JPH07104155A - Glass fiber for optical transmission and its production - Google Patents

Abstract

PURPOSE:To provide the glass fiber for optical transmission having excellent productivity and the process for production of such fiber. CONSTITUTION:At least >=1 kinds of common photopolymn. initiator: are previously added into a UV curing type resin for inside layer coating and a UV curing type resin for outside layer coating in such a manner that the content in the former is 1.5 to 4 times the content in the latter in the process for production of the glass fiber 1 for optical transmission by forming two layers of the coatings 3, 4; the inside layer coating 3 consisting of the soft UV curing type resin and the outside layer 4 consisting of the relatively hard UV curing type resin on the outer periphery of the glass fiber. Two layers of the coatings 3, 4 are formed by simultaneously applying the UV curing type resin for the inside layer and the UV curing type resin for the outside layer on the outer periphery of the glass fiber right after drawing. In succession, two layers of the coatings 3, 4 are cured. This glass fiber for optical transmission is produced by such process. Since the curability is good even by the coating method by simultaneous application of the two layers, the execution of the drawing with high productivity is possible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical transmission glass fiber used for optical communication and the like and a method for producing the same, and particularly to an optical transmission glass fiber having a coating structure using a coating material capable of being drawn with high productivity. The manufacturing method is related.

[0002]

2. Description of the Related Art Since a glass fiber as drawn from a glass preform has a small diameter and a small mechanical strength, it is generally coated on its outer periphery in the drawing step to obtain a glass fiber for optical transmission. FIG. 1 shows a cross-sectional structure of an example of the optical transmission glass fiber of the present invention. The glass fiber 2 having a core and a clad is the center, and the inner layer resin coating 3 is provided as a buffer coating layer on the outer periphery thereof. An outer resin coating 4 is provided as a protective coating layer. The inner layer resin coating 3 of the buffer coating layer doubles as a primary coating, and at the same time,
It has a cushioning effect and is made of a relatively soft resin with an elastic modulus of 1 kg / mm ² or less. The outer resin coating 4 of the protective coating layer, as a shell, imparts high mechanical strength to the glass fiber for optical transmission, It has the effect of suppressing an increase in loss, and a relatively hard resin having an elastic modulus of 10 kg / mm ² or more is used. From the viewpoint of productivity, an ultraviolet curable resin having a high curing speed is often used as the coating resin. In the ultraviolet curable resin, a photopolymerization initiator contained in the resin absorbs ultraviolet rays and is cleaved to cause a radical reaction to be cured.

The glass fiber 1 for optical transmission having the above structure
As a manufacturing method of the above, a so-called tandem manufacturing method in which a step of applying a coating resin to the drawn glass fiber 2 as shown in FIG. 3 is sequentially performed for each layer, and a two-layer coating resin shown in FIG. A two-layer simultaneous coating method is known in which the two are simultaneously coated and cured. Particularly in the latter case, when the inner layer resin coating 3 is cured, ultraviolet rays are radiated through the outer layer resin coating 4, so that the efficiency is lowered, and the ultraviolet ray irradiating device 1
I made 0 very powerful. Alternatively, a large number of devices may be arranged in series, or, for example, JP-A-1-27610.
As proposed in Japanese Patent No. 5, measures such as changing the effective absorption wavelength of the photopolymerization initiator in the ultraviolet curable resin depending on the material of the inner and outer layers are taken.

[0004]

However, in the case of the former,
In addition to the cost of a powerful output device and a large number of arrangements, there is a risk that the multilayer resin coating may be discolored by being exposed to excessive ultraviolet rays, being exposed to high temperatures, or in the worst case. When the photopolymerization initiators having different wavelengths are used like the latter, for example, Hiroshi Yamashita: “Thermosetting Resin”, No. 11
Vol. 2, No. 2, (1990), p48-62 (published by Synthetic Resin Industry Association), there is a large difference in curability between the photopolymerization initiators, and the productivity is taken into consideration. There is a problem that the combinations of photoinitiators having different absorption wavelengths that can be used are considerably limited. The present invention provides a glass fiber for optical transmission which can simultaneously form a two-layer coating with a simpler device structure with high production efficiency and has an appropriate coating, and a method for producing the same.

[0005]

According to the present invention for solving the above-mentioned problems, two layers, an inner layer coating made of a soft UV-curable resin and an outer layer made of a relatively hard UV-curable resin, are simultaneously formed on the outer circumference of a glass fiber. In the coated glass fiber for optical transmission, the inner layer ultraviolet curable resin and the outer layer ultraviolet curable resin contain at least one common photopolymerization initiator, and the inner layer ultraviolet curable resin contains the common photopolymerization initiator. The content of the photopolymerization initiator is 1.5 to 4 times the content of the common photopolymerization initiator in the outer layer ultraviolet curable resin. Further, the present invention is a method for producing a glass fiber for optical transmission, which forms a two-layer coating of an inner layer coating made of a soft UV-curable resin and an outer layer made of a relatively hard UV-curable resin on the outer periphery of the glass fiber, At least one common photopolymerization initiator is added to the UV-curable resin for coating the inner layer and the UV-curable resin for coating the outer layer so that the content in the former is 1.5 to 4 times that in the latter. In advance, the inner layer UV curable resin and the outer layer UV curable resin are simultaneously applied to the outer periphery of the glass fiber immediately after drawing to form a two-layer coating, and then the two-layer coating is cured. It is characterized by

[0006]

According to the present invention, in a glass fiber for optical transmission formed by simultaneously coating and curing two layers of an ultraviolet curable resin coating layer on the outer periphery of a glass fiber, the light in the ultraviolet curable resin forming each layer is formed. By selecting a material excellent in rapid curing as a polymerization initiator and blending the content of the photopolymerization initiator in the inner layer to be 1.5 to 4 times that of the outer layer, a special ultraviolet irradiation device or many It was possible to obtain a proper coating film for both the inner and outer layers even with simultaneous two-layer coating and curing drawing without the need for disposing an irradiation device.

Generally, the thickness of the coating applied to the glass fiber is about 10 μm to 100 μm for each layer, but at such a thickness, attenuation due to absorption of light cannot be ignored. In the case of the two-layer simultaneous coating curing drawing shown in FIG. 3, the curing of the ultraviolet curable resin in the inner layer is seriously affected. On the other hand, the curing reaction efficiency of the ultraviolet curable resin is, considering the radical generation efficiency of the photopolymerization initiator and the emission wavelength intensity of the ultraviolet irradiation device, the photopolymerization initiator usable for the ultraviolet curable resin of the present invention is As a result, the photoinitiator of the ultraviolet curable resin used for the outer layer absorbs the light of the effective wavelength, thereby hindering the curability of the inner layer. Therefore, in the ultraviolet curable resin of each layer, at least one kind among those used as a photopolymerization initiator is used as a common photopolymerization initiator, and each of the common one or more kinds of photopolymerization initiators is contained. The amount in the inner layer is preferably as large as 1.5 to 4 times the content in the outer layer. 1.
If it is less than 5 times, the curability of the inner layer is insufficient, and if it exceeds 4 times, the initiator remains after the completion of the curing reaction, changing the physical properties of the inner layer or, in the worst case, bleeding at the interface between the glass and the coating. As a result, the adhesion with the glass coating may be reduced, which may have an important adverse effect on reliability.

The proportion of the photopolymerization initiator in the resin for coating the outer layer (or the resin composition) is preferably 0.1 to 1.0% by weight, and the curing rate is less than 0.1% by weight. And the curability of the outer layer is insufficient, while 1.0
If it exceeds 5% by weight, the initiator remains as a residual component in the resin after the completion of the curing reaction, causing bleeding and sticking on the fiber surface, which is a problem in handling. Therefore, it is particularly preferable that the mixing ratio of the photopolymerization initiator in the resin for coating the inner layer (or the resin composition) is 0.15% by weight to 4.0% by weight. 0.15
If it is less than wt%, the curability of the inner layer is insufficient, and if it exceeds 4.0 wt%, the initiator remains after the completion of the curing reaction, changing the physical properties of the inner layer or, in the worst case, at the interface between the glass and the coating. Bleeding may reduce the adhesion to the glass coating and may have a significant adverse effect on reliability. The thickness of each coating in the present invention is 10 to 50 m for the inner layer and 1 for the outer layer.
Generally, it is about 0 to 50 μm.

As the photopolymerization initiator used in the present invention, a photopolymerization initiator generally used for this type of coating UV-curable resin can be used. As the photopolymerization initiator common to each layer, for example, benzophenone is used. Compounds, acylphosphine oxide compounds, acetophenone compounds,
Dicarbonyl compounds and the like are particularly preferable, and acylphosphine oxide compounds, which are very excellent in that they have high curability and small yellowing, specifically, 2,4,6-trimethyl-benzoyl-diphenyl- Examples thereof include phosphine oxide. Examples of the ultraviolet curable resin used in the present invention include urethane acrylate resin, epoacrylate resin, silicon acrylate resin, polyol acrylate resin, butadiene acrylate resin, polyester acrylate resin and the like. As a component of the coating resin or resin composition of the present invention, a photoreactive oligomer (prepolymer),
In addition to the photoreactive diluent (monomer) and photopolymerization initiator, an antioxidant, a release agent, a coupling agent, a polymerization inhibitor, a surface modifier, a sensitizer and the like can be contained. In the present invention, a urethane acrylate resin is used as the ultraviolet curable resin, and the inner layer coating has a Young's modulus of 0.05 to 0.5 kg.
/ mm ² urethane acrylate-based resin, Young's modulus 10-100 kg / mm ² urethane acrylate-based resin is used for the outer layer coating, and when acylsulfinoxide is used as a photopolymerization initiator common to both, particularly good light A glass fiber for transmission can be manufactured by a two-layer simultaneous coating curing drawing method.

[0010]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. [Example] A two-layer-coated glass fiber for optical transmission was manufactured by the two-layer simultaneous coating and curing drawing method shown in FIG. The obtained double-layer coated optical transmission glass fiber has an inner layer outer diameter of 200 μm and an outer layer outer diameter of 250 on the outer circumference of the glass fiber having an outer diameter of 125 μm.
Two-layer UV curable resin with a linear velocity of 500 μm / mi
n was applied and cured. The degree of curing of the UV curable resin in the inner layer was evaluated by the gel fraction by the solvent extraction method. As the coating resin, a soft urethane acrylate resin having a Young's modulus of 0.1 kg / mm ² was used for the inner layer, and a relatively hard urethane acrylate resin having a Young's modulus of 70 kg / mm ² was used for the outer layer. As the photopolymerization initiator, an acylphosphine oxide-based photopolymerization initiator (Luci) is used for both the inner layer and the outer layer.
rin (trademark), manufactured by BASF Co., Ltd. was used, and the respective contents were set to the ratios shown in Table 1. The results of the gel fraction of the inner layer resin and the presence or absence of bleeding of the photopolymerization initiator at the glass interface are also shown in Table 1. Here, the gel fraction is an index showing how hard the resin is, and when the initial weight of the coating is W0 and the coating weight after solvent extraction of the ungelled components from this coating is W, Gel fraction = (W / W0) x
It is shown by the formula of 100 (%). Therefore, a higher gel fraction is desirable. A gel fraction of 90% or more is generally desirable as a coating.

[0011]

[Table 1]

As is clear from the results shown in Table 1, in Examples 3 to 5 which are within the limits of the present invention, a gel fraction of 90% or more was obtained, and a preferable coating without bleeding at the glass interface was obtained. Had been formed.

As described above, according to the present invention, in the glass fiber for optical transmission, in which two layers of the ultraviolet curable resin coating layer are simultaneously formed on the outer periphery of the glass fiber,
A material excellent in rapid curing is commonly used as a photopolymerization initiator in the ultraviolet curable resin forming each layer, and the content of the specific polymerization initiator is increased so that the content in the inner layer is 1.5 to 4 times that in the outer layer. By blending, it is possible to obtain a coated optical fiber in a proper cured state for both the inner and outer layers even when two-layer simultaneous coating and curing drawing is performed without providing a special ultraviolet irradiation device or a large number of irradiation devices.

[Brief description of drawings]

FIG. 1 is a sectional view of a glass fiber for optical transmission according to the present invention.

FIG. 2 is a schematic explanatory view of a method for producing a glass fiber for optical transmission by double-layer simultaneous coating and curing drawing according to the present invention.

FIG. 3 is a schematic explanatory view of manufacturing a glass fiber for optical transmission by a conventional tandem method.

[Explanation of symbols]

1 glass fiber for optical transmission, 2 glass fiber, 3 inner layer resin coating, 4 outer layer resin coating,
5 base material feeding device, 6 wire drawing furnace, 7 wire drawing device, 8 base material, 9 two-layer coating simultaneous coating device,
10 ultraviolet irradiation device, 11 take-up capstan, 12 winding device, 13 ultraviolet irradiation device,
14 UV irradiation device, 15 coating device,
16 Coating device.

Claims (3)

[Claims] 1. A glass fiber for optical transmission in which two layers of an inner layer coating made of a soft UV-curable resin and an outer layer made of a relatively hard UV-curable resin are simultaneously coated on the outer circumference of the glass fiber. The curable resin and the outer layer UV curable resin contain at least one or more common photopolymerization initiators, and the content of the common photopolymerization initiator in the inner layer UV curable resin is in the outer layer UV curable resin. A glass fiber for optical transmission, wherein the content of the common photopolymerization initiator is 1.5 to 4 times. 2. A method of manufacturing a glass fiber for optical transmission, comprising forming two layers of coating on the outer circumference of the glass fiber, an inner layer coating made of a soft UV-curable resin and an outer layer made of a relatively hard UV-curable resin, At least 1 for the UV-curable resin for coating the inner layer and the UV-curable resin for coating the outer layer
One or more kinds of common photopolymerization initiators are added so that the content in the former is 1.5 to 4 times the content in the latter, and the ultraviolet curable resin for the inner layer is provided on the outer circumference of the glass fiber immediately after drawing. And the ultraviolet curable resin for the outer layer are simultaneously applied to form a two-layer coating, and then the two-layer coating is cured. 3. The method according to claim 2, wherein the ultraviolet curable resin is a urethane acrylate resin and the common photopolymerization initiator is an acylphosphine oxide compound.