Colored optical fiber and its manufacturing method

Abstract

To provide an optical fiber colored core wire that can reduce Young's modulus of a primary layer to desired Young's modulus and can suppress or prevent the Young's modulus from increasing, without accompanying a large change of a resin composition and a method for manufacturing the same.SOLUTION: An optical fiber colored core wire includes a bare optical fiber, a primary layer formed of a first ultraviolet curable resin that covers the bare optical fiber, and a secondary layer formed of a second ultraviolet curable resin that covers the primary layer. The primary layer has a carbon-sulfur bond and contains sulfur atoms of 0.03 wt% or more and 0.65 wt% or less, and an amount of increase in Young's modulus of the primary layer due to additional ultraviolet radiation to the primary layer is 0.09 MPa or less.SELECTED DRAWING: Figure 1A

Description

[Technical Field]

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

[0002] A technology for manufacturing a colored optical fiber is known (Patent Document 1), in which a primary layer covering a bare optical fiber, a secondary layer covering the primary layer, and a colored layer covering the secondary layer are each formed from an ultraviolet-curable resin so as to have a desired Young's modulus. When the Young's modulus of the primary layer is set low, it is possible to buffer the external force applied to the bare optical fiber and suppress the light transmission loss due to minute deformation of the bare optical fiber (hereinafter referred to as "microbend loss").

[0003] In order to lower the Young's modulus of the primary layer, it is necessary to design the saturated Young's modulus, which is the maximum Young's modulus that can be expressed by the UV-curable resin that constitutes the primary layer, to be low. However, lowering the saturated Young's modulus generally requires modifying the composition of the monomers and oligomers that make up the majority of the UV-curable resin, which requires significant changes to the resin composition.

[0004] In order to lower the Young's modulus without significantly changing the resin composition, it is conceivable to reduce the illuminance and dose of ultraviolet light irradiated during optical fiber manufacturing. However, in this case, even if the Young's modulus of the primary layer is low in the optical fiber immediately after manufacturing, the Young's modulus of the primary layer may increase if ultraviolet light is irradiated during the subsequent manufacturing process of the optical fiber ribbon. In response to this, methods for manufacturing colored optical fiber cores and optical fiber ribbons have been proposed in which the primary layer has a Young's modulus close to the saturated Young's modulus (Patent Documents 2 and 3).

[0005] On the other hand, UV-curable resins used in optical fiber coatings generally contain several additives. One such additive is a silane coupling agent, which improves the adhesion between the glass and the primary layer. It is known that when a mercapto group-containing silane coupling agent is used, the mercapto group acts as a polymerization inhibitor, reducing the curability of the coating resin (Patent Document 4). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-162522 [Patent Document 2] Patent No. 6841836 [Patent Document 3] Patent No. 6841837 [Patent Document 4] Japanese Patent Application Laid-Open No. 2013-88508 Summary of the Invention [Problem to be solved by the invention]

[0007] In order to improve the optical transmission capacity of the optical fiber by reducing the microbend loss, it is necessary to set the Young's modulus of the primary layer covering the bare optical fiber low, as described above. However, if the resin is not cured sufficiently and reactive groups that can participate in curing remain in the resin, an unexpected increase in Young's modulus may occur when the primary layer is exposed to ultraviolet light or light containing ultraviolet light during the coloring process, tape-making process, etc. after the optical fiber is manufactured.

[0008] On the other hand, in the case of a colored optical fiber core wire in which the primary layer has a Young's modulus close to the saturated Young's modulus as described in Patent Documents 2 and 3, the saturated Young's modulus of the resin is determined by the monomers, oligomers, etc. that make up the majority of the resin, so achieving a low Young's modulus requires a significant change in the resin composition. Also, the mercapto group-containing run coupling agent used as an additive to improve adhesion between the glass and the primary layer as described in Patent Document 4 cannot sufficiently reduce the Young's modulus of the primary layer even if it reduces hardening properties.

[0009] In view of the above-mentioned problems, the object of the present invention is to provide a colored optical fiber core wire and a manufacturing method thereof that can reduce the Young's modulus of the primary layer to a desired Young's modulus without significantly changing the resin composition, and can suppress or prevent an increase in the Young's modulus. [Means for solving the problem]

[0010] According to one aspect of the present invention, there is provided a colored optical fiber core wire 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 a carbon-sulfur bond and contains 0.03 wt% or more and 0.65 wt% or less of sulfur atoms; and the increase in Young's modulus of the primary layer due to additional ultraviolet irradiation of the primary layer is 0.09 MPa or less.

[0011] According to another aspect of the present invention, there is provided a method for manufacturing a colored 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; the primary layer has carbon-sulfur bonds and contains 0.03 wt% or more and 0.65 wt% or less of sulfur atoms, and the increase in Young's modulus of the primary layer due to additional ultraviolet irradiation of the primary layer is 0.09 MPa or less. [Effects of the Invention]

[0012] According to the present invention, the Young's modulus of the primary layer can be reduced to a desired value without any significant change in the resin composition, and an increase in the Young's modulus can be suppressed or prevented. [Brief explanation of the drawings]

[0013] [Figure 1A] 1 is a cross-sectional view of a colored optical fiber core wire according to one embodiment. [Figure 1B] 1 is a cross-sectional view of an optical fiber according to an embodiment. [Figure 2A] 1 is a schematic diagram showing a part of a manufacturing apparatus used in a manufacturing method of a colored optical fiber according to one embodiment. [Figure 2B] 3 is a schematic diagram showing another part of a manufacturing apparatus used in a manufacturing method of a colored optical fiber according to an embodiment of the present invention. FIG. [Figure 3A] 1 is a cross-sectional view of an example of an optical fiber ribbon according to an embodiment. [Figure 3B] FIG. 2 is a cross-sectional view of another example of an optical fiber ribbon according to an embodiment. [Figure 3C] FIG. 2 is a cross-sectional view of another example of an optical fiber ribbon according to an embodiment. [Figure 4] 1 is a schematic diagram of a ribbon forming apparatus used in an optical fiber ribbon manufacturing method according to one embodiment. [Figure 5] 1 is a flowchart of a method for manufacturing a colored optical fiber and an optical fiber ribbon according to an embodiment. [Figure 6] 1 is a graph showing the relationship between the Young's modulus difference between primary layers of a plurality of colored optical fiber core wires and the proportion of primary layers having a microbend loss difference of 0.05 dB / km or more. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Elements having common functions throughout the drawings will be designated by the same reference numerals, and duplicate descriptions may be omitted or simplified.

[0015] FIG. 1A is a cross-sectional view of a colored optical fiber 1 according to this embodiment. The colored optical fiber 1 comprises a bare optical fiber 2, a primary layer 3 coated on the outer periphery of the bare optical fiber 2, a secondary layer 4 coated on the outer periphery of the primary layer 3, and a colored layer 5 coated on the outer periphery of the secondary layer 4. The bare optical fiber 2 is coated with three coating layers: the primary layer 3, the secondary layer 4, and the colored layer 5. FIG. 1B is a cross-sectional view of an optical fiber 6 according to this embodiment. The optical fiber 6 is a fiber before the colored layer 5 is formed.

[0016] The bare optical fiber 2 is made of, for example, silica glass and transmits light. The primary layer 3, secondary layer 4, and colored layer 5 are each formed by curing an ultraviolet-curable resin by irradiating it with ultraviolet light. The ultraviolet-curable resin is not particularly limited as long as it can be polymerized by irradiating it with ultraviolet light. The ultraviolet-curable resin can be polymerized by, for example, photoradical polymerization.

[0017] 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 hardens 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.

[0018] Examples of the polymerizable unsaturated group in the ultraviolet-curable resin include groups having an unsaturated double bond such as a vinyl group, an allyl group, an acryloyl group, and a methacryloyl group, and groups having an unsaturated triple bond such as a propargyl group. Among these, an acryloyl group and a methacryloyl group are preferred in terms of polymerizability.

[0019] 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 with a degree of polymerization of 2 to 100. In this specification, "(meth)acrylate" refers to either or both of acrylate and methacrylate. The ultraviolet-curable resin contains any photopolymerization initiator (hereinafter referred to as "photoinitiator") that has sensitivity in the ultraviolet region.

[0020] Polyether-based urethane (meth)acrylates are compounds 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. Polyester-based urethane (meth)acrylates are compounds 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.

[0021] Furthermore, in addition to the oligomer and the photoinitiator, the UV-curable resin may contain, for example, a diluent monomer, a photosensitizer, a UV absorber, an antioxidant, a silane coupling agent, 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 refers to a monomer for diluting the UV-curable resin.

[0022] The primary layer 3 is a soft layer and has the function of buffering external forces applied to the bare optical fiber 2. When the optical fiber 6 is formed, there may still be room for hardening in the primary layer 3, but when it has hardened to the point where there is no room for hardening, the Young's modulus of the primary layer 3 reaches its maximum. In this embodiment, the maximum Young's modulus that the primary layer 3 of the optical fiber 6 can exhibit is defined as the "saturated Young's modulus."

[0023] The UV-curable resin constituting the primary layer 3 may contain a mercapto group-containing compound in order to form the primary layer 3 so as to have a carbon-sulfur bond, as described below. The mercapto group-containing compound is a compound having at least one mercapto group in one molecule. The mercapto group-containing compound reacts with a polymerizable compound such as urethane (meth)acrylate contained in the UV-curable resin via the mercapto group, thereby terminating the polymerization of the polymerizable compound. The mercapto group-containing compound is not particularly limited, and examples thereof include (3-mercaptopropyl)trimethoxysilane, isooctyl 3-mercaptopropionate, and 1-pentanethiol, as well as ethyl mercaptan, 1-butanethiol, 1-heptanethiol, 1-undecanethiol, 4-hydroxybenzenethiol, (2-mercaptoethyl)pyrazine, 2,3-butanedithiol, 3-methyl-2-butanethiol, Examples include 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-mercaptopropyl)triethoxysilane, 3-ethoxybenzenethiol, and pentaerythritol tetra(3-mercaptopropionate).

[0024] UV irradiation is performed at appropriate illuminance and dose as needed using, for example, a mercury lamp or UV-LED. The saturated Young's modulus varies depending on the optical fiber manufacturing conditions (e.g., drawing speed, UV irradiation intensity, UV light source type, resin application temperature, etc.), and cannot be uniquely determined by the UV-curable resin used.

[0025] The secondary layer 4 is a hard layer preferably having a Young's modulus of 500 MPa or more, and has the function of protecting the bare optical fiber 2 and the primary layer 3 from external forces.

[0026] The colored layer 5 is the outermost layer of the colored optical fiber core 1, and has the function of protecting the bare optical fiber 2, the primary layer 3, and the secondary layer 4 from external forces. The colored layer 5 is colored with a coloring agent containing a pigment, a lubricant, etc., to identify the colored optical fiber core 1. Examples of colors include white, black, gray, purple, blue, light blue, green, brown, yellow, orange, pink, and red.

[0027] The diameter of the bare optical fiber 2 may be, for example, 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 preferably 5 μm or more and 60 μm or less. The thickness of the secondary layer 4 may be preferably 5 μm or more and 60 μm or less. The thickness of the colored layer 5 may preferably be approximately several μm. Here, the diameter of the optical fiber 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, and the length twice the thickness of the secondary layer 4. Therefore, the diameter of the bare optical fiber 2, the thickness of the primary layer 3, and the thickness of the secondary layer 4 may each be selected so that the diameter of the optical fiber 6 is, for example, approximately 190 to 250 μm.

[0028] In this embodiment, the case where the colored layer 5 is formed separately from the secondary layer 4 will be described, but it is also possible to color the secondary layer 4 so that it also functions as a colored layer without forming the colored layer 5. In this case, the secondary layer 4 can be colored by adding a colorant similar to the colorant used to color the colored layer 5 to the ultraviolet-curable resin that constitutes the secondary layer 4.

[0029] Furthermore, the effective core area (Aeff) can be used as an index to indicate 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, for example, in 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 the 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 of a given intensity passes. Generally, 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. In other words, when the effective core area Aeff of the bare optical fiber 2 is large, light within the bare optical fiber 2 is more likely to leak due to an external force applied to the bare optical fiber 2. Therefore, 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 1.

[0030] The optical fiber bare wire 2 has an effective core area Aeff of 80 μm 2 or more (≧80μm 2 In optical fibers, Aeff is an index of microbending sensitivity, and the larger Aeff, the higher the microbending sensitivity (generally, Aeff>100μm 2 It is said that if Aeff is 130μm, the microbend sensitivity is high. 2 More than 150μm 2 If the thickness is less than or equal to the above, the optical fiber will have a high microbending sensitivity without any problems.

[0031] 2A is a schematic diagram showing a part of a manufacturing apparatus 10 used in the manufacturing method of the colored optical fiber 1 according to this embodiment. In FIG. 2A, the manufacturing apparatus 10 includes a heating device 20, a primary layer coating device 30, a secondary layer coating device 40, a guide roller 45, and a first winding device 50.

[0032] The optical fiber preform BM is made of, for example, silica-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. The end of the optical fiber preform BM is heated and melted by the heater 21 arranged around the optical fiber preform BM, and is then drawn to extract a bare optical fiber 2.

[0033] 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 irradiator 32. The resin applicator 31 holds an ultraviolet ray curable resin (hereinafter referred to as a "first ultraviolet ray curable resin"), which is a coating material for forming the primary layer 3. The resin applicator 31 applies the first ultraviolet ray curable resin to the bare optical fiber 2 drawn out from the optical fiber preform BM.

[0034] An ultraviolet irradiation device 32 is provided below the resin application device 31. The ultraviolet irradiation device 32 is equipped with any ultraviolet light source such as a metal halide lamp, a mercury lamp, or a UV-LED. A first ultraviolet-curable resin is applied to the bare optical fiber 2 by the resin application device 31, and the bare optical fiber 2 enters the ultraviolet irradiation device 32, where ultraviolet light is irradiated onto the first ultraviolet-curable resin. As a result, the first ultraviolet-curable resin is cured, and the primary layer 3 is formed.

[0035] 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 irradiation device 42. The resin coating device 41 holds an ultraviolet curable resin (hereinafter referred to as a "second ultraviolet curable resin"), which is a coating material for forming the secondary layer 4. The second ultraviolet curable resin is applied to the primary layer 3 by the resin coating device 41.

[0036] 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, on which the primary layer 3 is coated with the second ultraviolet-curable resin, enters the ultraviolet irradiation device 42, and ultraviolet light is irradiated onto the second ultraviolet-curable resin. As a result, the second ultraviolet-curable resin is cured, and the secondary layer 4 is formed. The primary layer 3 and the secondary layer 4 are coated onto the bare optical fiber 2, thereby forming an optical fiber strand 6.

[0037] The resin application device 31 may be configured to separately hold the first ultraviolet-curable resin and the second ultraviolet-curable resin. In this case, the resin application device 31 applies the first ultraviolet-curable resin to the bare optical fiber 2, and then applies the second ultraviolet-curable resin on the first ultraviolet-curable resin. Furthermore, in this case, the ultraviolet irradiation device 32 irradiates ultraviolet light onto the first ultraviolet-curable resin and the second ultraviolet-curable resin 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.

[0038] A guide roller 45 and a first winding device 50 are provided below the secondary layer coating device 40. The manufactured optical fiber 6 is guided by the guide roller 45 and wound around the first winding device 50.

[0039] 2B is a schematic diagram showing other parts of the manufacturing apparatus 10 used in the manufacturing method of the colored optical fiber 1 according to this embodiment. In FIG. 2B, the manufacturing apparatus 10 includes a bare fiber holding device 55, a guide roller 56, a colored layer coating device 60, a guide roller 65, and a second winding device 70. The manufacturing apparatus 10 manufactures the colored optical fiber 1 from the optical fiber 6 manufactured by the multiple devices shown in FIG. 2A.

[0040] The fiber holding device 55 holds the manufactured optical fiber 6 in a wound state. Note that, although the fiber holding device 55 is separate from the first winding device 50 in FIG. 2B, the first winding device 50 may also serve as the fiber holding device 55.

[0041] A colored layer coating device 60 is provided below the bare wire holding device 55. The optical fiber 6 drawn out from the bare wire holding device 55 is guided by guide rollers 56 provided between the bare wire holding device 55 and the colored layer coating device 60, and is transported into the colored layer coating device 60.

[0042] The colored layer coating device 60 includes a resin coating device 61 and an ultraviolet ray irradiation device 62. The resin coating device 61 holds an ultraviolet ray curable resin (hereinafter referred to as "third ultraviolet ray curable resin"), which is a coating material for forming the colored layer 5.

[0043] A third ultraviolet curing resin is applied to the optical fiber 6 by a resin applying device 61. An ultraviolet irradiation device 62 is provided below the resin applying device 61. The ultraviolet irradiation device 62 may be configured similarly to the ultraviolet irradiation devices 32 and 42.

[0044] The optical fiber 6 with the third ultraviolet-curable resin applied to the outer periphery of the secondary layer 4 enters an ultraviolet irradiation device 62, which irradiates ultraviolet rays onto the third ultraviolet-curable resin and the optical fiber 6. As a result, the third ultraviolet-curable resin is cured, and the colored layer 5 is formed.

[0045] The primary layer 3, secondary layer 4, and colored layer 5 are coated on the bare optical fiber 2 to form a colored optical fiber core wire 1. After being manufactured, the colored optical fiber core wire 1 is guided by a guide roller 65 provided below the colored layer coating device 60, and is wound up on a second winding device 70.

[0046] Note that if the secondary layer 4 is colored without forming the colored layer 5 so that the secondary layer 4 also functions as a colored layer, the above-described steps using the other parts of the manufacturing apparatus 10 shown in FIG. 2B can be omitted. In this case, a colorant can be added to the second ultraviolet-curable resin applied by the resin application apparatus 41 to color it, and the colored second ultraviolet-curable resin can be applied around the primary layer 3. This allows the secondary layer 4 to be colored with the colorant.

[0047] FIG. 3A is a cross-sectional view of an example of an optical fiber ribbon 100 according to this embodiment. The optical fiber ribbon 100 is configured by bundling n (n is a natural number equal to or greater than 2) colored optical fibers 1-1 to 1-n into a band-like shape via an adhesive layer 101. Note that the optical fiber ribbon 100 is not limited to the structure in which all of the colored optical fibers 1-1 to 1-n are bundled into a single ribbon as shown in FIG. 3A, but may also have an intermittent adhesive structure as shown in FIGS. 3B and 3C. In the optical fiber ribbon 100 having an intermittent adhesive structure, two or more colored optical fibers 1 arranged continuously in the width direction are bundled into a single band-like shape via an adhesive layer 101. FIGS. 3B and 3C show a structure in which every two colored optical fibers 1 arranged adjacent to each other in the width direction are bundled into a single band-like shape via an adhesive layer 101. In this case, as shown in Figure 3B, each optical fiber colored core wire 1 may be bundled with other optical fiber colored core wires 1, or as shown in Figure 3C, some of the multiple optical fiber colored core wires 1 may not be bundled with other optical fiber colored core wires 1.

[0048] In this embodiment, the same optical fiber ribbon 100 contains two or more types of colored optical fibers 1 having colored layers 5 of different colors.

[0049] It is also preferable that there be no difference in absorbance of ultraviolet light depending on the color of the colored layer 5. For example, if the colored optical fiber 1-1 has a white colored layer 5 and the colored optical fiber 1-n has a black colored layer 5, the absorbance of ultraviolet light may differ between these two colored optical fiber cores 1. One possible solution to this problem is to add an additive to the third ultraviolet-curable resin that forms the colored layer 5, in accordance with the color of the colored layer 5 to be formed, to adjust the absorbance of ultraviolet light of a predetermined wavelength. By appropriately adjusting the type and amount of additive for each color of the colored layer 5, it is possible to reduce the difference in absorbance between the multiple colored optical fiber cores 1-1 to 1-n.

[0050] It is preferable that at least a portion of the wavelength range (first wavelength range) in which the additive added to the third ultraviolet-curable resin absorbs ultraviolet light overlaps with the wavelength range (second wavelength range) in which the photoinitiator added to the first ultraviolet-curable resin absorbs ultraviolet light.

[0051] The adhesive layer 101 is formed by irradiating a coating material containing an ultraviolet-curable resin with ultraviolet light to cure it. In this specification, the adhesive layer 101 is also referred to as a ribbon layer. The ultraviolet-curable resin forming the adhesive layer 101 is composed of the same resin as the ultraviolet-curable resin forming the primary layer 3, the secondary layer 4, and the colored layer 5. The colored optical fiber 1 can be bundled at a high density by taking the form of an optical fiber ribbon 100. Note that the optical fiber ribbon 100 is not limited to the configuration shown in FIGS. 3A, 3B, and 3C. The optical fiber ribbon 100 may also take the form of an optical fiber ribbon cable in which the optical fiber ribbon 100 is housed in a sheath.

[0052] 4 is a schematic diagram of a ribbonizing device 80 used in the manufacturing method of the optical fiber ribbon 100 according to this embodiment. The ribbonizing device 80 has a resin applying device 81 and an ultraviolet ray irradiating device 82. The resin applying device 81 holds an ultraviolet ray curing resin (hereinafter referred to as a "fourth ultraviolet ray curing resin") that is a coating material for the adhesive layer 101.

[0053] A plurality of colored optical fiber core wires 1 prepared in different colors enter a ribbon forming device 80, where a fourth ultraviolet-curable resin is applied by a resin application device 81. The colored optical fiber core wires 1 coated with the fourth ultraviolet-curable resin are bundled together with a plurality of other colored optical fiber core wires 1 coated with the fourth ultraviolet-curable resin. An ultraviolet irradiation device 82 provided in the ribbon forming device 80 irradiates ultraviolet light onto the bundled plurality of colored optical fiber core wires 1. As a result, the fourth ultraviolet-curable resin is hardened to form an adhesive layer 101. The plurality of colored optical fiber core wires 1 arranged in parallel are connected via the adhesive layer 101. In this way, an optical fiber ribbon 100 is formed from the plurality of colored optical fiber core wires 1.

[0054] The ribbon forming device 80 may be, for example, the ribbon forming device described in Japanese Patent Application Laid-Open No. 2012-118358. As a result, the adhesive layers 101 are formed intermittently at predetermined intervals in the longitudinal direction of adjacent colored optical fiber cores 1, thereby forming an intermittently bonded optical fiber ribbon 100.

[0055] 5 is a flowchart of a method for manufacturing the colored optical fiber 1 and the optical fiber ribbon 100 according to this embodiment. First, the user places the optical fiber preform BM in the manufacturing apparatus 10 (step S101).

[0056] Next, the heater 21 provided in the heating device 20 heats the optical fiber preform BM, and drawing of the bare optical fiber 2 begins (step S102).

[0057] The primary layer coating device 30 applies a first ultraviolet curing resin to the periphery of the drawn bare optical fiber 2, and irradiates the first ultraviolet curing resin with ultraviolet light to form the primary layer 3 (step S103).

[0058] Next, the secondary layer coating device 40 applies a second ultraviolet-curable resin to the periphery of the primary layer 3 and irradiates the second ultraviolet-curable resin with ultraviolet light to form the secondary layer 4 (step S104). This results in the optical fiber 6. The manufactured optical fiber 6 is wound up by the first winding device 50.

[0059] Next, when the optical fiber 6 is pulled out from the fiber holding device 55 or the first winding device 50, the colored layer coating device 60 applies a third ultraviolet-curable resin to the periphery of the secondary layer 4 of the optical fiber 6 and irradiates the third ultraviolet-curable resin with ultraviolet light to form the colored layer 5 (step S105). By coating the periphery of the optical fiber 6 with the colored layer 5, the colored optical fiber 1 is obtained. After production, the colored optical fiber 1 is wound up by the second winding device 70. Note that step S105 can be omitted and the secondary layer 4 can be colored in step S104 so that the secondary layer 4 functions as a colored layer.

[0060] In this embodiment, a plurality of colored optical fibers 1 are manufactured, each having a different color of colored layer 5. Therefore, the processing in step S105 is performed by changing the manufacturing conditions, such as the composition of the third ultraviolet-curable resin, for each color.

[0061] Furthermore, it is not always necessary to irradiate the primary layer 3 with ultraviolet light in the step of forming the primary layer 3 (step S103). In this case, the primary layer 3 can be cured in the step of forming the secondary layer 4 (step S104).

[0062] After the colored layer 5 is formed in step S105, the ribbonizing device 80 applies a fourth ultraviolet curing resin to cover the multiple colored optical fibers 1 prepared in different colors, and irradiates the fourth ultraviolet curing resin with ultraviolet light to connect the multiple colored optical fibers 1 to each other (step S106). In this way, the optical fiber ribbon 100 is manufactured.

[0063] In the colored optical fiber 1 according to this embodiment, the primary layer 3 is made of an ultraviolet-curable resin (first ultraviolet-curable resin) containing a mercapto group-containing compound, and therefore has a mercapto group-containing compound or a structure derived from a mercapto group-containing compound. As a result of the reaction of the mercapto group-containing compound with a polymerizable compound such as urethane (meth)acrylate, the primary layer 3 has carbon-sulfur bonds and specifically contains 0.03 wt% to 0.65 wt% of sulfur atoms. The carbon-sulfur bond is a covalent bond between a carbon atom and a sulfur atom.

[0064] The presence or absence of carbon-sulfur bonds in the primary layer 3 can be confirmed by measurement using, for example, Fourier transform infrared spectroscopy (FT-IR), and the content of sulfur atoms in the primary layer 3 can be measured using, for example, elemental analysis (EA).

[0065] As described above, the mercapto group-containing compound has the effect of reacting with a polymerizable compound such as urethane (meth)acrylate contained in the UV-curable resin via the mercapto group to terminate the polymerization of the polymerizable compound. Therefore, the primary layer 3 has a lower saturated Young's modulus than when it is made of a UV-curable resin that does not contain a mercapto group-containing compound.

[0066] That is, the primary layer 3 has a low Young's modulus, while the increase in Young's modulus due to the additional ultraviolet irradiation of the primary layer 3 is kept low at 0.09 MPa or less. The primary layer 3 preferably has a Young's modulus of 0.15 MPa or more and 2.31 MPa or less. The additional ultraviolet irradiation is performed under the condition that the ambient temperature during ultraviolet irradiation is room temperature, and the illuminance is 1000 mW / cm, as will be described later. 2 and irradiation dose 1000mJ / cm 2 , illuminance 1000mW / cm 2 and irradiation dose 500mJ / cm 2 , illuminance 500mW / cm 2 and irradiation dose 1000mJ / cm 2 , and illuminance 500mW / cm 2and irradiation dose 500mJ / cm 2 It can be performed under either of the following conditions.

[0067] Furthermore, the saturated Young's modulus of the primary layer 3 made of the ultraviolet-curable resin containing the mercapto group-containing compound is preferably reduced by 10% or more compared to the saturated Young's modulus of the ultraviolet-curable resin before the addition of the mercapto group-containing compound, i.e., the primary layer made of the ultraviolet-curable resin not containing the mercapto group-containing compound.

[0068] Conventionally, as described in Patent Document 4, attention has been focused on the negative aspect of using a mercapto group-containing silane coupling agent in an ultraviolet-curable resin, namely, reduced curability. In contrast, in this embodiment, a desired Young's modulus can be easily achieved by appropriately adding a mercapto group-containing compound to an ultraviolet-curable resin. Furthermore, in this embodiment, even if the Young's modulus is low, reactive groups that react with radicals generated from a photoinitiator upon ultraviolet irradiation do not remain unreacted in the primary layer 3. This makes it possible to suppress or prevent new reactions due to ultraviolet irradiation or exposure to ultraviolet light after optical fiber production, thereby suppressing or preventing an increase in the Young's modulus of the primary layer 3 after curing.

[0069] Here, a correlation is observed between the amount of mercapto group-containing compound added to the ultraviolet curable resin constituting the primary layer 3 and the reduction in the saturated Young's modulus of the primary layer 3. Therefore, by controlling the amount of mercapto group-containing compound added based on the correlation between the two, the Young's modulus of the primary layer 3 can be easily reduced and controlled to a desired value.

[0070] In order to sufficiently reduce the Young's modulus of the primary layer 3, the ultraviolet-curable resin constituting the primary layer 3 preferably contains 0.2 wt% or more of a mercapto group-containing compound. In order to ensure the curability of the primary layer 3, the ultraviolet-curable resin constituting the primary layer 3 preferably contains 4 wt% or less of a mercapto group-containing compound. However, because the curability is determined by the number of mercapto groups added, there is no problem with adding 4 wt% or more of the mercapto group-containing compound depending on the molecular weight of the compound.

[0071] The mercapto group of the mercapto group-containing compound can reduce the Young's modulus by terminating the polymerization reaction, and therefore the repeating units of the main chain skeleton of the primary layer 3 do not contain carbon-sulfur bonds.

[0072] Here, the glass transition temperature is one of the indicators that represent the cured state of the ultraviolet-curable resin. It is preferable that the glass transition temperature of the primary layer 3 does not change significantly before and after the additional ultraviolet irradiation. Specifically, it is preferable that the change in glass transition temperature of the primary layer 3 after the additional ultraviolet irradiation is within ±1.3°C. It is preferable that the glass transition temperature of the primary layer 3 is -55°C or higher and room temperature or lower. In this specification, room temperature means 25°C.

[0073] As described above, according to this embodiment, the saturated Young's modulus can be more easily reduced to a desired value by simply intentionally adding a mercapto group-containing compound to the UV-curable resin that constitutes the primary layer 3. Moreover, according to this embodiment, it is possible to suppress or prevent the Young's modulus of the primary layer 3 from changing due to UV irradiation or exposure to UV light after the optical fiber is manufactured. In this way, it is possible to sufficiently reduce the Young's modulus of the primary layer 3 to a desired value and suppress or prevent an increase in the Young's modulus of the primary layer 3 without significantly changing the resin composition. [Example]

[0074] Hereinafter, the results of experimental evaluation of the properties of the cured product of the ultraviolet curable resin used as the primary layer 3 will be described using examples and comparative examples.

[0075] In the examples and comparative examples, the saturated Young's modulus was determined as the Young's modulus when ultraviolet-curable resin formed into a sheet of approximately 100 μm in thickness was cured by irradiating it with ultraviolet light so that the Young's modulus would not increase further even if it was irradiated with additional ultraviolet light. The ambient temperature during ultraviolet light irradiation was room temperature. For ultraviolet light irradiation, a mercury lamp, UV-LED or other UV light emitter was used. The main irradiation conditions were an illuminance of 1000 mW / cm 2 , irradiation amount 1000mJ / cm 2 ”, “Illuminance 1000mW / cm 2 , irradiation amount 500mJ / cm 2 ”, “Illuminance 500mW / cm 2 , irradiation amount 1000mJ / cm 2 ”, “Illuminance 500mW / cm 2 , irradiation amount 500mJ / cm 2 " was used. Note that other conditions for illuminance and dose may also be used. For illuminance measurement, a mercury lamp, such as the UV-351 manufactured by Oak Manufacturing Co., Ltd., or a UV-LED, such as the UVRT2 / UD-T3040T2 manufactured by Topcon Technohouse, was used. The Young's modulus was calculated by measuring the force at 2.5% elongation by using a Tensilon universal tensile tester in an atmosphere of 23°C and 50% relative humidity, pulling the sample with a width of 6 mm, a gauge spacing of 25 mm, and a pulling speed of 1 mm / min.

[0076] The Young's modulus of the primary layer 3 was defined as ISM (In Situ Modulus) measured by the following method.

[0077] First, a commercially available stripper was used to strip a few millimeters of the primary and secondary layers from the middle of a sample optical fiber. One end of the optical fiber with the coating layer formed thereon was then fixed to a glass slide with adhesive, and a load F was applied to the other end of the optical fiber with the coating layer formed thereon. In this state, the displacement δ of the primary layer at the boundary between the stripped portion and the coated portion was measured using a microscope. A graph of displacement δ versus load F was then created by varying load F to 10, 20, 30, 50, and 70 gf (i.e., 98, 196, 294, 490, and 686 mN, respectively). The primary modulus was then calculated using the slope obtained from the graph and the following equation (1). The calculated primary modulus corresponds to the so-called ISM, and will be referred to as P-ISM below. When drawing the colored optical fiber 1, the drawing speed and UV irradiance were controlled to adjust the P-ISM. P-ISM=(3F / δ)*(1 / 2πl)*ln(DP / DG) ···(1)

[0078] The unit of P-ISM is [MPa]. Furthermore, F / δ is the slope of the graph of displacement (δ) [μm] against load (F) [gf], 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 3 to the outer diameter (DG) [μm] of the cladding of the optical fiber. Therefore, when calculating P-ISM using the above formula (1) from the used F, δ, and l, a predetermined unit conversion is required. The outer diameter of the primary layer and the outer diameter of the cladding can be measured by observing the cross section of the optical fiber cut with a fiber cutter under a microscope.

[0079] There are various methods for measuring microbend loss. Here, we defined the microbend loss value as the difference between the transmission loss of the optical fiber to be measured in State A, where an optical fiber 400m or longer is wound in a single layer with no overlapping, at a tension of 100gf around a large bobbin wrapped with #1000 grit sandpaper, and the transmission loss of the optical fiber in State B, where the optical fiber is wound on the same bobbin as State A with the same tension and length as State A but without sandpaper. Here, the transmission loss of the optical fiber in State B does not include microbend loss and is considered to be the transmission loss inherent to the optical fiber itself.

[0080] 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 this measurement method, the transmission loss is measured at a wavelength of 1550 nm, so the microbend loss in this embodiment is also a value at a wavelength of 1550 nm.

[0081] In the examples and comparative examples, various properties were measured for the cured product obtained by irradiating a UV-curable resin formed into a sheet approximately 100 μm thick with a mercury lamp. 2,4,6-trimethylbenzoyl-diphenylphosphine oxide was added to the UV-curable resin as a photoinitiator. Although a mercury lamp was used as the UV light source in these examples and comparative examples, the UV light source is not limited to a mercury lamp and can also be UV-LEDs of various wavelengths.

[0082] In the examples, Additives A, B, and C were used as mercapto-containing compounds added to the UV-curable resin. Additive A was (3-mercaptopropyl)trimethoxysilane. Additive B was isooctyl 3-mercaptopropionate. Additive C was 1-pentanethiol.

[0083] In the examples and comparative examples, the Young's modulus after additional ultraviolet irradiation was measured by using a mercury lamp at 500 mW / cm for the cured product of the ultraviolet-curable resin. 2 , 500mJ / cm 2The Young's modulus of the cured product when irradiated again under the irradiation conditions was determined as Young's modulus of the cured product. In addition, by similarly irradiating the colored optical fiber 1 with additional ultraviolet light, it is possible to confirm whether or not the effect of the present invention is achieved.

[0084] The glass transition temperature can be measured using various analytical instruments such as differential scanning calorimetry (DSC), thermomechanical analysis (TMA), and dynamic mechanical analysis (DMA). However, the glass transition temperature value obtained varies depending on the type of measurement method, so in this example, the glass transition temperature was measured using dynamic mechanical analysis. In this specification, the glass transition temperature means the value measured using dynamic mechanical analysis.

[0085] Dynamic mechanical analysis is a measurement method that takes advantage of the fact that molecular motion increases significantly in the glass transition region, resulting in a large change in elastic modulus. In other words, as the resin transitions from a glassy state to a rubbery state, its Young's modulus changes by approximately three orders of magnitude, from approximately 1000 MPa to approximately 1 MPa, making it possible to measure the glass transition with high sensitivity.

[0086] Dynamic mechanical analysis measures the viscoelasticity observed when a periodically changing strain or stress is applied to an object. Measurements using dynamic mechanical analysis can obtain data on the storage modulus (G'), loss modulus (G"), and loss tangent (tanδ = G" / G'). Here, the storage modulus represents the elastic component of a material, and the loss modulus represents the viscous component of a material. The loss tangent is the loss modulus divided by the storage modulus, and represents the balance between the elastic and viscous components. In the case of a perfectly elastic material, stress and strain are proportional, and stress is detected without delay (zero phase difference) for a given stress. On the other hand, in the case of a perfectly viscous material, stress and strain rate are proportional, so when stress is applied as sin(ωt), the response strain is -cos(ωt) = sin(ωt - π / 2), and the strain is detected with a delay of 1 / 4 wavelength (phase difference π / 2) relative to the stress. The measurement involves applying an AC force to a sample, detecting the displacement of the sample, and then performing Fourier transformations to determine the phase difference between the applied AC force and the detected displacement. Typical polymers have properties intermediate between those of a perfect elastic body and a viscous body, resulting in a phase difference between 0 and π / 2. Dynamic mechanical analysis measures the relationship between stress and strain and outputs a loss tangent value, which represents the ratio of the storage modulus of the elastic component to the loss modulus of the viscous component, a mechanical property. In this invention, the temperature at which this loss tangent value reaches its maximum is defined as the glass transition temperature. The loss tangent value was measured using a TA Instruments RSA-G2 (registered trademark) dynamic viscoelasticity analyzer. A rectangular sample was cut from a cured sheet of UV-curable resin, fixed to a tensile jig, and measured under the following dynamic viscoelasticity test conditions. In this measurement, the temperature at which the maximum value appeared was defined as the glass transition temperature. <Dynamic viscoelasticity test conditions> Vibration frequency: 1Hz Sample heating rate: 5°C / min

[0087] The glass transition temperature of the primary layer 3 in an optical fiber can be measured in the same way by immersing the optical fiber in liquid nitrogen, stripping the coating with a stripper, and extracting the glass optical fiber from the optical fiber, leaving only the coating. In this case, the maximum value of the loss tangent due to the secondary layer 4 is also observed, but because the glass transition temperatures of the secondary layer 4 and the primary layer 3 are significantly different, the maximum value of the loss tangent due to the primary layer 3 can be easily distinguished.

[0088] The sheet-shaped cured product prepared when determining the saturated Young's modulus of the primary layer 3 before adding the mercapto group-containing compound additive shown in the Examples and Comparative Examples was cured by irradiating it with a mercury lamp (illuminance 1000 mW / cm 2 , irradiation amount 1000mJ / cm 2 The primary layer before the addition of the mercapto group-containing compound additive is the primary layer without the addition of the mercapto group-containing compound additive.

[0089] The saturated Young's modulus of the primary layer 3 shown in the examples and comparative examples is merely an example, and generally, the Young's modulus of the primary layer 3 can be in the range of 0.1 to 3.0 MPa. The Young's modulus of the secondary layer 4 can be in the range of 500 to 2000 MPa.

[0090] The Young's modulus of the secondary layer 4 can be measured using the following method. First, an optical fiber is immersed in liquid nitrogen, and the coating layer is stripped off using a stripper to create a sample of only the coating layer. The end of the sample is then fixed to an aluminum plate with an adhesive. The aluminum plate is then chucked using a Tensilon universal tensile tester in an atmosphere of 23°C and 50% relative humidity. Next, the sample is pulled with a gauge spacing of 25 mm and a pulling rate of 1 mm / min, and the force at 2.5% elongation is measured to calculate the elastic modulus (secondary elastic modulus) S-ISM (2.5% secant modulus) of the secondary layer 4.

[0091] In Example 1, 0.5 wt% of additive A was added to an ultraviolet curable resin having a saturated Young's modulus of 1.48 MPa and a glass transition temperature at the saturated Young's modulus of -28.5°C. The saturated Young's modulus of the ultraviolet curable resin to which additive A was added was 1.21 MPa, which was 18.2% lower than the saturated Young's modulus before the addition of the additive. 2 , irradiation amount 500mJ / cm 2 The Young's modulus of the cured product was 1.17 MPa and the glass transition temperature was -30.5°C. The cured product was then subjected to additional UV irradiation using a mercury lamp (illuminance 500 mW / cm 2 , irradiation amount 500mJ / cm 2 ), the Young's modulus was 1.21 MPa, with an increase of +0.04 MPa, less than 0.09 MPa. The glass transition temperature was -30.1°C, with an increase of +0.4°C, within ±1.3°C.

[0092] In Example 2, 1.0 wt% of additive A was added to an ultraviolet curable resin having a saturated Young's modulus of 1.48 MPa and a glass transition temperature at the saturated Young's modulus of -28.5°C. The saturated Young's modulus of the ultraviolet curable resin to which additive A was added was 1.03 MPa, which was 30.4% lower than the saturated Young's modulus before the addition of the additive. 2 , irradiation amount 500mJ / cm 2 The Young's modulus of the cured product was 1.00 MPa and the glass transition temperature was -31.0°C. The cured product was then subjected to additional UV irradiation using a mercury lamp (illuminance 500 mW / cm 2 , irradiation amount 500mJ / cm 2 ), the Young's modulus was 1.03 MPa, with an increase of +0.03 MPa, less than 0.09 MPa. The glass transition temperature was -29.7°C, with an increase of +1.3°C, within ±1.3°C.

[0093] In Example 3, 2.0 wt% of additive A was added to an ultraviolet curable resin having a saturated Young's modulus of 1.48 MPa and a glass transition temperature at the saturated Young's modulus of -28.5°C. The saturated Young's modulus of the ultraviolet curable resin to which additive A was added was 0.75 MPa, a decrease of 49.3% compared to the saturated Young's modulus before the addition of the additive. 2 , irradiation amount 500mJ / cm 2 The Young's modulus of the cured product was 0.66 MPa and the glass transition temperature was -31.0°C. The cured product was then subjected to additional UV irradiation using a mercury lamp (illuminance 500 mW / cm 2 , irradiation amount 500mJ / cm 2 ), the Young's modulus was 0.75 MPa, with an increase of +0.09 MPa, which was less than 0.09 MPa. The glass transition temperature was -31.5°C, with a change of -0.5°C, within ±1.3°C.

[0094] In Example 4, 3.0 wt% of additive A was added to an ultraviolet curable resin having a saturated Young's modulus of 1.48 MPa and a glass transition temperature at the saturated Young's modulus of -28.5°C. The saturated Young's modulus of the ultraviolet curable resin to which additive A was added was 0.46 MPa, a decrease of 68.9% compared to the saturated Young's modulus before the addition of the additive. 2 , irradiation amount 500mJ / cm 2 The Young's modulus of the cured product was 0.39 MPa and the glass transition temperature was -33.2°C. The cured product was then subjected to additional UV irradiation using a mercury lamp (illuminance 500 mW / cm 2 , irradiation amount 500mJ / cm 2 ), the Young's modulus was 0.46 MPa, with an increase of +0.07 MPa, less than 0.09 MPa. The glass transition temperature was -32.0°C, with a change of +1.2°C, within ±1.3°C.

[0095] In Example 5, 4.0 wt% of additive A was added to an ultraviolet curable resin having a saturated Young's modulus of 1.48 MPa and a glass transition temperature at the saturated Young's modulus of -28.5°C. The saturated Young's modulus of the ultraviolet curable resin to which additive A was added was 0.21 MPa, a decrease of 85.8% compared to the saturated Young's modulus before the addition of the additive. 2 , irradiation amount 500mJ / cm 2 The Young's modulus of the cured product was 0.15 MPa and the glass transition temperature was -33.8°C. The cured product was then subjected to additional UV irradiation using a mercury lamp (illuminance 500 mW / cm 2 , irradiation amount 500mJ / cm 2 ), the Young's modulus was 0.21 MPa, with an increase of +0.06 MPa, less than 0.09 MPa. The glass transition temperature was -33.0°C, with an increase of +0.8°C, within ±1.3°C.

[0096] In Example 6, 1.0 wt% of additive B was added to an ultraviolet curable resin having a saturated Young's modulus of 1.48 MPa and a glass transition temperature at the saturated Young's modulus of -28.5°C. The saturated Young's modulus of the ultraviolet curable resin to which additive B was added was 0.96 MPa, a decrease of 35.1% compared to the saturated Young's modulus before the addition of the additive. 2 , irradiation amount 500mJ / cm 2 The Young's modulus of the cured product was 0.95 MPa and the glass transition temperature was -31.7°C. The cured product was then subjected to additional UV irradiation using a mercury lamp (illuminance 500 mW / cm 2 , irradiation amount 500mJ / cm 2 ), the Young's modulus was 0.96 MPa, with an increase of +0.01 MPa, less than 0.09 MPa. The glass transition temperature was -30.8°C, with an increase of +0.9°C, within ±1.3°C.

[0097] In Example 7, 0.3 wt% of additive C was added to an ultraviolet curable resin having a saturated Young's modulus of 1.48 MPa and a glass transition temperature at the saturated Young's modulus of -28.5°C. The saturated Young's modulus of the ultraviolet curable resin to which additive C was added was 1.32 MPa, a decrease of 10.8% compared to the saturated Young's modulus before the addition of the additive. 2 , irradiation amount 500mJ / cm 2 The Young's modulus of the cured product was 1.32 MPa and the glass transition temperature was -30.0°C. The cured product was then subjected to additional UV irradiation using a mercury lamp (illuminance 500 mW / cm 2 , irradiation amount 500mJ / cm 2 ), the Young's modulus was 1.32 MPa, with a change of 0.00 MPa, less than 0.09 MPa. The glass transition temperature was -30.2°C, with a change of -0.2°C, within ±1.3°C.

[0098] In Example 8, 0.5 wt% of additive A was added to an ultraviolet curable resin having a saturated Young's modulus of 2.57 MPa and a glass transition temperature at the saturated Young's modulus of -54.0°C. The saturated Young's modulus of the ultraviolet curable resin to which additive A was added was 2.02 MPa, a decrease of 21.4% compared to the saturated Young's modulus before the addition of the additive. 2 , irradiation amount 500mJ / cm 2 The Young's modulus of the cured product was 2.00 MPa and the glass transition temperature was -53.6°C. The cured product was then subjected to additional UV irradiation using a mercury lamp (illuminance 500 mW / cm 2 , irradiation amount 500mJ / cm 2 ), the Young's modulus was 2.02 MPa, with an increase of +0.02 MPa, less than 0.09 MPa. The glass transition temperature was -53.7°C, with a change of -0.1°C, within ±1.3°C.

[0099] In Example 9, 1.0 wt% of additive A was added to an ultraviolet curable resin having a saturated Young's modulus of 2.57 MPa and a glass transition temperature at the saturated Young's modulus of -54.0°C. The saturated Young's modulus of the ultraviolet curable resin to which additive A was added was 1.73 MPa, a decrease of 32.7% compared to the saturated Young's modulus before the addition of the additive. 2 , irradiation amount 500mJ / cm 2 The Young's modulus of the cured product was 1.69 MPa and the glass transition temperature was -52.8°C. The cured product was then subjected to additional UV irradiation using a mercury lamp (illuminance 500 mW / cm 2 , irradiation amount 500mJ / cm 2 ), the Young's modulus was 1.73 MPa, with an increase of +0.04 MPa, less than 0.09 MPa. The glass transition temperature was -53.0°C, with a change of -0.2°C, within ±1.3°C.

[0100] In Example 10, 2.0 wt% of additive A was added to an ultraviolet curable resin having a saturated Young's modulus of 2.57 MPa and a glass transition temperature at the saturated Young's modulus of -54.0°C. The saturated Young's modulus of the ultraviolet curable resin to which additive A was added was 1.12 MPa, a decrease of 56.4% compared to the saturated Young's modulus before the addition of the additive. 2 , irradiation amount 500mJ / cm 2 The Young's modulus of the cured product was 1.12 MPa and the glass transition temperature was -52.8°C. The cured product was then subjected to additional UV irradiation using a mercury lamp (illuminance 500 mW / cm 2 , irradiation amount 500mJ / cm 2 ), the Young's modulus was 1.12 MPa with a change of 0.00 MPa, less than 0.09 MPa. The glass transition temperature was -52.8°C with a change of 0°C, within ±1.3°C.

[0101] In Example 11, 3.0 wt% of additive A was added to an ultraviolet curable resin having a saturated Young's modulus of 2.57 MPa and a glass transition temperature at the saturated Young's modulus of -54.0°C. The saturated Young's modulus of the ultraviolet curable resin to which additive A was added was 0.55 MPa, a decrease of 78.6% compared to the saturated Young's modulus before the addition of the additive. 2 , irradiation amount 500mJ / cm 2 The Young's modulus of the cured product was 0.53 MPa and the glass transition temperature was -52.8°C. The cured product was then subjected to additional UV irradiation using a mercury lamp (illuminance 500 mW / cm 2 , irradiation amount 500mJ / cm 2 ), the Young's modulus was 0.55 MPa, with an increase of +0.02 MPa, less than 0.09 MPa. The glass transition temperature was -52.8°C, with a change of 0°C, within ±1.3°C.

[0102] In Example 12, 0.2 wt% of additive B was added to an ultraviolet curable resin having a saturated Young's modulus of 2.57 MPa and a glass transition temperature at the saturated Young's modulus of -54.0°C. The saturated Young's modulus of the ultraviolet curable resin to which additive B was added was 2.31 MPa, a decrease of 10.1% compared to the saturated Young's modulus before the addition of the additive. 2 , irradiation amount 500mJ / cm 2 The Young's modulus of the cured product was 2.30 MPa and the glass transition temperature was -53.7°C. The cured product was then subjected to additional UV irradiation using a mercury lamp (illuminance 500 mW / cm 2 , irradiation amount 500mJ / cm 2 ), the Young's modulus was 2.31 MPa, with an increase of +0.01 MPa, less than 0.09 MPa. The glass transition temperature was -53.9°C, with a change of -0.2°C, within ±1.3°C.

[0103] In Example 13, 0.5 wt% of additive B was added to an ultraviolet curable resin having a saturated Young's modulus of 2.57 MPa and a glass transition temperature at the saturated Young's modulus of -54.0°C. The saturated Young's modulus of the ultraviolet curable resin to which additive B was added was 2.03 MPa, a decrease of 21.0% compared to the saturated Young's modulus before the addition of the additive. 2 , irradiation amount 500mJ / cm 2 The Young's modulus of the cured product was 2.00 MPa and the glass transition temperature was -53.6°C. The cured product was then subjected to additional UV irradiation using a mercury lamp (illuminance 500 mW / cm 2 , irradiation amount 500mJ / cm 2 ), the Young's modulus was 2.03 MPa, with an increase of +0.03 MPa, less than 0.09 MPa. The glass transition temperature was -53.7°C, with a change of -0.1°C, within ±1.3°C.

[0104] In Example 14, 1.0 wt% of additive B was added to an ultraviolet curable resin having a saturated Young's modulus of 2.57 MPa and a glass transition temperature at the saturated Young's modulus of -54.0°C. The saturated Young's modulus of the ultraviolet curable resin to which additive B was added was 1.73 MPa, a decrease of 32.7% compared to the saturated Young's modulus before the addition of the additive. 2 , irradiation amount 500mJ / cm 2 The Young's modulus of the cured product was 1.73 MPa and the glass transition temperature was -52.8°C. The cured product was then subjected to additional UV irradiation using a mercury lamp (illuminance 500 mW / cm 2 , irradiation amount 500mJ / cm 2 ), the Young's modulus was 1.73 MPa, and the increase was 0 MPa, less than 0.09 MPa. The glass transition temperature was -53.0°C, and the change was -0.2°C, within ±1.3°C.

[0105] In Example 15, 2.0 wt% of additive B was added to an ultraviolet curable resin having a saturated Young's modulus of 2.57 MPa and a glass transition temperature at the saturated Young's modulus of -54.0°C. The saturated Young's modulus of the ultraviolet curable resin to which additive B was added was 1.28 MPa, a decrease of 50.2% compared to the saturated Young's modulus before the addition of the additive. 2 , irradiation amount 500mJ / cm 2 The Young's modulus of the cured product was 1.27 MPa and the glass transition temperature was -52.8°C. The cured product was then subjected to additional UV irradiation using a mercury lamp (illuminance 500 mW / cm 2 , irradiation amount 500mJ / cm 2 ), the Young's modulus was 1.28 MPa, with an increase of +0.01 MPa, less than 0.09 MPa. The glass transition temperature was -52.8°C, with a change of 0°C, within ±1.3°C.

[0106] In Comparative Example 1, none of Additives A, B, or C was added to an ultraviolet-curable resin having a saturated Young's modulus of 1.48 MPa and a glass transition temperature at saturated Young's modulus of -28.5°C, and the irradiation dose was 12.5 mJ / cm 2 The Young's modulus of the cured product was 0.54 MPa, a decrease of 63.5% compared to the saturated Young's modulus. The glass transition temperature was -36.9°C. The cured product was further irradiated with UV light from a mercury lamp (illuminance 500 mW / cm 2 , irradiation amount 500mJ / cm 2 ), the Young's modulus was 1.48 MPa with an increase of +0.94 MPa, more than 0.09 MPa. The glass transition temperature was -29.8°C with an increase of +7.1°C, more than ±1.3°C.

[0107] In Comparative Example 2, none of Additives A, B, or C was added to an ultraviolet-curable resin having a saturated Young's modulus of 2.57 MPa and a glass transition temperature at saturated Young's modulus of -54.0°C, and the irradiation dose was 12.5 mJ / cm 2The Young's modulus of the cured product was 2.15 MPa, a decrease of 16.3% compared to the saturated Young's modulus. The glass transition temperature was -55.3°C. The cured product was further irradiated with UV light from a mercury lamp (illuminance 500 mW / cm 2 , irradiation amount 500mJ / cm 2 ), the Young's modulus was 2.57 MPa, an increase of +0.42 MPa, more than 0.09 MPa. The glass transition temperature was -53.9°C, an increase of +1.4°C, more than ±1.3°C.

[0108] The measurement results of the above-mentioned Examples and Comparative Examples are summarized in Table 1.

[0109] [Table 1]

[0110] In addition, 19 types of colored optical fiber core wires 1 were randomly selected, each with a secondary layer 4 having a Young's modulus of approximately 1000 MPa and a primary layer 3 having a different Young's modulus, and the difference in Young's modulus and microbend loss of each primary layer was calculated.

[0111] 6 is a graph showing the relationship between the Young's modulus difference and the percentage of primary layer 3 where the microbend loss difference is 0.05 dB / km or more, calculated by randomly selecting 19 types of colored optical fiber 1 in which the secondary layer 4 has a Young's modulus of approximately 1000 MPa and the primary layer 3 has a different Young's modulus. As shown in FIG. 6, the percentage of primary layer 3 where the microbend loss difference is 0.05 dB / km or more was calculated for every 0.05 MPa Young's modulus difference in the primary layer 3. It was confirmed that the percentage of primary layer 3 where the microbend loss difference is 0.05 dB / km or more increases sharply once the Young's modulus difference in the primary layer reaches 0.1 MPa. From this, it is considered preferable that even when a certain optical fiber is subjected to additional UV irradiation, the increase in the Young's modulus of the primary layer from before the additional UV irradiation to after the additional UV irradiation is 0.09 MPa or less. [Explanation of symbols]

[0112] 1. Colored optical fiber core 2 Bare optical fiber 3 Primary Layer 4 Secondary Tier 5 Colored layer 6 Optical fiber strand 100 Optical Fiber Ribbons 101 Adhesive layer

Claims

1. a bare optical fiber; a primary layer formed of a first ultraviolet curable resin covering the bare optical fiber; a secondary layer formed of a second ultraviolet curable resin covering the primary layer; Equipped with the primary layer has a carbon-sulfur bond and contains 0.09 wt % or more and 0.15 wt % or less of sulfur atoms; A colored optical fiber, characterized in that an increase in Young's modulus of the primary layer due to additional irradiation of the primary layer with ultraviolet light is 0.09 MPa or less.

2. The additional ultraviolet irradiation was performed at room temperature and with an illuminance of 1000 mW / cm ２ and an irradiation dose of 1000 mJ / cm ２ , illuminance 1000mW / cm ２ and an irradiation dose of 500 mJ / cm ２ , illuminance 500mW / cm ２ and an irradiation dose of 1000 mJ / cm ２ , and an illumination intensity of 500 mW / cm ２ and an irradiation dose of 500 mJ / cm ２ 2. The colored optical fiber according to claim 1, wherein the coloring is carried out under any one of the following conditions.

3. 3. The colored optical fiber according to claim 1, wherein the change in the glass transition temperature of the primary layer due to the additional ultraviolet irradiation is within ±1.3°C.

4. 3. The colored optical fiber according to claim 1, wherein the primary layer contains a mercapto group-containing compound.

5. 3. The colored optical fiber according to claim 1, wherein the first ultraviolet-curable resin contains 0.2 wt % or more of a mercapto group-containing compound.

6. 3. The colored optical fiber according to claim 1, wherein the primary layer has a Young's modulus of 0.15 MPa or more and 2.31 MPa or less.

7. 3. The colored optical fiber according to claim 1, wherein the glass transition temperature of the primary layer is −55° C. or higher and room temperature or lower.

8. 3. The colored optical fiber according to claim 1, wherein the primary layer does not contain the carbon-sulfur bond in the repeating unit of the main chain of the primary layer.

9. 3. The colored optical fiber core wire according to claim 1, wherein the saturated Young's modulus of the primary layer is lower by 10% or more than the saturated Young's modulus of the primary layer made of an ultraviolet-curable resin that does not contain a mercapto group-containing compound.

10. 3. An optical fiber ribbon comprising a plurality of colored optical fiber core wires according to claim 1 or 2.

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; and applying a second ultraviolet-curable resin around the primary layer to form a secondary layer, the primary layer has a carbon-sulfur bond, and the sulfur atoms contained in the primary layer are adjusted to 0.03 wt % or more and 0.65 wt % or less, thereby making the Young's modulus of the primary layer 0.15 MPa or more and 2.31 MPa or less; A method for producing a colored optical fiber, wherein an increase in Young's modulus of the primary layer due to additional ultraviolet irradiation of the primary layer is 0.09 MPa or less.

12. 12. The method for manufacturing a colored optical fiber according to claim 11, further comprising the step of applying a third ultraviolet curable resin around the secondary layer to form a colored layer.

13. 12. The method for manufacturing a colored optical fiber according to claim 11, wherein in the step of forming the secondary layer, the colored second ultraviolet curable resin is applied to the periphery of the primary layer.

14. 14. The method for manufacturing a colored optical fiber according to claim 11, wherein the first ultraviolet curable resin contains a mercapto group-containing compound.

15. 14. The method for manufacturing a colored optical fiber according to claim 11, wherein the step of forming the primary layer comprises irradiating the first ultraviolet-curable resin with ultraviolet light.

16. 14. The method for manufacturing a colored optical fiber according to claim 11, wherein the step of forming the secondary layer comprises irradiating the first ultraviolet-curable resin and the second ultraviolet-curable resin with ultraviolet light.

17. 3. A method for manufacturing an optical fiber ribbon, comprising manufacturing an optical fiber ribbon having a plurality of colored optical fiber core wires according to claim 1 or 2.

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