JPS62265605A - Optical fiber having clad part essentially consisting of fluorine polymer - Google Patents

Abstract

PURPOSE:To obtain an optical fiber having the excellent adhesiveness, of a core part and clad part weatherability, heat resistance, and good flexibility by forming the clad part of a material contg. a specific fluorine polymer as an essential component. CONSTITUTION:The clad part of the optical fiber is formed of the material essentially consisting of the fluorine polymer which is a copolymer formed of a fluoroolefin, vinyl ether and org. silicon compd. having a hydrolyzable group and an olefinic unsatd. bond, and is at least partly crosslinked. The fluoroolefin is preferably a fluoroolefin of 2 or 3C, more particularly preferably perfluoroolefin. The vinyl ether is preferably an alkyl vinyl ether bound with an alkyl group of 2-4C, more particularly preferably an alkyl vinyl ether of a chain alkyl group. Vinyloxy propyltrimethoxysilane, vinyltrimethoxysilane, etc., are used as the org. silicon compd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical fiber for transmitting optical signals, and is particularly characterized by the material forming the cladding portion thereof.

[Conventional technology]

Conventionally, a core part (A) having a refractive index n1 that guides light is surrounded by a clad part (B) having a refractive index n that is smaller than the refractive index n of the core part (A), and the core part In optical fibers that completely reflect incident light at the interface between the core and cladding and confine it in the core for transmission, core materials include silica glass containing 5102 as a main component,
Polymethyl methacrylate (PMMA), 4-methyl-
Plastics such as 1-pentene polymers and polycarbonates are used, and noricorn resins are known as cladding materials having a refractive index smaller than the refractive index n of these core materials.

[Problem that the invention seeks to solve]

However, the clad material does not have sufficient adhesion with the core material, and the interface with the core portion becomes irregular, causing light scattering loss and possibly deteriorating light transmission characteristics.

In addition, optical fibers are often used in extremely harsh environments, such as in the air or under the sea, in hot or cold places in factories, or in automobile engine rooms, so it is desirable that they have good weather resistance and heat resistance. It is rare.

Furthermore, since optical fibers are often used by being bent depending on the location where the optical transmission path is provided, it is preferable that they have excellent flexibility.

The present invention was made in view of the current situation, and it is an object of the present invention to provide an optical fiber that has excellent adhesion between the core portion and the cladding portion, has excellent weather resistance, heat resistance, etc., and has good flexibility. With the goal.

[Means for solving problems]

That is, in the present invention, the periphery of the core part (A) that guides light,
In an optical fiber surrounded by a cladding part (B) having a refractive index smaller than the refractive index of the core part (A),
The surface cladding portion was formed from a plastic material containing the following fluoropolymer as a main component.

This fluoropolymer is a copolymer consisting essentially of (a) a fluoroolefin, (b) a vinyl ether, and (c) an organosilicon compound having an olefinic unsaturated bond and a hydrolyzable group. It is a combination and is at least partially crosslinked.

[Effect]

The core portion (A) of the optical fiber of the present invention is made of quartz glass or plastic. The quartz glass used has 5iOy as its main component, and its refractive index is 1.45 to 1.
．． After 50ii, usually Ge, P, C.

The refractive index can be adjusted appropriately by adding a component such as A12.

In addition, the plastics used include polymethyl methacrylate (PMMA), 4-methyl-pentene polymer polycarbonate, ring-opening polymers of tetracyclododecenes, and ring-opening copolymers with norbornenes. Furthermore, copolymers of ethylene and cyclic olefins such as norbornene, tetracyclododecene, and methyltetracyclododecene are exemplified.

The specific fluoropolymer used in the cladding part (B) of the present invention is at least the above-mentioned (a), (b) and (c).
) A random copolymer consisting of three types of monomer component units, but a small amount of other copolymerizable monomer components, such as α-olefins, cycloolefins, unsaturated It does not matter if carboxylic acids or the like are copolymerized.

Fluoroolefin (a), which is a monomer component constituting the fluoropolymer, has at least one fluorine atom in the molecule, and preferably all hydrogen atoms of the olefin are substituted with fluorine atoms and other halogen atoms. Perfluoroolefins are preferred, and perfluoroolefins are particularly preferred. Furthermore, from the viewpoint of polymerizability and properties of the produced polymer, fluoroolefins having 2 or 3 carbon atoms, particularly perfluoroolefins, are preferred.

Examples of such fluoroolefins include CF, =CF
,, CIIF=CF,, CH,=CF2,
CH,=CHF, CC1=CC1, CHCl=
CF2CCl,=CF,, CCIF= CCIF%
CC1=CC1,,CH,=CCIF5CC1,=
Fluoroethylene type such as CCIF, CF, CF= CF
,, CF,CF=CHF, CF,CI(=C
F,,CF,CF=C! 1. , CF3CF=CH
F, CHF, CF= CIIFlCF, CI(=
C11,, CIl, CF= CF,, CH8CH=
CF,, Cl5CP=CI+,, CF, CICF
= CF2, CP, CC1= CF,, CF3CC=C
FCI, CF2ClCC1=CP, CF, CIC
F=CFCI.

CFCl, CF= CF,, CF3CC1= CCIF
1CF3CCI= CCl2, CCIFtCF= CC
l2, CC1, CF= CF,, CF, CICC1=
CCI,, CFCI, CC1= CC1t, CICC=
CHCl, CCIFtCF= CHCl, CF3C
C1=C)ICI, CHF, CC1=CC1,, CF
3CC1= CCl2, CF, CICC1=CHC1,
CCl5CF=CHC1,CF, 1cF=CFt.

CF, BrCH= CF,, CF3CC1= CHBr
5CF, CICC1=CI.

CI(JrCF=CCl2, CF3CC1=CHy,
CFaCII= CI! Br.

CF, BrCH= CHF, CF*BrCF=
Fluoropropene series such as CF, CF3CF, CF=
CF,, CF, CF= CFCF3, CF3CH= C
FCF,,CF,=CFCF,CHF,,CF3CF
, CF= CH,, CF, CI= ClCF3, CF2
= CFCF2CH3, CF, = CFCH, CH3C
F3CH2CH= CI(2, CF3C) I= C11
C1(3, CF2= CHCHtCH3, CH3CF2
CH= CH2, CFH, CH= CHCPI(,,C
H, CF, CH= C1,, Cl2= CFCH2CI
(3, CF, (cF,)2CF= CF,, CF3(c
F, )3CF=CFt, and other fluoroolefins having 4 or more carbon atoms can be mentioned.

Among these, as mentioned above, fluoroethylene and fluoropropene are preferred, and in particular, tetrafluoroethylene (cP, = CF), hexafluoropropene (cF, = CFCF3), and chlorotrifluoroethylene (cIFC = CF2) are preferred. In terms of safety and ease of handling, hexafluoropropene and chlorotrifluoroethylene are preferred.

In addition, in the present invention, the fluoroolefins may be used alone or in combination.

Vinyl ether (b) is a compound in which a vinyl group and an alkyl (including cycloalkyl) group, an aryl group, an aralkyl group, etc. are ether-bonded. Hereinafter, preferably an alkyl vinyl ether bonded with 2 to 4 alkyl groups is suitable. Furthermore, alkyl vinyl ethers in which the alkyl group is in the form of a chain are most preferred.

Examples of such vinyl ethers include linear alkyl vinyl ethers such as ethyl vinyl ether, propyl vinyl ether, isopropyl vinyl ether, butyl vinyl ether, tert-butyl vinyl ether, pentyl vinyl ether, hexyl vinyl ether, isopropyl vinyl ether, octyl vinyl ether, and 4-methyl-1-pentyl vinyl ether. cycloalkyl vinyl ethers such as cyclopentyl vinyl ether, cyclohexyl vinyl ether, phenyl pinylether)
Aralkyl vinyl ethers such as Li, o-, m, p-chlorophenyl vinyl ether, aryl vinyl ethers, benzylvinial alkyl vinyl ether, and phenethyl vinyl ether can be mentioned. Among these, chain alkyl vinyl ethers and cycloalkyl vinyl ethers are particularly preferred, and ethyl vinyl ether, propyl vinyl ether, and butyl vinyl ether are more preferred. Further, in the present invention, it goes without saying that the vinyl ether may be used alone or in a mixture of two or more vinyl ethers.

The organosilicon compound (c) may be one having an olefinic unsaturated bond and a hydrolyzable group in the molecule, and specifically, those shown in the following general formulas (1) to (3) are exemplified. can do.

R'R"SiY'Y" (1) R'X5iY'Y" (2) R'SiY'Y2Y3 (3) (In the formula, R1 and R2 have an olefinic unsaturated bond, and carbon, hydrogen and optionally Each group is composed of oxygen and is different or different from each other. ) More specific examples of R1 and R2 include vinyl allyl, butenyl, cyclohexenyl, and noclopentadienyl, with terminal olefinically unsaturated groups being particularly preferred.Other preferred examples include CtL=CHO (cH2)*- Cll2= C(cIl*) Coo (c1l-)3 having an ester bond of the other terminal unsaturated acid
-1CI! ,=C(cIF)Coo(cH,),
-0-(cH2)3-1CH,=C(c113)C
00C11, C1120CH, C11CII, 0(cI
+)3-1■ H and other groups can be mentioned. Among these, vinyl groups are most suitable. As a specific example of X, for example, 1
Examples of hydrocarbon groups include methyl, ethyl, propyl, tetradecyl, octadecyl, phenyl, hensyl, tolyl, and the like, and these groups may also be halogen-substituted hydrocarbon groups.

Specific examples of yl, yl, and Y3 include alkokyne groups, alkokinoalkoquino groups, formiloquine, such as methoxy, ethoxy, butoxy, and methoxynoethquino;
Acyloxy groups such as acetoquino, propynoquino, oximes, e.g. -oN=C(cH3),, -ON=
C) lcHfcJs and --ON=C(c-H
s)*, or substituted amino groups and arylamino groups such as -NHCH2, NHCJs and -NH(c,
H, ), and any other hydrolyzable organic groups.

Preferably used organosilicon compounds are those represented by the general formula (3), and organosilicon compounds in which the groups Y'SY'' and Y3 are the same are particularly suitable. Among these, R1 is a vinyloxyalkyl group (cI ,=CH-0(cHy)
n) or a vinyl group, and Yl-Y3 is preferably an alkoxy group or an alkoxyalkoxy group,
Examples include vinyloxypropyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, and vinyltris(methoxyethoxy)silane. However, vinylmethyljethoxysilane, vinylphenyldimethoxysilane, etc. can be used as well.

The content ratio of the monomer components (a) to (c) in the fluoropolymer is (a): 3 (1-70 mol%), (b): based on the total molar loss of (a) to (c). 20-6
0 mol%, (c): 1 to 80 mol% ((a) + (b)
+ (c) = too), preferably (a):
40-60 mol%, (b): 20-50 mol%, (
c): In the range of 1 to 25 mol%.

Here, (a) is set to 30 to 70 mol% because if it is less than 30 mol%, the durability will be poor, and if it is more than 70 mol%, the adhesion to the core material will be poor. The reason why the content is 1 to 80 mol % is because if it is less than 1 mol %, it will be difficult to cure and form a film, and if it is more than 80 mol %, the stability will be poor.

The fluoropolymer used in the present invention includes the above-mentioned (a) to (c).
It is produced by copolymerizing each of the monomers in the presence of a well-known radical initiator (or by heating in its absence). Each component (a) to (c) is important here. For example, copolymerization does not occur with components (a) and (c) alone, but by adding component (b), (a), The components (b) and (c) are copolymerized.

Various known radical initiators can be used for copolymerization. Specifically, organic peroxides, organic peresters such as benzoyl peroxide, dichlorobenzoyl peroxide, dicumyl peroxide, di-tert-butyl peroxide, 2,5-dimethyl-2
,5-di(peroxybenzoate)hexyne-3,1
, 4-bis (tert-butylperoxyisopropyl)benzene, lauroyl peroxide, tert-butyl peracetate, 2,5-dimethyl-2,5-di(
tert-butylperoxy)hexyne-3,2,5-
Dimethyl-2,5-di(tert-butylperoxy)
hexane, tert-butyl perbenzoate, tert
tert-butyl perphenylacetate, tert-butyl perisobutyrate, tert-butylperu 5ec-
Octoate, tert-butyl perpivalate, cumyl perpivalate, tert-butyl perdiethyl acetate, and other azo compounds such as azobis-isobutylnitrile, dimethylazoisobutyrate, and the like. Among these are dicumyl peroxide, diter
t-Butyl peroxide, 2,5-dimethyl-2,5-
di(tert-butylperoxy)hexyne-3,2,
Dialkyl peroxides such as 5-dimethyl-2,5-di(tert-butylperoxy)hexane and 1,4-bis(tert-butylperoxyisopropyl)benzene are preferred.

The copolymerization takes place in a reaction medium consisting of an organic solvent. The solvents used here include aromatic hydrocarbons such as benzene, toluene, and xylene, aliphatic hydrocarbons such as n-hexane, cyclohexane, and n-heptane, and chlorobenzene, bromobenzene, iodobenzene, and 0-bromotoluene. Examples include halogenated aromatic hydrocarbons, halogenated aliphatic hydrocarbons such as tetrachloromethane, 1.1,i-trichloroethane, tetrachloroethylene, and 1-chlorobutane.

Copolymerization is carried out by adding a radical initiator to the above solvent in a molar ratio of 10-1 to 2 X to-' based on the total number of moles of monomers. Also, the polymerization temperature is -30 to 200℃
, preferably 20~100℃, polymerization pressure θ~100k
g/cII*・G1 preferably O~50kg/c+n″
-G.

The molecular weight of the fluoropolymer thus obtained was determined by gel permeation cyclochromatography (GPC) using tetrahydrofuran as a solvent and monodisperse polystyrene of known molecular weight as a standard substance. Number average molecular weight (T'1li) is usually 30QO to 20000
It is desirable that it is 0, preferably 5000 to too
It is in the range of ooo. When the molecular weight is less than 300, it is generally difficult to form a coated stone, and when it exceeds 200,000, solvent solubility is often poor. By adopting the above composition ratio and the molecular weight described here, it becomes solvent-compatible, and after being cured by the method described below, it has excellent heat resistance, weather resistance, and mechanical properties. .

Another property of fluoropolymers is that they are non-polymerized or have low crystallinity, and many are non-polymerizable. Generally X
Many have a linear crystallinity of 0% and no melting point observed using a differential scanning calorimeter (DSC). Therefore, transparency is good.

The glass transition temperature (Tg) is usually -60 to +20°C, often -40 to +5 when measured by DSC at a heating rate of 10°C/rAin after cooling the sample to -120°C.
It is in the range of 0.

As for optical properties, the refractive index (nD) is usually 1.48 to I
.

34, mostly in the range of 1.44 to 1.36. Therefore, when quartz glass is used as the core material, this fluoropolymer is suitable for use as the cladding material since the refractive index of quartz glass is about 1.45 to 1.50.

A carboxyl group may be introduced into the molecular chain of the fluoropolymer used in the present invention. An example of this is a method of graft polymerizing unsaturated carboxylic acids and their derivatives. Examples of unsaturated carboxylic acids used for this purpose include acrylic acid, methacrylic acid, α-ethyl acrylic acid, and maleic acid. , fumaric acid, itaconic acid, citraconic acid, tetrahydrophthalic acid, methyltetrahydrophthalic acid, industrial cis-bicyclo(2,2,1)hept-5
-ene-2,3-dicarboxylic acid (nadic acid ■), methyl-endocys-bicyclo(2,2,1)hept-5
-Nin-2,3-dicarboxylic acid (methylnadic acid■)
unsaturated carboxylic acids such as unsaturated carboxylic acids, halides, amides, imides, acid anhydrides, esters of the unsaturated carboxylic acids, ie maleyl chloride, maleimide, maleic anhydride, citraconic anhydride, monomethyl maleate, dimethyl maleate, and the like.

The above-mentioned fluoropolymers are soluble in organic solvents at room temperature, such as hydrocarbon solvents such as benzene, toluene, xylene, and hexane, ketones such as acetone, methyl ethyl ketone, and butyl acetate, and esters. It is soluble in oxygenated solvents, ethers such as dimethyl ether, dimethyl ether, dipropyl ether, alcohols such as methanol, ethanol, halogenated hydrocarbons such as tokuchloroethane, dichloroethane, chlorobenzene, etc.

A method for forming an optical fiber by coating the core part (A) with the cladding material according to the present invention is to dissolve the fluoropolymer in the organic solvent and immerse the core part (A) in this solution. General methods for forming optical fibers can be used, such as a drawing method or a method of directly and continuously coating the stretch-molded core portion (A) with resin extruded from an extruder.

The polymer after coating can be cured either at room temperature or by heating (including steam heating).

By the way, since the fluoropolymer has a hydrolyzable organic group derived from the organosilicon compound (c), when exposed to moisture, a crosslinking reaction occurs between the molecular chains of the polymer and the polymer is cured. It is desirable that this crosslinking reaction is already completed when the optical fiber is commercialized, and therefore it is preferable to add a silanol condensation catalyst to promote the crosslinking reaction.

In this case, a silanol condensation catalyst is added in advance to an organic solvent solution in which a fluoropolymer is dissolved, and when the cladding part (B) is formed using this, the organic solvent evaporates and comes into contact with the moisture in the air. At the same time, a curing reaction occurs, and the film of the cladding portion CB) hardens.

Known silal catalysts can be used, such as carboxylic acid metal salts such as dibutyltin dilaurate, stannous acetate, stannous octoate, lead naphthenate, iron 2-ethylhexanoate, cobalt naphthenate, and organic bases. Examples include acids such as ethylamine, hexylamine, dibutylamine, piperidine, mineral acids and organic fatty acids.

Suitable catalysts are alkyltin salts of carboxylic acids, such as dibutyltin dilaurate, dibutyltin dioctoate, diptyltin diacetate.

The crosslinking reaction proceeds sufficiently at room temperature, that is, around room temperature (0 to 40°C), but if necessary, the tip fiber after molding may be heated to promote the crosslinking reaction in the cladding portion (B).

In addition, in order to improve the adhesion or adhesion of the fluoropolymer to the surface of the core part (A), the surface of the core part (A) may be subjected to surface treatment such as coating with a primer or degreasing treatment, if necessary. It is done.

The cladding part (B) made of a fluoropolymer after curing (after being left for 14 days) is JIS K 5400.
(1979) 6.16 pencil hardness is usually 3H to 2B
, most of them are in the H-H range, and JIS K (19
79) The bending resistance according to 6.16 usually passes 3 mmφ, and most pass 2ml11φ. This result shows that it has excellent flexibility.

In addition, the light transmittance after curing is usually 95% or more, often 9
It is 9% or more. Here, the light transmittance is determined by forming a film on a release base material, peeling it off after curing to form a film piece, fixing the film piece in a quartz cell and filling it with pure water, and filling it only with pure water. Using the quartz cell as a blank, JIS
It was carried out according to K6714.

As shown in the sectional view of FIG. 1, the optical fiber of the present invention consists of a core part (A) and a cladding part (B).
) has an outer diameter of usually about 20μ to toxx, preferably about 60μ
The thickness of the cladding part (B) is approximately 5μR to 1■, preferably approximately 10μttt-0,5xx.
It is.

If necessary, the optical fiber of the present invention may be further provided with a coating layer (c) on the outside thereof, as shown in the cross-sectional view of FIG. 3, for example.

Silicone resin, polyolefin resin, etc. are used for the coating layer (c).

〔Example〕

The present invention will be described in detail below, but unless otherwise specified, the present invention is not limited to these examples and can be modified in any manner without impairing the purpose of the present invention.

<Example 1> In this example, a cladding part was formed from a cladding material mainly composed of a fluorine-based polymer described below on a core part mainly composed of quartz glass.

We will discuss the manufacturing method and physical properties of the cladding material, which are its distinctive features.

80 g of benzene 1 butyl vinyl ether (BV E
) 25.2 g, m)-xyvinylsilane (TMVS) 7.1 g and dilauroyl peroxide Ig were charged, solidified with acetone and dry ice, and degassed.
Remove oxygen from the system. Then, 45 g of hexafluoropropene (HF P ) was introduced into the autoclave,
Increase temperature. When the temperature inside the autoclave reached 65°C, the pressure was 8.1 kg/c+++'. The reaction was continued for 8 hours with stirring, and when the pressure reached 4.6 kg/cm', the autoclave was cooled with water to stop the reaction.

After cooling, unreacted monomers were expelled, the autoclave was opened, and the reaction solution was taken out. After concentration, the mixture was washed with a benzene-methanol mixed solvent, concentrated again, and dried. The yield of Polymer A was 60 g.

The number average molecular weight of the obtained polymer A by GPC is t, o
x io', and the glass transition point was -14°C.

When the composition of this copolymer (A) was analyzed using elemental analysis and NMR, it was found that HF P / B V E / T
MVS = 48/40/12 (molar ratio).

5 kg of the polymer A thus obtained was mixed with 2 toluene.
．． Dissolve dibutyltin diurarate (D B
A sample containing 3.2 g of TDL) was prepared.

A solution of copolymer A was applied to quartz glass Vi (2xx thickness), and then air-dried at room temperature to form a film (50μ! thickness) made of the fluorine-based polymer on the surface.

When this fluoropolymer-coated quartz glass plate was immersed in water at 20°C for 10 days, no increase in weight was observed. Further, no change in the transmittance of light with a wavelength of 700 m before and after immersion was observed.

The glass plate was similarly heated at 150° C. x 4 br, but no change in light transmittance was observed.

Furthermore, when a quartz glass plate coated with a fluoropolymer was placed on a sunshine weatherometer for 3,000 hours, no change in light transmittance was observed before and after the test.

The refractive index of the cured polymer was 1.38.

<Example 2> This example also has a core made of quartz glass as a main component, and the material of the cladding, which is a characteristic part, will be described.

In the same manner as in Example I, n-butyl vinyl ether, II,
(BVE), ethyl vinyl ether (EVE), trimethoxyvinylsilane (TMVS), chlorotrifluoroethylene (cTFE), dilauroyl peroxide (DLPO)
) to obtain Polymer B.

GPC equivalent number average molecular weight of Polymer B is 0.85X10'
The glass transition point was -8°C.

In addition, the composition of polymer B is CTFE/EVE/B in molar ratio.
VE/TMVS =48/38/7/7.

A solution was prepared by dissolving 9 in Polymer B5 and 9 in 2.25 toluene, and adding 0.25 kg of tetramethyl orthosilicate [Methyl Silicate 39, manufactured by Colcoat Co., Ltd.] and 8 g of dibutyltin dilaurate.

In the same manner as in Example 1, quartz glass was temporarily applied,
A film (20 μm thick) was formed.

Adhesion water resistance and weather resistance tests were conducted in the same manner as in Example 1, and similar results were obtained.

Note that the refractive index of the cured product of copolymer B was 1.41.

<Example 3> To describe only the cladding material, cyclohexyl vinyl ether (cyI-(VE)) was prepared in the same manner as in Example 1.
, ethyl vinyl ether, trimethoxy, γ-vinyloxypropylsilane [0△△S to TMVPS: (OCll
, 3) 3], Polymer C was obtained using dilauroyl peroxide (DLPO).

The GPC equivalent number average molecular weight of Polymer C was 4×10', and the glass transition point was 00°C.

In addition, the composition of polymer C is CTFE/EVE/C in molar ratio.
yHVE/TMVPS=50/34/10/6.

Polymer C5K9 was dissolved in 5 kg of toluene and DBTD
L39 was added to prepare the solution.

This solution was applied to a quartz glass plate in the same manner as in Example 1, and
A coating film with a thickness of 0 μm was formed and tested, and the same results as in Example 1 were obtained.

<Example 4> 2 In the same manner as in Example 1, a polymer was prepared using cyclohexyl vinyl ether (cyHVE), ethyl vinyl ether (EVE), tripropenoquivinyl silane [TPOVS lene, and dilauroyl peroxide (DLPO)]. Obtained.

The GPC equivalent number average molecular weight of the polymer is 0.6X 10'
The glass transition point was -15°C.

In addition, the composition of the polymer is CTFE/EV E/
B VE/ T P OV S =53/ 32/
5/ LO teat.

5 kg of Polymer D was mixed with toluene/Nashisin-1/1 (wt%
) A solution was prepared by dissolving 2.5 kg.

Example 1 This was applied to a quartz glass plate (211 thick) and heated at 150°C for 10 minutes to form a 120 μm thick film.
Similar results were obtained for adhesion, water resistance, heat resistance, and weather resistance.

The refractive index of the cured copolymer was 1.40.

〔Effect of the invention〕

According to the present invention, an optical fiber with excellent adhesion between the core portion (A) and the cladding portion (B) is provided, and an optical fiber with excellent weather resistance and heat resistance is provided.

In particular, good weather resistance improves the durability of the end fiber, which is advantageous for optical fibers used in harsh environments.

Furthermore, since the clad material according to the present invention has excellent flexibility, the flexibility of the optical fiber itself of the present invention using the clad material improves, making it easier to use the optical fiber in bent places. Ta.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a specific example of an optical fiber, and FIG. 2 is a sectional view showing another specific example of an optical fiber. (A)...Core part, (B)...Clad part, (c)...Coating layer. Patent applicant: Mitsui Petrochemical Industries, Ltd. Figure 1

Claims (2)

[Claims] (1) In an optical fiber formed by surrounding a core portion (A) that guides light with a cladding portion (B) having a refractive index smaller than that of the core portion (A), the cladding portion (B) is , (a) a fluoroolefin, (b) a vinyl ether, and (c) an organosilicon compound having an olefinically unsaturated bond and a hydrolyzable group, the copolymer comprising at least one An optical fiber characterized in that it is formed of a material whose main component is a fluoropolymer that is crosslinked. (2) The optical fiber according to claim 1, wherein the core portion (A) is made of quartz glass containing SiO_2 as a main component.