JPH01126602A - Plastic clad light transmission fiber and bundled fiber - Google Patents

Abstract

PURPOSE:To obtain the title fibers which are low in transmission loss in a UV region by forming a clad material of a fluorine-contained polymer having a cyclic structure in the main chain. CONSTITUTION:The clad material of the plastic clad light transmission fiber having the core consisting of quartz glass or optical glass is formed of the fluorine-contained polymer having the cyclic chain in the main chain. The fluorine-contained polymer having the cyclic chain in the main chain has no crysatllinity and has a high content of fluorine; therefore, said polymer is transparent and is low in refractive index. Since the polymer has high strength and has a good leak characteristic to the core material, the strength of the light transmission fiber is high; furthermore, there are not cured parts and C-H bonds and, therefore, the light transmittance of the UV region (200-400nm) is high. Generation of heat by UV absorption is thereby decreased and the decrease in the transmission quantity of UV rays is obviated.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention provides a plastic clad optical transmission fiber with improved characteristics such as low transmission loss, particularly low loss in the ultraviolet region, and large NΔ, and core occupation area. This relates to a bundle fiber that can increase the

[Prior art] Plastic clad optical transmission fibers (hereinafter referred to as PCFs), which have a core of quartz glass or optical glass and a plastic cladding, have been known for some time, and have a particularly large numerical aperture (NA) and low transmission loss. Therefore, it is expected to be used in a wide range of fields such as optical communication, image transmission, and light guides.

Since the refractive index of PCF changes by changing the type of plastic used for the cladding, it is possible to obtain 13 CF with various numerical apertures. When the core is made of especially high-purity quartz glass, the refractive index is as small as 1.458, and therefore the plastic used as the Fullerad material must be selected from those having a refractive index lower than this. The properties of the cladding material are (a) colorless and transparent, (b) adhesion to the core, (
c) It is necessary to satisfy the condition that the material has excellent cladding properties and the like.

Therefore, the range of selection becomes extremely narrow.

Dimethyl silicone, fluororesin, etc. are available as cladding materials that satisfy the conditions described in item 1. PCFs using dimethyl silicone are well known, and such PCFs are widely used in practical use. In addition, in fluororesin as a cladding material, PcF (Japanese Patent Publication No. 1973-
2566), or I) CF using a detrafluoroethylene-vinylidene fluoride copolymer (see JP-A-51-52849), and furthermore, a solvent-soluble fluoropolymer having a curing site. pcF (see Japanese Unexamined Patent Publication No. 62-232601) and the like have been proposed.

[Problems to be Solved by the Invention] As mentioned above, although silicone PCF using dimethyl silicone as the cladding material may have satisfactory optical properties, the strength of silicone is low and the hardness is also low. Strength is 3-40kg/cm2,
Since the hardness is JIS A20-80, it has the disadvantage that it is difficult to connect with a connector. -20°C to +80°C, especially if adhesive is used to connect with the connector.
In the heat cycle test, due to the difference in expansion coefficient between the quartz glass core and the cladding material, stress acts on the interface, causing the tips of the wires to protrude.Furthermore, due to the unique properties of silicone resin, As silicone PCF has a relatively large moisture permeability coefficient, under high temperature and high humidity environments, moisture easily penetrates through the silicone and enters the interface between the core and cladding, promoting the growth of scratches on the core surface. do,
It also has the disadvantage of reducing the strength of the fiber.

On the other hand, a fluororesin PCF using an ordinary fluororesin as a cladding material has high strength and does not easily cause the phenomenon of protrusion from the connector, but it does not have excellent optical transmission characteristics. This is due to poor adhesion between the quartz glass core and the fluororesin. That is, since fluororesin generally dissolves in solvents and does not leak, the core is coated with fluororesin by extrusion molding instead of solution-type coating.
This causes poor attachment and increases transmission loss.

Even if fluororesin dissolves in a specific solvent, it will dissolve only 1
0-20% by weight is dissolved. and the viscosity of the solution,
There were problems in that it was not easy to adjust the boiling point, etc., and coating as a solution was difficult.

In order to solve these problems with conventional fluororesin PCF, an optical transmission fiber has been proposed in which the core is coated with a solution of a specific solvent-soluble fluorine-containing polymer and cured (Japanese Patent Application Laid-Open No. 1983-1992-1). (Refer to Publication No. 232601, etc.)
. This PCF fiber is ideal for use in optical signal transmission such as data transmission and image signal transmission, but it has problems such as not necessarily having a large NA and high loss in the ultraviolet region, and is not suitable for optical energy transmission. It's not enough. In particular, since the transmittance of fluorine-containing resin for ultraviolet light in the 0.2-0.4 μm band is poor, the transmission loss as a fiber is 0.
At 3 μm, it increases to 500 to 1000 dB/km. Furthermore, when transmitting ultraviolet light, the cladding material absorbs the ultraviolet light and generates heat, which causes the cladding material to deteriorate and increase transmission loss.

Therefore, the amount of optical energy sent through the optical fiber can be expressed by the following formula.

Transmission light energy oc (transmittance) (NA)" + fiber core diameter) 2 From the above formula, the optical energy transmission fiber has a good light transmittance (the larger the NA, the more suitable it is. Therefore, the light transmittance of the cladding material is It is necessary to reduce the refractive index without lowering it.

In addition to being used as a single core, energy transmission fibers are often used as bundles of multiple fibers. In that case, the thinner the cladding, the larger the area occupied by the core of the bundle. In order to make the clad thin, a rad material with high hardness, high tensile strength, and high tensile modulus is suitable.

The present invention was made based on such knowledge, and has low transmission loss, especially in the ultraviolet region and around 0.9 μm, large NA, thin cladding thickness, and is also suitable for energy transmission. One object of the present invention is to provide a clad optical transmission fiber.

[Means for solving the problems] The present invention has been completed based on the above-mentioned objectives,
First, there is provided a plastic clad optical transmission fiber whose core is quartz glass or optical glass, in which the cladding material is made of a fluorine-containing polymer having a ring structure in its main chain. Second, the core is made of quartz glass or optical glass, and the cladding material is a bundle made of a fluorine-containing polymer with a ring structure (-r). The present invention provides a bundle fiber characterized in that it is

That is, the present invention newly provides a PCF-end transmission fiber and a bundle fiber having the above-mentioned configuration and which are also suitable for energy transmission.In particular, the present invention provides a new PCF-end transmission fiber and bundle fiber having the above-mentioned configuration, and particularly the present invention uses a specific fluorine-containing polymer as the cladding material. 20μ
The present invention provides PCF optical transmission fibers and bundle fibers coated with a thin film of less than m.

In the present invention, examples of the fluorine-containing polymer having a ring structure in the main chain include those having a ring structure as shown in the general formula. Among these, polymers having the following ring structures are typical. However, the content of the present invention is not limited to these only.

There are two methods for producing these polymers: However, it is not limited to these manufacturing methods.

1. By cyclization m combination (USII 34111303. GR1106344
etc.) (USP 3202643 etc.) 2. Those using a ring-shaped knob (USP 39780)
30, etc.) Furthermore, there is no problem in using copolymerized components to the extent that the essence of these components is not impaired.

Other monomers to be copolymerized are not particularly limited as long as they are radically compatible, and include a wide range of fluorine-containing monomers, hydrocarbon monomers, and others. Of course, these other 14-monomers may be used alone or by radical copolymerization with the above-mentioned specific ring structure introduced into the main chain, or two or more of them may be used.
The above-mentioned copolymerization reaction may be carried out in combination with . In the present invention, it is usually desirable to select fluorine-containing monomers such as fluoroolefins and fluorovinyl ethers as other carriers. For example, tetrafluoroethylene.

Perfluoromethyl vinyl ether, perfluoropropyl vinyl ether, or perfluorovinyl ether containing a functional group such as a carboxylic acid group or a sulfonic acid group are preferred examples, and vinylidene fluoride, vinyl fluoride, chlorotrifluoroethylene, etc. may also be exemplified.

As for the co-in combination composition, in order to take advantage of solubility, film-forming properties, and properties as a fluorine-containing polymer, the composition of the cyclic structure is preferably 20% or more, more preferably 40%.
The above is desirable.

The above-mentioned specific fluorine-containing polymers are soluble in solvents, and the solvents used are not limited as long as they dissolve the above-mentioned polymers. (fluorinated solvent)
, "Florinate" (product name = liquid containing perfluoro(2-butyltetrahydrofuran) manufactured by 3M Company),
Trichlorotrifluoroethane and the like are preferred. As a matter of course, two or more appropriate types can be used in combination as a solvent. Particularly in the case of a mixed solvent, hydrocarbons, chlorinated hydrocarbons, fluorochlorinated hydrocarbons, alcohols, and other organic solvents can also be used in combination. Solution concentration is 0.01wL% ~
50wL%, preferably 0. IwL%~20wL%
It is.

The cladding material polymer of the present invention is “Florinat” FC.
It is soluble in fluorinated solvents such as -76 and can become a transparent viscous liquid. Furthermore, since the melting temperature is low and the viscosity is relatively low, it is easy to coat silica fibers made of quartz glass or optical glass as a cladding material.

The method of forming a cladding layer by treating the core of a silica fiber made of silica glass with the cladding material of the present invention is to coat the core with a solution of the cladding material polymer and remove the solvent, or to coat the core in a molten state. It is done by extrusion. In this method, the coating method is not particularly limited. For example, when coating solutions, it is preferred to use a conventional so-called wire-drawing device. The solvent is removed by heat treatment at the same time as coating, and the heat treatment conditions are arbitrarily set depending on the thickness of the cladding layer to be formed and the boiling point of the solvent.

Preferred embodiments of the cladding material polymer of the present invention include:
Preferably, perfluoropolymers are used. This perfluoro-11 combination has no crystallinity and has a high fluorine content, so it is transparent and has a low refractive index.
It is optimal from the perspective of l. In addition, this perfluoropolymer has high hardness, tensile strength, and tensile modulus, so it is possible to make the cladding material thinner, and when a bundle fiber is created by bundling multiple fibers together, a high core occupation rate can be obtained. Furthermore, since this perfluoropolymer does not have a general curing site or C-11 bond, it provides a cladding material with good light transmittance, which is the objective of the present invention, and has particularly excellent light transmittance in the ultraviolet region. Can be used for transmission bundle fiber.

In the present invention, when the core is made of silica glass, the refractive index of the cladding must be 1.45 μm or less, and preferably! , 40 or less, especially 1.37 or less when used for energy transmission.In addition, in the present invention, the thickness of the cladding layer formed on the quartz glass or optical glass of the core is preferably thinner considering the area occupied by the core of the bundle. However, in order to make it useful as a protective layer, it is appropriate to have a thickness of 5 to 20 μm, especially 7 to 10 μm.
It is preferable that

[Function] In the present invention, the fluorine-containing polymer having a ring structure in its main chain has no crystallinity and has a high fluorine content, so it is considered to be transparent and have a low refractive index. Furthermore, since the polymer has high strength and good leakage to the core material, it is thought that the strength of the optical transmission fiber is high. Furthermore, the cured site and C-11
Because there is no bond, the light transmittance in the ultraviolet region (200 to 400 nm) is high, and when bundled to transmit ultraviolet light,
The effect is that heat generation due to ultraviolet absorption is small and there is no decrease in the amount of ultraviolet light transmitted.

[Examples] Next, Examples of the present invention will be described in more detail, but it goes without saying that the present invention is not limited by such explanations.

Synthesis Example 1 30 g of perfluoroallyl vinyl ether, 30 g of trichlorotrifluoroethane and a polymerization initiator (CJt
10 mg of CO) x was placed in a 50 cc pressure-resistant ampoule. The pressure during the zero polymerization, which was polymerized at 20° C. for 16 hours after repeating freeze degassing twice, was lower than atmospheric pressure. ff1
As a result of the synthesis, 16 g of polymer was obtained.

When we measured the infrared absorption spectrum of this polymer, we found that
1790cm-' due to the double bond in the 1,000cm
There was no nearby absorption. Further, this polymer was dissolved in perfluorobenzene.

When the NMR spectrum was measured, a spectrum showing the following repeating structure was obtained.

The intrinsic viscosity [η] of this polymer is “Florinat” F
C-75 (product name: liquid mainly composed of perfluoro(2-butyltetrahydrofuran) manufactured by 3M Company, hereinafter referred to as F
C-75) at 30°C.

The transition point of the polymer is 69°C, and it is a tough, transparent, glass-like polymer at room temperature. Also, the 10% thermal decomposition temperature is 46
2°C, this polymer is colorless and transparent, has a low refractive index of 1.34, and has a light transmittance of 95% (visible light).
It was as high as 92% (ultraviolet light, wavelength 300 nn+). Furthermore, hardness Shore D65, breaking strength 315kg/c+++
", elongation 170%, tensile modulus 10200kg/cm"
Met. This polymer was press-molded at 250°C to a thickness of 1
Figure 1 shows the results of measuring the light transmittance using a 00μ film.
Shown below.

Example 1 10 g of the polymer obtained in Synthesis Example 1 was mixed with 90 g of FC-
75 to obtain a smooth polymer solution.

Next, this composition was applied to quartz glass 1. ) diameter 200μ from the material
It is applied immediately after spinning the fiber spun to mφ, and the temperature is approx.
The fiber was cured by passing through a heating furnace at 00° C. for about 2 to 3 seconds, and a 7 μm thick cladding layer made of the cured product was formed to obtain a fiber with a core-clad structure.

As a result of measuring the optical characteristics of this PCI, the transmission loss was 100 dB/km (300 nm), 5 dB/
km (850nm), 5dB/km (920nm)
), and the NA was 0.58. This fiber
Fifty fibers were bundled to make a bundle fiber with a diameter of about 5 mm and a length of 1 m, and a 100 W mercury lamp was used as a light source and a light guide. The core footprint of this bundle is 72%
It was possible to transmit approximately 2000 mW of ultraviolet light. Further, although irradiation was performed for about 1000 hours, no decrease in the amount of transmitted light was observed.

Figure 2 shows the transmission loss wavelength characteristics of this fiber. 920
Since there is no C-tl lattice vibration absorption appearing in nm, 6
It was possible to achieve less than IOd/km in the range of 00 to I000 nm.

Comparative Example 1 P using a terpolymer of tetrafluoroethylene/ethyl vinyl ether/hydroxybutyl vinyl ether
CF was produced.

The refractive index of the cured product of this ternary copolymer is 1.4+, and the light transmittance is 95% (visible light) and 60% (ultraviolet light, wavelength 300μ).
m). The light transmittance of this cured product is shown in FIG.

Using this methyl ethyl ketone solution of the ternary and 1R combination, it was applied to a fiber made of quartz glass in the same manner as in Example 1, and fired to form a cured product, resulting in a strand with a 15 μm thick cladding layer. Ta.

As a result of measuring the optical characteristics of this l) CF, the transmission loss was 500 dB/km (300 nml, 5 dB/k
m (850nm), 15d ports/km (920nm)
m) and the NA was 0.38. A bundle of 410 fibers has a length of approximately 5 m and mφ.

Make a bundle fiber with a length of 1 m and do the same as in Example 1! A 00W mercury lamp was used as a light source and a light guide. The core footprint of this bundle is 65%,
Approximately 1200mW of ultraviolet light could be transmitted. Also, about 1000
Although irradiation was performed for several hours, the transmitted light: 11 was reduced to 500 mW. Figure 2 shows the transmission loss wavelength characteristics of this fiber. There is C-11 lattice vibration absorption at 920 nm, and an increase in loss is observed.

Comparative Example 2 Commercially available dimethyl silicone (OF-106 manufactured by Shin-Etsu Chemical)
PCF was manufactured using

This silicone has a refractive index of 1.4+ and a light transmittance of 90%.
(visible light), 60% (ultraviolet light, wavelength 300 μm). The light transmittance of this cured product is shown in FIG.

Using this silicone, it was applied to a fiber made of quartz glass in the same manner as in Example 1 and fired to form a cured product, thereby obtaining a wire having a 25 μm thick cladding layer. As a result of measuring the optical characteristics of this PCF, the transmission loss was
1000dB/km (300nm), 5dB/km
[850nm), 20dB/km (920nm
l, and the NA was 0.39. This fiber
Fifty fibers were bundled to make a bundle fiber with a diameter of about 5 mm and a length of 1 m, and as in Example 1, a + OOW mercury lamp was used as a light source and used as a light guide. The core occupation area of this bundle was 55%, and approximately 850 mW of ultraviolet light could be transmitted. Further, although irradiation was performed for about 1000 hours, the amount of transmitted light decreased to 600 mW. FIG. 2 shows the transmission loss wavelength characteristics of this fine. An increase in loss is seen at 920 nm.

[Effects of the Invention] In the PCV optical transmission fiber of the present invention, the cladding layer is formed of a fluorine-containing polymer having a ring structure in a specific main chain,
What makes it so good is that it has low transmission loss and high NA. In particular, the transmission loss in the ultraviolet light region of 200 to 400 nm is small, making it an excellent fiber for ultraviolet light transmission. Furthermore, there is no deterioration in transmission loss due to ultraviolet light.

Conventional I'CF fibers have an increase in loss of 10 to 20 dB/km at 920 nm due to C-II lattice vibration absorption in the cladding layer, making it impossible to use a light source near 900 nm. -11
Absorption disappears and low loss around 900 nm can be achieved.
It is now possible to use light sources around 1100n.

The specific fluorine-containing polymer in the present invention has high hardness,
Since the tensile strength and tensile modulus are high, the cladding layer can be made thinner, and a thickness of 5 to 10 μm can be achieved. When this fiber is bundled, the core occupancy area is 70
% or more of bundled fibers can be obtained.

[Brief explanation of the drawing]

FIG. 1 shows the light transmittance of the cladding material, and FIG. 2 shows the transmission loss characteristics of the PCF fiber. In FIGS. 1 and 2, -
is Example 1, ----- is Comparative Example 1. -m- indicates the results of Comparative Example 2, respectively. 18t, 7jvya
o7*) Zura = Toko (AFIIin)

Claims (1)

[Claims] 1. A plastic clad optical transmission fiber whose core is made of quartz glass or optical glass, wherein the cladding material is made of a fluorine-containing polymer having a ring structure in its main chain. 2. A bundle fiber characterized in that a plurality of plastic clad optical transmission fibers whose core is made of quartz glass or optical glass and whose cladding material is made of a fluorine-containing polymer having a ring structure in the main chain are bundled together. . 3. Claim 2 in which the ring structure is a fluorine-containing ring structure
Bundled fibers as described in Section. 4. The bundle fiber according to claim 2 or 3, wherein the ring structure is a fluorine-containing ring structure containing an ether bond. 5. Claim 2 in which the ring structure is a 4- to 7-membered ring structure
The bundle fiber according to any one of Items 1 to 4. 6. The bundle fiber according to any one of claims 2 to 5, wherein the fluorine-containing polymer is a perfluoropolymer. 7. The bundle fiber according to any one of claims 2 to 6, wherein the cladding material has a thickness of 20 μm or less. 8. The plastic clad optical transmission fiber according to claim 1, wherein the thickness of the cladding material is less than 20 μm.