JP2968680B2 - Optical fiber manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an optical fiber, and more particularly to a method for forming a coating suitable for a high spinning speed during melt spinning.

[0002]

2. Description of the Related Art An optical fiber is generally provided with a soft primary coating layer and a hard secondary coating layer on a bare optical fiber. Various types have been proposed. Among these manufacturing methods, there is a method disclosed in Japanese Patent Application Laid-Open No. 2-64041.

[0003] In this manufacturing method, as shown in FIG.
Then, the optical fiber preform 2 is heated and melt-spun to form an optical fiber bare wire 3. The bare optical fiber 3 is introduced into a first resin coating device 4 and a first coating resin liquid to be a primary coating layer is applied. A secondary coating resin liquid to be a secondary coating layer is applied as it is. This is then used as a batch curing device 6
, And the two coating resin liquid layers are collectively cured to form the optical fiber 7.

As the primary and secondary coating resin liquids, an ultraviolet curing resin such as urethane acrylate or epoxy acrylate is mainly used, and as the batch curing device 6, an ultraviolet irradiation device such as an ultraviolet lamp is used. Can be In some cases, a silicone resin is used as the primary and secondary coating resin liquids. In this case, as the batch curing device 6, a heating device such as a heating furnace or an infrared lamp is used. Further, the primary coating resin liquid, Young's modulus after curing of 0.1~1kg / mm ² is the secondary coating resin solution Young's modulus after curing of 10~80kg / mm ² Used.

[0005] By the way, this production method has an advantage that the production line can be shortened because only one curing device is required.
If the spinning speed during melt spinning is relatively low, up to 500 m / min, good coating can be obtained, but the spinning speed is 50 m / min.
If it exceeds 0 m / min, the thickness of the coating layer, especially the secondary coating layer, becomes so uneven that there is a drawback that an optical fiber having a uniform coating thickness cannot be obtained.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of these circumstances, and is intended to provide an optical fiber having a quality of 500 m / mi with less uneven thickness and poor coating and good quality.
It is an object to provide a method for manufacturing at a high speed of n or more.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to apply a primary coating resin liquid to be a primary coating to a bare optical fiber after melt-spinning, and subsequently to apply a secondary coating resin liquid thereon to form a secondary coating. After the coating resin liquid is applied, in a method of manufacturing an optical fiber in which these are collectively cured, the ratio of the viscosity of the primary coating resin liquid to the viscosity of the secondary coating resin liquid at the time of application is 1.0 or more, preferably It can be solved by setting it to 1.0 to 1.6 .

[0008]

According to the method for manufacturing an optical fiber of the present invention, the viscosity ratio between the primary coating resin liquid and the secondary coating resin liquid is set to 1.0 or more, so that the interface between the primary coating layer and the secondary coating layer is increased. And the secondary coating layer can be formed thinly and uniformly on the primary coating layer.

Next, a method for manufacturing the optical fiber of the present invention will be described in detail with reference to FIG. First, an optical fiber preform 2 is heated and melt-spun in a spinning furnace 1 to form an optical fiber bare wire 3, which is led to a first resin coating device 4. In the first resin coating device 4, the primary coating resin liquid is supplied to the die pot 11, the primary coating resin liquid is applied on the bare optical fiber 3, and an uncured primary coating layer is formed. You. Next, the bare optical fiber 3 on which the primary coating layer is formed is guided to the second resin coating device 5 as it is. A secondary coating resin liquid to be a secondary coating layer is supplied to the die pot 11 of the second resin coating device 5, and the secondary coating resin liquid is applied on the uncured primary coating layer, thereby forming a secondary coating resin. A layer is formed.

This is then led to a batch curing device 6, where it is irradiated with ultraviolet light, heated, etc., to form first, second, and third curing units.
The secondary coating layer is simultaneously cured at the same time, and the optical fiber
Becomes At this time, control units 8 and 9 are provided in each of the resin coating devices 4 and 5 so as to prevent unevenness in the thickness of the applied coating layer.
Or to oscillate the die 12 relative to the optical fiber axis, Rishite the die diameter was possible fine adjustment, in the absence of the uneven thickness of the coating resin solution to the optical fiber surface at a die adjustment by the control device 8, 9 It can be applied.

In this operation, the ratio of the viscosity of the primary coating resin liquid to the viscosity of the secondary coating resin liquid applied by each of the resin coating devices 4 and 5 (hereinafter referred to simply as viscosity ratio or η ₁ / η ₂ ). Do)
Is adjusted to 1.0 or more, preferably 1.0 to 1.6, and more preferably 1.3 to 1.6. The viscosity can be adjusted by changing the composition of the coating resin liquid, adjusting the temperature of the coating resin liquid, adjusting the temperature at which the bare optical fiber enters the die pot 11, and the like. By controlling, the viscosity ratio can be set to 1.0 or more, preferably 1.0 to 1.6.

As the primary and secondary coating resin liquids, an ultraviolet curable resin such as urethane acrylate or epoxy acrylate is mainly used, and as the batch curing device 6, an ultraviolet irradiation device such as an ultraviolet lamp is used. Can be In some cases, a silicone resin is used as the primary and secondary coating resin liquids. In this case, as the batch curing device 6, a heating device such as a heating furnace or an infrared lamp is used. Further, the primary coating resin liquid, Young's modulus after curing of 0.1~1kg / mm ² is the secondary coating resin solution Young's modulus after curing of 10~80kg / mm ² Used.

In such an optical fiber manufacturing method, since the viscosity ratio between the primary coating resin liquid and the secondary coating resin liquid is set to 1.0 or more, the interface between the primary coating layer and the secondary coating layer is increased. However, since the secondary coating layer can be formed thin and uniform, the thickness of the coating layer can be prevented from being uneven, and line blur near the turn pulley 10 is greatly reduced. In addition, heat and ultraviolet rays sufficiently reach the primary coating layer in a short time, and sufficient curing can be obtained in a short curing time.

When operating the control devices 8 and 9, the surface temperature of the primary coating resin liquid immediately before the application of the secondary coating resin liquid (hereinafter, abbreviated as the input wire temperature) is 30 to 50 ° C.
It is preferable to adjust . The adjustment of the incoming wire temperature is performed by installing a heat insulating cylinder using a heater or the like or a cooling cylinder using a cooling gas such as He or Ar between the first resin coating device 4 and the second resin coating device 5. By doing so, the above-mentioned incoming wire temperature can be set to 30 to 50 ° C.

[0015] In such a production method, the spinning speed is 500-10.
This is an effective method at 00 m / min .

Next, the following measurement tests are performed to clarify the effects of the present invention. First, the relationship between the viscosity ratio and the quality of the optical fiber 7 was tested. FIG. 2 shows the relationship between the viscosity ratio and the amount of linear blur. Here, a single mode optical fiber having an outer diameter of 125 μm is used as the bare optical fiber 3, and the Young's modulus is 0.3 kg as a primary coating layer.
/ mm ² of urethane acrylate UV resin, the secondary coating urethane acrylate Young's modulus 50 kg / mm ² as a layer UV
The amount of line blur was measured using an optical fiber 7 coated with an outer diameter of 250 μm using a resin. The linear deviation was measured at a spinning speed of 1000 m / min.
This is a measured value near zero. The viscosity was adjusted by changing the temperature of the coating resin liquid to change the viscosity ratio. From this graph, it was demonstrated that when the viscosity ratio was 1.0 or more and 1.5 to 2.0, even at a high speed spinning of 1000 m / min, there was no line deviation due to this, and there was little uneven thickness.

FIG. 3 shows the relationship between the viscosity ratio and the spinning speed at which the amount of linear deviation becomes 0. The measurement conditions and the like are shown in FIG.
It is similar to that of From this graph, it can be seen that the spinning speed is 60
If it is 0 m / min or less, even if the viscosity ratio is 1.0 or less, no linear deviation occurs and no uneven thickness occurs, but 800 m / mi.
It is understood that if the viscosity ratio is not less than n, linear deviation occurs unless the viscosity ratio is 1.0 or more, and it is understood that the viscosity ratio must be at least 1.0 or more in high-speed spinning at 800 m / min or more.

Table 1 shows that the viscosity ratio is 0.4, 0.8,
It shows the result of measuring the thickness deviation of the optical fiber 7 prepared as 1.0, 1.2, 1.6. The numerical values in Table 1 are b / a values when the thinnest portion of the coating layer is a and the thickest portion is b. The thickness of the coating layer is measured by observing the cross section of the optical fiber 7 under a microscope, and other measurement conditions are the same as those in FIG. From this table, it can be seen that by setting the viscosity ratio to 1.0 or more, an optical fiber with less uneven thickness can be obtained.

[0019]

[Table 1]

FIG. 4 shows the relationship between the viscosity ratio and the loss increment. When 30 optical fiber wires 7 each having the viscosity ratio shown in Table 1 are prepared and wound with a winding force of 500 g. FIG. Other measurement conditions are the same as those in FIG. From this graph, by setting the viscosity ratio to 1.0 or more, the loss increment can be made 0.1 dB / km or less even at a high-speed spinning of 1000 m / min. Obtainable.

[0021]

According to the method for producing an optical fiber of the present invention, a bare resin wire after melt spinning is coated with a primary coating resin solution to be a primary coating, and then a secondary coating is formed on the resin solution. After the application of the secondary coating resin liquid, in a method of manufacturing an optical fiber in which these are collectively cured, the ratio of the viscosity of the primary coating resin liquid to the viscosity of the secondary coating resin liquid at the time of application is 1.0 or more, preferably Is 1.0 to 1.6, so that the primary coating layer and 2
The interface between the secondary coating layer and the secondary coating layer does not dissolve, and the secondary coating layer can be formed thinly and uniformly on the primary coating layer. Line blur is greatly reduced. In addition, heat and ultraviolet rays sufficiently reach the primary coating layer in a short time, and sufficient curing can be obtained in a short curing time .

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of a method for producing an optical fiber of the present invention.

FIG. 2 is a graph showing a relationship between a viscosity ratio and a spinning speed.

FIG. 3 is a graph showing a relationship between a viscosity ratio and a linear blur amount.

FIG. 4 is a graph showing a relationship between a viscosity ratio and a loss increment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Spinning furnace, 2 ... Optical fiber preform, 3 ... Optical fiber bare wire, 4 ... First resin coating device, 5 ... Second resin coating device, 6 ... Cooling device, 7 ... Optical fiber strand, 8.9 ...
Control device, 10: turn pulley, 11: die pot,
12 ... dice

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) C03C 25/02

Claims (2)

(57) [Claims] 1. After applying a primary coating resin liquid as a primary coating to the bare optical fiber after melt spinning, subsequently applying a secondary coating resin liquid as a secondary coating thereon, A method for producing an optical fiber, wherein the ratio of the viscosity of the primary coating resin liquid to the viscosity of the secondary coating resin liquid at the time of application is 1.0 or more. . 2. The method according to claim 1, wherein said viscosity ratio is 1.0 to 1.6.