JP2946789B2 - Optical fiber cladding material and coating material comprising fluorine-containing acrylate copolymer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to heat stability, solvent resistance,
The present invention relates to providing an optical fiber clad material and a coating material which are excellent in mechanical properties and weather resistance and which are excellent in properties of a low refractive index fluorine-containing acrylate copolymer.

[0002]

2. Description of the Related Art An optical fiber is generally composed of a combination of two kinds of materials, a core and a clad having a lower refractive index than the core.

For the core, a resin having excellent transparency such as quartz, multi-component glass or polymethyl methacrylate is used.

On the other hand, the clad is required to have a lower refractive index than the core material in order to keep light inside the core, and fluorine-containing resins are widely used.

As the fluorine-containing resin, in the case of a cladding material of an optical fiber having quartz as a core, a fluoroethylene / fluoropropylene copolymer (Applied Optics, 14, 15)
6 (1975)), and in the case of a cladding material for an optical fiber having a polymer mainly composed of polymethyl methacrylate as a core, a vinylidene fluoride / tetrafluoroethylene copolymer (JP-B-63-67164) Such a fluoroolefin resin or hexafluoroacetone / vinylidene fluoride copolymer (JP-A-61-22305) is known.

However, these resins have excellent mechanical properties, thermal stability and solvent resistance, but have a problem that they are crystalline and have poor transparency. In particular, when the film is rapidly cooled after being melted or cast from a solvent, the film is obtained in a transparent state, but has a serious drawback in that crystallization proceeds with an increase in temperature and transparency is impaired. For example,
In the case of a plastic optical fiber with a polymethyl methacrylate core and a clad vinylidene fluoride / tetrafluoroethylene copolymer, the maximum usable temperature is about 70 ° C, which is affected by the change in the shape of the clad material. It is because. As described above, even if the transparency is obtained by a special device at the time of shaping the polymer, the transparency is impaired by stimulus such as heat during use. For this reason, the performance of the optical fiber is significantly affected, and the cladding material for the optical fiber has not been sufficiently satisfactory.

Further, in order to improve the transparency of the optical fiber cladding material and to raise the operating temperature, a fluoroalkyl methacrylate copolymer is used. For example, a (meth) acrylate / methyl methacrylate copolymer having a linear fluoroalkyl group in the cladding material of an optical fiber having a polymer mainly composed of polymethyl methacrylate as a core (Japanese Patent Publication No. 43-8978), Alternatively, to increase the heat distortion temperature, a polymer mainly composed of t- or sec-fluoroalkyl methacrylate (Japanese Patent Publication No. 54-24302), a copolymer of fluoroalkyl methacrylate and bornyl methacrylate for the same purpose. Coupling (JP-A-61-258813) is known. Further, α-fluoro (fluoro) alkyl acrylate (co) polymer (Japanese Patent Application Laid-Open No. 58-361)
No. 1) is proposed as a fluoroalkyl methacrylate copolymer having a lower refractive index and an improved heat distortion temperature.

[0008]

However, a (meth) acrylate / α-fluoroacrylate copolymer is
Although it is generally an amorphous polymer and has the feature of being excellent in transparency, it has thermal stability, heat resistance, mechanical properties,
It has a drawback of poor adhesion or chemical resistance.

In particular, when the number of carbon atoms in the fluoroalkyl group is increased, thermal decomposition and photolysis of the copolymer are liable to proceed, and the copolymer has a disadvantage that the viscosity during melt extrusion and foaming are liable to occur. Further, even when used for a coating film, there is a defect that a surface is easily cracked when exposed to light or heat, and the adhesive strength is reduced.

An object of the present invention is to provide a fluorine-containing acrylate-based copolymer which solves the above-mentioned disadvantages of the prior art and has improved heat stability and weather resistance without impairing heat resistance and mechanical properties. Accordingly, an object of the present invention is to provide an optical fiber clad material having a low refractive index and excellent transparency, or a coating film excellent in weather resistance, heat resistance and solvent resistance.

[0011]

In order to achieve this object, an optical fiber cladding material according to claim 1 has a fluorine-containing acrylate-based unit of 30 to 99.8% by weight and is represented by the following general formula [I]. 7 N-alkylmaleimide units
A copolymer containing 0 to 0.2% by weight and having the following general formula [II] as the fluorine-containing acrylate-based unit:
And / or a fluorine-containing acrylate copolymer containing a (meth) acrylate unit represented by the following general formula [III].

[0012]

Embedded image

(Where R 1 represents an alkyl group selected from the group consisting of methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, tert-butyl, hexyl and cyclohexyl or a fluoroalkyl group therefrom)

[0014]

Embedded image

(Where X 1 is H or F, n is 1 or 2, m is an integer from 4 to 10, and X 2 is H or F)

[0016]

Embedded image

(Where X 3 is H, F or methyl, p
Is 1 or 2, k is an integer from 2 to 10, X4 is H or F, and R2 is an alkyl group selected from methyl, ethyl, and propyl. It is characterized by being composed of a copolymer.

The fluorine-containing acrylate copolymer used in the present invention is characterized mainly by copolymerizing an aliphatic N-substituted maleimide monomer unit. As the N-substituted alkyl group, an alkyl group selected from the group consisting of methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, tert-butyl, hexyl and cyclohexyl, and a fluoroalkyl group therefrom are required.

As the fluoroalkyl group, for example, a fluoroalkyl group such as trifluoromethyl, trifluoroethyl, tetrafluoropropyl and hexafluoropropyl can be used.

On the other hand, an aromatic N-substituted maleimide cannot be used because of its high refractive index and easy coloring of the monomer.

The fluoroalkyl acrylate resin obtained by copolymerizing N-alkylmaleimide not only significantly improves the thermal stability but also has the effect of increasing the thermal softening temperature of the fluoroalkyl acrylate resin.

That is, while the thermal softening temperature of the alkylmaleimide homopolymer used in the present invention is 200 ° C. or higher, fluoroalkyl acrylate is lower than the thermal softening temperature of methyl methacrylate and lacks heat resistance. However, by copolymerizing an alkylmaleimide, heat resistance can be improved as compared with a conventional fluoroalkyl acrylate resin.

In order to improve the thermal stability, it is necessary to copolymerize 0.2% by weight or more of alkylmaleimide.
Preferably, it is at least 1% by weight. As the amount of the alkylmaleimide monomer component increases, the heat stability, light stability, and heat resistance temperature improve. However, if the amount exceeds 70% by weight, the flexibility of the fluoroalkyl acrylate resin is impaired and the resin becomes brittle. It cannot be used for fiber cladding materials or coating materials. The preferred content of the N-alkylmaleimide monomer component in which heat stability and light stability are most balanced with heat resistance and mechanical properties is from 1% by weight to 70% by weight.

As the fluorine-containing acrylate-based unit, a unit represented by the above general formula [II] and / or a unit represented by the above general formula [III] may be used.

In general, as the fluorine content increases, the refractive index of the polymer decreases and the solvent resistance improves. If m in the above formula [II] or k in the above formula [III] exceeds 10, it cannot be used because the transparency of the polymer decreases. Further, when m is less than 4 or k is less than 2, properties such as low refractive index and excellent solvent resistance, which are inherent characteristics of the fluororesin, cannot be remarkably exhibited, so that they cannot be used.

Other third components can be copolymerized as long as the effects of the present invention are not impaired. As other copolymerization components, alkyl methacrylate, alkyl acrylate, α-fluoroalkyl acrylate and pentafluorostyrene, α, β, β-trifluorostyrene and α, β, β-trifluoropentafluorostyrene can be used. Yes, small amounts of multifunctional (meth) acrylate monomers can be used.

Further, an unsaturated silane compound such as γ
A small amount of (meth) acryloxypropyltrimethoxysilane can be copolymerized, and an alkoxysilane compound having a thiol group can be added to the polymer.

When the fluorine-containing acrylate-based copolymer of the present invention is melt-molded, the above-mentioned monomers can be produced in bulk, in solution, or by radical polymerization to produce the copolymer. .

Since the fluorine-containing acrylate copolymer of the present invention is excellent in thermal stability, unreacted monomers and solvents are continuously removed at a temperature of 200 ° C. or more by an extruder equipped with a vent port. You can also.

The fluorine-containing acrylate-based copolymer of the present invention, which can also use a general polymer polymerization method such as suspension polymerization or emulsion polymerization, can be used for a cladding material of an optical fiber having a plastic as a core. It is useful as a cladding material for an optical fiber having a quartz glass core.

It is also useful as a resin for a coating film. In this case, it is possible to adopt a method of forming a coating film by coating the prepolymer and then copolymerizing the coating with heat or ultraviolet irradiation.

[0032]

EXAMPLES The abbreviations and compositions of the monomers used in the following examples are shown below.

[0033]

Embedded image

CH-MID: N-cyclohexylmaleimide ipr-MID: N-isopropylmaleimide MMA: methyl methacrylate Example 1 Monomer 17FA 86.5 parts by weight N-cyclohexylmaleimide 13.5 parts by weight Azobisisobutyro A nitrile 0.01 part by weight n-butyl mercaptan 0.005 part by weight was charged into a glass ampule, and dissolved oxygen was removed.
Sealed.

Then, at 60 ° C. for 16 hours and at 100 ° C. for 8 hours.
Heating was carried out for an hour to complete the polymerization. Break this glass ampule, take out the contents, pulverize in liquid nitrogen,
Vacuum drying was performed at 0 ° C. for 48 hours to obtain a fluorine-containing acrylate copolymer.

The obtained copolymer has a glass transition point of 43.
° C, the refractive index was as low as 1.392, and the viscosity retention at 240 ° C was 86%, which was excellent in heat resistance.

The viscosity retention was measured by heating the polymer at 240 ° C. and measuring the polymer viscosities after 10 minutes and 60 minutes, and expressed as a value of the viscosity after 60 minutes with respect to the viscosity after 10 minutes.

The adhesion and bending characteristics were measured by the following methods, and as shown in Table 1, No. 1 was excellent.

The polymer was molded at 160 ° C. and had a thickness of 500 μm.
m sheet into a polymethyl methacrylate sheet (thickness 5
00 μm), and integrated by pressing at 200 ° C. for 10 minutes to form a sample having a width of 1 cm and a length of 10 cm. Next, this sample was bent at an R of 5 mm and bent at 180 ° for 5 minutes.
The evaluation was repeated up to 0 times to observe and evaluate the state of occurrence of polymer cracks and peeling. The evaluation results were as follows: ○ (good): no cracks and peeling even after 50 cycles, Δ (slightly inferior): cracks or peeling occurred in the second half of bending, × (bad): cracks or peeling in the first half of bending Occurred and expressed with.

An optical fiber was obtained by composite spinning by melt co-extrusion using the obtained polymer as a clad and ordinary polymethyl methacrylate as a core. The outer diameter of the obtained optical fiber was 1000 μm, and the thickness of the clad was 9 μm.

When the obtained optical fiber was evaluated, it was found to be excellent in light transmission performance, heat resistance and bending characteristics as follows.

Light transmission performance 129 dB / km (650 nm) Heat resistance (light retention after 500 hours at 90 ° C.) 1
Bending characteristics (Ratio of light quantity after 2500 bending 180 degrees at R5 mm) 98% The heat resistance of the optical fiber is 90% for the optical fiber 10 m.
After heating in an oven at a temperature of 500 ° C. for 500 hours, the amount of emitted light when a red LED was used as a light source was measured and compared with a blank to determine and evaluate the light amount retention.

Example 2 Monomer 17SFM 89.0 parts by weight N-cyclohexylmaleimide 31.0 parts by weight γ- (meth) acryloxypropyltrimethoxysilane 0.5 parts by weight Azobisisobutyronitrile 0.01 The mixture was mixed with an equivalent volume of a mixture of dry ethyl acetate (30 parts by weight) and hexafluoroxylene (70 parts by weight), charged into a glass ampule to remove dissolved oxygen, and then sealed.

Then, the mixture was heated at 60 ° C. for 24 hours to complete the polymerization. The obtained contents were transferred to a pot for optical fiber coating kept at 60 ° C. A 300 μ diameter quartz fiber was passed through the coating pot, and the polymer mixture in the pot was coated to a thickness of 10 μ. After coating, the mixture was continuously passed through a hot-air stove at 50 ° C. and then a hot-air stove at 100 ° C. to remove the solvent ratio, and wound around a drum.

The light transmission of the obtained fiber is 12 dB / km
And was good.

The bending characteristics of a 320 μm optical fiber obtained by coating and a 300 μm uncoated silica optical fiber are wrapped one by one from the larger diameter on a conical metal. The fracture diameter of the coated optical fiber was 12.5 mm, which is smaller than the fracture diameter of the uncoated optical fiber of 23 mm. I was

Example 3 Using the monomer compositions shown in Nos. 2 to 9 in Table 1, Example 1
The polymerization was carried out in the same manner as described above.

The properties of the obtained copolymer were as shown in Table 1.

As shown in Table 1, the copolymers (Nos. 2 to 5) used in the present invention were low in refractive index and excellent in heat resistance, adhesion and bending resistance.

On the other hand, the copolymer other than the present invention (No. 6)
9) were not satisfactory.

[0051]

[Table 1]

[0052]

According to the present invention, since a fluorine-containing acrylate-based copolymer containing a fluorine-containing acrylate-based unit and an N-alkylmaleimide unit in a specific ratio is used as a copolymer unit, it has a low refractive index. And thermal stability,
An optical fiber clad material and a coating material having excellent solvent resistance, mechanical properties, and weather resistance can be obtained.

That is, the fluorine-containing acrylate copolymer used in the present invention has the following excellent properties.

Excellent in chemical stability by heat and light.

High heat deformation temperature and excellent heat resistance.

Excellent in solvent resistance.

Excellent transparency and low refractive index.

Excellent in flexibility and adhesiveness.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-156115 (JP, A) JP-A-63-249112 (JP, A) JP-A-3-107105 (JP, A) JP-A-3-107 1114111 (JP, A) JP-A-4-204909 (JP, A) Patent 2507355 (JP, B2) JP-B 5-74049 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name) ) G02B 6/00 391 C08F 20/00-22/40 C08F 220/00-222/40

Claims (2)

(57) [Claims] 1. The method according to claim 1, wherein the fluorine-containing acrylate-based unit is 30 to
99.8% by weight, and N represented by the following general formula [I]
A copolymer containing from 70 to 0.2% by weight of an alkylmaleimide unit, and the fluorine-containing acrylate-based unit represented by the following general formula [II] and / or the following general formula [III] An optical fiber clad material comprising a fluorine-containing acrylate copolymer containing a (meth) acrylate unit represented by the following formula: Embedded image (Where R1 is methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, tert-butyl, hexyl,
Represents an alkyl group selected from the group of cyclohexyl or a fluoroalkyl group therefrom) (Where X1 is H or F, n is 1 or 2, m is 4
X2 represents H or F). (Where X3 is H, F or methyl, p is 1 or 2, k is an integer from 2 to 10, X4 is H or F, R
2 represents an alkyl group selected from methyl, ethyl and propyl) 2. A coating material comprising the fluorine-containing acrylate-based copolymer according to claim 1.