JP2005070556A - Optical waveguide, optical/electric hybrid substrate, and resin composition for formation of optical waveguide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical waveguide which has excellent waveguide characteristics such as transparency and heat resistance and which can be manufactured at a low cost in an easy process without requiring a developing process. <P>SOLUTION: At least either a core or a clad is made of a hardened product obtained by irradiating a resin composition which contains a reaction product by the reaction of a polyfunctional epoxy resin having three or more epoxy groups in the molecule and cinnamic acid, with UV rays and then thermally hardening the composition. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention is used in optical fields, micro-optical fields, optical information transmission fields, optical information processing fields, etc., optical waveguides used for optical elements, optical wiring boards, optical / electrical hybrid circuit boards, etc. The present invention relates to a resin composition for forming a substrate and an optical waveguide.

  As an optical waveguide used for information processing by light and the like, an optical waveguide using a polymer resin that can be formed by using an inexpensive material and a simple process has been studied. In this background, the light that has been the bottleneck in the past due to the fact that the frequency of information transmission is increasing and the limit of electric wiring is approaching, and the emergence of surface-emitting lasers (VCSEL), which are surface-mounted light-emitting elements. It is considered that the cost of the device is reduced and the cost of the entire system using the optical waveguide including mounting is considered to be lowered to an industrially usable level (Nikkei Electronics, December 2001). 3rd issue, see P109-).

  A surface-emitting laser (VCSEL), which is a surface-mounted light-emitting element, is also in commercial production with an emission wavelength of 850 nm, which is the wavelength of a semiconductor laser used in general long-distance optical communication. It is different from 1300nm (1.3μm) or 1550nm (1.55μm), so it will be used separately from these long-distance communication systems. Is the majority. In such a case, the optical waveguide cross section becomes a multimode optical circuit corresponding to 40 to 100 μm square, and the optical circuit and the electric circuit, preferably a printed wiring board made of an organic material, are integrated for high-density mounting. So-called optical / electrical composite circuit boards are desired. In such an application, a level of heat resistance required for a so-called printed wiring board is required for the resin forming the optical waveguide, and at the same time, the resin needs to have a small light loss.

  Here, for example, in Patent Document 1, an optical waveguide is manufactured by using a material blended with an alicyclic polyfunctional epoxy as a core material, and exposing and developing to remove unnecessary portions and form a core. Like to do. However, this method has a problem that it takes time and cost because it requires a developing step.

  Therefore, a method of forming a core by using a material whose refractive index is changed by irradiating ultraviolet rays and changing the refractive index by irradiating ultraviolet rays with a core pattern has been studied. According to this method, it is not necessary to remove unnecessary portions in the development process when forming the core, and a multimode optical waveguide can be formed by photolithography.

An example of a material whose refractive index changes when irradiated with such ultraviolet rays is polyvinyl cinnamate. By irradiating with ultraviolet rays, the vinyl group part of the two cinnamic acid units is dimerized to form a four-membered ring, the length of the conjugated system is shortened, and the refractive index can be lowered. Is. However, poly (vinyl cinnamate) has a problem that it is highly colored and difficult to transmit light, and has a problem that heat resistance is low.
Japanese Patent No. 30603903

  As described above, when forming a multimode optical waveguide by photosensitive polymer resin and photolithography, high heat resistance can be realized on the premise of combining with an electric circuit board, or the refractive index can be increased without sacrificing heat resistance. It is difficult to control, and the present situation is that a refractive index change type optical waveguide having excellent waveguide loss and not requiring development has not been realized.

  The present invention has been made in view of the above points, and has excellent waveguide characteristics such as transparency and heat resistance, and an optical waveguide that can be manufactured at a low cost by a simple process that does not require a development process. An object of the present invention is to provide an electric hybrid substrate and a resin composition for an optical waveguide.

  In the optical waveguide according to claim 1 of the present invention, a resin composition containing a reaction product obtained by reacting cinnamic acid with a polyfunctional epoxy resin having three or more epoxy groups in the molecule is irradiated with ultraviolet rays. A cured product obtained by thermosetting, wherein at least one of a core and a clad is formed.

  The invention of claim 2 is the invention according to claim 1, wherein the polyfunctional epoxy resin is a 1,2-epoxy-4- (2-oxiranyl) cyclohexane adduct of 2,2-bis (hydroxymethyl) -1-butanol. It is characterized by being.

  The invention of claim 3 is characterized in that in claim 1, the polyfunctional epoxy resin is at least one of a cresol novolac type epoxy resin and a phenol novolac type epoxy resin.

  The invention of claim 4 is characterized in that in claim 1, the polyfunctional epoxy resin is a compound represented by the following general formula (A).

(Where R ₁ is a glycidyl group, R ₂ is a glycidyl group or an allyl group, R ₃ and R ₄ are methyl groups or hydrogen, and n is an integer of 0 or more)
The invention of claim 5 is characterized in that in any one of claims 1 to 4, the resin composition contains an alicyclic epoxy resin.

  The invention of claim 6 is characterized in that, in any one of claims 1 to 5, the resin composition contains a bisphenol type epoxy resin.

  An optical / electrical hybrid substrate according to claim 7 of the present invention is an optical / electrical hybrid substrate in which the optical waveguide according to any one of claims 1 to 6 is formed on a surface of an electric circuit substrate provided with an electric circuit. Then, the glass transition temperature of the cured resin forming the optical waveguide is 140 ° C. or higher.

  The resin composition for an optical waveguide according to claim 8 of the present invention comprises a reaction product obtained by reacting cinnamic acid with a polyfunctional epoxy resin having three or more epoxy groups in the molecule. is there.

  The invention of claim 9 is characterized in that, in claim 8, a curing agent which undergoes a crosslinking reaction with an epoxy group is contained.

  The optical waveguide according to claim 1 of the present invention is excellent in waveguide characteristics such as transparency and heat resistance, and does not require a development step, and can be manufactured at a low cost by a simple process. is there.

  Further, the invention of claim 2 can form the optical waveguide with high transparency, can adjust the refractive index low, and can increase the moldability by reducing the viscosity of the resin composition. is there.

  In the invention of claim 3, the optical waveguide can be formed with high heat resistance and the refractive index can be adjusted high.

  The invention of claim 4 is capable of forming an optical waveguide having excellent transparency, high heat resistance, and flame retardancy.

  Further, the invention of claim 5 is capable of forming the optical waveguide with high transparency, adjusting the refractive index low, and reducing the viscosity of the resin composition to improve the moldability. is there.

  In the invention of claim 6, the optical waveguide can be formed with high heat resistance and the refractive index can be adjusted high.

  According to a seventh aspect of the present invention, there is provided an optical / electrical hybrid board including an optical waveguide having the above-described excellent characteristics, and characteristics of the optical waveguide in a solder reflow process when surface-mounting electric / electronic components on an electric circuit board. Can be prevented from deteriorating.

  The resin composition for an optical waveguide according to claim 8 of the present invention is capable of producing an optical waveguide excellent in waveguide characteristics such as transparency and heat resistance, and does not require a development step, and is simple. An optical waveguide can be manufactured at low cost by a simple process.

  According to the ninth aspect of the present invention, an optical waveguide with better heat resistance can be produced.

  Hereinafter, the best mode for carrying out the present invention will be described.

  The optical waveguide according to the present invention is obtained by thermally curing a resin composition containing a reaction product obtained by reacting a cinnamic acid with a polyfunctional epoxy resin having three or more epoxy groups in a molecule. The obtained cured product is formed with at least one of a core and a clad. The refractive index can be easily controlled to a level suitable for the core or the clad, and the core can be formed by photolithography. At the same time, the transparency is high and the optical waveguide loss can be kept low, the heat resistance of the final cured product is high, and the reliability of the optical waveguide can be obtained. Hereinafter, these contents will be described in order.

  In the present invention, as the polyfunctional epoxy resin having 3 or more epoxy groups in the molecule, as long as the resin composition immediately before irradiation with ultraviolet rays can maintain a solid state, a commercially available liquid epoxy resin or A solid epoxy resin can be used as appropriate.

  Specific examples of the polyfunctional epoxy resin include bisphenol A type novolak epoxy resin, bisphenol F type novolak epoxy resin, bisphenol S type novolac epoxy resin, biphenyl type novolak epoxy resin having a biphenyl skeleton, and naphthalene ring-containing novolak epoxy. Resin, dicyclopentadiene type epoxy resin having dicyclopentadiene skeleton, phenol novolac type epoxy resin, cresol novolac type epoxy resin, triphenylmethane type epoxy resin, bromine-containing epoxy resin, aliphatic epoxy resin, triglycidyl isocyanurate, etc. Among these, only one type or two or more types can be selected and used.

  Among these polyfunctional epoxy resins, cresol novolac type epoxy resins and phenol novolac type epoxy resins are particularly preferable. Resin obtained by reacting cresol novolac type epoxy resin or phenol novolac type epoxy resin with cinnamic acid as described later can adjust the refractive index of the cured product to be high, and is heat resistant. It is possible to produce a high-performance optical waveguide.

  In the present invention, 1,2-epoxy-4- (2-oxiranyl) cyclohexane addition of 2,2-bis (hydroxymethyl) -1-butanol as a polyfunctional epoxy resin having three or more epoxy groups in the molecule An alicyclic epoxy resin made of a product can also be used. The resin obtained by reacting such an alicyclic epoxy resin with cinnamic acid as described later can particularly increase the transparency of the finally obtained cured product and adjust the refractive index to be low. In addition, the heat resistance can be increased. Furthermore, the viscosity of the resin composition can be lowered, and the moldability can be improved.

Furthermore, in this invention, the compound represented by the said general formula (A) can also be used as a polyfunctional epoxy resin which has three or more epoxy groups in a molecule | numerator. This compound is obtained by reacting an epoxy group of a polyfunctional epoxy compound having an isocyanuric acid skeleton with a secondary amine of a compound having a hydantoin skeleton. Examples of the polyfunctional epoxy compound having an isocyanuric acid skeleton include monoallyl diglycidyl isocyanurate (abbreviated as MADGIC) and triglycidyl isocyanurate (also abbreviated as triEPoxy IsoCyanururate: TEPIC)) Can be illustrated. In the general formula (A), R ₁ is a glycidyl group and R ₂ is a glycidyl group, and TEPIC, R ₁ is a glycidyl group, and R ₂ is an allyl group is MADGIC. MADGIC is provided by Shikoku Kasei Kogyo Co., Ltd., and TEPIC is provided by Nissan Chemical Co., Ltd. As the compound having a hydantoin skeleton, dimethylhydantoin and methylhydantoin are preferable.

  In order to make these react, it is good to melt at the temperature more than each melting | fusing point, and if necessary, add a catalyst suitably and stir-mix. It has been found by the present inventors that hydantoin has a characteristic that the number of functional groups can be controlled by controlling the molar ratio because it reacts with epoxy to produce a product extending in a linear form. For example, in the case of 2 mol of epoxy resin and 1 mol of hydantoin, n = 0 in the general formula (A). In theory, in the case of 1 mol of epoxy resin and 1 mol of hydantoin, n = infinity in the general formula (A). Practically, the upper limit of the value of n is about 10.

  The resin obtained by reacting the compound represented by the general formula (A) with cinnamic acid as described below has high transparency and has a rigid molecular structure, so that a cured product having high heat resistance can be obtained. It is something that can be done. And since it has a higher refractive index than alicyclic epoxy resin, it can increase the degree of design freedom when forming the core, and it contains a lot of nitrogen atoms and is difficult to burn. It has preferred properties in use.

  In the present invention, among oxetane resins having a structure similar to an epoxy group that is a 3-membered ring ether and having a 4-membered ring ether structure that is a curable composition, a polyfunctional oxatan resin can be used in combination. . Oxetane resins are characterized in that the resin has high transparency, excellent electrical properties of the cured product, and has a high chain transfer performance and a high curing speed in a cationic curing system that easily exhibits high transparency. For example, an oxetane resin (trade name “OX-SQ”) having a γ- (3-ethyl-3-oxetanylmethoxy) propyl group on a silsesquioxane skeleton, available from Toa Gosei Co., Ltd., 3-ethyl- Examples thereof include oxetane resin (trade name “PNOX”) having a structure in which 3-oxetanylmethanol and phenol ether are novolakized.

  The reaction compound of a polyfunctional epoxy resin having three or more epoxy groups in the molecule and cinnamic acid is obtained by adding, for example, a polyfunctional epoxy resin and cinnamic acid to a toluene solvent, and the epoxy group of the polyfunctional epoxy resin and cinnamic acid. It is preferable to carry out this reaction by adding a catalyst such as triphenylphosphine (TPP) if necessary. The epoxy equivalent of the reaction product can be controlled by the amount of cinnamic acid added. The addition ratio of the polyfunctional epoxy resin and cinnamic acid is preferably in the range of 10: 3 to 10: 8 in terms of molar ratio. When the ratio of cinnamic acid is less than this range, the refractive index change hardly occurs. Conversely, when the ratio of cinnamic acid is more than this range, the heat resistance of the cured product tends to be low.

  In addition to this compound, other resins can be used in combination with the resin composition of the present invention used for forming an optical waveguide. For example, alicyclic epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, biphenyl type epoxy resin having biphenyl skeleton, naphthalene ring-containing epoxy resin, 3-ethyl-3-hydroxymethyl Oxetane (Toa Gosei Co., Ltd., trade name “OXT-101”), 1,4-bis {[(3-ethyl-3-oxetanyl) methoxy] methyl} benzene (Toa Gosei Co., Ltd., trade name “OXT-121”) ), 3-ethyl-3-phenoxymethyloxetane (Toa Gosei Co., Ltd., trade name “OXT-211”), bis (3-ethyl-3-oxetanylmethyl) ether (Toa Gosei Co., Ltd., trade name “OXT-221”) "), 3-ethyl-3- (2-ethylhexyloxymethyl) oxetane (east Gosei, can be cited such trade name "OXT-212") a monofunctional or bifunctional oxetane resins can be used, such as select one only or two or more from these.

  Among the above epoxy resins, it is preferable to use an alicyclic epoxy resin in combination. By using the alicyclic epoxy resin in combination, the transparency of the cured product can be increased and the refractive index of the cured product can be adjusted to be low, and the viscosity of the resin composition is lowered and molded. It is possible to improve the property. Among the alicyclic epoxy resins, those having no ester group in the molecular structure are preferable because they are excellent in hydrolysis resistance of the cured product. For example, hydrogenated bisphenol A type epoxy resin, hydrogenated bisphenol F type epoxy resin, epoxidized olefins with cyclic structure and two carbon-carbon double bonds, such as epoxidized bicyclohexene and epoxidized cyclooctadiene Can be exemplified.

  Further, among the above epoxy resin resins, it is preferable to use a bisphenol type epoxy resin in combination. By using a bisphenol-type epoxy resin in combination, the heat resistance of the cured product can be increased, and the refractive index of the cured product can be adjusted high.

  In the resin composition as described above, when the polyfunctional epoxy resin, cinnamic acid compound and another resin are used in combination, the ratio of the polyfunctional epoxy resin, cinnamic acid compound and the other resin is 1 in molar ratio. : The range of 0-1: 1 is preferable. When the ratio of the other resin is larger than this, the refractive index change hardly occurs.

  The resin composition of the present invention used for forming the optical waveguide contains the above-mentioned compound and a curing agent for curing the resin as an essential component. This curing agent initiates the curing reaction of the resin with active energy rays such as light or electron beam, or heat, and is called a curing initiator. Specifically, phosphonium salts, iodonium salts, sulfonium salts, silanol-aluminum complexes that initiate cationic polymerization with light or heat, diazabicycloalkenes or salts thereof, imidazoles or salts thereof, 1 to Examples thereof include tertiary amines or salts thereof, triazoles or salts thereof, organometallic complex salts, organic acid metal salts, quaternary ammonium salts, phosphines and the like. These are also referred to as curing catalysts and may be those that cause a curing reaction of an epoxy group or an oxetane group.

  Here, although not specifically limited, it is particularly preferable that the curing catalyst is a cationic polymerization catalyst that promotes self-polymerization of a resin in a cationic curing system. By using such a cationic polymerization catalyst, a cured product composed only of a highly transparent resin can be formed. Since this cured product has a three-dimensional network formed by an ether bond, it is difficult to be colored by a high temperature during curing or a high temperature received from the environment after curing, and is more suitable for an optical waveguide.

  Moreover, the hardening | curing agent which reacts with an epoxy resin or an oxetane resin, is taken in into a hardening structure, and forms the molecular structure of a three-dimensional network can be used. Curing acid anhydrides such as methyltetrahydrophthalic anhydride and methylhexahydrophthalic anhydride having one or more hydroxyl-free groups in one molecule as long as they do not interfere with the gist of the present invention such as transparency and heat resistance. , Phenolic curing agents such as bisphenol A, phenol novolak, cresol novolak, naphthol novolak, etc. having two or more phenolic hydroxyl groups in one molecule, and curing agents such as primary amine, secondary amine and dicyandiamide are used. be able to. The molar ratio of the above stoichiometric reactive groups between the epoxy resin or oxetane resin (this is called the main agent) and the curing agent, that is, the ratio (equivalent ratio) between the main agent equivalent and the curing agent equivalent is 100: 60-100. : 120 is preferable, and 100: 75 to 100: 100 is more preferable. When it is out of this range, that is, when the curing agent equivalent of the curing agent is less than 60 with respect to 100 equivalents of the main agent, the composition becomes difficult to cure, or even if cured, the heat resistance of the cured product decreases, There exists a possibility that the intensity | strength of hardened | cured material may fall. Conversely, if the curing agent equivalent exceeds 120, the heat resistance of the cured product may be reduced, the adhesive strength after curing may be reduced, or the moisture absorption rate of the cured product may be increased.

  In the resin composition of the present invention, at least one of a silane coupling agent or a titanate coupling agent can be used as a coupling agent. When these materials are contained in the resin composition, the adhesiveness at the interface between the cured product and the circuit board is improved, and the moisture resistance reliability of the device including the circuit board can be improved.

  Here, as the silane coupling agent, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, epoxysilane such as β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ, -Aminopropyltriethoxysilane, N-β (aminoethyl) γ-aminopropyltrimethoxysilane, N-β (aminoethyl) γ-aminopropylmethyldimethoxysilane, γ-aminopropyltrimethoxysilane, γ-ureidopropyltri Aminosilane such as ethoxysilane, mercaptosilane such as 3-mercaptopropyltrimethoxysilane, p-styryltrimethoxysilane, vinyltrichlorosilane, vinyltris (β-methoxyethoxy) silane, vinyltrimethoxysilane, vinyltriethoxysila Vinyl silanes such as γ-methacryloxypropyltrimethoxysilane, epoxy-based, amino-based, and vinyl-based polymer type silanes can be used, and epoxy silane, amino silane, and mercapto silane are particularly preferable. .

  On the other hand, titanate coupling agents include isopropyl triisostearoyl titanate, isopropyl tri (N-aminoethyl / aminoethyl) titanate, diisopropyl bis (dioctyl phosphate) titanate, tetraisopropyl bis (dioctyl phosphite) titanate, tetraoctyl bis ( Ditridecyl phosphite) titanate, tetra (2,2-diallyloxymethyl-1-butyl) bis (ditridecyl) phosphite titanate, bis (dioctyl pyrophosphate) oxyacetate titanate, bis (dioctyl pyrophosphate) ethylene titanate, etc. are used. be able to.

  These coupling agents may be used alone or in combination of two or more. At this time, as a content rate of a coupling agent, the range of 0.1-1 mass% is preferable with respect to the resin composition whole quantity.

  Furthermore, other substances can be added to the resin composition as necessary, as long as the object of the present invention is not impaired. Examples of such substances include photosensitizers, radical stabilizers, flame retardants, low elasticity agents, colorants, diluents, antifoaming agents, ion trapping agents, and the like.

  And the optical waveguide can be formed with this cured resin by molding and curing the resin composition according to the present invention. The optical waveguide is composed of a core having a high refractive index and a clad having a low refractive index, and is formed in a shape surrounding the core with the clad. One of the core and the clad is formed of the above resin composition, and the other is formed. May be formed of any other resin, and both the core and the clad may be formed of the above resin composition. Here, the B-stage product of the resin composition containing the compound of the polyfunctional epoxy resin and cinnamic acid has a refractive index lowered by irradiating ultraviolet rays by the same mechanism as that of the polyvinyl cinnamate described above. The refractive index can be fixed by subsequent thermosetting. Therefore, by partially irradiating the B-staged product of the resin composition containing the polyfunctional epoxy resin and cinnamic acid compound with ultraviolet rays, the refractive index is partially lowered, and then heat curing is performed, thereby producing ultraviolet rays. The difference in refractive index between the part irradiated and the part not irradiated can be fixed, and the part irradiated with ultraviolet light can be formed as a cladding and the part not irradiated can be formed as a core. Thus, it is not necessary to remove unnecessary portions, and an optical waveguide can be formed by photolithography. In addition, a cured product of a resin composition comprising a reaction compound of a polyfunctional epoxy resin and cinnamic acid has high heat resistance and excellent transparency, and excellent waveguide characteristics such as transparency and heat resistance. The optical waveguide can be manufactured at a low cost by a simple process that does not require a development step.

  Next, an example of forming an optical waveguide will be described. First, the resin composition 2 of the present invention is applied to the surface of the substrate 1 or the like as shown in FIG. 1 (a), and the entire surface is exposed by irradiating with ultraviolet rays. The lower clad 3 is formed of a cured resin as shown in FIG. 1B (in FIG. 1 and FIG. 2 to be described later, white is displayed before the refractive index is changed, and dots are displayed after the refractive index is changed). . The lower clad 3 may be obtained by using any other resin composition having a lower refractive index of cured product than the core 6 and curing it with ultraviolet rays or by heating. Next, the resin composition 2 of the present invention is applied onto the lower clad 3 and irradiated with ultraviolet rays through a positive mask 4 to form a clad other than the core formation portion of the resin composition 2 as shown in FIG. The portions are exposed and the clad formation portion of the resin composition 2 is made to have a low refractive index, and then heat-treated and thermally cured to form a low refractive index intermediate clad 5 as shown in FIG. The core 6 having a high rate is formed. Further, the resin composition 2 of the present invention is applied thereon as shown in FIG. 1 (e), and the whole surface is exposed by irradiating with ultraviolet rays to lower the refractive index, followed by heat treatment and thermosetting, and FIG. As shown in f), the upper clad 7 is formed of a cured resin. The upper clad 7 may be obtained by using any other resin composition having a refractive index equivalent to that of the upper cladding 7 and curing it with ultraviolet rays or by heating. In this manner, an optical waveguide 8 formed by surrounding the core 6 having a high refractive index with the lower clad 3, the intermediate clad 5 and the upper clad 7 having a low refractive index can be produced.

  Further, by forming the optical waveguide as described above on the surface of an electric circuit substrate such as a resin substrate provided with an electric circuit on the surface or inside thereof, an optical / electrical hybrid substrate can be manufactured. For example, in FIG. 1, an optical / electrical hybrid substrate can be manufactured by using an electric circuit substrate as the substrate 1. At this time, the cured resin forming the optical waveguide preferably has a glass transition temperature (Tg) of 140 ° C. or higher. If the Tg of the cured resin forming the optical waveguide is lower than 140 ° C., the characteristics of the optical waveguide may be deteriorated in the solder reflow process when the electric / electronic component is surface-mounted on the electric circuit substrate. In the temperature cycle test and the moisture resistance reliability test for evaluating whether or not the above is ensured, a defect occurs early. On the other hand, if the Tg of the cured resin forming the optical waveguide is high, there is no problem with respect to these performances, but it is generally difficult to make Tg higher than about 250 ° C. As the electric circuit board, an organic substrate including a fiber base material such as FR4 or FR5, a build-up type organic substrate not including the fiber base material, and a substrate such as an organic film such as polyimide or polyester can be used. .

  Next, the present invention will be specifically described with reference to examples.

(Synthesis Example of Compound 1)
1,2-epoxy-4- (2-oxiranyl) cyclohexane of 2,2-bis (hydroxymethyl) -1-butanol (manufactured by Daicel Chemical Industries, Ltd., product number “EHPE3150”, epoxy equivalent 185, molecular weight 2234) 37 0.0 g, trans-cinnamic acid (molecular weight 148) 14.8 g, toluene 50.0 g, and triphenylphosphine 0.126 g were placed in a glass flask, heated and stirred at 110 ° C. for 5 hours, and then toluene. Was evaporated in vacuo and allowed to cool to room temperature, yielding solid compound 1. When GPC analysis of this compound 1 was carried out, no monomer peak was observed, and it was oligomerized. Moreover, when the epoxy equivalent measurement based on JISK7236 was performed, the epoxy equivalent was 530.

(Synthesis Example of Compound 2)
Cresol novolak resin (Nippon Kayaku Co., Ltd., product number “EOCN-104S”, epoxy equivalent 218, molecular weight 2070) 21.8 g, trans-cinnamic acid (molecular weight 148) 9.87 g, toluene 32.0 g, tri 0.16 g of phenylphosphine was placed in a glass flask and heated and stirred for 3 hours while refluxing at 110 ° C., and then toluene was distilled off by heating under vacuum and allowed to cool to room temperature to obtain a solid compound 2 . When GPC analysis of this compound 2 was carried out, no monomer peak was observed, and it was oligomerized. Moreover, when the epoxy equivalent measurement based on JISK7236 was performed, the epoxy equivalent was 940.

(Synthesis Example of Compound 3)
29.7 g of triglycidyl isocyanurate (manufactured by Nissan Chemical Co., Ltd., product number “TEPIC-S”, molecular weight 297) and 12.6 g of dimethylhydantoin (manufactured by Mitsui Chemicals Fine Co., Ltd., product number “55DMH”, molecular weight 126) are made of stainless steel. While being melted at 150 ° C., 0.21 g of a 1% by weight 2-methoxypropanol solution of 1-benzyl-2-methylimidazole (Shikoku Kasei Kogyo Co., Ltd., product number “1B2MZ”) was added and stirred and mixed for 1 hour. Thereafter, the product was taken out from the flask and allowed to cool to room temperature to obtain an oligomer having a melting point of 70 ° C., wherein R ₁ and R ₂ are glycidyl groups and R ₃ and R ₄ are methyl groups. When GPC analysis was performed, no monomer peak was observed and oligomerization was observed. Further, when the epoxy equivalent of this oligomer resin was measured in accordance with JIS K7236, the epoxy equivalent was 300.

  Next, 30.0 g of this oligomer resin, 7.4 g of trans-cinnamic acid (molecular weight 148), 35.0 g of toluene, and 0.16 g of triphenylphosphine were placed in a glass flask and refluxed at 110 ° C. After stirring with heating for a period of time, toluene was distilled off by heating under vacuum, and the mixture was allowed to cool to room temperature, whereby solid compound 3 was obtained. When GPC analysis of this compound 3 was carried out, no monomer peak was observed, and it was oligomerized. Moreover, when the epoxy equivalent measurement based on JISK7236 was performed, the epoxy equivalent was 770.

(Synthesis Example of Compound 4)
37.0 g of bisphenol A type epoxy resin (manufactured by Dainippon Ink and Chemicals, product number “840-S”, epoxy equivalent 185), 7.4 g of trans-cinnamic acid (molecular weight 148), 50.0 g of toluene, After putting 0.22 g of triphenylphosphine into a glass flask and heating and stirring for 5 hours while refluxing at 110 ° C., toluene was distilled off by heating under vacuum and allowed to cool to room temperature to obtain a solid compound 4 It was. The GPC analysis monomer peak of this compound 4 was not recognized, but was oligomerized. Moreover, when the epoxy equivalent measurement based on JISK7236 was performed, the epoxy equivalent was 480.

(Preparation of refractive index change type photosensitive resin composition)
The photosensitive resin compositions of Examples 1 to 5 and Comparative Example 1 whose refractive index changes by irradiating with ultraviolet rays are blended in the amounts (parts by mass) shown in Table 1 below, and each component is a disper (special machine). The raw materials used in Table 1 are as follows.

(Epoxy resin)
Compound 1 (epoxy equivalent 530)
Compound 2 (epoxy equivalent 940)
Compound 3 (epoxy equivalent 770)
Compound 4 (epoxy equivalent 480)
Resin A: Cyclohexane alicyclic epoxy resin (manufactured by Daicel Chemical Industries, product number “Celoxide 2021P”, epoxy equivalent 136)
Resin B: Bisphenol A type epoxy resin (manufactured by Dainippon Ink and Chemicals, product number “840-S”, epoxy equivalent 185)
(Curing agent)
Curing agent: Dicyandiamide (flame retardant)
Flame retardant: cyclophosphazene oligomer (manufactured by Otsuka Chemical Co., Ltd., product number “SPB-100”)
Moreover, about the hardened | cured material of the resin composition of these Examples 1-5 and Comparative Example 1, the glass transition temperature (Tg), the refractive index, and the flame retardance were evaluated in the following procedure. That is, first, the varnish of the resin composition was cast on a PET film, dried at 150 ° C. for 5 minutes, and the dried product was pulverized, then formed into a 1 mm thickness by direct pressure molding at 170 ° C., and further 150 ° C. And heated for 1 hour to obtain a cured resin plate. A sample cut out from the cured resin plate was measured with a viscoelastic spectrometer “DMS110” manufactured by Seiko Denshi Kogyo Co., Ltd. to evaluate Tg. Similarly, the flame retardance test in accordance with UL standards was performed to evaluate the flame retardancy. Moreover, the refractive index was measured for the sample cut out from this resin cured board using the bromo naphthalene for the intermediate liquid with the refractive index measuring apparatus by an Atago company. This refractive index is a refractive index not irradiated with UV. On the other hand, a varnish of a resin composition was cast on a PET film, irradiated with ³ J / cm ² of UV with an ultra-high pressure mercury lamp, then heated at 150 ° C. for 1 hour to thermally cure, and a sample cut out from this cured resin plate The refractive index was measured in the same manner. This refractive index is the refractive index of UV irradiation. The results are shown in Table 1.

  As seen in Table 1, those in Examples 1 to 5 consisting of a resin composition containing a reaction product obtained by reacting cinnamic acid with a polyfunctional epoxy resin having three or more epoxy groups in the molecule are heat resistant. It is confirmed that the property is excellent. Moreover, it is confirmed that the thing of Example 3 using the alicyclic epoxy resin represented by general formula (A) as a polyfunctional epoxy resin is excellent also in a flame retardance.

(Fabrication of optical waveguide and optical / electric hybrid board)
Next, a method for producing an optical waveguide using the resin compositions of Examples 1 to 5 and Comparative Example 1 as a resin for cladding and a resin for core will be described below.

First, the surface of a 12 cm square flat plate mold 11 finished to a mirror surface is subjected to a bite process, and two V grooves 12 having a depth of 60 μm and an angle of 45 degrees are formed in parallel by a bite process at a distance of 10 cm. The surface of was released with a fluororesin. And the resin composition shown in Table 1 is applied to the surface of the mold 11 in which the V-groove 12 is formed, and a glass plate 13 which has been subjected to mold release treatment with a fluororesin through a spacer having a thickness of 40 μm is placed. After irradiating the entire surface with 5 J / cm ² of UV, it is heated and cured at 150 ° C. for 1 hour to form a V-grooved lower clad 3 (see FIGS. 2A and 2B).

  On the other hand, an electric circuit board 16 comprising a 12 cm square FR5 grade four-layer resin substrate with an electric circuit 14 provided on the inner layer and a copper foil 15 stretched on the surface was used, and the glass plate 13 was peeled off from the lower cladding 3. Thereafter, a two-component curable araldite adhesive is applied to the peeled surface, and the surface of the electric circuit board 16 from which the copper foil 15 has been removed by etching is pressed and held at 90 ° C. for 30 minutes. Thus, the lower clad 3 and the electric circuit board 16 were bonded (see FIG. 2C).

  Next, the integrated circuit board 16 and lower clad 3 were peeled from the mold 11. Then, gold was deposited to a thickness of 0.1 μm through a mask on the portion of the microprotrusion 19 formed by transferring the V groove 12 of the lower cladding 3 to form a micromirror 20 (see FIG. 2D).

Next, the same resin composition shown in Table 1 was applied to the surface of the lower clad 3 by a spin coater so as to have a thickness of 50 μm (see FIG. 2E). Projection exposure was performed through a positive pattern mask 21 capable of forming a waveguide having a width of 50 μm perpendicular to the micromirror 10. The exposure at this time was performed by irradiating UV of 3 J / cm ^{2 with} an ultra-high pressure mercury lamp, and further heat-cured by heating at 150 ° C. for 1 hour. In this way, the intermediate clad 5 was formed on the portion irradiated with UV, and the core 4 was formed on the portion not irradiated with UV (see FIGS. 3A and 3B).

  Thereafter, the same resin composition as shown in Table 1 was further spin-coated so as to have a thickness of 80 μm from above, and cured in the same manner as the lower clad 5 to form the upper clad 7. As described above, an optical / electrical hybrid substrate formed by providing the optical waveguide 8 composed of the core 6 and the clads 3, 5, 7 on the surface of the electric circuit substrate 16 having the electric circuit 14 formed therein was obtained. (See FIGS. 4A and 4B).

  The characteristics of the optical waveguide 8 produced as described above were measured as follows. A laser beam of 850 nm is incident in a direction perpendicular to the substrate with an optical fiber of 50 μmφ from directly above one of the opposing micromirrors 20, and perpendicularly toward the substrate surface by the other micromirror 20 via the core 6 of the optical waveguide 8. The optical path is bent, this light is received by an optical fiber of 125 μmφ, and guided to a power meter to measure the received light power P2. The total loss is determined by the following equation from the ratio of the power P1 measured when the optical fiber of the light emitting side of 50 μmφ and the light receiving side of 125 μmφ is abutted.

Total loss [dB] = − 10 × log (P2 / P1)
The “initial waveguide loss” in Table 2 is a total loss value obtained by measuring the optical / electrical hybrid board before the solder reflow process and the temperature cycle test.

  Also, “loss change due to solder reflow process” in Table 2 indicates that the above-mentioned optical / electrical hybrid board for which the initial waveguide loss was measured is subjected to solder reflow process with a profile of 220 ° C. or higher for 60 seconds and a peak temperature of 260 ° C. After circulation, the total loss was measured by the above method, and the difference between the total loss before and after the solder reflow treatment was taken.

  “Temperature cycleability” in Table 2 indicates that the above-mentioned optical / electrical hybrid substrate for which the initial waveguide loss was measured was: -55 ° C. for 30 minutes, room temperature for 5 minutes, 125 ° C. for 30 minutes, and room temperature for 5 minutes. A gas phase temperature cycle test is performed for one cycle, and total loss is measured every 200 cycles up to 2000 cycles, and the number of cycles in which the total loss value is twice or more the initial value is obtained.

  As can be seen from Table 2, when Examples 1 to 5 and Comparative Example 1 are compared, all of Examples have small initial waveguide loss, good solder reflow property, and temperature cycle. It turns out that it is excellent also in property.

An example of embodiment of this invention is shown and (a) thru | or (f) is a schematic sectional drawing, respectively. The manufacture example of the optical / electrical hybrid board | substrate in the Example of this invention is shown, (a) thru | or (e) is a schematic sectional drawing, respectively. It shows one process of the manufacturing example same as above, (a) is a front sectional view, (b) is a side sectional view. The optical / electrical hybrid board | substrate same as the above is shown, (a) is front sectional drawing, (b) is side sectional drawing.

Explanation of symbols

2 resin composition 3 lower clad 4 positive mask 5 intermediate clad 6 core 7 upper clad 8 optical waveguide

Claims (9)

  A cured product obtained by thermally curing a resin composition containing a reaction product obtained by reacting cinnamic acid with a polyfunctional epoxy resin having three or more epoxy groups in the molecule, An optical waveguide characterized in that at least one of clads is formed.   2. The light guide according to claim 1, wherein the polyfunctional epoxy resin is a 1,2-epoxy-4- (2-oxiranyl) cyclohexane adduct of 2,2-bis (hydroxymethyl) -1-butanol. Waveguide.   2. The optical waveguide according to claim 1, wherein the polyfunctional epoxy resin is at least one of a cresol novolac type epoxy resin and a phenol novolac type epoxy resin. The optical waveguide according to claim 1, wherein the polyfunctional epoxy resin is a compound represented by the following general formula (A).

(Where R ₁ is a glycidyl group, R ₂ is a glycidyl group or an allyl group, R ₃ and R ₄ are methyl groups or hydrogen, and n is an integer of 0 or more)   The optical waveguide according to claim 1, wherein the resin composition contains an alicyclic epoxy resin.   6. The optical waveguide according to claim 1, wherein the resin composition contains a bisphenol type epoxy resin.   An optical / electrical hybrid substrate in which the optical waveguide according to any one of claims 1 to 6 is formed on a surface of an electrical circuit substrate provided with an electrical circuit, and a glass transition temperature of a cured resin that forms the optical waveguide. An optical / electrical hybrid board characterized by having a temperature of 140 ° C. or higher.   A resin composition for forming an optical waveguide, comprising a reaction product obtained by reacting a polyfunctional epoxy resin having three or more epoxy groups in a molecule with cinnamic acid.   The resin composition for forming an optical waveguide according to claim 8, further comprising a curing agent that undergoes a crosslinking reaction with an epoxy group.

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