JPS61166505A - Optical fiber core - Google Patents

Abstract

PURPOSE:To improve the linear speed for production of an optical fiber core by specifying the coefft. of light absorption of a photosetting resin constituting a secondary coating layer. CONSTITUTION:The photosetting resins to be used for a primary coating layer 4 and a secondary coating layer 5 are both an urethane acrylate resin and the Young's moduli thereof at an ordinary temp. are <=1kgf/mm<2> with the for mer and >=15kgf/mm<2> with the latter. Part of the light such as UV ray irradiat ed for the purpose of curing the layer 5 transmits the layer 5 and contributes to the curing of the layer 4 on the inside thereof if the photosetting resin having <=3.0 value of the coefft. epsilon of light absorption, i.e., the photosetting resin which permits the easy transmission of light is used for the layer 5. The linear speed of production of the optical fiber core 6 is thus improved.

Description

Detailed Description of the Invention [Technical Field] The present invention relates to an optical fiber formed by applying a primary coating layer and a secondary coating layer made of a photocurable resin to one or more optical fibers having a core and a cladding. It concerns the core wire.

[Prior art]

an optical fiber 3 having a cladding 2 formed around it;
In addition, a primary coating layer 4 having a low Young's modulus and serving as a stress buffer layer, both of which are made of a photocurable resin, specifically an ultraviolet curable resin, and a secondary coating layer 5 having a high Young's modulus, which is provided in consideration of handleability, etc. A coated optical fiber core 6 is known.

By the way, when manufacturing an optical fiber core [6] in which both the primary coating layer 4 and the secondary coating layer 5 are made of a photocurable resin as described above, the optical fiber 3 is first coated with a photocuring layer for the primary coating layer 4. After applying a photocurable resin and curing it by irradiating it with light such as ultraviolet rays, a photocurable resin for the secondary coating layer 5 is further applied on this secondary coating N4, and it is irradiated with light. Here, the intensity of the light used to cure the low Young's modulus photocurable resin used for the primary coating layer 4 is set to I. If the intensity of light to cure the resin is 12, it is >11 because resins with lower Young's modulus generally require more light intensity.Therefore, the curing speed is limited by the above-mentioned curing speed. As a result, it is no longer possible to expect an improvement in productivity as long as manufacturing is carried out using the conventional method.

[Purpose of the invention]

In view of the above problems, an object of the present invention is to provide a coated optical fiber in which both the primary coating layer and the secondary coating layer are made of a photocurable resin, and which can improve productivity. .

[Structure of the invention]

In order to achieve the above object, the present invention includes a primary coating layer made of a photocurable resin applied around an optical fiber, and a secondary coating layer made of a photocurable resin applied around the primary coating layer. In the optical fiber core wire having the following coating layer,
Light absorption coefficient ε of the photocurable resin constituting the secondary coating layer
is the intensity of light at the transmission distances X1 and X2, respectively'(X
+l, 'LX*l L/ta.

[Embodiments of the invention]

Examples of the present invention will be described in detail below. A feature of the present invention is that the secondary coating layer 5 shown in FIG. 1 is made of a photocurable resin with good light transmittance. That is, when the photocurable resin for the secondary coating layer 5 coated on the primary coating layer 4 is irradiated with light, for example ultraviolet rays, to cure it, the photocurable resin for the secondary coating layer 5 is cured. A part of the ultraviolet rays irradiated onto the surface of the substrate are transmitted through the secondary coating layer 5, and this also contributes to the curing of the primary coating layer 4.

Based on this idea, we investigated various photocurable resins for the secondary coating layer 5, and found that the light absorption coefficient ε of the photocurable resin constituting the secondary coating layer 5 is It has been found that it is effective if the intensity of each is below I(Xl+ - 1Xxl L/).

A specific example is shown below. The photocurable resins used for the primary coating layer 4 and the secondary coating layer 5 are both urethane acrylate resins, and the Young's modulus at room temperature for the former is 1 kif/n+11" or less, and for the latter is 15 kgf. /II
The light absorption coefficient ε was measured for the resin before curing, and the light source used was a high-pressure mercury lamp manufactured by Nippon Battery Co., Ltd. having a wavelength distribution of 200 to 7° Ona+.

Furthermore, the sensor used has a peak at 350ns+,
This is a photometer manufactured by Oak Co., Ltd. whose wavelength sensitivity is 320 to 390 nm. Furthermore, the fact that the photocurable resin reaches a saturated gel fraction means that the photocurable resin is completely cured. Therefore, the maximum linear speed required for the photocurable resin to obtain a saturated gel fraction refers to the critical linear speed at which the photocurable resin will not be completely cured if the linear speed is increased further.

The dimensions of the optical fiber core 6 in the table above are as follows: the outer diameter of the optical fiber 3 is 0.125**, the outer diameter of the primary coating layer 4 is 0.3fi, and the outer diameter of the secondary coating layer 5 is 0. .9 m.

As shown in the above table, when a photocurable resin having a light absorption coefficient ε of 3.0 or less, that is, a photocurable resin through which light easily passes, is used as the secondary coating layer 5 as in the present invention, A part of the light such as ultraviolet rays irradiated to cure the secondary coating layer 5 passes through the secondary coating layer 5 and also contributes to curing the inner primary coating layer 4. As a result, as shown in the previous table, the manufacturing speed of the optical fiber core 6 can be improved. In this embodiment, an optical fiber 3 consisting of a core 1 and a cladding 2 is described, but the optical fiber 3 may be an optical fiber in which the cladding 2 is pre-coated with a thermosetting or thermoplastic resin. 3 is also included. That is, the present invention can always be applied to an optical fiber core 6 having a two-layered coating layer made of photocurable resin on the outer periphery. Furthermore, a plurality of optical fibers 3 are twisted together, and a primary coating layer 4 made of a photocurable resin is applied to this.
, a device coated with a secondary coating layer 5, a device in which a plurality of optical fibers 3 are arranged in parallel in a plane, and a primary coating layer 4 made of a photocurable resin and a secondary coating layer 5 are coated thereon; It goes without saying that the present invention can also be applied to multi-core optical fibers 6 such as the above.

〔Effect of the invention〕

As described above, according to the present invention, since a photocurable resin with good light transmittance is used as the secondary coating layer, a part of the light transmitted through the secondary coating layer is absorbed into the inner primary coating layer. It also contributes to curing, and as a result, the inner primary coating layer, which has been a problem in the past, is efficiently and quickly cured, thereby improving the manufacturing speed of optical fiber cores.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing one embodiment of a coated optical fiber to which the present invention relates. 3 - Optical fiber 4 ---- Primary coating layer 5 -
Secondary coating layer 6 --- Ikko Fiha core filament Tuna
Song Ding Quantity Mountain climbing 1 Figure 1 5 Secondary Handan layer t F7CfRl JJ knee t
＼ Japanese Fubl February 1985/S day

Claims (1)

[Claims] An optical fiber core wire having a primary coating layer made of a photocurable resin applied around the optical fiber, and a secondary coating layer made of a photocurable resin applied around the primary coating layer, The light absorption coefficient ε of the photocurable resin constituting the secondary coating layer is ε when the light intensity at the transmission distances X_1 and X_2 is I(X_1) and I(X_2), respectively.
=-I/(X_2-X_1)log_1_0[I(X_
2)]/[I(X_1)] is 3.0 (1/mm) or less.