JP5871435B2 - Overcoat core wire and optical fiber cable provided with the overcoat core wire - Google Patents

Description

  The present invention relates to an overcoat core wire and an optical fiber cable including the overcoat core wire. More specifically, the present invention relates to an overcoat core wire in which an overcoat layer is provided around an optical fiber colored core wire and an optical fiber cable including the overcoat core wire.

The optical fiber is coated with a two-layer structure of a primary coating layer (primary layer) and a secondary coating layer (secondary layer), and a colored layer is provided around it, or the secondary coating layer is colored. By forming a layer, the outermost layer is an optical fiber colored core. Also, for example, outer diameter 2
An outer diameter of 500 μm is formed by providing an overcoat layer on a 50 μm optical fiber colored core.
The overcoat core wire reinforced so as to improve the visibility of the core wire in the dark, the distinguishability, the handleability, etc. contribute to the simplification of the laying work and the shortening of the laying time.

  For such an overcoat core wire, it is necessary to remove the overcoat layer in connection or the like, but in the case of removing the overcoat layer, a material such as a polyol is interposed between the overcoat layer and the colored layer. Since it is interposed, a certain length can be removed. However, when connecting with a mechanical splice, it is necessary to remove a coating of 50 mm or more. On the other hand, the conventional overcoat core has a problem that it is difficult to remove the overcoat layer having such a length. In addition, the conventional overcoat core wire is coated at a low temperature (−20 ° C.) after aging for a long time (for example, a high temperature and humidity condition of 30 days at 85 ° C. × 85% RH, the same applies hereinafter). There was also a problem of poor removal.

  In the case of the conventional overcoat cord, the polyol on the surface of the overcoat layer is caused by a polyol or the like interposed between the overcoat layer and the colored layer or a polyol contained in the overcoat layer. If the polyol is bleeded on the surface of the overcoat layer in this way, the surface of the overcoat layer becomes sticky and several overcoat cords are bundled with a bundle string. When bundled and bundled, the overcoat cords may stick to each other due to the stickiness of the surface. In addition, when a cable is formed by extruding a flame retardant sheath material or the like on the overcoat core wire, moisture is adsorbed to the polyol in a humid state due to bleed of polyol or the like, and the sheath of the cable and the overcoat core are A cavity is formed at the interface of the wire with the overcoat layer, or foaming occurs on the inner surface of the sheath, thereby reducing the adhesion between the cable sheath and the overcoat layer of the overcoat core wire. In the heat cycle test, there was a case where the overcoat core wire moved (core wire move) due to a decrease in the adhesion force, resulting in spec out.

  In view of such a problem, for example, a primary coating layer for coating a glass optical fiber on an optical fiber, and a further resin on the outermost layer on the optical fiber colored core wire in which a colored coating is coated on a secondary coating layer for coating the primary coating layer In order to improve the coating removability of the overcoat layer in the overcoat core wire coated with a layer, a technology for regulating the range of Young's modulus of the overcoat layer and the degree of cure of the inner surface of the overcoat layer to a specific range is known. (For example, refer to Patent Document 1). In addition, the overcoat layer includes a first overcoat layer made of an ultraviolet curable resin containing an additive having a molecular weight of 5000 or more that imparts releasability to the optical fiber core, and an outer periphery of the first overcoat layer. A contact region having a thickness of 3 μm or more and 20 μm or less that is coated and in contact with the first overcoat layer has a second overcoat layer made of an ultraviolet curable resin having a crosslink density higher than that of the first overcoat layer. An overcoat core wire is provided (see, for example, Patent Document 2).

Japanese Patent No. 4500740 JP 2007-199525 A

  In Patent Document 1, the range of Young's modulus of the overcoat layer and the degree of cure of the inner surface of the overcoat layer are defined, which is good in the state after manufacture, but at -20 ° C. after aging (after aging). As a result of the coating removal test, satisfactory results were not obtained. In addition, bleeding such as polyol on the surface of the overcoat layer was also observed. Similarly, in Patent Document 2, the result of the coating removal test at −20 ° C. after aging was poor. From the above, overcoat cords that can efficiently remove the overcoat layer, including low temperature conditions after aging, and prevent bleeding such as polyol on the surface of the overcoat layer have not yet been provided, Improvement was desired.

This invention is made | formed in view of the said subject, In addition to the coating removal force for removing the overcoat layer 50 mm or more being favorable, in addition to the coating removability at -20 degreeC after aging. An object of the present invention is to provide an overcoat core wire that is excellent and can prevent bleeding of polyol or the like on the surface of the overcoat layer, and an optical fiber cable including the overcoat core wire.

  In order to solve the above-described problems, the overcoat core wire according to the present invention has at least two coating layers covering the glass optical fiber around the glass optical fiber, and the outermost layer of the coating layers is colored. An overcoat core wire in which an overcoat layer is formed around an optical fiber colored core wire, wherein the overcoat layer is formed in contact with the periphery of the optical fiber color core wire An inner layer and an overcoat outer layer that is formed around the inner layer of the overcoat and is an outermost layer, and the overcoat inner layer has a polyol having a weight average molecular weight of 3000 to 4000; 33% by mass, the overcoat outer layer contains substantially no polyol, and the Young's modulus of the overcoat layer is And less than or 0 MPa 140 MPa.

  The overcoat core wire according to the present invention is characterized in that, in the above-described present invention, the polyol contained in the overcoat inner layer is polypropylene glycol.

  An optical fiber cable according to the present invention includes the above-described overcoat core wire of the present invention.

  In the overcoat cord according to the present invention, the overcoat layer includes two layers, an overcoat inner layer and an overcoat outer layer, and the polyol having a weight average molecular weight of 3000 to 4000 is added to the overcoat inner layer with respect to the entire overcoat inner layer. It is contained in a specific range, and the Young's modulus at 23 ° C. of the entire overcoat layer is a specific range. Thereby, when removing the overcoat layer of the overcoat core wire, the maximum value of the coating removal force can be within an appropriate range, and the overcoat layer is quickly removed between the optical fiber colored core wire, Even if the length is 50 mm or more, the coating can be removed efficiently. Further, the present invention provides an overcoat core wire that can maintain excellent coating removal performance even at a low temperature of -20 ° C. after aging, and in addition, can prevent the occurrence of an optical fiber colored core wire after aging. Become. Furthermore, since the overcoat outer layer that does not substantially contain polyol is formed in the outermost layer, it prevents bleeding of polyol and the like on the surface of the overcoat layer, eliminates stickiness on the surface of the overcoat layer, and is cabled Prevents the formation of voids at the interface between the sheath and the overcoat layer and foaming of the sheath surface, and the resulting poor adhesion between the sheath and the overcoat layer, the overcoat core wire protruding, and the core wire movement, etc. Can be eliminated.

  In addition, since the optical fiber cable according to the present invention includes the overcoat core wire of the present invention described above, the above-described effect can be enjoyed, and the construction can be easily performed from the taken overcoat core wire after the cable is laid. It is possible to remove the overcoat layer, and the workability at the site is also good, and it is possible to prevent the formation of cavities and the foaming of the sheath at the interface between the sheath and the overcoat layer. Therefore, the optical fiber cable is free from defects such as poor adhesion between the sheath and the overcoat layer.

It is sectional drawing which showed an example of the structure of the overcoat core wire which concerns on this invention. It is sectional drawing which showed the other example of the structure of the overcoat core wire which concerns on this invention.

Hereinafter, one embodiment of the present invention will be described. FIG. 1 is a cross-sectional view showing an example of the structure of an overcoat core wire 1 according to the present invention. FIG. 2 is a sectional view showing another example of the structure of the overcoat core wire 1 according to the present invention. 1 and 2, 1 is an overcoat core wire, 10 is a glass optical fiber, 11 is a primary coating layer, 12 is a secondary coating layer, and 12a is a colored secondary coating layer (
2 only), 13 is a colored layer (only FIG. 1), 2 is an optical fiber colored core, 3 is an overcoat layer, 31 is an overcoat inner layer, and 32 is an overcoat outer layer.

The overcoat core wire 1 according to the present invention includes at least two coating layers (a primary coating layer 11, a secondary coating layer 12, and a colored secondary coating layer 12a) covering the glass optical fiber 10 around the glass optical fiber 10. The colored layer 13) is formed, and the overcoat inner layer 31 and the overcoat inner layer 31 are formed around the optical fiber colored core wire 2 formed by coloring the outermost layer of the coating layer. An overcoat layer 3 composed of the overcoat outer layer 32 is formed.

  In the configuration of FIG. 1, a primary coating layer 11 (also referred to as a primary layer; hereinafter the same) around the glass optical fiber 10, and a secondary coating layer 12 (also referred to as a secondary layer) around the primary coating layer 11. The same is true), and a colored layer 13 colored around the secondary coating layer 12 is formed in this order, and constitutes the optical fiber colored core 2. The colored layer 13 is the outermost layer of the optical fiber colored core wire 2.

  On the other hand, in the configuration of FIG. 2, the primary coating layer 11 and the secondary coating layer 12 a colored around the primary coating layer 11 are formed in this order around the glass optical fiber 10. It becomes the core wire 2. Further, the colored secondary coating layer 12 a becomes the outermost layer of the optical fiber colored core wire 2.

(A) Overcoat layer 3:
The overcoat layer 3 in the overcoat core wire 1 according to the present invention is a layer formed around the optical fiber colored core wire 2. The overcoat core wire 1 reinforces the optical fiber color core wire 2 by providing an overcoat layer 3 around the optical fiber color core wire 2 so that the core wire is visible, distinguishable and easy to handle in the dark. It is intended to improve and simplify the laying work and shorten the time.

  In addition, in the present invention, the overcoat layer 3 constituting the overcoat core wire 1 shown in FIGS. 1 and 2 includes an overcoat inner layer 31 and an overcoat outer layer formed around the overcoat inner layer 31. 32.

(A-1) Overcoat inner layer 31:
In the overcoat core wire 1 according to the present invention, the overcoat inner layer 31 is formed around the optical fiber colored core wire 2 so as to be in contact with the optical fiber core wire 2.

In the present invention, the component constituting the overcoat inner layer 31 includes a polyol having a weight average molecular weight (M _w ) of 3000 to 4000. A polyol having such a weight average molecular weight (hereinafter, sometimes simply referred to as “molecular weight”) can be present in the overcoat inner layer 31 without reacting with the mesh of the ultraviolet curable resin constituting the overcoat inner layer 31, and ultraviolet rays. The polyol swells in the dense network structure of the curable resin, and plays a role of a plasticizer for the ultraviolet curable resin. As a result, the Young's modulus of the overcoat inner layer 31 or the entire overcoat layer 3 can be lowered, and flexibility can be imparted to the overcoat layer 3 even under low temperature conditions. In addition, the polyol bleeds to the interface between the colored layer 13 in contact with the overcoat inner layer 31 and the overcoat inner layer 31 (which becomes the interface between the colored layer 13 and the overcoat layer 3), and the overcoat even under low temperature conditions. The interface is made slippery when the coating layer 3 is entirely removed. And if it is the range of this weight average molecular weight, since it becomes larger than the molecular weight of the colored layer 13, it does not pass through the mesh | network of the colored layer 13, and it does not transfer. Moreover, since the molecular weight of the polyol is as large as 3000 to 4000, the Young's modulus of the overcoat layer 3 as a whole can be controlled by increasing the polyol content. In this way, by making the overcoat inner layer 31 contain a polyol, it is possible to efficiently remove the coating even when the length is 50 mm or more, and the coating removal property is maintained even at a low temperature of −20 ° C. after aging. It will help you to do what you can.

  Examples of the polyol include polypropylene glycol, polyethylene glycol, and polytetramethylene glycol. Among these, those having no branched structure such as polyethylene glycol and polytetramethylene glycol are crystallized at low temperatures. Bend due to crystals at the interface between the colored layer 13 and the overcoat layer 3 (overcoat inner layer 31), which may cause an increase in loss. On the other hand, polypropylene glycol having a branched structure does not crystallize even at a low temperature of −60 ° C., and the effects of the above-described polyol can be reliably obtained. Therefore, it is preferable to use polypropylene glycol as the polyol. Polypropylene glycol is produced by addition polymerization of polypropylene oxide (PO) to polyfunctional alcohol using an alkali catalyst, but ethylene oxide (EO) may be added and used to enhance the reaction, but ethylene oxide is added. Then, since hydrophilicity becomes high, it is preferable to use only polypropylene oxide (PO) as an additional substance.

  The weight average molecular weight of the polyol contained in the overcoat inner layer 31 is set to 3000 to 4000 as described above. When the polyol has a weight average molecular weight of less than 3000, when the polyol passes through the colored layer 13 in contact with the overcoat inner layer 31 or is formed into an optical fiber cable, the sheath of an optical fiber cable (not shown) in contact with the overcoat layer 3 is used. In some cases, the transition may occur through the overcoat outer layer 32, and the above-described effects may not be achieved due to such a transition of the polyol. On the other hand, when the weight average molecular weight exceeds 4000, the viscosity increases when mixed with the ultraviolet curable resin, so that the coating amount when applying the overcoat inner layer 31 at the time of manufacture is reduced, causing fluctuations in the outer diameter. There is a case. Also, in order to increase the amount of coating, the viscosity can be lowered by increasing the heating temperature, etc., but if the heating temperature is increased too much, the volatilization amount of the ultraviolet curable resin will increase, causing contamination of the quartz tube etc. It may be a factor. In addition, what is necessary is just to employ | adopt the measured value by the method of measuring the molecular weight distribution, average molecular weight distribution, etc. of conventionally well-known polymeric substances, such as a gel permeation chromatograph (GPC), for the weight average molecular weight of a polyol.

  The content of the polyol contained in the overcoat inner layer 31 means the entire overcoat inner layer 31 (the whole component constituting the overcoat inner layer 31. Hereinafter, it may be simply referred to as “in the overcoat inner layer 31”. )) To 25 to 33% by mass. If the content of the polyol with respect to the overcoat inner layer 31 is within such a range, the Young's modulus of the entire overcoat layer 3 can be easily maintained within the range of 40 MPa or more and less than 140 MPa, and the covering removal force of the overcoat layer 3 is moderate. In addition to being in the range (approximately 1.4 to 3.5 N), the coating removal property after aging is also improved. In addition, protrusion of the optical fiber colored core wire 2 after aging can be prevented. On the other hand, when the content of the polyol with respect to the overcoat inner layer 31 is less than 25% by mass, the coating removal property after aging is poor, and particularly when the content is less than 20% by mass, the coating removal force is in an appropriate range (1. 4 to 3.5 N). On the other hand, if the content exceeds 33% by mass, the coating removal force may be smaller than the proper range, and in addition, the protruding property after aging may be adversely affected.

  In the overcoat inner layer 31 of the overcoat core wire 1 according to the present invention, the coating removal force of the entire overcoat layer 3 can be within an appropriate range by setting the polyol content in the above-described range. .4 to 3.5N can be maintained. The coating removal force means that the overcoat layer 3 of the overcoat core wire 1 is overcoated with a commercially available microstrip (for example, a 0.016 inch hole diameter blade manufactured by Microelectronics Inc.) with a length of 50 mm (5 cm). This refers to the force required to remove the overcoat layer 3 (coating) when removing the entire layer 3. Specifically, the microstrip blade is cut to a depth of 0.05 mm at a location 50 mm from the end of the overcoat core wire 1 to fix the blade, and the blade is directed toward the end of the optical fiber colored core wire 2. It moves along the axis of the optical fiber colored core 2 so that the 50 mm overcoat layer 3 is removed. In the present invention, the maximum value of the force applied at the time of coating removal is defined as the coating removal force.

  In the overcoat core wire 1 according to the present invention, the coating removal force of the entire overcoat layer 3 can be maintained at about 1.4 to 3.5 N. In the overcoat core wire 1, the maximum value of the coating removal force of the overcoat layer 3 is generally required to be 1.3 N or more. In the present invention, the maximum value is 1.4 N or more with a margin. . On the other hand, when it exceeds 3.5 N, the various characteristics after aging may be adversely affected.

  As other components constituting the overcoat inner layer 31, for example, UV curable resin for coating the optical fiber (glass optical fiber 10) and components generally used as an additive component thereof can be used. For example, oligomers, dilution monomers, photoinitiators, silane coupling agents, sensitizers, pigments, and other various additives can be used.

As the oligomer, for example, polyether urethane acrylate, epoxy acrylate, polyester acrylate, silicone acrylate and the like can be used. These may be used alone or in combination of two or more. The Young's modulus and glass transition temperature (T _g ) of the entire overcoat layer 3 can be adjusted by the skeleton structure and molecular weight of the oligomer, and the type and addition amount of the dilution monomer described later. As will be described later, Young's modulus and glass transition temperature (T _g ) can be adjusted by reducing the molecular weight of the oligomer or increasing the functional group of the monomer.

  When using a polyether urethane acrylate as an oligomer, for example, a polyol such as polypropylene glycol, polyethylene glycol, or polytetramethylene glycol can be used as the intermediate block, but a polypropylene glycol having a branched structure is used. It is preferable that such a polypropylene glycol is used as an intermediate block, and a hydroxy compound having an unsaturated double bond that is reactive to ultraviolet rays is bonded to the hydroxyl groups at both ends thereof via an aromatic diisocyanate as a skeleton component. It is preferable to use oligomers that have been allowed to form.

  Further, by using polypropylene glycol as a polyol and using an oligomer having polypropylene glycol as an intermediate block as an oligomer, crystallization at a low temperature of −60 ° C. is prevented, so that crystallization at a low temperature can be efficiently prevented. .

  As the oligomer to be used, those having a weight average molecular weight of 500 to 2500 are preferred, and those having a weight average molecular weight of 1000 to 2000 are particularly preferred.

  As the aromatic isocyanate, for example, aromatic diisocyanates such as tolylene diisocyanate (TDI) and isophorone diisocyanate (IPDI) can be used. Moreover, as a hydroxy type compound, hydroxyethyl acrylate (HEA) etc. can be used, for example.

  Since the viscosity of the oligomer alone may be too high, a dilution monomer can be blended mainly for viscosity adjustment. As a dilution monomer, a monofunctional monomer, a bifunctional monomer, a polyfunctional monomer, etc. can be used, for example.

  As a diluting monomer that can be added, in the monofunctional monomer, for example, PO-modified nonylphenol acrylate, isobornyl acrylate, 2-ethylhexyl acrylate, isononyl acrylate, isodecyl acrylate, polyethylene glycol acrylate, N-vinylpyrrolidone, N-vinyl Examples include caprolactam and lauryl acrylate. Moreover, as bifunctional monomer and polyfunctional monomer, 1-6 hexane diacrylate, bisphenol A epoxy acrylate, tripropylene glycol diacrylate, tricyclodecane dimethylol diacrylate, EO-modified bisphenol A diacrylate, hexanediol diacrylate, etc. Is mentioned. One of these may be used alone, or two or more thereof may be used in combination.

  Note that the monofunctional monomer has a greater effect of lowering the Young's modulus than the bifunctional monomer and the polyfunctional monomer. This is because the monofunctional monomer has a greater effect of reducing the crosslinking points in the molecular structure than the bifunctional monomer and the polyfunctional monomer.

  When the photoinitiator absorbs ultraviolet rays, the photoinitiator is radicalized, and the unsaturated double bond of the reactive oligomer and the reactive monomer can be continuously polymerized. Examples of the photoinitiator include alkylphenone photopolymerization initiators and acylphosphine oxide photopolymerization initiators such as 1-hydroxy-cyclohexyl-phenyl-ketone, 2-hydroxy-2-methyl-1-phenyl-propane- 1-one, 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, and the like can be used. These may be used individually by 1 type, or can be used in combination of 2 or more type.

  Examples of the sensitizer include triethylamine, diethylamine, N-methyldiethanolamine, 4-dimethylaminobenzoic acid, etc., and these may be used alone or in combination of two or more. can do.

  Other additives that can be added include, for example, antioxidants, ultraviolet absorbers, light stabilizers such as hindered amine light stabilizers, deterioration inhibitors such as thermal polymerization inhibitors, silane coupling agents, leveling agents, and hydrogen absorption. Agents, chain transfer agents, lubricants and the like.

(A-2) Overcoat outer layer 32:
The overcoat outer layer 32 is formed around the above-described overcoat inner layer 31 and becomes an outermost layer that appears outside. As the constituent material of the overcoat outer layer 32, among the materials constituting the overcoat inner layer 31, components excluding the polyol can be used, and the ultraviolet curing mentioned as the component constituting the above overcoat inner layer 31. Components such as an oligomer, a dilution monomer, a photoinitiator, a silane coupling agent, a sensitizer, a pigment, and various additives which are resins and additives thereof can be preferably used. The overcoat outer layer 32 is a layer that covers the overcoat inner layer 31 existing inside, and can prevent bleeding of the polyol contained in the overcoat inner layer 31 on the surface of the overcoat layer 3.

  In the present invention, since the polyol is not substantially contained as a constituent material of the overcoat outer layer 32, there is no bleeding of the polyol from the overcoat outer layer 32. Here, “substantially free of polyol” means that the content of the polyol in the overcoat outer layer 32 is sufficiently low, and a remarkable characteristic change based on the inclusion of the polyol occurs in the overcoat outer layer 32. This means that the content of polyol is generally 1% by mass or less based on the entire overcoat outer layer 32. Further, the polyol not contained in the overcoat outer layer 32 refers to a polyol (so-called non-reactive polyol) contained as an independent component, for example, used as an intermediate block of an oligomer, and other components (eg, polyether-based urethane). Polyols that are combined with acrylates or the like to form oligomers are excluded from the polyols that the overcoat outer layer 32 does not contain.

  In the configuration of the present invention, there is no need for a lubricating component such as polyol to intervene between the optical fiber colored core wire 2 and the overcoat layer 3 (overcoat inner layer 31). The resulting bleed to the surface of the overcoat layer 3 cannot occur, but even if it is interposed, bleed such as polyol can be prevented by the presence of the overcoat outer layer 32. In addition to the polyol, the cause of bleed may be caused by silicone having a relatively low molecular weight (weight average molecular weight). The overcoat outer layer 32 is substantially made of silicone having a weight average molecular weight of 3000 or less. It is preferable not to contain. Here, “substantially does not contain a silicone having a weight average molecular weight of 3000 or less” is the same as the above-mentioned “does not contain a polyol practically”, and the weight average molecular weight in the overcoat outer layer 32 is 3000 or less. This means that no significant change in properties based on the inclusion of silicone in the weight molecular weight range is caused in the overcoat outer layer 32. In general, the weight average molecular weight is 3000 or less. This indicates that the content of the silicone is 1% by mass or less based on the entire overcoat outer layer 32.

  Further, the overcoat outer layer 32 may be colored. When the overcoat outer layer 32 is colored, examples of the pigment to be added include phthalocyanine, quinacridone, dioxan, Bensuimidazolone organic pigment, carbon black, titanium oxide. And inorganic pigments. In addition, you may make it use the coloring material which mixed the pigment and the ultraviolet curable resin represented by the above-mentioned material as a coloring component. The content of the colorant may be determined as appropriate depending on the content of the pigment contained in the colorant, the type of other components such as an ultraviolet curable resin, etc., but the entire overcoat outer layer 32 (the component constituting the overcoat outer layer 32) It is preferable to set it as 2.0-3.0 mass% with respect to the whole.

  In the overcoat core wire 1 according to the present invention, the Young's modulus at 23 ° C. (hereinafter sometimes simply referred to as “Young's modulus”) of the entire overcoat layer 3 is 40 MPa or more and less than 140 MPa. By setting the Young's modulus at 23 ° C. in such a range, the coating removal force of the overcoat layer 3 is in an appropriate range (approximately 1.4 to 3.5 N) and the coating removal property after aging is also improved. . On the other hand, when the Young's modulus is less than 40 MPa, the external stress is affected by the protrusion and lateral pressure after aging, and when the Young's modulus exceeds 140 MPa, the -20 ° C coating removal property after aging is affected. Therefore, the Young's modulus at 23 ° C. of the entire overcoat layer 3 is set to 40 MPa or more and less than 140 MPa. The Young's modulus at 23 ° C. of the entire overcoat layer 3 is preferably 50 to 137 MPa.

  In order to adjust the Young's modulus of the overcoat layer 3 as a whole to the above-described range, for example, the components constituting the overcoat layer 3 can be adjusted. Specifically, the kind of polyol constituting the overcoat inner layer 31, the weight average molecular weight and content, the kind of oligomer constituting the overcoat layer 3 (overcoat inner layer 31 and overcoat outer layer 32), molecular weight and content, Adjust the Young's modulus (and glass transition temperature (Tg)) of the overcoat layer 3 as a whole depending on the type and amount of the diluted monomer, or the UV curing conditions such as the type and content of other components, and the amount of irradiation. Can do.

  For example, as a general tendency, the Young's modulus is increased or the glass transition temperature (Tg) is increased by decreasing the weight average molecular weight of the polyol as contained in the overcoat inner layer 31 or decreasing the content. The Young's modulus can be increased and the Tg can be increased by decreasing the molecular weight of the oligomer, and increasing the content of the diluted monomer and the functional group. On the other hand, if this is done, the crosslink density increases, shrinkage increases, and the coating removal force may be adversely affected. Therefore, it is preferable to adjust the balance in consideration of the balance.

  Further, in order to set the Young's modulus at 23 ° C. of the entire overcoat layer 3 within the range of 40 MPa or more and less than 140 MPa, the above-described components are adjusted, for example, the Young's modulus at 23 ° C. of the overcoat inner layer 31 is 20 to 20 ° C. 50 MPa is preferable, and the Young's modulus of the overcoat outer layer 32 at 23 ° C. is preferably 215 MPa or less. By setting the Young's modulus of the overcoat inner layer 31 and the overcoat outer layer 32 constituting the overcoat layer 3 within this range, the Young's modulus of the entire overcoat layer 3 can be easily kept within a range of 40 MPa or more and less than 140 MPa.

In addition, it is preferable to make it the glass transition temperature ( _Tg ) of the whole overcoat layer 3 to be 50-70 degreeC on the high temperature side, for example, and it is especially preferable to set it as 55-65 degreeC.

  In order to maintain the characteristics of the optical fiber colored core wire 2 and the overcoat core wire 1 in general, the outer diameter of the overcoat layer 3 in the overcoat core wire 1 is also the outer diameter of the overcoat core wire 1. It is preferable to be in the range of 470 μm to 530 μm.

  Among these, the outer diameter of the overcoat outer layer 32 is the same as the outer diameter of the overcoat layer 3 described above, but the outer diameter of the overcoat inner layer 31 is generally preferably in the range of 470 μm to 530 μm. Furthermore, the range of 490 micrometers-510 micrometers is preferable.

  The ratio of the cross-sectional area of the overcoat inner layer 31 to the cross-sectional area of the overcoat outer layer 32 (refers to the cross-sectional area of the overcoat inner layer 31 / the cross-sectional area of the overcoat outer layer 32. Hereinafter, it may be simply referred to as "inner layer / outer layer". Is preferably 0.05 to 0.8.

  The overcoat layer 3 may be formed with any layer other than the overcoat inner layer 31 and the overcoat outer layer 32 described above. Such an arbitrary layer can be formed so as to be interposed between the overcoat inner layer 31 and the overcoat outer layer 32, for example.

(B) Primary coating layer 11, secondary coating layer 12 and colored layer 13:
As described above, in the optical fiber (glass optical fiber 10), since transmission loss increases due to various external stresses and microbends generated thereby, it is necessary to protect the optical fiber from such external stresses. In general, a coating having a two-layer structure of a primary coating layer 11 and a secondary coating layer 12 is applied. The primary coating layer 11 is an inner layer that comes into contact with the quartz glass constituting the glass optical fiber 10, and a soft resin having a relatively low Young's modulus is used, and a hard resin having a relatively high Young's modulus is used for the outer layer. The secondary coating layer 12 was coated.

  Resin material that is a constituent material of the primary coating layer 11 (primary layer) and the secondary coating layer 12 (secondary layer) of the overcoat core wire 1 according to the present invention, and a constituent material of the color layer 13 of the optical fiber colored core wire 2 As mentioned above, the ultraviolet curable resin mentioned as the component constituting the overcoat layer 3 and its additives, oligomer, dilution monomer, photoinitiator, silane coupling agent, sensitizer, pigment, various additives Etc. can be preferably used. Of the additives described above, the lubricant may be added to the secondary coating layer 12 or the colored layer 13 as necessary.

  As the oligomer, for example, as the primary coating layer 11 and the secondary coating layer 12, an oligomer in which an aromatic isocyanate and hydroxyethyl acrylate are added to a polyol using polypropylene glycol, which is the same as the above-described overcoat layer 3. The Young's modulus can be adjusted by changing the molecular weight of the polyol (polypropylene glycol) in the intermediate block. The weight average molecular weight of the oligomer used is preferably 1000 to 4000 when used as the primary coating layer 11, and 500 to 2000 when used as the secondary coating layer 12. It is preferable to use 500 to 2000 when used as the colored layer 13, and 500 to 2000 when used as the colored secondary coating layer 12a. Is preferred.

  Moreover, as the oligomer which comprises the colored layer 13, the oligomer which added the aromatic isocyanate and hydroxyethyl acrylate to the polyol which uses polypropylene glycol similarly to the above-mentioned primary coating layer 11 and the secondary coating layer 12 is used. It is preferable that the Young's modulus can be adjusted by changing the molecular weight of the polyol (polypropylene glycol) in the intermediate block by using a bifunctional monomer or a polyfunctional monomer. Moreover, toughness can be raised by adding bisphenol A epoxy acrylate etc. to resin which comprises the colored layer 13, for example.

  In addition, as shown in FIG. 2, when the colored secondary coating layer 12a is the outermost layer of the optical fiber colored core wire 2 and the secondary coating layer 12 also serves as the colored layer 13, a pigment or the above-described By adding a coloring material to the secondary coating layer 12, a colored secondary coating layer 12a can be obtained.

  The Young's modulus at 23 ° C. of the primary coating layer 11 is preferably about 0.3 to 1.5 MPa. Moreover, it is preferable that the Young's modulus in 23 degreeC of the secondary coating layer 12 shall be about 500-1500 Mpa. The Young's modulus at 23 ° C. of the colored layer 13 is preferably in the range of about 1000 to 2500 MPa. In addition, when the secondary coating layer 12 serves also as the colored layer 13, it is preferable that the Young's modulus at 23 degreeC of this colored secondary coating layer 12a shall be 500-1500 Mpa.

  The outer diameter of each layer in the optical fiber colored core wire 2 is generally 80 μm to 125 μm in outer diameter of the primary coating layer 11 in order to maintain the characteristics as an optical fiber (see below). The diameter is preferably 120 μm to 200 μm, the outer diameter of the secondary coating layer 12 is preferably 165 μm to 242 μm, and the outer diameter of the colored layer 13 is preferably in the range of 135 μm to 255 μm. Further, as shown in FIG. 2, when the secondary coating layer 12 also serves as the colored layer 13, the colored secondary coating layer 12a preferably has an outer diameter in the range of 135 μm to 255 μm. .

(C) Manufacturing method of overcoat core wire 1:
An example of the manufacturing method of the overcoat core wire 1 which concerns on this invention is demonstrated. In the following, an optical fiber made of silica glass (glass optical fiber 10) coated with the primary coating layer 11 and the secondary coating layer 12 is called an optical fiber.

  In order to manufacture the overcoat core wire 1 according to the present invention, for example, first, a preform mainly composed of quartz glass is heated and melted in a drawing furnace to obtain an optical fiber made of quartz glass (glass optical fiber 10). To do. Next, a component containing a liquid ultraviolet curable resin is applied to the glass optical fiber 10 using a coating die, and then ultraviolet rays are applied to the component containing the ultraviolet curable resin applied by the ultraviolet irradiation device (UV irradiation device). Irradiate to cure such components. In this way, an optical fiber strand in which the glass optical fiber 10 is coated with the primary coating layer 11 and the secondary coating layer 12 is manufactured. In this way, after drawing, the outer periphery of the glass optical fiber 10 is immediately coated with a component containing an ultraviolet curable resin to form the primary coating layer 11 and the secondary coating layer 12, thereby reducing the strength of the obtained optical fiber strand. Can be prevented.

  In the next step, the optical fiber colored core wire 2 is manufactured by covering the outer periphery of the obtained optical fiber with the colored layer 13. In addition, as described above, the secondary coating layer 12 may be colored to form the optical fiber colored core wire 2 as the secondary coating layer 12 in which the outermost layer is colored.

  Then, by coating and curing the components constituting the overcoat layer 3 (the overcoat inner layer 31 and the overcoat outer layer 32) on the outer periphery of the obtained optical fiber colored core wire 2, the overcoat layer is coated. An overcoat core wire 1 coated with 3 is manufactured. In order to coat the overcoat layer 3 around the optical fiber colored core 2, for example, a polyol and an ultraviolet ray which constitutes the overcoat inner layer 31 which is drawn out from a bobbin wound with the optical fiber colored core 2 and kept warm in advance. The component containing the cured resin is sent to the die under pressure, applied by passing through the optical fiber colored core wire 2, and irradiated with ultraviolet rays when passing through the ultraviolet irradiation device (UV irradiation device). And cure. Next, the pressure is applied to the component constituting the overcoat outer layer 32 and containing the ultraviolet curable resin, and it is sent to the die and passed through the optical fiber colored core wire 2 in which the overcoat inner layer 31 is formed. The components are applied and cured by being irradiated with ultraviolet rays when passing through an ultraviolet irradiation device (UV irradiation device). And the overcoat core wire 1 in which the overcoat layer 3 (the overcoat inner layer 31 and the overcoat outer layer 32) was formed can be manufactured by winding around a bobbin with a take-up device.

  The overcoat layer 3 may be formed by forming the overcoat inner layer 31 and the overcoat outer layer 32 in separate steps, or forming these layers 31 and 32 in one step. . When forming in one step, as described above, the constituent material of the overcoat inner layer 31 may be applied and cured, and then the constituent material of the overcoat outer layer 32 may be applied and cured, or After applying the constituent material of the overcoat inner layer 31, the constituent material of the overcoat outer layer 32 may be applied, and then the two layers 31, 32 may be cured together, and this manufacturing method is arbitrary. . Alternatively, the constituent materials of the two layers 31 and 32 may be applied and cured by a so-called dual application method.

  In the overcoat cord 1 according to the present invention described above, the overcoat layer 3 includes two layers of the overcoat inner layer 31 and the overcoat outer layer 32, and the overcoat inner layer 31 has a weight average molecular weight of 3000 to 4000. Is contained in a specific range with respect to the entire overcoat inner layer 31, and the Young's modulus at 23 ° C. of the entire overcoat layer 3 is set in a specific range. Thereby, when the overcoat layer 3 of the overcoat core wire 1 is removed, the maximum value of the coating removal force can be within an appropriate range (approximately 1.4 to 3.5 N), and the overcoat layer 3 It is quickly removed from the fiber-colored core wire 2, and the coating can be removed efficiently even if the length is 50 mm or more. Moreover, the overcoat core wire 1 according to the present invention maintains excellent coating removal performance even at a low temperature of −20 ° C. after aging, and in addition, the optical fiber colored core wire 2 after aging does not protrude. The overcoat core wire 1 can be prevented.

  The overcoat core wire 1 according to the present invention has an overcoat outer layer 32 that is substantially free of polyol as the outermost layer, so that bleeding of polyol and the like on the surface of the overcoat layer 3 is prevented. The stickiness of the surface of the layer 3 is eliminated, and foaming and cavities are prevented from being formed at the interface between the sheath and the overcoat layer 3 when the cable is formed. Defects such as defects can be eliminated.

  Further, the overcoat core wire 1 according to the present invention has a heat cycle (for example, −40 ° C. to + 80 ° C. (or 10 cycles from −40 ° C. to + 80 ° C. with one cycle being 6 hours)) and Transmission loss after aging (loss level; the same applies hereinafter) and transmission loss after aging can be suppressed to a small level, and transmission loss can be generally suppressed to 0.05 dB / km or less at a wavelength of 1550 nm.

  And the optical fiber cable provided with the overcoat core wire 1 according to the present invention enjoys the effect of the overcoat layer 3 described above, and the sheath such as a sheath after aging or even in a high temperature and high humidity environment. Stable coating that can prevent migration of substances between layers of the overcoat core wire 1 and the overcoat layer 3 and the overcoat layer 3 of the overcoat core wire 1 taken out from the optical fiber cable is not different from that of the cable. Removability etc. can be maintained. Therefore, the overcoat layer 3 can be easily removed from the taken overcoat core wire 1 in the construction after the cable is laid, and the optical fiber cable is excellent in workability at the site.

  In addition, the optical fiber cable according to the present invention prevents the formation of cavities at the interface between the sheath and the overcoat layer 3, foaming of the sheath, and the like. The optical fiber cable is free from defects such as adhesion failure, overcoat core wire protrusion, and core wire movement.

  The configuration of the optical fiber cable is not particularly illustrated, but is not particularly limited as long as it includes the overcoat core wire 1 according to the present invention. For example, the overcoat core wire 1 and the overcoat core wire 1 The configuration is arbitrary, such as a configuration of an optical fiber cable or the like composed of a tension member arranged in parallel with the overcoat core wire 1 on both sides in the longitudinal direction and a sheath covering the overcoat core wire 1 and the like. It can be set as the structure of a conventionally well-known optical fiber cable also including a structure other than this. In addition, for example, a pair of notches formed in the longitudinal direction is formed on both sides of the optical fiber cable, and a support portion incorporating a support line is provided if necessary, so-called optical fiber 8-core DF (Distributing Frame). ) It does not matter as a cable configuration.

  The configuration of the optical fiber cable is not limited to the above configuration. For example, the type and thickness of the sheath, the number and size of the overcoat core wire 1, the type, number and size of the tension member, etc. , You can choose freely. Further, the outer diameter and cross-sectional shape of the optical fiber cable, the shape and size of the notch, whether or not the notch is formed, and the like can be freely selected.

EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example and a comparative example, this invention is not limited to these.

[Example 1 to Example 7, Comparative Example 1 to Comparative Example 5]
Production of overcoat core:
Using the components shown in Table 1 and below, the overcoat cords shown in FIGS. 1 and 2 were produced by the methods shown in (1) and (2) below.

(1) Production of optical fiber colored core:
The outer diameter of the primary coating layer (primary layer) is 195 μm and the outer diameter of the secondary coating layer (secondary layer) is 242 μm around a glass optical fiber made of quartz glass and having an outer diameter of 125 μm. An optical fiber was coated with the composition shown. With respect to the obtained optical fiber, a colored layer was coated around the secondary coating layer in a separate process to obtain an optical fiber colored core wire having an outer diameter of 255 μm (in a configuration corresponding to FIG. 1, Examples 1 and 3 to 7 among the examples, and Comparative Example 1, Comparative Example 2, Comparative Example 4, and Comparative Example 5 among the Comparative Examples are applicable.)

  When the secondary coating layer (secondary layer) is colored and the secondary coating layer also serves as a colored layer, the outer diameter of the primary coating layer (primary layer) is 185 μm, and the outer diameter of the secondary coating layer is 255 μm. Each layer was coated to obtain an optical fiber colored core wire (in the configuration corresponding to FIG. 2, Example 2 of the Examples and Comparative Example 3 of the Comparative Examples correspond).

  For the primary coating layer, secondary coating layer, and colored layer, an oligomer using polypropylene glycol as an ultraviolet curable resin (polypropylene glycol is used as an intermediate block, and a skeleton component has hydroxyl groups at both ends via tolylene diisocyanate. And oligomers to which hydroxyethyl acrylate is bonded.), Dilutable monomers, photoinitiators, and additives are mixed in appropriate amounts, and the Young's modulus is shown in Table 1 especially for the secondary coating layer and the colored layer. The molecular weight, the content, the type and number of functional groups in the dilutable monomer, the content, the UV curing conditions such as the irradiation amount, etc. were used in various ways so as to vary as shown in the values in Examples and It was set as a comparative example. In addition, the coloring material containing an appropriate amount of pigment was added to the colored secondary coating layer when the colored layer and the secondary coating layer also serve as the colored layer.

(2) Manufacture of overcoat core:
The optical fiber colored core wire was fed out from the bobbin wound with the optical fiber colored core wire obtained in (1), changed in the vertical direction with the upper guide roll, and kept warm as the material of the overcoat inner layer in Table 1. Pressure is applied to component A (or component B or component C) containing an ultraviolet curable resin containing polyol of the indicated weight average molecular weight and content, sent through a hose to a die, and an optical fiber colored core is passed through it. Thus, a component containing an ultraviolet curable resin containing a polyol was applied around the optical fiber colored core. Moreover, after applying such a component, when passing through the ultraviolet irradiation device (UV irradiation device), the ultraviolet ray is irradiated to cure the component including the ultraviolet curable resin containing the applied polyol, and the overcoat inner layer is formed. Formed.

  Next, as a material for the overcoat outer layer, pressure is applied to component A (or component B or component C) containing an ultraviolet curable resin, which has been kept warm, and sent to a die through a hose. The component containing an ultraviolet curable resin was apply | coated to the circumference | surroundings of an optical fiber colored core wire by allowing the optical fiber colored core wire of the state which apply | coated to pass through this. In addition, after applying such components, UV rays are irradiated when passing through the UV irradiation device (UV irradiation device), the components including the applied UV curable resin are cured, and an overcoat outer layer is formed. It was set as the coat layer (overcoat inner layer and overcoat outer layer). It should be noted that the number of lamps of the UV irradiation device is increased as necessary according to the linear velocity. Then, the direction was changed by the lower guide roll, the direction was changed five times by the pass line, and the bobbin was wound by the take-up device, and the overcoat cords shown in FIGS. 1 and 2 were obtained.

  In addition, about the constituent material of an overcoat inner layer and an overcoat outer layer, as shown in Table 1, as an overcoat layer base material, the following component A ("A" in Table 1) (all the examples, comparative example 1) Comparative Example 2 and Comparative Example 5), Component B ("B" in Table 1) (Comparative Example 3), and Component C ("C" in Table 1) (Comparative Example 4) were used. And about the overcoat inner layer, the polyol of the weight average molecular weight and content described in Table 1 was further added to the component A (or component B, component C). On the other hand, for the outer layer of the overcoat, a coloring material containing an appropriate amount of pigment was added to Component A (or Component B or Component C) at a content shown in Table 1 and used.

(Component A)
As an ultraviolet curable resin, an oligomer (an oligomer in which a polypropylene glycol having a weight average molecular weight of 2000 is used as an intermediate block and hydroxyethyl acrylate is bonded to hydroxyl groups at both ends as a skeleton component through tolylene diisocyanate). Isobornyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate and N-vinylcaprolactam were used as functional monomers, and tricyclodecane dimethylol diacrylate, EO-modified bisphenol A diacrylate, and hexanediol diacrylate were used as bifunctional monomers. As photoinitiator, 1-hydroxy-cyclohexyl-phenyl-ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one was used. In addition, an appropriate amount of hindered amine light stabilizer and silicone (weight average molecular weight: about 10,000, 2% by mass with respect to the overcoat inner layer and overcoat outer layer) are mixed as an additive as the light stabilizer (in the overcoat inner layer, The weight average molecular weight and content polyol listed in Table 1 are mixed), and the molecular weight, content, and dilution monomer of the oligomer are such that the Young's modulus and glass transition temperature (Tg) are the values shown in Table 1. The overcoat layers (Example 1 to Example 7, Comparative Example 1, Comparative Example 2 and Comparative Example 5) were used by changing the conditions of ultraviolet curing such as the type and number of functional groups, the content, and the irradiation amount. The constituent material of the overcoat inner layer and the overcoat outer layer).

(Component B)
An oligomer as an ultraviolet curable resin (an oligomer in which a polypropylene glycol having a weight average molecular weight of 1000 is an intermediate block and hydroxyethyl acrylate is bonded to hydroxyl groups at both ends as a skeleton component via tolylene diisocyanate). As dilutable monomers, isobornyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, N-vinylcaprolactam as monofunctional monomers, tricyclodecane dimethylol diacrylate, EO-modified bisphenol A diacrylate, hexanediol diacrylate as difunctional monomers used. As photoinitiators, 1-hydroxy-cyclohexyl-phenyl-ketone, 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide were used. In addition, an appropriate amount of a hindered amine light stabilizer is mixed as a light stabilizer (the polyol having the weight average molecular weight and content described in Table 1 is further mixed in the overcoat inner layer), and Young's modulus and glass transition temperature (Tg ) Is the value shown in Table 1, and the molecular weight and content of the oligomer, the type and number of functional groups in the dilutable monomer, the content, the UV curing conditions such as the irradiation amount, etc. were used for different comparisons. It was set as the constituent material of the overcoat layer (overcoat inner layer and overcoat outer layer) of Example 3.

(Component C)
An oligomer as an ultraviolet curable resin (an oligomer in which a polypropylene glycol having a weight average molecular weight of 1000 is used as an intermediate block and hydroxyethyl acrylate is bonded to hydroxyl groups at both ends as a skeleton component via isophorone diisocyanate). As diluting monomer, isobornyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, N-vinylcaprolactam as monofunctional monomer, tricyclodecane dimethylol diacrylate, EO-modified bisphenol A diacrylate, hexanediol diacrylate as bifunctional monomer, As photoinitiator, 1-hydroxy-cyclohexyl-phenyl-ketone, 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide was used. In addition, an appropriate amount of a hindered amine light stabilizer is mixed as a light stabilizer (the polyol having the weight average molecular weight and content described in Table 1 is further mixed in the overcoat inner layer), and Young's modulus and glass transition temperature (Tg ) Is the value shown in Table 1, and the molecular weight and content of the oligomer, the type and number of functional groups in the dilutable monomer, the content, the UV curing conditions such as the irradiation amount, etc. were used for different comparisons. The constituent material of the overcoat layer of Example 4 (overcoat inner layer and overcoat outer layer) was used.

[Test Example 1]
About the overcoat core wire of the obtained Example 1 thru | or Example 7 and the comparative example 1 thru | or the comparative example 5, "(1) Young's modulus", "(2) “Glass transition temperature (T _g )”, “(3) coating removal power”, “(4) coating removal test under low temperature environment after aging”, “(5) transmission loss after heat cycle and after aging”, Each test of “(6) Presence / absence of protrusion after aging” and “(7) Confirmation of foaming and cavities at the sheath interface” was carried out for comparison and evaluation. The results are shown in Table 1.

(1-1) Young's modulus of overcoat layer:
A sample was obtained by removing the coating of the overcoat layer from the overcoat core wire with a removal tool (trade name: Microstrip, manufactured by Microelectronics) using a blade having a hole diameter of 0.016 inches. The end portion of the sample was adhered and fixed to an aluminum plate with a gel-like instantaneous adhesive (trade name: Aron Alpha (registered trademark), manufactured by Toagosei Co., Ltd.). Then, the aluminum plate part was chucked by a Tensilon universal tensile tester in an atmosphere of 23 ° C. × 55% RH, and the force at 2.5% elongation was measured at a marked line interval of 25 mm and a tensile speed of 1 mm / min. From this, the Young's modulus (tensile Young's modulus) was calculated.

(1-2) Young's modulus of colored layer + secondary coating layer, etc .:
While immersing the optical fiber colored core wire in about 7 cm fiber stripper (trade name: MILLER FO-103-S Fiber Optical Stripper, manufactured by Ripley Company) in liquid nitrogen, slowly glass with the fiber stripper. A tubular sample of a colored layer + secondary coating layer + primary coating layer or a colored secondary coating layer + primary coating layer was produced by drawing. Then, under the same conditions as in (1-1), a force at 2.5% elongation was measured at a tensile speed of 1 mm / min using a Tensilon universal tensile tester, and the Young's modulus was calculated from the measured value.

  In the tensile test, the primary coating layer is pulled together with the secondary coating layer (and the colored layer), but since the elastic modulus at room temperature of the primary coating layer is 1 MPa or less, the secondary coating layer And the Young's modulus of the colored layer is different by about three orders of magnitude, so that the influence is considered to be an error range even if the primary coating layer is present. As described above, even if the primary coating layer is combined, its existence is within an error range, and therefore, the Young's modulus was calculated using the values of only the secondary coating layer and the colored layer as the cross-sectional area.

(2) Glass transition temperature (T _g ) of the overcoat layer:
Similarly to the measurement of the (1-1) Young's modulus, a sample was obtained by removing the coating of the overcoat layer of the overcoat cord using a removal tool. The tubular sample was subjected to a tensile method measurement using a DMA dynamic viscoelasticity test (trade name: RSA3, manufactured by TA) under the conditions of a frequency of 1 Hz, a distance between marked lines of 20 mm, and a temperature increase rate of 3 ° C./min. In this case, the peak values appearing on the low temperature side and the high temperature side of tan δ were measured as the glass transition temperature (T _g ).

(3) Cover removal power:
Removal tool (trade name: Microstrip, manufactured by Microelectronics) Using a blade with a hole diameter of 0.016 inches, fix the core wire to the chuck of the Tensilon Universal Tensile Tester while sandwiching the overcoat core wire with the removal tool. The other side of the wire was fixed to the chuck. Then, the length of 50 mm was measured, and the maximum value of the force required to remove the 50 mm overcoat layer was measured as the coating removal force in a 23 ° C. × 55% RH atmosphere at a tensile rate of 100 mm / min. The case where the maximum value of the coating removal force was 1.4 to 3.5 N was regarded as acceptable, and the case where it was out of the range was regarded as unacceptable.

  In the following evaluations (4) to (7), the overcoat core wire was made into a cable and evaluated. As for the cable formation of the overcoat core wire, a thermoplastic resin was coated on the overcoat core wire to form a cable as a sheath. In addition, the flame retardant polyolefin was used as a thermoplastic resin, the temperature of the thermoplastic resin was 219 ° C., and the extrusion pressure was 26 MPa.

(4) Coating removal test under low temperature environment after aging:
The overcoat core wire was converted into a cable, and the obtained cable was aged at 85 ° C. × 85% RH for 30 days, and then the overcoat core wire was taken out of the cable and removed in a −20 ° C. atmosphere (trade name: Microstrip, 100 coating removal tests were carried out using a blade having a hole diameter of 0.016 inches. A case where all 100 pieces could be removed was judged as “◯”, and a case where one piece out of 100 pieces could not be removed was judged as “x”. In addition, it was set as "x" when 50 mm removal was not able to be performed, or when the colored layer and the overcoat layer were closely_contact | adhered and the colored layer turned up or when the colored layer surface cracked.

(5) Transmission loss after heat cycle and after aging:
After forming the overcoat cable into a cable, the obtained cable was subjected to a heat cycle of -30 ° C to + 70 ° C for 10 cycles (1 cycle: 6 hours), and the transmission loss was 30 at 85 ° C x 85% RH. The transmission loss after aging was measured. The transmission loss is measured by using an optical pulse tester (trade name: MW9076B, manufactured by Anritsu Co., Ltd.) and measuring the transmission loss at a wavelength of 1.55 μm in the longitudinal direction by the optical backscattering loss coefficient (OTDR). Was done. In both cases, the criterion was that the transmission loss (loss level) at a wavelength of 1550 nm was 0.05 dB / km or less.

(6) Protrusion after aging:
After the aging of (5), the presence or absence of protrusion of the optical fiber colored core wire was confirmed from the end of the overcoat core wire. The case where the protrusion was 0.2 mm or less was determined as “◯”, and the case where the protrusion exceeded 0.2 mm was determined as “x”.

(7) Confirmation of foaming and cavities at the sheath interface:
After the overcoat core wire was turned into a cable, the sheath was disassembled, and the state of the interface between the sheath and the overcoat layer of the overcoat core wire was confirmed to be foamed of the sheath and whether a cavity was formed at the interface. A case where there was no foaming or a cavity was indicated as “◯”, and a case where there was at least one of foaming and a cavity was indicated as “X”.

  In addition, as for “overall judgment”, (1-1) the Young's modulus of the overcoat layer is within a range of 40 MPa or more and less than 140 MPa at 23 ° C., and (3) the coating removal force is within a range of 1.4 to 3.5 N, (4) Coating removal test after aging is “◯”, (5) Transmission loss is 0.05 dB / km or less, (6) Presence of protruding optical fiber colored core wire after aging is “◯”, (7) A case where foaming and cavity confirmation at the sheath interface satisfied all of “◯” was judged as “◯”, and even if one of the above-mentioned items failed, it was judged as “X”.

(Composition and results)

  As shown in Table 1, the optical fiber cables of Examples 1 to 7 passed the overall evaluation (“◯”).

  On the other hand, in Comparative Examples 1 to 5, the Young's modulus at 23 ° C. is outside the range of 40 MPa or more and less than 140 MPa, and the coating removal force in an atmosphere of 23 ° C. × 55% RH is 1.4 to 3.5 N. There is nothing that satisfies all of the following: the ability to remove the coating in a low-temperature environment after aging, the absence of foaming and voids at the interface between the sheath and the overcoat layer, and the overall evaluation is also rejected ("x"). It was.

In addition to good coating removal power, the present invention is excellent in coating removal at -20 ° C. after aging, and there is no protrusion of the glass optical fiber during aging. It can be effectively used as an overcoat core wire that does not cause bleed and has high industrial applicability.

DESCRIPTION OF SYMBOLS 1 ... Overcoat core wire 10 ... Glass optical fiber 11 ... Primary coating layer (primary layer)
12 …… Secondary coating layer (secondary layer)
12a ... Colored secondary coating layer 13 ... Colored layer 2 ... Optical fiber colored core wire 3 ... Overcoat layer 31 ... Overcoat inner layer 32 ... Overcoat outer layer

Claims (3)

At least two coating layers for coating the glass optical fiber are formed around the glass optical fiber, and an overcoat layer is formed around the optical fiber colored core wire formed by coloring the outermost layer of the coating layers. An overcoat cord,
The overcoat layer includes an overcoat inner layer formed in contact with the periphery of the optical fiber colored core, and an overcoat outer layer that is formed around the overcoat inner layer and serves as an outermost layer.
The overcoat inner layer contains 25 to 33 mass% of a polyol having a weight average molecular weight of 3000 to 4000 with respect to the entire overcoat inner layer,
The overcoat outer layer contains substantially no polyol,
The overcoat core wire, wherein the Young's modulus of the overcoat layer is 40 MPa or more and less than 140 MPa.   The overcoat core wire according to claim 1, wherein the polyol contained in the overcoat inner layer is polypropylene glycol. An optical fiber cable comprising the overcoat core wire according to claim 1.

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