JPH0524098B2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an optical fiber coating method and an optical fiber coating die, and in particular, it is not affected by fluctuations in the position of the glass fiber due to bending of the glass fiber core base material or fluctuation of the glass fiber due to purge gas in an electric furnace. The present invention relates to an optical fiber coating method and an optical fiber coating die that can uniformly coat the outer circumferential surface of a glass fiber with a coating material without unevenness in thickness and easily manufacture a high-quality optical fiber.

[Conventional technology]

Optical fiber spinning is performed by an optical fiber drawing apparatus shown in FIG. 11, and this optical fiber drawing apparatus 100 heats and melts an optical fiber preform 101 in an electric furnace 102 or the like and draws (referred to as drawing) a glass fiber. Make 110. The glass fiber 110 drawn out from the electric furnace 102 and spun is measured by an outer diameter measuring device 103 and controlled to have a predetermined outer diameter. In this state, the surface is easily scratched and its mechanical strength is weak, so in order to protect the surface, a primary coating of thermosetting resin (coating material 10 shown in FIG.
Apply as 9). This coating die 10
4 is fixed to the XY stage 105.
This XY stage 105 is for centering the coating die 104. That is, the X-Y stage 105 is controlled so that the glass fiber 110 passes through the center of the coating die 104 by moving in the X and Y directions as shown in FIG. The glass fiber 110 that has been primarily coated with this coating die 104 is heated in a drying oven 106, and since the primary coating material is a thermosetting resin, the glass fiber 110 is hardened and dried by the applied heat, and then taken to a capstan 107.
The film is wound onto the winding drum 108 via the winding drum 108. After being wound onto this winding drum 108, in the next step, a thermoplastic material such as nylon is used to make the optical fiber easier to handle and to serve as a protective layer when turning the optical fiber into a cable. It is then coated as a dressing. In this way, optical fibers are coated with primary coatings, secondary coatings, etc. to improve mechanical properties and ease of handling as optical fiber core wires. Conventionally, the coating die 104 that performs the primary coating of the optical fiber core wire manufactured in this manner is
It has a configuration as shown in FIGS. 13 to 17. That is, in the coating die 104, the upper openings 111 and 121 are as shown in FIGS. 14 and 16, and the lower openings 112 and 122 are as shown in FIGS.
As shown in FIGS. 5 and 17, it is formed in a circular or triangular shape, and the upper opening 111 is larger than the diameter of the lower opening 112 as shown in FIG. , 13th
As shown in the figure, a taper 113 is formed. For this reason, the X-
Centering was performed using the Y stage 105.

[Problem to be solved by the invention]

In addition, in the case of such conventional optical fiber coating dies, the setting position of the coating die at the start of optical fiber core production remains fixed from the start of the spinning operation until the end, and the shape of the coating die exit is fixed. , circular or triangular shapes that make it difficult to maintain the fiber position at the center at all times, and the glass fiber position may change due to bending of the optical fiber core base material, or the glass fiber may be wired due to purge gas in the electric furnace. Due to the shaking, uneven thickness occurs in the primary coating formed on the outer peripheral surface of the glass fiber, as shown in FIG. 18, and there is a problem in that it is not always possible to obtain a good optical fiber of constant quality. The present invention allows the coating material to be applied to the outer peripheral surface of the glass fiber without being affected by fluctuations in the position of the glass fiber due to bending of the glass fiber core base material or fluctuation of the glass fiber due to purge gas in the electric furnace. It is an object of the present invention to provide an optical fiber coating method and an optical fiber coating die that can coat uniformly without uneven thickness and easily manufacture optical fibers of good quality.

[Means to solve the problem]

In order to achieve the above object, in the optical fiber coating method of the present invention, the outer circumferential surface of the glass fiber is coated by supplying a coating material in an irregular cross-sectional outer circumferential shape. In addition, in order to achieve the above object, the optical fiber coating die of the present invention is configured by forming a plurality of protrusions toward the lower opening of the coating die from around the lower opening. be. Preferably, the plurality of protrusions formed in the lower opening have a curved shape having a predetermined curvature. Moreover, it is preferable that the plurality of protrusions formed in the lower opening are four. Furthermore, it is preferable that the protrusion is formed symmetrically about the center point. Furthermore, it is preferable that the width of each recess formed by the plurality of projections is smaller than the diameter of the glass fiber. Furthermore, it is preferable that each recess formed by the plurality of projections has a curved shape having a predetermined curvature.

[Effect]

When producing a cored optical fiber, a primary coating is applied through a coating die, and the glass fiber is centered and a coating material is supplied in an uneven cross-sectional outer circumferential shape to coat the outer circumferential surface of the glass fiber. In order to coat the coating material in this uneven cross-sectional outer peripheral shape, the coating die is configured by forming a plurality of protrusions from around the lower opening toward the lower opening. Therefore, immediately after coating the primary coating,
The outer circumferential surface of the glass fiber is formed with an uneven cross-section, but due to the surface tension of the coating material and resin pressure, the outer circumferential surface of the glass fiber is smoothed uniformly before it is thermally cured, and when curing is completed, the surface of the glass fiber is smoothed. The primary coating is uniformly coated on the outer circumferential surface without uneven thickness, and an optical fiber of good quality is manufactured.

【Example】

Examples of the present invention will be described below. First Embodiment (FIGS. 1 to 4) FIGS. 1 to 4 show a first embodiment of an optical fiber coating method and an optical fiber coating die according to the present invention. In the figure, the coating die is formed into a rectangular shape as shown in FIG. 12, and is configured to be fixed to the X-Y stage 105 shown in FIG. 11. As shown in FIG. 2, a through hole 8 is formed in the coating die 1, and as is clear from the plan view of the coating die 1 shown in FIG. It has a circular upper opening 2 at its upper part. Further, at the lower part of the coating die 1 from which the glass fiber 6 comes out, there is a lower opening 4 having a smaller diameter than the upper opening 2, as is clear from the bottom view of the coating die 1 shown in FIG. It is formed. A taper 3 is provided at a predetermined distance inside the through hole 8 that connects the upper opening 2 and the lower opening 4. As shown in FIG. 3, the lower opening 4 has a shape in which the four corners of a square opening are chamfered at a predetermined curvature. That is, from the opening, the four corners of the square opening are closed by a predetermined width by the projections 5 having a predetermined curvature. The coating material 7 is quantitatively supplied to the through hole 8 of the coating die 1 from a coating material supply device. This covering material 7 is made of a thermosetting material. The coating die 1 is set by the X-Y stage 105 so that the glass fiber 6 passes through the coating material 7 approximately at the center of the lower opening 4, and the glass fiber 6 is centered. After this centering has been carried out, the covering material 7
is supplied, and the glass fiber 6 passes through the covering material 7 and exits from the lower opening 4. When exiting from the lower opening 4 of the coating die 1, the initial coating shape of the coating material 7 formed on the outer peripheral surface of the glass fiber 6 is determined. Therefore, the coating material 7 applied to the glass fiber 6 immediately after exiting the lower opening 4 has the same cross-sectional shape as the lower opening 4 as shown in FIG. A protrusion 9 is formed in the direction. While the glass fiber 6 coated with the coating material 7 travels and reaches the drying oven 106,
In the coating material 7 of the glass fiber 6, the protrusion 9 formed in the outer circumferential direction is gradually smoothed due to the resin surface tension. That is, the shape of the coating material 7 coated on the glass fiber 6 is such that the protruding portion 9 formed in the outer circumferential direction moves into the recessed portion of the coating material 7, and the shape becomes as shown in FIG. 4B. As it runs, it further changes into the shape shown in FIG. Second Embodiment (FIGS. 5 to 7) FIGS. 5 to 7 show a second embodiment of the optical fiber coating method and optical fiber coating die according to the present invention. In the figure, the coating die 10 is formed into a rectangular shape similar to the first embodiment shown in FIG. 1, and is fixed to an X-Y stage 105 shown in FIG. 11. As shown in FIG. 5, this coating die 10 is formed with a through hole 14, into which the glass fiber 6 is inserted, as is clear from the plan view of the coating die 10 shown in FIG. The coating die 10 has a circular upper opening 11 at its upper part. Also, this glass fiber 6
As is clear from the bottom view of the coating die 10 shown in FIG. 6, a lower opening 12 having a smaller diameter than the upper opening 11 is formed in the lower part of the coating die 10 from which the coating die 10 exits. A through hole 14 connecting the upper opening 11 and the lower opening 12
A predetermined distance taper is provided inside the holder, similar to the first embodiment shown in FIG. As shown in FIG. 6, the lower opening 12 has a shape in which four sides of a square opening are chamfered at a predetermined curvature. That is, from the opening, the four sides of the square opening are blocked by a predetermined width by the projections 13 having a predetermined curvature. Through hole 1 of this coating die 10
A coating material 7 is quantitatively supplied to 4 from a coating material supplying device (not shown). The coating die 10 is set by the X-Y stage 105 so that the glass fiber 6 passes through the coating material 7 approximately at the center of the lower opening 12, and the glass fiber 6 is centered. After this centering has taken place, the dressing 7 is applied and the glass fiber 6 passes through the dressing 7 and exits through the lower opening 12. This coating die 10
When exiting from the lower opening 12 of the glass fiber 6, the initial coating shape of the coating material 7 formed on the outer peripheral surface of the glass fiber 6 is determined. Therefore, the coating material 7 applied to the glass fiber 6 immediately after exiting the lower opening 12 has the same cross-sectional shape as the lower opening 12 as shown in FIG. A protrusion 15 is formed in the direction. While the glass fiber 6 coated with the coating material 7 travels and reaches the drying oven 106, the coating material 7 of the glass fiber 6 has a protrusion 15 formed in the outer circumferential direction due to resin surface tension. It is gradually smoothed out. That is, the shape of the coating material 7 coated on the glass fiber 6 is such that the protruding portion 15 formed in the outer circumferential direction moves to the recessed portion of the coating material 7, and the shape becomes as shown in FIG. 7B. As it runs, the shape further changes to the shape shown in FIG. Third Embodiment (FIGS. 8 to 10) FIGS. 8 to 10 show a third embodiment of the optical fiber coating method and optical fiber coating die according to the present invention. In the drawing, the coating die 20 is formed into a rectangular shape, similar to the first embodiment shown in FIG. 1, and is fixed to an X-Y stage 105 shown in FIG. 11. As shown in FIG. 8, this coating die 20 is formed with a through hole 24, into which the glass fiber 6 is inserted, as is clear from the plan view of the coating die 20 shown in FIG. The upper part of the coating die 20 has a circular upper opening 21 . Also, this glass fiber 6
As is clear from the bottom view of the coating die 20 shown in FIG. 9, a lower opening 22 having a smaller diameter than the upper opening 21 is formed in the lower part of the coating die 20 from which the coating die 20 exits. A through hole 24 connecting this upper opening 21 and lower opening 22
A predetermined distance taper is provided inside the holder, similar to the first embodiment shown in FIG. As shown in FIG. 9, this lower opening 22 is formed by chamfering the four sides of a square opening with a predetermined curvature.
It also has a shape with four arcuate corners. That is, from the opening, the four sides of the square opening are blocked by a predetermined width by the projections 23 having a predetermined curvature. The coating material 7 is quantitatively supplied to the through hole 24 of the coating die 20 from a coating material supply device. The coating die 20 is controlled by the X-Y stage 105 so that the glass fiber 6 passes through the coating material 7 approximately at the center of the lower opening 22, and the glass fiber 6 is centered. After this centering has taken place, the dressing 7 is applied and the glass fiber 6 passes through the dressing 7 and exits through the lower opening 22. This coating die 20
When exiting from the lower opening 22 of the glass fiber 6, the initial coating shape of the coating material 7 formed on the outer peripheral surface of the glass fiber 6 is determined. Therefore, the coating material 7 applied to the glass fiber 6 immediately after exiting the lower opening 22 has the same cross-sectional shape as the lower opening 22 as shown in FIG. A protrusion 25 is formed in the direction. While the glass fiber 6 coated with the coating material 7 travels and reaches the drying oven 106, the coating material 7 of the glass fiber 6 is coated with a protrusion 25 formed in the outer circumferential direction due to resin surface tension.
is gradually smoothed out. That is, the shape of the coating material 7 coated on the glass fiber 6 is such that the protruding portion 25 formed in the outer circumferential direction moves into the recessed portion of the coating material 7, and the shape becomes as shown in FIG. 10B.
As the glass fiber 6 travels further, as shown in FIG.
The shape changes to the one shown in the figure, and the drying oven 10
In the vicinity of the entrance 6, the shape is almost a perfect circle.

【Effect of the invention】

Since the present invention is configured as described above, it has the effects described below. Since the cross-sectional shape of the opening of the coating die is uneven, the coating material is uniformly smoothed on the surface of the glass fiber while the fiber is running, and the position of the glass fiber changes due to bending of the base material, etc., and the glass fiber is damaged due to the purge gas in the electric furnace. It is possible to uniformly coat the outer circumferential surface of a glass fiber with a coating material without unevenness in thickness without being affected by line fluctuations, and to easily manufacture a high-quality optical fiber. In addition, since the coating die is constructed by forming a plurality of protrusions from around the lower opening toward the center of the lower opening of the coating die, even if the base material bends or the line sways due to purge gas, etc., the protrusions will not protrude. Since the fiber is held at the center of the die by the resin pressure of the concave resin flow formed between the concave portion and the protrusion, it is possible to easily manufacture optical fibers of good quality at all times. Since the plurality of protrusions formed in the lower opening have a curved surface shape with a predetermined curvature, the resin flow is stabilized and the coating material is more uniformly applied to the surface of the glass fiber while the glass fiber is running. Can be smoothed. Furthermore, by increasing the number of protrusions formed in the lower opening to four and forming them symmetrically around the center point,
The resin flow and resin pressure from each protrusion can be averaged, and the coating material can be coated more uniformly on the glass fiber surface. In addition, since the width of each recess formed by multiple protrusions is smaller than the diameter of the glass fiber, the glass fiber does not get stuck in the recess, and a constant amount of resin is always kept on the fiber surface. Since it is coated, the outer circumferential surface of the glass fiber can be coated uniformly without uneven thickness, making it possible to easily manufacture a high-quality optical fiber.

[Brief explanation of drawings]

1 to 4 show a first embodiment of the optical fiber coating method and optical fiber coating die according to the present invention, FIG. 1 is a sectional view of the coating die, and FIG. 2 is a cross-sectional view of the coating die shown in FIG. 1. 3 is a bottom view of the coating die shown in FIG. 1, and FIG. 4 shows the state in which the coating material is smoothed after being coated on the glass fiber by the coating die shown in FIG. 1. 5 to 7 show a second embodiment of the optical fiber coating method and optical fiber coating die according to the present invention, FIG. 5 is a plan view of the coating die, and FIG. 6 is a plan view of the coating die. FIG. 7 is a bottom view of the illustrated coating die; FIG. 5 is a diagram showing the state in which the coating material is smoothed after being coated on the glass fiber by the illustrated coating die; FIGS. 8 to 10. 8 shows a third embodiment of the optical fiber coating method and optical fiber coating die according to the present invention, FIG. 8 is a plan view of the coating die, FIG. 9 is a bottom view of the coating die shown in FIG. 8, and FIG. The drawings are a diagram showing the state in which the coating material is coated on the glass fiber by the coating die shown in FIG. 8 and then smoothed, FIG. 11 is a diagram of the drawing process, and FIG. - A diagram showing the relationship between the Y stage and the coating die, FIG. 13 is a sectional view of a conventional coating die, FIG. 14 is a plan view of the coating die shown in FIG. 13, and FIG. 15 is a diagram of the coating die shown in FIG. 13. A bottom view, FIG. 16 is a plan view of another conventional coating die, and FIG. 17 is a top view of another conventional coating die.
FIG. 18, a bottom view of the illustrated coating die, is a diagram showing a state in which a coating material is coated by a conventional coating die. 1, 10, 20...Coating die, 2, 1
1, 21... Upper opening, 4, 12, 22... Lower opening, 5, 13, 23... Protrusion, 6... Glass fiber, 7... Covering material, 8, 14, 24... Through hole, 9, 15, 25... protrusion.

Claims (1)

[Scope of Claims] 1. An optical fiber coating method in which the outer peripheral surface of a glass fiber is coated by supplying a coating material with an uneven cross-sectional outer peripheral shape. 2. An optical fiber coating die in which a plurality of protrusions are formed from around the lower opening of the coating die toward the center. 3. The optical fiber coating die according to claim 2, wherein the plurality of protrusions formed in the lower opening have a curved surface shape having a predetermined curvature. 4. The optical fiber coating die according to claim 2 or 3, wherein the number of the plurality of protrusions formed in the lower opening is four. 5. The optical fiber coating die according to claim 2, 3 or 4, wherein the protrusion is formed symmetrically about a center point. 6. Claim 2, 3, 4 or 5, wherein the width of each recess formed by the plurality of projections is smaller than the diameter of the glass fiber.
The optical fiber coating die described. 7. The optical fiber coating die according to claim 6, wherein each of the recesses formed by the plurality of projections has a curved shape having a predetermined curvature.