JP2008164763A - Film-like light waveguide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a film-like light waveguide having excellent flame retardancy and flexibility and exhibiting preferable ultraviolet ray transmission when a light receiving element and a light emitting element are joined using an UV curable adhesive. <P>SOLUTION: The film-like light waveguide 1 includes: a lower clad layer 3; a core part 4 formed on the upper face of the lower clad layer 3 and having specific width; an upper clad layer 5 formed to be laminated on the lower clad layer 3 and the core part 4; and a cover layer 2 formed to be laminated on the peripheral face of the lower clad layer 3 and the upper clad layer 5. The cover layer 2 is a polymerized substance with 10% or greater of light transmissivity (wavelength 400 nm) of a thickness direction by including aromatic polyimide and/or aromatic polyamic acid. Each of the lower clad layer 3, the core part 4 and the upper clad layer 5 is a cured matter of an optical curable composition such as (meta)acryl-based, and epoxy-based. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a film-shaped optical waveguide.

In the era of multimedia, optical waveguides are attracting attention as optical transmission media due to demands for large capacity and high speed information processing in optical communication systems and computers.
An optical waveguide is an interface for converting an electrical / optical signal by joining a light emitting element such as a photodiode and a light receiving element such as a surface emitting laser to one surface of the optical waveguide, and transmitting an optical signal transmitted from the light emitting element to the light receiving element. Used as a medium.

Conventionally, various techniques for forming each part (a lower clad layer, a core part, and an upper clad layer) of an optical waveguide using a photocurable composition have been proposed.
For example, as a (meth) acrylic photocurable composition, (A) a vinyl polymer having a carboxyl group, a polymerizable group and other organic groups, (B) two or more polymerizable reactions in the molecule A radiation curable composition for forming an optical waveguide containing a group-containing compound and (C) a radiation polymerization initiator has been proposed (Patent Document 1).
In addition, as an epoxy-based photocurable composition, a photosensitive resin composition for forming an optical waveguide containing (A) a specific novolac type epoxy resin and (B) a photoacid generator has been proposed (Patent Literature). 2).
JP 2003-195079 A JP 2005-274664 A

A conventional photocurable composition used as a material for forming an optical waveguide has transmission characteristics suitable for use as an optical signal transmission medium, and is used for bonding light emitting and receiving elements using a UV curable adhesive. Although it has suitable ultraviolet transmittance, there exists a problem that it is inferior to a flame retardance.
In order to increase the flame retardancy, when the existing halogen-based and antimony-based flame retardants are blended into the photo-curable resin composition, the reliability of the optical waveguide is lowered and environmental problems are also reduced. There is a problem that it may occur.
In addition, when an existing flame retardant is blended, there is a problem that the bonding of the light emitting / receiving element using the UV curable adhesive is hindered. This point will be described in detail. First, the light receiving element or the light emitting element is bonded to one side of the optical waveguide. As the joining means, a UV (ultraviolet) curable adhesive is suitably used from the viewpoints of workability, efficiency, cost, and the like. In this case, in the state where an adhesive layer made of a UV curable adhesive is interposed between one side of the optical waveguide and the light receiving element or the light emitting element arranged on the one side of the optical waveguide, The adhesive layer is cured by irradiating ultraviolet rays from the side of the surface, and the optical waveguide and the light receiving element or the light emitting element are joined. For this reason, when the existing flame retardant is contained in the resin composition forming the optical waveguide main body, there is a problem in that the ultraviolet ray is insufficiently transmitted and the joining operation cannot be performed. As described above, in order to efficiently perform the joining work, it is necessary that the transmittance of the ultraviolet light transmitting portion of the optical waveguide is high.
Furthermore, a film-like optical waveguide produced using the above-mentioned (meth) acrylic or epoxy photocurable resin composition has a problem that cracking or breaking occurs when it is bent.
Therefore, the present invention provides a film-like optical waveguide having excellent flame retardancy and bending resistance, and having a suitable ultraviolet transmission property when bonding a light receiving element and a light emitting element using a UV curable adhesive. The purpose is to provide.

  As a result of intensive studies to solve the above problems, the present inventor has obtained a lower clad layer of an optical waveguide film cut into a desired mounting shape in a film-shaped optical waveguide having a lower clad layer, a core portion and an upper clad layer, The light transmittance (wavelength 400 nm) when the thickness is 12 μm is 10% on the outer surface of each of the upper cladding layer and the film side surfaces (a pair of left and right surfaces excluding the front and rear surfaces where the core part is exposed). It has been found that by providing a coating layer containing the aromatic polyimide and / or aromatic polyamic acid as described above, a film-like optical waveguide excellent in all of flame retardancy, ultraviolet transmittance and bending resistance can be obtained. Completed the invention.

（式中、Ｘは２価の基であり、ベンゼン環のどの位置に結合していてもよい。）
［４］ 前記下部クラッド層、前記コア部分及び前記上部クラッド層が、アクリル系の光硬化性組成物を硬化させて得られたものである前記［１］〜［３］のいずれかのフィルム状光導波路。
［５］ 前記被覆層が、被覆層の形成用フィルムとして、接着層を有する芳香族ポリイミドフィルムを用いることによって形成されたものである前記［１］〜［４］のいずれかのフィルム状光導波路。
［６］ 前記被覆層が、被覆層の形成用材料として、芳香族ポリイミド及び／又は芳香族ポリアミック酸と、有機溶媒とを混合してなる液状物を塗布し、乾燥または加熱処理することによって形成されたものである前記［１］〜［４］のいずれかのフィルム状光導波路。 That is, the present invention provides the following [1] to [6].
[1] A film-shaped optical waveguide having a lower clad layer, a core portion, and an upper clad layer, wherein aromatic polyimide and / or aromatic polyamic acid is applied to the outer surface of each of the lower clad layer and the upper clad layer. A film-like optical waveguide comprising a coating layer that includes a light transmittance (wavelength 400 nm) in the thickness direction of 10% or more.
[2] The film-shaped optical waveguide according to [1], wherein the coating layer is formed on an outer surface of each of the lower clad layer and the upper clad layer excluding a surface where a core portion is exposed.
[3] The above-mentioned [1] or [2], wherein the coating layer comprises an aromatic polyamide and / or an aromatic polyamic acid obtained by reacting a compound represented by the following general formula (1) with an aromatic diamine. Film-shaped optical waveguide.

(In the formula, X is a divalent group and may be bonded to any position of the benzene ring.)
[4] The film form according to any one of [1] to [3], wherein the lower clad layer, the core portion, and the upper clad layer are obtained by curing an acrylic photocurable composition. Optical waveguide.
[5] The film-shaped optical waveguide according to any one of [1] to [4], wherein the coating layer is formed by using an aromatic polyimide film having an adhesive layer as a film for forming the coating layer. .
[6] The coating layer is formed by applying a liquid material obtained by mixing an aromatic polyimide and / or aromatic polyamic acid and an organic solvent as a material for forming the coating layer, followed by drying or heat treatment. The film-shaped optical waveguide according to any one of [1] to [4].

Since the film-form optical waveguide of this invention is equipped with the coating layer containing an aromatic polyimide and / or aromatic polyamic acid, it has the outstanding flame retardance.
Moreover, since the film-shaped optical waveguide of the present invention has a light transmittance in the thickness direction (wavelength 400 nm) of 10% or more, a UV curable adhesive is interposed between the light receiving element or the light receiving and emitting element. When irradiating with ultraviolet rays, the ultraviolet ray permeability in the coating layer is good, and as a result, the UV curable adhesive is cured in a short time, and the film-like optical waveguide and the light receiving element or light receiving and emitting element Can be efficiently joined. The film-shaped optical waveguide of the present invention is transmitted from a light emitting element to a light receiving element in an interface for converting an electric / optical signal by joining a light emitting element such as a photodiode and a light receiving element such as a surface emitting laser to one side of the optical waveguide. It can be suitably used as an optical signal transmission medium.
Furthermore, the film-shaped optical waveguide of the present invention has a coating layer on the outer surface of each of the lower clad layer and the upper clad layer in addition to the lower clad layer, the core portion, and the upper clad layer. Has flexibility.

  The film-shaped optical waveguide of the present invention has a lower clad layer, a core portion, and an upper clad layer, and the outer surfaces of the lower clad layer, the upper clad layer, and the side surfaces of the film (specifically, the lower clad layer) And the upper surface of the upper clad layer, and the cut surface of the film-shaped optical waveguide obtained by cutting a film having a large number of core portions into a mounting shape), a specific aromatic polyimide and / or It has a coating layer made of a polymer containing an aromatic polyamic acid.

（式中、Ｘは２価の基であり、ベンゼン環のどの位置に結合していてもよい。）
ここで、一般式（１）中のＸ（２価の基）は、例えば、−Ｏ−、−ＳＯ_２−、−ＣＯ−、−Ｓ−、−Ｃ（ＣＨ_３）_２−、−Ｓｉ（ＣＨ_３）_２−または−Ｓｉ（Ｐｈ）_２−であり、好ましくは、−Ｏ−、−ＳＯ_２−、より好ましくは−Ｏ−である。
成分（Ａ）の具体的な化合物名としては、４，４’−オキシジフタル酸二無水物（オルトジフェニルフタル酸二無水物）、３，３’，４，４’−ジフェニルスルホンテトラカルボン酸二無水物、３，３’，４，４’−ベンゾフェノンテトラカルボン酸二無水物、３，３’，４，４’−ジメチルジフェニルシランテトラカルボン酸二無水物、３，３’，４，４’−テトラフェニルテトラカルボン酸二無水物、２，２−ビス（３，４−ジカルボキシフェニル）プロパン二無水物等が挙げられる。
中でも、紫外線透過性の向上の観点から、４，４’−オキシジフタル酸二無水物、３，３’，４，４’−ジフェニルスルホンテトラカルボン酸二無水物等が、好ましく用いられ、４，４’−オキシジフタル酸二無水物が特に好ましく用いられる。 First, the aromatic polyimide and / or aromatic polyamic acid forming the coating layer will be described in detail.
Preferable examples of the aromatic polyimide and / or aromatic polyamic acid used in the present invention include those obtained by reacting the following component (A) and component (B).
[Component (A)]
Component (A) is an aromatic tetracarboxylic dianhydride represented by the following general formula (1).

(In the formula, X is a divalent group and may be bonded to any position of the benzene ring.)
Here, X (divalent group) in the general formula (1) represents, for example, —O—, —SO ₂ —, —CO—, —S—, —C (CH ₃ ) ₂ —, —Si ( CH ₃ ) ₂ — or —Si (Ph) ₂ —, preferably —O—, —SO ₂ —, more preferably —O—.
Specific compound names of component (A) include 4,4′-oxydiphthalic dianhydride (orthodiphenylphthalic dianhydride), 3,3 ′, 4,4′-diphenylsulfone tetracarboxylic dianhydride. 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride, 3,3 ′, 4,4′-dimethyldiphenylsilanetetracarboxylic dianhydride, 3,3 ′, 4,4′- Examples thereof include tetraphenyltetracarboxylic dianhydride and 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride.
Among these, 4,4′-oxydiphthalic dianhydride, 3,3 ′, 4,4′-diphenylsulfone tetracarboxylic dianhydride, and the like are preferably used from the viewpoint of improving ultraviolet transmittance. '-Oxydiphthalic dianhydride is particularly preferably used.

[Component (B)]
Component (B) is an aromatic diamine.
Examples of aromatic diamines used as component (B) include p-phenylenediamine, m-phenylenediamine, 3,3′-dimethyl-4,4′-diaminobiphenyl, 3,3′-dimethoxy-4,4. '-Diaminobiphenyl, 1,5-diaminonaphthalene, 9,9-bis (4-aminophenyl) -10-hydroanthracene, 4,4'-(p-phenyleneisopropylidene) bisaniline, 4,4 '-(m -Phenylene isopropylidene) bisaniline, 5-amino-1- (4'-aminophenyl) -1,3,3-trimethylindane, 6-amino-1- (4'-aminophenyl) -1,3,3- Trimethylindane, 2,7-diaminofluorene, 9,9-bis (4-aminophenyl) fluorene, 4,4'-diaminodiphenylmethane, 4,4'-di Aminodiphenylethane, 4,4′-diaminodiphenyl sulfide, 4,4′-diaminodiphenyl sulfone, 4,4′-diaminobenzanilide, 4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 3,3 '-Diaminobenzophenone, 3,4'-diaminobenzophenone, 4,4'-diaminobenzophenone, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis [4- (4- Aminophenoxy) phenyl] sulfone, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,3-bis (3-aminophenoxy) benzene, 4,4 ′ -(P-biphenylenedioxy) dianiline etc. are mentioned.
Among these, 1,4-bis (4-aminophenoxy) benzene and 4,4 ′-(p-biphenylenedioxy) dianiline are preferably used from the viewpoint of improving ultraviolet transmittance, and 4,4 ′-(p -Biphenylenedioxy) dianiline is particularly preferably used.

The aromatic polyimide and / or aromatic polyamic acid for forming the coating layer of the film-shaped optical waveguide of the present invention is produced by reacting the component (A) and the component (B).
Component (A) represented by the following formula (2) (4,4′-oxydiphthalic dianhydride) and component (B) represented by the following formula (3) (4,4 ′-(p- The reaction mechanism will be described by taking an example of producing an aromatic polyimide by reacting biphenylenedioxy) dianiline).

First, as shown in the following formulas (4) and (5), the acid anhydride group of the component (A) (see the chemical formula on the left side of the formula (4)) and the amino group of the component (B) (formula ( 4) on the right side) reacts to produce an aromatic polyamic acid (see formula (5)).

In the present invention, the formation of the aromatic polyamic acid by the reaction between the component (A) and the component (B) is performed at a temperature of -20 to 150 ° C, preferably 0 to 100 ° C in an organic solvent. (B) is performed by mixing and stirring.
The proportion of component (A) and component (B) is preferably such that the acid anhydride group of component (A) is 0.8 to 1.2 equivalents relative to 1 equivalent of amino group of component (B). The ratio which becomes 1.0-1.1 equivalent is more preferable. When the amount of the acid anhydride group of the component (A) is less than 0.8 equivalent or more than 1.2 equivalent with respect to 1 equivalent of the amino group of the component (B), the film is applied to the substrate and dried. May not be formed.
Examples of the organic solvent used in the present invention include, for example, N-methyl-2-pyrrolidone (NMP), N, N-dimethylacetamide, N, N-dimethylformamide, dimethyl sulfoxide, γ-butyrolactone, tetramethylurea , Aprotic polar solvents such as hexamethyl phosphortriamide; methyl acetate, ethyl acetate, n-propyl acetate, n-butyl acetate, methyl methoxypropionate, ethyl ethoxypropionate, diethyl oxalate, diethyl malonate, ethyl lactate And esters such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; phenols such as phenol, m-cresol, xylenol, and halogenated phenol. .
Among these, N-methylpyrrolidone (NMP) is preferably used from the viewpoint of solubility.

The amount of the organic solvent used is such that the mass ratio of the total amount of the component (A) and the component (B) in the total amount of the reaction solution containing the component (A), the component (B) and the organic solvent is 0.1 to 30. The amount is 1% by mass, preferably 1-20% by mass, more preferably 1-15% by mass.
The pressure at the time of reaction is not specifically limited, Usually, a normal pressure may be sufficient. The reaction time is usually 1 to 10 hours.

The aromatic polyamic acid represented by the formula (5) is heated in the state of a film formed by being applied to a substrate and dried, whereby the imidization proceeds to become an aromatic polyimide represented by the formula (6).

The heating temperature during imidization is 200 ° C to 400 ° C, preferably 250 ° C to 350 ° C. By heating within the temperature range, imidization of the aromatic polyamic acid can be sufficiently advanced. The heating time is preferably 30 to 120 minutes.
The imidation ratio of the aromatic polyamic acid is not particularly limited to 0 to 100%, but is preferably 50 to 100%, more preferably 80 to 100%. If the proportion is less than 50%, the water resistance of the film may be lowered.
The number average molecular weight of the aromatic polyimide and aromatic polyamic acid is preferably 3,000 or more from the viewpoint of mechanical strength as a polystyrene equivalent value measured by the GPC method.
The upper limit of the number average molecular weight of the aromatic polyimide and aromatic polyamic acid is not particularly limited, but is usually 500,000 or less.

Examples of the material for forming each part of the lower clad layer, the core part, and the upper clad layer in the film-shaped optical waveguide of the present invention include photo-curing or thermosetting materials.
Of these, (meth) acrylic or epoxy photocurable compositions are preferably used from the viewpoints of flex resistance and production efficiency. Here, examples of the (meth) acrylic photocurable composition include those described in JP-A No. 2003-195079 described in the above-mentioned “Background Art” section.

  Specifically, examples of the (meth) acrylic photocurable composition include a composition containing a resin having a polymerizable functional group such as an ethylenically unsaturated group, a polymerizable monomer, a photopolymerization initiator, and the like. It is done. The composition for the core can make the composition alkali developable by making the resin having a polymerizable functional group such as an ethylenically unsaturated group alkali-soluble.

  Here, the resin having a polymerizable functional group such as an ethylenically unsaturated group is, for example, a poly (meth) acrylate having a carboxyl group or a hydroxyl group, a compound containing a glycidyl group and an ethylenically unsaturated group, an isocyanate group, It can be obtained by addition reaction of a compound containing an ethylenically unsaturated group or acrylic acid chloride. At this time, acrylic resin or methacrylic acid is copolymerized, and a carboxyl group can be introduced into the resin to obtain a resin capable of alkali development. Moreover, the compound which has a polyethylene oxide structure, a polypropylene oxide structure, and the linear structure which has a urethane bond repeatedly, and has 2-6 (meth) acryloyl groups can also be used.

  Here, examples of the polymerizable monomer include trimethylolpropane tri (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol penta ( (Meth) acrylate, dipentaerythritol hexa (meth) acrylate, glycerin tri (meth) acrylate, tris (2-hydroxyethyl) isocyanurate tri (meth) acrylate, ethylene glycol di (meth) acrylate, 1,3-butanediol di (Meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, Ethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, bis (2-hydroxyethyl) isocyanurate di (meth) acrylate, bis ((meth) acryloyl) Oxymethyl) tricyclo [5.2.1.02,6] decane, and poly (meth) acrylates of ethylene oxide or propylene oxide adducts of starting alcohols in making these compounds, two or more in the molecule Examples include oligoester (meth) acrylates having a (meth) acryloyl group, oligoether (meth) acrylates, oligourethane (meth) acrylates, and oligoepoxy (meth) acrylates.

  Examples of photopolymerization initiators include 2,2-dimethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, 2,4,6- Trimethylbenzoyldiphenylphosphine oxide, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one, 2- (dimethylamino) -1- [4- (morpholinyl) phenyl] -2 -Phenylmethyl) -1-butanone and the like.

  The above-mentioned method of forming “a composition layer containing a resin having a polymerizable functional group such as an ethylenically unsaturated group, a polymerizable monomer, a photopolymerization initiator, etc.” on a film comprises the following components: methyl isobutyl ketone, Roll coat a composition dissolved in a solvent such as acetone, methyl ethyl ketone, cyclohexanone, tetrahydrofuran, dioxane, ethylene glycol monomethyl ether, ethylene glycol ethyl ether acetate, diethylene glycol ethyl ether acetate, toluene, ethyl acetate, ethyl 2-hydroxypropionate, etc. After applying to a film by a method such as gravure coating or die coating, the solvent can be removed (dried) to form a photosensitive composition layer. At this time, for example, about 5% by mass of the solvent may remain within a range that does not impair the properties as a dry film.

  Moreover, as an epoxy-type photocurable composition, what was described in Unexamined-Japanese-Patent No. 2005-274664 demonstrated in the column of the above-mentioned "background art" is mentioned, for example. Specifically, examples of the epoxy photocurable composition include a novolac type epoxy resin and a photoacid generator. Examples of commercially available products of novolak type epoxy resins include Epicoat 152, Epicoat 154 (above, Japan Epoxy Resin Co., Ltd.), Epicron N740, Epicron N770 (above, Dainippon Ink and Chemicals), Epototo YDPN638 (Toto Kasei Co., Ltd.) ), DER431, DER438 (above, manufactured by Dow Chemical Co.), Araldite EPN1138 (made by Ciba Geigy) (above, phenol novolac type epoxy resin), Epicoat 180 (made by Japan Epoxy Resin Co., Ltd.), Epicron N660, Epicron N670 (above , Manufactured by Dainippon Ink & Chemicals, Inc.), Epototo YDCN701, Epototo YDCN702 (above, manufactured by Tohto Kasei Co., Ltd.), Araldite ECN1273, Araldite ECN1280 (made by Ciba Geigy) (above, Crezo) Lunovolak type epoxy resin) and the like. Other examples of commercially available novolak epoxy resins include Epicoat 157S65, Epicoat 157S70 (manufactured by Japan Epoxy Resin Co., Ltd.), N865 (manufactured by Dainippon Ink & Chemicals, Inc.), and the like.

The photoacid generator is a photocationic polymerization initiator that releases Lewis acid by receiving light, and specific examples thereof include onium salts having a structure represented by the following general formula (7). . This onium salt has a substantial light absorption wavelength below 400 nm.
_{^{[R 6 a R 7 b R}} 8 c R 9 d Z] + m [MX n + m] -m (7)
(Wherein the cation is an onium ion, Z represents S, Se, Te, P, As, Sb, Bi, O, I, Br, Cl or N≡N, and R ⁶ , R ⁷ , R ⁸ and R ⁹ represents an organic group which is the same or different from each other, a, b, c and d are each an integer of 0 to 3, and (a + b + c + d) is equal to the valence of Z. M is a halide complex [ MX _{n + m} ] represents a metal or metalloid constituting the central atom of, for example, B, P, As, Sb, Fe, Sn, Bi, Al, Ca, In, Ti, Zn, Sc, V, Cr, Mn, Co, etc. X is a halogen atom such as F, Cl, Br, etc., m is the net charge of the halide complex ion, and n is the valence of M.] Examples of commercial products of photoacid generators As, Adekaoptomer SP-150, SP-15 , SP-170, SP-172 (above, manufactured by Asahi Denka Kogyo Co., Ltd.), UVI-6950, UVI-6970, UVI-6974, UVI-6990 (above, manufactured by Union Carbide), Irgacure 261 (Ciba Specialty Chemicals) CI-2481, CI-2624, CI-2638, CI-2064 (above, Nippon Soda Co., Ltd.), CD-1010, CD-1011, CD-1012 (above, Sartomer), DTS-102 , DTS-103, NAT-103, NDS-103, TPS-103, MDS-103, MPI-103, BBI-103 (manufactured by Midori Chemical Co., Ltd.), PCI-061T, PCI-062T, PCI-020T, PCI -022T (Nippon Kayaku Co., Ltd.) and the like.

  Furthermore, in addition to the above-mentioned components, butyl glycidyl ether, ethylene glycol diglycidyl for the purpose of adjusting the viscosity before curing of the resin composition, adjusting the refractive index after curing of the resin composition, increasing the curing rate, etc. Epoxy compounds such as ether, propylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, trimethylol triglycidyl ether, bisphenol A propylene oxide adduct diglycidyl ether, bisphenol A diglycidyl ether, and 3,4-epoxycyclohexenylmethyl -3 ′, 4′-epoxycyclohexenecarboxylate, ε-caprolactone modified 3,4-epoxycyclohexylmethyl-3 ′, 4′-epoxycyclohexanecarboxylate, epoxidized 3-cyclohexe 1,2 and cyclohexene oxide compound such as dicarboxylic acid bis (3-cyclohexenyl-methyl) modifications ε- caprolactone, phenyl oxetane may include oxetane compounds such as xylene dioxetane. Other various additives include, for example, antioxidants, ultraviolet absorbers, light stabilizers, silane coupling agents, coating surface improvers, thermal polymerization inhibitors, leveling agents, surfactants, colorants, and storage. Stabilizers, plasticizers, lubricants, solvents, fillers, anti-aging agents, wettability improvers, mold release agents, and the like can be blended as necessary.

Next, an example of the film-like optical waveguide of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view schematically showing an example of the film-shaped optical waveguide of the present invention, and FIG. 2 is a cross-sectional view showing an example of using the film-shaped optical waveguide shown in FIG. 1 together with a light receiving element and a light emitting element. is there.
[Structure of film-shaped optical waveguide]
In FIG. 1, a film-shaped optical waveguide 1 is laminated on a lower cladding layer 3, a core portion 4 having a specific width formed on the upper surface of the lower cladding layer 3, and the lower cladding layer 3 and the core portion 4. The upper clad layer 5 formed in this manner, and the lower clad layer 3 and the covering layer 2 formed so as to cover the periphery of the upper clad layer 5. An adhesive layer can be provided on the boundary surface between the coating layer 2 and the lower cladding layer 3 and the boundary surface between the coating layer 2 and the upper cladding layer 5 as necessary.
The thicknesses of the lower cladding layer 3, the core portion 4, and the upper cladding layer 5 are not particularly limited. For example, the thickness of the lower cladding layer 3 is 1 to 200 μm, the thickness of the core portion 4 is 3 to 200 μm, and the upper portion The thickness of the cladding layer 5 is determined to be 1 to 200 μm. Although the width | variety of the core part 5 is not specifically limited, For example, it is 1-200 micrometers.
The refractive index of the core portion 4 needs to be higher than any of the refractive indexes of the lower cladding layer 3 and the upper cladding layer 5. For example, for light having a wavelength of 400 to 1,600 nm, the refractive index of the core portion 4 is 1.420 to 1.650, and the refractive indexes of the lower cladding layer 3 and the upper cladding layer 5 are 1.400 to 1.648. In addition, it is preferable that the refractive index of the core portion 4 is at least 0.1% larger than the refractive indexes of the two cladding layers 3 and 5.

The light transmittance (wavelength 400 nm) in the thickness direction of the coating layer 2 is 10% or more, preferably 15% or more, more preferably 25% or more, still more preferably 35% or more, and particularly preferably 45% or more. If the light transmittance is less than 10%, the ultraviolet curable adhesive cannot be sufficiently cured, and the bonding strength between the light receiving element or the light emitting element and the optical waveguide is reduced or cannot be bonded. Absent.
The thickness of the coating layer is 1 to 50 μm, preferably 3 to 30 μm, and more preferably 5 to 20 μm from the viewpoint of imparting sufficient flame retardancy and obtaining high light transmittance.
The covering layer 2 includes at least the lower surface of the lower cladding layer 3, the upper surface of the upper cladding layer 5, and the side surfaces of the lower cladding layer 3 and the upper cladding layer 5 (where the core portion is exposed). It is preferably formed on the entire peripheral surface of the mounting-shaped film-shaped optical waveguide.
When an adhesive layer is provided on the boundary surface between the coating layer 2 and the cladding layers 3 and 5, the thickness of the adhesive layer is not particularly limited, but is usually 3 to 20 μm.
The material for forming the adhesive layer is not particularly limited as long as it is excellent in ultraviolet transmittance, and for example, a thermosetting epoxy resin or the like can be used.

[Method for producing film-shaped optical waveguide]
Next, the manufacturing method of the film-form optical waveguide of this invention is demonstrated.
First, an optical waveguide body composed of a lower cladding layer, a core portion, and an upper cladding layer is manufactured.
Specifically, a lower clad layer forming composition is applied to the upper surface of a substrate for forming an optical waveguide body having a flat surface such as a silicon wafer or a glass substrate, and dried or prebaked to form a lower layer thin film. Form. The lower layer thin film is irradiated with light and cured to form a lower clad layer that is a cured body.
Next, a core portion forming composition is applied to the upper surface of the lower clad layer, and dried or prebaked to form a core thin film. Thereafter, light irradiation (exposure) is performed on the upper surface of the core thin film according to a predetermined pattern, for example, through a photomask having a predetermined line pattern. As a result, only the portion irradiated with light in the thin film for the core is cured, so that the uncured portion other than that is developed and removed to remove the patterned cured film on the lower cladding layer. A large number of core portions can be formed.
Thereafter, an upper clad layer forming composition is applied to the upper surface of the core portion and the lower clad layer, and dried or prebaked to form an upper layer thin film. When this upper thin film is cured by irradiation with light, an upper clad layer is formed.
The film (aggregate of film-shaped optical waveguide bodies) composed of the lower clad layer, the multiple core portions and the upper clad layer formed as described above is placed between adjacent core portions so as to have a desired mounting shape. Is cut to obtain a film-like optical waveguide body (hereinafter sometimes abbreviated as “optical waveguide body”).

Next, a coating layer is formed on the peripheral surfaces (upper surface, lower surface and side surfaces) of the optical waveguide body. Examples of the method of forming the coating layer include (A) a method using a polyimide film having an adhesive layer, and (B) a method of applying and curing a coating layer forming material. Each of these two methods will be described.
(A) Method of using a polyimide film having an adhesive layer First, an organic solvent solution of the above polyamic acid (see the above formula (5)) is applied on a substrate and dried, and then the polyamic acid is partially heated. Alternatively, it is completely imidized to form an aromatic polyimide film. Then, the liquid thermosetting resin composition for adhesive layers is apply | coated to the upper surface of this film, it is made to semi-harden by heating, an adhesive layer is formed, and the polyimide film which has an adhesive layer is obtained. A polyimide film is laminated on both sides of the optical waveguide by thermal lamination so that the adhesive layer of the polyimide film faces each of the lower surface of the lower cladding layer and the upper surface of the upper cladding layer of the optical waveguide body. A film-like optical waveguide can be obtained by cutting the polyimide film portion so that the side surface is not exposed.

The substrate used for producing the polyimide film having an adhesive layer is not particularly limited as long as it has a flat surface, and examples thereof include a silicon wafer and a glass substrate.
As a coating method of the organic solvent solution of polyamic acid, any of spin coating method, dipping method, spray method, bar coating method, roll coating method, curtain coating method, gravure printing method, silk screen method, ink jet method, etc. Can be used. Among them, it is preferable to employ a spin coating method because a thin film having a uniform thickness can be obtained.

Examples of the method for applying the resin composition for the adhesive layer include the same method as the method for applying the organic solvent solution of polyamic acid. Moreover, the heating conditions of the resin composition for adhesive layers are 50-200 degreeC normally, Preferably it is 50-150 degreeC.
The thermal lamination is performed at 100 ° C. to 200 ° C., preferably 130 ° C. to 180 ° C., for 10 minutes to 2 hours.
As the resin composition for the adhesive layer, a thermosetting resin composition is preferable, and examples thereof include a thermosetting epoxy resin.

(B) Method of applying and curing the coating layer forming material First, by applying an organic solvent solution of polyamic acid on a substrate and heating, or by applying an organic solvent solution of polyimide and drying. After forming a thin film (first coating layer) containing polyimide, an optical waveguide body (lower cladding layer, core portion, upper cladding layer) prepared in advance by the same method as described above is installed on this thin film. To do. Next, an organic solvent solution of polyamic acid is applied on the optical waveguide body and the first coating layer and heated, or by applying an organic solvent solution of polyimide and drying, a thin film containing polyimide (first When the second coating layer is formed, a laminate (film optical waveguide) composed of the first and second coating layers and the optical waveguide body is completed. Finally, if the laminate is peeled from the substrate and the polyimide film portion is cut so that the side surface of the optical waveguide body is not exposed, a film-like optical waveguide can be obtained.

[Joint method of light receiving element or light emitting element]
When the film-shaped optical waveguide of the present invention is bonded to a light receiving element or a light-emitting element, an ultraviolet curable adhesive is applied to a part of the outer surface of the coating layer on one side of the film-shaped optical waveguide to form an adhesive layer. 7 is formed, and the light receiving element 8 (or light emitting element) is brought into contact with the surface of the adhesive layer 7. Thereafter, when the adhesive layer 7 is cured by irradiating ultraviolet rays from the surface of the film-shaped optical waveguide opposite to the surface on which the light receiving element 8 is disposed, the light receiving element 8 can be joined (FIG. 2). In addition, in FIG.1 and FIG.2, each part of the same name is shown with the same code | symbol.

Hereinafter, the present invention will be described with reference to examples.
[1. Preparation of resin composition for optical waveguide]
The following materials were prepared as materials for each part (lower clad layer, core part, and upper clad layer) of the optical waveguide body.
Opstar PJ3075 (manufactured by JSR Corporation) was used as a photocurable resin composition for forming the lower cladding layer and the upper cladding layer. Moreover, Opstar PJ3074 (made by JSR) was used as a photocurable resin composition for core formation.

[2. Production of optical waveguide]
A photocurable resin composition for forming a lower cladding layer (OPSTAR PJ3075; manufactured by JSR) was applied onto a silicon substrate with a spin coater, and pre-baked at 100 ° C. for 10 minutes using a hot plate to form a coating film. Formed. Subsequently, this coating film was irradiated with ultraviolet rays having a wavelength of 365 nm and an illuminance of 20 mW / cm ² for 75 seconds to be photocured. The cured film was post-baked at 150 ° C. for 1 hour to form a lower cladding layer having a thickness of 10 μm.
Next, a photocurable resin composition for forming a core part (OPSTAR PJ3074; manufactured by JSR) was applied onto the lower clad layer with a spin coater and prebaked at 100 ° C. for 10 minutes. Next, ultraviolet light having a wavelength of 365 nm and an illuminance of 20 mW / cm ² is applied to a coating film having a thickness of 50 μm on a coating film having a thickness of 50 μm made of a photocurable resin composition for forming a core part for 75 seconds. Irradiated and photocured. And the board | substrate which has the hardened coating film was immersed in the developing solution which consists of acetone, and the unexposed part of the coating film was dissolved. Thereafter, post-baking was performed at 150 ° C. for 1 hour, thereby forming a core portion having a thickness of 50 μm and a line pattern having a width of 50 μm.
On the upper surface of the lower clad layer having the core portion, a photocurable resin composition for forming the upper clad layer (OPSTAR PJ3075; manufactured by JSR) is applied with a spin coater, and using a hot plate at 100 ° C. for 10 minutes. Pre-baked. Thereafter, the coating film made of the photocurable resin composition for forming the upper clad layer is irradiated with ultraviolet rays having a wavelength of 365 nm and an illuminance of 20 mW / cm ² for 75 seconds to be photocured, and the thickness from the upper surface of the core portion is 10 μm. An upper waveguide layer was formed, and an optical waveguide film comprising a lower cladding layer, a core portion, and an upper cladding layer was obtained. Next, the optical waveguide film was cut into a desired mounting shape to produce an optical waveguide body (width 1.5 mm, length 100 mm, thickness 70 μm).

[3. Production of film-shaped optical waveguide]
[Example 1]
Under an N ₂ gas atmosphere, 5.4 g of 4,4 ′-(p-biphenylenedioxy) dianiline (manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved in 80 g of dehydrated N-methylpyrrolidone (NMP). Subsequently, 4.6 g of 4,4′-oxydiphthalic dianhydride (manac Co., Ltd., ODPA-M) was added and stirred at room temperature for 4 hours to obtain a polyamic acid varnish (an organic solvent solution of polyamic acid).
Next, this polyamic acid varnish was applied on a silicon wafer, dried at 120 ° C. for 5 minutes, and further dried at 200 ° C. for 5 minutes. Subsequently, imidation was performed by heating at 300 ° C. for 1 hour to obtain a film-like cured body made of polyimide having a thickness of 12 μm.
On the upper surface of this film-like cured product, 95 parts by mass of bisphenol A diglycidyl ether (Epicoat 828, manufactured by Japan Epoxy Resin Co., Ltd.) and an imidazole curing agent (Curesol 2E4MZ, manufactured by Shikoku Kasei Co., Ltd.) A mixture consisting of 5 parts by mass was applied to a thickness of 10 μm, and then heated at 100 ° C. for 2 minutes to form an adhesive layer to obtain a polyimide film having a coating layer.
The polyimide film adhesive layer is opposed to the lower surface of the lower clad layer and the upper surface of the upper clad layer of the optical waveguide main body (width 1.5 mm, length 100 mm, thickness 70 μm) that has been prepared. Thus, after laminating by heat lamination at 150 ° C. on both surfaces of the optical waveguide body, a film-like optical waveguide was obtained by heating at 150 ° C. for 1 hour. The film-shaped optical waveguide was cut at a distance of 1 mm from the end surface so that the side surface end surface of the film-shaped optical waveguide was not exposed. Moreover, the edge part of the length direction was cut | disconnected so that the cross section of the film-form optical waveguide might be exposed in order to mount.

[Example 2]
As a resin composition for forming a coating layer, “Liccacoat SN-20” (trade name, manufactured by Shin Nippon Chemical Co., Ltd., 3,3 ′, 4,4′-diphenylsulfonetetracarboxylic dianhydride and aromatic diamine) An N-methylpyrrolidone solution of polycondensate (an organic solvent solution of polyimide)) was prepared.
The first coating layer made of polyimide having a thickness of 12 μm is applied by applying “Liccacoat SN-20” on a silicon wafer using a spin coater, drying at 120 ° C. for 5 minutes, and further drying at 200 ° C. for 5 minutes. Formed.
After the prepared optical waveguide body is placed on the first coating layer, “Liccacoat SN-20” is applied to the upper surface of the optical waveguide body and the first coating layer using a spin coater. The film was dried at 120 ° C. for 5 minutes, and further dried at 100 ° C. for 3 hours to form a second coating layer made of polyimide having a thickness of 12 μm, thereby completing a film-shaped optical waveguide. Thereafter, the film-like optical waveguide was cut in the same manner as in Example 1.

[Comparative Example 1]
A film-shaped optical waveguide consisting only of the manufactured optical waveguide main body having no coating layer was defined as Comparative Example 1.
[Comparative Example 2]
Instead of the polyimide film of Example 1, a Kapton film (trade name, manufactured by Toray DuPont, made of polycondensate (aromatic polyimide) of pyromellitic dianhydride and 4,4′-diaminophenyl ether) A film-like optical waveguide was produced in the same manner as in Example 1 except that a polyimide film with an adhesive layer formed by forming an adhesive layer on one side was used. The adhesive layer in the polyimide film was formed in the same manner as in Example 1.
[Comparative Example 3]
A film was prepared in the same manner as in Example 1 except that “PI-100” (manufactured by Maruzen Petrochemical Co., Ltd.), which is an organic solvent solution of an alicyclic polyimide, was used instead of the polyamic acid varnish, and a polyimide film was produced. An optical waveguide was prepared.

[4. Evaluation of film-like optical waveguide]
Film-shaped optical waveguides (Examples 1 and 2 and Comparative Examples 1 to 3) were evaluated as follows.
[Ultraviolet transmission]
The light transmittance of a polyimide film (thickness: 12 μm) at a wavelength of 400 nm was measured.
As a result, it was 52% in Example 1, 19% in Example 2, 0% in Comparative Example 2, and 98% in Comparative Example 3.
The case where the light transmittance is 10% or more is “◯”, and the case where it is less than 10% is “x”.
[Flame retardance]
When the produced film-shaped optical waveguide is fixed vertically and the flame of the burner (butane gas, flow rate 5 cc / min, flame length 12 mm) is indirect flame for 5 seconds from the lower end, the film-shaped optical waveguide is burned out after flame contact. The case where it is not performed is indicated by “◯”, and the case where it is burned is indicated by “×”.
The results are shown in Table 1.

  From Table 1, it can be seen that Examples 1 and 2 are excellent in ultraviolet transmittance and flame retardancy. On the other hand, Comparative Example 1 is inferior in flame retardancy because it does not have a coating layer. In Comparative Example 2, since the coating layer does not have the light-transmitting condition defined in the present invention, the UV-transmitting property is inferior. Since Comparative Example 3 has a coating layer made of an alicyclic polyimide that does not belong to the present invention, it is inferior in flame retardancy. Each of Examples 1 and 2 and Comparative Examples 1 to 3 has bending resistance suitable for use as a film-like optical waveguide. 1 and 2) can exhibit more excellent bending resistance than the case where the coating layer is not provided (Comparative Example 1).

It is sectional drawing which shows typically an example of the film-form optical waveguide of this invention. It is sectional drawing which shows typically an example in the case of using the film-form optical waveguide shown in FIG. 1 with a light receiving element / light emitting element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Film-form optical waveguide 2 Covering layer 3 Lower clad layer 4 Core part 5 Upper clad layer 6 Adhesive layer 7 Light receiving element / light emitting element

Claims (6)

  A film-shaped optical waveguide having a lower clad layer, a core portion, and an upper clad layer, the outer surface of each of the lower clad layer and the upper clad layer containing an aromatic polyimide and / or an aromatic polyamic acid; and A film-shaped optical waveguide comprising a coating layer having a light transmittance in the thickness direction (wavelength 400 nm) of 10% or more.   The film-form optical waveguide according to claim 1, wherein the coating layer is formed on an outer surface of each of the lower clad layer and the upper clad layer except for a surface where the core portion is exposed. The film-form optical waveguide according to claim 1 or 2, wherein the coating layer comprises an aromatic polyamide and / or an aromatic polyamic acid obtained by reacting a compound represented by the following general formula (1) with an aromatic diamine. .

(In the formula, X is a divalent group and may be bonded to any position of the benzene ring.)   The film-form optical waveguide according to any one of claims 1 to 3, wherein the lower clad layer, the core portion, and the upper clad layer are obtained by curing an acrylic photocurable composition.   The film-shaped optical waveguide according to any one of claims 1 to 4, wherein the coating layer is formed by using an aromatic polyimide film having an adhesive layer as a film for forming the coating layer.   The coating layer is formed by applying a liquid material obtained by mixing an aromatic polyimide and / or aromatic polyamic acid and an organic solvent as a material for forming the coating layer, followed by drying or heat treatment. The film-shaped optical waveguide according to any one of claims 1 to 4.

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