JPH0269706A - Coated optical fiber - Google Patents

Abstract

PURPOSE:To reduce the coefficient of linear expansion of a jacket layer by incorporating silica powder whose particle size is <=1/10 as large as the film thickness of an external layer or silica powder and a silane coupling agent. CONSTITUTION:The silica powder whose particle size is <=1/10 as large as the film thickness of the external layer jacket and the silane coupling agent 4 are added and the UV resin jacket external layer 3 and a UV internal layer which is softer than the external layer 3 are provided. Consequently, the coefficient of linear expansion is reduced, various problems due to the addition of resin to a conventional coated optical fiber are solved, and the fiber is manufactured without decreases in curing performance for coating strength and a coating defect.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement in a coated optical fiber having a coating on its outer periphery.

[Prior Art] In optical fibers used for optical communications, whether they are optical glass fibers or quartz-based glass fibers, plastic is added to the outer periphery of the optical fibers immediately after they are made into fibers. It is said that it is preferable to apply mN.

This is to prevent the strength of Phi-tXI from deteriorating due to scratches on the fiber surface that occur when the fiber is made into a fiber, or cracks that grow when the bare fiber is exposed to air. For such plastic layers, thermosetting silicone 4Z resin or ultraviolet curable resin (hereinafter referred to as UV resin) is generally used, and in recent years the demand for this U resin-coated fiber has increased. .

This UV resin coating generally has a Young's modulus of 0.5 kg/m+* in order to maintain high transmission characteristics of the optical fiber.
'Inner layer with low Young's modulus of less than 5 kg/mm
``An optical fiber is protected by a two-layer coating consisting of an outer layer with a high Young's modulus of about
(See Publication No. 3).

FIG. 2 shows a cross-sectional view of an optical fiber having such a structure.

1 is a glass fiber (optical fiber), 2 is an IJV resin inner layer coating with a low Young's modulus, and 5 is a UV resin outer layer coating with a jS:J Young's modulus.

[Problems to be Solved by the Invention] However, in the conventional optical fiber having the structure shown in Fig. 2, the outer layer of the UV resin coating contracts in a low temperature range, causing the optical fiber to bend, resulting in an increase in transmission loss. was there. The shrinkage force of the coating that causes distortion in the optical fiber increases as the linear expansion coefficient of the optical fiber is high and the Young's modulus of the coating is large. The Young's modulus of the coating needs to be greater than a certain level in order to protect the glass, and there is a limit to how small it can be.

Therefore, resins with low coefficients of linear expansion, such as highly oriented resins and LCI), are being developed as materials that can be used in place of UV resins as outer layers to improve the temperature stability of optical fibers. However, these resins have been reported to be expensive and cannot be coated at high speed using dies and U-clamps like UV resins, so they have not yet reached the level of special use.

Incidentally, it is generally widely practiced to reduce the coefficient of linear expansion by adding a filler to a resin. For example, Hiroshi Kakiuchi (ed.), “New Epoxy Resin”, Shokodo, 249
In LT, "reduction of linear expansion coefficient of jj1 structural filler" is expressed as dimensional stability.

On the other hand, in the coating of optical fibers, adding fillers to thermosetting coatings to increase the strength has been proposed, for example, in Japanese Patent Laid-Open No. 6
This method has already been proposed in Publication No. 1-217011. In addition, for coloring, low hydrogenation, or improving radiation resistance, the outer layer UV
It is also known to add additives to resins.

However, conventionally, the addition of additives to coatings made of UV resins has had the following major problems. That is, (1) When additives are dispersed in the outer UV resin coating, the additive absorbs ultraviolet rays, which deteriorates the curing properties of the UV resin coating, and in particular, when the thickness of the coating becomes thick, the interior becomes hard to cure. ■The additive distributed on the surface of the UV resin outer layer causes defects in the coating, reducing the coating strength in this area.■
The addition of additives changes the thixotropy of the UV resin, which increases the resistance when the liquid resin flows through the gap between the goo and the optical fiber, especially when applying the resin by high-speed drawing using a die. This causes poor coating properties.

Due to these problems, it is possible to reduce the linear expansion coefficient of the UV resin coating layer by adding a filler to the UV resin coating layer, and to form a coating with good curability, strength, and applicability. It has not been possible to obtain an optical fiber that suppresses transmission loss in the low temperature range.

The purpose of the present invention is to solve these conventional problems and provide an optical fiber in which the linear expansion coefficient of the coating layer can be easily reduced at low cost by adding additives to the coating layer. It is something to do.

[Means for Solving the Problems] As a result of research efforts, the present inventors have developed a resin coating that solves the above-mentioned problems (■ to ■) associated with the addition of fillers and is effective in reducing the coefficient of linear expansion. With this heading, we have arrived at the present invention.

The present invention has a soft inner layer made of ultraviolet curing resin on the outer periphery of the glass fiber and a soft inner layer made of ultraviolet curing resin. A coated optical fiber and a glass fiber having a hard outer layer made of resin, characterized in that the extracurricular layer contains Silino J powder whose f1γ diameter is 1710 or less than the thickness of the outer layer. In a coated optical fiber having a soft inner layer made of an ultraviolet curable resin and a hard outer layer made of an ultraviolet curable resin on the outer periphery, the outer layer contains silica powder whose particle size is 1710 or less than the thickness of the outer layer. The present invention relates to a coated optical fiber characterized by containing a silane coupling agent.

The present invention will be specifically described below with reference to the drawings.

FIG. 1 is a cross-sectional view of one example of a coated optical fiber of the present invention, in which 1 is a glass fiber (optical fiber), 2 is an inner coating made of a UV resin with a low Young's modulus, and 3 is a tJ with a high Young's modulus.
The outer layer coating is made by adding VUV resin silica powder, and 4 is silica powder. In addition to silica powder, a silane coupling agent may be added to the outer layer at °C.

Conventionally known materials may be used for the glass fiber 1 and the inner coating of the present invention. The desired effect of the present invention can be obtained by using any communication glass fiber as the glass fiber, but in particular, S containing quartz glass as the main component, which is generally used for medium to long distance communication, can be used as the glass fiber.
M-type fiber C; I 't'! Great effects can be obtained when applied to fibers and the like. In addition, examples of the UV resin for the inner layer include polyurethane acrylate, polybutadiene acrylate, silicone acrylate +-,
u■ Curing silicone resin, polycarbonate resin, etc. can be used. The Young's modulus of the inner layer coating is -0.0 for boat fishing.
5 to 0.5 kg/■'', but is not limited to this.

As the UV resin used for the outer layer coating, which is a feature of the present invention, resins such as polyurethane acrylate, polybutadiene acrylate, epoxy acrylate, silicone acrylate, U-curing silicone, and polycarbonate can be used. can. Young's modulus is generally about 5 to 100 kg/1Tlff1'', but is not limited to this.

It is essential that the particle size of the silica powder added to these U-resins for the outer layer is 1/1O or less of the outer layer thickness. In addition, the particle size of [11] is 0°01~2μ
m is preferably within the range, particularly preferably 0.1
~2 μm. If it is less than 0.01 μm, the particle diameter is too small and the effect of reducing the linear expansion coefficient becomes low.

In addition, in ordinary optical fibers for long-distance communication, the outer layer thickness is often in the range of 20 to 60 μm, so in consideration of versatility, the particle size limit of the added silica powder is about 2 μm. . The amount added will be explained in the next section on effects.

In addition, examples of the silane coupling agent include vinyltriethoxysilane, 3-aminopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane,
-Glycidoxypropylmethyldimethoxysilane, 3-
Examples include methacryloxypropylmethyldimethoxysilane, and it is preferably added in an amount of 0.1 to IOj[tu%, particularly preferably 1 to 5% by weight.

The method for installing a coated optical fiber according to the present invention is a method using conventionally known UV rays.
A two-layer resin coating method may be used. For example, as shown in FIG. 5, the base material 6 is fed into the drawing furnace 8 by the base material feeding device 7 of the wire drawing device 9, heated and drawn to form the glass fiber I.
Next, the UV resin for the inner layer is applied using the coating device 11 and cured using the ultraviolet light source QJ equipment 12 to form an inner layer coating, and then the silica powder (and silane cup) for the outer layer (V) is coated using the coating device 13. Ring agent) Added UV resin is applied and cured with ultraviolet irradiation device 14 to form a two-layer coated optical fiber.
5, and a method of taking it up with a capstan 16 and winding it up with a winding device 17, etc.

[Function] As already explained, by adding silica powder as a filler to the UV resin of the outer layer as in the present invention, the coefficient of linear expansion can be reduced. It can prevent the optical fiber from bending,
Increase in transmission loss can be suppressed.

Generally speaking, the effect of reducing the coefficient of linear expansion becomes greater as the concentration of silica powder added increases, but if the amount is too large, the viscosity of the resin will increase to the point where it cannot be coated, so add it! IT naturally has an upper limit. The appropriate drying IX when applying using a normal die is 1000 to 10 at room temperature.
000 cps is desirable. The amount of silica powder added that satisfies this value varies depending on the particle size of the silica powder and the viscosity of the UV resin before it is added, so the relationship between the amount added and viscosity must be determined experimentally depending on each case. It is preferable to ask and determine. In addition, it was confirmed that the effect of reducing the coefficient of linear expansion by adding silica powder can be obtained even with the addition of a minute amount of silica powder, but the appropriate addition point in the present invention is 1% by weight or more when the particle size is 1 μm: It was less than 1%. When the particle diameter is larger than 1 μm, the addition f11 is in a range where the lower limit is smaller than this, and when the particle size is smaller than 1 μm, it is in a range where the upper and lower limits are larger than this.

In addition, the problems associated with conventional methods of adding resin to the outer layer resin can be resolved by using silica powder as a filler, which provides sufficient curability, and by adjusting the particle size of the silica powder to the thickness of the coating film. It will be explained in detail below that coating defects can be avoided by setting the ratio to 1/10 or less, and that coating strength can be guaranteed by using a silane coupling agent in combination.

Regarding the problem of ultraviolet absorption caused by additives, the present inventors mixed powders of various inorganic materials into resin and compared their curing properties. As a result, silica powder with a composition of S + Oz was found to be optimal. I came to the conclusion that there is. As an example, Fig. 3 shows silica powder and titanium oxide (TiO=) powder at t+V
Addition i when mixed into resin? The relationship between t (weight %, shown on the horizontal axis) and cured film thickness (mm, shown on the vertical axis) is shown. The white circle indicates silica powder, and the black circle indicates titanium oxide.

Here, the cured film thickness is the value obtained by irradiating ultraviolet light of IJ/cl' from the top of the uncured UV resin with a high-pressure mercury lamp and measuring the thickness of the cured film, and the value of the cured film thickness is small. The more the additive absorbs ultraviolet light, the worse the curability becomes. As is clear from Fig. 3, silica powder causes less decrease in cured film thickness due to increase in the amount of addition).
It can be seen that this is a material that is unlikely to cause deterioration in hardenability due to addition.

Next, there is the problem of additives distributed on the outer layer surface causing coating defects and reducing coating strength, but when silica powder is used, this problem can be easily solved by adding a silane coupling agent. Solvable. The silane coupling agent has the effect of forming a chemical bond with both the coating and the silica powder and enhancing the adhesion between them, so if the particle size of the silica powder is not very large (usually 50 μm or less), It is known that the combined effect actually increases the rupture effect (Ibid., edited by Hiroshi Kakiuchi, ("New Epoxy Resins"296J"r). The silane coupling agent that can be used in the present invention is based on the structure of UV resin. ``-1 It is preferable that the reactive group bonded to the resin side is a vinyl group, a methacrylic group, an acryloyl group, an amino group, or (, but other groups such as a mercapto group or an epoxy group may also be used. The effect was observed.Also, the effect was observed with most of the commonly used reactive groups that bond to the silica side, and typical examples include methoxy group, ethoxy group, and silanol group.

Addition amount of silane coupling agent 1;! ,Q,I~104
The amount is within the range of about T'Iglt%, but if it is too small than this range, sufficient effects cannot be obtained, and if it is too large, it will adversely affect the curability of the resin. Particularly preferably 1 to 5 cities 111
Within the range of %.

Regarding the influence on the coating properties ((2)), the present inventor, Kasa, investigated the relationship between the particle size of the silica powder added and the coating properties of the added resin, and discovered that the silica particle size greatly influenced the coating properties. In other words, the particle size is 1/1 of the thickness of the outer layer to be applied.
If it is less than 10, it is possible to coat with a uniform film thickness, and the dependence of the resin coating property on the amount of addition is small. ,
It was found that it could be kept within 0.5%, which is acceptable for practical use.

Figure 4 shows that silica powder is added to a "C" glass fiber using a die with a coating diameter of 400 μm and an outer layer thickness of 50 μm.
When a coated optical fiber is made by applying V-resin,
The relationship between the particle size of silica powder and the magnitude of variation in coating diameter is shown. In the figure, the horizontal axis is (silica powder j1''7. particle diameter/outer layer thickness), the vertical axis is coating diameter variation (%), the white circle is the addition month tlo weight %, and the black circle is the addition month tlo weight %. Figure 4 shows that regardless of the amount of silica powder added, if the particle diameter is 1710 or less of the film thickness, the diameter variation is reduced to 0.5.
It can be seen that it can be kept within %. Further, this relationship has been confirmed within the range of film thickness from 15 μm to 1-80 μm, and is valid over a wide range of film thicknesses.

[Example] Comparative Example 1 Single modulus 1j2 ("2" with a glass diameter of 125 μn1 using a die on the outer periphery of the optical fiber and a Young's modulus of 0 as the inner layer)
, 2 kg/am" ultraviolet curable urethane acrylate resin with a Young's modulus of 40 kg/IIm" as the outer layer.
UV-curable urethane acrylate resin with an inner layer diameter of 2
A coated optical fiber was prepared by coating the coated optical fiber so as to have an outer layer diameter of 00 μm and an outer layer diameter of 250 μm (outer layer thickness of 25 μm). When the transmission characteristics of the obtained coated optical fiber at a wavelength of 1.3 μm were investigated, it was found that the transmission characteristic at 23°C was 0°23 dB/, -60'
The loss in the low temperature range was large, with an I of 7 dB/km.

Example 1 5% by weight of silica powder with a particle size of 1 μm and 2% by weight of 3-methacryloxypropyltrimethoxysilane, a methacrylate-based silane coupling agent, were added to the same resin used for the outer layer of Comparative Example 1. An optical fiber of the present invention was produced in the same manner as in Comparative Example 1, except that the following was used as the outer layer resin. (Particle size/outer layer thickness - 1/25) The viscosity of this outer layer resin was 8000 cps at 23°C. When the transmission characteristics of the obtained coated optical fiber at a wavelength of 1.3 μm were investigated, it was found that the transmission characteristics at 23°C were 0 and 23 dll/@
, 0°2/1 dll8 at -60°C, which was very good even in the low temperature range.

Example 2 The same resin used for the outer layer of Comparative Example 1 had a particle size of 1 μT.
An optical fiber of the present invention was produced in the same manner as in Comparative Example 1, except that an outer layer resin containing silica powder of 5 weight and 41% was used. Wavelength 1 of the obtained coated optical fiber.
When we investigated the transmission characteristics at 3 μm, we found that it was +0.23 dB/+ at 23°C and 0.24 dB/+ at -60°C.
The performance was very good even in the low temperature range of km.

Comparative Example 2 A silica powder with a particle size of 5 μm at °C was used (f1
The same procedure as in Example 1 was carried out except for γ diameter/outer layer thickness - 1l5). A No. 11-covered optical fiber was fabricated. In this case, the coating diameter varied by 1% or more during manufacturing, and it was determined that the coating was defective. In addition, the transmission characteristics of the obtained coated optical fiber were 23
The transmission loss was 0.42 dB/km at -60°C (unmeasurable).

Comparative Example 3 An attempt was made to produce a coated optical fiber in the same manner as in Example 1 except that titanium oxide powder with a particle size of 1 μm was used instead of silica powder, but the outer layer had poor hardenability and a good coated optical fiber could not be obtained. could not be created.

Example 3 A coated optical fiber of the present invention was produced in the same manner as in Example 1 except that the amount of silica powder added was 0.5% by weight. In this example, the viscosity of the silica powder-added outer layer resin was 2
3000 cps at 3°C, and the transmission loss of the obtained coated optical fiber is 0.23 dll/ks at 23°C.

It was good even in the low temperature range with 0.7 d13/km at -60°C.

Comparative Example 4 A coated optical fiber was produced in the same manner as Comparative Example 1 except that the inner layer diameter was 300 μm and the outer layer diameter was 400 μm. The transmission loss of the coated optical fiber was 0.23 dB at 23°C.
The loss in the low humidity region was extremely large, 3.2 dB/km at -60°C.

Example 4 A coated optical fiber of the present invention was produced in the same manner as in Example 1 except that the inner layer diameter was 300 μm and the outer layer diameter was 400 μm (particle diameter/outer layer thickness = 115G). Obtained 'N1
．． The transmission loss of the covered fiber is 0°23 dB/ at 23°C.
The cocoon was 0.6 dB/kl+ at -60°C, which was good even in the low temperature range.

Example 5 A coated optical fiber of the present invention was produced in the same manner as in Example 4 except that the f, + and particle diameters of the silica powder were 5 μm (particle diameter/outer layer thickness = 115). The transmission loss of optical fiber is 0.23dIs/kr at 23℃
n, 0.25 dB/km at -60°C, which was very good.

[Effects of the Invention] As explained above, the present invention has a particle size of outer layer m II
By providing a hard UV resin outer layer containing silica powder and a silane coupling agent that are 1/10 or less of A thickness, and a UV resin inner layer that is softer than the outer layer, it is more effective than adding to the resin in conventional coated optical fibers. By solving the various problems that had arisen, we were able to realize a coated optical fiber with excellent temperature stability that can be manufactured without deterioration in curability or coating strength or coating defects.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view explaining the coated optical fiber of the present invention, FIG. 2 is a cross-sectional view of a general UV resin-coated optical fiber, and FIG.
The figure is a graph showing the relationship between silica powder addition fit and cured film thickness, Figure 4 is a graph showing the relationship between coating diameter variation and particle size, and Figure 5 is an example of the wrapping of the coated optical fiber of the present invention. FIG. 1 Ni glass fiber (optical fiber), 2: Low Young's modulus U
V resin coating inner layer, 3: high Young's modulus UV resin coating outer layer, 4
: Fine silica powder added to outer coating layer 3, s: UVP4
Grease coating inner coating layer I:) Material, 7: Base material feeding device, g: t
Q drawing furnace, 9: drawing device, ] O glass fiber, 11.
13: Coating device, 12.14: Ultraviolet irradiation device, 1
5: double-layer coated optical fiber, 16: take-off capstan,
17: Winding device.

Claims (2)

[Claims] (1) In a coated optical fiber having a soft inner layer made of an ultraviolet curable resin and a hard outer layer made of an ultraviolet curable resin around the outer periphery of the glass fiber, the particle diameter in the outer layer is 1/10 of the thickness of the outer layer. A coated optical fiber characterized by containing silica powder as follows. (2) In a coated optical fiber having a soft inner layer made of an ultraviolet curable resin and a hard outer layer made of an ultraviolet curable resin around the outer periphery of the glass fiber, the particle diameter in the outer layer is 1/10 of the thickness of the outer layer. A coated optical fiber characterized by containing the following silica powder and silane coupling agent.