JP2012025611A - Method for producing optical fiber strand - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for stably producing an optical fiber strand over a long period by a simple device and simple control.SOLUTION: The method for producing an optical fiber strand 4, wherein the outer circumference of a filament body 3 is coated with ultraviolet-curing resin, includes: a wire drawing process for drawing an optical fiber base material 1 into the filament body 3; an application process for applying the ultraviolet-curing resin to the filament body 3; and an irradiation process for irradiating the filament body 4 coated with the ultraviolet-curing resin by two or more ultraviolet radiation devices 6a and 6b. The ultraviolet-curing resin contains an acrylic monomer and a monomer including an N-vinyl group. In the irradiation process, the filament body 4 is irradiated with ultraviolet rays while passed through the inside of ultraviolet transmissive cylinder bodies inside the two or more ultraviolet radiation devices 6a and 6b, and the temperature of the ultraviolet transmissive cylinder body on the downstream side is kept at 70-180°C while at least the ultraviolet radiation device 6a on the upstream side is turned on among the optional adjacent two ultraviolet radiation devices 6a and 6b.

Description

  The present invention relates to a method for manufacturing an optical fiber.

  The optical fiber is manufactured by drawing an optical fiber preform to form a linear body, and immediately after that, the linear body is coated with a resin. For the coating of the striatum, an ultraviolet curable resin is applied to the surface of the striatum, and the striate passes through an ultraviolet transmitting cylindrical shape (hereinafter referred to as a transparent tube) disposed in the ultraviolet irradiation device. It is carried out by curing the ultraviolet curable resin by irradiating with UV rays.

  In the process of coating the UV curable resin, components that are relatively volatile, such as monomers in the UV curable resin, are volatilized due to reaction heat generated during curing and heat generated by absorption of irradiated light energy. Adhere to the inner surface of the tube. Since the resin component adhering to the inner surface of the transparent tube is altered by ultraviolet irradiation, the transparent tube becomes cloudy. When the transparent tube becomes cloudy in this way, the amount of ultraviolet irradiation to the ultraviolet curable resin decreases, and the ultraviolet curable resin does not sufficiently cure.

As described above, as a method of preventing insufficient curing of the ultraviolet curable resin due to clouding of the transparent tube, for example, in Patent Document 1, the oxygen concentration in the inert gas flowing in the transparent tube is set to 500 ppm to 5%. Discloses a method of thermally and oxidatively decomposing volatiles once attached to a transparent tube. Further, in Patent Document 2, in the period of increasing the drawing speed of the striatum, the value obtained by dividing the input power to the ultraviolet light source by the traveling speed is set to 0.5 to 50 W · min / m or less. A method of suppressing irradiation and preventing volatiles from adhering to the transparent tube is disclosed. Patent Document 3 discloses a method for thermally decomposing volatiles once attached to a transparent tube by setting the temperature of the transparent tube to 200 ° C. or higher.
On the other hand, with the recent increase in the drawing speed of optical fibers, there is a demand for ultraviolet curable resins having a high curing speed. As such a fast-curing type resin, for example, Patent Document 4 discloses a resin composition for coating an optical fiber in which a monomer containing an N-vinyl group is blended.

JP 2003-95704 A JP-A-2005-162521 JP 2005-189510 A JP-A-10-204250

  However, in the light irradiation apparatus described in Patent Document 1, since it is necessary to adjust the flow rate of the gas flowing in the transparent tube according to the drawing speed, there is a problem that the control becomes complicated. In the light irradiation device described in Patent Document 2, it is necessary to appropriately adjust the input power to the ultraviolet light source in accordance with the drawing speed of the striate body, and there is a problem that the control becomes complicated. In addition, since the light irradiation device described in Patent Document 3 requires heating at a high temperature of 200 ° C. or higher, a separate device for heating the transparent tube is required, which complicates the device. Moreover, the heat deterioration of a sealing material etc. tends to advance, and the malfunction that it cannot manufacture stably for a long time arises.

  The present invention has been made in view of the above, and provides a manufacturing method of an optical fiber that can manufacture an optical fiber stably for a long period of time with a simple device and simple control. With the goal.

  In order to achieve the above object, an optical fiber manufacturing method of the present invention is an optical fiber manufacturing method in which an outer periphery of a linear body is coated with an ultraviolet curable resin, and an optical fiber base material is used. A wire drawing step for drawing a wire, a coating step for applying the ultraviolet curable resin to the wire, and an ultraviolet irradiation device for two or more lamps on the wire coated with the ultraviolet curable resin And the ultraviolet curable resin contains an acrylic monomer and a monomer having an N-vinyl group, and the irradiation step transmits ultraviolet light in two or more ultraviolet irradiation devices. While passing through the cylindrical body, ultraviolet rays are irradiated, and at least the upstream ultraviolet irradiation device is lit in any two adjacent ultraviolet irradiation devices, the temperature of the ultraviolet transmission cylindrical body on the downstream side is always set. 70-18 ℃ characterized by a.

  The ultraviolet transmitting cylindrical body is provided in an ultraviolet irradiation device, and the temperature of the ultraviolet transmitting cylindrical body is controlled only by radiant heat from the ultraviolet irradiation device.

  According to the present invention, there is an effect that an optical fiber can be manufactured stably for a long period of time with a simple device and simple control.

It is the schematic of the optical fiber manufacturing apparatus which concerns on embodiment. It is a schematic sectional drawing of the ultraviolet irradiation device which concerns on embodiment.

  Hereinafter, a method for manufacturing an optical fiber according to an embodiment of the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

In manufacturing the optical fiber according to the embodiment of the present invention, an ultraviolet curable resin containing an acrylic monomer and a monomer having an N-vinyl group is used as a coating material. More specifically, for example, an ultraviolet curable resin composed of a urethane acrylate oligomer, an acrylic monomer, an N-vinyl group-containing monomer, and a photoinitiator can be used. Each material is illustrated below.
(Urethane acrylate oligomer)
The urethane acrylate oligomer is produced by reacting a polyol, diisocyanate and an ethylenically unsaturated group-containing compound.
(Acrylic monomer)
An acrylic monomer is a monomer having an acryloyl group (CH2 = CHCO-) or a methacryloyl group (CH2 = CCH3CO-) as a functional group, and 2-ethylhexyl (meth) acrylate, isodecyl (meth) acrylate, isooctyl (meth) acrylate. , Lauryl (meth) acrylate, isobornyl (meth) acrylate, 1,6-hexanediol di (meth) acrylate, and the like.
(N-vinyl group-containing monomer)
Examples of the compound having an N-vinyl group include N-vinyl pyrrolidone, N-vinyl caprolactam, N, N-dimethyl (meth) acrylamide and the like.
(Light starting material)
Examples of the photoinitiator include 2,4,6-trimethylbenzoyldiphenylphosphine oxide and 1-hydroxycyclohexyl phenyl ketone.

  Thus, by using a monomer having an N-vinyl group together with an acrylic monomer generally used as a reactive diluent, the curing speed can be increased, and the drawing speed of optical fibers in recent years has been increased ( For example, it is possible to cope with a drawing speed of 1000 m / min or more. The blending amount of the monomer having an N-vinyl group is preferably 3 wt% or more and 20 wt% or less from the viewpoint of curing speed. In addition, as an ultraviolet curable resin, other oligomers, monomers, commonly used additives, inorganic fillers, antioxidants, colorants, and the like can be added as long as required characteristics are not impaired. .

  Below, the manufacturing method of the optical fiber which concerns on embodiment of this invention is demonstrated in detail. In the following description, the same reference numerals are used for the same elements, and duplicate descriptions are omitted.

  FIG. 1 is a schematic diagram for explaining an apparatus for manufacturing an optical fiber according to an embodiment of the present invention. The optical fiber preform 1 is heated and melted by a heater 2 in a drawing furnace (not shown) and drawn. A glass optical fiber (strip) 3 formed by drawing passes through a downstream resin coating device 5, and an ultraviolet curable resin is applied to the outer periphery. Thereby, the optical fiber 4 is formed. The optical fiber 4 coated with the ultraviolet curable resin passes through further downstream ultraviolet irradiation devices 6a and 6b. The ultraviolet irradiation devices 6 a and 6 b irradiate the ultraviolet curable resin applied to the outer periphery of the glass optical fiber 3 with ultraviolet rays to cure the ultraviolet curable resin. In this manner, the optical fiber 4 is formed by passing the optical fiber 4 having the outer periphery of the glass optical fiber 3 coated with the ultraviolet curable resin through the ultraviolet irradiation devices 6a and 6b. The optical fiber 4 formed in this way is wound around a winding device 8 via a guide roller 7.

  Next, the ultraviolet irradiation device 6a will be described. As shown in FIG. 2, the ultraviolet irradiation device 6 a includes an ultraviolet irradiation device body 9, an intake device 10 provided on the upper portion of the ultraviolet irradiation device body 9, and an exhaust device 11 provided on the lower portion of the ultraviolet irradiation device body 9. Consists of.

  The intake device 10 is provided with an intake port 12 for intake of an inert gas and an optical fiber strand insertion port 13a for inserting the optical fiber strand 4 coated with an ultraviolet curable resin. Further, the exhaust device 11 is provided with an exhaust port 14 for exhausting the inhaled inert gas and an optical fiber strand insertion port 13b for inserting the coated optical fiber strand 4.

  In the resin coating device 5, the optical fiber strand 4 coated with the ultraviolet curable resin enters the intake device 10 through the optical fiber strand insertion port 13 a and passes through the transparent tube 15 installed in the ultraviolet irradiation device main body 9. pass. The ultraviolet irradiation apparatus body 9 includes an ultraviolet irradiation lamp 16 that is irradiated to cure the ultraviolet curable resin applied to the outer periphery of the glass optical fiber 3 and a mirror 17 that prevents unevenness of curing due to irradiation from one side. I have. In the transparent tube 15, a predetermined oxygen concentration is maintained by the amount of inert gas supplied and the exhaust flow rate from the lower part of the ultraviolet irradiation device. Thus, in order to maintain a predetermined oxygen concentration, the sealing material 18 is provided at the opening of the transparent tube 15. Moreover, when measuring the temperature of the transparent tube at this time, the center part of a transparent tube is measured, for example using the radiation thermometer which is not illustrated. Further, the ultraviolet irradiation device 6b has the same structure as the ultraviolet irradiation device 6a.

  In the irradiation process of irradiating the optical fiber 4 coated with the ultraviolet curable resin with ultraviolet rays, some components of the ultraviolet curable resin are irradiated with reaction heat generated when the ultraviolet curable resin is cured. Volatilizes due to heat generated by absorption of light energy. Then, some components of the volatilized ultraviolet curable resin adhere to the inner surface of the transparent tube 15. Furthermore, the resin component adhering to the inner surface of the transparent tube 15 is altered by ultraviolet irradiation. Thereby, the transparent tube 15 becomes cloudy, and the irradiation amount of the ultraviolet rays to the resin decreases. When the irradiation amount of ultraviolet rays decreases, there arises a problem that the ultraviolet curable resin is not sufficiently cured.

  In order to solve this problem, in the irradiation step of irradiating the optical fiber 4 coated with the ultraviolet curable resin with ultraviolet rays, the transparent tube 15 in the ultraviolet irradiation device installed downstream of the lit ultraviolet irradiation device is used. Adjustment was performed to keep the temperature at 70 ° C. or higher. As a method for adjusting the temperature of the transparent tube, the temperature of the transparent tube 15 is set to a desired temperature by appropriately adjusting the radiation heat generated from the ultraviolet irradiation device by appropriately adjusting the input power to the ultraviolet irradiation lamp light source. Thereby, the temperature of the transparent tube 15 can be set to a desired temperature. In addition, the temperature in a transparent tube should just be maintained at 70 degreeC or more, and the adjustment method of temperature is not limited to this. In addition, it is preferable to keep the temperature in the transparent tube at 180 ° C. or less from the viewpoint that thermal deterioration of the sealing material or the like can be suppressed.

  In addition, since the drawing speed of the optical fiber is slow at the start of drawing, setting the input power to the UV irradiation lamp light source in the same manner as in the steady state increases the UV irradiation time to the UV curable resin, and the amount of volatile matter generated is reduced. May increase. Therefore, in order to prevent the amount of UV irradiation from becoming excessively large, the power input to the UV irradiation lamp light source is reduced at the start of drawing, or the period of time until the drawing speed is increased to some extent is reduced. Adjustments such as turning on only one light and turning off the rest are common.

  On the other hand, in the present invention, the volatile components adhering to the transparent tube are rapidly re-volatilized by raising the temperature of the transparent tube rather than reducing the amount of volatile components generated by reducing the amount of UV irradiation, thereby preventing the transparent tube from clouding. More effective.

  By this method, the transparency of the transparent tube can be maintained, and the ultraviolet curable resin can be stably cured sufficiently for a long period of time without reducing the amount of ultraviolet irradiation.

  In the above-described embodiment, the temperature of the transparent tube is controlled using the radiant heat generated from the ultraviolet irradiation device, but other methods may be used as the method for heating the transparent tube. For example, a tape heater may be wound around the end of the transparent tube. However, when the temperature of the transparent tube is controlled by using radiant heat, a special heating means is not required, so that the equipment can be simplified and more preferable. Also, by adding an appropriate additive to the transparent tube, for example, a nickel complex, the infrared absorption rate is increased, the radiant heat from the lamp light source is efficiently absorbed, the temperature of the transparent tube is increased, or the indium tin oxide system The transparent tube temperature may be controlled by increasing the infrared reflectance by adding powder, reflecting the radiant heat from the lamp light source to reduce the absorption of the radiant heat to the transparent tube, and lowering the temperature of the transparent tube.

  In addition, in the optical fiber manufacturing apparatus shown in FIG. 1, although two ultraviolet irradiation devices are provided, the number of ultraviolet irradiation devices should just be two or more, and is not limited to this. For example, when three ultraviolet irradiation devices are provided, assuming that the ultraviolet irradiation devices are installed in the order of A → B → C from the upstream, the two adjacent ultraviolet irradiation devices are A and B and B and C. It becomes. Paying attention to A and B, “at least the upstream ultraviolet irradiation device is lit in the two adjacent ultraviolet irradiation devices” means that the temperature of the ultraviolet transmissive cylindrical body of B is while A is lit. It will be 70-180 degreeC. When attention is paid to B and C, the temperature of the ultraviolet ray transmitting cylindrical body of C is set to 70 to 180 ° C. while B is lit. That is, the lighting order of the ultraviolet irradiation device is C → B → A. In this embodiment, one resin coating device is provided. However, two or more resin coating devices may be provided, and an ultraviolet irradiation device may be provided for each resin coating device. That is, the present invention can also be applied to a case where an ultraviolet curable resin is further applied to an optical fiber once coated with an ultraviolet curable resin and then cured.

(Examples 1-3 and Comparative Examples 1-6)
Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples. Two types of ultraviolet curable resins having a composition containing an N-vinyl group-containing monomer shown in Table 1 and a composition not containing the urethane acrylate oligomer, various monomers, and a photoinitiator as main components were prepared. Examples 1 to 3 and Comparative Examples 1 to 5 are compositions containing an N-vinyl group-containing monomer, and Comparative Example 6 is a composition not containing an N-vinyl group-containing monomer. The two types of ultraviolet curable resins have the same composition except that they contain or do not contain an N-vinyl group-containing monomer.

The curability of each adjusted ultraviolet curable resin was evaluated by the following method.
1. Preparation of test piece: A liquid ultraviolet curable resin was applied to a glass plate using an applicator bar and irradiated with ultraviolet rays of 25 mJ / cm ² or 500 mJ / cm ² to obtain a cured film having a thickness of 200 μm. Next, the cured film was peeled off from the glass plate, and the test piece was placed at a temperature of 23 ° C. and a relative humidity of 50% for 24 hours.
2. Measurement of Young's modulus (based on JIS K7127): The Young's modulus of the test piece at a temperature of 23 ° C. was measured with a tensile tester under the conditions of a tensile speed of 1 mm / min and a distance between marked lines of 25 mm.
3. Judgment of curability: The value obtained by dividing the Young's modulus of the sheet irradiated with ultraviolet rays at 25 mJ / cm ² by the Young's modulus of the sheet irradiated with ultraviolet rays of 500 mJ / cm ² was used as a curability index. . Further, the degree of cure of the optical fiber coating layer itself was evaluated by a gel fraction by a solvent extraction method. Here, the gel fraction is an index indicating how hard the optical fiber coating layer is cured. The initial weight of the coating is defined as W _0, and the coating weight after solvent extraction of the non-gel component from this coating is defined as the gel fraction. When W
Gel fraction = (W / W ₀ ) × 100 (%)
Indicated by Therefore, a higher gel fraction is preferable. Generally, the gel fraction of the optical fiber coating layer is preferably 90% or more.

  Using the ultraviolet curable resin shown in Table 1, the input power to the ultraviolet irradiation lamp was adjusted so that the transparent tube temperature became the value shown in Table 1, and a 300 km optical fiber was manufactured. In Comparative Examples 1, 2, and 6, the second UV lamp (installed downstream) was turned off at the start of drawing, and turned on when it reached about half the predetermined drawing speed. The transparent tube temperature was room temperature (25 ° C.) until the UV lamp was turned on. The drawing speed was 1000 m / min. In Example 3 and Comparative Example 5, the first UV lamp was turned off at the start of drawing, and turned on when it reached about half the predetermined drawing speed. In Example 3, the first lamp was turned on and the input power of the second lamp was adjusted to increase the transparent tube temperature. The oxygen concentration in the transparent tube 15 was the same in any of Examples 1 to 3 and Comparative Examples 1 to 6.

After the production, the degree of cloudiness of the transparent tube was measured. The degree of fogging of the transparent tube was measured by measuring the illuminance of ultraviolet rays at the fiber passage position in the transparent tube, and the maintenance rate of the transparency was obtained as a transparency rate (%) of the transparent tube. The transparent tube clarity retention (%) is, the illuminance of the pre-production start Ls (W / ^cm 2), when the illuminance after end of production and Le (W / cm ^2),
Transparent tube transparency maintenance rate (%) = Le / Ls × 100
Is defined as

From the results in Table 1, the following became clear.
First, in Examples 1 to 3 and Comparative Examples 1 to 5 in which a monomer having an N-vinyl group is blended, the curability of the ultraviolet curable resin is as excellent as 0.81. However, in Comparative Examples 1 and 2 in which the second UV lamp is turned off at the start of drawing and is turned on when about half of the predetermined drawing speed is reached, the transparency maintenance rate of the second transparent tube is 67 to It has fallen to 68%.
In Comparative Example 3 in which the temperature of the second transparent tube was always 40 ° C., the transparency maintenance rate of the second transparent tube was reduced to 60%.
Further, in Comparative Example 4 in which the temperature of the first and second transparent tubes was always 250 ° C., the transparency maintenance rate of the transparent tubes was as good as 98%, but the appearance of the sealing material was confirmed after one week of use. Cracks occurred, sealing performance was impaired, and fluctuations in the oxygen concentration inside the quartz tube were observed during fiber production.
Also, the first UV lamp is turned off at the start of drawing, and turned on when it reaches about half of the predetermined drawing speed. At that time, the temperature of the second UV lamp transparent tube is raised from 40 ° C to 70 ° C. In Example 3, the transparency maintenance rate of the second UV lamp transparent tube was as high as 92%, whereas the first UV lamp was turned off at the start of drawing and reached about half of the predetermined drawing speed. In Comparative Example 5 in which the second tube UV lamp transparent tube temperature was always 40 ° C., the transparency maintenance rate of the second lamp UV lamp transparent tube was reduced to 65%.
On the other hand, in Comparative Example 6 containing no N-vinyl group-containing monomer, although the resin curability is as low as 0.6, the transparency maintenance rate is high at 98% for both the two lamps.

  As is apparent from this result, the curability of the ultraviolet curable resin itself is improved by adding a monomer having an N-vinyl group. However, the fogging of the transparent tube is promoted, the curing of the ultraviolet curable resin becomes insufficient, or the transparent tube needs to be cleaned and replaced after drawing. There are also changes in the appearance of the sealing material. On the other hand, by blending a monomer having no N-vinyl group, the fogging of the transparent tube is suppressed, but the resin curability is low, and the gel fraction, which is an index of coating curability, is lowered to 89%, so Is insufficient. In this case, there arises a problem that a desired strength cannot be obtained due to a decrease in the crosslinking density.

Moreover, as shown in Examples 1 to 3, while the upstream ultraviolet irradiation device is turned on, the temperature of the ultraviolet transmitting cylindrical body on the downstream side is constantly maintained at 70 to 180 ° C., thereby causing the transparent tube to become cloudy. Suppressed.

DESCRIPTION OF SYMBOLS 1 Optical fiber base material 2 Heater 3 Glass optical fiber 4 Optical fiber strand 5 Resin coating apparatus 6a, 6b Ultraviolet irradiation apparatus 7 Guide roller 8 Winding apparatus 9 Ultraviolet irradiation apparatus main body 10 Intake apparatus 11 Exhaust apparatus 12 Intake port 13a, 13b Optical fiber insertion port 14 Exhaust port 15 Ultraviolet transmitting cylindrical body, transparent tube 16 Ultraviolet irradiation lamp 17 Mirror 18 Sealing material

Claims (2)

It is a method for manufacturing an optical fiber that is formed by coating an outer periphery of a linear body with an ultraviolet curable resin,
A drawing process of drawing an optical fiber preform into a filament;
An application step of applying the ultraviolet curable resin to the linear body;
An irradiation step of irradiating the linear body coated with the ultraviolet curable resin with ultraviolet rays using two or more ultraviolet irradiation devices;
The ultraviolet curable resin includes an acrylic monomer and a monomer having an N-vinyl group,
In the irradiation step, ultraviolet rays are irradiated while passing through an ultraviolet transmitting cylindrical body in two or more ultraviolet irradiation devices, and at least an upstream ultraviolet irradiation device is turned on in any two adjacent ultraviolet irradiation devices. A method of manufacturing an optical fiber, wherein the temperature of the ultraviolet transmitting cylindrical body on the downstream side is always 70 to 180 ° C.   2. The method of manufacturing an optical fiber according to claim 1, wherein the temperature of the ultraviolet transmitting cylindrical body is controlled only by radiant heat from the ultraviolet irradiation device.