JPS62209401A - Plastic optical fiber - Google Patents

Abstract

PURPOSE:To assure the stability of long-term performances (such as transmittance and resilience) and to eliminate thermal deformation by using a copolymer of a monomer having the glass transition temp. of the homopolymer below a room temp. and multifunctional monomer having plural pieces of unsatd. bond components in the molecule as a core material of a plastic optical fiber. CONSTITUTION:The material having the glass transition temp. below room temp. is used for the core to assure the resilience of the fiber. The multi functional monomer having plural pieces of unsatd. bonds in the molecule is crosslinked by copolymn. to assure heat resistance at the same instant. The substantial light transmittance is assured as well. A clad material is not particu larly required to be limited and is preferably the material having the refractive index lower by 2-3% than the refractive index of the core material. Said material is more specifically exemplified by the material such as fluoroplastic or fluorine elastomer.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a plastic optical fiber that is flexible and has excellent heat resistance.

[Conventional technology]

Traditionally, plastic optical fibers have had higher optical transmission loss than optical fibers using quartz as a core, but they have superior flexibility even with large diameters and high numerical apertures, and are easy to process. There are great expectations for use in short-distance communications because of the advantages of being simple, being able to use visible light as a light source, being easy to store and handle, and being inexpensive.

Currently, the core material for plastic optical fibers is
Polymethyl methacrylate, polystyrene,
Many materials such as polycarbonate, ASi resin, and hard vinyl chloride resin have been studied and put into practical use.

[Problem that the invention seeks to solve]

However, all of the above polymers have a glass transition temperature of 100°C or higher, and a flexural modulus of elasticity, which is a measure of flexibility, of 20,000 to 40,000 k (1/c
Although quartz optical fibers have superior flexibility compared to quartz optical fibers, they are not necessarily satisfactory in applications that require greater flexibility.

This flexibility is particularly problematic in the case of optical fibers with large diameter and large aperture ratio shapes. In other words, in recent years, plastic optical fibers have become increasingly important for applications such as lighting light guides for medical equipment, and internal wiring for electronic equipment such as OA equipment and digital audio equipment. In such applications, a plastic optical 7-eyeper with a large diameter is required, and it is also extremely important that it be easy to wire within a limited space. For such applications, for example, the core material is polymethyl methacrylate with a glass transition temperature of 100-120°C, and the fiber diameter is 1.5°C. Plastic Hikari 7 Eyeper, which is an OMM, is difficult to apply because it easily breaks at a bending radius of 10 m or less.

Particularly when used as equipment wiring for light guides, if the bending radius is large, the wiring space becomes large, making it difficult to downsize the equipment.

As a solution to the above problem, a plastic optical fiber whose core material has a glass transition temperature below room temperature is considered, and as a method for lowering the glass transition temperature below room temperature,
Methods such as adding plasticizers are used. However, optical transmission loss increases, making it difficult to ensure stability in long-term performance (transmittance, flexibility, etc.).

Another method is to use a resin with a glass transition temperature below room temperature as the core material, but because the heat deformation resistance of plastic is poor, it is difficult to meet the requirement of no heat deformation at a temperature of at least 80°C. [Means for solving the problem] The present invention has been made in view of the above problem, and includes a monomer whose homopolymer has a glass transition temperature below room temperature in the core material of the plastic optical fiber. The present invention provides a plastic Hikari 7 Eyepa using a copolymer with a polyfunctional monomer having a plurality of unsaturated bonds in the molecule.

In other words, the flexibility of the fiber is ensured by using a material with a glass transition temperature below room temperature for the core, and crosslinking is achieved by copolymerizing a polyfunctional monomer that has multiple unsaturated bonds within the molecule. However, it also ensures heat resistance at the same time. At the same time, sufficient light transmittance is ensured.

In the present invention, examples of materials whose homopolymer glass transition temperature is room temperature or lower include polymethyl acrylate, polyethyl acrylate, polyn-butyl acrylate, poly(2-ethylhexyl) acrylate, polyoctyl acrylate, Polydodecyl acrylate, polyn-butyl acrylate, poly(2-ethylhexyl methacrylate), polyoctyl methacrylate, poly(4-butyl)styrene, poly(4-hexyl)styrene, poly(4-nonyl)styrene, etc. The monomers mentioned above and used in the copolymer in the present invention are the monomers of the above-mentioned polymers.

In addition, examples of polyfunctional monomers having unsaturated bonds in the molecule include ethylene glycol diacrylate, l, 4
-Butadiol diacrylate, 1,6-hexanediol diacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, l,4-butadiol diacrylate, 1,6-hexadiol dimethacrylate, polyethylene Examples include glycol diacrylate, trimethylolpropane trimethacrylate, and pentaerythol tetramec acrylate.

In the present invention, the monopolymer having a glass transition temperature of not more than room temperature may be used not only one type but also a combination of two or more.

Of course, the copolymerization of the above homopolymer with a monomer whose glass transition temperature is below room temperature and a polyfunctional monomer having multiple unsaturated bonds in the molecule differs depending on the type of hexamer used. Unless the polymerization rate is significantly different, the polymerization will normally proceed by simply leaving it under normal conditions, but it is preferable to accelerate it by heating or irradiating with radiation such as electron beams or ultraviolet rays. .

In particular, when irradiating with ionizing radiation, the mixing ratio of the heptamer and the polyfunctional monomer in the core material does not need to be particularly limited, and can be changed as appropriate depending on the irradiation dose or the required physical properties of the core material. In addition, the core material polymer can ignore viscosity effects such as general ductal heating, resulting in a core material polymer with an extremely high polymerization rate, and since there is no scattering of L light in the remaining monomer, optical transmission loss is further reduced. Can be reduced.

The atmosphere may be in air, but it is preferable to carry out under an inert gas atmosphere in order to suppress polymerization due to the influence of oxygen or eliminate coloring due to oxidation. Furthermore, when copolymerizing monomers with significantly different polymerization rates, It is possible to obtain a copolymer having a crosslinked structure by using a polymerization initiator that selectively promotes polymerization by using monomers, or by appropriately selecting a polymerization mechanism such as radical polymerization or ionic polymerization.

In the present invention, the cladding material is not particularly limited, but it is desirable to use a material with a refractive index 2 to 3% lower than that of the core material. can be mentioned.

〔Example〕

Example 1 Glass transition temperature & (Tg) of homopolymer
Norbutyl acrylate (homopolymer Tg knee 20-20°C) is used as a monomer whose temperature is below room temperature, and ethylene glycol dimecacrylate is used as a polyfunctional monomer having multiple unsaturated bonds in the molecule at 99/l.
benzoyl peroxide (BPO), which is a polymerization initiator, to 100 parts by weight of the resulting monomer mixture (weight ratio).
) was added and mixed well until BPO was dissolved.

Next, the above monomer and polymer initiator mixture tc was placed in a polyvinylidene 7trate tube (length 1.5 m) with an inner diameter of 1.8 m and an outer diameter of 2.0 H, and both ends were closed.
When we cut both ends of a 0°C tube that was polymerized for 24 hours while immersed in a water bath at 0°C, and measured the optical transmission loss of the resulting plastic optical fiber, we found that , 400-800 dB/KM
Met.

Moreover, this plastic optical fiber has a bending radius of 5 to 1
There is no breakage at all even at 0MM, and it is extremely flexible.
No thermal deformation was observed even after leaving it for 12 hours in a °C atmosphere.

Example 2 Norbutyl acrylate (homopolymer Tg knee 7)
Azobisinbutyronitrile (AIBN ) was added and mixed well until AIBN was dissolved.

The above monomer and polymerization initiator mixture was mixed with an inner diameter of 1. Off polyvinylidene tube with outer diameter 1.2 sheath (length 2.
0 m), both ends were closed, and the polymer was polymerized for 30 hours while immersed in a water bath at 55°C.

Both ends of the obtained tube were cut to make a plastic optical fiber, and the optical transmission loss was measured to be 500 to 80 (
350-650 dB/K for visible light of 11 wavelengths
The optical transmission loss was n.

This plastic optical fiber showed no breakage even at a bending radius of 2 to 5H, was extremely flexible, and was suitable for local wiring.

In addition, no thermal deformation was observed even after being left at 80° C. for 12 hours.

Example 3 Normal octyl meccrylate (Tg of homopolymer
-70℃) and 1,6-hexanethiol dimecrylate (weight ratio) of 9674 (weight ratio) monomer mixture (AIBN)
0.3 parts by weight was added and mixed well until the AIBN was dissolved.

The above monomer and polymerization initiator mixture was heated to an inner diameter of 1.5 ytty.
7-vinylidene tube with an outer diameter of 1.75 fl (1,
5777 length), both ends were closed, and the polymer was polymerized for 24 hours while immersed in a water bath at 55°C.

When both ends of the tube were cut and the optical transmission loss of the obtained plastic fiber was measured, it was 350 to 650 dB//& for visible light with a wavelength of 500 to 800 mm.

No breakage was observed in this plastic fiber even at a bending radius of 2 to 5 mm, and local wiring was extremely easy.

Furthermore, there was no thermal deformation at all even after leaving it at 80°C for 12 hours.

Example raw FEP (tetrafluoroethylene-hexafluoropropylene copolymer) tube (inner diameter 1.0 gg).

Outer diameter 1. 1 NM) and methyl methacrylate in
．． A 99/1 mixture (weight ratio) of 4-butanediol and dimethacrylate was filled, and both ends were closed. An electron beam with an accelerating voltage of 1.0 M e V was applied to this tube at 24 Mrad.
The tube was irradiated to polymerize the seven polymers in the tube.

The transmission port of the plastic fiber thus obtained or 4
100-150 for visible light with a wavelength of 00-800H
It was dB/K111.

Example 5 A FEP tube (inner diameter 1.0 mm, outer diameter 1.1 mm) was filled with a 99.510.5 mixture (weight ratio) of norbutyl methacrylate and trimethylolpropane trimecacrylate, and both ends were closed. . This tube has an accelerating voltage of 1
．． The monomer inside the tube was cured by irradiation with a 5 M e V electron beam at 12 Mrad.

The transmission port or 1 of the plastic fiber thus obtained
It was 60-200dB/& (400-800M).

Comparative Example Methyl methacrylate (Tg of homopolymer approximately 100~
B as a polymerization initiator to 100 parts by weight of monomer at 120°C)
0.5 parts by weight of PO was added and mixed well until BPO was dissolved. This monomer and polymerization initiator mixture was
Vinylidene fluoride tube with an outer diameter of 2.0 mm (length l,
5 m), both ends of which were closed, and immersed in a 50°C water tank for 24 hours to polymerize.

Both ends of the tube were cut, and the optical transmission loss of the resulting plastic 7-iper was 300 to 800 dB/M for visible light with a wavelength of 500 to 800 fl.

This plastic fiber has a bending radius of 10 to 151 ff.
It broke.

Procedures Amendment Document November 13, 1985 1. Case description 1986 Patent Application No. 53417 2. Name of the invention Plastic optical fiber 1. Person making the amendment. Relationship with the case. Patent applicant. Location: Kitahama, Higashi-ku, Osaka. 5-15 Name (
213) Kawakami, President, Sumitomo Electric Industries, Ltd.
Tetsubu 4, Agent address: Sumitomo Electric Industries, Ltd., 1-1-3 Shimaya, Konohana-ku, Osaka (FF1, Osaka 401-1031) Voluntary amendment 6: Detailed explanation of the invention in the specification subject to amendment 7. Contents of the amendment (1) First, delete "High numerical aperture" on page 2, line 4 of the old specification.

■Line 3 of the bottom 3 pages of the statement Delete "shape with large aperture ratio".

(3) Page 6, line 12 of the specification Delete "te".

Claims (2)

[Claims] (1) In a plastic optical fiber consisting of a core and a cladding provided on the core, the core is composed of a monomer whose glass transition temperature is below room temperature and a polyfunctional polymer having a plurality of unsaturated bonds in the molecule. 1. A plastic optical fiber characterized in that the plastic optical fiber is made of a copolymer with a transparent monomer and has a higher refractive index than the cladding and is transparent. (2) The weight ratio of the monomer whose glass transition temperature is below room temperature and the polyfunctional monomer is 99.5/0.5 or more
The plastic optical fiber according to claim (1), which is 95/5.