CA1290175C

CA1290175C - Optical fiber

Info

Publication number: CA1290175C
Application number: CA000530223A
Authority: CA
Inventors: Akio Ohdaira; Shunji Abe; Noboru Wakatsuki; Akira Tanaka
Original assignee: Fujitsu Ltd
Current assignee: Fujitsu Ltd
Priority date: 1986-02-24
Filing date: 1987-02-20
Publication date: 1991-10-08
Anticipated expiration: 2008-10-08
Also published as: JPH0610684B2; DE3785470T2; DE3785470D1; KR870008202A; KR900008606B1; US5018828A; EP0234918A3; JPS62195606A; EP0234918B1; EP0234918A2

Abstract

ABSTRACT OF THE DISCLOSURE

An optical fiber of heat resistance, low-temperature resistance, flexural resistance, water absorption resistance, chemical resistance, etc., is provided by comprising a composition in which a core component comprises a polycarbonate or a silica type glass, a clad component comprises a graft-modified poly (4-methyl-1-pentene).

Description

~9~)175 OPTICAL FIBER

BACKGROUND OF THE_INVENTION

1, Field of the Invention The present invention relates to an optical fiber for transmitting optical signals, particularly to an optical fiber having an excellent heat resistance and flexural resistance.

2. Description of the Related Art In the prior art for the plastic optical fibers, polystyrene (PS) or polymethyl-methacrylate (PMMA) are used as the core material. However, since such materials have a glass transition temperature ~Tg) as low as 100C, the core material will be softened and become fluid in a high :;~
temperature atmosphere of 100C or higher, ~nd:
therefore, the upper limit of the usable temperature is about 80C.
As~a method for improving such a disadvan~-tager various~ plastic optical fibers using:a :~
polycarbonate having excellent transparency:and a high ~g:of about 150C have been mentioned ~for: ~ :
example,:U.S.P. 3,999,834, Japanese Unexamined Patent Publication~Kokai) No.;57-4~204 and Japanese Unexamined Patent Publica~tion (Kokai)~No. 6~0 32004j. However, according to~the~method discl~sed in V.S.P. 3,999,834, crosslinking treatment of the clad material is required a~ter the polycarbonate i8 coated with the clad material, and therefore, a disadvantage is involved in that the preparation process is cumbersome and also a long time is required for the treatment. On the other hand, Japanese Unexamined Patent Publication ~Kokai) No.

.

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57-46204 discloses a plastic optical fiber having a polycarbonate coated with a clad material comprisinq polymethylmethacrylate and so on. However, these clad materials are not sufficient for heat resistance comparing to polycarbonate. And Japanese Unexamined Patent Publication (Kokai) No. 60-32004 discloses a plastic optical fiber having a core material comprising a polycarbonate coated with a clad material comprising 4-methyl-1-pentene, and further, that an unsaturated carboxylic acid such as acrylic acid may be copolymerized for improvement of the interlayer peel-off strength between the polycarbonate and the clad material. Due to poor adhesion between poly ~4-methyl-1-pentene) and polycarbonate, a flexural resistance thereof as an optical fiber is inferior and the adhesiveness cannot be improved in some cases by mere copo:lymerization with an unsaturated carboxylic acid. Thus; under the present situationl an optical fiber having an excellent heat resistance and flexural resistance has not been practically realized.

SUMMARY OF THE INVENTION

Accordingly, the present invention provides an optical fiber having an excellent heat resistancet low-temperature resistance, flexural resistance, water absorption resistance, chemical resistance, etc., comprising a composition in which:
~ a) a core component comprises a poly-carbonate or a silica type glass, (b) a clad component comprises at least 0.1% by weight, and preferably at least 0.5%
by weight, of a yraft-modlfied poly (4-methyl-1 ~-.-..

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~2~310175 pentene) (A) which is partially or entirely ~raft-modified with an unsaturated carboxylic acid or its derivative at a grafted amount within the range of from 0.01 to 10~ by weight, is formulated, which graft-modified poly-4-methyl-1-pentene (A) may be further formulated with a low molecular weight .
compound (B) having a number-average molecular weight of 300 to 5,000.
. .
DESCRIPTION OE' TI~E_PREE ERRED EMBODIMENT

The polycarbonate comprising the core of the present invention (hereinafter abbreviated as PC) (A) includes various polycarbonates and copoly-carbonates obtained by the reactions of dihydroxyl compounds with phosgen or diphenylcarbonate according to known methods. Examples o~ the dihydroxyl compounds include hydroquinone, rezorcinol, 4,4'-dihydroxy-diphenylmethane, 4,4'-dihydroxy-diphenyl-ethane, 4r4idihydroxy-diphe.~yl-n-butane, 4,4'-dihydroxy-diphenylheptane, 4,4' dihydroxy-diphenyl-phenyl-methane, 4,4'-dihydroxy-diphenyl-2,2-propane (bisphenol A), 4,4'-dihydroxy-3,3'-dimehtyl-diphenyl-2,2-propane, 4,4'-dihydroxy-3,3'-diphenyl-diphenyl-2,2-propane, 4,4'-dihydroxy-dichloro-diphenyl-2,2-propane, 4,4'-dihydroxy-diphenyl-l,l-cyclopentane, 4,4'-dihydroxy-diphenyl-l,i-cyclohexane, 4,4'-dihydroxydiphenyl-methyl-phenyl-methane, 4,4'-dihydroxydiphenyl-ethyl-phenyl~methane, 4,4'-dihydroxydiphenyl-2,2,2-trichloro-l,l-ethane, 2,2'-dihydroxydiphenyl, 2,6-dihydroxynaphthalene, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydorxy-3,3!-dichloro `diphenyl ether, and 4,4'-dihydroxy-2,5-diethoxyphenyl ether. Among these polycarbonates, those having a Tg of 140CC or .

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, higher are preferred with respect to heat resistance. Particularly, polycarbonates by use of 4,4'-dihydroxydiphenyl-2,2-propane ~bisphenol A~
having a viscosity-average molecular weight within the range from 1.4 to 2.5 x 104 are preferred because they have a most excellent transparency, mechanical performance, heat resistance, low temperature resistance, and impact resistance. -- -- The silica type glass comprising the core according to the present invention comprises SiO2 as the main component, and generally also contains such components as, or example, Ge, P, C, and Al, for control of the refractive index.
The graft-modified poly (4-methyl-1-pentene) (A) comprising the clad of the present invention has a grafted amount of an unsaturated carboxylic acid or its derivative within the range of from 0.01 to 10~by~weight, preferably from 0.05 to 5~ by weight havin~ generally an intrinsic~
viscosity [~] of 0.3 to 1~0 dl/g, prefe~rably ~.5 to~S
dl~g, in decalin solvent at 135C. When a graft ;
polymer with a grafted amount of the unsaturated carboxylic acid or its derivative less than 0.01% by wei~ht is used, the interlayer adhesiveness with the polycarbonate~or the quartz, which is the core cannot be improved. On the other hand, a~raft polymer with~a grafted amount exceeding 10%;by weight will have a lower water absorption resist~ance and transparency.
The poly ~4-methyl-1-pentene) tE), which i~
the base materiaI for the graft-modified poly (4-meth~ pentenej ~) to be used in the present invention, iB a homopolymer of 4-methyl-1-pentene or a copolymer of 4-methyl-1-pentene with an a-olefin having 2 to 20 carbon atoms such~as ethylene, ~::,: ; .

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30~L75 propylene, l-butene, l-hexene, 1 octene, l-decene, l-tetradecene, l-octadecene, and the like, which is generally a polymer composed mainly of 4-methyl-1-pentene containing 8S mol~ or more of 4-methyl-1-pentene, preferably a crystalline polymer having a melting point (ASTM D 3418) of 230C or higher and an intrinsic viscosity [n] in decaline solvent at 135C of 0.5 to 25 (dl/g). --When the clad according to the present invention is comprised of a composition containing further a low molecular weight compound (B) having a number-average molecular weight (Mn) of 300 to 5,000, preferably 300 to 2,000 formulated in the above ~raft-modified poly (4-methyl-1-pentene) (A) in an amount generally of 1 to 15% by weight, further 2 to 10~ by weight, based on 100 pa~ts by weight of the composition, adhesiveness wi~h the above core, interface smoothnessj flexural resistance, low-temperature resistance, and the like can be further preferably improved. At a level less than 1~ by weight of the low molecular weight compound (B) formulated, a fuxther improved effect of the above characteristics cannot be exhibited, while at a level exceeding 15% by weight, heat resistance o~ the composition may be lowered or the low molecular weight compound (B) may seep out onto the interface to make it sticky. A compound having an Mn of less than 300 tends to seep out onto the ; surface and not give an improved effect o~ flexural ' ' - , . ~ . - . -. ~ - -.

~:901~5 resistance and low-temperature resistance. On the other hand, a compound having a Mn in excess of 5,000-tends not to give an improved effect of flexural resistance and low-temperature resistance.
Specific examples of the low molecular weight compound having an Mn of 300 to S000 to be formulated in the graft-modified poly (4-methyl-1-pentene) (A) include, for example, mineral oils such --as paraffinic process oils, naphthenic process oils, aromatic process oils, and the like, aliphatic hydrocarbon compounds such as paraffinic waxes, low molecular weight polymers obtained by polymerization (copolymerization) of ~-olefins such as ethylene, propylene, l-butene,~ and the like, alicyclic hydro-car~on compounds, aromatic hydrocarbons, fatty acids, aliphatic alcohols, fatty acid amides, fatty acid esters, aliphatic mercaptans, aliphatic aldehydes, aliphatic ketones, aroma~tic ethers~, ànd~
the like, having l ~r more ~unctional groups such as carboxylic group, hyroxyl group, carbamoyl;~group, ester group, mercapto group, carbonyl group, and the like, at the terminal`ends or internally o~
aliphatlc,~alicycl~ic or aromatic hydrocarbon groups.
Of these~low~molecular weight compound (B), aliphatic hydrocarbon compounds and alicyclic hydrocarb~on compounds are preferable becau~se of`
thelr excellent dispersibility in the above graft-modi~ied poly ~4-methyl-1-pentene) (A).
Particularly~ ethylene-~-olefin random copolymers (C) having an eth~lene content of 10 to 95 mol%, preferably 40 to 92 mol%t a crystallinity by X-ray o~ 0 to 20%, a number-avera~e molecular weight (Mn) ;
of 300 to saoo, preferably 300 to 2000~ prefe~ably a .
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~90~75 ratio of weight average molecular weight (Mw) to Mn exhibiting the molecular weight distribution Mw/Mn of 3 or less, further 2 or less and/or oligomers (D) represented by the formula: ' .

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0~75 cHc}~2cH2~cH2cHcH2cH2~cH2 tm --~C~2CH~H2CH2 ~ R
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~wherein n and p are integers of 0 or more, m is 0 or l, and R is > CHCH2- or CH3CH2CHCH2-), :
having an Mn of 300 to 5,000, further 300 to 2,00Q, preferably Mw/Mn of 3~or less, further 2; or less,~
: : are preferred, because they have a~most excellent :dispersibili~ty in~the above graft-modified~poly~
; ::(4-methyl-l-pentene) (A) and have excellent:improved effects such:~as inte~rlayer adhesi~veness,~flexural~
resistance,:~low-t~emperature~resistance,:and:th:e~

: In;the:above-mentioned ethylene-~-olefin random copolyme~r (C~ the ~-olefin~:to be:~
copolymérized~ with e:thylene generally includes~
olefins having~3 to~20~carbon:atoms,~specif:ically,~
:for~example,:;propylene~ butenè, l-hexene,~
:4-methy~ pentene, l-octene, l-decen:e`, l~
;tetradeoene, l-octadecene~and the;like~ which may~
comprise each~individual:compound~-or:a~mixturq of~
:two or more compoun~8.
: AccordLng to one method for producing the~
:~: : above-mentioned ethylene--olefin random copolymer~
(C)r ethylene and;~an~a-olefin are continuousl:y copolymerized in;ligui;d~phase by~using a catalyst~
; ormed from a soluble vanadium compound~and an~

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organi~ aluminum compound in the presence of hydrogen, wherein the vanadium compound concentration in the polymerization system is 0.3 mmO15 or more per liter of the liquid phase, and the vanadium compound supplied to the polymerization medium to 5-fold or less of the vanadium compound concentration in the polymerization system. A more detailed method is described in Japanese Unexamined Patent Publication tKokai~ No. 57-123205.
As the oligomer ~D) represented by the ~ormula:

CH3 ¦ ¦ ~
CHCH2CH2-tCH2C~CH2CH2t-~-tCH2 t~m t C~2C~CH2CH2 ~ R

C~3 When m is 0 and R is C~3CH2CHCH2-, it is a hydro-genated product of polyisoprene. For obtaining a hydrogenated product of polyisoprene, it can be easily produced by carrying out anion polymerization of isoprene in a cyclohexane solution under the co-presence of sec-butyl lithium catalyst and then hydrogenating the polymer in the presence of a nickel naph~henate catalyst. On the other hand, CH3~
when m is 1, n and p are 2, and R is /C~CH2-, it is squalane obtained by hydrogenation of squalene with a nickel catalyst. Squalene which is a starting material of squalane is contained in liver .

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oil o~ a deep sea shark, and it can be obtained by subjecting the unsaponified product of shark liver oil to fractional distillation, deacidification and further to fractional distillation in the presence of metallic sodium, or condensing farnesyl chloride or farnesyl bromide in the presence of metallic magnesium, or carrying out Wittig reaction on trans-geraniol acetone.
- In the above description, the ethylene ---content was measured according to the so-called 13C-NMR method, the melting point was measured according to ASTM D 3418, the crystallinity was measured according to the X-ray diffraction method and Mn and Mw/Mn was measured according to ge1 permeation chromatography (GPCj by using tetrahydrofuran as the solvent and polystyrene of a known molecular weight and squalane as the standard substances at 25C. ~ ~
The unsaturated carboxylic acid or its derivative to be grafted onto the above poly (4-methyl-l-pentene) (B) to be used ln the present invention may include unsaturated carboxylic acids such as acrylic acid, maleic acid,~fumar~ic acid, tetrahydrophthalic acid, i~taconic~acid,~citraconic acid, chrotonic~acid, isocrotonic acid, Nagic Acid~
(endo-cis-bicyclo 12,2,1] hept-5-one-2,3-dicarboxylic acid) and the like, or their derivatives such as acid halides, amides, imides, anhydride~, esters, and the like. Specific examples may include maleyl chloride, maleimide, maleic anhydride, aitraconic anhydride, monomethylmaleate, dimethylmaleate, glycidylmaleate, and the like.
Among them, unsaturated dicarboxylic acids or acid anhydrides thereof are pre~erred, particuIarly maleic acid, Nagic Acid~ or acid anhydrides thereof ~are preferred.

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For preparation of a modified product by graft copolymerizing a graft monomer selected from the above-mentioned unsaturated carboxylic acids or derivatives thereof with the above poly (4-methyl-1-pentene) ~E), various methods known-in the art may be employed. For example, there may be employed the method in which graft copolymerization is carried out by melting the poly (4-methyl-1-pentene) (E) and adding a graft monomer thereto or the method in ~
which graft copolymerization is carried out by adding a graft monomer to a solution of the polymer dissolved in a solvent. In either case, for efficient graft copolymerization is carried out by adding a graft monomer to a solution of the polymer ~ ~-dissolved in a soIvent. In either case, for efficient graft copolymerization of the above-mentioned graft monomer, it is preferable to practice the reaction in the presence of a radical initiator. The graft reaction is carried out generally at a temperature of from 60 to 350~. The amount of the radical initiator to~be used is generally within the range of~from 0.001 to 1 part by weight per 100 parts by weight of the poly (4-methyl-1-pentene) (E). The radical initiator may include organic peroxides, organic peresters, and otherwise azo compounds. Of thèse radical initiators, diaikyl peroxides such as dicumyl peroxide, di-tert-butyl peroxide, 2,5-dimethyl-2,5-diltert-butyl-peroxy)hexyne-3, 2,5-dimethyl-2,5-dittert-butyl-peroxy)hexane, 1,4-bis~tert-butylperoxy-isopropyl)benzene, and the like are preferred.
The graft-modified poly ~4-methyl-1-pentene) (A) comprising the clad of the present invention may be either entlrely ~raft-modified with ~: , ~ ... . ~ .... . . . . .. ... .. .

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~.2~0175 an unsaturated carboxylic acid, and the like, or a mixture of an entirely graft-modified poly (4-methyl-l~pentene) and an unmodified poly (4-methyl-1-pentene) ~E) {namely a graft modified poly~4-methyl-1-pentene} which is partially modified), provided that the grafted amount of the unsaturated carboxylic acid or its derivative is within the-range as spesified above. When mixed with an unmodified poly (4-methyl-1-pentene) (E), (namely 2 graft modified poly ~4-methyl-1-pentene) and-an unmodified poly ~4-methyl~l-pentene) which is partially snodified), provided that the grafted amount of the unsaturated carboxylic acid or its derivative is within the range as specified above.
When mixed with an unmodified poly (4-methyl-1-pentene) ~E), it is also possible to use a graft-modified poly (4-methyl-1-pentene) containing a slightly hiyher concentration of graft content generally up to 25%~by weight, provided that the grafted amount of the unsaturated carboxylic acid, etc. in the mixture falls within the range as specified above.
,. .
i The composition in which the low molecular compound (B) is formulated in the graft-modified poIy (4-methyl-1-pentene~ (A)l which is one of the clad materials of the present invention, may be either a composition~in which the low molecular weight compound (B) is added to the modified poly ~4-methyl-1-pentene) ~A) previou~ly graft-modified with an unsaturated carboxylic acid and the like or a composition which i8 graft-modified with the above-mentioned unsatura~ed carboxylic acid and the like, during mixing or after mixing of an unmodified poly (4-methyl-1-pentene) ~E) with the low molecular compound ~B).

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The optical fiber according to the present invention may be coated with, for example, a thermoplastic resin comprising polypropylene or -polyethylene as the main component which has an improved heat resistance by intramolecular cross-linking thereof, outside the clad comprising the above graft-modified poly (4-methyl-1-pentene? ~A) as the constituent for protection of the clad material. Further, to prevent external dist~bing --light from outside, the coating material may be colored with a pigment, or a flame retardant may be added therein to improve the flame retardancy.
The optical fiber according to the present învention can be prepared according to various methods known-in the art, specifically according to, for example, the method in which the core material and the clad material are extruded simultaneously by the melt composite spinning method comprising a `~
double nozzle with the core material as the core ~omponent and the clad material being covered to a thickness of 5 to 50 ~m at the outer circu~ferential portion, the method in which the core material is first molded by extrusion and thereafter the clad material is covered by extrusion or the method in which the core material is molded and then a clad material dissolved in a solvent is coated thereon, :
followed by, for Qxample, drying. When a polycarbonate is used as the core material, the temperature at the double nozzle portion is controlled generally between 220 and 250C.
The~optical ~iber according to the present invention comprising a core comprising a polycar-bonate or a silica and a clad mainly comprising of the graft-modified poly ~g-methyl-l-pentene) has ~n excellent heat res~istance and low-temperature :

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~2~ 5 resistance and the polycarbonate core optical fiber also has an excellent flexural resistance, and therefore, it can be preferably used as a sensor for an optical data link i.n the engine room of an automobile or for detection or a material for a moldin~ machine for which heat resistance is demanded. Also, since the quartz glass type optical fiber has an excellent light transmittance, it can be preferably used for optical transmission and ~~
optical LAN between private instruments/instruments ~ in a factory.

: EXAMPLES

: The present invention is described in more .:~ detail by referring to the following Examples, but ~: the pxesent invention is not limited by the~e :
Examples within the spirit of the invention.
. ~ :
:: ~xample 1 <Preparation of maleic anKydride graft-: : modified poly ~4-methyl-1-pentene)~
After mixing 0.7 part by weight of maleic anhydride and 0.5 part by weight of 2,5-dimethyl-2,5-di(tert-but~ylperoxy)hexyne-3 with 100 parts by ~ ~.
weight of a poly(4-methyl-l-pentene)~ ~hereinafter abbreviated as PMP-l) having an intrinsic viscosity lnl: 3.3 dl/g, Tm = 233C and containing 6 mol% of l hexadecene/1-octadecene ~weight ratio l/l~ by a .
Henschel mixer, the~mixture was melted and mixed through an extruder set at a temperature of ~60C to obtain a malei:c anhydride graft-modified poly (4-methyI-l-pentene) (hereinafter abbreviated as M~H-` PMP-l) having an intrinsic viscosity lnl: 1.4 dl/g ~ and a grafted amount of maleic anhydride: 0.5 g/lO0 ~ g polymer.

:.

1290~7S

<Preparation of optical fiber~
After mixing 96% by weight of the above MA~-PMP-l and 4~ by weight of squalane by a ~enschel mixer, the mixture was melted and kneaded through an :
extruder (molding temperature: 250C) to obtain a composition-I for clad. Subsequently, a polycarbonate (optical grade having a viscosity-average molecular weight of 2.0 to 2.2 x 104) was --separately melted through an extruder ~molding temperature: 240C) and then supplied to a double nozzle die, and the composition-I melted through another extruder (moldlng temperature:- 250C) was supplied to the above-mentioned die to obtain an : optical fiber-I with a:core diameter of l,OOD ~m and ~: a clad thickness of 50 ~m. The optical fiber ; obtained was evaluated according to the methods:
: described belo~
Light transmission loss: By passing a :
: current of 30 mA through ~ED:with~the : : maximum emission wavelength of S60:nm~
FH-511, produced by Stanray), light :~ was emitted~from~an ~ED, the optical :
fibers with~lengths of~ m~and lO:m~
were~connected by means of connectors : on one~side to the~LED side;~and the~
output energy~from~the~:other~end was~
: measur~ed by means of an:optical power : meter,~and the difference in outputted light between 11 m and 10 m is , :: ~

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~290175 represented as the light transmission loss per 1 m (dB/m).
Heat resistance test: An optical fiber of ~ 10 m is inserted into a thermostatic bath of 130C, ~ith the both ends of the optical fiber beinq taken out into the outer atmosphere from the thermostatic bath, and the change in - light transmission loss was measured ~~~
by use of an LED and optical power meter used as in the measurement of the above light transmission loss to determine the value after the elapse of 1,000 hours.
; ; Flexural resistance test: The optical fiber was fIexed at +180 with a radlus of cur~ature of 5 mm, and~ ~he ~ :
changed amount of light transmiss~ion~
loss~after repeatlng~th1s for 1,000 cycles~was measured.
he~results are~shown in ~able 1.

Example 2 ~
Example~l;was repeated except that a composition~ or~ clad comprising 2% by weight o~a maleic anhydride graft-modified poly~(4-methyl~
pentene) ob~tained in the~same manner~as in Example~
having an~intrinsic viscosity ln]: l.O dl/g, Tm:~
233C~ containing 6;mol~ of l-hexadecene/l-octadecene tweight ratio 1/1) and having a grafted amount of~maleic anhydride of 1.2 9/100 g polymer, ~; 4% by weight o~ squalane and 94% by weight of a~
po}y(4-methyI-l-pentene)~having an intrinsic vicosity [~]: ~2.4 dl/g and containing 6 mol% of hexadecene/l-octadecene~(weight ratio 1/1) :

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~29017S

(hereinafter abbreviated as PMP-2) was used in lieu of the composition-I used in Example l to obtain an optical fiber II with a core diameter of l,000 ~m and a clad thickness of 50 ~m. The optical fiber II
obtained was evaluated according to the methods as described in Example l. The results are shown in Table l.

Example 3 --Example l was repeated except that a composition-III (grafted amount of maleic anhydride: 0.5 g/lO0 g polymer) obtained by mixing 96% by weight of PMP-l and 4~ by weight of squalane and 0.7 parts by weight of maleic anhydride and 0.05 -~
parts by weight of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3 (Perhexyne 25B, produced by : Nippon Yushi) based on lO0 parts of PMP-l + squalane by a ~enschel mixer and thereafter melt mixing the mixture through afi extruder set at a temperature of :~
: 260C was used in lieu o the composition-I used in Example l to obtain an optical fiber III with a core diameter of lo 000 ~m and a clad thickness of 50 ~m, :
: The evaluation results are shown in Table l.

: : :Example 4 Example 3 was repeated ex~ept for using an ethylene-propylene random:copolymer (ethylene content 55 mol%, Mw/Mn: :1.4 and the c~rystall1nity:
: 0%) having a Mn of 350 in place of s~ualane used in Example 3. The results.are shown in Table l.

Example 5 Example i was repeated except that the MAH-PMP-l obtained in Example l alone (i.e. without ;

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added squalane) was used in place of the composition-I used in Example 1. The results are shown in Table 1.

Comparative Example 1 Example 1 was repeated except that composition-IV having an intrinsic viscosity [n] Of 2.0 dl/g obtained by mixing 96% by weight of PMP-2 and 4% by weight of squalane by a ~enschel mixer was used and then melt mixing the mixture through an extruder set at a temperature of 260C was melt mixed in lieu of the composition-I obtained in Example 1. The results are shown in Table 1.
.
: Comparative Example 2 Comparative example 1 was repeated except ~ that the PMP-l used in Comparative Example 1 was : used alone. The results are shown in Table 1. ~ :
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~L290175 .
Table 1 Light transmission Change of light loss ~dB/m) trsnsmissio~ loss (dB/m) ~est Flexural Initialresistance resistance Example 1 1.0 . 2.0 0.2 . --Example 2 1.05 1.8 0.2 Example 3 1.0 l.S 0.2 :~ Example 4 1.1 1.6 0.2 Example 5 1.0 2.0 0.4 ` ~ Comparative Example 1 1.15 8.0 0.8 Comparative E~ample 2 1.2: 6.5 1.4 :

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Example 6 ~: Si}ica preform fused;in an electric over~
i ~ was formed into fibers at a speed of 30 m/min to ; ~ obtain a quartz~co;re. The composi~ion used in Example l was heated~and;melted;at a molding ~ :
temperature of 250C in an extruder and the mol~en~
: composition was~coated on~the outer~ per~iphery of~the~
: silica core.~Thus~, optical fiber VIII~having a core:: ::
~ : diameter of:200 ~m and a clad thickness oE 100 ~m:
: . was obtained.
he o~tical ~iber V}II obtained above was evaluated in the~same manner as in Example 1. As a result~, the initial llght transmission loss was 48 :
dBjkm at a wavelength of 66~0 nm, the light transmission~:loss a~ter the heat resistance test;was .. : . .. ~ . :

.:

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7.5 50 dB/km, and the light transmission loss after flexural resistance test was 52 dB/km.

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Claims

1. An optical fiber comprising:
(a) a core component comprising a polycarbonate or a silica type glass and (b) a clad component comprising at least 0.1% by weight of a graft-modified poly (4-methyl-l-pentene) (A) which is partially or entirely graft-modified with an unsaturated carboxylic acid or its derivative at a grafted amount within the range of from 0.01 to 10% by weight.

2. An optical fiber according to claim 1 wherein said graft-modified poly (4-methyl-1-pentene) (A) contains 1 to 15% by weight of a low molecular weight compound having a number-average molecular weight of 300 to 5,000.

3. An optical fiber according to claim 2 wherein the low molecular weight compound is an aliphatic hydrocarbon compound.

4. An optical fiber according to claim 2 wherein the low molecular weight compound is an alicyclic hydrocarbon compound.

5. An optical fiber according to claim 3 wherein the aliphatic hydrocarbon compound is an ethylene-.alpha.-olefin random copolymer.

6. An optical fiber according to claim 5 wherein the ethylene-.alpha.-olefin random copolymer is having an ethylene content of 10 to 95 mol%, a crystallinity by X-ray of 0 to 20% and a molecular weight distribution of 3 or less.

7. An optical fiber according to claim 3 wherein the aliphatic hydrocarbon compound is an oligomer (D) represented by formula:

(wherein n and p are integers of 0 or more, m is 0 or 1, and R is , having a molecular distribution of 3 or less.

8. An optical fiber according to claim 7 wherein the oligomer is a hydrogenated product of polyisoprene.

9. An optical fiber according to claim 7 wherein the oligomer is a squalane.

10. An optical fiber according to claim 1 wherein the unsaturated carboxylic acid or its derivative is an unsaturated dicarboxylic acid or an acid anhydride.

11. An optical fiber according to claim 10 wherein the unsaturated dicarboxylic acid is maleic acid.

12. An optical fiber according to claim 10 wherein the unsaturated carboxylic acid anhydride is maleic anhydride.

13. An optical fiber according to claim 1 wherein the said clad component comprises at least 0.5% by weight of said graft-modified poly(4-methyl-l-pentene) (A).

14. The use of an optical fiber of Claim 1 for the transmission of optical signal.