JPS60262115A - Fiber for optical transmission - Google Patents

Abstract

PURPOSE:To decrease an intitial transmission loss and the change in the transmission loss when temp. is low by providing a protective film layer consisting of a UV-curing resin added with a plasticizer having lubricity onto a quartz optical fiber strand. CONSTITUTION:The protective coating layer 2 consisting of the UV-curing resin added with the plasticizer such as oleic amide having lubricity is provided on the quartz optical fiber strand 1. A secondary protective coating layer 3 consisting of nylon-12, etc. is further provided on the layer 2 in tight contact therewith. The adhesive strength of the UV-curing type resin to the quartz optical fiber is decreased by the lubricating effect of the plasticizer and the strain generated in the stage of production and remaining in the fiber is relieved and decreased by the slipping at the quartz optical fiber boundary so as not to generate the stress in the strand 1.

Description

Detailed Description of the Invention (Technical Field of the Invention) The present invention provides a protective coating layer made of an ultraviolet curable resin on a quartz-based optical fiber wire, and a secondary protective coating layer in close contact with the protective coating waste. This invention relates to an improvement of a so-called tight structure optical transmission fiber (hereinafter abbreviated as tight core fiber).

(Background of the Invention) In recent years, optical transmission fibers that use ultraviolet curable resin as the primary protective coating layer of quartz-based optical fibers have been manufactured at a faster manufacturing speed than conventional silicone resin-coated wires. Demand is increasing from the viewpoint of cost reduction due to rising prices and lower material costs, and development is progressing rapidly. The optical transmission fiber equipped with a protective coating layer made of this ultraviolet curable resin is further coated with a protective coating layer to protect the above-mentioned protective coating waste during the cable production process.
Secondly, a secondary protective coating layer is provided, and the present invention particularly aims at achieving good initial transmission loss characteristics and temperature characteristics in tight core wires in which this secondary protective coating is provided closely to the primary protective coating. It was done to give something.

Conventional optical transmission fibers with a protective coating layer made of ultraviolet curable resin have secondary coating waste, such as nylon-
Tight core wires with a tight extrusion coating of No. 12 were used, but the transmission loss after extrusion of the secondary coating increased, and the resulting tight core wires had a large deterioration in transmission loss in the temperature characteristics at low temperatures. There was a problem. Such a phenomenon was not noticeable in the optical transmission fiber before the secondary coating was applied, and it was significantly inferior to the conventional/recone resin coated optical fiber.

Therefore, in order to overcome these problems, we conducted a detailed study on the transmission characteristics of tight core wires equipped with a protective coating layer made of ultraviolet curable resin. It was concluded that the increase in transmission loss and deterioration of low-temperature characteristics is due to the phenomenon that distortion is applied to the protective coating layer made of ultraviolet curable resin during secondary coating extrusion, which in turn causes distortion to the quartz fiber strand. .

Therefore, as a result of various studies as a method for relieving or absorbing the strain imparted to the above-mentioned protective coating layer as early as possible to compensate for the above-mentioned defects in transmission characteristics, we found that the above-mentioned protective coating layer in contact with the silica-based fiber strands It has been found that by adding a lubricating substance to the material, it is possible to reduce or quickly eliminate the increase in transmission loss after extrusion of the secondary coating, and to improve the temperature characteristics at low temperatures.

(Disclosure of the Invention) When manufacturing an optical fiber by applying an ultraviolet curable resin immediately after melt-spinning a quartz-based optical fiber and curing the resin layer by irradiating ultraviolet rays, the ultraviolet curable resin is cured. At times, shrinkage occurs, causing non-uniform strain in the ultraviolet curable resin layer itself, which also applies strain stress to the lime-based optical fiber strands, adversely affecting transmission characteristics. Furthermore, when this optical fiber is closely extruded and coated with a thermoplastic resin such as nylon-12 as a secondary protective coating layer to make a tight core, the secondary coating material is strained due to extrusion residual strain or heat shrinkage during extrusion. As a result, the lime-based optical fiber is further subjected to non-uniform strain through the ultraviolet curable resin layer, causing so-called microbending loss and increasing transmission loss.
The low-temperature properties of the obtained tight cord also tend to be very poor.

One possible way to minimize these generated strains is to reduce the curing strain of the ultraviolet curable resin during the production of optical fibers, and to suppress the strain induced by the secondary coating when applying the secondary coating. However, it is extremely difficult to completely eliminate these distortions by manufacturing means during manufacturing.

Therefore, as a method for reducing or completely eliminating these generated strains over time within a relatively short period of time, we came up with the idea of easing the strains generated in the protective coating layer made of ultraviolet curable resin. Focusing on the adhesive strength of the ultraviolet curable resin to the quartz-based optical fiber, we developed a method that reduces the adhesive strength of the above-mentioned resin to the silica-based optical fiber without impairing the protective effect of the silica-based optical fiber. The strain that sometimes occurs and remains is alleviated and reduced by the slip phenomenon of the ultraviolet curing resin at the interface of the silica-based optical fiber so that no stress is generated in the lime-based optical fiber strand.

The means for reducing the adhesive force of the ultraviolet curable resin to the lime-based optical fiber will be described in detail.

Generally, an ultraviolet curable resin composition is comprised of a basic combination of a prepolymer, a reactive diluent, a polymerization initiator, a photosensitizer, and various stabilizers. Examples of prepolymers include urethane acrylates, epoxy/acrylates, or mixtures thereof, butanoene acrylates, and silicone acrylates. As a reaction diluent, various acrylic acid ester monomers can be used alone or as a mixture of two or more.

By adding an appropriate amount of an organic compound with lubricating properties to the ultraviolet curable resin as described above, it becomes a lubricant (or mold release agent) that remains during the curing of the resin without being affected by the curing reaction. ). Examples of such organic compounds with lubricating properties include various acid amides such as oleic acid amide, fluorine-based mold release agents, and non-reactive auxiliary compounds that act as lubricants. may be any UV-curable resin as long as it remains sufficiently in the resin after curing and acts as a lubricant (or mold release agent) on the interface of the pod-based optical fiber. These additives also play the role of plasticizers for the resin, so they are expressed using the term plasticizer.

Fig. 1 is a vertical cross-sectional view of a tight core wire provided with a protective coating layer made of an ultraviolet curable resin according to the present invention, (1) is a quartz-based optical fiber strand, and ■ is a lubricating layer of the ultraviolet curable resin. The protective coating layer (8) to which a certain plasticizer has been added is a secondary protective coating layer of nylon-12 or the like provided in close contact with the protective coating layer (1).

As shown in Figure 1, the protective coating layer made of ultraviolet curable resin is generally a single layer, but as a result of further investigation,
It has been found that a two-layer protective solution, including a 1:'' top layer, as shown in FIG. 2, provides an optical fiber core with superior transmission characteristics and manufacturing process. That is, the first ultraviolet curable resin m (2 cL) has a Young's modulus of 1 to
A soft layer of 30 kg/c+1'' is disposed, and an appropriate amount of a plasticizer having a lubricating effect is naturally added to the first layer that is in close contact with the quartz-based optical fiber (1).

In addition, a second ultraviolet curable resin layer (with a Young's modulus of 50 to
A hard layer (a layer with no tackiness upon hardening) of lGOOOkg/c♂ is arranged, and a lubricating plasticizer may not be added to this second layer, or may be added if necessary. Young's modulus defined here is JISK711
JI No. 82 dumbbell specified in 3 (thickness 250!1m)
This is the secant modulus at an elongation of 2.5% when evaluated at a tensile rate of 11IIIZ.

The reason why the ultraviolet curable resin layer has a two-layer structure is that in order to reduce the influence of microbending due to distortion during extrusion when extrusion coating the secondary protective coating layer,
- Low Young's modulus (1 to 30 kg) for the next protective coating
/ am”), but it shows tackiness even after the resin is cured, and it causes various troubles such as wire runout and smearing during the manufacturing of the wire and the extrusion coating of the secondary protective coating layer. Therefore, as a second layer, we use a hard layer with a relatively high Young's modulus (Young's modulus of 50 to l) that does not show tank properties after curing.
This is because by applying oooOkg/c11'), these manufacturing problems can be eliminated.

Furthermore, as mentioned above, by adding a lubricating plasticizer to the second layer (24), a slip effect is created that alleviates the distortion that occurs when applying the secondary protective coating layer, resulting in excellent ultraviolet curing. A tight core wire coated with mold resin is obtained.

(Example) Example 1: A plasticizer that has a lubricating effect on various urethane acrylate ultraviolet curable resins was added to a GI type optical fiber with a core diameter of 50μ, a cladding diameter of 125μ, and a relative refractive index difference △n = 1%. Wire (outer diameter 4) coated and cured with a composition containing
A tight core wire coated with ultraviolet resin (outer diameter 0.9 m) as shown in Fig. 1 obtained by extrusion coating nylon-12 on
), the results of investigating the initial transmission loss and low temperature characteristics are shown in Table 1.

From the results shown in Table 1, it can be seen that adding a lubricating plasticizer to the ultraviolet curable resin results in an increase in transmission loss after cording and better temperature characteristics at low temperatures.

Example 2: Used the same GI type optical fiber as Example 1.

Various urethane acrylate-based ultraviolet curing resins
The layer is covered with a protective coating layer with a two-layer structure consisting of a soft layer with a low Young's modulus (thickness 300μ) and a second layer with a hard layer (thickness 400μ) with a relatively high Young's modulus. The initial transmission loss and low-temperature characteristics of the ultraviolet curable resin-coated tight core wire as shown in Fig. 2 obtained by manufacturing a wire to which a plasticizer has been added and then extruding and coating it with nylon-12 are as follows. Table 2 shows the results of examining the temperature characteristics of .

Table 2 Example 3: UV-curable resin coating as shown in Figure 2, in which the UV-curable resin layer has a two-layer structure as in Example 2, and a lubricating plasticizer is added to both layers. Table 3 shows the results of investigating the initial transmission loss and temperature characteristics at low temperatures for the tie 1 core wire.

, 1.1 1'1 Table 3 From the results in the above table, it is better to add a lubricating plasticizer to both the first and second layers of the ultraviolet curable resin layer.
It can be seen that the transmission loss and low-temperature characteristics are superior to when it is added only to the first layer.

(Effects of the Invention) As described above, according to the optical transmission fiber of the present invention, which is provided with a protective coating layer made of an ultraviolet curable resin and a lubricating plasticizer added to the quartz-based optical fiber, the initial transmission The loss is also sufficiently low, making it possible to reduce changes in transmission loss at low temperatures.

Furthermore, by applying the protective layer as described in 1 above to a two-layer structure in which the first layer is a soft layer and the second layer is a hard layer, an optical transmission fiber with good transmission characteristics can be obtained without any problems in the manufacturing process. Furthermore, by adding a lubricating plasticizer to both the first layer and the second layer, an extremely excellent optical transmission fiber can be obtained.

Although the present invention has been described using an ultraviolet curable resin for the protective coating layer, the same effect can be expected by using other radiation, such as an electron beam curable resin.

[Brief explanation of the drawing]

The drawings all show embodiments of the optical transmission fiber according to the present invention, and Fig. 1 is a cross-sectional view of one protective coating layer made of ultraviolet curable resin + I&, and Fig. 2 is a cross-sectional view of the above protective coating layer. is a cross-sectional view of a 2-layer + il structure. 1... Quartz-based optical fiber wire, 2... Protective coating layer,
26L... Soft layer of protective coating, 2... Hard layer of protective coating, 3... Secondary protective coating layer. ] 72- Large figure 1 Large figure 2 b l

Claims (4)

[Claims] (1) In an optical transmission fiber comprising a protective coating layer made of an ultraviolet curable resin on the strand of a stone capsule-based optical fiber, and a secondary protective coating layer provided in close contact with the protective coating layer, the ultraviolet curable type An optical transmission fiber characterized by adding a lubricating plasticizer to the resin. (2) Young's modulus of 1 to 30 k provided on the side where the protective coating waste made of ultraviolet curable resin is in contact with the quartz-based optical fiber bare wire
The optical transmission fiber according to claim 1, characterized in that it has a two-layer structure: a soft layer with a Young's modulus of 50 to 10,000 kg/c♂ and a hard layer provided outside the soft layer with a Young's modulus of 50 to 10,000 kg/cm. (3) The optical transmission fiber according to claim 2, wherein a plasticizer having a lubricating effect is added to the soft layer. (4) Claim 2 of Claim 5'1 characterized in that a plasticizer with lubricating action is added to both the soft layer and the hard layer.
Optical transmission fiber described in section.