JP2003202440A - Optical waveguide and waveguide optical device - Google Patents

Abstract

An optical waveguide having good initial mechanical characteristics and optical characteristics, little deterioration of optical characteristics even when used for a long time at a high temperature, and a function of bending light efficiently by 90 degrees. And a waveguide-type optical device. The following formula (1), the following formula (2), or the following formula (3)
A fluorine-containing polymer containing at least one cyclic structure repeating unit selected from is used as an optical waveguide material.
Tadashi, Q represents a R ^f -O, R ^f represents one or more carbon atoms to chlorine atoms 10 following fluorinated alkylene group. [Chemical 1]

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical waveguide made of a fluoropolymer and a waveguide type optical device including the optical waveguide.

[0002]

2. Description of the Related Art An amorphous fluoropolymer having a ring structure in its main chain is excellent in mechanical strength and optical transparency.
It can be used for optical materials such as optical fibers and optical waveguides. Patent Document 1 discloses an optical waveguide using such an amorphous fluoropolymer.

Specifically, perfluoroallyl vinyl ether polymers and perfluoro (2,2-dimethyl-
It is described that a copolymer of 1,3-dioxole) and tetrafluoroethylene is useful as a material for an optical waveguide. However, since the former polymer has a low glass transition temperature (hereinafter referred to as Tg), an optical waveguide made of this polymer has a drawback that its optical characteristics change when it is used at a high temperature for a long time.

In the latter copolymer, a copolymer having a high Tg can be obtained by increasing the copolymerization ratio of tetrafluoroethylene, but it is partially crystallized and the transparency is lowered. Therefore, the latter optical waveguide made of the copolymer has a drawback that the loss becomes large. Further, since the former polymer and the latter copolymer are both perfluoro resins and have low density, the refractive index is extremely low. Therefore, it cannot be applied to an optical waveguide and a waveguide-type optical device having a 45-degree reflection structure for bending light by 90 degrees, which is often used when a signal is taken out to a component mounted on a substrate in a flat-plate type optical circuit. It has the drawback of That is, because of the low refractive index, the total reflectance at 45 degrees is low, and the amount of leaked signals is large. Therefore, development of a material having good transparency, higher Tg, and higher refractive index is desired.

Further, although the above-mentioned amorphous fluoropolymer having a ring structure in the main chain has suppressed water absorption, it has a large water vapor permeability coefficient due to its low density, and is added for increasing the refractive index. When an additive such as a high-refractive-index low-molecular compound is reactive with water, there is a drawback that the characteristics change in long-term use.

On the other hand, Patent Document 2 describes that Tg can be increased by introducing a bulky substituent or a crosslinked structure into an amorphous fluoropolymer having a ring structure in its main chain. There is. However, in such a method, the polymer becomes brittle, or the optical characteristics or heat resistance is deteriorated. Therefore, the optical waveguide made of these polymers is difficult to handle, and the optical characteristics and heat resistance are not sufficient.

[0007]

[Patent Document 1] Japanese Patent Laid-Open No. 4-190202

[Patent Document 2] Japanese Patent Laid-Open No. 2000-81519

[0008]

DISCLOSURE OF THE INVENTION The present invention is intended to solve the above-mentioned drawbacks of the prior art, has good initial mechanical properties and optical properties, and shows no deterioration in optical properties even when used at high temperatures for a long time. Further, there is provided an optical waveguide and a waveguide type optical device having a 45-degree reflection structure and having a function of bending light by 90 degrees.

[0009]

The present invention provides the following formula (1),
An optical waveguide comprising a fluoropolymer containing at least one repeating unit having a ring structure selected from the following formula (2) or (3).

[0010]

[Chemical 2]

However, Q represents R ^f -O, R ^f has one or more chlorine atoms, and may have an etheric oxygen atom in R ^f. Represents an alkylene group. Further, the present invention is a waveguide type optical device including the above optical waveguide.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The fluoropolymer of the present invention is a polymer containing at least one repeating unit having a ring structure represented by the formula (1) to the formula (3). The repeating units represented by the formulas (1) to (3) are CF ₂ = CF-Q-C.
It is a repeating unit formed by cyclopolymerization of a fluorine-containing diene represented by F = CF ₂ . Depending on the type of Q and the cyclopolymerization method, one or more units represented by the formulas (1) to (3) are produced. Therefore, the fluoropolymer may contain two or more of these units. R ^f is a fluorine-containing alkylene group having 10 or less carbon atoms which may contain an etheric oxygen atom inside. The carbon number of R ^f excluding the side chain is preferably 3 or less. One or more chlorine atoms may be present in R ^f . From the viewpoint of stability, R ^f is preferably a highly fluorinated fluorinated alkylene group other than a chlorine atom. Particularly, it is preferable that all atoms other than chlorine atom are fluorine atoms. Highly fluorinated means that the ratio of the number of fluorine atoms to the total number of hydrogen atoms and fluorine atoms bonded to carbon atoms is 80% or more. R ^f may have a side chain composed of a fluorine-containing alkyl group which may contain an etheric oxygen atom. Further, this side chain may have an etheric oxygen atom.

The chlorine atom may be directly bonded to the carbon atom constituting the ring in R ^f , or may be bonded to the carbon atom in the side chain in R ^f . In particular, it is preferable that the chlorine atom forms a ring and is directly bonded to the carbon atom adjacent to the oxygen atom. Furthermore, it is most preferable that the oxygen atom is an etheric oxygen atom. The reason for this is not clear, but since the chlorine atom is bonded to the carbon atom adjacent to the oxygen atom, the Tg increases, but there is some flexibility, so the fluoropolymer is extremely hard and brittle. It is thought that it will never happen. The number of chlorine atoms may be one or more, but one or two is preferable from the viewpoint of maintaining good thermal stability. Particularly preferred R
^f is (CF ₂ ) _n CClF or (CF ₂ ) _n CCl
₂ and most preferably (CF ₂ ) _n CClF. However, n is an integer of 1 to 3.

The method for obtaining the fluoropolymer in the present invention is as follows. Cyclopolymerization of a fluorodiene that gives one or more ring structures represented by formulas (1) to (3) by cyclopolymerization. Or by copolymerizing the fluorine-containing diene with a copolymerizable monomer.

The above-mentioned copolymerizable monomer is not particularly limited as long as it is a monomer copolymerizable with a fluorine-containing diene, and it may be a fluorine-containing monomer, a hydrocarbon-based monomer or other monomer. The body can be extensively illustrated. Particularly, a monomer having radical copolymerizability is preferable.

Specifically, an olefin such as ethylene or a fluoroolefin such as tetrafluoroethylene is preferable. Fluorine-containing vinyl ether monomers such as perfluoro (alkyl vinyl ether), fluorine-containing diene monomers such as perfluoro (butenyl vinyl ether) and perfluoro (allyl vinyl ether),
A monomer having a ring structure such as perfluoro (2,2-dimethyl-1,3-dioxole) is also preferable. These copolymerizable monomers may be used alone or in combination of two or more.

The repeating unit of the ring structure of the fluoropolymer in the present invention has good transparency, excellent solubility in a fluorine-containing solvent, and excellent physical properties. It is preferably 20 mol% or more, and particularly preferably 50 mol% or more, based on the repeating units.

The molecular weight of the fluoropolymer is 10,000 to 1
It is preferably, 000,000, and particularly preferably 20,000 to 500,000. Examples of the fluorine-containing solvent include fluorinated chlorinated hydrocarbons, fluorinated hydrocarbons and hydrofluoroethers. Specific examples include perfluorohexane, perfluorooctane, perfluorobenzene, perfluoro (2-butyltetrahydrofuran), (perfluorobutyl) methyl ether, (perfluorobutyl) ethyl ether, perfluorotributylamine, and perfluorotripropylamine.

The fluorinated polymer in the present invention preferably contains a repeating unit having a ring structure formed by cyclopolymerization of the fluorinated diene represented by the formula (4). CF ₂ ═CF (CF ₂ ) _n CXYOCF═CF ₂ (4) However, X and Y are each independently a fluorine atom or a chlorine atom, and at least one is a chlorine atom. Also,
n represents an integer of 1 to 3.

The fluorine-containing diene represented by the formula (4) is obtained by dehalogenating the fluorine-containing compound represented by the formula (5). CF ₂ Z ¹ CFZ ² (CF ₂ ) _n CXYOCFZ ³ CF ₂ Z ⁴ (5) where Z ¹ , Z ² , Z ³ and Z ⁴ are each independently a halogen atom selected from a chlorine atom, a bromine atom and an iodine atom. Represents Further, X and Y are fluorine atoms or chlorine atoms, and at least one is a chlorine atom. Also,
n represents an integer of 1 to 3.

As the X and Y in the formulas (4) and (5), a combination in which one is a chlorine atom and the other is a fluorine atom is preferable. Further, as Z ¹ , Z ² , Z ³ and Z ⁴ , at least one is preferably a chlorine atom, and particularly preferably all are chlorine atoms.

The fluorine-containing compound represented by the formula (5) in which all of Z ¹ , Z ² , Z ³ and Z ⁴ are chlorine atoms is obtained by reacting iodine chloride with trifluorochloroethylene at low temperature. From the compound represented by the formula (6) obtained by reacting 1,2-dichloro-1,2,2-trifluoro-2-iodoethane with a predetermined amount of tetrafluoroethylene in the presence of a radical initiator, known compounds are known. Can be synthesized by the method. CF ₂ ClCFCl (CF ₂ ) _{n + 1} I (6) For example, the compound represented by the formula (6) is oxidized with fuming sulfuric acid to give a terminal —COF, and then after alkylesterification,
Formula (7) after reduction with sodium borohydride
A terminal alcohol compound represented by

Then, a metal is added to the terminal alcohol compound.
With the metal alkoxide produced by the action of hydride
Reacted with tetrafluoroethylene and represented by formula (8)
The compound obtained was obtained. A salt of the compound represented by the formula (8)
When hydrogenated to replace all hydrogen atoms with chlorine atoms,
In the formula (5), chlorine atom is added to the saturated bond.
X, Y, Z¹, Z^Two, Z^ThreeAnd Z^FourAre all chlorine atoms
A fluorine-containing compound represented by the formula (9)
It was In addition, the compound represented by the formula (9) is an ammonium trifluoride.
By fluorinating with Zimon, Y in formula (5)
Is fluorine, X, Z ¹, Z^Two, Z^ThreeAnd Z^FourIs all
A fluorine-containing compound having a chlorine atom was obtained. Note that the formula
When synthesizing the compound represented by (6), tetrafluoro
By changing the reaction amount of ethylene, n is 1 or 3
Was obtained. CF_TwoClCFCl (CF_Two)_nCH_TwoOH (7), CF_TwoClCFCl (CF_Two)_nCH_TwoOCF = CF_Two            (8), CF_TwoClCFCl (CF_Two)_nCCl_TwoOCFClCF_TwoCl (9).

The fluoropolymer in the present invention may or may not have a functional group, but the adhesion to the substrate, the adhesion to other layers to be laminated, the dye and the large electro-optical property. From the viewpoint of uniform dispersibility of low-molecular compounds having effects and the like, a fluorine-containing polymer having a functional group is preferable. However, when thermal stability is particularly required or when improvement of the transmittance in the low wavelength region of 190 nm to 400 nm or the near infrared region of 700 nm to 1700 nm is required, the terminal functional group may be treated with fluorine gas or the like. It may be fluorinated and stabilized.

As the method of introducing the functional group, (a) a method of copolymerizing a functional group-containing copolymerizable monomer with a fluorine-containing diene, or (b) a polymerization initiator or a chain transfer agent, etc. Examples thereof include a method of utilizing the derived polymer terminal group as a functional group.

In the method (a), a group that can be converted into a functional group (hereinafter referred to as "precursor functional group") is introduced in place of the functional group, and the precursor functional group is converted into a functional group after polymerization. It is also possible to obtain a fluoropolymer having a target functional group. Because the installation operation is easy,
The method of introducing a functional group by the method (b) is preferable. The polymer end group may be used as it is as a functional group, or this functional group may be converted into another functional group.

Examples of the functional group include a carboxylic acid group, a sulfonic acid group, a group having an ester bond, an alkenyl group, a hydroxyl group, a maleimide group, an amino group, a cyano group, and an isocyanate group. Carboxylic acid groups are particularly preferred from the viewpoints of good adhesion to a substrate and stability during storage. The precursor functional group is, for example, an alkoxycarbonyl group, and this alkoxycarbonyl group is converted into a carboxylic acid group by hydrolysis.

The number of functional groups in the fluoropolymer is 0.00 per 1 g of the fluoropolymer from the viewpoint of ensuring adhesion with the substrate.
It is preferably 1 mmol or more. Further, since the solubility or dispersibility in a solvent is good, 1 g of a fluoropolymer
It is preferably 1 mmol or less. It is particularly preferably 0.01 to 0.2 mmol per 1 g of the fluoropolymer.

The fluorine-containing polymer of the present invention is capable of exposing light to 9
In order to apply to an optical waveguide and a waveguide type optical device having a 45 ° reflection structure for bending by 0 °, it is preferable that the total reflection angle of light with respect to air is around 45 °. The total reflection angle of air of the present fluoropolymer is preferably 47 degrees or less so that the waveguide type optical device can be easily assembled and the coupling efficiency is not deteriorated. Further, in order to suppress the scattering loss to be low and to maintain the performance of the waveguide type optical device as a whole at a high level, it is preferable that the total reflection angle with respect to air is 42 degrees or more. More preferable total reflection angle is 44 degrees or more and 47 degrees or less.

Generally, the total reflection angle θ (degree) with respect to air is
It is represented by θ = sin ⁻¹ (1 / n ₀ ). Here, n ₀ represents the refractive index of the substance. Therefore, in order to apply to a waveguide type optical device having a 45-degree reflection structure, the refractive index of the material may be about 1.41 and is preferably 1.37 or more and 1.49 or less. . More preferably, it is 1.37 or more and 1.46 or less.

Further, the fluoropolymer in the present invention is
Due to the presence of chlorine, the water vapor transmission coefficient is small. The water vapor transmission coefficient is very important for improving the reliability of the device. When the water vapor transmission coefficient is large, water molecules are likely to enter the inside of the resin, so that the refractive index is likely to change during long-term use, which affects stability. Further, due to the large absorption in the general communication wavelength band (1400 to 1500 nm) of water molecules, there arises a problem that the propagation loss value is increased. Furthermore, when a hydrolyzable dopant is used to increase the refractive index, the dopant may absorb water and change, resulting in a change in the entire characteristic value.
The water vapor permeability coefficient of the fluoropolymer used for the optical waveguide of the present invention is 7.4 × 10 ⁻⁷ (cm ³ · cm / cm ² · s).
-Pa) or less is preferable.

The fluorine-containing polymer in the present invention is also optically transparent and has a characteristic that it has a higher refractive index than a conventional amorphous transparent fluororesin (hereinafter referred to as a conventional transparent fluororesin). From this, conventional transparent fluororesins such as CYTOP (trade name, manufactured by Asahi Glass Co., Ltd.), Teflon
Optical devices such as high-performance optical fibers and optical waveguides can be obtained by combining with AF (manufactured by DuPont, product name) and the like, and optical waveguides and waveguide type optical devices having more complicated shapes can be manufactured. Is also possible.

Since the fluoropolymer in the present invention and the conventional transparent fluororesin have high transparency in the ultraviolet region to the near infrared region, various light sources such as LD and LED can be selected as the light source. Is. Further, it is possible to deal with light of any mode such as a single mode and a multi mode. Due to the above characteristics, the optical waveguide and the waveguide type optical device of the present invention have a high degree of freedom in system design and can be applied to a wide range of applications.

The optical waveguide of the present invention comprises a clad portion formed on the substrate, a core portion formed on the clad portion, and a clad portion formed on the core portion. As a substrate, from the viewpoint of preventing stress generation during semiconductor waveguide such as silicon wafer or optical waveguide molding,
A plastic substrate having the same coefficient of linear expansion as the clad is preferred.

When a device for extracting light is made on the substrate side, the substrate is preferably transparent at the wavelength used. In order to propagate light efficiently,
The refractive index of the material of the core part is set higher than that of the material of the clad part. The propagating light is confined in the core portion of the waveguide and moves in the waveguide. Further, not only a simple core / clad relationship but also a more complicated refractive index distribution can be provided.

The fluorine-containing polymer in the present invention can be used as both the material for the core and the material for the clad of the optical waveguide of the present invention. When used as the material for the clad portion, any material having a higher refractive index than the fluoropolymer of the present invention can be used as the material for the core portion. In this case, for example, a mixture of a high-refractive index compound used for improving the refractive index of a conventional transparent fluororesin and the fluoropolymer of the present invention is preferable in terms of its physical properties and adhesion to the clad portion.

When the fluoropolymer of the present invention is used as the material of the core portion, a material having a lower refractive index than that of the fluoropolymer of the present invention may be used as the material of the cladding portion. A conventional transparent fluororesin is preferable because of its physical properties and adhesion to the clad portion. Further, in order to increase the refractive index of the core part, it is also preferable to add a high refractive index compound to the fluoropolymer of the present invention. Examples of the high refractive index compound include halogenated aromatic hydrocarbons containing no hydrogen atom bonded to a carbon atom, and oligomers of halogenated olefins.

As the halogenated aromatic hydrocarbon, in particular, a halogenated aromatic hydrocarbon containing only a fluorine atom as a halogen atom or a halogenated aromatic hydrocarbon containing a fluorine atom and another halogen atom is a fluorine-containing polymer. Is preferable in terms of compatibility. Examples of such a halogenated aromatic hydrocarbon include, for example, a formula Φ-Z _b (Φ is a b-valent perfluoroaromatic ring residue, Z is a halogen atom other than fluorine,
Represents R ^F , COR ^F , OR ^F , or CN. However,
R ^F represents a perfluoroalkyl group, a perhaloalkyl group containing one or more fluorine atoms, or a monovalent perfluoroaromatic ring residue, and b is an integer of 0 or more. ). The aromatic ring is preferably a benzene ring or a naphthalene ring, and the carbon number of R ^F is preferably 5 or less. As a halogen atom other than a fluorine atom, a chlorine atom or a bromine atom is preferable.

Specific examples of the halogenated aromatic hydrocarbon compound include 1,3-dibromotetrafluorobenzene, 1,4-dibromotetrafluorobenzene and 2
-Bromotetrafluorobenzotrifluoride, chloropentafluorobenzene, bromopentafluorobenzene, iodopentafluorobenzene, decafluorobenzophenone, perfluoroacetophenone, perfluorobiphenyl, perfluoro (1,3,5-triphenylbenzene), chlorohepta Examples include fluoronaphthalene and bromoheptafluoronaphthalene.

As the oligomer of halogenated olefin, homopolymerization oligomer of fluorinated olefin such as tetrafluoroethylene, chlorotrifluoroethylene, dichlorodifluoroethylene, hexafluoropropylene and perfluoro (alkyl vinyl ether), or 2 of these monomers can be used. Examples include copolymerized oligomers of two or more kinds. _{Further, -CF 2 CF (CF 3)} O- or - (CF
_{2) n} O- _(n it can be used also such as perfluoropolyethers having a structural unit of an integer of 1 to 3). This oligomer may have a functional group.

Further, in the general formula ^{_{R a m MR b 4-m}} ( wherein,
A plurality of R ^a are the same or different from each other and have a non-hydrolyzable organic group having 1 to 14 carbon atoms, R ^b is a hydrolyzable group, and m is 0 to
An integer of 3, M represents Si, Ti, Zr, Hf or Th. ) Or a partial hydrolysis-condensation product of this compound (hereinafter, both are collectively referred to as compound a).
, Even if blended with the fluoropolymer in the present invention, a high refractive index, it is possible to form a good core portion of mechanical properties,
It can be adopted as a high refractive index compound. 1 for compound a
One kind may be used, and two or more kinds selected from the compound a may be used in combination. Further, the compound a in which M is Si is particularly preferable.

As the hydrolyzable group R ^b , an alkoxy group, a fluorine-containing alkoxy group, an alkoxyalkoxy group,
Examples thereof include an acyloxy group, an aryloxy group, an aminoxy group, a carbamoyl group, a ketoxime group, an isocyanate group and a halogen atom. Preferred is a group obtained by removing a hydrogen atom from a hydroxyl group of a monohydric alcohol such as an alkoxy group or an alkoxyalkoxy group. An alkoxy group is particularly preferable, and the number of carbon atoms is preferably 4 or less, particularly preferably 1 or 2.

At least one of the non-hydrolyzable organic groups R ^{a in} the compound a is preferably an organic group having a functional group. When R ^a has ^a non-hydrolyzable organic group having no functional group, the organic group is usually an alkyl group. As the functional group, for example, an amino group, an epoxy group,
There are glycidyloxy group, mercapto group, isocyanate group and the like. A more preferred functional group is an amino group,
It is an epoxy group.

As a method of forming the optical waveguide of the present invention, any method can be adopted as long as it can have a structure in which the periphery of the core portion is surrounded by the cladding portion, but the following method is preferable. To be done. That is, a clad portion is formed on a substrate, a core portion is formed on the clad portion, and then a part of the core portion is removed by applying a photolithography method or the like, and the clad portion is left on the remaining core portion. Method of forming, or forming a clad portion on the substrate,
A method may be adopted in which a mold having a desired pattern is transferred by heating and pressure to form a groove to be a core portion, the core portion is embedded therein, and then the clad portion is re-formed. The fluoropolymer in the present invention has good releasability and good pattern transferability.

The optical waveguide of the present invention has a thickness of about 1 μm on the substrate.
The method of molding from a solution is particularly preferable because it is necessary to form a thin film of a polymer having a thickness of m to 1000 μm. The fluorine-containing polymer in the present invention is soluble in a fluorine-containing solvent, and the solution obtained by dissolving in these solvents is applied onto a substrate by spin coating, spraying, etc., and then the solvent is evaporated and dried. A thin film having a desired film thickness can be formed.

When the optical waveguide of the present invention is prepared,
The cross-sectional shape of the core portion of the optical waveguide is 1 to 30 on each side.
A rectangle having a length of 0 μm is preferable, and the length of one side can be arbitrarily selected depending on the kind (wavelength or mode) of propagating light and the difference in refractive index between the material of the core and the material of the clad. Further, when connecting an optical waveguide or a waveguide-type optical device to an optical fiber, depending on the size of the diameter of the optical fiber to be connected,
The length of the side can be arbitrarily selected. When connecting with a single mode optical fiber, it is desirable that the shape is square.

When light is processed by an external stimulus, it is desirable that the core part and the clad part are formed so as to satisfy the above-mentioned single mode condition. Here, the single-mode condition is a condition for propagating only single-mode light, and is a condition that is satisfied when V = 2.15 or less in the following formula (I). When connecting to a general optical fiber for communication, it is desirable to set the relative refractive index difference expressed by the following formula (II) to about 0.3%. It is desirable to make it as large as possible. ^{_{V = k 0 a√ (n 1}} 2 -n 2 2) (I) _where a _k 0 = _2π / _{λ, λ} is the wavelength, a is the core size, _{n 1} is the refractive index of the core portion material, n ₂ represents the refractive index of the material of the clad portion. Δ = (n ₁ ² −n ₂ ² ) / 2n ₁ ² (II) where Δ is the relative refractive index difference, n ₁ is the refractive index of the core material, and n ₂ is the refractive index of the cladding material. .

In the waveguide type optical device of the present invention, various kinds of optical waveguides are combined or members having other functions are combined so that propagating light is generated by an external field (a signal from the outside or a core portion in proximity). For example, a directional coupler, an optical modulator, an optical switch, a variable optical attenuator, a wavelength selection device, and an optical integrated circuit are controlled. The optical waveguide of the present invention can be applied with a 45-degree reflection structure and can impart a function of bending light by 90 degrees at an extremely short distance. Therefore, an optical surface used when mounting an optical device on a printed wiring board or the like. Packaging Technology (Uchida, Masuda: Optical Surface Mounting Technology / Optical SMT, IEICE 1990 Autumn National Convention Proceedings Volume 4, C-
189) and the like.

A substrate to which these are applied is a high-speed optical LAN,
System that uses high-speed electronic circuit components such as subscriber optical communication and optical switching information processing together with optical signal transmission system, and optical and electrical connection with a package or a printed wiring board equipped with an integrated optoelectronic integrated circuit in the equipment. It can be applied to optoelectronic printing and the like. When the optical waveguide and the waveguide-type optical device of the present invention are used for these applications, the fluorine-containing polymer of the present invention shows low loss and low birefringence. Can be formed.
Further, it is possible to construct a highly reliable system with high environmental resistance, which makes use of the characteristics of low water absorption and high Tg.

Generally, when two optical waveguides having the same phase velocity are arranged close to each other, the light propagating in one optical waveguide gradually moves to the other optical waveguide. An element having such a basic structure is called a directional coupler. The directional coupler produced using the optical waveguide of the present invention exhibits a very low coupling loss value due to its low birefringence, and exhibits extremely high reliability due to its properties of low water absorption and high Tg.

Further, an optical switch or a wavelength selection device using the directional couplers in combination in multiple stages or in parallel,
Similarly excellent characteristics are exhibited in a waveguide type optical device such as an optical modulator. Among them, wavelength division multiplexing (W
A wavelength selection device (for example, AWG (Arrayed-Wav) used as a main component of a DM) communication system.
(eg, Eggide Grating)), low birefringence is indispensable for improving wavelength division accuracy, and when the optical waveguide of the present invention is used, a wavelength selection device having high wavelength accuracy can be obtained. Further, by combining with a conventional transparent fluororesin, it is possible to make a large difference in refractive index, so that it is possible to make the device compact and highly integrated.

On the other hand, as an application example of a plastic optical waveguide, which has been attracting attention in recent years, a thermo-optical switch (hereinafter referred to as T, which takes advantage of the large temperature dependence (thermo-optical constant) of the refractive index).
It is described as an O switch. ). In the case of a quartz type, a Mach-Zehnder (MZ) type that utilizes a phase difference is generally used in a TO switch, but in a plastic type, a simple digital switch is possible by utilizing a large thermo-optic constant.

Also in the case of the digital switch comprising the optical waveguide of the present invention, since it can be constructed only by a simple branch structure, it can be miniaturized and highly integrated, and is very useful in mass production and cost reduction. Is. Further, the fluorine-containing polymer of the present invention has a chlorine atom, and thus has a larger thermo-optical constant than a polymer without a chlorine atom. Therefore, it is possible to obtain a TO switch that has a high response speed and consumes less power. At the same time, the properties of the fluoropolymer of the present invention such as low birefringence, low water absorption and high Tg can greatly contribute to high performance and high reliability of the TO switch.

Further, the fluoropolymer in the present invention is
Since the refractive index is around 1.4, which is very close to the refractive index (1.45) of quartz fiber, it is possible to reduce the reflection loss due to the refractive index difference, which is a problem when connecting. It can be used with very low loss even when used for.

[0055]

EXAMPLES Examples of the present invention will be shown below, but the present invention is not limited to these examples. (Synthesis example 1) CF ₂ ClCFClCF ₂ CFClOCF
ClCF ₂ Cl synthesis stirrer, reflux condenser, 500 m equipped with dropping funnel
100g of antimony trifluoride in L four-necked flask
(0.56 mol) was charged, and C was added under an inert gas atmosphere.
F ₂ ClCFClCF ₂ CCl ₂ OCFClCF ₂ Cl
215 g (0.47 mol) of the above and 16.8 g (0.056 mol) of antimony pentachloride were charged. Then, while stirring well, the internal temperature is heated to 110 to 120 ° C,
The reaction was carried out at that temperature for 4 hours. After that, the remaining solid is removed by filtration, and the crude product is distilled to obtain CF ₂ ClCFClCF ₂ CFClOCFClC.
F ₂ Cl (1,2,4,6,7-pentachloro-1,
1,2,4,5,5,6,7,7-nonafluoro-3-
130 g of oxa-heptane was obtained (yield 62.
%). The boiling point was 0.75 kPa and 62 ° C. CF
^a ₂ ClCF ^b ClCF ^c ₂ CF ^d ClOCF ^e ClC
¹⁹ F NMR data when F ^f ₂ Cl is used is shown below.

¹⁹ F NMR (CDCl ₃ , CFCl ₃
Standard) δ ppm; -64.0 and -70.8 (F
^{a and F f, 4F),} - 68.5~-74.5
(F ^d , 1F), −78.0 (F ^e , 1F), −10
^{7.2~-115.2 (F c, 2F} ), - 125~-1
32 (F ^b , 1F).

(Synthesis example 2) CF ₂ = CFCF ₂ CFCl
500 m with OCF = CF ₂ synthesis stirrer, reflux condenser, dropping funnel
120g of zinc (1.84mo
l) Charge, 200 ml of dimethylformamide was charged under an inert gas atmosphere. Subsequently, the system was depressurized to 4 kPa, the internal temperature was further adjusted to 50 to 55 ° C., and the CF ₂ ClCFClCF ₂ CFClOC obtained in Synthesis Example 1 was added thereto.
100 g (0.23 mol) of FClCF ₂ Cl was slowly added dropwise through a dropping funnel, and the product was rapidly extracted by distillation during the reaction. Then, by rectifying the crude product, CF ₂ = CFCF ₂ CFClOC
F = CF ₂ (4-chloro-1,1,2,4,5,5,5
6,7,7-nonafluoro-3-oxa-hepta-1,
39 g of 6-diene) was obtained (60% yield). The boiling point was 61 ° C. at 33 kPa. Hereinafter, this compound is referred to as Monomer A. IR and ¹⁹ F NMR of Monomer A are as follows. _{^{IR: 1785cm -1 (CF 2 =}} CF -), 1835
_{^{cm -1 (CF 2 = CFO-)}} .

[0058]

[Chemical 3]

[0059]¹⁹F NMR (CDCl_Three, CFCl_Three
Standard) δ ppm; -114.9 (F ^a, J_ab= 83H
z, J_ac= 65 Hz), -112.3 (F^b, J_bc
= 111Hz, J_bd= 6 Hz), -135.3
(F^c, J_cd= 10 Hz), -74.9 (F^d), −
117.3 (F^e, J_ef= 14Hz, J_eg= 6H
z, J _eh= 27 Hz), -188.2 (F^f, J_fg
= 39Hz, J_fh= 118 Hz), -89.1
(F^g, J_gh= 50 Hz), -105.4 (F^h).

(Synthesis Example 3) Polymerization of Monomer A 1, 2, 1 was placed in a 100 ml stainless autoclave.
50 of trichloro-1,2,2-trifluoroethane
g, 30 g of monomer A (0.097 mol), and 0.1 g of diisopropyl peroxydicarbonate (4.
85 × 10 ⁻⁴ mol) was charged. The autoclave was heated and stirred at 50 ° C. for 3 days. Then, the autoclave was opened and the product was washed with methanol. The solvent and the remaining monomer were distilled off from the washed product under reduced pressure to obtain 29 g of a colorless and transparent polymer (hereinafter referred to as polymer A). The yield of the obtained polymer A was 96%. The molecular weight of this polymer A converted into polymethylmethacrylate by GPC using a dichloropentafluoropropane solvent (hereinafter, referred to as R225) (also in the following molecular weight measurement) was 42500 in number average molecular weight (Mn), and weight. 12 in average molecular weight (Mw)
It was 3000.

A film prepared by press-molding the polymer A had a refractive index of 1.3 as measured by an Abbe refractometer.
7, T measured by differential scanning calorimetry (DSC)
g was 126 ° C. The tensile properties of the polymer were measured and the tensile modulus was 1700 MPa and the yield stress was 50 MP.
a, the yield elongation was 3.8%.

The infrared absorption spectrum of polymer A was measured.
However, the CF found in the monomer_Two= CF-based 17
85 cm^-1And CF_Two= 1835 based on CFO-
cm ^-1Had disappeared. This polymer A is a pen
High reaction rate with no double bond and no cross-linking reaction
However, since it is completely soluble in R225, it is a cyclized polymer.
I found out that Also,¹⁹Below by F NMR analysis
It was confirmed that the polymer had a repeating unit of the above structure.
won.

[0063]

[Chemical 4]

(Synthesis Example 4) CF ₂ = CFCF ₂ CCl ₂
Synthesis of OCF = CF _{2 In} Synthesis Example 2, CF ₂ ClCFClCF ₂ CFClO
Instead of 100 g of CFClCF ₂ Cl, CF ₂ Cl
CFClCF ₂ CCl ₂ OCFClCF ₂ Cl 100
CF ₂ is operated in the same manner as in Synthesis Example 2 except that g is used.
= CFCF ₂ CCl ₂ OCF = 42 g of CF ₂ was obtained (yield 62%).

[0065]

[Chemical 5]

[0066]¹⁹F-NMR (CDCl_Three, CFCl_Three
Standard) δppm; -111.3 (F ⁱ, J_ab= 83H
z, J_ac= 65 Hz), -115.6 (F^j, J_bc
= 111 Hz), -140.2 (F^k), -115.5
(F^s), -183.6 (F^t, J_ef= 39Hz, J
_eg= 118 Hz), -83.9 (F^u, J_fg= 50
Hz), -97.3 (F^v).

(Synthesis Example 5) Polymerization of Monomer B 5 g of Monomer B and 12.5 mg of diisopropyl peroxydicarbonate were placed in a glass ampoule, frozen in liquid nitrogen, deaerated under vacuum, and sealed. After heating in an oven at 40 ° C. for 20 hours, the solidified contents were taken out, washed with methanol, and dried at 200 ° C. for 1 hour. The yield of the obtained polymer (hereinafter, referred to as polymer B) was 80%. When a part of the polymer B was dissolved in R225 and the intrinsic viscosity was measured, it was 0.20 dl / g. The polymer B had a number average molecular weight (Mn) of 44,500 and a weight average molecular weight (Mw) of 121,500.

The refractive index of the film prepared by press-molding the polymer B was 1.4 as measured with an Abbe refractometer.
1, T measured by differential scanning calorimetry (DSC)
The g was 168 ° C. The tensile properties of this polymer were measured to find a tensile elastic modulus of 1690 MPa and a yield stress of 50 MP.
a, the yield elongation was 3.6%.

The infrared absorption spectrum of polymer B was measured.
However, the CF found in the monomer_Two= CF-based 17
85 cm^-1And CF_Two= 1835 based on CFO-
cm ^-1Had disappeared. This polymer B is a pen
High reaction rate with no double bond and no cross-linking reaction
However, since it is completely soluble in R225, it is a cyclized polymer.
I found out that Also,¹⁹Below by F NMR analysis
It was confirmed that the polymer had a repeating unit of the above structure.
won.

[0070]

[Chemical 6]

Next, the polymer B was heat-treated in air at 300 ° C. for 3 hours and then immersed in water to obtain a heat-treated polymer. A peak attributed to a carboxylic acid group was confirmed in the IR spectrum of this heat-treated polymer, and the amount of the carboxylic acid group was 0.03 mmol per 1 g of the polymer. In addition, the light transmittance in the visible to near-infrared region is as high as 95% or more and 30
It was found that the 0 ° C. treatment had no effect on the transparency.

(Example 1) CF ₂ = CFOCF ₂ CF ₂ CF = C having a carboxylic acid as a functional group described in [Example 1 (synthesis example)] of Example of JP-A-2000-81519.
A polymer solution (hereinafter, referred to as C1 liquid) was prepared by dissolving 10 g of a polymer of F ₂ (hereinafter referred to as polymer C) in 90 g of perfluorotributylamine. 10 g of Polymer A, 90 g of CF ₂ ClCFClCF ₂ CFCl ₂
Was prepared (hereinafter, referred to as A1 liquid).

Liquid C1 was applied on a silicon substrate by spin coating and heated at a temperature of 250 ° C. for 60 minutes to form a lower clad portion of polymer C having a thickness of 10 μm. Liquid A1 was further spin-coated on the lower clad portion and heated at a temperature of 250 ° C. for 60 minutes to form a layer of the polymer A having a thickness of 5 μm. Next, a resist solution (manufactured by Tokyo Ohka Co., Ltd.,
Product name OFPR-800) is applied, pre-baked, exposed,
By performing development and post-baking, a resist layer composed of a straight line having a width of 5 μm was formed. The polymer A not protected by the resist layer was removed by dry etching.

Then, the remaining resist which protected the polymer A was removed by wet etching to give a cross section of 5 μm.
A rectangular column-shaped core portion made of the polymer A and having a rectangular shape of × 5 μm was formed on the lower clad. On the core portion thus formed, the upper clad portion made of the polymer C is formed by using the C1 liquid in the same manner as the formation of the lower clad portion, and the linear optical waveguide formed on the silicon substrate is obtained. It was

In this optical waveguide, the refractive indexes of the clad portion and the core portion were 1.340 and 1.370, respectively. When the propagation loss of this optical waveguide was measured using a semiconductor laser light source, a wavelength of 650 nm and a wavelength of 13
The optical waveguide was 0.2 dB / cm or less with light of 00 nm, and was an optical waveguide capable of favorably transmitting light from visible light to near infrared light. Moreover, when the optical waveguide was heat-treated in an oven at 120 ° C. for 1 hour and the propagation loss was measured, no change was observed.

Example 2 10 g of polymer B, CF ₂ C
A composition consisting of 90 g of 1CFClCF ₂ CFCl ₂ (hereinafter referred to as B1 liquid) was prepared. A1 of Example 1
An optical waveguide was obtained in the same manner as in Example 1 except that the liquid was changed to the B1 liquid. In this optical waveguide, the refractive indexes of the clad part and the core part were 1.340 and 1.410, respectively. When the propagation loss of this optical waveguide was measured using a semiconductor laser light source, a wavelength of 650 nm and a wavelength of 1
It was 0.2 dB / cm or less at 300 nm light, and was an optical waveguide capable of favorably transmitting light from visible light to near infrared light. Moreover, when the optical waveguide was heat-treated in an oven at 120 ° C. for 1 hour and the propagation loss was measured, no change was observed.

(Comparative Example 1) An optical waveguide was prepared according to Example 4 described in JP-A-2000-81519. When the propagation loss of this optical waveguide was measured by the same method as in Example 1, it was 0.2 dB / cm or less. Then, the optical waveguide was heat-treated in an oven at 120 ° C. for 1 hour, and the propagation loss was measured. As a result, the loss value increased to 0.3 dB / cm or more, and a change in characteristics was observed.

(Example 3) The linear optical waveguide obtained in Example 2 was cut into a length of 5 cm by using a dicing device so that both end surfaces were perpendicular to the silicon substrate. Next, after adjusting the blade of the dicing device so as to be 45 degrees with respect to the silicon substrate, the center part of the cut out optical waveguide is cut, and one end surface is perpendicular to the silicon substrate and the other is 45 degrees. An optical waveguide having a certain 45-degree reflection structure was obtained. When a semiconductor laser beam of 850 nm was made incident from the end face at a right angle and the amount of light emitted at a position of 90 degrees above the end face of 45 degrees was measured, it was found that 8
The emitted light could be detected with a high efficiency of 0% or more.

Comparative Example 2 The waveguide prepared in Comparative Example 1 was cut in the same manner as in Example 3 to prepare an optical waveguide having a 45 ° reflection structure. When a semiconductor laser beam of 850 nm was made incident from the end face at a right angle and the amount of light emitted at the position of 90 degrees above the 45 ° end face was measured, it was 6 with respect to the incident light.
Only 0% or less of the emitted light could be detected.

[0080]

EFFECTS OF THE INVENTION The optical waveguide of the present invention has good initial mechanical properties and optical properties due to the properties of the fluorine-containing polymer used, and does not deteriorate in optical properties even when used at high temperatures for a long time. In addition, the optical waveguide of the present invention has excellent water resistance, and therefore, is highly reliable in combination with the above-mentioned high temperature durability. Further, by providing the 45-degree reflection structure, an optical waveguide having a function of bending light by 90 degrees can be obtained.

The optical waveguide of the present invention can be applied as various waveguide type optical devices. For example, a Y-branch type waveguide and a directional coupler are generally used for multiplexing and splitting light, but the waveguide type optical device of the present invention uses a material having a low birefringence. Even if the signal is branched in multiple stages, there is little signal deterioration or attenuation. Further, when a TO switch, which is a kind of waveguide type optical device, is used, the size and the integration are reduced.
Higher response speed and lower power consumption are possible. Further, the connection loss with the quartz fiber can be reduced.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Norihide Sugiyama             1150 Hazawa-machi, Kanagawa-ku, Yokohama-shi, Kanagawa             Asahi Glass Co., Ltd. F term (reference) 2H047 KA04 LA09 PA02 PA21 PA24                       PA28 QA05                 4J100 AE84P BB01P BB07P BB12P                       JA32

Claims (7)

[Claims] 1. The following formula (1), the following formula (2) or the following formula (3):
An optical waveguide comprising a fluoropolymer containing at least one repeating unit having a ring structure selected from [Chemical 1] However, Q represents R ^f —O, R ^f has one or more chlorine atoms, may have an etheric oxygen atom inside R ^f, and has a side chain composed of a fluorine-containing alkyl group. It represents a fluorine-containing alkylene group having 10 or less carbon atoms, which may be possessed. 2. The optical waveguide according to claim 1, wherein the chlorine atom in R ^f is bonded to a carbon atom which constitutes a ring and is adjacent to an oxygen atom. 3. The fluorinated polymer is a fluorinated polymer containing a repeating unit of a ring structure formed by cyclopolymerization of a fluorinated diene represented by the formula (4).
The optical waveguide described in. _{CF 2 = CF (CF 2)} n CXYOCF = CF 2 ··· (4) However, X, Y are each independently a fluorine atom or a chlorine atom, at least one is a chlorine atom. Also,
n represents an integer of 1 to 3. 4. In the formula (4), X is a chlorine atom,
The optical waveguide according to claim 3, wherein Y is a fluorine atom. 5. The optical waveguide according to any one of claims 1 to 4, wherein the fluoropolymer is a fluoropolymer further having a functional group. 6. The optical waveguide according to claim 1, wherein the optical waveguide has a 45-degree reflecting structure capable of bending light by 90 degrees. 7. A waveguide type optical device comprising the optical waveguide according to claim 1.