JPS6098407A - Low loss optical fiber - Google Patents

Abstract

PURPOSE:To improve moisture resistance and flexibility by using a polymer consisting principally of deutero methyl methacrylate contg. a specific range amt. of cyclohexyl methacrylate compd. as a core component and a transparent polymer having the refractive index lower by a specific ratio or below than the refractive index of the core component as a sleeve component. CONSTITUTION:A polymer for a core component consisting principally of deutro methyl methacrylate is required to be incorporated therein with 10-40% cyclohexyl methacrylate compd. as the constituting component thereof. If the content is below 10%, the effect of improving the resistance to moisture absorption is not enough and if the content exceeds 40%, mechanical properties and above all flexibility are not enough and are undesirable for practicability. A transparent resin or fluoro-rubber having the refractive index smaller by at least 3% than the refractive index of the core component is used as a sleeve component. If the difference in the refractive index is smaller than 3%, the ratio of reflection of light by the sleeve component decreases and the loss of photoconduction increases.

Description

[Detailed description of the invention] The present invention relates to a low two-loss optical fiber with excellent moisture resistance.

Optical #41fm fibers are conventionally manufactured using glass-based materials as a base material, and are widely used as optical signal transmission media for measurement control between and within devices, for data transmission, for medical purposes, for decoration, and for image transmission. . However, optical woven fibers made from glass-based materials have a thin inner diameter, are less flexible, have a large specific gravity, and are expensive, including connectors. Plasti this
Various attempts have been made to make it with Tsuku.

The major characteristics of using Plasti Luri are that it is lightweight, and even with thick fibers in the inner bag, it is strong and has excellent tenacity.Therefore, high opening degree and large diameter are possible, and it is suitable for use with light receiving and emitting elements. It is easy to connect and has excellent operability. A common method for producing such optical≠4 fibers using plastics is that they have a large refractive index and
The core component is Plasti-7, which also has good light transmittance.
A fiber having a core-sheath structure with a refractive index smaller than this and a transparent plastic as the sheath component is formed. This method transmits light by reflecting it at the core-sheath interface, and the larger the difference in refractive index between the plastics that make up the core and sheath, the better the light transmission properties.

Spiritual name: Nagi name, small name, Irafuki, 6 prefectures, 1st floor, Kami Preferably, medium-sized materials, and industrially, polymethyl methacrylate and polystyrene are the materials that are attracting attention (for example,
3-8978, Japanese Patent Publication No. 53-21660).

However, such plastic fibers have a disadvantage in that they have a greater optical transmission loss than optical fibers made of inorganic glass. In other words, the cause of the transmission loss of plastic light≠sacrificial fiber is essentially due to the high frequency of infrared vibration of carbon-hydrogen that constitutes it, and the carbon-hydrogen infrared absorption of hydrogen bonded to aliphatic carbon. The 7th harmonic of vibration has a wavelength of 560 nm, the 6th harmonic has a wavelength of 645 nm, and the 5th harmonic has a wavelength of 760 nm.
The seventh overtone of the carbon-hydrogen infrared absorption vibration of hydrogen bonded to aromatic carbon appears at a wavelength of 530 nm, the sixth overtone at 610 nm, and the fifth overtone at 71 Q nrn . Due to these absorption paths, the optical transmission loss in the so-called loss window increases. For this,
As a method for reducing or eliminating the carbon-hydrogen absorption vibration, a method has been devised in which hydrogen is replaced with deuterium to eliminate the 0-H absorption vibration. For example, a light coconut fiber having a core made of a resin made of deuterated methyl methacrylate has already been proposed (Japanese Unexamined Patent Publication No. 1983-65555). This optical transmission fiber has low loss from the visible light region to the near-infrared light region (Toshikuni Rokuno, Michiya Fujiki, Shigeo Nara, Pnl
ymc rr'r (! p5i + mountain, J co11) old l anus,
544 (I981)), 17 However, optical sacrificial fibers whose core material is deuterated methyl methacrylate are highly hygroscopic, and the increase in loss due to moisture absorption is primarily determined by the relative humidity of the surrounding environment. 84 Q at 60% relative humidity.
n1ll 550 dB/l<+n, 746 n
An increase in loss of 450 dB/I and mO''I was observed, and therefore it was found that it could not be used as a fiber optic fiber in a system using a near-infrared light source.

The inventors have developed a plastic optical sacrificial fiber that has excellent moisture resistance, flexibility, and low light transmission loss over a wide range from the visible light region to the near-infrared light region. As a result of intensive studies, we have arrived at the present invention.

That is, the present invention uses a polymer mainly composed of deuterated methyl methacrylate containing 10 to 40% by weight (F, simply referred to as %) of a cyclohexyl methacrylate compound as a core component, and The object of the present invention is to provide a low-loss optical fiber with excellent moisture resistance and flexibility, which is characterized by having a transparent polymer having a refractive index lower by at least 3% as a sheath component.

The light-wound fiber of the present invention suffers from light guide loss that occurs with increased humidity in the temperature range from room temperature to around 80°C, compared to the conventionally proposed Koyaro fiber that uses polymethyl methacrylate as the core component. The rate of decrease in the optical signal transmission medium is small, and the reliability as an optical signal transmission medium can be significantly improved.

Examples of the noclohexyl methacrylate compound used in the production of the core component polymer in the present invention include noclohexyl methacrylate, methylcyclohexyl methacrylate, and dimethylcyclohexyl methacrylate.

It is necessary that the core component polymer mainly composed of deuterated methyl methacrylate used in the present invention contains 10 to 40% of its constituent component cyclohexyl methacrylate compound.

If it is less than 10%, the moisture absorption resistance improvement effect is not sufficient, and 40%
If it exceeds %, mechanical strength, especially flexibility, is insufficient;
Practically unfavorable. Deuterated methyl methacrylate includes +1+ to 118 monomers, with d8 monomers being particularly preferred. Incidentally, a copolymer can also be formed by using deuterated styrene together with deuterated meth/methyl acrylate.

The core component polymer of the present invention can be produced by conventionally known methods such as suspension polymerization and bulk polymerization. However, in the suspension polymerization method, since a large amount of water is used, foreign substances contained therein are likely to get mixed into the polymer, and there is also a possibility that foreign substances can get mixed in during the dehydration process. If necessary, foreign substances such as dust are removed by a filtration method or a distillation method before polymerization. A more desirable method is to first produce the core component polymer in two steps: a continuous bulk polymerization step at a high temperature, followed by a continuous separation step of volatile components mainly containing residual unreacted monomers; There is a method in which the steps of manufacturing the core component polymer and the step of manufacturing the fibers are carried out in a continuous process. Another desirable method is an IC manufacturing method in which the core component is bulk polymerized, and then both the core component and the sheath component are formed from the obtained polymer by a double extrusion method.

The radical polymerization initiator used in each of the above polymerizations is, for example, 2,2'-azohis (isobutyroni-1-
), 1,1'-Azohis (Nclohexane-Ruboni!-Ryl), 2,2'-Azohis (2,4-dimethylvaleronitrile), Azohis-isobutanol diacetate
azo compounds such as tert-butane, di-tert-butyl peroxide, lefmil peroxide, methyl ethyl henoperoxide, di-tert-butyl barphthale-1, di-tert-butyl peracet-1, ') Examples include organic peroxides such as -tert-amyl peroxide. The addition ratio of these polymerization initiators is preferably 0.001 to 1 mol % based on the monomer.

In addition, in the polymerization system, in order to control the molecular weight, lert-butyl, jl-butyl, tl-octyl, 11-dotenormel, etc. are added as chain transfer agents in an amount of about 1 mol % or less based on the monomers. Sa11ru.

On the other hand, the sheath component polymer can be produced by conventionally known methods. In the case of the sheath component polymer, in the case of the core component polymer, the manufacturing method has no effect on light transmission properties, so it should be treated at 17 to prevent foreign matter such as dust from getting mixed in, and if necessary, it should be filtered. It is preferable to remove foreign substances from the sheath component by a method or the like to produce the sheath component polymer.

The ratio of the core component to the sheath component is approximately 7030 to 98.
2, preferably 80:2Q to 95°5. In addition, the outer diameter of the optical fiber with a core-sheath structure is approximately 0.1
5-1.5M, preferably about 0.20-1.0
It is mm.

On the other hand, as the sheath component, which is another important element constituting the present invention, a transparent resin or fluororubber having a refractive index that is at least 3% lower than that of the core component is used. If the difference in refractive index is smaller than 3%, the proportion of light reflected by the sheath component will be small and the light guide loss will be large. Specifically, it is preferable that the refractive index is 1.42 or more F, and it is preferable that the polymer be a non-crystalline, nearly amorphous polymer, and that has good adhesion to the core component.

Preferred transparent resins include fluororesins, thermoplastic fluororubbers, and fluororubbers. With fluororesin and jl,
For example, vinyl fluoride, vinylidene fluoride, trifluoroethylene, tetrafluoroethylene, hexafluoropropene, trifluoromethyl trifluorohinyl ether, perfluoroprobyl trifluorovinyl ether, perfluoroprovir methacrylate, perfluoro-tert methacrylate. -Fluorine-containing polymers such as butyl can be mentioned. Among these, particularly preferred fluororesins include hnylidene fluoride-tetrafluoroethylene copolymer, trifluoroethylene-vinylidenofluoride copolymer, and hnylidene fluoride-tetrafluoroethylene-hexafluoropropetrope. copolymer, perfluoroisopropyl methacrylate polymer, perfluoro-te methacrylate
r1. -Can you name a butyl polymer?

In addition, thermoplastic fluororubber has a soft segment consisting of a fluororesin phase and a hard segment consisting of a fluororesin phase in its molecule, and has comb elasticity due to physical crosslinking in the fluororesin phase at room temperature. At high temperatures, it behaves similar to thermoplastic plastics.

Soft segment vinylidene fluoride/hexafluoropropylene or pentafluoropropylene/tetrafluoroethylene (mole ratio 45-90, 5-50:O-35) polymer and perfluoro(alkyl hinyl ether)/teI
・Rafluoro15-75: 0-850-85) Molecular weight selected from polymer go, ooo ~ 1.200.00
The fluororesin phase forming the hard segment with 10 to 95 parts of 0-fluororubber is a polymer of hinylidenofluoride/te1-rafluoroethylene (molar ratio 0-100:O-100). l: thermoplastic fluororubber bound with 5 to 90 parts of a fluororesin having a molecular weight of 1.0, 000 to 400,000 selected from polymers of ethylene and tetrafluoroethylene (molar ratio 40 to 60: 60 to 40). You can give it to me. Typical thermoplastic fluororubbers include:
Guyer Thermoplasti (Taikino Kogyo Co., Ltd.)
Company-made products are available.

Preferred fluororubbers include vinylidene fluoride-hexafluoropropeno copolymer, vinylidene fluoride-pentafluoropene copolymer, vinylitine fluoride-chlorotrisiloloethylene copolymer, and the like. can. Particularly preferred is vinylidene fluoride-hexafluoropropeno copolymer.

As mentioned above, the present invention uses a specific polymer as the core component in optical fibers having a core-sheath structure, thereby increasing the applicable humidity range of conventional plasti and 7-ri optical trunk sacrificial fibers to 111%. It provides a low-loss optical fiber that can be expanded, and its industrial value is extremely high.

Since the normal humidity can be set to 75% relative humidity or higher, it can be used, for example, in automobiles, ships, robots, etc.

This makes it possible to apply this method to

Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these in any way.In addition, in the Examples, a halokenotanogusten lamp was used as the light source for measuring the light guide loss. Using a diffraction grating spectrometer, 650
The output intensities of the optical fiber to be measured and the reference light≠M fiber at the nm wavelength were read using a Noricon photodiode. Light with different fiber lengths [・(krn)≠M] Let the light intensities at the entrance and exit of the fiber be Io and I, respectively,
The light guide loss α was calculated using the following formula.

10 I In this equation, the smaller the α value, the better the optical transmission properties.

After the elapse of time, it was taken out and the light guide loss was determined using the method described above. Measurements were taken within 1 hour.

Example 1 Deuterated methyl methacrylate (18 monomers, 70
28 parts of cyclohexyl methacrylate, 2 parts of methyl acrylate, 0.14 parts of 7-so-Lert-butane,
0.18 part of n-butylmercaptaf was added to each by distillation. Thoroughly mix this 1 ift body mixture,
After bulk polymerization at 30°C for 148 hours, the temperature was gradually raised and finally heated at 180°C for 124 hours to complete the polymerization and obtain a core component polymer, """0.60. n 1
．． 49) Konoi coalescence ([η] 2°. P Melt-spun at 210″C to obtain fibers with diameters of 0.85 and 2-trifluoromethyl methacrylate-3,8,3 as a sheath component. -1-Lifluoropropyl-methyl methacrylate copolymer (copolymerization ratio: 90:10 (%)
.

r1201.40, melt viscosity 1.0X10 Boise (
A photonic fiber having a core-sheath structure with a film thickness of 0.1 thick was obtained by applying a 30% solution of hexafluorometa-xylene of 220"C)).

When the light guide loss was measured, it was found to be 1 at a wavelength of 84 oz.
It was 10 dB/km.

After the optical fiber was left at 40°C with a relative humidity of 90% for 24 hours, the light guide loss was measured at 140 dB/
It was km.

I Examples 2 to 3 By the same operation as in Example 1, optical transmission fibers (085 to 0.75I+II+
After obtaining Iψ), a moisture resistance test was conducted at a wavelength of 840 nm.

All of the fibers had light≠# woven fibers showing excellent moisture resistance (Table 1).

Comparative Example 1 A light-poor fiber was obtained using the same sheath components as in Example 1, except that deuterated methacrylic acid was synthesized as a core component, and by the same operations.

When the light guide loss was measured, at 840 nm,
9 Q d'l-L/lun. When the light trunk fiber was left standing at 50°C with a relative humidity of 90% for 24 hours, the loss of 1 u of guided light was measured and was 750 dB/1 (nl), indicating that the transmission loss was significantly increased in Comparative Example 2 and 3 Optical co-wound fibers were obtained using the same core component as in Comparative Example 1 and Examples 2 and 3 as sheath components.The light guide loss was measured to be 12Q dB/km and 9Q d, respectively.
B/km Relative humidity of fiber 9
After standing at 0% and 50°C for 24 hours, the light guide loss was measured to be 789 dB/m and 600 dB/m, respectively.
dB/km, and the transmission loss increased significantly.

Claims (1)

[Claims] Noclohexyl methacrylate compound 10-40% by weight
Loss light characterized in that the core component is a polymer mainly composed of deuterated methyl methacrylate containing the following, and the sheath component is a transparent polymer having a refractive index that is at least 3% lower than that of the core component. Stem mulberry fiber.