JP2001074943A - High-numerical aperture plastic optical fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a POF(plastic optical fiber) having a high numerical aperture and characteristics good in balance, such as heat resistance, bending resistance and environmental resistance, and its cord. SOLUTION: When the plastic optical fiber consists of a core and clad, the core consists of a (co)polymer essentially consisting of methyl methacrylate and the clad consists of a copolymer having a copolymer composition composed of 30 to 45 wt.% vinylidene fluoride, 40 to 55 wt.% tetrabluoroethylene and 5 to 15 wt.% hexafluoropropylene and having a fluorine composition weight rate of >=60 wt.%. The numerical aperture thereof is >=0.58.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to a plastic optical fiber which is as high as above and which has excellent heat resistance, bending resistance, environmental resistance and the like in a well-balanced manner.

[0002]

2. Description of the Related Art A plastic optical fiber (hereinafter abbreviated as POF) is superior to a glass-based optical fiber in terms of workability, handleability, manufacturing cost, and the like. Used in Particularly in the field of light guides, it is preferable to transmit a wide-angle light amount or an absolutely large amount of light amount.
POF with a high degree is used, and a POF with an even higher numerical aperture is also required. In the communications field,
In particular, in applications that need to be arranged in a narrow space, such as in the field of automobiles, a high numerical aperture POF having excellent bending characteristics is required.

The numerical aperture of an optical fiber is a theoretical numerical aperture determined from the refractive index values of a core and a clad as shown in the following equation. Numerical aperture = [(refractive index of core) ² − (refractive index of clad) ² ] ^1/2

[0004] POF is composed of two kinds of polymers, a core and a clad. The core has excellent transparency and excellent weather resistance as represented by polymethyl methacrylate (hereinafter abbreviated as PMMA). Good polymers are generally used. On the other hand, the cladding needs to have a lower refractive index than the core in order to confine light inside the core, and fluorine-containing polymers are widely used. As the fluorine-containing polymer for the cladding, the following three types are generally used, and each has advantages and disadvantages.
They are properly used in terms of numerical aperture, heat resistance, mechanical properties, and the like.

(1) Fluorination of vinylidene fluoride / tetrafluoroethylene copolymer (JP-B-63-67164), vinylidene fluoride / hexafluoroacetone copolymer (JP-A-61-22305), etc. Vinylidene copolymer. (2) Copolymer of fluoroalkyl methacrylate and methyl methacrylate (JP-B-43-8978)
POF using as a cladding. (3) Copolymer of long-chain fluoroalkyl methacrylate and methyl methacrylate (JP-A-62-265606)
No. 4, JP-A-4-204909).

The vinylidene fluoride-based copolymer (1) is composed of P
It has good compatibility with polymers mainly composed of methyl methacrylate such as MMA.
F has good interfacial adhesion to the core and good mechanical properties. However, the POF using these as cladding has a low heat resistance of about 70 ° C., and its use is limited. Further, since all of these vinylidene fluoride-based copolymers are crystalline polymers, the vinylidene fluoride composition is substantially 70 to 85.
It shows colorless transparency only within a limited range of mol%.
Therefore, the current P using a vinylidene fluoride copolymer
The numerical aperture of the MMA-based POF is around 0.50, and a further increase in the numerical aperture cannot be expected.

(2) The fluoroalkyl methacrylate-based copolymer has excellent lightness and a high glass transition temperature.
Although it is excellent at 5 ° C., it is brittle and has poor compatibility with a polymer mainly composed of methyl methacrylate. Therefore, a POF using such a clad as a clad has poor mechanical properties such as bending resistance. Moreover, as the composition ratio of fluoroalkyl methacrylate increases, the mechanical properties tend to be inferior.
The numerical aperture of the MMA-based POF is around 0.47, and a large increase in the numerical aperture cannot be expected.

On the other hand, the long-chain fluoroalkyl methacrylate-based copolymer (3) may have improved mechanical properties and higher fluorine content and lower refractive index than (2). When the value is too high, there arises a problem that cloudiness or thermal stability is inferior and foaming is caused to deteriorate light transmittance. Therefore, the numerical aperture of the current PMMA-based POF using a long-chain fluoroalkyl methacrylate-based copolymer is around 0.49. Therefore, the numerical aperture cannot be increased much.

From the above, in order to obtain a POF having a high numerical aperture, it is necessary to copolymerize a monomer having a higher fluorine content and a lower refractive index. One of the reasons is that a transparent vinylidene fluoride-based copolymer is used. Patent 2857 to improve performance
As shown in Japanese Patent Publication No. 411, a POF using a non-crystalline polymer for the clad by copolymerizing hexafluoropropylene as a third component has been proposed. It has a high numerical aperture and excellent translucency, but its copolymer has poor flex resistance, and its glass transition temperature is within the operating temperature range, and its environmental resistance is poor, or its cladding material is flexible. There are problems such as sticking during winding.

As an improvement, Japanese Patent Application Laid-Open No. H11-95044 has been proposed.
As described in JP-A-10-274716, a POF having a two-layer clad structure by further covering the vinylidene fluoride-based copolymer shown in (1) above to form a second clad has been proposed. I have. However, the two-layer clad requires a special die, and has a problem that the production capacity is low and the cost is high as compared with the one-layer clad.

[0011]

SUMMARY OF THE INVENTION Accordingly, as a result of studying a polymer composition of a clad material capable of solving the above-mentioned problem even with a single clad material, the present invention has been accomplished. The main object of the present invention is to provide a POF having a high numerical aperture and well-balanced properties such as heat resistance, bending resistance and environmental resistance.
Is to provide.

[0012]

In order to achieve the above object, a high numerical aperture plastic optical fiber according to the present invention comprises: a core comprising a (co) polymer having methyl methacrylate as a main component; A clad comprising a copolymer having a copolymer composition of 5 to 15% by weight, 40 to 55% by weight of tetrafluoroethylene, and 30 to 45% by weight of vinylidene fluoride and having a fluorine composition weight percentage of 69% by weight or more; Wherein the numerical aperture of the optical fiber is 0.58 or more.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The (co) polymer comprising methyl methacrylate as the main component of the present invention is a copolymer mainly composed of PMMA and methyl methacrylate (for example, (meth) acrylate). , (Meth) acrylic acid, substituted styrene, N-substituted maleimide, etc.), or modified polymers such as glutaric anhydride and glutarimide obtained by polymerizing them. Examples of the (meth) acrylate include methyl acrylate, ethyl methacrylate, butyl methacrylate, t-butyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, and phenyl methacrylate. -Substituted styrene, methylstyrene, α-methylstyrene, and the like; and N-substituted maleimides, such as N-isopropylmaleimide and N-cyclohexyl. Maleimide, N-methylmaleimide, N-ethylmaleimide, No-o-methylphenylmaleimide and the like can be mentioned. These copolymer components may be used in plural,
A small amount of other components may be used. Further, a stabilizer such as an antioxidant may be contained in an amount that does not adversely affect the light transmittance. Among these polymers, it is most preferable that the polymer is substantially PMMA in terms of productivity, light transmittance, environmental resistance and the like.

The clad according to the present invention comprises 5 to 15% by weight of hexafluoropropylene and 40 to 40% of tetrafluoroethylene.
It must be made of a copolymer having a copolymer composition of 55% by weight and 30 to 45% by weight of vinylidene fluoride and having a fluorine composition weight ratio of 69% by weight or more. This copolymer may be copolymerized with a monomer component other than those described above as long as it is in a small amount within a range not to impair the desired effect of the present invention, but is preferably a three-component copolymer having the above composition. If the copolymer composition is out of this range, a low refractive index and low crystallization (low translucency) cannot be achieved, or the adhesion of the core to a methyl methacrylate-based (co) polymer is poor. In addition, there are problems that mechanical properties such as bending resistance are greatly reduced, and that there is tackiness.

In the present invention, a one-layer clad made of the above-mentioned copolymer may be used, and further, as the second clad, a vinylidene fluoride / tetrafluoroethylene copolymer or a vinylidene fluoride / hexafluoroacetone copolymer may be used. An optical fiber structure covered with a vinylidene fluoride-based copolymer can also be used.

The POF of the present invention may be manufactured in the same manner as a general manufacturing method. For example, a composite spinning method in which a core material and a clad material are discharged from a concentric composite die in a heated and molten state to form a core / clad two-layer core-sheath structure is preferably used. Subsequently, a stretching process of about 1.2 to 3 times is generally performed for the purpose of improving the mechanical properties, and POF is obtained. The outer diameter of this POF is usually 0.1 to 3
mm, and may be appropriately selected depending on the purpose.
It is preferably 0.5 to 1.5 mm from the viewpoint of handleability and the like.

The POF of the present invention further comprises polyethylene, polypropylene or a copolymer or blend thereof, an olefin polymer containing an organosilane group,
A cord can be formed by coating a resin such as a polyamide resin such as ethylene-vinyl acetate, polyvinyl chloride, polyvinylidene fluoride, or nylon 12, a polyester resin, a nylon elastomer, a polyester elastomer, or a urethane resin or a fluorine resin. These coating materials may contain stabilizers such as antioxidants, antiaging agents, and UV stabilizers, in addition to flame retardants.

[0018]

The present invention will be described in more detail with reference to the following examples. Light transmission: Measured by a 30/2 m cutback method using halogen parallel light (wavelength 650 nm). Fluorine composition weight ratio (fluorine ratio): determined by elemental analysis. Refractive index: Measured in a 25 ° C. atmosphere at room temperature using an Abbe refractometer as a measuring device.

Number of continuous bending breaks: A load of 500 g is applied to one end of the optical fiber, and the optical fiber is supported by a mandrel having a diameter of 30 mmφ.
The number of rotations until the fiber was cut was measured by continuously rotating at ° (average value of n = 5). Heat resistance: High-temperature oven (PHH manufactured by Tabai Espec Inc.)
-200), a fiber having a test length of 28 m (each end at 1 m outside the oven) was introduced at 85 ° C. for 500 hours, and the amount of light before and after the test was measured, and the amount of change was used as an index (average value of n = 3). , Minus indicates light down).

Heat shock: A fiber having a test length of 28 m (each end of each end is 1 m outside the oven) is put into a composite environmental tester, and the temperature is raised to -40 ° C. and 85 ° C. (temperature rise or fall in 5 minutes, 2 minutes).
The change was measured as an index (average value of n = 3; minus indicates decrease in light amount).

Example 1 2F shown in Table 1 was used as a cladding material.
The / 4F / 6F copolymer (refractive index: 1.366, fluorine content: 69.5%) was supplied to the composite spinning machine. Furthermore, PMMA ((refractive index 1.49
2) is supplied as a core material to a composite spinning machine, and the core and clad are subjected to core-sheath composite melt spinning, and the fiber diameter is 1000 μm.
A bare fiber having a core diameter of 980 μm and a clad thickness of 10.0 μm was obtained. Furthermore, coating with polyethylene
The code was 2 mm. The POF code thus obtained was evaluated by the above evaluation method, and the results are shown in Table 1. As can be seen from Table 1, translucency, repetitive flexibility,
The heat resistance and the heat resistance against humidity were good, and it was suitable as a high numerical aperture POF.

Examples 2 to 4 and Comparative Examples 1 to 4 POF and its cord were obtained in the same manner as in Example 1 except that the clad material was changed as shown in Table 1. These POs
The same evaluation as in Example 1 was performed using the F code, and the results are shown in Table 1. Examples 2 to 4 of the present invention were all excellent in light transmission, repeated bending, heat resistance and heat shock resistance. On the other hand, Comparative Examples 1 and 3 are inferior in bending resistance and environmental resistance, and 2F / 4F as in Comparative Example 2.
The copolymer was inferior in light transmission, heat resistance and heat shock resistance.

[0023]

[Table 1] Note) PMMA: polymethyl methacrylate, 2F: vinylidene fluoride, 4F: tetrafluoroethylene,
6F: Hexafluoropropylene

[0024]

According to the present invention, the use of a specific polymer for a clad material provides a high aperture having a well-balanced heat resistance, bending resistance, environmental resistance, etc., even though the numerical aperture is as high as 0.58 or more. Several plastic optical fibers and their codes can be used.

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[Procedure amendment]

[Submission Date] October 10, 2000 (2000.10.
10)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0021

[Correction method] Change

[Correction contents]

[Example 1] As a clad material, 2F /
The 4F / 6F copolymer (refractive index: 1.366, fluorine content: 69.5%) was supplied to the composite spinning machine. In addition, continuous mass
PMMA prepared by Jo polymerization (refractive index 1.492)
Was supplied to a composite spinning machine as a core material, and the core and the clad were subjected to core-sheath composite melt spinning to obtain a bare fiber having a fiber diameter of 1000 μm (core diameter: 980 μm, clad thickness: 10.0 μm). In addition, 2.2 mm
Code. The POF code thus obtained was evaluated by the above evaluation method, and the results are shown in Table 1. As can be seen from Table 1, translucent, flex resistance, heat resistance, 耐Hi
The heat shock property was good, and it was suitable as a high numerical aperture POF.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0022

[Correction method] Change

[Correction contents]

[0022] [Examples 2-4 and Comparative Example 1 to 3 clutch
POF and its cord were obtained in the same manner as in Example 1 except that the material was changed as shown in Table 1. The same evaluation as in Example 1 was performed using these POF codes, and the results are shown in Table 1. Examples 2 to 4 of the present invention are translucent and bend-resistant.
The heat resistance, heat resistance and heat shock resistance were all excellent, whereas Comparative Examples 1 and 3 showed flex resistance, heat resistance and heat shock resistance.
And the heat shock resistance was poor, and as in Comparative Example 2, the 2F / 4F copolymer was poor in light transmission, heat resistance, and heat shock resistance.

Claims (1)

[Claims] 1. A core comprising a (co) polymer having methyl methacrylate as a main component, 5 to 15% by weight of hexafluoropropylene, 40 to 55% by weight of tetrafluoroethylene, and 30 to 45% of vinylidene fluoride. A plastic optical fiber having a copolymer composition of 0.1% by weight and a cladding made of a copolymer having a fluorine composition weight percentage of 69% by weight or more, wherein the numerical aperture of the optical fiber is 0.1%.
A high numerical aperture plastic optical fiber having a numerical aperture of 58 or more.