JPH11337745A - Apparatus for production of plastic optical fiber and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to produce a plastic optical fiber which is smaller in outside diameter fluctuation by providing the lower side of a heating and melting furnace with a constant temp. maintaining means for heating and controlling a plastic optical fiber so as to maintain the fiber at the specified temp. lower by a specific temp. or above than the glass transition point of the material forming the fiber. SOLUTION: A constant temp. heating section 20 comprises a cylindrical sub-furnace core tube 24 which is arranged to cover the drawing out route of the plastic optical fiber F drawn out downward from the heating and melting furnace 2 over a prescribed length L right below the heating and melting furnace 2, a sub-heater 26 which is disposed on the outer circumference thereof and a thermally insulating wall 28 which is disposed to enclose the outer circumference thereof. The sub-heater 26 is so controlled by a heating control means as to maintain the plastic optical fiber F drawn out of the heating and melting furnace 2 at the specified temp. lower by >=50 deg.C, more preferably >=60 deg.C than the glass transition point of the material forming the plastic optical fiber. Then, the plastic optical fiber F is eventually cooled successively at a prescribed temp. pattern change.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and a method for manufacturing a plastic optical fiber for manufacturing a plastic optical fiber by drawing from a preform.

[0002]

2. Description of the Related Art As an apparatus for producing a plastic optical fiber, for example, there is an apparatus using a drawing method as disclosed in JP-A-7-234324 and JP-A-7-234325.

[0003] This plastic optical fiber manufacturing apparatus includes:
As shown in FIG. 6, a heating / melting furnace 202 is formed by disposing a heating / melting heater 202 around an outer periphery of a furnace tube 201 and further surrounding the outer periphery with a heat insulating wall 203. A gas supply pipe 205 is provided in the heating and melting furnace 204.
An inert gas such as a nitrogen gas or a rare gas is sent in through the.

[0004] A preform P made of plastic is introduced into the heating and melting furnace 204 at a constant speed to be heated and melted, and a plastic optical fiber F is drawn from the preform P into a fiber shape and heated and melted. Furnace 2
04. When the plastic optical fiber F is drawn as described above, the polymer as the material for forming the plastic optical fiber F is oriented along the fiber axis direction.

By the way, in the above-mentioned manufacturing apparatus, generally, a plastic optical fiber F to be drawn is used.
Of the preform P to the heating and melting furnace 204
Between the introduction speed (V) of the preform P, the radius (R) of the preform P, and the drawing speed (v) of the plastic optical fiber F, a relationship represented by the following equation: 2r = 2R (V / v) ^1/2 is there.

For this reason, generally, manufacturing conditions such as the drawing speed (v) of the plastic optical fiber F are determined according to the radius (r) of the plastic optical fiber F to be manufactured.

However, even if the manufacturing conditions such as the drawing speed (v) of the plastic optical fiber F are determined in accordance with the above equation, the manufactured plastic optical fiber F has an outer diameter variation.

This is because the radius (r) of the plastic optical fiber F is also affected by the temperature of the melting heater 202. That is, if the heating temperature of the preform P is not constant, the outer diameter of the plastic optical fiber F may vary. Is considered to be the main factor.

For example, the temperature of the melting heater 202 is set to ± 0.
While controlling at 5 ° C. and setting various production conditions such as the drawing speed (v) so as to obtain a plastic optical fiber F having a diameter of 750 μm, the production was performed, and the outer diameter varied by ± 80 μm. Further, when the temperature of the melting heater 202 was controlled with an accuracy of ± 0.2 ° C., the outer diameter varied by ± 50 μm.

[0010]

By the way, considering the coupling between the plastic optical fibers F and the insertion of the plastic optical fiber F into the ferrule, it is preferable that the outer diameter fluctuation of the plastic optical fiber F be as small as possible.

For example, in the JIS C6837 standard, ± 6%
% Or less. That is, if the diameter of the plastic optical fiber F is 750 μm, the outer diameter fluctuation is required to be ± 45 μm or less, and if the diameter is 500 μm, the outer diameter fluctuation is required to be ± 30 μm or less.

However, merely improving the accuracy of the temperature control of the melting heater 202 cannot sufficiently suppress the variation in the outer diameter.

Therefore, if the factors affecting the outer diameter variation of the plastic optical fiber F besides the heating temperature of the melting heater 202 are clarified, the cooling step of the plastic optical fiber F drawn from the heating / melting furnace 204 is also required. It was found that there was a factor of diameter variation.

This is because, for example, in the manufacturing apparatus shown in FIG. 6, the plastic optical fiber F immediately after being drawn from the heating / melting furnace 204 having a length of 200 mm has a temperature of about 72 ° C. It is considered that the optical fiber F is deformed so as to cause an outer diameter variation due to its viscoelasticity.

The present invention has been made in order to solve the above-described problems, and provides a plastic optical fiber manufacturing apparatus and a manufacturing method capable of manufacturing a plastic optical fiber having a smaller outer diameter variation. The purpose is to:

[0016]

In order to solve the above-mentioned problems, a plastic optical fiber manufacturing apparatus according to claim 1 of the present invention introduces a preform made of plastic into a heating and melting furnace. A device for producing a plastic optical fiber which is heated and melted and stretched into a fibrous shape,
Below the heating and melting furnace, a constant temperature maintaining means that is controlled so as to have a constant temperature of at least 50 ° C. lower than the glass transition point of the material forming the plastic optical fiber is provided. The drawn plastic optical fiber is cooled by passing through the constant temperature maintaining means.

A plastic optical fiber manufacturing apparatus according to a second aspect of the present invention is a plastic optical fiber manufacturing apparatus for introducing a preform made of plastic into a heating and melting furnace, heating and melting the preform, and stretching the plastic preform. A plurality of constant temperature maintaining means are provided below the heating / melting furnace along the drawing direction of the plastic optical fiber from the heating / melting furnace, and each of the constant temperature maintaining means is provided on the downstream side in the drawing direction of the plastic optical fiber. Heating is controlled so that the temperature becomes gradually lower than the heating temperature of the heating and melting furnace as it goes, and the lowest temperature maintaining means among them is the glass transition point of the material forming the plastic optical fiber. The heating temperature is controlled to be a constant temperature lower by at least 50 ° C. than that of the plastic drawn out from the heating and melting furnace. Tic optical fiber are cooled sequentially through the plurality of temperature-maintaining means.

Further, according to a third aspect of the present invention, there is provided an apparatus for producing a plastic optical fiber, wherein a preform made of plastic is introduced into a heating and melting furnace, heated and melted, and drawn into a fibrous form. In the manufacturing apparatus, provided below the heating and melting furnace, a cooler controlled to be cooled to a constant temperature lower than the external atmosphere temperature, and a plastic optical fiber drawn out from the heating and melting furnace in a fiber form. Cooling is performed through the cooler.

According to a fourth aspect of the present invention, there is provided an apparatus for producing a plastic optical fiber, wherein a preform made of plastic is introduced into a heating and melting furnace, heated and melted, and stretched into a fibrous form. In the manufacturing apparatus, a cooling chamber is formed by covering a path portion of the drawing path of the plastic optical fiber drawn from the heating and melting furnace below the heating and melting furnace with a heat-insulating container. Circulating means for circulating a cooling gas whose temperature is controlled to be a constant temperature lower by at least 50 ° C. than a glass transition point of a material forming the plastic optical fiber in a cooling chamber, wherein the fiber drawn from the heating and melting furnace is provided. A plastic optical fiber is passed through the cooling chamber to be cooled.

According to a fifth aspect of the present invention, there is provided an apparatus for producing a plastic optical fiber, wherein a preform made of plastic is introduced into a heating and melting furnace, heated and melted, and stretched into a fibrous form. In a manufacturing method, a plastic optical fiber drawn out of the heating / melting furnace is sequentially heated in an atmosphere adjusted to a constant temperature of 50 ° C. or more lower than a glass transition point of a material forming the plastic optical fiber. To cool the plastic optical fiber.

Further, in the apparatus for manufacturing a plastic optical fiber according to the present invention, a preform made of plastic is introduced into a heating / melting furnace, heated and melted, and stretched into a fibrous form. In a manufacturing method, a plastic optical fiber drawn from the heating and melting furnace is sequentially passed through an atmosphere adjusted to a constant temperature lower than an external atmosphere temperature, thereby cooling the plastic optical fiber. Like that.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A plastic optical fiber manufacturing apparatus according to a first embodiment of the present invention will be described below.

As shown in FIG. 1, this manufacturing apparatus includes a heating and melting furnace 2 for heating and melting a preform P to draw a fibrous shape, and a constant temperature maintaining means provided below the heating and melting furnace 2. And a constant temperature heating unit 20 as Here, the preform P is finished in a rod-like shape having a refractive index distribution in which the refractive index gradually decreases from its central axis toward the outer peripheral side. Then, the GI-type plastic optical fiber F is formed.

The drawing tension for pulling out the plastic optical fiber F depends on the material and outer diameter of the plastic optical fiber F, but the material is made of polymethyl methacrylate (PM).
In the case of drawing with a diameter of 750 μm by MA), the weight should be approximately 50 g.

The heating and melting furnace 2 has a heater 6 disposed around the outer periphery of a tubular furnace tube 4 and the heater 6.
Is surrounded by a heat insulating wall 8.

The heating heater 6 is controlled by a well-known heating control means so as to have a constant temperature at which the preform P can be heated and melted, that is, a constant temperature higher than the glass transition point of the material forming the preform P. You. For example, GI
When the plastic optical fiber F of the mold is formed by PMMA, the glass transition point T _G of the PMMA is 1
The heating is controlled so as to be a constant temperature higher than 00 to 110 ° C.

At this time, the heating control of the heater 6 is desirably performed not by the ON-OFF control but by a control using a thyristor system or the like in order to maintain the heating and melting temperature of the preform P more constant. Further, if the temperature in the furnace tube 4 is controlled as a control target value, accurate control cannot be performed due to a time lag. Therefore, it is desirable to control the temperature of the heater 6 itself as the control target value.

Further, the constant temperature heating unit 20 is a cylindrical member disposed so as to cover a drawing path of the plastic optical fiber F drawn downward from the heating and melting furnace 2 over a predetermined length L immediately below the heating and melting furnace 2. , A sub-heater 26 disposed on the outer periphery of the sub-core tube 24, and a heat insulating wall 28 disposed so as to surround the outer periphery of the sub-heater 26.

The sub-heater 26 has a constant temperature T _A lower than the glass transition point _TG of the material forming the plastic optical fiber F drawn out of the heating and melting furnace 2 by 50 ° C. or more, more preferably 60 ° C. or more. Is controlled by known heating control means.

For example, when the GI-type plastic optical fiber F is formed of PMMA, the glass transition point T _G of the PMMA is 100 ° C. which is higher than 100 ° C. to 110 ° C. by 50 ° C.
The temperature is controlled so as to be a lower constant temperature, for example, a constant temperature T _A = 50 ° C. When the SI-type plastic optical fiber F is manufactured, the heating temperature may be set based on the glass transition point _TG of the material forming the clad.

At this time, in order to allow the plastic optical fiber F drawn from the heating and melting furnace 2 to be cooled with a predetermined temperature pattern change, control is performed by a thyristor method for the same reason as described above. It is desirable to control the temperature of the heater 26 itself as a control target value.

Further, the required length L of the constant temperature heating unit 20 covering the drawing path of the plastic optical fiber F is such that the plastic optical fiber F drawn through the constant temperature heating unit 20 has a glass transition point T of the forming material. _The length is set such that the temperature is sufficiently lower than _G , that is, close to the temperature T _A.

In addition, a plurality of gas supply pipes 10 and 30 are provided at equal intervals along the circumferential direction on the upper portions of the furnace core tube 4 and the sub-core tube 24, respectively. The nozzles 11 and 31 at the tip of the core tubes 4 and 24 are mounted so as to face the insides of the respective core tubes 4 and 24. Then, by introducing a medium gas into each of the core tubes 4 and 24 via the gas supply tubes 10 and 30, the temperature in each of the core tubes 4 and 24 is stabilized. As the medium gas, any gas that does not cause a chemical reaction with the plastic optical fiber F may be used, and for example, a nitrogen gas, a rare gas (argon gas, helium gas, or the like) can be used.

The gas inflow from the gas supply pipes 10 and 30 is controlled by a regulator so as to be constant. The gas inflow rate is determined by the capacity of the furnace tubes 4 and 24 and the like, and is, for example, about 3 to 20 l / min for the furnace tube 4 having an inner diameter of 30 mm. Since the purpose of flowing the medium gas is to prevent the outside air from flowing into the furnace tubes 4 and 24 to change the temperature inside the furnace tubes 4 and 24, turbulent flow occurs inside the furnace tubes 4 and 24. It is not desirable to set the flow rate and the injection pressure to such a large value as to cause a laminar flow therein.

The method of manufacturing the plastic optical fiber F by the manufacturing apparatus having the above-described structure will be described.
The preform P is introduced into the heating and melting furnace 2 at a constant speed, heated and melted, drawn into a fiber shape, and the drawn plastic optical fiber F is drawn out below the heating and melting furnace 2. next,
Plastic optical fiber F drawn from the heating and melting furnace 2
Is drawn downward through the inside of the auxiliary core tube 24 of the constant temperature heating unit 20. At this time, the plastic optical fiber F immediately after being drawn from the heating melting furnace 2 has a glass transition temperature T _G near the temperature of the forming material, i.e., a temperature higher than the heating temperature T _A of the constant temperature heating portion 20 Therefore, when passing through the inside of the constant temperature heating unit 20, the cooling is sequentially performed in a predetermined temperature pattern change. Then, the plastic optical fiber F cooled to a temperature close to the temperature T _A of the constant temperature heating unit 20, that is, a temperature sufficiently lower than the glass transition point _TG , is drawn out of the constant temperature heating unit 20, and thereafter, not shown. It will be wound and stored in the winding device.

According to the plastic optical fiber F manufacturing apparatus constructed as described above, the glass of the material forming the plastic optical fiber F is placed below the heating and melting furnace 2 along the drawing direction of the plastic optical fiber F. Since the constant temperature heating unit 20 heated to a constant temperature lower than the transition point _TG by 50 ° C. or more is provided, the plastic optical fiber F drawn from the heating / melting furnace 2 is sequentially subjected to a predetermined temperature pattern by the constant temperature heating unit 20. (Ie, the plastic optical fiber F drawn from the heating and melting furnace 2 is sequentially cooled under the same condition of the same ambient temperature without being influenced by fluctuations in the cooling conditions such as the ambient temperature. Will be done). Accordingly, the plastic optical fiber F rich in viscoelasticity immediately after being drawn from the heating and melting furnace 2 is cooled by a predetermined temperature pattern change, and the plastic optical fiber F having a smaller outer diameter variation is manufactured. It becomes possible.

In Example 1, a plastic optical fiber F was actually manufactured by a plastic optical fiber F manufacturing apparatus having the following configuration.

First, the heater 6 of the heating / melting furnace 2 is ±
Heating control is performed within the range of 0.2 ° C., and the sub-heater 26 of the constant-temperature heating unit 20 has a transition temperature _TG of 100
Heated to a constant temperature of T _A = 40 ° C. 60-70 ° C. lower than １１０110 ° C. Further, the drawing path of the plastic optical fiber F extends over the length L = 1000 mm and the constant temperature heating unit 20.
Covered by. The flow rate of the medium gas from the gas supply pipes 10 and 30 is 3 l / min.

The diameter 2 formed by PMMA
A 0 mm preform P was drawn at a linear velocity of 10 m / min to produce a GI type plastic optical fiber F having a diameter of 750 μm.

In this case, the temperature of the plastic optical fiber F immediately after being drawn from the constant temperature heating unit 20 is 43 ° C., and the plastic optical fiber F
Was cooled to a temperature at which it was difficult to deform due to its viscoelasticity. The temperature of 43 ° C. is sufficiently lower than the temperature of 72 ° C. of the plastic optical fiber F immediately after being drawn from the heating and melting furnace 204 in the conventional example shown in FIG. The variation in outer diameter of the plastic optical fiber F thus manufactured is ± 18 μm, and the variation in outer diameter when manufactured by the conventional manufacturing apparatus shown in FIG.
It can be seen that the variation in outer diameter is smaller than that of m.

Next, a plastic optical fiber manufacturing apparatus according to a second embodiment of the present invention will be described with reference to FIG.

Since the heating and melting furnace 2 of this manufacturing apparatus has the same configuration as the heating and melting furnace 2 of the plastic optical fiber manufacturing apparatus of the first embodiment, the same components are denoted by the same reference numerals. Description is omitted.

In this manufacturing apparatus, a first constant temperature heating unit 40 and a second constant temperature heating unit 60 are sequentially provided below the heating and melting furnace 2 as constant temperature maintaining means in the drawing direction of the plastic optical fiber F. It has a configuration provided.

The first constant-temperature heating section 40 and the second constant-temperature heating section 60 are respectively the constant-temperature heating section 2 of the first embodiment.
Similarly to the case 0, the first cylindrical sub-core tube 44 is disposed so as to sequentially cover the drawing path of the plastic optical fiber F drawn downward from the heating and melting furnace 2 over predetermined lengths L ₁ and L _2.
And a second sub-core tube 64. A first sub-heater 46 and a second sub-heater 66 are provided around the first sub-core tube 44 and the second sub-core tube 64, respectively.
Is provided, and the outer periphery of each of the first sub-heater 46 and the second sub-heater 66 is surrounded by the first heat-insulating wall 48 and the second heat-insulating wall 68.

The first constant temperature heating unit 40 and the second constant temperature heating unit 60 are provided with gas supply pipes 60 and 80 having the same configuration as the gas supply pipe 30 of the first embodiment. Each of the first sub core tube 44 and the second sub core tube 64 is configured so that the medium gas can flow into the inside.

Then, the second sub-heater 66 is
Low 50 ° C. or higher than the glass transition point T _G of the material forming the plastic optical fiber F, which is controlled by known heating control means as more preferably a 60 ° C. or more lower constant temperature T _A.

Further, as the first sub heater 46 is a constant temperature T _B greater than the heating temperature T _A of the second sub heater 66 to a temperature lower than the heating temperature of the heater 6 Heating is controlled.

That is, the first sub-heater 46 and the second sub-heater 66 are heated so that the temperatures T _A and T _B decrease gradually as they go downstream in the drawing direction of the plastic optical fiber F. It has a controlled configuration.

In this plastic optical fiber manufacturing apparatus, the high-temperature plastic optical fiber F immediately after being drawn from the heating and melting furnace 2 first passes through the inside of the first sub-core tube 44 of the first constant temperature heating section 40. , So that the heating temperature T
_{Cools down to} near _B. Then, after passing through the inside of the second auxiliary core tube 64 of the second low-temperature heating unit 60, it is further cooled to near the heating temperature T _A , and thereafter, is taken up and stored in winding means (not shown). Will be.

According to the plastic optical fiber manufacturing apparatus constructed as described above, the plastic optical fiber F rich in viscoelasticity immediately after being drawn out of the heating / melting furnace 2 is used as in the case of the first embodiment. Is cooled by the first constant-temperature heating unit 40 and the second constant-temperature heating unit 60 in a predetermined temperature pattern change, so that it is possible to manufacture the plastic optical fiber F having a smaller outer diameter variation.

The manufacturing apparatus according to the second embodiment has the following advantages as compared with the manufacturing apparatus according to the first embodiment.

That is, in the first embodiment, in order to cool the plastic optical fiber F drawn from the heating / melting furnace 2 to a temperature sufficiently lower than the glass transition temperature _TG , the constant temperature over a certain length L is required. It is necessary to provide a heating unit 20,
For this reason, it is necessary to lengthen the sub heater 26 inevitably. However, it is difficult to control the heating of such a long sub-heater 26 to a constant temperature T _A.

However, like the manufacturing apparatus of the second embodiment, two first constant temperature heating sections 40 and a second constant temperature heating section 60 are provided below the heating / melting furnace 2 and Since the drawn-out plastic optical fiber F is cooled to a lower temperature sequentially by the first constant-temperature heating section 40 and the second low-temperature heating section 60, the individual first sub-heaters 46 and the second Length L of sub heater 66
₁ and L ₂ can be shortened, so that it is easy to control the first sub-heater 46 and the second sub-heater 66 to a constant temperature.

It should be noted that more constant temperature heating units may be provided below the heating and melting furnace 2.

As a second embodiment, a plastic optical fiber F was actually manufactured by a plastic optical fiber F manufacturing apparatus having the following configuration.

First, the heater 6 of the heating / melting furnace 2 is ±
The heating control is performed within the range of 0.2 ° C., and the first sub-heater 46 of the first constant temperature heating unit 40 is set at T _B = 60 ° C.
The second sub-heater 66 of the constant temperature heating unit 60
65 ° C to 75 ° C higher than the transition point of 100 to 110 ° C
The heating was controlled to a constant temperature of low T _A = 35 ° C. First, the first constant-temperature heating unit 40 sets the length L _{1 of} the plastic optical fiber F drawn from the heating and melting furnace 2 to L ₁ =
It was covered over 300 mm, and its downstream side was covered by the second constant temperature heating unit 60 over a length L ₂ = 500 mm.

Then, the diameter 2 formed by PMMA
A 0 mm preform P was drawn at a linear velocity of 10 m / min to produce a GI type plastic optical fiber F having a diameter of 750 μm.

In this case, the temperature of the plastic optical fiber F immediately after being pulled out from the second constant temperature heating unit 60 is 45 ° C.
Thus, the plastic optical fiber F has been cooled to a temperature at which the plastic optical fiber F is not easily deformed due to its viscoelasticity. The variation in outer diameter of the plastic optical fiber F manufactured in this manner is ± 20 μm, and the variation in outer diameter in the conventional case is ± 20 μm.
It was found to be smaller than 50 μm.

Next, a plastic optical fiber manufacturing apparatus according to a third embodiment of the present invention will be described with reference to FIG.

Since the heating and melting furnace 2 of this manufacturing apparatus has the same configuration as the heating and melting furnace 2 of the plastic optical fiber manufacturing apparatus of the first embodiment, the same components are denoted by the same reference numerals. Description is omitted.

In this manufacturing apparatus, the external atmosphere temperature (the temperature of the ambient atmosphere of the heating and melting furnace) is provided below the heating and melting furnace 2.
A cooler 80 cooled to a lower constant temperature T _C is provided so that the plastic optical fibers F drawn from the heating and melting furnace 2 are rapidly cooled in sequence.

The cooler 80 is provided with a cooling section 82 having a predetermined length L ₃ formed by winding a copper pipe in a serpentine shape along the drawing direction of the plastic optical fiber F.
Is surrounded by a heat insulating wall 84.

A cooling medium is circulated in the copper pipe of the cooling unit 82, and the cooling unit 8 is cooled by well-known cooling control means.
2 is configured to be cooled controlled at a constant temperature T _C. The cooling control means is preferably controlled by a thyristor method or the like for the same reason as in the heating control means of the first embodiment, and is controlled by using the temperature of the cooling section 82 itself as a control target value. Is preferred.

A dried medium gas flows through the inside of the cooler 80 through a gas supply pipe 88 to stabilize the temperature inside the cooler 80 and prevent dew condensation inside the cooler 80. . As the medium gas, any material may be used as long as it does not cause a chemical reaction with the material forming the plastic optical fiber F, and a nitrogen gas, a rare gas (argon gas, helium gas, or the like) can be used.

Further, a heat insulating partition 90 is provided between the heating / melting furnace 2 and the cooler 80 so that the heating / melting furnace 2 and the cooler 80 do not affect each other thermally.

In the plastic optical fiber manufacturing apparatus thus configured, the plastic optical fiber F drawn from the heating and melting furnace 2 is then drawn downward through the cooler 80. At this time, a relatively high temperature plastic optical fiber F of immediately after being drawn out from the heating melting furnace 2, a cooler which is cooled to a constant temperature T _C is lower than the external ambient temperature (temperature of the ambient atmosphere of the heating melting furnace 2) It cools rapidly within 80 and reaches a temperature well below the glass transition point _{TG of the} material forming the plastic optical fiber F. in this way,
Thereafter, the cooled plastic optical fiber F is wound and housed by winding means (not shown).

The temperature change of the plastic optical fiber F during the production by this production apparatus will be described with reference to FIG. In FIG. 4, T _H indicates a temperature change in the heating and melting furnace 2, T _F indicates a temperature change of the plastic optical fiber F itself, and T _N indicates natural cooling without the cooler 80. 5 shows a temperature change of the plastic optical fiber F in the case. Further, _TG indicates a glass transition point, and T _A indicates a temperature 60 ° C. lower than the glass transition point (a temperature at which the plastic optical fiber F is hardly deformed due to its viscoelasticity).

First, the preform P introduced into the heating and melting furnace 2 is heated and melted to a temperature equal to or higher than the glass transition point _TG of the forming material, and is drawn into a fiber. The plastic optical fiber F immediately after being drawn out of the heating and melting furnace 2 has a temperature slightly lower than the glass transition point _TG , but is still at a relatively high temperature. And this plastic optical fiber F
When passing through the cooler 80, the plastic optical fiber F is rapidly cooled to the temperature T _A or lower as compared with the case where the plastic optical fiber F is cooled naturally without passing through the cooler 80. It is withdrawn from the cooler 80.

According to the plastic optical fiber manufacturing apparatus configured as described above, the plastic optical fiber F
A cooler 80 cooled to a constant temperature T _C lower than the external atmosphere temperature (the temperature of the ambient atmosphere of the heating and melting furnace 2) is provided below the heating and melting furnace 2 in the drawing direction of the heating and melting furnace 2. The plastic optical fiber F of a relatively high temperature drawn out of is cooled rapidly and sequentially. For this reason,
Since the time during which the plastic optical fiber F is in a state of being easily deformed due to its viscoelasticity at a relatively high temperature is short, the outer diameter hardly changes due to the viscoelasticity after being drawn out of the heating and melting furnace 2. Thus, a plastic optical fiber F having a smaller variation in outer diameter can be manufactured.

As a third embodiment, a plastic optical fiber F was actually manufactured using a plastic optical fiber F manufacturing apparatus having the following configuration.

First, the heater 6 of the heating / melting furnace 2 is ±
Heating is controlled within the range of 0.2 ° C, and the length L
₃ = A cooler 80 was provided over 280 mm, and the cooler 80 was set to be constant at -40 ° C. Then, a preform P having a diameter of 20 mm formed by PMMA is drawn at a linear velocity of 10 m / min, and a diameter of 750 μm is formed.
m of GI type plastic optical fiber F was manufactured.

In this case, the temperature of the plastic optical fiber F immediately after being pulled out from the cooler 80 is 42 ° C., and the plastic optical fiber F has been cooled to a temperature at which deformation due to viscoelasticity of the plastic optical fiber F hardly occurs. The variation in outer diameter of the plastic optical fiber F thus manufactured is ± 1.
7 μm, indicating that the outer diameter fluctuation is smaller than the outer diameter fluctuation ± 50 μm when manufactured by the conventional manufacturing apparatus shown in FIG.

As Example 4, the case where the cooler 80 set at a constant temperature of 10 ° C. was provided below the heating and melting furnace 2 over a length L ₃ = 400 mm and the plastic optical fiber F Was manufactured. The cooling unit 82 is formed by winding a copper pipe having a diameter of 3 mm in a serpentine tube, and the other conditions are the same as those of the third embodiment.

In this case, the temperature of the plastic optical fiber F immediately after being pulled out from the cooler 80 is 48 ° C., and the plastic optical fiber F has been cooled to a temperature at which deformation due to viscoelasticity of the plastic optical fiber F hardly occurs. The variation in outer diameter of the plastic optical fiber F thus manufactured is ± 2.
0 μm, and it was also found that the outer diameter variation was smaller than in the conventional case.

Finally, an apparatus for manufacturing a plastic optical fiber according to a fourth embodiment of the present invention will be described with reference to FIG.

The heating / melting furnace 2 of this manufacturing apparatus has the same configuration as the heating / melting furnace 2 of the plastic optical fiber manufacturing apparatus of the first embodiment. Description is omitted.

In this manufacturing apparatus, a heat insulating container 100 is provided below the heating and melting furnace 2, and a temperature controller 110 is provided as a circulating means beside the heat insulating container 100.

The heat-insulating container 100 is configured to hermetically cover the downstream side of the heating and melting furnace 2 in the drawing path of the plastic optical fiber F drawn from the heating and melting furnace 2 over a predetermined length L _4. As a result, a predetermined cooling chamber L is formed.

The temperature controller 110 is provided with a well-known cooler, heater, blower, and the like, and cools or heats the cooling gas so that the temperature of the molding material of the plastic optical fiber F becomes higher than the glass transition point _TG . The temperature can be controlled to be constant at a temperature T _D lower by 50 ° C. or more, more preferably 60 ° C. or more.

The heat insulating container 100 and the temperature controller 1
10 are connected by an air feed pipe 120 and an air return pipe 122. Insulating container 100 of air feed pipe 120
The air outlet 121 on the side faces the upper part in the heat insulating container 100, and the suction port 123 on the heat insulating container 100 side of the air return pipe 122 faces the lower part in the heat insulating container 100.

Then, the cooling gas whose temperature has been adjusted by the temperature controller 110 to a constant temperature T _D is sent into the cooling chamber L in the heat insulating container 100 via the air feed pipe 120. The cooling gas flows from the upper part to the lower part in the cooling chamber L, and is then sucked into the suction port 123 below the cooling gas,
The air returns to the temperature controller 110 again through the air return pipe 122. The returned cooling gas is supplied to the temperature controller 11.
The temperature is adjusted again so as to be a constant temperature T _{D at} 0, and thereafter, the temperature is again sent to the cooling chamber L side.

The gas to be circulated may be any gas as long as it does not chemically react with the material of the plastic optical fiber, and nitrogen gas, rare gas (argon gas, helium gas, etc.) can be used.

In the plastic optical fiber F manufacturing apparatus configured as described above, the plastic optical fiber F drawn from the heating and melting furnace 2 is drawn downward through the cooling chamber L of the heat insulating container 100. . At this time, the relatively high-temperature plastic optical fiber F immediately after being drawn out of the heating / melting furnace 2 is sequentially cooled by a predetermined temperature pattern change by the cooling gas in the cooling chamber L, and the glass transition of the forming material of the plastic optical fiber F is performed. The temperature becomes much lower than the point _TG . The plastic optical fiber F thus rapidly cooled is wound and accommodated by winding means (not shown).

According to the plastic optical fiber manufacturing apparatus configured as described above, the plastic optical fiber F
The cooling chamber L is formed by covering the downstream side of the heating and melting furnace 2 of the drawing path with the heat-insulating container 100 and forming the cooling chamber L in the heat-insulating container 100 from the glass transition point of the material forming the plastic optical fiber F. Constant temperature T lower than 50 ° C
By circulating the cooling gas of _D , the plastic optical fiber F drawn from the heating and melting furnace 2 is sequentially cooled by a predetermined temperature pattern change, so that the viscoelasticity immediately after being drawn from the heating and melting furnace 2 is reduced. Since the abundant plastic optical fiber F is subsequently cooled by a predetermined temperature pattern change, the outer diameter hardly fluctuates, and the plastic optical fiber F with a smaller outer diameter fluctuation can be manufactured.

In particular, when a cooling gas having a temperature lower than the external atmosphere temperature (the temperature of the surrounding atmosphere of the heating and melting furnace 2) is circulated in the heat insulating container 100, the plastic optical fiber F drawn from the heating and melting furnace 2 is circulated. Because it cools quickly,
The outer diameter of the plastic optical fiber F is less likely to vary.

As a fifth embodiment, a plastic optical fiber F was actually manufactured by a manufacturing apparatus having the following configuration.

First, the heater 6 of the heating / melting furnace 2 has ±
Heating is controlled within the range of 0.2 ° C, and the length L
₄ = The heat insulating container 100 was provided over 300 mm, and a cooling gas of nitrogen at a constant temperature T _D = 10 ° C was circulated in the heat insulating container 100 at a flow rate of 3 l / min.

In this case, the temperature of the plastic optical fiber F immediately after being pulled out from the heat insulating container 100 is 45 ° C., and the plastic optical fiber F has been cooled to a temperature at which deformation due to viscoelasticity of the plastic optical fiber F hardly occurs. . Further, the outer diameter fluctuation of the plastic optical fiber F manufactured in this manner is ± 21 μm, and the outer diameter fluctuation is smaller than the outer diameter fluctuation ± 50 μm when manufactured by the conventional manufacturing apparatus shown in FIG. It turned out to be smaller.

Further, as the sixth embodiment, the heat insulating container 100
A plastic optical fiber F was similarly manufactured in a case where a cooling gas of nitrogen cooled to a constant temperature T _D = -10 ° C. was circulated therein at a flow rate of 3 l / min. The other conditions are the same as those of the fifth embodiment.

In this case, the temperature of the plastic optical fiber F immediately after being pulled out from the heat insulating container 100 is 25
° C, and the plastic optical fiber F has been cooled to a temperature at which deformation due to viscoelasticity is unlikely to occur. Also,
The variation of the outer diameter of the plastic optical fiber F manufactured in this manner is ± 18 μm, which is smaller than the variation of the outer diameter ± 50 μm when manufactured by the conventional manufacturing apparatus shown in FIG. I understood that.

[0091]

As described above, according to the apparatus for manufacturing a plastic optical fiber according to the first aspect of the present invention, the glass transition point of the material forming the plastic optical fiber is 50 ° C. or more below the heating and melting furnace. A constant temperature maintaining means heated to a low constant temperature is provided, and the plastic optical fiber drawn out from the heating and melting furnace in a fiber form is cooled through the constant temperature maintaining means, so that immediately after being drawn from the heating and melting furnace. The plastic optical fiber rich in viscoelasticity is thereafter cooled by a predetermined temperature pattern change, and the outer diameter hardly fluctuates, so that a plastic optical fiber having a smaller outer diameter fluctuation can be manufactured.

According to the apparatus for manufacturing a plastic optical fiber according to the second aspect of the present invention, a plurality of constant temperature maintaining means are provided below the heating / melting furnace along the drawing direction of the plastic optical fiber from the heating / melting furnace. And heating control at a constant temperature that is lower than the heating temperature of the heating and melting furnace as each of the constant temperature maintaining means goes downstream in the drawing direction of the plastic optical fiber, and the most downstream constant temperature maintaining means among them. Is controlled to a constant temperature that is at least 50 ° C. lower than the glass transition point of the material forming the plastic optical fiber, and the plastic optical fiber drawn from the heating and melting furnace is cooled by sequentially passing through the plurality of constant temperature maintaining means. Therefore, the plastic optical fiber rich in viscoelasticity immediately after being drawn from the heating and melting furnace is Cooled in degrees pattern change, likely to make the variation in outer diameter, it is possible to further produce a small plastic optical fiber having an outer diameter fluctuation. Further, since the length of each of the constant temperature maintaining means can be shortened, it becomes easy to control the heating of them to a constant temperature.

According to the apparatus for manufacturing a plastic optical fiber according to the third aspect of the present invention, the plastic optical fiber is cooled to a constant temperature lower than the external atmosphere temperature downstream of the heating and melting furnace along the drawing direction of the plastic optical fiber. The plastic optical fiber drawn out of the heating and melting furnace is cooled through this cooler, so that the plastic optical fiber rich in viscoelasticity immediately after being drawn out of the heating and melting furnace is rapidly cooled. After being cooled, the outer diameter is less likely to fluctuate due to the influence of subsequent fluctuations in cooling conditions, and a plastic optical fiber having a smaller outer diameter fluctuation can be manufactured.

According to the apparatus for manufacturing a plastic optical fiber according to the fourth aspect of the present invention, the part of the plastic optical fiber drawing path downstream of the heating and melting furnace is covered with a heat insulating container. A cooling means for forming a cooling chamber, and circulating means for circulating a cooling gas having a constant temperature lower than the glass transition point of the material forming the plastic optical fiber by 50 ° C. or more in the cooling chamber, and the plastic light drawn from the heating and melting furnace; Since the fiber is cooled by passing it through the cooling chamber, the plastic optical fiber rich in viscoelasticity immediately after being drawn from the heating and melting furnace is cooled by a predetermined temperature pattern change, so that the outer diameter fluctuates. It becomes difficult to manufacture a plastic optical fiber having a smaller variation in outer diameter.

Further, according to the method for manufacturing a plastic optical fiber according to the fifth aspect, the plastic optical fiber drawn out of the heating and melting furnace is successively lower by 50 ° C. or more than the glass transition point of the material forming the plastic optical fiber. Since the plastic optical fiber is cooled by passing through an atmosphere adjusted to a constant temperature, the plastic optical fiber rich in viscoelasticity immediately after being pulled out of the heating and melting furnace is thereafter cooled to a predetermined temperature. It is cooled by the temperature pattern change, making it difficult for the outer diameter to fluctuate,
A plastic optical fiber having a smaller variation in outer diameter can be manufactured.

Further, according to the method of manufacturing a plastic optical fiber according to the sixth aspect, the plastic optical fibers drawn from the heating and melting furnace are placed in an atmosphere whose temperature is successively adjusted to a constant temperature lower than the external atmosphere temperature. The plastic optical fiber is cooled by passing through it, so that the plastic optical fiber rich in viscoelasticity immediately after being pulled out of the heating and melting furnace is rapidly cooled, and the influence of subsequent fluctuations in cooling conditions, etc. As a result, fluctuations in the outer diameter are less likely to occur, and a plastic optical fiber having a smaller fluctuation in the outer diameter can be manufactured.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an apparatus for manufacturing a plastic optical fiber according to a first embodiment of the present invention.

FIG. 2 is a schematic view showing an apparatus for manufacturing a plastic optical fiber according to a second embodiment of the present invention.

FIG. 3 is a schematic view showing an apparatus for manufacturing a plastic optical fiber according to a third embodiment of the present invention.

FIG. 4 is a diagram showing a state of a temperature change of a plastic optical fiber in a manufacturing apparatus.

FIG. 5 is a schematic view showing an apparatus for manufacturing a plastic optical fiber according to a fourth embodiment of the present invention.

FIG. 6 is a schematic view showing a conventional plastic optical fiber manufacturing apparatus.

[Explanation of symbols]

 2 Heating and melting furnace 20 Constant temperature heating section P Preform F Plastic optical fiber

Claims (6)

[Claims] 1. An apparatus for manufacturing a plastic optical fiber for introducing a preform formed of plastic into a heating and melting furnace, heating and melting the preform, and stretching the fiber into a fibrous shape. Providing a constant-temperature maintaining means that is controlled to be at a constant temperature of at least 50 ° C. lower than the glass transition point of the material forming the optical fiber, and maintains the plastic optical fiber drawn out from the heating and melting furnace into a fibrous state at the constant temperature. An apparatus for producing a plastic optical fiber which is cooled through a means. 2. An apparatus for producing a plastic optical fiber in which a preform made of plastic is introduced into a heating and melting furnace, heated and melted, and stretched into a fibrous shape. A plurality of constant temperature maintaining means are provided along the drawing direction of the plastic optical fiber from the melting furnace, and each of the constant temperature maintaining means is sequentially lower than the heating temperature of the heating melting furnace as going toward the downstream side in the drawing direction of the plastic optical fiber. The heating is controlled so as to be a constant temperature, and the most downstream constant temperature maintaining means among them is heated so as to have a constant temperature lower than the glass transition point of the material forming the plastic optical fiber by 50 ° C. or more. Controlled, the plastic optical fiber drawn out from the heating and melting furnace in a fibrous form is sequentially passed through the plurality of constant temperature maintaining means. Apparatus for manufacturing a plastic optical fiber so as to retirement. 3. An apparatus for manufacturing a plastic optical fiber for introducing a preform made of plastic into a heating and melting furnace, heating and melting the preform, and stretching the fiber into a fibrous shape. Manufacturing a plastic optical fiber in which a cooler controlled to be cooled to a constant temperature lower than the temperature is provided, and the plastic optical fiber drawn out from the heating and melting furnace into a fiber shape is cooled by passing through the cooler. apparatus. 4. An apparatus for producing a plastic optical fiber for introducing a preform formed of plastic into a heating and melting furnace, heating and melting the preform, and stretching the plastic optical fiber into a fibrous shape. A cooling chamber is formed by covering a path portion of the fiber drawing path below the heating and melting furnace with a heat insulating container, and a glass transition point of a material forming the plastic optical fiber is formed in the cooling chamber. Also provided is a circulating means for circulating a cooling gas whose temperature has been adjusted to a constant temperature lower by at least 50 ° C. so that the fibrous plastic optical fiber drawn from the heating and melting furnace is cooled by passing through the cooling chamber. Manufacturing equipment for plastic optical fibers. 5. A method for producing a plastic optical fiber in which a preform made of plastic is introduced into a heating and melting furnace, heated and melted, and stretched into a fibrous shape, wherein the plastic light drawn from the heating and melting furnace is provided. A plastic in which the plastic optical fiber is cooled by sequentially passing the fiber through an atmosphere adjusted to have a constant temperature of at least 50 ° C. lower than the glass transition point of the material forming the plastic optical fiber. Optical fiber manufacturing method. 6. A method for producing a plastic optical fiber in which a preform made of plastic is introduced into a heating and melting furnace, heated and melted, and stretched into a fibrous shape, wherein the plastic light drawn from the heating and melting furnace is provided. A method of manufacturing a plastic optical fiber, wherein the plastic optical fiber is cooled by sequentially passing the fiber through an atmosphere adjusted to a constant temperature lower than the external atmosphere temperature.