JPH0522204B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to an optical fiber having excellent heat resistance. [Prior Art] Fluoroalkyl methacrylate polymers have a low refractive index and have conventionally been used as optical fiber sheath materials. However, this polymer lacks heat resistance, so optical fibers using it are
It was not possible to install it near a heat generating element such as a vehicle engine. In order to improve this, recently,
It has been proposed to use a fluoroalkyl acrylate polymer having fluorine at the α position as a sheath material (see Japanese Patent Application Laid-Open No. 59-227908), but this polymer still has satisfactory heat resistance. I haven't. [Object of the Invention] As a result of intensive studies on optical fiber sheath materials with excellent heat resistance, the present inventors found that an acrylate polymer having chlorine at the α-position is significantly superior in this property to a fluorine-containing polymer. The present invention has been developed based on the discovery that An object of the present invention is to provide an optical fiber with excellent heat resistance. [Structure of the Invention] The present invention provides an optical fiber composed of a core and a sheath, in which the sheath has the formula: (In the formula, R represents an organic group having 1 to 30 carbon atoms.)
An optical fiber characterized by being a polymer essentially composed of monomers represented by: The monomers may be a mixture of those encompassed by the above formula. Other ethylenically unsaturated monomers can be contained in the polymer within a range (usually 50% by weight or less) that does not impair the physical or chemical properties of the polymer. Examples of other ethylenically unsaturated monomers include methyl methacrylate, ethyl methacrylate, ethyl acrylate, vinylidene fluoride, vinyl chloride, styrene, ethylene, propylene, 2,2,
Examples include, but are not limited to, 3,3,3-pentafluoropropyl methacrylate, 2,2,2-trifluoroethyl-α-fluoroacrylate, and α-chloroacrylic acid. In the present invention, the R group contained in the monomer is not particularly limited as long as it does not increase the refractive index of the polymer. An example of an R group is the formula: _-CH2CH2N ( ^R1 ) _{SO2 -} Rf (wherein ^R1 is an alkyl group having 1 to 4 carbon atoms, Rf
is a fluoroalkyl group having 1 to 9 carbon atoms (excluding perfluoroalkyl groups), -((CF ₂ CF ₂ ) _n
(O) _o ) _q CF (Rf ¹ ) CF ₃ group [However, m is an integer of 1 to 5, n is 0 or 1, q is an integer of 1 to 5, Rf ¹ is fluorine or -CF ₃ group be. ] or −CF
( _CF3 )O( _CF2CF ( _CF3 )O) _pCF ( ^Rf1 ) _CF3 group [However, p is 0 or an integer of 1 to 5, and ^Rf1 is the same as above. ]. ), Formula: _-CH2CH (OZ) _CH2 -Rf (In the formula, Z is hydrogen or an acetyl group, Rf is the same as above.), Formula: -Ph-O- ^Rf2 group (In the formula, Ph is Phenylene group, Rf ² has 6 or more carbon atoms
12 fluoroalkylene groups are shown. ) or a fluorine-containing organic compound represented by the formula: -(CR ¹ R ² ) _h Rf (wherein, h is an integer of 1 to 5, R ¹ and R ² are hydrogen or a methyl group, and Rf is the same as above). or an alkyl group having 1 to 20 carbon atoms, a dialkylaminoalkyl group having 1 to 20 carbon atoms, a glycidyl alkyl group having 1 to 20 carbon atoms, a hydroxyalkyl group having 1 to 20 carbon atoms, a cyclohexyl group, a phenyl group, etc. Examples include organic groups that do not contain fluorine. A fluorine-containing group is preferred because it has a low refractive index. Specific examples _{of R} groups include _-CH2CF3 , _{-CH2CF2CHF2 , -CH2}
CF ₂ CF ₃ , -CH ₂ (CF ₂ CF ₂ ) ₂ H, -CH ₂ CH ₂ (CF ₂
CF ₂ ) ₃ CF ₂ CF ₃ , −CH ₂ CH ₂ (CF ₂ CF ₂ ) ₃ CF (CF ₃ ) ₂ ,
_-C ( _CH3 ) _{2CF2CHF2 , -CH2CF2CHFCF3 , -C}
(CH ₃ ) ₂ CF ₂ CHFCF ₃ , -CH ₂ CH ₂ N (CH ₂ CH ₃ )
SO ₂ (CF ₂ CF ₂ ) ₃ CF ₂ CF ₃ , −CH ₂ CF (CF ₃ ) OCF ₂
CF ₂ CF ₃ ,

Fluorine-containing organic groups such as [Formula], and -CH ₃ , -CH ₂ CH ₃ , -CH ₂ CH
(CH ₃ ) ₂ , −(CH ₂ ) ₁₁ CH ₃ , −CH ₂ CH ₂ N(CH ₃ ) ₂ , −
_{CH2CH2OH ,}

【formula】

【formula】 〔Example〕

Examples 1 to 5 100 g of monomer represented by the formula: CH ₂ = CClCOOCH ₂ CH ₂ C ₈ F ₁₇ , 0.1 g of azobisisobutyronitrile
and 0.001 g of lauryl mercaptan was kept at 60° C. for 24 hours to carry out bulk polymerization. The resulting polymer had a melting point (Tm, differential scanning calorimeter, heating rate: 20°C) of 144°C, a refractive index (n _D ²⁵ , Atsube refractometer) of 1.37, an intrinsic viscosity ([η], solvent: meth) xylene hexafluoride, temperature: 35°C) was 0.83. 10% by weight of polymer 1,1,2-trichloro-
A 1,2,2-trifluoroethane solution was prepared, and fibers with a diameter of 500 μm made of the materials shown in Table 1 were dipped into this solution at a speed of 2 cm/sec to coat the polymer, and then heated at 100°C for 60 minutes. It was dried to obtain an optical fiber.
When the cross sections were observed with a scanning electron microscope, the thickness of the sheath material polymer was approximately 30 μm in each case. The light transmittance immediately after preparation at a wavelength of 650 to 680 nm per 500 nm optical fiber and the light transmittance after heating at 120°C for 1000 hours were measured. The results are shown in Table 1. For reference, the table shows the glass transition temperature (Tg, differential scanning calorimeter, heating rate: 20℃) of the core material (polymer).
and the refractive index (n _D ²⁵ ).

[Table] Example 6 Replace the monomer used in Example 1 with formula: CH ₂ =
A polymer was prepared in the same manner as in Example 1, except that a monomer represented by CClCOOCH ₂ CF ₃ was used.
The Tg of the polymer is 130℃, n _D ²⁵ is 1.426, [η] is 0.69
(However, solvent: methyl ethyl ketone, temperature: 35℃)
It was hot. The obtained polymer was added to a mixed solvent consisting of ethyl cellosolve acetate and acetone in a ratio of 7:3 by weight for 10 minutes.
The formula: CD ₂ =
1 fiber with a diameter of 300 μm made of a monomer polymer (number average molecular weight: 300,000) represented by CFCOOCD ₃
After dipping at a speed of cm/sec, it was dried at 100°C for 60 minutes to obtain an optical fiber. When the light transmittance was measured using the same procedure as in Example 1, the light transmittance after heating was 75%, which was the same as that immediately after preparation. Examples 7-8 As the sheath material, in Example 7, the formula: CH ₂ =
A polymer of monomers represented by CClCOOCH ₂ CF ₂ CF ₃ , in Example 8 the formula: CH ₂ =CClCOOCH ₂ CF ₂
Monomer and formula represented by CHF ₂ : CH ₂ =
A copolymer of monomers represented by CClCOOCH ₃ (copolymerization ratio: 7:3 by weight) was used as the core material in both Examples 7 and 8, and the polymer used in Example 4 was used immediately after preparation. The light transmittance and the light transmittance after heating at 120°C for 1000 hours were measured. Table 2 shows the Tg, n _D ²⁵ and [η] of the sheath material polymer.
Also, the light transmittance immediately after preparation and after heating is shown.

〔Effect of the invention〕

The optical fiber of the present invention has better heat resistance than conventional optical fibers, so it can be installed in the engine compartment of a vehicle. Further, the optical fiber of the present invention has good flexibility and good adhesion between the core material and the sheath material.

Claims (1)

[Claims] 1. In an optical fiber composed of a core and a sheath, the sheath has the formula: (In the formula, R represents an organic group having 1 to 30 carbon atoms.)
An optical fiber characterized by being a polymer essentially consisting of a monomer represented by: