JPH01213610A - Coated optical fiber - Google Patents

Abstract

PURPOSE:To obtain a coated optical fiber which has high strength and reliability, can be formed to the finer diameter and has good productivity by using a ladder type silicone resin as the primary covering layer of the optical fiber. CONSTITUTION:The ladder type silicone resin is the polyorganosilsesquioxane obtd. by heating an organosilsesquioxane oligomer to condense the same so that the crosslinking between the respective ladder ends and ladders takes place and the Si-O-Si bond grows. The hardness and heat resistance of the ladder type silicone resin can be properly adjusted by using the resin having the structures in which the molar ratios of the methyl group and phenyl group of the side chains are variously changed. This ladder type silicone resin is coated to about 3-10mum thickness by which the primary covering layer 2 is formed. A secondary covering layer 4 is further provided on the outside circumferential part thereof by which the optical fiber 5 is constituted. The optical fiber which has the high strength, excellent weatherability, corrosion resistance, scratching resistance, etc., and excellent electrical properties such as electrical insulating characteristic and arc resistance is thereby obtd.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to optical fibers, and in particular enables improvement in strength reliability, reduction in diameter of optical fibers, and improvement in optical fiber manufacturability. It is something.

[-Prior Art] Conventionally, silica glass optical fibers have been widely used as optical fibers for light transmission, but these glass fibers are brittle, easily damaged, and have poor flexibility. Since glass fibers are easily broken by even the slightest external force, their surfaces are coated with a resin or the like as soon as they are manufactured. Conventionally, epoxy resins, urethane resins, silicone resins, and the like have been used as such coating resins, and coatings have usually been applied by coating methods.

[Problems to be Solved by the Invention] However, when coating the outer periphery of the glass fiber with the resin, the glass fiber rubs against the die of the coating device, which damages the glass fiber and causes breakage. There were many. Particularly, when attempting to reduce the diameter of the optical fiber by forming this secondary coating layer thinly, it is inevitably necessary to reduce the die diameter. For this reason, the above-mentioned problem cannot be taken lightly, and conventionally it has been considered impossible to reduce the diameter of the optical fiber.

Furthermore, even if a primary coating layer made of resin as described above is provided, these secondary coating layers have low strength and poor scratch resistance, so it is difficult to form a secondary coating layer on the outer periphery. In many cases, problems similar to those described above occur within the die of the coating device, causing damage to the primary coating layer and causing breakage.

For this reason, it has been considered impossible to reduce the diameter of the optical fiber by setting the thickness of the secondary coating layer to 20 μm or less.

In addition, the above-mentioned resins have a problem that stress corrosion is more likely to occur due to moisture because the resin itself has a high water absorption rate.

In order to solve this problem of stress corrosion, it has been proposed to coat the outer periphery of the glass fiber with a metal such as aluminum or tin, or with a ceramic material such as silicon nitride. Optical fiber coated with metal has been effective in reducing stress corrosion, but when reducing the diameter of the core, it is necessary to eliminate the inconvenience of scratches caused by the glass fiber rubbing against the die. I couldn't. Furthermore, although it was possible to similarly reduce stress corrosion in optical fibers coated with ceramic, it became necessary to use special equipment such as plasma equipment or sputtering equipment to coat the ceramic.
There were problems in terms of productivity.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and provide a coated optical fiber that has high strength reliability, can be reduced in diameter, and has good productivity.

[Means for Solving the Problems] The present invention uses a ladder-type silicone resin as the primary coating layer of the optical fiber core.

Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 1 shows an example of the structure of a coated optical fiber according to the present invention.

In FIG. 1, reference numeral 1 indicates a glass fiber. A normal silica glass fiber with a diameter of about 80 to 150 μm is used as the glass fiber l, and a primary coating layer 2 made of ladder-type silicone resin is provided on the outer periphery of the glass fiber l. A strand 3 is formed.

Here, the above-mentioned ladder type silicone resin is, for example, the following (
1) It is a thermosetting resin having a chemical structure as shown in the formula.

This ladder-type silicone resin is condensed by heating the organosilsesquioxane oligomer to form bridges at each ladder end and between the ladders.
It is a polyorganosilsesquioxane obtained by growing i -0-S i bonds. In addition to the structure shown in formula (I) above, this ladder type silicone resin may have a structure in which the molar ratio of the methyl group to the phenyl group in the side chain is varied. This makes it possible to appropriately adjust the hardness and heat resistance of the condensation-cured ladder-type silicone resin.

The primary coating layer 2 is formed by coating this ladder-type silicone resin to a thickness of about 3 to 10 μm.

Further, a secondary coating layer 4 is usually further provided on the outer periphery of the secondary coating layer 2 to form an optical fiber core 5. Here, an ultraviolet curable resin or a thermosetting silicone resin is suitably used, and the secondary coating layer 4 is formed by coating to a thickness of about 10 to 60 μm.

Next, a method for manufacturing such a coated optical fiber 5 will be explained.

First, the organosilsesquioxane oligomer is dissolved in an appropriate solvent. This oligomer is in the form of a powder before curing and is soluble in various solvents. Specifically, it can be dissolved in polar solvents such as alcohols, esters, ketones, etc., and aromatic solvents such as toluene. The mixing ratio of the oligomer and the solvent at this time may be determined as appropriate depending on the desired thickness of the primary coating layer 2 of the optical fiber core 5.
From the viewpoint of viscosity and workability, the ratio is preferably about 3:1-1:2.

Next, the obtained oligomer solution is used to form a primary coating layer 2 on the outer periphery of the glass fiber 1.

Specifically, for example, the oligomer solution is applied onto the glass fiber 1 using a coating apparatus as shown in FIG. That is, the oligomer solution 2a is introduced into this coating device, the glass fiber 1 is passed through the solution, and the solution is continuously drawn off from a die 6 installed at the bottom of the device. The linear speed at this time is desirably determined appropriately depending on the viscosity of the oligomer solution 2a, the desired thickness of the primary coating layer 2, etc., and is usually preferably about 60 ta/ff1 inch. Thereby, the oligomer solution 2a can be applied to the outer periphery of the glass fiber 1 passing through the die 6 and taken off. Furthermore, by passing the glass fiber l coated with the oligomer solution 2a through a heating furnace 7 or an infrared furnace,
Heating to a temperature of about 400 to 700°C, oligomer solution 2
At the same time as the solvent content in a is evaporated, the condensation reaction of the oligomer is allowed to proceed and harden. Here, an appropriate catalyst may be added in advance to the oligomer solution 2a as required, thereby allowing the condensation reaction to proceed at a low temperature and in a short time. It is also possible to add various dyes, pigments, etc. for coloring.

Next, using a coating device similar to that described above, a secondary coating layer 4 is applied.
form. Specifically, an ultraviolet curable resin or a thermosetting silicone resin is introduced into the coating device, and the resin is applied to the outer periphery of the optical fiber 3 on which the second coating layer 2 has been formed. While coating, line speed approximately 60m/lll1
Then, the resin is cured using a heating furnace or an ultraviolet lamp to form the secondary coating layer 4.

In the optical fiber core 5 obtained in this way,
- Since the next coating layer 2 is made of ladder-type silicone resin, it has high strength and is excellent in weather resistance, corrosion resistance, hardness, scratch resistance, heat resistance, flame resistance, etc. Also,
It also has the advantage of excellent electrical properties such as electrical insulation and arc resistance.

In addition, during this second coating, a solution of organosilsesquioxane oligomer, which is an oligomer of ladder-type silicone resin, is prepared, and this oligomer solution is applied onto the glass fiber l and then condensed and cured to apply the coating. It has good workability and can increase the line speed, so it is possible to improve productivity. In addition, since the oligomer solution with an appropriate concentration can be adjusted in advance according to the desired thickness of the primary coating layer 2, even if the diameter of the die 6 of the coating device is increased, the primary coating layer 2 with a small thickness can be It can also be formed. Therefore, when passing through the die 6, the glass fiber l
The coating can be applied without abrading the die 6. Therefore, the glass fiber l will not be damaged,
It will not cause breakage. Further, it is possible to prevent a decrease in initial strength, and at the same time, it is possible to reduce the diameter of the core wire.

Furthermore, since this secondary coating layer 2 has high strength and scratch resistance, even when forming the secondary coating layer 4 on the outer periphery, even if the diameter of the die 6 is made small, the primary coating layer 2 can be Even if the layer 2 rubs against the die 6, the secondary coating layer 2 will not be damaged. Therefore, in addition to not causing a decrease in strength, it is also possible to reduce the diameter of the optical fiber core 5, which was previously considered impossible.

Moreover, in the optical fiber core 5 formed with such a secondary coating layer 4, the lateral pressure characteristics of optical transmission loss can be improved, and the strength reliability is further improved.

[Example] (Example 1) A solution was prepared in which an organosilsesquioxane oligomer was dissolved in a methyl acetate solvent at a ratio of 1:1 (weight ratio).

A glass fiber with a diameter of 0.125 mm was passed through the oligomer solution, and the solution was applied onto the glass fiber through a die with a diameter of 0.26n+s+φ while being drawn continuously at a linear speed of 60 m/lll1n.
It was passed through a heating furnace at 00°C to condense and harden to form a 3 μm thick primary coating layer made of ladder type silicone resin.

Next, using a die with a diameter of 0.16+nmφ, the above-mentioned -
The next coating layer is made of ultraviolet curable resin with a thickness of 10 um.
A secondary coating layer was formed to obtain a coated optical fiber having the coating structure shown in FIG. 1 and having an outer diameter of 0.15+++a+φ.

(Comparative Example) A comparative example was manufactured by providing a 3 μm thick primary coating layer made of an ultraviolet curable resin on the outer periphery of the glass fiber, and further forming a 10 μm thick secondary coating layer made of an ultraviolet curable resin. did.

Using the optical fiber cores of the example and comparative example obtained as described above, the initial strength, strength reliability, and lateral pressure characteristics of optical transmission loss were measured for each, and the results were reported. They are shown in FIGS. 3, 4, and 5, respectively. Here, the initial strength was measured by applying stress to the optical fiber under the conditions that the span (distance between chucks) was 50 cm and the tensile rate was 10%/min, and the breaking strength was measured. The strength stability was measured by immersing the optical fiber in hot water at 80° C. and measuring the strength retention rate. The lateral pressure characteristics of optical transmission loss were measured by measuring the increase in transmission loss (loss) due to lateral pressure.

As a result of the above, as is clear from FIG. 3, the optical fiber of the example of the present invention has a higher initial strength than the comparative example, and the probability of breakage is significantly lower even when a large stress is applied. It has been found.

Furthermore, in the measurement of strength stability by immersion in hot water, as is clear from Figure 4, the strength stability of the example of the present invention was better than that of the comparative example, and the retention rate was 90% even after 20 days after immersion in hot water. It showed a high value.

Furthermore, in the measurement of the lateral pressure characteristics of optical transmission loss, as is clear from FIG. It was found that the increase in transmission loss (loss) was small.

[Effects of the Invention] As explained above, the optical fiber core of the present invention uses a ladder-type silicone resin as the primary coating layer of the optical fiber core, so it has high strength, weather resistance, It has excellent corrosion resistance, hardness, scratch resistance, heat resistance, flame resistance, etc., and also has good electrical properties such as electrical insulation and arc resistance.

In addition, during this next coating, a solution of organosilsesquioxane oligomer, which is an oligomer of ladder-type silicone resin, is prepared, and this oligomer solution is applied onto the glass fiber and then condensed and cured to apply the coating. Since it has good properties and can increase the linear speed, it is possible to improve productivity. In addition, since the oligomer solution can be adjusted in advance to an appropriate concentration depending on the desired thickness of the primary coating layer, even if the die diameter of the coating device is increased,
It is also possible to form a primary coating layer with a small thickness. Therefore, the coating can be applied without the glass fiber rubbing against the die when passing through the die. Therefore, the glass fiber will not be damaged and will not cause breakage. Further, it is possible to prevent a decrease in initial strength, and at the same time, it is possible to reduce the diameter of the core wire.

Furthermore, this secondary coating layer has high strength and scratch resistance, so even when forming a secondary coating layer on the outer periphery, even if the die diameter is reduced, the primary coating layer will Even if it is scratched, the second coating layer will not be damaged. Therefore, in addition to no reduction in strength, it is also possible to reduce the diameter of the optical fiber, which was previously considered impossible.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view showing an example of the coating structure of the optical fiber coated wire of the present invention, and FIG. 2 is a schematic sectional view showing an example of the coating device used when manufacturing the coated optical fiber of the present invention. FIG. 3 is a graph showing the initial strength of each of the optical fiber core wires of the example of the present invention and the comparative example, and FIG. FIG. 5 is a graph showing the strength stability of each of the optical fiber cores; FIG. 5 is a graph showing the lateral pressure characteristics of optical transmission loss of each of the optical fiber cores of Examples and Comparative Examples of the present invention. l...Glass fiber, 2......-
Next coating layer, 5...optical fiber core.

Claims (1)

[Claims] An optical fiber coated wire characterized in that a ladder-type silicone resin is used as a primary coating layer of the optical fiber coated wire.