JPH0652330B2 - Fluoroplastic optical fiber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fluorinated plastic optical fiber,
More specifically, it uses a transparent copolymer of fluorinated methacrylate and styrene as a core polymer, has a high light guiding performance in a wavelength range of 600 nm or more, and has a low hygroscopic property,
Moreover, the present invention relates to a plastic optical fiber whose performance does not change with time.

In recent years, plastic optical fibers have a larger aperture than inorganic optical fibers such as glass, and are excellent in flexibility and workability and workability, so that the field of short-range visible light transmission, for example, Demand has rapidly expanded in fields such as computer terminal wiring, panel wiring, in-vehicle signal transmission, and other office automation equipment and home appliances.

By the way, in the conventionally known plastic optical fiber, the most transparent methyl methacrylate resin in plastics is used as the core polymer, but this one absorbs light in the long wavelength region of 700 nm or more. Since the loss is large, especially in the long wavelength region of 850 nm where the quartz fiber is mainly used, it is almost impossible to use the plastic fiber instead of the quartz fiber in this region. .

On the other hand, an optical fiber using a deuterated polymer is known to have excellent performance in a long wavelength region.

However, this deuterated polymer has not been put into practical use due to the drawbacks such as difficulty in obtaining raw materials and high cost.

In view of such circumstances, the present inventors have made extensive studies to develop a practical medium-range plastic optical fiber using an inexpensive material, and as a result, have identified a specific molar ratio as a core polymer. The inventors have found that the object can be achieved by a plastic optical fiber using a transparent copolymer of fluorinated methacrylate and styrene which satisfy the conditions, and have completed the present invention based on this finding.

That is, the present invention, in the plastic optical fiber having a structure consisting of a core and a sheath, the core polymer is a copolymer in the range of 40:60 to 60:40 molar ratio of fluorinated methacrylate units and styrene units, In addition, it is a transparent copolymer in which the ratio of the number of carbon atoms and fluorine atoms in the sum of the number of carbon atoms and hydrogen atoms and the number of carbon atoms and fluorine atoms in the copolymer is 17 to 22%. To provide a plastic optical fiber.

Examples of the fluorinated methacrylate monomer used in the transparent copolymer for the core polymer in the present invention include tetrafluoropropyl methacrylate and trifluoroethyl methacrylate.

Copolymerization of these fluorinated methacrylates and styrene has an extremely narrow range of conditions under which transparency can be maintained, as compared with ordinary copolymerization of methyl methacrylate and styrene. This is particularly remarkable in batch polymerization. For example, the ratio of both is 1% by weight in order to obtain the most transparent copolymer.
It must be within the precision.

Generally, in a polymerization system of methyl methacrylate and styrene, in the case of imparting transparency to a copolymer to be obtained, a transparent copolymer is obtained by differentially polymerizing using a complete mixing type one-stage polymerization tank. The ratio of the two for obtaining the above can be expanded to a considerably wide range, but in the polymerization system of the fluorinated methacrylate and styrene of the present invention, even if such differential polymerization is carried out, a completely transparent polymer can be obtained. The ratio of both of them is limited to a narrow range.

Since these properties are essentially present in the polymerization system of fluorinated methacrylate and styrene, it is considered that the copolymers obtained from the past have been overlooked as objects of plastic optical fibers.

Therefore, the present inventors have made a strict examination of the relationship between the ratio of the fluorinated methacrylate and styrene and the transparency of the obtained copolymer, and found that the fluorinated methacrylate unit and the styrene unit It has been found that copolymers whose proportions are in the range of 40:60 to 60:40 in molar ratio show extremely high transparency.

Furthermore, if the ratio of the number of bonds of carbon atoms and fluorine atoms to the sum of the number of bonds of carbon atoms and hydrogen atoms and the number of bonds of carbon atoms and fluorine atoms of this copolymer is 17 to 22%, 700 nm
It was found that the light guide loss in the above long wavelength region can be significantly reduced.

Further, in the copolymerization of fluorinated methacrylate and styrene in the present invention, it is not preferable to use a peroxide as a catalyst because the obtained copolymer is colored, and the general formula R ₁ -N = N An azoalkane represented by —R ₂ (wherein R ₁ and R ₂ are hydrocarbon groups having 1 to 8 carbon atoms) is preferable as the polymerization initiator, and the copolymer obtained using this does not color. As such an azoalkane, an asymmetric azoalkane can be used in addition to a symmetrical azoalkane such as azobis-tert-butane or azobisoctane.

Further, in the copolymerization of fluorinated methacrylate and styrene in the present invention, it is desirable to use mercaptan as a polymerization regulator. Examples of the mercaptan include n-butyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan, and tert-dodecyl mercaptan.

The refractive index of the fluorinated methacrylate-styrene transparent copolymer thus obtained is higher than the refractive index of the fluorinated methacrylate homopolymer, and is in the range of 1.46 to 1.51, with a methyl methacrylate resin. It is about the same.

Thus, the transparent copolymer of fluorinated methacrylate and styrene used as the core polymer in the present invention,
Since the refractive index is sufficiently high, the sheath material can be easily selected, and an optical fiber having a large numerical aperture can be obtained.

On the other hand, as the sheath material, a polymer having a refractive index lower than that of the transparent copolymer used as the core material, for example, a fluorinated methacrylate homopolymer, a fluorinated methacrylate and a fluorinated acrylate copolymer. A polymer, a copolymer of vinylidene fluoride and tetrafluoroethylene or hexafluoropropylene, and the like can be used, and among them, of the monomer units in the transparent copolymer particularly used as a core material, One homopolymer of fluorinated methacrylate is preferable also from the viewpoint of adhesion between the core and the sheath.

The plastic optical fiber of the present invention can be obtained by composite spinning the polymer used for the core material and the polymer used for the sheath material. This one is 700n
It has high light guiding performance in the wavelength range of m or more, has extremely low hygroscopicity, and has the characteristic that it does not change with time even in a high humidity atmosphere, making it a practical optical fiber for medium distances. is there.

Next, the present invention will be described in more detail with reference to Examples.

Example 1 Tetrafluoropropyl methacrylate, styrene, azobis-tert-butane and n-butyl mercaptan were each purified by distillation and used.

Tetrafluoropropylmethacrylate 59.4 g, styrene 25.5 g, azobis-tert-butane 0.0533 g and n-butyl mercaptan 0.101 g were weighed out at -60 ° C.
After degassing under reduced pressure with the evaporation of the raw material substantially zero at low temperature, the whole was distilled at 60 ° C. in a closed system to a glass-made polymerization ampoule. This fraction is He
-The bright spot material on the optical path was not detected by the Ne laser beam.

Place the polymerization ampoule in a constant temperature bath, 130 ℃ for 20 hours, 180
Polymerization was carried out at 10 ° C. for 10 hours and 190 ° C. for 10 hours to obtain a completely transparent polymer.

The obtained polymer was subsequently subjected to composite spinning with a tetrafluoropropyl methacrylate homopolymer used as a sheath material at a temperature of 160 ° C. to obtain an optical fiber having a core diameter of 1 mmφ. This optical fiber 15m
Was used to measure the light guide performance. FIG. 1 is a pattern showing the light guide spectrum.

As you can see from this figure, 580nm, 658nm, 720nm, 770nm, 83
Has a window in the wavelength range of 0 nm and 870 nm, and the light guide loss is
186dB / Km, 152dB / Km, 1164dB / Km, 360dB / Km, 1042dB / Km
And 1583 dB / Km, especially 160 dB / Km in the wavelength range of the red LED of 660 nm.

The core polymer had a refractive index of 1.482 and the sheath polymer had a refractive index of 1.425, and had a sufficient numerical aperture and good adhesiveness at the joint surface between the core and the sheath. When the polymer of the core material was immersed in water at 20 ° C. for 10 days in a 1 mmφ strand state, the water absorption rate showed only an increase of 0.13% on a weight basis, and was extremely excellent in moisture absorption resistance.

For comparison, as a polymerization initiator, azobis-tert-
Using tert-butylperoxy-2-ethylhexanoate instead of butane, polymerization was carried out as follows to obtain a copolymer.

That is, tetrafluoropropyl methacrylate 59.4
g, styrene 25.5 g, tert-butylperoxy-2-ethylhexanoate 0.05 g, n-octyl mercaptan 0.1
After charging g into a glass ampoule and degassing under reduced pressure at -60 ° C, polymerization was carried out under conditions of 65 ° C for 20 hours, 90 ° C for 2 hours, and 180 ° C for 15 hours. The obtained polymer was colored to a pale yellow color with the naked eye.

Comparative Example Polymerization was carried out in a glass ampoule in the same manner as in Example 1 except that 84.9 g of methyl methacrylate was used instead of tetrafluoropropyl methacrylate and styrene in Example 1, and the obtained polymer was used as a core material and An optical fiber was obtained by using a copolymer of fluoropentyl methacrylate and tetrafluoropropyl methacrylate as a sheath material. The light guide performance was measured using this optical fiber 15m. FIG. 2 is a pattern showing the light guide spectrum.

As can be seen from this figure, there are windows in the wavelength range of 570 nm, 650 nm, 770 nm and 830 nm, and the light guide loss is 79 dB / Km and 148 dB, respectively.
/ Km, 663 dB / Km and 1800 dB / Km, which showed higher performance than Example 1 in the wavelength range of 650 nm or less, but 660 nm
209 dB / Km in the wavelength range of, and the larger light guide loss than that in Example 1 was exhibited in all other wavelength ranges of 700 nm or more.

Example 2 Trifluoroethyl methacrylate 51.6 g, styrene 28.
6g, Azobisoctane 0.050g, n-butyl mercaptan
0.10 g of each was weighed out, charged into a glass polymerization ampoule that had been thoroughly washed with a liquid of the same composition through an ultrafiltration membrane, degassed under reduced pressure at a low temperature, and sealed.

Place this polymerization ampoule in a constant temperature bath at 90 ° C for 10 hours,
Polymerize under conditions of 0 ° C for 10 hours and 180 ° C for 10 hours,
A transparent polymer free of bubbles was obtained. This polymer is then added to 17
An optical fiber was obtained by performing composite spinning with a tetrafluoropropyl methacrylate homopolymer used as a sheath material at a temperature of 0 ° C.

When the light guide performance was measured using the obtained optical fiber 15m, 580nm, 658nm, 720nm, 770nm, 830n
In the wavelength range of m and 870 nm, the guided loss is 202 dB / Km and 16 respectively.
1dB / Km, 1218dB / Km, 371dB / Km, 1058dB / Km, 1607dB / Km
The result is obtained with a window that is

The refractive index of the core polymer and the refractive index of the sheath polymer were 1.484 and 1.425, respectively, and the adhesion between the core and the sheath was good. When the core polymer was soaked in water at 20 ° C. for 10 days in a 1 mmφ strand state, the water absorption rate showed only an increase of 0.14% or less on a weight basis, and was excellent in moisture absorption resistance.

[Brief description of drawings]

FIG. 1 is a light guide spectrum of the plastic optical fiber obtained in the example, and FIG. 2 is a light guide spectrum pattern of the plastic optical fiber obtained in the comparative example.

Claims (2)

[Claims] 1. A plastic optical fiber having a structure comprising a core and a sheath, wherein the core polymer comprises a fluorinated methacrylate unit and a styrene unit in a molar ratio of 40:60.
To 60:40, and the ratio of the number of bonds of carbon atoms and fluorine atoms to the sum of the number of bonds of carbon atoms and hydrogen atoms and the number of bonds of carbon atoms and fluorine atoms of the copolymer. Is a transparent copolymer having a content of 17 to 22%. A plastic optical fiber. 2. A transparent copolymer of fluorinated methacrylate and styrene has the general formula R ₁ --N = N--R ₂ (where R ₁ and R ₂
Is a hydrocarbon group having 1 to 8 carbon atoms), and the plastic optical fiber according to claim 1, which is obtained by using an azoalkane and a mercaptan.