Optical fiber ribbon and method for manufacturing the same

Abstract

To suppress increase in the Young's modulus of a primary layer to additional ultraviolet irradiation in a ribbon formation step.SOLUTION: An optical ribbon includes: an optical fiber bare wire; a plurality of optical fiber colored core wires including a primary layer formed of a primary layer material covering the optical fiber bare wire and a secondary layer formed of a secondary layer material covering the primary layer; and an adhesive layer formed of an adhesive layer material covering the plurality of optical fiber colored core wires and connecting the plurality of optical fiber colored core wires. The Young's modulus of the primary layer is lower than the maximum Young's modulus after curing the primary layer material; and at least a part of a first wavelength range of ultraviolet absorbed by the adhesive layer material overlaps a second wavelength range of ultraviolet absorbed by a photoinitiator added to the primary layer material.SELECTED DRAWING: Figure 3

Description

[Technical field]

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

[0002] A technology is known for manufacturing colored optical fiber by forming a primary layer covering a bare optical fiber, a secondary layer covering the primary layer, and a colored layer covering the secondary layer from ultraviolet-curable resin so that each has a desired Young's modulus (Patent Documents 1 and 2). 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 optical transmission loss (microbend loss) caused by minute deformation of the bare optical fiber, whereas when the Young's modulus of the secondary layer is set high, it is possible to protect the bare optical fiber and the primary layer from external forces. In addition, optical fiber ribbons are manufactured by covering a plurality of colored optical fiber cores with an ultraviolet-curable resin and connecting the plurality of colored optical fiber cores to each other by irradiating ultraviolet light. Even if the Young's modulus of the primary layer is low in the optical fibers before the manufacturing process of the optical fiber ribbon, the Young's modulus of the primary layer increases when irradiated with UV light in the manufacturing process of the optical fiber ribbon, which causes microbend loss. In response to this, a method has been proposed for manufacturing an optical fiber ribbon in which the primary layer has a Young's modulus close to the saturated Young's modulus (Patent Document 3), and a method has been proposed for preventing an unintended increase in Young's modulus due to UV exposure in later processes by adding an ultraviolet absorber to the primary layer (Patent Document 4). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2005-162522 A [Patent Document 2] Special Publication No. 2002-524581 [Patent Document 3] International Publication No. 2018 / 062364 [Patent Document 4] Special Publication No. 2019-505648 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the manufacturing method described in Patent Document 3, it is necessary to cure at a Young's modulus close to the saturated Young's modulus, which imposes restrictions on the manufacturing conditions of the colored optical fiber. Similarly, in the manufacturing method described in Patent Document 4, it is necessary to minimize the spectral overlap of the photoinitiator and the UV absorber, which imposes considerable restrictions on the options for the resin composition of the colored optical fiber.

[0005] The present invention has been made in consideration of the above-mentioned problems, and aims to provide an optical fiber ribbon and a manufacturing method for an optical fiber ribbon that can suppress an increase in the Young's modulus of the primary layer due to additional ultraviolet light irradiation in the ribbonization process, without imposing significant restrictions on the manufacturing conditions of the colored optical fiber core or the resin composition that forms the primary layer. [Means for solving the problem]

[0006] According to one aspect of the present invention, a fiber optic cable is provided, comprising: a bare optical fiber; a plurality of colored optical fiber core wires, each of which has a primary layer formed from a primary layer material covering the bare optical fiber; and a secondary layer formed from a secondary layer material covering the primary layer; and an adhesive layer formed from an adhesive layer material covering the plurality of colored optical fiber core wires and connecting the plurality of colored optical fiber core wires, wherein the Young's modulus of the primary layer is lower than the maximum Young's modulus after hardening of the primary layer material, The adhesive layer material has at least one ultraviolet absorption maximum point in a first wavelength range of 350 nm to 392 nm, and the photoinitiator added to the primary layer material has absorption over at least a second wavelength range of 340 nm to 410 nm. An optical fiber ribbon is provided.

[0007] According to another aspect of the present invention, the present invention provides a method for manufacturing a colored optical fiber, comprising the steps of: drawing a bare optical fiber from an optical fiber preform; applying a primary layer material around the bare optical fiber to form a primary layer; applying a secondary layer material around the primary layer and irradiating the secondary layer material with ultraviolet light to form a secondary layer, thereby manufacturing a colored optical fiber; and applying an adhesive layer material around a plurality of the colored optical fiber cores and irradiating the adhesive layer material with ultraviolet light to form an adhesive layer connecting the plurality of the colored optical fiber cores, wherein the Young's modulus of the primary layer is lower than the maximum Young's modulus after hardening of the primary layer material, The adhesive layer material has at least one maximum point in a first wavelength range of 350 nm to 392 nm, and the photoinitiator added to the primary layer material has absorption over at least a second wavelength range of 340 nm to 410 nm. The present invention provides a method for manufacturing an optical fiber ribbon. Effect of the Invention

[0008] According to the present invention, an optical fiber ribbon and a manufacturing method for an optical fiber ribbon can be provided that can suppress an increase in the Young's modulus of the primary layer due to additional ultraviolet light irradiation in the ribbonization process, without imposing significant restrictions on the manufacturing conditions of the colored optical fiber core or the resin composition forming the primary layer. [Brief description of the drawings]

[0009] [Figure 1A] 1 is a cross-sectional view of a colored optical fiber core according to an embodiment of the present invention. [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 method for manufacturing a colored optical fiber according to an embodiment of the present invention. [Figure 2B] 4 is a schematic diagram showing another part of the manufacturing apparatus used in the method for manufacturing a colored optical fiber according to the first embodiment. FIG. [Diagram 3] 1 is a cross-sectional view of an optical fiber ribbon according to one 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. FIG. [Diagram 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] FIG. 11 is a diagram showing changes in ultraviolet absorption wavelength depending on the type and amount of additive in the optical fibers according to the examples and the comparative examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] 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.

[0011] Fig. 1A is a cross-sectional view of a colored optical fiber 1 according to this embodiment. The colored optical fiber 1 includes 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, namely, 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.

[0012] The bare optical fiber 2 is made of, for example, quartz glass or the like, and transmits light. The primary layer 3, the secondary layer 4, and the 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.

[0013] 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.

[0014] Examples of the polymerizable unsaturated group in the ultraviolet curable resin include groups having an unsaturated double bond such as vinyl group, allyl group, acryloyl group, and methacryloyl group, and groups having an unsaturated triple bond such as propargyl group, etc. Among these, acryloyl group and methacryloyl group are preferred in terms of polymerizability.

[0015] 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 (hereinafter referred to as "photoinitiator") that has sensitivity in the ultraviolet region.

[0016] Polyether-based urethane (meth)acrylate is a compound having a polyether segment, (meth)acrylate, and 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)acrylate is a compound having a polyester segment, (meth)acrylate, and urethane bond, such as a reaction product of a polyol having a polyester skeleton with an organic polyisocyanate compound and a hydroxyalkyl (meth)acrylate.

[0017] Furthermore, the ultraviolet curable resin may contain, in addition to the oligomer and the photoinitiator, for example, a diluent monomer, a photosensitizer, a chain transfer agent, and various additives. As the diluent monomer, a monofunctional (meth)acrylate or a polyfunctional (meth)acrylate is used. Here, the diluent monomer means a monomer for diluting the ultraviolet curable resin.

[0018] The primary layer 3 is a soft layer and has a 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 the primary layer 3 is hardened to the point where there is no room for hardening, the Young's modulus of the primary layer 3 is at 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 "maximum Young's modulus."

[0019] The ultraviolet irradiation is performed at appropriate illuminance and dose using, for example, a mercury lamp or UV-LED. The maximum Young's modulus varies with optical fiber manufacturing conditions (for example, line speed, UV irradiation intensity, type of UV light source, resin application temperature, etc.) and cannot be uniquely determined by the ultraviolet-curable resin used. In the bare fiber, colored optical fiber, and optical fiber ribbon of this embodiment, the Young's modulus of the primary layer 3 is lower than the maximum Young's modulus. The Young's modulus of the primary layer 3 is less than 90% of the maximum Young's modulus at the stage when the manufacture of the optical fiber ribbon is completed by carrying out the ribbonizing process described below.

[0020] The secondary layer 4 is preferably a hard layer having a Young's modulus of 500 MPa or more, and has a function of protecting the bare optical fiber 2 and the primary layer 3 from external forces. The colored layer 5 is colored to identify the colored optical fiber 1. The colored secondary layer 4 may be the outermost layer of the colored optical fiber 1. When the secondary layer 4 is colored, the secondary layer 4 is colored by adding a coloring agent containing a pigment, a lubricant, etc. to the secondary layer 4. The content of the coloring agent in the colored secondary layer 4 can be appropriately determined depending on the content of the pigment contained in the coloring agent and the type of other components such as ultraviolet-curable resin.

[0021] The diameter of the optical fiber strand 6 may be preferably 260 μm or less, for example, about 250 μm. 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.

[0022] Here, the diameter of the optical fiber 6 can be determined by the sum of the diameter of the bare optical fiber 2, twice the length of the thickness of the primary layer 3, and twice the length of 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 can each be selected so that the diameter of the optical fiber 6 is about 250 μm.

[0023] 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.

[0024] 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.

[0025] A primary layer coating device 30 is provided below the heating device 20. The primary layer coating device 30 has a resin applicator 31 and an ultraviolet ray irradiation device 32. The resin applicator 31 holds an ultraviolet ray curable resin (hereinafter referred to as "primary layer material") which is a coating material for forming the primary layer 3. The primary layer material is applied by the resin applicator 31 to the bare optical fiber 2 drawn out from the optical fiber preform BM.

[0026] An ultraviolet ray irradiation device 32 is provided below the resin applicator 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. A primary layer material is applied to the bare optical fiber 2 by the resin applicator 31, and the bare optical fiber 2 enters the ultraviolet ray irradiation device 32, where the primary layer material is irradiated with ultraviolet rays. As a result, the primary layer material is hardened and the primary layer 3 is formed.

[0027] 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 curing resin (hereinafter referred to as "secondary layer material") which is a coating material for forming the secondary layer 4. The secondary layer material is applied to the primary layer 3 by the resin coating device 41.

[0028] An ultraviolet irradiator 42 is provided below the resin coating device 41. The ultraviolet irradiator 42 may be configured similarly to the ultraviolet irradiator 32. The bare optical fiber 2 coated with the secondary layer material enters the ultraviolet irradiator 42, and the secondary layer material is irradiated with ultraviolet light. As a result, the secondary layer material is hardened and a secondary layer 4 is formed. The bare optical fiber 2 is coated with the primary layer 3 and the secondary layer 4, thereby forming an optical fiber strand 6.

[0029] The resin applicator 31 may be configured to hold the primary layer material and the secondary layer material separately. In this case, the resin applicator 31 applies the primary layer material to the bare optical fiber 2, and then applies the secondary layer material on the primary layer material.

[0030] The ultraviolet irradiation device 32 irradiates ultraviolet light onto the primary layer material and the secondary layer material 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 include the secondary layer coating device 40.

[0031] 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.

[0032] Fig. 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 has a bare wire 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 bare wire 6 manufactured by the multiple devices shown in Fig. 2A.

[0033] The bare fiber holding device 55 holds the manufactured bare optical fiber 6 in a wound state. Note that, although the bare fiber holding device 55 is a device separate from the first winding device 50 in FIG. 2B, the first winding device 50 may also function as the bare fiber holding device 55.

[0034] 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.

[0035] 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 curing resin (hereinafter referred to as "colored layer material") which is a coating material for forming the colored layer 5.

[0036] A coloring layer material is applied to the optical fiber strand 6 by a resin applicator 61. An ultraviolet ray irradiation device 62 is provided below the resin applicator 61. The ultraviolet ray irradiation device 62 may be configured similarly to the ultraviolet ray irradiation devices 32 and 42.

[0037] The optical fiber 6 with the color layer material applied to the outer periphery of the secondary layer 4 enters the ultraviolet irradiator 62, where ultraviolet rays are irradiated onto the color layer material and the optical fiber 6. As a result, the color layer material is hardened, and the color layer 5 is formed.

[0038] The primary layer 3, the secondary layer 4, and the colored layer 5 are applied to the bare optical fiber 2 to form the colored optical fiber 1. The manufactured colored optical fiber 1 is guided by a guide roller 65 provided below the colored layer application device 60, and taken up by the second winding device 70.

[0039] 3 is a cross-sectional view of an optical fiber ribbon 100 according to this embodiment. The optical fiber ribbon 100 is formed by bundling a plurality of colored optical fibers 1 into a band shape with an adhesive layer 101 interposed therebetween.

[0040] 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 core wires 1 can be bundled at a high density by taking the form of an optical fiber ribbon 100. The optical fiber ribbon 100 is not limited to the configuration shown in FIG. 3. The optical fiber ribbon 100 may also be in the form of an optical fiber ribbon cable in which the optical fiber ribbon 100 is housed in a sheath.

[0041] In this embodiment, an additive is added to the ultraviolet curing resin forming the adhesive layer 101. At least a part of the wavelength range in which the adhesive layer 101 absorbs ultraviolet light overlaps with the wavelength range in which the photoinitiator added to the primary layer material absorbs ultraviolet light. Details of the type and amount of additive will be described later.

[0042] 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 applicator 81 and an ultraviolet ray irradiator 82. The resin applicator 81 holds an ultraviolet ray curing resin (hereinafter referred to as "adhesive layer material") which is a coating material for the adhesive layer 101.

[0043] A plurality of prepared colored optical fiber core wires 1 enter a ribbon forming device 80, where an adhesive layer material is applied by a resin application device 81. The colored optical fiber core wires 1 to which the adhesive layer material has been applied are bundled together with a plurality of other colored optical fiber core wires 1 to which the adhesive layer material has also been applied. The bundled plurality of colored optical fiber core wires 1 are irradiated with ultraviolet light by an ultraviolet irradiation device 82 provided in the ribbon forming device 80. As a result, the adhesive layer material is hardened to become 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 manner, an optical fiber ribbon 100 is formed from a plurality of small-diameter colored optical fiber core wires 1.

[0044] The ribbon forming device 80 may be, for example, the ribbon forming device described in JP 2012-118358 A. In this way, the adhesive layer 101 is intermittently formed at a predetermined interval in the longitudinal direction of the adjacent colored optical fiber cores 1, and an intermittently bonded optical fiber ribbon 100 is formed.

[0045] 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, a user places the optical fiber preform BM in the manufacturing apparatus 10 (step S101).

[0046] 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).

[0047] The primary layer coating device 30 applies a primary layer material around the drawn bare optical fiber 2, and irradiates the primary layer material with ultraviolet light to form the primary layer 3 (step S103).

[0048] Next, the secondary layer coating device 40 applies a secondary layer material around the primary layer 3 and irradiates the secondary layer material 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.

[0049] Next, the colored layer coating device 60 pulls out the optical fiber 6 from the fiber holding device 55 or the first winding device 50, applies a colored layer material around the secondary layer 4 of the optical fiber 6, and irradiates the colored layer material with ultraviolet light to form a colored layer 5 (step S105). By coating the optical fiber 6 with the colored layer 5, the colored optical fiber 1 is obtained. The manufactured colored optical fiber 1 is wound up by the second winding device 70.

[0050] 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.

[0051] After the colored layer 5 is formed in step S105, the ribbon forming device 80 applies an adhesive layer material so as to cover the multiple prepared colored optical fiber core wires 1, and irradiates the adhesive layer material with ultraviolet light to connect the multiple colored optical fiber core wires 1 to each other (step S106). In this way, the optical fiber ribbon 100 is manufactured.

[0052] In the process of manufacturing the optical fiber ribbon 100 from the colored optical fiber core 1, ultraviolet light is irradiated onto the colored optical fiber core 1. In this embodiment, the type and amount of additive are adjusted so that at least a part of the wavelength range in which the adhesive layer 101 absorbs ultraviolet light overlaps with the wavelength range in which the photoinitiator added to the primary layer material constituting the primary layer 3 absorbs ultraviolet light.

[0053] As a result, even if the colored optical fiber core 1 is additionally irradiated with ultraviolet light in the process of manufacturing the optical fiber ribbon 100, the ultraviolet light is absorbed by the adhesive layer 101 because at least a part of the wavelength range (first wavelength range) in which the adhesive layer material absorbs ultraviolet light overlaps with the ultraviolet light absorption wavelength range (second wavelength range) of the photoinitiator added to the primary layer 3. This suppresses further curing of the primary layer 3 by ultraviolet light, making it possible to suppress an increase in the Young's modulus of the primary layer 3. As a result, microbend loss can be suppressed.

[0054] In the present embodiment, when at least a portion of the first wavelength range in the adhesive layer 101 overlaps with the second wavelength range in the primary layer 3, the change in Young's modulus of the primary layer 3 before and after the manufacture of the optical fiber ribbon 100 is smaller than when the adhesive layer 101 is formed using an adhesive layer material whose absorption wavelength range does not overlap with the second wavelength range.

[0055] Furthermore, since it is only necessary to adjust the type and amount of additive added to the adhesive layer material constituting the adhesive layer 101, which is the outermost layer of the optical fiber ribbon 100, there are no significant restrictions on the composition of the ultraviolet-curable resin constituting the optical fiber colored core 1.

[0056] Moreover, the additive having the property of absorbing ultraviolet light in the first wavelength range is preferably added to the adhesive layer material at a concentration of 0.05 wt% or more. When the optical fiber ribbon 100 is manufactured by adding the additive to the adhesive layer material at this ratio, the Young's modulus of the primary layer 3 is lower, for example, less than 90%, than when the optical fiber ribbon 100 is manufactured without adding the additive to the adhesive layer material. This makes it possible to suppress an increase in the Young's modulus of the primary layer 3 even when ultraviolet light is irradiated in a later process as described above.

[0057] Also, if the amount of additive added is too large, the curing of the adhesive layer material may be inhibited. Therefore, the additive is preferably added in an amount of 10.0 wt% or less relative to the adhesive layer material. Furthermore, the additive is more preferably added in an amount of 5.0 wt% or less relative to the adhesive layer material. EXAMPLES

[0058] Hereinafter, a description will be given of the results of an experiment conducted to simulate the ribboning process on the colored optical fiber 1 according to the embodiment of the present invention.

[0059] Here, when additional UV irradiation was performed on the colored optical fiber core 1, in order to simulate the ribboning process of the optical fiber, the ultraviolet-curable resin constituting the adhesive layer (ribbon layer) 101 was applied to a thickness of 30 μm ± 3 μm on the quartz glass that does not have absorption properties for the UV light used, and the colored optical fiber core 1 was covered. When additives were added, they were added to the ultraviolet-curable resin constituting the adhesive layer 101. The ultraviolet-curable resin constituting the adhesive layer 101 is composed of oligomers, monomers, etc., and may also contain additives such as photoinitiators, photosensitizers, ultraviolet absorbers, and antioxidants. [Table 1]

[0060] Table 1 shows the Young's modulus (MPa), maximum Young's modulus (MPa), type of additive, additive amount (wt%), Young's modulus after additional UV irradiation (MPa), Young's modulus after additional UV irradiation / maximum Young's modulus (%), evaluation (evaluation 1) regarding suppression of increase in Young's modulus in the primary layer 3, and evaluation (evaluation 2) regarding suppression of microbend loss in the primary layer 3 in Examples 1 to 7 and Comparative Example 1. The outer diameter of the secondary layer 4 of the optical fiber colored core 1 in Examples 1 to 7 and Comparative Example 1 is 250 μm.

[0061] The "maximum Young's modulus" in Table 1 is the maximum Young's modulus that can be exhibited by the primary layer 3 of the optical fiber 6. Moreover, the "Young's modulus" in Table 1 is the ISM (In Situ Modulus) of the primary layer 3 of the colored optical fiber 1. In this specification, the ISM is defined as being measured by the following method.

[0062] 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 3 at the boundary between the part where the coating layer is stripped off and the part where the coating layer is formed is read under a microscope. Then, a graph of the displacement δ against the load F is created by setting the load F to 10, 20, 30, 50, and 70 gf (i.e., 98, 196, 294, 490, and 686 mN, respectively). Then, the primary elastic modulus is calculated using the slope obtained from the graph and the following formula (1). The calculated primary elastic modulus corresponds to the so-called ISM, and is hereinafter referred to as P-ISM as appropriate. When drawing the colored optical fiber 1, the drawing speed and the illuminance of the ultraviolet light were controlled to adjust the P-ISM. P-ISM=(3F / δ)*(1 / 2πl)*ln(DP / DG) (Formula 1)

[0063] Here, the unit of P-ISM is [MPa]. F / δ is the slope of the graph of the displacement (δ) [μm] against the 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 from the F, δ, and l used, a predetermined 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.

[0064] The "Young's modulus after additional UV irradiation" in Table 1 is 1500mW / cm using a 365nm±20nm UV-LED on the manufactured optical fiber colored core 1. 2 , 50mJ / cm 2 The Young's modulus of the primary layer 3 when UV is re-irradiated at 1000 nm is defined as P-ISM.

[0065] "Rating 1" in Table 1 indicates whether the P-ISM of the colored optical fiber core 1 after additional UV irradiation is lower than the maximum Young's modulus. If the P-ISM is lower than the maximum Young's modulus, the evaluation is judged as pass (OK). Conversely, if the P-ISM is not lower than the maximum Young's modulus, the evaluation is judged as fail (NG). If the evaluation result is pass (OK), it indicates that the additive added to the ultraviolet-curable resin that constitutes the adhesive layer 101 has been able to suppress an increase in the Young's modulus in the primary layer 3 when the colored core is exposed to UV light.

[0066] "Rating 2" in Table 1 indicates whether the microbend loss in the optical fiber colored core 1 after additional UV irradiation meets a specified standard (0.1 dB / km or less). If the microbend loss meets the standard, the rating is judged as pass (OK), and if the microbend loss does not meet the standard, the rating is judged as fail (NG).

[0067] There are various methods for measuring microbend loss. In this specification, the value of microbend loss is defined as the difference between the transmission loss of the optical fiber to be measured in state A, in which an optical fiber of 400 m or more in length is wound in a single layer without overlapping with a tension of 100 gf around a large bobbin wrapped with sandpaper of #1000 grit, and the transmission loss of the optical fiber in state B, which is wound around 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 a transmission loss inherent to the optical fiber itself.

[0068] This measurement method is similar to the fixed diameter drum method specified 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 values ​​below are also values ​​at a wavelength of 1550 nm.

[0069] The effective core area can be used as an index to indicate the susceptibility of an optical fiber to microbend loss. The effective core area is expressed by the following formula (2). (effective core cross-sectional area)=(πk / 4)*(MFD) 2 ...(Formula 2) Here, the effective core area 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 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 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 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 of ​​the bare optical fiber 2 is large, microbending loss is more likely to occur in the colored optical fiber 1.

[0070] In this embodiment, the optical fiber has an effective core area (Aeff) of 80 μm 2 The effective core area of ​​an optical fiber is an index of microbending sensitivity, and the larger the effective core area, the higher the microbending sensitivity. Generally, an effective core area of ​​100 μm 2 If the effective core area exceeds 130 μm, the microbending sensitivity is said to be high. 2 More than 150μm 2 If the thickness is equal to or less than this, the optical fiber will have a high microbending sensitivity without any problems.

[0071] In the colored optical fiber core 1 used in Examples 1 to 7 and Comparative Example 1, first, a primary layer material was applied around a drawn bare optical fiber 2, and then the primary layer material was irradiated with ultraviolet rays to form a primary layer 3.

[0072] Next, a secondary layer material was applied around the primary layer 3, and the secondary layer material was irradiated with ultraviolet light to form the secondary layer 4. It is also possible to color the secondary layer 4 itself. When drawing the bare optical fiber 6 or the colored optical fiber core 1, the drawing speed and illuminance were controlled to adjust the P-ISM. 2,4,6-trimethylbenzoyl-diphenylphosphine oxide was used as the photoinitiator for the primary layer 3 of the colored optical fiber core 1. When this photoinitiator is used in a reaction by UV irradiation, the absorbance in the vicinity of 340 to 410 nm decreases.

[0073] By comparing the absorbance before and after UV irradiation to confirm the change in absorbance, it is possible to detect the absorption wavelength of the photoinitiator contained in the primary layer 3. Of course, it is easy to determine whether the absorption wavelength is derived from the photoinitiator without using this method. For example, it is possible to determine the absorption wavelength of the photoinitiator added to the primary layer 3 by comparing it with the absorption wavelength of photoinitiators available on the market.

[0074] The diameter of the bare optical fiber 2 was 125 μm. The thickness of the primary layer 3 was 30 μm. The thickness of the secondary layer 4 was 30 μm. The thickness of the colored layer 5 was 3 μm. The thickness of the colored optical fiber core wire 1 was 251 μm. And, the thickness of the colored optical fiber core wire 1 was 251 μm.

[0075] In Examples 1 to 7 and Comparative Example 1, the optical fiber colored core wires 1 manufactured under the same conditions were used, and the Young's modulus of the primary layer 3 was 0.14 MPa, and the maximum Young's modulus was 0.60 MPa.

[0076] Additive A is 2,4,6-trimethylbenzoyl-diphenylphosphine oxide. Additive B is 2,4-Diethyl-9H-thioxanthen-9-one. Additive C is 2,2',4,4'-Tetrahydroxybenzophenone. All of the additives have at least a portion of the absorption region in the same region as the photoinitiator 2,4,6-trimethylbenzoyl-diphenylphosphine oxide of the primary layer 3.

[0077] In Example 1, the colored optical fiber core 1 was covered with an ultraviolet-curable resin containing 10 wt% additive A. After that, the colored optical fiber core 1 was irradiated with additional UV. The Young's modulus of the primary layer 3 after the colored optical fiber core 1 was irradiated with additional UV was 0.47 MPa, and the ratio of the Young's modulus after additional UV irradiation to the maximum Young's modulus was 78.3%. Therefore, Evaluation 1 was passed (OK). In addition, the microbend loss was below the specified reference value (0.1 dB / km), and Evaluation 2 was passed (OK).

[0078] In Example 2, the colored optical fiber core 1 was covered with an ultraviolet-curable resin containing 0.1 wt % additive B. After that, the colored optical fiber core 1 was irradiated with additional UV. The Young's modulus of the primary layer 3 after the colored optical fiber core 1 was irradiated with additional UV was 0.54 MPa, and the ratio was 89.3%. Therefore, Evaluation 1 was passed (OK). In addition, the microbend loss was below the specified reference value (0.1 dB / km), and Evaluation 2 was passed (OK).

[0079] In Example 3, the colored optical fiber core 1 was covered with an ultraviolet-curable resin containing 1 wt % additive B. After that, the colored optical fiber core 1 was irradiated with additional UV. The Young's modulus of the primary layer 3 after the colored optical fiber core 1 was irradiated with additional UV was 0.15 MPa, and the ratio was 25.0%. Therefore, Evaluation 1 was passed (OK). In addition, the microbend loss was below the specified reference value (0.1 dB / km), and Evaluation 2 was passed (OK).

[0080] In Example 4, the colored optical fiber core 1 was covered with an ultraviolet-curable resin containing 0.05 wt% additive C. After that, the colored optical fiber core 1 was additionally irradiated with UV. The Young's modulus of the primary layer 3 after the colored optical fiber core 1 was additionally irradiated with UV was 0.34 MPa, and the ratio was 56.7%. Therefore, Evaluation 1 was passed (OK). In addition, the microbend loss was below the predetermined reference value (0.1 dB / km), and Evaluation 2 was passed (OK).

[0081] In Example 5, the colored optical fiber core 1 was covered with an ultraviolet-curable resin containing 0.1 wt % additive C. After that, the colored optical fiber core 1 was additionally irradiated with UV light. The Young's modulus of the primary layer 3 after the colored optical fiber core 1 was additionally irradiated with UV light was 0.21, and the ratio was 35.0%. Therefore, Evaluation 1 was passed (OK). In addition, the microbend loss was below the predetermined reference value (0.1 dB / km), and Evaluation 2 was passed (OK).

[0082] In Example 6, the colored optical fiber core 1 was covered with an ultraviolet-curable resin containing 1 wt % additive C. After that, the colored optical fiber core 1 was additionally irradiated with UV light. The Young's modulus of the primary layer 3 after the colored optical fiber core 1 was additionally irradiated with UV light was 0.14 MPa, and the ratio was 23.3%. Therefore, Evaluation 1 was passed (OK). In addition, the microbend loss was below the predetermined reference value (0.1 dB / km), and Evaluation 2 was passed (OK).

[0083] In Example 7, the colored optical fiber core 1 was covered with an ultraviolet-curable resin containing 0.01 wt% additive C. After that, the colored optical fiber core 1 was additionally irradiated with UV light. The Young's modulus of the primary layer 3 after the colored optical fiber core 1 was additionally irradiated with UV light was 0.55 MPa, and the ratio was 91.7%. Therefore, Evaluation 1 was passed (OK). However, since the microbend loss was equal to or greater than the reference value (0.1 dB / km), Evaluation 2 was failed (NG).

[0084] In Comparative Example 1, the colored optical fiber core 1 was covered with an ultraviolet-curable resin containing no additives. After that, the colored optical fiber core 1 was additionally irradiated with UV light. The Young's modulus of the primary layer 3 after the colored optical fiber core 1 was additionally irradiated with UV light was 0.60 MPa, and the ratio was 100.0%. For this reason, Evaluation 1 was a failure (NG). Furthermore, the microbend loss was equal to or greater than the reference value (0.1 dB / km), and therefore Evaluation 2 was a failure (NG).

[0085] Fig. 6 is a diagram showing changes in ultraviolet absorption wavelength depending on the type and amount of additive in the optical fibers according to the examples and the comparative examples, in which the horizontal axis represents wavelength (nm) and the vertical axis represents absorbance.

[0086] The photoinitiator used in the primary layer 3 in the present embodiment and the comparative embodiment has a property of absorbing ultraviolet rays with a wavelength of 340 to 410 nm. On the other hand, as shown in FIG. 6, the additive A used in the embodiment 1 has a property of absorbing ultraviolet rays with a wavelength of 340 to 410 nm. In addition, in the range of the absorption wavelength of the additive A, the maximum point where the amount of ultraviolet light absorbed is maximized is 380 nm ± 5 nm. In addition, the additive B used in the embodiments 2 and 3 has a property of absorbing ultraviolet rays with a wavelength of 340 to 410 nm (maximum point is 387 nm ± 5 nm), and the additive C used in the embodiments 4 to 6 has a property of absorbing ultraviolet rays with a wavelength of 310 to 400 nm (maximum point is 355 nm ± 5 nm). Therefore, there is an effect that the ultraviolet rays absorbed by the photoinitiator used in the primary layer 3 are shielded in the adhesive layer 101. As a result, it is possible to suppress an increase in the Young's modulus of the primary layer 3 due to ultraviolet light irradiation.

[0087] In this way, by adding an additive whose absorption wavelength at least partially overlaps with the absorption wavelength of the photoinitiator used in the primary layer 3 to the ultraviolet-curable resin that forms the adhesive layer 101, the increase in Young's modulus of the primary layer 3 due to ultraviolet irradiation can be suppressed.

[0088] More preferably, the absorption maximum point of the additive added to the UV-curable resin forming the adhesive layer 101 is included within the absorption wavelength range of the photoinitiator used in the primary layer 3. As a result, during irradiation with additional UV, most of the UV light in the wavelength range that can cause the photoinitiator to start a photopolymerization reaction is absorbed by the additive in the adhesive layer 101, so that the UV curing of the primary layer 3 is more efficiently suppressed.

[0089] In addition, in the present embodiment and the comparative example, the Young's modulus after additional UV irradiation was 1500 mW / cm for the colored optical fiber 1 using a UV-LED with an irradiation wavelength of 365 nm ± 20 nm. 2 , 50mJ / cm 2However, the UV light source is not limited to UV-LEDs with a wavelength of 365nm±20nm. For example, the same effect can be achieved when additives with an absorption range within the range are used for UV-LEDs with different wavelengths, such as UV-LEDs with a wavelength of 385nm±20nm and UV-LEDs with a wavelength of 395nm±20nm, and for UV-LEDs that emit UV light, such as metal halide lamps and mercury lamps, other than UV-LEDs.

[0090] In addition, the same effect can be obtained even if the illuminance and dose are irradiated under other conditions. For example, 50 mJ / cm 2 If additional UV irradiation is performed with the above amount of irradiation, the amount of UV irradiation received by the primary layer 3 will be further increased.

[0091] Furthermore, the additives used in Examples 1 to 7 are merely examples, and are not limited to photoinitiators, photosensitizers, and UV absorbers, but may be any additive having an absorption wavelength that overlaps even partially with the absorption wavelength range of the photoinitiator used in primary layer 3. In addition to additives A, B, and C, compounds such as bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, 2-isopropylthioxanthone, 2,2-dihydroxy-4,4-dimethoxybenzophenone, 2,4,6-tris[4-(hexyloxy)-2-hydroxy-3-methylphenyl]-1,3,5-triazine, and 2-(2-hydroxy-5-methylphenyl)benzotriazole can also be used as additives.

[0092] It is also clear that the type of effective additive varies depending on the absorption wavelength of the photoinitiator used in the primary layer 3. Therefore, by adding an additive having an absorption wavelength range that is at least partially the same as that of the photoinitiator used, it is possible to suppress an increase in Young's modulus even when exposed to UV light after production of the colored optical fiber 1.

[0093] The Young's modulus of the primary layer 3 shown in Examples 1 to 7 and Comparative Example 1 is merely an example and is not limited to this. For example, the Young's modulus of the primary layer 3 can be in the range of 0.1 to 2.0 MPa.

[0094] As described above, according to this embodiment, it is possible to suppress an increase in the primary Young's modulus due to UV exposure in the ribboning process, without imposing significant restrictions on the resin composition of the colored optical fiber core 1.

[0095] 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.

[0096] 1. Colored optical fiber 2 Bare optical fiber 3 Primary Layer 4 Secondary Tier 5 Colored layer 6 Optical fiber 100 Optical Fiber Ribbon 101 Adhesive layer

Claims

1. a plurality of colored optical fiber core wires, each of which has a bare optical fiber, a primary layer formed of a primary layer material covering the bare optical fiber, and a secondary layer formed of a secondary layer material covering the primary layer; an adhesive layer formed of an adhesive layer material covering the plurality of colored optical fiber cores and connecting the plurality of colored optical fiber cores; Equipped with the Young's modulus of the primary layer is less than the maximum Young's modulus of the primary layer material after curing; the adhesive layer material has at least one maximum point at which the amount of ultraviolet light absorbed is maximized in a first wavelength range of 350 nm or more and 392 nm or less; The photoinitiator added to the primary layer material has absorption over at least a second wavelength range of 340 nm to 410 nm.

1. An optical fiber ribbon comprising:

2. The additive that absorbs the ultraviolet light in the second wavelength range is added to the adhesive layer material at 0.05 wt % or more.

2. The optical fiber ribbon according to claim 1.

3. In the first wavelength range, at least the maximum point at which the absorption amount of the ultraviolet light is maximized is included in the second wavelength range.

3. The optical fiber ribbon according to claim 1 or 2.

4. The Young's modulus is less than 90% of the maximum Young's modulus.

4. The optical fiber ribbon according to claim 1, wherein the optical fiber ribbon is a ferroelectric.

5. The additive is added in an amount of 10.0 wt % or less to the adhesive layer material.

3. The optical fiber ribbon according to claim 2.

6. The adhesive layer is formed intermittently at a predetermined interval in the longitudinal direction of the adjacent colored optical fiber.

6. The optical fiber ribbon according to claim 1, wherein the optical fiber ribbon is a ferroelectric.

7. A step of drawing a bare optical fiber from an optical fiber preform; applying a primary layer material around the bare optical fiber to form a primary layer; a step of applying a secondary layer material around the primary layer and irradiating the secondary layer material with ultraviolet light to form a secondary layer, thereby producing a colored optical fiber; applying an adhesive layer material around the plurality of colored optical fiber cores and irradiating the adhesive layer material with the ultraviolet light to form an adhesive layer connecting the plurality of colored optical fiber cores; Equipped with the Young's modulus of the primary layer is less than the maximum Young's modulus of the primary layer material after curing; the adhesive layer material has at least one maximum point at which the absorption amount of the ultraviolet light is maximized in a first wavelength range of 350 nm or more and 392 nm or less; The photoinitiator added to the primary layer material has absorption over at least a second wavelength range of 340 nm to 410 nm. A method for manufacturing an optical fiber ribbon comprising the steps of:

8. An additive that absorbs the ultraviolet light in at least a part of the second wavelength range is added to the adhesive layer material in an amount of 0.05 wt % or more.

8. The method for producing an optical fiber ribbon according to claim 7.

9. In the step of forming the primary layer, the primary layer material is irradiated with the ultraviolet light.

9. The method for producing an optical fiber ribbon according to claim 7 or 8.

10. In the step of forming the secondary layer, the primary layer material and the secondary layer material are irradiated with the ultraviolet light.

9. The method for producing an optical fiber ribbon according to claim 7 or 8.

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