JP2006308780A - Method of manufacturing coated optical fiber, method of manufacturing pigmented coated optical fiber, and method of manufacturing optical fiber ribbon - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a coated optical fiber in which a covering layer is formed in a single layer, and the hardness of the covering layer increases from the inside toward the outside of the layer. <P>SOLUTION: In the method of manufacturing the coated optical fiber, the covering layer is formed by forming a glass fiber 17 by drawing while heating and melting a glass fiber base material 15, applying an ultraviolet-setting resin on the outer periphery of the glass fiber 17, and irradiating the ultraviolet-setting resin with an ultraviolet ray. The ultraviolet-setting resin is applied on the glass fiber 17 after cooling the glass fiber immediately after the drawing to a temperature of -50 to <30°C, and the ultraviolet ray irradiation is performed in a state in which a temperature difference exists between the inside and the outside of the ultraviolet-setting resin, thereby forming the covering layer such that a crosslink density of the covering layer becomes higher from the inside toward the outside. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical fiber core in which a coating layer is formed on the outer periphery of a glass fiber. Further, the present invention relates to a method of manufacturing a colored optical fiber having a colored layer, and a tape fiber core having a plurality of optical fiber cores. It relates to a manufacturing method.

  In general, the optical fiber core includes a glass fiber formed of quartz glass as a main component and a coating layer provided around the glass fiber and formed of an ultraviolet curable resin. The coating layer is provided on the outer periphery of the glass fiber and is formed of a relatively soft ultraviolet curable resin, and the primary coating layer is provided on the outer periphery of the primary coating layer, and is formed of a relatively hard ultraviolet curable resin. Generally, it is composed of a secondary coating layer.

  The primary coating layer serves as a buffer layer for preventing impact on the glass fiber, and the Young's modulus of the ultraviolet curable resin forming the primary coating layer is about 0.5 to 10 MPa. The secondary coating layer has a role as a protective layer for preventing external damage and the like, and the Young's modulus of the ultraviolet curable resin forming the secondary coating layer is about 50 to 2000 MPa.

  Further, in order to make the optical fiber identifiable, an optical fiber having a colored layer as the outermost layer is used.

  As a coating method for providing a coating layer, a wet on dry method in which an ultraviolet curable resin is coated while being cured to form each coating layer separately, and a wet on wet method in which two layers of an ultraviolet curable resin are simultaneously coated and cured. There is a method.

  While the demand for optical fibers in an advanced information society is increasing, there is an increasing demand for cost reduction of optical fibers. For this reason, the drawing speed of the optical fiber has been increased, and at present, the optical fiber is manufactured at a drawing speed of 1000 to 2000 m / min, and the speed is further increased.

JP 2001-114535 A

  In order to increase the drawing speed, there are a point of increasing the curability of the resin as an element relating to the material and a point of increasing the ultraviolet ray intensity and the number of installed lamps of the ultraviolet lamp as an element relating to the equipment. Today, there is a limit to speeding up the drawing only by increasing the curability of the resin itself, and in the ultraviolet irradiation zone in the drawing device, measures can be taken by increasing the illuminance of the UV lamp and increasing the number of lamps. ing.

  Further, as the drawing speed increases, it is necessary to cool the glass fiber to 40 to 50 ° C. in the previous step of coating the resin around the glass fiber, and a cooling zone is provided before the resin coating. Generally, a forced cooling zone for blowing helium gas or the like onto a glass fiber is provided.

  As described above, in order to increase the drawing speed, it is necessary to ensure the above-described ultraviolet irradiation zone and cooling zone to be long, so that the height of the drawing tower (optical fiber core manufacturing apparatus) is further increased. Need to be high. In particular, in the wet on dry method, since the primary coating layer and the secondary coating layer are formed separately, it is necessary to ensure a long ultraviolet irradiation zone.

  On the other hand, the wet on wet method in which both coating layers are coated simultaneously has one ultraviolet irradiation zone, and therefore has an advantage that the space can be reduced as compared with the wet on dry method. However, since two types of liquid UV-curing resins are simultaneously overcoated, the viscosity of the material to be combined is likely to be restricted, and the thickness of each coating layer cannot be managed over the entire length for simultaneous coating. is there.

  Furthermore, in any method, since the primary coating layer and the secondary coating layer are formed, since two types of resins are used, it is necessary to manage each resin individually, and when changing each material It is necessary to evaluate the compatibility between the resins, and it takes time.

  In addition, there is a single-coated fiber core wire that is further coated with an ultraviolet curable resin having a Young's modulus between the primary coating layer and the secondary coating layer. In the single-coated fiber core, a single coating layer having a constant Young's modulus has a role as a buffer layer and a protective layer. For this reason, if the Young's modulus is too large, the side pressure characteristics of the fiber core will be inferior, and if the Young's modulus is too small, the coating layer will be easily damaged and inferior in durability. There is a problem that is not suitable for.

  Therefore, an object of the present invention is to provide a method of manufacturing an optical fiber core having a structure in which a coating layer is formed of a single layer and the hardness of the coating layer is increased from the inside to the outside.

In order to achieve the above object, the invention of claim 1 is to form a glass fiber by drawing a glass fiber preform while heating and melting it, and applying an ultraviolet curable resin to the outer periphery of the glass fiber. In the manufacturing method of the optical fiber core wire in which the coating layer is formed by irradiating the resin with ultraviolet rays,
The glass fiber immediately after the drawing is cooled to −50 ° C. or higher and lower than 30 ° C., and then an ultraviolet curable resin is applied, and ultraviolet rays are irradiated in a state where a temperature difference is generated inside and outside the ultraviolet curable resin. It is a manufacturing method of an optical fiber core wire which forms a coating layer whose crosslink density increases from the inside toward the outside.

According to the second aspect of the present invention, a glass fiber preform is drawn by heating and melting to form a glass fiber, an ultraviolet curable resin is applied to the outer periphery of the glass fiber, and the ultraviolet curable resin is irradiated with ultraviolet rays to be coated. In the manufacturing method of the optical fiber core wire forming the layer,
An optical fiber core wire in which a UV-curable resin is applied to a drawn glass fiber, and then the UV-curable resin is sequentially irradiated with ultraviolet rays having different light intensities to form a coating layer in which the crosslinking density increases from the inside toward the outside. It is a manufacturing method.

  According to a third aspect of the present invention, there is provided the optical fiber core manufacturing method according to the second aspect, wherein the intensity of the irradiated ultraviolet light is gradually reduced from the front side to the rear side.

According to the invention of claim 4, a glass fiber preform is drawn by heating and melting to form a glass fiber, an ultraviolet curable resin is applied to the outer periphery of the glass fiber, and the ultraviolet curable resin is irradiated with ultraviolet rays to be coated In the manufacturing method of the optical fiber core wire forming the layer,
By applying a polymerization inhibitor on the outer periphery of the glass fiber immediately after the drawing, applying an ultraviolet curable resin on the polymerization inhibitor, and irradiating the ultraviolet curable resin with ultraviolet rays, the crosslink density of the coating layer is increased. It is a manufacturing method of the optical fiber core wire which forms the coating layer which becomes higher toward the outside from the center.

  According to a fifth aspect of the present invention, in the optical fiber core manufacturing method according to any one of the first to fourth aspects, a colored layer is formed on the outer periphery of the manufactured optical fiber core. It is a manufacturing method of a core wire.

  A sixth aspect of the invention is a method for manufacturing a colored optical fiber according to the fifth aspect of the invention, wherein the plurality of colored optical fiber cores are collectively covered with an ultraviolet curable resin. .

  According to this invention, the outstanding effect that the optical fiber core wire suitable for long-distance transmission can be manufactured is exhibited.

  As an optical fiber core, there is one in which a coating layer of the optical fiber core has a single layer structure, and the coating layer is hardened from the inside to the outside (the Young's modulus is increased) (for example, JP-A-8-82727) ). As a result of studying a manufacturing method of an optical fiber core having a single-layer coating layer structure, the present inventor has found the following method and arrived at the present invention.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a schematic view of a manufacturing apparatus showing a first preferred embodiment of a method for manufacturing an optical fiber core according to the present invention.

  As shown in FIG. 1, an optical fiber core wire manufacturing apparatus 10 includes a drawing furnace 11, a cooling device 12, a coating material coating device 13, and a coating material curing device 14, and a glass fiber preform 15. Are arranged in the order of drawing furnace 11, cooling device 12, coating material coating device 13, and coating material curing device 14 in this order (from top to bottom in FIG. 1). A thermometer for measuring the temperature of the glass fiber 17 is provided between the cooling device 12 and the coating material coating device 13, and the non-contact thermometer 18 is used in the present embodiment.

  The drawing furnace 11 includes a heater 16 for heating and melting the glass fiber preform 15. The cooling device 12 is a device that cools the glass fiber 17 by blowing a cooling gas onto the glass fiber 17. The cooling gas is not particularly limited, but nitrogen is used in the present embodiment.

  The coating material coating device 13 is a device that coats the outer periphery of the glass fiber 17 with an ultraviolet curable resin, and a die or the like used in a general-purpose optical fiber drawing device is used.

  The coating material curing device 14 is a device that irradiates the ultraviolet curable resin applied to the glass fiber 17 with ultraviolet rays, and includes one or a plurality of ultraviolet lamps.

  One or more pulleys 21 may be provided below the coating material curing device 14 in order to form a drawing path for the optical fiber core wire 20.

  Next, the manufacturing method of an optical fiber core wire is demonstrated.

  First, the glass fiber preform 15 is heated and melted in the drawing furnace 11, and a part of the melted glass preform 15 falls and hardens to form the glass fiber 17. The glass fiber 17 is drawn by take-up means (not shown).

  The glass fiber 17 formed by heating and melting is rapidly cooled by blowing a cooling gas in the cooling device 12 during drawing. The temperature of the glass fiber 17 cooled in the cooling device 12 is preferably −50 ° C. or higher and lower than 30 ° C., and is preferably cooled to room temperature or lower. It is more preferable to cool to -20 to 10 ° C. The temperature of the glass fiber 17 is determined according to the crosslinking density of the coating layer, and when the crosslinking density of the coating layer is reduced, an optimum temperature may be selected according to the degree to which the crosslinking density is reduced. The temperature of the glass fiber 17 after cooling is measured by a non-contact thermometer 18, and the flow rate of the cooling gas is controlled so as to reach a desired temperature.

  The cooled glass fiber 17 is coated with an ultraviolet curable resin on the outer periphery thereof by the coating material coating device 13. Examples of the ultraviolet curable resin include polyether urethane (meth) acrylate, polyester urethane (meth) acrylate, polycarbonate urethane (meth) acrylate, polyester (meth) acrylate, epoxy (meth) acrylate, polybutadiene (meth) ) Known acrylates, fluorine (meth) acrylates and the like, and not particularly limited.

  The ultraviolet curable resin applied to the outer periphery of the glass fiber 17 is irradiated with ultraviolet rays by the coating material curing device 14. The ultraviolet curable resin irradiated with ultraviolet rays is cured to form a coating layer. A coating layer is provided on the glass fiber 17 to form an optical fiber core 20, and the optical fiber core 20 is wound around another drawing device (not shown).

  The manufacturing method of the optical fiber core wire 20 of this Embodiment makes the glass fiber 17 low temperature, and coat | covers near glass fiber 17 by apply | coating an ultraviolet curable resin to the outer surface of the glass fiber 17 made into the low temperature state. The temperature of the layer is lowered to suppress the reaction rate, and the crosslinking density is lowered.

  That is, when an ultraviolet curable resin is applied, a temperature difference is provided between the inside and outside of the ultraviolet curable resin (the inner layer side of the coating layer and the outer layer side of the coating layer), and the resin reacts by irradiation with ultraviolet rays in the coating material curing device 14. This makes a difference in the reaction rate of the resin. The reaction rate of the ultraviolet curable resin is fast in the outer layer of the coating layer, and the reaction rate of the ultraviolet curable resin is slow in the inner layer of the coating layer. When the reaction rate is high, the resin is sufficiently cured and hardened, and when the reaction rate is low, the resin is not sufficiently cured and many uncured portions remain. Accordingly, the outer layer of the resin has a high crosslink density and the inner layer of the resin has a low crosslink density, so that the cover layer has a distribution of the crosslink density.

  In the present embodiment, the crosslinking density distribution of the coating layer is adjusted by controlling the cooling temperature of the glass fiber 17 so that the crosslinking density is lower on the inner side (glass fiber side) of the coating layer and higher on the outer side. is doing. The coating layer thus formed has a higher Young's modulus of the resin forming the coating layer from the inner side to the outer side. In other words, the inner side is softer and the outer side is harder. Here, having a distribution of crosslink density means that the composition and function of the ultraviolet curable resin exhibit a continuous or stepwise change in the fiber radial direction (coating layer thickness direction).

  The crosslink density distribution of the optical fiber core manufactured by the manufacturing method of the present embodiment was measured.

  First, a method for manufacturing a sample is described.

  As shown in FIG. 2A, the optical fiber core wire 20 is embedded in a thermosetting resin 22. Next, as shown in FIG. 2B, the optical fiber core wire 20 embedded in the thermosetting resin 22 of FIG. Next, as shown in FIG. 2C, the sample 24 of 5 mm square is sliced in the cross-sectional direction with a microtome while being cooled. An infrared absorption spectrum is measured for each about 10 μm square area 25 in the thickness direction of the coating layer of the sliced sample 24 (in the radial direction of the fiber core wire 20 in FIG. 2C). A reaction rate was obtained from the measured ratio of spectral changes, and the reaction rate was converted into a crosslinking density ratio to obtain a graph showing the relationship between the position in the thickness direction of the coating layer and the crosslinking density ratio.

  As shown in FIG. 3, the distribution density ratio distribution of the cross-linking density ratio of the coating layer of the optical fiber core wire 20 manufactured by the manufacturing method of the present embodiment is as shown by a distribution line 31.

  The graph of FIG. 3 represents the relationship between the distance from the glass surface (the outer periphery of the glass fiber 17) and the crosslink density ratio in the coating layer provided in the optical fiber core wire. The crosslinking density ratio is a ratio to the crosslinking density at the outermost part of the coating layer, and is 1 at the outermost part. The other distribution lines 32, 33 and 34 will be described later.

  The optical fiber core 20 manufactured by the manufacturing method of the present embodiment has the lowest crosslink density ratio of about 0.45 at the portion (10 μm) closest to the glass fiber 17 in the coating layer, and crosslinks as the distance from the glass fiber 17 increases. The density ratio monotonously increases, and the crosslink density ratio is approximately 1 at a position of 50 μm from the glass fiber 17.

  The distribution of Young's modulus of the coating layer of the optical fiber core 20 obtained by the manufacturing method of the present embodiment is 0.3 to 10 MPa in the vicinity of the glass fiber 17 (inner layer side of the coating layer), 10 to 150 MPa in the intermediate portion, In the vicinity of the outer surface (outer layer side of the coating layer), it is preferably formed at 150 to 1000 MPa. This is because if the Young's modulus in the vicinity of the glass fiber 17 is smaller than 0.3 MPa, the inner curing is hardly promoted, and the coating layer is likely to change with time. This is because if the Young's modulus in the vicinity of the outer surface of the coating layer is greater than 1000 MPa, it is difficult to control the Young's modulus in the vicinity of the glass fiber due to the difference in crosslink density to 0.3 to 10 MPa.

  As described above, according to the manufacturing method of the present embodiment, when an ultraviolet curable resin is applied, by providing a temperature difference between the inside and outside of the resin, shock is buffered on the inner layer side of the coating layer, and the outer layer of the coating layer An optical fiber core wire suitable for long-distance transmission can be manufactured with a single-layer coating layer that can protect the optical fiber from external damage on the side.

  Further, in the manufacturing apparatus for realizing the manufacturing method of the present embodiment, the apparatus for forming the coating layer can be reduced, and the manufacturing apparatus such as the height of the drawing tower can be reduced. .

  Furthermore, as shown in FIG. 6, a colored optical fiber 60 may be formed by providing a colored layer 62 on the outer periphery of the optical fiber 20. The colored layer 62 is a layer provided as the outermost layer of the optical fiber core wire in order to identify the optical fiber core wire 20, and is formed of, for example, an ultraviolet curable resin to which a colorant such as a pigment is added.

  Further, as shown in FIG. 7, a plurality of colored optical fiber cores 60 in FIG. 6 (four in FIG. 7) are arranged in a row, and they are collectively covered with an ultraviolet curable resin 71, and a tape fiber core wire 70 is attached. It may be formed.

  Next, a preferred second embodiment of the method for manufacturing an optical fiber core wire will be described.

  As shown in FIG. 4, the optical fiber core manufacturing apparatus 40 is provided with a plurality of coating material curing apparatuses 14 by omitting the cooling device 12 and the non-contact thermometer 18 of the optical fiber core manufacturing apparatus 10 of FIG. 1. It is.

In the present embodiment, a coating material coating device 13 and a plurality of coating material curing devices 14 are arranged below the drawing furnace 11 in this order. The plurality of coating material curing devices 14 (14a, 14b... 14n in FIG. 4) emit ultraviolet rays having different intensities. The UV intensity output from each coating material curing device 14 is different, and in this embodiment, the intensity is set to 50, 40, 30, ²⁰ , 10 mW / cm ² in order from the front side to the rear side. Each coating material curing device 14 may be arranged so that the light intensity of the emitted ultraviolet light is arranged in ascending or descending order from the drawing furnace 11 side or emitted if the ultraviolet curable resin is sequentially irradiated with ultraviolet light having different light intensity. You may arrange | position regardless of the light intensity of an ultraviolet-ray. However, in order to prevent the possibility that only the outer side of the coating layer is cured and the inner side remains uncured, the respective coating material curing devices 14 are arranged so that the light intensity is descending from the drawing furnace 11 side. Is preferred.

The resin applied to the glass fiber 17 is first irradiated with ultraviolet light having the strongest light intensity of 50 mW / cm ^2, and the ultraviolet light is transmitted inside the resin and absorbed inside and outside the resin. Next, the glass fiber 17 is drawn downward and irradiated with 40 mW / cm ² of ultraviolet light having a light intensity lower than that of the ultraviolet light. The ultraviolet light has a lower light intensity that passes through the resin than the ultraviolet light of 50 mW / cm ² , and is difficult to reach the resin on the inner layer side. In other words, since ultraviolet rays pass through the resin while being absorbed by the resin, ultraviolet rays with low light intensity have a shallower depth of the resin that transmits light than ultraviolet rays with high light intensity. The inner layer side of the layer is more difficult to solidify.

Further, by gradually irradiating ultraviolet rays with weak light intensity of 30, 20, 10 mW / cm ² , the outer resin sufficiently absorbs ultraviolet rays and is cured with a high crosslinking density. On the other hand, the deeper the resin on the inside, the lower the light intensity of the absorbed ultraviolet light, and the hardened the resin with a low crosslink density.

  As shown in FIG. 3, the cross-link density distribution of the optical fiber core by the optical fiber core manufacturing method of the present embodiment becomes a distribution line 32, and from the inside to the outside of the coating layer as in the previous embodiment. The crosslink density ratio increases monotonically, and the optical fiber core has the same effect as the optical fiber core of the previous embodiment.

  In addition, although a plurality of coating material curing devices 14a, 14b,... 14n that output ultraviolet rays having different intensities are provided, a plurality of ultraviolet lamps that output ultraviolet rays having different strengths are provided in one coating material curing device 14, respectively. You may make it irradiate sequentially the ultraviolet rays of each intensity | strength within one apparatus.

  In the method of manufacturing the optical fiber core according to the present embodiment, the coating layer is formed by irradiating ultraviolet rays having different light intensities. However, an ultraviolet curable resin having a photoinitiator having a different absorption wavelength is applied to the outer peripheral surface of the glass fiber 17. It may be coated and irradiated with a plurality of ultraviolet rays having different wavelengths to form a coating layer having a crosslink density distribution.

  The photoinitiator can adjust the wavelength and the amount of ultraviolet light absorbed by the ultraviolet curable resin depending on the type and the amount contained in the ultraviolet curable resin, such as acetophenone-based, benzoin-based, thioxanthone-based, acylphosphine oxide-based, etc. A well-known thing is mentioned.

  Next, a preferred third embodiment of the method for manufacturing an optical fiber core wire will be described.

  As shown in FIG. 5, the basic components of the optical fiber core manufacturing apparatus 50 of the present embodiment are substantially the same as those of the optical fiber manufacturing apparatus 10 of FIG. 1 described above. The same reference numerals as those in the case of 1 are given. However, the optical fiber core manufacturing apparatus 50 omits the cooling device 12 and the non-contact thermometer 18 of the optical fiber core manufacturing apparatus 10 of FIG. 1, and is provided with a polymerization inhibitor coating apparatus 51 and a near infrared irradiation apparatus 52. Is. Specifically, a polymerization inhibitor coating device 51 and a near infrared irradiation device 52 are arranged in this order from the drawing furnace 11 side between the drawing furnace 11 and the coating material coating apparatus 13.

  The polymerization inhibitor coating apparatus 51 is an apparatus that applies a solution obtained by dissolving a polymerization inhibitor in an organic solvent to the outer peripheral surface of the glass fiber 17. Polymerization inhibitors are those that inhibit UV curable resins from forming crosslinks, such as hydroquinone, methoquinone, p-benzoquinone, phenothiazine, mono-t-butylhydroquinone, catechol, pt-butylcatechol, benzoquinohydroxy. Well-known things, such as toluene, are mentioned. Further, highly volatile methanol was used as a solvent for dissolving the polymerization inhibitor.

  The near-infrared irradiation device 52 is a device that irradiates near-infrared rays and dries the methanol solution applied to the surface of the glass fiber 17 by the heat. The methanol solution may be dried by natural drying, but can be dried at high speed by irradiating near infrared rays.

  A methanol solution containing a polymerization inhibitor is applied to the glass fiber 17 by the polymerization inhibitor coating device 51, and only the polymerization inhibitor is attached by the near infrared irradiation device 52. An ultraviolet curable resin is applied onto the polymerization inhibitor by the coating material resin application device 13. At the same time as the UV curable resin is applied, the polymerization inhibitor is diffused to the resin side. At this time, since the polymerization inhibitor is applied to the surface of the glass fiber 17, the polymerization inhibitor increases toward the inner layer side of the resin and decreases toward the outer layer side.

  Next, when the resin containing the polymerization inhibitor is irradiated with ultraviolet rays by the coating material curing device 14, since the polymerization inhibitor is more on the inner layer side of the resin, the proportion of the resin that forms a crosslink even when irradiated with ultraviolet rays is small. Since the polymerization inhibitor is less on the outer layer side, the ratio of forming a crosslink by irradiation with ultraviolet rays is large. Therefore, it is possible to form the optical fiber core wire 20 having a lower crosslink density of the cover layer toward the inner layer side of the cover layer and a higher crosslink density of the cover layer toward the outer layer side.

  As shown in FIG. 3, the cross-link density distribution of the optical fiber core by the optical fiber core manufacturing method of the present embodiment is a distribution line 33, and from the inside to the outside of the coating layer as in the previous embodiment. The crosslink density ratio increases monotonically, and the optical fiber core has the same effect as the optical fiber core of the previous embodiment.

  The manufacturing methods of the first to third embodiments described above are not only used alone, but may be combined. For example, after the glass fiber 17 is cooled by the cooling device 12, a polymerization inhibitor is applied to the outer peripheral surface of the glass fiber 17, an ultraviolet curable resin is applied, and then ultraviolet rays having different light intensities are sequentially irradiated to form a coating layer. May be.

  Next, embodiments of the present invention will be described based on examples, but the embodiments of the present invention are not limited to these examples.

Example 1
Pressurized die of urethane acrylate UV curable resin (Young's modulus: 200 ± 50MPa) heated to 50 ° C at a speed of 1800m / min on the outer circumference of quartz glass fiber (diameter d = 125 ± 1μm) cooled to 5 ℃ Then, the resin was cured by irradiating ultraviolet rays with an ultraviolet irradiation device (Fusion, 6 kW × 5 lamp, output 80%) to cure the ultraviolet curable resin, and an optical fiber core having an outer diameter of 245 μm was obtained.

(Example 2)
A urethane acrylate UV curable resin (Young's modulus: 200 ± 50 MPa) heated to 50 ° C at a speed of 1800 m / min is applied to the outer periphery of a quartz glass fiber (diameter d = 125 ± 1 μm) with a pressure die, and ultraviolet rays are applied. UV curable resin is passed through the UV irradiation device with UV light intensity of 50, 40, 30, ^20, and 10 mW / cm ² respectively, with 5 UV irradiation devices equipped with transmission filters (transmission wavelength 300-400nm, maximum transmission wavelength 360nm) Was cured to obtain an optical fiber core having an outer diameter of 245 μm.

(Example 3)
A methanol solution with a concentration of polymerization inhibitor 2,5-bis (1,1-dimethylbutyl) hydroquinone of 2 wt% was applied to the outer periphery of quartz glass fiber (diameter d = 125 ± 1μm), and a near-infrared furnace (furnace) After passing through a length of 200 mm x 1), apply a urethane acrylate UV curable resin (Young's modulus: 200 ± 50 MPa) heated to 50 ° C with a pressure die, and then irradiate an ultraviolet irradiation device (Fusion, 6 kW x 5 lights) , Output 80%), the UV curable resin was cured to obtain an optical fiber core with an outer diameter of 245 μm.

(Comparative example)
Urethane acrylate UV curable resin (Young's modulus: 200 ± 50MPa) heated to 50 ° C at a speed of 1800m / min on the circumference of quartz glass fiber (diameter d = 125 ± 1μm) at 30 ° C with a pressure die After coating, the ultraviolet curable resin was cured with an ultraviolet irradiation device (Fusion, 6kW × 5 lamp, output 80%) to obtain an optical fiber core having an outer diameter of 245 μm.

  The characteristics of the optical fiber cores obtained in Examples 1 to 3 and the comparative example were evaluated by the following evaluation methods.

<Bending test>
The amount of increase in loss when an optical fiber core was wound 10 times around a cylinder with a radius of 15 mm was measured using a power meter.

<Initial loss measurement>
Three optical fiber cores with a 1000 m bundle were prepared, and transmission losses at wavelengths of 1.31 μm and 1.55 μm were measured using the OTDR (Optical Time Domain Refractometer) method in accordance with IEC60793-1-40.

<Temperature characteristics test>
Prepare 3 bundles of 1000m bundle optical fiber, perform 10 cycles at -60 ~ 70 ℃ (temperature change rate 1 ℃ / min) according to IEC60793-1-52, loss of fiber optic cable Changes were measured.

<Moist heat test>
Three bundles of 1000 m bundles of optical fiber were prepared, and the loss change of the optical fiber after 30 days at 85 ° C.-85% RH was measured according to IEC60793-1-50.

<Jelly immersion test>
Three bundles of 1000 m optical fiber cores were prepared, and the loss change of the optical fiber cores after 30 immersions in 85 ° C. jelly was measured according to Bellcore standard GR-20.

<Curl radius>
The curl radius of the optical fiber core wire was measured in accordance with IEC60793-1-34. Here, the curl radius is a value that represents the magnitude of bending that is naturally formed in the optical fiber core after drawing, and the greater the curl radius, the greater the curvature of the bend and the closer to a straight line the optical fiber. It can be said that it is a heart line.

  Table 1 summarizes the evaluation of each test of the optical fiber cores produced in Examples 1 to 3 and Comparative Example.

  The loss characteristics and curl radii of Examples 1 to 3 were all better than the comparative examples. Thereby, it can be said that each optical fiber core wire of Examples 1-3 is an optical fiber core wire suitable for long-distance transmission, having various durability and high reliability.

  The crosslink density distribution of the coating layer of the optical fiber core wire produced in the comparative example is as shown by the distribution line 34 shown in FIG. 3, and the crosslink density of the coating layer is substantially constant in the fiber radial direction.

It is the schematic of the manufacturing apparatus explaining suitable 1st Embodiment of the manufacturing method of the optical fiber core wire which concerns on this invention. FIG. 2A to FIG. 2C are schematic diagrams illustrating a method for preparing a sample when measuring the crosslink density ratio of the coating layer. It is a figure which shows the relationship between the distance from the glass fiber of a coating layer, and a crosslinking density ratio. It is the schematic of the manufacturing apparatus explaining suitable 2nd Embodiment of the manufacturing method of an optical fiber core wire. It is the schematic of the manufacturing apparatus explaining suitable 3rd Embodiment of the manufacturing method of an optical fiber core wire. It is a cross-sectional view which shows a colored optical fiber core wire. It is a cross-sectional view which shows a tape fiber core wire.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Optical fiber manufacturing apparatus 11 Drawing furnace 12 Cooling device 13 Coating material coating apparatus 14 Coating material hardening apparatus 17 Glass fiber 20 Optical fiber core wire

Claims (6)

An optical fiber core in which a glass fiber preform is drawn by heating and melting to form a glass fiber, an ultraviolet curable resin is applied to the outer periphery of the glass fiber, and the ultraviolet curable resin is irradiated with ultraviolet rays to form a coating layer In the manufacturing method of the wire,
The glass fiber immediately after the drawing is cooled to −50 ° C. or higher and lower than 30 ° C., and then an ultraviolet curable resin is applied, and ultraviolet rays are irradiated in a state where a temperature difference is generated inside and outside the ultraviolet curable resin. A method of manufacturing an optical fiber core, comprising forming a coating layer having a crosslinking density that increases from the inside toward the outside. An optical fiber core in which a glass fiber preform is drawn by heating and melting to form a glass fiber, an ultraviolet curable resin is applied to the outer periphery of the glass fiber, and the ultraviolet curable resin is irradiated with ultraviolet rays to form a coating layer In the manufacturing method of the wire,
After coating the drawn glass fiber with an ultraviolet curable resin, the ultraviolet curable resin is sequentially irradiated with ultraviolet rays having different light intensities to form a coating layer whose crosslink density increases from the inside to the outside. An optical fiber core manufacturing method.   The method of manufacturing an optical fiber core wire according to claim 2, wherein the intensity of the irradiated ultraviolet light is gradually weakened from the front side to the rear side. An optical fiber core in which a glass fiber preform is drawn by heating and melting to form a glass fiber, an ultraviolet curable resin is applied to the outer periphery of the glass fiber, and the ultraviolet curable resin is irradiated with ultraviolet rays to form a coating layer In the manufacturing method of the wire,
By applying a polymerization inhibitor on the outer periphery of the glass fiber immediately after the drawing, applying an ultraviolet curable resin on the polymerization inhibitor, and irradiating the ultraviolet curable resin with ultraviolet rays, the crosslink density of the coating layer is increased. A method of manufacturing an optical fiber core, comprising: forming a coating layer that increases from the outside toward the outside.   5. The method of manufacturing a colored optical fiber according to claim 1, wherein a colored layer is formed on an outer periphery of the manufactured optical fiber. 6. The method for producing a colored optical fiber according to claim 5, wherein a plurality of the produced colored optical fibers are collectively covered with an ultraviolet curable resin.

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