JPH01225911A - Manufacture of hermetic-coat optical fiber - Google Patents

Abstract

PURPOSE:To fix the linear speed of optical fibers so as to realize a uniform coating which is free from unevenness in film thickness in the length direction of the fibers by not performing the hermetic coat to the fibers in tandem with a spinning (wire drawing) process, but as a separate process. CONSTITUTION:In order to prevent optical fibers just wire-drawn from being scratched, the fibers are first covered with an ordinary coating material immediately after they are wire-drawn, thereafter, hermetic coat is performed on the fibers after the coating material is removed by means of a non-contacted means in another process. The above-mentioned non-contacted means means heat- resolution performed on the coating material covering the fibers and, as occasion demands, a removing means using an etching gas is added to the heat-resolution. In other words, the hermetic coat is performed on the optical fibers 1 by means of a coating device 4 of a process which is different from the spinning (wire- drawing) process. Therefore, control of the feeding speed of the optical fibers 1 becomes unnecessary in the coating process since the control of the outer diameter of the fibers is already performed in the spinning process. As a result, unevenness in the thickness of the coating thin film caused by unevenness in speed can be eliminated and a uniform thickness is obtained.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention provides a method for manufacturing a hermetic coated optical fiber suitable for use in special environments, which is characterized by high strength, water resistance, hydrogen resistance, heat resistance, etc. It provides a method for applying the coating to a uniform thickness.

(Prior art) Glass fibers for optical transmission are coated immediately after spinning, while their surfaces are still intact, by coating and curing extremely common thermosetting or ultraviolet curing resins. In addition to forming the hermetic materials carbon, amorphous carbon, silicon oxynitride, silicon carbide, titanium carbide, anhydrous hydrocarbons,
1 Gos, ZnOz, etc. are formed by CVD, plasma, and sputtering.

(Problem to be Solved by the Invention) In the former case, water cannot be essentially blocked, and therefore vermech coating is impossible. On the other hand, in the latter case, the film thickness formed depends on the fiber drawing speed, so in order to keep it constant, the drawing speed must be kept constant, but conversely, the diameter of the glass fiber must be kept constant. In order to achieve this, it is necessary to control the drawing speed, which takes priority, so if drawing and coating are performed in tandem, the thin film formed will be uneven in the length direction, which will reduce the strength of the fiber. There was something about it that caused it.

(Means for Solving the Problems) In order to solve the above problems, the present invention is a method that separates the hermetic coating from the drawing of the glass fiber and performs it off-line. Immediately after drawing the wire, a coating material inside the electrode (-film) is applied, and then the previously applied coating material is removed by non-contact means in a separate process, and then a hermetic coating is applied. The contact means refers to thermal decomposition of the coating material coated on the fiber, and if necessary, means to add removal means using etching gas.Specifically, the coating material is 500~ UV curable resin that decomposes when heated to a temperature of about 600℃, 200
Examples include POM, which decomposes at about ℃. Note that in order to promote the decomposition of the coating material, electron beam irradiation or oxygen or the like may be added.

Etching gases include SF4, CF4, and CC.
l1zFz is mentioned.

(Function) By applying the hermetic coating in a process separate from the glass fiber spinning (drawing) process, the outer diameter of the glass fiber has already been controlled in the drawing process, so there is no need to control the glass fiber delivery speed. It is possible to obtain a uniform thickness by eliminating unevenness in the thickness of the thin film due to unevenness in speed.

(Example) FIG. 1 is a schematic diagram of an apparatus used in the method of this invention, and the configuration thereof will first be explained.

Reference numeral 1 denotes a coated fiber wire delivered from the delivery bobbin 10, which has been previously coated with a coating layer by the dip method immediately after spinning (drawing) the bare fiber in a previous step and wound onto the bobbin 10. It is. 2 is a device for decomposing the coating layer coated on the fiber; the quartz glass tube 22 is generally cylindrical and has a small diameter at both ends to form an entrance and exit through which the fiber is passed; heater 23 wound around the quartz glass tube 22, a decomposition aid supply port 24 and an exhaust port 25 provided in the center of the quartz glass tube 22, and external air infiltration ports provided at narrow diameter portions at both ends of the quartz glass tube 22. Seal gas supply port 2 for targeting
It consists of 6.26. Reference numeral 3 denotes an etching device located after the decomposition device 2, and its structure is the same as that of the decomposition device 2, the only difference being that the decomposition aid supply port is replaced by the etching gas and plasma gas supply port 34. Then, the coating material or its residue still attached to the glass fiber is removed by etching, including the glass surface layer. Reference numeral 4 denotes a coating device located after the etching device 3, and its structure is the same as that of the decomposition device 2, the only difference being that the decomposition aid supply port is replaced by the reaction gas and plasma gas supply port 44.

A hermetic coating layer is then applied onto the bare fiber from which the coating has been removed. Note that 50 is a bobbin for winding up the fiber coated with a hermetic coating layer.

(Specific example) On a bare fiber with a diameter of 125 μm, immediately after spinning, 20
A coated fiber 1 coated with urethane acrylate to a μm thickness was sent out from a bobbin 10, passed through a decomposition device 2, an etching device 3, and a coating device 4 in order, and wound onto a bobbin 50 at a winding speed of 1 m/min. The conditions of the decomposition device 2, etching device 3, and coating device 4 at this time were as follows.

Decomposition device 2 Temperature inside quartz glass tube 800 °C 0□ Gas supply amount 217 minutes^r Seal gas supply amount If/min Etching device 3 AC plasma output 3KW plasma gas meter Pressure inside quartz glass tube 1 torr Etching gas (CF,
) 500cc/min Ar seal gas supply amount 1j? /min Coating device 4 AC plasma output 5KW plasma gas Ar quartz glass tube pressure 1 torr Reaction gas NH3500cc/min SiH* 200cc/min Ar sealing gas supply rate 117 minutes Coating material (Si3Nm) film thickness 0.05 μm/min A UV resin was further applied onto the silicon nitride thin film (0.5 μm thick) obtained by the method of the present invention to obtain a coated fiber with an outer diameter of 250 μm. Comparison of the tensile rupture strength and static fatigue properties of this fiber and that of a coated fiber with an outer diameter of 250 μm by applying a silicon nitride thin film in tandem immediately after spinning the fiber using the conventional method and applying UV resin thereon. Regarding the former, the conventional product had a maximum strength of 7.5 kg/125 μm and an average strength of 3.
．． 0kg/125μm, but this invention has a maximum strength of 8.0kg/125 #m and an average strength of 6.5kg.
/125 pm. Regarding the latter, the temperature is 30
．． 60. When the fatigue coefficient n was measured when immersed in water at 80°C, the conventional product had n = 20 to 30, but this invention's product was independent of the temperature (n-100 or more, which was higher than the conventional product). The lifespan was 3 to 4 times longer than that of other products.

The advantages of this invention over conventional products are as follows:
This is thought to be because the hermetic coating can be applied while keeping the fiber moving speed constant, which suppresses coating unevenness, prevents the occurrence of pinholes, and improves the uniformity in the fiber length direction.

(Effect of the invention) As described above, the method of this invention does not involve performing the hermetic coating on the fiber in tandem with the spinning (drawing) process (because it is performed in a separate process), the fiber drawing speed is kept constant. This allows the fiber to be coated with an even and uniform coating thickness in the longitudinal direction of the fiber, thereby providing excellent hermetic properties.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the apparatus used in the method of this invention. In the figure, 1... coated fiber, 2... decomposition device, 3... etching device, 4... coating device. Agent Patent Attorney Mamoru Takeuchi

Claims (1)

[Claims] A coating layer is applied to a glass fiber for optical transmission immediately after spinning, and then this coating layer is removed by a non-contact means in a separate process, and a hermetic layer is subsequently provided in tandem with this removal process. A method for manufacturing hermetic coated optical fiber.