Optical fibers and optical fiber GM

Abstract

This optical fiber comprises a glass fiber, including a core and a clad, and a covering resin layer that covers the glass fiber. The covering resin layer has a primary resin layer in contact with the glass fiber and covering the glass fiber, and a secondary resin layer for covering the primary resin layer. The primary resin layer includes a cured product of a first resin composition containing a silicone (meth)acrylate and a photopolymerization initiator, the secondary resin layer includes a cured product of a second resin composition containing a urethane (meth)acrylate and a photopolymerization initiator, and the amount of tin included in the covering resin layer is 150 ppm or less by mass ratio.

Description

[Technical Field]

[0001] This disclosure relates to optical fibers and optical fiber ribbons. This application claims priority under Japanese application No. 2021-039007 filed on March 11, 2021, and incorporates all the provisions of the said Japanese application. [Background technology]

[0002] Generally, optical fibers are equipped with a protective resin coating layer to shield the glass fiber, which is the optical transmission medium. The resin coating layer consists of two layers, for example, a primary resin layer that is in contact with the glass fiber and a secondary resin layer formed on the outer layer of the primary resin layer.

[0003] To improve the low-temperature characteristics of optical fibers by lowering the Young's modulus of the primary resin layer, it has been investigated to form the primary resin layer using a silicone resin that exhibits little change in Young's modulus from that at room temperature, even at low temperatures (see, for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2000-26559 [Overview of the Initiative]

[0005] An optical fiber according to one aspect of the present disclosure comprises a glass fiber including a core and a cladding, and a coating resin layer covering the glass fiber, wherein the coating resin layer has a primary resin layer in contact with the glass fiber and covering the glass fiber, and a secondary resin layer covering the primary resin layer, the primary resin layer contains a cured product of a first resin composition containing silicone (meth)acrylate and a photopolymerization initiator, the secondary resin layer contains a cured product of a second resin composition containing urethane (meth)acrylate and a photopolymerization initiator, and the amount of tin contained in the coating resin layer is 150 ppm or less by mass ratio. [Brief explanation of the drawing]

[0006] [Figure 1] Figure 1 is a cross-sectional view showing an example of an optical fiber according to this embodiment. [Figure 2] Figure 2 is a cross-sectional view showing an example of an optical fiber ribbon according to this embodiment. [Modes for carrying out the invention]

[0007] [Issues this disclosure aims to address] One application of optical fibers is the loose-tube type optical cable, in which the optical fiber is housed within the cable along with a filler primarily composed of hydrocarbon oil. The toughness of the optical fiber's coating resin layer tends to decrease when it absorbs hydrocarbon oil. Oil absorption is greater in the primary resin layer, which has a low Young's modulus, and silicone resin in particular readily absorbs oil due to its low polarity. The coating resin layer that has absorbed oil has reduced adhesion to the glass fiber, which can degrade the optical fiber's low-temperature transmission characteristics. Therefore, the coating resin layer of an optical fiber is required to have excellent oil resistance.

[0008] The purpose of this disclosure is to provide optical fibers and optical fiber ribbons that have a coating resin layer with excellent oil resistance and excellent transmission characteristics at low temperatures.

[0009] [Effects of this disclosure] According to this disclosure, it is possible to provide optical fibers and optical fiber ribbons that have a coating resin layer with excellent oil resistance and excellent transmission characteristics at low temperatures.

[0010] [Description of Embodiments in this Disclosure] First, the contents of embodiments of the present disclosure will be listed and explained. An optical fiber according to one aspect of the present disclosure comprises a glass fiber including a core and a cladding, and a coating resin layer that is in contact with and covers the glass fiber. The coating resin layer has a primary resin layer that is in contact with and covers the glass fiber, and a secondary resin layer that covers the primary resin layer. The primary resin layer comprises a cured product of a first resin composition containing silicone (meth)acrylate and a photopolymerization initiator, and the secondary resin layer comprises a cured product of a second resin composition containing urethane (meth)acrylate and a photopolymerization initiator, wherein the amount of tin contained in the coating resin layer is 150 ppm or less by mass ratio.

[0011] Optical fibers having a coating resin layer containing a silicone resin in the primary resin layer and a urethane (meth)acrylate resin in the secondary resin layer may experience a decrease in transmission characteristics after absorbing oil and being exposed to low temperatures. When the inventors observed optical fibers with reduced transmission characteristics, they found that delamination occurred at the interface between the primary resin layer and the glass fiber, and that tin components were present at the delamination site. A tin catalyst is used in the synthesis of urethane (meth)acrylate, and it is thought that components originating from the tin catalyst migrated to the primary resin layer. Therefore, the inventors considered that adjusting the amount of tin catalyst used when synthesizing the urethane (meth)acrylate for the secondary resin layer would be effective in suppressing the migration of tin components to the primary resin, and thus found the configuration of the optical fiber according to this disclosure. The optical fiber according to this embodiment has a coating resin layer with excellent oil resistance and exhibits excellent transmission characteristics at low temperatures.

[0012] From the viewpoint of improving the balance between the lateral pressure characteristics and oil resistance of the optical fiber at low temperatures, it is preferable that the pressure is between 80 MPa and 2000 MPa at 23°C.

[0013] The second resin composition preferably further contains epoxy (meth)acrylate having an aromatic ring. By using epoxy (meth)acrylate having an aromatic ring, the surface hardness of the secondary resin layer can be increased and deformation of the coating resin layer can be suppressed, thereby further improving the lateral pressure characteristics of the optical fiber. In addition, this component can suppress the migration of the tin catalyst to the primary resin due to the effect of non-covalent bonding between the aromatic rings.

[0014] The optical fiber ribbon according to this disclosure comprises a plurality of optical fibers arranged in parallel, and a connecting resin layer that covers and connects the plurality of optical fibers. Such an optical fiber ribbon exhibits excellent transmission characteristics at low temperatures.

[0015] [Details of the embodiments of this disclosure] Specific examples of optical fibers and optical fiber ribbons according to embodiments of this disclosure will be described with reference to the drawings as necessary. This disclosure is not limited to these examples and is indicated by the claims, and all modifications within the meaning and scope equivalent to the claims are intended to be included. In the following description, the same elements as in the description of the drawings are denoted by the same reference numerals, and redundant descriptions are omitted. In this embodiment, (meth)acrylate means acrylate or the corresponding methacrylate, and the same applies to other similar expressions such as (meth)acryloyl.

[0016] (Optical fiber) Figure 1 is a schematic cross-sectional view showing an example of an optical fiber. The optical fiber 10 comprises a glass fiber 13 including a core 11 and a cladding 12, and a coating resin layer 16 including a primary resin layer 14 and a secondary resin layer 15 provided on the outer circumference of the glass fiber 13.

[0017] The cladding 12 surrounds the core 11. The core 11 and cladding 12 mainly contain glass such as quartz glass. For example, the core 11 can be made of germanium-added quartz glass or pure quartz glass, and the cladding 12 can be made of pure quartz glass or fluorine-added quartz glass.

[0018] In FIG. 1, for example, the outer diameter (D2) of the glass fiber 13 is about 100 μm to 125 μm, and the diameter (D1) of the core 11 constituting the glass fiber 13 is about 7 μm to 15 μm. The thickness of the coating resin layer 16 is usually about 22 μm to 70 μm. The thickness of each of the primary resin layer 14 and the secondary resin layer 15 may be about 5 μm to 50 μm.

[0019] When the outer diameter (D2) of the glass fiber 13 is about 125 μm and the thickness of the coating resin layer 16 is 60 μm or more and 70 μm or less, the thickness of each of the primary resin layer 14 and the secondary resin layer 15 may be about 10 μm to 50 μm. For example, the thickness of the primary resin layer 14 may be 35 μm and the thickness of the secondary resin layer 15 may be 25 μm. The outer diameter of the optical fiber 10 may be about 245 μm to 265 μm.

[0020] When the outer diameter (D2) of the glass fiber 13 is about 125 μm and the thickness of the coating resin layer 16 is 27 μm or more and 48 μm or less, the thickness of each of the primary resin layer 14 and the secondary resin layer 15 may be about 10 μm to 38 μm. For example, the thickness of the primary resin layer 14 may be 25 μm and the thickness of the secondary resin layer 15 may be 10 μm. The outer diameter of the optical fiber 10 may be about 179 μm to 221 μm.

[0021] When the outer diameter (D2) of the glass fiber 13 is about 100 μm and the thickness of the coating resin layer 16 is 22 μm or more and 37 μm or less, the thickness of each of the primary resin layer 14 and the secondary resin layer 15 may be about 5 μm to 32 μm. For example, the thickness of the primary resin layer 14 may be 25 μm and the thickness of the secondary resin layer 15 may be 10 μm. The outer diameter of the optical fiber 10 may be about 144 μm to 174 μm.

[0022] From the viewpoint of improving the oil resistance of the coating resin layer and enhancing the transmission characteristics of the optical fiber at low temperatures, the amount of tin contained in the coating resin layer 16 is 150 ppm or less, preferably 120 ppm or less, more preferably 100 ppm or less, and even more preferably 80 ppm or less, based on the total amount of the coating resin layer. The less tin contained in the coating resin layer 16, the better. However, since tin is added as a synthesis catalyst for the urethane acrylate resin, if the amount is too small, the synthesis may take too long or may not be possible. Therefore, the lower limit of the amount of tin may be 10 ppm or more, 20 ppm or more, 40 ppm or more, or 50 ppm or more. In this specification, the amount of tin (ppm) is a mass ratio.

[0023] The primary resin layer 14 can be formed by curing a first resin composition containing silicone (meth)acrylate and a photopolymerization initiator. The first resin composition is an ultraviolet-curable resin composition. By including a resin component derived from silicone (meth)acrylate, the primary resin layer 14 can improve the adhesion of the primary resin layer to the glass fiber and improve the oil resistance of the coating resin layer.

[0024] As the silicone (meth)acrylate, a compound having (meth)acryloyl groups at both ends of the siloxane structure can be used. The silicone (meth)acrylate may be a compound obtained by reacting a silane compound having (meth)acryloyl groups with a cyclic polysiloxane.

[0025] Examples of silicone (meth)acrylates include silicone di(meth)acrylate, represented by the following formula (1). [ka]

[0026] In formula (1), R 1 R represents a hydrogen atom or a methyl group. 2 , R 3 , R 4 and R5 Each independently represents a monovalent hydrocarbon group, L 1 and L 2 Each of these independently represents a divalent hydrocarbon group, and n is an integer between 10 and 1200.

[0027] Examples of monovalent hydrocarbon groups include linear, branched, or cyclic alkyl groups having 1 to 6 carbon atoms, aryl groups having 6 to 10 carbon atoms, and aralkyl groups having 7 to 10 carbon atoms. The monovalent hydrocarbon group may be at least one group selected from the group consisting of methyl, ethyl, phenyl, and benzyl groups. Examples of divalent hydrocarbon groups include alkylene groups having 1 to 5 carbon atoms. The divalent hydrocarbon group may be at least one group selected from the group consisting of methylene, ethylene, and propylene groups. n may be 50 to 1000, 80 to 800, or 100 to 600.

[0028] As the silicone (meth)acrylate, for example, a compound described in Japanese Patent Publication No. 2000-26559 may be used.

[0029] The secondary resin layer 15 can be formed by curing a second resin composition containing urethane (meth)acrylate and a photopolymerization initiator. The second resin composition is an ultraviolet-curable resin composition. By including a resin component derived from urethane (meth)acrylate, the Young's modulus of the secondary resin layer 15 can be made higher than that of the primary resin layer.

[0030] The urethane (meth)acrylate may be a compound obtained by reacting a polyol compound, a polyisocyanate compound, and a hydroxyl group-containing (meth)acrylate compound.

[0031] Examples of polyol compounds include polytetramethylene glycol, polypropylene glycol, and bisphenol A-ethylene oxide adduct diols. From the viewpoint of adjusting Young's modulus, the number-average molecular weight (Mn) of the polyol compound may be 300 to 8000, preferably 400 to 5000, more preferably 600 to 4000, and even more preferably 700 to 3500. Examples of polyisocyanate compounds include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, isophorone diisocyanate, and dicyclohexylmethane 4,4'-diisocyanate. Examples of hydroxyl group-containing (meth)acrylate compounds include 2-hydroxyethyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 1,6-hexanediol mono(meth)acrylate, pentaerythritol tri(meth)acrylate, 2-hydroxypropyl (meth)acrylate, and tripropylene glycol (meth)acrylate.

[0032] Organotin compounds are used as catalysts when synthesizing urethane (meth)acrylate. Examples of organotin compounds include dibutyltin dilaurate, dibutyltin diacetate, dibutyltin maleate, dibutyltin bis(2-ethylhexyl mercaptoacetate), dibutyltin bis(isooctyl mercaptoacetate), and dibutyltin oxide. From the viewpoint of availability or catalytic performance, it is preferable to use dibutyltin dilaurate or dibutyltin diacetate as a catalyst. Urethane (meth)acrylate contains tin derived from organotin compounds. The amount of tin contained in the coating resin layer can be adjusted by changing the amount of organotin compound added when synthesizing urethane (meth)acrylate.

[0033] Lower alcohols with 5 or fewer carbon atoms may be used during the synthesis of urethane (meth)acrylates. Examples of lower alcohols include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-2-propanol, 1-pentanol, 2-pentanol, 3-pentanol, 2-methyl-1-butanol, 3-methyl-1-butanol, 2-methyl-2-butanol, 3-methyl-2-butanol, and 2,2-dimethyl-1-propanol.

[0034] From the viewpoint of increasing the Young's modulus of the secondary resin layer, the second resin composition may further contain epoxy (meth)acrylate. Epoxy (meth)acrylate is a compound obtained by reacting an epoxy compound having two or more glycidyl groups with a compound having a (meth)acryloyl group. To improve lateral pressure characteristics, it is preferable that the epoxy (meth)acrylate has an aromatic ring. Examples of epoxy (meth)acrylates having an aromatic ring include novolac epoxy (meth)acrylate, "Viscoat #540" manufactured by Osaka Organic Chemical Industry Co., Ltd., and "Epoxy Ester 3002M," "Epoxy Ester 3002A," "Epoxy Ester 3000MK," and "Epoxy Ester 3000A" manufactured by Kyoeisha Chemical Co., Ltd.

[0035] The epoxy (meth)acrylate content may be 5 parts by mass or more, 10 parts by mass or more, 15 parts by mass or more, or 20 parts by mass or more, based on the total amount of the resin composition, and may be 70 parts by mass or less, 65 parts by mass or less, 60 parts by mass or less, or 50 parts by mass or less.

[0036] The resin composition according to this embodiment may further contain photopolymerizable compounds other than silicone (meth)acrylate, urethane (meth)acrylate, and epoxy (meth)acrylate (hereinafter referred to as "monomers"). As monomers, monofunctional monomers having one polymerizable group and polyfunctional monomers having two or more polymerizable groups can be used. Two or more monomers may be used in mixture form.

[0037] Examples of monofunctional monomers include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, s-butyl (meth)acrylate, tert-butyl (meth)acrylate, isobutyl (meth)acrylate, n-pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, isoamyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl 2-Phenoxyethyl (meth)acrylate, 3-Phenoxybenzyl acrylate, phenoxydiethylene glycol acrylate, phenoxypolyethylene glycol acrylate, 4-tert-butylcyclohexanol acrylate, tetrahydrofurfuryl (meth)acrylate, benzyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyl (Meth)acrylate monomers such as methenyloxyethyl (meth)acrylate, dicyclopentanyl (meth)acrylate, nonylphenol polyethylene glycol (meth)acrylate, nonylphenol ethylene oxide modified (meth)acrylate, nonylphenoxy polyethylene glycol (meth)acrylate, isobornyl (meth)acrylate; (meth)acrylic acid, (meth)acrylic acid dimer, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, ω-Cal Carboxyl group-containing monomers such as boxy-polycaprolactone (meth)acrylate; heterocyclic-containing (meth)acrylates such as N-acryloylmorpholine, N-vinylpyrrolidone, N-vinylcaprolactam, N-acryloylpiperidine, N-methacryloylpiperidine, N-acryloylpyrrolidine, 3-(3-pyridyl)propyl (meth)acrylate, and cyclic trimethylolpropane formal acrylate; maleimide monomers such as maleimide, N-cyclohexylmaleimide, and N-phenylmaleimide;Examples include amide monomers such as (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N-hexyl(meth)acrylamide, N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N-butyl(meth)acrylamide, N-methylol(meth)acrylamide, and N-methylolpropane(meth)acrylamide; aminoalkyl (meth)acrylate monomers such as aminoethyl (meth)acrylate, aminopropyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, and tert-butylaminoethyl (meth)acrylate; and succinimide monomers such as N-(meth)acryloyloxymethylenesuccinimide, N-(meth)acryloyl-6-oxyhexamethylenesuccinimide, and N-(meth)acryloyl-8-oxyoctamethylenesuccinimide.

[0038] Examples of polyfunctional monomers include ethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, di(meth)acrylate of alkylene oxide adducts of bisphenol A, tetraethylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate of hydroxypivalate, and 1,4-but Isopentyl diol di(meth)acrylate, 1,6-Hexanediol di(meth)acrylate, 1,9-Nonanediol di(meth)acrylate, 1,12-Dodecanediol di(meth)acrylate, 1,14-Tetradecanediol di(meth)acrylate, 1,16-Hexadecanediol di(meth)acrylate, 1,20-Eicosanediol di(meth)acrylate, Isopentyldiol di(meth)acrylate, 3-Ethyl-1,8-Octanediol di(meth)acrylate, Bisphenol A ethylene oxide adduct di(meth)acrylate, trimethylolpropane tri(meth)acrylate, trimethyloloctan tri(meth)acrylate, trimethylolpropane polyethoxytri(meth)acrylate, trimethylolpropane polypropoxytri(meth)acrylate, trimethylolpropane polyethoxypolypropoxytri(meth)acrylate, trimethylolpropane polyethoxytri(meth)acrylate, tris[(meth)acryloyloxyethyl]isocyanurate, pentaerythritol tri(meth)acrylate, pentaerythritol Examples include lythritol polyethoxytetra(meth)acrylate, pentaerythritol polypropoxytetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, ditrimethylolpropanetetra(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and caprolactone-modified tris[(meth)acryloyloxyethyl]isocyanurate.

[0039] As a photopolymerization initiator, one can be appropriately selected and used from known radical photopolymerization initiators. Examples of photopolymerization initiators include 1-hydroxycyclohexylphenyl ketone (Omnirad 184, IGM Resins), 2,2-dimethoxy-2-phenylacetophenone, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-propan-1-one (Omnirad 907, IGM Resins), 2,4,6-trimethylbenzoyldiphenylphosphine oxide (Omnirad TPO, IGM Resins), and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (Omnirad 819, IGM Resins).

[0040] The resin composition according to this embodiment may further contain a silane coupling agent, a photoacid generator, a leveling agent, an antifoaming agent, an antioxidant, a sensitizer, and the like.

[0041] The silane coupling agent is not particularly limited as long as it does not prevent the curing of the resin composition. Examples of the silane coupling agent include tetramethyl silicate, tetraethyl silicate, mercaptopropyl trimethoxysilane, vinyl trichlorosilane, vinyl triethoxysilane, vinyl tris(β-methoxy-ethoxy)silane, β-(3,4-epoxycyclohexyl)-ethyl trimethoxysilane, dimethoxydimethylsilane, diethoxydimethylsilane, 3-acryloxypropyl trimethoxysilane, 3-glycidoxypropyl trimethoxysilane, 3-glycidoxypropyl methyldiethoxysilane, 3-methacryloxypropyl trimethoxysilane, N-(β-aminoethyl)-γ-aminopropyl trimethoxysilane, N-(β-aminoethyl)-γ-aminopropyl trimethyldimethoxysilane, N-phenyl-3-aminopropyl trimethoxysilane, 3-chloropropyl trimethoxysilane, 3-mercaptopropyl trimethoxysilane, 3-aminopropyl trimethoxysilane, bis-[3-(triethoxysilyl)propyl]tetrasulfide, bis-[3-(triethoxysilyl)propyl]disulfide, γ-trimethoxysilylpropyl dimethylthiocarbamyl tetrasulfide, and γ-trimethoxysilylpropyl benzothiazyl tetrasulfide.

[0042] As the photoacid generator, an onium salt having the structure of A + B - may be used. Examples of the photoacid generator include sulfonium salts such as UVACURE1590 (manufactured by Daicel Cytec), CPI-100P, 110P, 210S (manufactured by San-Apro), and iodonium salts such as Omnicat 250 (manufactured by IGM Resins), WPI-113 (manufactured by Fujifilm Wako Pure Chemical), Rp-2074 (manufactured by Rhodia Japan).

[0043] From the viewpoint of improving the lateral pressure characteristics of the optical fiber, a lower Young's modulus of the primary resin layer is desirable. On the other hand, as the Young's modulus decreases, the curability of the resin decreases, so it is necessary to set an appropriate Young's modulus. The Young's modulus of the primary resin layer 14 is preferably 0.04 MPa to 2.0 MPa at 23°C, more preferably 0.05 MPa to 1.8 MPa, and even more preferably 0.06 MPa to 1.5 MPa.

[0044] From the viewpoint of increasing the rigidity of the optical fiber and improving lateral pressure characteristics, a higher Young's modulus of the secondary resin layer 15 is desirable. On the other hand, if the difference in Young's modulus between the primary resin layer and the secondary resin layer becomes large, the difference in curing shrinkage between the resin layers becomes large, and delamination is more likely to occur at the interface between the primary resin layer and the glass fiber. The Young's modulus of the secondary resin layer is preferably 80 MPa to 2000 MPa at 23°C, more preferably 180 MPa to 1800 MPa, and even more preferably 300 MPa to 1600 MPa.

[0045] The optical fiber according to this embodiment can be manufactured by a method that includes a coating step of applying a first resin composition and a second resin composition to the outer circumference of a glass fiber, and a curing step of curing the resin composition by irradiating it with ultraviolet light after the coating step.

[0046] In the coating process, the first resin composition is applied to the surface of the glass fiber 13 to form a first resin layer (corresponding to the primary resin layer 14 after curing) made of the first resin composition on the surface of the glass fiber 13, and the second resin composition is applied to the surface of the first resin layer to form a second resin layer (corresponding to the secondary resin layer 15 after curing) made of the second resin composition on the surface of the first resin layer.

[0047] In the curing process, the first resin layer and the second resin layer are cured by ultraviolet irradiation to form a primary resin layer 14 from the first resin layer and a secondary resin layer 15 from the second resin layer. Examples of ultraviolet light sources include ultraviolet LEDs and ultraviolet lamps.

[0048] A colored layer, which serves as an ink layer for identifying optical fibers, may be formed on the outer surface of the secondary resin layer 15 constituting the coating resin layer 16. Alternatively, the secondary resin layer 15 may be used as the colored layer. From the viewpoint of improving the identifiability of optical fibers, the colored layer preferably contains a pigment. Examples of pigments include colored pigments such as carbon black, titanium dioxide, and zinc oxide; inorganic pigments such as γ-Fe2O3, mixed crystals of γ-Fe2O3 and γ-Fe3O4, CrO2, cobalt ferrite, cobalt-coated iron oxide, barium ferrite, magnetic powders such as Fe-Co and Fe-Co-Ni; and organic pigments such as azo pigments, phthalocyanine pigments, and dyed lake pigments. The pigments may be subjected to various surface modifications, composite pigment formation, and other treatments.

[0049] (Fiber optic ribbon) An optical fiber ribbon can be manufactured using the optical fiber according to this embodiment. Figure 2 is a schematic cross-sectional view showing an optical fiber ribbon according to one embodiment. The optical fiber ribbon 100 has a plurality of optical fibers 10 and a connecting resin layer 40 in which the optical fibers 10 are (integrally) covered and connected with ribbon resin. In Figure 2, four optical fibers 10 are shown as an example, but the number is not particularly limited. The optical fiber ribbon according to this embodiment has excellent transmission characteristics at low temperatures.

[0050] The optical fibers 10 may be integrated in a parallel arrangement in contact with each other, or some or all of the optical fibers 10 may be integrated in a parallel arrangement with a certain interval between them. The center-to-center distance F between adjacent optical fibers 10 may be 220 μm or more and 280 μm or less. When the center-to-center distance is 220 μm or more and 280 μm or less, it is possible to obtain an optical fiber ribbon that is easy to place in existing V grooves and has excellent single-piece fusion bonding properties. The thickness T of the optical fiber ribbon 100 depends on the outer diameter of the optical fibers 10, but may be 164 μm or more and 285 μm or less. The resin for the ribbon is not particularly limited, and the connecting resin layer may include, for example, urethane (meth)acrylate resin. [Examples]

[0051] The present disclosure will be further explained by presenting the results of evaluation tests using experimental examples (examples and comparative examples) related to this disclosure. However, the present invention is not limited to these examples.

[0052] (Synthesis of urethane acrylate) (UA-1) Polypropylene glycol with a Mn of 2000, isophorone diisocyanate, and hydroxyethyl acrylate were reacted using dibutyltin dilaurate as a tin catalyst to synthesize urethane acrylate (UA-1). Dibutyltin dilaurate was added so that the amount of tin in the coating resin layer was 60 ppm.

[0053] (UA-2) Polypropylene glycol with a Mn of 1500, isophorone diisocyanate, and hydroxyethyl acrylate were reacted with dibutyltin dilaurate to synthesize urethane acrylate (UA-2). Dibutyltin dilaurate was added so that the amount of tin in the coating resin layer was 60 ppm.

[0054] (UA-3) Polypropylene glycol with a Mn of 1500, isophorone diisocyanate, and hydroxyethyl acrylate were reacted with dibutyltin dilaurate to synthesize urethane acrylate (UA-3). Dibutyltin dilaurate was added so that the amount of tin in the coating resin layer was 100 ppm.

[0055] (UA-4) Polypropylene glycol with a Mn of 1000, isophorone diisocyanate, and hydroxyethyl acrylate were reacted with dibutyltin dilaurate to synthesize urethane acrylate (UA-4). Dibutyltin dilaurate was added so that the tin content in the coating resin layer was 60 ppm.

[0056] (UA-5) Polypropylene glycol with a Mn of 700, isophorone diisocyanate, and hydroxyethyl acrylate were reacted with dibutyltin dilaurate to synthesize urethane acrylate (UA-5). Dibutyltin dilaurate was added so that the amount of tin in the coating resin layer was 60 ppm.

[0057] (UA-6) Polypropylene glycol with a Mn of 3000, isophorone diisocyanate, and hydroxyethyl acrylate were reacted with dibutyltin dilaurate to synthesize urethane acrylate (UA-6). Dibutyltin dilaurate was added so that the amount of tin in the coating resin layer was 60 ppm.

[0058] (UA-7) Polypropylene glycol with a Mn of 1500, isophorone diisocyanate, and hydroxyethyl acrylate were reacted with dibutyltin dilaurate to synthesize urethane acrylate (UA-7). Dibutyltin dilaurate was added so that the amount of tin in the coating resin layer was 200 ppm.

[0059] (First resin composition for primary resin) Resin composition P1 was prepared by mixing 70 parts by mass of silicone diacrylate (organopolysiloxane having acryloyl groups at both ends), 25 parts by mass of nonylphenol ethylene oxide modified acrylate, and 5 parts by mass of Omnirad TPO.

[0060] [Experimental Example 1] (Second resin composition for the secondary resin layer) Resin composition S1 was prepared by mixing 58 parts by mass of urethane acrylate (UA-1), 20 parts by mass of bisphenol A-based epoxy acrylate, 10 parts by mass of isobornyl acrylate, 10 parts by mass of N-vinylcaprolactam, and 2 parts by mass of Omnirad TPO.

[0061] (Optical fiber) A glass fiber with a diameter of 125 μm, consisting of a core and cladding, was coated with a resin composition P1 for the primary resin layer and a resin composition S1 for the secondary resin layer. The resin compositions were then cured by irradiation with ultraviolet light to form a 35 μm primary resin layer, and a secondary resin layer with a thickness of 25 μm was further formed on its outer periphery to create an optical fiber with an outer diameter of 245 μm. The linear velocity was set to 500 m / min.

[0062] [Experimental Example 2] Resin composition S2 was prepared by mixing 58 parts by mass of urethane acrylate (UA-2), 20 parts by mass of bisphenol A-based epoxy acrylate, 10 parts by mass of isobornyl acrylate, 10 parts by mass of N-vinylcaprolactam, and 2 parts by mass of Omnirad TPO. Optical fibers were fabricated in the same manner as in Experimental Example 1, except that resin composition S2 was used as the resin composition for the secondary resin layer.

[0063] [Experimental Example 3] Resin composition S3 was prepared by mixing 58 parts by mass of urethane acrylate (UA-3), 20 parts by mass of bisphenol A-based epoxy acrylate, 10 parts by mass of isobornyl acrylate, 10 parts by mass of N-vinylcaprolactam, and 2 parts by mass of Omnirad TPO. Optical fibers were fabricated in the same manner as in Experimental Example 1, except that resin composition S3 was used as the resin composition for the secondary resin layer.

[0064] [Experimental Example 4] Resin composition S4 was prepared by mixing 58 parts by mass of urethane acrylate (UA-4), 20 parts by mass of bisphenol A-based epoxy acrylate, 10 parts by mass of isobornyl acrylate, 10 parts by mass of N-vinylcaprolactam, and 2 parts by mass of Omnirad TPO. Optical fibers were fabricated in the same manner as in Experimental Example 1, except that resin composition S4 was used as the resin composition for the secondary resin layer.

[0065] [Experimental Example 5] Resin composition S5 was prepared by mixing 48 parts by mass of urethane acrylate (UA-4), 40 parts by mass of bisphenol A-based epoxy acrylate, 10 parts by mass of isobornyl acrylate, and 2 parts by mass of Omnirad TPO. Optical fibers were fabricated in the same manner as in Experimental Example 1, except that resin composition S5 was used as the resin composition for the secondary resin layer.

[0066] [Experimental Example 6] Resin composition S6 was prepared by mixing 58 parts by mass of urethane acrylate (UA-5), 20 parts by mass of bisphenol A-based epoxy acrylate, 10 parts by mass of isobornyl acrylate, 10 parts by mass of N-vinylcaprolactam, and 2 parts by mass of Omnirad TPO. Optical fibers were fabricated in the same manner as in Experimental Example 1, except that resin composition S6 was used as the resin composition for the secondary resin layer.

[0067] [Experimental Example 7] Resin composition S7 was prepared by mixing 48 parts by mass of urethane acrylate (UA-6), 40 parts by mass of bisphenol A-based epoxy acrylate, 10 parts by mass of isobornyl acrylate, and 2 parts by mass of Omnirad TPO. Optical fibers were fabricated in the same manner as in Experimental Example 1, except that resin composition S7 was used as the resin composition for the secondary resin layer.

[0068] [Experimental Example 8] Resin composition S8 was prepared by mixing 58 parts by mass of urethane acrylate (UA-6), 20 parts by mass of bisphenol A-based epoxy acrylate, 10 parts by mass of isobornyl acrylate, 10 parts by mass of N-vinylcaprolactam, and 2 parts by mass of Omnirad TPO. Optical fibers were fabricated in the same manner as in Experimental Example 1, except that resin composition S8 was used as the resin composition for the secondary resin layer.

[0069] [Experimental Example 9] Resin composition S9 was prepared by mixing 58 parts by mass of urethane acrylate (UA-7), 20 parts by mass of bisphenol A-based epoxy acrylate, 10 parts by mass of isobornyl acrylate, 10 parts by mass of N-vinylcaprolactam, and 2 parts by mass of Omnirad TPO. Optical fibers were fabricated in the same manner as in Experimental Example 1, except that resin composition S9 was used as the resin composition for the secondary resin layer.

[0070] The optical fibers fabricated in Experimental Examples 1 to 9 were evaluated as follows. The results are shown in Table 1.

[0071] (Young's modulus of the secondary resin layer) The Young's modulus of the secondary resin layer was determined from the 2.5% secant value obtained by performing a tensile test at 23°C (gauge distance: 25 mm) on a pipe-shaped coating resin layer (length: 50 mm or more) obtained by immersing an optical fiber in a solvent (ethanol:acetone = 3:7) and removing the glass fiber.

[0072] (Tin content in the coating resin layer) A sample was prepared by adding 7 mL of nitric acid and 1 mL of 46% by mass hydrofluoric acid to 0.05 g of the coating resin layer peeled off from an optical fiber, and heating it in a microwave decomposition apparatus at 220°C for 15 minutes. Then, pure water was added to the sample to a final volume of 50 mL, and the tin content was measured using a high-frequency inductively coupled plasma emission spectrometer (Agilent Technologies, Inc.'s "ICP-MS Agilent 7700x").

[0073] (Oil resistance) Optical fibers were immersed in mineral oil at 85°C for 30 days, ensuring that the entire coating resin layer was completely submerged. The transmission characteristics of a 1550nm wavelength signal were measured under both 23°C and -40°C temperature conditions, and the transmission loss at 23°C and -40°C was evaluated. A difference of 0.05 dB / km or less (less transmission loss at -40°C) was evaluated as "A," and a difference greater than 0.05 dB / km was evaluated as "B."

[0074] (Lateral pressure characteristics) Optical fibers were wound onto a 280mm diameter quartz glass bobbin with its surface covered with sandpaper (grit 1000). The transmission characteristics of a 1550nm wavelength signal were measured under two temperature conditions, 23°C and -40°C, and the transmission loss difference was evaluated. A transmission loss difference of 0.1dB / km or less was classified as "A," a transmission loss difference between 0.1dB / km and 0.3dB / km was classified as "B," and a transmission loss difference greater than 0.3dB / km was classified as "C."

[0075] [Table 1]

[0076] By comparing Experimental Examples 1 to 8 with Experimental Example 9, it can be confirmed that reducing the amount of tin contained in the coating resin layer improves the oil resistance of the optical fiber. [Explanation of Symbols]

[0077] 10 Optical Fibers 11 cores 12 clad 13. Glass fiber 14 Primary resin layer 15. Secondary resin layer 16. Coating resin layer 40 Connecting resin layer 100 Fiber Optic Ribbons

Claims

1. It comprises a glass fiber including a core and a cladding, and a coating resin layer covering the glass fiber, The coating resin layer comprises a primary resin layer that is in contact with and covers the glass fiber, and a secondary resin layer that covers the primary resin layer. The primary resin layer comprises a cured product of a first resin composition containing silicone (meth)acrylate and a photopolymerization initiator. The secondary resin layer comprises a cured product of a second resin composition containing urethane (meth)acrylate and a photopolymerization initiator. An optical fiber in which the amount of tin contained in the coating resin layer is 150 ppm or less by mass ratio.

2. The optical fiber according to claim 1, wherein the Young's modulus of the secondary resin layer is 80 MPa or more and 2000 MPa or less at 23°C.

3. The optical fiber according to claim 1 or claim 2, wherein the second resin composition further contains an epoxy (meth)acrylate having an aromatic ring.

4. The optical fiber according to any one of claims 1 to 3, wherein the amount of tin is 10 ppm or more by mass ratio.

5. The optical fiber according to any one of claims 1 to 4, wherein the first resin composition further contains a nonylphenol ethylene oxide-modified (meth)acrylate.

6. A plurality of optical fibers according to any one of claims 1 to 5 arranged in parallel, An optical fiber ribbon comprising a connecting resin layer that covers and connects a plurality of the aforementioned optical fibers.

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