JPH03186807A - Polymer clad fiber for light transmission - Google Patents

Abstract

PURPOSE:To improve a transmission loss characteristic, the adhesiveness to a core and heat resistance by forming a clad layer of the reaction hardened matter of a resin compsn. contg. ladder type polymethyl siloxane, straight chain polymethyl siloxane having an OH group and solvent. CONSTITUTION:The clad material is formed of the reaction hardened matter of the resin compsn. contg. the ladder type polymethyl siloxane (A), the straight chain polymethyl siloxane (B) having the OH group and the solvent (C). Namely, the resin compsn. essentially consisting of the ladder type polymethyl siloxane (A) is used for the clad, by which the sufficiently large refractive index difference between the core and the clad is attained, and the light transmission loss characteristics are excellent since the small light transmission loss of the clad layer is small. The polymethyl siloxane (B) having the OH group is incorporated into the ladder type polymethyl siloxane (A) of the clad layer, by which the suitable hardness, the sufficient elongation and the heat resistance are imparted to the optical fiber.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a polymer-clad optical transmission fiber having a core of quartz glass and a polymer cladding, and more specifically, a fiber for optical transmission having a ladder-like polymethylsiloxane as the main cladding material. The present invention relates to polymer-clad optical fibers used in the present invention.

[Conventional technology]

Conventionally, cladding polymers for polymer clad silica optical fibers (abbreviated as PCF), which have a core of quartz glass or optical glass and a polymer cladding, include silicone resin (described in Japanese Patent Publication No. 562321, etc.),
Fluoroalkyl methacrylate polymer (JP-A-58
-121461 etc.), vinylidene fluoride/
Tetrafluoroethylene copolymer (Special Publication No. 56-41
No. 966, etc.), polyether ester amide (Japanese Unexamined Patent Publication No. 56-60402), ultraviolet curable fluorinated acrylate composition (U.S. Pat. No. 4,211,20),
No. 9 specification, etc.) are used.

However, these clad polymers cannot meet the recent demands for increasingly sophisticated properties such as lower optical transmission loss, easier caulking-type connector attachment, and more stable temperature characteristics of optical transmission loss. It's impossible.

In contrast, ladder-like polysiloxane (organosilsesquioxane) is attracting attention as a cladding material as a material that satisfies the requirements (U.S. Pat. No. 4,835,0
(described in Specification No. 57, etc.).

[Problem to be solved by the invention]

However, the cured product of ladder-shaped polysiloxane has very low elongation, and when it is coated on glass fiber as a cladding material, it suffers from bending strain or distortion due to differences in expansion coefficients, and even when the ladder-shaped polysiloxane is cured. It has the disadvantage that cracks occur on its surface due to distortion caused by shrinkage. On the other hand, ladder-like polysiloxanes are generally dissolved or dispersed in a solvent to form a liquid, then coated on a fiber, and heated to volatilize the solvent and simultaneously cross-link and harden the cladding layer. There are bubbles caused by volatilization of the solvent in a certain ladder-like polysiloxane after crosslinking and curing, which also has the fatal drawback of high optical transmission loss.

The prior art described in the above-mentioned US Pat. No. 4,835,057 has not yet solved these drawbacks.

An object of the present invention is to provide a polymer-clad optical transmission fiber with improved mechanical strength and optical transmission characteristics by solving the disadvantages of using the above-mentioned ladder-like polysiloxane as a cladding material. be.

[Means to solve the problem]

As a result of repeated research to solve the above problems, the present inventors found that
As a cladding material for PCF, a coating film (coating) with sufficient elongation is obtained by curing a blend of ladder-like polymethylsiloxane and linear polymethylsiloxane having OH groups in a solvent. The present inventors have found that the coating is particularly excellent in that it prevents air bubbles from entering the coating, achieves low optical transmission loss, and achieves high mechanical strength, leading to the completion of the present invention.

That is, the present invention provides a polymer clad fiber for optical transmission having a core of silica glass or optical glass.
The cladding material is ladder-like polymethylsiloxane (A),
A polymer clad fiber for light transmission is provided, which is a reaction cured product of a resin-bound acid product containing a linear polymethylsiloxane (B) having an OH group and a solvent (C).

As the ladder-like polymethylsiloxane (A) used in the present invention, those represented by the following general formula (I) can be typically mentioned.

The ladder-like polymethylsiloxane (A) used in the present invention preferably has a number average molecular weight of 5.000 to 100.000.

The ladder-like polymethylsiloxane (A) used in the present invention has a refractive index of 1,40 to 1,42, and is 1.45.
It is suitable as a cladding material for a polymer clad fiber having a core of quartz glass or optical glass having a refractive index of about 100%.

The ladder-like polymethylsiloxane (A) of the present invention can be produced by a known method such as that described in JP-A-53-88099.

The linear polymethylsiloxane (B) having an OH group used in the present invention is a linear polymethylsiloxane represented by the following general formula (n), as long as it has an OH group in the side chain or terminal. There are no particular limitations.

Linear polymethylsiloxane (B) having this OH group
The number average molecular weight of is preferably about 500 to 100,000, particularly preferably about i,ooo to about 20,000.

The refractive index of the linear polysiloxane (B) is 1.40 to 1.
．． 44, and after mixing and dissolving with ladder polymethylsiloxane (A) and curing by heating etc., it is 1.41
Since it has a refractive index of ~1.43, it is suitable as a cladding material for a polymer clad fiber having a core of quartz glass or optical glass having a refractive index of about 1.45.

The solvent (C) used in the present invention may be one that is compatible with the ladder polymethylsiloxane (A) and the linear polymethylsiloxane (B) having an OH group.
There are no particular restrictions. It is preferable that the solvent (C) volatilizes during heat curing and does not remain in the resin. Therefore, it is preferable to use something with a somewhat low boiling point so that it can easily volatilize. However, if the boiling point is too low, there is a problem that foaming occurs during volatilization and bubbles remain in the coating. Therefore, the solvent (C) has a boiling point of 70°C to 20°C.
A temperature of 0°C is preferred.

As such a solvent (C), for example, ethanol n-
Alcohols such as propatool, impropatool, n-butanol, ketones such as methyl ethyl ketone and diethyl ketone, and ethyl acetate.

Esters such as n-butyl acetate, aromatic hydrocarbons such as toluene and xisane, and the like can be used.

The resin composition obtained by dispersing or dissolving ladder-shaped polymethylsiloxane (A) used in the present invention in linear polymethylsiloxane (B) having an OH group and a solvent (C) is a viscous liquid at room temperature. By adjusting the amount of the solvent (C), it is possible to obtain a resin composition that can be easily applied onto a fiber core made of quartz glass or optical glass.

Moreover, by heating after applying the resin composition,
The solvent (C) evaporates and a ladder-like polymethylsiloxane (
A condensation reaction occurs between A) and/or the linear polymethylsiloxane (B) having an OH group, resulting in curing to form a tough and heat-resistant coating film.

In the present invention, the hardness and heat resistance of the cladding layer can be adjusted as desired by adjusting the blending ratio of the linear polymethylsiloxane (B) having an OH group and the ladder-like polysiloxane (A).

That is, by increasing the blending ratio of ladder-like polymethylsiloxane (A), it is possible to form a clad layer with high hardness and excellent heat resistance. Furthermore, when the blending ratio of linear polymethylsiloxane (B) is increased, the elongation of the material itself increases, making it possible to form a cladding layer with excellent flexibility.

In the present invention, generally, the blending ratio of the ladder-like polymethylsiloxane (A), the OH group-containing linear polymethylsiloxane (B), and the solvent (C) is within the shaded area in FIG. It is preferable that

The numbers in FIG. 1 represent weight %. If it is outside this range, first of all, if there is a large amount of ladder-like polymethylsiloxane, that is, if there is a small amount of OH group-containing linear silicone oil,
The elongation becomes smaller and it becomes easier to break. When the amount of ladder-like polysiloxane is small (when the amount of linear silicone oil containing OH groups is large), the film becomes soft and it becomes impossible to attach the connector by caulking. Further, if there is a large amount of solvent, the viscosity will be low, and if there is little solvent, the viscosity will be too high, making it difficult to draw the wire properly.

In addition to the above-mentioned essential components (A), (B), and (C), the silicone resin composition used as the cladding material of the present invention may optionally contain a catalyst, etc. to assist in synthesis and curing reactions. It may be Examples of the catalyst include Lewis acids, Lewis bases, zinc naphthenate, lead naphthenate, and the like.

To explain the method for manufacturing the polymer-clad optical fiber of the present invention, the core silica glass or optical glass fiber may be similar to that used in conventional PCFs. That is, it can be manufactured by melt-spinning high-purity quartz-based or optical glass, and then a coating technique common in this type of field is applied to coat the outer periphery of the glass fiber with the resin composition of the present invention. The cladding layer may be formed using the following steps.

For example, a resin composition in which a quartz-based glass base material is melt-spun, ladder-like polymethylsiloxane (A) is dispersed or dissolved in a linear polymethylsiloxane (B) having an OH group, and a solvent (C) is prepared. It is possible to employ a method such as applying the coating onto the spun fiber using a die or the like and then curing the coating layer in a thermosetting furnace to form a cured coating. Conditions for curing include, for example, passing through an infrared furnace at a temperature of 200 to 300° C. and a length of 1 to 3 m, but are not limited thereto, of course.

Further, the thickness of the silicone resin cladding layer consisting of (A) and (B) of the present invention can be, for example, 10 to 30/ffi, but this is also not limited and can be applied to the target fiber. An appropriate one may be selected depending on the structure.

Further, polyethylene, polyamide,
An outer cover made of a thermoplastic resin such as ETFE or PFA may be provided.

[Effect]

Since the polymer clad fiber for optical transmission of the present invention uses a resin composition mainly composed of ladder-like polymethylsiloxane (A) as the cladding, it is possible to realize a sufficiently large refractive index difference between the core and the cladding. Since the optical transmission loss is small, it has excellent optical transmission loss characteristics.

In addition, ladder-like polymethylsiloxane (A
) contains polymethylsiloxane (B) having an OH group, so it has appropriate hardness, sufficient elongation, and heat resistance, and can be used at temperatures above 200°C without increasing optical transmission loss. can withstand.

Further, in the present invention, by adding a solvent (C) to the resin composition used as the cladding material, the viscosity can be adjusted to a value suitable for coating on glass.

〔Example〕

Hereinafter, the structure and effects of the present invention will be explained in more detail based on Examples, but the present invention is not limited thereto.

Example 1 A flaky ladder-like polymethylsiloxane with a refractive index of 1.42 and an average molecular weight of e,ooo was prepared with a refractive index of 1.43.
, linear dimethylsiloxane-based silicone oil with a viscosity of 300 cps, an average molecular weight of 10,000, and a portion of the side chain is alcohol (S-ROH group is bonded), and n-butanol, I 9 :I:2 weight ratio to prepare a resin composition having a refractive index of 1.42 and a viscosity of 6.0 OOc ps.

A core fiber with an outer diameter of 200/J11 is drawn using an anhydrous synthetic quartz rod, and at the same time, the above resin composition is applied to the outer periphery of the fiber using a die, and is hardened at approximately 250°C through a baking oven to form the fiber shown in Figure 2. An outer diameter 2 having a polymer cladding layer 2 on the outer periphery of a quartz glass core 1 as shown.
A 30p polymer clad fiber was obtained.

For this fiber with a length of 1km, the wavelength is 850n.
When the transmission loss at m was measured, it was found to be 7.5 dB/km, which was good.

Further, no cracking of the coating was observed, no increase in loss was observed even when the connector was attached by caulking, and the adhesion force of the connector to the fiber was 1.5 kg, which was sufficiently satisfactory.

In addition, when the tensile strength was evaluated at a standard distance of 300 mm and a tensile speed of 100 mm/min, it was found to be 14 to 15 k.
g and showed sufficient strength.

Furthermore, the adhesion between the cladding layer and the core material was good, 2 and it could be used even in an environment of 200°C.

Comparative Example 1 The same flaky ladder polymethylsiloxane used in Example 1, with a refractive index of 1.42 and an average molecular weight of e, ooo, was dissolved in n-butanol at a weight ratio of 75:25, and the viscosity was 3,000c. A resin composition of ps was created.

A core fiber with an outer diameter of 200 mm is drawn using an anhydrous synthetic quartz rod, and at the same time, the resin composition prepared above is applied using a die, and the baking process is performed by passing it through a furnace and heat-curing it at a temperature of about 250°C. Same structure as Figure 2, outer diameter 230
A μ polymer clad fiber (comparative product) was obtained.

When the fiber was evaluated in the same manner as in Example 1, the transmission loss at a wavelength of 800 nm was 200 dB/k.
It was as high as m. Further, when the coating was closely observed under a microscope, it was confirmed that there were cracks in some places. Furthermore, the tensile strength varied greatly from 3 to 15 kg.
, viscosity 200 cps, average molecular weight io, oo.

Then, a linear dimethylsiloxane silicone oil having -ROH groups at both ends was dissolved in ethyl acetate at a weight ratio of 8:2:2, and 1% by weight of naphthenic acid was added to the ladder polymethylsiloxane. A resin composition containing lead (refractive index 1.42, viscosity 5.000 c p S) was obtained. Using this, a polymer clad fiber with a similar structure was obtained in the same manner as in Example 1, and when the fiber was evaluated in the same manner, almost the same results were obtained.

〔Effect of the invention〕

As explained above, the polymer clad fiber for optical transmission of the present invention has a cladding layer containing ladder-like polymethylsiloxane (A), linear polymethylsiloxane having an OH group (B), and a solvent (C). Since it is made of a reaction cured product of a resin composition, it is extremely excellent in terms of transmission loss characteristics, strength for caulking type connector attachment, adhesion to the core, and heat resistance.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the preferred blending ratio range (wt%) of the resin composition used for the cladding material of the polymer clad fiber for optical transmission of the present invention, and FIG. FIG. 2 is a cross-sectional view of a specific example of a fiber. In the figure, 1 indicates the core, 2 indicates the cladding, and the shaded area indicates the preferred blending ratio range.

Claims (1)

[Claims] (1) In a polymer clad fiber for optical transmission having a core of quartz glass or optical glass, the cladding materials are ladder-like polymethylsiloxane (A), linear polymethylsiloxane having an OH group (B), and solvent (C). ) A polymer clad fiber for optical transmission, characterized in that it is a reaction cured product of a resin composition containing: