Title of invention: Method and apparatus for manufacturing optical fiber
Technical field
[0001]
　The present invention relates to a method for manufacturing an optical fiber strand. Further, the present invention relates to an optical fiber element manufacturing apparatus.
Background technology
[0002]
　The optical fiber element wire is composed of (1) a bare optical fiber wire made of glass and (2) a resin coating covering the side surface of the optical fiber element wire. The coating plays a role of relieving lateral pressure on the bare optical fiber and improving external damage resistance. In the manufacture of optical fiber bare wires, it is common to coat the side surface of the bare optical fiber with an ultraviolet curable resin and then irradiate it with ultraviolet rays to cure the ultraviolet curable resin.
[0003]
　Further, in manufacturing an optical fiber element wire, it is known to provide a plurality of irradiation steps for irradiating ultraviolet rays. For example, Patent Document 1 describes that the surface layer of the ultraviolet curable resin is cured by the first irradiation step and then the inner layer is cured by the second irradiation step. Further, in Patent Document 2, the optical fiber strand partially cured of the ultraviolet curable resin in the first irradiation step is cooled by passing through a cooling pipe through which a cooling gas flows, and the second irradiation step is performed. It is described to be performed.
Prior art documents
Patent literature
[0004]
Patent Document 1: Japanese Unexamined Patent Publication “JP-2014-77918” (published on May 1, 2014)
Patent Document 2: Japanese Unexamined Patent Publication “JP-A-10-297942” (November 1998) Published on 10th)
Summary of the invention
Problems to be Solved by the Invention
[0005]
　However, in the conventional method for manufacturing an optical fiber element wire, there is a problem that if the inner layer of the coating of the optical fiber element wire is not sufficiently cured, the coating may be cracked in the optical fiber element wire after the manufacturing. It was
[0006]
　The present invention has been made in view of the above problems, and an object of the present invention is to realize a manufacturing method and a manufacturing apparatus of an optical fiber element wire in which a coating crack is less likely to occur in the manufactured optical fiber element wire.
Means for solving the problem
[0007]
　In order to solve the above problems, the method for producing an optical fiber element wire of one aspect of the present invention is, among the ultraviolet curable resin constituting the coating, at least the ultraviolet curable resin constituting the surface layer of the coating is in an uncured state. The first irradiation step of irradiating each point of the optical fiber strand with ultraviolet rays, and the ultraviolet curable resin constituting at least the surface layer of the coating obtained by performing the first irradiation step is cured. A second irradiation step of irradiating each point of the optical fiber wire with an ultraviolet ray, and the temperature of the optical fiber wire immediately before performing the second irradiation step is 50° C. or higher and 300° C. It is characterized by the following.
[0008]
　Further, in order to solve the above problems, in the optical fiber element manufacturing apparatus of one aspect of the present invention, among the ultraviolet curable resins constituting the coating, at least the ultraviolet curable resin constituting the surface layer of the coating is uncured. A first irradiation part that irradiates ultraviolet rays to each point of the optical fiber element in the state, and at least a surface layer of the coating obtained by irradiating the ultraviolet light by the first irradiation part A second irradiation unit that irradiates ultraviolet rays to each point of the optical fiber strand where the ultraviolet curable resin is cured, and the optical fiber immediately before the ultraviolet ray is irradiated by the second irradiation unit. The temperature of the wire is 50° C. or higher and 300° C. or lower.
Effect of the invention
[0009]
　According to one aspect of the present invention, it is possible to realize a manufacturing method and a manufacturing apparatus of an optical fiber element wire in which a coating crack is less likely to occur in the manufactured optical fiber element wire.
Brief description of the drawings
[0010]
FIG. 1 is a cross-sectional view showing a cross section of an optical fiber element wire manufactured in each embodiment of the present invention.
FIG. 2 is a block diagram showing a configuration of an optical fiber element manufacturing apparatus according to the first embodiment of the present invention.
FIG. 3 is a diagram showing an example of spectra of ultraviolet rays emitted from a UV lamp of a primary irradiation unit and a UVLED of a secondary irradiation unit in the first embodiment of the present invention.
FIG. 4 is a cross-sectional view of a first irradiation unit that constitutes a primary irradiation unit according to the first embodiment of the present invention.
FIG. 5 is a cross-sectional view of a second irradiation unit that constitutes a secondary irradiation unit according to the first embodiment of the present invention.
FIG. 6 is a graph showing the relationship between the temperature of the optical fiber element wire immediately before entering the secondary irradiation section and the degree of cure of the primary coating after manufacturing in the first embodiment of the present invention.
FIG. 7 is a flowchart illustrating a method for manufacturing an optical fiber element wire according to the first embodiment of the present invention.
MODE FOR CARRYING OUT THE INVENTION
[0011]
　Hereinafter, an optical fiber manufacturing apparatus and manufacturing method according to each embodiment of the present invention will be described. In addition, in each embodiment, the same reference numerals are given to the same configurations and steps, and duplicate description will be omitted.
[0012]
　[Structure of Optical Fiber Element Wire]
　First, an optical fiber element wire 10 manufactured by an optical fiber manufacturing apparatus and a manufacturing method according to each embodiment described below will be described with reference to FIG. 1. FIG. 1 is a cross-sectional view showing a cross section (cross section orthogonal to the optical axis) of the optical fiber element wire 10.
[0013]
　The optical fiber element wire 10 includes a cylindrical optical fiber bare wire 11 and a coating 12 that covers a side surface of the optical fiber bare wire 11.
[0014]
　The bare optical fiber 11 includes a cylindrical core 11a and a cylindrical clad 11b that covers the side surface of the core 11a. Both the core 11a and the clad 11b are made of quartz glass. However, the refractive index of the silica glass forming the clad 11b is lower than the refractive index of the silica glass forming the core 11a. The refractive index difference between the core 11a and the clad 11b is, for example, by adding a dopant (for example, germanium) for increasing the refractive index to the silica glass forming the core 11a, or the quartz glass forming the clad 11b. It is formed by adding a dopant (for example, fluorine) for lowering the refractive index. The reason why the refractive index of the clad 11b is lower than that of the core 11a is to give the bare optical fiber 11 a function of confining light in the core 11a.
[0015]
　The coating 12 is composed of a cylindrical primary coating 12a that covers the side surface of the bare optical fiber 11 (the outer surface of the cladding 11b) and a cylindrical secondary coating 12b that covers the outer surface of the primary coating 12a. ing. Both the primary coating 12a and the secondary coating 12b are made of an ultraviolet curable resin. However, the Young's modulus of the ultraviolet curable resin constituting the primary coating 12a is lower than the Young's modulus of the ultraviolet curable resin constituting the secondary coating 12b. The Young's modulus difference between the primary coating 12a and the secondary coating 12b is formed by, for example, varying the degree of polymerization of the ultraviolet curable resin forming the primary coating 12a and the secondary coating 12b. The Young's modulus of the secondary coating 12b is relatively high, and the Young's modulus of the primary coating 12a is relatively low. This is because the coating 12a improves impact absorption.
[0016]
　A photopolymerization initiator is contained in each of the ultraviolet curable resins constituting the primary coating 12a and the secondary coating 12b. Curing of these ultraviolet curable resins is initiated by ultraviolet rays having a wavelength belonging to the absorption wavelength band of the photopolymerization initiator. It should be noted that the higher the curing temperature is, the more easily the ultraviolet curable resin forming the secondary coating 12b is cured, and the ultraviolet curable resin forming the primary coating 12a is less likely to be cured. Further, the lower the curing temperature is, the harder the curing of the ultraviolet curable resin forming the secondary coating 12b is likely to proceed, and the more likely the curing of the ultraviolet curable resin forming the primary coating 12a proceeds.
[0017]
　First Embodiment
　(Configuration of Optical Fiber Manufacturing Apparatus)
　The configuration of the manufacturing apparatus 1 according to the first embodiment of the present invention will be described with reference to FIG. FIG. 2 is a block diagram showing the configuration of the manufacturing apparatus 1.
[0018]
　The manufacturing apparatus 1 is an apparatus for manufacturing the optical fiber strand 10 (see FIG. 1), and includes a wire drawing portion 101, a cooling portion 102, a bare wire outer diameter measuring portion 103, a coating portion 104, and a wire outer diameter measurement. The unit 105 includes a primary irradiation unit 106, a take-up unit 107, a secondary irradiation unit 108, and a winding unit 109. These constituent elements are arranged in this order along the traveling path of the optical fiber strand 10. Further, the manufacturing apparatus 1 includes a control unit 110 that controls the coating unit 104 and the take-up unit 107 by referring to the monitor signals acquired from the bare wire outer diameter measuring unit 103 and the bare wire outer diameter measuring unit 105. The manufacturing apparatus 1 also includes a plurality of pulleys 111_1 to 111_6. The traveling path of the optical fiber strand 10 is defined by these pulleys 111_1 to 111_6.
[0019]
　The primary irradiation unit 106 constitutes an example of the first irradiation unit of the present invention. Further, the secondary irradiation unit 108 constitutes an example of the second irradiation unit of the present invention.
[0020]
　The drawing portion 101 is a means for drawing a preform which is a base material of the bare optical fiber 11. In this embodiment, a heating furnace is used as the wire drawing portion 101. The preform is heated and melted by this heating furnace. Then, the melted preform is stretched by its own weight. Such melting and stretching of the preform is called "drawing". The preform drawn in the drawing unit 101 is sent to the cooling unit 102 arranged below the drawing unit 101.
[0021]
　The cooling unit 102 is a means for cooling the drawn preform. In this embodiment, a cooling cylinder is used as the cooling unit 102. The drawn preform is cooled and hardened by the cooling gas flowing in the cooling cylinder. As a result, the bare optical fiber 11 is obtained. The bare optical fiber 11 obtained in the cooling unit 102 passes through the bare wire outer diameter measuring unit 103 for measuring the outer diameter of the bare optical fiber 11, and then the coating unit disposed below the cooling unit 102. It is sent to 104.
[0022]
　The coating unit 104 is a unit for coating the uncured ultraviolet curable resin, which is the base material of the coating 12, on the side surface of the bare optical fiber 11. In the present embodiment, a double coating die in which two coating dies are stacked is used as the coating unit 104. The uncured ultraviolet curing resin, which is the base material of the primary coating 12a, is applied to the side surface of the bare optical fiber 11 by the application die on the upstream side, and the downstream side is applied to the outer surface of the primary coating 12a. An uncured ultraviolet curable resin which is a base material of the secondary coating 12b is applied by the application die. Thereby, the optical fiber element wire 10 in which both the primary coating 12a and the secondary coating 12b are in an uncured state is obtained. Hereinafter, the optical fiber strand 10 in this state is referred to as an optical fiber strand 10α. The optical fiber element wire 10α obtained in the coating section 104 passes through an element wire outer diameter measuring section 105 for measuring the outer diameter of the optical fiber element wire 10α, and then is placed below the coating section 104. It is sent to the irradiation unit 106.
[0023]
　The thickness of the ultraviolet curable resin applied by the application unit 104 is variable, and is controlled by the control unit 110 based on the outer diameter of the optical fiber strand 10α measured by the strand outer diameter measurement unit 105. There is. When the outer diameter of the optical fiber element wire 10α is smaller than a predetermined value, the control unit 110 controls the coating unit 104 to increase the thickness of the ultraviolet curable resin to be coated. Conversely, when the outer diameter of the optical fiber element wire 10α is larger than a predetermined value, the control unit 110 controls the application unit 104 so that the thickness of the ultraviolet curable resin to be applied is reduced. As a result, the outer diameter of the obtained optical fiber strand 10 can be brought close to a predetermined value.
[0024]
　The primary irradiation unit 106 is means for irradiating the optical fiber strand 10α with ultraviolet rays using a UV lamp (ultraviolet lamp) in a low oxygen atmosphere. In the present embodiment, n (n is a natural number of 1 or more) UV lamp units 106_1 to 106_n using a UV lamp as a light source are used as the primary irradiation unit 106. The configuration of each UV lamp unit 106 — i (i is a natural number of 1 or more and n or less) will be described later with reference to the drawings. Although FIG. 2 illustrates the case where n=3, the number of UV lamp units 106_i forming the primary irradiation unit 106 is arbitrary.
[0025]
　The ultraviolet curable resin, which is the base material of the coating 12, is sequentially cured from the outside by ultraviolet irradiation using a UV lamp in the primary irradiation unit 106. In the UV irradiation using the UV lamp in the primary irradiation unit 106, the UV curable resin which mainly constitutes the secondary coating 12b is cured. However, at the stage when the ultraviolet irradiation using the UV lamp in the primary irradiation unit 106 is completed, it is sufficient that at least the ultraviolet curable resin forming the surface layer of the secondary coating 12b is sufficiently cured, and the remaining ultraviolet curable resin is used. May be in an uncured state or a semi-cured state. The optical fiber strand 10 in this state is hereinafter referred to as an optical fiber strand 10β. The optical fiber strand 10β obtained in the primary irradiation unit 106 is sent to the take-up unit 107 after passing through the pulley 111_1. The pulley 111_1 functions as a turn pulley that changes the traveling path of the optical fiber element wire 10β from a first direction (downward in FIG. 2) parallel to the gravity direction to a second direction (rightward in FIG. 2) perpendicular to the gravity direction. ..
[0026]
　The take-up unit 107 is means for taking the optical fiber strand 10β at a specific take-up speed. Here, the take-up speed is the length of the optical fiber element wire 10β taken by the take-out unit 107 per unit time. In this embodiment, a capstan is used as the take-up unit 107. The optical fiber element wire 10β taken by the take-off section 107 passes through the pulleys 111_2 to 111_6 and is then sent to the secondary irradiation section 108 arranged on the side of the take-off section 107. Here, the pulley 111_5 is a dancer pulley that is displaceable in parallel to the first direction (vertical direction in FIG. 2). By urging the pulley 111_5 in the first direction (downward in FIG. 2), tension is applied to the optical fiber strand 10β.
[0027]
　The take-up speed of the take-up unit 107 is variable, and is controlled by the control unit 110 based on the outer diameter of the bare optical fiber 11 measured by the bare wire outer diameter measuring unit 103. When the outer diameter of the bare optical fiber 11 is smaller than a predetermined value, the control unit 110 controls the pulling unit 107 so that the pulling speed decreases. Conversely, when the outer diameter of the bare optical fiber 11 is larger than a predetermined value, the control unit 110 controls the take-up unit 107 so that the take-up speed increases. Thereby, the outer diameter of the obtained bare optical fiber 11 can be brought close to a predetermined value.
[0028]
　The secondary irradiation unit 108 is a means for irradiating the optical fiber strand 10β with ultraviolet rays using a UVLED (ultraviolet light emitting diode). In this embodiment, m (m is a natural number of 1 or more) UVLED units 108_1 to 108_m using UVLEDs as light sources are used as the secondary irradiation unit 108. The configuration of each UVLED unit 108_j (j is a natural number of 1 or more and m or less) will be described later with reference to the drawings. Although FIG. 2 illustrates the case of m=2, the number of UVLED units 108_j forming the secondary irradiation unit 108 is arbitrary.
[0029]
　Among the UV curable resins that are the base material of the coating 12, the UV curable resin that has not been sufficiently cured by the UV irradiation using the UV lamp in the primary irradiation unit 106 is the UV light using the UVLED in the secondary irradiation unit 108. Curing is completed by irradiation. In the UV irradiation using the UVLED in the secondary irradiation unit 108, the UV curable resin mainly constituting the primary coating 12a is cured. Thereby, the optical fiber strand 10 is obtained. The optical fiber strand 10 obtained in the secondary irradiation unit 108 is sent to the winding unit 109.
[0030]
　The winding unit 109 is means for winding the optical fiber strand 10. In this embodiment, a winding drum 109a having a rotation axis parallel to the second direction and a pulley 109b that can be displaced parallel to the second direction are used as the winding unit 109. By rotating the winding drum 109a and reciprocally moving the pulley 109b in parallel with the second direction, the optical fiber wire 10 is evenly wound around the winding drum 109a.
[0031]
　As described above, in the manufacturing apparatus 1, the UV lamp is used as the light source of the primary irradiation unit 106 and the UVLED is used as the light source of the secondary irradiation unit 108. This is for the following reason.
[0032]
　UV LEDs consume less power than UV lamps. Further, since the UVLED does not easily reach a high temperature, the cooling device can be simplified, and as a result, the power consumption during operation can be further suppressed. Further, the UVLED has an advantage that it is possible to suppress deterioration of the ultraviolet curable resin that may occur in a high temperature environment. However, if the UVLED is used as the light source of the primary irradiation unit 106, the following problems occur.
[0033]
　That is, as shown in FIG. 3, the ultraviolet rays emitted from the UVLED have a narrower spectral width than the ultraviolet rays emitted from the UV lamp. Therefore, it is highly possible that the peak wavelength of the UVLED is different from the absorption wavelength of the photopolymerization initiator contained in the secondary coating 12b. In addition, the secondary coating 12b tends to be cured more easily as the fiber temperature during curing is higher. Therefore, when UVLED is used for the primary irradiation unit 106, there is a high possibility that the ultraviolet curable resin forming the surface layer of the secondary coating 12b cannot be sufficiently cured in the primary irradiation unit 106. Then, when the optical fiber element wire 10β comes into contact with the pulley 111_1, the surface of the secondary coating 12b adheres to the pulley 111_1 and is peeled off.
[0034]
　Therefore, in the manufacturing apparatus 1, these problems are avoided by using a UV lamp as the light source of the primary irradiation unit 106.
[0035]
　Furthermore, the manufacturing apparatus 1 employs the following configuration in the above-mentioned primary irradiation unit 106.
[0036]
　That is, the primary irradiator 106 irradiates the optical fiber element 10α with ultraviolet rays using a UV lamp in a low oxygen atmosphere with an oxygen concentration of 2% or less. This is to prevent the curing inhibition of the ultraviolet curable resin by oxygen. Specifically, the primary irradiation unit 106 is configured so that an inert gas having an oxygen concentration of 2% or less flows through a quartz tube in which an optical fiber element wire 10α that irradiates ultraviolet rays emitted from a UV lamp runs. ..
[0037]
　Further, the primary irradiation unit 106 is configured to irradiate each point of the optical fiber element wire 10α with ultraviolet rays using a UV lamp for 0.01 seconds or more. This is an irradiation time for sufficiently curing the ultraviolet curable resin forming at least the surface layer of the secondary coating 12b. The irradiation time refers to the time from when each point of the optical fiber element wire 10α enters the ultraviolet irradiation section by the primary irradiation unit 106 until it advances. For example, assume that the drawing speed is 3000 meters/minute. In this case, in order to secure the irradiation time of 0.01 seconds, the length of the irradiation section in the low-oxygen atmosphere in the primary irradiation unit 106 may be 0.6 meters or more.
[0038]
　Furthermore, the primary irradiation unit 106 is configured such that the irradiation time of ultraviolet rays using a UV lamp is 0.07 seconds or less for each point of the optical fiber strand 10α. This is an irradiation time for sufficiently curing the ultraviolet curable resin that constitutes at least the surface layer of the secondary coating 12b, but preventing the deterioration of the ultraviolet curable resin that may occur in a high temperature environment by the UV lamp. For example, assume that the drawing speed is 1000 meters/minute. In this case, in order to reduce the irradiation time to 0.07 seconds or less, the length of the irradiation section in the low oxygen atmosphere in the primary irradiation unit 106 may be 1.2 meters or less.
[0039]
　Furthermore, the manufacturing apparatus 1 may employ the following configuration in the above-mentioned secondary irradiation unit 108.
[0040]
　That is, the secondary irradiation unit 108 may use, as the UVLED, a UVLED that emits ultraviolet rays having the absorption wavelength of the photopolymerization initiator contained in the ultraviolet curable resin forming the primary coating 12a. In the present embodiment, it is highly possible that the ultraviolet curable resin forming the secondary coating 12a has been cured to some extent by passing through the primary irradiation unit 106 in the optical fiber strand 10β. Therefore, in the optical fiber strand 10β, the part of the ultraviolet curable resin that is the base material of the coating 12 that is not sufficiently cured is considered to be mainly the ultraviolet curable resin that constitutes the primary coating 12a.
[0041]
　(Structures of UV Lamp Unit and UVLED Unit) The
　structure of the UV lamp unit 106_i forming the primary irradiation unit 106 will be described with reference to FIG. FIG. 4 is a cross-sectional view of the UV lamp unit 106_i.
[0042]
　The UV lamp unit 106_i includes a housing 106a, a quartz tube 106b penetrating the housing 106a, a UV lamp 106c housed inside the housing 106a, and a quartz tube 106b and a UV lamp 106c inside the housing 106a. And a surrounding reflector 106d. Examples of the UV lamp 106c include a metal halide lamp. The ultraviolet light emitted from the UV lamp 106c is applied to the optical fiber element wire 10α running inside the quartz tube 106b directly or after being reflected by the reflecting plate 106d.
[0043]
　The housing 106a is provided with an air supply port 106a1 for supplying the cooling gas into the housing 106a and an exhaust port 106a2 for exhausting the cooling gas to the outside of the housing 106a. There is. The UV lamp 106c housed inside the housing 106a is cooled by this cooling gas.
[0044]
　Further, the UV lamp unit 106_i further includes an upper cap 106e that houses the upper end of the quartz tube 106b that projects upward from the housing 106a, and a lower cap 106f that houses the lower end of the quartz tube 106b that projects downward from the housing 106a. And are equipped with. The upper cap 106e is provided with a supply port 106e1 for supplying a low oxygen concentration inert gas into the upper cap 106e, and the lower cap 106f exhausts this inert gas to the outside of the lower cap 106f. An exhaust port 106f1 for this purpose is provided. Examples of the inert gas include nitrogen, argon, and helium. The insides of the upper cap 106e, the quartz tube 106b, and the lower cap 106f are filled with this inert gas. Therefore, the optical fiber wire 10α running inside the quartz tube 106b is irradiated with ultraviolet rays in a low oxygen atmosphere.
[0045]
　In the present embodiment, such UV lamp units 106_1 to 3 are arranged continuously. It is assumed that the total length of the sections irradiated with the ultraviolet rays in each UV lamp unit 106 — i is such that the irradiation time becomes 0.01 seconds or more and 0.07 seconds or less as the take-up speed changes.
[0046]
　Next, the configuration of the UVLED unit 108_j forming the secondary irradiation unit 108 will be described with reference to FIG. FIG. 5 is a cross-sectional view of the UVLED unit 108_j.
[0047]
　The UVLED unit 108_j includes a housing 108a, a quartz tube 108b penetrating the housing 108a, a UVLED bar 108c housed inside the housing 108a, and quartz so as to face the UVLED bar 108c inside the housing 108a. And a reflector 108d surrounding the tube 108b. The UVLED bar 108c is an ultraviolet light source in which a plurality of UVLED elements 108c1 to 108c5 are linearly arranged. The ultraviolet light emitted from the UVLED bar 108c is applied to the optical fiber element wire 10β running inside the quartz tube 108b either directly or after being reflected by the reflector 108d.
[0048]
　(Temperature of Optical Fiber Element 10β Immediately Before Entering
　Secondary Irradiation Unit 108 ) The temperature of optical fiber element 10β immediately before entering the secondary irradiation unit 108 is preferably 50° C. or more and 300° C. or less. Therefore, in the present embodiment, the secondary irradiation from the primary irradiation unit 106 is performed so that the temperature of the optical fiber strand 10β immediately before entering the secondary irradiation unit 108 by natural cooling becomes 50° C. or higher and 300° C. or lower. The length of the running path of the optical fiber strand 10β to the portion 108 is set to be sufficiently long. The rate of temperature decrease due to natural cooling of the optical fiber element wire 10β is, for example, in the range of 400° C./sec or more and 1400° C./sec or less. However, the rate of temperature decrease due to the natural cooling of the optical fiber strand 10β changes according to the drawing rate. Therefore, the length of the traveling path of the optical fiber strand 10β from the primary irradiation unit 106 to the secondary irradiation unit 108 is also set to a value according to the drawing speed.
[0049]
　Here, the reason why it is preferable that the temperature of the optical fiber strand 10β immediately before entering the secondary irradiation unit 108 is 50° C. or higher and 300° C. or lower will be described with reference to FIG. FIG. 6 is a graph showing the relationship between the temperature of the optical fiber element wire 10β immediately before entering the secondary irradiation unit 108 and the degree of curing of the primary coating 12a constituting the manufactured optical fiber element wire 10. Here, the gel fraction is used as an index showing the degree of curing of the primary coating 12a. According to the graph shown in FIG. 6, when the temperature of the optical fiber element wire 10β immediately before entering the secondary irradiation unit 108 is 50° C. or higher and 300° C. or lower, the gel fraction of the primary coating 12a is 85% or higher. It turns out that
[0050]
　When lateral pressure is applied to the optical fiber element wire 10 in a process after manufacturing, the coating 12 may be cracked. According to the knowledge obtained by the inventors of the present application, (1) when the gel fraction of the primary coating 12a is less than 80%, the number of optical fiber strands 10 in which the coating 12 is cracked is several tens% of the whole. (2) When the gel fraction of the primary coating 12a is 80% or more and less than 85%, the number of the optical fiber strands 10 in which the coating 12 is cracked is several% of the whole, and (3) of the primary coating 12a When the gel fraction is 85% or more, the optical fiber wire 10 that causes the coating 12 to crack does not occur. Therefore, when the temperature of the optical fiber element wire 10β immediately before entering the secondary irradiation unit 108 is 50° C. or higher and 300° C. or lower, the gel fraction of the primary coating 12a becomes 85% or more, and as a result, It is possible to prevent possible cracks.
[0051]
　Furthermore, it is preferable that the temperature of the optical fiber element wire 10β immediately before entering the secondary irradiation unit 108 is 63° C. or higher and 100° C. or lower. In this case, the gel fraction of the primary coating 12a is further increased, and as a result, cracks that may occur in the coating 12 can be further prevented.
[0052]
　(Temperature
　of Optical Fiber Element Wire 10β Immediately After Passing Primary Irradiation Unit 106 ) The temperature of optical fiber element wire 10β immediately after passing the primary irradiation unit 106 is preferably 300° C. or lower. This is because if the temperature of the optical fiber element wire 10β immediately after passing through the primary irradiation unit 106 is 300° C. or less, the temperature of the optical fiber element wire 10β immediately before entering the secondary irradiation unit 108 is surely 300° C. or less. Because it can be
[0053]
　The temperature rising rate of the optical fiber element 10α in the primary irradiation unit 106 is 3000° C./sec or more and 24000° C./sec or less. For example, when the temperature rising rate of the optical fiber element wire 10α in the primary irradiation section 106 is 3000° C./second, the time for the optical fiber element wire 10α to pass through the primary irradiation section 106 is 0.1 seconds or less. If the drawing speed is set to, the temperature of the optical fiber strand 10β immediately after passing through the primary irradiation unit 106 can be suppressed to 300° C. or lower. Further, when the temperature rising rate of the optical fiber strand 10α in the primary irradiation unit 106 is 24000° C./sec, the time for the optical fiber strand 10α to pass through the primary irradiation unit 106 is 0.0125 seconds or less. If the drawing speed is set to, the temperature of the optical fiber strand 10β immediately after passing through the primary irradiation unit 106 can be suppressed to 300° C. or lower.
[0054]
　(Method for Manufacturing Optical Fiber Element)
　The method S1 for manufacturing the optical fiber element 10 according to the first embodiment of the present invention will be described with reference to FIG. 7. FIG. 7 is a flowchart showing a method S1 of manufacturing the optical fiber strand 10. The manufacturing method S1 is a method for manufacturing the optical fiber element wire 10 (see FIG. 1), and includes steps S101 to S109 described below.
[0055]
　Step S101: The drawing unit 101 draws a preform which is a base material of the bare optical fiber 11.
[0056]
　Step S102: The cooling unit 102 cools the preform drawn in step S101. As a result, the bare optical fiber 11 is obtained.
[0057]
　Step S103: The bare wire outer diameter measurement unit 103 measures the outer diameter of the bare optical fiber 11 obtained in step S102, and provides a monitor signal indicating the measured value of the outer diameter to the control unit 110.
[0058]
　Step S104 (coating step): The coating section 104 coats the side surface of the bare optical fiber 11 whose outer diameter has been measured in step S103 with an uncured ultraviolet curable resin which is a base material of the coating 12. Specifically, the coating unit 104 applies the uncured ultraviolet curable resin, which is the base material of the primary coating 12a, to the outer surface of the bare optical fiber 11 and the outer surface of the primary coating 12a. The work of applying the uncured ultraviolet curable resin which is the base material of the secondary coating 12b is collectively performed. Thereby, the optical fiber strand 10α is obtained.
[0059]
　The thickness of the ultraviolet curable resin applied in step S104 is adjusted by the control of the control unit 110 based on the outer diameter of the optical fiber element wire 10α measured in step S105 described later.
[0060]
　Step S105: The element wire outer diameter measuring unit 105 measures the outer diameter of the optical fiber element wire 10α obtained in step S104, and provides the control unit 110 with a monitor signal indicating the measured value of the outer diameter.
[0061]
　Step S106 (first irradiation step): The primary irradiation unit 106 irradiates the optical fiber wire 10α obtained in step S105 with ultraviolet rays using a UV lamp. As a result, the ultraviolet curable resin, which is the base material of the secondary coating 12b, is mainly cured, and the optical fiber element wire 10β is obtained. At least the ultraviolet curable resin forming the surface layer of the secondary coating 12b is sufficiently cured in this step. At this time, the temperature of the obtained optical fiber strand 10β is 300° C. or lower.
[0062]
　Step S107: The take-up unit 107 takes in the optical fiber strand 10β obtained in the step S106 at a particular take-up speed.
[0063]
　The take-up speed for taking the optical fiber strand 10β in step S107 is adjusted by the control of the control unit 110 based on the outer diameter of the bare optical fiber 11 measured in step S103 described above.
[0064]
　Step S108 (second irradiation step): The secondary irradiation unit 108 irradiates the optical fiber strand 10β taken in step S107 with ultraviolet rays by using a UVLED. As a result, the ultraviolet curable resin, which is the base material of the primary coating 12a, is mainly cured, and the optical fiber element wire 10 is obtained. The temperature of the optical fiber strand 10β immediately before performing step S108 is 50° C. or more and 300° C. or less after being naturally cooled after performing step S106.
[0065]
　Step S109: The winding unit 109 winds the optical fiber element wire 10 obtained in step S108 on the winding drum 109a. As a result, the optical fiber element wire 10 wound around the winding drum 109a is obtained.
[0066]
　In the step S106 described above, the ultraviolet irradiation by the primary irradiation unit 106 using the UV lamp is performed for 0.01 seconds or more in a low oxygen atmosphere having an oxygen concentration of 2% or less, as described above.
[0067]
　As described above, according to the present embodiment, the oxygen concentration is 2% in a low oxygen atmosphere with respect to each point of the optical fiber wire in which a portion including at least the surface layer of the ultraviolet curable resin forming the coating is uncured. Then, the UV irradiation with the UV lamp is performed for 0.01 seconds or more. After that, in the present embodiment, each point of the optical fiber strand is irradiated with ultraviolet rays by the UVLED.
[0068]
　Here, the absorption wavelength of the photopolymerization initiator contained in the secondary coating 12b is highly likely to be contained in ultraviolet rays having a broad spectral width emitted from a UV lamp. In addition, the secondary coating 12b tends to be more easily cured as the fiber temperature during curing is higher.
[0069]
　Therefore, in the present embodiment, at least the surface layer of the secondary coating 12b can be sufficiently cured in the irradiation before the manufacturing process of the optical fiber element wire 10. As a result, in the present embodiment, in the manufacturing apparatus 1 that applies the primary coating 12a and the secondary coating 12b collectively, it is possible to manufacture the optical fiber element wire 10 in which the surface property is less likely to deteriorate than in the conventional case.
[0070]
　(Modification) In the
　present embodiment, the UV lamp units 106_1 to 106_3 constituting the primary irradiation unit 106 are described as being irradiated in a low oxygen atmosphere with an oxygen concentration of 2% or less. However, the UV irradiation in one or more UV lamp units 106_i on the downstream side of the UV lamp units 106_i forming the primary irradiation unit 106 does not necessarily have to be performed in a low oxygen atmosphere. That is, if the irradiation time of 0.01 seconds or more is secured by the one or more UV lamp units 106_i on the upstream side, the remaining UV lamp units 106_i on the downstream side may irradiate the ultraviolet rays in the air. I do not care. That is, the low-oxygen concentration inert gas does not have to flow in the UV lamp unit 106_i on the downstream side.
[0071]
　This is because if the surface layer of the UV curable resin forming the secondary coating 12b in the UV lamp unit 106_i on the upstream side of the primary irradiation unit 106 is sufficiently cured, the remaining UV curable resin is not exposed, and therefore the oxygen is not exposed. This is because it is not necessary to prevent the inhibition of curing due to.
[0072]
　In such a configuration, the first half of the first irradiation step in the present invention is performed by one or more upstream UV lamp units 106_i that irradiate ultraviolet rays in a low oxygen atmosphere in the primary irradiation unit 106. It After that, the latter half of the first irradiation step in the present invention is performed by the remaining UV lamp unit 106_i on the downstream side of the primary irradiation unit 106 that irradiates ultraviolet rays in the air. Then, the 2nd irradiation process in this invention is implemented by the secondary irradiation part 108.
[0073]
　Further, in the present embodiment, an example in which the coating 12 of the optical fiber element wire 10 is composed of two layers of a primary coating 12a and a secondary coating 12b has been described. However, this embodiment is also applicable to the case where the coating 12 is composed of one layer. In that case, in the present embodiment, the coating unit 104 may be configured to coat the bare optical fiber 11 with the ultraviolet curable resin that forms the coating 12 formed of one layer.
[0074]
　Further, in the present embodiment, the cooling of the optical fiber strand 10β in the section from the primary irradiation unit 106 to the secondary irradiation unit 108 is realized by natural cooling. However, the present invention is not limited to this. That is, the cooling of the optical fiber element wire 10β in the section from the primary irradiation unit 106 to the secondary irradiation unit 108 can be realized by forced cooling. In this case, a cooling unit for forced cooling is provided in the section from the primary irradiation unit 106 to the secondary irradiation unit 108. This cooling unit cools the optical fiber element wire 10β so that the temperature immediately before entering the secondary irradiation unit 108 is 50° C. or higher and 300° C. or lower. In addition, this cooling unit is configured by, for example, a cooling cylinder through which cooling gas flows.
[0075]
　Further, in the present embodiment, the UV irradiation in the primary irradiation unit 106 is realized by the UV lamp, and the UV irradiation in the secondary irradiation unit 108 is realized by the UVLED. However, the present invention is not limited to this. That is, the UV irradiation in the primary irradiation unit 106 can be realized by the UVLED. Further, the UV irradiation in the secondary irradiation unit 108 can be realized by a UV lamp.
[0076]
　[Summary] In the
　method for manufacturing an optical fiber element wire (10) of one embodiment of the present invention, at least the surface layer of the coating (12b) of the ultraviolet curable resin constituting the coating (12, 12a, 12b) is configured. At least the above-mentioned coating obtained by performing a first irradiation step of irradiating ultraviolet rays on each point of the optical fiber element wire (10α) in which the ultraviolet curable resin is in an uncured state and the first irradiation step ( And a second irradiation step of irradiating each point of the optical fiber element wire (10β) in which the ultraviolet curable resin constituting the surface layer of 12b) is cured with the second irradiation step. The temperature of the optical fiber strand (10β) immediately before is 50° C. or higher and 300° C. or lower.
[0077]
　An apparatus for manufacturing an optical fiber element wire (10) according to an embodiment of the present invention is an ultraviolet curable resin that constitutes at least the surface layer of the coating (12b) among the ultraviolet curable resins that constitute the coating (12, 12a, 12b). Each point of the uncured optical fiber element wire (10α) is irradiated with the ultraviolet ray by the first irradiation section (106) for irradiating the ultraviolet ray and the first irradiation section (106). A second irradiation part (108) for irradiating ultraviolet rays to each point of the optical fiber strand (10β) obtained by curing at least the ultraviolet curable resin constituting the surface layer of the coating (12b). And the temperature of the optical fiber element wire (10β) immediately before being irradiated with the ultraviolet rays by the second irradiation section (108) is 50° C. or higher and 300° C. or lower.
[0078]
　According to the above configuration, the optical fiber element wire in which at least the surface layer of the coating is cured by the first irradiation step (first irradiation section) is immediately before entering the second irradiation step (second irradiation section). In, the temperature is 50° C. or higher and 300° C. or lower. By irradiating the optical fiber strand that has rushed in this temperature range with ultraviolet rays, the inner layers other than the surface layer of the coating are sufficiently hardened as compared with the prior art. As a result, even if lateral pressure is applied to the coating in the post-manufacturing process, the frequency of cracking of the coating is reduced.
[0079]
　In the method for manufacturing an optical fiber element wire (10) according to one embodiment of the present invention, the temperature of each point of the optical fiber element wire (10β) immediately after performing the first irradiation step is 300° C. or less. Is preferred.
[0080]
　According to the above configuration, the temperature of the optical fiber element wire immediately before entering the second irradiation step can be more surely set to 50° C. or higher and 300° C. or lower.
[0081]
　In the method for manufacturing an optical fiber element wire (10) according to one embodiment of the present invention, it is preferable that the first irradiation step is performed in a low oxygen atmosphere having an oxygen concentration of 2% or less.
[0082]
　According to the above configuration, it is possible to prevent the inhibition of curing of the ultraviolet curable resin by oxygen.
[0083]
　In the method for manufacturing an optical fiber strand (10) according to an embodiment of the present invention, the temperature of the optical fiber strand (10β) immediately before performing the second irradiation step by natural cooling is 50° C. or higher and 300° C. or higher. The length of the traveling path of the optical fiber wire (10β) from the execution of the first irradiation step to the execution of the second irradiation step is set so as to be equal to or lower than °C. It is preferable.
[0084]
　According to the above configuration, the above effects can be obtained without adding a configuration such as a cooling unit.
[0085]
　[Additional Remarks] The
　present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims, and the technical means disclosed in the different embodiments are appropriately combined. The obtained embodiments are also included in the technical scope of the present invention.
Explanation of symbols
[0086]
　　DESCRIPTION OF SYMBOLS 　　1 Manufacturing apparatus
　　10 Optical fiber strand
　　11a Core
　　11b Clad
　　12a Primary coating
　　12b Secondary coating
　　11 Optical fiber bare wire
　　12 Coating
101 Wire drawing
　　part 102 Cooling part
　　103 Bare wire outer diameter measuring part
　　104 Coating part
　　105 Element wire outer diameter measurement Part
　　106 Primary irradiation part
　　107 　　Pulling part
　　108 Secondary irradiation part
　　109 Winding part
　　110 Control part
111_1 to 111_6 Pulleys
　　106a, 108a Housings
　　106b, 108b Quartz tube
　　106c UV lamp
　　108c UVLED bar
　　106a1,
　　106e1 Air supply port 106a2, 106f2 Exhaust port
　　106d, 108d Reflector plate
The scope of the claims
[Claim 1]
　Of the ultraviolet curing resin constituting the coating, for each point of the optical fiber of the ultraviolet curable resin is uncured state constituting the surface layer of at least the coating, a first irradiation step of irradiating ultraviolet rays,
　the first A second irradiation step of irradiating each point of the optical fiber element wire in which the ultraviolet curable resin forming the surface layer of the coating is obtained, which is obtained by carrying out the irradiation step of 1. A method for manufacturing an optical fiber element wire, wherein
　the temperature of the optical fiber element wire immediately before performing the second irradiation step is 50° C. or higher and 300° C. or lower
.
[Claim 2]
　The
method for manufacturing an optical fiber element wire according to claim 1, wherein the temperature of the optical fiber element wire immediately after performing the first irradiation step is 300° C. or lower .
[Claim 3]
　The second irradiation step is performed after the first irradiation step is performed so that the temperature of the optical fiber strand immediately before performing the second irradiation step by natural cooling becomes 50° C. or higher and 300° C. or lower. The
method for manufacturing an optical fiber element wire according to claim 1 or 2, wherein a length of a traveling path of the optical fiber element wire before the step is performed is set .
[Claim 4]
　The method for manufacturing an optical fiber strand according to any one of claims 1 to 3, wherein the first irradiation step is performed in a low oxygen atmosphere having an oxygen concentration of 2% or less.
[Claim 5]
　Of the ultraviolet curing resin constituting the coating, for each point of the optical fiber of the ultraviolet curable resin is uncured state constituting the surface layer of at least the coating, a first irradiation unit for irradiating ultraviolet light,
　the first Second irradiation for irradiating ultraviolet rays to at least each point of the optical fiber element wire obtained by irradiating the ultraviolet ray by the irradiating unit 1 at least with the ultraviolet curable resin forming the surface layer of the coating cured includes a part, a
　temperature of the optical fiber immediately before the ultraviolet rays are irradiated by the second irradiation unit is 50 ° C. or higher 300 ° C. or less,
the production of optical fiber, characterized in that apparatus.