JPS6340105A - Optical transmission fiber - Google Patents

Abstract

PURPOSE:To obtain an optical transmission fiber having excellent heat resistance by forming a core material of a copolymer essentially consisting of methacrylate and N-allyl maleimides and forming a clad material of a polymer which is lower in refractive index by >=3% than the core material and exhibits noncrystallinity. CONSTITUTION:This optical transmission fiber is made by forming the core material of the copolymer essentially consisting of the methacrylate and N-allyl maleimides and forming the clad material of the polymer which is lower in the refractive index by >=3% than the core material and exhibits the noncrystallinity. The copolymer which consists essentially of the methacrylate and N-allyl maleimides and is to be used includes an ethyl methacrylate, propyl methacrylate, etc., as the methacrylate and includes N-phenyl maleimide, N-2- methyl-phenyl maleimide, etc., as the N-allyl maleimide.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical transmission fiber having a core and clad structure, and more particularly to an optical transmission fiber having excellent heat resistance for information transmission.

[Conventional technology]

Conventionally, optical transmission fibers were made of glass fiber.
It has been widely used for information transmission, industrial purposes, medical purposes, etc.

However, glass optical transmission fibers have the characteristic of low optical transmission loss, but are expensive and have poor flexibility.
Furthermore, since there are drawbacks such as difficulty in connecting glass fibers, the development of optical transmission fibers using synthetic polymers has been progressing recently.

When synthetic polymers are used, a polymer with a high refractive index and good light transmittance is used as the core, and a polymer with a lower refractive index and good transparency is used as the cladding. Materials having a core and clad structure are common. In this case, the core material is required to have good light transmittance and do not decrease in light transmittance even after long-term use, and preferred materials include polymethyl methacrylate, which is an amorphous polymer. Polystyrene is often used for F11. For example, if a polymer containing polymethyl methacrylate as the main component is used as the core material, a fluorine-containing polymer may be used as the cladding material, or a core material using polystyrene and a cladding material containing polymethyl methacrylate as the main component. Products using polymers have been developed.

[Problems to be solved by the invention]

However, conventional optical transmission fibers using synthetic polymers have drawbacks such as low heat resistance and poor light transmittance in the infrared region.

Means for Solving Problem C] The present inventors have conducted intensive studies to improve the heat resistance of the optical transmission fiber made of the above-mentioned synthetic polymer, and have completed the present invention.

That is, the present invention provides an optical transmission fiber consisting of a core material and a crund material, in which the core material is made of a copolymer containing methacrylic acid ester and N-allylmaleimides as main components, and the cladding material has a refractive index of 3% higher than that of the core material. This optical transmission fiber is characterized by being made of a polymer that exhibits low crystallinity and amorphous properties.

The copolymers mainly composed of methacrylic ester and N-allylmaleimide used as the core material in the present invention include ethyl methacrylate, propyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, and methacrylic acid. Benzyl, etc., and N-allylmaleimides such as N-phenylmaleimide, N-2-methyl-phenylmaleimide, N-allylmaleimide, and N-allylmaleimide.
-Chlorphenylmaleimide, N-2-methoxyphenylmaleimide, bismaleimide S2, etc. In addition to these, monomers that can be copolymerized with both components, for example,
It is also possible to use an ethylene pear-shaped polymer within a range where the core material is amorphous and maintains transparency.

The ratio of methacrylic esters and N-allylmaleimides used is 65 to 99% by weight of methacrylic esters.
, preferably 85 to 95% by weight, N-allylmaleimides in a range of 1 to 35% by weight, preferably 5 to 1% by weight, and those outside the above range have poor transparency and heat resistance. Unfavorable in some respects.

The above-mentioned copolymers mainly composed of methacrylic acid esters and N-allylmaleimides can be easily produced by commonly known polymerization methods, and because they contain N-allylmaleimides in the molecule, they have unprecedented heat resistance. It is something that has a nature.

As the polymer that has a refractive index lower than the core material by 3% or more and is amorphous, it is preferable to use a polymer that has heat resistance equal to or higher than that of the core component and has good adhesion to the core material. A material in which the refractive index of the core material is lowered by 3% or more by using more methyl methacrylate than the copolymer component used as a copolymer component, or a fluorine-containing polymer containing 30-t% or more of fluorine atoms. methacrylic acid perfluoro-butyl ester,
Copolymers containing one or more of vinylidene fluoride and tetrafluoroethylene are also preferred examples.

The cladding material must have a lower optical refractive index than the core component, and the difference in refractive index between the core material and cladding material is 3% based on the numerical aperture, the critical angle at which light rays are totally reflected in the optical fiber, etc. or more is required.

The thickness of the cladding material relative to the core material should theoretically be at least the wavelength of light, but is usually 5 to 20 microns.

Optical transmission fibers having a core and clad structure can be manufactured by the following various methods.

(1) A method of imparting a core and cladding structure by blending and discharging both core and cladding components in a molten state through a special nozzle, a so-called composite spinning method.

(2) A method in which a core component is first shaped into a predetermined fiber and then coated with a cladding component dissolved in an appropriate solvent or a molten cladding component to form an optical fiber, the so-called coating method.

(3) A method in which a core component rod and a hollow vibrator having an inner diameter equal to the diameter of the rod are formed, and then they are fitted together and stretched in a furnace to form an optical fiber of a predetermined diameter, the so-called pie-blonde method.

The optical transmission fiber having a core and cladding structure according to the present invention can be manufactured by any of the above three methods, but among them, the composite spinning method is a highly productive and labor-saving process with simple equipment, and can be manufactured in a wide range of optical thicknesses. It is preferable because fibers can be produced.

〔Example〕

The present invention will be explained in more detail below with reference to Examples.

Example 1 A copolymer (A) consisting of 70 parts of methyl methacrylate, 30 parts of N-phenylmaleimide, and 0.1 part of benzoyl peroxide as a catalyst was obtained. The softening point was 148°C.

On the other hand, a thin film of a copolymer (B) consisting of 90 parts of methyl methacrylate, 10 parts of N-phenylmaleimide, and 0.1 part of benzoyl peroxide as a catalyst had a refractive index of 1.
．． 49 It was a transparent film with a Vicat softening point of 124°C.

Using core and clad spinnerets, core and clad spinnerets are used.
'The clad polymer was extruded at 280°C and wound at a speed of 201/min to a diameter of 0.25 mm and a core diameter of 0.23 mm.
An n+n+ composite filament was obtained. When observed under a microscope, the interface between the core and the cladding was found to be almost perfectly circular, and no air bubbles or foreign matter were observed.

The white light transmittance of this filament per 53 cm (using a tungsten lamp as a light source) was 80%, and it was found that it was sufficiently durable for practical use.

Example 2 The polymer (A) of Example 1 was used as the core material, and methacrylic acid chloride and perfluoro-t- were used as the cladding material.
Perfluoro-t methacrylate produced from butanol
- Butyl ester is polymerized with abbisisobutyronitrile as a catalyst, with a Vicat softening point of 160°C and a refractive index of 1.
40 polymer (C) was obtained. These polymers (A), (
C) was prepared in the same manner as in Example 1 to obtain a bubble-free composite filament having a diameter of 0.25 m+n and a core diameter of 0.23 mm.

The white light transmittance of this filament per 50C11 is 8
2%, and an optical fiber with improved heat resistance was obtained.

Example 3 A polymer obtained from 95 parts of vinylidene fluoride and 5 parts of tetrafluoroethylene was used as a cladding material (D). This polymer had a refractive index of 1.49 and was transparent.

Using the apparatus of Example 1, a bubble-free composite filament with a diameter of 0.25 ml11 and a core diameter of 0.23 mm was obtained from polymers (A) and (D). This filament had a white transmittance of 81% per 500, and an optical fiber with improved heat resistance was obtained.

Comparative Example 1 A copolymer (E) was obtained from 95 parts of methyl methacrylate and 5 parts of methacrylic acid. The thin film of copolymer (E) was a transparent film with a Vicat softening point of 110°C.

On the other hand, a copolymer consisting of 90 parts of methyl methacrylate and 10 parts of perfluoro-t-butyl methacrylate (
F) had a Vicat softening point of 120°C.

Optical fibers were obtained in which the copolymers (E) and (F) were used as a core and as a cladding, respectively. Table 1 shows the heat resistance when compared with Examples.

The heat resistance evaluation method was as follows: The optical fiber obtained in each example and comparative example was cut into a length of 5 cm, one end of which was fixed, and
The optical fiber was left in a gear oven at ℃ for 2 hours, and the degree of sagging of the optical fiber was determined.

○: Sagging condition less than 0.5 cI1 ×: Sagging condition 0.5 cm or more Table 1 [Effects] The optical transmission fiber according to the present invention has excellent heat resistance, so it can be used for information transmission in industrial, medical, etc. It can be widely used as

Claims (3)

[Claims] (1) In an optical transmission fiber consisting of a core material and a cladding material, the core material is made of a copolymer whose main components are methacrylic acid ester and N-allylmaleimide, and the cladding material has a refractive index lower than the core material by 3% or more. An optical transmission fiber characterized in that it is made of a polymer that exhibits amorphous properties. (2) The optical transmission fiber according to claim 1, wherein the cladding material is made of a fluorine-containing polymer containing 30 wt% or more of fluorine atoms. (3) Optical transmission according to claim 1, wherein the cladding material is made of a copolymer containing one or more of perfluoro-t-butyl methacrylate, vinylidene fluoride, and tetrafluoroethylene. fiber.