JPS60155553A - Method for coating optical fiber - Google Patents

Abstract

PURPOSE:To prevent the uneven thickness of a resin coating layer, by coating the outer periphery of an optical fiber with an uncured ultraviolet curing resin, heating the resin film, and curing the resin film by irradiation with ultraviolet light. CONSTITUTION:An optical fiber 1 after spinning is passed through a coating vessel 2 containing an uncured ultraviolet curing resin, and the outer periphery of the fiber 1 is coated with the resin in passing through a die part 3. The coated optical fiber 1 is then heated in a heating furnace 6 to reduce the viscosity of the resin and coat the optical fiber 1 without causing uneven distribution of the resin. In this state, the coated resin is cured by irradiation with ultraviolet light from an ultraviolet irradiator 4. Thus, the aimed optical fiber 1 having a coating layer 5 of uniform thickness is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of coating an optical fiber using an ultraviolet curable resin as a coating material.

Generally, a thermosetting resin is used as the primary coating layer of an optical fiber, and a thermoplastic resin is used as the secondary coating layer, but recently, the primary coating layer etc. are being made of ultraviolet curable resin. Proposals have also been made to obtain coated optical fibers with good characteristics.

When forming a coating layer made of an ultraviolet curable resin around the outer periphery of an optical fiber, a die type coater and an ultraviolet irradiator as shown in FIG. 1 are usually used, and the optical fiber is coated as follows.

That is, the optical fiber 1 after spinning is drawn into the coater 2 containing an uncured (liquid) ultraviolet curable resin, and when the optical fiber 1 passes through the die part 3 of the coater 2, The above resin is applied to the outer periphery of the optical fiber, and the ultraviolet curable resin on the outer periphery of the optical fiber is cured by receiving curing energy from the ultraviolet irradiator 4 located next to the coating device 2, thereby forming a coating layer 5. Ru.

The thickness of the coating layer 5 formed in this way is determined by the outer diameter of the original fiber 1 and the diameter of the die part 3. Within the range, the coating resin (uncured) has a low viscosity and the coating thickness is 30
μm or more, the coating layer 5 is formed without uneven thickness due to the surface tension of the uncured coating resin,
The viscosity of the coating resin is 500 to 10,000 cps.

If the coating thickness is less than 30 μm, the surface tension of the resin cannot overcome its viscosity, and if vibrations of the optical fiber 1 are added to this, the coating will deteriorate in the radial and longitudinal directions as shown in Figures 2 and 3. Thickness unevenness of layer 5 occurs and is also noticeable.

The present invention aims to provide a new method for coating an optical fiber using an ultraviolet curable resin as a coating material, which can eliminate uneven thickness of the coating layer.

The present invention relates to an optical fiber coating method in which a coating layer made of an ultraviolet curable resin is formed on the outer periphery of the optical fiber, in which an uncured ultraviolet curable resin is applied to the outer periphery of the optical fiber, heated, and then the resin is coated. It is characterized by curing it by irradiating it with ultraviolet rays.

Examples of the method of the present invention will be described below with reference to the drawings.

In FIG. 4, numeral 1 is an optical fiber made of quartz or formed glass, and numeral 2 is a die-shaped coating device similar to that described in FIG. 1, which has a die portion 3.

4 is also the same ultraviolet irradiator as described in FIG. 1, and is usually equipped with a vertically elongated ultraviolet lamp.

Reference numeral 6 denotes a heating furnace disposed between the coating device 2 and the ultraviolet irradiator 4, and this heating furnace 6 is equipped with an electric heater.

When forming the coating layer 5 on the outer periphery of the optical fiber 1 in FIG. 4, a known ultraviolet curable resin (uncured) such as epoxy acrylate type or urethane acrylate type is stored in the coater 2, and The optical fiber 1 spun by the means is drawn into the coater 2.

When the optical fiber 1 passes through the die section 3 of the coater 2, the resin is applied to the outer periphery of the optical fiber 1 to a predetermined thickness, and the coated optical fiber 1 heads toward the ultraviolet irradiator 4. However, before reaching the ultraviolet irradiator 4, the uncured coating resin on the outer periphery of the optical fiber is heated in a heating furnace 6 to reduce its viscosity.

For example, the viscosity before heating is 500 to 1.0000 cp
Even with the above-mentioned resin, which has a viscosity of 50
The viscosity is reduced to 0 cps or less or 100 cps or less, and the surface force exceeds the viscosity.

Due to the above-mentioned surface tension, the uncured coating resin covers the optical fiber 1 without causing distortion, and in this state, when the optical fiber 1 reaches the position of the ultraviolet irradiator 4,
The coated resin is cured by irradiation with ultraviolet rays, and a coating layer 5 of uniform thickness is formed as shown in FIG.

After the coating layer 5 has been formed, the optical fiber 1 may be wound as is, but usually, a coating layer of thermosetting or ultraviolet curable resin is applied on the coating layer 5 in succession to the coating process described above. After approximately two layers have been formed, they are rolled up, and then a thermoplastic resin coating layer is formed by extrusion coating means.

Note that the coating means described by Mayu is also effective when further forming a coating layer made of ultraviolet curable resin on the coating layer 6, and the coating device used for this coating may be of the open type as shown in the figure. , pressurized type can also be adopted.

Furthermore, if the uncured resin is applied to the outer periphery of the optical fiber 1 by a spray method or a contact coating method using a resin-impregnated material (for example, felt, sponge, cotton, etc.) as a coating means, the coating will break off. By using the irradiation means, a coating layer 5 having a uniform thickness can be formed.

As a specific example, an optical fiber was coated under the following conditions.

Optical fiber 1: Quartz-based, outer diameter 125 μm Dice part 3 of coater 2: Diameter 150 μm Ultraviolet irradiation furnace 4: Output several hundred watts Coating layer 5: Main component is epoxy acrylate with a viscosity of 2500 cps (uncured) UV curable resin, average coating thickness 5 μm Heating furnace 6: temperature 150°C, furnace length 1 m When the coating layer 5 was formed around the outer periphery of the optical fiber 1 according to the above specific example, its maximum thickness and minimum thickness were The difference between
Good results were obtained with the following.

For comparison, when the heat treatment was omitted in the above specific example, the difference between the maximum thickness and the minimum thickness of the coating layer 5 was as much as 5 μm, and the amount of thickness deviation became extremely large.

As explained above, when using the method of the present invention, the ultraviolet curable resin (uncured) on the outer periphery of the optical fiber is heated and then the resin is cured, so the viscosity of the resin decreases during heating and its surface tension increases. A resin coating state with no thickness deviation is naturally obtained, and therefore a coating layer with extremely small thickness deviation can be formed around the outer periphery of the optical fiber.

[Brief explanation of drawings]

Fig. 1 is a schematic explanatory diagram of the conventional method, Fig. 2 is an enlarged view of the main part of the same as above, Fig. 3 is a sectional view of an optical fiber coated with uneven thickness, and Fig. 4 is a schematic illustration of an embodiment of the method of the present invention. FIG. 5 is a sectional view of a coated optical fiber according to the method of the present invention. 1. ■... Optical fiber 2... Coating device 4... Ultraviolet irradiator 5... Coating layer 6... Heating furnace agent Patent attorney Yoshio Saifuji No. 1 Illustration 4 @ 2 Sendai 3 [4 Haku 5 Self

Claims (1)

[Claims] 1. A method for coating an optical fiber, which comprises applying an ultraviolet curable resin of chemical formula, heating the resin, and then irradiating the resin with ultraviolet rays to cure the resin.