JPS6177645A - Clad material for optical glass fiber - Google Patents

Abstract

PURPOSE:To maintain initial strength of optical fiber immediately after it is prepd. by cladding the surface of an optical glass fiber for light transmission with at least two kinds of 1,4-polybutadiene having functional groups as main material. CONSTITUTION:The surface of optical glass fiber is coated with <=two kinds of 1,4-polybutadiene having at least two functional groups such as OH group, COOH group, isocyanate group, epoxy group, etc. in a molecule succeeding to the spinning stage of the optical fiber. The optical fiber has quicker curing characteristic due to mutual reaction of the functional groups with each other, and the fiber is prepd. with superior productivity and the initial strength immediately after spinning is maintained for a long time, and the optical fiber is durable to withstand use for a long period.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a material for coating optical glass fins for light transmission.

Optical glass fibers (hereinafter simply referred to as optical fibers) used as optical transmission media usually have a diameter of 20 mm.
Since it is less than 0 μm and the material is brittle, scratches are likely to occur on the surface during manufacturing, cable production, and storage, and these scratches become a source of stress concentration, making it easy to damage when external stress is applied. The disadvantage is that the optical fiber may break.

For this reason, it is extremely difficult to use optical fiber as it is as an optical transmission medium. Therefore, conventionally, attempts have been made to provide a plastic coating on the surface of an optical fiber, thereby maintaining the initial strength immediately after manufacturing the optical fiber and manufacturing an optical fiber that can withstand long-term use.

This plastic coating generally consists of a primary coating to maintain initial strength, a secondary coating made by extrusion of a thermoplastic resin such as polyamide or polyethylene to cope with subsequent handling such as cabling, and It consists of three steps in which a buffer layer is provided between the primary coating and the secondary coating in order to prevent an increase in transmission loss, and the formation of the secondary coating and buffer layer is usually done in a process subsequent to the spinning process of the optical fiber. There is.

However, urethane-based and epoxy-based thermosetting resins, which are conventional primary coating materials, have a slow curing speed and require a long time to cure and dry, which limits the drawing speed of optical fibers.
This is one of the problems in mass production of optical fibers. Furthermore, since these resins cannot be coated thickly, they also have the disadvantage of weakening the strength of the optical fiber. Furthermore, as a conventional buffer layer forming material, silicone rubber that cures at room temperature is used for reasons of transmission properties, but this silicone rubber increases its viscosity just by leaving it at room temperature, making it resistant to long-term spinning. In addition, because of its relatively high tackiness, it has the disadvantage that dust and the like easily adhere to it, which adversely affects the secondary coating.

The present invention avoids these drawbacks and provides a new and useful coating material for optical fibers that is a primary coating material that can improve the mass productivity and strength of optical fibers, and that can also serve as a buffer layer. The gist of this is that two or more types of 1,4-polybutadiene having functional groups are used as the main material of the coating material, and the functional groups of each polybutadiene react with each other. An optical fiber coating material characterized by:

That is, since the coating material of the present invention is mainly made of 1,4-polybutadiene, the coating film is made of other polymers such as 1,2-polybutadiene, compared to conventional thermosetting resins. It is extremely flexible compared to . Therefore, there is no need to further provide a buffer layer on this secondary coating layer, and since the main material is a combination of two or more types of 1,4-polybutadiene containing functional groups that react with each other, the functional groups Since it has the property of being heated and cured by a reaction between the coating materials and its curing speed is faster than that of conventional coating materials, the coating work is significantly improved and the mass productivity of optical fibers can be greatly improved.

In addition, the flexibility of the film not only provides good results in terms of strength, but also suppresses the increase in transmission loss caused by microbending, which is seen in conventional thermosetting resins, and provides highly reliable optical fibers. It becomes possible to manufacture fibers. In addition, 1,4-polybutadiene is a relatively high molecular weight substance that is liquid at room temperature and has a very low viscosity compared to 1,2-polybutadiene, so it can be used as a solvent-free type or as a coating material with a small amount of organic solvent. As a result, it becomes easy to apply a uniform thick coating, which also improves the strength of the optical fiber. Further, by using the above-mentioned solvent-free type, it is not only advantageous from the viewpoints of resource saving and pollution-free, but also suppresses foaming of the coating and generation of pinholes due to solvent removal.

The 1,4-polybutadienes having a functional group used as the main material in this invention have at least two functional groups such as a hydroxyl group, a carboxyl group, an isocyanate group, or an epoxy group in the molecule, particularly preferably at both ends of the molecule. It is a 1,4-polybutadiene having the above-mentioned functional groups, and a commercially available product may be used as it is, or if necessary, it can be synthesized by a method such as reacting a dicarboxylic linkage or a diisocyanate compound with 1,4-polybutadiene containing a hydroxyl group. You may.

Two or more 1,4-polybutadienes having such functional groups are used as a coating material that is cured by a reaction between the functional groups. If the functional groups have very high reactivity with each other, they may be made into a two-component type, if necessary.

The coating material of the present invention may contain a modifying resin and various additives as required, and may be diluted with a solvent if desired. The modifying resin is used in an amount equal to or less than the amount of the main material, preferably 1/4 or less. Specific examples thereof include epoxy resin, polyamide, polyurethane, polyether, polyamideimide, silicone resin, and phenol resin. In addition, the above additives include cobalt naphthenate, zinc naphthenate,
Examples include curing accelerators such as dimethylaniline and dibutyltin dilaurate, organosilicon compounds, and surfactants.

In this invention, the method for coating an optical fiber is performed immediately after the spinning process of the optical fiber, that is, the process of heating and stretching a rod-shaped material or block-shaped material for an optical fiber to spin it into an optical fiber of a desired diameter. After the coating material of the present invention is applied to the surface of the optical fiber, it is usually cured by applying heat. .

This curing provides a flexible primary coating, which is then directly subjected to the secondary coating process without providing a buffer layer.

The rod-shaped material for the optical fiber is generally called a base material of quartz fiber, and the block-shaped material is a material spun by a double crucible method for multi-component fiber. In addition, the desired diameter of the optical fiber is usually 2
00 μm or less.

As explained above, the optical fiber coating material of the present invention comprises two or more types of 1,4-
Because it uses polybutadiene as the main material,
Compared to conventional materials, the curing speed is faster, which not only improves the productivity of optical fibers, but also improves the strength and reliability of optical fibers by forming flexible coatings and thick coatings.

The present invention will be described below with reference to Examples, but the present invention is not limited to these Examples in any way. In addition, hereinafter, parts mean parts by weight.

Example 1 100 parts of 1,4-polybutadiene having isocyanate i in the molecule (1,4-polybutadiene/tolylene diisocyanate adduct; isocyanate group content: 9% by weight), 1,4-polybutadiene having a hydroxyl group at the end of the molecule (
A coating material for an optical fiber of the present invention was prepared by mixing 257 parts of hydroxyl group content (0.83 milliliter/g) and 0.05 part of siftylstin dilaurate.

Comparative Example 1 Epoxy resin Epon-828 (manufactured by Shell Oil Company) 10
0 parts, 5 parts of 2-ethyl-4-methylimidazole was dissolved to prepare a coating material for optical fiber.

Comparative Example 2 100 parts of 1,2-polybutadiene having an isocyanate group in the molecule (1,2-polybutadiene/tolylene diisocyanate adduct; isocyanate group content: 8% by weight), 1,2-polybutadiene having a hydroxyl group at the end of the molecule (
A coating material for optical fiber was prepared by mixing 200 parts of hydroxyl group content (0.95 milliliter/g) and 0.05 part of siftylstin dilaurate.

When the characteristics of each material of Example 1 and Comparative Example 1.2 were investigated, they were as shown in Table 1 below.

In Table 1 above, Shore hardness A was measured as follows. That is, each material was heated to 150°C.

It was heat-cured for 15 minutes to create a plate-like material with a thickness of 2, and this was used for measurement.

Next, using the coating materials of Example 1 and Comparative Examples 1.2 above, optical fibers were actually coated and their performance was tested as shown in Test Example 1 and Comparative Test Examples 1 and 2 below. .

Test Example D In a step subsequent to the spinning process, Example 1
After applying the coating material shown in 340
It was heat cured at °C. The outer diameter of the optical fiber after coating was approximately 225 μm, and the breaking strength was 6.2 kg.
No increase in transmission loss was observed up to -40°C.

Comparative Test Example 1 Following the spinning process (in the process), Comparative Example 1
After applying the coating material shown in , it was cured using an electric furnace at 650°C. The outer diameter of the optical fiber after coating is 150
It varied in the range of ~310 μm. Furthermore, in the obtained optical fiber, a rapid increase in transmission loss was observed at temperatures below 20°C.

Comparative Test Example 2 Coating was carried out in the same manner as in Test Example 1, except that the coating material of Comparative Example 2 was used instead of the coating material of Example 1. The outer diameter of the optical fiber after coating varied from about 169 to 335 μm. Furthermore, the breaking strength was 4.7 ktr, and a rapid increase in transmission loss was observed below -40°C.

As explained above, the optical fiber coating material of the present invention has a low viscosity and a fast curing speed, so it can be coated quickly and with good adhesion during the optical fiber spinning process, and it is flexible after curing. Optical fiber has excellent transmission characteristics because it is highly versatile.

There is an advantage that a bar coated body can be obtained.

Claims (1)

[Claims] (1) A coating material for optical glass fiber, characterized in that two or more types of 1,4-polybutadienes having functional groups are used as the main material, and the functional groups of each polybutadiene type react with each other.