JP2945108B2 - Manufacturing method of plastic optical fiber - Google Patents

Description

The present invention relates to a method for producing a low-loss, heat-resistant plastic optical fiber.

(Prior Art) Conventionally, a fiber for transmitting light is made of quartz glass or plastic. Silica glass-based optical fibers are widely used for long-distance transmission because of their low loss. Although plastic optical fibers have higher transmission loss than quartz-based optical fibers, they have good flexibility, are lightweight, and are easy to process, and are therefore used in electronic devices and the like for short-distance transmission.

Many plastic optical fibers currently in practical use have a core material made of poly (methyl methacrylate) with good transparency, but the glass transition point of poly (methyl methacrylate) is 100 ° C or less. Therefore, these plastic optical fibers cannot be used for control signals in an engine room of an automobile which is heated to a high temperature (for example, 150 ° C. or more). Therefore, various attempts have been made to improve the heat resistant temperature of the plastic optical fiber.
For example, in order to improve the heat resistance of poly (methyl methacrylate), a method of copolymerizing methacrylic acid and N-arylmaleimide (Japanese Patent Publication No. 43-9975) or a method of imidizing a part of poly (methyl methacrylate) (JP-A-60-184212
No.) and other methods have been proposed.

Recently, polycarbonate has been used as a core material other than poly (methyl methacrylate) (JP-A-57-46204, JP-A-61-6604).

(Problems to be Solved by the Invention) However, when obtaining a plastic optical fiber having heat resistance such as plastic, particularly a conventional polycarbonate, the molding temperature is increased and coloring due to thermal deterioration of the resin occurs. In addition, when this molding is performed by a normal extrusion method, the resin and the metal body come into contact with each other, impurities are mixed in the resin, and the resin is not completely extruded and remains in the extruder, so that coloring may occur. In addition, ram extrusion under reduced pressure has also been studied, but preforming is necessary, and in this case, contact and friction between the metal and the core material occur at high temperatures, which has caused coloring of the core material. .

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a low-loss heat-resistant plastic optical fiber by solving the above problems.

(Means for Solving the Problems) The above object of the present invention has been achieved by the following inventions.

(1) A method for producing a plastic optical fiber having a core formed by stretching a plastic preform, the glass preform having a glass transition point higher than the softening point of the core material, and a main chain containing a fluorine-substituted alicyclic group or heterocyclic group. The concave portion of the mold is coated with a solution of a fluororesin having a solution, the core material is introduced into the mold, and the temperature is increased to at least the melting point of the core material at least finally under an inert gas or vacuum, and defoaming is performed. A method for producing a plastic optical fiber, wherein a core preform is obtained by cooling the preform.

(2) The method for producing a plastic optical fiber according to (1), wherein the core material is polycarbonate or polyarylate.

In the present invention, since the fluorocarbon resin having a fluorine-substituted alicyclic group or heterocyclic group in the main chain is coated in the inside of the mold, there is no contact between the resin and the casting and contamination of impurities into the resin is small.

Further, since the fluororesin and these core materials have good releasability, they can be obtained from the mold without damaging the preform.

Here, the fluorine-substituted alicyclic group or heterocyclic group in the main chain is
It is preferably a 5- to 7-membered saturated group, and specific examples of the fluororesin include, but are not limited to, the following.

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

Among these, the following fluororesins having a ring structure in the main chain are typical.

With a copolymer.

Such a fluororesin having a cyclic group in its main chain is available as a commercial product, for example, Teflon AF-1600 (glass transition point 160 ° C), Teflon AF-2400 (glass transition point 240 ° C).
(Both trade names, manufactured by DuPont), CYTOP (glass transition point: 130 ° C.) (trade name, manufactured by Asahi Glass Co., Ltd.) and the like.

And such fluororesin are usually fluorinated hydrocarbon _{(C m F m, F m} H p F n) to dissolve in, dissolved in the fluorine-containing solvent, is applied to the mold surface with a solution. The solvent is removed to obtain a fluororesin coating layer on the mold surface.

Further, it is preferable to select such a fluororesin having a glass transition point higher than that of the core material by 20 ° C. or more. If the temperature is lower than 20 ° C., the coating material may be dissolved during melt molding of the core material.

The mold may be made of metal, glass, quartz, or the like, and is not particularly limited.

In addition, since these fluororesins have better adhesiveness to the above-mentioned glass, quartz, and metal than the resin used as the core material, once applied and coated, they can be used repeatedly.

Next, in the deaeration, dehydration, defoaming and molding of the core material, the water in the core material resin is removed under reduced pressure at a temperature not higher than the glass transition point, and the temperature is increased under reduced pressure to a temperature above the glass transition point and the melting point. It is preferable to perform degassing while keeping the temperature below, and defoaming while maintaining the glass transition point or higher and the melting point or higher, thereby simultaneously preforming the preform. The dehydration temperature is preferably between the glass transition point of the resin minus 60 ° C. and the glass transition point. This is because if the temperature is lower than the glass transition point by 60 ° C. or more, dehydration is not performed efficiently. If the temperature is higher than the glass transition point, foaming may occur.

There is no problem if the degassing temperature is higher than the glass transition point and lower than the melting point, but a temperature lower by about 10 to 20 ° C. than the melting point is preferable in order to proceed efficiently.

The molding is performed at a temperature higher than the melting point under reduced pressure, but preferably at a temperature lower than the melting point plus 100 ° C. If the temperature is too high, the resin is decomposed and colored.

The molding may be performed in a state where the reduced pressure is maintained during the molding, but may be a state where an inert gas is introduced under normal pressure or under pressure, or a combination of reduced pressure and increased pressure. The inert gas referred to here is a gas that does not attack a core material such as polycarbonate at a high temperature, and examples thereof include argon, helium, and nitrogen.

By maintaining the pressure above the melting point under reduced pressure, impurities of low molecular weight are also removed at the same time, the purity of the core material is increased, and the transparency is improved. Also, because it is degassed under reduced pressure,
Air bubbles remaining in the preform are removed, and an increase in loss due to scattering can be prevented.

Further, when cooling the formed preform, although there is no particular limitation, it is better to perform slow cooling. Further, it is preferable to perform cooling while pressurizing with an inert gas. This is because the preform is easily distorted when cooled rapidly or under reduced pressure. After cooling, the preform is preferably washed with the above-mentioned fluorine-containing solvent. In this case, if not washed, there is a possibility that the preform is stuck with the fluororesin.

A core part is obtained by stretching the obtained preform at a temperature equal to or higher than the glass transition point and equal to or lower than the melting point. In performing the stretching, it is preferable to perform the stretching at a temperature higher than the glass transition point by 15 ° C. or more. If the temperature is too low, the resin may be whitened.

The formation of the clad portion is performed by, for example, applying a fluororesin having the above-mentioned cyclic group dissolved in a fluorinated solvent that does not attack the core material to the outside of the core portion, and removing the solvent. The fluororesin to be applied may be the same or different from the fluororesin coated on the mold, and is not particularly limited.

Also, by applying a fluororesin having the above-mentioned cyclic group to the same or different main chain dissolved in a fluorinated solvent to the preform obtained by the above-described method and removing the solvent, the core portion preform outside the preform A plastic optical fiber having a core-cladding portion may be obtained by obtaining a preform in which a fluororesin layer is laminated and stretching the preform above the glass transition point and the melting point of the core material. At this time, a resin whose glass transition point is the same as or higher than that of the core material and which is not higher than 80 ° C. is selected. When the glass transition point of the clad material is lower than that of the core material, a flow occurs at the time of stretching, and the heat resistance of the practicable optical fiber is reduced. If the temperature difference is larger than 80 ° C., stretching may not be performed properly.

(Examples) The present invention will be described in more detail based on examples.

Example 1 Teflon AF-2400 (trade name, manufactured by Dubon) was dissolved in Fluorinert FC-72 (trade name, manufactured by Sumitomo 3M) as a 1% solution, and a pre-form was formed as a ground portion 1 as shown in FIG. It was applied to the inner surface of a mold of a preform made of glass comprising part 2 and the solvent was removed. Panlite L-1250 (trade name, manufactured by Teijin Chemicals Ltd.) (glass transition point: 149 ° C., softening point: 170 ° C.) was added as a polycarbonate, and 130
Vacuum was applied at 8 ° C. for 8 hours. 210 under vacuum
It was evacuated at 8 ° C. for 8 hours, and was further exposed at 270 ° C. for 5 hours to mold. Nitrogen was introduced, and the mixture was gradually cooled to room temperature in 6 hours to obtain a preform.
After washing with FC-77, a good preform without scratches was obtained.

The obtained preform was stretched in a furnace set at 240 ° C. to obtain a core portion.

Teflon AF-2400 was dissolved in Fluorinert FC-72 as a 2% solution, and the above solution was applied using a coating apparatus as shown in FIG. 3 and the solvent was degassed to form a clad layer (thickness: 5%).
μm). In the figure, 10 is a core material, 11 is a nipple, 12 is a die (fluororesin solution part), and a fluororesin solution is applied to a core passing therethrough. Reference numeral 13 denotes a coating chamber (constant temperature chamber), 14 denotes a gas inlet thereof, and 15 denotes a gas outlet thereof. 16
Is a solvent removal chamber (constant temperature chamber), which has the function of removing the solvent from the fluororesin solution applied to the core to form a clad layer, 17 is a heater, 18 is a gas inlet, and 19 is a gas outlet. Show. 20 indicates a take-up machine.

The transmission loss of the obtained plastic optical fiber is 11m−1
It was 800 dB / km (770 nm) as determined by the cutback method at m.

Example 2 Teflon AF-2400 was dissolved in Fluorinert FC-72 as a 1% solution, and was applied to the inner surface of a preform mold made of stainless steel consisting of a joint part 3 and a preform forming part 4 as shown in FIG. Apply and remove solvent. Panlite L-1250 was put therein, and evacuated at 130 ° C. for 8 hours. Evacuation was performed at 210 ° C. for 8 hours in a state of being evacuated, and the molded article was further exposed at 270 ° C. for 5 hours.
Nitrogen was introduced therein, and the mixture was gradually cooled to room temperature at 10 atm for 6 hours to obtain a preform, which was washed with Prolinert FC-77 to obtain a good preform without scratches. The obtained preform was stretched in a furnace set at 240 ° C. to obtain a core portion.

Teflon AF-2400 is dissolved in Fluorinert FC-72 as a 2% solution, and the above solution is applied using a coating apparatus as shown in FIG. 3 and the solvent is degassed to obtain a clad layer (about 5 μm thick). Was.

The transmission loss of the obtained plastic optical fiber is 11m−1
It was 800 dB / km (770 nm) as determined by the cutback method at m.

Example 3 Teflon AF-2400 was dissolved in Fluorinert FC-72 as a 1% solution, applied to the inner surface of a preform mold made of stainless steel as shown in FIG. 2, and the solvent was removed. Panlite L- 1250 was put therein, and evacuated at 130 ° C. for 8 hours. Further molding was performed by exposing at 270 ° C. for 8 hours. Nitrogen was introduced, and the mixture was gradually cooled to room temperature at 10 atm for 6 hours to obtain a preform, which was washed with Fluorinert FC-77 to obtain a good preform without scratches.

The obtained preform was stretched in a furnace set at 240 ° C. to obtain a core portion. Teflon AF-2400 was dissolved in Fluorinert FC-72 as a 2% solution, and the above solution was applied using a coating apparatus as shown in FIG. 3 and the solvent was degassed to obtain a clad layer.

The transmission loss of the obtained plastic optical fiber is 11m−1
It was 800 dB / km (770 nm) as determined by the cutback method at m.

Comparative Example 1 Panlite L-1250 was placed in a preform mold made of stainless steel as shown in FIG. 2 and evacuated at 130 ° C. for 8 hours. Evacuation was performed at 210 ° C. for 8 hours in a state of being evacuated, and the molded article was further exposed at 270 ° C. for 5 hours. Nitrogen was introduced into the mixture, and the mixture was gradually cooled to room temperature at 10 atm for 6 hours.

When the preform was taken out of the mold, the preform adhered to the mold, the surface was peeled off, and the preform was damaged and no good preform was obtained.

Comparative Example 2 Panlite L-1250 was placed in a mold of a preform made of glass as shown in FIG. 1 and evacuated at 130 ° C. for 8 hours. Evacuation was performed at 210 ° C. for 8 hours in a state of being evacuated, and the molded product was further exposed at 270 ° C. for 8 hours. This was introduced with elemental material, and gradually cooled to room temperature in 6 hours. The glass broke during cooling. I tried to strip the glass and core material but it didn't work.

Example 4 Teflon AF-2400 was dissolved in Fluorinert FC-72 as a 1% solution, applied to the surface of a preform mold made of glass as shown in FIG. 1, and the solvent was removed. The pan light L-1250 was put in this, and it evacuated. Table 1 shows the preform molding conditions. The molding and cooling method of the preform was performed in the same manner as in Example 3. Also,
Table 1 shows the moldability. The obtained preform was washed with Fluorinert FC-77.

The obtained preform was stretched in a furnace set at 240 ° C. to obtain a core portion.

Teflon AF-2400 was dissolved in Fluorinert FC-72 as a 2% solution, and the above solution was applied using a coating apparatus as shown in FIG. 3 and the solvent was degassed to obtain a clad layer.

Table 1 shows the transmission loss (770 nm) of the obtained plastic optical fiber obtained by the cutback method at 11 m-1 m.

Example 5 Teflon AF-2400 was dissolved in Florinert FC-72 as a 1% solution, applied to the inner surface of a preform mold made of glass as shown in FIG. 1, and the solvent was removed. Among these, polyarylate resin U-polymer P-5001 (trade name,
(A glass transition point of 180 ° C. and a softening point of 200 ° C.) were added, and the mixture was evacuated at 140 ° C. for 8 hours. Evacuation was performed at 230 ° C. for 8 hours in a state of being evacuated, and the molded product was further exposed at 320 ° C. for 5 hours. Nitrogen was introduced therein, and the mixture was gradually cooled to room temperature in 6 hours to obtain a preform. The obtained preform was washed with Fluorinert FC-77.

The obtained preform was stretched in a furnace set at 240 ° C. to obtain a core portion. Fluorinert Teflon AF-2400
The clad layer was obtained by dissolving in FC-72 as a 2% solution, applying the above solution using a coating apparatus as shown in FIG. 3, and degassing the solvent.

The transmission loss of the obtained plastic optical fiber is 11m−1
1500dB / km (770nm) as determined by the cutback method at m
Met.

Example 6 Teflon AF-2400 was dissolved in Florinert FC-72 as a 1% solution, applied to the inner surface of a glass preform mold as shown in FIG. 1, and the solvent was removed. Panlite L-1250 was put therein, and evacuated at 130 ° C. for 8 hours. Vacuuming was performed at 210 ° C. for 8 hours in a vacuum state, and the temperature was raised to 270 ° C. and the pressure was gradually reduced to maintain the temperature for 5 hours, and nitrogen was introduced for 1 hour to perform molding. This was gradually cooled to room temperature under 10 atm for 6 hours to obtain a preform. The obtained preform was washed with Fluorinert FC-77.

The obtained preform was stretched in a furnace set at 240 ° C. to obtain a core portion.

Teflon AF-2400 was dissolved in Fluorinert FC-72 as a 2% solution, and the above solution was applied using a coating apparatus as shown in FIG. 3 and the solvent was degassed to obtain a clad layer.

The transmission loss of the obtained plastic optical fiber is 11m−1
It was 800 dB / km (770 nm) as determined by the cutback method at m.

Example 7 Teflon AF-2400 was dissolved in Florinert FC-72 as a 1% solution, applied to the inner surface of a glass preform mold as shown in FIG. 1, and the solvent was removed. Panlite AD-5503 (trade name, manufactured by Teijin Chemicals Ltd.) (glass transition point 142 ° C., softening point 170 ° C.) was put therein, and evacuated at 130 ° C. for 8 hours. Evacuation was performed at 210 ° C. for 8 hours in a state of being evacuated, and the molded article was further exposed at 270 ° C. for 5 hours. Nitrogen was introduced therein, and the mixture was gradually cooled to room temperature in 6 hours to obtain a preform. The obtained preform was washed with Fluorinert FC-77.

Teflon AF-1600 was dissolved in Fluorinert FC-72 as a 4% solution in the obtained preform, and was repeatedly applied to the surface to form a clad layer.

The preform thus obtained was drawn and spun at 225 ° C.

Thus, a plastic optical fiber having a clad layer was obtained. The transmission loss of the plastic optical fiber thus obtained by the 11-1m cutback method is 1500 dB / km (770
nm).

Comparative Example 3 Panlite AD-5503 as core material, clad material
FEPs were selected and introduced into a double extruder equipped with a spinning nozzle. The double extruder head was set at 320 ° C. and spun with an inner diameter of 1 mm and an outer diameter of 1.1 mm.

The fiber loss value at 770 nm was 1600 dB / km.

(Effects of the Invention) In the present invention, by mixing a specific fluororesin on the inner surface of a mold with a solution, introducing a core material, forming a preform, and stretching the preform, contamination of the core material with impurities is prevented. A plastic optical fiber with reduced transmission loss is obtained. By using this fluororesin, it is also possible to wash with a solvent after molding the preform to remove what has adhered to the preform. In the present invention, by performing defoaming and molding of the preform, low molecular weight impurities are simultaneously removed, and the purity and transparency of the core material can be improved.

[Brief description of the drawings]

FIG. 1 is a perspective view of one example of a preform mold used for carrying out the present invention, and FIG. 2 is a side view of another example of the same mold. FIG. 3 is a sectional view of an optical fiber cladding layer coating apparatus. DESCRIPTION OF SYMBOLS 1 ... Joining part 2 ... Preform forming part 3 ... Joint part 4 ... Preform forming part

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Michio Yamaguchi 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Co., Ltd. (56) References JP-A-63-104003 (JP, A) (58) ) Surveyed field (Int.Cl. ⁶ , DB name) G02B 6/00

Claims (2)

(57) [Claims] 1. A process for producing a plastic optical fiber having a core formed by stretching a plastic preform, wherein the main chain has a glass transition point higher than the softening point of the core material, and the main chain has a fluorine-substituted alicyclic group or heterocyclic group. Fluoropolymer having a group is coated with a solution on the concave portion of the mold with a solution, the core material is introduced into the mold, and the temperature is raised to at least the melting point of the core material at least finally under an inert gas or vacuum, and defoaming and molding are performed. And a method of producing a plastic optical fiber, wherein the core preform is obtained by cooling the preform. 2. The method according to claim 1, wherein the core material is polycarbonate or polyarylate.