JP2004067466A - Method for curing ultraviolet curing resin - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for sufficiently curing an ultraviolet curing resin applied on an optical fiber. <P>SOLUTION: The optical fiber F coated with the ultraviolet curing resin by a die is introduced into a protective quartz tube 13 in a UV curing furnace 26. Cooling air is introduced into the UV-curing furnace 26 from an introducing tube 3 and discharged from an exhaust tube 4 so as to cool a UV lamp 1. At this time, the cooling air does not enter into the protective tube 13 because the absolute value of exhaust pressure is higher than the introducing pressure of the cooling air. Substantially oxygen-free gaseous nitrogen is supplied into an upper oxygen-free chamber 24 installed above the UV-curing furnace 26, and the gaseous nitrogen is supplied to the insides of a tube 23 and the protective tube 13, too. Thereby, the oxygen concentration of the atmosphere at the periphery of the optical fiber F is maintained to be ≤1,000 ppm until the curing of the resin by irradiation with ultraviolet ray is completed. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method of curing an ultraviolet-curable resin for curing an ultraviolet-curable resin applied to an optical fiber.
[0002]
[Prior art]
In recent years, optical communication for transmitting a large amount of information has been widely spread. The demand for optical fibers used for the optical communication is also increasing. Optical fibers for optical communication are made of quartz.However, if the surface of the optical fiber is damaged, it will be broken by a small force from the damaged part. It has been subjected. As a resin for resin coating, an ultraviolet curable resin having a short curing time after application is generally used for improving productivity. The one coated with resin immediately after drawing the optical fiber from the base material is called a strand, and the one coated with resin again is called a core. In addition, in order to handle multi-channel signals, a plurality of optical fiber cores are usually arranged in parallel and taped and used (hereinafter, the taped one is referred to as an optical fiber tape core).
[0003]
Such an optical fiber ribbon is prepared by arranging single-core optical fibers coated in advance with resin, applying an ultraviolet curable resin in a tape shape, and curing the resin by irradiation with ultraviolet light. Each single-core optical fiber core is colored differently so that it can be distinguished which channel is used. This color is formed by preliminarily mixing a pigment or the like into a resin coated on each optical fiber.
[0004]
Further, the ultraviolet curable resin applied to the optical fiber is cured by being irradiated with ultraviolet light in a curing furnace, and the UV lamp that emits ultraviolet light is forcibly cooled by cooling air to reach a high temperature.
[0005]
When using the above-mentioned optical fiber tape, the resin applied in the tape shape is peeled off and separated into single fibers for connection to optical equipment or another optical fiber.
[0006]
[Problems to be solved by the invention]
However, if the curing of the resin coating of each single core is insufficient, the resin applied in the form of a tape comes into close contact with the resin coating of the single core, and a problem occurs that the resin cannot be separated into single cores. Sometimes. The reason why the single-core resin coating is insufficiently cured is that the resin surface is exposed to oxygen during the period from application of the resin to curing by ultraviolet rays. In other words, the curing reaction is hindered by oxygen, so that poor curing occurs on the surface of the resin, and if an ultraviolet-curable resin is further applied to this surface to form a tape, the interface is strongly adhered. It is considered that this oxygen often comes from the cooling air of the UV lamp.
[0007]
The present invention has been made in view of such circumstances, and an object of the present invention is to provide a method of curing an ultraviolet curable resin that sufficiently cures an ultraviolet curable resin applied to an optical fiber.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, a negative pressure is set in the curing furnace to prevent the cooling air of the curing furnace from flowing around the optical fiber.
[0009]
Specifically, the invention according to claim 1 is an ultraviolet curable resin that applies an ultraviolet curable resin to an optical fiber, and then cures the ultraviolet curable resin by inserting the optical fiber into a curing furnace and irradiating ultraviolet rays. For curing methods.
[0010]
Then, a protective tube that penetrates the curing furnace in advance and allows the optical fiber to pass therethrough is provided, and when ultraviolet light is applied to the ultraviolet curable resin applied to the optical fiber by inserting the optical fiber into the protective tube. The pressure inside the curing furnace is set to be higher inside the protection tube than outside the protection tube.
[0011]
According to the method of claim 1, since the air in the curing furnace does not enter the protective tube due to the pressure difference, the ultraviolet curable resin applied to the surface of the optical fiber inserted into the protective tube is not used. In addition, the curing of the ultraviolet-curable resin is hardly inhibited by oxygen, and the ultraviolet-curable resin can be sufficiently cured even on the application surface. Therefore, even if an ultraviolet curable resin is further applied thereon and cured, the interface does not adhere and the peeling does not become difficult.
[0012]
Next, in the invention according to claim 2, when irradiating ultraviolet rays to the ultraviolet curing resin applied to the optical fiber in the curing furnace, cooling air is introduced into the curing furnace and outside the protective tube. The inside of the curing furnace is cooled, and then the cooling air is discharged out of the curing furnace and the absolute value of the discharge pressure is made higher than the introduction pressure of the cooling air, so that the air pressure inside the curing furnace is reduced toward the inside of the protective tube. 2. The method for curing an ultraviolet curable resin according to claim 1, wherein the height of the ultraviolet curable resin is set to be higher than the outside of the protective tube.
[0013]
According to the method of the second aspect, it is possible to easily prevent the cooling air introduced into the curing furnace from entering the protection tube, and it is possible to prevent the curing failure of the ultraviolet curing resin.
[0014]
Next, a third aspect of the present invention is the method for curing an ultraviolet curable resin according to the first or second aspect, wherein a substantially oxygen-free gas is supplied into the protective tube.
[0015]
According to the method of the third aspect, it is possible to reliably prevent air in the curing furnace from entering the protective tube, and to easily set the periphery of the uncured ultraviolet curable resin in a substantially oxygen-free state. can do.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0017]
(Embodiment)
FIG. 1 schematically shows an ultraviolet curing resin coating device 20 according to the embodiment. The ultraviolet curable resin coating device 20 is a device for coating a colored ultraviolet curable resin on the optical fiber F by coating and curing to form a colored optical fiber core T.
[0018]
The ultraviolet curable resin coating device 20 includes a delivery bobbin 21, a supply sheave 22 provided diagonally above the delivery bobbin 21, a die 25, a cylinder 23, and a UV curing furnace using ultraviolet rays, which are sequentially arranged below the delivery bobbin 21. 26 (curing furnace) and an outer diameter measuring device 27, a direction changing sheave 28 provided below the outer diameter measuring device 27, and first and second windings provided diagonally above the direction changing sheave 28. The take-up auxiliary sheaves 29 and 30, the dancer roller 31 provided between the first and second take-up auxiliary sheaves 29 and 30, and the take-up bobbin 32 provided diagonally below the second take-up auxiliary sheave 30. Have.
[0019]
The optical fiber F is wound around the delivery bobbin 21, and the optical fiber F is drawn obliquely upward by the winding force of the winding bobbin 32. The optical fiber F wound around the delivery bobbin 21 is primarily coated with resin at the time of drawing so that the optical fiber composed of the core and the clad prevents scratches on the surface of the bare fiber and does not cause brittle fracture of the glass. This is what is called a so-called optical fiber.
[0020]
The supply sheave 22 winds the optical fiber F drawn from the delivery bobbin 21 to change the running direction downward.
[0021]
The dice 25 is provided with a hole in the vertical direction, the diameter of which is larger than the diameter of the optical fiber F. The optical fiber F supplied from the supply sheave 22 is inserted through the hole, and the surface of the optical fiber F is inserted during the insertion. Is coated with an uncured liquid colored ultraviolet curable resin.
[0022]
The tube 23 is provided between the die 25 and the UV curing furnace 26, and the optical fiber F passes through the inside of the tube 23.
[0023]
The UV curing furnace 26 is provided with an optical fiber F in which an uncured liquid UV-curable resin is applied, and the UV-curable resin is cured by UV irradiation while entering through an entrance and exiting through an exit. A core wire T is formed.
[0024]
The outer diameter measuring device 27 is inserted with the optical fiber core T coming out of the UV curing furnace 26, detects the outer diameter width of the optical fiber core T during the insertion, and sends the information to a control device (not shown). It is configured to judge whether or not a product within a predetermined tolerance is manufactured and detect an abnormality.
[0025]
The direction changing sheave 28 wraps the optical fiber core T from the outer diameter measuring device 27 and changes the traveling direction of the optical fiber core T running downward to diagonally upward.
[0026]
The first and second winding assist sheaves 29 and 30 are wound around the optical fiber core T from the direction changing sheave 28 in order, and guide the optical fiber core T to the winding bobbin 32. In the direction changing sheave 28 to the first and second winding assist sheaves 29 and 30, the heated optical fiber core T is cooled with the curing of the ultraviolet curable resin.
[0027]
The dancer roller 31 applies a predetermined load to the optical fiber core T between the first and second winding auxiliary sheaves 29 and 30 and winds the optical fiber core T around the winding bobbin 32 with a constant tension applied. To be able to
[0028]
The take-up bobbin 32 takes up the manufactured optical fiber core T from the second take-up auxiliary sheave 30 under tension.
[0029]
The UV-curable resin in the die 25 contains a polymer monomer and a polymerization initiator that is activated by being decomposed or the like by irradiation with ultraviolet light, and it is preferable to use an acrylic, epoxy, or urethane-based resin. Can be. Here, if oxygen is present, activation of the polymerization initiator is inhibited, resulting in insufficient or no polymerization. The ultraviolet curing resin is colored with a pigment or the like, and the optical fiber core T is coated with a desired color such as red or blue and wound.
[0030]
Next, the curing step will be described.
[0031]
FIG. 4 is a schematic vertical sectional view of the UV curing furnace 26, and FIG. 5 is a schematic horizontal sectional view. A quartz protective tube 13 is placed inside the UV curing furnace 26 so as to penetrate vertically, and an optical fiber F passes through the tube. The protective tube 13 and the UV lamp 1 are placed inside the curing furnace 26 and are surrounded by the reflector 2. The reflector 2 has an elliptical horizontal cross section. The UV lamp 1 and the optical fiber F are placed on the two focal points and extend vertically. Therefore, the ultraviolet light 7 emitted from the UV lamp 1 passes directly through the protective tube 13 and is irradiated on the optical fiber F, or the ultraviolet light 7 emitted in the other direction is reflected by the reflection plate 2 to be highly efficient and uniform. The ultraviolet curing resin applied to the optical fiber F and applied to the surface of the optical fiber F is uniformly cured.
[0032]
Since the temperature of the UV lamp 1 becomes extremely high, cooling air is introduced into the UV curing furnace 26 from the introduction pipe 3, and the cooling air passes through the many holes 5 formed in the reflecting plate 2 to cool the UV lamp 1. After cooling and flowing outside the protection tube 13, the gas is discharged from the exhaust pipe 4 through the hole 5. Since the optical fiber F is protected by the protective tube 13 from touching the cooling air, the optical fiber F is not shaken by the flow of the cooling air, and the dust in the cooling air does not adhere.
[0033]
The protection tube 13 extends to the upper oxygen-free chamber 24 and the lower oxygen-free chamber 35 installed above and below the UV curing furnace 26 in order to avoid the influence of cooling air. It is open. Respective boundaries between the main body of the UV curing furnace 26 and the upper oxygen-free chamber 24 and the lower oxygen-free chamber 35 are separated by walls. Nitrogen gas is introduced into the upper oxygen-free chamber 24 and the lower oxygen-free chamber 35 from nitrogen introduction pipes (supply pipes) 11 and 36, respectively, so that the interior is substantially oxygen-free. If a commercially available cylinder-filled nitrogen gas is used as the nitrogen gas, the oxygen content is 10 ppm or less, and if the nitrogen gas is from a PSA device using an adsorption method, the oxygen content is 100 ppm or less. For these, these gases can be said to be substantially oxygen-free gases. The nitrogen gas is also supplied from the upper and lower oxygen-free chambers 24 and 35 into the protective tube 13, and the atmosphere around the optical fiber F in the UV curing furnace 26 is almost nitrogen gas.
[0034]
Next, the portion from the exit of the die 25 to the entrance of the UV curing furnace 26 will be described. FIG. 3 is a schematic sectional view between the die 25 and the UV curing furnace 26 according to the present embodiment.
[0035]
In the present embodiment, the upper surface of the upper oxygen-free chamber 24 is the iris 12, so that the size of the central hole can be changed. The iris 12 is used to minimize the leakage of ultraviolet rays from the UV curing furnace 26 to the outside, and to first pass the optical fiber F into the UV curing furnace 26 or to perform maintenance work. This is for ease. The iris 12 is similarly installed in the lower oxygen-free chamber 35.
[0036]
An O-ring 14 is provided between the protection tube 13 and a hole of the upper oxygen-free chamber 24 through which the protection tube 13 is inserted. 13 is sealed so as not to enter. The O-ring 14 is also installed in the lower oxygen-free chamber 35.
[0037]
Although this O-ring 14 is made of heat-resistant fluoro rubber, it becomes very high temperature by the UV lamp 1, so when the pressure in the UV curing furnace 26 becomes higher than the pressure in the upper oxygen-free chamber 24 to some extent, The seal is broken and cooling air enters the upper oxygen-free chamber 24. In this case, the ultraviolet curing resin on the surface of the optical fiber F in the protective tube 13 comes into contact with oxygen, and the curing is inhibited. Therefore, in the present embodiment, the absolute value of the discharge pressure of the cooling air is set higher than the introduction pressure. With this setting, the space in the UV curing furnace 26 through which the cooling air flows has a negative pressure, and the inside of the protection tube 13 in the UV curing furnace 26 has a higher pressure than the outside of the protection tube 13. The seal of the O-ring 14 is not broken and the cooling air does not enter the upper oxygen-free chamber 24. This is the same in the lower oxygen-free chamber 35. Even if the pressure in the UV curing furnace 26 is higher to some extent than in the upper oxygen-free chamber 24, the O-ring 14 seals the cooling air so as not to enter the upper oxygen-free chamber 24. Since the discharge pressure is not constant, unless the absolute value of the cooling air discharge pressure is set higher than the introduction pressure, it is difficult to reliably prevent the cooling air from entering the upper oxygen-free chamber 24. is there.
[0038]
In the present embodiment, since the cylinder 23 is installed and connected between the upper oxygen-free chamber 24 and the lower surface of the die 25, the state from the outlet of the die 25 to the upper oxygen-free chamber 24 is completely shut off from the outside air. It has become. Therefore, when the nitrogen gas is supplied into the upper oxygen-free chamber 24, the nitrogen gas is also supplied into the cylinder 23 from the central hole of the iris 12, and the lower part of the die 25 is filled with the nitrogen gas. . Since no air enters the cylinder 23 from the outside, this state does not change regardless of whether the optical fiber F is running or not, so that the curing is completed even if the ultraviolet curable resin is applied at a high speed. The atmosphere around the optical fiber F is in a gas state from which oxygen has been substantially removed, and the ultraviolet curable resin is completely cured to the surface. Therefore, even if this optical fiber core wire T is processed into a tape core wire, no peeling failure occurs when the optical fiber core wire T is peeled off from the tape into a single core.
[0039]
On the other hand, in the apparatus in which the cylinder 23 is removed as shown in FIG. 2, the nitrogen gas is supplied into the upper oxygen-free chamber 24 and exits from the hole of the iris 12 when the optical fiber F is not running. The oxygen-free chamber 24 is filled with nitrogen gas and is substantially in an oxygen-free state. However, when the optical fiber F is moved from the top to the bottom of the figure for applying the ultraviolet curing resin, the iris is The air existing up to 12 is drawn into the upper oxygen-free chamber 24 by the traveling optical fiber F. Accordingly, oxygen enters the upper oxygen-free chamber 24 and further enters the protection tube 13, and the curing of the ultraviolet curable resin on the surface of the optical fiber F is hindered. Since the amount of oxygen entering increases in proportion to the traveling speed of the optical fiber F, in this apparatus, if the ultraviolet curable resin is not coated at a low speed of less than 400 m / min, poor curing will occur, and productivity will increase. Is difficult to raise. In this apparatus, a large amount of nitrogen gas should be flowed in order to prevent air from being drawn in due to the running of the optical fiber F. In this case, the nitrogen gas is blown violently onto the optical fiber F. The optical fiber F is shaken, and so-called line blur occurs, which is not preferable.
[0040]
Here, the atmosphere around the optical fiber F when the nitrogen gas is supplied depends on the amount of oxygen initially present in the cylinder 23, the UV curing furnace 26, and the upper and lower oxygen-free chambers 24 and 35. It is determined by the amount of cooling air leaking to the upper and lower oxygen-free chambers 24 and 35 and the flow rate of nitrogen gas. This is preferable because there is no substantial problem. Actually, the flow rate of the nitrogen gas may be adjusted so that the oxygen concentration becomes 1000 ppm or less. When the oxygen concentration is 500 ppm or less, the occurrence of poor curing hardly occurs, which is more preferable. Also in this case, the adjustment is made by the flow rate of the nitrogen gas. Further, since the space closed by the cylinder 23 is formed, the amount of the supplied nitrogen gas is small, and it is not necessary to supply the nitrogen gas in such a large amount as to shake the optical fiber F. Furthermore, even if the traveling speed of the optical fiber F is increased, curing failure of the ultraviolet curable resin does not occur, and the productivity is greatly improved.
[0041]
In the present embodiment, the oxygen pressure in the protective tube 13 is reduced from 2.3% to 400 ppm by changing the inlet pressure of the cooling air from 235 kPa and the discharge pressure of −88 kPa to the inlet pressure of 166 kPa and the discharge pressure of −176 kPa. Poor curing of the cured resin has been drastically reduced.
[0042]
As described above, the method for curing the ultraviolet curable resin and the apparatus for applying the ultraviolet curable resin according to the present embodiment include both a die 25 and an upper oxygen-free chamber 24 provided above a UV curing furnace 26. The air can be prevented from entering from the outside by a simple method of installing the cylinder 23 connected to the outside. Since the absolute value of the discharge pressure is higher than the introduction pressure of the cooling air in the UV curing furnace 26, it is possible to prevent the cooling air from entering the upper oxygen-free chamber 24. Further, by supplying an oxygen-free nitrogen gas to the upper oxygen-free chamber 24, the atmosphere around the optical fiber F, that is, the atmosphere around the surface of the uncured ultraviolet-curable resin is made almost free of oxygen, and curing failure of the ultraviolet-curable resin is reduced. Even if the coating speed is increased, poor curing does not occur and productivity is improved.
[0043]
(Other embodiments)
The above embodiment is an exemplification, and the present invention is not limited to this example. Argon gas or the like may be used instead of nitrogen gas, and any gas may be used as long as it is a substantially oxygen-free gas. The configuration, structure, and process of the ultraviolet curable resin coating device 20 are not limited to those described in the embodiment, and another member or process may be inserted, or some members may be removed. Further, the structure and shape of the cylinder 23 and the UV curing furnace 26 are not limited. For example, instead of the iris 12, a disk having a hole at the center may be used. Further, the method of the present invention or the apparatus of the embodiment may be used in the step of coating with an ultraviolet curable resin at the time of drawing or at the time of forming into a tape.
[0044]
Further, as shown in FIG. 6, the upper end of the cylinder 23 may not be connected to the lower surface of the die 25, and a gap may be provided between the two. Here, there is a gap of about 3 mm between the cylinder 23 and the lower surface of the die 25. However, since this gap is narrow, even if the optical fiber F runs at high speed, it is obstructed by the nitrogen gas flowing out from this gap and externally. Air cannot enter the cylinder 23. Therefore, the same operation and effect as the embodiment can be obtained. Even if this gap is widened to 10 mm, the supply of nitrogen gas is increased to such an extent that the optical fiber F is not displaced, thereby preventing the intrusion of external air and allowing the inside of the cylinder 23, the upper oxygen-free chamber 24 and The oxygen concentration in the protective tube 13 can be set to 1000 ppm or less, and poor curing of the ultraviolet curable resin can be prevented.
[0045]
【The invention's effect】
The present invention is implemented in the form described above, and has the following effects.
[0046]
Since the pressure inside the UV curing furnace is set to be higher inside the protection tube than outside the protection tube, the cooling air inside the UV curing furnace does not enter the inside of the protection tube, so that the curing inhibition of the ultraviolet curing resin can be prevented. Since the absolute value of the discharge pressure is higher than the inlet pressure of the cooling air, it is possible to easily prevent the cooling air from entering the protection tube. Since an oxygen-free gas is supplied into the protective tube, poor curing of the ultraviolet curable resin can be easily and reliably prevented, and the application speed of the ultraviolet curable resin can be increased.
[Brief description of the drawings]
FIG. 1 is a schematic view of an ultraviolet curable resin coating device according to an embodiment, as viewed from the side.
FIG. 2 is a schematic vertical sectional view of an apparatus having no cylinder between a lower surface of a die and an upper portion of a UV curing furnace.
FIG. 3 is a schematic vertical sectional view between a lower surface of a die and an upper part of a UV curing furnace according to the embodiment.
FIG. 4 is a schematic vertical sectional view of a UV curing furnace according to the embodiment.
FIG. 5 is a schematic horizontal sectional view of a UV curing furnace according to the embodiment.
FIG. 6 is a schematic vertical sectional view between a lower surface of a die and an upper portion of a UV curing furnace according to another embodiment.
[Explanation of symbols]
7 Ultraviolet rays 11, 36 Nitrogen introduction pipe (supply pipe)
13 Protection tube 26 UV curing furnace (curing furnace)
F Optical fiber

Claims (3)

An ultraviolet curing resin is applied to the optical fiber, and thereafter, the ultraviolet curing resin is cured by inserting the optical fiber into a curing furnace and irradiating ultraviolet rays to cure the ultraviolet curing resin,
A protective tube that penetrates the curing furnace in advance and inserts the optical fiber is provided, and when irradiating ultraviolet rays to the ultraviolet curing resin applied to the optical fiber by inserting the optical fiber into the protective tube, A method for curing an ultraviolet curable resin, wherein the pressure inside a curing furnace is set to be higher inside the protective tube than outside the protective tube. When irradiating the ultraviolet curable resin applied to the optical fiber with ultraviolet light in the curing furnace, cooling air is introduced into the curing furnace and outside the protective tube to cool the inside of the curing furnace. By discharging the air outside the curing furnace and making the absolute value of the discharge pressure higher than the introduction pressure of the cooling air, the pressure inside the curing furnace is made higher inside the protection tube than outside the protection tube. 2. The method for curing an ultraviolet curable resin according to claim 1, wherein the setting is performed. 3. The method according to claim 1, wherein a substantially oxygen-free gas is supplied into the protective tube.

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