JPS597656B2 - Manufacturing method of glass fiber for optical transmission - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of coating a resin on the surface of a glass fiber for optical transmission.

If the surface of the glass fiber is in direct contact with the outside air, its strength will rapidly decrease due to contact with moisture or other foreign matter in the outside air.

Therefore, it is necessary to protect the fiber surface with a resin composition. In the conventional coating method, a resin composition is applied to the fiber immediately after spinning using a die before it comes into contact with other foreign matter, and the resin composition is hardened in a baking furnace. In this method, in order to suppress the inner side of the coating and prevent contact between the die hole and the fiber, the film thickness must be at least 10 μm or more.

On the other hand, when making a permanent connection between fibers, the process of bringing the fiber end faces together and fixing them becomes important.

When the coating thickness is 10 μm or more, the flexibility of the resin itself makes it extremely difficult to abut the end faces and fix the resin, and it is necessary to remove the coating and fix the resin. The problem here is that since the coating has been removed, there is a concern that the strength will decrease in that area. As a solution to this problem, it has been required to reduce the thickness of the coating to such an extent that fiber end faces can be easily brought together and fixed without removing the coating.

However, the conventional thin coating methods are to reduce the size of the die hole or to apply fibers impregnated with a resin composition to felt or the like without using a die, but both methods are effective in reducing the coating film. Problems such as increased thickness and decreased fiber strength have not been resolved. The reason for this is that in both cases, the fiber is passed through a narrow space and the resin is applied, so it is impossible to prevent the fiber from coming into contact with the die, felt, or the like. The present invention provides a method that enables thin coating and prevents uneven coating thickness and reduction in fiber strength, and will be described in detail below with reference to the drawings.

FIG. 1 is a schematic diagram of a conventional thick coating device. A glass rod 1, which is a base material, is heated and spun in a spinning furnace 2, and the spun fiber 3 is coated with a resin composition 5 through a large-diameter die 4, and the resin is hardened in a baking furnace 6 and wound onto a winding bobbin 7. . On the other hand, in the coating method according to the present invention, as shown in FIG. 2, a nozzle 10 is provided at the bottom of a conventional large-diameter die 4 for blowing off excess resin applied to the fiber.

Air is suitable as the gas to be blown, but air can also be used as long as it is an inert gas. The thickness of the resin to be coated can be adjusted by adjusting the flow rate, pressure, or spraying position of this blown gas. Currently, it is possible to control down to a minimum of 1 μm.

FIG. 3 is an enlarged view of the nozzle 10, which is designed to spray gas uniformly in the circumferential direction of the fiber.
If the gas is not sprayed uniformly, problems such as contact with the nozzle due to fiber deflection and uneven thickness of the resin may occur, so special care must be taken. Further, control of the coating film thickness is greatly influenced by the viscosity of the coating resin, and control is easier with a resin having a relatively low viscosity. As described above, the present invention uses a conventional die with a large die hole diameter to blow off the applied resin by blowing gas, thereby reducing the thickness without problems such as a decrease in strength and an uneven thickness of the film. It is characterized by making it possible to cover.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a conventional thick coating method. FIG. 2 is a schematic diagram of a thin coating according to the invention. Figure 3 shows
It is an enlarged view of the blowing nozzle, 1 is the fiber base material, 2
1 is a spinning furnace, 3 is an optical fiber, 4 is a die, 5 is a resin to be applied, 6 is a baking furnace, 7 is a winding bobbin, 10 is a nozzle, 11 is a blowing nozzle gas reservoir, and 12 is a gas inlet.

Claims (1)

[Claims] 1 A glass base material for optical transmission is heated and spun, a resin composition is applied to the surface of the spun optical fiber through a die, and when the resin composition is baked and hardened, air or inert gas is blown onto the lower part of the die, and the resin composition is applied. A method for manufacturing a glass fiber for optical transmission, characterized by adjusting the thickness of a resin composition.