Patent Description:
The present application claims priority based on <CIT>.

Generally, an optical fiber has a thin colored outermost layer called as ink layer in order to identify an optical fiber consisting of a glass fiber and a coating resin layer covering the glass fiber (for example, refer to Patent Literature <NUM>).

An optical fiber ribbon including a plurality of optical fibers arranged and collectively integrated with a coating layer is known. For example, for densification and thinning of an optical fiber cable that accommodates an optical fiber ribbon, optical fibers having a thin outer diameter of <NUM> or less connected with a resin are disclosed in Patent Literature <NUM>.

Further relevant prior art is <CIT>, which discloses an optical fiber including a glass fiber and a coating resin layer with which the glass fiber is covered, wherein the coating resin layer includes tin and a cured ultraviolet curable resin composition containing <NUM>,<NUM>,<NUM>-trimethylbenzoyldiphenyl phosphine as a photoinitiator, a percentage of uncured components having a molecular weight of <NUM> or less included in the coating resin layer is <NUM>% by mass or less, and a fraction of an amount of a phosphorus-tin complex with respect to an amount of hydrocarbon on the surface of coating resin layer is <NUM> ppm or less.

The optical fiber ribbon according to the present invention is defined in appended claim <NUM>.

A small-diameter optical fiber is more susceptible to lateral pressure due to bending than an optical fiber having an outer diameter of <NUM>, when the optical fiber ribbon is wound around a bobbin or made into an optical cable, so that the lateral pressure resistance is weak and transmission loss tends to increase. Further, in the case of an optical fiber ribbon having small-diameter optical fibers, the contact area between the optical fibers and the ribbon resin coating the optical fibers is small, so that low adhesion of the ribbon resin to the optical fibers tends to cause peeling of the ribbon resin. On the other hand, excessively high adhesion of the ribbon resin to the optical fiber tends to cause difficulty in separation of the optical fibers into single fibers when fixing a terminal of the optical fiber ribbon.

An object of the present disclosure is to provide an optical fiber ribbon composed of small-diameter optical fibers that can achieve both peeling resistance and single-fiber separability and suppress an increase in transmission loss of an optical cable.

According to the present disclosure, an optical fiber ribbon composed of small-diameter optical fibers that can achieve both peeling resistance and single-fiber separability and suppress an increase in transmission loss of an optical cable can be provided.

First, the embodiments of the present disclosure will be listed and described. The optical fiber ribbon according to the present invention is as defined by appended claim <NUM>.

The optical fiber ribbon according to the present invention can achieve both peeling resistance and single-fiber separability, can be bent sharply when densely accommodated in a cable, and can suppress an increase in transmission loss during bobbin winding or cable making.

Due to superior single-fiber separability of optical fibers, it is preferable that the amount of the phosphorus-tin complex be <NUM> ppm or more and <NUM> ppm or less. Due to easiness in obtaining an optical fiber ribbon having excellent fusion splicing property, it is preferable that the average distance between the centers of adjacent optical fibers among the plurality of optical fibers be <NUM> or more and <NUM> or less.

Due to easiness in controlling the adhesion between the colored secondary resin layer and the ribbon resin, the resin composition contains a polyfunctional monomer having a bisphenol moiety, and a silicone-based lubricant.

Due to superior single-fiber separability of the optical fibers, the resin composition may further contain <NUM>-hydroxycyclohexyl phenyl ketone as a photopolymerization initiator.

Due to more suppression of increase in transmission loss of the optical cable, it is preferable that the Young's modulus of the colored secondary resin layer be <NUM> MPa or more at <NUM>.

Due to easy deformation of the optical fiber ribbon when accommodated in a cable, the optical fiber ribbon according to the present embodiment may have a connecting portion and a non-connecting portion intermittently in the longitudinal direction and the width direction.

Due to easy deformation of the optical fiber ribbon when accommodated in a cable, the connecting resin layer may have a recess at the portion connecting adjacent optical fibers among the plurality of optical fibers.

In the optical fiber cable according to one aspect of the present disclosure, the optical fiber ribbon is incorporated in a cable. The optical fiber cable provided with the optical fiber ribbon according to the present embodiment can achieve both high lateral pressure characteristics and low transmission loss.

Specific examples of the optical fiber ribbon and the optical fiber cable according to embodiments of the present disclosure will be described with reference to drawings on an as needed basis. The present disclosure is not limited to these examples, being shown in the scope of claims and is only limited by the scope of the claims. In the following description, the same elements will be denoted by the same reference numerals in the description of the drawings, and duplicate description will be omitted. In the present embodiment, a (meth)acrylate means an acrylate or a methacrylate corresponding thereto, and the same applies to other similar expressions such as (meth)acryloyl.

The optical fiber ribbon according to the present embodiment includes a plurality of optical fibers arranged in parallel which are coated with a ribbon resin. The ribbon resin connects the plurality of optical fibers to form a connecting resin layer.

<FIG> is a schematic cross-sectional view showing an example of an optical fiber. An optical fiber <NUM> includes a glass fiber <NUM> including a core <NUM> and a cladding <NUM>, and a coating resin layer <NUM> including a primary resin layer <NUM> and a colored secondary resin layer <NUM> provided on the outer periphery of a glass fiber <NUM>.

The cladding <NUM> surrounds the core <NUM>. The core <NUM> and the cladding <NUM> are glass such as silica glass. For example, the core <NUM> may be made of silica glass with addition of germanium or pure silica glass, and the cladding <NUM> may be made of pure silica glass or silica glass with addition of fluorine.

In <FIG>, the outer diameter of the optical fiber <NUM> is <NUM> or less, and may be <NUM> or more and <NUM> or less, or <NUM> or more and <NUM> or less. The outer diameter (D2) of the glass fiber <NUM> is about <NUM> to <NUM>, and the diameter (D1) of the core <NUM> constituting the glass fiber <NUM> may be about <NUM> to <NUM>. The thickness of each of the primary resin layer <NUM> and the colored secondary resin layer <NUM> may be about <NUM> to <NUM>.

The colored secondary resin layer <NUM> may be formed by curing, for example, an ultraviolet curable resin composition containing a photopolymerizable compound, a photopolymerization initiator, and a pigment. The resin composition contains <NUM>,<NUM>,<NUM>-trimethylbenzoyldiphenylphosphine oxide (Omnirad TPO, manufactured by IGM Resins, hereinafter abbreviated as "TPO") as a photopolymerization initiator, which is an essential component, and the colored secondary resin layer <NUM> contains a cured product of a resin composition containing <NUM>,<NUM>,<NUM>-trimethylbenzoyldiphenylphosphine as a photopolymerization initiator.

TPO, which is a phosphorus-based photopolymerization initiator, is effective for enhancing the curability of the coating resin layer. On the other hand, phosphorus (P) is known to form a complex (P-Sn complex) with tin (Sn). A tin catalyst may be used as a catalyst for urethane synthesis, in which case tin remains in urethane (meth)acrylate. In the case where TPO is used as the photopolymerization initiator and urethane (meth)acrylate is used as the photopolymerizable compound, phosphorus derived from TPO and tin mixed in the urethane (meth)acrylate form a P-Sn complex in the secondary resin layer. In the case where the P-Sn complex is localized at the surface of the secondary resin layer, the adhesion of the interface between the secondary resin layer and the ribbon resin during production of the optical fiber ribbon is lowered, and peeling is likely to occur during the production of the optical fiber ribbon.

In contrast, since the optical fiber of the present embodiment has a content of phosphorus in the colored secondary resin layer <NUM> of <NUM> mass% or more and <NUM> mass% or less, and an amount of the P-Sn complex at the surface of the colored secondary resin layer <NUM> of <NUM> ppm or more and <NUM> ppm or less, both curability and adhesion of the colored secondary resin layer can be achieved.

The content of phosphorus may be <NUM> mass% or more and <NUM> mass% or less, or <NUM> mass% or more and <NUM> mass% or less. The amount of phosphorus complexed with tin may be adjusted by the amount of TPO compounded in the resin composition. The content of phosphorus may be measured by ICP emission spectrometry. Specifically, <NUM> of sulfuric acid and <NUM> of nitric acid are added to <NUM> of a resin composition for forming the colored secondary resin layer and the mixture is heated for <NUM> minutes. Then, <NUM> of perchloric acid is added thereto and the mixture is heated until insoluble substances disappear. The mixture is then diluted with water to a volume of <NUM> for measurement by ICP emission spectrometry.

Due to superior single-fiber separability of the optical fibers, the amount of the P-Sn complex is preferably <NUM> ppm or more and <NUM> ppm or less, more preferably <NUM> ppm or more and <NUM> ppm or less, and still more preferably <NUM> ppm or more and <NUM> ppm or less. The amount of the P-Sn complex may be adjusted by the amount of TPO and urethane (meth)acrylate compounded in the resin composition. The amount of P-Sn complex may be measured by analyzing the surface of the coating resin layer using TOF-SIMS. In the present specification, the amount of the P-Sn complex (ppm) is expressed in a mass ratio.

The resin composition may further contain another photopolymerization initiator. The other photopolymerization initiator may be appropriately selected from known radical photopolymerization initiators for use. Examples of the other photopolymerization initiators include <NUM>-hydroxycyclohexyl phenyl ketone (Omnirad <NUM>, manufactured by IGM Resins), <NUM>,<NUM>-dimethoxy-<NUM>-phenylacetophenone, <NUM>-(<NUM>-isopropylphenyl)-<NUM>-hydroxy-<NUM>-methylpropane-<NUM>-one, bis(<NUM>,<NUM>-dimethoxybenzoyl)-<NUM>,<NUM>,<NUM>-trimethylpentylphosphine oxide, <NUM>-methyl-<NUM>-[<NUM>-(methylthio)phenyl]-<NUM>-morpholino-propane-<NUM>-one (Omnirad <NUM>, manufactured by IGM Resins) and bis(<NUM>,<NUM>,<NUM>-trimethylbenzoyl)phenylphosphine oxide (Omnirad <NUM>, manufactured by IGM Resins).

As the other photopolymerization initiator, a photopolymerization initiator that forms no complex with tin is preferred, and Omnirad <NUM> is more preferred. The resin composition including <NUM>,<NUM>,<NUM>-trimethylbenzoyldiphenylphosphine oxide and <NUM>-hydroxycyclohexyl phenyl ketone in combination as a photopolymerization initiator enables the single-fiber separability of the optical fibers to be further improved.

Due to containing a pigment, the colored secondary resin layer <NUM> forms a colored layer that serves as ink layer for identifying an optical fiber. Examples of the pigment include a colored pigment such as carbon black, titanium oxide and zinc flower, a magnetic powder such as γ-Fe<NUM>O<NUM>, a mixed crystal of γ-Fe<NUM>O<NUM> and γ-Fe<NUM>O<NUM> CrO<NUM>, cobalt ferrite, cobalt-deposited iron oxide, barium ferrite, Fe-Co and Fe-Co-Ni, an inorganic pigment such as MIO, zinc chromate, strontium chromate, aluminum tripolyphosphate, zinc, alumina, glass and mica; and an organic pigment such as an azo-based pigment, a phthalocyanine-based pigment, and a dyed lake pigment. The pigment may be subjected to treatments such as various types of surface modification and pigment hybridization.

The photopolymerizable compound may contain an oligomer and a monomer. Examples of the oligomer include a urethane (meth)acrylate and an epoxy (meth)acrylate.

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.

Examples of the polyol compound include polytetramethylene glycol, polypropylene glycol, and bisphenol A/ethylene oxide addition diol. From the viewpoint of adjusting Young's modulus, the number average molecular weight of the polyol compound may be <NUM> or more and <NUM> or less. Examples of the polyisocyanate compound include <NUM>,<NUM>-tolylene diisocyanate, <NUM>,<NUM>-tolylene diisocyanate, isophorone diisocyanate, and dicyclohexylmethane <NUM>,<NUM>'-diisocyanate. Examples of the hydroxyl group-containing (meth)acrylate compound include <NUM>-hydroxyethyl (meth)acrylate, <NUM>-hydroxybutyl (meth)acrylate, <NUM>,<NUM>-hexanediol mono(meth)acrylate, pentaerythritol tri(meth)acrylate, <NUM>-hydroxypropyl (meth)acrylate and tripropylene glycol (meth)acrylate.

An organometallic catalyst may be used as a catalyst for synthesizing urethane (meth)acrylate, and an organotin compound may be used from the viewpoint of manufacturability. Examples of the organotin compound include dibutyltin dilaurate, dibutyltin diacetate, dibutyltin malate, dibutyltin bis(<NUM>-ethylhexyl mercaptoacetate), dibutyltin bis(isooctyl mercaptoacetate), and dibutyltin oxide. From the viewpoint of easy availability or catalytic performance, it is preferable to use dibutyltin dilaurate or dibutyltin diacetate as the catalyst. Although it is desirable to use a large amount of catalyst from the viewpoint of productivity, it is desirable to control the amount in an appropriate range to avoid precipitation on the surface of the resin layer which easily reduces the adhesion between the ribbon resin and the colored secondary resin layer.

A lower alcohol having <NUM> or less carbon atoms may be used for synthesizing the urethane (meth)acrylate. Examples of the lower alcohol include methanol, ethanol, <NUM>-propanol, <NUM>-propanol, <NUM>-butanol, <NUM>-butanol, <NUM>-methyl-<NUM>-propanol, <NUM>-pentanol, <NUM>-pentanol, <NUM>-pentanol, <NUM>-methyl-<NUM>-butanol, <NUM>-methyl-<NUM>-butanol, <NUM>-methyl-<NUM>-butanol, <NUM>-methyl-<NUM>-butanol, and <NUM>,<NUM>-dimethyl-<NUM>-propanol.

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.

As the monomer, a monofunctional monomer having one polymerizable group and a polyfunctional monomer having two or more polymerizable groups may be used. Two or more types of monomers may be mixed for use.

Examples of the monofunctional monomer include (meta)acrylate-based monomers such as 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, <NUM>-ethylhexyl (meth)acrylate, n-octyl (meta)acrylate, isooctyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, <NUM>-phenoxyethyl (meth)acrylate, <NUM>-phenoxybenzyl acrylate, phenoxydiethylene glycol acrylate, phenoxypolyethylene glycol acrylate, <NUM>-tert-butylcyclohexanol acrylate, tetrahydrofurfuryl (meth)acrylate, benzyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, dicyclopentanyl (meth)acrylate, nonylphenolpolyethylene glycol (meta)acrylate, nonylphenol EO-modified acrylate, nonylphenoxypolyethylene glycol (meth)acrylate, and isobornyl (meth)acrylate; carboxyl group-containing monomers such as (meth)acrylic acid, (meth)acrylic acid dimer, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, and ω-carboxy-polycaprolactone (meth)acrylate; heterocyclic ring-containing (meth)acrylates such as N-acryloyl morpholine, N-vinylpyrrolidone, N-vinylcaprolactam, N-acryloyl piperidine, N-methacryloyl piperidine, N-acryloyl pyrrolidine, <NUM>-(<NUM>-pyridyl)propyl (meth)acrylate, and cyclic trimethylolpropane formal acrylate; maleimide-based monomers such as maleimide, N-cyclohexyl maleimide, and N-phenyl maleimide; N-substituted amide-based 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-based monomers such as aminoethyl (meth)acrylate, aminopropyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, and tert-butylaminoethyl (meth)acrylate; and succinimide-based monomers such as N-(meth)acryloyl oxymethylene succinimide, and N-(meth)acryloyl-<NUM>-oxyhexamethylene succinimide, and N-(meth)acryloyl-<NUM>-oxyoctamethylene succinimide.

Examples of the polyfunctional monomer 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 adduct of bisphenol compound, tetraethylene glycol di(meth)acrylate, neopentyl glycol hydroxypivalate di(meth)acrylate, <NUM>,<NUM>-butanediol di(meth)acrylate, <NUM>,<NUM>-hexanediol di(meth)acrylate, <NUM>,<NUM>-nonanediol di(meth)acrylate, <NUM>,<NUM>-dodecanediol di(meth)acrylate, <NUM>,<NUM>-tetradecanediol di(meth)acrylate, <NUM>,<NUM>-hexadecane diol di(meth)acrylate, <NUM>,<NUM>-eicosane diol di(meth)acrylate, isopentyl diol di(meth)acrylate, <NUM>-ethyl-<NUM>,<NUM>-octane diol di(meth)acrylate, di(meth)acrylate of EO adduct of bisphenol compound, trimethylolpropane tri(meth)acrylate, trimethyloloctane tri(meth)acrylate, trimethylolpropane polyethoxy tri(meth)acrylate, trimethylolpropane polypropoxy tri(meth)acrylate, trimethylolpropane polyethoxypolypropoxy tri(meth)acrylate, tris[(meth)acryloyloxyethyl]isocyanurate, pentaerythritol tri(meth)acrylate, pentaerythritol polyethoxy tetra(meth)acrylate, pentaerythritol polypropoxy tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and caprolactone-modified tris[(meta)acryloyloxyethyl]isocyanurate.

Examples of the bisphenol compound include bisphenol A, bisphenol AP, bisphenol B, bisphenol BP, bisphenol C, and bisphenol E. As the polyfunctional monomer, a polyfunctional monomer having a bisphenol moiety is used, and in particular, it is preferable to use a polyfunctional monomer having a bisphenol A moiety. By adjusting the amount of the polyfunctional monomer having a bisphenol A moiety, the amount of surface precipitation of the P-Sn complex can be easily adjusted. As the polyfunctional monomer having a bisphenol moiety A, an epoxy acrylate having a bisphenol A moiety n may be used.

From the viewpoint of further enhancing the adhesion to the ribbon resin, the content of the polyfunctional monomer having a bisphenol moiety in the colored secondary resin layer based on the total amount of the resin composition for forming the colored secondary resin layer may be <NUM> mass% or more and <NUM> mass% or less, <NUM> mass% or more and <NUM> mass% or less, or <NUM> mass% or more and <NUM> mass% or less.

The resin composition may further contain a silane coupling agent, an inorganic oxide particle, a lubricant, a photoacid generator, a leveling agent, an antifoaming agent, an antioxidant, a sensitizer, etc..

The silane coupling agent is not particularly limited as long as it causes no inhibition in curing of the resin composition. Examples of the silane coupling agent include tetramethyl silicate, tetraethyl silicate, mercaptopropyl trimethoxysilane, vinyltrichlorosilane, vinyltriethoxysilane, vinyltris(β-methoxy-ethoxy)silane, and β-(<NUM>,<NUM>-epoxylcyclohexyl)-ethyltrimethoxysilane, dimethoxydimethylsilane, diethoxydimethylsilane, <NUM>-acryloxypropyl trimethoxysilane, <NUM>-glycidoxypropyl trimethoxysilane, <NUM>-glycidoxypropylmethyl diethoxysilane, <NUM>-methacryloxypropyl trimethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, N-((<NUM>-aminoethyl)-γ-aminopropyltrimethyl dimethoxysilane, N-phenyl-<NUM>-aminopropyl trimethoxysilane, <NUM>-chloropropyl trimethoxysilane, <NUM>-mercaptopropyl trimethoxysilane, <NUM>-aminopropyl trimethoxysilane, bis-[<NUM>-(triethoxysilyl)propyl]tetrasulfide, bis-[<NUM>-(triethoxysilyl)propyl] disulfide, γ-trimethoxysilylpropyl dimethylthiocarbamyl tetrasulfide, and γ-trimethoxysilylpropyl benzothiazyl tetrasulfide.

The inorganic oxide particle is not particularly limited. From the viewpoint of excellent dispersibility in the resin composition and easy adjustment of Young's modulus, it is preferable that the inorganic oxide particle be a particle containing at least one selected from the group consisting of silicon dioxide (silica), zirconium dioxide (zirconia), aluminum oxide (alumina), magnesium oxide (magnesia), titanium oxide (titania), tin oxide, and zinc oxide. It is more preferable to use silica particle as the inorganic oxide particle, from the viewpoints of low cost, easy surface treatment, ultraviolet permeability, and capability of imparting appropriate hardness to a cured product easily.

It is preferable that the inorganic oxide particle be hydrophobic. Specifically, it is preferable that the surface of the inorganic oxide particle be hydrophobically treated with a silane compound. The hydrophobic treatment means introducing a hydrophobic group into the surface of an inorganic oxide particle. The inorganic oxide particle with a hydrophobic group introduced has excellent dispersibility in a resin composition. Examples of the hydrophobic group may include an ultraviolet curable reactive group such as a (meth)acryloyl group and a vinyl group, or a non-reactive group such as a hydrocarbon group (for example, alkyl group) and an aryl group (for example, phenyl group). In the case where the inorganic oxide particle has a reactive group, a resin layer having a high Young's modulus may be easily formed.

Examples of the silane compound having a reactive group include a silane compound such as <NUM>-methacryloxypropyl trimethoxysilane, <NUM>-acryloxypropyl trimethoxysilane, <NUM>-methacryloxypropyl triethoxysilane, <NUM>-acryloxypropyl triethoxysilane, <NUM>-methacryloxyoctyl trimethoxysilane, <NUM>-acryloxyoctyl trimethoxysilane, <NUM>-octenyl trimethoxysilane, vinyl trimethoxysilane, and vinyl triethoxysilane.

Examples of the silane compound having an alkyl group include methyl trimethoxysilane, dimethyl dimethoxysilane, ethyl trimethoxysilane, propyl trimethoxysilane, butyl trimethoxysilane, pentyl trimethoxysilane, hexyl trimethoxysilane, and octyl trimethoxysilane, methyl triethoxysilane, dimethyl diethoxysilane, ethyl triethoxysilane, propyl triethoxysilane, butyl triethoxysilane, pentyl triethoxysilane, hexyl triethoxysilane, and octyl triethoxysilane.

The inorganic oxide particle may be dispersed in a dispersion medium when added to the resin composition. By using the inorganic oxide particles dispersed in the dispersion medium, the inorganic oxide particles may be uniformly dispersed in the resin composition, so that the storage stability of the resin composition can be improved. The dispersion medium is not particularly limited as long as it causes no inhibition of the curing of the resin composition. The dispersion medium may be reactive or non-reactive.

As the reactive dispersion medium, a monomer such as a (meth)acryloyl compound or an epoxy compound may be used. Examples of the (meth)acrylic compound include <NUM>,<NUM>-hexanediol di(meth)acrylate, EO-modified bisphenol A di(meth)acrylate, polyethylene glycol di(meth)acrylate, PO-modified bisphenol A di(meth)acrylate, polypropylene glycol di(meth)acrylate, polytetramethylene glycol di(meth)acrylate, <NUM>-hydroxy-<NUM>-phenoxypropyl acrylate, (meth)acrylic acid adduct of propylene glycol diglycidyl ether, (meth)acrylic acid adduct of tripropylene glycol diglycidyl ether, and (meth)acrylic acid adduct of glycerol diglycidyl ether. As the dispersion medium, a (meth)acryloyl compound such as the monomer described above may be used.

As the non-reactive dispersion medium, a ketone solvent such as methyl ethyl ketone (MEK) and methyl isobutyl ketone (MIBK), an alcohol solvent such as methanol (MeOH) and propylene glycol monomethyl ether (PGME), or an ester solvent such as propylene glycol monomethyl ether acetate (PGMEA) may be used. In the case of the non-reactive dispersion medium, after mixing of the base resin and inorganic oxide particles dispersed in a dispersion medium, a part of the dispersion medium may be removed to prepare a resin composition.

From the viewpoint of excellent dispersibility in the resin composition, the average primary particle size of the inorganic oxide particles may be <NUM> or less, preferably <NUM> or less, more preferably <NUM> or less, still more preferably <NUM> or less. From the viewpoint of excellent strength after curing, the average primary particle size of the inorganic oxide particles is preferably <NUM> or more, more preferably <NUM> or more. The average primary particle size may be measured by, for example, image analysis of an electron micrograph, a light scattering method, a BET method, or the like. The dispersion medium in which the primary particles of the inorganic oxide having a small particle size are dispersed is visually transparent. The dispersion medium in which the primary particles having a relatively large particle size (<NUM> or more) are dispersed is cloudy, though no sediment is observed.

The content of the inorganic oxide particles based on the total amount of the resin composition may be <NUM> mass% or more and <NUM> mass% or less, <NUM> mass% or more and <NUM> mass% or less, or <NUM> mass% or more and <NUM> mass% or less. With a content of the inorganic oxide particles of <NUM> mass% or more, a tough cured product tends to be formed. With a content of the inorganic oxide particles of <NUM> mass% or less, a cured product in which the inorganic oxide particles are suitably dispersed tends to easily be formed. The total amount of the resin composition and the total amount of the cured product of the resin composition may be substantially the same.

The lubricant is a silicone-based lubricant such as silicone oil. The silicone oil may be a high molecular weight silicone oil or a modified silicone oil having a part of the dimethylsiloxane moiety modified with an organic group. Examples of the modified silicone oil include a polyether-modified, amine-modified, epoxy-modified, mercapto-modified, (meth)acrylic-modified, or carboxyl-modified silicone oil. The colored secondary resin layer has lower curability than the secondary resin layer containing no pigment, and the adhesive force with the tape resin layer tends to increase. However, by using a resin composition containing a silicone-based lubricant, the adhesion between the colored secondary resin layer and the ribbon resin tends to be easily adjusted.

The content of the silicone-based lubricant in the colored secondary resin layer based on the total amount of the resin composition for the secondary resin layer is preferably <NUM> mass% or less, more preferably <NUM> mass% or more and <NUM> mass% or less. With a too small molecular weight, the silicone-based lubricant tends to precipitate, so that the adhesion to the connecting resin layer or the primary resin layer decreases. With a too large molecular weight of the silicone-based lubricant, the compatibility with the resin component decreases. It is preferable that the average molecular weight of the silicone oil be <NUM> or more and <NUM> or less.

As the photoacid generator, an onium salt having an A+B- structure may be used. Examples of the photoacid generator include a sulfonium salt such as UVACURE1590 (manufactured by Daicel-Cytec), CPI-100P, 110P, and <NUM> (manufactured by San-Apro), and an iodonium salt such as Omnicat <NUM> (manufactured by IGM Resins), WPI-<NUM> (manufactured by Fujifilm Wako Pure Chemical Corporation), and Rp-<NUM> (manufactured by Rhodia Japan).

The Young's modulus of the colored secondary resin layer at <NUM> is preferably <NUM> MPa or more, more preferably <NUM> MPa or more, and still more preferably <NUM> MPa or more. The Young's modulus of the colored secondary resin layer at <NUM> may be <NUM> MPa or less, <NUM> MPa or less, <NUM> MPa or less, or <NUM> MPa or less. With a Young's modulus of the colored secondary resin layer of <NUM> MPa or more, the lateral pressure resistance characteristics are easily improved, while with a Young's modulus of <NUM> MPa or less, the colored secondary resin layer has an appropriate breaking elongation to be hardly broken during coating removal, resulting in excellent coating removability.

The primary resin layer <NUM> may be formed by curing an ultraviolet curable resin composition containing a photopolymerizable compound, a photopolymerization initiator, and a silane coupling agent. The polymerizable compound, the photopolymerization initiator, and the silane coupling agent may be appropriately selected from the resin compositions described as examples for forming the colored secondary resin layer. However, the resin composition for forming the primary resin layer has a composition different from the resin composition for forming the colored secondary resin layer.

From the viewpoint of suppressing the generation of voids in the optical fiber, the Young's modulus of the primary resin layer at <NUM> is preferably <NUM> MPa or more and <NUM> MPa or less, more preferably <NUM> MPa or more and <NUM> MPa or less, and still more preferably <NUM> MPa or more and <NUM> MPa or less.

The characteristics of the optical fiber used in the present disclosure may include, for example, a mode field diameter of <NUM> or more and <NUM> or less at a wavelength of <NUM>, a cable cutoff wavelength of <NUM> or less, and a loss increase of <NUM> dB or less at a wavelength of <NUM> when wound with <NUM> turns around a mandrel having a radius of <NUM> (per <NUM> turns), or a loss increase of <NUM> dB or less at a wavelength of <NUM> when wound with <NUM> turns around a mandrel having a radius of <NUM> (per <NUM> turns).

<FIG> is a schematic cross-sectional view showing an optical fiber ribbon according to an embodiment. An optical fiber ribbon <NUM> has a plurality of optical fibers <NUM> and a connecting resin layer <NUM> in which the optical fibers <NUM> are (integrally) coated with a ribbon resin and connected. In <FIG>, four optical fibers <NUM> are shown as an example, though the number thereof is not particularly limited.

The optical fibers <NUM> in contact with each other in parallel may be integrated, or a part or all of the optical fibers <NUM> in parallel at regular intervals may be integrated. However, in the case where a part or all of the optical fibers <NUM> in parallel at regular intervals are integrated, the average distance F between the centers of the adjacent optical fibers <NUM> may be <NUM> or more and <NUM> or less. In the case where the distance between the centers is controlled to <NUM> or more and <NUM> or less, it is easy to place the optical fibers in existing V-grooves, so that an optical fiber ribbon having excellent batch fusion property can be obtained. The thickness T of the optical fiber ribbon <NUM> may be <NUM> or more and <NUM> or less, though depending on the outer diameter of the optical fiber <NUM>.

The resin composition for the ribbon may contain urethane (meth)acrylate, a monomer and a photopolymerization initiator. The urethane (meth)acrylate, the monomer and the photopolymerization initiator may be appropriately selected from the resin compositions for forming the colored secondary resin layer described as examples. By containing a cured product of urethane (meth)acrylate in the ribbon resin (connecting resin), the elasticity of the connecting resin layer can be improved.

The ribbon resin may further contain a silicone-based lubricant. Due to containing a silicone-based lubricant, the ribbon resin can suppress the sticking of the optical fiber ribbons to each other, and allows the loss increase to be easily reduced when made into a cable.

The Young's modulus of the ribbon resin at <NUM> may be <NUM> MPa or more and <NUM> MPa or less, or <NUM> MPa or more and <NUM> MPa or less, from the viewpoint of ensuring compatibility between the lateral pressure resistance characteristics and flexibility of the optical fiber ribbon.

<FIG> is a schematic cross-sectional view showing an example of the optical fiber ribbon having optical fibers integrated in parallel at regular intervals. An optical fiber ribbon 100A shown in <FIG> includes six sets of two optical fibers <NUM> at regular intervals connected by a ribbon resin. The ribbon resin forms a connecting resin layer <NUM>.

In the case where the optical fibers <NUM> are arranged in parallel at regular intervals, that is, in the case where the adjacent optical fibers <NUM> are joined through the ribbon resin without contacting each other, the thickness of the connecting portion at the center of the optical fibers <NUM> may be <NUM> or more and <NUM> or less. The optical fiber ribbon may have a recess at the connecting portion of the optical fiber, due to easy deformation of the optical fiber ribbon when accommodated in a cable. The recess may be formed in a triangular shape having a narrow angle on one surface of the connecting portion.

The optical fiber ribbon according to the present embodiment may have a connecting portion and a non-connecting portion intermittently in the longitudinal direction and the width direction. <FIG> is a plan view showing the appearance of the optical fiber ribbon according to an embodiment. An optical fiber ribbon 100B has a plurality of optical fibers, a plurality of connecting portions <NUM>, and non-connecting portions (dividing portions) <NUM>. The non-connecting portion <NUM> is formed intermittently in the longitudinal direction of the optical fiber ribbon. The optical fiber ribbon 100B is an intermittently connected optical fiber ribbon in which the connecting portion <NUM> and the non-connecting portion <NUM> are intermittently provided in the longitudinal direction for each of the two optical fibers 10A. The "connecting portion" refers to a portion in which adjacent optical fibers are integrated through a connecting resin layer, and the "non-connecting portion" refers to a portion in which adjacent optical fibers are not integrated through a connecting resin layer, having a gap portion between the optical fibers.

Since the optical fiber ribbon having the structure described above is provided with the non-connecting portion <NUM> intermittently in the connecting portion <NUM> for each of the two fibers, the optical fiber ribbon is easily deformed. Therefore, the optical fiber ribbon is easily rolled for incorporation in the optical fiber cable, so that the optical fiber ribbon suitable for high-density packaging can be obtained. Further, since the connecting portion <NUM> can be easily torn from the non-connecting portion <NUM> as a starting point, single fiber separation of the optical fibers <NUM> in the optical fiber ribbon is easily performed.

The intermittently connected optical fiber ribbon may be manufactured by using, for example, a manufacturing apparatus having a swing blade described in <CIT>, <CIT>, or <CIT>.

The optical fiber cable according to the present embodiment includes the optical fiber ribbon incorporated in the cable. Examples of the optical fiber cable include a slot-type optical fiber cable having a plurality of slot grooves. The optical fiber ribbon can be incorporated in the slot groove, such that the packaging density in each of the slot grooves is about <NUM>% to <NUM>%. The packaging density means the ratio of the cross-sectional area of the optical fiber ribbon incorporated in the slot groove relative to the cross-sectional area of the slot groove.

Hereinafter, the results of the evaluation tests in Examples and Comparative Examples according to the present disclosure will be shown to describe the present disclosure in more detail. The present invention, however, is not limited to these Examples.

As the photopolymerizable compounds, a urethane acrylate, which is a reaction product of polypropylene glycol having a molecular weight of <NUM>, isophorone diisocyanate, and <NUM>-hydroxyethyl acrylate, an epoxy acrylate having a bisphenol A moiety, isobornyl acrylate, N-vinylcaprolactam, and tripropylene glycol diacrylate were prepared.

As photopolymerization initiators, <NUM>,<NUM>,<NUM>-trimethylbenzoyl diphenylphosphine oxide (TPO) and <NUM>-hydroxycyclohexyl phenyl ketone (Omnirad <NUM>) were prepared.

As the silicone-based lubricant, a modified silicone oil (polyether modified, average molecular weight: <NUM>) was prepared.

As the pigments, titanium oxide and copper phthalocyanine were prepared.

A resin composition S1 for a colored secondary resin layer was prepared by mixing <NUM> parts by mass of urethane acrylate, <NUM> parts by mass of epoxy acrylate, <NUM> parts by mass of isobornyl acrylate, <NUM> parts by mass of N-vinylcaprolactam, <NUM> parts by mass of tripropylene glycol diacrylate, <NUM> parts by mass of TPO, <NUM> part by mass of Omnirad <NUM>, <NUM> part by mass of silicone oil, <NUM> parts by mass of titanium oxide, and <NUM> parts by mass of copper phthalocyanine.

A resin composition S2 was prepared in the same manner as in Preparation Example <NUM>, except that the amount of isobornyl acrylate was changed to <NUM> parts by mass and the amount of TPO was changed to <NUM> parts by mass.

A resin composition S3 was prepared in the same manner as in Preparation Example <NUM>, except that the amount of isobornyl acrylate was changed to <NUM> parts by mass, and the amount of TPO was changed to <NUM> parts by mass.

A resin composition S4 was prepared in the same manner as in Preparation Example <NUM>, except that the amount of urethane acrylate was changed to <NUM> parts by mass, the amount of epoxy acrylate was changed to <NUM> parts by mass, the amount of isobornyl acrylate was changed to <NUM> parts by mass, and the amount of TPO was changed to <NUM> parts by mass.

A resin composition S5 was prepared in the same manner as in Preparation Example <NUM>, except that the amount of urethane acrylate was changed to <NUM> parts by mass, the amount of epoxy acrylate was changed to <NUM> parts by mass, the amount of isobornyl acrylate was changed to <NUM> parts by mass, and the amount of TPO was changed to <NUM> parts by mass.

A resin composition S6 was prepared in the same manner as in Preparation Example <NUM>, except that the amount of urethane acrylate was changed to <NUM> parts by mass, the amount of epoxy acrylate was changed to <NUM> parts by mass, the amount of isobornyl acrylate was changed to <NUM> parts by mass, and the amount of TPO was changed to <NUM> parts by mass.

A resin composition S7 was prepared in the same manner as in Preparation Example <NUM>, except that the amount of urethane acrylate was changed to <NUM> parts by mass, the amount of epoxy acrylate was changed to <NUM> parts by mass, the amount of isobornyl acrylate was changed to <NUM> parts by mass, and the amount of TPO was changed to <NUM> parts by mass.

A resin composition S8 was prepared in the same manner as in Preparation Example <NUM>, except that the amount of urethane acrylate was changed to <NUM> parts by mass, the amount of epoxy acrylate was changed to <NUM> parts by mass, the amount of isobornyl acrylate was changed to <NUM> parts by mass, and the amount of TPO was changed to <NUM> parts by mass.

A resin composition S9 was prepared in the same manner as in Preparation Example <NUM>, except that the amount of isobornyl acrylate was changed to <NUM> parts by mass, and the amount of TPO was changed to <NUM> parts by mass.

A resin composition S10 was prepared in the same manner as in Preparation Example <NUM>, except that the amount of urethane acrylate was changed to <NUM> parts by mass, the amount of epoxy acrylate was changed to <NUM> parts by mass, the amount of isobornyl acrylate was changed to <NUM> part by mass, and the amount of TPO was changed to <NUM> parts by mass.

A resin composition for the primary resin layer was prepared by mixing <NUM> parts by mass of urethane acrylate, which is a reaction product of polypropylene glycol having a molecular weight of <NUM>, <NUM>,<NUM>-tolylene diisocyanate, <NUM>-hydroxyethyl acrylate and methanol, <NUM> parts by mass of nonylphenol EO-modified acrylate, and <NUM> parts by mass of N-vinylcaprolactam, <NUM> parts by mass of <NUM>,<NUM>-hexanediol diacrylate, <NUM> part by mass of TPO, and <NUM> part by mass of γ-mercaptopropyl trimethoxysilane.

A resin composition for ribbon was prepared by mixing <NUM> parts by mass of polypropylene glycol having a molecular weight of <NUM>, <NUM>,<NUM>-tolylene diisocyanate and <NUM>-hydroxyethyl acrylate, <NUM> parts by mass of <NUM>-phenoxyethyl acrylate, <NUM> parts by mass of tripropylene glycol diacrylate, <NUM> parts by mass of N-vinylcaprolactam, <NUM> part by mass of TPO, and <NUM> part by mass of Omnirad <NUM>.

A resin composition for a primary resin layer and a resin composition for a secondary resin layer are applied to the outer periphery of a glass fiber having a diameter of <NUM> composed of a core and a cladding, and then irradiated with ultraviolet rays to cure the resin composition, so that an optical fiber having an outer diameter of <NUM> including a primary resin layer having a thickness of <NUM> and a colored secondary resin layer having a thickness of <NUM> on the outer periphery thereof was prepared. The line speed was <NUM>/min.

A resin composition for a ribbon was applied around <NUM> colored optical fibers and then cured by irradiation with ultraviolet rays to form a connecting resin layer, so that an optical fiber ribbon shown in <FIG> was prepared. <FIG> is a schematic cross-sectional view showing a prepared optical fiber ribbon 100C. The optical fibers <NUM> are connected by a ribbon resin at regular intervals. The thickness of the connecting portion between the optical fibers was <NUM> to <NUM>, the distance between the centers of the adjacent optical fibers was <NUM>, the thickness of the optical fiber ribbon was <NUM> ± <NUM>, and the width of the optical fiber ribbon was <NUM> ±<NUM>.

The following evaluations were made on the optical fiber and the optical fiber ribbon. The evaluation results of the optical fiber and the optical fiber ribbon prepared in Examples are shown in Table <NUM>, and the evaluation results of the optical fiber and the optical fiber ribbon prepared in Comparative Examples are shown in Table <NUM>.

The Young's modulus of the primary resin layer was measured by the Pullout Modulus (POM) method at <NUM>. Two points of the optical fiber were fixed with two chuck devices, and the coating resin layer (primary resin layer and secondary resin layer) portion between the two chuck devices was removed. Then, one chuck device was fixed and the other chuck device was gently moved in the opposite direction of the fixed chuck device. When the length of a portion of the optical fiber grasped by the moving chuck device is represented by L, the moving amount of the chuck by Z, the outer diameter of the primary resin layer by Dp, the outer diameter of the glass fiber by Df, and the Poisson's ratio of the primary resin layer by n, and the load during movement of the chuck device by W, the Young's modulus of the primary resin layer was obtained from the following formula. The Young's modulus of the primary resin layer was <NUM> MPa.

The Young's modulus of the colored secondary resin layer was obtained from the <NUM>% secant line value in a tensile test (distance between marked lines: <NUM>) at <NUM> of a pipe-shaped coating resin layer (length: <NUM> or more) obtained by immersing an optical fiber in a solvent (ethanol: acetone=<NUM>:<NUM>) and pulling a glass fiber out.

The surface of the colored secondary resin layer was analyzed by TOF-SIMS. The apparatus used was TRIFT V nanoTOF, with an ion species Au+, and an acceleration voltage of <NUM> kV. The measurement was performed by irradiating an ion beam from the side of the optical fiber. The ratio between the peak value at +<NUM> (m/z) (representing the amount of phosphorus-tin complex) and the peak value at +<NUM> (m/z) (representing the amount of hydrocarbon), i.e. (peak value at +<NUM>/peak value at +<NUM>), expressed in ppm was designated as an amount of P-Sn complex.

An optical fiber ribbon having a length of <NUM> was stored in an environment at <NUM> and <NUM>% for <NUM> days. The optical fiber ribbon was bared to the single fiber at an end over several cm and separated in the longitudinal direction of the optical fiber ribbon. The ribbon resin tended to remain on the end of the optical fiber ribbon. In the evaluation, the case where the ribbon resin was peeled for a length of <NUM> without break was evaluated as "A", the case where the ribbon resin was peeled for a length of <NUM> within <NUM> times of break of the ribbon resin was evaluated as "B", and the case where the break of ribbon resin occurred <NUM> times or more, the case where the ribbon resin was unable to be peeled, or the case where the colored layer was peeled even though the peeling was possible, was evaluated as "C".

After compressing the optical fiber ribbon <NUM> times in the width direction, the case where no fiber spill occurred was evaluated as "OK", and the case where fiber spill occurred was evaluated as "NG".

The optical fiber cable was allowed to stand in an environment of <NUM>, and the value of the transmission loss for a wavelength of signal light of <NUM> was measured. The measured values were evaluated according to the following criteria.

Claim 1:
An optical fiber ribbon (<NUM>, 100A, 100B, 100C) comprising:
a plurality of optical fibers (<NUM>, 10A) arranged in parallel; and
a connecting resin layer (<NUM>) containing a ribbon resin for coating and connecting the plurality of optical fibers (<NUM>, 10A),
wherein each of the plurality of optical fibers (<NUM>, 10A) has an outer diameter of <NUM> or less;
each of the plurality of optical fibers (<NUM>, 10A) includes a glass fiber (<NUM>) containing a core (<NUM>) and a cladding (<NUM>), a primary resin layer (<NUM>) in contact with the glass fiber (<NUM>) for coating the glass fiber (<NUM>), and a secondary resin layer (<NUM>) for coating the primary resin layer (<NUM>);
the secondary resin layer (<NUM>) contains a cured product of a resin composition containing <NUM>,<NUM>,<NUM>-trimethylbenzoyldiphenylphosphine as a photopolymerization initiator and a polyfunctional monomer having a bisphenol moiety; and
a content of phosphorus in the secondary resin layer (<NUM>) is <NUM> mass% or more and <NUM> mass% or less, and an amount of a phosphorus-tin complex at the surface of the secondary resin layer (<NUM>) is <NUM> ppm or more and <NUM> ppm or less;
wherein the content of phosphorus in the secondary resin layer (<NUM>) and the amount of a phosphorus-tin complex at the surface of the secondary resin layer (<NUM>) are determined as described in the specification;
characterized in that
the secondary resin layer (<NUM>) is colored; and
the resin composition further contains a silicone-based lubricant.