JP2010271371A - Flexible optical waveguide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flexible optical waveguide which is superior in bending durability and has less optical loss. <P>SOLUTION: In the flexible optical waveguide having a lower cladding layer 2 and a core layer 6, the cross sectional area of one end of the core layer 6 is smaller than the cross-sectional area of the other end, and the flexible optical waveguide has a bending part, which is thinner than at least one end. In a photoelectric composite wiring board, the flexible optical waveguide is compounded into a flexible electric wiring board. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a flexible optical waveguide having excellent bending durability.

  In recent years, in high-speed and high-density signal transmission between electronic devices and between wiring boards, signal transmission interference and attenuation are barriers in conventional transmission using electric wiring, and the limits of high-speed and high-density have begun to appear. In order to overcome this problem, a technique for optically connecting electronic elements and wiring boards, so-called optical interconnection, has been studied. As an optical transmission line, polymer optical waveguides are attracting attention because of their ease of processing, low cost, high flexibility in wiring, and high density. In particular, the use of optical waveguides in mobile phones, notebook computers, and the like has been studied.

By the way, in an electronic device such as a mobile phone, when a flexible optical waveguide is used for signal transmission between two mechanisms that can be opened and closed, the flexible optical waveguide may straddle the connecting portion (hinge) of the two mechanisms. Conceivable. In this case, the flexible optical waveguide is bent by the hinge, and a crack or a crack may occur due to the bending. In particular, because of recent demands for downsizing electronic devices, it is required that the hinge be bent with a small bending radius of about 1 to 2 mm. there were.
In particular, an opto-electric hybrid board that combines optical wiring and electrical wiring is desired in order to cope with space saving and thinning. However, the thickness of the opto-electric hybrid board is further increased. The bending durability was demanded.

  As a method of improving the bending durability of the flexible optical waveguide, there is a method of reducing the thickness of the bent portion. To reduce the thickness of the flexible optical waveguide film, the core size of the flexible optical waveguide film is reduced. It is necessary. Since it is considered that the optical coupling efficiency is reduced when the core size is reduced, a flexible optical waveguide film having a portion where the film thickness is thinner than the light input portion has been proposed (see Patent Document 1). There has been a demand for improved bending durability and reduced light loss.

International Publication 2007/026601 Pamphlet

  In view of the above problems, an object of the present invention is to provide a flexible optical waveguide having excellent bending durability and low optical loss.

As a result of intensive studies, the inventors have found that the cross-sectional area of one end of the core layer is smaller than the cross-sectional area of the other end, and has a bent portion, and the bent portion is at least one end portion. It has been found that the above problem can be solved by using a thin structure.
That is, the present invention
(1) A flexible optical waveguide having a lower cladding layer and a core layer, wherein the cross-sectional area of one end of the core layer is smaller than the cross-sectional area of the other end, and has a bent portion, A flexible optical waveguide characterized by being thinner than at least one end;
(2) An opto-electric composite wiring board obtained by combining the flexible optical waveguide according to (1) above with a flexible electric wiring board,
Is to provide.

  ADVANTAGE OF THE INVENTION According to this invention, it is excellent in bending durability and can provide the flexible optical waveguide with few optical losses.

It is a schematic diagram which shows the one aspect | mode of the flexible optical waveguide of this invention. It is a schematic diagram which shows each process of the manufacturing method suitable in order to obtain the flexible optical waveguide of this invention. It is a figure explaining the resin film for clad layer formation used for manufacture of the flexible optical waveguide of this invention. It is a figure explaining the resin film for core layer formation used for manufacture of the flexible optical waveguide of this invention. It is a schematic diagram which shows a part of process of the manufacturing method of the flexible optical waveguide of this invention. It is a schematic diagram which shows the other one aspect | mode of the flexible optical waveguide of this invention. It is a schematic diagram which shows the other one aspect | mode of the flexible optical waveguide of this invention. It is a schematic diagram which shows the other one aspect | mode of the flexible optical waveguide of this invention. It is a conceptual diagram which shows the content of a bending durability test.

As shown in FIG. 1, the flexible optical waveguide of the present invention is a flexible optical waveguide having a lower clad layer (first clad layer) 2 and a core layer 6, wherein one end of the core layer 6 is cut off. The area is smaller than the cross-sectional area of the other end portion, and has a bent portion, and the bent portion is thinner than at least one end portion.
The flexible optical waveguide of the present invention further has an upper clad layer (second clad layer) 7, and the lower clad layer 2, the core layer 6 and the upper clad layer 7 are preferably laminated in this order.

  In the flexible optical waveguide of the present invention, an optical signal is input from the optical input portion of the core layer and output to the optical output portion through the bent portion, but the optical input / output portion is optically coupled with other optical components to There is no particular limitation, and for example, one end of the core layer may be a light input unit and the other end may be a light output unit. Further, the light input / output unit may be provided between the end and the intermediate part instead of the end. In this case, for example, a path is provided as a path for entering light into the core of the optical waveguide and a path for emitting light from the core. Also good.

In the flexible optical waveguide of the present invention, it is preferable that the core layer 6 has a larger cross-sectional area as a light input portion and a smaller cross-sectional area as a light output portion.
In this way, by setting the larger cross-sectional area of the core layer as the light incident side, it is possible to prevent positional deviation from a light emitting element such as a surface emitting laser (VCSEL), and to obtain a high optical coupling ratio. it can. On the other hand, by setting the smaller cross-sectional area as the emission side, high coupling efficiency can be obtained even with a light receiving element such as a photodiode. That is, the optical waveguide can be manufactured so that the coupling efficiency is optimized in both the input portion and the output portion.
In addition, by making the thickness of the core layer 6 thinner at the bent portion than at least one of the end portions, it is possible to make the core layer 6 excellent in bending durability. Further, when the flexible optical waveguide of the present invention further includes the upper cladding layer 7 and the lower cladding layer 2, the core layer 6 and the upper cladding layer 7 are laminated in this order, the core layer 6 and the upper cladding layer 7 are provided. By making the total thickness of the bent portion thinner than at least one of the end portions, it becomes possible to have a superior bending durability. From such a viewpoint, in the core layer, the ratio of the thickness of the bent portion / the thickness of the end portion (at least one end portion) is preferably 0.3 to 0.8, and preferably 0.4 to 0.00. 6 is more preferable. When the upper clad layer 7 is provided, the ratio of the thickness of the bent portion / the thickness of the end portion (at least one end portion) is 0.3 to 0.3 in the total thickness of the core layer and the upper clad layer. 0.9 is preferable, and 0.4 to 0.7 is more preferable.
Further, the thickness of the bent portion of the flexible optical waveguide of the present invention, that is, the total thickness of the flexible optical waveguide of the present invention at the bent portion (the lower cladding when the flexible optical waveguide of the present invention does not have the upper cladding layer 7) The total thickness of the layer 2 and the core layer 6, or the total thickness of the lower cladding layer 2, the core layer 6, and the partial cladding layer 7 when the upper cladding layer 7 is provided ) To 0.3 to 0.9, it is excellent in bending resistance, and is preferable in terms of ensuring low mechanical loss and film formability with low light loss. In the total thickness of the flexible waveguide, the ratio of the thickness of the bent portion / the thickness of the end portion (at least one end portion) is more preferably 0.4 to 0.7.

The cross-sectional area of one end of the core layer is 0.2 to 0.8 with respect to the other end, and / or the thickness of one end of the core layer is It is preferable that it is 0.2-0.8 with respect to the other end part from the reason of suppressing optical loss while improving the favorable coupling efficiency of an optical element and an optical waveguide.
Further, in the flexible optical waveguide of the present invention, as shown in FIG. 5G ′, the core layer is formed with the core pattern 8, and the core pattern 8 is surrounded by the lower cladding layer 2 and the upper cladding layer 7. It is preferable that it is a shape.

As a suitable manufacturing method for obtaining the flexible optical waveguide of this invention, the method which has the (I)-(V) process as described below can be mentioned, for example. Hereinafter, it describes in detail for every process, referring to FIG.
In the manufacturing method described below, when forming the clad layer and the core layer, the clad layer and core layer forming resin can be laminated by application such as spin coating. It is more preferable to use a resin film for forming a core layer. By using such a film, the film thickness can be easily controlled and the handleability is excellent. In the process diagram shown in FIG. 2, a case where a resin film is used will be described as an example.

(I) Step (I) Step is a step of forming a first cladding layer. There are various methods for forming the first cladding layer. As shown in FIG. 2A, the first cladding layer is formed by curing the cladding layer forming resin of the cladding layer forming resin film. A method of forming the (lower cladding layer) 2 is preferable.
As shown in FIG. 3, the clad layer forming resin film 10 used here is obtained by coating a base film 11 with a clad layer forming resin 12, and a protective film (separator) 13 is provided as necessary. It has a laminated structure.
In addition, the protective film is provided for the purpose of improving the winding property when manufacturing the clad layer forming resin film or in the form of a roll in the production of the clad layer forming resin film, The thing similar to what is illustrated as a base film mentioned later can be used. The protective film is preferably not subjected to an adhesive treatment such as a corona treatment in order to facilitate peeling from the clad layer forming resin film, and may be subjected to a release treatment or an antistatic treatment as necessary. .

  As the base film 11, the clad layer forming resin 12 is applied, and it becomes a support base in the subsequent optical waveguide manufacturing process, and there is no particular limitation on the material, but flexibility and toughness From the viewpoint of having polyester, such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyethylene, polypropylene, polyamide, polycarbonate, polyphenylene ether, polyether sulfide, polyphenylene sulfide, polyarylate, liquid crystal polymer, polysulfone, polyethersulfone , Polyether ether ketone, polyether imide, polyamide imide, polyimide, aramid and the like.

Among these substrate films, in the production of optical waveguides, polyethylene terephthalate, polyethylene naphthalate, etc. from the viewpoint of heat resistance that can be produced, resistance to developer, ultraviolet transparency for curing the clad layer, and availability Polyester, polyamide, polyphenylene sulfide, and aramid are preferably used for the base film. In particular, aramid, polyamide film, polyethylene naphthalate film and polyphenylene sulfide film are used from the viewpoint of heat resistance and low shrinkage during the production of optical waveguides, and polyethylene is used from the viewpoint of ultraviolet transparency for curing the cladding layer. A terephthalate film is particularly preferred.
The surface of the base film may be treated in order to improve adhesion with the clad layer forming resin 12, for example, physical or chemical surface treatment such as an oxidation method or an unevenness method. Can be mentioned. Examples of the oxidation method include corona treatment, chromium oxidation treatment, flame treatment, hot air treatment, ozone / ultraviolet treatment method, and examples of the unevenness method include a sand blast method and a solvent treatment method.

  In the step (I), when a protective film 13 is provided on the opposite side of the base film of the clad layer forming resin film (see FIG. 3), the protective film is peeled off, and then the clad layer forming resin film is removed. The first clad layer (lower clad layer) 2 is formed by curing with light (ultraviolet light (UV) or the like) or heating.

The clad layer forming resin used in the present invention is not particularly limited as long as it is a resin composition that has a lower refractive index than the core layer and is cured by light or heat, and includes a thermosetting resin composition and a photosensitive resin composition. Can be used.
More preferably, the clad layer forming resin is composed of a resin composition containing (A) a base polymer, (B) a light or thermopolymerizable compound, and (C) a light or thermopolymerization initiator. preferable.

The (A) base polymer used here is for forming a clad layer and ensuring the strength of the clad layer, and is not particularly limited as long as the object can be achieved, phenoxy resin, epoxy resin, (Meth) acrylic resin, polycarbonate resin, polyarylate resin, polyether amide, polyether imide, polyether sulfone, etc., or derivatives thereof. These base polymers may be used alone or in combination of two or more.
Of the base polymers exemplified above, from the viewpoint of high heat resistance, the main chain preferably has an aromatic skeleton, and particularly preferably a phenoxy resin.
From the viewpoint of three-dimensional crosslinking and improving heat resistance, an epoxy resin, particularly an epoxy resin that is solid at room temperature is preferable. Furthermore, (B) compatibility with the light or thermopolymerizable compound, which will be described in detail later, is important for ensuring the transparency of the resin film for forming the clad layer. From this point, the above phenoxy resin and (meta ) Acrylic resin is preferred. Here, (meth) acrylic resin means acrylic resin and methacrylic resin.

  Among phenoxy resins, phenoxy resin using at least one selected from bisphenol A, bisphenol A type epoxy compound, bisphenol F, bisphenol F type epoxy compound and derivatives thereof as a copolymerization component has heat resistance, adhesion and solubility. It is preferable because it is excellent. Preferred examples of the bisphenol A or bisphenol A type epoxy compound include tetrabromobisphenol A and tetrabromobisphenol A type epoxy compounds. Moreover, as a derivative of bisphenol F or a bisphenol F-type epoxy compound, tetrabromobisphenol F, a tetrabromobisphenol F-type epoxy compound, etc. are mentioned suitably. Specific examples of the bisphenol A / bisphenol F copolymer type phenoxy resin include “Phenotote YP-70” (trade name) manufactured by Toto Kasei Co., Ltd.

  Specific examples of the bisphenol A type epoxy resin include, for example, “Epototo YD-7020, Epototo YD-7019, Epototo YD-7007” (all trade names) manufactured by Toto Chemical Co., Ltd. “Epicoat 1010, Epicoat 1009, Epicoat 1008” (all trade names) manufactured by Japan Epoxy Resin Co., Ltd. and the like can be mentioned.

  (A) The molecular weight of the base polymer is preferably 5,000 or more in terms of number average molecular weight, more preferably 10,000 or more, and particularly preferably 30,000 or more, from the viewpoint of film formability. Although there is no restriction | limiting in particular about the upper limit of a number average molecular weight, From the viewpoint of (B) compatibility with light or a thermopolymerizable compound, light or thermosetting (exposure developability), it is 1,000,000 or less. It is preferable that it is 500,000 or less, particularly 200,000 or less. The number average molecular weight in the present invention is a value measured by gel permeation chromatography (GPC) and converted to standard polystyrene.

  (A) It is preferable that the compounding quantity of a base polymer shall be 10-80 mass% with respect to the total amount of (A) component and (B) component. When the blending amount is 10% by mass or more, there is an advantage that it is easy to form a thick film having a thickness of about 50 to 500 μm necessary for forming an optical waveguide. On the other hand, when it is 80% by mass or less, light or heat is obtained. The curing reaction proceeds sufficiently. From the above viewpoint, the blending amount of (A) the base polymer is more preferably 20 to 70% by mass.

  Next, (B) the light or thermopolymerizable compound is not particularly limited as long as it is polymerized by irradiation with light such as ultraviolet rays or heating, and a compound or molecule having two or more epoxy groups in the molecule. And compounds having an ethylenically unsaturated group.

  Specific examples of compounds having two or more epoxy groups in the molecule include bisphenol A type epoxy resins, tetrabromobisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol AD type epoxy resins, naphthalene type epoxy resins, etc. Bifunctional aromatic glycidyl ether; phenol novolac type epoxy resin, cresol novolac type epoxy resin, dicyclopentadiene-phenol type epoxy resin, tetraphenylol ethane type epoxy resin, etc. polyfunctional aromatic glycidyl ether; polyethylene glycol type epoxy resin, Bifunctional aliphatic glycidyl ether such as polypropylene glycol type epoxy resin, neopentyl glycol type epoxy resin, hexanediol type epoxy resin; hydrogenated bisphenol A type epoxy Bifunctional alicyclic glycidyl ethers such as resins; polyfunctional aliphatic glycidyl ethers such as trimethylolpropane type epoxy resins, sorbitol type epoxy resins and glycerin type epoxy resins; bifunctional aromatic glycidyl esters such as phthalic acid diglycidyl esters; Bifunctional alicyclic glycidyl esters such as tetrahydrophthalic acid diglycidyl ester and hexahydrophthalic acid diglycidyl ester; bifunctional aromatic glycidyl amines such as N, N-diglycidylaniline and N, N-diglycidyltrifluoromethylaniline N, N, N ′, N′-tetraglycidyl-4,4-diaminodiphenylmethane, 1,3-bis (N, N-glycidylaminomethyl) cyclohexane, N, N, O-triglycidyl-p-aminophenol Polyfunctional aromatic glycidi such as Amines; bifunctional alicyclic epoxy resins such as alicyclic diepoxy acetals, alicyclic diepoxy adipates, alicyclic diepoxy carboxylates, vinylcyclohexene dioxide; bifunctional heterocyclic epoxy resins such as diglycidyl hydantoin A polyfunctional heterocyclic epoxy resin such as triglycidyl isocyanurate; a bifunctional or polyfunctional silicon-containing epoxy resin such as an organopolysiloxane type epoxy resin;

  These compounds having two or more epoxy groups in the molecule usually have a molecular weight of about 100 to 2,000, more preferably about 150 to 1,000, and those that are liquid at room temperature are suitably used. Moreover, these compounds can be used individually or in combination of 2 or more types, Furthermore, it can also be used in combination with another photo or thermopolymerizable compound. In addition, the molecular weight of the light or thermopolymerizable compound in the present invention can be measured by GPC method or mass spectrometry.

  Specific examples of the compound having an ethylenically unsaturated group in the molecule include (meth) acrylate, vinylidene halide, vinyl ether, vinyl pyridine, vinyl phenol, etc. Of these, transparency and heat resistance are included. From the viewpoint, (meth) acrylate is preferable, and any of monofunctional, bifunctional, trifunctional or higher can be used. Here, (meth) acrylate refers to acrylate or methacrylate. An acrylate means a compound having an acryloyl group, and a methacrylate means a compound having a methacryloyl group. Moreover, monofunctional here means having any one of an acryloyl group and a methacryloyl group.

  Monofunctional (meth) acrylates include methoxypolyethylene glycol (meth) acrylate, phenoxypolyethylene glycol (meth) acrylate, lauryl (meth) acrylate, isostearyl (meth) acrylate, and 2- (meth) acryloyloxyethyl succinic acid. , Paracumylphenoxyethylene glycol (meth) acrylate, 2-tetrahydropyranyl (meth) acrylate, isobornyl (meth) acrylate, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, benzyl (meth) acrylate Etc.

  As the bifunctional (meth) acrylate, ethoxylated 2-methyl-1,3-propanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 1,6-hexanediol di (meth) Acrylate, 2-methyl-1,8-octanediol diacrylate, 1,9-nonanediol di (meth) acrylate, 1,10-nonanediol di (meth) acrylate, ethoxylated polypropylene glycol di (meth) acrylate, propoxy Ethoxylated bisphenol A diacrylate, ethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol Di (meth) acrylate, ethoxylated bisphenol A di (meth) acrylate, tricyclodecane di (meth) acrylate, ethoxylated cyclohexanedimethanol di (meth) acrylate, 2-hydroxy-1-acryloxy-3-methacryloxypropane, 2-hydroxy-1,3-dimethacryloxypropane, 9,9-bis [4- (2-acryloyloxyethoxy) phenyl] fluorene, 9,9-bis [3-phenyl-4-acryloylpolyoxyethoxy) fluorene Bisphenol A type, phenol novolak type, cresol novolak type, glycidyl ether type epoxy (meth) acrylate, and the like.

  Furthermore, as tri- or more functional (meth) acrylates, ethoxylated isocyanuric acid tri (meth) acrylate, ethoxylated glycerin tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, ethoxylated trimethylolpropane tri (meth) Acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, ethoxylated pentaerythritol tetra (meth) acrylate, propoxylated pentaerythritol tetra (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, caprolactone modified ditri Examples include methylolpropane tetraacrylate and dipentaerythritol hexa (meth) acrylate. These can be used alone or in combination of two or more.

  Here, (meth) acrylate means acrylate and methacrylate. The blending amount of the (B) light or thermopolymerizable compound is preferably 20 to 90% by mass with respect to the total amount of the component (A) and the component (B). When the blending amount is 20% by mass or more, the base polymer can be easily entangled and cured, and when it is 90% by mass or less, a sufficiently thick clad layer can be easily formed. it can. From the above viewpoint, the blending amount of the (B) light or thermopolymerizable compound is more preferably 30 to 80% by mass.

  Next, the photo or thermal polymerization initiator of component (C) is not particularly limited. For example, as an initiator for an epoxy compound, aryl diazonium salts such as p-methoxybenzenediazonium hexafluorophosphate; diphenyliodonium hexafluorophosphonium salt; Diaryl iodonium salts such as diphenyliodonium hexafluoroantimonate salt; triphenylsulfonium hexafluorophosphonium salt, triphenylsulfonium hexafluoroantimonate salt, diphenyl-4-thiophenoxyphenylsulfonium hexafluoroantimonate salt, diphenyl-4-thiophenoxy Phenylsulfonium hexafluoroantimonate salt, diphenyl-4-thiophenoxyphenylsulfonium pentafluorohydroxyantimonate Triarylsulfonium salts such as salts; Triarylselenonium salts such as triphenylselenonium hexafluorophosphonium salt, triphenylselenonium borofluoride salt, triphenylselenonium hexafluoroantimonate salt; dimethylphenacylsulfonium hexafluoroantimonate Salts, dialkylphenazylsulfonium salts such as diethylphenacylsulfonium hexafluoroantimonate salt; dialkyl-4-hydroxyphenyl such as 4-hydroxyphenyldimethylsulfonium hexafluoroantimonate salt, 4-hydroxyphenylbenzylmethylsulfonium hexafluoroantimonate salt Sulfonium salt; α-hydroxymethylbenzoin sulfonate, N-hydroxyimide sulfonate, α-sulfo Rokishiketon, such as sulfonic acid esters, such as β- sulfo Niro carboxymethyl ketone.

  Moreover, the initiator of the compound which has an ethylenically unsaturated group in a molecule | numerator can also be used, for example, benzophenone, N, N'-tetramethyl-4,4'-diaminobenzophenone (Michler ketone), N, N'-tetraethyl- 4,4′-diaminobenzophenone, 4-methoxy-4′-dimethylaminobenzophenone, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butan-1-one, 2,2-dimethoxy- 1,2-diphenylethane-1-one, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1- [4- (2-hydroxyethoxy) phenyl] -2 -Hydroxy-2-methyl-1-propan-1-one, 1,2-methyl-1- [4- (methylthio) pheny Aromatic ketones such as 2-morpholinopropan-1-one; 2-ethylanthraquinone, phenanthrenequinone, 2-tert-butylanthraquinone, octamethylanthraquinone, 1,2-benzanthraquinone, 2,3-benzanthraquinone, 2-phenylanthraquinone, 2,3-diphenylanthraquinone, 1-chloroanthraquinone, 2-methylanthraquinone, 1,4-naphthoquinone, 9,10-phenanthraquinone, 2-methyl 1,4-naphthoquinone, 2,3- Quinones such as dimethyl anthraquinone; benzoin ether compounds such as benzoin methyl ether, benzoin ethyl ether and benzoin phenyl ether; benzoin compounds such as benzoin, methyl benzoin and ethyl benzoin; Benzyl derivatives such as 2-aryl; 2- (o-chlorophenyl) -4,5-diphenylimidazole dimer, 2- (o-chlorophenyl) -4,5-di (methoxyphenyl) imidazole dimer, 2- ( o-fluorophenyl) -4,5-diphenylimidazole dimer, 2- (o-methoxyphenyl) -4,5-diphenylimidazole dimer, 2- (p-methoxyphenyl) -4,5-diphenylimidazole 2,4,5-triarylimidazole dimer such as dimer; bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide, bis (2,6-dimethoxybenzoyl) -2,4,4- Phosphine oxides such as trimethylpentylphosphine oxide and 2,4,6-trimethylbenzoyldiphenylphosphine oxide Sides; acridine derivatives such as 9-phenylacridine and 1,7-bis (9,9'-acridinyl) heptane; N-phenylglycine, N-phenylglycine derivatives, coumarin compounds and the like. In the above 2,4,5-triarylimidazole dimer, the aryl group substituents of the two 2,4,5-triarylimidazoles may give the same and symmetrical compounds, or differently asymmetrical A compound may be provided. Moreover, you may combine a thioxanthone type compound and a tertiary amine compound like the combination of diethyl thioxanthone and dimethylaminobenzoic acid. Of these compounds, aromatic ketones and phosphine oxides are preferred from the viewpoint of improving the transparency of the core layer and the cladding layer. These (C) light or thermal polymerization initiators can be used alone or in combination of two or more.

  (C) It is preferable that the compounding quantity of light or a thermal-polymerization initiator shall be 0.1-10 mass parts with respect to 100 mass parts of total amounts of (A) component and (B) component. If it is 0.1 part by mass or more, sensitivity to light and heat is sufficient, while if it is 10 parts by mass or less, only the surface of the optical waveguide is selectively cured, and curing does not become insufficient. Further, it is preferable that the propagation loss does not increase due to absorption of light or the thermal polymerization initiator itself. From the above viewpoint, the blending amount of (C) light or the thermal polymerization initiator is more preferably 1 to 5 parts by mass.

  In addition to the above, the clad layer forming resin of the present invention contains an antioxidant, an anti-yellowing agent, an ultraviolet absorber, a visible light absorber, a colorant, a plasticizer, a stabilizer, and a filler as necessary. You may add what is called additives, such as an agent, in the ratio which does not have a bad influence on the effect of this invention.

  The resin film for forming a clad layer can be easily produced by dissolving a resin composition containing the components (A) to (C) in a solvent, applying the resin composition to the base film, and removing the solvent. The solvent used here is not particularly limited as long as it can dissolve the resin composition. For example, acetone, methyl ethyl ketone, methyl cellosolve, ethyl cellosolve, toluene, N, N-dimethylacetamide, propylene glycol monomethyl ether, A solvent such as propylene glycol monomethyl ether acetate, cyclohexanone, N-methyl-2-pyrrolidone, or a mixed solvent thereof can be used. The solid content concentration in the resin solution is preferably about 30 to 80% by mass.

  Regarding the thickness of the first cladding layer, the thickness after drying is preferably in the range of 5 to 500 μm. When the thickness is 5 μm or more, a clad thickness necessary for light confinement can be secured, and when the thickness is 500 μm or less, it is easy to control the film thickness uniformly. From the above viewpoint, the thickness of the cladding layer is preferably in the range of 10 μm to 100 μm.

  Further, the first clad layer (lower clad layer) formed first and the second clad layer (upper clad layer) for embedding a core pattern described later may be the same or different. However, in order to embed the core pattern, it is preferable that the thickness of the second cladding layer (upper cladding layer) is larger than the thickness of the core layer.

Step (II) The step (II) is a step of forming a first core layer by laminating a resin film for forming a core layer on an end portion on the first cladding layer (lower cladding layer).
As a method of laminating the core layer forming resin film to form the first core layer, the core layer forming resin film is cut into a required size and heated at one end or both ends. It can be obtained by bonding using pressure bonding or an adhesive / pressure-sensitive adhesive.

Further, as shown in FIG. 2 (b), a masking film 4 is disposed in a portion other than the end portion, and includes a first portion including both a portion where the masking film 4 is disposed and a portion where the masking film 4 is not disposed. The first core layer is formed by laminating the core layer forming resin film 20 on the entire surface of the cladding layer 2 and peeling off the core layer forming resin film on the masking film together with the masking film. (See FIG. 2 (c)).
The method has no step of cutting the core layer forming resin film in advance compared to the above method using the core forming resin film cut to a required size, and the step of laminating the core layer forming resin film Is also efficient and preferable since it may be performed once.
In the present invention, the end portion refers to a range that does not reach the bent portion. The length can be freely changed depending on the design, but it should be about 3 to 20% of the total length of the optical waveguide from the end of the optical waveguide toward the waveguide direction from the viewpoint of ease of handling. Is preferred.

The masking film 4 is not particularly limited as long as it can be easily peeled off from the first clad layer 2, and is the same as that exemplified as the base film of the clad layer forming resin film. A polyester film such as a PET film is preferable from the viewpoint of easy handling.
The masking film is also preferably not subjected to an adhesive treatment such as corona treatment in order to facilitate peeling from the clad layer 2, and may be subjected to a mold release treatment or an antistatic treatment as necessary. .

Examples of the core layer forming resin film used in the present invention include those obtained by coating a core layer forming resin on a base film, or those composed of a core layer forming resin alone. It is easier to handle and it is preferable to use a film in which a core layer forming resin is formed on a film. More specifically, a configuration as shown in FIG. That is, the core layer forming resin 22 is formed on the base film 21, and the core layer forming resin film is protected for the purpose of, for example, improving the winding property at the time of manufacturing in a roll shape. A protective film 23 is provided on the opposite side of the base film 21. As a protective film, the thing similar to what was mentioned as an example as a base film of the said resin film for clad layer formation can be used.
The protective film and the base film are preferably not subjected to an adhesion treatment such as a corona treatment in order to facilitate peeling from the core layer forming resin film, and are subjected to a release treatment or an antistatic treatment as necessary. May be.

When laminating the core layer-forming resin film 20, it is preferable to laminate the core layer-forming resin film under reduced pressure from the viewpoint of adhesion and followability. The heating temperature here is preferably 50 to 130 ° C., and the pressure bonding pressure is preferably about 0.1 to 1.0 MPa (1 to 10 kgf / cm ² ). There is no particular limitation.
Moreover, it is preferable to laminate | stack using a roll laminator from a viewpoint of preventing mixing of the bubble between a 1st clad layer and a core layer.

  The resin film for forming a core layer used in the present invention can use a resin composition that is designed so that the core layer has a higher refractive index than that of the cladding layer and can form a core pattern with actinic rays. Compositions are preferred. Specifically, it is preferable to use the same resin composition as that used in the clad layer forming resin. That is, it is a resin composition containing the components (A), (B) and (C) and optionally containing the optional components.

  The resin film for forming a core layer can be easily produced by dissolving a resin composition containing the components (A) to (C) in a solvent, applying the resin composition to a base film, and removing the solvent. The solvent used here is not particularly limited as long as it can dissolve the resin composition. For example, acetone, methyl ethyl ketone, methyl cellosolve, ethyl cellosolve, toluene, N, N-dimethylformamide, N, N-dimethyl A solvent such as acetamide, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, cyclohexanone, N-methyl-2-pyrrolidone, or a mixed solvent thereof can be used. The solid content concentration in the resin solution is usually preferably about 30 to 80% by mass.

The thickness of the resin film for forming the core layer is not particularly limited, and is appropriately determined according to the thickness of the core layer after drying. The optical waveguide obtained by the present invention has a core used in the steps (II) and (III) so that the thickness of the core layer is different between at least one end and the other end, and each has a desired thickness. The thickness of the layer forming resin film is controlled.
The optical waveguide obtained by the present invention is adjusted so that the thickness of the core layer at the end is usually 10 to 100 μm. When the thickness of the core layer is 10 μm or more, there is an advantage that the alignment tolerance can be increased in the coupling with the light emitting / receiving element or the optical fiber after the optical waveguide is formed, and when the thickness is 100 μm or less, the light receiving / emitting after the optical waveguide is formed. In coupling with an element or an optical fiber, there is an advantage that coupling efficiency is improved. From the above viewpoints, the thickness of the core layer at the end is preferably in the range of 30 to 70 μm.
On the other hand, the thickness of the core layer other than the end portion is more advantageous for bending durability as it is thinner, and a certain amount of thickness is necessary from the viewpoint of suppressing optical loss. From the above viewpoint, the minimum thickness of the core layer in the portion other than the end is preferably in the range of 30 to 80%, more preferably in the range of 40 to 60% with respect to the thickness of the end.

When the core layer-forming resin film is obtained by forming the core layer-forming resin on the base film, the base film and the core layer-forming resin film are composed of the core layer-forming resin alone. In this case, the material of the base film used in the process of manufacturing the resin film for forming the core layer is not particularly limited, but it is easy to peel off later, and has a viewpoint of heat resistance and solvent resistance. Preferred examples thereof include polyesters such as polyethylene terephthalate, polypropylene, and polyethylene.
Moreover, it is preferable that the thickness of this base film is 5-50 micrometers. When it is 5 μm or more, there is an advantage that the strength as a support is easily obtained, and when it is 50 μm or less, there is an advantage that a gap with the mask at the time of pattern formation becomes small and a finer pattern can be formed. From the above viewpoint, the thickness of the base film is more preferably in the range of 10 to 40 μm, and particularly preferably 15 to 30 μm.

Moreover, it is preferable to use a highly transparent flexible base material in order to improve the transmittance of exposure light and reduce the side wall roughness of the core pattern. The haze value of the highly transparent base film is preferably 5% or less, more preferably 3% or less, and particularly preferably 2% or less. The haze value is measured in accordance with JIS K7105, and can be measured with a commercially available turbidimeter such as NDH-1001DP (manufactured by Nippon Denshoku Industries Co., Ltd.). Such a base film is available from Toyobo Co., Ltd. under the trade names “Cosmo Shine A1517” and “Cosmo Shine A4100”.
In addition, in order to make peeling easily, the said base film may be subjected to mold release treatment, antistatic treatment or the like.

Step (III) In step (III), as shown in FIG. 2D, a core layer-forming resin film 20 is laminated on the entire surface of the first core layer 3 and the first cladding layer 2 to form a first step. This is a step of forming the second core layer 5.
The resin film for forming the core layer used here is the same as that used for forming the first core layer 3 described above from the viewpoint of obtaining stable light propagation characteristics. preferable.
Further, regarding the lamination conditions of the core layer forming resin film, the same conditions as those for forming the first core layer 3 are preferable.

On the surface of the second core layer 5 formed as described above, a step is generated between the portion where the first core layer 3 is formed and the other portions as shown in FIG. In the step (III), from the viewpoint of reducing optical loss, a core layer-forming resin film is laminated on the entire surface of the first core layer and the first cladding layer, and then the step on the surface is smoothed and tapered. It is preferable to form a second core layer having a shape. As a method of smoothing, as shown in FIG. 2 (e), there is a method of compressing the laminate obtained from the steps (I) to (III) from above and below. The compression method is not particularly limited, but a flat plate laminator is preferably used from the viewpoint that smoothing can be performed efficiently.
In the present invention, the flat plate type laminator refers to a laminator in which a laminated material is sandwiched between a pair of flat plates and pressed by pressing the flat plate. As the flat plate laminator, for example, a vacuum and pressure laminator described in JP-A-11-320682 can be suitably used.
The pressurizing material 31 is not particularly limited as long as it has a certain hardness, and examples thereof include a metal plate such as a SUS plate, high hardness silicone rubber, and the like.

The smoothing using the flat plate laminator is preferably performed in a reduced pressure atmosphere from the viewpoint of smoothing and the improvement of adhesion. The upper limit of the degree of vacuum, which is a measure of pressure reduction, is preferably 10,000 Pa or less, and more preferably 1000 Pa or less. On the other hand, the lower limit of the degree of vacuum is preferably about 10 Pa from the viewpoint of productivity (the time required for evacuation). The heating temperature is preferably 40 to 130 ° C., and the pressing pressure is preferably 0.1 to 1.0 MPa (1 to 10 kgf / cm ² ).

By smoothing the step on the surface of the second core layer as described above, the first core layer 3 and the second core layer 5 are integrated as shown in FIG. 6, the core is thick at the end and thin at other portions, and has a taper shape with no step from the thick to the thin.
The thickness of the core is as described above, and the inclination angle from the thick part to the thin part is preferably in the range of 0.1 to 2 degrees from the viewpoint of low optical loss, A range of 1 degree is more preferred.

Step (IV) The step (IV) is a step of patterning the core layer 6 (first core layer and second core layer). As a patterning method, various methods can be used, but it is preferable to carry out exposure and development using a photosensitive resin as the core layer forming resin. FIG. 5 (f ′) shows the stacked body after patterning viewed from the x direction in FIG. 2 (f).
As an exposure method, specifically, an actinic ray is irradiated in an image form through a negative mask pattern. Examples of the active light source include known light sources that effectively emit ultraviolet rays, such as carbon arc lamps, mercury vapor arc lamps, ultrahigh pressure mercury lamps, high pressure mercury lamps, and xenon lamps. In addition, those that effectively emit visible light, such as a photographic flood light bulb and a solar lamp, can be used.

Next, after the post-exposure heating as necessary, if the base film of the core layer forming resin film remains, the base film is peeled off, and the unexposed portion is removed by wet development, dry development, or the like. To develop a core pattern. In the case of wet development, among organic solvents, alkaline aqueous solutions, aqueous developers, etc., using a developer corresponding to the composition of the resin film, for example, by a known method such as spraying, rocking immersion, brushing, scraping, etc. develop.
As the developer, an organic solvent, an alkaline aqueous solution or the like that is safe and stable and has good operability is preferably used. Examples of the organic solvent developer include 1,1,1-trichloroethane, N-methylpyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide, cyclohexanone, methyl isobutyl ketone, and γ-butyrolactone. It is done. These organic solvents may be added with water in the range of 1 to 20% by mass in order to prevent ignition.

  Examples of the base of the alkaline aqueous solution include alkali hydroxides such as lithium, sodium, or potassium hydroxide, alkali carbonates such as lithium, sodium, potassium, or ammonium carbonate or bicarbonate, potassium phosphate, and phosphoric acid. Alkali metal phosphates such as sodium and alkali metal pyrophosphates such as sodium pyrophosphate and potassium pyrophosphate are used. Examples of the alkaline aqueous solution used for development include a dilute solution of 0.1 to 5% by mass of sodium carbonate, a dilute solution of 0.1 to 5% by mass of potassium carbonate, and a dilute solution of 0.1 to 5% by mass of sodium hydroxide. Preferred examples include a solution and a dilute solution of 0.1 to 5% by mass sodium tetraborate. Moreover, it is preferable to make pH of the alkaline aqueous solution used for image development into the range of 9-14, and the temperature is adjusted according to the developability of the layer of the photosensitive resin composition. In the alkaline aqueous solution, a surfactant, an antifoaming agent, a small amount of an organic solvent for accelerating development, and the like may be mixed.

  The aqueous developer comprises water or an alkaline aqueous solution and one or more organic solvents. Examples of the alkaline substance include borax, sodium metasilicate, tetramethylammonium hydroxide, ethanolamine, ethylenediamine, diethylenetriamine, 2-amino-2-hydroxymethyl-1,3-propanediol, 1 , 3-diaminopropanol-2, morpholine and the like. The pH of the developer is preferably as low as possible within a range where the resist can be sufficiently developed, preferably pH 8-12, more preferably pH 9-10. Examples of the organic solvent include triacetone alcohol, acetone, ethyl acetate, alkoxyethanol having an alkoxy group having 1 to 4 carbon atoms, ethyl alcohol, isopropyl alcohol, butyl alcohol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono And butyl ether. These are used alone or in combination of two or more. The concentration of the organic solvent is usually preferably 2 to 90% by mass, and the temperature can be adjusted according to the developability. Further, a small amount of a surfactant, an antifoaming agent or the like can be mixed in the aqueous developer.

Moreover, you may use together 2 or more types of image development methods as needed. Examples of the development method include a dip method, a battle method, a spray method such as a high-pressure spray method, brushing, and slapping.
As the treatment after development, the core pattern may be further cured and used by heating at about 60 to 250 ° C. or exposure at about 0.1 to 1000 mJ / cm ² as necessary.

Step (V) The step (V) is a step of embedding the core pattern by forming a second clad layer on the core pattern obtained by a method such as exposure and development of the core layer 6 and the first clad layer. The step is preferably performed using a clad layer forming resin film, and after embedding the core pattern, the resin of the clad layer forming resin film is cured to form a second clad layer (upper clad layer). Is preferably formed (see FIG. 2G and FIG. 5G ′).
At this time, the thickness of the second cladding layer is preferably larger than the thickness of the core layer (core pattern). The second clad layer forming resin can be cured by light or heat in the same manner as the first clad layer is formed.

The second clad layer forming resin film used here is the same as the first clad layer forming resin film, and as shown in FIG. 3, the clad layer forming resin 12 is laminated on the base film 11. The protective film (separator) 13 is laminated as necessary. The material of the base film 11 is the same as that of the base film in the first clad layer forming resin film. Further, the clad layer forming resin is the same as the clad layer forming resin in the first clad layer forming resin film.
Further, when a protective film is provided on the opposite side of the base film of the second clad layer forming resin film (see FIG. 3), the protective film is peeled off and then the clad layer forming resin film is lighted or heated. To form a second cladding layer. The protective film is preferably not subjected to adhesion treatment in order to facilitate peeling from the clad layer forming resin film, and may be subjected to mold release treatment or antistatic treatment as necessary.
In the flexible optical waveguide of the present invention, the first and second clad layer forming resin films may be peeled after the second clad layer (upper clad layer) is formed.

In the present invention, the base film of the resin film for forming a clad layer also serves as a support in the manufacturing process of the flexible optical waveguide. Since this base film can be larger than a silicon substrate or the like conventionally used as a support, it is easy to increase the area and provides a method for manufacturing a flexible optical waveguide with excellent productivity. be able to.
The base film may be left on one side of the flexible optical waveguide, but a flexible optical waveguide with less warpage can be produced by using a symmetrical structure in which both sides are peeled off. Moreover, the flexible optical waveguide can be thinned by peeling the base film.

  Moreover, it is preferable that a humidification process is included in the process of peeling a base film. This is because the humidification treatment can reduce the adhesion between the base film and the clad layer and can easily peel the base film without damaging the optical waveguide. The humidification treatment is preferably performed under high temperature and high humidity conditions, boiling conditions, pressure cooker conditions, and the like, since the treatment time can be shortened when heating is used in combination.

  As is clear from the description of the step (V), the flexible optical waveguide of the present invention has a shape in which the core pattern is surrounded by the upper clad layer and the lower clad layer. Have.

  As shown in FIG. 6, the flexible optical waveguide of the present invention has two or more cores 8, and the core 8 has a cross-sectional area larger than that of the core 8 at the other end. There may be both small cores. Further, as shown in FIG. 7, the end portion with the smaller cross-sectional area of the core 8 may be closer to the center along the light propagation axis than the end portion with the larger cross-sectional area of the core 8.

Further, as shown in FIG. 8, it is preferable that the width of the upper clad layer is smaller than the width of the lower clad layer in the intermediate portion (FIG. 8 shows a perspective view seen from the upper clad side). This is because the bending durability is further improved by the narrow width of the upper cladding layer. The smaller the width of the upper clad layer in the intermediate part, the better the bending durability in the intermediate part. However, in order to exert a sufficient function as the clad layer, the upper clad layer completely covers the core part. The width is required to be embedded and maintain good light propagation characteristics. Considering the above points, the width x of the upper cladding layer is preferably about 20 to 60%, more preferably 20 to 50% with respect to the width y of the lower cladding layer.
Thus, as a method of making the width of the upper clad layer smaller than the width of the lower clad layer in the intermediate portion, the second clad layer forming resin film is exposed and developed, and the core pattern is embedded. There is a method of forming a second clad layer (upper clad layer) 7 having a smaller width than the first clad layer (lower clad layer) 2 in the intermediate portion. In addition, an upper clad layer forming resin film having a shape in which the width of the upper clad layer in the intermediate portion is smaller than the width of the lower clad layer is prepared in advance, and this is laminated on the core pattern. A method of embedding the core pattern can also be used.

By combining the flexible optical waveguide of the present invention with a flexible electrical circuit board (hereinafter referred to as FPC), a flexible type opto-electric composite circuit board can be produced. In the photoelectric composite wiring board combined with the FPC, the entire thickness increases by the FPC, so that the thickness of the optical waveguide at the bent portion is very important for improving the flexibility.
As a method of compounding, in addition to a method of laminating separately manufactured optical waveguides and electrical wiring boards using an adhesive, etc., a method of building up an optical waveguide on an FPC, and a polyimide with copper foil Another example is a method of forming an FPC after forming an optical waveguide on a top by patterning a copper circuit.

Examples of the configuration of the optoelectric composite wiring board of the present invention include, for example, one in which an optical waveguide is bonded to one side of an electrical wiring board. Moreover, you may have an optical waveguide on both surfaces of an electrical wiring board. With such a configuration, the number of optical wirings of the photoelectric composite wiring board can be increased, and the optical transmission capacity can be increased. Moreover, since it becomes a vertically symmetrical structure, the warpage of the photoelectric composite wiring board can be suppressed.
Moreover, the structure which has an adhesive bond layer on both sides of an optical waveguide, and has an electrical wiring board on both surfaces may be sufficient. By adopting such a configuration, a vertically symmetrical structure is obtained, so that it is possible to suppress warpage of the photoelectric composite wiring board and to improve bending resistance. Note that the electrical wiring board does not necessarily have to be provided on both sides, and for the purpose of suppressing warpage and improving bending resistance, a material having the same physical properties as the electrical wiring board, such as a base material of the electrical wiring board or an electrical insulating layer, is used. A cover film may be provided on the opposite side of the electric wiring board.
Furthermore, a structure in which the optical waveguide and the opto-electric composite circuit board are multilayered may be used. With such a configuration, the signal transmission capacity can be further increased.

EXAMPLES The present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples.
1. Tensile modulus and tensile strength From a film to be measured, a sample having a width of 10 mm and a length of 70 mm was obtained, and a tensile tester (“RTM-100” manufactured by Orientec Co., Ltd.) was used in accordance with JIS-K7127. Measurement was performed under the following conditions.
Conditions: distance between grippers 50 mm, temperature 25 ° C., pulling speed 50 mm / min
The tensile elastic modulus was calculated by the following formula using the first linear portion of the tensile stress-strain curve. In the tensile stress-strain curve, the maximum strength until breakage was taken as the tensile strength.
1. Tensile modulus (MPa) = Stress difference between two points on a straight line (N) ÷ Original average cross-sectional area of optical waveguide film (mm ² ) ÷ Strain difference between the same two points Bending durability test Bending durability test for the photoelectric composite wiring boards manufactured in each example and comparative example using a sliding bending durability tester (manufactured by Daisho Electronics Co., Ltd.) as shown in FIG. Went. The test was performed on the photoelectric composite wiring board 41 obtained in each example and comparative example with the flexible optical waveguide disposed inside the bending shaft 44. Also, the bending radius (R), carried out under the condition of 1.5 mm, slide speed 80 mm / sec, the test under the conditions of a distance 20mm between X ¹ to X ² was carried out. For the evaluation, the maximum number of times of breaking was determined by observing the presence or absence of breaking every 10,000 times. The bending axis 44 does not actually exist, but is a virtual axis when the photoelectric composite wiring board is bent and slid.

Example 1
(1) Production of a resin film for forming a cladding layer (A) As a binder polymer, 48 parts by mass of a phenoxy resin (trade name: Phenototo YP-70, manufactured by Toto Kasei Co., Ltd.), (B) a light or thermopolymerizable compound As an alicyclic diepoxycarboxylate (trade name: KRM-2110, molecular weight: 252, manufactured by Asahi Denka Kogyo Co., Ltd.) 49.6 parts by mass, (C) as light or thermal polymerization initiator, triphenylsulfonium hexa Fluoroantimonate salt (trade name: SP-170, manufactured by Asahi Denka Kogyo Co., Ltd.) 2 parts by mass, as a sensitizer, SP-100 (trade name, manufactured by Asahi Denka Kogyo Co., Ltd.) 0.4 parts by mass, 40 parts by mass of propylene glycol monomethyl ether acetate as an organic solvent was weighed into a wide-mouthed plastic bottle, and the temperature was set at 25 ° C. using a mechanical stirrer, shaft and propeller. The mixture was stirred for 6 hours under the conditions of ° C and a rotational speed of 400 rpm to prepare a clad layer forming resin varnish A. After that, using a polyfluorone filter (trade name: PF020, manufactured by Advantech Toyo Co., Ltd.) with a pore size of 2 μm, it is filtered under pressure at a temperature of 25 ° C. and a pressure of 0.4 MPa, and further reduced in pressure using a vacuum pump and a bell jar. Degassed under reduced pressure for 15 minutes under the condition of a degree of 50 mmHg.
The clad layer-forming resin varnish A obtained above was coated on a corona-treated surface of an aramid film (trade name: Miktron, manufactured by Toray Industries, Inc., thickness: 12 μm) (Multicoater TM-MC, ( Coated with Hirano Techseed Co., Ltd., dried at 80 ° C. for 10 minutes, then at 100 ° C. for 10 minutes, and then released as a protective film PET film (trade name: Purex A31, Teijin DuPont Films, Inc.) 25 μm) was attached so that the release surface was on the resin side, and a resin film for forming a clad layer was obtained. At this time, the thickness of the resin layer can be arbitrarily adjusted by adjusting the gap of the coating machine. In this embodiment, the thickness of the lower clad film is adjusted to 20 μm, and the upper clad film is adjusted to 66 μm. did.

(2) Preparation of resin film for forming core layer (A) As binder polymer, 26 parts by mass of phenoxy resin (trade name: Phenototope YP-70, manufactured by Toto Kasei Co., Ltd.), (B) photo or thermopolymerizable compound As a product, 36 parts by mass of 9,9-bis [4- (2-acryloyloxyethoxy) phenyl] fluorene (trade name: A-BPEF, manufactured by Shin-Nakamura Chemical Co., Ltd.) and bisphenol A type epoxy acrylate (trade name) : EA-1020, manufactured by Shin-Nakamura Chemical Co., Ltd.) 36 parts by mass, (C) bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide (trade name: Irgacure 819) as light or thermal polymerization initiator 1 part by weight of Ciba Specialty Chemicals) and 1- [4- (2-hydroxyethoxy) phenyl] -2-hydroxy-2 -Methyl-1-propan-1-one (trade name: Irgacure 2959, manufactured by Ciba Specialty Chemicals) 1 part by weight, except that 40 parts by weight of propylene glycol monomethyl ether acetate was used as the organic solvent Resin varnish B for forming a core layer was prepared in the same manner and conditions. Thereafter, pressure filtration and degassing under reduced pressure were carried out under the same method and conditions as in the above production example.
The resin layer varnish B for core layer formation obtained above is applied to a non-treated surface of a PET film (trade name: Cosmo Shine A1517, manufactured by Toyobo Co., Ltd., thickness: 16 μm) in the same manner as in the above production example. Then, release PET film (trade name: PUREX A31, Teijin DuPont Films Co., Ltd., thickness: 25 μm) is applied as a protective film so that the release surface is on the resin side to form the core layer A resin film was obtained. In this example, the gap of the coating machine was adjusted so that the film thickness was 40 μm.

(3) Fabrication of flexible optical waveguide The release PET film (Purex A31), which is a protective film for the resin film for forming the lower clad layer obtained above, is peeled off, and an ultraviolet exposure machine (EXM, manufactured by Oak Manufacturing Co., Ltd.). -1172), the resin side (opposite side of the base film) was irradiated with ultraviolet rays (wavelength 365 nm) at 1 J / cm ² , and then heat-treated at 80 ° C. for 10 minutes, whereby the first cladding layer (lower cladding layer) ) Was formed (step (I)). The thickness of the lower cladding layer was about 20 μm.

Next, a PET film (trade name: Cosmo Shine A31, manufactured by Toyobo Co., Ltd., thickness: 25 μm) is disposed as a masking film on a portion (90 mm) other than one end of the lower cladding layer, On the lower clad layer (length 20 mm from the end) remaining on one end and the masking film, a roll laminator (HLM-1500, manufactured by Hitachi Chemical Technoplant Co., Ltd.) is used, pressure 0.5 MPa, temperature 50 The core layer-forming resin film was laminated under the conditions of 0 ° C. and a laminating speed of 0.2 m / min.
Next, the core layer forming resin on the masking film was peeled off together with the masking film to obtain a first core layer at one end on the lower cladding layer (step (II)). The thickness of the first core layer was about 40 μm.

  Next, a roll laminator (HLM-1500, manufactured by Hitachi Chemical Technoplant Co., Ltd.) is used on the entire surface including the lower clad layer and the first core layer, pressure 0.5 MPa, temperature 50 ° C., laminating speed 0.2 m / Under the condition of min, the core layer forming resin film was laminated to form a second core layer (step (III)). The thickness of the core layer at one end portion was 77 μm, and the thickness of the core layer at the bent portion was 38 μm.

Next, a vacuum pressurization laminator (MVLP-500, manufactured by Meiki Seisakusho Co., Ltd.) was used as a flat plate laminator, and after evacuation at 500 Pa or less for 7 seconds, pressure 0.4 MPa, temperature 60 ° C., pressurization time 30 seconds. (Step (III)). Note that a SUS plate was used as the pressurizing material.
As a result of the smoothing, the core layer has an inclination that becomes thinner in a tapered shape from one end to the other, and the inclination angle is 0.15 degrees.

Next, ultraviolet rays (wavelength 365 nm) were irradiated with 0.6 J / cm ² with a UV photomask through a negative photomask having a width of 50 μm, followed by heating at 80 ° C. for 5 minutes. Thereafter, the PET film as the support film was peeled off, and the core pattern was developed using a developer (propylene glycol monomethyl ether acetate / N, N-dimethylacetamide = 8/2, mass ratio). Then, it wash | cleaned using the washing | cleaning liquid (isopropanol), and heat-dried at 100 degreeC for 10 minute (s), and obtained the core pattern ((IV) process).

Next, the above clad layer forming resin film was laminated as an upper clad layer under the same laminating conditions as described above (step (V)). Furthermore, after UV irradiation (wavelength 365 nm) is applied to both surfaces at a total of 25 J / cm ² , heat treatment is performed at 160 ° C. for 1 hour to form an upper cladding layer (step (V)), and the base film is placed outside A flexible optical waveguide was manufactured. Furthermore, for peeling off the aramid film, the flexible optical waveguide was treated under high temperature and high humidity conditions of 85 ° C./85% for 24 hours to produce a flexible optical waveguide from which the base film was removed. Table 1 shows the film thickness measurement results of one end and the bent portion of the produced flexible optical waveguide, and the cross-sectional area measurement results of one end and the other end.

In addition, when the refractive index of the core layer and the clad layer was measured by a prism coupler (Model2010) manufactured by Metricon, the core layer was 1.584 and the clad layer was 1.550 at a wavelength of 830 nm. In addition, the insertion loss of the produced flexible optical waveguide (FIG. 1) is calculated by using a surface-emitting laser (850 nm manufactured by EXFO, FLS-300-01-VCL) as a light source, and Q82214 manufactured by Advantest Co., Ltd. as a light receiving sensor. Measured using a GI-50 / 125 multimode fiber (NA = 0.20) as the input fiber and SI-114 / 125 multimode fiber (NA = 0.22) as the output fiber, 1.0 dB there were. As shown in Comparative Example 1 described later, since the insertion loss was 0.8 dB in the flexible optical waveguide having a constant core thickness of 80 μm, the loss increase due to the introduction of the taper structure is sufficiently small as 0.2 dB. It was confirmed.
Moreover, as a result of measuring the tensile elasticity modulus and tensile strength of the obtained flexible optical waveguide by the above method, the tensile elasticity modulus was 2100 MPa and the tensile strength was 100 MPa.

(4) Production of photoelectric composite wiring board (4-1) Production of sheet adhesive HTR-860P-3 (manufactured by Teikoku Chemical Industry Co., Ltd., trade name, glycidyl group-containing acrylic rubber, molecular weight 1 million, Tg- 7 ° C) 100 parts by mass, YDCN-703 (manufactured by Toto Kasei Co., Ltd., trade name, o-cresol novolac type epoxy resin, epoxy equivalent 210), 5.4 parts by mass, YDCN-8170C (manufactured by Toto Kasei Co., Ltd.) Product name, 16.2 parts by mass of bisphenol F type epoxy resin, epoxy equivalent 157), PRIOFEN LF2882 (manufactured by Dainippon Ink & Chemicals, Inc., product name, bisphenol A novolac resin), 15.3 parts by mass, NUCA-189 (Nihon Unicar Co., Ltd., trade name, γ-mercaptopropyltrimethoxysilane) 0.1 parts by mass, NUCA-1160 (Nihon Unica Co., Ltd., trade name, γ-ureidopropyltriethoxysilane) 0.3 parts by mass, A-DPH (Shin Nakamura Chemical Co., Ltd., trade name, dipentaerythritol hexaacrylate) 30 parts by mass, Irgacure 369 (Ciba Specialty Chemicals, trade name, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1-one: I-369) 1.5 parts by mass, cyclohexanone was added The mixture was stirred and mixed and vacuum degassed to obtain an adhesive varnish. This adhesive varnish was applied on a protective film made of 75 μm thick surface release-treated polyethylene terephthalate (Teijin Limited, Teijin Tetron Film: A-31), and dried by heating at 80 ° C. for 30 minutes. An adhesive sheet comprising an adhesive layer and a protective film was obtained. On the adhesive layer side of this adhesive sheet, a light-transmitting support substrate having a thickness of 80 μm (manufactured by Thermo Co., Ltd., low density polyethylene terephthalate / vinyl acetate / low density polyethylene terephthalate three-layer film: FHF- 100) were laminated together to produce a sheet-like adhesive comprising a protective film (surface release-treated polyethylene terephthalate), an adhesive layer, and a light-transmitting support substrate. The thickness of the adhesive layer was 10 μm.

(4-2) Production of photoelectric composite wiring board Using the roll laminator (HLM-1500, manufactured by Hitachi Chemical Technoplant Co., Ltd.), the pressure of 0.4 MPa, the temperature of 50 ° C., and the laminate of the flexible optical waveguide produced above. The laminate was laminated on the adhesive layer side of the sheet-like adhesive from which the protective film was peeled off under the condition of a speed of 0.2 m / min. Next, ultraviolet light (365 nm) is irradiated from the support substrate side of the sheet-like adhesive at 250 mJ / cm ² to reduce the adhesive force between the adhesive layer and the support substrate interface and peel off the support substrate. , An ultraviolet exposure machine (manufactured by Dainippon Screen Co., Ltd., MAP-1200-L) is attached to a predetermined portion of an FPC having an electric circuit pattern (base material: Kapton EN, 12.5 μm, copper circuit thickness: 5 μm) Positioning using the above-mentioned mask aligner mechanism, vacuuming for 30 seconds at 500 Pa or less using the above-described vacuum pressure laminator, followed by pressure bonding under conditions of pressure 0.4 MPa, temperature 100 ° C., and pressure time 30 seconds. After that, the flexible optical waveguide and the FPC were bonded by heating in a clean oven at 180 ° C. for 1 hour to obtain a photoelectric composite wiring board.
When the repeated slide test (bending durability test) of the obtained photoelectric composite wiring board was performed by the above method, the optical waveguide was not broken even after 100,000 times had passed, and the bending durability (sliding durability) was good. ) (See Table 1).

Comparative Example 1
In Example 1, a flexible optical waveguide having a constant core thickness of 80 μm was prepared in the same manner as in Example 1 except that the step (II) was not performed and a core film having a thickness of 80 μm was used in the step (III). did. In addition, a photoelectric composite wiring board was produced in the same manner as in Example 1. In this case, the insertion loss was 0.8 dB. However, in the repeated slide test of the photoelectric composite wiring board, the optical waveguide was broken after 5000 times, and sufficient bending durability (sliding durability) was not obtained ( (See Table 1).

Example 2
In Example 1, a flexible optical waveguide and a photoelectric composite wiring board were produced in the same manner as in Example 1 except that smoothing by a flat plate type vacuum pressure laminator was not performed. Table 1 shows the film thickness measurement results of one end and the bent portion of the produced flexible optical waveguide, and the cross-sectional area measurement results of one end and the other end. In the repeated slide test of the opto-electric composite wiring board, the optical waveguide was not broken even after 100,000 times, and showed good bending durability (sliding durability). On the other hand, the insertion loss is 2.2 dB, an increase of 1.2 dB compared to the case where smoothing is performed, and it is confirmed that smoothing is preferable in applications where high optical characteristics are required. It was. (See Table 1).

  The flexible optical waveguide of the present invention is extremely useful as a highly practical flexible optical waveguide because it has excellent bending durability and low optical loss.

1; flexible optical waveguide 2; first cladding layer (lower cladding layer)
3; first core layer 4; masking film 5; second core layer 6; core layer 7; second clad layer (upper clad layer)
8; Core pattern 10; Cladding layer forming resin film 11; Base film (for forming clad layer)
12; Cladding layer forming resin 13; Protective film 20; Core layer forming resin film 21; Base film (for core layer forming)
22; core layer forming resin 23; protective film 30; flat plate laminator 31; pressurizing material 41; opto-electric composite wiring board 42; flexible optical waveguide 43; flexible electrical wiring board (FPC)
44: Bending axis (virtual axis)

Claims (12)

  A flexible optical waveguide having a lower cladding layer and a core layer, wherein the cross-sectional area of one end of the core layer is smaller than the cross-sectional area of the other end, and has a bent portion, and the bent portion is at least one of the bent portions. A flexible optical waveguide characterized by being thinner than an end.   The flexible optical waveguide according to claim 1, further comprising an upper clad layer, wherein the lower clad layer, the core layer, and the upper clad layer are laminated in this order.   The flexible optical waveguide according to claim 1, wherein a thickness of the bent portion is 0.3 to 0.9 with respect to the at least one end portion.   The flexible optical waveguide according to claim 1, wherein a cross-sectional area of one end portion of the core layer is 0.2 to 0.8 with respect to the other end portion. The flexible optical waveguide according to claim 1, wherein one end portion of the core layer is thinner than the other end portion.   The flexible optical waveguide according to claim 1, wherein a thickness of one end portion of the core layer is 0.2 to 0.8 with respect to the other end portion.   The flexible optical waveguide according to claim 1, wherein the core layer is formed with a core pattern.   The flexible optical waveguide according to claim 2, wherein the core layer forms a core pattern, and the core pattern is surrounded by the lower cladding layer and the upper cladding layer.   The flexible optical waveguide according to claim 1, wherein the core layer has a larger cross-sectional area as a light input portion and a smaller cross-sectional area as a light output portion.   The flexible optical waveguide according to any one of claims 1 to 9, wherein there are two or more cores, and a cross-sectional area of the core at one end is larger than a cross-sectional area of the core at the other end, A flexible optical waveguide characterized by having both.   11. The flexible optical waveguide according to claim 10, wherein the end portion having the smaller core cross-sectional area is closer to the center of the light propagation axis than the end portion having the larger cross-sectional area of the core. Waveguide.   An opto-electric composite wiring board in which the flexible optical waveguide according to claim 1 is combined with a flexible electric wiring board.

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