxy resin, commercially available products include "Epiclon (registered trademark) 850S" manufactured by DIC Corporation and "JER (registered trademark) 825" manufactured by Mitsubishi Chemical Corporation. Furthermore, when a solid bisphenol A type epoxy resin is used as the epoxy resin, commercially available products include "1001", "1002", "1003", "1055", "1004", "1004AF", "1003F", "1004F", "1005F", "1004FS", "1006FS", and "1007FS" manufactured by Mitsubishi Chemical Group Corporation.

[0023] These epoxy resins may be used alone or in combination of two or more.

[0024] The amount of epoxy resin blended during the production of an epoxy-modified compound for optical waveguides may be adjusted depending on the types of epoxy resin and acid anhydride described below so that the equivalent ratio of reactive groups of the acid anhydride described below to reactive hydroxyl groups of the epoxy resin is 0.04 or more and 2.0 or less.

[0025] In this specification, the "equivalent ratio of reactive groups of acid anhydride to reactive hydroxyl groups of epoxy resin" means the ratio calculated by dividing the "amount of reactive groups (amount of acid anhydride groups) (mol) of acid anhydride (blended during production)" by the "amount of reactive hydroxyl groups (mol) of epoxy resin (blended during production)." Furthermore, in this specification, the "amount of reactive hydroxyl groups (mol) of epoxy resin (blended during production)" can be calculated from the amount of epoxy resin (g), the molecular weight of the epoxy resin (g / mol), and the number of reactive alcoholic hydroxyl groups contained in the repeating skeleton of the epoxy resin.

[0026] (Acid Anhydride) The acid anhydride is not particularly limited as long as it does not impair the effects of suppressing light loss according to the present embodiment and good storage stability and developability.Specific examples of the acid anhydride include cyclic aliphatic acid anhydrides such as maleic anhydride, succinic anhydride, alkenyl succinic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, tetrahydrophthalic anhydride, nadic anhydride, and methylnadic anhydride, aliphatic acid anhydrides such as polyadipic anhydride, polyazelaic anhydride, and polysebacic anhydride, and aromatic acid anhydrides such as phthalic anhydride and trimellitic anhydride.

[0027] More specifically, examples of the acid anhydride include 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (hereinafter also simply referred to as "6FDA"), 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA), 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride (DSDA), 4,4'-oxydiphthalic anhydride (ODPA), 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride (BPADA), p-phenylenebis(trimellitic acid monoester acid anhydride) (TAHQ), 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 2,3',3,4'-biphenyltetracarboxylic dianhydride, and 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA).

[0028] Of these, from the viewpoint of suppressing optical loss, it is preferable that the acid anhydride contains a fluorine element.

[0029] These acid anhydrides may be used alone or in combination of two or more.

[0030] The amount of acid anhydride blended during the production of the epoxy-modified compound for optical waveguides may be adjusted depending on the types of the epoxy resin and acid anhydride so that the equivalent ratio of the reactive groups of the acid anhydride to the reactive hydroxyl groups of the epoxy resin is 0.04 or more and 2.0 or less.

[0031] In this specification, the term "reactive group of an acid anhydride" refers to an acid anhydride group capable of forming a bond with a reactive alcoholic hydroxyl group contained in the repeating backbone of the aforementioned epoxy resin. For example, when 6FDA is used as the acid anhydride, the reactive group of the acid anhydride is a carboxyl group. Furthermore, when 6FDA is used as the acid anhydride, the number of reactive groups of the acid anhydride, i.e., carboxyl groups, per molecule is four, and the carboxyl group equivalent is 111 (g / eq). Note that the "amount of reactive groups (amount of acid anhydride groups) (mol) of the acid anhydride (blended during production)," which relates to the blending ratio with the aforementioned epoxy resin, can be calculated from the acid anhydride group equivalent, the molecular weight (g / mol) of the acid anhydride, and the blending amount (g) of the acid anhydride.

[0032] Next, specific steps of the method for producing the epoxy-modified compound for optical waveguide according to this embodiment will be described below.

[0033] The method for producing an epoxy-modified compound for optical waveguides according to this embodiment includes carrying out a synthesis reaction using an epoxy resin having a reactive hydroxyl group and an acid anhydride such that the equivalent ratio of the reactive hydroxyl group to the reactive group of the acid anhydride is 0.04 or more and 2.0 or less.

[0034] When the equivalent ratio of the reactive groups of the acid anhydride to the reactive hydroxyl groups of the epoxy resin is 0.04 or more, an epoxy-modified compound for optical waveguides capable of suppressing optical loss in the 1310 nm wavelength band can be obtained. The equivalent ratio of the reactive groups of the acid anhydride to the reactive hydroxyl groups is preferably 0.06 or more, more preferably 0.08 or more, and particularly preferably a value selected from the group consisting of 0.10, 0.11, and 0.12 or more.

[0035] When the equivalent ratio of the reactive groups of the acid anhydride to the reactive hydroxyl groups of the epoxy resin is 2.0 or less, an epoxy-modified compound for optical waveguides having high storage stability and good developability can be obtained. The equivalent ratio of the reactive groups of the acid anhydride to the reactive hydroxyl groups is preferably 1.8 or less, more preferably 1.6 or less, even more preferably 1.54 or less, and particularly preferably a value selected from the group consisting of 1.0, 0.90, 0.80, and 0.77 or less.

[0036] Such a synthesis reaction is not particularly limited and may be carried out by any method known to those skilled in the art. For example, the synthesis reaction can be carried out by mixing an epoxy resin, an acid anhydride, and a catalyst, preferably a basic catalyst, at a reaction temperature of 80°C or higher. By using a basic catalyst as the catalyst for the synthesis reaction, the synthesis reaction by bonding between the reactive hydroxyl group of the epoxy resin and the reactive group of the acid anhydride can proceed smoothly. An example of a production method will be described below.

[0037] First, an epoxy resin and an acid anhydride are weighed so that the equivalent ratio of reactive groups of the acid anhydride to reactive hydroxyl groups of the epoxy resin is 0.04 to 2.0, and then placed in any reaction vessel known to those skilled in the art, such as a flask (e.g., a separable flask).Furthermore, a solvent such as NMP, methyl ethyl ketone, or toluene, and a basic catalyst such as an amine are added to the reaction vessel.

[0038] The basic catalyst that can be used is not particularly limited, but examples thereof include triethanolamine, triethylamine, dimethylethanolamine, and diethylethanolamine.

[0039] The amount of the basic catalyst is not particularly limited, and may be appropriately determined depending on the equivalent ratio of reactive groups of the acid anhydride to reactive hydroxyl groups of the epoxy resin and the type of basic catalyst used.

[0040] If the reaction temperature during mixing is 80°C or higher, the synthesis reaction due to bonding between the reactive hydroxyl groups of the epoxy resin and the reactive groups of the acid anhydride can proceed smoothly. The reaction temperature is more preferably 82°C or higher, and even more preferably 85°C or higher. The upper limit of the reaction temperature is not particularly limited as long as it ultimately results in an epoxy-modified compound for optical waveguides in this embodiment that has the effects of suppressing optical loss and having good storage stability and developability, but it is preferably a temperature below the boiling point of the solvent used.

[0041] In the epoxy-modified compound produced by such a synthesis reaction, the reactive alcoholic hydroxyl group contained in the repeating skeleton of the epoxy resin forms a bond with the reactive group of the acid anhydride.

[0042] It is known that the reactive alcoholic hydroxyl groups contained in the repeating skeleton of an epoxy resin have a significant effect on optical loss in the 1310 nm wavelength band. Therefore, in the epoxy-modified compound for optical waveguides produced by the method according to this embodiment, the reactive alcoholic hydroxyl groups form bonds with the reactive groups of the acid anhydride, and it is therefore presumed that when an optical waveguide is formed using this epoxy-modified compound for optical waveguides, optical loss in the 1310 nm wavelength band can be suppressed.

[0043] As described above, the epoxy-modified compound for optical waveguides according to this embodiment produced in this manner can suppress optical loss in the 1310 nm wavelength band, has high storage stability, and exhibits good developability. Furthermore, the epoxy-modified compound for optical waveguides produced in this manner can be mixed with a curing agent and optional additives to prepare a resin composition for optical waveguides. The curing agent is not particularly limited, as long as it is any curing agent known to those skilled in the art that can promote photocuring of a resin composition containing an epoxy resin. Examples of curing agents include antimony-based curing agents, phosphorus-based curing agents, special phosphorus-based curing agents, and borate-based curing agents.

[0044] The prepared resin composition for an optical waveguide can satisfactorily suppress optical loss in the 1310 nm wavelength band, and can therefore be suitably used as a material for a dry film used in producing an optical waveguide. However, the resin composition for an optical waveguide does not necessarily have to be used after forming a dry film in producing an optical waveguide.

[0045] The dry film includes a layer of an uncured or semi-cured resin composition for an optical waveguide. The method for producing the dry film is not particularly limited. For example, a solvent or the like is added to the resin composition for an optical waveguide as needed to form a varnish-like resin composition, and the varnish is then applied to a film substrate. The applied varnish is then dried at an appropriate temperature and for an appropriate time, thereby forming a dry film. The dry film including the resin composition layer thus produced is used as a material for an optical waveguide.

[0046] The resin composition for an optical waveguide or the dry film may be used when producing a core layer or a cladding layer of an optical waveguide. However, optical loss in the 1310 nm wavelength band occurs mainly in the core. Therefore, the epoxy-modified compound for an optical waveguide produced by the method according to this embodiment can be used to finally produce a resin composition for an optical waveguide or a dry film for the core, thereby more effectively suppressing optical loss in the 1310 nm wavelength band.

[0047] In the optical waveguide thus finally manufactured, optical loss in the 1310 nm wavelength band can be suppressed, and excellent optical communication can be realized. Therefore, a substrate having such an optical waveguide formed thereon is preferably used as an optical transmission printed wiring board, and is preferably used for, for example, a mobile phone, a personal digital assistant, etc.

[0048] As described above, this specification discloses various aspects of the technology, the main aspects of which are summarized below.

[0049] A method for producing an epoxy-modified compound for optical waveguides according to a first aspect of the present invention includes carrying out a synthesis reaction using an epoxy resin having a reactive hydroxyl group and an acid anhydride such that the equivalent ratio of the reactive hydroxyl group to the reactive group of the acid anhydride is 0.04 or more and 2.0 or less.

[0050] A method for producing an epoxy-modified compound for optical waveguides according to a second aspect of the present invention is the method for producing an epoxy-modified compound for optical waveguides according to the first aspect, wherein the epoxy resin is a bis-A type epoxy resin and the acid anhydride contains a fluorine element.

[0051] A method for producing an epoxy-modified compound for optical waveguides according to a third aspect of the present invention is the method for producing an epoxy-modified compound for optical waveguides according to the first or second aspect, wherein the synthesis reaction includes mixing the epoxy resin having a reactive hydroxyl group, the acid anhydride, and a basic catalyst at a reaction temperature of 80°C or higher.

[0052] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples in any way.

[0053] In this example, various epoxy-modified compounds for optical waveguides were actually produced by varying the equivalent ratio of reactive groups of acid anhydride to reactive hydroxyl groups of epoxy resin.Then, using the produced epoxy-modified compounds for optical waveguides, the stability, developability, and optical loss in the 1310 nm wavelength band of resin varnishes were evaluated.

[0054] First, the raw materials used in the production of the epoxy-modified compound for optical waveguides in this example are summarized below.

[0055] [Epoxy resin] "Epiclon (registered trademark) 850S" (hereinafter also simply referred to as "850S"): liquid bisphenol A type epoxy resin, manufactured by DIC Corporation, epoxy equivalent: 184 to 194 g / eq. [Acid anhydride] "6FDA": 4,4'-(hexafluoroisopropylidene)diphthalic anhydride, manufactured by Daikin Industries, Ltd., reactive group equivalent (carboxyl group equivalent): 111 g / eq. [Catalyst] "Triethanolamine": manufactured by Tokyo Chemical Industry Co., Ltd., molecular weight: 149 g / mol.

[0056] Next, the methods for producing the epoxy-modified compound for optical waveguides in each Example and Comparative Example, as well as the methods for evaluating the stability of the resin varnish, the methods for evaluating the developability, and the methods for evaluating the optical loss in the 1310 nm wavelength band will be described below.

[0057] <Method for Producing Epoxy-Modified Compound for Optical Waveguide> In each Example and Comparative Example, the components were blended in the actual blend amounts (g) shown in Table 1 below, placed in a separable flask, and covered with a separable cover. The components were then mixed for 4 hours while being heated to 90°C using an oil bath, producing the epoxy-modified compounds for optical waveguides in Examples 1 to 3 and Comparative Examples 1 and 2. Table 1 below also shows the amount of reactive groups (amount of carboxyl groups) (mol) of 6FDA and each molecular weight (mol) as synthesis ratios when the amount of reactive hydroxyl groups (mol) of 850S (liquid bisphenol A epoxy resin) is taken as 1.00.

[0058] <Method for Evaluating Resin Varnish Stability> A resin varnish was prepared by dissolving the epoxy-modified compound for optical waveguides of each Example and Comparative Example in 40 parts by mass of N-methyl-2-pyrrolidone (NMP) per 100 parts by mass of the epoxy-modified compound for optical waveguides. Approximately 30 ml of the resin varnish thus prepared was placed in a 50 ml glass bottle, sealed, and allowed to stand at room temperature. After one week, the resin varnish was visually observed for gelation. If no gelation was observed, the stability of the resin varnish was evaluated as good, and if gelation was observed, the stability of the resin varnish was evaluated as poor. The evaluation results of the resin varnish stability for each Example and Comparative Example are summarized in Table 1 below.

[0059] <Method for Evaluating Developability (Developability of Epoxy-Modified Compound for Optical Waveguide)> Developability (developability of epoxy-modified compound for optical waveguide) was evaluated by the following method. First, the epoxy-modified compound for optical waveguide of each Example and Comparative Example was coated on a PET film and then dried. Thereafter, the PET film was shaken for 1 minute in a flux remover (Pine Alpha ST-100SX), and it was observed whether the epoxy-modified compound for optical waveguide was removed. If removal of the epoxy-modified compound was confirmed, the developability was evaluated as good. If removal of the epoxy-modified compound was not confirmed, the developability was evaluated as poor. The evaluation results of developability for each Example and Comparative Example are summarized in Table 1 below.

[0060] <Method for Evaluating Optical Loss in the 1310 nm Wavelength Band> Optical loss in the 1310 nm wavelength band was evaluated by measuring transmittance using a spectrophotometer ("U-4100", manufactured by Hitachi High-Tech Science Corporation). Specifically, the transmittance at 1310 nm wavelength of the epoxy-modified compounds for optical waveguides in each Example and Comparative Example was measured in a liquid state, and the optical loss value in the 1310 nm wavelength band was calculated using the following formula. The calculation results for optical loss in the 1310 nm wavelength band for the epoxy-modified compounds for optical waveguides in each Example and Comparative Example are summarized in Table 1 below. An optical loss of 0.40 dB / cm or less was evaluated as having well-suppressed optical loss, and an optical loss of more than 0.40 dB / cm was evaluated as having poorly suppressed optical loss. Optical loss in the 1310 nm wavelength band (dB / cm) = -10 x LOG (transmittance (%) / 100)

[0061] The evaluation and calculation results for each of the above examples and comparative examples are summarized in Table 1 below, along with the blending amounts and synthesis ratios of the raw materials of the epoxy-modified compounds for optical waveguides.

[0062]

[0063] <Discussion> As shown in Table 1 above, the epoxy-modified compounds for optical waveguides in Examples 1 to 3, in which the synthesis reaction was carried out with an equivalent ratio of reactive groups of the acid anhydride (specifically, 6FDA) to reactive hydroxyl groups of the epoxy resin (specifically, 850S) of 0.04 to 2.0, provided resin varnishes with good stability and developability, and were also able to suppress optical loss in the 1310 nm wavelength band. This is presumably because the reactive alcoholic hydroxyl groups contained in the repeating skeleton of the epoxy resin form bonds with carboxyl groups derived from the acid anhydride.

[0064] Specifically, the epoxy-modified compounds for optical waveguides produced in Examples 1 to 3 can be explained and discussed in detail as follows.

[0065] First, the structural formulas of 850S (liquid bisphenol A type epoxy resin, epoxy equivalent weight 184 to 194 g / eq) and 6FDA are shown below.

[0066]

[0067] Converting from the epoxy equivalent, n of 850S in the above structural formula is estimated to be approximately 0.13. Meanwhile, as mentioned above, there are four carboxyl groups per molecule of 6FDA. In the manufacturing method of the epoxy-modified compound for optical waveguides in Examples 1 to 3, the actual blending amounts of each are appropriately adjusted based on the number of reactive hydroxyl groups of 850S per molecule and the number of carboxyl groups of 6FDA per molecule, so that the equivalent ratio of the carboxyl groups of 6FDA to the reactive hydroxyl groups of 850S is within the range of 0.04 to 2.0. As a result, it is estimated that one or more of the following four epoxy-modified compounds will be synthesized:

[0068]

[0069]

[0070]

[0071]

[0072] As shown above, in all of the epoxy-modified compounds with four structures, the carboxyl group derived from the acid anhydride group of 6FDA forms a bond with the reactive alcoholic hydroxyl group contained in the repeating skeleton of 850S. Therefore, it is presumed that when an optical waveguide is formed using the epoxy-modified compounds for optical waveguides produced by the methods of Examples 1 to 3, optical loss in the 1310 nm wavelength band can be suppressed.

[0073] In particular, as shown in Examples 1 and 2 in Table 1 above, it can be seen that the optical loss in the 1310 nm wavelength band can be more significantly suppressed by using an epoxy-modified compound for optical waveguides in which the synthesis reaction was carried out with an equivalent ratio of the reactive groups of the acid anhydride to the reactive hydroxyl groups of the epoxy resin set to 0.10 or more and 0.80 or less.

[0074] On the other hand, in Comparative Example 1, in which the amount of reactive groups (amount of carboxyl groups) in the acid anhydride was large, the optical loss in the 1310 nm wavelength band could not be suppressed, and the stability and developability of the resin varnish were also deteriorated.Furthermore, in Comparative Example 2, in which a liquid bisphenol A-type epoxy resin not modified with acid anhydride was used, the optical loss in the 1310 nm wavelength band could not be suppressed.

[0075] This application is based on Japanese Patent Application No. 2023-202840 filed on November 30, 2023, the contents of which are incorporated herein by reference.

[0076] The embodiments and examples disclosed herein should be understood to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0077] According to the present invention, there is provided a method for producing an epoxy-modified compound for optical waveguides, which can suppress optical loss in the 1310 nm wavelength band, has high storage stability, and exhibits good developability. By producing an optical waveguide using the epoxy-modified compound for optical waveguides obtained by this production method, the optical waveguide can be preferably used as an optical transmission printed wiring board for, for example, a mobile phone, a personal digital assistant, etc.

Claims

1. A method for producing an epoxy-modified compound for optical waveguides, comprising carrying out a synthesis reaction using an epoxy resin having a reactive hydroxyl group and an acid anhydride such that the equivalent ratio of the reactive hydroxyl group to the reactive group of the acid anhydride is 0.04 or more and 2.0 or less.

2. The method for producing an epoxy-modified compound for optical waveguides according to claim 1, wherein the epoxy resin is a bis-A type epoxy resin, and the acid anhydride contains a fluorine element.

3. The method for producing an epoxy-modified compound for optical waveguides according to claim 1, wherein the synthesis reaction includes mixing the epoxy resin having a reactive hydroxyl group, the acid anhydride, and a basic catalyst at a reaction temperature of 80°C or higher.

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