JPH0224771B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for continuously manufacturing optical quartz glass multiple fibers suitable as image transmission lines for image guides. Conventionally, multiple fibers have been arrayed and manufactured by the so-called single fiber winding method, but this method is extremely inefficient and is a major factor in increasing the cost of multiple fibers. Furthermore, with the recent development of low-loss silica glass optical fibers, it is thought that multiple fibers made of these fibers can transmit images even over long lengths of several tens of meters. Since it is virtually impossible to manufacture quartz glass fibers, the advantages of quartz glass multiple fibers cannot be fully utilized. The present inventors previously developed a method for manufacturing multiple fibers in which a bundle consisting of a large number of silica-based optical fibers is drawn. By the way, in order to make this manufacturing method continuous, it is necessary to wind the drawn multiple fibers around a drum, but in the case of thick multiple fibers with an outer diameter of 1 mm or more, drum winding is necessary due to the rigidity unique to quartz glass. However, if drum winding is carried out, there is a problem that the multiple fibers may break. In the production of silica glass optical fibers, there is a well-known technique for forming an extremely thin organic polymer layer of approximately 20 μm or less on the fiber immediately after drawing in order to improve the flexibility and strength of the fiber. (For example, Special Publication No. 56-19296, Special Publication No. 55-
30201). According to the research conducted by the present inventors, in order to improve the flexibility of a thin optical fiber obtained by drawing a single quartz-based optical fiber base material,
Although the formation of the above-mentioned extremely thin organic polymer layer is sufficiently effective, a large number of quartz-based optical fibers or optical fibers obtained by drawing the base material, for example, tens to thousands of fibers, may be used. In some cases, when tens of thousands of fibers are drawn in a bundle to produce thick multiple fibers with an outer diameter of 1 mm or more, a thin layer of organic polymer as described above is added to the multiple fibers obtained by drawing. Even if layers are formed, the flexibility etc. of the multiple fiber cannot actually be improved. There are various reasons for this, but the following are the main reasons. In other words, in the case of manufacturing optical fibers, since the target of drawing is a single base material, centering of the drawing is easy, and therefore, it is easy to draw a thin organic layer onto the drawn optical fiber. Although it is easy to apply a uniform molecular layer, in the production of multiple fibers, the object of drawing is a large number of optical fibers or their base material (hereinafter referred to as optical fiber raw material). A bundle or a quartz glass skin pipe containing the bundle. No matter how homogeneous the optical fiber strands contained in the above bundle are, the bundle or the bundle may be compared with a single optical fiber base material to be drawn in the production of optical fibers. The homogeneity of the skin pipe containing the fiber in its cross section is significantly inferior to that of a single optical fiber base material in the case of optical fiber production.
That is, it is heterogeneous. Because of this non-uniformity, centering is not easy during wire drawing, and the cross section of the drawn wire tends to be irregular. This tendency is particularly strong when the wire is thick with an outer diameter of 1 mm or more after drawing. Poor centering during wire drawing and irregularly shaped cross sections of the drawn wire both make it difficult to form a uniformly thin organic polymer layer. The present invention solves the above problems and has an outer diameter of 1 to 5.
This paper proposes a continuous manufacturing method for quartz glass-based multiple fibers for optical use of mm in thickness.
100μm or more, elongation 3% or more, tensile modulus 1000
It is characterized by forming an adhesive organic polymer layer of Kg/cm ² or more. In the present invention, the reason why the outer diameter of the multiple fiber to be manufactured is limited to 1 to 5 mm is 1 mm.
This is because, for multiple fibers with a diameter of less than This is because even if a thick organic polymer layer is applied, flexibility cannot be improved to the extent shown. In addition, the reason why the physical properties of the organic polymer layer applied to the multiple fibers are limited as described above is that the organic polymer layer that does not satisfy the above physical properties will not be flexible even if it is thicker than 100 μm. This is because it has little effect on improving sex. It is important that the organic polymer layer on the multiple fibers has good adhesion to the multiple fibers, and in practice, the organic polymer layer on the multiple fibers must be in good contact with the multiple fibers. There must be. Those having a peel strength of 50 g/mm or more as measured by the method described below can satisfy the above adhesion requirements. Peel strength: An organic polymer layer is formed by coating and drying or baking on a glass plate with a width of 20 to 30 mm whose surface has been sufficiently removed from solids, oil, fat, moisture, etc., and the organic polymer layer is peeled at a peeling angle of 90 degrees. Peel off the molecular layer. The above-mentioned good adhesion is achieved by applying an organic polymer, especially a polar organic polymer, and then chemically hardening it by drying, hardening, irradiation, baking, or other treatments. In particular, an organic polymer layer that stably satisfies the above physical properties can be formed by applying an organic polymer varnish and then chemically curing it through treatments such as irradiation and baking. Note that many organic polymer varnishes have a problem in that their viscosity temporarily decreases at high temperatures during bake-hardening, resulting in a wall thickness that becomes thinner than a predetermined thickness after hardening. Therefore, in such cases, care must be taken to use a varnish with as high a viscosity as possible or to perform baking at as low a temperature as possible.
In this respect, varnishes that can be cured by radiation are suitable for carrying out the present invention because they can be cured at low temperatures. Particularly preferred are UV-curable ones having a viscosity of 10 ³ to 5×10 ⁴ cp at room temperature. Examples of such varnishes include epoxy-acrylic varnishes 3031, 3041, and 3051 manufactured by ThreeBond, and RCP-611HV and RCP-611 manufactured by WR Grace. In the present invention, in order to achieve as good adhesion as possible between the multiple fibers and the organic polymer layer, the organic polymer layer is formed by applying paint while the surface is still free from contamination immediately after drawing. It is more preferable to apply the above-mentioned thickness in one application rather than to form a layer of 100 μm or more by multiple applications. The reason for this is that when multiple coatings are applied, foreign matter is likely to get mixed into the organic polymer layer, and there is a great risk that foreign matter will reduce the flexibility of the multiple fibers. Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples. [Examples 1 to 5, Comparative Examples 1 to 3] A cladding layer with a thickness of 35 μm made of quartz glass doped with B ₂ O ₃ and F on the outside of the core portion made of pure silica glass and having an outer diameter of 300 μm, and further Outer diameter with a 15μm thick quartz glass support layer on top of it
20 pieces of 11,000 optical fibers with a length of 400μm and a length of 40cm
They were washed in a hydrofluoric acid aqueous solution of % by volume and then in distilled water by applying ultrasonic waves, and bundled in distilled water. The bundle of strands was stored approximately in the middle of a synthetic quartz pipe (skin pipe) with an inner diameter of 48 mm and an outer diameter of 51 mm, and then B ₂ O ₃ was attached to the surface of each strand to ensure good adhesion between the strands. At least the synthetic quartz pipe was drawn at 2000℃ to create multiple fibers with an outer diameter of 2.0mm. Out of the wire drawing furnace, still
An organic polymer layer was formed on the multiple fibers at a high temperature of 100° C. or higher under the conditions shown in Table 1. The table summarizes the varnish used, various properties of the organic polymer layer formed, and the flexibility of the multiple fibers having the organic polymer layer. Among these, flexibility is expressed as the bending radius (mm) of the multiple fiber when it breaks. In addition, in Comparative Examples 2 and 3 and Examples 1 to 5, the applied varnish was made using an ultraviolet crosslinking device manufactured by Igraphik Co., Ltd.
1~ at output 1000W level using UB011-3A/B
It was cured by irradiating ultraviolet rays under optimal crosslinking conditions for about 3 seconds. 【table】

Claims (1)

[Scope of Claims] 1. A bundle of multiple quartz glass optical fibers is drawn to form multiple fibers with an outer diameter of 1 to 5 mm, and the drawn multiple fibers are coated with paint to a thickness of 100 μm or more. , elongation 3%
The above is a continuous method for producing optical quartz glass-based multiple fibers, which is characterized by forming an adhesive organic polymer layer with a tensile modulus of 1000 Kg/cm ² or more. 2. The continuous manufacturing method according to claim 1, characterized in that the adhesive organic polymer layer is formed immediately after drawing the multiple fibers and by applying a paint once.