JP2002311254A - Method for manufacturing optical resin material having graded refractive index - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a new optical resin material with graded refractive index, having heat resistance, moisture resistance, chemical resistance and incombustibility and transmitting light ranging from ultraviolet rays to near infrared rays with an extremely small loss by using a monomer. SOLUTION: The optical resin material having graded refractive index is composed of an amorphous fluorine containing polymer (a) with practically no C-H bond and at least one kind of substance (b) with a refractive index higher by 0.001 or more compared with that of the fluorine containing polymer (a) where the substance (b) is distributed in the fluorine containing polymer (a) along a specified direction with a concentration gradient. The optical resin material having graded refractive index is manufactured by polymerizing a mixture of the substance (b) or a monomer forming the substance (b) and the monomer forming the fluorine containing polymer (a).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a refractive index distribution type optical resin material having high transparency and heat resistance, which has been difficult to realize with conventional optical resins. )).

[0002] The optical resin material of the present invention may itself be an optical transmission body such as an optical fiber, or may be a base material of an optical transmission body such as an optical fiber preform.

[0003] The optical transmission material, which is an optical resin material in the present invention, is a non-crystalline resin, which does not scatter light and has very high transparency in a wide wavelength band from ultraviolet light to near infrared light. It can be effectively used for optical systems of various wavelengths. In particular, 1300 nm and 1550 nm, which are wavelengths used for mainline quartz fibers in the optical communication field.
And a low-loss optical transmitter.

[0004] The optical transmission material of the present invention, which is an optical resin material, has heat resistance, chemical resistance, moisture resistance, and nonflammability that can withstand severe use conditions in an engine room of an automobile or the like.

[0005] The optical transmission material which is an optical resin material in the present invention includes a refractive index distribution type optical fiber, a rod lens, an optical waveguide, an optical splitter, an optical multiplexer, an optical demultiplexer, an optical attenuator, an optical switch, an optical switch. It is useful as a variety of refractive index distribution type optical transmitters such as an isolator, an optical transmission module, an optical reception module, a coupler, a deflector, and an optical integrated circuit. Here, the refractive index distribution means a region in which the refractive index changes continuously along a specific direction of the optical transmission body.For example, the refractive index distribution of a refractive index distribution type optical fiber is radial from the center of the fiber. The refractive index decreases in a curve close to a parabola.

When the optical resin material in the present invention is a base material of an optical transmission body, the optical transmission medium such as a refractive index distribution type optical fiber can be manufactured by spinning the optical transmission material by heat drawing or the like.

[0007]

2. Description of the Related Art Conventionally known resins for graded-index plastic optical transmission bodies include optical resins represented by methyl methacrylate resins and WO94 / 049.
49, a tetrafluoroethylene resin and a vinylidene fluoride resin have been proposed.

[0008] As a step-refraction type plastic optical fiber, a core is made of methyl methacrylate resin, styrene resin,
Many proposals have been made to use an optical resin such as a carbonate resin or a norbornene resin and to make the cladding a fluoropolymer. Also, Japanese Patent Application Laid-Open No. 2-244007 proposes using a fluorine-containing resin for the core and the clad.

[0009]

SUMMARY OF THE INVENTION The present invention is required in automobiles, office automation (OA) equipment, home electric appliances, etc., which cannot be achieved by optical transmission media such as methyl methacrylate resin, carbonate resin, norbornene resin and the like. An object of the present invention is to provide a method for producing an optical resin material having heat resistance, moisture resistance, chemical resistance, and nonflammability.

Further, the present invention makes it possible to use ultraviolet light (wavelength from 200 nm to 400 nm) and near-infrared light (wavelength from 700 nm to 2500 nm), which could not be reached by an optical transmitter such as methacrylate resin, carbonate resin, norbornene resin, etc. It is another object of the present invention to provide a novel method for producing an optical resin material having a low optical transmission loss over a wide transmission range.

[0011]

The present inventors have made intensive studies based on the recognition of the above-mentioned problems, and as a result, have obtained heat resistance, moisture resistance, chemical resistance, non-combustibility and near infrared light. It has been found that a fluoropolymer substantially free of C—H bonds is optimal for eliminating C—H bonds (ie, carbon-hydrogen bonds) that cause light absorption. This fluoropolymer has a C—F bond (that is, a carbon-fluorine bond) instead of a C—H bond.

That is, when a substance is irradiated with light, light having a wavelength that causes a stretching vibration of a bond between certain atoms or a resonance vibration with a bending vibration is preferentially absorbed. Until now, polymer materials used in plastic optical fibers were mainly C
It was a compound having a -H bond. In the polymer substance based on the C—H bond, the hydrogen atoms are lightweight and easily vibrate.
m). Therefore, in the near-infrared to infrared region (600 to 1550 nm), which is the wavelength of the light source, relatively low overtone absorption of the C—H stretching vibration appears discretely, which is a major cause of absorption loss.

When the hydrogen atom is replaced with a fluorine atom, the wavelength of the overtone absorption peak shifts to the longer wavelength side, and the absorption in the near infrared region decreases. From the theoretical value, in the case of PMMA (polymethyl methacrylate) having a C—H bond, the absorption loss of the C—H bond at a wavelength of 650 nm is estimated to be 105 dB / km, and at a wavelength of 1300 nm, 10,000 dB. / Km
That is all.

On the other hand, in a substance in which a hydrogen atom is replaced with a fluorine atom, there is substantially no loss due to absorption at a wavelength of 650 nm, and even at a wavelength of 1300 nm, a 1 dB / sound between the sixth and seventh harmonics of the stretching vibration of the CF bond. It can be considered that there is no absorption loss on the order of km. For that we have C
It is proposed to use a compound having a -F bond.

It is desirable to exclude functional groups such as a carboxyl group and a carbonyl group, which are factors that inhibit heat resistance, moisture resistance, chemical resistance, and nonflammability. In addition, since the presence of a carboxyl group causes absorption of near-infrared light and the presence of a carbonyl group causes absorption of ultraviolet light, it is desirable to exclude these groups. In order to further reduce transmission loss due to light scattering, it is important to use a non-crystalline polymer.

Further, in the case of a step-index optical fiber,
Multimode light propagates while being reflected at the interface between the core and the cladding. As a result, mode dispersion occurs and the transmission band decreases. However, in the graded index optical fiber, mode dispersion hardly occurs and the transmission band increases.

Accordingly, C--H is substantially used as the optical resin material.
Amorphous fluorine-containing polymer having no bond, especially a fluorine-containing polymer having a ring structure in the main chain, and an optical material having a gradient in a specific direction in which the concentration of a substance having a different refractive index compared to the polymer has a gradient. A resin material has been found, and a method for producing the optical resin material using a monomer capable of forming a fluoropolymer has been newly found, leading to the following present inventions (a) and (b).

(A) a non-crystalline fluorine-containing polymer (a) having substantially no C—H bond and a fluorine-containing polymer (a)
And at least one substance (b) having a refractive index higher than that of the substance (b) by 0.001 or more, and the substance (b) has a concentration gradient along a specific direction in the fluoropolymer (a). A method for producing a distributed refractive index distribution type optical resin material, wherein a fluoropolymer (a) containing a substance (b) is formed inside a tube made of a hollow fluoropolymer (a). A method for producing a refractive index distribution type optical resin material, comprising sealing a monomer and polymerizing the monomer while rotating a tube.

(B) A non-crystalline fluorine-containing polymer (a) having substantially no C—H bond, and a fluorine-containing polymer (a)
And a substance (b) that is at least one polymer having a difference in refractive index of 0.001 or more as compared with
A method for producing a refractive index distribution type optical resin material, in which a substance (b) is distributed with a concentration gradient along a specific direction in a fluoropolymer (a), comprising: ) And the monomer forming the substance (b), and using two kinds of monomers having different reactivities, the composition of the fluoropolymer (a) and the substance (b) formed A method for producing a refractive index distribution type optical resin material, wherein a polymerization reaction is advanced so that a ratio continuously changes from a peripheral portion toward a center.

As the fluorinated polymer, tetrafluoroethylene resin, perfluoro (ethylene-propylene) resin, perfluoroalkoxy resin, vinylidene fluoride resin, ethylene-tetrafluoroethylene resin, chlorotrifluoroethylene resin and the like have been widely used. Are known. However, since these fluorine-containing resins have crystallinity, scattering of light occurs, transparency is not good, and it is not preferable as a material of a plastic optical transmission body.

On the other hand, the non-crystalline fluorine-containing polymer is excellent in transparency because light is not scattered by crystals.
The fluoropolymer (a) in the present invention is not particularly limited as long as it is a non-crystalline fluoropolymer having no C—H bond produced by in-situ polymerization from a monomer. Fluorine-containing polymers having a ring structure are preferred.
As the fluorine-containing polymer having a ring structure in the main chain, a fluorine-containing polymer having a fluorine-containing aliphatic ring structure, a fluorine-containing imide ring structure, a fluorine-containing triazine ring structure or a fluorine-containing aromatic ring structure is preferable. Among the fluorinated polymers having a fluorinated aliphatic ring structure, those having a fluorinated aliphatic ether ring structure are more preferred.

The fluorinated polymer having a fluorinated aliphatic ring structure is more heat-stretched or melted as described later than a fluorinated polymer having a fluorinated imide ring structure, a fluorinated triazine ring structure or a fluorinated aromatic ring structure. This is a more preferable polymer because the polymer molecules are less likely to be oriented during fiber formation by spinning, and as a result, light is not scattered.

The viscosity of the fluoropolymer (a) in the molten state is 10 ³ to 10 at a melting temperature of 200 ° C. to 300 ° C.
10 ⁵ poise is preferred. If the melt viscosity is too high, not only is melt spinning difficult, but also necessary for forming a refractive index distribution,
Diffusion of the substance (b) hardly occurs, and it becomes difficult to form a refractive index distribution. On the other hand, if the melt viscosity is too low, practical problems arise. That is, when used as an optical transmitter in an electronic device, an automobile, or the like, it is exposed to a high temperature and softened, and the light transmission performance is reduced.

The number average molecular weight of the fluoropolymer (a) is
It is preferably from 10,000 to 5,000,000, and more preferably from 50,000 to 1,000,000. If the molecular weight is too small, heat resistance may be impaired, and if it is too large, it becomes difficult to form a light transmitting body having a refractive index distribution, which is not preferable.

Examples of the polymer having a fluorinated aliphatic ring structure include those obtained by polymerizing a monomer having a fluorinated ring structure and those obtained by cyclopolymerizing a fluorinated monomer having at least two polymerizable double bonds. The polymer having a fluorinated aliphatic ring structure in the main chain obtained by the above method is preferred.

A polymer having a fluorinated alicyclic structure in the main chain obtained by polymerizing a monomer having a fluorinated alicyclic structure is known from JP-B-63-18964. That is, perfluoro (2,2-dimethyl-
A monomer having a fluorinated aliphatic ring structure such as 1,3-dioxole) is homopolymerized, and this monomer is converted into a radical polymerizable monomer such as tetrafluoroethylene, chlorotrifluoroethylene, or perfluoro (methyl vinyl ether). By copolymerizing with the above, a polymer having a fluorinated aliphatic ring structure in the main chain is obtained.

A polymer having a fluorinated aliphatic ring structure in the main chain obtained by cyclopolymerization of a fluorinated monomer having at least two polymerizable double bonds is disclosed in
238111 and JP-A-63-238115. That is, by subjecting a monomer such as perfluoro (allyl vinyl ether) or perfluoro (butenyl vinyl ether) to cyclopolymerization, or by subjecting such a monomer to tetrafluoroethylene, chlorotrifluoroethylene, perfluoro (methyl vinyl ether), or the like. By copolymerizing with a radical polymerizable monomer, a polymer having a fluorinated aliphatic ring structure in the main chain can be obtained.

Further, perfluoro (2,2-dimethyl-
Monomers having a fluorinated aliphatic ring structure such as 1,3-dioxole) and perfluoro (allyl vinyl ether)
A polymer having a fluorinated aliphatic ring structure in the main chain can also be obtained by copolymerizing a fluorinated monomer having at least two polymerizable double bonds such as fluorinated or perfluoro (butenyl vinyl ether).

Specific examples of the polymer having a fluorinated aliphatic ring structure include those having a repeating unit selected from the following formulas (I) to (IV). In addition, the fluorine atom in these polymers having a fluorinated aliphatic ring structure may be partially substituted with a chlorine atom in order to increase the refractive index.

[0030]

Embedded image

In the above formulas (I) to (IV), l is 0 to 5, m is 0 to 4, n is 0 to 1, and l + m + n is 1 to 5.
6, o, p, and q are 0 to 5, respectively, and o + p + q is 1 to
6, R is F or CF ³ , R ¹ is F or CF ³ , R ² is F
Or CF ³ , X ¹ is F or Cl, X ² is F or Cl
It is. As the polymer having a fluorinated aliphatic ring structure, a polymer having a ring structure in the main chain is suitable, but a polymer containing 20 mol% or more, preferably 40 mol% or more of polymer units having a ring structure is preferred. It is preferable in terms of transparency, mechanical properties, and the like.

The substance (b) is at least one substance having a refractive index difference of 0.001 or more as compared with the fluoropolymer (a), and has a higher refractive index than the fluoropolymer (a). It may be a refractive index or a low refractive index. In an optical fiber or the like, a substance having a higher refractive index than the fluoropolymer (a) is usually used.

The substance (b) is preferably a low molecular compound, oligomer or polymer containing an aromatic ring such as a benzene ring, a halogen atom such as chlorine, bromine or iodine, or a bonding group such as an ether bond. Further, the substance (b) is preferably a substance having substantially no C—H bond for the same reason as the fluoropolymer (a). The difference in the refractive index from the fluoropolymer (a) is preferably 0.005 or more.

The substance (b), which is a polymer composed of an oligomer or a polymer, comprises a polymer of a monomer forming the above-mentioned fluoropolymer (a), and is compared with the fluoropolymer (a). The difference in refractive index is 0.001
The oligomer or polymer described above may be used. The monomer is selected from those which form a polymer having a difference in refractive index of 0.001 or more as compared with the fluoropolymer (a). For example, two types of fluoropolymers (a) having different refractive indexes can be used, and one polymer (a) can be distributed as a substance (b) in another polymer (a).

These substances (b) have a solubility parameter difference of 7 (cal) in comparison with the above matrix.
/ Cm ³ ) is preferably within ^1/2 . Here, the solubility parameter is a characteristic value serving as a measure of the miscibility between substances, and the solubility parameter is δ, the molecular cohesion energy of the substance is E, and the molecular volume is V, and the equation δ = (E / V) ^{1 / 2} .

As the low molecular weight compound, for example, there is a halogenated aromatic hydrocarbon containing no hydrogen atom bonded to a carbon atom. 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 preferable from the viewpoint of compatibility with the fluorine-containing polymer (a). Further, it is more preferable that these halogenated aromatic hydrocarbons do not have a functional group such as a carbonyl group and a cyano group.

Examples of such a halogenated aromatic hydrocarbon include, for example, the formula Φ ^r -Z ^b [Φ ^r is a b-valent fluorinated aromatic ring residue in which all of the hydrogen atoms are replaced by fluorine atoms, and Z is fluorine Other than a halogen atom, -Rf, -CO-Rf,-
O-Rf, or -CN. Here, Rf is a perfluoroalkyl group, a polyfluoroperhaloalkyl group, or a monovalent Φ ^r . b is 0 or an integer of 1 or more. ] The compound represented by these. The aromatic ring includes a benzene ring and a naphthalene ring. The perfluoroalkyl group or polyfluoroperhaloalkyl group as Rf preferably has 5 or less carbon atoms. As a halogen atom other than fluorine, a chlorine atom or a bromine atom is preferable.

Specific compounds include, for example, 1,3-
Dibromotetrafluorobenzene, 1,4-dibromotetrafluorobenzene, 2-bromotetrafluorobenzotrifluoride, chloropentafluorobenzene,
Bromopentafluorobenzene, iodopentafluorobenzene, decafluorobenzophenone, perfluoroacetophenone, perfluorobiphenyl, chloroheptafluoronaphthalene, bromoheptafluoronaphthalene, and the like.

The substance (b), which is a polymer composed of a polymer or oligomer, having a repeating unit of the above (I) to (IV), has a refractive index different from that of the fluorine-containing polymer (a) to be combined. A fluorine-containing polymer (for example, a combination of a fluorine-containing polymer containing only a fluorine atom as a halogen atom and a fluorine-containing polymer containing a fluorine atom and a chlorine atom, polymerizing two or more monomers of different types and different ratios) The combination of the two kinds of obtained fluoropolymers is preferable.

In addition to the above fluorine-containing polymers having a ring structure in the main chain, they do not contain hydrogen atoms such as tetrafluoroethylene, chlorotrifluoroethylene, dichlorodifluoroethylene, hexafluoropropylene, and perfluoroalkylvinyl ether. Oligomers composed of monomers, copolymer oligomers of two or more of these monomers, and the like can also be used as the substance (b). Also, -C
F ² CF (CF ³⁾ O- or ^{- (CF 2) n O- (} n is 1-3
Can also be used. The molecular weight of these oligomers is selected from the range of non-crystalline molecular weight, and has a number average molecular weight of 300.
It is preferably from 10,000 to 10,000. In consideration of the ease of diffusion, a number average molecular weight of 300 to 5000 is more preferable.

A particularly preferred substance (b) is a chlorotrifluoroethylene oligomer because of its good compatibility with the fluoropolymer (a), especially the fluoropolymer having a ring structure in the main chain. Due to the good compatibility, the fluorinated polymer (a), particularly the fluorinated polymer having a ring structure in the main chain, and the chlorotrifluoroethylene oligomer are easily mixed by heating and melting at 200 to 300 ° C. be able to. After dissolving and mixing in a fluorine-containing solvent, the two can be uniformly mixed by removing the solvent. The preferred molecular weight of the chlorotrifluoroethylene oligomer is a number average molecular weight of 500 to 15
00.

In the present invention, the optical resin material is most preferably a refractive index distribution type optical fiber. In this optical fiber, the substance (b) is distributed in the fluoropolymer (a) with a concentration gradient from the center to the periphery. Preferably, the substance (b) is a fluoropolymer (a)
This is an optical fiber in which the substance (b) is distributed with a concentration gradient in which the concentration decreases from the center to the peripheral direction of the optical fiber. In some cases, the substance (b) is a substance having a lower refractive index than the fluoropolymer (a), and this substance is distributed with a concentration gradient in which the concentration decreases from the periphery of the optical fiber toward the center. Optical fibers are also useful. The former optical fiber such as an optical fiber can be usually manufactured by arranging the substance (b) at the center and diffusing it toward the peripheral direction. The latter optical transmission medium such as an optical fiber can be manufactured by diffusing the substance (b) from the periphery toward the center.

The optical transmission material of the present invention, which is an optical resin material, can have a transmission loss of 100 db or less at a wavelength of 700 to 1,600 nm at 100 m. In particular, in the case of a fluoropolymer having an aliphatic ring structure in the main chain, the transmission loss at 100 m can be reduced to 50 db or less at the same wavelength. At a relatively long wavelength of 700 to 1600 nm, it is extremely advantageous to have such a low level of transmission loss. That is, since the same wavelength as that of the quartz optical fiber can be used, connection with the quartz optical fiber is easy, and a light source that is less expensive than a conventional plastic optical fiber that has to use a wavelength shorter than 700 to 1,600 nm. It has the advantage of ending. In the production of such an optical resin material, the molding of the resin and the formation of the refractive index distribution may be performed simultaneously or separately. For example, an optical resin material can be manufactured by forming a refractive index distribution at the same time as forming a refractive index distribution by spinning or extrusion molding. After the resin is formed by spinning or extrusion, a refractive index distribution can be formed. Furthermore, an optical resin material such as an optical fiber can be manufactured by manufacturing a preform (base material) having a refractive index distribution and molding (for example, spinning) the preform. Note that, as described above, the optical resin material of the present invention also means a preform having the above-described refractive index distribution.

As a method for producing the optical resin material in the present invention, for example, there are the following methods (1) to (7). However, it is not limited to these. Among these production methods, the present invention (a) is the method (3), and the present invention (b) is the method (4).

(1) The fluorinated polymer (a) is melted, and the substance (b) or the fluorinated polymer (a) containing the substance (b) is placed at the center of the melt of the fluorinated polymer (a). , And molding while diffusing the substance (b) or after diffusing it.

In this case, the substance (b) can be implanted not only when only one layer of the substance (b) is implanted in the center but also in the center.
The substance (b) may be injected in multiple layers at the center. Examples of the molding include extrusion melt molding suitable for molding a rod-shaped base material such as an optical fiber preform and melt spinning molding suitable for molding an optical fiber.

(2) The substance (b) or the fluoropolymer (a) containing the substance (b) is repeatedly dipped on a core material composed of the fluoropolymer (a) obtained by melt spinning or drawing. How to coat.

(3) A hollow tube made of a fluoropolymer (a) is formed using a rotating glass tube or the like, and a fluoropolymer (a) containing a substance (b) is formed inside the polymer tube. ), Wherein the monomer phase is sealed and polymerized while rotating at a low speed.

In the case of this interfacial gel copolymerization, in the polymerization process, the tube made of the fluoropolymer (a) swells into the monomer phase, a gel phase is formed, and the monomer molecules are selectively diffused into the gel phase. While being polymerized.

(4) A monomer forming the fluoropolymer (a) and a monomer forming the substance (b), which are different from each other in reactivity, are used.
A method in which the polymerization reaction proceeds so that the composition ratio of the generated fluoropolymer (a) and the substance (b) changes continuously from the peripheral portion toward the center.

(5) Fluoropolymer (a) and substance (b)
After uniformly mixing in a solvent or in a solvent, the mixture obtained by volatilizing and removing only the solvent is fiberized by hot drawing or melt extrusion, and then heated (or immediately after fiberization). A method of forming a refractive index distribution by contacting an active gas to volatilize the substance (b) from the surface. Alternatively, after forming the fiber, the fiber is immersed in a solvent that dissolves only the substance (b) without dissolving the fluoropolymer (a), and the substance (b) is eluted from the fiber surface to obtain a refractive index. How to form the distribution.

(6) The rod or fiber made of the fluoropolymer (a) is coated with only the substance (b) having a lower refractive index than the fluoropolymer (a), or the fluoropolymer (a) ) And a mixture of the substance (b), and then diffusing the substance (b) by heating to form a refractive index distribution.

(7) The high-refractive-index polymer and the low-refractive-index polymer are heated and melted or mixed in a solvent-containing solution state, and are subjected to multilayer extrusion in different mixing ratios (or after extrusion). A method in which both are diffused with each other to finally obtain a fiber having a refractive index distribution. In this case, the high refractive index polymer may be the fluoropolymer (a) and the low refractive index polymer may be the substance (b), or the high refractive index polymer may be the substance (b) and the low refractive index polymer may be the substance (b). ).

[0054]

EXAMPLES Next, examples of the present invention will be described more specifically, but it goes without saying that this description does not limit the present invention. A synthesis example is a production example of a polymer, and a reference example is an example in which an optical resin material is produced by a method other than the present invention.

"Synthesis Example 1" Perfluoro (butenylvinyl)
35 g of [PBVE], 1,1,2-tri
5 g of chlorotrifluoroethane (R113), ion
150 g of exchanged water, and ((CH^Three)^Two
CHOCOO)^Two90 mg of 200 ml
It was placed in a pressure glass autoclave. Nitrogen in the system three times
After the replacement, suspension polymerization was performed at 40 ° C. for 22 hours. That
As a result, the number average molecular weight was about 1.5 × 10 ^FivePolymer (hereinafter, referred to as
28 g of polymer A) was obtained.

The intrinsic viscosity [η] of the polymer A was 0.50 at 30 ° C. in perfluoro (2-butyltetrahydrofuran) [PBTHF]. The glass transition point of the polymer A was 108 ° C., and at room temperature, it was a tough and transparent glassy polymer. The 10% thermal decomposition temperature is 465 ° C,
The solubility parameter was 5.3 (cal / cm ³ ) ^1/2 and the refractive index was 1.34. FIG. 1 shows the light transmittance of the polymer A.

"Synthesis Example 2" Perfluoro (2,2-dimethyl-1,3-dioxole) [PDD] and radical polymerization of tetrafluoroethylene in a weight ratio of 80:20, and a number average molecular weight at a glass transition point of 160 ° C. About 5 × 10 ⁵ polymers (hereinafter, referred to as polymer B) were obtained. Polymer B was colorless and transparent, had a refractive index of 1.3 and a high light transmittance.

Further, PDD and chlorotrifluoroethylene (CTFE) are radically polymerized at a weight ratio of 75:25, and a polymer having a glass transition point of 150 ° C. and a number average molecular weight of about 3 × 10 ⁵ (hereinafter referred to as polymer C) is obtained. Obtained. Polymer C was colorless and transparent, had a refractive index of 1.4 and a high light transmittance.

"Synthesis Example 3" 8 g of PBVE and 2 of PDD
g, 10 g of PBTHF, and as a polymerization initiator ((C
20 mg of H ³ ) ² CHOCOO) ² in an inner volume of 50 ml
Into a pressure-resistant glass ampule. After purging the system three times with nitrogen, polymerization was carried out at 40 ° C. for 20 hours. as a result,
6.7 g of a transparent polymer having a number average molecular weight of about 2 × 10 ⁵ (hereinafter referred to as polymer D) was obtained.

The polymer D had a glass transition point of 157 ° C., a refractive index of 1.32, and the polymerized unit content of PDD was determined to be 12% by weight based on the absorbance at 1930 cm ^{−1 in} the IR spectrum.

Also, 2 g of PBVE, 8 g of PDD, P
10 g of BTHF, ((CH ³ ) ² CH
20 mg of (OCOO) ² was placed in a pressure-resistant glass ampoule having an inner volume of 50 ml. After freezing and degassing the system three times,
Polymerization was carried out at 0 ° C. for 20 hours. As a result, a transparent polymer having a number average molecular weight of about 3 × 10 ⁵ (hereinafter, referred to as polymer E)
Was obtained in an amount of 7 g.

The polymer E had a glass transition point of 210 ° C., a refractive index of 1.29, and a polymerized unit content of PDD determined from the absorbance at 1930 cm ^{−1 in} the IR spectrum, which was 82% by weight.

Reference Example 1 Polymer A obtained by the above synthesis
Was dissolved in a PBTHF solvent, the refractive index of which was 1.52, and the difference in solubility parameter from Polymer A was 3.2 (c).
Al / cm ³ ) ^1/2 of 1,3-dibromotetrafluorobenzene (DBTFB) was added in an amount of 12% by weight to obtain a mixed solution. The solution was desolvated to obtain a transparent mixed polymer (hereinafter, referred to as polymer F).

The polymer A is melted and melt-spun at 300 ° C. while injecting the polymer F of the melt into the center thereof, whereby an optical fiber whose refractive index gradually decreases from the center to the periphery can be obtained. Was.

The optical transmission characteristics of the obtained optical fiber are 7
300 dB / km at 80 nm, 130 d at 1550 nm
It was B / km, and it was confirmed that the optical fiber could transmit light from visible light to near-infrared light well.

Example 1 40 g of PBVE and 500 ml of ((CH ³ ) ² CHOCOO) ² as a polymerization initiator were added to a glass tube, and the mixture was deaerated by freezing and then polymerized while rotating at high speed. The synthesized hollow tube was taken out of the glass tube to obtain a tube made of a polymer having a number average molecular weight of about 1 × 10 ⁵ . 20 g of PBVE, 2 g of DBTFB as a high refractive index substance, and 200 ml of ((CH ³ ) ² CHOCOO) ² as a polymerization initiator were added to the hollow portion of the tube.
It was sealed and polymerized while rotating at low speed.

In the polymerization process, the polymer in the tube swells in the monomer phase to form a gel phase, so that the polymerization reaction is accelerated in the gel phase by the gel effect, and the polymer phase is formed from the peripheral portion. At this time, the monomer molecules are selectively diffused into the gel phase because the molecular size is smaller than the high refractive index substance molecules, and the high refractive index substance is collected at the center and polymerized. A refractive index distribution in which the refractive index gradually decreases toward the peripheral portion is formed. An optical fiber having a refractive index distribution was obtained by thermally stretching the thus obtained preform.

The optical transmission characteristics of the obtained optical fiber are 6
500 dB / km at 50 nm, 150 d at 1550 nm
It was B / km, and it was confirmed that the optical fiber could transmit light from visible light to near-infrared light well.

Reference Example 2 Polymer D obtained by the above synthesis
Produced a core material of 30 microns. Also, a solution containing polymer D at a concentration of 1% by weight in a PBTHF solvent (hereinafter referred to as solution D)
Was adjusted). Similarly, a solution containing polymer E at 1% by weight in a PBTHF solvent (hereinafter referred to as solution E) was prepared. The solution D was dip-coated on the core material of the polymer D at a lifting speed of 6 cm and dried at 180 ° C. It was confirmed that the diameter of the polymer D increased by 100 nm. The solution E was added to the solution D at a ratio of 1/250 by weight, and dip coating and drying were repeated 500 times. Finally, dip coating and drying of the solution E having a concentration of 10% by weight were repeated 5 times 180 times.
Dried for 2 hours at ° C. An optical fiber having a diameter of about 600 microns and a refractive index gradually decreasing from the center toward the periphery was obtained.

The optical transmission characteristics of the obtained optical fiber are 6
1050dB / km at 50nm, 460d at 950nm
B / km was 130 dB / km at 1300 nm, and it was confirmed that the optical fiber could transmit light from visible light to near-infrared light well. Reference Example 3 Equivalent amounts of polymer B and polymer C synthesized above were dissolved and mixed in a PBTHF solvent. The solvent was removed therefrom to obtain a transparent polymer mixture (B + C). The polymer B is melted, and the melted polymer mixture (B + C) is melt-spun while pouring the melted polymer C into the center, so that the refractive index gradually increases from the center toward the periphery. A falling optical fiber was obtained.

The optical transmission characteristics of the obtained optical fiber are 6
550 dB / km at 50 nm, 130 d at 1550 nm
It was B / km, and it was confirmed that the optical fiber could transmit light from visible light to near-infrared light well.

Reference Example 4 An optical fiber was obtained in the same manner as in Example 1 except that 30% by weight of a CTFE oligomer having a number average molecular weight of 800 was used instead of using 12% by weight of DBTFB. The refractive index of this oligomer was 1.41, and the difference in solubility parameter from Polymer A was 1.4 (c
al / cm ³ ) ^1/2 . The obtained optical fiber had a gradually decreasing refractive index from the center toward the periphery.

The optical transmission characteristics of this optical fiber are 780
nm at 280 dB / km, 1550 nm at 120 dB / km
km, and was confirmed to be an optical fiber capable of transmitting light from visible light to near infrared light well.

Example 2 Reactivity ratio r ¹ (PDD / PB
The ratio of the formation rate constant of the PDD homopolymer to the formation rate constant of the VE copolymer (the ratio of the formation rate constant of the PDD homopolymer) to 1.9 and the reactivity ratio r ² (the ratio of the PBVE homopolymer to the formation rate constant of the PDD / PBVE copolymer). (Rate of formation rate constant) is 0.1
A solution prepared by dissolving 50 parts of PBVE of No. 9 and 1 part of dialkoxyacetophenone as a photoinitiator in 5 parts of HCFC225 was placed in a glass ampule and the system was frozen and degassed three times, and then photopolymerized using a low-pressure mercury lamp. However, a preform having a continuous refractive index distribution of 1.33 at the center with a refractive index of 1.31 at the periphery was obtained. This was thermally drawn to obtain an optical fiber having a refractive index distribution.

The optical transmission characteristics of the obtained optical fiber are 6
320 db / Km at 50 nm, 250 d at 1550 nm
b / Km, and it was confirmed that the optical fiber could transmit light from visible light to ultraviolet light well.

Reference Example 5 85 parts of polymer A and DBTFB
15 parts were melt-mixed to form a rod. This rod was heated and drawn at 200 ° C. to produce a fiber. At this time, the fiber exiting from the heating and drawing section is passed through a 1 m long electric furnace heated to 120 ° C. Dry air preheated to 120 ° C. was flowed into the electric furnace, thereby evaporating DBTFB from the surface of the fiber to obtain an optical fiber having a refractive index distribution.

The optical transmission characteristics of the obtained optical fiber are 65
420 dB / km at 0 nm, 250 dB / km at 780 nm
It was 110 dB / km at km and 1300 nm, and it was confirmed that the optical fiber could transmit light from visible light to near-infrared light well.

Reference Example 6 90 parts of PBVE and CTFE1
By polymerizing 0 parts with a number average molecular weight of about 2 × 10 ⁵
(Hereinafter, referred to as polymer F) was obtained. A CTFE oligomer having a number average molecular weight of 800 was melted and uniformly mixed with the polymer F to obtain a rod having an oligomer content of 20% by weight.

This was thermally drawn to prepare a fiber having a diameter of 500 μm. The fiber was passed through ethanol to elute the CTFE oligomer, and then dried by passing through a cylindrical heating furnace heated to 200 ° C. for a residence time of about 10 seconds. As a result, the refractive index of the outer peripheral portion is 1.36.
An optical fiber having a refractive index distribution of 1.38 at the center was obtained.

The optical transmission characteristics of the obtained optical fiber are 6
250 db / Km at 50 nm, 150 d at 1550 nm
b / Km, and it was confirmed that the optical fiber could transmit light from visible light to ultraviolet light well.

Reference Example 7 Polymer C was spun at 270 ° C. by an extrusion method, and the resulting fiber was immediately heated to 220 ° C. in hexafluoropropylene oxide (HFP).
O) It was passed through an oligomer (number average molecular weight 2100) such that the residence time was 3 minutes. As a result, an optical fiber having an outer diameter of 600 μm was obtained, in which the HFPO oligomer diffused and penetrated into the fiber, and the refractive index changed continuously from the outer periphery toward the center. At this time, the refractive index at the outer peripheral portion was 1.34, and the refractive index at the central portion was 1.35.

The optical transmission characteristics of the obtained optical fiber are 6
300 db / Km at 50 nm, 130 d at 1550 nm
b / Km, and it was confirmed that the optical fiber could transmit light from visible light to ultraviolet light well.

Reference Example 8 PDD and PBVE were polymerized to give a PDD content of 20% by weight and a number average molecular weight of about 1 × 10
Polymer of ⁵ (hereinafter referred to as polymer G) and 60% by weight
Having a number average molecular weight of about 5 × 10 ⁵ (hereinafter referred to as polymer H
It was synthesized. The refractive index of the polymer G was 1.33, and the refractive index of the polymer H was 1.31, respectively.

Polymers G and H were dissolved in perfluorotributylamine / perfluorooctane = 20/80 (weight ratio) so that the polymer concentration became 20% by weight. After adjusting 11 kinds of mixed solutions, the solvent was partially volatilized by heating to about 30
A gel-like solution of 000 cP was obtained. While heating these 11 types of gels having different mixing ratios to 80 ° C., multilayer fibers were extruded concentrically using a multilayer nozzle. This fiber is placed in a heating furnace through which air is circulated (about 150 to 20).
(0 ° C.) to remove residual solvent. As a result, a fiber having a refractive index distribution was obtained.

The optical transmission characteristics of the obtained optical fiber are 6
350 dB / km at 50 nm, 150 dB at 950 nm
/ Km, 120 dB / km at 1300 nm, and it was confirmed that the optical fiber could transmit light from visible light to near infrared light well.

[Comparative Example] In the refractive index distribution type plastic optical fiber, the optical transmission loss of PMMA was 650 wavelength.
about 400 dB / km in nm, wavelength 780 nm, 13
At the wavelengths of 00 nm and 1550 nm, the transmission loss was extremely large and was not practical as an optical transmitter.

Further, in the step refractive index type plastic optical fiber, the fluororesin optical fiber whose core and cladding are capable of transmitting light from visible light to near infrared light, the light transmission loss is reported to be about 300 dB / km. I have.

In contrast, the refractive index distribution type transparent fluororesin optical fiber according to the present invention can transmit light from visible light to near infrared light with extremely low loss.

[0089]

[Table 1]

[0090]

According to the present invention, there is provided a method for producing a gradient index optical resin material using a monomer capable of forming a non-crystalline fluororesin, and a gradient index optical resin material obtained by the method of the present invention. The use of non-crystalline fluorine resin in a wide variety of plastic optical transmission media such as graded index optical fibers, graded index optical waveguides, graded index rod lenses, etc. Can be transmitted with extremely low loss.

In particular, a graded index optical fiber is suitable for short-distance optical communication because it is flexible and easy to branch and connect despite its large diameter, but a practically usable low-loss optical fiber has been proposed. Was not done. The present invention provides a method for manufacturing a low-loss optical fiber that can be used for short-range optical communication.

The optical transmitter obtained by the present invention is:
An object of the present invention is to provide a plastic optical transmitter having heat resistance, chemical resistance, moisture resistance, and nonflammability, which can withstand severe use conditions in an engine room, an OA device, a plant, a home appliance, and the like of an automobile. Further, the refractive index distribution type optical resin material obtained by the present invention can be used not only as an optical fiber but also as a plate type or rod type lens. In that case, it is possible to function as a convex lens and a concave lens depending on whether the change in the refractive index from the center to the periphery is reduced or increased.

[Brief description of the drawings]

FIG. 1 is a diagram showing light transmittance of a polymer A.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) G02B 3/00 G02B 3/00 B 6/18 6/18 F term (reference) 2H050 AA17 AB47Z AB48Z AC05 4J011 AA01 AA05 AB01 GA00 GA02 PA66 PB07 PB08 PC02 PC08 PC12 4J026 AA23 AA26 BA09 BA11 DA10 DB07 FA01 GA02

Claims (6)

[Claims] 1. A non-crystalline fluorine-containing polymer (a) having substantially no C—H bond and at least one having a refractive index higher than that of a fluorine-containing polymer (a) by 0.001 or more.
A method for producing a refractive index distribution type optical resin material comprising a substance (b) and a substance (b) distributed with a concentration gradient along a specific direction in a fluoropolymer (a) Wherein a monomer forming the fluoropolymer (a) containing the substance (b) is sealed in a hollow tube made of the fluoropolymer (a), and the monomer is polymerized while rotating the tube. A method for producing a refractive index distribution type optical resin material, comprising: 2. The monomer forming the fluoropolymer (a) is at least one selected from a monomer having a fluorinated ring structure and a fluorinated monomer having at least two polymerizable double bonds. 2. The production method according to 1. 3. The method according to claim 1, wherein the optical resin material is a base material for producing an optical fiber. 4. A difference in refractive index between the amorphous fluoropolymer (a) having substantially no C—H bond and the fluoropolymer (a) is 0.001 or more. A refractive index distribution type comprising a substance (b) which is at least one kind of polymer, wherein the substance (b) is distributed with a concentration gradient along a specific direction in the fluoropolymer (a). A method for producing an optical resin material, comprising using two kinds of monomers that are a monomer that forms a fluoropolymer (a) and a monomer that forms a substance (b) and that have different reactivities of the monomers. A refractive index distribution type optical resin material characterized in that the polymerization reaction proceeds so that the composition ratio of the generated fluoropolymer (a) and the substance (b) changes continuously from the peripheral portion toward the center. Production method. 5. The monomer forming the fluorinated polymer (a) is at least one selected from a monomer having a fluorinated ring structure and a fluorinated monomer having at least two polymerizable double bonds. 5. The production method according to 4. 6. The production method according to claim 4, wherein the optical resin material is a base material for producing an optical fiber.