JP3489764B2 - Refractive index distribution type optical resin material - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a refractive index distribution type optical resin material having high transparency and heat resistance, which has been difficult to realize with conventional optical resins (hereinafter, may be abbreviated as optical resin material). ), And useful end-stabilized chlorotrifluoroethylene-based oligomers that can be used therein.

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

The optical transmission material which is the optical resin material of the present invention is
Since it is an amorphous resin, it does not scatter light and has extremely high transparency in a wide wavelength band from ultraviolet light to near infrared light, so it can be effectively used for optical systems of various wavelengths. In particular, the present invention provides an optical transmission body having low loss at wavelengths of 1300 nm and 1550 nm, which are used for trunk silica fibers in the field of optical communication.

The optical transmission material, which is the optical resin material of the present invention, has heat resistance, chemical resistance, moisture resistance, and nonflammability, which can withstand the severe conditions of use in the engine room of automobiles.

The optical transmission material which is the optical resin material of the present invention is
Graded-index optical fiber, rod lens, optical waveguide, optical splitter, optical multiplexer, optical demultiplexer, optical attenuator, optical switch, optical isolator, optical transmitter module, optical receiver module, coupler, deflector, light It is useful as a wide range of graded index optical transmitters such as integrated circuits. Here, the refractive index distribution means a region in which the refractive index continuously changes along a specific direction of the optical transmission body, and for example, the refractive index distribution of a gradient index optical fiber is a radial direction from the center of the fiber. The refractive index decreases toward a curve close to a parabola.

When the optical resin material of the present invention is a base material for an optical transmission medium, it can be spun by thermal drawing or the like to produce an optical transmission medium such as a gradient index optical fiber.

[0007]

2. Description of the Related Art As a conventionally known resin for a gradient index plastic optical transmission body, an optical resin represented by a methylmethacrylate resin or WO94 / 049.
The tetrafluoroethylene resin and vinylidene fluoride resin described in No. 49 have been proposed.

The core of the graded-refraction plastic optical fiber is methyl methacrylate resin, styrene resin,
Many proposals have been made to use an optical resin such as a carbonate resin or norbornene resin and to make the clad a fluoropolymer. Further, JP-A-2-244007 proposes using a fluorine-containing resin for the core and the clad.

[0009]

SUMMARY OF THE INVENTION The present invention is required for automobiles, office automation (OA) equipment, home electric appliances and the like, which cannot be achieved by optical transmission materials such as methyl methacrylate resin, carbonate resin and norbornene resin. Provided is 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 200 nm to 400 nm) and near infrared light (wavelength 700 nm to 2500 nm) that cannot be reached by optical transmission materials such as methacrylate resin, carbonate resin, norbornene resin, Furthermore, an optical resin material having a low optical transmission loss in a wider transmission region band is newly provided.

[0011]

Means for Solving the Problems As a result of extensive studies based on the recognition of the above problems, the present inventor has provided heat resistance, moisture resistance, chemical resistance, and nonflammability and has a near-infrared light. It was found that a fluorine-containing polymer substantially containing no C—H bond is optimal for eliminating the C—H bond (that is, carbon-hydrogen bond) in which light absorption occurs. This fluoropolymer has a C—F bond (that is, a carbon-fluorine bond) instead of the C—H bond.

That is, when a substance is irradiated with light, the stretching vibration of a bond between certain atoms and the light having a wavelength that causes resonant vibration with the bending vibration are preferentially absorbed. The polymeric substances used in plastic optical fibers so far are mainly C
It was a compound having a -H bond. In the polymer substance based on this C—H bond, since the hydrogen atom is light and easily vibrates, the basic absorption is in the infrared region on the short wavelength side (3400 n).
appear in 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 this C—H stretching vibration appears in abrupt manner, which is a major cause of absorption loss.

Therefore, when hydrogen atoms are replaced with fluorine atoms, the wavelengths of their overtone absorption peaks shift to the long wavelength side, and the absorption amount in the near infrared region decreases. From the theoretical value, in the case of PMMA (polymethylmethacrylate) having a C—H bond, the absorption loss of the C—H bond is estimated to be 105 dB / km at a wavelength of 650 nm, and 10,000 dB at a wavelength of 1300 nm. / Km
That's all.

On the other hand, in a substance in which hydrogen atoms are replaced by fluorine atoms, there is practically no loss due to absorption at a wavelength of 650 nm, and even at a wavelength of 1300 nm, between 1 and 6 dB between the 6th and 7th overtones of the stretching vibration of the C—F bond. It is on the order of km and it can be considered that there is no absorption loss. For that we are C
It is proposed to use compounds with a -F bond.

Further, it is desirable to exclude functional groups such as a carboxyl group and a carbonyl group, which are factors that hinder heat resistance, moisture resistance, chemical resistance, and incombustibility. Further, a carboxyl group absorbs near infrared light, and a carbonyl group absorbs ultraviolet light. Therefore, it is desirable to exclude these groups. Further, in order to reduce the transmission loss due to light scattering, it is important to use an amorphous polymer.

Further, in the case of a graded index optical fiber,
Multimode light propagates while being reflected at the interface between the core and the clad. Therefore, modal dispersion occurs and the transmission band is reduced. However, in the graded index optical fiber, mode dispersion hardly occurs and the transmission band increases.

Therefore, as an optical resin material, substantially C--H
An amorphous fluoropolymer having no bond, particularly a fluoropolymer having a ring structure in the main chain, and a concentration of a substance having a refractive index different from that of the polymer have a gradient in a specific direction. An optical resin material and a useful terminal-stabilized chlorotrifluoroethylene-based oligomer that can be used for the optical resin material have been newly found, and the inventions (1) and (2) described below have been reached.

(1) Non-bonding having substantially no C--H bond
Crystalline fluoropolymer (a) and fluoropolymer (a)
The difference in the refractive index is 0.001 or more in comparison with
Fluorine-containing polymerization consisting of at least one substance (b)
Concentration gradient of substance (b) in body (a) along a specific direction
In graded-index optical resin materials that are distributed with
The substance (b) is a chlorotrifluoroethylene-based oligo
End-stabilized chlorotrifluoro obtained by fluorinating mer
Refractive index component characterized by being an ethylene-based oligomer
Cloth type optical resin material.

(2) The refractive index distribution type optical resin material is refracted
It is a rate-distributed optical fiber with end-stabilized chlorotrif
Luoroethylene-based oligomers around the optical fiber
Above characterized by being present in high density in the center
The gradient index optical resin material according to (1).

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

On the other hand, the non-crystalline fluoropolymer is excellent in transparency because it does not scatter light due to crystals.
As the fluoropolymer (a) in the present invention, C-H
There is no limitation as long as it is a non-crystalline fluoropolymer having no bond, but a fluoropolymer having a ring structure in its main chain is preferable. The fluorine-containing polymer having a ring structure in the main chain, a fluorine-containing aliphatic ring structure, a fluorine-containing imide ring structure,
A fluoropolymer having a fluorine-containing triazine ring structure or a fluorine-containing aromatic ring structure is preferable. Among the fluoropolymers having a fluorinated aliphatic ring structure, those having a fluorinated aliphatic ether ring structure are more preferable.

The fluorine-containing polymer having a fluorine-containing alicyclic structure is compared with the fluorine-containing polymer having a fluorine-containing imide ring structure, a fluorine-containing triazine ring structure or a fluorine-containing aromatic ring structure, which will be described later in the heat drawing or melting. It is a more preferable polymer because it is difficult for the polymer molecules to be oriented even when it is made into fibers by spinning, and as a result, light is not scattered.

The viscosity of the fluorinated polymer (a) in the molten state is from 10 ^{3 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 it is necessary to form a refractive index distribution.
Diffusion of the substance (b) is less likely to occur, making it difficult to form a refractive index distribution. In addition, if the melt viscosity is too low, there will be a practical problem. That is, when it is used as an optical transmitter in electronic devices, automobiles, etc., it is exposed to high temperatures and softens, and the optical transmission performance deteriorates.

The number average molecular weight of the fluoropolymer (a) is
It is preferably 10,000 to 5,000,000, more preferably 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 an optical transmission medium having a refractive index distribution, which is not preferable.

The polymer having a fluorinated alicyclic structure is obtained by polymerizing a monomer having a fluorinated ring structure, or a fluorinated monomer having at least two polymerizable double bonds is subjected to cyclopolymerization. A polymer having a fluorinated alicyclic structure in the main chain obtained as described above is suitable.

A polymer having a fluorinated alicyclic structure in its main chain obtained by polymerizing a monomer having a fluorinated alicyclic structure is known from Japanese Patent Publication No. 63-18964. That is, perfluoro (2,2-dimethyl-
1,3-dioxole) and other monomers having a fluorine-containing alicyclic structure are homopolymerized, and this monomer is also radical-polymerizable monomer such as tetrafluoroethylene, chlorotrifluoroethylene, and perfluoro (methyl vinyl ether). A polymer having a fluorinated alicyclic structure in its main chain can be obtained by copolymerizing with.

Further, a polymer having a fluorinated alicyclic structure in its main chain obtained by cyclopolymerization of a fluorinated monomer having at least two polymerizable double bonds is disclosed in JP-A-63-
It is known from JP-A-238111 and JP-A-63-238115. That is, by cyclopolymerizing monomers such as perfluoro (allyl vinyl ether) and perfluoro (butenyl vinyl ether), or by using such monomers as tetrafluoroethylene, chlorotrifluoroethylene, perfluoro (methyl vinyl ether), etc. A polymer having a fluorine-containing alicyclic structure in its main chain can be obtained by copolymerizing with the radical-polymerizable monomer.

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

Specific examples of the above-mentioned polymer having a fluorinated alicyclic structure include those having a repeating unit selected from the following formulas (I) to (IV). The fluorine atoms in the polymers having these fluorine-containing alicyclic structures may be partially substituted with chlorine atoms in order to increase the refractive index.

[0030]

[Chemical 1]

[In the above formulas (I) to (IV), p is 0 to 5, q is 0 to 4, r is 0 to 1, and p + q + r is 1 to 1.
6, s, t and u are 0 to 5, respectively, and s + t + u 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
Is. The polymer having a fluorinated alicyclic structure is preferably a polymer having a ring structure in its main chain, but 20 mol% or more, preferably 40 mol% of polymerized units having a ring structure.
Those contained above are preferable from the viewpoints of transparency, mechanical properties and the like.

The substance (b) is a terminal-stabilized chlorotrifluoroethylene-based oligomer having a refractive index difference of 0.001 or more in comparison with the fluoropolymer (a),
The refractive index may be higher or lower than that of the fluoropolymer (a). In optical fibers and the like, a substance having a higher refractive index than the fluoropolymer (a) is usually used.

The substance (b) is preferably a substance having substantially no C--H bond for the same reason as the fluorine-containing polymer (a). Further, the fluoropolymer (a)
The difference in the refractive index between and is preferably 0.005 or more.

Due to the good compatibility, the fluoropolymer (a), particularly the fluoropolymer having a ring structure in the main chain, and the substance (b) can be easily melted by heating at 200 to 300 ° C. It can be mixed. Further, both can be mixed uniformly by dissolving in a fluorine-containing solvent and mixing and then removing the solvent.

In the present invention, the chlorotrifluoroethylene-based oligomer means a homopolymerization oligomer consisting only of chlorotrifluoroethylene and a copolymerization oligomer of chlorotrifluoroethylene and one or more other copolymerizable monomers. .

As the above-mentioned copolymerizable monomer, perhaloolefins such as tetrafluoroethylene, dichlorodifluoroethylene and hexafluoropropylene, perfluoro (alkyl vinyl ether), perfluoro (allyl vinyl ether), perfluoro (butenyl vinyl ether). , Perfluoro (2,2-dimethyl-
1,3-dioxole) and the like, and those having substantially no C—H bond are preferable.

The copolymerization ratio of chlorotrifluoroethylene in the copolymerized oligomer is not particularly limited, and may be, for example, 1-9.
It can be selected from a wide range of 9 mol%. When a terminal-stabilized copolymerization oligomer is used as the above-mentioned substance (b) by the method described below, the copolymerization ratio of chlorotrifluoroethylene is preferably 50 mol% or more.

The molecular weight of the chlorotrifluoroethylene-based oligomer terminal-stabilized by the method described below is selected from the molecular weight range in which it becomes amorphous, and the number average molecular weight is from 300 to 10,
000 is preferable. When used as the substance (b), considering the ease of diffusion, the number average molecular weight is 300 to 50.
00 is more preferable.

Applications of these oligomers include oils and lubricants in addition to the above-mentioned optical resin materials.

A usual chlorotrifluoroethylene-based oligomer has a partially unstable terminal group. That is, in manufacturing,
Particularly, it contains a carboxylic acid derived from an initiator or the like, an end group having a C—H bond, and the like.

Generally, a chlorotrifluoroethylene-based oligomer contains several hundred ppm or more of these unstable terminal groups,
When these are used for applications such as optical fibers, absorption due to expansion and contraction of these unstable terminal groups in the near infrared region, bending vibration, etc., work to increase loss, and limit the wavelength used for the fibers.

Further, when the fiber or the like is molded, it is exposed to a high molding temperature, so that the thermal decomposition of the unstable terminal group occurs and the material is colored, or a new absorption due to the structure derived after the decomposition occurs. Result in loss. Further, the decomposed gas causes foaming in the molded body, which greatly contributes to an increase in transmission loss.

Those whose end is stabilized by fluorinating the above chlorotrifluoroethylene-based oligomer or the like do not have absorption in the near infrared and can be prevented from decomposing even at high temperature.

That is, the unstable terminal group is fluorinated to form CF.
It is preferable to use a chlorotrifluoroethylene-based oligomer having a stable terminal group such as ₃ as an optical material such as an optical fiber.

The fluorination conditions are not particularly limited. If the concentration of fluorine gas is high, the reaction tends to runaway, and the chlorine atoms in the chlorotrifluoroethylene-based oligomer are
There is a high possibility that it will be replaced with a fluorine atom. There is also a danger in operation.

On the other hand, when the concentration of fluorine gas is too low, it takes a long time to complete the reaction. Therefore, it is preferable to use a fluorine gas diluted with nitrogen gas to 5 to 50% so that the reaction can be gently completed.

The fluorination temperature condition is not preferable if it is too high or too low. When the temperature is 150 ° C. or lower, the reaction is difficult to proceed, and the reaction is difficult to complete even after a long time. On the other hand, if the temperature exceeds 300 ° C., the reaction tends to runaway, and the chlorine atom in the main chain is easily replaced with the fluorine atom.
Therefore, by selecting a fluorination temperature of preferably 160 to 290 ° C, more preferably 200 to 250 ° C, it is possible to complete the reaction gently and completely.

The reaction pressure is not particularly limited, but if it is too low, the volumetric efficiency of the reaction is poor, and if it is high, the risk of leakage of the fluorine gas is high, so it is 1 to 10 k.
It is preferable to complete the reaction gently at a pressure of about g / cm ² .

The fluorinated chlorotrifluoroethylene-based oligomer is preferably further distilled before use in order to remove impurities and make the molecular weight distribution uniform.

The distillation conditions are not particularly limited, but in the case of a chlorotrifluoroethylene-based oligomer having an average molecular weight of about 1000, it is reduced under a reduced pressure of about 1 to 10 mmHg.
Fractions of about 50 to 200 ° C can be collected.

The optical resin material of the present invention is most preferably a gradient index optical fiber. In this optical fiber, the substance (b) is distributed in the fluoropolymer (a) with a concentration gradient from the center to the peripheral direction.
Preferably, the substance (b) is a substance having a higher refractive index than the fluoropolymer (a), and the substance (b) has a concentration gradient in which the concentration decreases from the center of the optical fiber to the peripheral direction. It is a distributed 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. Fiber optics are also useful. The former optical transmission body such as an optical fiber can be manufactured by arranging the substance (b) at the center and diffusing it toward the peripheral direction. The latter optical transmission body such as an optical fiber can be manufactured by diffusing the substance (b) from the periphery toward the center.

The optical transmission material which is the optical resin material of the present invention is
At a wavelength 700～1,600Nm, can be the transmission loss of 100m is less 100d B. Particularly in the case of a fluoropolymer having an alicyclic structure in its main chain, the
0m transmission loss can be less 50d B. At relatively long wavelengths of 700 to 1,600 nm, such a low level of transmission loss is extremely advantageous. 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 compared with the conventional plastic optical fiber which has no choice but to use a wavelength shorter than 700 to 1,600 nm, it is an inexpensive light source. It has the advantage of being completed. In the production of the optical resin material of the present invention, the molding of the resin and the formation of the refractive index distribution may be performed simultaneously or separately. For example, the optical resin material of the present invention can be manufactured by forming the refractive index distribution by spinning or extrusion molding and simultaneously forming the refractive index distribution. Further, the refractive index distribution can be formed after molding the resin by spinning or extrusion molding. Furthermore, a preform (base material) having a refractive index distribution can be manufactured, and this preform can be molded (for example, spun) to manufacture an optical resin material such as an optical fiber. As described above, the optical resin material of the present invention also means a preform having the above refractive index distribution.

Examples of the method for producing the optical resin material of the present invention include the following methods (1) to (7). However, it is not limited to these. A particularly preferred method is the method (1).

(1) The fluoropolymer (a) is melted to contain the substance (b) or the substance (b) in the center of the melt of the fluoropolymer (a). And molding the compound (b) while diffusing the substance (b) or after diffusing the substance (b).

In this case, in order to inject the substance (b), not only the case of injecting the substance (b) in only one layer in the central portion,
The substance (b) may be injected in multiple layers in the central portion. The molding includes 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) Repeated dipping of the substance (b) or the fluoropolymer (a) containing the substance (b) on the core material made of the fluoropolymer (a) obtained by melt spinning or drawing. How to coat.

(3) A hollow fluorinated polymer (a) tube is formed using a rotating glass tube or the like, and the substance (b) or the substance (b) is contained inside the polymer tube. A method in which the monomer phase forming the fluoropolymer (a) 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 to form a gel phase, and the monomer molecules selectively diffuse into the gel phase. While being polymerized.

(4) Using two kinds of monomers which are a monomer forming the fluoropolymer (a) and a monomer forming the substance (b) and having different reactivity of the monomers,
A method of advancing the polymerization reaction so that the composition ratio of the resulting fluoropolymer (a) and the substance (b) continuously changes from the peripheral portion toward the center.

(5) Fluorine-containing polymer (a) and substance (b)
Is mixed uniformly or in a solvent, and then the mixture obtained by volatilizing and removing only the solvent is made into a fiber by hot drawing or melt extrusion, and then (or immediately after being made into a fiber) in a heated state. A method of forming a refractive index profile by contacting with 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 surface of the fiber to obtain a refractive index. How to form a distribution.

(6) The rod or fiber made of the fluoropolymer (a) is coated only with the substance (b) having a smaller refractive index than the fluoropolymer (a), or the fluoropolymer (a) ) And the substance (b) are coated, and then the substance (b) is diffused by heating to form a refractive index profile.

(7) The high-refractive-index polymer and the low-refractive-index polymer are melted by heating or mixed in a solution containing a solvent, and while multi-layer extrusion is performed (or after extrusion) under different mixing ratios. A method in which both are diffused to obtain a fiber with a final 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), the high refractive index polymer may be the substance (b) and the low refractive index polymer may be the substance (b). ) Is okay.

[0063]

BEST MODE FOR CARRYING OUT THE INVENTION Next, examples of the present invention will be described more specifically, but it goes without saying that the description does not limit the present invention.

Synthesis Example 1 Perfluoro (butenyl vinyl ether) [PBVE]
35 g, 150 g of ion-exchanged water, and 90 mg of ((CH ₃ ) ₂ CHOCOO) ₂ as a polymerization initiator were placed in a pressure-resistant glass autoclave having an internal volume of 200 ml.
After purging the system with nitrogen three times, suspension polymerization was carried out at 40 ° C. for 22 hours. As a result, the number average molecular weight is about 1.5 × 10 ^5.
28 g of the polymer (hereinafter referred to as 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 it was a tough and transparent glassy polymer at room temperature. 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 The difference in solubility parameter from Polymer A was 1.4 (cal
/ Cm ³ ) ^1/2 is chlorotrifluoroethylene (CT
500 g of the FE) oligomer was charged into a 1-liter Hastelloy C autoclave, degassed under reduced pressure, and then 20% fluorine gas diluted with nitrogen gas was introduced so as to have a pressure of ² kg / cm ² . Raise the temperature of the reactor to 220 ° C,
After continuing stirring for 15 hours, the reactor was cooled and nitrogen gas was purged to remove residual fluorine gas from the system. The obtained CTFE oligomer (number average molecular weight 1000, refractive index 1.42) was distilled under reduced pressure of 4 mmHg to give 170-
Fraction at 190 ° C (hereinafter referred to as CTFE oligomer B)
Collected.

Example 1 The polymer A obtained by the above synthesis was dissolved in a PBTHF solvent, and CTFE oligomer B was added thereto in an amount of 15% by weight to obtain a mixed solution. The solution was desolvated to obtain a transparent mixed polymer (hereinafter referred to as polymer C).

A colorless and transparent optical fiber whose refractive index is gradually decreased from the central part to the peripheral part by melting the polymer A and melt-spinning at 250 ° C. while pouring the melted polymer C into the center thereof. (Hereinafter, referred to as an optical fiber D) was obtained. The fiber diameter was 500 μm, the outer layer had a refractive index of 1.34, and the central portion had a refractive index of 1.36.

The optical transmission characteristic of the optical fiber D is 780n.
120 dB / km at m, 50 dB / km at 1550 nm
It was confirmed that the optical fiber can satisfactorily transmit light from visible light to near infrared light. In addition, no absorption peak, which is considered to be derived from the terminal group, was detected in that wavelength range. When the fractured surface of the optical fiber D was observed by SEM, the surface was smooth and no particular nonuniform structure was observed.

Comparative Example A gradient index plastic optical fiber having a fiber diameter of 500 μm (hereinafter referred to as “optical fiber E”) was prepared in the same manner as in Example 2 except that the CTFE oligomer was not fluorinated.
I got). The center of the optical fiber E is slightly yellowed, and the optical transmission loss is 900 dB / km at a wavelength of 780 nm.
It was 600 dB / km at 1550 nm. Also, 95
At around 0 nm and 1400 nm, an absorption peak which is considered to be derived from the OH bond of the carboxylic acid was detected, and it was found that the transmission loss was very large at this wavelength and it could not be used for optical communication. Further, by SEM observation of the fractured surface of this fiber, foaming of several tens of μm size, which is considered to be derived from the decomposition of the CTFE oligomer end, was observed in the fiber E,
It was found that this increased the transmission loss.

[0071]

INDUSTRIAL APPLICABILITY According to the present invention, an amorphous fluororesin is used in a wide variety of plastic optical transmitters such as graded index optical fibers, graded index optical waveguides, graded index rod lenses, etc. It has become possible to transmit light from light to near infrared light with extremely low loss.

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

Further, the optical transmission body of the present invention is a plastic light having heat resistance, chemical resistance, moisture resistance and nonflammability, which can withstand severe use conditions in engine rooms of automobiles, OA equipment, plants, home appliances and the like. A transmitter is provided. Further, the gradient index optical resin material of the present invention can be used not only as an optical fiber but also as a flat plate type or rod type lens. In that case, depending on whether the refractive index change from the central portion to the peripheral portion is made low or high, it can function as a convex lens and a concave lens.

[Brief description of drawings]

FIG. 1 is a view showing the light transmittance of polymer A.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI G02B 6/18 G02B 6/12 N (72) Inventor Tokuhide Sugiyama 1150 Hazawa-machi, Kanagawa-ku, Yokohama-shi, Kanagawa Asahi Glass Co., Ltd. In-house (56) References JP-A-5-170811 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C08F 8 / 00-8 / 50

Claims (2)

(57) [Claims] 1. A difference in refractive index between the non-crystalline fluoropolymer (a) having substantially no C—H bond and the fluoropolymer (a) is 0.001 or more. A refractive index distribution type optical resin material comprising at least one kind of substance (b), wherein the substance (b) is distributed in the fluoropolymer (a) with a concentration gradient along a specific direction. , The substance (b) is a chlorotrifluoroethylene-based oligo
A graded-index optical resin material, characterized in that it is a terminal-stabilized chlorotrifluoroethylene-based oligomer obtained by fluorinating a mer . 2. A refractive index distribution type optical resin material, a refractive index distribution type optical fiber, terminal stabilization chlorotrifluoroethylene oligomer is characterized in that is present in high density in the center than the periphery of the optical fiber Note 1
The graded-index optical resin material listed above.