JP2004067429A - Method of manufacturing optical fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problems of the fluctuation of the outer diameter or the like of a resin layer coated on an optical fiber at the time of drawing with a high speed, and to provide a resin which is used for coating of the optical fiber and has excellent production stability. <P>SOLUTION: Drawing is carried out in a temperature range in which the ratio of the value of the dielectric dissipation factor at the coating resin temperature in the optical fiber drawing process to the value of the dielectric dissipation factor at the dielectric dissipation factor peak temperature at a frequency of 1 Hz of the resin for the coating of the optical fiber becomes ≥0.8. Alternatively, drawing is carried out at a temperature at which the ratio of the value of the dielectric dissipation factor at the coating resin temperature in the optical fiber drawing process to the value of the dielectric dissipation factor at the dielectric dissipation factor peak temperature at a frequency of 1 Hz of the resin for the coating of the optical fiber becomes ≥0.8 and in a range between the temperature in the higher temperature side than the dielectric dissipation factor peak temperature and the dielectric dissipation factor peak temperature. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a resin-coated optical fiber. More specifically, the present invention relates to a method for producing a resin-coated optical fiber which can form a resin-coated layer having a small outer diameter variation and an excellent appearance at a high drawing speed.
[0002]
[Prior art]
Generally, an optical fiber is manufactured as follows. First, the preform is heated and melted by a heater and stretched to obtain a bare optical fiber having a predetermined diameter. The bare optical fiber is passed through a coating die to apply a liquid resin to the outer periphery. Subsequently, the resin is passed through a curing device to cure the applied liquid resin to form a resin coating layer (primary coating layer).
[0003]
In the step of applying the liquid resin, the liquid resin heated to a certain temperature is supplied to the coating die. Usually, another resin coating layer (secondary coating layer) is further formed to improve the mechanical strength of the optical fiber such as scratch resistance and lateral pressure characteristics.
[0004]
In recent years, the usage of optical fibers has increased with the increase in communication capacity, and the production of optical fibers has increased significantly. As a countermeasure, it is necessary to increase the drawing speed to improve productivity. However, the draw speed could not be increased because problems such as poor appearance may occur. Therefore, it is necessary to solve a problem occurring in a step of drawing a resin-coated optical fiber at an early stage. In particular, at the time of high-speed drawing such as 1000 m / min or more, poor appearance of the coating resin has been one of the problems.
[0005]
The appearance defect is a problem of an outer diameter fluctuation at the time of drawing or a non-uniformity observed at an interface between the primary resin coating layer and the secondary resin coating layer of the optical fiber after drawing. The non-uniformity observed at the interface between the primary resin coating layer and the secondary resin coating layer of the optical fiber is that when this interface is observed with a microscope, the interface line is straight because the interface is not smooth. This is a phenomenon that looks uneven.
[0006]
[Problems to be solved by the invention]
As a method for solving the above problem, for example, Japanese Patent Application Laid-Open No. 7-33482 discloses a wide drawing speed by setting the peak temperature of dielectric loss before curing to 32 ° C. or less when the measurement frequency is 1 Hz. A technique has been disclosed in which a resin coating layer having a uniform thickness can be provided without being adjusted in temperature and the like and without uneven thickness.
[0007]
However, the above technique may be effective for uneven thickness when the drawing speed is changed, but it does not solve problems such as abnormal outer diameter and appearance problem of the coating resin at a constant drawing speed. However, it did not guarantee production stability.
[0008]
Therefore, an object of the present invention is to solve appearance problems such as outer diameter fluctuation in an optical fiber coating resin layer and non-uniformity observed at an interface between a primary resin coating layer and a secondary resin coating layer during high-speed drawing. Another object of the present invention is to provide an optical fiber coating resin having excellent production stability.
[0009]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, a first aspect of the present invention is to provide a method for forming a dielectric tangent at a coating resin temperature in an optical fiber drawing process with respect to a dielectric tangent value of a dielectric tangent peak temperature at a frequency of 1 Hz of an optical fiber coating resin. Is drawn within a temperature range corresponding to a value of 0.8 or more.
[0010]
According to a second aspect of the present invention, the ratio of the value of the dielectric loss tangent at the coating resin temperature in the optical fiber drawing process to the value of the dielectric loss tangent at the dielectric loss tangent peak temperature at a frequency of 1 Hz of the optical fiber coating resin is 0.8. A method for producing a resin-coated optical fiber, characterized in that drawing is performed within a range between a temperature corresponding to the above and higher than the dielectric loss tangent peak temperature and a dielectric tangent peak temperature.
[0011]
A third aspect of the present invention is a method for producing a resin-coated optical fiber, wherein the viscosity of the resin for coating an optical fiber is in the range of 0.1 to 10 Pa · s.
[0012]
A fourth aspect of the present invention is a method for producing a resin-coated optical fiber, wherein the resin for coating an optical fiber is an ultraviolet curable resin.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described. The present inventors have conducted intensive studies to solve the above-described problems, and as a result, the dielectric loss tangent value at the peak temperature of the dielectric loss tangent of the resin for optical fiber coating, and the dielectric loss tangent value of the resin temperature in the drawing step. A correlation was found between them, and the present invention was completed.
[0014]
That is, the ratio of the value of the dielectric tangent at the temperature of the coating resin in the optical fiber drawing process to the value of the dielectric tangent at the peak temperature of the dielectric tangent at a frequency of 1 Hz of the optical fiber coating resin is 0.8 or more. This is a method for producing a resin-coated optical fiber, characterized by drawing inside.
[0015]
The background to the present invention will be described below. Here, the dielectric loss means that when an AC electric field is applied to the dielectric, the dipole present in the molecule vibrates in response to the electric field, but as the frequency increases, the vibration of the dipole can follow the electric field. It refers to the phenomenon or the amount of energy that is lost and lost as energy by causing a shift (such as friction).
[0016]
The magnitude is calculated by the ratio between the real part ε ′ and the imaginary part ε ″ of the complex permittivity, and is represented by a dielectric tangent tan δ (= ε ″ / ε ′).
[0017]
The complex permittivity is defined by the ratio between the electric flux density D and the electric field E. When the change in the electric flux density D has a phase delay, it is expressed by the following equation.
ε = D / E = ε′−iε ″
Here, ε ′ and ε ″ are real numbers.
[0018]
Further, assuming that the angular frequency is ω and the loss angle is δ,
_{E = E 0 exp (iωt)} , D = D 0 exp (ωt-δ)
Then
ε ′ = (D ₀ / E ₀ ) cos δ, ε ″ = (D ₀ / E ₀ ) sin δ
It becomes.
[0019]
The dielectric loss tangent is a value defined by ε ″ / ε ′ = tan δ, and changes with temperature and frequency.
[0020]
An example of a method for measuring the dielectric constant (ε ′) and the dielectric loss coefficient (ε ″) of the resin according to the present invention will be described with reference to FIGS. 6 and 7. As the measurement method, the parallel plate method shown in FIG. There are bulk measurement and fringe field measurement in which a pair of comb-shaped electrodes are designed on the planar substrate shown in FIG.
[0021]
In FIG. 6, the dielectric constant (ε ′) and the dielectric loss coefficient (ε ″) are such that an ineffective resin 61 is sandwiched between the electrodes 62 and an AC voltage 73 is excited between the two contacted electrodes. This is based on a method of measuring a sinusoidal current as a response.
[0022]
In FIG. 7, for example, when the gap between the electrodes is set to 100 μm, for example, an ineffective resin 71 is applied to a thickness of 200 μm or more so as to have a thickness equal to or more than this gap, and then contacted. This is based on a method of exciting an AC voltage 73 to one electrode and measuring a sinusoidal current as a response.
[0023]
Here, when the excitation frequency, electrode area, and distance between electrodes are known, changes in the phase and amplitude of the response are converted into the basic dielectric properties of dielectric constant (ε ') and dielectric loss (ε "). Can be.
[0024]
FIG. 5 shows an example of the temperature characteristic of the dielectric loss at a constant frequency. When the horizontal axis is temperature, the left vertical axis is the dielectric constant (ε ′) and the dielectric loss coefficient (ε ″), and the right vertical axis is the dielectric loss tangent tanδ, the dielectric loss tangent is a curve having a convex maximum value. The temperature at which the dielectric loss tangent is maximized is called the peak temperature.
[0025]
In the present invention, for the correlation between the dielectric loss tangent value at the peak temperature of the dielectric loss tangent and the manufacturing stability, the reason is not clear, but after conducting a number of tests, a temperature range where the change in the value of the dielectric loss tangent is large is large. It was found that the production stability was not good.
[0026]
That is, in the present invention, the type of the raw material resin, the additive, and the compounding ratio thereof are appropriately selected, and the value of the dielectric tangent at the peak temperature of the dielectric tangent at a frequency of 1 Hz is compared with the value of the coating resin temperature in the optical fiber drawing step. It was found that favorable results could be obtained by drawing within a temperature range in which the ratio of the dielectric loss tangents was 0.8 or more. Within this temperature range, it is possible to obtain a resin-coated optical fiber that has good production stability even at the time of high-speed drawing and does not cause any appearance problem.
[0027]
An embodiment will be described with reference to FIG. The vertical axis of FIG. 2 shows the relationship between tan δ and temperature measured for one example of the resin. The measured value shows a gentle curve, the temperature at the maximum point is 40 ° C., and the value of tan δ is 9.5. In the present invention, the resin is coated within a range corresponding to a value obtained by multiplying the value of tan δ by 0.8, that is, a temperature corresponding to 7.6. That is, it is sufficient to carry out in a range of 15 ° C. to 65 ° C. The object of the present invention can be achieved by coating the optical fiber within this temperature range.
[0028]
Further, in the present invention, the ratio of the value of the dielectric loss tangent at the coating resin temperature in the optical fiber drawing step to the value of the dielectric loss tangent at the dielectric loss tangent peak temperature at a frequency of 1 Hz is a temperature corresponding to 0.8 or more. It was found that a more favorable result could be obtained by drawing a line within the range between the temperature higher than the tangent peak temperature and the dielectric tangent peak temperature. Within this temperature range, it is possible to obtain a resin-coated optical fiber that has good production stability even at the time of high-speed drawing and does not cause any appearance problem.
[0029]
That is, the description will be continued with reference to the example of FIG. In the case of coating at a peak dielectric loss tangent between 40 ° C. and 15 ° C., the resin viscosity is high, so that the coating property on the glass fiber is poor. Therefore, it is desirable to coat at a peak temperature of the dielectric loss tangent between 40 ° C. and 65 ° C. However, there is a problem that the viscosity decreases when the temperature approaches 65 ° C.
[0030]
On the other hand, if the temperature exceeds 65 ° C., the viscosity is too low, and the variation in the thickness to be applied is undesirably large. Accordingly, the ratio of the value of the dielectric loss tangent at the coating resin temperature in the optical fiber drawing step is a temperature corresponding to 0.8 or more, and the temperature higher than the dielectric loss tangent peak temperature and the dielectric loss tangent peak temperature are within the range. It is desirable to draw with.
[0031]
Incidentally, the raw material resin used for the resin for coating an optical fiber of the present invention is not particularly limited, and may be a resin generally used for coating an optical fiber. That is, a resin that is cured by light such as ultraviolet light or heat is preferably used. Specifically, a photocurable resin such as an ultraviolet-curable urethane resin, an ultraviolet-curable (meth) acrylate resin, an ultraviolet-curable silicone resin, an ultraviolet-curable epoxy resin, or a copolymer or a mixture thereof is used. .
[0032]
The viscosity of the resin for coating an optical fiber of the present invention is not particularly limited, but is preferably in the range of 0.1 to 10 Pa · s. If it is lower or higher than this, the applicability to the glass fiber deteriorates, and the dimensional stability decreases.
[0033]
【Example】
Hereinafter, the method for producing an optical fiber of the present invention will be described in more detail with reference to examples. A drawing apparatus as shown in FIG. 1 was used. That is, the preform 11 was heated and melted by the heater 12 and stretched to obtain a bare optical fiber 13 having an outer diameter of 125 μm. The bare optical fiber 13 was passed through a coating die 14 and an ultraviolet curable resin 15 was applied. Subsequently, the liquid resin applied by passing through the ultraviolet irradiation device 16 was cured. Then, a resin-coated optical fiber 18 was obtained by forming a resin-coated layer (primary coating layer). The drawing speed was 1500 m / min.
[0034]
When the secondary coating layer is formed, similarly to the case of the primary coating layer, a coating die, an ultraviolet irradiation device, and a tank for the ultraviolet curing resin for the secondary coating layer are further provided below the outer diameter measuring device. Can be done by
[0035]
The ultraviolet curable resin was supplied from the ultraviolet curable resin tank 19 to the coating die 14. The outer diameter fluctuation of the resin-coated optical fiber 18 was measured using the outer diameter measuring device 17. The interface between the primary coating layer and the secondary coating layer in the resin coating layer of the optical fiber was observed with a microscope. Hereinafter, examples and comparative examples will be described. The results are summarized in Table 1 as FIG.
[0036]
(Example 1)
FIG. 2 shows the measurement results of the dielectric loss tangent of the resin for coating the optical fiber (resin A). The peak temperature of the dielectric loss tangent of the resin A at a frequency of 1 Hz is 40 ° C. The temperature of the dielectric loss tangent (tan δ) at which the ratio of the peak temperature of the dielectric loss tangent to the dielectric loss tangent (tan δ) at 40 ° C. becomes 0.8 or more is 15 ° C. to 65 ° C. Therefore, using an ultraviolet curable resin having the above characteristics, drawing was performed at a resin temperature of 40 ° C.
[0037]
(Example 2)
As in Example 1, the peak temperature of the dielectric loss tangent of the resin for coating the optical fiber (resin A) at a frequency of 1 Hz is 40 ° C., and the temperature at which the ratio of the dielectric loss tangent to the dielectric loss tangent value at the peak temperature is 0.8 is 65. An ultraviolet curable resin having a temperature of ° C. was used. However, drawing was performed at a resin temperature of 60 ° C.
[0038]
(Example 3)
FIG. 3 shows the measurement result of the dielectric loss tangent of the resin for coating the optical fiber (resin B). The peak temperature of the dielectric loss tangent of the resin B at a frequency of 1 Hz is 35 ° C. The temperature of the dielectric loss tangent (tan δ) at which the ratio of the peak temperature of the dielectric loss tangent to the dielectric loss tangent (tan δ) at 35 ° C. becomes 0.8 or more is 20 ° C. to 50 ° C. Using an ultraviolet-curable resin having this property, drawing was performed at a resin temperature of 35 ° C.
[0039]
(Example 4)
As in Example 3, the peak temperature of the dielectric loss tangent of the resin for coating the optical fiber (resin B) at a frequency of 1 Hz is 35 ° C., and the temperature at which the ratio of the dielectric loss tangent to the dielectric loss tangent value at the peak temperature is 0.8 is 50. An ultraviolet curable resin having a temperature of ° C. was used. However, drawing was performed at a resin temperature of 50 ° C.
[0040]
(Comparative Example 1)
UV curable resin having a peak temperature of a dielectric tangent of 40 ° C. at a frequency of 1 Hz of the resin for coating an optical fiber (resin A) and a temperature of 65 ° C. at which the ratio of the dielectric tangent at the peak temperature of the dielectric tangent to 0.8 is 0.8 ° C. Was used. However, the temperature of the resin was set to 70 ° C., and the drawing was performed at a temperature outside the range.
[0041]
(Comparative Example 2)
UV curable resin having a dielectric tangent peak temperature of 35 ° C. at a frequency of 1 Hz of the optical fiber coating resin (resin B) and a temperature of 50 ° C. at which the ratio of the dielectric tangent value at the dielectric tangent peak temperature to 0.8 is 0.8 ° C. Was used. However, the temperature of the resin was 55 ° C., and the drawing was performed at a temperature outside the range.
[0042]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to the optical fiber manufacturing method of this invention, the optical fiber coating resin excellent in the external appearance and manufacturing stability of an optical fiber coating resin layer can be obtained even at the time of high-speed drawing of 1000-2000 m / min. . Specifically, the resin for coating an optical fiber of the present invention has a ratio of the dielectric tangent value of the temperature of the coating resin in the optical fiber drawing process to the dielectric loss tangent value at the peak temperature of the dielectric tangent measured at a frequency of 1 Hz of 0. .8 or more.
[Brief description of the drawings]
FIG. 1 is an example of an optical fiber drawing apparatus.
FIG. 2 shows the results of dielectric loss tangent measurement of resin A.
FIG. 3 shows the results of dielectric loss tangent measurement of resin B.
FIG. 4 is a list of results of Examples and Comparative Examples, which is Table 1 shown in FIG.
FIG. 5 is a diagram illustrating a dielectric constant, a dielectric loss, and a dielectric loss tangent.
FIG. 6 is a schematic view of a bulk measurement method using a parallel plate method. FIG. 7 is a schematic view showing a fringe field measurement method in which a pair of comb-shaped electrodes is designed on a planar substrate.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 Preform 12 Heater 13 Optical fiber bare wire 14 Coating die 15 Ultraviolet curing resin 16 Ultraviolet irradiation device 17 Outer diameter measuring device 18 Resin coated optical fiber 19 Ultraviolet curing resin liquid tank 61 Uncured resin 62 Plate electrode 71 Uncured Resin 72 Comb electrode 73 AC power supply

Claims (4)

The ratio of the value of the dielectric loss tangent at the coating resin temperature in the optical fiber drawing process to the value of the dielectric loss tangent of the dielectric loss tangent peak temperature at a frequency of 1 Hz of the optical fiber coating resin is within a temperature range corresponding to 0.8 or more. A method for producing a resin-coated optical fiber, comprising: The ratio of the dielectric loss tangent value at the coating resin temperature in the optical fiber drawing process to the dielectric loss tangent value at the dielectric tangent peak temperature at a frequency of 1 Hz of the optical fiber coating resin is a temperature corresponding to 0.8 or more and The method for producing a resin-coated optical fiber according to claim 1, wherein the drawing is performed within a range between a temperature higher than the tangent peak temperature and a dielectric tangent peak temperature. The method for producing a resin-coated optical fiber according to claim 1, wherein the viscosity of the resin for coating an optical fiber is in a range of 0.1 to 10 Pa · s. The method for producing a resin-coated optical fiber according to any one of claims 1 to 3, wherein the resin for coating an optical fiber is an ultraviolet curable resin.

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