Optical fiber core wire and method for manufacturing optical fiber core wire

Abstract

To provide an optical fiber core wire and a method for manufacturing an optical fiber core wire which can set the Young's modulus and elongation at break of a primary layer to be appropriate values.SOLUTION: An optical fiber core wire includes an optical fiber bare wire, a primary layer which covers the optical fiber bare wire and is formed of a first ultraviolet curable resin, and a secondary layer which covers the primary layer and is formed of a second ultraviolet curable resin, wherein the primary layer has a crosslinking point derived from an unsaturated carbon bond and a crosslinking point derived from a silane coupling agent, and the primary layer contains 0.014 wt.% or more and 0.72 wt.% or less of a silicon atom.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, the Young's modulus is not the only characteristic required for the primary layer. For example, if the breaking elongation of the primary layer is insufficient, a problem may arise in that the primary layer is easily peeled off from the bare optical fiber.

[0006] An object of the present invention is to provide an optical fiber and a method for manufacturing the optical fiber, which enable the Young's modulus and breaking elongation of the primary layer to be set to appropriate values. [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 crosslinking points derived from unsaturated carbon bonds and crosslinking points derived from a silane coupling agent, and the primary layer contains 0.014 wt % or more and 0.72 wt % or less of silicon atoms.

[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 that forms a primary layer around the bare optical fiber to form a primary layer, and applying a second ultraviolet-curable resin that forms a secondary layer around the primary layer and irradiating the second ultraviolet-curable resin with ultraviolet light to form a secondary layer, wherein the primary layer has crosslink points derived from unsaturated carbon bonds and crosslink points derived from a silane coupling agent, and the primary layer contains 0.014 wt % or more and 0.72 wt % or less of silicon atoms. Effect of the Invention

[0009] According to the present invention, it is possible to provide an optical fiber and a method for manufacturing the optical fiber, which enable the Young's modulus and breaking elongation of the primary layer to be set to appropriate values. [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 the change over time in Young's modulus of an ultraviolet curable resin after ultraviolet irradiation. [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. [Figure 9] 1 is a graph showing the Young's modulus and breaking elongation of cured resins in Examples and Comparative Examples. 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 glass or the like, 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 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 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 interval 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 silane coupling agent as an additive. The ultraviolet-curable resin and the silane coupling agent 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, for example, a diluent monomer, a photosensitizer, an ultraviolet absorber, an antioxidant, a chain transfer agent, and various additives. 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] As described above, the ultraviolet curable resin of the primary layer 3 has unsaturated carbon bonds. Therefore, the primary layer 3 has crosslinking points derived from the unsaturated carbon bonds due to polymerization of the ultraviolet curable resin of the primary layer 3.

[0033] [Silane coupling agents] The silane coupling agent is used to adhere the primary layer 3 to the surface of the bare optical fiber 2. The silane coupling agent is a compound containing Si (silicon, silane). The silane coupling agent contains an organic reactive site that reacts with an organic compound and an inorganic reactive site that reacts with an inorganic compound. The organic reactive site may be, for example, an amino group, an epoxy group, a (meth)acryloyloxy group, a vinyl group, or a mercapto group. The inorganic reactive site may be, for example, a methoxy group, an ethoxy group, or an acetoxy group. Specific examples of the silane coupling agent include vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, allyltrimethoxysilane, allyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethysilane, and 3-acryloxypropyltrimethoxysilane. It may be xysilane, 3-(trimethoxysilyl)propyl methacrylate, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, tris-(trimethoxysilylpropyl)isocyanurate, 3-ureidopropyltrialkoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-isocyanatopropyltriethoxysilane, etc. It is to be noted that a silane coupling agent containing both an organic reactive site and an inorganic reactive site may be used in combination with a silane coupling agent containing only an inorganic reactive site.This can promote the crosslinking reaction of the ultraviolet curable resin of the primary layer 3 by the silane coupling agent described later. Specific compounds of the silane coupling agent containing only inorganic reactive sites can be, for example, tetramethyl silicate, tetraethyl silicate, and the like.

[0034] The organic reactive sites of the silane coupling agent bond with the ultraviolet-curable resin of the primary layer 3. The silane coupling agent bonded with the ultraviolet-curable resin of the primary layer 3 reacts with the surface of the bare optical fiber 2 through hydrolysis at the inorganic reactive sites and subsequent dehydration condensation with the hydroxyl groups on the surface of the bare optical fiber 2. The ultraviolet-curable resin of the primary layer 3 and the bare optical fiber 2 bond via the silane coupling agent, thereby bringing the primary layer 3 and the bare optical fiber 2 into close contact with each other.

[0035] [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.

[0036] 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.

[0037] 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 the ultraviolet ray curable resin of the primary layer 3. The ultraviolet ray curable resin of the primary layer 3 contains the above-mentioned silane coupling agent as an additive. The ultraviolet ray curable resin of 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.

[0038] 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.

[0039] 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.

[0040] An ultraviolet irradiation device 42 is provided below the resin coating device 41. The ultraviolet irradiation device 42 may be configured similarly to 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 light is 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, and the optical fiber core 1 is formed.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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 .

[0045] 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.

[0046] An ultraviolet irradiation device 52 is provided below the resin application device 51. The ultraviolet irradiation device 52 may be configured similarly to the ultraviolet irradiation devices 32 and 42. The optical fiber 1 coated with the ultraviolet curable resin of the colored layer 5 enters the ultraviolet irradiation device 52, and the ultraviolet curable resin of the colored layer 5 is irradiated with ultraviolet light. As a result, the ultraviolet curable resin of the colored layer 5 is cured, and the colored layer 5 is formed. The optical fiber 1 is coated with the colored layer 5, and a colored optical fiber 6 is formed.

[0047] 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.

[0048] [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).

[0049] 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).

[0050] 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 silane coupling agent as an additive.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] [Effects] According to this embodiment, it is possible to provide a colored optical fiber 6 that allows the Young's modulus and breaking elongation of the primary layer 3 to be set to appropriate values. The effects of this embodiment will be described in detail below in comparison with the prior art.

[0055] 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.

[0056] However, Young's modulus is not the only characteristic required for the primary layer 3 to buffer the external force applied to the bare optical fiber 2. For example, if the primary layer 3 has a low breaking elongation, the primary layer 3 is likely to peel off from the bare optical fiber 2. If the primary layer 3 peels off, problems such as an increase in microbend loss may occur.

[0057] 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.

[0058] 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.

[0059] In this embodiment, the present inventors have found for the first time through their research that the primary layer 3 is crosslinked via a silane coupling agent. According to the research of the present inventors, the inorganic reaction site of a silane coupling agent reacts with the inorganic reaction site of another silane coupling agent. The reaction between silane coupling agents may be, for example, dehydration condensation. As a result, the ultraviolet curing resin of the primary layer 3 is crosslinked via the silane coupling agent, and the primary layer 3 has crosslinking points derived from the silane coupling agent. That is, the primary layer 3 has crosslinking points derived from the unsaturated carbon bonds of the first ultraviolet curing resin and crosslinking points derived from the silane coupling agent. Therefore, according to this embodiment, the Young's modulus and breaking elongation of the primary layer 3 can be set to appropriate values ​​by appropriately setting the silicon atom concentration in the primary layer 3.

[0060] In this embodiment, the primary layer 3 preferably contains 0.014 wt % or more and 0.72 wt % or less of silicon atoms, so that crosslinking points derived from the silane coupling agent in the primary layer 3 can effectively improve the breaking elongation of the primary layer 3.

[0061] According to the study by the present inventors, the presence of crosslinking points derived from the silane coupling agent can be confirmed by the change over time in Young's modulus of the ultraviolet curable resin after ultraviolet irradiation. FIG. 5 is a graph showing the change over time in Young's modulus of the ultraviolet curable resin after ultraviolet irradiation, where the horizontal axis represents the time elapsed since ultraviolet irradiation and the vertical axis represents the Young's modulus of the ultraviolet curable resin. In FIG. 5, the measurement points represented by "x" indicate the Young's modulus of the sheet-shaped cured resin obtained by adding 1 wt% of 3-mercaptopropyltrimethoxysilane (MPTMS) to the ultraviolet curable resin and irradiating it with ultraviolet rays. Also, the measurement points represented by "▲" indicate the Young's modulus of the sheet-shaped cured resin obtained by adding 1.2 wt% of 3-mercaptopropyltriethoxysilane (MPTES) to the ultraviolet curable resin and irradiating it with ultraviolet rays. The amount of substance (mol) of MPTMS is almost equal to the amount of substance (mol) of MPTES. As shown in Figure 5, the Young's modulus of both the UV-curable resin to which MPTMS has been added and the UV-curable resin to which MPTES has been added increases over time. This is believed to be due to the fact that the silane coupling agents bonded to the UV-curable resin bond with each other after UV irradiation, resulting in the generation of new crosslinking points. Also, as shown in Figure 5, the increase in Young's modulus of the UV-curable resin to which MPTMS has been added is observed up to 20 days after UV irradiation, while the increase in Young's modulus of the UV-curable resin to which MPTES has been added is observed up to 60 days after UV irradiation. Here, MPTMS has a methoxy group or a methoxysilyl group as an alkoxy group, and MPTES has an ethoxy group or an ethoxysilyl group as an alkoxy group. In addition, generally, the methoxy group is more easily hydrolyzed than the ethoxy group, and the methoxysilyl group is more easily hydrolyzed than the ethoxysilyl group. Therefore, it is believed that the Young's modulus of the UV-curable resin to which MPTES has been added increases over a longer period of time than that of the UV-curable resin to which MPTMS has been added. On the other hand, ethoxysilanes such as MPTES have high stability when added to a resin before curing, compared to methoxysilanes such as MPTMS.Therefore, when comparing MPTMS and MPTES, MPTMS is superior in terms of the period during which Young's modulus increases after UV irradiation, while MPTES is superior in terms of the stability of the silane coupling agent in the UV-curable resin before curing.

[0062] In addition, the primary layer 3 in this embodiment is preferably acidic. The crosslinking reaction of the ultraviolet curable resin of the primary layer 3 by the silane coupling agent may proceed for a long period of time. In this case, the Young's modulus of the primary layer 3 increases over time after the optical fiber is manufactured, and the microbend loss of the optical fiber after shipment may not be effectively suppressed. By making the primary layer 3 acidic, the reaction between the silane coupling agents is promoted, and the crosslinking of the ultraviolet curable resin of the primary layer 3 via the silane coupling agent can be completed in a short period of time. This makes it possible to suppress the increase in the Young's modulus of the primary layer 3 over time after the optical fiber is manufactured, and to effectively suppress the microbend loss. In addition, a method of making the primary layer 3 acidic may be a method of adding a photoacid generator to the ultraviolet curable resin of the primary layer 3.

[0063] [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.

[0064] 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.

[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 light. 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.

[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 the present embodiment, the primary layer 3 also has cross-linking points derived from unsaturated carbon bonds and cross-linking points derived from a silane coupling agent. Therefore, it is possible to provide an optical fiber ribbon 8 in which the Young's modulus and breaking elongation of the primary layer 3 can be set to appropriate values.

[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 embodiment and the comparative example, Young's modulus and breaking elongation were 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 using a mercury lamp to an ultraviolet-curable resin for the primary layer formed into a sheet shape with a thickness of about 100 μm. The ultraviolet-curable resin for the primary layer is urethane acrylate. 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 an illuminance of 1000 mW / cm. 2 , irradiation amount 500mJ / cm 2 However, the irradiation conditions are not limited to these. The illumination intensity is 1500 mW / 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 / cm 2 ”, “Illuminance 500mW / cm 2 , irradiation amount 1000mJ / cm 2" Furthermore, a UV-LED may be used as the ultraviolet light source instead of a mercury lamp. For illuminance measurement, for example, UV-351 manufactured by Oak Manufacturing Co., Ltd. is used for the mercury lamp, and for example, UVRT2 / UD-T3040T2 manufactured by Topcon Technohouse is used for the 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 Young's modulus adjuster (IOMP) added to the UV-curable resin of the primary layer, the silicon content (wt%) of the cured resin, the Young's modulus (MPa) of the cured resin, and the breaking elongation (%) of the cured resin.

[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 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 added to adjust the Young's modulus of the cured resin. IOMP is a mercapto-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-containing compound used to adjust the Young's modulus is not limited to IOMP. The mercapto-containing compound can be, for example, 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).

[0078] 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 silicon content of 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] The breaking elongation can be measured by the following method. In an atmosphere of 23°C and 50% relative humidity, a Tensilon universal tensile tester was used to stretch a sample with a width of 6 mm, a gauge interval of 25 mm, and a tensile speed of 50 mm / min, and the elongation at break was measured and the breaking elongation was calculated. Note that the breaking elongation was the highest measured value in the n4 or higher breaking test.

[0081] In the examples and comparative examples, MPTMS is added to the UV-curable resin of the primary layer, so that the cured resin can contain crosslinking points derived from the silane coupling agent. The crosslinking points derived from the silane coupling agent in the cured resin can be confirmed by using Fourier transform infrared spectroscopy (FT-IR).

[0082] In Example 1, 0.10 wt% of MPTMS was added to the ultraviolet curable resin of the primary layer. In addition, IOMP was not added to the ultraviolet curable resin of the primary layer. The cured resin after ultraviolet irradiation contained crosslinking points derived from the silane coupling agent. The amount of silicon in the cured resin was 0.014 wt%. The Young's modulus of the cured resin was 2.20 MPa. The breaking elongation of the cured resin was 200%.

[0083] In Example 2, 0.20 wt% of MPTMS was added to the ultraviolet curable resin of the primary layer. In addition, IOMP was not added to the ultraviolet curable resin of the primary layer. The cured resin after ultraviolet irradiation contains crosslinking points derived from the silane coupling agent. The amount of silicon in the cured resin was 0.029 wt%. The Young's modulus of the cured resin was 2.10 MPa. The breaking elongation of the cured resin was 219%.

[0084] In Example 3, 0.50 wt% of MPTMS was added to the ultraviolet curable resin of the primary layer. In addition, IOMP was not added to the ultraviolet curable resin of the primary layer. The cured resin after ultraviolet irradiation contains crosslinking points derived from the silane coupling agent. The amount of silicon in the cured resin was 0.072 wt%. The Young's modulus of the cured resin was 1.99 MPa. The breaking elongation of the cured resin was 267%.

[0085] In Example 4, 2.0 wt% of MPTMS was added to the ultraviolet curable resin of the primary layer. In addition, IOMP was not added to the ultraviolet curable resin of the primary layer. The cured resin after ultraviolet irradiation contains crosslinking points derived from the silane coupling agent. The silicon content in the cured resin was 0.29 wt%. The Young's modulus of the cured resin was 1.80 MPa. The breaking elongation of the cured resin was 288%.

[0086] In Example 5, 3.0 wt% of MPTMS was added to the ultraviolet curable resin of the primary layer. In addition, IOMP was not added to the ultraviolet curable resin of the primary layer. The cured resin after ultraviolet irradiation contains crosslinking points derived from the silane coupling agent. The silicon content in the cured resin was 0.43 wt%. The Young's modulus of the cured resin was 1.91 MPa. The breaking elongation of the cured resin was 298%.

[0087] In Example 6, 4.0 wt% of MPTMS was added to the ultraviolet curable resin of the primary layer. In addition, IOMP was not added to the ultraviolet curable resin of the primary layer. The cured resin after ultraviolet irradiation contains crosslinking points derived from the silane coupling agent. The silicon content in the cured resin was 0.57 wt%. The Young's modulus of the cured resin was 2.15 MPa. The breaking elongation of the cured resin was 285%.

[0088] In Example 7, 5.0 wt% of MPTMS was added to the ultraviolet curable resin of the primary layer. In addition, IOMP was not added to the ultraviolet curable resin of the primary layer. The cured resin after ultraviolet irradiation contained crosslinking points derived from the silane coupling agent. The silicon content in the cured resin was 0.72 wt%. The Young's modulus of the cured resin was 2.32 MPa. The breaking elongation of the cured resin was 245%.

[0089] In Example 8, 0.10 wt% of MPTMS was 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 cured resin after ultraviolet irradiation contains crosslinking points derived from the silane coupling agent. 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 breaking elongation of the cured resin was 447%.

[0090] In Example 9, 0.20 wt% of MPTMS was 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 cured resin after ultraviolet irradiation contains crosslinking points derived from the silane coupling agent. 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 breaking elongation of the cured resin was 441%.

[0091] In Example 10, 0.50 wt% of MPTMS was 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 cured resin after ultraviolet irradiation contains crosslinking points derived from the silane coupling agent. 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 breaking elongation of the cured resin was 456%.

[0092] In Example 11, 2.0 wt% of MPTMS was 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 cured resin after ultraviolet irradiation contains crosslinking points derived from the silane coupling agent. The silicon content in the cured resin was 0.29 wt%. The Young's modulus of the cured resin was 0.69 MPa. The breaking elongation of the cured resin was 521%.

[0093] In Example 12, 3.0 wt% of MPTMS was added to the ultraviolet curable resin of the primary layer. 4.0 wt% of IOMP was added to the ultraviolet curable resin of the primary layer. The cured resin after ultraviolet irradiation contained crosslinking points derived from the silane coupling agent. The silicon content in the cured resin was 0.43 wt%. The Young's modulus of the cured resin was 0.80 MPa. The breaking elongation of the cured resin was 446%.

[0094] In Example 13, 0.20 wt% of MPTMS was 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 cured resin after ultraviolet irradiation contains crosslinking points derived from the silane coupling agent. 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 breaking elongation of the cured resin was 567%.

[0095] In Example 14, 0.20 wt% of MPTMS was 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 cured resin after ultraviolet irradiation contains crosslinking points derived from the silane coupling agent. 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 breaking elongation of the cured resin was 657%.

[0096] 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 cured resin after ultraviolet irradiation did not contain crosslinking points derived from the silane coupling agent. The silicon content in the cured resin was 0 wt%. The Young's modulus of the cured resin was 2.25 MPa. The breaking elongation of the cured resin was 184%.

[0097] In Comparative Example 2, MPTMS was not added to the ultraviolet curable resin of the primary layer. 0.10 wt of IOMP was added to the ultraviolet curable resin of the primary layer. The cured resin after ultraviolet irradiation did not contain crosslinking points derived from the silane coupling agent. The silicon content in the cured resin was 0 wt%. The Young's modulus of the cured resin was 2.19 MPa. The breaking elongation of the cured resin was 184%.

[0098] In Comparative Example 3, MPTMS was not added to the ultraviolet curable resin of the primary layer. 0.30 wt of IOMP was added to the ultraviolet curable resin of the primary layer. The cured resin after ultraviolet irradiation did not contain crosslinking points derived from the silane coupling agent. The silicon content in the cured resin was 0 wt%. The Young's modulus of the cured resin was 1.99 MPa. The breaking elongation of the cured resin was 192%.

[0099] In Comparative Example 4, MPTMS was not added to the ultraviolet curable resin of the primary layer. 0.50 wt of IOMP was added to the ultraviolet curable resin of the primary layer. The cured resin after ultraviolet irradiation did not contain crosslinking points derived from the silane coupling agent. The silicon content in the cured resin was 0 wt%. The Young's modulus of the cured resin was 1.84 MPa. The breaking elongation of the cured resin was 224%.

[0100] In Comparative Example 5, MPTMS was not added to the ultraviolet curable resin of the primary layer. IOMP was added to the ultraviolet curable resin of the primary layer by 1.0 wt. The cured resin after ultraviolet irradiation did not contain crosslinking points derived from the silane coupling agent. The silicon content in the cured resin was 0 wt.%. The Young's modulus of the cured resin was 1.48 MPa. The breaking elongation of the cured resin was 264%.

[0101] In Comparative Example 6, MPTMS was not added to the ultraviolet curable resin of the primary layer. 2.0 wt of IOMP was added to the ultraviolet curable resin of the primary layer. The cured resin after ultraviolet irradiation did not contain crosslinking points derived from the silane coupling agent. The silicon content in the cured resin was 0 wt%. The Young's modulus of the cured resin was 1.15 MPa. The breaking elongation of the cured resin was 278%.

[0102] In Comparative Example 7, MPTMS was not added to the ultraviolet curable resin of the primary layer. 3.0 wt of IOMP was added to the ultraviolet curable resin of the primary layer. The cured resin after ultraviolet irradiation did not contain crosslinking points derived from the silane coupling agent. The silicon content in the cured resin was 0 wt%. The Young's modulus of the cured resin was 0.75 MPa. The breaking elongation of the cured resin was 347%.

[0103] In Comparative Example 8, MPTMS was not added to the ultraviolet curable resin of the primary layer. IOMP was added to the ultraviolet curable resin of the primary layer at 4.0 wt. The cured resin after ultraviolet irradiation did not contain crosslinking points derived from the silane coupling agent. The silicon content in the cured resin was 0 wt.%. The Young's modulus of the cured resin was 0.53 MPa. The breaking elongation of the cured resin was 397%.

[0104] In Comparative Example 9, MPTMS was not added to the ultraviolet curable resin of the primary layer. 5.0 wt of IOMP was added to the ultraviolet curable resin of the primary layer. The cured resin after ultraviolet irradiation did not contain crosslinking points derived from the silane coupling agent. The silicon content in the cured resin was 0 wt%. The Young's modulus of the cured resin was 0.32 MPa. The breaking elongation of the cured resin was 434%.

[0105] In Comparative Example 10, MPTMS was not added to the ultraviolet curable resin of the primary layer. 5.5 wt of IOMP was added to the ultraviolet curable resin of the primary layer. The cured resin after ultraviolet irradiation did not contain crosslinking points derived from the silane coupling agent. The silicon content in the cured resin was 0 wt%. The Young's modulus of the cured resin was 0.28 MPa. The breaking elongation of the cured resin was 488%.

[0106] In Comparative Example 11, 0.02 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 cured resin after ultraviolet irradiation contained crosslinking points derived from the silane coupling agent. The amount of silicon in the cured resin was 0.003 wt%. The Young's modulus of the cured resin was 2.24 MPa. The breaking elongation of the cured resin was 184%.

[0107] In Comparative Example 12, 0.02 wt% of MPTMS was added to the ultraviolet curable resin of the primary layer. 4.0 wt% of IOMP was added to the ultraviolet curable resin of the primary layer. The cured resin after ultraviolet irradiation contained crosslinking points derived from the silane coupling agent. The amount of silicon in the cured resin was 0.003 wt%. The Young's modulus of the cured resin was 0.54 MPa. The breaking elongation of the cured resin was 382%.

[0108] In Comparative Example 13, 4.0 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 cured resin after ultraviolet irradiation contained crosslinking points derived from the silane coupling agent. The amount of silicon in the cured resin was 0.57 wt%. The Young's modulus of the cured resin was 0.87 MPa. The breaking elongation of the cured resin was 329%.

[0109] In Comparative Example 14, 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 cured resin after ultraviolet irradiation contained crosslinking points derived from the silane coupling agent. The amount of silicon in the cured resin was 0.72 wt%. The Young's modulus of the cured resin was 0.88 MPa. The breaking elongation of the cured resin was 287%.

[0110] The breaking elongation of the cured resin is preferably 200% or more, which ensures a sufficient breaking elongation of the primary layer and makes it possible to prevent the primary layer from peeling off from the bare optical fiber.

[0111] Fig. 9 is a graph showing the Young's modulus and breaking elongation of the cured resin in the examples and comparative examples in Table 1, where the horizontal axis represents the Young's modulus of the cured resin and the vertical axis represents the breaking elongation of the cured resin. In Fig. 9, the measurement points represented by "●" represent the Young's modulus and breaking elongation of the cured resin in Comparative Example 1 to Comparative Example 10. Furthermore, the measurement points represented by "▲" represent the Young's modulus and breaking elongation of the cured resin in Examples 1 to 14. Furthermore, the measurement points represented by "X" represent the Young's modulus and breaking elongation of the cured resin in Comparative Examples 11 to 14.

[0112] Fig. 9(a) shows the Young's modulus and breaking elongation of the cured resin in Comparative Examples 1 to 10. As shown in Fig. 9(a), there is a tendency that the lower the Young's modulus of the cured resin, the greater the breaking elongation of the cured resin.

[0113] FIG. 9(b) shows the Young's modulus and breaking elongation of the cured resins in Comparative Example 1 to Comparative Example 10 and Example 1 to Example 14. As shown in FIG. 9(b), Example 1 to Example 14 show a larger breaking elongation in a wide range of Young's modulus compared to Comparative Example 1 to Comparative Example 10. As described above, the cured resins in Comparative Example 1 to Comparative Example 10 do not contain crosslinking points derived from the silane coupling agent, while the cured resins in Examples 1 to 14 contain crosslinking points derived from the silane coupling agent. Therefore, it is considered that the breaking elongation is increased by the crosslinking points derived from the silane coupling agent. In FIG. 9(b), the amount of silicon at which an increase in breaking elongation was confirmed is 0.014 wt% or more and 0.72 wt% or less.

[0114] FIG. 9(c) shows the Young's modulus and breaking elongation of the cured resins in Comparative Examples 1 to 10, Examples 1 to 14, and Comparative Examples 11 to 14. As shown in FIG. 9(c), no difference in breaking elongation is confirmed between Comparative Examples 11 to 14 and Comparative Examples 1 to 10. As described above, the cured resins in Comparative Examples 1 to 10 do not contain crosslinking points derived from the silane coupling agent, and the cured resins in Comparative Examples 11 to 14 contain crosslinking points derived from the silane coupling agent. That is, the cured resins in Comparative Examples 11 to 14 have breaking elongation similar to that of Comparative Examples 1 to 10, even though they contain crosslinking points derived from the silane coupling agent. This is considered to be because the amount of silicon in the cured resin is not appropriate. When the amount of silicon in the cured resin is too small, the increase in breaking elongation due to the crosslinking points derived from the silane coupling agent is considered to be small. In addition, when the amount of silicon in the cured resin is too large, the ratio of crosslinking of the ultraviolet curable resin via the silane coupling agent to the total crosslinking in the cured resin increases. For this reason, it is considered that the Young's modulus of the cured resin increases the Young's modulus increase rate of the cured resin, and the increase in the breaking elongation of the cured resin is suppressed. The silicon content of the primary layer is preferably 0.014wt% or more and 0.43wt% or less. This allows the breaking elongation of the primary layer to be effectively increased by the crosslinking points derived from the silane coupling agent contained in the primary layer.

[0115] As described above, according to the present invention, it is possible to provide an optical fiber core in which the Young's modulus and breaking elongation of the primary layer can be set to appropriate values.

[0116] 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]

[0117] 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 crosslinking points derived from unsaturated carbon bonds and crosslinking points derived from a silane coupling agent, The primary layer contains silicon atoms in an amount of 0.014 wt % or more and 0.72 wt % or less.

2. 2. The optical fiber according to claim 1, wherein the primary layer has a breaking elongation of 200% or more.

3. 2. The optical fiber according to claim 1, wherein the primary layer contains silicon atoms in a range of 0.014 wt % to 0.43 wt %.

4. 2. The optical fiber according to claim 1, wherein the Young's modulus of the primary layer is 0.29 MPa or more.

5. 2. The optical fiber according to claim 1, wherein the Young's modulus of the primary layer is 2.32 MPa or less.

6. 2. The optical fiber according to claim 1, wherein the primary layer is acidic.

7. 7. The optical fiber according to claim 1, wherein the primary layer has an increased breaking elongation compared to a primary layer not containing crosslinking points derived from a silane coupling agent.

8. 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.

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

10. A plurality of colored optical fiber core wires according to claim 8 or 9; and a ribbon layer formed of a fourth ultraviolet curing resin covering the colored optical fiber core.

11. 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 crosslinking points derived from unsaturated carbon bonds and crosslinking points derived from a silane coupling agent, The method for producing an optical fiber core, wherein the primary layer contains 0.014 wt % or more and 0.72 wt % or less of silicon atoms.

12. 12. The method for producing an optical fiber according to claim 11, wherein the primary layer has a breaking elongation of 200% or more.

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

14. 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 11, and irradiating the third ultraviolet-curable resin with ultraviolet light to form a colored layer.

15. 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 11.

16. 15. The method for producing a colored optical fiber according to claim 14, wherein in the step of forming the primary layer, the first ultraviolet-curable resin forming the primary layer is irradiated with ultraviolet light.

17. 16. 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 14 or 15; and irradiating the fourth ultraviolet-curing resin with ultraviolet light to form a ribbon layer.

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