Coated optical fiber and method for manufacturing coated optical fiber

Abstract

To provide a coated optical fiber in which resistance against high temperature and high humidity of a primary layer is improved.SOLUTION: A coated optical fiber comprises an optical fiber bare wire, a primary layer which coats the optical fiber bare wire and is formed of first ultraviolet curable resin, and a secondary layer which coats the primary layer and is formed of a second ultraviolet curable resin. The primary layer has a carbon-sulfur bond, the primary layer includes 1.08 wt.% or less of sulfur atom, youngs modulus of the primary layer is 0.21 MPa or more and 2.36 MPa or less, and a variation of youngs modulus of the primary layer when being exposed under the environment of 85°C and humidity of 85% for two days is 0.09 MPa or less.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an optical fiber and a method for manufacturing an optical fiber. [Background technology]

[0002] In optical fiber cores, a technology is known in which a primary layer covering a bare optical fiber and a secondary layer covering the primary layer are each set to a desired Young's modulus by using an ultraviolet-curable resin (Patent Document 1). For example, the Young's modulus of the primary layer is set low, so that the primary layer can buffer external forces applied to the bare optical fiber and suppress optical transmission loss (microbend loss) caused by minute deformation of the bare optical fiber. In addition, the Young's modulus of the secondary layer is set higher than that of the primary layer, so that the secondary layer protects the bare optical fiber and the primary layer from external forces.

[0003] Since it is desirable for the Young's modulus of the primary layer to be low, the technique described in Patent Document 2 sets the maximum Young's modulus (saturated Young's modulus) that can be achieved by the ultraviolet curable resin of the primary layer 3 low. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2005-162522 A [Patent Document 2] International Publication No. 2018 / 062364 Summary of the Invention [Problem to be solved by the invention]

[0005] However, even if the Young's modulus of the primary layer is set to an appropriate value, the Young's modulus of the primary layer may change significantly when the optical fiber is placed in a high-temperature and high-humidity environment. If the Young's modulus of the primary layer increases, the microbend loss of the optical fiber may increase. If the Young's modulus of the primary layer decreases, the strength of the optical fiber may decrease and the force of the primary layer to hold the bare optical fiber may decrease.

[0006] An object of the present invention is to provide an optical fiber having a primary layer with improved resistance to high temperature and high humidity. [Means for solving the problem]

[0007] According to one aspect of the present invention, there is provided an optical fiber core comprising: a bare optical fiber; a primary layer formed of a first ultraviolet-curable resin covering the bare optical fiber; and a secondary layer formed of a second ultraviolet-curable resin covering the primary layer, wherein the primary layer has carbon-sulfur bonds, the primary layer contains 1.08 wt % or less of sulfur atoms, the Young's modulus of the primary layer is 0.21 MPa or more and 2.36 MPa or less, and the absolute value of the change in Young's modulus of the primary layer when exposed to an environment of 85°C and humidity of 85% for two days is 0.09 MPa or less.

[0008] According to another aspect of the present invention, there is provided a method for manufacturing an optical fiber core, comprising the steps of: drawing a bare optical fiber from an optical fiber preform; applying a first ultraviolet-curable resin around the bare optical fiber to form a primary layer, and applying a second ultraviolet-curable resin around the primary layer to form a secondary layer, and irradiating the second ultraviolet-curable resin with ultraviolet light to form a secondary layer, wherein the primary layer has carbon-sulfur bonds, the primary layer contains 1.08 wt % or less of sulfur atoms, the Young's modulus of the primary layer is 0.21 MPa or more and 2.36 MPa or less, and the absolute value of the change in Young's modulus of the primary layer when exposed to an environment of 85°C and 85% humidity for two days is 0.09 MPa or less. Effect of the Invention

[0009] According to the present invention, it is possible to provide an optical fiber having a primary layer with improved resistance to high temperatures and high humidity. [Brief description of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view of an optical fiber according to a first embodiment. [Diagram 2] 1 is a schematic diagram showing a part of a manufacturing apparatus used in a manufacturing method of an optical fiber according to a first embodiment. [Diagram 3] 1 is a schematic diagram showing a part of a manufacturing apparatus used in a manufacturing method of an optical fiber according to a first embodiment. [Figure 4] 4 is a flowchart of a method for manufacturing an optical fiber according to the first embodiment. [Diagram 5] 1 is a graph showing a microbend loss difference versus a Young's modulus difference of a primary layer. [Figure 6] 5 is a cross-sectional view of an optical fiber ribbon according to a second embodiment. FIG. [Figure 7] 5 is a schematic diagram of an optical fiber ribbon manufacturing apparatus according to a second embodiment. FIG. [Figure 8] 10 is a flowchart of a method for manufacturing an optical fiber ribbon according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. Elements having common functions are designated by the same reference numerals throughout the drawings, and duplicated descriptions may be omitted or simplified.

[0012] [First embodiment] Fig. 1 is a cross-sectional view of an optical fiber according to a first embodiment. Fig. 1 shows a colored optical fiber 6 as an example of the optical fiber according to this embodiment. The colored optical fiber 6 includes an optical fiber 1 and a colored layer 5 that covers the outer periphery of the optical fiber 1. The optical fiber 1 also includes a bare optical fiber 2, a primary layer 3 that covers the outer periphery of the bare optical fiber 2, and a secondary layer 4 that covers the outer periphery of the primary layer 3. The bare optical fiber 2 is covered with three coating layers, namely the primary layer 3, the secondary layer 4, and the colored layer 5.

[0013] The bare optical fiber 2 is formed of, for example, silica-based glass and transmits light. The primary layer 3 is a soft layer and has a function of buffering external forces applied to the bare optical fiber 2. The Young's modulus of the primary layer 3 may preferably be 0.1 MPa or more and 3.0 MPa or less. The secondary layer 4 is a hard layer and has a function of protecting the bare optical fiber 2 and the primary layer 3 from external forces. The Young's modulus of the secondary layer 4 may preferably be 500 MPa or more and 2000 MPa or less. The colored layer 5 is colored to identify the colored optical fiber core 6. The colored layer 5 may be the secondary layer 4 colored with a coloring agent. The coloring agent may be a mixture containing a pigment or a lubricant.

[0014] When an external force is applied to the bare optical fiber 2, a transmission loss of light (microbend loss) occurs due to minute deformation of the bare optical fiber 2. By setting the Young's modulus of the primary layer 3 low, the function of buffering the external force of the primary layer 3 is improved, and the microbend loss of the colored optical fiber core 6 is suppressed.

[0015] The diameter of the colored optical fiber core 6 may be 190 μm or more and 260 μm or less. The diameter of the optical fiber core 1 may be 190 μm or more and 250 μm or less. The diameter of the bare optical fiber 2 may be 80 μm or more and 150 μm or less, and preferably 124 μm or more and 126 μm or less. The thickness of the primary layer 3 may be 5 μm or more and 60 μm or less. The thickness of the secondary layer 4 may be 5 μm or more and 60 μm or less. The thickness of the colored layer 5 may be several μm. Here, the diameter of the colored optical fiber core 6 may be determined by the sum of the diameter of the bare optical fiber 2, the length twice the thickness of the primary layer 3, the length twice the thickness of the secondary layer 4, and the length twice the thickness of the colored layer 5. Therefore, the diameter of the bare optical fiber 2, the thickness of the primary layer 3, the thickness of the secondary layer 4, and the thickness of the colored layer 5 may be selected so that the diameter of the colored optical fiber core 6 is 190 μm or more and 260 μm or less.

[0016] The Young's modulus of the primary layer 3 of the optical fiber is ISM (In Situ Modulus), and the Young's modulus of the primary layer 3 can be measured by the following method.

[0017] First, a commercially available stripper is used to strip off the primary layer 3 and the secondary layer 4 from the middle of the sample optical fiber by a length of several mm, and then one end of the optical fiber on which the coating layer is formed is fixed on a slide glass with an adhesive, and a load F is applied to the other end of the optical fiber on which the coating layer is formed. In this state, the displacement δ of the primary layer at the boundary between the part where the coating layer has been stripped off and the part where the coating is formed is read under a microscope. Then, the rate (slope) of change in the load F with respect to the displacement δ is calculated by setting the load F to 10, 20, 30, 50, and 70 gf (i.e., 98, 196, 294, 490, and 686 mN, respectively). The primary elastic modulus is calculated using the calculated slope and the following formula (1). The calculated primary elastic modulus is the so-called ISM, and hereinafter the primary elastic modulus is appropriately referred to as P-ISM. When drawing the optical fiber, the drawing speed and the irradiance of the ultraviolet light are controlled to adjust the P-ISM. P-ISM=(3F / δ)*(1 / 2πl)*ln(DP / DG) ···(1)

[0018] The unit of P-ISM is [MPa]. In the right side of formula (1), F / δ is the rate (slope) of change in load (F) [gf] relative to displacement (δ) [μm], l is the sample length (e.g., 10 mm), and DP / DG is the ratio of the outer diameter (DP) [μm] of the primary layer to the outer diameter (DG) [μm] of the cladding of the optical fiber. Therefore, when calculating P-ISM using formula (1) from the F, δ, and l used, a certain unit conversion is required. The outer diameter of the primary layer 3 and the outer diameter of the cladding can be measured by observing the cross section of the optical fiber cut by a fiber cutter under a microscope.

[0019] Furthermore, the Young's modulus of the secondary layer 4 of the optical fiber is an ISM (In Situ Modulus), and the Young's modulus of the secondary layer 4 can be measured by the following method.

[0020] First, the optical fiber is immersed in liquid nitrogen, and the coating layer is stripped off with a stripper to produce a sample of only the coating layer by pulling out the bare optical fiber 2 from the optical fiber. The end of the sample is fixed to an aluminum plate using an adhesive. The aluminum plate is chucked using a Tensilon universal tensile tester in an atmosphere of 23°C temperature and 50% relative humidity. Next, the sample is stretched with a gauge spacing of 25 mm and a tensile speed of 1 mm / min, and the force at 2.5% stretch is measured to calculate the elastic modulus S-ISM (2.5% Secant Modulus) of the secondary layer.

[0021] The effective core area (Aeff) is an index that indicates the susceptibility of an optical fiber to microbend loss. The effective core area (Aeff) is expressed by the following formula (2). The effective core area (Aeff) is described in, for example, C-3-76 and C-3-77 of the 1999 Electronics Society Conference Proceedings of the Institute of Electronics, Information and Communication Engineers. Aeff = (πk / 4) * (MFD) 2 (2) Here, the effective core area Aeff is a value at a wavelength of 1550 nm, MFD is a mode field diameter (μm), and k is a constant. The effective core area Aeff represents the area of ​​a portion of a cross section perpendicular to the axis of the bare optical fiber 2 through which light having a predetermined intensity passes. In general, the larger the effective core area Aeff of the bare optical fiber 2, the weaker the optical confinement in the cross section of the bare optical fiber 2. That is, when the effective core area Aeff of the bare optical fiber 2 is large, the light in the bare optical fiber 2 is more likely to leak out due to an external force applied to the bare optical fiber 2. For this reason, when the effective core area Aeff of the bare optical fiber 2 is large, microbending loss is more likely to occur in the colored optical fiber 6.

[0022] On the other hand, by increasing the effective core area of ​​the bare optical fiber 2, it is possible to reduce the light intensity per unit area in the cross section of the bare optical fiber 2. This makes it possible to suppress the nonlinear optical effect of the bare optical fiber 2.

[0023] The colored optical fiber 6 according to this embodiment has a primary layer 3 that can effectively suppress microbending loss. That is, even when the effective core area of ​​the bare optical fiber 2 is large, the microbending loss of the colored optical fiber 6 can be effectively suppressed.

[0024] The effective core area Aeff of the bare optical fiber 2 is 80 μm 2 More than, for example, 130 μm 2 More than 150μm 2 It is preferable that the above-mentioned condition is satisfied. In this manner, the colored optical fiber 6 capable of suppressing the nonlinear optical effect of the bare optical fiber 2 can be obtained.

[0025] The primary layer 3, the secondary layer 4, and the colored layer 5 are formed by curing an ultraviolet-curable resin by irradiation with ultraviolet light. The ultraviolet-curable resin (first ultraviolet-curable resin) of the primary layer 3 in this embodiment contains a mercapto group-containing compound as an additive. The ultraviolet-curable resin and the mercapto group-containing compound are described in detail below.

[0026] [UV curable resin] The ultraviolet curable resin is a resin that is polymerized and hardened by irradiation with ultraviolet rays. The ultraviolet curable resin is not particularly limited as long as it can be polymerized by irradiation with ultraviolet rays. The ultraviolet curable resin can be polymerized by, for example, photoradical polymerization.

[0027] The ultraviolet-curable resin is, for example, an ultraviolet-curable resin having a polymerizable unsaturated group such as an ethylenically unsaturated group that polymerizes and cures when exposed to ultraviolet light, such as urethane (meth)acrylates such as polyether-based urethane (meth)acrylates and polyester-based urethane (meth)acrylates, epoxy (meth)acrylates, and polyester (meth)acrylates, and preferably has at least two polymerizable unsaturated groups.

[0028] The polymerizable unsaturated group in the ultraviolet curable resin may be, for example, a group having an unsaturated double bond such as a vinyl group, an allyl group, an acryloyl group, or a methacryloyl group, or a group having an unsaturated triple bond such as a propargyl group, etc. Among these, an acryloyl group or a methacryloyl group is preferred in terms of polymerizability.

[0029] The ultraviolet curable resin may be a monomer, oligomer, or polymer that initiates polymerization and hardens upon irradiation with ultraviolet light, but is preferably an oligomer. An oligomer is a polymer having a degree of polymerization of 2 to 100. In this specification, "(meth)acrylate" means one or both of acrylate and methacrylate. The ultraviolet curable resin contains any photopolymerization initiator (photoinitiator) that has sensitivity in the ultraviolet region.

[0030] A polyether-based urethane (meth)acrylate is a compound having a polyether segment, a (meth)acrylate, and a urethane bond, such as a reaction product of a polyol having a polyether skeleton with an organic polyisocyanate compound and a hydroxyalkyl (meth)acrylate. A polyester-based urethane (meth)acrylate is a compound having a polyester segment, a (meth)acrylate, and a urethane bond, such as a reaction product of a polyol having a polyester skeleton with an organic polyisocyanate compound and a hydroxyalkyl (meth)acrylate.

[0031] The ultraviolet curable resin may contain, in addition to the oligomer and the photoinitiator, a lubricant and various additives, such as a diluent monomer, a photosensitizer, an ultraviolet absorber, an antioxidant, a chain transfer agent, and a silane coupling agent. The diluent monomer may be a monofunctional (meth)acrylate or a polyfunctional (meth)acrylate. Here, the diluent monomer means a monomer for diluting the ultraviolet curable resin.

[0032] [Mercapto group-containing compounds] The mercapto group-containing compound is a compound that has a mercapto group and contains S (sulfur). The mercapto group-containing compound is added to the ultraviolet curable resin of the primary layer 3. The mercapto group-containing compound inhibits the polymerization reaction of the ultraviolet curable resin of the primary layer 3. The mercapto group-containing compound may be any compound that can inhibit the polymerization reaction of the ultraviolet curable resin of the primary layer 3. Specific examples of the mercapto group-containing compound include ethyl mercaptan, 1-butanethiol, 1-heptanethiol, 1-undecanethiol, 4-hydroxybenzenethiol, (2-mercaptoethyl)pyrazine, 2,3-butanedithiol, 3-methyl-2-butanethiol, 3-mercapto-1,2,4-triazole, 1,3,4-thiadiazole-2-thiol, isobutyl mercaptan, 4-methoxy-α-toluenethiol, 4,4′-biphenyldithiol, trimethylsilylmethanethiol, 1,4-butanedithiol, 1,8-octanedithiol, 3-ethoxybenzenethiol, pentaerythritol tetra(3-mercaptopropionate), isooctyl-3-mercaptopropionate, (3-mercaptopropyl)trimethoxysilane, and (3-mercaptopropyl)triethoxysilane.

[0033] The mercapto group of the mercapto group-containing compound reacts with the ultraviolet curable resin of the primary layer 3, such as urethane acrylate, and suppresses the polymerization reaction of the ultraviolet curable resin of the primary layer 3. The reaction between the mercapto group-containing compound and the ultraviolet curable resin of the primary layer 3 may be an enethiol reaction. This allows the primary layer 3 to have a carbon-sulfur bond. The mercapto group-containing compound suppresses the polymerization reaction of the ultraviolet curable resin of the primary layer 3, so that the Young's modulus of the primary layer 3 can be set low.

[0034] [Manufacturing equipment] Next, a manufacturing apparatus used in the manufacturing method of the optical fiber according to this embodiment will be described. Fig. 2 is a schematic diagram showing a part of a manufacturing apparatus 10 used in the manufacturing method of the optical fiber according to this embodiment. The manufacturing apparatus 10 has a heating device 20, a primary layer coating device 30, a secondary layer coating device 40, a guide roller 60, and a winding device 70. The manufacturing apparatus 10 shown in Fig. 2 manufactures an optical fiber 1 from an optical fiber preform BM.

[0035] The optical fiber preform BM is made of, for example, quartz-based glass, and is manufactured by a well-known method such as the VAD method, the OVD method, or the MCVD method. The heating device 20 has a heater 21. The heater 21 can be any heat source such as a tape heater, a ribbon heater, a rubber heater, an oven heater, a ceramic heater, or a halogen heater. An end of the optical fiber preform BM is heated and melted by the heater 21 arranged around the optical fiber preform BM, and is drawn to draw out a bare optical fiber 2.

[0036] A primary layer coating device 30 is provided below the heating device 20. The primary layer coating device 30 has a resin applicator 31 and an ultraviolet ray irradiation device 32. The resin applicator 31 holds an ultraviolet ray curable resin for the primary layer 3. The ultraviolet ray curable resin for the primary layer 3 contains the above-mentioned mercapto group-containing compound as an additive. The ultraviolet ray curable resin for the primary layer 3 is applied by the resin applicator 31 to the bare optical fiber 2 drawn out from the optical fiber preform BM.

[0037] An ultraviolet ray irradiation device 32 is provided below the resin application device 31. The ultraviolet ray irradiation device 32 includes any ultraviolet ray light source such as a metal halide lamp, a mercury lamp, a UV-LED, or the like. The resin application device 31 applies an ultraviolet ray curable resin of the primary layer 3 to the bare optical fiber 2, and the bare optical fiber 2 enters the ultraviolet ray irradiation device 32, where the ultraviolet ray curable resin of the primary layer 3 is irradiated with ultraviolet rays. As a result, the ultraviolet ray curable resin of the primary layer 3 is cured, and the primary layer 3 is formed.

[0038] A secondary layer coating device 40 is provided below the primary layer coating device 30. The secondary layer coating device 40 has a resin coating device 41 and an ultraviolet ray irradiation device 42. The resin coating device 41 holds an ultraviolet ray curable resin (second ultraviolet ray curable resin) of the secondary layer 4. The ultraviolet ray curable resin of the secondary layer 4 is applied to the primary layer 3 by the resin coating device 41.

[0039] An ultraviolet irradiation device 42 is provided below the resin application device 41. The ultraviolet irradiation device 42 may be configured in the same manner as the ultraviolet irradiation device 32. The bare optical fiber 2, in which the ultraviolet-curable resin of the secondary layer 4 is coated around the primary layer 3, enters the ultraviolet irradiation device 42, and ultraviolet rays are irradiated onto the ultraviolet-curable resin of the secondary layer 4. As a result, the ultraviolet-curable resin of the secondary layer 4 is cured, and the secondary layer 4 is formed. The bare optical fiber 2 is coated with the primary layer 3 and the secondary layer 4, thereby forming the optical fiber core 1. Note that if uncured reaction points remain in the primary layer 3, the primary layer 3 can be further cured by irradiation of ultraviolet rays by the ultraviolet irradiation device 42.

[0040] The resin coating device 31 may be configured to separately hold the ultraviolet curable resin of the primary layer 3 and the ultraviolet curable resin of the secondary layer 4. In this case, the resin coating device 31 coats the ultraviolet curable resin of the primary layer 3 on the bare optical fiber 2, and then coats the ultraviolet curable resin of the secondary layer 4 around the ultraviolet curable resin of the primary layer 3. Furthermore, in this case, the ultraviolet irradiating device 32 irradiates ultraviolet rays onto the ultraviolet curable resin of the primary layer 3 and the ultraviolet curable resin of the secondary layer 4 that have been applied to the bare optical fiber 2. This forms the primary layer 3 and the secondary layer 4. In this case, the manufacturing apparatus 10 does not necessarily need to have the secondary layer coating device 40.

[0041] A guide roller 60 and a winding device 70 are provided below the secondary layer coating device 40. The manufactured optical fiber 1 is guided by the guide roller 60 and wound around the winding device 70.

[0042] Fig. 3 is a schematic diagram showing a part of a manufacturing apparatus 10 used in the manufacturing method of the optical fiber according to this embodiment. The manufacturing apparatus 10 has a colored layer coating device 50, guide rollers 61, 62, and winding devices 70, 71. In Fig. 3, the manufacturing apparatus 10 is an apparatus for manufacturing a colored optical fiber 6 from an optical fiber 1.

[0043] The optical fiber 1 wound by the winding device 70 is guided by a guide roller 61 and transported to the colored layer coating device 50 .

[0044] The colored layer coating device 50 has a resin applicator 51 and an ultraviolet ray irradiation device 52. The resin applicator 51 holds an ultraviolet ray curable resin (third ultraviolet ray curable resin) of the colored layer 5. The ultraviolet ray curable resin of the colored layer 5 is applied to the optical fiber 1 by the resin applicator 51.

[0045] An ultraviolet irradiator 52 is provided below the resin applicator 51. The ultraviolet irradiator 52 may be configured similarly to the ultraviolet irradiators 32 and 42. The optical fiber core 1 coated with the ultraviolet curable resin of the colored layer 5 enters the ultraviolet irradiator 52, and ultraviolet light is irradiated onto the ultraviolet curable resin of the colored layer 5. As a result, the ultraviolet curable resin of the colored layer 5 is cured, and the colored layer 5 is formed. The optical fiber core 1 is coated with the colored layer 5, and the colored optical fiber core 6 is formed. If uncured reaction points remain in the primary layer 3, the primary layer 3 can be further cured by irradiation of ultraviolet light by the ultraviolet irradiator 52.

[0046] Below the colored layer coating device 50, a guide roller 62 and a winding device 71 are provided. The manufactured colored optical fiber core wire 6 is guided by the guide roller 62 and wound around the winding device 71.

[0047] [Manufacturing method] Next, a method for manufacturing the optical fiber according to this embodiment will be described. Fig. 4 is a flow chart of a method for manufacturing the optical fiber colored core 6 according to this embodiment. First, the optical fiber preform BM is placed in the manufacturing apparatus 10 (step S101).

[0048] Next, the heater 21 provided in the heating device 20 heats the optical fiber preform BM, and drawing of the bare optical fiber 2 starts (step S102).

[0049] The primary layer coating device 30 applies an ultraviolet-curable resin for the primary layer 3 around the drawn bare optical fiber 2, and irradiates the ultraviolet-curable resin for the primary layer 3 with ultraviolet light to form the primary layer 3 (step S103). The ultraviolet-curable resin for the primary layer 3 contains the above-mentioned mercapto group-containing compound as an additive.

[0050] Next, the secondary layer coating device 40 applies an ultraviolet-curable resin of the secondary layer 4 around the primary layer 3, and irradiates the ultraviolet-curable resin of the secondary layer 4 with ultraviolet light to form the secondary layer 4 (step S104). This results in the optical fiber 1. The manufactured optical fiber 1 is wound up by the winding device 70.

[0051] Next, the colored layer coating device 50 applies an ultraviolet-curable resin of the colored layer 5 around the optical fiber core 1, and irradiates the ultraviolet-curable resin of the colored layer 5 with ultraviolet light to form the colored layer 5 (step S105). This results in the colored optical fiber core 6. The manufactured colored optical fiber core 6 is wound up by the winding device 71.

[0052] It is not always necessary to irradiate the primary layer 3 with ultraviolet light in the step (step S103) of forming the primary layer 3. In this case, the primary layer 3 can be cured in the step (step S104) of forming the secondary layer 4.

[0053] [Effects] According to this embodiment, it is possible to provide a colored optical fiber 6 having improved resistance to high temperature and high humidity in the primary layer 3. The effects of this embodiment will be described in detail below in comparison with the prior art.

[0054] One possible technique for suppressing microbend loss in an optical fiber is to set the Young's modulus of the primary layer 3 low, as described in WO 2018 / 062364. By setting the Young's modulus of the primary layer 3 low, the primary layer 3 can buffer the external force applied to the bare optical fiber 2, and suppress microbend loss due to minute deformation of the bare optical fiber 2.

[0055] However, even if the Young's modulus of the primary layer 3 is set to an appropriate value, the Young's modulus of the primary layer 3 may change significantly when the optical fiber is placed in a high-temperature and high-humidity environment. If the Young's modulus of the primary layer 3 increases, the microbend loss of the optical fiber may increase. If the Young's modulus of the primary layer 3 decreases, the strength of the optical fiber may decrease and the force of the primary layer 3 to hold the bare optical fiber 2 may decrease.

[0056] There are various methods for measuring microbend loss, and the microbend loss can be measured by the following method. First, the transmission loss of the optical fiber wound around a bobbin wrapped with sandpaper is measured, and the transmission loss at this time is defined as the transmission loss of the optical fiber in state A. Next, the transmission loss of the optical fiber wound around a bobbin not wrapped with sandpaper is measured, and the transmission loss at this time is defined as the transmission loss of the optical fiber in state B. The difference between the transmission loss of the optical fiber in state A and the transmission loss of the optical fiber in state B is defined as the microbend loss of the optical fiber. Here, the transmission loss of the optical fiber in state B does not include the transmission loss due to external forces, and is considered to be the transmission loss inherent to the optical fiber. The grit size of the sandpaper is #1000, and the length of the optical fiber is 400 m or more. The optical fibers in states A and B are wound around the bobbin so as not to overlap each other. In other words, the optical fibers in states A and B are wound around the bobbin in a single layer.

[0057] This measurement method is similar to the fixed diameter drum method defined in JIS C6823:2010. This measurement method is also called the sandpaper method. In addition, this measurement method measures the transmission loss at a wavelength of 1550 nm, so the microbend loss in this embodiment is also a value at a wavelength of 1550 nm.

[0058] In this embodiment, the polymerization reaction of the ultraviolet curable resin of the primary layer 3 is suppressed by the mercapto group-containing compound. Due to the reaction between the ultraviolet curable resin of the primary layer 3 and the mercapto group-containing compound, the primary layer 3 has a carbon-sulfur bond and a more complicated cross-linked structure. This reduces the amount of change in Young's modulus of the primary layer 3 in a high-temperature, high-humidity environment. That is, by making the primary layer 3 contain sulfur atoms, the resistance of the primary layer 3 to high temperature and high humidity can be improved. In addition, the mercapto group-containing compound suppresses the polymerization reaction of the ultraviolet curable resin of the primary layer 3, so that the Young's modulus of the primary layer 3 can be set low. Therefore, according to this embodiment, by appropriately setting the sulfur atom content in the primary layer 3, the Young's modulus and resistance to high temperature and high humidity of the primary layer 3 can be set to appropriate values.

[0059] FIG. 5 is a graph showing the microbend loss difference versus the Young's modulus difference of the primary layer 3. In FIG. 5, the Young's modulus difference and the microbend loss difference of the primary layer 3 were calculated for two optical fibers selected from 19 optical fibers each having a different Young's modulus of the primary layer 3. The secondary layer 4 of each optical fiber may be about 1000 MPa. FIG. 5 classifies optical fiber combinations according to the Young's modulus difference of the primary layer 3, and shows the proportion of optical fiber combinations in each classification that have a microbend loss difference of 0.05 dB / km or more. In FIG. 5, the Young's modulus difference of the primary layer 3 is classified into 0 to 0.05 MPa, 0.05 to 0.10 MPa, 0.10 to 0.15 MPa, 0.15 to 0.20 MPa, 0.20 to 0.25 MPa, 0.25 to 0.30 MPa, 0.30 to 0.35 MPa, 0.35 to 0.40 MPa, 0.40 to 0.45 MPa, and 0.45 to 0.50 MPa. 0~0.05MPa, 0.05~0.10MPa, 0.10~0.15MPa, 0.15~0.20MPa, 0.20~0.25MPa, 0.25~0.30MPa, 0.30~0.35MPa, 0.35~0.40MPa, 0.40~0.45MPa, 0.45~0.50MPa are Young's modulus differences that are greater than 0MPa and less than 0.05MPa, greater than 0.05MPa and less than 0.10MPa, greater than 0.10MPa and less than 0.15MPa, and 0. The Young's modulus difference is greater than 15 MPa and not greater than 0.20 MPa, greater than 0.20 MPa and not greater than 0.25 MPa, greater than 0.25 MPa and not greater than 0.30 MPa, greater than 0.30 MPa and not greater than 0.35 MPa, greater than 0.35 MPa and not greater than 0.40 MPa, greater than 0.40 MPa and not greater than 0.45 MPa, and greater than 0.45 MPa and not greater than 0.50 MPa. As shown in Fig. 5, when the Young's modulus difference of the primary layer 3 is 0.10 MPa or less, the proportion of microbend loss differences of 0.05 dB / km or more is low, and an increase in microbend loss with an increase in the Young's modulus of the primary layer 3 is not observed to be significant.On the other hand, when the Young's modulus difference of the primary layer 3 is larger than 0.10 MPa, the proportion of microbend loss differences of 0.05 dB / km or more increases, and the increase in microbend loss accompanying the increase in Young's modulus of the primary layer becomes rapidly large. Therefore, in order to effectively suppress microbend loss, the increase in Young's modulus of the primary layer 3 of the optical fiber can be set to 0.10 MPa, preferably 0.09 MPa or less.

[0060] In this embodiment, the primary layer 3 preferably contains 1.08 wt % or less of sulfur atoms, which allows the Young's modulus and resistance to high temperature and high humidity of the primary layer 3 to be set to appropriate values.

[0061] In this embodiment, when the mercapto group-containing compound is a silane coupling agent, the mercapto group of the silane coupling agent reacts with the ultraviolet curable resin of the primary layer 3. As a result, the ultraviolet curable resin of the primary layer 3 is crosslinked via the silane coupling agent, and the Young's modulus and breaking elongation of the primary layer 3 increase. This allows the breaking elongation of the primary layer 3 to be set to an appropriate value. Also, when the mercapto group-containing compound is other than a silane coupling agent, the Young's modulus of the primary layer 3 can be set low.

[0062] [Second embodiment] 6 is a cross-sectional view of an optical fiber ribbon 8 according to the second embodiment. The optical fiber ribbon 8 has a plurality of colored optical fiber core wires 6 according to the first embodiment and a ribbon layer 7. The plurality of colored optical fiber core wires 6 are arranged side by side. The ribbon layer 7 covers and connects the plurality of colored optical fiber core wires 6.

[0063] The ribbon layer 7 is made of an ultraviolet curable resin. The ultraviolet curable resin of the ribbon layer 7 (fourth ultraviolet curable resin) may be the same resin as the ultraviolet curable resin forming the primary layer 3, the secondary layer 4, and the colored layer 5.

[0064] The optical fiber ribbon 8 is not limited to the configuration shown in Fig. 6. The optical fiber ribbon 8 may be an intermittent type optical fiber ribbon. When the optical fiber ribbon 8 is an intermittent type optical fiber ribbon, the optical fiber ribbon 8 forms adhesive parts (ribbon layers 7) intermittently in the longitudinal direction of the colored optical fiber core wires 6 in the region where two adjacent colored optical fiber core wires 6 contact each other.

[0065] 7 is a schematic diagram of an apparatus 80 for manufacturing an optical fiber ribbon 8 according to this embodiment. The manufacturing apparatus 80 has a plurality of supply bobbins 81, guide rollers 82, a resin application device 83, an ultraviolet ray irradiation device 84, a guide roller 85, and a bobbin 86. The manufacturing apparatus 80 is an apparatus for manufacturing an optical fiber ribbon 8 from a colored optical fiber core 6.

[0066] A plurality of supply bobbins 81 are arranged side by side. The colored optical fiber 6 is wound around the supply bobbin 81. The colored optical fiber 6 wound around the supply bobbin 81 is guided by a guide roller 82 and transported to a resin application device 83.

[0067] The resin applicator 83 holds the ultraviolet curing resin of the ribbon layer 7. The ultraviolet curing resin of the ribbon layer 7 is applied to the plurality of colored optical fiber core wires 6 by the resin applicator 83.

[0068] An ultraviolet irradiation device 84 is provided below the resin application device 83. The ultraviolet irradiation device 84 may be configured similarly to the ultraviolet irradiation devices 32, 42, and 52. The plurality of colored optical fiber core wires 6 coated with the ultraviolet curable resin of the ribbon layer 7 enter the ultraviolet irradiation device 84, and the ultraviolet curable resin of the ribbon layer 7 is irradiated with ultraviolet rays. As a result, the ultraviolet curable resin of the ribbon layer 7 is cured, and the ribbon layer 7 is formed. The plurality of colored optical fiber core wires 6 are covered and connected by the ribbon layer 7, and an optical fiber ribbon 8 is formed. Note that, if uncured reaction points remain in the primary layer 3, the primary layer 3 can be further cured by irradiation of ultraviolet rays by the ultraviolet irradiation device 84.

[0069] 8 is a flowchart of a method for manufacturing an optical fiber ribbon 8 according to this embodiment. Steps S101 to S105 are the same as those in the first embodiment. The manufacturing apparatus 80 applies an ultraviolet curing resin of the ribbon layer 7 to a plurality of colored optical fiber cores 6, and irradiates the ultraviolet curing resin of the ribbon layer 7 with ultraviolet light to form the ribbon layer 7 (step S106). In this way, the optical fiber ribbon 8 is obtained.

[0070] In this embodiment as well, the primary layer 3 contains sulfur atoms, making it possible to provide an optical fiber ribbon 8 in which the resistance of the primary layer 3 to high temperatures and high humidity is improved.

[0071] [Example] The measurement results of the ultraviolet curable resin of the primary layer according to the embodiment of the present invention will be described below. In this example and the comparative example, Young's modulus was measured after the crosslinking derived from the silane coupling agent was completed by adding the photoacid generator.

[0072] [Table 1]

[0073] The examples and comparative examples in Table 1 are cured resins obtained by irradiating ultraviolet rays at room temperature using a mercury lamp to an ultraviolet-curable resin for the primary layer formed into a sheet of about 100 μm in thickness. The photoinitiator added to the ultraviolet-curable resin for the primary layer is 2,4,6-trimethylbenzoyldiphenylphosphine oxide. The irradiation conditions for the mercury lamp are "illuminance 1000 mW / cm2" 2 , irradiation amount 500mJ / cm 2 ”, “Illuminance 1500mW / cm 2 , irradiation amount 500mJ / cm 2 ”, “Illuminance 500mW / cm 2 , irradiation amount 500mJ / cm 2 ”, “Illuminance 1500mW / cm 2 , irradiation amount 1000mJ / cm 2 ”, “Illuminance 1000mW / cm 2 , irradiation amount 1000mJ / cm2 ”, “Illuminance 500mW / cm 2 , irradiation amount 1000mJ / cm 2 ”, “Illuminance 200mW / cm 2 , irradiation amount 5mJ / cm 2 ". Furthermore, a UV-LED may be used as the ultraviolet light source instead of a mercury lamp. The wavelength of the ultraviolet light irradiated by the UV-LED may be set arbitrarily. For illuminance measurement, for example, UV-351 manufactured by Oak Manufacturing Co., Ltd. is used in the case of a mercury lamp, and for example, UVRT2 / UD-T3040T2 manufactured by Topcon Technohouse is used in the case of a UV-LED.

[0074] Table 1 shows the amount (wt%) of silane coupling agent (MPTMS) added to the UV-curable resin of the primary layer, the amount (wt%) of mercapto group-containing compound (IOMP) added to the UV-curable resin of the primary layer, the amount of sulfur (wt%) in the cured resin, the amount of silicon (wt%) in the cured resin, Young's modulus (MPa) of the cured resin after high temperature and humidity treatment (MPa), the change in Young's modulus due to high temperature and humidity treatment (MPa), Young's modulus (MPa) of the cured resin after additional UV irradiation, the change in Young's modulus due to additional UV irradiation (MPa), an evaluation of the resistance of the cured resin to high temperature and humidity treatment, and an evaluation of the resistance of the cured resin to additional UV irradiation.

[0075] The silane coupling agent added to the UV-curable resin of the primary layer is, but is not limited to, 3-mercaptopropyltrimethoxysilane (MPTMS). The silane coupling agent may be, for example, vinyltrimethoxysilane, allyltrimethoxysilane, 3-(trimethoxysilyl)propyl methacrylate, 3-mercaptopropyltriethoxysilane, or 3-isocyanatopropyltriethoxysilane.

[0076] A photoacid generator is added to the UV-curable resin of the primary layer. The photoacid generator generates acid by UV light, and promotes the bonding between the silane coupling agent and the bare optical fiber and the formation of crosslinking points derived from the silane coupling agent. The photoacid generator is CPI (registered trademark)-200K by San-Apro Co., Ltd., but may be any photoacid generator that generates acid by UV light irradiation.

[0077] Isooctyl-3-mercaptopropionate (IOMP) is a mercapto group-containing compound that terminates the polymerization reaction of ultraviolet curable resins such as urethane acrylate through an enethiol reaction. This allows the Young's modulus of the cured resin to be set low. The mercapto group-containing compound used to adjust the Young's modulus is not limited to IOMP.

[0078] The sulfur content is the amount of sulfur atoms contained in the cured resin, and is calculated using the amount of MPTMS added, the molecular weight of MPTMS, the amount of IOMP added, and the molecular weight of IOMP. The silicon content is the amount of silicon atoms contained in the cured resin, and is calculated using the amount of MPTMS added and the molecular weight of MPTMS. The sulfur content and silicon content in the cured resin may also be measured by elemental analysis (EA).

[0079] Young's modulus can be measured by the following method: Using a Tensilon universal tensile tester, a sample was stretched in an atmosphere of 23° C. and 50% relative humidity with a width of 6 mm, a gauge interval of 25 mm, and a tensile speed of 1 mm / min, and the force at 2.5% elongation was measured to calculate Young's modulus.

[0080] In the examples and comparative examples, the presence of carbon-sulfur bonds in the cured resin may be confirmed using Fourier transform infrared spectroscopy (FT-IR).

[0081] "Rating 1" in Table 1 indicates whether the absolute value of the change in Young's modulus of the cured resin due to high temperature and humidity treatment meets the standard (0.09 MPa or less). High temperature and humidity treatment involves exposing the cured resin to an environment of 85°C and 85% humidity for two days. If the absolute value of the change in Young's modulus meets the standard, the evaluation is judged as good (OK), and if the absolute value of the change in Young's modulus does not meet the standard, the evaluation is judged as poor (NG).

[0082] "Evaluation 2" in Table 1 indicates whether the absolute value of the change in Young's modulus of the cured resin due to additional UV irradiation meets the standard (0.09 MPa or less). "Evaluation 2" indicates whether the change in Young's modulus due to the reaction between the photoinitiator remaining in the cured resin and the unsaturated double bonds is below the standard. The light source for the additional UV irradiation was a mercury lamp, and the irradiation conditions were an illuminance of 1000 mW / cm. 2 , irradiation amount 500mJ / cm 2 When the absolute value of the change in Young's modulus meets the standard, the evaluation is judged as good (OK), and when the absolute value of the increase in Young's modulus does not meet the standard, the evaluation is judged as bad (NG).

[0083] In Example 1, MPTMS was not added to the ultraviolet curable resin of the primary layer. Also, 1.1 wt% of IOMP was added to the ultraviolet curable resin of the primary layer. The amount of sulfur in the cured resin was 0.16 wt%. The amount of silicon in the cured resin was 0 wt%. The Young's modulus of the cured resin was 1.48 MPa. The Young's modulus of the cured resin after high temperature and high humidity treatment was 1.44 MPa. The change in Young's modulus of the cured resin due to high temperature and high humidity treatment was -0.04 MPa. The Young's modulus of the cured resin after additional ultraviolet irradiation was 1.49 MPa. The change in Young's modulus of the cured resin due to additional ultraviolet irradiation was 0.01 MPa. The absolute value of the change in Young's modulus due to high temperature and high humidity treatment was 0.09 MPa or less, and Evaluation 1 was good (OK). The absolute value of the change in Young's modulus due to additional ultraviolet irradiation was 0.09 MPa or less, and Evaluation 2 was good (OK).

[0084] In Example 2, MPTMS was not added to the ultraviolet curable resin of the primary layer. In addition, 2.0 wt% of IOMP was added to the ultraviolet curable resin of the primary layer. The amount of sulfur in the cured resin was 0.29 wt%. The amount of silicon in the cured resin was 0 wt%. The Young's modulus of the cured resin was 1.15 MPa. The Young's modulus of the cured resin after high temperature and high humidity treatment was 1.08 MPa. The change in Young's modulus of the cured resin due to high temperature and high humidity treatment was -0.07 MPa. The Young's modulus of the cured resin after additional ultraviolet irradiation was 1.11 MPa. The change in Young's modulus of the cured resin due to additional ultraviolet irradiation was -0.04 MPa. The absolute value of the change in Young's modulus due to high temperature and high humidity treatment was 0.09 MPa or less, and Evaluation 1 was good (OK). The absolute value of the change in Young's modulus due to additional ultraviolet irradiation was 0.09 MPa or less, and Evaluation 2 was good (OK).

[0085] In Example 3, MPTMS was not added to the ultraviolet curable resin of the primary layer. In addition, 3.0 wt% of IOMP was added to the ultraviolet curable resin of the primary layer. The amount of sulfur in the cured resin was 0.44 wt%. The amount of silicon in the cured resin was 0 wt%. The Young's modulus of the cured resin was 0.75 MPa. The Young's modulus of the cured resin after high temperature and high humidity treatment was 0.69 MPa. The change in Young's modulus of the cured resin due to high temperature and high humidity treatment was -0.06 MPa. The Young's modulus of the cured resin after additional ultraviolet irradiation was 0.75 MPa. The change in Young's modulus of the cured resin due to additional ultraviolet irradiation was 0 MPa. The absolute value of the change in Young's modulus due to high temperature and high humidity treatment was 0.09 MPa or less, and Evaluation 1 was good (OK). The absolute value of the change in Young's modulus due to additional ultraviolet irradiation was 0.09 MPa or less, and Evaluation 2 was good (OK).

[0086] In Example 4, MPTMS was not added to the ultraviolet curable resin of the primary layer. In addition, 4.0 wt% of IOMP was added to the ultraviolet curable resin of the primary layer. The amount of sulfur in the cured resin was 0.59 wt%. The amount of silicon in the cured resin was 0 wt%. The Young's modulus of the cured resin was 0.53 MPa. The Young's modulus of the cured resin after high temperature and high humidity treatment was 0.49 MPa. The change in Young's modulus of the cured resin due to high temperature and high humidity treatment was -0.04 MPa. The Young's modulus of the cured resin after additional ultraviolet irradiation was 0.52 MPa. The change in Young's modulus of the cured resin due to additional ultraviolet irradiation was -0.01 MPa. The absolute value of the change in Young's modulus due to high temperature and high humidity treatment was 0.09 MPa or less, and Evaluation 1 was good (OK). The absolute value of the change in Young's modulus due to additional ultraviolet irradiation was 0.09 MPa or less, and Evaluation 2 was good (OK).

[0087] In Example 5, MPTMS was not added to the ultraviolet curable resin of the primary layer. In addition, 5.0 wt% of IOMP was added to the ultraviolet curable resin of the primary layer. The amount of sulfur in the cured resin was 0.73 wt%. The amount of silicon in the cured resin was 0 wt%. The Young's modulus of the cured resin was 0.32 MPa. The Young's modulus of the cured resin after high temperature and high humidity treatment was 0.29 MPa. The change in Young's modulus of the cured resin due to high temperature and high humidity treatment was -0.03 MPa. The Young's modulus of the cured resin after additional ultraviolet irradiation was 0.32 MPa. The change in Young's modulus of the cured resin due to additional ultraviolet irradiation was 0 MPa. The absolute value of the change in Young's modulus due to high temperature and high humidity treatment was 0.09 MPa or less, and Evaluation 1 was good (OK). The absolute value of the change in Young's modulus due to additional ultraviolet irradiation was 0.09 MPa or less, and Evaluation 2 was good (OK).

[0088] In Example 6, MPTMS was not added to the ultraviolet curable resin of the primary layer. In addition, 5.5 wt% of IOMP was added to the ultraviolet curable resin of the primary layer. The amount of sulfur in the cured resin was 0.81 wt%. The amount of silicon in the cured resin was 0 wt%. The Young's modulus of the cured resin was 0.27 MPa. The Young's modulus of the cured resin after high temperature and high humidity treatment was 0.26 MPa. The change in Young's modulus of the cured resin due to high temperature and high humidity treatment was -0.01 MPa. The Young's modulus of the cured resin after additional ultraviolet irradiation was 0.27 MPa. The change in Young's modulus of the cured resin due to additional ultraviolet irradiation was 0 MPa. The absolute value of the change in Young's modulus due to high temperature and high humidity treatment was 0.09 MPa or less, and Evaluation 1 was good (OK). The absolute value of the change in Young's modulus due to additional ultraviolet irradiation was 0.09 MPa or less, and Evaluation 2 was good (OK).

[0089] In Example 7, MPTMS was not added to the ultraviolet curable resin of the primary layer. In addition, 6.0 wt% of IOMP was added to the ultraviolet curable resin of the primary layer. The amount of sulfur in the cured resin was 0.88 wt%. The amount of silicon in the cured resin was 0 wt%. The Young's modulus of the cured resin was 0.22 MPa. The Young's modulus of the cured resin after high temperature and high humidity treatment was 0.21 MPa. The amount of change in Young's modulus of the cured resin due to high temperature and high humidity treatment was -0.01 MPa. The Young's modulus of the cured resin after additional ultraviolet irradiation was 0.23 MPa. The amount of change in Young's modulus of the cured resin due to additional ultraviolet irradiation was 0.01 MPa. The absolute value of the amount of change in Young's modulus due to high temperature and high humidity treatment was 0.09 MPa or less, and Evaluation 1 was good (OK). The absolute value of the amount of change in Young's modulus due to additional ultraviolet irradiation was 0.09 MPa or less, and Evaluation 2 was good (OK).

[0090] In Example 8, 0.01 wt% of MPTMS was added to the ultraviolet curable resin of the primary layer. Also, 4.0 wt% of IOMP was added to the ultraviolet curable resin of the primary layer. The amount of sulfur in the cured resin was 0.59 wt%. The amount of silicon in the cured resin was 0.001 wt%. The Young's modulus of the cured resin was 0.55 MPa. The Young's modulus of the cured resin after high temperature and high humidity treatment was 0.52 MPa. The change in Young's modulus of the cured resin due to high temperature and high humidity treatment was -0.03 MPa. The Young's modulus of the cured resin after additional ultraviolet irradiation was 0.53 MPa. The change in Young's modulus of the cured resin due to additional ultraviolet irradiation was -0.02 MPa. The absolute value of the change in Young's modulus due to high temperature and high humidity treatment was 0.09 MPa or less, and Evaluation 1 was good (OK). The absolute value of the change in Young's modulus due to additional ultraviolet irradiation was 0.09 MPa or less, and Evaluation 2 was good (OK).

[0091] In Example 9, 0.02 wt% of MPTMS was added to the ultraviolet curable resin of the primary layer. Also, 4.0 wt% of IOMP was added to the ultraviolet curable resin of the primary layer. The amount of sulfur in the cured resin was 0.59 wt%. The amount of silicon in the cured resin was 0.003 wt%. The Young's modulus of the cured resin was 0.53 MPa. The Young's modulus of the cured resin after high temperature and high humidity treatment was 0.50 MPa. The change in Young's modulus of the cured resin due to high temperature and high humidity treatment was -0.03 MPa. The Young's modulus of the cured resin after additional ultraviolet irradiation was 0.51 MPa. The change in Young's modulus of the cured resin due to additional ultraviolet irradiation was -0.02 MPa. The absolute value of the change in Young's modulus due to high temperature and high humidity treatment was 0.09 MPa or less, and Evaluation 1 was good (OK). The absolute value of the change in Young's modulus due to additional ultraviolet irradiation was 0.09 MPa or less, and Evaluation 2 was good (OK).

[0092] In Example 10, 0.1 wt% of MPTMS was added to the ultraviolet curable resin of the primary layer. Also, 4.0 wt% of IOMP was added to the ultraviolet curable resin of the primary layer. The amount of sulfur in the cured resin was 0.60 wt%. The amount of silicon in the cured resin was 0.014 wt%. The Young's modulus of the cured resin was 0.52 MPa. The Young's modulus of the cured resin after high temperature and high humidity treatment was 0.48 MPa. The change in Young's modulus of the cured resin due to high temperature and high humidity treatment was -0.04 MPa. The Young's modulus of the cured resin after additional ultraviolet irradiation was 0.51 MPa. The change in Young's modulus of the cured resin due to additional ultraviolet irradiation was -0.01 MPa. The absolute value of the change in Young's modulus due to high temperature and high humidity treatment was 0.09 MPa or less, and Evaluation 1 was good (OK). The absolute value of the change in Young's modulus due to additional ultraviolet irradiation was 0.09 MPa or less, and Evaluation 2 was good (OK).

[0093] In Example 11, 0.2 wt% of MPTMS was added to the ultraviolet curable resin of the primary layer. Also, 4.0 wt% of IOMP was added to the ultraviolet curable resin of the primary layer. The amount of sulfur in the cured resin was 0.62 wt%. The amount of silicon in the cured resin was 0.029 wt%. The Young's modulus of the cured resin was 0.54 MPa. The Young's modulus of the cured resin after high temperature and high humidity treatment was 0.51 MPa. The change in Young's modulus of the cured resin due to high temperature and high humidity treatment was -0.03 MPa. The Young's modulus of the cured resin after additional ultraviolet irradiation was 0.55 MPa. The change in Young's modulus of the cured resin due to additional ultraviolet irradiation was 0.01 MPa. The absolute value of the change in Young's modulus due to high temperature and high humidity treatment was 0.09 MPa or less, and Evaluation 1 was good (OK). The absolute value of the change in Young's modulus due to additional ultraviolet irradiation was 0.09 MPa or less, and Evaluation 2 was good (OK).

[0094] In Example 12, 0.2 wt% of MPTMS was added to the ultraviolet curable resin of the primary layer. Also, 5.0 wt% of IOMP was added to the ultraviolet curable resin of the primary layer. The amount of sulfur in the cured resin was 0.77 wt%. The amount of silicon in the cured resin was 0.029 wt%. The Young's modulus of the cured resin was 0.36 MPa. The Young's modulus of the cured resin after high temperature and high humidity treatment was 0.34 MPa. The change in Young's modulus of the cured resin due to high temperature and high humidity treatment was -0.02 MPa. The Young's modulus of the cured resin after additional ultraviolet irradiation was 0.36 MPa. The change in Young's modulus of the cured resin due to additional ultraviolet irradiation was 0 MPa. The absolute value of the change in Young's modulus due to high temperature and high humidity treatment was 0.09 MPa or less, and Evaluation 1 was good (OK). The absolute value of the change in Young's modulus due to additional ultraviolet irradiation was 0.09 MPa or less, and Evaluation 2 was good (OK).

[0095] In Example 13, 0.2 wt% of MPTMS was added to the ultraviolet curable resin of the primary layer. Also, 5.5 wt% of IOMP was added to the ultraviolet curable resin of the primary layer. The amount of sulfur in the cured resin was 0.84 wt%. The amount of silicon in the cured resin was 0.029 wt%. The Young's modulus of the cured resin was 0.29 MPa. The Young's modulus of the cured resin after high temperature and high humidity treatment was 0.29 MPa. The change in Young's modulus of the cured resin due to high temperature and high humidity treatment was 0 MPa. The Young's modulus of the cured resin after additional ultraviolet irradiation was 0.30 MPa. The change in Young's modulus of the cured resin due to additional ultraviolet irradiation was 0.01 MPa. The absolute value of the change in Young's modulus due to high temperature and high humidity treatment was 0.09 MPa or less, and Evaluation 1 was good (OK). The absolute value of the change in Young's modulus due to additional ultraviolet irradiation was 0.09 MPa or less, and Evaluation 2 was good (OK).

[0096] In Example 14, 0.5 wt% of MPTMS was added to the ultraviolet curable resin of the primary layer. Also, 4.0 wt% of IOMP was added to the ultraviolet curable resin of the primary layer. The amount of sulfur in the cured resin was 0.67 wt%. The amount of silicon in the cured resin was 0.072 wt%. The Young's modulus of the cured resin was 0.56 MPa. The Young's modulus of the cured resin after high temperature and high humidity treatment was 0.54 MPa. The amount of change in Young's modulus of the cured resin due to high temperature and high humidity treatment was -0.02 MPa. The Young's modulus of the cured resin after additional ultraviolet irradiation was 0.57 MPa. The amount of change in Young's modulus of the cured resin due to additional ultraviolet irradiation was 0.01 MPa. The absolute value of the amount of change in Young's modulus due to high temperature and high humidity treatment was 0.09 MPa or less, and Evaluation 1 was good (OK). The absolute value of the amount of change in Young's modulus due to additional ultraviolet irradiation was 0.09 MPa or less, and Evaluation 2 was good (OK).

[0097] In Example 15, 2.0 wt% of MPTMS was added to the ultraviolet curable resin of the primary layer. Also, IOMP was not added to the ultraviolet curable resin of the primary layer. The amount of sulfur in the cured resin was 0.33 wt%. The amount of silicon in the cured resin was 0.29 wt%. The Young's modulus of the cured resin was 1.81 MPa. The Young's modulus of the cured resin after high temperature and high humidity treatment was 1.72 MPa. The change in Young's modulus of the cured resin due to high temperature and high humidity treatment was -0.09 MPa. The Young's modulus of the cured resin after additional ultraviolet irradiation was 1.83 MPa. The change in Young's modulus of the cured resin due to additional ultraviolet irradiation was 0.02 MPa. The absolute value of the change in Young's modulus due to high temperature and high humidity treatment was 0.09 MPa or less, and Evaluation 1 was good (OK). The absolute value of the change in Young's modulus due to additional ultraviolet irradiation was 0.09 MPa or less, and Evaluation 2 was good (OK).

[0098] In Example 16, 2.0 wt% of MPTMS was added to the ultraviolet curable resin of the primary layer. Also, 4.0 wt% of IOMP was added to the ultraviolet curable resin of the primary layer. The amount of sulfur in the cured resin was 0.91 wt%. The amount of silicon in the cured resin was 0.29 wt%. The Young's modulus of the cured resin was 0.70 MPa. The Young's modulus of the cured resin after high temperature and high humidity treatment was 0.70 MPa. The change in Young's modulus of the cured resin due to high temperature and high humidity treatment was 0 MPa. The Young's modulus of the cured resin after additional ultraviolet irradiation was 0.73 MPa. The change in Young's modulus of the cured resin due to additional ultraviolet irradiation was 0.03 MPa. The absolute value of the change in Young's modulus due to high temperature and high humidity treatment was 0.09 MPa or less, and Evaluation 1 was good (OK). The absolute value of the change in Young's modulus due to additional ultraviolet irradiation was 0.09 MPa or less, and Evaluation 2 was good (OK).

[0099] In Example 17, 3.0 wt% of MPTMS was added to the ultraviolet curable resin of the primary layer. Also, IOMP was not added to the ultraviolet curable resin of the primary layer. The amount of sulfur in the cured resin was 0.49 wt%. The amount of silicon in the cured resin was 0.43 wt%. The Young's modulus of the cured resin was 1.91 MPa. The Young's modulus of the cured resin after high temperature and high humidity treatment was 1.87 MPa. The amount of change in Young's modulus of the cured resin due to high temperature and high humidity treatment was -0.04 MPa. The Young's modulus of the cured resin after additional ultraviolet irradiation was 1.95 MPa. The amount of change in Young's modulus of the cured resin due to additional ultraviolet irradiation was 0.04 MPa. The absolute value of the amount of change in Young's modulus due to high temperature and high humidity treatment was 0.09 MPa or less, and Evaluation 1 was good (OK). The absolute value of the amount of change in Young's modulus due to additional ultraviolet irradiation was 0.09 MPa or less, and Evaluation 2 was good (OK).

[0100] In Example 18, 3.0 wt% of MPTMS was added to the ultraviolet curable resin of the primary layer. Also, 3.0 wt% of IOMP was added to the ultraviolet curable resin of the primary layer. The amount of sulfur in the cured resin was 0.93 wt%. The amount of silicon in the cured resin was 0.43 wt%. The Young's modulus of the cured resin was 1.00 MPa. The Young's modulus of the cured resin after high temperature and high humidity treatment was 1.00 MPa. The change in Young's modulus of the cured resin due to high temperature and high humidity treatment was 0 MPa. The Young's modulus of the cured resin after additional ultraviolet irradiation was 1.04 MPa. The change in Young's modulus of the cured resin due to additional ultraviolet irradiation was 0.04 MPa. The absolute value of the change in Young's modulus due to high temperature and high humidity treatment was 0.09 MPa or less, and Evaluation 1 was good (OK). The absolute value of the change in Young's modulus due to additional ultraviolet irradiation was 0.09 MPa or less, and Evaluation 2 was good (OK).

[0101] In Example 19, 4.0 wt% of MPTMS was added to the ultraviolet curable resin of the primary layer. Also, IOMP was not added to the ultraviolet curable resin of the primary layer. The amount of sulfur in the cured resin was 0.65 wt%. The amount of silicon in the cured resin was 0.57 wt%. The Young's modulus of the cured resin was 2.15 MPa. The Young's modulus of the cured resin after high temperature and high humidity treatment was 2.13 MPa. The change in Young's modulus of the cured resin due to high temperature and high humidity treatment was -0.02 MPa. The Young's modulus of the cured resin after additional ultraviolet irradiation was 2.18 MPa. The change in Young's modulus of the cured resin due to additional ultraviolet irradiation was 0.03 MPa. The absolute value of the change in Young's modulus due to high temperature and high humidity treatment was 0.09 MPa or less, and Evaluation 1 was good (OK). The absolute value of the change in Young's modulus due to additional ultraviolet irradiation was 0.09 MPa or less, and Evaluation 2 was good (OK).

[0102] In Example 20, 5.0 wt% of MPTMS was added to the ultraviolet curable resin of the primary layer. Also, IOMP was not added to the ultraviolet curable resin of the primary layer. The amount of sulfur in the cured resin was 0.82 wt%. The amount of silicon in the cured resin was 0.72 wt%. The Young's modulus of the cured resin was 2.32 MPa. The Young's modulus of the cured resin after high temperature and high humidity treatment was 2.30 MPa. The change in Young's modulus of the cured resin due to high temperature and high humidity treatment was -0.02 MPa. The Young's modulus of the cured resin after additional ultraviolet irradiation was 2.36 MPa. The change in Young's modulus of the cured resin due to additional ultraviolet irradiation was 0.04 MPa. The absolute value of the change in Young's modulus due to high temperature and high humidity treatment was 0.09 MPa or less, and Evaluation 1 was good (OK). The absolute value of the change in Young's modulus due to additional ultraviolet irradiation was 0.09 MPa or less, and Evaluation 2 was good (OK).

[0103] In Example 21, 3.0 wt% of MPTMS was added to the ultraviolet curable resin of the primary layer. Also, 4.0 wt% of IOMP was added to the ultraviolet curable resin of the primary layer. The amount of sulfur in the cured resin was 1.08 wt%. The amount of silicon in the cured resin was 0.43 wt%. The Young's modulus of the cured resin was 0.79 MPa. The Young's modulus of the cured resin after high temperature and high humidity treatment was 0.85 MPa. The change in Young's modulus of the cured resin due to high temperature and high humidity treatment was 0.06 MPa. The Young's modulus of the cured resin after additional ultraviolet irradiation was 0.89 MPa. The change in Young's modulus of the cured resin due to additional ultraviolet irradiation was 0.10 MPa. The absolute value of the change in Young's modulus due to high temperature and high humidity treatment was 0.09 MPa or less, and Evaluation 1 was good (OK). The absolute value of the change in Young's modulus due to additional ultraviolet irradiation was greater than 0.09 MPa, and Evaluation 2 was poor (NG).

[0104] In Comparative Example 1, MPTMS was not added to the ultraviolet curable resin of the primary layer. Also, IOMP was not added to the ultraviolet curable resin of the primary layer. The amount of sulfur in the cured resin was 0 wt%. The amount of silicon in the cured resin was 0 wt%. The Young's modulus of the cured resin was 2.25 MPa. The Young's modulus of the cured resin after high temperature and high humidity treatment was 1.68 MPa. The change in Young's modulus of the cured resin due to high temperature and high humidity treatment was -0.57 MPa. The Young's modulus of the cured resin after additional ultraviolet irradiation was 2.24 MPa. The change in Young's modulus of the cured resin due to additional ultraviolet irradiation was -0.01 MPa. The absolute value of the change in Young's modulus due to high temperature and high humidity treatment was greater than 0.09 MPa, and Evaluation 1 was poor (NG). The absolute value of the change in Young's modulus due to additional ultraviolet irradiation was less than 0.09 MPa, and Evaluation 2 was good (OK).

[0105] In Comparative Example 2, MPTMS was not added to the ultraviolet curable resin of the primary layer. Also, IOMP was not added to the ultraviolet curable resin of the primary layer. The amount of sulfur in the cured resin was 0 wt%. The amount of silicon in the cured resin was 0 wt%. The Young's modulus of the cured resin was 1.38 MPa. The Young's modulus of the cured resin after high temperature and high humidity treatment was 0.61 MPa. The amount of change in Young's modulus of the cured resin due to high temperature and high humidity treatment was -0.77 MPa. The Young's modulus of the cured resin after additional ultraviolet irradiation was 2.25 MPa. The amount of change in Young's modulus of the cured resin due to additional ultraviolet irradiation was 0.87 MPa. The absolute value of the amount of change in Young's modulus due to high temperature and high humidity treatment was greater than 0.09 MPa, and Evaluation 1 was poor (NG). The absolute value of the amount of change in Young's modulus due to additional ultraviolet irradiation was greater than 0.09 MPa, and Evaluation 2 was poor (NG).

[0106] In Comparative Example 3, MPTMS was not added to the ultraviolet curable resin of the primary layer. 0.01 wt% of IOMP was added to the ultraviolet curable resin of the primary layer. The amount of sulfur in the cured resin was 0.001 wt%. The amount of silicon in the cured resin was 0 wt%. The Young's modulus of the cured resin was 2.24 MPa. The Young's modulus of the cured resin after high temperature and high humidity treatment was 2.05 MPa. The change in Young's modulus of the cured resin due to high temperature and high humidity treatment was -0.19 MPa. The Young's modulus of the cured resin after additional ultraviolet irradiation was 2.23 MPa. The change in Young's modulus of the cured resin due to additional ultraviolet irradiation was -0.01 MPa. The absolute value of the change in Young's modulus due to high temperature and high humidity treatment was greater than 0.09 MPa, and Evaluation 1 was poor (NG). The absolute value of the change in Young's modulus due to additional ultraviolet irradiation was less than 0.09 MPa, and Evaluation 2 was good (OK).

[0107] In Comparative Example 4, 0.01 wt% of MPTMS was added to the ultraviolet curable resin of the primary layer. Also, IOMP was not added to the ultraviolet curable resin of the primary layer. The amount of sulfur in the cured resin was 0.002 wt%. The amount of silicon in the cured resin was 0.001 wt%. The Young's modulus of the cured resin was 2.25 MPa. The Young's modulus of the cured resin after high temperature and high humidity treatment was 2.05 MPa. The change in Young's modulus of the cured resin due to high temperature and high humidity treatment was -0.20 MPa. The Young's modulus of the cured resin after additional ultraviolet irradiation was 2.21 MPa. The change in Young's modulus of the cured resin due to additional ultraviolet irradiation was -0.04 MPa. The absolute value of the change in Young's modulus due to high temperature and high humidity treatment was greater than 0.09 MPa, and Evaluation 1 was poor (NG). The absolute value of the change in Young's modulus due to additional ultraviolet irradiation was less than 0.09 MPa, and Evaluation 2 was good (OK).

[0108] In Comparative Example 5, 5.0 wt% of MPTMS was added to the ultraviolet curable resin of the primary layer. Also, 4.0 wt% of IOMP was added to the ultraviolet curable resin of the primary layer. The amount of sulfur in the cured resin was 1.40 wt%. The amount of silicon in the cured resin was 0.72 wt%. The Young's modulus of the cured resin was 0.86 MPa. The Young's modulus of the cured resin after high temperature and high humidity treatment was 0.96 MPa. The amount of change in Young's modulus of the cured resin due to high temperature and high humidity treatment was 0.10 MPa. The Young's modulus of the cured resin after additional ultraviolet irradiation was 0.95 MPa. The amount of change in Young's modulus of the cured resin due to additional ultraviolet irradiation was 0.09 MPa. The absolute value of the amount of change in Young's modulus due to high temperature and high humidity treatment was greater than 0.09 MPa, and Evaluation 1 was poor (NG). The absolute value of the amount of change in Young's modulus due to additional ultraviolet irradiation was less than 0.09 MPa, and Evaluation 2 was good (OK).

[0109] As described above, according to the present invention, it is possible to provide an optical fiber having a primary layer with improved resistance to high temperatures and high humidity.

[0110] The primary layer preferably contains 1.08 wt% or less of sulfur atoms. By making the content of sulfur atoms in the primary layer 1.08 wt% or less, the change in Young's modulus of the primary layer due to high-temperature and high-humidity treatment is sufficiently small. This makes it possible to provide an optical fiber having a primary layer with improved resistance to high temperatures and high humidity.

[0111] Furthermore, it is more preferable that the primary layer contains 0.93 wt% or less of sulfur atoms. By making the content of sulfur atoms in the primary layer 0.93 wt% or less, the change in Young's modulus of the primary layer caused by high-temperature, high-humidity treatment and additional ultraviolet irradiation is sufficiently small. This makes it possible to suppress hardening of the primary layer caused by high-temperature, high-humidity treatment and additional ultraviolet irradiation, and to effectively suppress microbend loss.

[0112] The present invention is not limited to the above-described embodiments and can be modified in various ways. For example, an example in which a part of the configuration of any of the embodiments is added to another embodiment, or an example in which a part of the configuration of another embodiment is replaced with another embodiment is also an embodiment of the present invention. Furthermore, with respect to parts not specifically described or illustrated in the embodiments, well-known or publicly known techniques in the relevant technical field can be appropriately applied. [Explanation of symbols]

[0113] 1 Optical fiber core 2 Bare optical fiber 3 Primary Layer 4 Secondary Tier 5 Colored layer 6. Colored optical fiber

Claims

1. A bare optical fiber; a primary layer formed of a first ultraviolet curing resin covering the bare optical fiber; a secondary layer formed of a second ultraviolet curable resin covering the primary layer; the primary layer has carbon-sulfur bonds; The primary layer contains 1.08 wt % or less of sulfur atoms, The Young's modulus of the primary layer is 0.21 MPa or more and 2.36 MPa or less, An optical fiber core, characterized in that the absolute value of the change in Young's modulus of the primary layer when exposed to an environment of 85° C. and 85% humidity for two days is 0.09 MPa or less.

2. 2. The optical fiber according to claim 1, wherein the primary layer contains 0.93 wt % or less of sulfur atoms.

3. Illuminance 1000mW / cm ２ , irradiation amount 500mJ / cm ２ 3. The optical fiber according to claim 2, wherein the absolute value of the change in Young's modulus of the primary layer when additionally irradiated with ultraviolet light from a mercury lamp is 0.09 MPa or less.

4. a mercapto group-containing compound other than a silane coupling agent is added to the primary layer; 2. The optical fiber according to claim 1, wherein the Young's modulus of the primary layer is 0.21 MPa or more and 1.49 MPa or less.

5. The optical fiber core wire according to claim 1 , a third colored layer formed of an ultraviolet-curable resin covering the secondary layer of the optical fiber.

6. 2. The colored optical fiber according to claim 1, wherein the secondary layer of the optical fiber is colored.

7. A plurality of colored optical fiber core wires according to claim 5 or 6; and a ribbon layer formed of a fourth ultraviolet curing resin covering the colored optical fiber core.

8. A step of drawing a bare optical fiber from an optical fiber preform; a step of applying a first ultraviolet curing resin around the bare optical fiber to form a primary layer; applying a second ultraviolet-curable resin around the primary layer to form a secondary layer, and irradiating the second ultraviolet-curable resin with ultraviolet light to form a secondary layer; the primary layer has carbon-sulfur bonds; The primary layer contains 1.08 wt % or less of sulfur atoms, The Young's modulus of the primary layer is 0.21 MPa or more and 2.36 MPa or less, A method for manufacturing an optical fiber, wherein the absolute value of the change in Young's modulus of the primary layer when exposed to an environment of 85° C. and 85% humidity for two days is 0.09 MPa or less.

9. 9. The method for manufacturing an optical fiber according to claim 8, wherein in the step of forming the primary layer, the first ultraviolet-curable resin forming the primary layer is irradiated with ultraviolet light.

10. 9. A method for manufacturing a colored optical fiber, comprising the steps of applying a third ultraviolet-curable resin that forms a colored layer around the secondary layer of the optical fiber core described in claim 8, and irradiating the third ultraviolet-curable resin with ultraviolet light to form a colored layer.

11. 9. A method for producing a colored optical fiber, comprising the step of forming a colored layer by coloring the secondary layer of the optical fiber of claim 8.

12. 11. The method for producing a colored optical fiber according to claim 10, wherein in the step of forming the primary layer, the first ultraviolet-curable resin forming the primary layer is irradiated with ultraviolet light.

13. 12. A method for manufacturing an optical fiber ribbon, comprising the steps of: applying a fourth ultraviolet-curing resin that forms a ribbon layer around the plurality of colored optical fiber cores according to claim 10 or 11; and irradiating the fourth ultraviolet-curing resin with ultraviolet light to form a ribbon layer.

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