JP2000180676A - Coated optical fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coated optical fiber capable of selecting a coating mate rial without restriction by water absorption rate in selection of the coating material and having high strength retention of glass fiber by controlling the drawing-out force of the coating to be above a predetermined value and using only a phenol material as an antioxidant to be added to the coating material. SOLUTION: In a coating optical fiber comprising a coating 4 made of a photo-curing resin around a glass fiber 1, a drawing-out length is 10 mm, the drawing-out force of the coating at 10 mm/min. of drawing-out speed is above 200 g, and an antioxidant to be added to a coating material is only a phenol material. Whereby high strength retention of the glass fiber can be obtained. The coating material can be easily selected without considering the water absorption rate and the optical fiber can be easily manufactured only by manufacturing the optical fiber while adding the phenol antioxidant to the photo-curing resin as the coating material, and controlling the manufacturing condition to increase the drawing-out force.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coated optical fiber in which a coating made of a photocurable resin is provided around a glass fiber.

[0002]

2. Description of the Related Art As a coated optical fiber, a coating composed of a primary coating made of a relatively soft photocurable resin around a glass fiber and a secondary coating made of a relatively hard photocurable resin thereon. Is used. Various proposals have been made to enhance the stability of the glass fiber strength of the coated optical fiber. JP-A-7-
Japanese Patent No. 215738 discloses a method for reducing the dynamic fatigue of a glass fiber by limiting the water absorption of a coating material.
Further, Japanese Patent No. 2768674 describes a method of increasing the tensile strength retention of a glass fiber by limiting the water absorption of the coating material and keeping the adhesive force between the coating and the glass fiber within a certain range.

On the other hand, in coating of coated optical fibers, an antioxidant is added to the coating material in order to stabilize the coating properties for a long time. It is known that antioxidants include sulfur, phenol, phosphorus, and amine types.

[0004]

SUMMARY OF THE INVENTION The above-mentioned Japanese Patent Application Laid-Open No. 7-215 is disclosed.
According to the proposals of Japanese Patent No. 738 and Japanese Patent No. 2768674, a trial production was performed with limiting the water absorption of the coating material. Also,
When the water absorption is limited, the range of resin materials that can be selected becomes considerably narrow, and it has been difficult to simultaneously satisfy various requirements such as ease of production and other various requirements. An object of the present invention is to provide a coated optical fiber which can be selected without being limited by a water absorption rate in selecting a coating material of the coated optical fiber, and which has a high strength retention of a glass fiber.

[0005]

The coated optical fiber of the present invention is a coated optical fiber in which a coating made of a photocurable resin is provided around a glass fiber, and has a drawing length of 10 mm.
200 g of pulling force of coating at a drawing speed of 10 mm / min.
As described above, the antioxidant to be added to the coating material is only the phenolic material. By using such a coated optical fiber, a glass fiber having a high strength retention can be obtained as described later.

[0006]

FIG. 1 is a cross-sectional view showing an embodiment of a coated optical fiber of the present invention, wherein 1 is a glass fiber, 2 is a primary coating, 3 is a secondary coating, and 4 is a primary coating 2. And the secondary coating 3. The primary coating 2 is made of a relatively soft urethane acrylate resin, and the secondary coating is made of a relatively hard urethane acrylate resin. In this embodiment, a two-layer coating structure is shown.
It is not limited to that. Further, the photocurable resin to be coated is not limited to the urethane acrylate resin.

[0007] In the coated optical fiber of the present invention, only a phenolic material is added as an antioxidant to the photocurable resin constituting the coating material. If the coating consists of a primary coating and a secondary coating, the only antioxidant added to the material of both coatings is a phenolic material only. In addition, a hindered amine light stabilizer or the like may be included as a light stabilizer. Further, the coating force is adjusted so that the drawing force is 200 g or more. The increase in the pull-out force is caused by a polar monomer of the photocurable resin, for example, acrylamide, N-vinylpidroline,
It can be achieved by increasing the amount of acryloyl morpholine, etc., or by adding a silane coupling agent for the photocurable resin, and adjusting the pull-out force by selecting the material and adjusting the irradiation amount of ultraviolet light. Can be done.

The reason why such a coated optical fiber according to the present invention has been found to be a glass fiber having a high strength retention will be described. When investigating the cause of the glass fiber strength deterioration, it was found that not only the adhesion between the glass fiber and the primary coating, but also the antioxidant added to the resin had a significant relationship with the glass fiber strength deterioration. I understood. The results are shown below.

[0009] Diameter 125 μm mainly composed of quartz glass
A primary coating made of a relatively soft urethane acrylate resin is provided around the glass fiber having a diameter of 200 μm.
And a secondary coating made of a relatively hard urethane acrylate resin having an outer diameter of 24
A coated optical fiber having a thickness of 0 μm was manufactured by changing the type of the antioxidant added to the primary coating and the secondary coating.

As an antioxidant, a sulfur type antioxidant, Sumilizer TPS manufactured by Sumitomo Chemical Co., Ltd., is used.
(-R) as a phenol-based compound (Sumitomo Chemical Co., Ltd.)
Sumitizer BHT and Sumitomo Chemical Co., Ltd. Sumilizer TPP-R were used as phosphorus-based materials.

Further, the amount of the polar monomer of the photocurable resin,
By adjusting the amount of the silane coupling agent to be added and the conditions of the ultraviolet irradiation, the coating was produced with variously changing the pull-out force.

The pulling force of the various coated optical fibers manufactured as described above and the strength retention of the glass fiber were examined by the following methods. The pull-out force is 1 from the end of the coated optical fiber.
At 0 mm, a cut was made in the cross-section direction in the coating, and the cutout was fitted with a U-groove of a thin plate-like member having a U-groove having a width slightly larger than the outer diameter of the glass fiber, and the plate-like member was subjected to a tensile tester. And pulled in the direction of the end of the coated optical fiber at a speed of 10 mm / min.
The maximum value of the tensile strength was defined as the pull-out force. The other end of the coated optical fiber was fixed to the other chuck of the tensile tester.

The pull-out force of the coating is determined by the aforementioned patent No. 2768.
In No. 674, a plate-shaped test piece is used instead of the adhesive force. However, since the actual coated optical fiber is affected by residual stress at the time of manufacture, etc., measurement using a plate-shaped test piece can be sufficiently substituted. Absent. Further, there is an example in which the drawing force is examined at a drawing length of 30 mm and a drawing speed of 500 mm / min. However, if the drawing is performed at such a high speed, the characteristics of the secondary coating appear strongly, and the characteristics between the glass fiber and the coating are reduced. Not suitable to figure out. Therefore, in the test of the pulling force of the coated optical fiber of the present invention, the drawing length is set to 10 mm and the drawing speed is set to 10 mm / min as described above.

The strength retention of the glass fiber was determined by the following method. Put coated optical fiber in hot water at 85 ° C for 60
The strength of the glass fiber after immersion for one day was measured, and the value was divided by the value of the strength measured with the glass fiber not immersed to obtain the strength retention of the glass fiber. The strength of the glass fiber was measured using a tensile tester at a mark interval of 300 mm and a tensile speed of 100 mm / min in the state of the coated optical fiber.
At 0, it was determined with a 50% breaking probability. Further, the measurement of the tensile strength is performed in the state of the coated optical fiber. However, since the strength of the glass fiber is much larger than the strength of the coating, the value of the coated optical fiber is used as the strength of the glass fiber.

FIG. 2 shows the results of measuring the pulling force of various manufactured coated optical fibers and the strength retention of glass fibers. From these results, in order to increase the strength retention of the glass fiber to 90% or more, a phenol-based material was selected as an antioxidant, and the drawing force was 200 g.
It can be seen that the above should be sufficient. If the drawing force is small even when a phenolic antioxidant is used, the strength retention of the glass fiber is low, and the effect of the phenolic antioxidant is not exhibited. Further, those using a sulfur-based or phosphorus-based antioxidant are inferior in the strength retention of the glass fiber as compared with those using a phenol-based antioxidant.

The reason for obtaining such a result is that phenolic antioxidants do not generate hydrophilic ones because they are radical chain inhibitors, whereas sulfur and phosphorus antioxidants do not. It is presumed that this is because alcohol is generated by hydroperoxide decomposition and water is easily attracted into the coating. Among the antioxidants, amine-based antioxidants also have a radical chain inhibiting action, but amine-based antioxidants have coloring properties, and have an adverse effect on the identification of colored coated optical fibers. In the experiments leading to the present invention, amine antioxidants were excluded.

[0017]

According to the coated optical fiber of the present invention, the pull-out force of the coating made of the photocurable resin is set to 200 g or more, and the antioxidant added to the coating material is made only of the phenolic material. A material having a high strength retention can be obtained. Also, as a coating material, a phenolic antioxidant may be added to the photocurable resin, and the production conditions may be adjusted so that the drawing force is increased. Can be selected, the selection is easy, and the manufacturing is easy.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a coated optical fiber of the present invention.

FIG. 2 is a diagram showing the relationship between the pull-out force of the coating and the strength retention of the glass fiber when the type of antioxidant is changed.

[Explanation of symbols]

 1: glass fiber 2: primary coating 3: secondary coating 4: coating

 ──────────────────────────────────────────────────続 き Continued on front page F term (reference) 2H050 BA03 BA32 BB07Q BB07S BB14Q BB14S BB17Q BB17S BB19Q BB19S BB33Q BB33S BC03

Claims (1)

[Claims] 1. A coated optical fiber in which a coating made of a photo-curable resin is provided around a glass fiber, the coating has a drawing force of 200 g or more at a drawing length of 10 mm and a drawing speed of 10 mm / min. A coated optical fiber characterized in that an antioxidant to be added is only a phenolic material.