JPH04124602A - Manufacture of plastic optical fiber - Google Patents

Abstract

PURPOSE:To obtain the plastic optical fiber which is large in the adhesive strength between the core and clad and small in loss by coating the core material such as polycarbonate with fluororesin which has a fluoridated ring part at a principal chain. CONSTITUTION:After the core material is made of heat-resisting synthetic resin like polycarbonate, its outside is coated with the fluororesin which has a fluorine-substituted alicyclic group or heterocyclic group at a principal chain while dissolved in a fluorine solvent; and the solvent is removed to form a clad layer. The alicyclic group or heterocyclic group of the principal chain shown here is preferably a saturated 5 - 7 member ring and shown by, for example, formulas (a), (b), and (c). Thus, the soluble fluororesin is applied to grow the clad layer and then resin which does not have excellent adhesive strength to the fluororesin like the polycarbonate resin is liquid at the time of core-clad contact, so that adhesive strength between the core and clad is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method of manufacturing a plastic optical fiber having high heat resistance.

(Prior Art) Conventionally, fibers for transmitting light have been made of quartz glass or plastic. Silica glass-based optical fibers have low loss, so they are currently used for long-distance transmission.Although plastic optical fibers have higher transmission loss than silica-based fibers, they are flexible, lightweight, and Furthermore, because it is easy to process, it is used in electronic equipment and the like for short-distance transmission.

Many of the plastic optical fibers currently in practical use have a core material made of highly transparent poly(methyl methacrylate), but poly(methyl methacrylate)
Since the glass transition point of plastic optical fibers is below 100°C, these plastic optical fibers cannot be used for control signals in the engine room of an automobile where the temperature is high (for example, above 150°C). Various attempts have been made to improve this.

For example, in order to improve the heat resistance of poly(methyl methacrylate), there is a method of copolymerizing methacrylic acid and N-arylmaleimide (Japanese Patent Publication No. 43-9753), and a method of imidizing a part of poly(methyl methacrylate). (Unexamined Japanese Patent Publication 1986)
184212) have been proposed.

Furthermore, in recent years, polycarbonate has come to be used as a core material other than poly(methyl methacrylate) (Japanese Patent Application Laid-Open Nos. 57-46204 and 61-6604).

(Problem to be Solved by the Invention) However, conventionally, fluororesins such as FEP and PFA have been used as the sheath material (cladding material) of Plus Deck optical fibers made of heat-resistant core materials such as polycarbonate. was. However, these resins have low adhesion to polycarbonate, resulting in peeling between the core and cladding.Also, although there are recent examples of coatings with fully substituted fluororesins having cycloaliphatic moieties in the main chain, ordinary double-layered In the extrusion method, peeling occurs between the polycarbonate core material and the polycarbonate core material.

An object of the present invention is to provide a method for manufacturing a highly heat-resistant plastic optical fiber with good adhesion between the core and cladding.

(Means for Solving the Problems) The above object of the present invention is to form a core material, and then, on the outside thereof, a fluorine-containing material having a fluorine-substituted alicyclic group or a heterocyclic group in its main chain is dissolved in a fluorine-based solvent. This was achieved by a method of manufacturing a plastic optical fiber, which is characterized in that a resin layer is formed by applying a resin and removing a solvent.

The main chain alicyclic group or heterocyclic group shown here is preferably a saturated 5- to 7-membered ring, and examples include the following, but the present invention is not limited thereto.

(c) (d) A copolymer of one or more of the monomers constituting the above (a), (b), and (c) and another copolymerizable fluorine-containing monomer.

Among these, fluororesins having a ring structure in the main chain as shown below are representative.

/\ FJCFJ Copolymer.

Such fluororesins having a cyclic group in the main chain are available as commercial products, such as Teflon AF-1600, Theon AF-2400 (trade name, manufactured by DuPont), and Cytotsubu (trade name, manufactured by Asahi Glass Co., Ltd.). etc.

When a cladding layer is grown by applying the above-mentioned soluble fluororesin using the method of the present invention, even materials such as polycarbonate resin, which do not have very good adhesion to the fluororesin, remain in a liquid state when in contact with the core cladding. This increases the adhesion between the core cladding.

In the present invention, the fluorine-containing solvent for dissolving the fluororesin can be appropriately selected and used. For example, CmF
n (fluorine carbide) is used.

This fluorine-containing solvent does not attack the core material.

The coating step and the solvent removal step are carried out under a dry atmosphere containing 1% or less of moisture, preferably under an inert gas atmosphere. If the moisture content is more than 1%, the cladding layer will contain moisture, which will reduce transparency and increase transmission loss.Furthermore, if the moisture content is less than 1%, the adhesion between the core and cladding will increase. In addition, it is preferable to perform the coating under an inert gas in order to improve the adhesion between the core and cladding. Furthermore, it is preferable that the amount of water in the coating solvent is 500 ppm or less.
If it exceeds ppm, the transparency of the cladding portion may decrease and the adhesion between the core and cladding may decrease.

This fluororesin may be applied once, but it is better to apply it repeatedly. If the cladding layer is formed by one coating, the cladding layer may be too thin or the cladding layer may be formed non-uniformly. By repeating the application, the cladding layer becomes thicker and grows more uniformly.

However, when repeating the two steps of the above-mentioned coating step and solvent removal step, it is preferable that the concentration of the above-mentioned fluororesin in the above-mentioned fluorine-containing solvent be as high as possible without re-precipitation, and more preferably in a saturated state. If the fluororesin concentration is low, the coated cladding layer may dissolve into the solution again. Further, if the fluororesin is in a suspension state beyond a saturated solution state, the transparency of the coated fluororesin will be significantly reduced. The solubility of the fluororesin in a fluorine-containing solvent is usually 0.5% or more, preferably 0.8% or more.

The thickness of the cladding layer is usually up to 50 LLm, but it can be made thicker as appropriate.

In addition, regarding the relationship between the temperatures of the coating process and the solvent removal process, it is better to perform the solvent removal process in an atmosphere where the temperature of the solvent removal process is higher than the coating process by 5℃ or more. The solvent is removed and lamination proceeds. Further, the temperature of the solvent removed in the solvent removal step must be set below the boiling point of the solvent. This is because when the removal solvent reaches a temperature higher than its boiling point, foaming occurs and it no longer functions as a cladding layer.

Further, it is preferable to add a drying step of drying at a temperature higher than the boiling point of the solvent after repeatedly laminating the cladding layers or after a solvent removal step of removing each solvent. By adding this drying step, an annealing effect appears and the adhesion between the core and cladding becomes good. In addition, this solvent removal step must be performed after the solvent has been completely removed, and must be performed at a temperature below 25°C, which is the glass transition point of the core material. When proceeding to the drying process, foaming of the cladding layer occurs.

(Example) The present invention will be explained in more detail based on examples.

Examples 1 to 5 The cladding layer growth apparatus shown in FIG. 1 was used to apply the cladding layer and remove the solvent. In the figure, 1 is a nipple and 2 is a die (fluororesin solution part), through which the fluororesin solution is applied to the core. 3 indicates a coating chamber (temperature-controlled room), 4 its gas inlet, and 5 its gas outlet. 6
is a solvent removal chamber (constant temperature room), which has the function of removing the solvent from the fluororesin solution applied to the core to form a cladding layer; 7 is a heater; 8 is a gas inlet; 9 is a gas exhaust The outlet is shown, 10 is the core material, and 11 is the take-up machine. Polycarbonate-Panlite AD-55 as core material
03 (trade name, manufactured by Ondai Kasei Co., Ltd.), a core with a diameter of 1 mm was obtained by extrusion. Head temperature was 250°C. The fluororesin is Teflon AF-1600 (product name,
(manufactured by DuPont), and the fluorinated solvent used was (trade name) Fluorinert FC-72 (manufactured by Sumitomo 3M).

The coating conditions are shown in Table 1.

Further, the atmospheric temperature during coating was 20°C, and the atmospheric temperature during solvent removal was 35°C. In addition, Teflon AF-16
The solubility of 00 in FC-72 was about 4. Note that in Example 2, the test was carried out under an argon atmosphere. In Examples 1 to 5, the thickness of the cladding layer was 5 to 15 μm.

Transmission loss was measured for the obtained plastic optical fiber. Table 1 shows the increase in transmission loss when the wire was wound 10 times around a mandrel with a diameter of 20 mm.

Comparative Example 1.2 Polycarbonate Panlite AD-55 as core material
03. FEP (manufactured by Daikin Industries, Ltd.) and Teflon AF1600 were selected as cladding materials, and a plastic optical fiber was obtained by introducing the resin into a normal double extruder. The temperature of the die part was 350°C. The core diameter was 1 mm, and the cladding thickness was about 0.1 mm.

Transmission loss was measured for the obtained plastic optical fiber. Table 2 shows the increase in transmission loss when the wire was wound 10 times around a mandrel with a diameter of 20 mm.

Table 2 Example 6.7 Using the cladding layer growth apparatus shown in FIG. 1, the cladding layer was applied and the solvent was removed. The core material used was polycarbonate-Panlite AD-5503, and a core with a diameter of 1 mm was obtained in the same manner as in Example 1. Teflon AF-1600 was used as the fluorine resin, and Fluorinert FC-72 was used as the fluorine solvent. The coating conditions are shown in Table 3.

Further, the atmospheric temperature during coating was 20°C, and the atmospheric temperature during solvent removal was 35°C. The thickness of the cladding layer of the obtained fiber was 5 to 15 μm.

Transmission loss was measured for the obtained plastic optical fiber. Table 3 shows the increase in transmission loss when the wire was wound 10 times around a mandrel with a diameter of 20 mm.

Table 3 Example 8.9 The cladding layer growth apparatus shown in FIG. 1 was used to apply the cladding layer and remove the solvent. The core material used was polycarbonate-Panlite AD-5503, and a core with a diameter of 1 mm was obtained in the same manner as in Example 1. The fluororesin used was Teflon AF-2400 (trade name, manufactured by DuPont), and the fluorine solvent used was Fluorinert FC-72. The coating conditions are shown in Table 4.

The ambient temperature during coating was 20°C, and the ambient temperature during solvent removal was 40°C. In addition, Teflon AF-2
The solubility of 400 in FC-72 was about 2.

Also, the water content of the solution in which Teflon AF is dissolved is 300p.
It was about pm. Further, in Example 6, after the third solvent was completely removed, annealing was performed at 120° C. for 3 hours. The thickness of the obtained cladding layer is 5 to 15 μm
Met.

Transmission loss was measured for the obtained plastic optical fiber. Table 4 shows the increase in transmission loss when the wire was wound 10 times around a mandrel with a diameter of 20 mm.

Table 4 Example 10.11 The cladding layer growth apparatus shown in FIG. 1 was used to apply the cladding layer and remove the solvent. The core material used was polycarbonate-Panlite AD-5503, and a core with a diameter of 1 mm was obtained in the same manner as in Example 1. The fluororesin used was Teflon AF-2400, and the fluorinated solvent used was Fluorinert FC-72. The coating conditions are shown in Table 5.

Further, the atmospheric temperature during coating was 20°C, and the atmospheric temperature during solvent removal was 40°C. In addition, Teflon AF-2
The solubility of 400 in FC-72 was about 2.

Also, the water content of the solution in which Teflon AF is dissolved is 600p.
It was about pm.

Further, in Example IO, after the third solvent was completely removed, annealing was performed at 120° C. for 3 hours.

Transmission loss was measured for the obtained plastic optical fiber. Table 5 shows the increase in transmission loss when the wire was wound 10 times around a mandrel with a diameter of 20 mm.

Table 5 Comparative Example 3.4 The cladding layer growth apparatus shown in FIG. 1 was used to apply the cladding layer and remove the solvent. The core material used was polycarbonate-Panlite AD-5503, and a core with a diameter of 1 mm was obtained in the same manner as in Example 1. The fluororesin used was Teflon AF-2400, and the fluorinated solvent used was Fluoriner). A mixed solution of FC-72 and Freon was used. The coating conditions are shown in Table 6.

Further, the atmospheric temperature during coating was 20°C, and the atmospheric temperature during solvent removal was 40°C. In addition, Teflon AF-24
The solubility of 00 in the mixed solution was about 0.4.

Further, the water content of the solution of Comparative Example 3 was about 400 ppm, and the water content of the solution of Comparative Example 4 was about 600 ppm.

Transmission loss was measured for the obtained plastic optical fiber. Table 6 shows the increase in transmission loss when the wire was wound 10 times around a mandrel with a diameter of 20 mm.

Table 6 (Effects of the invention) In the present invention, by applying a fluororesin having a fluorinated ring to the main chain dissolved on the outside of a core material such as polycarbonate and removing the solvent,
A plastic optical fiber with high core-clad adhesion and low loss can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing one example of a cladding layer growth apparatus used for carrying out the present invention. l...Nipple 2...Dice 3...Coating chamber 4...Gas inlet 5...Gas outlet 6...Solvent removal chamber 7...Heater 8...Gas inlet 9 ...Gas discharge port 10...Core material 11...Take-up machine Figure ■

Claims (1)

[Claims] After forming the core material, a fluororesin having a fluorine-substituted alicyclic group or a heterocyclic group in the main chain dissolved in a fluorine-based solvent is applied to the outside of the core material, and a cladding layer is formed by removing the solvent. A method for manufacturing a plastic optical fiber, characterized by: