JPS6120907A - Production of optical fiber - Google Patents

Abstract

PURPOSE:To obtain an optical fiber having excellent optical transmittability and flexibility and good heat resistance by producing the opticl fiber of which the cladding component consists of a polymer contg. F at a specific ratio or above and the core component consists of a polymer composed essentially of methyl methacrylate under specific extrusion conditions. CONSTITUTION:The polymer contg. >=20wt% fluorine, for example, the (co) polymer such as alpha-fluoroacrylic acid/2,2,2-trifluoromethyl is used for the cladding component and the copolymer contg. 3-40wt% methacrylate and consisting of the balance essentially of methyl methacrylate is used for the core component. The core component polymer is extruded under the conditions expressed by the formula [T is a die temp. ( deg.C) and E is thermal shrinkage (%)] and the cladding component polymer is melt-coated thereon. The optical fiber which has the good adhesiveness of the cladding component and the core component, excellent mechanical strength and good transparency and has the good heat resistance to make the fiber serviceable normally at 110 deg.C is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing an optically delicate material having a core-sheath structure and having excellent light transmission properties and flexibility.

Optical fibers are conventionally manufactured using glass-based materials as a base.
It is widely used as an optical signal transmission medium for measurement control between and within devices, for data transmission, for medical purposes, for decoration, and for image transmission.

However, optical fibers based on glass-based materials have the disadvantage of poor flexibility unless they are made with a thin inner diameter.
In addition, recently various attempts have been made to make wires out of plastic because they are easily broken, have a large specific gravity, and are expensive including the connector.

The major characteristics of using plastic are that it is lightweight, and even fibers with a thick inner diameter are strong and flexible.Therefore, high apertures and large diameters are possible, and it is easy to combine with light receiving and emitting elements. It has excellent operability. Such optical lI using plastic
The general method for manufacturing A-fibers is to use a core made of plastic with a high refractive index and good light transmittance, and a core made of a transparent plastic with a smaller refractive index as a sheath. This forms fibers having a sheath structure. 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.

As a plastic with high light transmittance, an amorphous material is preferable, and polymethyl methacrylate and polystyrene are attracting attention industrially (for example,
-8978 Publication).

Core - Saya! There are two methods for manufacturing optical fibers. One is a method of imparting a core-sheath structure by blending and discharging both core-sheath components using a special nozzle in a bath-molten state, and is a so-called composite spinning method. The other method is a so-called coating method in which a core component is first shaped into a predetermined fiber, and then the core component is coated with a suitable bath additive and a detoxifying agent is applied to form an optical fiber.

When manufacturing optical fibers, it is fundamentally important to increase the difference in refractive index between the core and sheath, but it is also important to consider the adhesion state at the interface between the core and sheath and the polymer that forms the optical fiber. The physical and mechanical properties of the material are also important factors.

In this sense, an optical fiber made of a combination of a polymethyl methacrylate resin and a certain fluorine-containing polymethacrylate resin proposed in Japanese Patent Publication No. 4B-8978 is noteworthy. However, as shown in the same publication, a type of fluorine-containing polymethacrylate resin is simply melted into the core component polymer as a sheath component.
In the coating method, the mechanical properties of the optical fiber,
In particular, the flexibility is poor, and as a result, micro cracks occur on the surface of the core component polymer, the light guide loss is significantly reduced, the reliability is low, and it can no longer be used industrially.There are still points that need to be improved. many. In addition, optical l611 fibers containing polymethyl methacrylate as a core component have insufficient heat resistance and have a drawback of being limited in their uses. For example, due to its shortcomings in heat resistance, it is used in moving objects such as automobiles, ships, aircraft, etc.
When applied to trains, robots, etc., there are restrictions on the purpose and place of application. In other words, the upper limit temperature at which polymethyl methacrylate (the same is true for polystyrene) can be used is approximately 80°C, and at higher temperatures, heat shrinkage increases, deformation occurs, and microstructural fluctuations occur. So, optics! It has drawbacks such as not being able to function as a pongee, and once it is used at a temperature of 80°C or higher, the light guide loss becomes large even when the temperature is returned to room temperature, so it cannot be used again. It can only be used in a narrow temperature range. Therefore, it has been desired to develop a low-loss plastic optical fiber with excellent heat resistance.

The present inventors investigated the development of plastic optical fibers with excellent heat resistance and light transmission properties, and first developed a plastic optical fiber using a methacrylic acid ester having an alicyclic hydrocarbon group having 8 or more carbon atoms in the ester moiety. We succeeded in obtaining an optical fiber with excellent heat resistance, which has a core component of a polymer of 58-22180
No. 8).

In the case of the core component polymer used in the optical fiber of the invention according to the application, the heat resistance and low light guiding loss were satisfactory, but there is still room for consideration regarding flexibility. Ta.

Therefore, the present inventors conducted extensive research into developing an optical fiber with excellent light transmission properties and flexibility, and as a result, they arrived at the present invention.

That is, the present invention provides an optical fiber having a core-sheath structure in which the core component is a polymer mainly composed of methyl methacrylate and the sheath component is a polymer containing at least 20% by weight of fluorine. An optical device characterized in that the core component of the fiber is manufactured under the following general formula: % formula % (where, T: die temperature (°C), E: heat shrinkage rate (X)) A method for producing fibers is provided.

The optical fiber manufacturing method of the present invention has excellent light guiding loss and flexibility in the core component polymer, and can significantly improve reliability as an optical signal transmission medium. Furthermore, unexpectedly, it is possible to provide an optical fiber with excellent flexibility and almost no decrease in light guiding loss even at temperatures at which the conventionally proposed optical fibers mentioned above cannot be used at all. It is.

The features of the present invention can be summarized in the following points.

1) When the core component is manufactured under the general formula % formula % (where, T: die temperature ("C), E: heat shrinkage rate (%)), light transmission and flexibility will be improved. It can be greatly improved.

2) The sheath component has good adhesion with the core component, and a transparent sheath component with excellent mechanical strength such as flexibility can be stably formed.

3) The thermal properties of optical fibers are improved. In particular, when a polymer mainly composed of methyl methacrylate containing a methacrylic acid ester having an alicyclic hydrocarbon group having 8 to 20 carbon atoms is used as a core component, the heat resistance is significantly improved.

The polymer mainly composed of methyl methacrylate used as the core component in the present invention is a homopolymer or a copolymer of methyl methacrylate containing at least 60% by weight of repeating units of methyl methacrylate, and includes ethyl methacrylate, ethyl methacrylate,
Propyl methacrylate, butyl methacrylate, methacrylic ester, cyclohexyl methacrylate, or a copolymer containing a methacrylic ester having an alicyclic hydrocarbon group having 8 to 20 carbon atoms in the ester moiety, and 10% by weight or less of these Copolymers of methyl acrylate, ethyl acrylate, 2-ethylhexyl acrylate, and the like are useful. Among these, a copolymer containing 70% or more of methyl methacrylate units is particularly preferred as a core component because it is highly pure, extremely transparent, and easily available.

The methacrylic acid ester having an alicyclic hydrocarbon group having 8 to 20 carbon atoms in the ester moiety is obtained by esterifying methacrylic acid or more preferably its acid chloride with an alicyclic hydrocarbon monool of the formula ROH. It is created by

Alicyclic hydrocarbons/monols include 1-adamantanol, 2-adamantanol, 8-methyl-1-adamantanol, 8,5-dimethyl-1-adamantanol, 8-ethyladamantanol, 8-methyl- 5-Ethyl-1-adamantanol, 8,5.8-)liethyl-1-adamantanol and 8,5-dimethyl-8-ethyl-1-adamantanol, octahydro-4,7-
Mentafinden-5-'-ol, octahydro-4
, 7-mentunoinden-1-ylmethanol, p-menthanol 8, p-menthanol-2,8-hydroxy-2°6,6-trimethyl-bicyclo[8,1,1]hebutane, 8,7. Alicyclic hydrocarbons such as 7-drimethyl-4-hydroxy-bicyclo[4,1,O]hebutane, borneol, 2-methylcamphonol, fenthyl alcohol, t-menthanol, 2,2゜5-trimethylcyclohexanol, etc.・You can give monool,
A copolymer consisting of a methacrylic ester corresponding to this can be exemplified.

Among these methacrylic acid esters, particularly preferred are 1-adamantyl methacrylate, 2-adamantyl methacrylate, 8,5-dimethyl-1-adamantyl methacrylate, bornyl methacrylate, and P-methacrylate.
Menthane, 2-methylcamphon methacrylate, fentyl methacrylate, 2-menthyl methacrylate, and 2,2.5-trimethylcyclohexane methacrylate can be mentioned.

Another important component of the present invention, the sheath component, is a polymer containing at least 20% by weight of fluorine. Preferred polymers include fluororesins, thermoplastic fluororubbers, and fluororubbers. Examples of the fluororesin include fluoroalkyl σ-fluoroacrylates, alkyl α-fluoroacrylates, fluoroalkyl methacrylates, fluorine-containing polymers and copolymers of fluorine-containing olefins, and the like.

α-Fluoroalkyl acrylate polymer, α-
The alkyl fluoroacrylate and fluoroalkyl methacrylate polymers are preferably those whose homopolymer has a softening temperature of about 50° C. or higher and a refractive index of 1.48 or lower.

Specifically, the preferable α-fluoroalkyl acrylate or fluoroalkyl methacrylate polymer used in the present invention includes α-fluoroacrylate 2
, 2.2-trifluoroethyl, α-fluoroacrylate 1,1,1゜3,3.8-hexafluoro-2-propyl, α-fluoroacrylate 1,1-diethyl-2゜2.8, 4,4.4-hexafluoro-1-butyl, α
-1-propyl-fluoroacrylate-2,2,8,4,
4,4-hexafluoro-1-butyl, 1,1-dimethyl-8-trifluoromethyl-α-fluoroacrylate
2,2,4,4゜4-pentafluorobutyl, α-fluoroacrylic acid 2-trifluoromethyl-2,2,8゜8-tetrafluoropropyl, α-fluoroacrylic acid 2,2,3,3- Tetrafluoropropyl, 1,1-dimethyl-2,2,3,3-tetrafluoropropyl α-fluoroacrylate, 2-trifluoromethyl-3,3,8-trifluoropropyl α-fluoroacrylate, and Examples include corresponding fluoroalkyl methacrylates, methyl α-fluoroacrylate, ethyl α-fluoroacrylate, propyl α-fluoroacrylate, and the like.

Particularly preferred is α-fluoroacrylic acid 2°2, 2-
1 Lifluoroethyl 1. 2゜2.2-)lifluoroethyl methacrylate, α-fluoroacrylic acid 2,2,3,
3-tetrafluoropropyl, methacrylic acid 2,2,3
, 3-tetrafluoropropyl, α-fluoroacrylate 1゜1-dimethyl-2,2,3,3-tetrafluoropropyl, 1,1-dimethyl-2,2,3 methacrylate
, 3-tetrafluoropropyl, α-fluoroacrylate 2-trifluoromethyl-8,8,8-trifluoropropyl, 2-trifluoromethyl-8 methacrylate,
8,8-Trifluoropropyl, methacrylic acid 2.2.
8゜3,3-pentafluoropropyl, α-fluoroacrylic acid 1,1,1,3,3.8-hexafluoro-
2-propyl, methacrylic acid 1,1,1゜3,3.8-
Examples include polymers consisting of hexafluoro-2-propyl, methyl α-fluoroacrylate, and the like.

In addition, examples of the fluorine-containing olefin polymer include vinylidene fluoride-tetrafluoroethylene copolymer, trifluoroethylene-vinylidene fluoride copolymer,
Examples include vinylidene fluoride-tetrafluoroethylene-hexafluoropropene copolymer.

Thermoplastic fluororubber has a soft segment made of a fluororubber phase and a hard segment made of a fluororesin phase in its molecule, and physical crosslinking occurs in the fluororesin phase at room temperature.

It has rubber elasticity and behaves similar to thermoplastic plastics at high temperatures above its melting point. A typical example is Daiel Thermoplastic (manufactured by Daikin Industries, Ltd.).

Preferred fluororubbers include vinylidene fluoride-hexafluoropropene copolymer, vinylidene fluoride-pentafluoropropene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, and the like. Particularly preferred is vinylidene fluoride-hexafluoropropene copolymer.

The most important constituent feature of the present invention is that when manufacturing an optical fiber having a core-sheath structure consisting of the above-mentioned core and sheath components, the core component of the optical fiber is expressed by the general formula; T: Gui temperature (℃), E: Heat shrinkage rate (
%). ) The purpose of the present invention is to manufacture optical fibers with excellent light transmission properties and flexibility, which are manufactured under regulations to satisfy the following conditions.

As mentioned above, there are two methods for producing optical fibers with a core-sheath structure: the composite spinning method and the coating method. In both methods, the drawing is usually performed using a guide set at a predetermined temperature when shaping the core component. This is done by adjusting the discharge amount and winding speed. At that time, spinning is carried out continuously while maintaining a substantially constant value that satisfies the range of the above general formula.

Optical ls whose E-TXIO value exceeds 1.9
The optical transmission properties of the fibers are significantly lowered, and if the fiber does not reach 1.0, the flexibility is significantly lowered, making it impossible to use it as an optical W4 fiber in practice. If the value of T exceeds 250, the optical fiber tends to be colored pale yellow, resulting in a decrease in light transmission properties. Moreover, if it does not reach 200, the flexibility of the optical fiber will be significantly reduced and it will become unusable for practical use. E is the shrinkage rate (%) after heating at 150° C. for 1 hour.

Here, the heat shrinkage rate at 150°C was measured by the following method. First, eight optical fibers cut into lengths of io and o were placed on an aluminum plate (0.6 m thick, surface coated with fine talc powder) that had been placed in an electric oven at 150°C.・After 1 hour, the aluminum plate was gently taken out of the electric oven, cooled to room temperature, and then the heat shrinkage rate was measured by measuring the length of the shrunken optical fiber. When the diameters of the optical fibers were different, correction was made based on the relationship between the fiber diameter and shrinkage rate determined in advance.

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, it is easy for foreign substances contained in the water to get mixed into the polymer.Also, since there is a possibility that foreign substances can be mixed in during the dehydration process, foreign substances can be removed by filtration. It is necessary to remove. A more desirable method is to produce the core component polymer in two steps: a continuous bulk polymerization step at high temperature and a subsequent continuous separation step of volatile components mainly containing residual unreacted monomers. There is a method in which the polymer manufacturing step and the optical fiber manufacturing step are performed in a continuous process. A production method in which the core component is bulk-polymerized and then the shape of the core component and the sheath component are formed from the obtained polymer by double extrusion is also a desirable method.

Examples of the radical polymerization initiator used in each of the above polymerizations include 2,2'-azobis(isobutyronitrile), 1,1'-azobis(cyclohexanecarbonitrile), 2,2'-azobis(2,4 azo compounds such as -dimethylvaleronitrile), azobisisobutanol diacetate azo-text-butane;
t-butyl peroxide, dicumyl peroxide,
Examples include organic peroxides such as methyl ethyl ketone peroxide, di-tert-butyl perphthalate, di-@ert-butyl peracetate, and di-tert-amyl peroxide. The addition ratio of the polymerization initiator is preferably 0.001 to 1 mol % based on the monomer.

Additionally, in order to control the molecular weight, tert-butyl, n-butyl, n-octyl, n-dodecyl mercaptan, etc. are used as chain transfer agents in the polymerization system in an amount of about 1% per monomer.
It is added in an amount of mol% or less.

- 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, there is no effect on optical transmission due to the manufacturing method, but dust should be removed by filtration methods to prevent foreign matter from getting mixed in. It is preferable to manufacture a polymer.

The ratio of core component to sheath component is approximately 70280-98 by weight.
:2, preferably about 80:20 to 95:5. Furthermore, the outer diameter of the optical fiber having a core-sheath structure is approximately 0.
15-1.5 m, preferably about 0.20-1.5 m.
0 wam.

As described above, the present invention is a manufacturing method for optically delicate products having a core-sheath structure, which has excellent light transmission properties and flexibility by drawing down a core component having a specific melt flow index at a specific ratio. Furthermore, by using a specific polymer for the core component, it is possible to widen the applicable temperature range of conventional optical fibers, and it also has excellent heat resistance and flexibility. The present invention provides optical fibers with extremely high industrial value.

Since the optical fiber manufactured by the method of the present invention can have a normal temperature of 110°C or higher, for example,
This enables application to automobiles, ships, aircraft, robots, etc. In addition, the range of application can be expanded by relaxing temperature-limiting conditions for in-plant and in-building communications.

Next, the present invention will be explained in more detail with reference to examples, but the present invention should not be limited by these in any way.

In addition, a diffraction grating spectrometer using a halogen tungsten lamp as a light source was used to measure the light guide loss in the examples.
The output intensities of the optical fiber to be measured and the reference optical fiber at a wavelength of nm were read using a silicon photodiode. Letting the intensities of light at the entrance and exit of optical llll1 with different fiber lengths L (Km) be Io and I, respectively, the light guide loss α was determined by the following formula.

(dB/h) = 'L-1'''g (+) In this equation, the smaller the α value, the better the optical transmission performance.

The flexibility test was performed by tying a knot using an optical fiber with a length of 15 m, pulling both ends at a pulling speed of 2 w/min, and measuring the knot strength when cutting.

Further, the heat resistance test was conducted by heating the obtained optical fiber for a predetermined period of time, and then measuring and comparing the light guide loss at the initial stage and after heating.

Example 1 25% by weight of bornyl methacrylate, 72NIL% of methyl methacrylate, 8% by weight of methyl acrylate purified by vacuum distillation, and further 0.025% by weight of n-dodecylmercaptan, 2,2% based on these monomers. '-Azobis(2,4-dimethylvaleronitrile) 0.10% by weight was added to prepare a monomer mixture in the absence of oxygen,
The mixture was sent to a reaction tank maintained at 150° C. and prepolymerized with a residence time of 8 hours. Next, polymerization was completed in a screw conveyor maintained at 200°C with a residence time of 2 hours;
゛C, Intrinsic viscosity determined from chloroform solution [η]: 0.
90 and a refractive index of 1.49. Further, this polymer was fed to a vented extruder heated to 245"C,
The polymer in the form of a strand with a diameter of 7 ribs is discharged from the center of a double extrusion nozzle maintained at 225°C as a core component, and while it is drawn down, α-fluoroacrylic [2,2,3, 3-Tetrafluoropropyl-methyl methacrylate-methyl acrylate copolymer (copolymer composition = 87:10:3% by weight), monthly refraction rate 1.41, molten
A strand with a core-sheath structure having a diameter of 1 mm and a heat shrinkage rate of 70% was obtained by melt-coating a strand with a viscosity of 8 x 10 voids (210''C) as a sheath component.The thickness of the sheath was 1.0 lm.

When the light guide loss of this optical fiber was measured at 25°C and 80°C, it was found that at a wavelength of 650 nm, it was 2.
They were 20dB/Km and 220dB/Km. After heat-treating this optical fiber at 120° C. for 72 hours, the light guide loss was measured again and was 240 dB/Km, indicating excellent heat resistance. Nodule strength is 6.2 Kf/lj
Met.

Examples 2 to 5 After obtaining core component polymers in the same manner as in Example 1, by adding die temperatures, T, and draw-down speeds, optical fibers with different heat shrinkage rates and E (0.85 to 0.85%) were obtained. 75 m)
was manufactured. Table 1 shows the results of measuring the light guide loss, heat resistance, and flexibility of the obtained optical fiber.

Comparative Examples 1 to 4 In Examples 2 to 5, optical la! with different heat compressibility by adding die temperature was used. # was manufactured.

Table 2 shows the results of measuring the light guide loss, heat resistance, and flexibility of the obtained optical fiber.

Claims (3)

[Claims] (1) When producing an optical fiber having a core-sheath structure in which the core component is a polymer mainly composed of methyl methacrylate and the sheath component is a polymer containing at least 20% by weight of fluorine, the core component of the optical fiber is General formula: 1≦E・T×10＾−＾4≦1.9 200≦T≦250 (where, T: die temperature (°C), E: heat shrinkage rate (
%). ) A method for producing an optical fiber, characterized in that it is produced under the following conditions. (2) A patent characterized in that a polymer mainly composed of methyl methacrylate contains 3 to 40% by weight of a methacrylic ester having an alicyclic hydrocarbon group having 8 to 20 carbon atoms in the ester moiety A method for manufacturing an optical fiber according to claim 1. (3) The polymer containing at least 20% by weight of fluorine is α
-2,2,2-trifluoroethyl fluoroacrylate, 2,2,2-trifluoroethyl methacrylate, α-
2,2,3,3-tetrafluoropropyl fluoroacrylate, 2,2,3,3-tetrafluoropropyl methacrylate, 1,1-dimethyl α-fluoroacrylate
2,2,3,3-tetrafluoropropyl, 1,1-dimethyl-2,2,3,3-tetrafluoropropyl methacrylate, 2-trifluoromethyl-3,3,3-triα-fluoroacrylate Fluoropropyl, 2-trifluoromethyl-3,3,3-trifluoropropyl methacrylate, 2,2,3,3,3-pentafluoropropyl methacrylate, α-fluoroacrylic acid 1,1,1,
Polymer consisting of 3,3,3-hexafluoro-2-propyl, 1,1,1,3,3,3-hexafluoro-2-propyl methacrylate, methyl α-fluoroacrylate, vinylidene fluoride-tetra Claim 1, which is a fluoroethylene copolymer, a trifluoroethylene-vinylidene fluoride copolymer, a vinylidene fluoride-tetrafluoroethylene-hexafluoropropene copolymer, or a vinylidene fluoride-hexafluoropropene copolymer A method for producing an optical fiber as described in Section 1.