JPS60208716A - Optical fiber - Google Patents

Abstract

PURPOSE:To prevent clouding and embrittling of a buffer layer by using a nonstyrenic resin as a thermosetting resin when an optical fiber strand, on which a buffer layer of silicone is formed, is coated with a fiber-reinforced thermosetting resin. CONSTITUTION:A buffer layer 3 of silicone is formed on the outer circumference of an optical fiber constituted of a core part 1 and a clad part 2, and a layer 5 of fiber-reinforced thermosetting resin (hereinafter called FRP layer) is formed on the outer circumference of the obtained optical fiber strand 4. The FRP layer 5 is formed by immersing a reinforcing fiber into a mixture contg. a polymerizable monomer (e.g., glycidyl methacrylate) consisting of a nonstyrenic compd., a curing agent, and an unsaturated alkyd resin to impregnate the fiber, and coating the mixture on the outer circumference of the strand 4. A thermoplastic resin layer 6 is subsequently coated on the outer circumference of the FRP layer 5, and the FRP layer 5 is then cured by heating to obtain the desired optical fiber.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical fiber, and more particularly to an optical fiber that prevents deterioration of a coating layer of an optical fiber.

BACKGROUND OF THE INVENTION In recent years, in the field of telecommunications, communication systems using optical fibers, which have characteristics such as broadband, wireless communication, low loss, and light weight, have been put into practical use.

Optical fiber cables basically consist of a core made of glass that transmits optical signals, and a cladding that seals the signals within the core.The outer periphery of the cladding is reinforced with mechanical strength. , primary coat for purposes such as improving transfer reliability.

Various coatings such as buffer coat are applied,
A wire in this state is usually called an optical fiber wire. .

In order to further increase the mechanical strength, the optical fiber is secondarily coated with a synthetic resin or the like to form a cored optical fiber.

By the way, one type of this secondary coating is so-called fiber-reinforced plastics (hereinafter referred to as "fiber-reinforced plastics"), which are made by integrally binding 11 reinforcing fibers such as glass with synthetic resin.

(abbreviated as R, P).

This kind of optical fiber has high tensile strength and lateral pressure resistance.

It has various excellent properties such as dimensional stability against temperature changes.

On the other hand, silicone is often used as the coating material due to its excellent temperature characteristics, good interaction with glass materials, and good durability.
As the synthetic resin, a thermosetting resin containing a styrene-based polymerizable 'Il1 substance is often used because of its durability and adhesion to reinforcing fibers.

However, according to the knowledge of the present inventors, optical fibers employing such a combination of resins have the following problems.

In other words, when silicone is used as a buffer coating for optical fibers, this layer becomes cloudy and cloudy.
It may become brittle and change in quality, and as a result, it loses its flexibility and becomes unable to relieve stress from the outside, resulting in a decline in its essential function of preventing deterioration in transmission characteristics due to microbending.

In addition, primary coating is applied to improve reliability by reinforcing the strength of the optical fiber 7/river and to improve transmission characteristics by preventing light leakage from re-entering. However, if silicone is used for this coating, There is also a risk that the substance that has caused cloudiness and embrittlement in the buffer coating may migrate into the primary coating or to the interface, reducing its functionality.

Furthermore, a poly-macrad type optical fiber in which the cladding part is formed of an organic polymer is also available, but in the case of using silicone as the cladding part, if the above-mentioned clouding and embrittlement phenomena occur in this part. change in refractive index,
This results in loss of transparency and damage to adhesion to the core, resulting in loss or deterioration of the essential functions of the optical fiber.

The present invention has been made in view of the above-mentioned problems, and its purpose is to provide an optical fiber whose silicone clad coating, primary coat, and buffer coat do not undergo deterioration such as clouding or embrittlement. It is in.

As a result of intensive investigation into the causes of the above-mentioned problems, the inventors of the present invention have found that the causes are as follows, and have completed the present invention.

That is, the thermosetting 11 resin used for F, R, and P is
For example, unsaturated alkyd resin consists of a single polymerizable monomer and a catalyst as a curing reaction initiator, but it has been found that styrene, which is commonly used as a polymerizable monomer component, tends to alter the quality of silicone resin. I figured it out.

This conclusion was confirmed by the following experiment.

Polymerizable monomers for unsaturated polyester resins generally include styrene-based monomers such as styrene and α-methylstyrene, vinyl-based monomers such as vinylbenzene and divinylbenzene, allyl-based monomers such as diallyl phthalate and triallyl phthalate, methacrylic acid, Butyl methacrylate, methyl methacrylate, cyclohexyl methacrylate, ethylene dimethacrylate.

It is roughly divided into four types of methacrylic acids, such as 2-hydroxyethyl methacrylate and glycidyl methacrylate.

Among these prefectures, styrene, divinylbenzene, diallyl phthalate, and glycidyl methacrylate were selected,
Four types of unsaturated polyester resins were prepared by mixing these polymerizable monomers with an unsaturated alkyd and a catalyst, and a silicone rubber sheet was immersed in the resin to examine the state of deterioration of the silicone rubber sheet.

The silicone rubber seals 1 to 1 used in the test were 1 mm thick A
It is a transparent polysiloxane-based material used as a buffer coating material by the company.

Table 1 below shows the swelling effect of resins using the various monomers mentioned above on silicone rubber sheets, determined by the rate of increase in weight before and after immersion in the resin.

As is clear from the results in Table 1, in the case of using styrene as the polymerizable monomer, the weight increase rate was extremely large at 90%, and the swelling was significant.

On the other hand, in the case of diallylic acid phthalate and glycidyl methacrylate, the rate of increase in serious injuries was as low as 10%.

Next, the silicone rubber sheet was immersed in the four types of resin, and after the resin was cured at 95° C., it was peeled off, and the total light transmittance and haze value of the silicone rubber sheet were measured.

The total light transmittance was measured with an integrating sphere type light transmittance measuring device, and the haze value was calculated using the following formula by measuring the diffused light beam with the same device.

Table 2 shows the above measurement results, and also shows the total light transmittance and haze value of the untreated silicone rubber sheet as a reference.

Table 2 From the above results, it was found that the rate of decrease in total light transmittance and rate of increase in haze value were significantly greater when styrene was used as the polymerizable monomer.

Further, the styrene-used Rubber Sheet 1 sample was also visually judged to be completely cloudy.

On the other hand, in other specimens, the rate of decrease in total light transmittance and the rate of increase in haze value were small enough to cause no practical problems, and no clouding was observed by visual inspection.

Next, the cloudy silicone rubber seal 1~sample was
After immersing it in chloroform, we attempted to extract the cloudy substance and conducted infrared absorption analysis on the substance.

As a result, it was determined that the substance that caused the silicone rubber sheet to become cloudy was a white, finely granular solid substance, which was styrene cured by interlinkage.

Based on the above experimental results, the inventors of the present application have discovered that when a silicone coating layer is formed and the photonic line is coated with a thermosetting resin, styrene is used as the polymerizable monomer of the resin. It has been found that when the above substance is used, after the thermosetting resin is cured, property changes such as clouding of the ]-ning layer occur.

Based on this knowledge, the present inventors made the secondary coating of a synthetic resin, such as a thermosetting resin, to prevent changes in the properties of the coating layer as a double layer, and the inner shell or the entire secondary coating, for example, It was concluded that it is effective to use a thermosetting resin mixed with a non-styrene polymerizable monomer such as vinyl, allyl, or methacrylic acid, and the present invention was completed.

Specific examples of the present invention will be described below.

(Example 1) As shown in FIG. 1, a core part 1 and a cladding part 2 are formed concentrically from quartz glass with an outer diameter of 125B, a buffer layer 3 is formed from silicone rubber on the outer periphery of the cladding part 2, and a buffer layer 3 is formed from silicone rubber on the outer circumference of the cladding part 2. Using an optical fiber wire 4 having a diameter of 0.4 mm, F, R, and P layers 5 were applied to the outer periphery of the wire by the coating method shown below.

The F, R, and P layers 5 are made of unsaturated polyester resin mixed with unsaturated alkyd, glycidyl methacrylate as a polymerizable monomer, and a curing catalyst, using glass roving as a reinforcing fiber bundle. This is soaked and impregnated, attached longitudinally to the outer periphery of the cable wire 4, and shaped by a molding nozzle. After extruding the uncured F, R, and P layers into a cloth using a rad die, the outermost periphery is It is coated with thermoplastic resin 6 (linear low-density polyethylene), cooled, and cured for 1μ in a steam heating bath at 140°C.The polyethylene jacket is then shaped to form an optical fiber core. manufactured the wire.

The dimensions of the optical fiber core are the outermost diameter of 1.13111111
．． [, R, P layer 5 outer diameter 1, 2 mm, hall l? F
J3) The outer diameter was 0.4 mm.

After manufacturing, the thermoplastic resin of the optical fiber core is heated to 6°F, R,
When the P layer 5 was peeled off and the state of the Balanoa layer 3 was observed, no changes in quality such as clouding or embrittlement that were conventionally observed when styrene was used as the polymerizable monomer were observed.

(Example 2) As shown in FIG. 2, the same optical fiber wire 4 as in Example 1
After coating the inner shell part 7 of a thermosetting resin containing glycidyl methacrylate and a curing catalyst as a polymerizable monochain on the outer periphery, thermosetting using styrene as a polymerizable monomer is performed. After vertically attaching glass rovings impregnated with a synthetic resin, the optical fiber core wire was coated with the outermost diameter of 1.8 mm and the outer diameters of the F, R, and P layers 5 were 1.8 mm and 1.8 mm, respectively, in the same manner as in Example 1 above.
2mm.

The inner shell portion 7 was manufactured with an outer diameter of 0.4.5n+n+.

The coating of this optical fiber core wire is also peeled off in the same way,
The properties of the buffer layer 3 were observed, but no changes in properties such as cloudiness were observed.

The optical fiber shown in Example 1.2 has transmission loss below the allowable value, J, [breaking strength is high,
There was no problem in practical use.

As explained in detail above, in the present invention, J: cloudiness of the buff 7 coat in contact with the secondary coating of the thermosetting resin;
Since embrittlement is effectively prevented, even in optical fibers in which silicone is used not only in the buffer coat but also in the primary coat or cladding portion, cloudiness and embrittlement are prevented from transferring to these portions.

Therefore, the essential functions of these layers (residual resin, for example, microbending of the buffer coat, buffering function to prevent transmission characteristics from deteriorating, high transparency as a cladding part, stability of refractive index, etc.) are the core. This ensures close adhesion to the fiber, making it possible to provide a highly reliable optical fiber.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a first embodiment of the present invention, and FIG. 2 is a sectional view of a second embodiment. 1... Core part 2... Clad part 3... r Buffer layer 4...
......Optical fiber wire 5...F, R
,'l) Layer 6......Thermopossible t! i! f1 Resin 7・・・・・・Inner shell patent applicant Ube Nitto Kasei Co., Ltd. J (Kai Ne J Agent Patent attorney - Irokanosuke Figure 1 Figure 2

Claims (4)

[Claims] (1) An optical fiber in which the outer periphery of an optical fiber wire on which a silicone coating layer is formed is secondarily coated with a fiber-reinforced thermosetting resin, and at least the interface of the coating layer of the second coating is polymerized. 1. An optical fiber characterized in that a thermosetting resin made of a non-styrene compound is in contact with a thermosetting monomer. (2) The optical fiber according to claim 1, wherein the polymerizable monomer of the thermosetting resin of the secondary coating is a non-styrene type. (3) The thermosetting resin of the secondary coating includes an inner shell portion formed of a thermosetting resin in which the polymerizable monomer is a non-styrene compound, and which is in contact with the coating layer; Claim 1, characterized in that the outer shell is made of a thermosetting resin made of a styrene compound.
Optical fiber described in section. (4) The optical fiber according to claim 1, 2, or 3, wherein the non-styrenic polymerizable material is either acrylic acid-based or allyl-based.