JPS63243903A - Plastic optical fiber - Google Patents

Abstract

PURPOSE:To obtain at a low cost the titled fiber having the excellent heat resistance and durability by using a polymer having a prescribed composition for a core component, and a composition having a prescribed composition for a shell component respectively. CONSTITUTION:The core component is composed of >=2wt.% a ring structural unit shown by formula I, and <=98wt.% a monomer unit contg. methyl methacrylate as a main component. The shell component is composed of the coatings obtd. by curing a photocurable resin composition contg. a fluoroalkyl acrylate monomer shown by formula II, a cross-linkable monomer having >=2 polymerizable functional groups in 1mol., and a photopolymerization initiator with a light. And, in formula I, X is oxygen atom. or a group shown by formula III wherein R is hydrogen atom., 1-20C an aliphatic, an aromatic or an alicyclic hydrocarbon group. And, in formula II, Y is hydrogen or fluorine atom., Rf is fluoroalkyl group.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a plastic optical fiber that can be used as an optical fiber core, an optical fiber cord, an optical fiber cable, or the like.

[Conventional technology]

Composite fibers have a concentric core-sheath structure in which the core is made of highly transparent synthetic polymers such as polystyrene or polymethyl methacrylate, and the sheath material is a synthetic polymer with a lower refractive index than the core material. Optical fibers are well known in which the light incident on one end of the fiber is reflected in the length direction of the fiber and transmitted through total internal reflection.

Conventional optical fibers are obtained by melting a core material and a sheath material and performing composite spinning.

[Problem that the invention seeks to solve]

Usually, polymethyl methacrylate, polystyrene, etc. are used for plastic optical fiber core materials.
These polymers have the drawback of low softening temperature (110° C. or lower) and low decomposition temperature (260° C. or lower). In addition, copolymers of vinylidene fluoride and tetrafluoroethylene and polymers containing fluorinated alkyl methacrylate as main components are mainly used for the sheath material. It has good adhesion and excellent workability, but
Essentially a crystalline polymer, it easily crystallizes when heated or cooled, resulting in the growth of spherulites.As a result, light passing through the heartwood is scattered by the crystallized state of the sheath, resulting in poor light transmission performance. It has the disadvantage that it decreases. On the other hand, polymers whose main component is fluorinated alkyl methacrylate are essentially non-quality polymers, and when used as a sheath material for optically transmitting fibers, they maintain good transparency, but they do not adhere well to the core material. It also has disadvantages such as poor processability and low softening temperature (IOO'C or lower). For this reason, both of the above two types of materials are difficult to use at high temperatures.

In addition, in the conventional spinning method for plastic optical fibers, the core and sheath components are generally melted and extruded simultaneously from a double nozzle, which may result in the sheath becoming thicker than the core or the adhesion between the core and sheath. If it is insufficient, the attenuation of light becomes significant, and the optical fiber tends to have poor optical transmission efficiency. Therefore, in conventional plastic optical fibers, the properties of the core and sheath components, such as elongation, softening temperature, and melting temperature, as well as the selection and combination of these components, are complicated.

[Means for solving problems]

The present inventors have made extensive studies in view of the current situation, and have thus arrived at the present invention.

The present invention is based on the following formula (wherein X represents an oxygen atom or a group, N-R, where R
means a hydrogen atom, an aliphatic, aromatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms) 2.
The core component is a polymer consisting of at least 98% by weight and 98% or less of monomer units mainly composed of methyl methacrylate, and has the general formula (in the formula, Y is a hydrogen atom or a fluorine atom, and Rf represents a fluoroalkyl group). A coating cured by light from a photocurable resin composition containing a fluoroalkyl acrylate monomer represented by, a crosslinkable monomer having two or more polymerizable functional groups in one molecule, and a photopolymerization initiator. It is an optical fiber consisting of a core and sheath, characterized in that it consists of a sheath component.

The core component of the optical fiber of the present invention is a polymer consisting of 2% by weight or more of ring structural units represented by formula I and 98% by weight or less of monomer units whose main component is methyl methacrylate.

Among the above components, the ring structural unit is a component necessary to maintain heat resistance and optical properties as a light transmitting fiber,
In order to obtain particularly excellent heat resistance, the content is preferably 10% by weight or more. If the amount of ring structural units is less than 2% by weight, the effect of improving the heat resistance of the obtained polymer will be insufficient.

On the other hand, the monomer component containing methyl methacrylate as a main component is a component necessary for maintaining basic optical properties, weather resistance, and mechanical properties as a light transmitting fiber.

When X in the ring structure (I) is a group>N R, the ring structure needs to be a saturated or unsaturated aliphatic, alicyclic or aromatic hydrocarbon group. From the point of view of improving heat resistance, the substituent H
The shorter the chain length, the better.

Examples of the substituent R include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tertiary butyl group, a phenyl group, a substituted phenyl group, and a methyl group is particularly preferred.

In addition to the methyl methacrylate component, the monomer component containing methyl methacrylate as a main component preferably includes other components of up to 20% by weight, such as methyl acrylate, ethyl methacrylate, butyl methacrylate, and cyclohexyl methacrylate. , benzyl methacrylate, methacrylic acid, acrylic acid, styrene, and α-methylstyrene. In addition to these copolymerized components,
It may contain the following components. For example, polyfunctional reactive monomers such as divinylbenzene, triallyl cyanurate, triallyl isocyanurate, ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, trimethylolpropane trimethacrylate.

In formula (2), when X is an oxygen atom, the ring structure becomes methacrylic anhydride. In that case, a reaction precursor that produces a methacrylic anhydride component, such as a polymer consisting of methacrylic acid, tertiary butyl methacrylate, a copolymer with methyl methacrylate containing these reaction precursors, or the other components mentioned above. The desired methacrylic anhydride polymer can be obtained by heating a copolymer containing the above to cause a condensation reaction.

The heat treatment temperature when producing methacrylic anhydride is 100
℃ or higher, 160 to 450℃, especially 150 to 600℃
A temperature range of 0.degree. C. is preferred.

Further, in order to prevent the formation of abnormal reactants, it is preferable to perform heat treatment in an autoclave under an inert gas atmosphere such as nitrogen or argon.

In formula (2), when X is a group N--H, the ring structure becomes methacrylimide. In this case, the desired methacrylimide polymer can be obtained by subjecting polymethyl methacrylate or the aforementioned copolymer containing methyl methacrylate monomer as a main component to a thermal condensation reaction with an imidizing agent. As the imidizing agent, for example, anhydrous ammonia, aqueous ammonia solution, -class aliphatic amine, aromatic amine, urea that generates ammonia when heated, 1,3-disubstituted urea that generates primary amine when heated, etc. are used.

The heat treatment temperature when producing methacrylimide is 100°C
or more, 130 to 450°C, especially 150 to 300°C
A temperature range of is preferred. Further, in order to prevent abnormal reactions from occurring, it is preferable to carry out the heat treatment in an autoclave under an inert gas atmosphere such as nitrogen or argon.

Normal radical polymerization methods, ionic polymerization methods, etc. are used to produce polymethyl methacrylate or a polymer mainly composed of polymethyl methacrylate, which is the raw material for obtaining the above-mentioned methacrylimide component. From the viewpoint of properties, radical polymerization is preferred. Examples of polymerization catalysts include azobisisobutyronitrile, 2,2'-azobis-(
azobis-based catalysts such as 2,4-dimethylvaleronitrile), diacyl peroxide-based catalysts such as lauroyl peroxide, pensoyl peroxide, bis-(3,5,5-)limethylhexanoyl) peroxide, and percarbonate-based catalysts. Catalysts etc. are used.

When producing a core component polymer, a thermal deterioration inhibitor such as an antioxidant may be added to prevent thermal deterioration of the polymer during heating reaction. Examples of the antioxidant include phosphite-based antioxidants, hindered phenol-based antioxidants, sulfur-based antioxidants, and amine-based antioxidants. Examples of phosphite antioxidants include phosphite esters such as tricresyl phosphite, cresyl phenyl phosphite, tributyl phosphite, and tryptoxyethyl phosphite. Examples of hindered phenol antioxidants include hydroquinone, cresol, and phenol. Examples of sulfur-based antioxidants such as derivatives include alkyl mercaptans and dialkyl disulfite derivatives; examples of amine-based antioxidants include naphthylamine,
Examples include phenylenediamine and hydroquinoline derivatives.

In the present invention, examples of the fluoroalkyl acrylate monomer of formula (2) used as the sheath component include the following compounds. 2,2゜6.6-titrafluoroglobyl acrylate, trifluoroethyl acrylate, 2,2,3,3.3=pentafluoropropyl acrylate, 1-trifluoromethyl-21212-
Trifluoroethyl acrylate, 1-trifluoromethyl-1,2,2,2-tetrafluoroethyl acrylate, 2.2,3,4,4.4-hexafluorobutyl acrylate, 1-methyl-2,2,3 ,4,4,4-
Hexafluorobutyl acrylate, 1,1,2.2-
tetrahydroperfluorododecyl acrylate,
1,1゜2.2-nato2hydroperfluorodecyl acrylate, 1,1-dihydroperfluorobutyl acrylate, 1,1-dimethyl-2,2,3,3,-tetrafluoroethyl acrylate, 1,1- dimethyl-
2,2,3,6,4,4,5,5-octafluoropentyl acrylate, 1,1-dimethyl-2,2,3,4
゜4.4-Hexafluorobutyl acrylate, methyl-α-fluoroacrylate, 2.2.3.3.3-pentafluoropropyl-α-fluoroacrylate, 2
, 2.5,4,4,4-hexafluorobutyl-α-fluoroacrylate, 2,2.2-trifluoroethyl-α-fluoroacrylate, and the like.

Adjustment monomers may be added to the fluoroalkyl acrylate monomer (lI) as necessary in order to obtain the required numerical aperture for each application determined by the refractive index of the core component and the sheath component, or to improve the adhesion with the core component. It can be included.

Adjusting monomers include acrylic acid, methacrylic acid, acrylic esters, methacrylic esters such as methyl acrylate, ethyl acrylate, n-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate and the like are used. The content of the adjusting monomer is not limited as long as it does not impair the properties of the sheath component, but it is usually within a range of 30% by weight or less based on the fluoroalkyl acrylate.

Examples of the polyfunctional crosslinkable monomer having two or more polymerizable functional groups in one molecule used in the present invention include, for example, the following compounds.

1.3-butanediol diacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, diethylene glycol diacrylate, neopentyl glycol diacrylate, polyethylene glycol diacrylate, tripropylene glycol diacrylate, hydroxy Pivalic acid ester neopentyl glycol diacrylate, hydroxypivalic acid ester neopentyl glycol derivative diacrylate, neopentyl glycol-modified trimethylolpropane diacrylate, hexafunctional monomers such as trimethylolpropane triacrylate, pentaerythritol triacrylate, pentafunctional Monomers such as dipentaerythritol monohydroxypentaacrylate, hexafunctional monomers such as dipentaerythritol hexaacrylate, etc.

The content of crosslinkable monomers is preferably 80% or less of the total polymerizable monomers.

The photopolymerization initiators used in the present invention include various compounds that are generally used as initiators and sensitizers for UV-curable paints, such as benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, and benzoin. Butyl ether, 2-methylbenzoin, benzophenone, Michler's ketone, benzyl, benzyl dimethyl ketal, benzyl diethyl ketal, anthraquinone, methyl anthraquinone, diacetyl, acetophenone, diphenyl disulfide, anthracene, etc., and these in combination with small amounts of sensitizing aids such as amines. Examples include things that have been done.

The amount of photopolymerization initiator used is preferably in the range of 0.1 to 10 parts by weight per 100 parts by weight of the fluoroalkyl acrylate monomer. If the amount of photopolymerization initiator used is less than 0.1 part by weight, it will be difficult to initiate sufficient polymerization, and if it is more than 10 parts by weight, it will be difficult to dissolve in the fluoroalkyl acrylate monomer, and if the amount is increased, No particular effect was observed.

In order to adjust the viscosity, the sheath component resin composition of the present invention contains 5 to 50% by weight of an oligomer or polymer having good compatibility with the monomer composition, such as a homopolymer or copolymer of a compound of the formula
It is preferable that it contains.

Additionally, additives may be added to the sheath component resin composition within acceptable ranges such as curing conditions and compatibility. For example, by adding an oligomer component containing a polymerizable unsaturated group, the viscosity of the resin composition can be adjusted and the curing speed can be improved. Furthermore, an improving agent or the like may be added to improve the adhesion with the optical fiber core component.

When manufacturing the optical fiber of the present invention.

First, a core component polymer is spun by a conventional method to produce a core component fiber. The diameter of this core component fiber is 10 to 2000 μm
is preferred. Next, the core fiber is coated with a sheath component resin composition and then cured by light irradiation to obtain the desired optical fiber. The thickness of the sheath portion is preferably 6 to 100 μm.

〔Effect of the invention〕

The optical fiber of the present invention is significantly superior in heat resistance and durability as compared to conventional plastic optical fibers having core components of polymethyl methacrylate or polystyrene. Further, the optical fiber of the present invention is relatively inexpensive, easy to handle, and has an extremely well-balanced variety of properties. Therefore, the optical fiber of the present invention can be used for wiring in the engine compartment of a car, and therefore has extremely high industrial significance and value as it can respond to the advancement of car electronics. Furthermore, since the photocurable resin composition can be cured by light irradiation to form a sheath, it is possible to solve the problem of combining complicated conditions as in conventional composite spinning.

In the following examples, the optical transmission performance of the fibers was determined according to Japanese Patent Application Laid-open No. 58-
Measurement and evaluation were carried out using the apparatus shown in FIG. 4 of Publication No. 7602. The measurement conditions are as follows.

Interference filter (main wavelength): 650μm (total length of fiber): 5ml (cutting length of fiber): 4m D (diameter of bobbin): 190g Example 1 Tertiary dodecyl per 100 parts by weight of methyl methacrylate After adding and dissolving 0.75 parts by weight of mercaptan and 0.4 parts by weight of lauroyl peroxide, seven thermocouples were placed in a cell formed by two tempered glass plates facing each other at a distance of three dragons through a polyvinyl chloride gasket. Then, the monomer solution described above was poured into this cell, and the cell was immersed in warm water at 80° C. for polymerization and curing. 60 minutes after the internal temperature reached a peak due to exothermic polymerization, it was taken out of the hot water and heat treated in an air heating oven at 120°C for 2 hours.

After cooling, the cell was removed, and the resulting resin plate with a thickness of about 6 mm was crushed in a clean box. M of the obtained polymer
The I value (230°C, load 3.8 kg) was 13.0, the refractive index np was 1.4920, the specific gravity was 1°190, and the heat distortion temperature was 105°C.

100 parts by weight of this polymer and an aqueous methylamine solution (40 parts by weight)
%) in a 61-volume autoclave and reacted for 6 hours in an oil bath at 230°C with repeated nitrogen substitution to obtain a transparent resinous N-methyl methacrylimide-methyl methacrylate copolymer. Ta. The infrared absorption spectrum showed absorption peculiar to methacrylimide, and the imidization rate was 40%. The MI value of the obtained polymer (23
0℃, load 6.8y) is 5.7, refractive index is 1.530,
The specific gravity was 1.20 and the heat distortion temperature was 147°C.

This core component polymer was spun using a vent spinning machine at a temperature of 240.
The fiber was taken at a spinning speed of 6 m/min at 1° C. to obtain a fiber containing only the core component. On the surface of this core component fiber, 15 parts by weight of a polymer of 2,2,2-trifluoroethyl methacrylate, 2
12+2 h') 50 parts by weight of fluoroethyl acrylate, 50 parts by weight of 1,1,2.2-tetrahydroperfluorodecyl acrylate, 10 parts by weight of 1,4-butanediol diacrylate, and benzyl dimethyl ketal (Ciba) as a photopolymerization initiator. - A photocurable resin composition consisting of Irgacure 651) 4 snowscape part manufactured by Geigi Co., Ltd. was applied. Next, this was photopolymerized using an ultraviolet exposure device equipped with a high-pressure mercury lamp with irradiation energy of 80 W/- to form a sheath component, thereby obtaining a core-sheath optical fiber. The optical transmission loss of this optical fiber is 5
It was 435 dB/km at 90 nm and 525 dB/km at 650 nm. Further, even when this optical fiber was wound around a cylinder having a diameter of 511E, no cracks were generated in the cladding component, and there was no separation between the core and sheath.

Even after this optical fiber was kept in a 165°C thermostatic oven for 1000 hours, there was almost no change in thermal shrinkage, and the optical transmission loss was 535 dB/km at 650 nm.
And it didn't change much.

Examples 2 to 4 Optical fibers consisting of a core and sheath were obtained in the same manner as in Example 1 except that the photopolymerizable resin composition serving as the sheath component had the composition shown in the table below. The optical transmission loss of this optical fiber and 1
The table also shows the optical transmission loss after being kept in a constant temperature bath at 35°C for 1000 hours.

Example 5 10 parts of methacrylic acid, 0.75 parts of tertiary dodecyl mercaptan and 0.4 parts of lauroyl peroxide were added and dissolved in 90 parts of methyl methacrylate, and a methyl methacrylate-methacrylic acid copolymer was prepared in the same manner as in Example 1. was manufactured.

100 parts by weight of this copolymer and an aqueous methylamine solution (4 parts by weight)
N-methyl methacrylimide-methyl methacrylate copolymer was obtained in the same manner as in the imidization method in Example 1 using 25 parts by weight of 0%). ° MI of the obtained polymer
Value (230℃, load 3.8 ky+) is 8.2, refractive index is 1.528, specific gravity is 1.20, heat distortion temperature is 138
It was ℃. Further, the imidization rate, which indicates the ratio of the ring structural units of formula I, was 30%.

A fiber containing only the core component was obtained in the same manner as in Example 1. 2.2.2-) 100 parts by weight of IJ fluoroethyl acrylate, 10 parts by weight of trimethylolpropane triacrylate, and 2,2,2-trifluoroethyl methacrylate/methyl methacrylate/methacrylic acid = 7K 1 on the surface of this core component fiber. - After applying a photocurable resin composition to which 5 parts by weight of 'roxycyclohexyl phenyl ketone has been added, photopolymerization is carried out using an ultraviolet exposure device equipped with a high-pressure mercury lamp with an irradiation energy of 80 W/crrI. - An optical fiber with a sheath structure was obtained.

The optical transmission loss of this optical fiber is 450 dB/km at 570 nm and 5 at 650 nm.
30dB/km, and 100dB/km in a 160°C thermostatic oven.
550 dB at 650 nm after holding for 0 hours
/km, and the heat resistance was also good.

Claims (1)

[Claims] The following formula▲There are mathematical formulas, chemical formulas, tables, etc.▼(I) (In the formula, X is an oxygen atom or group▲There are mathematical formulas, chemical formulas, tables, etc.▼, where R is a hydrogen atom 2% by weight or more of ring structural units (meaning aliphatic, aromatic or alicyclic hydrocarbon groups having 1 to 20 carbon atoms) and 98% or less of monomer units mainly composed of methyl methacrylate. The core component is a polymer consisting of a fluoroalkyl acrylate monomer represented by the general formula ▲ There are mathematical formulas, chemical formulas, tables, etc. The sheath component is a coating cured by light from a photocurable resin composition containing a polymer, a crosslinkable monomer having two or more polymerizable functional groups in one molecule, and a photopolymerization initiator. An optical fiber consisting of a core and one sheath.