Resin composition for optical fiber connection, and optical fiber ribbon

Abstract

The present disclosure can provide: a resin composition for optical fiber connection, wherein the resin composition can form a connection part that exhibits an excellent adhesiveness and toughness; and an optical fiber ribbon having a connection part formed using this resin composition.　The resin composition for optical fiber connection comprises: photopolymerizable compounds comprising a monofunctional (meth)acryloyl compound (A) and a difunctional (meth)acryloyl compound (B); and a photopolymerization initiator. The (meth)acryloyl compound (B) comprises: an epoxy di(meth)acrylate having a bisphenol A skeleton; and an ethylene oxide-modified di(meth)acrylate in which the number of ethylene oxide groups is at least 6 and not more than 28.

Description

Resin composition for optical fiber connection and optical fiber ribbon

[0001] This disclosure relates to a resin composition for optical fiber connections and an optical fiber ribbon. This application claims priority to Japanese Application No. 2024-129142, filed August 5, 2024, and incorporates by reference all of the contents of said Japanese application.

[0002] It is known to use an optical fiber ribbon (optical fiber tape core wire) in which a plurality of optical fibers are intermittently connected (bonded) together (for example, Patent Documents 1 and 2).

[0003] JP 2017-62431 A JP 2017-102373 A

[0004] The resin composition for optical fiber connection according to the present disclosure comprises a photopolymerizable compound containing a monofunctional (meth)acryloyl compound (A) and a bifunctional (meth)acryloyl compound (B), and a photopolymerization initiator, wherein the (meth)acryloyl compound (B) contains an epoxy di(meth)acrylate having a bisphenol A skeleton and an ethylene oxide-modified di(meth)acrylate having 6 or more and 28 or less ethylene oxide groups.

[0005] Fig. 1 is a plan view showing the appearance of an optical fiber ribbon according to this embodiment. Fig. 2 is a schematic cross-sectional view showing an optical fiber ribbon according to an embodiment. Fig. 3 is a schematic cross-sectional view showing an optical fiber ribbon according to a modified embodiment. Fig. 4 is a schematic cross-sectional view showing an optical fiber ribbon according to an embodiment.

[0006] In recent years, there has been an increasing demand for cables with high optical fiber density. To achieve this, optical fiber ribbons are used, in which multiple optical fibers are intermittently connected. In optical fiber ribbons in which optical fibers are intermittently connected, the bonding area at the connection is small, so external forces can cause the bonded area to break (interfacial failure or cohesive failure), resulting in separation of the optical fibers. To prevent separation of the optical fibers, optical fiber connection sections are required to have appropriate adhesiveness and toughness. Therefore, an object of the present disclosure is to provide a resin composition capable of forming a connection section with excellent adhesiveness and toughness, and an optical fiber ribbon having a connection section formed from the resin composition.

[0007] According to the present disclosure, it is possible to provide a resin composition for optical fiber connection that can form a connection part having excellent adhesive properties and toughness, and an optical fiber ribbon having a connection part formed using the resin composition.

[0008] The contents of the embodiments of the present disclosure will be described.

[0009] (1) A resin composition for optical fiber connection according to one embodiment of the present disclosure comprises a photopolymerizable compound containing a monofunctional (meth)acryloyl compound (A) and a bifunctional (meth)acryloyl compound (B), and a photopolymerization initiator, wherein the (meth)acryloyl compound (B) contains an epoxy di(meth)acrylate having a bisphenol A skeleton and an ethylene oxide-modified di(meth)acrylate having 6 or more and 28 or less ethylene oxide groups.

[0010] Such a resin composition can form optical fiber joints with excellent adhesive properties and toughness.

[0011] (2) In the resin composition described in (1) above, the epoxy di(meth)acrylate may be modified with caprolactone, which can further increase the adhesive strength of the connecting portion.

[0012] (3) In the resin composition described in (2) above, the content of the caprolactone-modified epoxy di(meth)acrylate may be 20 parts by mass or more and 40 parts by mass or less per 100 parts by mass of the total amount of the photopolymerizable compounds. In this case, the Young's modulus of the connecting portion does not become too high, and the breaking strength of the connecting portion is less likely to decrease.

[0013] (4) In the resin composition according to any one of (1) to (3), the (meth)acryloyl compound (A) may contain a (meth)acrylate having a phenoxy group. In this case, a connecting portion having better adhesiveness can be formed.

[0014] (5) In the resin composition described in (4) above, the content of the (meth)acrylate having a phenoxy group may be 10 parts by mass or more and 30 parts by mass or less per 100 parts by mass of the total amount of the photopolymerizable compound. In this case, the toughness of the connecting parts can be further increased and the degree of adhesiveness of the connecting parts can be reduced.

[0015] (6) An optical fiber ribbon according to an embodiment of the present disclosure includes a plurality of optical fibers arranged in parallel and a connecting portion that intermittently connects adjacent optical fibers, the connecting portion including a cured product of the resin composition described in any one of (1) to (5). In such an optical fiber ribbon, the optical fibers are less likely to be separated by an external force, and therefore degradation of transmission characteristics can be prevented.

[0016] (7) An optical fiber ribbon according to an embodiment of the present disclosure includes sub-ribbons each having a plurality of optical fibers arranged in parallel and a collective coating layer covering the plurality of optical fibers, and a connecting portion intermittently connecting the plurality of sub-ribbons arranged in parallel and adjacent sub-ribbons, the connecting portion including a cured product of the resin composition described in any one of (1) to (5). In such an optical fiber ribbon, the optical fibers are less likely to be separated by an external force, and therefore degradation of transmission characteristics can be prevented.

[0017] [Details of the Embodiments of the Present Disclosure] Specific examples of the resin composition for optical fiber connection and the optical fiber ribbon according to the present embodiment will be described with reference to the drawings as necessary. The present disclosure is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims. It should be understood that at least one configuration and feature described in each embodiment can be combined with other embodiments and can be modified in various ways. In the following description, the same elements in the drawings will be designated by the same reference numerals, and redundant explanations will be omitted. In this specification, (meth)acryloyl means acryloyl or the corresponding methacryloyl. The same meaning applies to other similar expressions such as (meth)acrylate and (meth)acrylamide. Ethylene oxide-modified (EO-modified) refers to a compound having a structure in which (C ２ H ４ O) ｎ Propylene oxide-modified (PO-modified) means that the propylene oxide-modified (PO-modified) has an ethylene oxide group represented by (C ３ H ６ O) ｎ "Caprolactone-modified" means that the polymer has a functional group formed by ring-opening of caprolactone or a functional group formed by ring-opening and polymerization of caprolactone. n is an integer of 1 or more.

[0018] (Resin composition for optical fiber connection) The resin composition for optical fiber connection according to this embodiment contains a photopolymerizable compound including a monofunctional (meth)acryloyl compound (A) and a bifunctional (meth)acryloyl compound (B), and a photopolymerization initiator, wherein the (meth)acryloyl compound (B) contains an epoxy di(meth)acrylate having a bisphenol A skeleton and an ethylene oxide-modified di(meth)acrylate having 6 or more and 28 or less ethylene oxide groups.

[0019] The resin composition according to this embodiment contains a specific photopolymerizable compound, and thus can form a connecting portion having excellent adhesiveness and toughness.

[0020] The (meth)acryloyl compound (A) is a compound having one (meth)acryloyl group. From the viewpoint of adjusting the viscosity and curing rate of the resin composition and the physical properties of the cured product, the content of the (meth)acryloyl compound (A) may be 40 parts by mass or more, 45 parts by mass or more, or 50 parts by mass or more, and may be 70 parts by mass or less, 65 parts by mass or less, or 60 parts by mass or less, relative to 100 parts by mass of the total amount of the photopolymerizable compound.

[0021] Examples of the (meth)acryloyl compound (A) include monofunctional (meth)acrylate compounds and monofunctional (meth)acrylamide compounds.

[0022] Examples of the monofunctional (meth)acrylate compound include (meth)acrylates having a phenoxy group, such as phenol EO-modified (meth)acrylate, nonylphenol EO-modified (meth)acrylate, phenol PO-modified (meth)acrylate, nonylphenol PO-modified (meth)acrylate, phenoxyethyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, and 3-phenoxybenzyl (meth)acrylate. Examples of monofunctional (meth)acrylate compounds 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 (meth)acrylate, isooctyl (meth)acrylate, and isodecyl (meth)acrylate compounds having no phenoxy group, such as (meth)acrylate, lauryl (meth)acrylate, 4-tert-butylcyclohexanol (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, benzyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, dicyclopentanyl (meth)acrylate, isobornyl (meth)acrylate, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, and ω-carboxy-polycaprolactone (meth)acrylate, are examples of such (meth)acrylate compounds.

[0023] Examples of monofunctional (meth)acrylamide compounds include dimethyl(meth)acrylamide, diethyl(meth)acrylamide, (meth)acryloylmorpholine, hydroxymethyl(meth)acrylamide, hydroxyethyl(meth)acrylamide, isopropyl(meth)acrylamide, dimethylaminopropyl(meth)acrylamide, dimethylaminopropylacrylamide methyl chloride, diacetone acrylamide, (meth)acryloylpiperidine, (meth)acryloylpyrrolidine, (meth)acrylamide, N-hexyl(meth)acrylamide, N-methyl(meth)acrylamide, N-butyl(meth)acrylamide, N-methylol(meth)acrylamide, and N-methylolpropane(meth)acrylamide.

[0024] From the viewpoint of forming a connecting portion with superior adhesiveness, the (meth)acryloyl compound (A) may contain a (meth)acrylate having a phenoxy group. From the viewpoint of further improving the adhesiveness of the connecting portion, the (meth)acryloyl compound (A) may contain one or more (meth)acrylates selected from phenol EO-modified (meth)acrylate, nonylphenol EO-modified (meth)acrylate, phenol PO-modified (meth)acrylate, and nonylphenol PO-modified (meth)acrylate. The number of ethylene oxide (EO) groups or propylene oxide (PO) groups may be 1 or more, 2 or more, or 3 or more, and may be 10 or less, 8 or less, or 6 or less.

[0025] From the viewpoint of further improving the toughness of the connecting portion, the content of the (meth)acrylate having a phenoxy group may be 10 parts by mass or more, 12 parts by mass or more, or 15 parts by mass or more, relative to 100 parts by mass of the total amount of the photopolymerizable compound. From the viewpoint of reducing the degree of adhesion of the connecting portion, the content of the (meth)acrylate having a phenoxy group may be 30 parts by mass or less, 28 parts by mass or less, or 25 parts by mass or less, relative to 100 parts by mass of the total amount of the photopolymerizable compound. Reducing the degree of adhesion of the connecting portion prevents adhesion between adjacent optical fibers, making it easier to reduce transmission loss. From these viewpoints, the content of the (meth)acrylate having a phenoxy group may be 10 parts by mass or more and 30 parts by mass or less, 12 parts by mass or more and 28 parts by mass or less, or 15 parts by mass or more and 25 parts by mass or less, relative to 100 parts by mass of the total amount of the photopolymerizable compound.

[0026] The (meth)acryloyl compound (B) is a compound having two (meth)acryloyl groups. The photopolymerizable compound according to this embodiment contains, as the (meth)acryloyl compound (B), an epoxy di(meth)acrylate having a bisphenol A skeleton and an ethylene oxide-modified di(meth)acrylate having 6 to 28 ethylene oxide groups as essential components. In this disclosure, the epoxy di(meth)acrylate having a bisphenol A skeleton may be referred to as "epoxy di(meth)acrylate (B1)." In this disclosure, the ethylene oxide-modified di(meth)acrylate having 6 to 28 ethylene oxide groups may be referred to as "EO-modified di(meth)acrylate (B2)." The epoxy di(meth)acrylate (B1) and the EO-modified di(meth)acrylate (B2) are photopolymerizable compounds that do not have a urethane bond.

[0027] As the epoxy di(meth)acrylate (B1), for example, a reaction product of a diglycidyl ether compound having a bisphenol A skeleton and a compound having a (meth)acryloyl group, such as (meth)acrylic acid, can be used.

[0028] In order to further increase the strength of the connecting portion, the epoxy di(meth)acrylate (B1) may be modified with caprolactone. Examples of the caprolactone-modified epoxy di(meth)acrylate (B1) include EBECRYL (registered trademark) 3708 (manufactured by Daicel Corporation).

[0029] From the viewpoint of achieving better toughness, the content of the epoxy di(meth)acrylate (B1) may be 20 parts by mass or more, 25 parts by mass or more, or 30 parts by mass or more, and may be 45 parts by mass or less, 40 parts by mass or less, or 36 parts by mass or less, relative to 100 parts by mass of the total amount of the photopolymerizable compounds.

[0030] When the epoxy di(meth)acrylate (B1) is caprolactone-modified, the content of the caprolactone-modified epoxy di(meth)acrylate (B1) may be 20 parts by mass or more, 22 parts by mass or more, or 24 parts by mass or more, relative to 100 parts by mass of the total amount of the photopolymerizable compounds, from the viewpoint of adjusting the Young's modulus. The content of the caprolactone-modified epoxy di(meth)acrylate (B1) may be 40 parts by mass or less, 38 parts by mass or less, or 36 parts by mass or less, relative to 100 parts by mass of the total amount of the photopolymerizable compounds, from the viewpoint of adjusting the breaking strength. When the content of the caprolactone-modified epoxy di(meth)acrylate (B1) is 20 parts by mass or more, relative to 100 parts by mass of the total amount of the photopolymerizable compounds, the Young's modulus does not become too high, and when it is 40 parts by mass or less, the breaking strength is less likely to decrease.

[0031] Examples of the EO-modified di(meth)acrylate (B2) include polyethylene glycol di(meth)acrylate, isocyanuric acid ethylene oxide-modified di(meth)acrylate, ethylene oxide-modified bisphenol F di(meth)acrylate, ethylene oxide-modified bisphenol A di(meth)acrylate, ethylene oxide-modified bisphenol A di(meth)acrylate, and ethylene oxide-modified neopentyl glycol di(meth)acrylate.

[0032] The number of EO groups in the EO-modified di(meth)acrylate (B2) may be 8 or more and 26 or less, 8 or more and 24 or less, or 10 or more and 22 or less, from the viewpoint of achieving better adhesiveness and toughness.

[0033] From the viewpoint of achieving better adhesion and toughness, the content of the EO-modified di(meth)acrylate (B2) may be 1 part by mass or more, 2 parts by mass or more, or 3 parts by mass or more, and may be 15 parts by mass or less, 13 parts by mass or less, or 11 parts by mass or less, relative to 100 parts by mass of the total amount of the photopolymerizable compound.

[0034] The (meth)acryloyl compound (B) may further contain an EO-modified di(meth)acrylate having 1 to 5 EO groups or an EO-modified di(meth)acrylate having 29 or more EO groups. Hereinafter, an EO-modified di(meth)acrylate having 1 to 5 EO groups and an EO-modified di(meth)acrylate having 29 or more EO groups may be referred to as "EO-modified di(meth)acrylate (B3)." The content of the EO-modified di(meth)acrylate (B3) may be 1 part by mass or more, 2 parts by mass or more, or 3 parts by mass or more, or may be 8 parts by mass or less, 7 parts by mass or less, or 6 parts by mass or less, relative to 100 parts by mass of the total amount of the photopolymerizable compound.

[0035] The photopolymerization initiator can be appropriately selected from known radical photopolymerization initiators. Examples of the photopolymerization initiator include 1-hydroxycyclohexyl phenyl ketone (Omnirad (registered trademark) 184, manufactured by IGM Resins), 2,2-dimethoxy-2-phenylacetophenone (Omnirad 651, manufactured by IGM Resins), 2,4,6-trimethylbenzoyldiphenylphosphine oxide (Omnirad TPO H, manufactured by IGM Resins), ethyl (2,4,6-trimethylbenzoyl)-phenylphosphinate (Omnirad TPO-L, manufactured by IGM Resins), and 2-benzyl-2-dimethylamino-4'-morpholinobutyrophenone (Omnirad 369, manufactured by IGM Resins). Examples of suitable amines include 2-dimethylamino-2-(4-methyl-benzyl)-1-(4-morpholin-4-yl-phenyl)-butan-1-one (Omnirad 379, IGM Resins), bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (Omnirad 819, IGM Resins), and 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one (Omnirad 907, IGM Resins).

[0036] Two or more types of photopolymerization initiators may be used in combination. The photopolymerization initiator may include 1-hydroxycyclohexyl phenyl ketone, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, or 2,4,6-trimethylbenzoylphenylphosphonic acid ethyl ester. These photopolymerization initiators are excellent in fast-curing properties of the resin composition.

[0037] The content of the photopolymerization initiator may be 0.5 parts by mass or more and 10 parts by mass or less, 1 part by mass or more and 6 parts by mass or less, or 2 parts by mass or more and 4 parts by mass or less, relative to 100 parts by mass of the total amount of the photopolymerizable compounds.

[0038] The resin composition according to this embodiment may further contain one or more of a sensitizer, a photoacid generator, a surfactant, a leveling agent, an antifoaming agent, an antioxidant, and an ultraviolet absorber.

[0039] The resin composition according to the present embodiment can be used to connect optical fibers together. For example, the optical fibers can be connected together by arranging a plurality of optical fibers in parallel, applying the resin composition to the contact points between the optical fibers using a dispenser, and then irradiating the resin composition with ultraviolet light to harden it and form a connection.

[0040] From the viewpoint of excellent applicability using a dispenser, the viscosity of the resin composition according to this embodiment may be 40 mPa·s or more and 200 mPa·s or less, 45 mPa·s or more and 150 mPa·s or less, 50 mPa·s or more and 100 mPa·s or less, or 55 mPa·s or more and 80 mPa·s or less at 60°C.

[0041] (Optical fiber ribbon) An optical fiber ribbon according to one embodiment of the present disclosure comprises a plurality of optical fibers arranged in parallel and a connecting portion that intermittently connects adjacent optical fibers, and the connecting portion contains a cured product of the resin composition for optical fiber connection described above.

[0042] FIG. 1 is a plan view showing the appearance of an optical fiber ribbon according to this embodiment. The optical fiber ribbon 100A includes a plurality of optical fibers 10, a plurality of connecting portions 20, and a non-connecting portion (segmented portion) 21. The non-connecting portions 21 are formed intermittently in the longitudinal and width directions of the optical fiber ribbon 100A. The optical fiber ribbon 100A is an intermittently connected optical fiber ribbon in which connecting portions 20 and non-connecting portions 21 are provided intermittently in the longitudinal and width directions for every two optical fibers 10. A "connecting portion" refers to a portion where adjacent optical fibers are integrated with a connecting resin. A "non-connecting portion" refers to a portion where adjacent optical fibers are not integrated with a connecting resin and there is a gap between the optical fibers. While FIG. 1 shows 12 optical fibers as an example, the number of optical fibers is not particularly limited.

[0043] Fig. 2 is a schematic cross-sectional view showing an optical fiber ribbon 100A according to an embodiment of the present disclosure. Fig. 2 is a cross-sectional view perpendicular to the longitudinal direction of the optical fiber ribbon 100A. In the optical fiber ribbon 100A shown in Fig. 2, adjacent optical fibers 10 are connected by a connecting portion 20. Fig. 2 shows, as an example, an optical fiber having two coating resin layers including a primary resin layer 32 and a secondary resin layer 33. In the optical fiber ribbon according to this embodiment, the number and types of layers in the coating resin layers of the optical fibers are not particularly limited.

[0044] The optical fiber 10 includes a glass fiber 31 and a coating resin layer 34 including a primary resin layer 32 and a secondary resin layer 33 provided on the outer periphery of the glass fiber 31. The glass fiber 31 includes a core and a cladding. The core and the cladding mainly contain glass. For example, the core may be made of germanium-doped silica glass or pure silica glass. For example, the cladding may be made of pure silica glass or fluorine-doped silica glass. The outer diameter D of the glass fiber 31 (i.e., the outer diameter of the cladding) is, for example, 125 μm.

[0045] The primary resin layer 32 and the secondary resin layer 33 can be formed using a resin material generally known as a resin material for forming a coating resin layer of an optical fiber, such as an ultraviolet-curable resin such as urethane (meth)acrylate or epoxy (meth)acrylate.

[0046] The thickness of the primary resin layer 32 may be, for example, 25 μm or more and 35 μm or less. The thickness of the secondary resin layer 33 may be, for example, 25 μm or more and 35 μm or less.

[0047] From the viewpoint of improving the microbending resistance of the optical fiber, the Young's modulus of the primary resin layer 32 may be, for example, 0.80 MPa or less, 0.70 MPa or less, 0.60 MPa or less, or 0.55 MPa or less at 23° C.±2° C. From the viewpoint of further improving the low-temperature properties of the optical fiber, the Young's modulus of the primary resin layer may be 0.10 MPa or more, 0.15 MPa or more, 0.20 MPa or more, or 0.35 MPa or more at 23° C.±2° C.

[0048] The Young's modulus of the primary resin layer 32 can be measured by the Pullout Modulus (POM) method at 23°C. Two locations on the optical fiber are fixed with two chuck devices (a first chuck device and a second chuck device), and the portion of the coating resin layer (the primary resin layer and the secondary resin layer) between the two chuck devices is removed. Next, the first chuck device is fixed, and the second chuck device is slowly moved in a direction away from the first chuck device. When the length of the portion of the optical fiber sandwiched between the moving chuck devices is L, the amount of chuck movement is Z, the outer diameter of the primary resin layer is Dp, the outer diameter of the glass fiber is Df, the Poisson's ratio of the primary resin layer is n, and the load during movement of the chuck devices is W, the Young's modulus of the primary resin layer can be calculated using the following formula: Young's modulus (MPa) = ((1 + n)W / πLZ) × ln(Dp / Df)

[0049] From the viewpoint of improving the microbending resistance of the optical fiber, the Young's modulus of the secondary resin layer 33 may be 750 MPa or more, 800 MPa or more, 900 MPa or more, or 1000 MPa or more at 23° C.±2° C. From the viewpoint of imparting appropriate toughness to the secondary resin layer, the upper limit of the Young's modulus of the secondary resin layer may be 2000 MPa or less, 1800 MPa or less, or 1500 MPa or less at 23° C.±2° C. The upper limit of the Young's modulus of the secondary resin layer is not particularly limited.

[0050] The Young's modulus of the secondary resin layer 33 can be measured, for example, by the following method. First, the optical fiber is immersed in a mixed solvent of acetone and ethanol, and only the coating resin layer is extracted in a cylindrical shape. At this time, the primary resin layer and the secondary resin layer remain integrated. Since the Young's modulus of the primary resin layer is 1 / 10,000 to 1 / 1,000 of that of the secondary resin layer, the Young's modulus of the primary resin layer can be ignored. Next, the solvent is removed from the coating resin layer by vacuum drying, and then a tensile test (tensile speed: 1 mm / min) is performed at 23°C, and the Young's modulus can be determined using the secant equation with 2.5% strain.

[0051] The connecting portion 20 includes a cured product of the resin composition for optical fiber connection described above. The connecting portion 20 connects a plurality of optical fibers to each other by intermittently bonding adjacent optical fibers together. The connecting portion 20 is in contact with the coating resin layer 34 of the optical fiber 10.

[0052] The thickness H of the connecting portion 20 (the length in the direction perpendicular to the longitudinal direction and width direction of the optical fiber ribbon 100A) is, for example, 80 μm or more and 125 μm or less. The range of 80 μm or more and 125 μm or less is an example, and the numerical value of the thickness H is not limited to this numerical range. The thickness H of the connecting portion 20 is the thickness at the center position in the width direction between two adjacent optical fibers 10. This width direction refers to the width direction of the optical fiber ribbon 100A. Because the optical fiber ribbon is easily deformed when inserted into a cable, the surface 20a of the connecting portion 20 may have a recess. The recess may be formed on the surface 20a of the connecting portion 20. As a modified example of the optical fiber ribbon according to an embodiment of the present disclosure, FIG. 3 shows an optical fiber ribbon in which the surface 20a of the connecting portion 20 has a recess. The connecting portion 20 may be provided on both sides of the optical fiber ribbon. When the connecting portion 20 is provided on both sides of the optical fiber ribbon, the total thickness H of the connecting portion 20 is, for example, 90 μm or more and 150 μm or less. The range of 90 μm or more and 150 μm or less is an example, and the total thickness H of the connecting portion 20 is not limited to this numerical range.

[0053] From the viewpoints of the ease of storing the optical fiber ribbon in a cable, ease of handling, and flexibility, the lengths of the connecting portion 20 and the non-connecting portion 21 can be appropriately adjusted depending on the adhesive strength of the connecting resin. The length of the connecting portion 20 may be, for example, 20 mm to 40 mm or 25 mm to 35 mm. The length of the non-connecting portion 21 in the longitudinal direction of the optical fiber may be, for example, 100 mm to 120 mm or 105 mm to 115 mm.

[0054] The connecting portion 20 can be formed by curing the resin composition for connecting optical fibers described above. Examples of a method for curing the resin composition include a method of irradiating it with ultraviolet light.

[0055] From the viewpoint of excellent durability of the connecting portion, the Young's modulus of the cured product of the resin composition may be 10 MPa or more, 12 MPa or more, or 15 MPa or more at 23±2°C, or may be 30 MPa or less, 28 MPa or less, or 25 MPa or less.

[0056] From the viewpoint of excellent durability of the connecting portion, the breaking strength of the cured product of the resin composition may be 25 MPa or more, 27 MPa or more, or 30 MPa or more at 23±2°C, and may be 50 MPa or less, 47 MPa or less, or 45 MPa or less.

[0057] To improve the toughness of the connecting portion, the elongation at break of the cured product of the resin composition may be 200% or more, 250% or more, or 300% or more, or 500% or less, 450% or less, or 400% or less. The Young's modulus, breaking strength, and breaking elongation can be measured by the methods described in the Examples. For example, various fracture analyses can be performed on the connecting portion to examine the contents of the resin composition that is the material of the connecting portion.

[0058] An optical fiber ribbon according to one embodiment of the present disclosure comprises a sub-ribbon having a plurality of optical fibers arranged in parallel and a collective coating layer that coats the plurality of optical fibers, and a connecting portion that intermittently connects the plurality of sub-ribbons arranged in parallel and adjacent sub-ribbons, and the connecting portion contains a cured product of the resin composition described above.

[0059] Fig. 4 is a schematic cross-sectional view showing an optical fiber ribbon according to an embodiment of the present disclosure. The optical fiber ribbon 100B shown in Fig. 4 includes sub-ribbons 50 each having a plurality of optical fibers 10 arranged in parallel and a collective coating layer 40 that coats the plurality of optical fibers 10, and connecting portions 20 that intermittently connect the plurality of parallel-arranged sub-ribbons 50 and adjacent sub-ribbons, the connecting portions 20 including a cured product of the resin composition described above. The optical fiber ribbon 100B shown in Fig. 4 is an intermittently connected optical fiber ribbon in which adjacent sub-ribbons 50 are connected by the connecting portions 20, so that connecting portions and non-connecting portions are intermittently provided between every two sub-ribbons in the longitudinal and width directions.

[0060] The sub-ribbon 50 has a plurality of optical fibers 10 arranged in parallel and a collective coating layer 40 that coats the plurality of optical fibers 10. Fig. 4 shows, as an example, a sub-ribbon having two optical fibers and a collective coating layer. The number of optical fibers included in the sub-ribbon may be two, three, four, five or more. There is no particular limitation on the number of optical fibers included in the sub-ribbon.

[0061] The optical fibers 10 may be coated with the batch coating layer 40 in a state where adjacent optical fibers 10 are arranged in parallel and in contact with each other. The optical fibers 10 may be coated with the batch coating layer 40 in a state where some or all of the optical fibers 10 are arranged in parallel with a fixed interval between them. The center-to-center distance F between adjacent optical fibers 10 in the sub-ribbon 50 in a cross section perpendicular to the longitudinal direction 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, the optical fibers can be easily placed in the V-groove of an existing jig used for fusion splicing, and an optical fiber ribbon with excellent batch fusion properties can be obtained.

[0062] The thickness T of the sub-ribbon 50 is not particularly limited and may be adjusted appropriately depending on the outer diameter of the optical fiber 10. The thickness T of the sub-ribbon 50 may be, for example, 164 μm or more and 285 μm or less.

[0063] In this embodiment, the connecting portions 20 may also be provided on both sides of the optical fiber ribbon. Although the thickness H of the connecting portions 20 is not shown in FIG. 4 , the thickness H is set in the same manner as in FIGS. 2 and 3 in this embodiment. In this embodiment, the surface 20a of the connecting portions 20 may also have a recess. In this embodiment, the thickness H of the connecting portions 20 is, for example, 80 μm or more and 125 μm or less. The range of 80 μm or more and 125 μm or less is an example, and the value of the thickness H is not limited to this numerical range. The connecting portions 20 may also be provided on both sides of the optical fiber ribbon. When the connecting portions 20 are provided on both sides of the optical fiber ribbon, the total thickness H of the connecting portions 20 is, for example, 90 μm or more and 150 μm or less. The range of 90 μm or more and 150 μm or less is an example, and the total thickness H of the connecting portions 20 is not limited to this numerical range.

[0064] The collective covering layer 40 can be formed using a resin material generally known as a ribbon material. Examples of the ribbon material include thermosetting resins such as silicone resin, epoxy resin, and urethane resin, and ultraviolet-curing resins such as epoxy acrylate, urethane acrylate, and polyester acrylate.

[0065] In the optical fiber ribbon of this embodiment, the optical fibers have connecting portions formed from the above-mentioned resin composition, making it difficult for the optical fibers to separate due to external forces, and preventing a deterioration in transmission characteristics.

[0066] The present disclosure will be described in more detail below by showing the results of evaluation tests using examples and comparative examples according to the present disclosure, but the present disclosure is not limited to these examples.

[0067] The following photopolymerizable compounds and photopolymerization initiators were prepared. ((Meth)acryloyl compounds (A)) M1604: nonylphenol EO-modified (meth)acrylate (manufactured by Miwon, trade name "Miramer (registered trademark) M1604", EO number: 4) ACMO (registered trademark): acryloylmorpholine (epoxy di(meth)acrylate (B1)) EBE3708: caprolactone-modified epoxy diacrylate having a bisphenol A skeleton (manufactured by Daicel-Ornix Corporation, trade name "EBECRYL3708") (EO-modified di(meth)acrylate (B2)) M2100: EO-modified diacrylate (manufactured by Miwon, trade name "Miramer M2100", EO number: 10) M2200: EO-modified diacrylate (manufactured by Miwon, trade name "Miramer M2200", EO number: 20) (EO-modified di(meth)acrylate (B3)) M240: EO-modified diacrylate (manufactured by Miwon, trade name "Miramer M240", EO number: 4) M2300: EO-modified diacrylate (manufactured by Miwon, trade name "Miramer M2300", EO number: 30) (Other (meth)acryloyl compounds (B)) Urethane diacrylate: reaction product of polypropylene glycol, 2,4-tolylene diisocyanate, and hydroxyethyl acrylate (Photopolymerization initiator) Omnirad 184: 1-hydroxycyclohexylphenyl ketone (manufactured by IGM Resins B.V.) Omnirad TPO H: 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (manufactured by IGM Resins B.V.)

[0068] [Resin Composition for Optical Fiber Connection] A photopolymerizable compound and a photopolymerization initiator were mixed in the amounts (parts by mass) shown in Table 1 to prepare the resin compositions of each test example. Test Examples 1 to 3 correspond to working examples, and Test Examples 4 to 6 correspond to comparative examples. The compounds contained in the resin composition can be identified by chemical analysis techniques such as gel permeation chromatography, infrared spectroscopy, gas chromatography-mass spectrometry, and nuclear magnetic resonance spectroscopy, or by combining multiple chemical analysis techniques. The chemical analysis techniques used are not limited to these. By combining multiple chemical analysis techniques, the content of the compound relative to the total amount of photopolymerizable compound can also be measured.

[0069] (Viscosity) The viscosity of the resin composition at 60°C was measured using a rheometer ("MCR-102" manufactured by Anton Paar) with a cone plate CP25-2 and a shear rate of 10 s －１ The measurement was carried out under the following conditions.

[0070] [Resin Film] Using a spin coater, the resin composition of each test example was applied onto a polyethylene terephthalate (PET) film. Here, Toyobo Ester (registered trademark) Film E5101, a 188 μm-thick PET film, was used. Then, under a nitrogen atmosphere, an electrodeless UV lamp system (D bulb, manufactured by Heraeus) was used to apply the resin composition onto a polyethylene terephthalate (PET) film with an integrated light intensity of 1000 mJ / cm. ２ and an illumination intensity of 1500 mW / cm ２ The resin layer was peeled off from the PET film to obtain a resin film.

[0071] (Young's Modulus) A resin film was punched into a dumbbell shape according to JIS K 7127 Type 5, and pulled using a tensile tester at 23±2°C, 50±10% RH, at a pulling rate of 1 mm / min, and with a gauge length of 25 mm, to obtain a stress-strain curve. The Young's modulus (MPa) of the resin film was calculated by dividing the stress obtained by the secant equation at 2.5% strain by the cross-sectional area of ​​the resin film.

[0072] (Breaking Strength and Breaking Elongation) The resin film was punched into a dumbbell shape according to JIS K 7127 Type 5 and pulled using a tensile tester at 23±2°C, 50±10% RH, a pulling rate of 50 mm / min, and a gauge length of 25 mm to obtain a stress-strain curve. The breaking strength (MPa) of the resin film was determined by dividing the force at break by the cross-sectional area of ​​the resin film. The breaking elongation (%) of the resin film was determined by dividing the displacement at break by the gauge length.

[0073] (Peel Strength) Toyobo Ester (registered trademark) Film E5101, a 188 μm thick PET film, was used as the substrate. The resin composition of each test example was applied onto the substrate using a spin coater. Then, under a nitrogen atmosphere, an electrodeless UV lamp system (D bulb, manufactured by Heraeus) was used to apply an integrated light dose of 100±2 mJ / cm. ２ and illuminance 100±2 mW / cm ２ The resin composition was cured by irradiating it with ultraviolet light for 30 seconds under the conditions of (a) and (b). As a result, a resin layer having a thickness of 120±10 μm was formed on the substrate (a sample for measuring peel strength). The connecting resin layer was peeled off from the substrate, and the peel strength was measured.

[0074] A test piece for measuring peel strength having a width of 15 mm was prepared from the sample for measuring peel strength. A 180-degree peel test was performed on the test piece using a Techno Graph TGE-5k (manufactured by MinebeaMitsumi Inc.) to peel the connecting resin layer from the PET film at a tensile speed of 200 mm / min. The measured value at the flat point of the measurement result was taken as the peel strength (N / 15 mm). When the peel strength was 3.0 (N / 15 mm) or more, it was evaluated as A; when the peel strength was 1.0 (N / 15 mm) or more and less than 3.0 (N / 15 mm), it was evaluated as B; and when the peel strength was less than 1.0 (N / 15 mm), it was evaluated as C. When the evaluation was A, the connecting resin layer and the substrate were firmly bonded, and there was no problem in using the cured product of the resin composition as the connecting part 20. When the evaluation was B, there was no problem in using the cured product of the resin composition as the connecting part 20. If the evaluation is C, the adhesive strength between the connecting resin layer and the substrate is low, and when the cured product of the resin composition is used as the connecting part 20, peeling (destruction of the adhesive part) occurs between the connecting part 20 and the coating resin layer 34.

[0075] [Optical Fiber Ribbon] Twelve supply bobbins around which optical fibers were wound were prepared. The 12 optical fibers unwound from each supply bobbin were passed through a coating die of a manufacturing device while being in contact with each other, and the resin composition S was applied to the outer circumference of each of the two optical fibers by the coating die. The resin composition S can be formed using a resin material generally known to form a resin coating layer on optical fibers. Examples of the resin material include ultraviolet-curable resins such as urethane (meth)acrylate and epoxy (meth)acrylate. The optical fibers coated with the resin composition S were irradiated with ultraviolet light using a curing device to harden the resin composition S. Six sub-ribbons were thus produced. Next, the resin composition of each test example was intermittently applied between adjacent sub-ribbons using a dispenser. The resin composition coated on the sub-ribbons was irradiated with ultraviolet light using a curing device to harden the resin composition, forming a joint, and the connected optical fiber ribbon was wound onto a take-up bobbin. As a result, an optical fiber ribbon was obtained in which the connected portions (bonded portions) were about 30 mm long and the non-connected portions (non-bonded portions) were about 110 mm long and intermittently connected.

[0076] The non-bonded portion between the two bonded portions between the third and fourth sub-ribbons from the end of the optical fiber ribbon was manually spread widthwise, and the fracture behavior of the bonded portion was observed. The distance (mm) between the sub-ribbons when the bonded portion completely cohesively or interfacially failed was measured at either of the bonded portions at both ends of the spread non-bonded portion.

[0077]

[0078] 10... Optical fiber 20... Connection portion 20a... Surface of connection portion 21... Non-connection portion 31... Glass fiber 32... Primary resin layer 33... Secondary resin layer 34... Coating resin layer 40... Collective coating layer 50... Sub-ribbon 100A, 100B... Optical fiber ribbon D... Outer diameter of glass fiber F... Center-to-center distance of optical fibers H... Thickness of connection portion T... Thickness of sub-ribbon

Claims

1. A resin composition for optical fiber connection comprising: a photopolymerizable compound containing a monofunctional (meth)acryloyl compound (A) and a bifunctional (meth)acryloyl compound (B); and a photopolymerization initiator, wherein the (meth)acryloyl compound (B) comprises an epoxy di(meth)acrylate having a bisphenol A skeleton and an ethylene oxide-modified di(meth)acrylate having 6 to 28 ethylene oxide groups.

2. The resin composition according to claim 1, wherein the epoxy di(meth)acrylate is caprolactone-modified.

3. A resin composition according to claim 2, wherein the content of the caprolactone-modified epoxy di(meth)acrylate is 20 parts by mass or more and 40 parts by mass or less per 100 parts by mass of the total amount of the photopolymerizable compound.

4. A resin composition according to any one of claims 1 to 3, wherein the (meth)acryloyl compound (A) includes a (meth)acrylate having a phenoxy group.

5. A resin composition according to claim 4, wherein the content of the (meth)acrylate having a phenoxy group is 10 parts by mass or more and 30 parts by mass or less per 100 parts by mass of the total amount of the photopolymerizable compound.

6. An optical fiber ribbon comprising a plurality of optical fibers arranged in parallel and a connecting portion that intermittently connects adjacent optical fibers, wherein the connecting portion comprises a cured product of the resin composition described in any one of claims 1 to 5.

7. An optical fiber ribbon comprising: a sub-ribbon having a plurality of optical fibers arranged in parallel and a collective coating layer that coats said plurality of optical fibers; and a connecting portion that intermittently connects said plurality of sub-ribbons arranged in parallel and adjacent said sub-ribbons, said connecting portion comprising a cured product of the resin composition described in any one of claims 1 to 5.

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