JPH02187713A - Silica glass filament - Google Patents

Abstract

PURPOSE:To improve the adhesive property of a coating layer to a silica glass filament and to make it possible to use the filament over a long period of time even in a high temp. atmosphere in which heating and cooling are repeated by forming a cured coating layer of polyimide contg. bonded siloxane having a three-dimensional structure on the periphery of the filament. CONSTITUTION:A cured coating layer of polyimide contg. chemically bonded siloxane having a three-dimensional structure is formed on the periphery of a silica glass filament. The polyimide is obtd. by chemically bonding Si-O bond parts to polyimide and has a three-dimensional network structure. Unlike org. polyimide the polyimide contg. the chemically bonded siloxane has considerably improved matchability with SiO2 forming the silica glass, the adhesive property of the coating layer is remarkably improved and the coefft. of thermal expansion is made close to that of the silica glass because of heat curing to further improve the adhesive property. The coated filament is stably used over a long period of time in a high temp. atmosphere.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a silica glass filament that is used for optical fibers, image guides, light guides, capillary tubes, etc., and is particularly useful when used in high-temperature atmospheres. It is.

[Prior Art] Silica glass filaments have superior translucency compared to ordinary optical glasses, and are widely used as optical transmission bodies such as optical fibers, image guides, and light guides. It is well known that there are. This silica glass striatum is I! ! It is also used in gas chromatograph capillary columns instead of conventional stainless steel and hard glass because it can reduce impurities that become adsorbent during the manufacturing process.

Minute scratches are likely to occur on the outer surface of these filaments during manufacturing, and the presence of such scratches may cause a notch effect during handling, which may damage the filament. Therefore, when manufacturing the filament, a coating made of silicone, ultraviolet curing resin, etc. is usually applied to prevent the above-mentioned damage and greatly improve handling properties.

[Problems to be solved by the invention] The above-mentioned optical fibers and image guides are often used in high-temperature atmospheres such as remote monitoring around high-temperature furnaces, and the capillary tube of the Gask 17 matograph itself is used at high temperatures. However, when used at such high temperatures, the coating material has its own limitations, and the actual situation is that it cannot necessarily be said that sufficient coating is achieved.

In other words, polyimide is a material that can withstand use in the above-mentioned high-temperature atmosphere and has a heat resistance of about 300°C, or polyimide has poor adhesion to silica glass and has a significantly larger coefficient of thermal expansion than glass. Therefore, in applications where heating and cooling are repeated, there is a tendency for polyimide and glass to separate, resulting in a significant decrease in the protective effect of the coating layer, which may cause damage by bending the filament. becomes very large.

Attempts have also been made to add a silane coupling agent to the paint solution in order to improve contact with crows, but this was not satisfactory as it was observed that a reaction occurred during mixing resulting in gelation.

Conversely, methods have been attempted in which a silane coupling agent is applied to the surface of the striatum and then coated with polyimide, but this method was also not satisfactory due to time and space constraints before coating with polyimide. .

Although polyimide having a coefficient of thermal expansion comparable to that of silica glass has been developed, its molecular chain has a rigid structure and is therefore unsuitable for applications where it is bent like a silica glass filament.

The present invention solves the 1 #1 problem of the conventional technology as described in (-), has excellent adhesion to glass, and can be used for a long period of time without fear of peeling even in applications where heating and cooling are repeated. It is an object of the present invention to provide a polyimide-coated silica glass strip.

[Means for Solving the Problems 1] The present invention provides a conversion coating made of polyimide, which is formed by chemically bonding a three-dimensional structure of siloxane to the outer periphery of a silica glass filament! The silica glass filament referred to herein is a solid type or tube-shaped filament formed from silica glass or silica glass to which dopant 1~ is added.

Polyimide with chemically bonded three-dimensional siloxane I structure is chemically bonded to the polyimide portion and the 5i-0 bond portion! It is made of 1A structure, and the following structure is given as an example.

Here, R1 and R2 can be listed as shown below, but if they fall within the category of polyimide VI4 resin, the chemical structure is the above formula % R2 = (PMD, A) In the polyimide according to the invention, as shown in the above formula, the siloxane portion consists entirely of 81-0 bonds and has a three-dimensional network structure. As described above, since siloxane consisting only of inorganic components is glassy, when it is used as a coating layer, it is harder than polyimide alone and has a smaller thermal expansion.

In the present invention, it is intended that the glass surface be directly coated, but the glass surface may be coated with a thin layer of 1 μm or less in thickness, for example, a S 1 a Na * C * surface treatment agent, etc. 6 There is no difference.

Although the coating according to the present invention is sufficiently effective when used alone, it is also possible to coat the outer periphery with polyimide or other plastics known in the prior art, such as fluororesin.
It may be coated with polyether sulfone, polyether ether ketone, etc.

1 Effect] The polyimide coating according to the present invention is different from conventional polyimide that is composed only of organic substances, and has a three-dimensional network structure formed by Si-0 bonds. The consistency of the adhesive has been improved to a large rlJ, greatly improving adhesion, and when it is heated and cured, its coefficient of thermal expansion approaches that of glass, resulting in long-term adhesive stability in high-temperature atmospheres and heating-cooling atmospheres. be done.

[Example 1 The present invention will be described below with reference to Examples.

Example 1 A single-mode optical fiber base material consisting of a silica glass core doped with germanium oxide and a silica glass cladding was drawn into an optical fiber with an outer diameter of 1) 5 μm using a drawing furnace, and a siloxane-modified polyimide solution having the following structural formula was drawn. (N-methylpyrrolidone dilution, viscosity 1.0OOCIIS
) was passed through a coating die containing a The drawing speed was 50 m/(Iin, and the coating thickness was 20 μm.

Immediately place the coated fiber in a heating furnace (350℃)
The modified polyimide was cured by passing it through a tube and then wound onto a bobbin. The tensile strength of the coated optical fiber obtained in this way was 6 kg on average, which was comparable to that of ordinary coated optical fiber. As a result of measuring the optical transmission loss,
The fluctuation rate was within 0.2 dB/km.

Example 2 A synthetic silica glass tube was drawn in an optical fiber drawing furnace to produce a capillary tube with an outer diameter of 320 μm and an inner diameter of 250 μm, and immediately a siloxane-modified polyimide solution having the same composition as in Example 1 was added to a thickness of 20 μm. coated with. #A melon was drawn at a speed of 20 m/min, and was immediately passed through a heating furnace (300° C.) to harden and wound onto a bobbin.

This capillary tube (50m) wound around an aluminum reel with an outer diameter of 150+m+ was heated in a constant temperature bath at 400℃ for 15 hours in a N2 atmosphere without any scratches or peeling of the coating. By silylating agent and fixing agent =? - When the inked capillary column was installed in a gas chromatograph, it was confirmed that it had sufficient separation function without any problems.

Example 3 Example 2 except that a siloxane-modified polyimide solution having the following structural formula (N-methylpyrrolidone dilution, viscosity 2,000 cps) was used in the synthetic silica glass tube of Example 2.
The same capillary tube was manufactured.

The same capillary tube as in Example 2 was manufactured except for the following.

As a result of carrying out the same test as in Example 2 using this, the same results as in Example 2 were obtained.

As a result of conducting the same test as in Example 2 using this, the same results as in Example 2 were obtained.

Example 4 The synthetic silica glass tube of Example 2 was filled with 30,000 image guide wires of Example 5 using siloxane-modified polyimide solution 1 (diluted with N-methylpyrrolidone, viscosity 1.500 cps) having the following structural formula. After drawing the silica glass tube in a drawing furnace to an outer diameter of 2 mm, immediately apply the siloxane-modified polyimide solution used in Example 1 to a film thickness of 20 mm.
It was coated to a thickness of μm.

As a result of winding this image kite (length 1 ml) around a mandrel with an outer diameter of 150 rm, none of the 10 samples were broken.

Example 6 Immediately after coating the siloxane-modified polyimide in Example 2, the polyimide used in the following comparative example was coated with a thickness of 20 μm.
The film was coated to a thickness of m and cured by heating to form a double coating layer, which was then wound onto a bobbin.

The same test as in Example 2 was conducted on this capillary tube, and the same results as in Example 2 were obtained.

Comparative Example The other conditions were as in Example 2, except that instead of the siloxane-modified polyimide in Example 2, a conventional polyimide solution having the structural formula shown below (diluted with N-methylpyrrolidone, viscosity 2,000 cps) was coated. Samples were prepared in exactly the same manner.

As a result of heating 50 m of this capillary tube wound around an aluminum reel with an outer diameter of 150 mm in a N2 atmosphere in a constant temperature bath at 400°C, the coating partially peeled off and broke in two places. It was approved as N.

As can be seen from the above examples, the filament according to the present invention has improved adhesion to silica glass by chemically bonding polyimide and a three-dimensional siloxane structure as a coating material, and is unique to polyimide. Since it is harder, it is less likely to be scratched and its mechanical strength is improved. Therefore, the conventional orcasiloxane-modified polyimide having an organic group in its side chain is different from the polyimide according to the present invention.
As a result, the excellent effects described above cannot be expected.

[Effects of the Invention] As described above, the silica glass filament according to the present invention maintains strong adhesion of the coating layer and is stable over a long period of time in a high-temperature atmosphere or an atmosphere where heating and cooling are repeated. It can be used for many purposes, and it has great significance in expanding its range of applications.

Claims (1)

[Claims] (1) A silica glass filament formed by forming a cured coating layer made of polyimide, which is formed by chemically bonding siloxane having a three-dimensional structure, on the outer periphery of a filamentous silica glass.